Emerging Technologies for Construction Delivery (2007)

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41 DESCRIPTION OF TECHNOLOGY Traditionally, architects and engineers have expressed their design intentions to contractors and other project stakehold- ers through 2D paper-media contract drawings developed as part of the contract documents. The contract specifications provide an additional medium to communicate product and process details that are too extensive for paper drawing notes. Additionally, it is common for designers and builders to develop scaled physical models to visualize the as-built prod- uct. These physical models have proven beneficial to all the major project participants (e.g., owners, designers, and builders) not only in their ability to allow visualization of the future completed facility, but also the opportunity to test aes- thetic preferences, component building systems, and spatial relationships of external entities surrounding the proposed facility. Design prototyping in the vertical construction in- dustry also typically includes physical mock-ups for the test- ing of building system component compatibility, material fabrication, etc. (Gopinath and Messner 2004). Over the last 20 years, with the advancement of computer technology, CAD has enabled the efficient production of 2D construction contract drawings. During the past decade, CAD software applications that enable production of designs in three dimensions have be- come increasingly mature. The use of 3D CAD implementa- tion of the (z) coordinate to 2D CAD’s (x) and (y) coordinates allows for the plotting of quantitative data in 3D space (al- though still viewed in a 2D surface). When three or more coordinates are connected in a 3D space, surfaces and vol- umes of the design can be visualized. These techniques are referred to as 3D objects or 3D models, which allow 3D information displays of quantitative data and virtual space (Issa et al. 2003; F. Shiratuddin, University of Mississippi, personal communication, June 1, 2006). 4D CAD consists of a 3D CAD model with the added di- mension of time (in its simplest form). The time element typ- ically consists of a Gantt chart, critical chain, or critical path method construction work schedule. Linking schedule activ- ities to components in the 3D model allows for sequential visualization of the construction design plan. 4D CAD mod- els, which typically refer to 4D CAD plus additional datasets and features such as estimates and virtual reality (VR), allow project stakeholders to visualize, measure, and quantify di- rect components and spatial relations of the facility included in the design, as well as visualize the time-lapsed construc- tion sequence. These capabilities are available very early in the facility life-cycle process. An important distinction is the difference between simula- tion and VR. Although there is no universal definition of VR, 4D CAD is always a simulation and can be VR. Simulation is defined as: • Imitation or representation, as of a potential situation or in experimental testing (The American Heritage Dictio- nary . . . 2000); • Representation of the operation or features of one process or system through the use of another; • A mathematical exercise in which a model of a system is established, then the model’s variables are altered to determine the effects on other variables (Scott 2003); or • The technique of representing the real world by a com- puter program; a simulation should imitate the internal processes and not merely the results of the thing being simulated [WordNet(r) 2.0 2003]. VR has been defined as meeting the following four crite- ria (T. Sulbaran, University of Mississippi, personal commu- nication, June 6, 2006): • It must be computer generated. • It must provide 3D visualization (clues). • The user must have the ability to navigate through the simulation and interact with the environment (i.e., chang- ing perspectives and views). • The simulation must occur in real time. It has also been defined simply as “the suspension of dis- belief” when viewing or imagining something which is not real (D. Fletcher, University of Mississippi, personal com- munication, May 25, 2006). Unless specific software applications are used, 4D CAD will only simulate the building sequence, although that in itself has tremendous value. Currently, the volume of aca- demic and industrial research conducted in the areas of VR and BIM causes difficulty in separating them from 4D CAD. VR and BIM will be discussed in chapter seven. There are two primary software applications (modeling tools) required to produce 4D CAD capability: CHAPTER FIVE FOUR-DIMENSIONAL COMPUTER-AIDED DRAFTING MODELING

