Fit for the Future

A meticulous renovation that respected the historical fabric and original design, coupled with an ambitious seismic retrofit and base isolation, has rendered the Utah State Capitol capable of serving the people of Utah for many years to come. By Jerod G. Johnson, S.E., LEED AP, and René Vignos, S.E.

anuary 4 of each year commemorates Utah’s statehood, but in 2008 it was marked by the return of the people to the people’s house—the Utah State Capitol. Not only has this undertaking returned the capitol to its original architectural configuration; it has also elevated the capitol’s anticipated seismic performance from a status best characterized as deplorable to one that will perhaps allow immediate occupancy after a major seismic event.

The Utah State Capitol was designed and constructed in the early 1900s under the direction of Richard Karl August Kletting, often referred to as the dean of Utah architecture. The structure is composed primarily of reinforced concrete, an innovative choice of material for such an application at that time. The choice was dictated by its fire-resistive properties, an important consideration in the aftermath of the earthquake and ensuing fire that hit San Francisco in 1906. The building is perched atop Capitol Hill (formerly known as Arsenal Hill), at the north end of the Salt Lake valley, and stands as a beacon of Utah’s history, culture, and government that is visible from virtually any point in the valley. Its location is within a few hundred yards of the Warm Springs trace of the Wasatch Fault, an active fault capable of delivering a magnitude 7.3 event at any time.

The building measures roughly 400 by 215 ft (121.9 by 65.5 m) in plan and incorporates four stories as well as a partial basement, an attic, and a monumental drum and dome rising nearly 280 ft (85.3 m) above ground level. The overall building is reminiscent of the U.S. Capitol—borrowing many of the same architectural features, configurations, geometries, and proportions—and most of the materials used in its construction were drawn from local sources.

When the site for the building was selected, knowledge of the region’s seismic potential was nonexistent. Furthermore, the sciences of structural dynamics and earthquake engineering had not yet emerged. These issues compounded to paint a disturbing picture of expected seismic performance for the building. About the same time that knowledge of the region’s seismic potential came to light, concerns regarding the inventory of Utah’s historically important buildings and their expected seismic performance began to rise. The Utah State Capitol was preeminent among buildings within this inventory. Early studies diagnosed the building as having countless seismic deficiencies, and the late 1990s saw the publication of the Utah State Capitol Building & Grounds Restoration Master Plan & Historic Structures Report, or, as it is more commonly referred to, the Historic Structures Report, a work commissioned by the Utah State Capitol Preservation Board under the direction of the architect David H. Hart, AIA, who is now the architect of the capitol. The purpose of the report, which was prepared by Cooper Roberts Simonsen Architects, of Salt Lake City, was to document the state of the building and to characterize its expected seismic performance. This report was the first comprehensive investigation addressing all of the building’s systems jointly while paying due respect to the historical richness of the building’s fabric. Together with its predecessors, it provided the background necessary to procure funds for the comprehensive restoration and seismic upgrade. The design work for the upgrade officially began in the fall of 2002; construction commenced in the fall of 2004.

Hart developed a singular approach to the management of the design and construction of this monumental project. Before selecting a design team or general contractor, he embarked on a survey of all completed projects of a similar nature throughout the United States. This provided a wealth of information regarding the various approaches and management strategies that would make it possible to complete the project successfully. Chief among the concerns was the potential for enormous cost overruns.

Forell/Elsesser

The seismic upgrade of the capitol involved the placement of conventional and posttensioning reinforcement at the southeast rotunda pier. Temporary support of existing columns adjacent to the rotunda was provided by large steel beams, flat jacks, and posttensioned thread bars.

