LESSONS FROM USING BIM TO INCREASE DESIGN
Transcription
LESSONS FROM USING BIM TO INCREASE DESIGN
1 LESSONS FROM USING BIM TO INCREASE 2 DESIGN-CONSTRUCTION INTEGRATION 3 Gregory P. Luth, M.ASCE1; Alyssa Schorer, M.ASCE2; Yelda Turkan, M.ASCE3 4 Abstract 5 Building Information Modeling (BIM) has started to become a common practice in the Architectural, 6 Engineering, Construction and Facilities Management (AEC-FM) Industry. The benefits of BIM have 7 been recognized in the AEC-FM industry, and numerous design firms and contractors reported benefits of 8 utilizing BIM in their projects. However, the full potential of BIM tools has not yet been achieved. In 9 current practice, design and construction phases are not well integrated. Conventional practice is to 10 produce a conceptual design based on no particular construction sequence, means or methods. 11 Construction knowledge must be deployed to support design. This way, the full potential of BIM can also 12 be exploited. The term High Definition Building Information Modeling (HiDef BIM) is used to describe 13 BIM that is detailed and precise enough to create shop drawings directly from the model. Additionally, 14 the use of HiDef BIM offers the opportunity to examine construction sequence in order to produce a 15 design that can be less expensive, save time, and be of a higher quality. This paper explores the benefits 16 of utilizing HiDef BIM and the lessons learned through a case study. 17 18 19 Keywords: High Definition Building Information Modeling (HiDef BIM), Construction Sequence, 20 Integrated Project Delivery (IPD). 1 President, Ph.D., S.E., Gregory P Luth & Associates (GPLA), 3350 Scott Blvd, Bldg 48, Santa Clara, CA 95054. Email: [email protected] 2 Design Engineer, M.S., P.E., Gregory P Luth & Associates (GPLA), 3350 Scott Blvd, Bldg 48, Santa Clara, CA 95054. Email: [email protected] 3 Assistant Professor, Ph.D., Department of Civil, Construction and Environmental Engineering, Iowa State University, 428 Town Engineering Building, Ames, Iowa 50011-3232. Email: [email protected] 1 21 Introduction 22 Current design and construction processes must change in order to get maximum benefit from the 23 latest design tools and technologies. Building Information Modeling (BIM) is one of the latest 24 technologies that have changed how the Architectural, Engineering, Construction and Facility 25 Management (AEC-FM) industry does business. BIM is defined as a digital representation of physical 26 and functional characteristics of a facility (National BIM Standards, 2007). It is reported in previous 27 research that utilizing BIM improves processes and supports decision making throughout the life cycle of 28 a project by enabling accurate and rapid update of design changes and integration of life-cycle data 29 (National BIM Standards, 2007; Becerik-Gerber and Rice, 2010; Staub-French and Khanzode, 2007; 30 Arayici et al. 2011). The benefits of BIM have been recognized in the AEC-FM industry, and numerous 31 design firms and contractors reported the benefits of utilizing BIM in their projects. However, the full 32 potential of BIM technology has not yet been achieved. 33 In current practice, design and construction phases are not well integrated. Conventional practice 34 is to produce a conceptual design based on no particular construction sequence, means or methods. 35 Therefore, currently BIM models are created based on approximate design intent, and used for clash 36 detection, or worse, simply provided as a requirement of the contract, whether useful or not. In order to 37 take full advantage of BIM tools, the design model should be detailed and precise enough to create shop 38 drawings. This requires incorporating construction means, methods and sequencing knowledge into the 39 design model, i.e. construction knowledge must be employed to support design. In this paper, authors use 40 the term High Definition BIM (HiDef BIM) to describe BIM that is created at a shop drawing level of 41 detail. HiDef BIM has been employed on several Gregory P. Luth & Associates (GPLA) projects, and its 42 benefits have been substantial. 43 44 The following section summarizes the significant progress that has been made toward virtual design and construction using BIM tools while identifying remaining knowledge gaps. The subsequent 2 45 section reviews relevant concepts related to HiDef BIM and Integrated Project Delivery. Then, one of the 46 GPLA projects is presented as a case study and benefits of using HiDef BIM are evaluated. 