• 3D CAD application: Software that encapsulates the “object-oriented” CAD model should contain the entire scope of project design data. • Scheduling application: There currently exists an eclec- tic set of available scheduling applications that vary by feature, price, and licensing. The construction activities contained in the project schedule are linked, through the coupling module, to design objects in the 3D CAD model. Additional software applications that may be required are: • Coupling module/application programming interface: An application programming interface is the interface that a computer system, software library, or software application provides to allow requests for service to be made of it by other computer programs and/or to allow data to be exchanged between them (Wikipedia 2006). This tool acts as a “junction box” that ties data struc- tures and program functions together between the other three applications. It acts as the interpreter of the differ- ing computer languages and data structures. • Simulation and/or simulation viewer application: Typi- cally, the visualization can be viewed through the 3D CAD application in time-lapse sequences determined by the schedule application. Visualizations desired beyond the basic schedule sequencing will require additional software applications. When these tools are properly coupled and synchronized, the result is a 4D CAD project model. This product then al- lows simulated visualization of the design model’s intentions according to the scheduling application’s timing and logic. The viewer can see the facility’s construction components evolve in time-lapse into the completed product. Some commercial products have emerged that encapsu- late all required software functionalities to produce 4D CAD models. These suites interface with most popular commercial 3D CAD applications. Many of these all-in-one 4D modeling applications have originated from academic research and the growing service industry that 4D CAD has spawned (consul- tation and assistance in development of the 3D and 4D mod- els). As often happens with information technology tools, personnel who have the knowledge and expertise can de- velop their own tools in-house. It is often more economical to purchase these applications from commercial vendors than to finance their creation, depending on the level of complex- ity desired. One of the most expensive components of devel- oping 4D CAD is the creation and linkage of the 3D model to the schedule. Hardware requirements consist of computers with fast pro- cessing and graphical rendering capability. Optimization of these computer processing features necessitates components such as large capacities of RAM, fast microprocessors, and state-of-the-art video cards. With the popularity of computer 42 gaming and the current availability of dual processor mother- boards, video cards and processing speed should become more affordable with time. In addition, the availability of microprocessors with 64-bit processing functionality is be- coming widespread and should aid processing speeds. Large capacities of storage media is also a requirement as the mod- els and datasets are typically measured in gigabytes (Shep- pard 2004). BENEFITS OF TECHNOLOGY Material Fabrication and Procurement The process of developing 3D and 4D models, with early in- volvement of collaborative project stakeholder teams, lends itself well to projects with fabrication-intensive materials and equipment requirements (see Table 25). The emergent philos- ophy of Lean Construction encourages the use of 3D modeling with emphasis on reducing lead time for engineered-to-order products, incorporation of cost modeling, integrating product and process design, and supply-chain management (LCI Research n.d.). Constructability Review Construction project constructability reviews are “peer- review” sessions of a project’s design intentions. Various project stakeholders review the design to add perspective on construction efficiency and effectiveness, suggest changes in relation to cost-effectiveness and assembly relationships, and value engineer major component parts of the design. 4D CAD is an effective tool for this purpose. Not only does it force the stakeholders to collaborate early in the manufacture of the required 3D model, but the visualization of the se- quential building process illuminates material staging and fabrication issues, spatial requirements not easily detected without visualization, and reveals conflicts, errors, and in- consistencies in the planning stage. Detection of interferences during the design process pro- vides opportunities for quality assurance in the construction phase (i.e., on site) (Gao et al. 2005). Communication of Building Methods and Systems Case studies have proven 4D CAD models to be the most ef- fective system to date that communicates the design intention to all project stakeholders. The ability to visualize sequential planned construction operations allows project participants to consider (experience) constructability issues that can only be imagined (from prior experience in similar situations) using 2D tools. Most case studies emphasize the benefit of spatial analysis regarding avoidance of trade stacking, equip- ment placement, material fabrication and staging, and site organization. The phenomenon has been referred to as exe- cution space (Heesom and Mahdjoubi 2004). In applications