Those surveys of other projects, coupled with concerns about cost overruns, prompted the selection of a construction manager and general contractor as the first step in the actual renovation process. In the summer of 2002, the services of Jacobsen Hunt, of Salt Lake City—a joint venture of Jacobsen Construction, of Salt Lake City, and Hunt Construction Group, of Scottsdale, Arizona—were retained to manage the entire renovation process. Estimators with Jacobsen Hunt began almost immediately to develop a cost model for the project and to steer the project in the direction of optimal feasibility in terms of budget and constructability. Not long thereafter, the Capitol Restoration Group—an architectural team composed of Valentiner Crane Brunjes Onyon Architects, of Salt Lake City, Max J. Smith Architects, also of Salt Lake City, and Schooley Caldwell Associates, of Columbus, Ohio—won the bid to provide architectural design services for the project. Reaveley Engineers + Associates, of Salt Lake City, and the subconsultant Forell/Elsesser Engineers, Inc., of San Francisco, were next hired as the structural engineering team for the project. While Reaveley Engineers + Associates provided structural engineering services for the project as a whole, including service as the engineer of record, Forell/Elsesser provided invaluable service with respect to the design and specification of the base isolators used on the project. Forell/Elsesser brought a wealth of experience to the project, having provided design services for countless base isolation projects for buildings of historical importance. It also provided the design for the load transfer and installation of isolators at the base of the rotunda structure.

While the structural design team was charged with developing the seismic renovation scheme for the project, amec, of Salt Lake City and Riverside, California, and Geomatrix, of Oakland, California, which were serving as the geoseismic engineers for the project, were also given the task of characterizing the expected ground motions for the site. Using state-of-the-art methods, amec and Geomatrix developed a suite of artificial acceleration records utilized by the structural engineering team to design the base isolation system jointly with retrofit elements of the superstructure.

Don Green

Architect David H. Hart, AIA, now the architect of the capitol, went to great lengths to ensure that the ambitious renovation and seismic upgrade project did not result in cost overruns and delays. Prior to selecting a design team and general contractor he undertook a survey of all completed projects of a similar nature throughout the United States, an endeavor that provided a wealth of information regarding various approaches to the project as well as management strategies.

Although the primary structural material of the original capitol building is reinforced concrete, the engineers used this characterization carefully since the amount of reinforcement for most elements in this building is far less than the minimum amount required by a modern standard for reinforced concrete. This translates into a lack of ductility of the primary structural system. The building simply cannot experience significant interstory drifts without serious impairment to its ability to support gravity loads. The recent retrofit notwithstanding, the structural system consists of columns regularly spaced at about 14 ft (4.2 m) in each direction. These are interconnected by concrete beams framing into the columns to provide beam-column lateral resistance. Such systems can be effective when detailed as prescribed by modern codes, but they typically constitute relatively limber systems regardless of detailing. For the less frequent longer spans, the original designers opted for rolled steel, either as shapes or as trusses composed of rolled shapes with riveted connections. With the exception of steel trusses, all rolled shapes within the primary structure were encapsulated in concrete, thereby addressing the fire protection issues.

One of the purposes of the Historic Structures Report was to characterize the expected seismic performance of the structure. Nonlinear analysis methods indicated a maximum capable displacement at the roof level of the structure of approximately 4 in. (101.6 mm) before brittle failure mechanisms would begin to mobilize. The characteristic earthquake would be expected to force at least 9 in. (228.6 mm) of rooftop displacement. Analyses of the dome and drum structure revealed similar performance, the maximum capable deflections being approximately 10 in. (254 mm) and more than 20 in. (508 mm) of displacement forced by the expected quake. Later analyses accompanying the survey and discovery phase of the renovation design indicated that performance would probably be worse, with a significant likelihood of structural collapse and loss of life. Concrete specimens extracted from the building in the early phases of the renovation design indicated respectable concrete strengths—as high as 5,600 psi (38,612 kPa). However, these strengths were determined for concrete at the foundations of the building, whereas the balance of concrete had strengths decreasing with building height. Some specimens at the dome were extracted as rubble, while the weakest specimen that actually could be tested came in with a compressive strength of only 230 psi (1,586 kPa). This heightened concerns over the previously determined seismic deficiencies of the dome and drum, painting an even more disconcerting picture of expected seismic performance.

Don Green

The dome and drum of the capitol have been repaired and reclad with new terra-cotta to realize the 90-year-old vision for the structure’s exterior. The rotunda load transfer and isolation system is made up of large posttensioned-concrete beams and girders that completely wrap around the “stem” of the existing pier footing, effectively “recycling” the large footing to function as a composite load transfer system.

