VDC and the Continuum

Gregory P. Luth, Ph.D., S.E. Gregory P. Luth & Associates, Inc.

Abstract In this paper we provide a brief overview of the historical underpinnings of the -construction industry and the development of design engineering and construction engineering as independent, but related sub-disciplines of civil engineering. The effects of the 1st and 2nd generation of computer tools on the design engineering are identified. The complementary and evolving definitions of Construction Engineering and Design Engineering are examined, specifically in the context of Structural Design Engineering activities and deliverables and the corresponding Construction Engineering activities and deliverables. The concept of an “Engineering Continuum” is introduced and the process is recast in light of that concept. Several case studies are used to examine the promise of third generation design-construction computing technologies such as Virtual Design and Construction and their potential beneficial impact on the cost and schedule of the typical design- construction project. Refinements to the definitions of construction and design engineering that have the potential to maximize the benefits of 3rd generation technology are proposed with an eye towards the form of 4th generation computing technologies that are on the horizon.

Keywords: VDC, integration, detailed construction model, simulation

1 Introduction It is always fascinating to study the historical context that underpins the current topics of discussion. Civil engineering dates back over 5000 years to when the technical focus was on the art of transporting and stacking large rocks for projects such as Stonehenge and the Pyramids. Structural engineering evolved as distinct discipline within civil engineering in the mid-19th century in response to the increased complexity that came with better understanding of the science, development of analytical tools, and the evolution of long span bridges and high rise buildings enabled by the perfection of steel making in the latter half of the century. Bridges such as the Eads Bridge in St. Louis (James Eads, 1874) and the Brooklyn Bridge in New York (John Roebling, 1883) were designed and built by teams working under the direction of the chief civil engineer who designed the bridge, obtained financing, organized the construction, developed innovative construction methods (pneumatic caissons in the case if Eads), and supplied the material (cables in the case of Roebling). The architect William LeBaron Jenney and his protégé, Louis Sullivan, brought the new technology to buildings with the Home Insurance Building in Chicago and the 10 story Wainwright

Building in St. Louis and both are credited with being the “father of the modern skyscraper” – but the engineer who designed the structures for both, Dankmar Adler, is seldom given the credit for his work. Other engineers toiled in anonymity working for steel fabricators as did the engineer who designed the Denver Tramway Building in 1910 for Whitney – Steen, Engineers and Builders. The drawings for that building, prepared by the eminent Denver firm of Fischer and Fischer, had meticulous millwork drawings, but no structural plans or details. By the time they had excavated a square block for the basement using horses and wagons to haul away the material, built the 3 story long span steel car barn, and the 7 story reinforced concrete tower of the Denver Tramway in the astonishing time of 11 months, the company that constructed it had become Whitney – Steen, Builders; a portend of a professional division that would ripple across the next century of construction in the US. For a brief 25 year period of time from 1890 to 1915, buildings were constructed through a collaboration of architects, engineer, and builders. Integrated Project Delivery, IPD, is the process of:  incorporating detailed construction knowledge and planning into the design to support;  the construction means, methods, and sequences;  of all trades required to construct the building;  to optimize the construction activities on site;  to minimize cost and schedule;  to maximize the value of the to the owner and society. Integrated Project Delivery is where the industry was a century ago and where it has to go to in the future to regain its competitiveness. Good building teams never stopped doing it. Even while specializing, they developed the ability to team and collaborate across contractual boundaries to accomplish the project goals.

2 Evolution of Construction Engineering and Design Engineering The 20th century was a century characterized by a philosophy of “divide and conquer” when it came to the accomplishment of increasingly complex objectives whether it was assembling an automobile or constructing a high rise building. The individual tasks were identified, categorized, and assigned to specialists who could perform a very small part of the whole process efficiently. Construction engineering developed in the middle of the 20th century in response to the ever-increasing complexity of construction systems and the need to understand and manage those systems. When disputes inevitably arose about responsibilities for various parts of the process, lawyers were only too happy to wade into the fray applying post-project definitions of the process. In self-defense, the participants developed well defined scope descriptions within which they could operate, creating silos of activities. However, design and construction, by their nature, are collaborative, risky, and opportunistic undertakings that cannot be successfully executed from within the confines of the silos. As significant as the cost of litigation is, it pales in comparison to the costs due to the loss of efficiency, the suppression of creativity, the barriers to communication, and resulting loss of innovation caused by defensive design and adversarial construction that result from this process. At the beginning of the 21st century, the industry finds itself at a cross road trying to reinvent the process to take advantage of the promise of the new technologies that continue to develop at a breathtaking rate while correcting the deficiencies of a process that has become unwieldy and inefficient. The path forward will of necessity involve changing how we do things. In order to do that we find ourselves at an uncharacteristic moment of introspection asking: “What things should we be doing?”