47 Literature Review 48 The benefits of BIM have been recognized in the AEC-FM industry, and numerous design firms 49 and contractors reported the benefits of utilizing BIM in their projects. Previous research results reported 50 that utilizing BIM improves processes and supports decision making throughout the life cycle of a project 51 by enabling accurate and rapid update of design changes and integration of life-cycle data (Arayici et al. 52 2011; Becerik-Gerber and Rice, 2010; National BIM Standards, 2007; Kvan, 2000; Ku et al., 2008; 53 Staub-French and Khanzode, 2007; Young et al., 2009). Furthermore, the benefits related to the 54 preconstruction phase, which includes enabling prefabrication, and identification of design conflicts prior 55 to construction, were reported by several researchers (National BIM Standards, 2007; Shen & Issa, 2010; 56 Staub-French and Khanzode, 2007). However, the full potential of BIM technology has not yet been 57 achieved. 58 BIM is becoming a common practice in the AEC/FM industry, and the potential benefits of BIM 59 are much talked about. However, there is still a need for understanding the value added by BIM for 60 construction projects. BIM usage for all stages of a project is not yet a common practice. Therefore, there 61 have been numerous case studies identifying the benefits, and testing the capabilities and limitations of 62 BIM (Barlish and Sullivan 2012; Sacks and Barack, 2008; Succar, 2009). 63 While BIM benefits are vital to quantify, it is also very important to identify its level of detail 64 (LoD) to achieve the planned value added by its usage. Various researchers stated that BIM model’s LoD 65 depends on the application, such as creating shop drawings, energy simulations, cost estimating, clash 66 detection etc., it will be used for (Eastman et al., 2008; Fischer and Kunz, 2003; Staub-French and 67 Khanzode, 2007). A study by Leite et al, (2011) showed that more detail in a model does not necessarily 68 mean more modeling work. Futhermore, they concluded that such additional effort can actually lead to 69 higher precision, better supporting decisions during design and construction. 3 70 HiDef BIM and Integrated Project Delivery (IPD) with HiDef BIM 71 Conventional practice is to create a conceptual design and model based on no particular 72 construction sequence or means or methods. The ubiquitous use of “typical details” is meant to provide a 73 generic scenario that supposedly allows the project to be completed in full; however, situations invariably 74 arise where the typical solution is ill-suited or impossible to build given the conditions. This leads to 75 RFI’s, change orders, construction delays, and a lot of paperwork. Subcontractors bid a fixed price based 76 on incomplete design details since final quantities are not known until after shop drawings, and because 77 the “typical details” are not easily translated into material lists and labor estimates. Therefore, they have 78 to cover risk in price, and often get away with charging more for changes that the designer did not 79 anticipate. 80 IPD with HiDef BIM is based on a complete design product based on the most efficient 81 construction sequence. Unit price is based on exact quantities in the model and adjusted based on the 82 actual quantities delivered. It gives an advantage to the subcontractor with the most efficient and cost 83 effective way to fabricate and deliver. This requires incorporating detailed construction knowledge and 84 planning into the design. 85 There are two major ways in which a design professional can influence BIM on his or her project. 86 The first is internally, within his or her own design. The second is project wide, requiring collaboration 87 between many parties. Ideally, this includes involving those responsible for the construction of the 88 building early on in the project. Input not only from the contractor, but from the subcontractors who 89 fabricate and place the parts, is the ultimate collaboration tool. Unfortunately, it is not always possible to 90 involve all critical parties at the time of design, in which case the responsibility falls on the engineer to 91 produce a conscious and efficient design. HiDef BIM requires the structural engineer to pose questions 92 not only about his or her own structure, but about the other elements of the building as well such as 93 mechanical, electrical, plumbing, fire proofing, and other special systems. Any engineer can anticipate a 94 construction sequence within their own design. This requires experience as well as a little out-of-the-box 95 thinking in order to solve some of the most frequent and simple problems. For example, consider a 4 96 building of steel and precast concrete. Is it designed in such a way that some steel must be erected, then 97 all of the precast, and then further steel must be connected to embeds in the precast? Is there a better way 98 to design the structure so that the steel erector does not have to make multiple appearances in the 99 schedule? A building may fulfill all building code requirements, but it is also very important that it 100 fulfills a logical construction sequence. Designing a structure that allows each subcontractor to complete 101 his or her job without depending on another trade is a good example of using construction sequence to 102 create an intelligent design. 