The Wasatch Fault is capable of delivering an event with a magnitude as high as 7.3 at any time. In fact, modern codes for seismic design, in particular, Minimum Design Loads for Buildings and Other Structures (ASCE 7-05), characterize the potential ground motions along the Wasatch Fault with seismic accelerations similar in magnitude to those in San Francisco. More than 700 measurable earthquakes are recorded in Utah each year. Most are relatively small and pass without remark. The balance serve as disconcerting reminders of the large earthquakes that occur on a regular basis as measured in geological time but have not occurred since pioneers founded the region, approximately 150 years ago. The Wasatch Fault is divided into 10 primary segments extending from Brigham City at the north end to Levan at the south end. Studies indicate that a quake large enough to cause a surface rupture occurs approximately every 350 years at some point along the Wasatch Fault and that any individual segment experiences a surface rupture roughly every 1,300 years. The consensus among geoseismic engineers is that the last significant rupture of the Salt Lake segment occurred approximately 1,300 years ago, thereby marking the site as “overdue” in the eyes of many.

The Historic Structures Report served not only to characterize the expected seismic performance of the building but also to explore potential methods of seismic retrofit. Although many systems were suggested as potential candidates, most had one major drawback: their implementation would have significantly disrupted the spaces and even the original fabric of the building. Studies determined that seismic base isolation would be the optimal system in this regard. Not only was it among the most cost-efficient solutions; it was also by far the most sensitive to the building’s historically important fabric. As a primary objective for the project, the Utah State Capitol Preservation Board mandated that, irrespective of the systems implemented, the character, look, and overall feel of the building could not change and that the only permissible changes in this regard would be those associated with a return to the original design established by Kletting. Base isolation made this possible since its effectiveness stems from lowering seismic demand, as opposed to more conventional approaches that simply add “raw” strength to a building structure. The option of adding strength to the building as a primary retrofit solution was considered. However, the magnitude of earthquake forces predicated a quantity and size of shear walls that could not have fit inconspicuously within the original fabric of the building, a result hardly in keeping with the goals of historic preservation. Furthermore, this approach would have made the structure stiffer and more rigid, thereby increasing its potential for resonance with the site and the expected ground motions. This would have required a far more aggressive approach in stabilizing and seismically bracing the many massive stone and plaster ornamentation assemblies throughout the building.

Forell/Elsesser

The interior of the rotunda features marble cladding and panoramic artwork reflecting Utah’s heritage. An important directive of the renovation program was to protect and preserve the original ornamentation to the fullest possible extent.

Seismic base isolation as a primary solution has the purpose of changing the natural dynamics of the global system. It decouples the building from the ground, thereby enabling it to sway from side to side with a fundamental period vastly longer than that of the site. This largely precludes resonance between the site and the building, thereby diminishing the accelerations that would normally accompany a fixed-base system. The seismic base isolation system used for the capitol reduces accelerations (and overall lateral earthquake forces) by as much as 75 to 80 percent.

The installation of 280 isolators at the base of the building was a monumental undertaking and required new and innovative approaches to bring about the complete removal and replacement of the foundation systems and the placement of isolators without raising or lowering the building by more than 1/16 in. (1.587 mm). As a primary solution, large concrete beams with significant amounts of reinforcement were cast around existing columns. At the midpoint between existing columns a temporary jacking system was placed to effectively relieve loads from existing footings and foundations. Upon transferring loads, existing columns and footings below the load transfer beams were removed, thereby providing space in which to suspend the seismic base isolators. A new mat foundation was constructed below the isolators, and the column loads were then transferred from the temporary system back to their original path, which now passed through an isolator.