2.1 Definition of Construction Engineer Construction engineering comprises a series of technical activities throughout the project to assist in meeting the project goals (Tatum, 2005) in the areas of schedule, cost, functionality, aesthetics, quality, and the efficient use of labor and material resources. Construction engineers need to understand the engineering fundamentals used in each discipline, how they are applied in analysis and design of the permanent facility and temporary works, and what are reasonable results. (Tatum, 2010) The construction engineer must have detailed knowledge of the common means, methods, and sequences of construction (“construction plan”) of the building systems and must be able to communicate with the design engineers, architects, and the construction tradesmen for the purpose of applying that knowledge in the unique project context to optimizing these systems for constructability. Construction engineering activities are critical for project success in meeting all types of objectives. Completing many of these activities early in the project increases the alternatives available for design, construction, and the value chain, along with the potential for integration and innovation. (Tatum, 2010) This requires that the construction engineer be capable of focusing on the essential characteristics of the problems at an abstract while manipulating the concepts. The construction engineer must be adept at dealing with the uncertainties and ambiguities of the design process where multiple versions of the complete must be processed in parallel and studied in various combinations until a reasonably optimized design is achieved. To the characteristics suggested by Tatum, the author would add that the construction engineer must be able to use first principles to adapt the available knowledge to new contexts and must be capable of communicating concepts effectively to both design and construction personnel. The construction engineer must be capable of developing new construction means, methods, and sequences in response to unique project or context constraints, assessing and mitigating the risks involved in applying an untested construction plan, and developing alternative strategies in response to unanticipated events that occur during construction. The construction engineer must be willing and able to mobilize knowledge from diverse resources both on the team and outside the team to achieve the project goals. While the above description might seem to require superhuman capabilities on the part of the “construction engineer,” it is not inconsistent with the characteristics of the most effective individuals in construction with whom the author has worked over the years. It should also be noted that on large projects the requisite knowledge and experience requirements can only be met by a team of individuals that is so well integrated that its process is as seamless as if it were a single individual. Based on the above, the following definition of construction engineering is offered:

A construction engineer has familiarity with, knowledge of, and appreciation for the fundamentals of engineering and architectural design and deep knowledge of construction means and methods and uses this knowledge to create safe and reliable alternatives for the construction plan in collaboration with the design team to help identify the optimum design concepts and details for a constructed project, and to execute the construction activities in a safe, economical, efficient, and timely manner to maximize the quality and value of the project to the owner and society

2.2 Definition of The very definition of “Construction Engineering” demands in response a definition of “Design Engineering.” Using structural engineering as an example, a search reveals a number of candidate definitions, all from the latter half of the 20th century:

Structural engineering is a field of engineering dealing with the analysis and design of structures that support or resist loads. . . . Structural engineering theory is based upon physical laws. Structural engineering design utilizes a relatively small number of basic structural elements to build up structural systems that can be very complex. Structural engineers are responsible for making creative and efficient use of funds, structural elements and materials to achieve these goals. (Wikipedia, 2010)

Structural engineering is the art of modeling materials we do not wholly understand into shapes we cannot precisely analyze so as to withstand forces we cannot properly assess in such a way that the public at large has no reason to suspect the extent of our ignorance. (BROWN 1967)

Design engineers from each discipline apply engineering fundamentals to define the function and performance of permanent systems and to analyze and design the systems that make up the facility. (Tatum, 2010)

The morphology of a structure is intimately linked to both the material and the construction method, and the design cannot be separated from them. Joint consideration of all these factors at the very beginning of the project, and during development of the preliminary sketches, will determine the success of the structure, justify its design and even the . For, ingenuity in solving all problems encountered has been, and will always be, the essential quality of the true engineer. (TORROJA, 1958)

The essence of structural engineering is understanding the materials and the systems so completely that the structure can be made to behave precisely as the engineer wills it. is the art of discovering the essence of the project, the enabling details, and the keys to constructability. (LUTH, 2008)

The four views of design engineering implied by the definitions above can be concisely characterized as: scientific, cynical, pragmatic, realistic, and optimistic. The latter two definitions come closest to essential characteristic of design engineering that is the key to unlocking the vast potential for improvement in the design and construction industry – creativity. The design engineer manipulates the features of the structural system to satisfy both architectural and construction constraints, while satisfying all performance objectives, by applying deep scientific knowledge of the behavior of the materials and systems. The design engineer must use creative reasoning to manipulate the structural system in the context of the complex system of architectural and construction constraints and the physical laws that govern behavior to yield the desired performance. To be effective, the design engineer must think qualitatively during the development of design concepts, focusing on the essence of the problems. Good design does not come out of a handbook a computer. Based on the above, the following definition of design engineering is offered:

A design engineer is an individual who has familiarity with, knowledge of, and appreciation for, architectural design and construction means, methods, and sequences and a deep knowledge of the behavior and performance of engineered systems; and applies this knowledge creatively to develop compatible, safe, functional, economical, and reliable design alternatives; to help identify the optimum design and construction concepts and details; and to define the form of the engineered system in such a way as to facilitate the construction in a safe, economical, efficient, and timely manner; to maximize the quality and value of the architecture to the owner and society

