Since the late 1980s, architects at The Estopinal Group (TEG) have provided facilities solutions on more than 500 projects, with significant attention to healthcare-related assignments. President R. Wayne Estopinal, AIA, AHCA, founded TEG and has grown it into a 65-person firm with a national scope and offices in Jeffersonville, Indiana; Evansville, Indiana; and Shreveport, Louisiana.

Suri Ramanna, PE, SE, founded TRC Worldwide Engineering (TRC) in the late 1980s. Through a long-term strategy for growth, TRC now has more than 400 professionals in 14 offices on two continents. The firm has a long history of project success on a wide variety of structures and in 2007 climbed to 422 on Engineering News Record's list of Top 500 Design Firms. In addition to comprehensive structural engineering services, TRC has developed a Global Delivery Model to increase value to clients by providing in-house support services for structural engineering, precast engineering, and steel detailing.

TEG and TRC began working together from the inception of both firms. One of their most successful collaborations has been for Willis-Knighton Health System (WKHS). WKHS began serving the Shreveport, Louisiana community in 1925. Since then, it has grown to become the largest healthcare organization in the state and one of the top 100 hospitals in the country. In 1983, Willis-Knighton South opened as South Park Hospital and became the first satellite hospital in Louisiana. By 1989 it had extended its focus on women's services, carrying out a major renovation and expansion to open the Center for Women's Health.

Planning and design of this three-story, 69,540-square-foot wing of the hospital had been undertaken in 1987 by Estopinal during his tenure as vice-president at VHA Health Facilities Group in Irving, Texas, with additional design services performed by the Dallas firm of Page Southerland Page (PSP). The new wing would include what was then considered a state-of-the-art Neonatal Intensive Care Unit (NICU).

Anticipating later growth of the NICU, PSP developed the structural frame to accept a future fourth-floor vertical expansion, with seismic requirements based on the most recent regulations at the time, the 1984 Uniform Building Code (UBC). By 2005, the Shreveport community had developed a need for more extensive neonatal care, and WKHS was ready to embark on construction of an upgraded and expanded facility.

Challenges

Initially asked to provide a proposal for a two-story addition, TEG and TRC knew they faced several daunting challenges. The first and most important of these was the need to keep the facility operational while minimizing disruption during construction, not only because of the critical role of the facility in the community, but also because of the necessity of keeping expectant mothers and mothers with newborns as calm and comfortable as possible. Another challenge lay in extending the existing stairs to the new floor and roof while maintaining egress from the other floors during the entire construction process. Minimizing the downtime of rooftop units during construction of new mechanical penthouse facilities was also a crucial consideration. Overall budget and a 365-day construction schedule rounded out the list of principal issues.

Seismic dilemma

These challenges were trumped, however, during preliminary structural analysis. Seismic design for the proposed new addition would be per the requirements of the 2000 International Building Code (IBC). Given that seismic design conditions had increased substantially since the 1989 renovation, project architects and engineers discovered the existing structure could no longer be considered able to support even one additional floor without significant modifications to the building and its foundation. In fact, governing seismic loads had increased 70% from the 1984 UBC requirements to those of the 2000 IBC. Since the level of modifications required would mean shutting down the facility during construction, the project was on the verge of demise.

Fortunately, neither WKHS, nor TEG or TRC were ready to give up so easily. WKHS agreed to scale back their initial request for a two-level addition in favor of a 23,180-square-foot single level, with penthouse areas for elevators, stairs, and mechanical units. This would limit the amount of additional seismic forces on the existing structure to the columns and foundation only.