Produced by Dynamic Isolation Systems, of Sparks, Nevada, the isolators are cylindrical bearings composed of alternating layers of rubber and steel laminated together. They measure between 34 and 44 in. (863.6 and 1,176 mm) in diameter and are approximately 20 in. (508 mm) high. The elastomeric layers within the bearings provide for relatively low stiffness in the horizontal direction while the steel layers give the isolators the vertical stiffness needed to support column loads in excess of 800,000 lb (3,558.4 kN) in some cases. The isolators are capable of at least 24 in. (609.6 mm) of horizontal displacement in any direction and effectively decouple the building and change the fundamental period to approximately 3.0 seconds, far beyond the original building period of 0.60 second and a similar site period.

While base isolation can effectively reduce the horizontal accelerations propagating into the building, the effectiveness of the system as a whole is enhanced when the structure above can be made as stiff as possible. This limits interstory drifts and deformations and significantly diminishes the formation of brittle failure mechanisms in the lightly reinforced existing structure.

New concrete shear walls have been strategically located within the building to provide optimal structural stiffness that will act in concert with the base isolation system. Ventilation shafts abandoned in previous decades became the locations of many new concrete walls, as did the walls lining new stair and elevator shafts at back-of-house locations. New concrete shear walls were provided within the hollow spaces of the rotunda piers, while others were added to replace and reinforce the deficient concrete of the dome and drum. In all cases, the wall locations and dimensions were carefully selected so as to be as inconspicuous as possible with regard to the original building layout. In fact, to the unknowing eye the new shear walls are practically nonexistent in comparisons between the renovated building and the original configuration.

he dome and drum of the capitol building are supported on a series of arched beams at the main roof level that transfer the load into four large concrete towers. These towers pick up further tributary floor loads at floors below and are founded on massive (30 ft [9.4 m] wide by 38 ft [11.5 m] long) footings at the basement. The existing dead load on these footings before the retrofit was estimated at 7,000 kips (31,136 kN). Given the high load to be transferred and the brittle finishes in the superstructure and dome above, it was imperative to create a load transfer and permanent isolation system that could safely transfer the load with nearly zero deflection.

The conventional way to install isolation under an existing footing is to temporarily shore the column above, place a new foundation and isolator, and then preload and connect the isolator to the column. This method, however, would have been highly impractical, if not impossible, for such a tower. The next idea considered was to dig several tunnels under the footing in phases to incrementally build new footings below the new and existing footings and to put isolators in place. However, the contractor objected to this idea because it could have jeopardized worker safety. With some creative thinking, the design team was able to develop a method of permanently resupporting the rotunda with a unique circumferential posttensioned-concrete load transfer scheme that obviated the need for temporary support of the existing footings, eliminated the risk of differential settlement, minimized the need for demolition, and made it unnecessary to excavate beneath the existing footings while under load. The selected scheme engages the existing footing by “grasping” it with a posttensioned-concrete element that enables the resulting composite assembly to span the distance to supporting isolators and footings outside the footprint of the existing footing.

This rotunda load transfer and isolation system is made up of large posttensioned-concrete beams and girders that completely wrap around the “stem” of the existing pier footing, effectively “recycling” the large footing to function as a composite load transfer system. The resulting composite beam footing assembly spans 51 ft (15.5 m) between girders. The supporting girders are each supported on four large-diameter lead and rubber isolation bearings. These bearings are founded on new footings placed outside of the footprint of the original rotunda footing. At each rotunda footing the new composite beam section supports the design loads through the use of 16 posttensioning tendons, each comprising 37 strands that are 0.6 in. (15.24 mm) in diameter. These tendons are both vertically and horizontally draped on a skewed plane so that they simultaneously “hug” the existing concrete tower base and balance the high vertical loads. To ensure full composite action of the existing footing and the new concrete, 112 vertical posttensioning rods 13/8 in. (34.9 mm) in diameter were anchored into the previously unreinforced portion of the flange of each existing footing and then anchored and stressed into the new concrete beams. Furthermore, 98 vertical posttensioning rods 13/8 in. (34.9 mm) in diameter were used in each pair of girders to prevent splitting caused by high bursting stresses arising from the high forces at tendon anchorage zones.