In this definition, the emphasis on the form of the system is added because therein lies the ambiguity in current practice. In current practice, the detailed “form” of what is to be built is contained not on the “design drawings,” which are conceptual in nature, but on the shop drawings. It is the author’s contention that this approach is the source of much of the inefficiency, waste, and litigation that is endemic in current practice, and that it is anachronistic in the light of current and emerging technologies. The definitions of design and construction engineering are symmetrical and differ only in emphasis and nuance. The engineering on a project is a continuum with elements of both construction and design engineering echoing throughout the entire life cycle. There should be a substantial overlap in the knowledge and experience of design and construction engineers. In practice, this knowledge is gained through the daily interface and collaboration that occurs naturally on projects when all members of the design/construction team work toward maximizing the success of a project. At their core, both construction engineering and design engineering must be creative endeavours. For, ingenuity in solving all problems encountered has been, and will always be, the essential quality of the true engineer. (TORROJA, 1958) And this applies whether it is a “construction” engineer or a “design” engineer.

3 Impact of 1st and 2nd Generation Computing on Design and Construction Engineering The 1st Generation of computer tools, developed in the 1970’s, provided the means for performing powerful numerical analyses of structures that were previously designed by manual methods using simplifications and approximations. This freed up the engineers to design soaring structures that used significantly less material to accomplish the same performance objectives with the same level of reliability. The 2nd Generation of computer tools brought CADD, computer aided design and drafting; small utility analysis programs, that allowed the development of customized proprietary tools for analyzing and designing buildings that did not justify the use of the sophisticated 1970’s analysis tools. Some programs were refined to automatically generate code wind and seismic loads, assemble all the load cases based on the increasingly complex codes, interface with CAD programs so the engineer could automate the design and generate the CAD drawings from the analytical model. The price that was paid for the convenience of automating everything from the initial modeling to the design was that the structures had to follow the rigid rules on which the prototype analysis and design programming was based to get the full advantage of the productivity gains. Code developers, seeing the ease with which the standard could be automated no longer felt the need to keep the codes simple and over the course of 3 decades increased the complexity of the codes by orders of magnitude creating a substantial incentive for design engineers to design within the constraints of the design software. Defensive design permeates the software industry exactly the way it permeates the design and construction industries. Programs are developed to be “fail-safe” when used by inexperienced or non-expert . If the software is used out of the box without adjustments that only and “expert” would know how to make, the results are conservative and the material quantities increase significantly. The software does not have the capability of handling non-standard designs – particularly when used by non-experts. Hence, special designs are forced into the standard template which may not be appropriate or efficient. Computer analysis should be used as a means of validating the behavior through analyses only after the design engineer has developed a sufficiently comprehensive and detailed vision and description of the structural system to allow it to be defined as a mathematical model. Current computer programs are not capable of the creative thought that is required to get to that point. The standardized design software led to a generation of “canned” designs. Design engineers became

“analysts.” The analysts became button pushers who turned over many of the design decisions to anonymous programmers unfamiliar with the “art” of structural engineering or the craft of building. More insidiously, the use of “black box” design programs have reduced the ability of two generations of engineers to solve problems by first principals, which is the key to solving non-typical problems and thinking outside the box to solve the typical problems in new ways that facilitate huge gains in construction productivity. Design engineers are admonished that means, methods, and sequences are the purview of the contractor and that the design should be performed independent of any particular means, methods, or sequences. This has fostered a neglect of constructability in the education of design engineers and in the development of concept designs. Much of the profession has lost the ability to tell the difference between a good design and a marginal one. We can now turn out automated designs in a fraction of the time – but they may not make any sense. On the CAD side, chief draftsman, who once were the key to putting together a constructible set of drawings were replaced by CAD operators who were more adept at assembling electronic files than they were at detailing a building. On the construction side of the fence, the old-fashioned hand detailers, like the chief draftsmen, who knew how to make a buildable set of shop drawings based on the “design intent” engineering drawings, were replaced by CAD detailers and within a generation that knowledge was lost to the industry. As Einstein said, “Insanity is doing the same thing over and over and expecting different results.” The effect of the 1st and 2nd generation software has been to create a generation of design engineers and CAD operators that do the same thing over and over because they can only do what the software has been programmed to do or what the standard detail database has in it. We cannot progress as a profession or an industry until this aberration is resolved.