43 to transportation facilities that are commonly constructed under traffic use, the project phasing can be designed while a series of scenarios are visually analyzed, because traffic count can be an included dataset of the 4D model. If suffi- cient detail is included in the model, the driver’s perspective can be simulated or experienced through VR. This is an in- credible design and planning advantage because planners can adjust roadway and bridge elevations for maximum driver safety. In addition, the visualization of the phasing from the drivers perspective can aid planners in the design and place- ment of traffic control and maintenance devices, permanent and temporary signage, and other safety features. It has been proposed that database object libraries be created (standards) for use in 4D models specific to these highway and traffic elements (Liapi 2003). Quantity Tracking When modelers develop 3D CAD models, they typically embed building objects with quantity data. When these ob- jects are linked to construction activities in a schedule, quan- tity information is made available to the 4D model. When the quantity data contained in the 3D models is associated with construction activities in the 4D model, it is easy to produce quantity surveys of a facility’s components. The 4D model al- lows comparison of as-designed, as-bid, and as-built material and component quantities. This fringe benefit of the modeling process, which is currently time intensive and costly, should be considered as “debit” cost, and subtracted from the nor- mally time-intensive estimating process of the project deliv- ery life cycle. As-Built Documentation 4D modeling allows the user to shift time in the proposed construction work plan either forward or backwards. This ability, given that the scope detail is sufficient and that the component quantity datasets are a part of the model, allows the potential of documenting as-built quantities by declaring the percent complete of either tasks (as is typically done in 2D schedules) or facility components. Fischer and Liston (2001) describe separate schedules and models for as-built, as-planned, as-revised, and as-proposed projects. With the ability to set a baseline construction work plan, users could track as-built quantity variance from as-designed and as-bid work plans. Smith (2001) discusses the potential of capturing as-built data in the model to serve for information and knowl- edge throughout the operations and maintenance stages of the facility life cycle. Public Relations 4D CAD has been widely reported to be a valuable tool in ex- pressing design intentions and construction sequence plans to individuals not familiar with visualizing from 2D media. For transportation agencies, the use of 4D CAD can effectively devaS )s(ecruoseR tnemevorpmI ssecorP noitacilppA Material fabrication and procurement Can occur before construction phase Lead and waiting time, project duration Constructability review 3D versus conventional 2D, can evaluate spatial limitations and challenges Change order count, project duration lacisyhp ,emit noitaroballoC ssenevitceffE smetsys gnidliub fo noitacinummoC mock-ups Quantity tracking Reduction of paper documentation, instantaneous Data entry iterations, information cycle time As-built documentation Reduction of paper documentation, instantaneous, organization/sole source of data Data entry iterations, information cycle time, loss of as-built data capture ,scitsigol ,emit noitatneserP ssenevitceffE snoitaler cilbuP physical mock-ups Schedule optimization Reduction of omitted activities and logic error Scope problems, change order count, project duration Incidental project resource requirements Reduces imagination and dependence on experience required during normal planning operations Project delays caused by inadequate resources Change management Design changes can be experienced virtually before physical construction implementation Strategic project design and planning duration TABLE 25 BROAD BENEFITS OF 4D CAD MODELING USE

communicate the phasing or staging sequences of projects that are long in duration and complex in relation to 2D visu- alization. Schedule Optimization From the case studies collected in a literature search of build- ing construction, a common reported benefit is the identifica- tion of omitted schedule activities. By visualization of the work progress, missing activities become apparent. One of the major improvements over earlier applications is the ability within Schedule Simulator to automatically pass changes to the information in the scheduling program to update the 4D model. This allows you to try many different options before committing to a particular model or schedule (Smith 2001). Incidental Project Resource Requirements The simulations visible as a result of 4D CAD models are a function of the datasets included in the model. Because designers and constructors have differing perspectives of the same project (model), it is