ModelSmart 3D™

Transcription

ModelSmart 3D™

ModelSmart 3D
™
3D Drawing with SpaceGuide™
Explore Structural Engineering
Build and Test 3D Models on Your Computer
Pre-Engineering
Software
Corporation
Pre-Engineering Software Corporation
presents
ModelSmart3D

3D Drawing with SpaceGuide™
A 3D Structural Spreadsheet for
Model Builders
Written by: Robert A. Wolf III, P.E.
Cover Art by: Bret Guidry
Illustrations by: Bret Guidry & Robert Wolf
Microsoft Windows98, Me, NT, 2000, XP & Vista
CD-ROM
License Agreement
Copyright 1998-2010, Pre-Engineering Software Corporation.
All rights reserved.
License Agreement
This software is licensed to the user for use on only one computer. In the
case of a multiple license purchase, refer to the license certificate for the
number of computers upon which the program may be installed. This
software may not be duplicated or transmitted in any form by parties who
have not received written authorization from the owner, Pre-Engineering
Software Corporation (Licensor).
Licensor does not warrant this software or its user's manual to be totally
error free.
Licensor does warrant that the software will perform
substantially in accordance with the user's manual and that the disk media is
free from any material defect that would impair the performance of the
software for a period of 90 days after the purchase date.
This software is for educational purposes only and is not intended for
design of load bearing structures or other professional use. Do not stand on,
sit on, walk on or hang from any model constructed with information
obtained from this software or the user's manual. Do not attempt actual
load testing of models without proper protection against flying debris.
Always wear proper eye protection. This is an experimental program actual
results will vary.
Neither Licensor, nor its owners, officers, employees or representatives
shall be liable for any damages arising out of the use of this software or
user’s manual. Licensee agrees to defend and hold harmless Licensor its
owners, employees, officers and representatives against any suit or claim
arising in connection with use of this software. Neither Licensor, nor its
owners, officers, employees or representatives shall be liable for any
incidental or consequential damages, or any damages in excess of the
original license fee.
Some states do not allow the exclusion or limitation of implied warranty;
therefore, portions of the above may not apply to you.
iii
Warnings and Limitations
Warnings and Limitations
WARNING! Actual load testing of models can be dangerous.
Structural models are capable of storing large amounts of energy that can be
released suddenly and without warning at or before complete model failure.
As a result, actual load testing of a model can result in the release of high
velocity projectiles, falling objects and failure of the testing apparatus. The
actual load testing of any model can cause injury to participants and
bystanders.
Do not stand on, sit on, walk on or hang from any model. Do not attempt
actual load testing of models without qualified adult supervision and proper
protection against flying and falling debris. Always wear proper eye
protection.
This software is for educational purposes only and is not intended for
design of load bearing structures or other professional use. As this software
is based on engineering science theory, actual results, including failure
loads, will vary due to factors such as, but not limited to, building material
quality and construction techniques. Neither Pre-Engineering Software
Corporation, nor its owners, officers, employees or representatives shall be
liable for any damages arising in connection with the use of this software.
Acknowledgment of Trademarks
ModelSmart and ModelSmart3D are trademarks of Pre-Engineering
Software Corporation. SpaceGuide and the SpaceGuide screen are
trademarks of Pre-Engineering Software Corporation.
Trademarks found in the ModelSmart3D program and documentation are
the property of their respective holders. The following is a partial list of
mentioned trademarks and their holders:
Adobe and Reader are registered trademarks of Adobe Systems
Incorporated.
Windows and Microsoft are registered trademarks of Microsoft
Corporation.
Pentium is a registered trademark of Intel Corporation. Celeron is a
trademark of Intel Corporation.
iv
Table of Contents
TABLE OF CONTENTS
Subject
Chapter
Part I - Quick Start
Introduction
Installation & Setup
Quick Start Example
1
2
3
Part II - Reference Section
Definitions
Navigation
The Toolbar
Menu Options
Data Dialogs
Results Dialogs
Material Grade
Changing the Default Member Material
Changing the Default Member Shape
4
5
6
7
8
9
10
11
12
Part III - A Bridge Building Primer
How Engineers Think About Forces
Truss Bridges
Tension Forces
Compression Forces
Failure Modes
Lateral Support and Bracing
Extra For Experts
A Bridge Building Project
Technical Support
v
13
14
15
16
17
18
19
20
21
Introduction
Introduction to ModelSmart3D
The purpose of ModelSmart3D is to allow students to
interactively design and test structural models on the computer.
By using a simulation, rather than actual construction and
testing, the student has the opportunity to design and test a
greater number of structures in less time and with less material
waste. For a hands-on component, construct a model of the
final design then break the computer model and bring the real
model home!
ModelSmart3D uses a modern transparent structural analysis
package that has been especially configured with the properties
of balsa and basswood to make designing and testing the model
as structurally realistic as possible.
Using ModelSmart3D as a structural spread sheet, you can
design model bridges, cranes, towers and miscellaneous
structural systems and subsystems. When you’re ready
ModelSmart3D will test your model and simulate the results by
showing a deflected shape or collapse. Then with a click of the
mouse button, you can view a report that shows the efficiency
of each member.
Let’s get started. To install ModelSmart3D, read and follow
the instructions in the next chapter. Then turn to chapter 3 for
a quick example.
1-1
Introduction
Notes:
1-2
INSTALLATION & SETUP
Installation
1.) Verify that there are at least 5 megs of free space available
on your hard drive. It’s a good idea to reserve an
additional 10% to 20% of your drive’s capacity for general
workspace.
2.) Put the ModelSmart3D CD-ROM in the drive. The "Setup"
program should run automatically. If "Setup" does not
autorun, Click the "Start" button, select "Run" then type
"X:\setup" (where X represents your CD-ROM drive
letter). Click "OK".
Running ModelSmart3D for the First Time
&
Entering the Certificate Number
1.) Locate the "License Certificate" included with the package.
2.) Double click the ModelSmart3D shortcut icon on your
desktop to run the program.
3.) Enter the “Certificate No.” and “License to:” information.
4.) Click the “OK” button.
Place the installation disk in a safe place for backup.
2-1
Setting up the User's Manual
for use from the Program Help Menu:
If you did not install ModelSmart3D in the default directory,
you will need to define the path to the online user's manual in
the program's preferences dialog. Use these steps to reset the
path:
1. Run the program by double clicking the "ModelSmart3D"
shortcut on your desktop. Select "Edit|Preferences…" from
the menu.
2. Click the "Browse" button to the right of the "User's
Manual" edit box.
3. Locate
the
file
"MS3Dmanual.pdf"
“ModelSmart3D\manual” folder.
in
the
4. ModelSmart3D uses the “Adobe Reader”(www.adobe.com)
plug-in for your Internet browser to view the online
manual. If "Iexplorer.exe" is not your default browser you
must also reset this path. Otherwise, click the "Save"
button, then "OK" to close the dialog.
After these paths are set, you will have access to the
"ModelSmart3D Manual" from the "Help" menu.
Please work through the example structure user's manual.
Select "View|Advanced Options" from the menu to turn on all
menu options.
If you need assistance, please contact us by phone at 225 7693728. If you would like us to contact you, please e-mail your
name and phone number to "[email protected]".
2-2
Quick Start Example
Quick Start Example
Welcome to ModelSmart3D. The purpose of this chapter is to
help you design and analyze your first model.
ModelSmart3D is capable of analyzing many different types of
structures such as bridges (cantilever, suspension, underslung,
etc.), cranes, and towers.
For your first structure, let's design a truss bridge.
Step#1 - Select the Desired Units for Your New Model
We will use U.S. customary units for the example. Select
"File|New| U.S. Customary Units" from the menu.
Step #2 - Adjust the size of the "Workspace"
3-1
Quick Start Example
Select "Edit|Preferences..." to display the "ModelSmart3D
Preferences" dialog. Input 24 for Xmax, 18 for Ymax, and 18
for Zmax (see "Program Sign Convention" - below). Click
"OK". Press "F1" to re-center the workspace ("F1" also returns
the viewer to the start position.).
Program Sign Convention
Xmax is the length of the WorkSpace.
Ymax is the height of the WorkSpace.
Zmax is the width of the WorkSpace.
Now the WorkSpace is appropriately sized for example
structure. An unnecessarily large WorkSpace will slow down
the program with needless screen searching.
3-2
Quick Start Example
Step#3 - Start Building - Adding the First Joints
Your bridge will be built from individual elements called
members (see the "Definitions" chapter). These members
represent the physical sizes of the material you have chosen. A
member can only be placed between existing joints. A joint
represents the starting point or ending point of a member as
well at the connection (usually glued) of one member to
another member or members.
Let's place some joints that we can use to connect members
into the WorkSpace. Press the "+"key (on the numeric keypad)
to raise the observer's viewpoint (see "Viewpoint
Movements").
Click (to toggle off) the
(XY "Show/Hide GuidePlane")
button and the
(YZ "Show/Hide GuidePlane") button on
the toolbar (see "The ModelSmart3D Toolbar") to remove
these two GuidePlanes. Removing these two GuidePlanes
from the WorkSpace will make it easier (and faster) to do the
next step - to add joints to the XZ GuidePlane.
3-3
Quick Start Example
Select "Joint|Add" from the menu or click the
Joint") button on the toolbar.
("Add
Move the cursor until the coordinate at the upper left of the
window reads "X=4.0, Y=4.0, Z=10.00".
Click the left mouse button to add the new joint.
That's it. This is how you will add joints to the model. Later we
will add members between joints.
3-4
Quick Start Example
Let's add 3 more joints to the model.
Place a joint at each of the following coordinates:
X=16.0, Y=4.0, Z=10.0
X=16.0, Y=4.0, Z=8.0
X=4.0, Y=4.0, Z=8.0
Your model should now look similar to the above picture.
3-5
Quick Start Example
Step#4 - Build the Near Side Truss
Let's start working on the vertical structure of our bridge.
Click
(XZ "Show/Hide GuidePlane") to turn off the
transverse GuidePlane.
(XY "Show/Hide GuidePlane") to turn on the
Click
vertical GuidePlane.
Let's move the XY GuidePlane forward until the plane
intersects the front 2 joints. To do this, select "Guide|XY
Plane|Move Plane to Joint" from the menu (this option is not
available on the toolbar).
Move the cursor to point at the left most joint in the front of the
WorkSpace. Wait for the joint to become highlighted yellow.
Click the left mouse button.
3-6
Quick Start Example
The vertical GuidePlane will move to a position that cuts
through the center of the chosen joint (see the picture below).
Now, press the "-" key a few times to lower the viewpoint.