4 Potential Impact of 3rd Generation Computer Technologies Third generation computer technologies include 3D database-linked models, 3D and conflict checking, and 4D (time) and 5D (cost) simulation and visualization, automated layout using GPS linked to precision models, and automated CNC fabrication from precision 3D models. These technologies offer the potential of a paradigm shift at the most fundamental levels of design and construction engineering that is breathtaking in its scope compared to what has been seen through the first two generations of computing in building engineering. The traditional means of communication among the participants in the design-construct-own process is combination of symbolic diagrams contained on 2D drawings and written specifications. While there are some similarities in the symbolism used on the 2D drawings, there are substantial variations among industries, among countries, among regions within a country, among companies within a region, and among individuals within a company. This fundamental characteristic of an industry in which effective communication is the single most important contributor to success is the Achilles heel of the industry. The ambiguities and imprecision of the fundamental building blocks of our contract documents prevent us from progressing beyond the contentious reality of current practice. The trend toward 3D modelling offers the promise of drastically reducing the ambiguities that arise from the use of symbolism. The communication of the form in a model relies on neither language nor symbolism for communication. What you see is what you get. Not all models are created equal. There is a subtle difference between “what you see is what you get” and “what you model is what you fabricate,” and that difference lies in the precision of the model. Through the first decade of adoption of the new technologies there have been two threads – adoption for construction purposes and adoption for “design” purposes. The most common approach on projects is for the design team to produce a “design intent” model that “looks” right, while the

construction team produces a construction model that “is” right, i.e., has the dimensional accuracy and precision required to do layout and fabrication. While the level of communication and coordination has certainly improved with the use of 3D models (as long as everyone on the team is using them), in many ways the evolving practice in 3D modelling preserves many of the disadvantages of the current system. For many practitioners, the term Building Information Model, or its acronym, BIM, as it is more commonly referred to, means the 3D “design intent” model that is used only for visualization. The term should be retired from that use as it perpetuates the notion that models need not be accurate or precise. A more accurate definition of a Building Information Model is as follows:

A building information model is a database of all the information required to design, construct and manage a building, including the underlying knowledge, heuristics, and context that controlled the design and construction direction and decisions

A BIM need not include graphical data. Graphical user interfaces may be used to edit or visualize the data, but they need not be the only means of editing the data. The process of using the model as a construction aid for estimating, scheduling, and simulation is called Virtual Design and Construction, or VDC.

Virtual Design and Construction, VDC, is the process of using an accurate and precise 3D Building Information Model to facilitate visualization, communication, coordination, estimation, simulation, purchasing, fabrication, sequencing, scheduling, and site layout.

Done properly, precision BIM models with construction-level detail can be used to:  visualize and plan more efficient construction sequences  enable prefabrication of materials that have traditionally been site fabricated such as carpentry, light gage, rebar, and MEP assemblies  coordinate down to the level of hanger and embed locations  produce shop drawings for structural steel, rebar, light gage, and MEP  perform automated CNC layout with total station equipment (i.e. Trimble technology) BIM models with construction-level detail can only be produced in collaboration between design and construction professionals with deep knowledge – a functional integrated project delivery (IPD) process. IPD starts with good design. Good design must to consider:  means, methods, and sequences of construction  the enabling details that make both the architecture and the construction work  opportunities for prefabrication  Precision required for coordination and layout

5 Case Studies In this section, four case studies are presented illustrating the application of these principles on actual projects, the manner in which the BIM model facilitated IPD, and the resulting economies gained in the construction (where data available). The case studies are the USC School of Cinema, the Tri- Valley Performing Arts Center, the Interlocken Office Building, and the Castro Valley Sutter Hospital. On all projects the sequence of construction has to be considered in the design either explicitly or implicitly. On unique projects, it sometimes has an enormous affect on the cost and schedule, to the

point where the feasibility of the project is predicated on a particular sequence and method of construction. In two of the four case studies that follow, the construction sequence is a major driver of cost and schedule. In these two projects the construction sequence dictates both the structure topology and the details. In both of these projects, the most economical construction sequence is one that relies on temporary bracing for stability of the structure during some phases of construction and was included as part of the base building design. Prefabrication of assemblies that are designed to be easily erected minimizes on site labor, reduces site congestion, increases quality, and decreases waste. When prefabrication is an objective of the design details, another layer of discipline is applied to the design. This has the effect of increasing the quality and precision of the design – an additional benefit to the project. In Case studies 1 and 2 prefabrication of major elements was considered as a part of design. In current construction practice we take as a given that certain elements of the construction cannot be planned in detail during the design process. Among these are reinforcing steel, carpentry, and light gage framing. The standard design approach to these materials is to represent the scope of work symbolically or with a narrative and address the details of the construction with representative sections and typical details. The shop drawings, if there are any, do not address the details of the installation, but repeat the general details with an estimate of the amount of material needed. The actual details of the installation are determined by the labourers in the field. The conundrum is what level of detail to show with these systems in a 3D design or construction model. Showing the complete details of the system is a radical departure from both design and construction practice and is ineffective unless there is a corresponding cultural change in the labor force. There is a substantial investment of time and effort in the modelling phase if these systems are taken to construction level detail. The questions are whether the investment of effort should be made during design or shop drawing phase and whether there is sufficient benefit to justify the investment. Case studies 1, 3, and 4 suggest that the appropriate time to make the investment is during design and that the potential savings just in labor and material justify the investment.