103 HiDef BIM success is defined by the benefit it brings to the project. Having a BIM model is only 104 effective if it is being used, and the more team players that use it, the more value it can add to the project. 105 This is where the “HiDef” part of the concept comes in. A mechanical contractor can create a 3D model 106 for his or her design to clash detect between his or her own systems. This model becomes more useful 107 when it is shared with the other trades: the structural engineer, for example, can coordinate where ducts 108 penetrate stud walls using the mechanical 3D model. Knowing where penetrations are would allow each 109 stud to be modeled, sized and spaced appropriately around penetrations. Furthermore, having each stud 110 modeled accurately leads to the possibility of running a materials report that is correct, and not estimated 111 with 20% overages. Accurate stud models also make it possible to create shop drawings from the design 112 model. 113 The case study that follows will go into greater detail of how HiDef BIM can have a significant 114 impact on a project; the key is that the more information that goes into the model, the more opportunity 115 the team has to reap a benefit. It takes discipline and ingenuity to orchestrate a cooperative atmosphere, 116 and the alternative is no longer affordable or practical. Design intent should be to deliver shop drawings 117 by the time the contract is awarded. 118 Case study 119 The University of Southern California (USC) School of Cinematic Arts consists of six buildings 120 constructed in three phases, and Gregory P Luth & Associates (GPLA) is the structural engineering firm 5 121 for all six buildings. The owner specified that the buildings must be Venetian stucco, with no joints, 122 which would require a concrete substrate. GPLA was also committed to maintaining an efficient 123 construction schedule on par with a steel structure. GPLA used Tekla Structures to model the entire 124 project in 3D. 125 In order to erect the buildings as quickly as possible, the main building frame was designed to be 126 structural steel, with braces at the stair wells which enabled the structure to withstand lateral loads before 127 installation of the concrete shear walls on the exterior. Furthermore, this also allowed for quick steel 128 erection of one entire building giving the interior trades the opportunity to begin working immediately 129 while the more time intensive concrete shear walls were poured. The concrete shear walls are “rocking 130 wall” panels that fit between steel columns, with an innovative design to connect them to the steel 131 structure. “Butterfly plates fuses” were welded to the steel columns and plates in strategic locations that 132 had welded hoops that were cast into the walls at a later time. The “butterfly plates” are designed to yield 133 along their perforations in order to minimize the damage done to the structure’s integrity and appearance 134 during a seismic event. In a worst case scenario, an interior wall could be opened up to replace the 135 damaged plates. This method exploits ingenuity in order to improve design and to deliver an aesthetically 136 pleasing product that performs unparalleled to others. Moreover, it also made use of BIM which allowed 137 each embed and rebar to be placed exactly where they needed to be. 138 The second way in which concrete wall construction was sped up, without sacrificing quality, was 139 to use pre-fabricated rebar mats. GPLA created the BIM model in such detail that it was possible to 140 produce shop drawings of the rebar mats, accompanied by barlists. Prefabrication would not have been 141 possible without modeling the exact rebar placement around embeds and penetrations. Moreover, stick- 142 building these complex shear walls would have been a debilitating time sink in the schedule. 