The XY GuidePlane is now positioned at Z=10.0".
Let's use a simpler notation for joint coordinates. The notation
(7.0, 4.0, 10.0) is called an ordered set and has the same
meaning as (X=7.0, Y=4.0, Z=10.0).
Add 3 joints at the height Y=4.0". Place these 3 joints at (7.0,
4.0, 10.0), (10.0, 4.0, 10.0), and (13.0, 4.0, 10.0).
Then add another 3 joints at a height of Y=7.0.
Place these joints at (7.0, 7.0, 10.0), (10.0, 7.0, 10.0), and
(13.0, 7.0, 10.0). Now your model should look similar to the
picture above.
3-7
Quick Start Example
Step#5 - Save Your Work
Select "File|Save Model As ..." from the menu.
3-8
Quick Start Example
Type "Example.3dd" for the "File name" then click the "Save"
button.
3-9
Quick Start Example
Step #6 - Adding Joints the Easy Way - Joint Replication
We need to add the same 6 joints to a vertical plane 2 inches
behind the current plane (the far truss). We could move the
XY GuidePlane back 2 inches and add the joints one at a time.
A faster way to add these joints is to "Replicate" selected
joints.
Here's how joint replication works.
Click the
("Select Joint") button.
3-10
Quick Start Example
Select each joint that you want to replicate (point to the joint,
wait for it to highlight then click the left mouse button).
The 6 selected joints should now appear red.
(NOTE: Do not select joints opposite joints that already appear
in the plane that will receive the replicated joints – select 6
joints only.)
3-11
Quick Start Example
Press the right arrow key a few times to move the viewpoint to
the position shown above
Select "Guides|XY Plane|Replicate Joint(s) and Move Plane to
Joint" from the menu.
3-12
Quick Start Example
Point the cursor to the joint at coordinate (4.0, 4.0, 8.0), wait
for the joint to highlight then click the left mouse button.
(Select "Edit|Undo" if you make a mistake.)
Clear the joint selections by clicking the "Clear All Joint
Selections" button.
3-13
Quick Start Example
That's all of the joints needed for our bridge. Select "File|Save
Model" from the menu to save your work once again.
Step #7 - Adding Members to the Near Side Truss
Use the cursor keys to move the viewpoint until your
WorkSpace appears similar to the above.
Click the
,
all GuidePlanes.
,
GuidePlane buttons to turn off
Before adding members we must select the type of material and
the shape of the member's cross-section.
3-14
Quick Start Example
Select "Member|Set Default Material and Shape..." from the
menu.
Material is what your member is made of - balsa wood,
basswood, steel etc. Let's leave this one as "BalsaD2" (the
default). This is a medium grade (see "Grading Material")
Balsa.
For the shape (cross-section) click the down arrow in the dialog
box and select "5/16x5/16".
After selecting the "Shape" click the "OK" button.
3-15
Quick Start Example
Select "Member|Add" or click the
button.
("Member Add")
Move the cursor to point to the joint (this is the starting joint)
shown above and wait for it to highlight.
3-16
Quick Start Example
Click and hold the left mouse button.
Move the cursor to point at the joint to the right of the starting
joint. Wait for it to highlight then release the mouse button.
You have just added your first member to the model.
("Focus") button and then click on the front
Click the
center joint to re-center the model in the screen.
3-17
Quick Start Example
Click the up arrow key to move the observer into the model.
The left and right arrow keys will now rotate the model about
the new focus.
3-18
Quick Start Example
("Add Members") button once again and
Click on the
add the members show above.
3-19
Quick Start Example
Step #8 - Adding Members to the Far Side Truss
Use the "Arrow Keys" to move viewpoint until you can see the
other side of the model.
3-20
Quick Start Example
Add the far-side truss members to the bridge as shown above.
3-21
Quick Start Example
Step #9 - Adding Members - The Floor Beams
Use the "Arrow Keys" to move the viewpoint until the view
looks similar to the one above.
Click the
beams.
("Add Member") button and add the floor
3-22
Quick Start Example
Now add the upper struts.
Adding the top struts will complete the structure.
3-23
Quick Start Example
Step #10 - Painting Members
Move the viewpoint once again until the view is similar to the
one above.
3-24
Quick Start Example
Let's paint some of the members.
Select "Members|Color|Set Default Color" from the menu.
Select the blue color as shown above then click "OK".
3-25
Quick Start Example
Select "Members|Color|Paint Members" from the menu. Move
the cursor to point at one of the lower chord members. Wait for
the member to highlight then click the left mouse button.
Continue this procedure until you have painted all of the lower
chord members.
Select "Members|Color|Set Default Color" from the menu once
again. This time select the orange color. Click "OK".
3-26
Quick Start Example
Select "Members|Color|Paint Members" from the menu.
Color the portal (or sway) frame members as shown above.
3-27
Quick Start Example
Step #11 - Adding Supports
Now we must attach the bridge to its surroundings.
To do this we use supports.
The hinge-roller support combination is a good choice if you
want to simulate a model placed on a test apparatus.
Unless you plan to glue your model to the test stand there will
be rotation and slippage occurring as the load is applied. The
hinge is required on one side to keep the model from acting
like a skateboard.
From the menu click the
("Hinge Support") button or
select "Supports|Universal Hinge" from the menu.
3-28
Quick Start Example
Point the cursor at the left most joint in the near truss and click
the left mouse button.
Now move the cursor arrow to point at the joint just behind this
new support and add a hinge support to the left most joint in
the far truss.
3-29
Quick Start Example
Click the
("Roller Support") or select "Supports|X
Roller" from the menu and add supports to the right most joint
in the near and far trusses.
3-30
Quick Start Example
Step #12 - Adding Loads
There is one more step before we can analyze the structure.
We need to give the model something to do - carry a load.
Let's put some load on the model by attaching a couple of force
vectors to it.
Select "Loads|Set Default Force" from the menu. Type "-250"
into the "Force Y" edit box. Click on the "Translated" radio
button (this means the force vector will be attached to the
structure by its tail). Click "OK".
3-31
Quick Start Example
Select "Loads|Add/Change Force Y" from the menu.
3-32
Quick Start Example
Move the cursor until it points at the joint in the middle bottom
of the near truss. Wait for the joint to highlight, then click the
left mouse button. Repeat this for the corresponding joint in the
far truss.
Select "File|Save Model" to save your work one more time.
We're ready to analyze!
3-33
Quick Start Example
Step #13 - Analyzing the Model.
There are many analysis options that we could select.
To simplify this example, let's use the defaults.
Select "Analysis|Run the Analysis!" from the menu or click the
analysis button.
Oh No!
What happened?
Four members (the ones painted red) in the top chords of the
bridge failed.
3-34
Quick Start Example
Step#14 - Adjusting the design.
Let's see what we can do to strengthen the bridge.
We have three choices:
1. Use a stronger material for the members that failed.
2. Use a larger shape (cross-section) for the members that
failed.
3. Change the overall geometric design of our bridge.
Let's change the shape of the failed members to a larger crosssection (3/8x3/8).
Select "Members|Set Default Material and Shape... " from the
menu. Select "3/8x3/8" from the "Shape" drop down edit box.
3-35
Quick Start Example
Select "Members|Change Shape" from the menu then point the
cursor at each of the failed members and click the left mouse
button to change their shapes.
Let's re-analyze. Select "Analysis|Start the Analysis!" from the
menu once again. It worked!
This completes the example. Now it's your turn.
3-36
Definitions
Definitions
The Completed Example Structure
ModelSmart Definitions
SpaceGuide - This is the CAD engine that ModelSmart3D
uses to enable the user to draw models in 3D.
WorkSpace - The WorkSpace is the space defined by the three
BasePlanes.
GuidePlane - A GuidePlane is one of the three moveable
planes uses to create joints in a 3D. The GuidePlane is also
used to define the plane to be printed (Not available in trial
version.).
4-1
Definitions
Shape (Cross-Section) - If you were to take a knife and cut
across (perpendicular to the member's longitudinal axis) the
member and then look at ends of the pieces, you would see a
shape. This shape is the cross-section. A member shape of
5/16x5/16 has a cross-section that appears as a square that
measures 5/16" wide by 5/16" high. A member shape of
1/8x1/4 has a cross-section that appears as a rectangle that
measures 1/8" wide by 1/4" high.
General Engineering Definitions
Length - Linear or curvilinear distance between two points.
Linear distance is the length along a straight line. For example,
determine the length of a string that can stretch between two
points on your classroom floor. Curvilinear distance can be the
distance around a circle or other curved shape. For example,
determine the length of a string (also a line) that can stretch
around your wrist. Typical units for length are inches, feet,
meters, centimeters, etc.
Area - This is the two-dimensional size, or amount, of surface
expressed in square units such as square inches, square feet and
square meters. Think of it, for example, as how many square
inches can you paste onto the surface of something (i.e. the
floor of your classroom or a basketball). The surface can be flat
or curved.
Volume - The three-dimensional measure of the space
occupied by an object or substance. Expressed in cubic units
such as cubic inches, cubic feet and cubic meters. For example,
how much volume does your classroom occupy? Or, how many
cubic feet will fit into your classroom.
4-2
Definitions
Force - Any action applied to an object which would cause the
object to move, change the way it is currently moving, or
change its shape. A force can also be thought of as a push
(compressive force) or pull (tensile force) acting on an object.
For example, you might push or pull a desk to move it. You
might want to exert a force on a soccer ball to prevent it from
going into the goal. Some typical units are pounds, newtons,
tons and kips (kilo-pounds, 1 kip = 1000 lbs).
Force Vector - A force vector is a graphical representation of a
force. Force vectors are drawn as arrows and show size,
direction and point of application. Let's assume that you want
to draw a sketch of a desk and show a force vector that
represents someone pushing it with a force of 15 pounds. You
could draw a rectangle for the desk then draw an arrow for the
force vector. Place the head of the arrow at the point where the
person is touching the desk and align the stem of the arrow in
the direction of the push (see "How Engineer's Think About
Forces").
Pressure - An external force applied over some area.
Expressed in force per area unit. For example, let's say there is
a one foot cube that weighs 200 pounds sitting on the driveway
at your house. How much pressure is the box exerting on your
driveway? Pressure equals force divided by area. Therefore,
the pressure equals 200 pounds divided by an area of 1 square
foot (one times one - the surface of the box in contact with the
ground). The answer is 200 psf (pounds per square foot).
Stress - Stress can be thought of as pressure created within an
object. For example, if I apply a tensile force (see force
definition above) at both ends of a board, how much stress will
I create in the board? See page 15-1. Stress equals force
divided area. If the tension force were 50 pounds and the board
was a 2x4 (1.5"x3.5") the stress would equal 50/(1.5x3.5) or
about 9.52 psi (pounds per square inch).