5.1 Case Study #1 – USC School of Cinema, Los Angles, California This complex of five buildings on an urban campus in Los Angeles was designed and built in two phase over a three and a half year period from 2006 to 2010. The first phase consisted of four story classroom building with state-of-the-art screening rooms, numerous special purpose labs, the central plant for the complex, and an inner courtyard, with 130,000 square feet of programmed area. The owner required the design team and contractor to implement BIM technologies in the design and construction of the building. Among the functional and aesthetic requirements the owner had for the project were that the Mediterranean revival architecture faithfully reproduce the Venetian stucco and stone facade without the pattern of joints required by modern construction methods and codes and that the building be designed for a useful life of 100 years. Effectively these two combine to dictate a monolithic cornet substrate designed to be repairable after a major earthquake. The structural concept that accomplishes this is a system of 10 ft wide rotating concrete wall panels with rotation provision at the base and floors installed between and attached to steel columns with ductile slit shear plates on the inside face that act as fuses. The infilled shotcrete walls serve as the permanent lateral system. The construction sequence that was the basis for design and that was eventually implemented by the construction team was: 1) build 4 story steel frame and composite slabs first using temporary bracing that was designed by the EOR and included on the permit drawings; 2) start MEP installation as soon as floors are cast; 3) install roof simultaneously with MEP 4) scaffold building exterior,

5) form infilled walls from floors, 6) swing prefabricated rebar cages into place using steel erection crane, 7) shotcrete the exterior shear walls from scaffold 8) remove temporary bracing and complete interior partition work 9) apply finish stucco and stone working from scaffolding. This sequence saved 6 months on the construction schedule. The inclusion of the design of the temporary bracing with the base building design avoided potential problems with building department approval and assured that all required modifications to accommodate the bracing were included in the building frame. The cost of the temporary bracing was a fraction of the savings due to the reduction in schedule. The structural engineer prepared a comprehensive structural model with construction level detail using Tekla Structures, the same software used by detailers to prepare steel shop drawings. The model was handed off to the steel detailers, shaving additional weeks off the schedule and virtually eliminating RFI’s. The embedded plates, which had welded hoops at 4 inches on center to resist the yield forces of the shear plates and slit shear plates themselves, were shop welded to the steel columns so that they were in place at the end of steel erection. The reinforcing bar between the columns was designed to swing in horizontally interleaving with the rebar on the embeds. The structural BIM included an accurate, comprehensive, and precise rebar model that was used to detail the rebar panels. The individual panels, which were 50 ft long, 10 ft wide, and weighed about 2 tons were flown in by crane (Figure 1). The panel shown in Figure 1 was picked off a truck on the far side of the site, erected blind approximately 200 ft from the crane, positioned and anchored, and hook released in approximately 15 minutes. The savings in schedule on the duration of rebar erection relative to the original plan was 6 weeks – an enormous benefit to the project and a financial windfall for the subcontractor.

Figure 1, Photo sequence of rebar panel being flown into place

The first phase of the project was designed over a 9 month period and constructed in 18 months, on schedule and on budget. The BIM model produced by the design team was updated continuously to reflect as-built conditions and at the end of Phase 1 was adapted to serve as the interface to the suite of software used by the university to manage the facility.

The success of the team on the first phase generated enthusiasm for continuing and improving the process on the second phase of the project which was roughly equal in cost to the first but included four buildings, one of which was a three story classroom building that utilized the same structural system as Phase 1, and two of which were sound stages requiring long-span steel trusses supporting gabled Spanish tile roofs that were sound proofed with 2” of sound board plus two layers of gyp on the inside of the top chord of the truss. On phase 2, the rebar shop drawings were produced directly from the design model, completely eliminating RFI’s and the normal shop drawings preparation and review. The design engineers worked directly with the rebar foreman and project manager to determine the size of the prefabricated panels for erection and the sequence of construction and then built those details directly into the model and shop drawings. The long-span trusses on the sound stages, which exceeded the maximum shipping size in both length and height, were designed and detailed as three shop welded assemblies – bottom half in two pieces plus a gable piece – and field bolted together in pairs along with the included bridging to form a stable erection piece that allowed the hook to be released immediately upon initial setting. The shop drawings for all the structural steel in phase 2 were produced directly from the design model. The trusses supported a roof sandwich that consisted of 10 inch light gage rafters with plywood and Spanish tile, batt insulation, 2 layers of gyp, and 2 inches of sound board. The design details were based on a panelizing scheme for the light gage framing. After the contract was awarded, the structural engineers worked with the successful subcontractor – who was initially reluctant to embrace the concept – to refine the details to address the subcontractor’s concerns. Panels were constructed with the plywood roof sheathing, the batt insulation, and the gypsum board pre-applied. Each of the 10,000 sf roofs was erected in a matter of a few days, cutting the construction schedule for those element in half (Figure 2).

