In order to meet these stringent requirements, owners, architects, structural engineers, contractors, and other specialists alike have been forced to re-think their design and construction strategies. An accepted structural design solution to achieve seismic performance in California has been to use base-isolated structural systems. These systems have been cost effective on some projects (despite relatively high first costs), but not necessarily on all hospitals. For example, on sites with a steep grade it is difficult to build the moat around the facility as needed to allow the base-isolated structure to displace horizontally.

This article describes collaboration efforts of a project team that implemented lean concepts in the course of structural system selection during the design phase of a hospital project. Out-of-the-box thinking, contractual incentives for team work, early collaboration, and a set-based design approach led to the development of an innovative and cost-effective structural system that may set precedent for other medical facilities to be constructed in seismically active zones.

The structural design team on this project rigorously explored the design space and tested design alternatives against project value propositions. When encouraged by the owner to think more broadly, the structural engineer proposed a structural system using viscous damping walls, a concept developed in Japan but not yet tried on hospital projects in the United States. Because it is a first, this solution requires rigorous analysis by the structural engineer, independent laboratory testing (to calibrate analysis modeling techniques), and a detailed investigation by the state’s regulatory agency, OSHPD. This article describes the team’s efforts at defining the design space and the set-based design approach they used. A key lesson from this case study is that teams have a lot to learn about how to make requests and commitments while pursuing set-based design to be lean.

Case Study Background

The California Pacific Medical Center’s (CPMC) Cathedral Hill project is a new 555-bed hospital in San Francisco, Calif., budgeted at $1.7 billion. The hospital is one million sf with a total of 15 floors above and two below grade stories, and includes 555 parking stalls. The project is sited on sloping terrain, about seven miles from the nearest active earthquake fault. Design of the Cathedral Hill hospital began in 2005, and the project is expected to complete in 2013.

CPMC is an affiliate of Sutter Health, a major healthcare provider in Northern California. Sutter Health has shown a commitment to lean practices in its hospital design and delivery processes, and is managing a portfolio of lean projects. As a part of this lean implementation, Sutter Health encourages project teams to implement the “Five Big Ideas”: Collaborate, Really Collaborate; Increase Relatedness; Projects as a Network of Commitments; Tightly Couple Learning with Action; and Optimize the Whole. These ideas, implemented using a relational contract, have fostered an environment of collaboration and innovation on the project.

Design Theory and Methodology

The design of a project in the AEC industry, like the development of a new product in other industries, can be managed in different ways. Set-based and iterative design management approaches can be applied to projects depending upon whether the project is more uncertain or ambiguous, respectively. Scholars in complexity management use ‘uncertainty’ to refer to a lack of information and ‘ambiguity’ refers to a lack of clarity. The observations that set-based design strategies work best in uncertain environments whereas iterative design strategies work best in ambiguous environments are pertinent to this case study.

Research on another project showed successful use of a constraint-based approach has been successful for managing a steel frame building project. Project participants used an Internet-based collaborative tool to decide on diameters and locations of ductwork holes in the steel beams. This approach reduced rework as the steel fabricator was able to fabricate components based on reliable information, rather than with assumed values that later changed. Reliable promising—clearly communicating requests and committing to deliver on those requests—is part of the lean strategy implemented on the Cathedral Hill project.

Contrary to the more common point-based design methodology, set-based design allows for commitment to a specific solution to be postponed, allowing designers to consider multiple alternatives for longer than is typical. A design team can review sets of design alternatives available to each team participant, integrate these sets to find compatible combinations for the project as a whole, and weigh inputs from several project participants at the same time. Using set integration throughout project delivery, the design team can study tradeoffs between what is of value to individual participants and what is of value to the project as a whole. Set-based communication helps participants avoid rework and, through teamwork, develop a more globally satisfactory design than would otherwise be the case.

Relational Contracting

Relational contracts can be used to spur the formation and successful collaboration of integrated project teams. The Integrated Form of Agreement (IFOA) manages the risk of defects and the risk of cost overruns. On the Cathedral Hill project, risks and their associated costs are shared among team members. The owner, jointly with members of the integrated project team, put money into a shared risk pool. Each team member commits 25 percent of their profit towards the risk of cost overruns. Unforeseen project costs are paid out of the risk pool, spending the owner’s portion of the risk pool first, followed by the team members’ if necessary.

The IFOA also has an incentive sharing provision. If the owner’s portion of the risk pool is not spent, that money is divided up among the team members according to the amount they contributed to the pool. This pay structure supports collaboration and innovation, as there is an incentive for the entire team, not just one team member, to increase value. The IFOA mandated that project participants collaborate and use set-based design from the moment they are brought onto the team.