4-3
Definitions
Mass - This is the amount of matter contained in an object. It's
best to think of mass while in deep space - away from the
effects of gravity. Pretend you are space walking outside your
craft. There is an object nearby that you must move into the
cargo bay of your space ship. If the object has little mass like a
block of balsa wood, it might be easy to get it to move toward
the cargo bay. Let's say there is another object with the same
physical size (i.e. occupies the same volume) as the balsa
wood. However, this new object is solid steel. It will be much
harder to get the steel object to start moving toward the cargo
bay. The steel object has more mass.
Weight - The force of attraction caused by gravitational pull.
We need to think of gravity right here on earth (or on some
other planet). Weight (here on earth) is a force that acts on a
body or object and is directed toward the center of the earth.
What is your weight? This force, that is your weight, is
directed along a line of action that goes through you and the
center of the earth (really the center of mass of the earth).
Density - There are two kinds of density - mass density and
weight density. Both types are a measure of how much matter
is in a given volume.
Let's consider a block of balsa wood. If you look very closely
at the end grain of the wood you will see little holes. This
means that the block is not entirely composed of wood matter.
There is air occupying the space defined by the holes. Actually
there are many tiny holes and gaps that you can't see (without a
microscope).
4-4
Definitions
This means that density is also a measure of how porous (filled
with holes and gaps) the material is.
Mass density is the mass of the object divided by the volume of
space that the object occupies. Weight density is the weight of
the object divided by the volume of space that the object
occupies.
For example, let's calculate the weight density of a 1/8"x 1/8"x
24" stick of balsa wood. The volume of the wood is
V=(.125)(.125)(24) = .375 cubic inches. Next, you must take
the stick of balsa to a scale and weigh it. Let's say it weighs
.053 oz. Then the weight density is D =.053/.375 = .1413 oz
per cubic inch.
If we divide by 16 we get D=.00883 pounds per cubic inch.
And if we convert the units to pcf (pounds per cubic foot) we
will have our answer in the units that are normally used to
express the density of wood. D=.00883(12)(12)(12) = 15.3
pcf.
The weight density of balsa wood varies greatly.
In
comparison, the weight density of southern pine is about 36
pcf. Remember, from the definition of density, the greater the
density the greater the matter (wood in this case) within the
volume. And, generally, that means there are more wood fibers
in the volume available of resist load.
Loads - When engineers refers to loads they usually mean the
entire collection of forces acting on the object. This includes
axial forces (pushing and/or pulling) and bending (moments see below).
4-5
Definitions
Moment - A measure of the tendency of a force to cause
rotation about an axis. The graphical representation of a
moment acting on an object is called a curl. A curl is an arc
shaped arrow drawn near and about the axis of rotation.
Typical units are in-lbs, ft-lbs and ft-kips, N-m (some
professions use lb-ft and kip-ft, many engineers like the more
common ft-lbs and ft-kips - either is correct). Moment(M) =
Force(F) times the perpendicular distance to the axis(d). M = F
x d.
4-6
Navigation
Navigation
ModelSmart3D uses the "observer's viewpoint" to position the model in the
window. The following actions are used to position an imaginary observer
in relation to the model:
Primary Arrow Keys
Up Arrow
Move the observer's viewpoint toward the model.
Down Arrow
Move the observer's viewpoint away from the
model.
Move the observer's viewpoint to the left of the
model. The observer remains a fixed distance from
the model.
Move the observer's viewpoint to the right of the
model. The observer remains a fixed distance from
the model.
Left Arrow
Right Arrow
Numeric Keypad
"/" (division key)
Move the observer's viewpoint directly toward the
focal point.
"*"
(multiplication
key)
"+"(addition key)
Move the observer's viewpoint directly away from
the focal point.
"-"(minus key)
Up Arrow
(On Keypad)
Down Arrow
(On Keypad)
Left Arrow
(On Keypad)
Right Arrow
(On Keypad)
Move the observer's viewpoint up while remaining
focused on the model.
Move the observer's viewpoint down while
remaining focused on the model.
Move the observer's viewpoint and focus up.
Move the observer's viewpoint and focus down.
Move the observer's viewpoint and focus left.
Move the observer's viewpoint and focus right.
5-1
Navigation
Function Keys
F1
Starting position
F2
View of Left side - Near
F3
Top View
F4
Bottom View
F5
Perspective
F6
Not Used
F7
Back View
F8
Front View - Far
F9
Perspective - Near
F10
Not Used
F11
Show All
F12
Hide All
5-2
Navigation
Special Purpose Keys
Ctrl - "1"
Save observers location as " Position 1 " ("1").
Ctrl - "2"
Ctrl - "3"
Ctrl - "4"
5-3
Navigation
5-4
The Toolbar
The ModelSmart3D Toolbar
Set Focus - Use this option to change the focal point of
the observer.
Select Joint - This option allows the user to select joints
for moving and replicating.
Cancel All Selected Joints
Add Joint - Click this button to place the program in the
add joint mode then click on a GuidePlane to add a joint.
(Remember, place the member's joints before adding the
member.)
Add Member - This button places ModelSmart3D in the
add member mode. (Remember, you can only draw members
from existing joint to existing joint.)
6-1
The Toolbar
XY GuidePlane Toggle - To show this GuidePlane
depress the button. If the plane is not needed, hiding it will
allow the program to run more efficiently.
Move XY GuidePlane - Click this button to move the
XY GuidePlane. To position the plane to a new location, drag
the plane along either of the other two BasePlanes (sides of the
WorkSpace).
XZ GuidePlane Toggle - To show this GuidePlane
Move XZ GuidePlane - Click this button to move the
XZ GuidePlane. To position the plane to a new location, drag
WorkSpace).
YZ GuidePlane Toggle - To show this GuidePlane
6-2
The Toolbar
Move YZ GuidePlane - Click this button to move the
YZ GuidePlane. To position the plane to a new location, drag
WorkSpace).
Add an "X" Roller Support - After clicking this button
ModelSmart3D places an "X Roller" support at the next joint
clicked (wait for the joint to highlight before clicking).
Add a Universal Hinge Support - After clicking this
button ModelSmart3D places a universal hinge support at the
next joint clicked. Two universal hinges at one end and two X
rollers at the other is a good support combination for bridges.
This classic hinge-roller support combination means that the
bridge is not glued to the test surface. It allows slip in the X
direction when the load is applied. No movement in the support
is allowed in the Y direction.
Add a Fixed Support - After clicking this button
ModelSmart3D places a fixed support at the next joint that you
highlight and click. A fixed support is a fully rigid condition.
Think of this support as imbedding the end of the member in a
large mass of concrete.
Run the Current Analysis - Click this button to run the
analyzer with the current analysis option settings.
6-3
The Toolbar
Notes:
6-4
Menu Options
Menu Options
File Menu
New
This option deletes the current structure and readies the
program for a new one. Select "File|New|U.S. Customary
Units" to work in pounds and inches or select "File|New|Metric
Units" to work with Newtons and meters.
Open Model
Select this option to retrieve a previously stored model.
Save Model
After using "Save Model As…" to save your structure for the
first time you can then select this option to quickly save your
model under the same file name.
Save Model As …
To save a model, select this option and navigate to the
directory where you want to store it. Type a file name then
click "Save".
Import ModelSmart 2D File…
Use this option to import a model that was previously saved
with ModelSmart (version 1.XX).
Export VRML 2.0 File…
Use this option to create a 3D virtual reality file that can be
posted on the Internet. Your file will be stored as a ".wrl" file
and can be viewed with any VRML 2.0 enabled browser.
7-1
Menu Options
Tile Orientation
Use these options to orient the graphic print tiles. Do not use
the portrait/landscape in the print dialog to orient the graphic
print tiles.
Print XY Plane
Print the projected image of the structure that is within 1/2" (or
3 cm) of the current position of the XY GuidePlane.
XY Plane Tiles
After selecting "File | Portrait" or "File | Landscape", select
"File | XY Plane Tiles | Show Tiles" to show what will print on
each page. You may adjust the location of the tiles by selecting
"File | XY Plane Tiles | Move Tiles" then clicking on the XY
GuidePlane to re-locate the tile or tile group.
Print XZ Plane
3 cm) of the current position of the XZ GuidePlane.
XZ Plane Tiles
"File | XZ Plane Tiles | Show Tiles" to show what will print on
"File | XZ Plane Tiles | Move Tiles" then clicking on the XZ
Print YZ Plane
3 cm) of the current position of the YZ GuidePlane.
7-2
Menu Options
YZ Plane Tiles
"File | YZ Plane Tiles | Show Tiles" to show what will print on
"File | YZ Plane Tiles | Move Tiles" then clicking on the YZ
Save Output File - All numerical values are available in the
Model Data, Member Results Dialog and Joints Results Dialog
can be saved to file. If you want to save your analysis results to
a file check this option. ModelSmart3D will request a filename
for this output file. You can use a word processor to make a
hard copy of the numerical data.
Include in Output File - The output file created when the
above option is checked can be quite extensive. Use this popup menu to select the information to be stored in the file.
Exit ModelSmart3D
Select this option or click the X-box in the upper left corner of
the window to exit the program.
Edit Menu
Undo
Use this option to restore the model to a state prior to executing
the previous option.
Copy to Clipboard
This option copies the window’s client area to the clipboard for
pasting into other programs.(View|Toolbar toggles the toolbar.)
Preferences…
Select this option to access the paths to various help files and
viewers. The preferences dialog also allows the user to change
other program settings such as WorkSpace size and observer
movement speed.
7-3
Menu Options
View Menu
Toolbar
Toggle (Display/Hide) the ModelSmart3D toolbar.
Advanced Options
The "Members | Edit Material List" and "Members | Edit Shape
List" are grayed unless this option is checked. These options
are for advanced users only and are not available in the trial
version.
Refresh Screen
This option cleans the window and erases the results of options
that cause information to be printed on individual members of
the model.
Joints
Toggle (Display/Hide) the blue ball that represents a joint
(glued connection) in the model. You may adjust the size of the
joint by using the "Joints | Size |…" option.
Loads
Toggle (Display/Hide) the red arrows that represent forces on
the model.
Supports
Toggle (Display/Hide) the graphic images that represent the
various types of supports on the model.
XY BasePlane
Toggle (Display/Hide) the rear wall (XY BasePlane) of the
ModelSmart3D WorkSpace.