Figure 2, Prefabricated roof trusses and panelized roof/ceiling sandwich panels

Similar productivity gains were realized in the construction of the building MEP systems, again aided by a detailed construction model that was developed by the design engineers, and again despite the initial reluctance of the subcontractors to use the design model. The second phase of the project was finished 116 days - an astounding 30% - ahead of schedule.

5.2 Case Study 2 – Tri-valley Regional Performing Arts Center The Tri-valley Regional Performing Arts Center (TPAC) is a 2000 seat performing arts center planned for Livermore, California in the seismically active San Francisco Bay area. The project design used many of the same strategies as the USC School of Cinema including the detailed construction model prepared by the structural engineer, rebar and structural steel modeled in detail, and panelization strategies. However, this discussion will focus on the construction sequence. The architectural concept uses a truncated pie shaped concrete-enclosed volume for the auditorium generated from a center point located at center stage and clipped by the 120 ft x 70 ft x 90 ft tall stage and fly gallery. The balcony volume extends 30 ft into the over the lobby 30 ft above the floor and is bounded by a conical section of slab at the bottom, a carved back wall, the concrete roof, and the concrete side walls. When completed, the cantilevered section encompassing the balcony forms a self-supported concrete box structure.

Figure 3, Phase construction sequence of the Tri-Valley Performing Arts Center

The roof of the auditorium requires 8 inches of concrete for sound and is constructed as a two pour composite slab spanning to composite 24 inch steel beams that span 50 ft to deep steel trusses spanning approximately 130 ft. The end wall of the balcony picks up one end of the last bay of steel beams. There are three levels of composite floors in a narrow band surrounding the auditorium to provide circulation, access, and support. The lobby is a 50 ft tall space with the roof framing into the mid height of the back wall of the auditorium. Since the basic architecture forms a stable concrete box structure there is no reason, other than constructability, to use a redundant permanent steel structure to form the box. The decision that the design team had to make was where to transition from concrete to steel and how to sequence the construction operations.

The initial design concept was to build monolithic concrete to the spring point of the balcony while the structural steel was being fabricated and then erect the steel roof and surrounding floors using erection columns where necessary. Along with the steel, temporary steel columns at the location of the back wall and temporary steel bracing to provide lateral support for the concrete roof slab would be installed allowing construction of the roof slab, roofing, and mechanical infrastructure below the roof to proceed in a continuous sequence. All of this was modeled in Tekla structures as part of the concept design which was then used to procure pre-construction services from a general contractor. The challenge of communicating the complexities of both the design and construction sequence in a set of concept 2D documents was addressed by including on the documents a sequence of nine axonometric views of the structure at each stage of construction, similar to Figure 3, along with a detailed narrative. This was augmented by using a feature of Tekla that allows the model to be posted to a web site as an XML model where it can be viewed by anyone using the ActiveX, a standard feature of Microsoft Explorer. With ActiveX the viewer can rotate, pan, and zoom as well as cut multiple sections through the model. It is an extraordinary help in communicating the nuances of complex designs. It is standard practice in the author’s office to post the web model weekly throughout the design and construction phases. Once the GC was on board, the design team met with the superintendants for a work session with the model. During that session the entire concept was questioned and alternatives ranging from building an entire steel frame first and infilling the concrete walls and slabs to building sufficient shoring and false work to build all the concrete first and then erect the steel inside the concrete were examined from a conceptual cost and schedule point of view. The architect weighed in with a request that all of the concrete, including the soffit below the balcony, be exposed architectural concrete. None of the alternatives had the schedule, cost, and constructability advantages of the proposed sequence. The meeting ended with the superintendents poring over the model asking detailed questions and asking for different views so they could better envision the construction details. They were engaged on the most fundamental level in the construction planning – at the concept design stage. It is rare to see construction teams at that level of engagement until the reality of the construction hits a couple of weeks before mobilization. The GC asked for a couple of days to mull over the process while examining the web model. In the final analysis, the sequence proposed by the design team was adopted, but the line of transition was raised from the lower end of the conical slab below the balcony to the upper end, in order to avoid the complications of pouring that slab around a steel structure. The final construction sequence is represented on the permit set the same way it was represented for the concept design discussion. An abbreviated version of the axonometric views of the model used to produce the construction sequence is shown in Figure 3. Tekla utilizes an independent database that resides as a separate file on the file server. The graphical interface accesses only the data it requires for the operation at hand and it can project the data using a wide variety of graphical conventions. The database is scalable. The construction sequence is generated by associating the individual structural elements with a particular phase of construction and then linking the graphical view to that attribute.