143 A third use of BIM in this project that stands out as an exemplary use of 3D technology to 144 improve construction is the panelization of the light gauge panels for the complex hip and valley roof. 145 GPLA designed the light gauge roof connections to the main steel frame in such a way that panels could 146 be made ahead of time in the shop and simply lifted into place on site. Not only was time saved through 6 147 both rebar and light gauge detailing, but also the prefabricated materials were manufactured at a higher 148 standard of quality under a controlled environment, as opposed to stick-building on site where conditions 149 are often changing or uncertain. Furthermore, installation of prefabricated assemblies tends to put 150 construction crews at less risk, which is another welcome benefit of employing BIM models on a project. 151 Employing IPD and BIM technology are simply contractual obligations to some firms within the 152 AEC-FM industry. Currently, the most common way of employing BIM technology is to create 3D 153 models for each trade, and to use them for clash detection after the design is finalized. Clash detection 154 itself already indicates that something in the process has failed. Clashes can be avoided before the final 155 design if the trades exchange information during the design process. Clash detection is a passive use of 156 BIM rather than proactive, and the ultimate goal should not be only to avoid a pipe hitting a beam. The 157 ultimate goal should be discovering a way to build faster, less expensive, and safer. In order to achieve 158 the full potential of BIM technology, it should be utilized throughout the entire construction process, i.e. 159 from design to field. 160 What is the journey of the rebar from the shop to the field? 161 In order to provide fully detailed rebar at the USC School of Cinema, GPLA had to examine the 162 whole rebar fabrication process. GPLA began by tracing each step of the project that involved rebar; 163 essentially, the journey of a piece of rebar, from the time it is cut and bent to the moment it is buried in 164 concrete and finally a part of a building. Along each step of the journey that the rebar is modified or 165 moved, GPLA had to consider whether that process could be made easier, or improved. GPLA examined 166 the following when deciding the most efficient way to improve certain processes: 167 How does the rebar fabricator read the bar sizes and shapes into a machine? 168 What sizes and shapes does he prefer to make? 169 What sizes and shapes can be lifted by a single man, or two men? 170 What sizes and shapes can be transported conveniently? 171 How is the rebar unloaded from the truck? 7 172 How is it lifted into place? 173 The answers to these questions informed the whole process from design, to detailing, and to shop 174 drawings. Along the way, issues arose where something could have been a little different or a little better, 175 and those are the lessons learned that must be remembered, so the right questions are asked the next time. 176 GPLA produced bar lists exported directly from Tekla to MS Excel, which were formatted to be 177 read into Soulé, the system that fabricates the rebar. Tekla Structures offers many forms of customization, 178 so that the information in the database of the building model can be extracted in a variety of ways and 179 formats. Having a BIM model that can be easily viewed or exported to other file formats is vital; 180 otherwise the value in BIM would be null. 181 The next step was to detail the rebar so that it could be pre-fabricated where possible. The 182 foundations were detailed with 30’-0” bars wherever possible since that was a readily available stock 183 length. The basement wall cages (Figure 1) were designed to be 25’-0” wide maximum as requested by 184 the foreman, so that they could be lifted into place on site with minimal equipment. Each cage had a set of 185 splice bars tied to them which were used to splice the wall horizontals once the next cage was in place 186 (Figure 2). Additionally, the basement walls are riddled with embeds for columns and rocking walls 187 above, and steel beams that form the first floor. A large amount of congestion meant that bar layering and 188 spacing was absolutely critical. The HiDef BIM model deployment on this project allowed any 189 difficulties to be identified ahead of time and resolved with a clear detail, rather than discovering these 190 problems during placement (Figure 3). Details shown in these figures were produced directly from the 191 HiDef BIM model, as are all details shown in this paper. 8 192 193 194 195 196 Figure 1: An example of a rebar shop drawing detail that exactly specifies how the rebar are layered in order to coordinate the placement of embeds and penetrations in the basement walls at USC. 197 198 199 200 201 202 Figure 2: Detail from a rebar shop drawing at USC, showing where two typical prefabricated basement wall mats come together at a corner with a prefabricated corner cage. Loose splice bars are indicated where the wall horizontals are spliced between mats and cages. Note that bar layering is critical so that cages may fit within one another and still allow room for top-of-wall embeds. 