understandable that each would op- timize the model from their own viewpoint. The designer’s contribution of the 3D model emphasizes design components, and the constructor’s schedule emphasizes the application of the design intention. From the case studies reviewed, the missing model elements revealed by the 4D model simulation are typically incidental project resource requirements that are beneficial to both perspectives. These omitted resources tend to include items such as scaffolding, falsework, temporary traffic control devices, and other items not contained in the direct design components or specifically defined as a sched- uled work package. The ability to visualize construction tasks at the operations level, in context of their spatial environ- ments, has also proven beneficial as an aid to constructors in specifying their task resource requirements. As stated, 4D CAD can depict the evolution of the construction product but not the interaction of the resources that build it . . . opera- tions visualization therefore differs significantly in concept, content, and usage when compared to 4D CAD (Kamat and Martinez 2002). Improved Change Management Possessing the capability with a 4D model to visualize (and experience) the impact of design changes in the construction delivery stage of a facility enables users to make strategic design decisions earlier than with the traditional process of 2D constructability reviews. Every case study encountered in the literature review reported significant reductions in change or- ders and constructor information requests to the designers. When the constructors are involved early in the model creation (planning) and analysis, the team is empowered with the capa- bility to run “what-if” scenarios and almost instantaneously evaluate the ramifications of the episode. Typically this exer- 44 cise results in the discovery of errors and omissions, both in the design and schedule elements of the models. Making, identi- fying, and correcting the mistakes in simulated construction or VR has reduced their occurrence in actual construction project delivery. EXTENT OF USE 4D CAD modeling currently is not significantly utilized by transportation agencies according to the synthesis survey re- sponses. Of 47 transportation agencies responding to this section of the questionnaire, only 5 indicated experience with 4D CAD modeling. Table 26 is a summary of the responses. Table 27 displays the small sample of respondents that have experience with 4D CAD. The driving application would appear to be communicating construction project plans to the public. Construction delivery-related applications have some use, whereas quantity tracking has none. Table 28 and Figure 36 display 4D CAD application use by project participant. Table 29 reveals the project procurement methods in which 4D CAD has been used by respondents. REPORTED BARRIERS TO IMPLEMENTATION Cost Costs and return on investment are always determining considerations when contemplating investment in technology, especially technology that disrupts status quo business processes. 4D modeling for construction delivery is the perfect application of the statement. The costs for using it include soft- ware licensing and hardware purchases, service costs of outside consultants if used for model creation or assistance, training, and in-contract salary costs of the model-building collaboration teams required at the outset. The total project cost percentage normally expended in the design development stage will increase substantially when 3D and 4D models are central to the project’s strategic planning. Currently, in this early-adoption stage of the technology’s history, the signifi- cant costs enable only large projects to absorb them. Project Count No. of Responses Response Ratio None 39 83% 10 or less 3 6% 10–30 1 2% 30 or more 1 2% Other* 3 6% *Other responses: 1. Not used. 2. We use 3D and 2D CAD in all our work. 3. I donít know. TABLE 26 AGENCY 4D CAD UTILIZATION

45 The most expensive variable discovered in the literature review was the cost of the time investment required for model creation and participant collaboration: Benefits need to be weighed against the time investment to build models . . . spent over 300 man-hours building a 3D model of Bay Street, primarily because only 2D CAD data [were] avail- able. But we’ll recoup it in time savings (Roe 2002). The return on investment has been well documented in project case studies conducted on vertical building projects. There is evidence that, in building construction, the technol- ogy can save, at a minimum, between 4% and 6% of the total project cost (Emerging Technology for Design and Con- struction 2005). The case studies have also revealed that project teams become more efficient in applying the process with successive iterations of projects completed involving the technology, thus lowering costs (Sawyer 2005). Further research would be beneficial involving total cost studies of such projects and determination of cost–benefit ratios to contract