5.3 Case Study 3 – Interlocken Core As the result of the rebar detailing that was done on the USC School of Cinema project, the author’s firm was asked to provide rebar detailing for a 10 story core and foundation structure in Denver, Colorado for which the firm was not the EOR. The 3D model was constructed and rebar placing drawings and bar lists were generated from the model. This process is normal and worked quite handily using the 3D model.

The additional benefit that the modeling provided was that the superintendents and foremen could study the model and plan for pre-assembly of portions of the rebar and areas of congestion could be identified and eliminated. The inset in Figure 4 shows a corner where the vertical bars are lap splice at the intersection of heavily reinforced grade beams. The design drawings called for several layers of #11 bars to hook at the corner. As the result of working with the EOR over the model, these conditions were cleaned up.

Figure 4, 3D rebar model of Interlocken core and foundations

The unanticipated benefits of using the 3D model to detail the rebar were that the waste was reduced to 1%, the actual quantities delivered to the site were 15% less than what was in the bid, and the unit cost was reduced by 10% because of the reduction in placing labor. These are not surprising results when you consider the ambiguities and vagaries of the current design product. In conversations the author has had with rebar suppliers, the biggest single complaint is that the drawings they bid from are incomplete and they have to practice defensive bidding, adding tonnage to protect themselves from what might be added through the detailing and shop drawings review processes. A subcontractor needs to be part riverboat gambler to succeed.

5.4 Case Study 4 – Castro Valley Sutter Hospital Sutter Hospital has been a pioneer in the use of IPD contracts to improve their design and construction processes. The Castro Valley project is being constructed using a Sutter IPD contract. In this case IPD is a legal and contractual characterization as distinct from the functional definition that the author provided in the introduction to this paper. Key members of the design/construction team are parties to the IPD contract. The rebar supplier was not. For purposes of the IPD contract, the rebar is considered a commodity that is competitively bid. Nonetheless, the team wanted the rebar to be included in the 3D BIM model and included the production of such a model in the scope of the reinforcing steel contract. The successful bidder approached the author’s firm to team with them to

produce steel shop drawings using a 3D model. At the time, no reinforcing steel suppliers were using 3D technology. Unlike the previous projects, this one had a technology transfer component. Early in the project, the rebar modeling team - which consisted of all structural engineers – met with representatives of the reinforcing steel supplier from all over the country to demonstrate the technology. The general consensus of the supplier’s representative at the end of the demonstration was that it would not be feasible for them to adopt this technology in the near future. Figure 5 shows views of the 2D design drawings and the 3D model. Note that in the 2D drawing, the rebar hook is drawn short to make it fit. In the author’s office, the engineers do all the modeling as a natural part of the building design. The rule is that everything is modeled accurately forcing the designers to deal with conflicts such as this rather than leaving them to be solved during construction as is common with the “concept” design documents produced in current practice.

Rebar hooks are not drawn to scale actual standard hooks project out of form. #5 Ties @ 3 ½” 2-3 Layers of Ties Allows < 1.5” for horizontals to pass through

Figure 5. Examples of conflicts trapped by 3D rebar BIM

The process of producing the shop drawings was similar to the previous projects with the addition of weekly coordination meetings held on GoToMeeting over the rebar detailing model. The rebar detailers were provided with IFC models of the MEP systems, the embeds for the cladding, and the structural steel, around which the heavily reinforced concrete walls were built, and asked to coordinate the locations of the bars with the other trades as part of the process. The engineers worked with the combined BIM model in Tekla to achieve these objectives. The EOR used Revit to produce the design BIM on this project. The structural BIM did not contain construction level detail. As is common in current practice, the structural design drawings were conceptual in nature. The details, rather than being taken from the model were drawn in CAD by a CAD operator. The biggest problems and the ones that required the most time to resolve resulted from trying to satisfy mutually exclusive requirements contained in the “typical” details on the structural CAD drawings and making the details that were not drawn to scale or that were drawn without an awareness of the 3D context work. The fact that the rebar detailer was also a structural engineer and could negotiate acceptable engineering alternatives with the EOR was what finally enabled the process to work. The lesson is that the structural design itself should have been carried to an accurate level of construction detail and the design modifications made prior to construction. In

current practice, these problems would have been discovered during rebar placement with resulting cost and schedule implications. Eventually the project will get built. The only question is what compromises have to be made in the quality or what increases in cost will need to be incurred to get there and how many workmen have to be held up while the negotiations take place. Identifying the problems ahead of time, in the 3D detailing if necessary, but preferably during the design, allows solutions to be developed that do not require a compromise in quality or an increase in cost. The other significant outcome of this case study is that by the end of the project the rebar supplier had acquired 7 more Tekla licenses, had trained their staff to do the modelling and produce the shop drawings, and had reached the point where they were able to be cost effective doing all their projects this way. This suggests that they realized significant savings in labor and material as was the case in on the Interlocken project.