7-4
Menu Options
XZ BasePlane
Toggle (Display/Hide) the bottom wall (XZ BasePlane) of the
YZ BasePlane
Toggle (Display/Hide) the left wall (YZ BasePlane) of the
Rulers
Toggle (Display/Hide) the yellow BasePlane rulers.
Show All
Display all guides and model objects in the window.
Hide All
Hide all guides and model objects in the window.
Show Origin
Toggle (Display/Hide) the symbol representing coordinate
X=0, Y=0, Z=0 (0,0,0).
Show Focus
Toggle (Display/Hide) the symbol representing the observer's
focal point.
Background Color ...
This option opens a color selection dialog for selecting a new
environment color. This is the color of the background behind
and around the WorkSpace.
Ambient Light Intensity ...
This option opens an intensity dialog for selecting a new
lighting level for the ambient light. Ambient light is the light
present when the direct light intensity is zero.
7-5
Menu Options
Direct Light Intensity ...
This option opens an intensity dialog for selecting a new
lighting level for direct lighting. This is a lamp focused on the
model and located at the coordinate (36.0, 96.0, 72.0).
Reset to Default Lighting
Click this option to immediately reset all lighting to the
original default levels.
Go to
Use these options to move the observer to one of the preset
locations.
Guides Menu
XY GuidePlane, XZ GuidePlane, YZ GuidePlane
SpaceGuide , the computer aided design engine used in
ModelSmart3D , includes a WorkSpace with moveable
GuidePlanes.
Each GuidePlane is capable of performing each of the
following functions:
Show Plane
Toggle (Display/Hide) the GuidePlane.
Move Plane
Select this option, then click and drag the GuidePlane to a new
location relative to the BasePlanes.
7-6
Menu Options
Move Plane to Joint
To move a GuidePlane until it intersects a joint on the current
model, select this option then point to one of the model's joints.
Wait for the joint to highlight then click the left mouse button.
Move Joint(s) and Plane
To move the selected joints with the GuidePlane to a new
location, select this option then click and drag the GuidePlane
to a new location relative to the BasePlanes.
Replicate Joint(s) and Move Plane
To move a GuidePlane and create duplicates of the selected
joints at a new location, select this option then click and drag
the GuidePlane to a new location relative to the BasePlanes.
All selected joints will be duplicated at a distance equal to the
distance the GuidePlane was moved.
Replicate Joint(s) and Move Plane to Joint
To move a GuidePlane and create duplicates of the selected
joints at a new location corresponding to an existing joint on
the model, select this option then point to one of the model's
joints. Wait for the joint to highlight then click the left mouse
button. All selected joints will be duplicated at a distance equal
to the distance the GuidePlane was moved.
7-7
Menu Options
Move Focus
Select a joint to become the observer's focal point. After
selecting a joint as the new focal point, the observer will move
in relation to this point.
Move Origin
The default location of the origin (coordinate (0,0,0)) is the
common intersection of the WorkSpace BasePlanes. You may
move the origin to a new location by selecting this option then
clicking on one of the model's joints. Wait for the joint to
highlight before clicking the mouse button.
Reset Origin
This option moves the location of the origin to the common
intersection of the WorkSpace BasePlanes (0,0,0).
Members Menu
Add
With this option selected you can add members to your model
using the following procedure:
4. Move the cursor arrow to point at the joint where you
want to start the member (wait for the joint to
highlight).
5. Click and hold the left mouse button down.
6. Move the cursor arrow to point at the joint where you
want to end the member (wait for the joint to highlight).
7. Release the mouse button
7-8
Menu Options
Hide
Use this function to temporarily replace the member with a
wire frame line. Click this option then click on a member. This
feature does not effect the analysis. It hides the member from
view and selection only.
Hide All
Use this function to temporarily replace all members with wire
frame lines. This feature does not effect the analysis. It hides
the members from view and selection only.
Show
Use this function to reverse the effect of the hide function.
Click this option then click on a member.
Show All
Use this function to reverse the effect of the hide function for
all hidden members.
Negate
Use this function to temporarily negate a member from the
analysis. Click this option then click on a member. The model
will omit all negated members from the analysis.
Negate All
To negate all members from the analysis select this option. Do
not try to analyze the model with all members negated.
Restore
Use this function to reverse the effect of the negate function.
Click this option then click on a member.
7-9
Menu Options
Restore All
Use this function to reverse the effect of the "Negate" function
for all negated members.
Set Default Material and Shape…
This option displays a dialog for selecting the default material
and shape to be used when adding members.
Copy Properties
To set the default material and shape to that of an existing
member, click this option then click on a member.
Change Material
Select this option then click on a member to change that
member's material to the current default material type.
Show Material Numbers
To show all of the material numbers used in the model select
this option. Each member's material number will be printed on
the projected image of the member into the picture plane.
Zoom into the model before selecting this option to avoid
having the material numbers overlap one another. Use "View |
Refresh Screen" to erase the material numbers.
Edit Material List…
Use this advanced feature to alter or add materials to the
material list. Click this option to open the material editor
dialog. The maximum number of materials per model is 10.
Change Shape
The shape of a member refers to its cross-section. Use this
option to change the size of a member's cross-section. Select
this option then click on a member to change that member's
shape to the current default shape.
7-10
Menu Options
Show Shape Numbers
To show all of the shape numbers used in the model select this
option. Each members shape number will be printed on the
projected image of the member into the picture plane. Zoom
into the model before selecting this option to avoid having the
shape numbers overlap one another. Use "View | Refresh
Screen" to erase the shape numbers.
Edit Shape List…
Use this advanced feature to alter or add shapes to the shape
list. Click this option to open the shape editor dialog. The
maximum number of shapes per model is 10.
Show Member Numbers
Select this option to display the member number on a projected
image of the member into the picture plane. To avoid
overlapping members numbers zoom into the model before
selecting this option. Use "View | Refresh Screen" to erase the
member numbers.
Color
Use these options to alter the color of member(s):
Paint Member - Select this option then click on a
member to change its color to the current default color.
Set Default Color - Change the current default color
using this dialog.
Copy Color - Change the current default color to the
same color as an existing member. Select this option
then click on a member to copy its color. Then select
the "Members|Color|Paint Member" option to paint an
existing member.
7-11
Menu Options
Reset All Member Fixities - Select this option to return all
member end fixities to their defaults - fixed ends (glued). This
is an advanced feature.
Properties…
Use this dialog to inspect the current properties of a member.
Select the option then click on a member to open the dialog.
Joints Menu
Add
With this option selected you can add joints to your model
using the following procedure:
1. Move the cursor arrow to point at a location on one of
the GuidePlanes where you want to create a new joint.
2. Wait for the blue ball to appear.
3. Look at the coordinates in the upper left corner of the
window to verify that the joint will be correctly placed.
4. Click (and release) the left mouse button.
To place a joint in an existing member click on the member
while using the "Joint|Add" option.
To place a joint in a member at a precise location use the
"Joint| Use "Create Joint in Member" dialog" option.
Select a Joint
Use this option to select a joint to be used with the features in
the "Guides" menu. A joint turns red when it is selected.
7-12
Menu Options
Select All Joints
Use this option to select all joints in the model.
Clear Joint Selections
After selecting this option, all selected members (red) will
become unselected (blue).
Use "Create Joint in Member" Dialog
Turn this option on to precisely locate a joint within an existing
member. When a joint is placed in a member, with this option
on, a dialog will appear requesting a location for the joint
within the member. The number you enter into the dialog is
the percent distance of the joint from the joint nearer the lower
left corner of the window.
Delete
To delete a member, select this option, point the cursor at a
member, wait for the member to highlight, then click the left
mouse button to delete it.
Size
When working with small models it is sometimes necessary to
reduce the size of the joint. Joint size is for graphical
representation only and has no effect on the analysis of your
model. You may select small, default or large.
Properties…
To inspect the properties of any joint, select this option then
click on a joint. A dialog will open allowing you to see all
properties associated with that joint.
7-13
Menu Options
Support Menu
XY Roller
This option creates a support at a joint that allows translation in
the XY direction and prevents translation in the Z direction.
This support allows rotation of the joint around any axis. Select
this option, point the cursor at an existing joint, wait for the
joint to highlight, then click the left mouse button to create the
support.
XZ Roller
the XZ direction and prevents translation in the Y direction.
support. This support simulates setting the model on a flat
surface. It allows slippage indicating that the model is not
glued to the table. (Two universal hinges in addition to the XZ
rollers are required to prevent the model from skating around
the tabletop.)
YZ Roller
the YZ direction and prevents translation in the X direction.
support.
7-14
Menu Options
X Roller
the X direction and prevents translation in the Y and Z
directions. This support allows rotation of the joint around the
Z axis. Select this option, point the cursor at an existing joint,
wait for the joint to highlight, then click the left mouse button
to create the support.
Y Roller
the Y direction and prevents translation in the X and Z
Z axis. Select this option, point the cursor at an existing joint,
Z Roller
the Z direction and prevents translation in the X and Y
Y axis. Select this option, point the cursor at an existing joint,
Universal Hinge
This option creates a support at a joint that allows rotation
around any axis and prevents translation in all directions.
Select this option, point the cursor at an existing joint, wait for
the joint to highlight, then click the left mouse button to create
the support.
7-15
Menu Options
Fixed
This option creates a support at a joint that prevents all rotation
and translation. Select this option, point the cursor at an
existing joint, wait for the joint to highlight, then click the left
mouse button to create the support.
Delete
To remove a support, select this option then click the support
(at the joint). This option will not delete the joint.
Loads Menu
Add/Change Force X
This option can be used to add or change the "X" force at a
joint. Select this option then click on a joint to add a force or
click an existing force vector (at its joint) to change the force to
the current default. Select the "Loads | Set Default Force…"
option to change the current default force.
Add/Change Force Y
This option can be used to add or change the "Y" force at a
Add/Change Force Z
This option can be used to add or change the "Z" force at a
7-16
Menu Options
Show X Forces
This option displays the magnitude of all forces on the model
acting in the X direction.
Show Y Forces
acting in the Y direction.
Show Z Forces
acting in the Z direction.
Delete
To delete all forces at a joint select this option, wait for the
joint to highlight, then click on a joint.
Set Default Force…
This option displays the "Default Forces" dialog. Use this
dialog to set the magnitude of the default forces for all
directions.
Normally the head of the force vector is connected to the joint.
Select "Translated" to attach the tail of the force vector to the
joint. This has no effect on the analysis.
Analysis Menu
Run the Analysis!
This option immediately starts the analysis engine. Set all
desired analysis options before selecting this option.
7-17
Menu Options
Analysis Options
"Run the Analysis" solves for all numerical results and
then performs one of the following three animations:
No Animation - When this option is checked the
program jumps (in one step) to the final displacement
for the applied load.