Forell/Elsesser, all

In the step-by-step depiction of the rotunda load transfer and isolator installation, top, the existing footing and pier, gray, are flanked by, two o’clock position, a new mat foundation; the isolators, green, are placed atop new mat footings while surfaces of the existing footing and pier, four o’clock, are prepared to receive new concrete; the new posttensioning reinforcement, red, eight o’clock, is placed; and the new concrete, blue, is placed above the existing footing and around the existing rotunda pier stem wall. Four large rotunda piers support the dome and drum assembly, center. Each pier bore atop a spread footing measures approximately 30 by 40 ft (9.14 by 12.19 m) in plan, carrying approximately 7 million lb (31,136 kN) of load. New posttensioned concrete encapsulated the entire rotunda assembly at the basement level, bottom. All four piers are interlocked to enhance the overall stability of the system.

One of the main challenges of the transfer system design was working out a possible sequence of construction that would allow complete installation without compromising the existing structure’s load capacity or its brittle finishes. The following sequence was used by the contractor to safely transfer the loads from the existing footings to the new isolators while minimizing any potentially detrimental movement in the rotunda:

1. Some general demolition of the existing floor slabs in the area of the rotunda was carried out to clear space for subsequent operations. This initial step involved the temporary shoring of several main building columns.
2. Soil improvement measures were implemented in the areas outside of the existing footing, and the new footings that would eventually support the rotunda loads through the isolators were installed.
3. The isolators were mounted on the new footings along with flat jacks that could be used to ensure adequate load transfer into the isolators.
4. The existing footings were partially demolished and carefully roughened and keyed to provide room for the new concrete beam sections and ensure good composite action.
5. The next step involved the intricate installation of the doubly curved posttensioning tendons, vertical posttensioning rods, the orthogonal rebar cage, and a plethora of posttensioned anchorage reinforcement.
6. With the rebar and posttensioning in place, the entire beam and girder system at each tower was cast in one continuous pour with a mix that advanced the goals of sustainable development by having a high fly ash content. The mix was internally vibrated and form-vibrated into place.
7. After the concrete had cured and attained adequate strength, the load transfer to the isolators was initiated. The flat jacks on top of the isolators were preloaded to their expected final dead load as the posttensioning tendons were stressed up to their design level. This allowed any settlement of the footings to be taken up by inflation of the flat jack as the posttensioning transferred the vertical loads to the isolators.
8. When all four quadrants were complete, they were connected with closure pours to tie together the overall rotunda system and allow transfer of overturning forces between quadrants.
9. The contractor removed the soil from beneath the existing footings to allow free movement of the isolated structure.

he deficient concrete of the dome and drum was a serious concern for the designers. Its cause became a paramount issue when it was also discovered that the structural steel of the dome had experienced severe corrosion in many locations. The infiltration of fluids—exacerbated by runoff from the copper-clad roof of the dome—is believed to have at least contributed to the observed corrosion. Therefore, as part of the renovation solution, a system to actively combat corrosion at the dome and drum was integrated, along with aggressive measures for waterproofing the new and existing assemblies. The system selected for active corrosion prevention was a cathodic protection system receiving just 3.78 A of current. Since corrosion forms part of an electrolytic cycle, it can be altered and even arrested with the appropriate prescription of forced current. The interior surfaces of the structural steel trusses of the dome and of the reinforced concrete of the dome and drum have been connected to the cathodic protection system. Such systems have proved effective but have never been applied in this way. Nevertheless, designers of the system agree that it will vastly reduce corrosion and significantly extend the life of the entire structural assembly. This is thought to be a pioneering application of cathodic protection.

Among countless subassemblages within the building requiring careful structural and seismic detailing were the stone columns, parapets, pediments, and interior partition walls. Exterior stone columns adorn the south, east, and west facades of the building. These cylinders of granite measure nearly 4 ft (1.2 m) in diameter and are interlocked with nothing more than friction and a 1 in. (25.4 mm) diameter by 8 in. (203.2 mm) long alignment pin. Although these columns are primarily a part of the facade system, they do carry a half bay of building structure at both the attic and the roof level. The columns were characterized as a seismic deficiency not only because their collapse would compromise the assemblies they support but also because 18 of the 56 columns are located at paths of primary egress from the building.