size. All of the case studies gathered in the literature review were consistent in that money expended upfront in the process resulted in savings during the construction delivery stage. One of the largest barriers to implementation (at least in the con- ventional AEC industry) is that 4DCAD technology requires engineering designs as 3D models, something currently uncom- mon. From 75 to 80 percent of a 4D model’s cost involves cre- ation of the underlying 3D model. When the design team works in 3D, that cost becomes a project benefit. Model costs on large projects might run as low as one-half a percent of the project budget, yet be returned 50 to 100 times over in project savings. However, if project participants don’t clearly establish a 4D model’s scope and purpose and level of detail prior to its model- ing, the cost-benefit ratio decreases (Sheppard 2004). Software Interoperability Issues As stated earlier, the current primary cost driver of 4D CAD modeling is the production of digital models. Dependent on the desired level of detail and output of the models, this in- volves manipulation of software application source code (pro- gramming) and/or linking database fields and objects between various datasets. Many of the 4D CAD commercial applica- tions available contain tools that act as a data bridge between the 3D CAD model and the construction schedule. Not only are skills and knowledge of design and construction required to link the datasets, so is experience with programming objects and database schemas. The main point is that currently oitaR esnopseR sesnopseR fo .oN noitacilppA %76 4 snoitaler cilbuP %33 2 noitatnemucod tliub-sA %33 2 weiver ytilibatcurtsnoC Material fabrication and procurement 1 17% %71 1 *rehtO Communication of building methods/systems 0 0% Quantity tracking 0 0% *Other response: We do not use. TABLE 27 AGENCY 4D CAD APPLICATIONS Note: The percentage indicates total respondent ratio; the number represents actual number of respondents selecting the option. N/A = not available. Agency Consultant Contractor N/A Application Reported Percentages/Respondent Count Material fabrication 33% (3) 22% (2) 22% (2) 67% (6) As-built documentation 25% (2) 25% (2) 13% (1) 75% (6) Constructability review 38% (3) 13% (1) 0% (0) 63% (5) Communication of methods/systems 0% (0) 0% (0) 0% (0) 100% (7) Quantity tracking 14% (1) 0% (0) 14% (1) 86% (6) Public relations 50% (4) 0% (0) 0% (0) 50% (4) Other 0% (0) 0% (0) 0% (0) 100% (6) TABLE 28 4D CAD TECHNOLOGY APPLICATION USE BY PROJECT PARTICIPANT

off-the-shelf software is incapable of linking the datasets of various software applications that constitute the 4D model. Not all 3D models have sufficient attribute information to facil- itate automatic linking, so the user has to identify which activity in the project scheduling software program is the activity that drives the component in the model (Smith 2001). Contract Specification Issues In CAD software applications the use of multiple drawing lay- ers that overlap foundational design concepts is determined by 46 the user’s preference. Standardization of this practice would aid in the development of 3D and 4D models because produc- ers would know where to look for specific datasets. Agency Procedural Issues The integration of 4D (and 3D) modeling disrupts the tradi- tional project life-cycle delivery system common to public contracting practices. Although design–build contract pro- curement is not new to public agencies, the creation of multi-dimensional building models requires the project stake- holders to collaborate much sooner in the early stages of the design process than is otherwise required traditionally. With- out this early collaboration, many of the benefits of modeling are lost. Users may need to create new methods of project pro- curement and contracting, or the contractor could be paid in a separate contract for early collaboration and constructability review. The sharing of project information between the proj- ect stakeholders early in the design process is critical. End-User Technical Skill and Training Not only do designers need design and construction engineer- ing knowledge and skills to build a successful model, they may also need to have scheduling expertise and considerable com- puter science, database, and programming skills. The indirect costs of this skill and knowledge must be factored into the total return on investment. fo .oN Responses Response Ratio Design–build 3 38% %83 3 *rehtO Both design–build and design–bid–build 2 25% Design–bid–build 1 13% Projects over a certain contract size 1 13% *Other responses: 1. Not used. 2. Megaprojects > $70 million. 3. Demonstration only. TABLE 29 USE OF 4D CAD BY CONTRACT TYPE 0% 0% 0% 0% 0% 0% 14% 14% 13% 13% 25% 38% 50% 25% 22% 22% 33% 0% 60%50%40%30%20%10%0% Material fabrication As-built documentation Constructability review Communication of methods/systems Quantity tracking Public relations Contractor Consultant Agency FIGURE 36 4D CAD technology application use by project participant.