Animate Displacement - When this option is checked
the program animates the application of the load.
Animate Collapse - When this option is checked the
program animates the application of the load and a
collapse if the structure fails.
The following analysis options control the visual
representation of the results:
Displacement Magnification - It is helpful to observe
how the structure moves when the load is applied. With
this option you can magnify the actual movements of
the model to make them easier to study.
Color Axial Stresses - Use this option to display the
relative intensity of the actual axial forces. This option
also reveals which members are in tension and
compression. Members in tension are shown in blue.
Darker blue indicates higher stress. This option cannot
be used in conjunction with the "Animate collapse"
option.
Color Bending Stresses - This option reveals members
with large bending stresses.
7-18
Menu Options
Color Failed Members - When this option is checked,
ModelSmart3D paints failed members red.
Consider - This pop-up menu tells ModelSmart3D how
to define failure. If you want the program to just check
for tension and compression failures, check "axial
stress" and leave the other options unchecked.
Include Self Weight - When this option is checked
ModelSmart3D calculates each member's actual weight
and adds it to the analysis. Teachers may choose to
uncheck this option to avoid over complication when
teaching vector analysis.
Include Eccentricity at Connection – When single
members are lapped the longitudinal axes of the
members will not coincide. This creates extra bending
at the end of the member and the connection. We say
we have eccentricity at the connection. If you want
ModelSmart3D to consider this, check this option.
Find Breaking Force(s) – With this option checked,
ModelSmart3D will adjust the force vectors placed on
the model to the maximum the model can withstand.
Global Data…
This option opens a dialog that displays general data about the
model such as the number of members and joints used and the
weight of the model. Maximum displacement is current to the
previous analysis.
7-19
Menu Options
Member Results…
This option opens a dialog that displays the member results for
the latest analysis. It contains information as the actual forces
in the member, the members ultimate forces, member lengths,
and efficiency ratios.
Joint Results…
This option opens a dialog that displays the joint results for the
latest analysis. It contains information such as the joint
displacement (Vertical displacement is called deflection.
Horizontal displacement is called drift.) due to load. This
dialog also shows the maximum displacement allowed by the
program before the movement is considered or unstable failure.
Reset Geometry - Select this option to revert to the original
geometry before the application of the load.
Clear Results - This option to removes the red from the failed
members and clears all numerical results.
Launch File Viewer - You can use this option to launch an
application for viewing the ModelSmart3D numerical output
file. This file is created after analysis if the option "Analysis|
Analysis Options | Print Output File" is checked.
Launch Graphic Viewer - If you would like to save a picture
of the screen press Alt-Print Screen to copy an image of the
screen to the clipboard then select this option to bring up your
chosen graphic viewer and paste the image from the clipboard
into the viewer.
7-20
Menu Options
Help Menu
The ModelSmart3D Manual
This option makes use of your Internet browser to view the
table of contents to the ModelSmart3D manual. Use the
"Edit|Preferences" dialog to set the path to the ModelSmart3D
"docs" folder and the path to your browser.
Visit PESC's Internet Site
This option will start your browser and connect you to the PreEngineering Software Corporation Web site.
Show Warning Message
This option displays a warning message about model testing.
Please read it carefully.
Copyright Notice ...
This selection opens a dialog box displaying the program's
copyright notice. Do not make illegal copies of this or any
program.
7-21
Menu Options
Notes:
7-22
Data Dialogs
Data Dialogs
The following is a brief description of the information
available from the ModelSmart3D Data Dialogs:
The Program Preferences Dialog
This dialog is available from the "Edit|Preferences…" menu
option. The following is a description of the items found in the
dialog:
WorkSpace Size - The WorkSpace is part of the SpaceGuide
3D drawing engine used in ModelSmart3D. When drawing in
this environment ModelSmart3D uses the WorkSpace and the
associated GuidePlanes (moveable drawing planes) to
determine where to locate points in space.
8-1
Data Dialogs
A large WorkSpace requires more time for ModelSmart3D to
search the GuidePlanes. You should select a size for the
WorkSpace that is a little larger than your planned model.
Xmax,Ymax and Zmax are described graphically below:
WorkSpace Limits
Note: The maximum size allowed for the WorkSpace is 48
units. This limitation is meant deter the use of
ModelSmart3D for full size load bearing structures or
other professional use.
Navigation Speed
Linear - This is the amount, in inches, (or centimeters for
metric units) the observer moves when the movement keys are
pressed.
8-2
Data Dialogs
Angular - This number is the amount the observer rotates
when the left and right arrow keys are pressed. The values are
in degrees when using U.S. Customary units and radians when
using metric units.
Helper Applications and Documents
These edit boxes contain paths to the following Applications
and Documents:
Results Viewer - Use this application to view the
ModelSmart3D results file. This application can be any
program that can view a text file.
Graphic Viewer - To take a picture of the ModelSmart3D
screen, press "Alt-Print Screen" to copy the screen image into
the clipboard then launch your graphic viewer (any paint
program) and paste the image into your viewer.
Internet Browser - You will use your browser to view the
ModelSmart3D user's manual and to visit the PESC site on the
Internet.
User's Manual - This is the path to the entry page of the user's
manual. The name of this file is "manual.html" and it is found
in the ModelSmart3D "docs" folder.
8-3
Data Dialogs
The "Save" button saves the data from the preferences dialog
box to the " Prefs.MS3" file in the ModelSmart3D directory.
This file is automatically loaded when the program is started. If
the file becomes corrupted you can reset the data to the defaults
using the "Default" button then click the "Save" button to
restore the file. The "OK" button will cause the program to use
the current data without saving any changes. Use the "Cancel"
button to close the dialog box and cancel current changes.
The Default Properties Dialog
Use this dialog to select the Material and Shape (cross-section)
to be used when adding members.
Click the down arrow to open the selection menu. Click "OK"
to accept the new material and/or shape or click "Cancel" to
cancel any changes.
To add your own custom materials and shapes select
"Members|Edit Materials" and "Members|Edit Shapes". This
option is not available in the trial version.
8-4
Data Dialogs
The Joint Properties Dialog
Use this dialog to add, move or more accurately locate a joint.
You may also use this dialog as another way to alter the forces
on the structure. Joint coordinates are reported relative to the
current location of the origin. For example, the force in the
above dialog indicates a force of 10 pounds directed in the
negative global (WorkSpace) Y direction (down).
We designed this dialog with the buttons on the top so that you
could move the dialog to the bottom of the main window (off
of the current model) while you step through the joints with the
"Next" and "Previous" buttons.
8-5
Data Dialogs
Checking "Trans." has the effect of translating the force vector
along its line of action until the vectors tail becomes the point
of attachment to the model. This has no effect on the analysis.
This option is provided for clarity.
The Member Properties Dialog
Use this dialog to examine individual member properties. To
activate this dialog, select "Members|Properties…" from the
menu, then click on a member. Once the dialog is on the screen
you can click a member to reveal its properties or use the
"Previous/Next" buttons to find a member.
8-6
Data Dialogs
The following is a description of the information available in
the "Member Properties" dialog:
Hide - Check this box to hide a member if your model
becomes too cluttered.
Negate - Use this option to hide a member from view and from
the analysis. Use this to study how the analysis results change
when you omit selected members from the analysis.
Actual Length - This is the physical length of the member.
Eff. Length zz - This is the effective length of the member for
buckling considerations about the local (member) zz axis (the
horizontal axis of the member's cross-section if the roll angle is
zero - buckling up and down).
Eff. Length yy - This is the effective length of the member for
buckling considerations about the yy axis (the vertical axis of
the member's cross-section if the roll angle is zero).
For example, consider the two red (dark) members in the above
picture. Their actual length and effective length (yy) are 4.25
but their effective length (zz - for buckling up and down) is 2
times 4.25 inches or 8.5.
8-7
Data Dialogs
As another example, consider the two green (dark) members in
the picture above. Their actual length and effective length (zz)
is 8.5 inches but their effective length (yy - in and out of the
screen buckling) is 17.0 inches. This makes a huge difference
in the buckling characteristics of these members and thus the
model as a whole.
Shape - This is the current shape (cross-section) used by the
member. You may change the shape by clicking the down
arrow key to reveal available shapes then clicking on a new
shape.
Material - This is the current material used by the member.
You may change the material by clicking the down arrow key
to reveal available materials then clicking on a new material.
Roll Angle - Use this edit box to enter an angle to rotate the
member about its longitudinal axis.
This next group of options is not displayed unless
"View|Advanced Options" is check in the menu.
Myy - Remove the check to free "yy" bending in the joint from
entering the member from the joint.
8-8
Data Dialogs
Mzz - Remove the check to free "zz" bending in the joint from
entering the member from the joint.
(Caution - If you uncheck the above options on all members
connected to a joint, you will create an unstable condition (a
spinning joint). This unstable condition will cause the analysis
to halt.)
Torsion - Remove this check to prevent twisting forces from
being transmitted from the joint to the member.
Offset y (& Offset z) – This to adjusts a member relative to its
local coordinate system to simulate a member glued to the
outside face of another – lapped. This will introduce additional
bending in the member due to the eccentricity of the
connection.
The Default Load Dialog
8-9
Data Dialogs
Use the “Default Load” dialog to set the amount of force to be
applied to the structure (at a joint) when the
"Loads|Add/Change".
Translated
Check this option to move the force vector along the line of
action so that it is connected to the joint at its tail rather than its
head. Translating a force vector does not change the effect of
the force on the structure. Use translation of a vector to make
your model easier to view. Force directions are in global
(WorkSpace) coordinates (see below).
Global Coordinates
8-10
Data Dialogs
The English and SI Material Properties Dialogs
Use this dialog to adjust the member properties to more closely
match the actual materials that you are using to construct your
model. Your changes will be saved in the same file as your
model. The material properties are reset to the program's
default properties when the "File|New" menu option is
selected. If you want to save these changes for use in another
model, save the material changes in an empty file (no members
or joints). Then load the file with your new material properties
to start a new model instead of using the "File|New" menu
option.
8-11
Data Dialogs
Below is a brief description of the properties available for edit:
Change Color - We have assigned a color to each material so
that you can identify the material used for a member without
having to display the member properties dialog. You can
change this color to any color your wish. You should not use
red since the program uses red to show failed members.
Density - This is the weight density ([mass x acceleration of
gravity] per unit volume) of the material. The units are in
pounds per cubic foot (pcf) when using English units or
Newtons per cubic centimeter (N/cm^3) when using SI units.
This is the average density for the indicated strength of
material.