The IFOA is being used on this project in conjunction with target costing. Cost targets are set for each scope of work, and each set of design alternatives is evaluated against these targets. The aim of target costing is not to minimize project cost; rather, it is to maximize project value while remaining within the allowable budget. This effort may result in shifting costs from the construction phase to the design phase, or between target cost categories. For example, on the Cathedral Hill project fabrication drawings will be produced and paid for during the design phase rather than billed as a construction cost. The owner’s willingness to invest upfront pays for production of details and removes uncertainty from the project delivery process well before construction begins.

Mapping the Design Spaces

The first step in set-based design is to map the design spaces in order to define the decisions to be made and the available design alternatives. As a project progresses, the sets examined become increasingly detailed. Clearly articulating the level of detail necessary to define alternatives at a given point in the design phase requires open communication and understanding of the values each party can bring and constraints that affect them in that phase. Lack of clarity on these is an obstacle to set-based design. Each project participant must understand not only what is asked, but also the issue at hand and the purpose of what they are to deliver in order to make a reliable promise. Too much detail too early forces unrealistic and undesirable commitment, while too little detail may result in otherwise avoidable rework.

The following set-based design examples reflect decisions made during the Concept/Schematic Design (SD) phase and the Preliminary Design/Design Development (DD) phase on the Cathedral Hill project. During SD, the material and structural system were decided. During DD, the structural system details and preliminary mechanical, electrical, and plumbing (MEP) layouts were decided.

Problem of Too Much Detail

The difficulty of defining the level of detail needed for reliable promising is illustrated by conversations that occurred during project team meetings discussing wall penetrations and the exterior skin system.

Wall Penetrations: In order to define the structural system details, the structural engineer needed to know the location of wall openings required by the MEP team. In the spirit of collaboration, the MEP team started to precisely determine all of the design tasks necessary to identify all their penetrations; they thought that locations of openings down to ±4 inches had been asked for. This was a difficult if not an impossible task to do so early in the design process because other system parameters had not yet been pinned down. That is, there was still too much uncertainty in the design for the MEP team to confidently give the structural engineer the location of all wall openings. This roadblock was resolved when the structural engineer clarified what had not yet been made explicit, namely that only locations of openings on the order of 8 ft × 8 ft or larger were of consequence to develop structural system details. With this clarification, the set definition proceeded for structural system detailing.

Skin of the Structure: The weight of the exterior skin affects the building loads and the demands on structural elements at the periphery of the structure. In order to develop structural system details, the structural engineer asked the architect for this information, but at that time the skin weight was still uncertain. This roadblock was resolved when the structural engineer clarified that the exact weight was not needed, but rather only whether the skin was ‘heavy’ (~75 psf) vs. ‘light’ (~25 psf). The architect's clarification that the skin would not be of the heavier variety allowed the structural engineer to continue with detailing and the architect to postpone commitment to a particular skin type and manufacturer.

In both of these examples, one party assumed that more detail (precision) was needed than was necessary for the other party in that phase of design, or is typically considered appropriate for that phase of the process. Such uncertainty supports the use of a set-based design approach, as commitment to very specific values for wall openings and skin weights can be postponed. Designers must learn to articulate what they really need for their own work and what they should request from (and give to) others with reasons why while recognizing that their and others’ needs change with different project phases. Simply stated, foot-level details may be appropriate in early phases whereas inch-level details may be appropriate later. Degrees of required specificity must be articulated for geometric and non-geometric design attributes.

Problem of Too Little Detail

Beam Layout: The choices of floor-system beam depth and spacing are important to resolve early in design since they impact how ductwork is laid out. The structural engineer and MEP team wanted to coordinate their parameter choices so the ducts could fit in-between the beams and girders, thus saving floor height (no additional vertical space needed to fit ducts). The structural engineer and MEP team coordinated their work by agreeing upon the maximum depth of beams and girders.

However, the team initially failed to discuss another variable: beam orientation. The MEP team assumed the beams would be laid out perpendicular to the external wall so ducts could run from the building interior through the length of the patient rooms using the space between the beams. The structural engineer assumed beams would run parallel to the external wall. Each took it for granted that the other would intuitively opt for the same orientation, so neither party explicitly specified the orientation they planned to work with. Here, the set parameter specification should have included beam depth, spacing, and orientation. The team did not realize all three were required at this stage of design, until they discovered the conflict.