47 Benefit Awareness The benefits of 4D CAD are being revealed to those in the construction industry who have not yet experienced it. Peri- odicals are showcasing the benefits from successful cases on large and high-profile building projects. Additional mecha- nisms are needed, similar to this report, for disclosing to the industry the benefits of digital modeling to the entire project life cycle. One of the biggest hurdles appears to be quantifi- cation of the costs and the uncertainty to owners of the potential payoff (Gao et al. 2005). Non-Cooperation of Designers Digital modeling puts more responsibility and accountabil- ity on the design engineers. Their early contributions to the project are the foundation on which all other data hinge (as has always been); however, now the design information is used instantaneously, in real time. In this case, the contrac- tor is not reengineering the designer’s work to complete his/her, but both disciplines collaborate in creation of the model. This will require a transparency (on both sides) that is not the norm. 4D CAD will require that designers think ahead as to how others will use their data and that they de- sign in 3D. All of the project stakeholders will have to con- sider the other’s perspective. One mistake commonly made by designers is to take the 3D design to construction and say “Here, use it.” However, the construction crew cannot use it because it represents the design version of the project. “The construction guy thinks differently than the designer.” The whole database must be converted to a format construction people can use, which has never been done, according to Burger (as quoted in Smith 2001). “The facility design needs to be converted into the construction configuration in which it’s going to be built, not the way it’s been designed. Once you do that, in 3D or a data- base model in such a way that the construction guy can deal with it, it becomes much more appealing” (Smith 2001). The availability of 3D design data has been a stumbling block, says Martin Fischer, director of Stanford University’s Center for Integrated Facilities Engineering and a long-time 4D researcher. Much of today’s 3D CAD data is based on sim- ple CAD entities and not on still-evolving industry-standard object definitions, he says. Also, he notes that owners are often unwilling to pay for true 3D design and liability-conscious designers are often unwilling to share data (Roe 2002). Lack of Technology Standards and References A significant barrier to digital modeling is the lack of stan- dards that can link the datasets of the project stakeholders together. Digital integration requires the ability to link design components to construction components effectively and effi- ciently. Users are beginning to define common schemas for data classification or Industrial Foundation Classes for the vertical construction industry. Without this standardization for transportation construction, the effort (and cost) of digi- tal modeling will remain high(er). Research has shown that the use of data exchange standards, such as Industrial Foundation Classes (IFCs), have, to a certain extent, improved information modeling and exchange between various applications in 4D planning. However, most of this research is still at its infancy. As a result, manual data input still prevails in the industry (Heesom and Mahdjoubi 2004). [A]lthough some research initiatives have attempted to intro- duce a certain level of automation in data exchange, most appli- cations still require some manual input between CAD and data- bases or databases and schedule information. This labour intensive activity could be considered as a potential reason for the slow uptake of 4D simulations by the construction industry. It was proposed by Kim and Gibson (2003) that one of the main rea- sons for the low take up of new prototype computer systems in the construction industry was due to their complexity. Therefore, in order to facilitate more widespread diffusion of 4D simulations in the construction industry, 4D systems should be easy to use and require a minimum level of input, allowing the planner to under- stand and quickly use the tools with a minimal lead in time (Hee- som and Mahdjoubi 2004). Table 30 presents the responses of agencies using 4D CAD of factors that restrict implementation. The sample group is so small that single responses designate the rankings of the factors. Topping the list is agency procedural issues, followed by a tie of end-user technical skill/training and unawareness of the potential benefits. All of the categories received votes, including software interoperability issues, contract specification issues, conflicting technology stan- dards, agency budgeting, hardware availability, and non- cooperation of designers. Factor No. of Responses Response Ratio Agency procedural issues 4 57% End-user technical skill/training 3 43% Unawareness of benefits 3 43% Software interoperability issues 2 29% Contract specification issues 2 29% Conflicting technology standards 2 29% %92 2 *rehtO Cost (agency budgeting) 1 14% Hardware availability 1 14% Non-cooperation of designers 1 14% *Other responses: 1. Only for public awareness. 2. Requires signal traffic information and development. TABLE 30 FACTORS RESTRICTING IMPLEMENTATION OF 4D CAD