Going forward with this adjusted scope of work, the idea of petitioning for a variance to the building code was explored. Specifically, Section 1614.1.1 of the 2000 IBC stated:

An addition that is not structurally independent from an existing structure shall be designed and constructed such that the entire structure conforms to the seismic force resistance requirements for new structures unless the following conditions are satisfied: 1) The addition conforms with the requirements for new structures, and 2) The addition does not increase the seismic forces in any structural element by more than 5%, unless the element has the capacity to resist the increased forces determined in accordance with Sections 1613 through 1622 [i.e., Earthquake Loads and Seismic Design]. (331)

In other words, any vertical addition to the facility would require the entire existing structure to meet the latest seismic force requirements. If work on the project were to continue, this section of the IBC would have to be waived by local building officials.

The arguments for considering a variance request were based on several factors. The first was that seismic consideration for the new addition would be in compliance with the original 1984 UBC, meaning the design strength of the existing structural elements would not be reduced. The new addition also would be detailed and connected to the existing structure as required by the 2000 IBC and include provisions to reinforce existing members to transmit loads to the foundation. The proposed alterations would not create a structural irregularity or increase the severity of any existing irregularities. Finally, the risk of seismic activity in Shreveport was considered relatively low.

However, before active pursuit of a variance request got under way, TEG and TRC agreed that even with the variance, any and all seismic strengthening of the building through the existing structure would create too much disruption if not outright shutdown of the facility. The severity of the predicament was clear: increasing the capacity of neonatal care in the community was vital, yet just as vital was the necessity of continuing uninterrupted care in the existing facility.

The solution

Proactively responding to complex design problems often requires an organizational commitment to innovative solutions, and creating a culture of innovation throughout a design firm starts at the top. In responding to the challenges of this project, the innovative solution was a product of the heads of both firms.

Estopinal and Ramanna reduced the problem to its basic parameters—effectively reduce shear loads in the new addition until no seismic strengthening of the existing structural frame would be required. After reviewing the feasibility of removing shear forces through reinforcement of the stair towers on the north and south elevations, they seized upon the idea to create a central seismic tower off the face of the west elevation (figure 1).

A central seismic tower off the face of the west elevation was created

This braced seismic tower would accomplish several goals. First and foremost, it appeared to solve the fundamental problem of how to bypass any additional seismic shear loads through the existing columns and foundation in favor of structurally draining them down a braced-frame tower located outside the functional footprint of the building (figure 2). By designing the tower as a vertical tube truss, fabrication could be done in sections either in the shop or on the ground near the site. The sections could then be lifted into place as complete units, infill members installed and connections to the existing structure completed in less time, further reducing the impact of construction on the existing facility.

The braced seismic tower solved the fundamental problem of how to bypass any additional seismic shear loads through the existing columns and foundation in favor of structurally draining them down a braced-frame tower

The tower would be clad in new materials to complement vertical and horizontal elements on the structure. A panel system matched the sheathing on the new elevator tower on the north face, while open aluminum frames on the outer face of the tower corresponded to existing vertical glass areas over the front entrance, as well as to window rows along the west elevation. In addition to its structural functionality, the new tower also provided an important aesthetic function in breaking up the otherwise unremarkable horizontal flow of the existing west elevation.

Ground was broken on the project in May 2006; the new 42-bed Level III NICU opened one year later (figure 3). Only the third floor was temporarily vacated during construction of the stair towers and fourth floor. Though some disturbance to facility operations was unavoidable, the overall impact was considerably less than anticipated and construction flowed smoothly.

The new 42-bed Level III NICU opened in May 2007

Conclusions

The innovative seismic tower solution created by the design team allowed the project to proceed swiftly and efficiently while keeping disruption of a critical facility to a minimum. In addition to bringing the project in on time and under budget, the solution furthered the history of successful collaboration between TEG and TRC and reinforced an already-strong relationship with WKHS through urgent and committed action by the design and construction teams. Most importantly, the continued operation of the facility and the successful opening of the new NICU earned the likely gratitude of many area families and their newest members. HD

Steve Wylie is Vice-President, Total Steel Service, with TRC Worldwide Engineering, Inc., in Brentwood, Tennessee. For more information, contact 615.661.7979, e-mail

swylie@trcww.com, or visit

http://www.trcww.com.

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