Report - Structural Research Laboratory

 Structural Behavior of Anchored Plates in Tilt-up Construction
Ulric Ibanez, REU Student
Bill Sheu, Graduate Mentor
Y. L. Mo, Faculty Advisor
8/6/2010
Contents
Abstract ......................................................................................................................................................... 3 1. Introduction ........................................................................................................................................... 3 2. Experimental Program .......................................................................................................................... 5 2.1 Materials ................................................................................................................................................. 5 2.2 Specimens ........................................................................................................................................... 7 2.3 Loading Protocol ................................................................................................................................. 8 3. Experimental Results ............................................................................................................................ 9 3.1 Panel 1 ................................................................................................................................................. 9 3.2 Panel 2 ............................................................................................................................................... 10 3.3 Panel 3 ............................................................................................................................................... 11 3.4 Panel 4 ............................................................................................................................................... 12 3.5 Panel 5 ............................................................................................................................................... 13 3.6 Panel 6 ............................................................................................................................................... 14 4. Conclusion .......................................................................................................................................... 15 5. References ........................................................................................................................................... 17 6. Acknowledgements ............................................................................................................................. 17 2 Abstract
One of the most important connections in tilt up construction is the anchorage plates which are
connecting the walls with the roof trusses. The main goal of this research project was to find the
effect of the number studs, their arrangement, and their length on the ultimate load capacity of
the whole anchorage plate. After testing six different anchored plate configurations, it seems that
the major contributing factors to the capacity are the stud length and the distance between studs.
1. Introduction
For the summer of 2010 I am assisting Bill Sheu with his research concerning the structural
behavior of anchored plates in tilt-up construction.
This research will consist of several
experimental tests using the universal panel tester. This panel tester was constructed at the
University of Houston in 1986 (Hsu et al. 1995). Each specimen will be made of concrete and
have an attached anchored plate with several legs protruding from the plate and bonded to the
concrete. A concentrated load will then be applied to the anchored plate until failure. The results
will then be analyzed and used in Bill Sheu's thesis defense. Figures 1 and 2 show the universal
panel tester and the typical set up for each of the experiments
3 Figure 1: Universal Panel Tester
Figure 2: Typical setup for testing a panel
4 2. Experimental Program
2.1 Materials
For each anchored plate that was going to be tested a Reinforced concrete panel with dimensions
of 55" x 55" x 7" was constructed to resemble the vertical tilt up wall in the real practice. Each
panel has a simple mesh reinforcement configuration using number 6 rebar. The rebar's are
welded to inserts and then placed into the pattern as shown below in Figure 3.
Figure 3: Reinforcement Configuration
Sheplers Premium concrete mix is being used to make the panel (Sheplers Premium Concrete
Mix). This particular concrete meets ASTM Spec C 387 and meets or exceeds 4000 psi. Each
panel requires two batches of concrete from the concrete mixer being used. One batch is made
from eleven bags of the Sheplers Premium concrete mix and the second made from ten bags.
Water was added using engineering judgment until the desired workability was obtained. A
slump test was done for each batch to check the workability ,and more water was added if
needed. From each batch there was a minimum of two 4 x 8 cylinders taken to obtain a more
precise measurement of the concrete strength. The anchored plate is attached to the panel
reinforcement using steel ties around the center of the panel. Once the concrete was poured into
5 the form work and leveled, it was set to cure for about two weeks. Figures 4 and 5 show the
pouring process and how the anchored plate is tied into the panel.
Figure 4: Pouring Concrete to fill the form
Figure 5: The anchored plate is tied to the steel reinforcement
6 2.2 Specimens
Each of the anchored plates has a different configuration. In total there are six anchored plates
that will be tested and each configuration is shown below.
Plate Configuration
1
8” x 10” with four ½” dia. X 4” stud
2
8” x 10” with four ½” dia. X 5” stud
3
8” x 12” with six ½” dia. X 4” stud ( three studs on each side)
4
8” x 12” with six ½” dia. X 5” stud ( three studs on each side)
5
8” x 12” with six ½” dia. X 4” stud ( three studs on top and bottom)
6
12” x 8” with six ½” dia. X 4” stud (three studs on top and bottom)
Each plate in placed in the center of panel and tied to the reinforcement to prevent it from
moving during the pouring process. A o-ring is welded on top of the plate in order to guide the
loading rod to prevent from shifting laterally during testing. Figure 6 shows the attached o-ring
on the anchored plate.
Figure 6: O-ring used to guide the loading rod
7 2.3 Loading Protocol
Each test is done using the universal panel tester. A custom rod was fabricated by Jeff to apply
the concentrated load onto the angle. The rod is attached to one of the actuators on the universal
panel tester and lowered to apply the load. Before the test is conducted two LVDT sensors are
attached to the angle and extend upward and attach to fixed angles. These sensors will be used
to monitor the deflection or vertical movement the angled plate. Below is a figure of a two inch
LVDT.
Figure 7: 2" LVDS used on the panels
Once the LVDTs are in place the loading rod is lowered until it is barley touching the plate. The
loading is done in steps and continued until failure. Below is a table of the loading steps.