6 The Future – 4th Generation Computer Technologies It is imperative that the industry move toward adoption of a standard project database schema. The current IFC schema has served it’s purpose – interoperability among legacy software packages. However, it is bogged down with the graphical representation of database objects. What is needed is a streamlined schema for the database containing the actually data describing the form, function, and behavior of the building systems. The graphical user interface for the database can be tailored to suit the individual users of the database over the life cycle and remain the domain of software vendors. If the database follows a universal standard for schema and content, there is no need for interoperability – everyone operates on the same database. The adoption of a universal database schema will be a seminal event that will mark the transition of the design and construction industry from 19th century methods to methods that will continue to be developed for the 21st century and beyond. It will mark the beginning of the end for 1st generation software since structural analysis and design can be performed in the object oriented database. Building behavior will be a byproduct of using a schema that captures Behavior as well as Form. The holy grail of this technology will be capturing Function (Luth, 1991). When that happens, the software can finally support the thought process of designers whose leaps of imagination far outstrip anything the plodding prescriptive 2nd generation software can produce. The future of both design and construction engineering will have one thing in common – simulation. Simulations using the universal database will be used for energy analysis and design, mechanical systems controls for smart buildings, structural analysis and design, lighting studies, and construction means, methods, and sequences. Barriers to adoption of the new technologies abound on all sides. In practice, the author has chosen to focus on the functional approach, implementing policies and procedures that provide the functional benefits of the technology to each new project and let the business and legal issues sort themselves out. Culturally, design engineers have been conditioned to reason conceptually and have a well deserved reputation for imprecision in their documentation. Part of the problem is that most design offices continue to rely on CAD operators to translate red marks onto design documents. Modelling is a completely different process, literally one of virtual construction. It is virtually impossible to represent on a set of 2D drawings the detail available in the most elementary of 3D models. This renders the standard practice of red lining 2D drawings of limited utility, not to mention a waste of trees. The author has found that once one embraces the concept of virtual building, it is most expedient to allow the design engineers to be the virtual builders. In order to do this effectively, the design engineers have to communicate with the actual builders – the construction engineers, superintendents,

foremen, and labourers. The hands-on approach turns out to be intellectually stimulating with the serendipitous result that young engineers absorb knowledge at a phenomenal rate. It will be interesting to see to what heights these new renaissance engineers will carry the profession and industry.

7 Conclusions Throughout the mankind’s history of building, the most effect processes used some form of and construction. The replacement of the master-builder who was architect, engineer, and builder, with the discrete disciplines of current practice is a recent development of the past century. The trend in the last century, driven by the legal profession and exacerbated by 1st and 2nd generation computer technologies, has been for the discrete professions to operate within silos that disrupt what should be a free flow of information and thoughtful consideration of alternatives that reflect the true life cycle costs and values of a project. Design and construction engineering form a continuum that is severed only at the peril of the project success. The use of “design intent” models rather than models that accurately depict the details of the construction is an anachronistic concept that should be abandoned. There should be a single Building Information Model that is used throughout the life cycle process. It should be accurate, precise, and robust. It should be independent of the individual software packages and graphical interfaces that are used to manipulate the data, perform various analyses, and modify the data for design, construction, and facilities management. 4th generation computer technologies, Building Information Modeling, and Virtual Design and Construction offer a way back to an integrated process for design and construction. These technologies are disruptive and will require substantial changes in the culture and practice of the profession. The use of detailed construction models produced through a collaborative effort of designers and constructors has already shown that it yields efficiencies on a fine-grained level such as moving labor from the field to the shop, decreasing crane time, decreasing waste, and increasing safety. On current projects, the detailed construction model is already being used in the construction trailer for coordination and communication among subs and designers. There are instances of the models being available on small portable devices connected to a server in the construction trailer that allow viewing of the model on site at the point of construction. The inclusion of construction constraints such as sequence as a consideration in the design criteria can have an enormous effect on economy and schedule, dwarfing such things as optimizing the amount of material in the project. In the future, detailed lift drawings showing all rebar, PT, steel embeds, conduit, sleeves, and hangers precisely located and scheduled to enable CNC placement with laser technology. Individual components will be bar coded with ID’s linked to a database that will record planned and actual location of the component in the construction. Workmen will carry mobile scanning devices that interface with the central database that will allow precise positioning of elements in a fraction of the time it now takes. Precision in the field construction will facilitate mass prefabrication and the resulting economies of scale. The application of creative engineering on a macroscopic level to produce detailed construction/facility management models produced through a collaborative effort of designers, builders, and users will have a have a substantial effect on construction sequence, literally determining the viability of the project in some cases.

The use of a project database that accurately captures design concepts as well as physical data will make it possible to maximize the sustainability of future projects while minimizing life cycle and first costs. In summary, the use of 4th generation computer technologies, Building Information Modeling, and Virtual Design and Construction will result in higher quality buildings, that can be managed more efficiently, built safer, for less cost, in less time, with maximum sustainability.

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