Balsa and Bass Buttons - ModelSmart3D can calculate the
material properties of Balsa and Bass wood. To use this
option, type a name ( for example, “Balsa13.5”) for your
material in the “Material Name” edit box, enter the density of
the balsa stick in the “Density” edit box (for example, 13.5)
then click the appropriate button (Balsa or Bass). All other
material properties will be filled in.
Young's Modulus (E) - This property is also known as the
Modulus of Elasticity. It represents the stiffness of the material.
The formula for Young's modulus is E=stress/strain. In other
words how much does the member deform when subjected to
load. Steel has a Young's modulus of 29,000,000 psi while our
Balsa D1 has a modulus of 400,000 psi.
To deter the use of ModelSmart3D for load bearing or
other professional use, we have limited the Young's
Modulus to 3,000,000 units.
8-12
Data Dialogs
WARNING!
Actual load testing of models can be dangerous.
Structural models are capable of storing large amounts of
energy that can be released suddenly and without warning
at or before complete model failure. As a result, actual load
testing of a model can result in the release of high velocity
projectiles, falling objects and failure of the testing
apparatus. The actual load testing of any model can cause
injury to participants and bystanders.
Do not stand on, sit on, walk on or hang from any model.
Do not attempt actual load testing of models without
qualified adult supervision and proper protection against
flying and falling debris. Always wear proper eye
protection.
This software is for educational purposes only and is not
intended for design of load bearing structures or other
professional use. As this software is based on engineering
science theory, actual results, including failure loads, will
vary due to factors such as, but not limited to, building
material quality and construction techniques. Neither PreEngineering Software Corporation, nor its owners, officers,
employees or representatives shall be liable for any
damages arising in connection with the use of this software.
Shear Modulus (G) - ModelSmart3D uses this property to
measure the resistance of a member to twisting forces (torque).
Ultimate Tensile Stress - This is the probable maximum
tension stress (force/area) that the member can withstand
without pulling apart. This stress is never achieved if the
member pulls the face grain off of a joining member.
8-13
Data Dialogs
Ultimate Compression Stress - This is the probable
maximum compressive stress that the member can withstand
without failing. This stress is never achieved if the members
fails by buckling.
Ultimate Bending Stress - This is the probable maximum
bending stress that the member can withstand without failing.
This stress is not achieved if the member fails by lateral
torsional buckling.
When a member is bent one side of the beam is in compression
and the other side is in tension. For example, picture someone
standing on a board that is spanning a ditch - the top of the
board is in compression, due to bending, and the bottom of the
board is in compression. Since the top half of the board is in
compression it is also acting somewhat like a column.
Columns like to buckle an since this column cannot buckle in a
vertical direction because the bottom of the beam is there, it
will want to buckle side to side and tend to make the beam as a
whole want to flop over on its side.
The taller the beam the greater this tendency. To reduce the
possibility of the member failing in this mode, you should use
members where the height of the cross-section is less that two
times the width of the cross-section. A square member would
be even better.
Ultimate Shear Stress - This is the probable maximum shear
stress that the member can withstand without failing. Shear is
created by forces perpendicular to the longitudinal axis of the
member. Since equilibrium requires that a transverse shear
stress be balanced by horizontal shear stress, don't look for
shear crack across the grain of a wood member. Wood is
weaker in shear along the grain therefore a shear crack will
show up as a horizontal crack.
8-14
Data Dialogs
The English and SI Shape Properties Dialogs
Use this advanced option to add custom member shapes (crosssections).
To deter the use of ModelSmart3D for load bearing or
other professional use, we have limited the height of custom
shapes to 1.27 units.
Avoid the use of member cross-sections where the height
exceeds two times the width to limit the effects of lateral
torsional buckling of tall bending members.
8-15
Data Dialogs
If the separation distance is zero the member is not doubled.
After entering the “Height” and “Width” of the cross-section
click on the "Rectangular Section" button to have
ModelSmart3D fill in the remaining properties for a
rectangular cross-section. Or, click on the "Circular Section"
button to have ModelSmart3D fill in the remaining properties
for a circular cross-section – in this case the height is assumed
to be the diameter.
See Warning on page 8-13
Description of shape properties
Area - This is simply the height of the cross-section times the
width of the cross-section. A=(h)(w).
Ix - Torsional constant (polar moment of inertia). Think of this
as a measure of the twisting resistance of the member. The
larger this number the greater the twisting resistance.
Iy - Moment of inertia about the vertical centroidal axis of the
cross-section. This is a measure of resistance to bending about
this yy axis (vertical axis of the cross-section if the roll angle is
zero).
Iz - Moment of inertia about the horizontal centroidal axis of
the cross-section. This is a measure of resistance to bending
about this zz axis (horizontal axis of the cross-section if the roll
angle is zero).
8-16
Data Dialogs
Sy - Section modulus about the yy axis (the same axis as Iy).
The formula for section modulus is S=I/y, where I is the
moment of inertia about the axis in question and y is the
distance from the neutral axis to the extreme fiber of the crosssection.
Sz - Section modulus about the zz axis (the same axis as Iz).
The formula for section modulus is S=I/y, where I is the
moment of inertia about the axis in question and y is the
distance from the neutral axis to the extreme fiber of the crosssection.
If there is bending about both the yy and zz axes, the effects are
additive.
8-17
Data Dialogs
Notes:
8-18
Results Dialogs
Results Dialogs
available from the ModelSmart3D Results Dialog windows:
The Model Data Dialog
This dialog is always available. It contains information about
the model as a whole (global information) such as:
Model Weight - The weight is reported in both English
(pounds - lbs) and SI (grams) units.
Number of Joints - The current number of joints (connections)
used in the structure. The maximum number of joints that can
be used in a single model is 100.
9-1
Results Dialogs
Number of Members - The current number of members used
in the structure. The maximum number of members that can be
used in a single model is 300.
Maximum Deflection - This is the maximum amount that the
model moved in the previous analysis due to the applied
external forces.
The Member Results Dialog
C
Use this dialog to investigate the internal forces generated in a
member due to the current applied loads and the member's
ability to withstand these forces. This dialog is available
immediately after analysis.
9-2
Results Dialogs
available in this dialog:
Actual Forces
The actual force is the internal force in the member caused by
the externally applied forces on the model. Actual forces are
reported for the start (1) and the end (2) of the members.
Axial1 - This is the force generated along the longitudinal
(local x) axis of the member. The "1" indicates that the force
acts at the start of the member. A positive number (at the start)
indicates that this force is directed in the positive local x
direction causing compression in the member. A negative
number would indicate tension in the member since it would
point in the opposite direction. (Also, a “T” or “C” is printed to
the right of the member number indicating tension or
compression.)
9-3
Results Dialogs
Axial2 - This is the force generated along the longitudinal
(local x) axis of the member. The "2" indicates that the force
acts at the end of the member. A positive number (at the end)
indicates that this force is directed in the positive local x
direction causing tension in the member. A negative number
would indicate compression in the member since it would point
in the opposite direction.
Shear1zz - This is a transverse force - it acts perpendicular to
the longitudinal axis of the member. The "1" indicates that the
force acts at the start of the member. It might seem that this
force is mislabeled, but the zz indicates that the shear force is
acting perpendicular to the zz axis of the member.
Shear1yy - This is a transverse force - it acts perpendicular to
force acts at the start of the member. It might seem that this
force is mislabeled, but the yy indicates that the shear force is
acting perpendicular to the yy axis of the member.
Shear2zz - This is a transverse force - it acts perpendicular to
force acts at the end of the member. It might seem that this
force is mislabeled, but the zz indicates that the shear force is
acting perpendicular to the zz axis of the member.
Shear2yy - This is a transverse force - it acts perpendicular to
force acts at the end of the member. It might seem that this
force is mislabeled, but the yy indicates that the shear force is
acting perpendicular to the yy axis of the member.
9-4
Results Dialogs
Torsion1 - This is a bending force (torque) directed around the
longitudinal axis of the member. The member is being twisted.
The "1" indicates that the force acts at the start of the member.
The sign convention of torsion obeys the "right hand rule".
Imagine grabbing the local x axis with your right hand so that
your thumb points in the positive x direction. The curl of your
fingers would point in the direction of a positive torsion force.
Torsion2 - This is a bending force (torque) directed around the
longitudinal axis of the member. The member is being twisted.
The "2" indicates that the force acts at the end of the member.
The sign convention of torsion obeys the "right hand rule".
Imagine grabbing the local x axis with your right hand so that
your thumb points in the positive x direction. The curl of your
fingers would point in the direction of a positive torsion force.
9-5
Results Dialogs
M1yy - This force indicates bending about the yy axis of the
member and acting at the start of the member. The sign
convention is "right hand rule".
M1zz - This force indicates bending about the zz axis of the
member and acting at the start of the member. The sign
M2yy - This force indicates bending about the yy axis of the
member and acting at the end of the member. The sign
M2zz - This force indicates bending about the zz axis of the
member and acting at the end of the member. The sign
9-6
Results Dialogs
Ultimate Forces
These forces are a measure of the strength of the members you
have chosen. These are the forces the members can probably
support without failing. There is no safety factor.
See Warning on Page 8-14
Axial T - This is the probable maximum tension force that the
member can withstand without pulling apart.
Axial C - This is the probable maximum compression force
that the member can withstand without buckling or crushing.
Shear - This is the probable maximum shearing force that the
member can withstand without braking due to a force directed
perpendicular to the longitudinal axis of the member.
Torsion - This is the probable maximum twisting force that
the member can withstand without sustaining permanent
damage.
Myy - This is the probable maximum yy (see sketch above)
bending force that the member can withstand without braking.
Mzz - This is the probable maximum zz (see sketch above)
bending force that the member can withstand without braking.
Good Guys versus Bad Guys
Think of the ultimate forces as the good guys (the forces that
the member, you have chosen, can probably withstand) and
actual forces as the bad guys (the forces that the member must
be capable of withstanding - these forces are caused by the
external load applied to the model).
9-7
Results Dialogs
Lengths
Actual - This is the physical length of the members between
joints.
Lzz - This is the length that the program uses for calculating
the ultimate compression force when considering buckling
about the zz axis.
Lyy - This is the length that the program uses for calculating
the ultimate compression force when considering buckling
about the yy axis.
Mode Ratios
The mode ratio is the (actual force)/(ultimate force). It
represents the decimal amount of the member's strength used to
support the load. If any of these numbers exceeds 1.0 the
member will probably fail. Use the "Analysis|Analysis
Options" menu to neglect or consider selected modes.