Both parties specified less than they actually required at this stage in the process and this miscommunication resulted in negative iteration (rework) to find a satisfactory design. This breakdown in communication illustrates the importance of defining the set properly and exploring it to obtain input from other project participants before proceeding with decisions. If the two sets’ definitions had included the variable ‘orientation,’ options could have been evaluated and decided on without requiring rework.

Structural System Selection

In the validation phase of design, lateral force resisting systems were compared on a whiteboard matrix. Each system controls seismic-induced inter-story drift using a different mechanism. Four different systems were considered for advantages. The moment-resisting frame system relies on the stiffness of its columns and girders, as well as the strength of the connections between these elements, to resist lateral deflections. The piston-damper system controls inter-story drift by increasing energy dissipation in a braced frame configuration. The viscous damping wall system controls displacement by shearing and distributes the force transfer along the entire wall length via the top and bottom connections to beams. The base isolation system controls inter-story drift by concentrating large displacements at the base level, but requires a special moat around the perimeter of the building to accommodate the large displacements.

Although base isolation was the initial choice for this project, this plan was scrapped due to the cost associated with building and maintaining the displacement moat given the sloping site. The base isolation system would also be taller than the other options and require special two-story trusses at the mid-height mechanical floor to stiffen the superstructure. Using a moment-resisting frame would have required about 50 percent to 75 percent more steel for stiffness than, for example, viscous damping walls would, in order to meet inter-story drift limits.

As an alternative, the viscous damping wall system was chosen. These damping walls are full-story height and are bolted to steel beams on the top and at the bottom. In Japan, such walls have been used in high rise buildings, but in the United States, their use on Cathedral Hill will be a first. This structural system does not require a displacement moat. A viscous damping wall is self-contained inside a wall which reduces the likelihood of clashing with MEP and architectural features. It is also considerably less expensive, saving about one percent of the total project cost. Furthermore, after a seismic event, the bolting system allows for easy bolt replacement if necessary. The structural steel frame is expected to remain elastic and therefore would not need to be replaced. Thus, from a lifecycle perspective, this system is favored, as the expected repair costs are lower than those of most other systems.

By including everyone on the team in the IFOA and rewarding team participants for innovation while having them share risks, more optimal system solutions can be developed for the owner. For example, use of innovations like the viscous damping wall requires advanced nonlinear structural analysis in order to justify the system’s ability to meet structural performance goals. Additional design time is needed to resolve modeling issues and ensure the solution will meet all project-specific requirements. On Cathedral Hill, the owner is encouraging the structural engineers, and all other team members, to carry out additional analysis by paying them on a time-and-materials basis. That is, the owner took a share of the risk of new, innovative system development by not imposing a fixed design fee on an uncertain process to achieve success. If team members are at risk for additional time that may be required to develop innovations, they will be more likely to stick to ‘conventional’ systems that may not be as optimal for the entire project.

Permitting

The process for permitting this project is also innovative. OSHPD is using Phased Plan Review to review portions of the design while other parts of the design are still being developed. A preliminary design submittal—mostly structural design information such as system type (viscous damping walls), design criteria, gravity system, and loading—was sent to OSHPD in order to obtain buy-in and concept approval on basic issues.

It is better to negotiate changes during design than during construction. The process for making changes to construction drawings, especially once field work has begun, could take up to two weeks for a minor design change and possibly months, if not years, if drawings need to be re-submitted to OSHPD for permitting. A long turn-around time for permitting results in an unpredictable schedule and delays. Problems during construction often involve differences between typical details and the real conditions in the field (another example of the too-little-detail problem). The IFOA, with the companies that are committed to building the project under contract during the design phase, allows for coordination between designers and builders before permitting, thereby reducing the need to make changes or document specific details during construction, and thus avoiding delays due to re-permitting.

Conclusions

Sutter Health created a collaborative and innovative project team to build the Cathedral Hill project through the use of its “Five Big Ideas”. The use of set-based design and out-of-the-box thinking enabled the project team to develop a design within the target cost boundaries. Thinking in a set-based manner has changed the conversations between team participants. It has spurred innovation by encouraging consideration of alternatives and evaluating tradeoffs between them, while keeping overall project value in mind. The owner’s incentives for teamwork, including payment for additional analysis to develop the viscous damping wall system, led to selection of a system that better meets not only the structural performance but also the project goals compared to other options, that is, it better optimizes the whole.

Reprinted with Permission
© 2008 Kristen Parrish, John Michael Wong, Iris D. Tommelein, and Bozidar Stojadinovic.