9 203 204 205 206 207 208 209 Figure 3: USC site photo of placed rebar at a similar condition to the shop drawing shown in Figure 2. Note the embed at top-of-wall, which was designed to fit efficiently within the rebar layers. At corners especially, using a HiDef BIM model to produce rebar was essential to identify difficulties ahead of time, and avoid any delays in the field. 210 window openings in different locations. Moreover, all the wall panels have butterfly plate embeds and 211 heavily reinforced boundary elements. GPLA wanted the rocking walls to be constructed quickly, but 212 with the utmost attention to accuracy. After getting the rebar foreman’s feedback, it was determined that 213 the easiest way to build the cages would be to fabricate them in a shop. The widths of the walls were 214 chosen during schematic design to be small enough for shipping on a truck bed, and they could be stacked 215 in a pile onto a truck in the order they would be placed, so that the pile would not be shuffled once on site. 216 The order the wall barlists were released mimicked the order of the wall construction. Whether a wall had 217 openings or not, the wall horizontal and vertical bars were modeled continuous, and all the loose bars 218 needed to slide through embeds were tied to the cages. The HiDef BIM model actually had two sets of 219 rebar – one for “as detailed” for the fabricator and one “as designed” for permit drawings. Each bar in the The rocking wall cages are the most complex rebar on this particular job. Many of the walls have 10 220 wall cages was specifically dimensioned so that when the cage arrived, it would fit perfectly around steel 221 members and embeds. In order to make the openings, once a cage was placed, the horizontal and vertical 222 bars were trimmed according to the dimensions of the opening. A bundle of u-bars to lap the cut bars 223 were on hand when needed. This was achieved by simply exporting two separate Excel sheets for barlists 224 from Tekla Structures software. The fabricators requested that the wall cages be in one list with the 225 opening u-bars omitted, and a second bar list for the u-bars alone. This streamlined the fabrication process 226 so bars that were tied into cages together were made together, and the extra bars added in were in their 227 own package. There were two lessons learned from the wall cages installation. The first lesson was 228 related to cage lifting. Procedure for this operation was not initially discussed. Nevertheless, just before 229 the shop drawing process began, GPLA was able to add two #10 horizontal bars on each wall (Figure 4), 230 as requested by the foreman. These extra bars served as pick points for the crane (Figure 5). The second 231 lesson learned was to have early conversations with those responsible for building the project. During 232 construction of the first and second phases of the project, the wall cages lifted in to place had to be 233 shimmed up to “float” so they did not rest on the basement walls below. By the third phase of the project, 234 the foreman mentioned that having a way to shim the rebar panels built in ahead of time would save time 235 for him. His suggestion was to space the horizontal ties in the boundary elements more closely around the 236 wall embeds at the steel columns, so the panels could “hang”. GPLA incorporated this request into the 237 detailing of the third phase, and this simple change made for quicker, easier construction. (Figure 6). This 238 lesson learned was a convincing reminder of the importance of examining each step of construction, and 239 involving those who are responsible for that step. 11 240 241 242 243 244 Figure 4: This is a shop drawing detail from the rocking wall rebar cages. The exact spacing of the horizontal and vertical bars is given, as well as the necessary embed bars. The #10 bars labeled “Pick bars” are the additional bars added for the crane to lift the cage. The dotted lines indicate the surrounding steel structure that the wall cage must fit around. 12 245 246 247 Figure 5: A rocking wall prefabricated rebar cage being lifted into place by a crane at USC. Each wall cage was installed in a matter of minutes, rather than hours or days of stick-building. 13 248 249 250 251 252 Figure 6: A site photo of a rocking wall rebar cage before the window opening has been cut. Note the closely spaced ties around the hoop embeds on either side, from which the cage hangs. 