Axial - If the actual axial force in the member is compression,
this value is Axial1/Axial C. If the actual axial force in the
member is tension, this value is Axial2/Axial T. (Note: The
absolute value of Aixal1 equals the absolute value of Aixal2.)
Shear ZZ - The absolute value of Actual Shear1zz / Ultimate
Shear. If this ratio exceeds 1.0 the member probably fails.
Shear YY - The absolute value of Actual Shear1yy / Ultimate
Shear. If this ratio exceeds 1.0 the member probably fails.
9-8
Results Dialogs
Torsion - The absolute value of Actual Torsion1 / Ultimate
Torsion. If this ratio exceeds 1.0 the member probably fails.
MomentZZ - The absolute value of Actual M1zz / Ultimate
Mzz. If this ratio exceeds 1.0 the member probably fails.
MomentYY - The absolute value of Actual M1yy / Ultimate
Myy. If this ratio exceeds 1.0 the member probably fails.
Interaction Ratios
These ratios are a result of simultaneous effects on the
member.
A-M - This ratio is the axial mode ratio plus the moment YY
and moment ZZ mode ratios. If this number exceeds 1.0 and
you have chosen to consider both axial and bending effects, the
member will probably fail.
S-T - This ratio is the torsion mode ratio plus the maximum of
the shearYY and shearZZ mode ratios. If this number exceeds
1.0 and you have chosen to consider both shear and twisting
effects, the member will probably fail.
Note:
Ratios may not correspond exactly to the simple ratio of actual
force divided by allowable force when the “Include
Eccentricity at Connection” option is selected because this
effect creates an additional bending term.
9-9
Results Dialogs
The Joint Results Dialog
Use this dialog to investigate structural movement displacement. This dialog is available immediately after
analysis. The following is a brief description of the information
available in this dialog:
9-10
Results Dialogs
Global Sign Convention
Actual Displacements
Actual displacements are the distances and angles that the
joints moved and rotated due to the applied forces.
Translations
X - This
direction
applied.
Y - This
direction
applied.
Z - This
direction
applied.
is the distance that the joint moved in the global X
(see the sign convention above) when the force was
is the distance that the joint moved in the global Y
is the distance that the joint moved in the global Z
9-11
Results Dialogs
Rotations
ModelSmart3D uses a right-handed sign convention ("Right
Hand Rule"). This means that you can use your right hand to
determine the meaning of positive and negative rotations. For
example, to determine the meaning of a positive X rotation,
pretend you are putting your right hand around the X axis in
such a way that your thumb points in the positive X direction.
The curl of your fingers will be in the direction of positive
rotation.
X - Rotation about the X axis. Rotation is from the Y to the Z
axis.
Y - Rotation about the Y axis. Rotation is from the Z to the X
axis.
Z - Rotation about the Z axis. Rotation is from the X to the Y
axis.
9-12
Results Dialogs
Displacement Limits
These limits are used by the program to check for an unstable
condition.
Translations
X - Allowable movement (displacement) in the global X
direction.
Y - Allowable movement (displacement - negative is a
deflection downward) in the global Y direction.
Z - Allowable movement (displacement) in the global Z
direction.
Rotations
X - Allowed rotation about the global X axis. Rotation is from
the Y to the Z axis.
Y - Allowed rotation about the global Y axis. Rotation is from
the Z to the X axis.
Z - Allowed rotation about the global Z axis. Rotation is from
the X to the Y axis.
9-13
Results Dialogs
Notes:
9-14
Material Grade
Determining the Material Grade
During the development of ModelSmart3D, a large variation in
the material properties of balsa and to a lesser extent basswood
was discovered. To categorize the different structural qualities
of woods, we developed a grading scale and a simple test to
determine the grade of tested balsa and basswood sticks. For
balsa wood we use seven grades - BalsaD1, BalsaD1.1,
BalsaD1.2, BalsaD2, BalsaD2.1, BalsaD2.2, & BalsaD3. For
Bass wood we use three grades - BassD1 BassD1.1, & BassD2.
You may have noticed these grade names in the "Default
Properties" dialog.
The material grade designation can be determined by either of
two methods - a deflection test or weighing the specimen to
determine its weight density.
The Deflection Test Method
Deflection Test General Instructions
Cantilever the test piece from a smooth horizontal surface (see
the sketch on page 10-2) such as a tabletop. The cantilever span
must be 12" and the part of the stick on the table top should be
at least 3 inches long (longer is OK) and held flat to the
surface.
Use a yardstick to measure the height of the free end of the
cantilever from the floor. This measurement is the initial
position (unloaded). Now place the test weight at the free end
of the cantilever and again measure the distance to the floor.
The second measurement is the final position (loaded). Take
the difference between the two positions to obtain the
deflection of the free end of the cantilever.
10-1
Material Grade
Deflection Test Example
Determine the grade of 1/8" x1/8" Balsa.
Assume that your initial reading (unloaded) was 29.875",
And that your final reading (loaded) was 29.00".
The difference in the two reading is the deflection:
29.875-29.00 = .875"
This value exceeds the threshold for BalsaD1.2 (see table on
page 10-3 & 10-4), therefore it is a grade BalsaD1.1.
The amount of test load and the deflection criteria vary
depending on the size and type of wood tested. Below is a chart
listing some of the shapes used in ModelSmart3D and the
associated test weight and deflection criteria.
10-2
Material Grade
Material
Grade
BalsaD1
BalsaD1.1
BalsaD1.2
BalsaD2
BalsaD2.1
BalsaD2.2
BalsaD3
BalsaD1
BalsaD1.1
BalsaD1.2
BalsaD2
BalsaD2.1
BalsaD2.2
BalsaD3
Shape
Cantilever Test Weight
Size
Span(in.)
(grams)
in x in
1/8 x 1/8
1/8 x 1/8
1/8 x 1/8
1/8 x 1/8
1/8 x 1/8
1/8 x 1/8
1/8 x 1/8
3/16 x
3/16
3/16 x
3/16
3/16 x
3/16
3/16 x
3/16
3/16 x
3/16
3/16 x
3/16
3/16 x
3/16
Deflection
Threshold
(in.)
Density
(pcf)
12
12
12
12
12
12
12
10
10
10
10
10
10
10
1.0
.92
.83
.75
.67
.58
.50
12
14
16
18
20
22
24
12
20
.625
12
12
20
.58
14
12
20
.54
16
12
20
.50
18
12
20
.46
20
12
20
.42
22
12
20
.375
24
10-3
Material Grade
Material
Grade
BalsaD1
BalsaD1.1
BalsaD1.2
BalsaD2
BalsaD2.1
BalsaD2.2
BalsaD3
BassD1
BassD1.1
BassD2
Shape
Cantilever Test Weight
Size
Span(in.)
(grams)
in x in
1/4 x 1/4
1/4 x 1/4
1/4 x 1/4
1/4 x 1/4
1/4 x 1/4
1/4 x 1/4
1/4 x 1/4
3/32 x
3/32
3/32 x
3/32
3/32 x
3/32
BassD1 1/8 x 1/8
BassD1.1 1/8 x 1/8
BassD2 1/8 x 1/8
Deflection
Threshold
(in.)
Density
(pcf)
12
12
12
12
12
12
12
50
50
50
50
50
50
50
.50
.46
.42
.375
.33
.29
.25
12
14
16
18
20
22
24
12
10
2.0
26
12
10
1.75
28
12
10
1.50
30
12
12
12
20
20
20
1.60
1.30
1.00
26
28
30
It is very important to make sure that the piece under
consideration has straight grain and no imperfections such as
knots or holes.
If the cross-section (shape) that you want to use is not listed in
the above tables, you can use the density test to determine its
grade (see the example on page 10-5).
10-4
Material Grade
Weight Density Test Example
Determine the grade of a 1/8"x1/4"x36" stick of Balsa.
Step #1 - Weigh the stick.
Let's assume the weight of the stick is 6 grams.
Step #2 - Convert the weight to pounds.
W = 6 / 454 = .01322 lbs.
Step #3 - Calculate the volume of the stick.
V = (.125)(.25)(36) = 1.125 cubic inches.
Step #4 - Convert volume to cubic feet.
V = 1.125/1728 = .000651 cubic feet
Step #5 - Calculate the density.
D= W / V = .01322 / .000651 = 20.3 pcf (lbs per cubic foot)
Step#6 - Look up the grade in the table.
20.3 is greater than 20 (20.3>20)
therefore, the stick is a grade BalsaD2.1
10-5
Material Grade
Notes:
10-6
To change the current default material select "Set Default
Material and Shape..." from the menu
Click the drop down arrow to reveal the possible material
selections (materials shown in your version of ModelSmart3D
may vary). Click on the desired material.
Click "OK" to close the dialog and confirm the selection.
11-1
11-2
To change the current default shape select "Set Default
Material and Shape..." from the menu
Click the drop down arrow to reveal the possible shapes (crosssections) selections. Click the desired shape then click "OK" to
close the dialog and confirm the selection.
12-1
Notes:
12-2
How Engineers
Think About Forces
Engineers represent forces with arrows. The arrow (force
vector) must show both magnitude (M) and direction.
Weight (W) of an object is a force directed toward the center of
the earth.
13-1
Forces are sometimes measured in pounds or kips.
1 kip = 1000 pounds
13-2
Truss Bridges
Truss Bridges
Truss Bridge
There are many types of bridges. The bridge shown above is a
truss bridge. Bridges support forces such as the weight of
trucks and cars. The elements of a truss bridge are:
•
Abutments - supports at the ends of the bridge.
•
Members - framework of the bridge truss.
•
Joints - connect the members together and connect the
bridge truss to the abutments.
Simply supported bridges use a hinge-roller support
combination. The roller support allows a real bridge to expand
on hot days and contract on cold days. In model building this
more nearly represents the slip that occurs between the model
and the test stand.
14-1
Truss Bridges
The external forces on a truss bridge create two basic types of
internal forces in the bridge members. These two internal
forces are tension and compression.
14-2
Tension Forces
Tension Forces
Tension forces try to pull things apart.
15-1
Tension Forces
Notes:
15-2
Compression Forces
Compression Forces
Compression forces try to crush things.
Compression forces also try to buckle things.
16-1
Compression Forces
Notes:
16-2
Truss Member Failure Modes
Pulling
Apart
Buckling
Crushing
If a truss bridge’s members pull apart, buckle or crush due to
overload the bridge will collapse. The bigger the size of a
member, the less the chance of overload. Generally, a large
heavy member is stronger.
Individual member failure is not the only reason a bridge can
fail. The bridge might fail because it is unstable.
17-1
There are two possible types of geometric instability in a truss
bridge:
First, a truss bridge will fall down if it is not made of triangles.