STEP
LOAD (KIPS)
TIME (SEC)
1
0-10
600
2
10-20
600
3
20-30
600
4
30-40
600
5
40-50
900
6
50-60
1200
7
60-70
1200
8 3. Experimental Results
3.1 Panel 1
Panel one was test on June 21st, 2010. Panel 1 reached a maximum load of about 46 kips. Panel
1's failure mode was a mixture of tension and bending. The angle was pulled out of the concrete
panel a bit which is the bending, and further loading caused the legs of the studs to rupture.
Figure 8, below, shows the angled plate after the top three studs ruptured.
Figure 8: Panel 1 after failure
9 3.2 Panel 2
Panel 2 was tested on June 29th, 2010. Panel 2 reached a maximum load of about 52 kips. Panel
2's failure mode was due to shear. Unlike panel 1, panel 2 did not pull out of the concrete. The
angle plate on panel 2 shifted straight down and was loaded until all four studs on the plate failed
due to shear. The figure below shows how the studs sheared off the anchored plate.
Figure 9: This is Panel 2 after failure. The anchored plate was completely sheared off.
10 3.3 Panel 3
Panel 3 was tested on July 9th, 2010. Panel 3 reached a maximum load of about 56 kips. Panel
3's failure was due to shear cone failure in the concrete (Embedment Properties of Headed
Studs). Panel 3's failure was complete different from the failure of the previous two panels. For
this panel the concrete failed before the studs or plate did. The figure below shows the effect of
shear cone failure. A great deal of the concrete separated from the panel
Figure 10: This is Panel 3 showing the concrete failure
11 3.4 Panel 4
Panel 4 was tested on July 22nd 2010. Panel 4 reached a maximum load of about 68 kips. Panel
4's failure was similar to panel 1. The failure was due to a mix of bending and tension. One key
difference was that panel 4's plate consisted of 6, 5" studs and not 4, 4" studs like the first panel.
Still the plate bent away from the wall and the two studs on the most top of the plate ruptured.
The figure below shows the anchored plate after the rupture of the two studs.
Figure 11: This Panel 4 after failure.
12 3.5 Panel 5
Panel 5 was a bit of a deviation from the other. For this panel the plate was rotated 90°. This
panel was tested on July 27th 2010. This panel was similar to panel 3 in that the concrete failed
due to shear cone failure. Like before, the concrete failed before the studs did. This panel was
able to reach a capacity of 52 kips. Below is a picture showing the shear cone failure of panel 5.
Figure 12: This Panel 5 after failure.
13 3.6 Panel 6
Panel 6 was tested on July 30th 2010. This panel had an anchored plate with six ½” dia. X 4”
stud (three studs on top and bottom). This was the weakest of all the panels having a maximum
load of 40 kips. Below is a picture of panel 6 after testing.
Figure 13: This Panel 6 after failure.
14 4. Concclusion
When loooking at th
he aftermathh of each experiment
e
i may be difficult
it
d
to see any kinnd of
correlatioon between the anchoreed plate andd the failuree mode. Whhen lookingg at the Loaad vs.
Deflectioon curve the you will be able to see the coorrelation beetween the anchored plate's
p
constructting and its capacity.
c
Figure 14:: Load defleection curvee for all the plates.
f
40 kipss to about 688 kips. Alsoo, the
From thee plot you caan see that thhe range of capacity is from
panels thhat had an an
nchored platte with 5" loong studs aree much moree ductile then those that have
4" long studs.
s
It is in
nteresting too see that thee anchored plates
p
put onn panels 3 annd 5 are the exact
same plaate just orien
ntated differeently, but stiill cause the same failurre. Both pannels failed due
d to
the shearr cone creaated in the concrete (E
Embedment Properties of
o Headed Studs).
Fuurther
experimeentation shou
uld be conduucted to connclude if this particular setup is proone to shear cone
failure inn 3000 psi concrete or iff it is just cooincidental. It can also be noted thhat decreasinng the
space bettween the studs increasees the capaciity accordingg to panels 5 and 6. Pannels 5 and 6 have
15 the same anchored plate but the distance between the studs in higher on panel 6 than 5. Panel 5
has a higher capacity than panel 6. The increase in space between the studs allows for more
bending causing the lower capacity. The two major contributors to the capacity seem to be the
length of the stud and the distance between the studs.
16 5. References
1. "What is Tilt- Up Construction?
Tiltup.com,
August
5th
How are Tilt-Up Concrete Buildings Constructed?"
2010.
<http://www.tiltup.com/commercial-construction-
articles/concrete-panel-building/>
2. Hsu, Thomas T. C.; Belarbi A.; and Pang. X.B., "Universal Panel Tester," Journal of testing
and Evaluations, ASTM, V.23, No. 1, 1995, pp. 41-19
3. "Shep Premium Concrete Mix" cmcconstructionservices.com, August 5th 2010.
< http://www.cmcconstructionservices.com/en/catalogs/items/view.asp?catalogid=526>
4. Embedment Properties of Head Studs. TRW Inc., 1977
6. Acknowledgements
The research study described herein was sponsored by the National Science Foundation
under the Award No. EEC-0649163. The opinions expressed in this study are those of the
authors and do not necessarily reflect the views of the sponsor.
17