253 would have been to stick build the congested rebar and wait on an RFI every time something was unclear. 254 However, it is known that on Phase I changing the sequence from a floor-by-floor approach to building 255 the steel structure in its entirety first, and then building the exterior walls while completing the interior 256 MEP work saved in excess of 6 months. The preconstruction personnel at the construction company 257 estimated and scheduled the project using the former methodology even though the structure was It is difficult to quantify the savings for this part of the job since the alternative to prefabrication 14 258 designed based on the latter approach. The general superintendent communicated with the engineer about 259 the schedule to make him aware that the latter approach was the basis of design. Therefore, the new 260 schedule was created based on the new methodology and compared with the previous schedule which 261 indicated more than 6 months of time saving. 262 A similar occurrence happened with the rebar which was bid based on a stick-built process. The 263 rebar foreman agreed to try the prefabrication method, and he tested 5 prefabricated panels several weeks 264 ahead of his scheduled start date. The schedule was based on stick-building 1 panel a day, and there were 265 65 panels. Nonetheless, he brought out 5 panels and had them installed in 3 hours. The general 266 contractor immediately flipped his sequence, and put the rebar ahead of all other sequences. The rebar 267 was completed in 6 weeks less time than was allocated in the schedule – with 50% of savings. 268 Additionally, the team was able to achieve a quality product in a controlled shop environment rather than 269 struggling with complicated reinforcement and embeds on site. 270 The light gauge detailing on USC Phase 3 also has some quantifiable data that shows the use of 271 HiDef BIM improved the project. GPLA attended a meeting with the metal fabricators before the 272 detailing began, and at first the pre-construction team decided not to use panelization and stay with the 273 traditional stick building. Once the idea of panelization trickled down to the field team, the idea was 274 revisited and chosen as the method for construction. Collaboration among the teams led to the 275 modification of the original eave detail that GPLA had initially designed. The fabricator also agreed that 276 having a few typical details for the connections was a good choice; for example, typical details for screw 277 patterns between panels which would be the same throughout the roof. 278 Again, the journey of the light gauge pieces from the point of fabrication to their completed 279 placement in the structure was considered in an attempt to streamline all aspects of the process. Each 280 panel would have a materials list on the sheet, so the pieces could be cut at the mill with minimal material 281 waste. Tekla Structures has the capability of recognizing panel assemblies that are the same and creating a 282 tally for each panel type. Panels were held to a width of 10’-0” for transportation purposes. The eaves 283 were built directly into the panels so that they were set down in one self-contained piece to form the 15 284 whole roof structure. Blocking was built into the panels where they attached to the main structure to 285 provide a surface to screw to (Figure 7). The panels even had the majority of the plywood sheathing 286 installed in the shop. GPLA also planned for a 1/8” tolerance between each panel. 287 GPLA learned the most important lesson by watching the panels get erected. First, a truck would 288 arrive with a load of panels, which had to be offloaded so they could be “prepped” for lifting. This step 289 was necessary because no pick points or means of lifting had been incorporated into the shop drawings, 290 and the team was forced to fasten the pick points to the panels while they were on the ground (Figure 8). 291 292 293 294 295 296 Figure 7: A screenshot from Tekla Structures showing one light gauge roof panel. Note the blocking for attachment is already built in (pink members). Additionally, the eave detail at the bottom edge is already included, so each panel is an all-inclusive piece of roof. 297 off the truck if they had come with pick points. Unloading the panels took eight men one hour, and 298 erecting each panel took 8 – 10 minutes (Figure 9). The superintendent estimated that had the panels 299 come prepped for lifting, the time would be cut in half for each panel. Indeed, Tekla Structures software 300 has the capability of locating the center of gravity of each panel. The pick points must be located at a 301 precise location in order for the assembly to hang at the proper angle for installation. The 3D technology The fabricator believes that the panels could have been lifted by the crane and installed straight 16 302 that Tekla offers makes it a relatively trivial exercise to locate the precise location for the pick point on 303 each panel during shop drawings preparation, and GPLA can incorporate this into future shop drawings. 