These bridges are called “internally unstable”.
Second, a bridge will fall down if it is not supported by both
abutments. These bridges are called “externally unstable”.
In a three dimensional structure (towers or bridges) you must
also provide lateral stiffness. See the next chapter for an
example of how to laterally brace a truss bridge.
17-2
(Additional bracing requirements for a 3D Bridge)
Lateral Load
Y
X
Z
In-plane Load
When designing a 3D structure, you should keep in mind that
you will need to provide adequate lateral support. That is,
support in the Z direction. For example, in the case of a bridge
with structure above the roadbed level, the top of the structure
might fall over before the truss fails due to in-plane loading.
The classic structural sub-system used to provide lateral
support is a portal frame ( sometimes called a sway frame).
18-1
Portal frame
Isometric of Bridge
drift
Lateral Load
Portal Frame
(with no lateral bracing)
The portal frame (typical bridge cross-section), will probably
require extra bracing to limit its drift and provide adequate
lateral strength.
18-2
Braced
Portal frame
Isometric of Bridge
drift
Lateral Load
Portal Frame
(with lateral bracing)
The portal above has bracing to limit drift. Remember, in the
case of a bridge (with an overhead superstructure), the brace
must go in the top of the portal because traffic is driving
through the bottom portion of the portal.
18-3
Above are some typical examples of ways to brace a portal.
Use ModelSmart3D to experiment with the different types.
Apply a horizontal force at the top of the portal of
approximately 2-5% of the compressive force in the upper
chord of main bridge truss to give ModelSmart3D a load to use
in the analysis.
18-4
Longitudinal
bracing at
midpoint of
portal
Longitudinal Bracing of Portal
Don’t forget to brace the top of the portal if you have placed a
connection there that requires lateral support. Add longitudinal
bracing in the horizontal plane to brace the portal.
18-5
Sloped Portal
Frame
Brace in Sloped Portal
The above sketch shows the last structural sub-system required
in the bridge superstructure. Turn the diagonal braces at the
entrance of the truss into a braced portal.
18-6
Extra For Experts
Extra for Experts
User Defining (UD) the Effective Length of a Member
(Re: Page 8-7)
ModelSmart3D assumes that you will provide lateral
support, both in plane and perpendicular to the plane of
the screen (monitor), for all joints in the model.
ModelSmart3D also assumes that the effective length (column
mode buckling length) of a member is the distance between
joints.
Unless you plan to use the “Advanced Features” in
ModelSmart3D to user define (UD) the effective length, do not
place unbraced joints in the model.
A Bridge Example
Consider the two horizontal members 7 & 8 in the figure on the
next page. The unbraced joint “7” causes ModelSmart3D to
incorrectly assume that the effective length of member “7” is
the distance from joint “5” to joint “7”. In addition,
ModelSmart3D will incorrectly assume the effective length of
member “8” is the distance from joint “7” to joint “6”. This is
a modeling error!
To fix this error, either remove the joint replacing the two
members “7” and “8” with a single member spanning from
joint 5 to joint 6 or use the advanced options to correct the
model by user defining (UD) the effective (buckling) length of
the members.
19-1
Extra For Experts
Let’s assume for some reason you want to leave joint “7” in the
model unbraced. First, turn on “Advanced Options” by
selecting the “View|Advanced Options…” menu option. Next
select the “Member|Properties…” menu option. Click on the
member “8. Change the effective length yy to 4” and check
“UD”.
.
19-2
Extra For Experts
If member 8 were to fail in compression by buckling it would
fail together with member 7, therefore we need to change what
ModelSmart3D assumes as the effective length from the
member’s actual length (2”) to the total length of both
members (4”). Actually, since the member can buckle in either
the vertical or horizontal plane, this must be done for the zz
effective and the yy effective length. (The zz and yy notations
define the member’s local bending axes. See below.)
y
z
z
y
With the member in its default orientation (no roll angle)
bending about the zz local member axes corresponds to
buckling in the vertical (XY) plane and bending about the yy
axis corresponds to buckling in the horizontal (XZ) plane.
The effective lengths of both members 7 and 8 must be set to
4” for both the yy and zz bending axes. Once this is done,
ModelSmart3D will know that the members 7 and 8 can buckle
as a unit (in either direction) and you will get a better
prediction of the actual failure load for the model.
Remember, unless you brace a joint in two orthogonal
planes, you will need to manually “user define” (UD) the
effective length(s).
19-3
Extra For Experts
The other end of the bracing member must also be braced!
Suppose you want to provide lateral bracing for joint 7 so that
you do not have to increase the effective length of members 7
and 8 (or members 21 and 22). (Let’s consider bracing in the
XZ plane first.) If you only provide a single horizontal
member extending from joint 7 to joint 15 all you will
accomplish is ensuring that both members buckle at the same
time with no increase in strength.
If you wanted to brace joints 7 (and 15) in the horizontal plane
you would need to provide some diagonal bracing in that plane.
19-4
Extra For Experts
7
15
The figure above shows a possible configuration for bracing
joints 7 and 15 in the horizontal plane. The two diagonals in
the horizontal plane effectively brace joints 7 and 15 so that
you can use an effective length of 2” for the top chord
members.
Members 7 & 8 and 21 & 22 can also buckle vertically. You
would still need to change the zz effective length to 4” for all
those members. Unless…
19-5
Extra For Experts
We also provide bracing against buckling in the vertical plane
as well. The addition of the diagonal web members in both the
near and far main trusses provide this needed bracing. Now
you can use an effective length of 2” for the top chord
compression members for both yy and zz!
But what about the members in the bottom chords? There’s an
unbraced joint in the each of the bottom chords.
True, but the bottom chord will never go into compression.
That is, if you will be loading the model with a downward load
anywhere along the span.
There is another bracing problem in the model!
19-6
Extra For Experts
It racks rather easily. It can flop over. The only thing keeping
it from flopping over is the stiffness of the glue joints where
the upper and lower chords attach to the horizontal members
connecting the two trusses.
To get an idea (or “feel”) for the lateral stiffness of your bridge
you should apply some notional (imaginary) forces.
They don’t really exist but might arise due the secondary effect
caused by unbalanced vertical load or a less than perfectly
constructed bridge. As a rule of thumb, your bridge should be
able to support a lateral load of approx 2-5% of the actual load
in the top chords.
19-7
Extra For Experts
The added diagonals between the bottom chords and bracing in
the main end diagonals help provide additional lateral stiffness.
The coordinates that you use to describe your bridge to
ModelSmart3D assume that you will build you bridge
perfectly.
ModelSmart3D will not check the lateral stiffness of the
bridge without the application of some load. You should
use notional loading when there is no design load specified.
19-8
Extra For Experts
A Tower Example
Y
Z
X
Consider member 15. What is the appropriate effective length
for this member?
Remember, in a 3D analysis, there are 2 effective lengths - yy
and zz. The zz axis for a vertical column (with no roll angle)
relates to buckling in the XY plane. This tower is fully braced
at its joints in the XY plane therefore, member 15, if it buckled,
would buckle between joints 2 and 20 – its actual length.
Therefore, the effective length (zz) equals the actual distance
(3” in this case) between those joints.
19-9
Extra For Experts
What about buckling in the YZ plane? Joint 20 is not braced
in the YZ plane Therefore, member 15 could buckle in the YZ
plane between joints 2 and 10 ( instead of joints 2 and 20).
Both members 15 and 16 should have their effective lengths
(yy) set to the sum of the length of members 15 and 16 – 6”, at
least! If fact, when a tower is not braced against sidesway
(lateral movement), the resulting deformation of the frame
tends to magnify the effective length.
This magnification is a
function of the relative
stiffness of the connecting
members. For instance (in
this case), if the horizontal
member 29 connecting to
joint 10 is as stiff as the
column then, the total
actual length of members
15 and 16 would need to
be magnified by a factor of
1.9!
29
In this case, the correct
effective length (yy) to use
for both member 15 and 16
would be:
Effective
Length
Y
Z
(3”+3”)x 1.9 = 11.4”
An 11.4 inch long 1/8”x1/8” balsa wood member supports
much less load than a 1/8”x1/8”x 3” member!
Fully bracing all sides of the tower eliminates the need to
magnify the effective lengths.
19-10
The Goal of Exercise
To reinforce the student's science and mathematics skills
through the adventure of solving a realistic structural
engineering problem.
The Problem
To design, build and test a safe and efficient bridge that
satisfies the following requirements:
Allowable Materials:
1/8" x 1/8" balsa wood strips
Water soluble glue
(such as "Elmer's Carpenter's Wood Glue")
1/8" x 1-1/4" (maximum size) strips of hat buckram
(to reinforce tension connections)
20-1
Structure's Size Requirements:
Clear Span = 16"
The overall length of the bridge must be approximately 16-1/2"
(plus or minus 1/8").
The test vehicle carries a 2" x 3" x 5-7/8" (approximate
dimensions) steel block.
The top of the runners/roadbed must be 3/8" above the
abutment support surface.
Vehicle & Load
The test vehicle carries a block of steel (approximately 10 lbs).
The vehicle has 2 axles spaced 4-3/8 inches apart. The lateral
spacing of the wheels is approximately 2-1/8".
The total load on the front axle is 6 lbs 12 oz. and the total on
the rear axle is 3 lbs 12 oz. The entire vehicle weighs 10.5 lbs
Each wheel has an outer radius of 1-1/8" and a width of 5/16".
The overall height of the vehicle with the load block is 4-7/16".
The overall width of the vehicle is 2-5/8" (out to out of wheel
hubs).
20-2
Serviceability
The structure must safely support the truck and its load at any
location along the span.
The structure must not deflect more than 1/4".
20-3
Notes:
20-4
Technical Support
Technical Support
We are always looking for ways to improve our product. If
you have any questions, concerns or suggestions, please do not
hesitate to call or write.
Attn: Technical Support
241 E Woodgate Court
Baton Rouge, LA 70808
Phone:
Fax:
E-mail:
URL:
(225) 769-3728
(225) 769-3661
[email protected]
http://www.pre-engineering.com
Resources, Updates, FAQ, etc.:
http://www.pre-engineering.com/modelsmart3d/latestchanges.html
Registration form:
http://www.pre-engineering.com/forms/registerms3d.html
The following is helpful if you are having problems:
* The program’s name & license certificate number.
* The type of hardware you’re using.
(processor, ram size, disk size, graphics card type)
* Operating System (Windows95, 98 ,NT ,XP, Vista, etc.)
* Any error codes.
21-1
Technical Support
Notes:
21-2
www.pre-engineering.com

ModelSmart 3D™

Transcription

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