Strategies to Overcome Barriers • Document and advertise 4D CAD benefits: Document time and cost issues, as well as publicly share the expe- riences within the transportation industry. Develop a knowledge base of multiple case studies similar to what Gao and colleagues (2005) did for building projects. • Change design development procedures: Encourage de- signers to create 3D models. • Change project procurement procedures: Develop pro- cedures that enable the early collaboration in the cre- ation of digital project models (within or around existing statutory requirements). • Develop 4D CAD specifications: Develop a methodol- ogy for designing in 3D and subsequent 4D. • Develop model object libraries: Develop a set of Indus- trial Foundation Classes for transportation construction. • Make agency training available to stakeholders outside: Open any training delivered to agency personnel in re- spect to digital modeling to the contractor community. MODEL FOR SUCCESSFUL IMPLEMENTATION Table 31 reflects the responses of agencies in ranking factors that have contributed to successful implementation of 4D CAD modeling. In the vertical construction industry, practices that have contributed to successful project implementations include (as reported in the Engineering News-Record) the Denver Art Museum project, which was a publicly funded project: • Early up-front stakeholder collaboration and mainte- nance of that collaboration with disciplined periodic team meetings. 48 • Owner requirements of 3D digital models from the designer as a contractual requirement. • Detailed and specific contract language concerning iterations of data “hand-off” between the involved proj- ect stakeholders. • Education of field personnel regarding aspects of the system. • Design model sharing between the parties required intellectual property and implied warranty rights be al- tered or suspended (Post 2006a,b). • A successful General Motors project that used digital models; any approved savings or schedule efficiencies were shared among the stakeholders (Sawyer 2005). BARRIERS TO OVERCOME The following are both technical and commercial barriers (Wood and Alvarez 2005). Technical Issues • Designers must create new models for each project in the transportation industry because the terrain or site model is typically a large percentage of the 3D model. • Designers must create new models for differing levels of required model detail. • Access to sophisticated modeling tools requires licensing. • There is a high cost associated with providing collabo- rative environments. • Analysis methods are not yet fully integrated into the simulation. • The challenges of accommodating differing design, work process, and other database schemas by the proj- ect stakeholder involved. Factor 1 High 2 Medium 3 Low N/A Cooperation/support of software application vendors 14% (1) 29% (2) 14% (1) 43% (3) Comprehensive implementation plan 0% (0) 29% (2) 29% (2) 43% (3) )3( %34 )2( %92 )1( %41 )1( %41 gniniart esu-dnE Knowledge of expected benefits 14% (1) 29% (2) 14% (1) 43% (3) )3( %34 )2( %92 )2( %92 )0( %0 esu fo esaE )3( %34 )1( %41 )2( %92 )1( %41 troppus lacinhcet esuoh-nI Cooperation of designers 0% (0) 57% (4) 0% (0) 43% (3) Note: The percentage indicates total respondent ratio; the number represents actual number of respondents selecting the option. N/A = not available. TABLE 31 FACTORS CONTRIBUTING TO SUCCESSFUL IMPLEMENTATION OF 4D CAD

49 Commercial Issues • The difficulties in determining equitable methods to distribute modeling costs to project participants and beneficiaries (Wood and Alvarez 2005). • The challenges of getting multiple project stakeholder buy-in (Wood and Alvarez 2005). UNEXPECTED OUTCOMES From reported case studies in the literature search, we dis- covered the following unintended consequences formed as a result of 4D CAD modeling implementation: • The process forces early collaboration and time expendi- tures by parties to the contract (Wood and Alvarez 2005). • Designers are unaccustomed to scrutiny of early design decisions and fear mistake exposures (Wood and Alvarez 2005). • Decision is strategic regarding level of model detail. If the project embarks on the wrong detail level, bad con- sequences can occur. Software products are needed that allow the evolution of detail to change as the project progresses. • In a survey of architects being released this week, 74% of respondents said they use some form of 3D model- ing/BIM (Post 2006a,b). The survey does not indicate how many are sharing 3D models with constructors. Many maintain that if they give a BIM to the contrac- tor, they must make design decisions earlier in the process. That could be an issue. • Contractors and designers experienced in such proj- ects report that the second iteration through the pro- cess is much more efficient, suggesting that the initial project will have unforeseen associated incidental costs. This suggests the need for a pertinent knowl- edge base. • Legal determination of which party (if any) controls the model—power issues (Hohner 2006). • A market is developing of consultants with the exper- tise to develop the 3D and 4D models (from traditional 2D design documents). • New project development delivery processes will change functional roles; that is, estimators may become planners (Post 2006a,b). • Incorporation of subcontractors (sometimes less techni- cally knowledgeable) into the model team.