304 305 306 307 308 Figure 8: A close-up of a roof panel pick point, installed by workers on-site. GPLA could have streamlined the roof installation by incorporating pick points in their shop drawings, which would be installed ahead of time. 17 309 310 311 312 313 314 315 Figure 9: On-site photo from roof panel installation at USC. Shop crews labeled each panel according to a key plan provided by GPLA (this panel is labeled LR-8). Note that while the roof is installed, only two men were required to be on top of the roof structure, making this installation safer than a stick-built roof, which would require upwards of 10 men in harnesses. Time & cost savings 316 In a post-construction discussion with the steel team who fabricated and installed the roof panels, 317 a lot of the benefits and savings were brought to light. One of the most important benefits was that rather 318 than having 10 – 12 men in harnesses stick building the roof, there were 2 or 3 men guiding the panels 319 into place, making the process much safer. The use of scaffolding was avoided, as well as the time it 320 would have taken to set it up and break it down. The panels were built in a controlled area with less 321 expensive labor. There were also significant material savings. The panel contractor used GPLA’s shop 322 drawings and bill of materials which allowed them to cut almost everything right at the mill, and to 323 deliver the pieces in bundles for the typical panels. Furthermore, there were also important time savings: a 324 relatively inexperienced apprentice could sort the cut pieces in much less time than cutting them from a 325 long stock. 18 326 The superintendent also provided GPLA with a constructive list of what could be done 327 differently. He pointed out that the panel pick points being pre-installed rather than field installed would 328 save time. He also stated that the 12 gauge metal is difficult to screw in the field and a lot of screws were 329 stripped and wasted. Preferably, next time the design would be in a lighter gauge. Additionally, in some 330 cases the 1/8” tolerance was not quite enough when panels had to sandwich between hard points on either 331 end. The best solution would be to brainstorm some type of adjustable tolerance connection. The team 332 also found that a 35’-0” length of panel is the ideal maximum length that could be easily handled. 333 Anything larger might require a larger crane that would “eat away” at any savings. Lastly, he indicated 334 that if the MEP hanger locations could be coordinated ahead of time, the blocking for those attachments 335 could also be done in the shop. 336 Conclusions and Lessons Learned 337 Perhaps the most rewarding benefit is seeing figures in writing of the savings. This is the sell 338 point BIM needs. However, benefits of BIM are often hard to quantify on paper. While GPLA firmly 339 believes that HiDef BIM leads to a better product and a faster, safer construction schedule, there is rarely 340 a cut-and-dry analysis that can prove it. 341 The light gauge superintendent provided GPLA information on how the panelization process 342 benefitted his company. His estimate for erecting the light gauge via a traditional stick-built method was 343 between 190 and 210 man-days from start to finish. The actual time spent was 80 man-days, and this 344 could be reduced further if some of the productivity lessons learned had been incorporated earlier. GPLA 345 spent approximately 185 hours modeling and producing shop drawings for the roof panels. This being the 346 first time GPLA had the opportunity to detail light gauge panels, it can only be assumed that the process 347 will get even shorter in the future. Based on the figures above, and rates provided by the superintendent, 348 the steel contractor saved in the range of $54,000 - $63,700 on labor alone. Additional material savings, 349 human safety savings, and the savings from pre-installing the sheathing are not factored into this number. 350 GPLA spent approximately $23,000 to detail the job and to create the shop drawings, which is well below 19 351 the amount saved by the contractor. 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