Forell/Elsesser

The Utah State Capitol was designed and constructed in the early 1900s under the direction of Richard Karl August Kletting, often referred to as the dean of Utah architecture. A significant component of the renovation program was the Utah State Capitol Building & Grounds Restoration Master Plan & Historic Structures Report, which was commissioned by the Utah State Capitol Preservation Board under the direction of David H. Hart, AIA, now the architect of the capitol, to ensure that the renovation program was aligned with historic preservation practices.

Several approaches were considered for the seismic bracing and stabilization of these columns, but most were deemed ineffective, too expensive, or aesthetically lacking and were abandoned. The final solution involved injecting epoxy into the joints between column segments, effectively “gluing” together adjacent segments and enabling the column segments to develop tensile stress across joints and act as a solid monolithic column. The epoxy bonding was limited to the interior of the joint interface, where it could be completely hidden, while the outer 1 in. (25.4 mm) of the joints was repointed to match its previous condition. The final result is a series of stacked granite columns that can now develop significant tensile stresses across their joints and have an appearance exactly matching the original condition.

The building’s massive parapet and pediments are composed of unreinforced brick clad with stone. Experience has shown that earthquakes exact a heavy toll on assemblies of this type. The brittle assemblies of unreinforced brick, coupled with the precarious location of the parapets around the edge of the roof and the gable-shaped pediments above the primary entrances, were seen as classic seismic deficiencies common to buildings of this type. Fortunately, the attic, with its approximately 6 ft (1.8 m) of space, provided the optimal location for new structural steel trusses to brace the massive pediments. The parapets too were braced at their center of mass with a steel-framed solution that also provides positive drainage for the roof system. Both the pediment bracing and the parapet bracing are totally inconspicuous. The parapets themselves were also cored so that grouted reinforcement could be installed to impart added strength, and many of the pins and anchors were replaced with galvanized or stainless steel elements.

Hollow clay tile is a very brittle material that can be found in abundance in older buildings of this type. It was used as a forming material or a backing material or simply for filling voids within architectural and structural assemblies. Hollow clay tiles measuring 4 in. (101.6 mm) thick were used as partitions and as a backing material for many decorative walls and other walls clad in plaster. This vulnerable material has little capacity for out-of-plane loading during seismic activity and therefore is cause for concern, particularly at paths of egress. Oftentimes such assemblies can be braced with such modern materials as steel studs. However, making connections to the brittle clay material is rarely easy. Drilling holes for wedge or chemical anchoring is difficult because the brittle material crumbles easily. An innovative approach was developed for attaching new metal stud bracing assemblies to existing hollow clay tile walls. To fasten the clay tile to the studs, a system of expanded metal lath and sprayed polyurethane was used to connect the two. Experimentation with polyurethane and other foam adhesives indicated a very good bond of the foam to the tile. When complemented with expanded lath that can readily connect to metal studs, the system becomes effectively braced and capable of remaining intact during seismic activity. This was the approach used for bracing hollow clay tile assemblies within the building.

The interior of the building is replete with marble ornamentation, much of it suspended above paths of primary egress. The potential for projectiles in paths of egress presented a challenge to the designers. An important directive for this project was to avoid disruption of the original ornamentation. Anchoring ornamental stone elements to substructure requires surface drilling so that the stone can be engaged with the structure beyond. Careful selection of a recessed face-mounted anchoring system, coupled with placement of anchors at natural flaws and discontinuities in the stone, made it possible to place hundreds of stone anchors in areas where historic preservation was of the utmost importance. To the untrained eye, the points of anchorage are virtually invisible.

Over the decades many spaces within the building were altered, and their configurations were hardly consistent with the intent of the original design. For instance, approximately 100 office spaces had been added to the building between its original opening, in 1918, and the fall of 2004. These changes and others altered the configuration of the building. As a result, many public spaces became smaller. At other locations the addition of suspended ceilings concealed decorative plaster moldings and other ornamentation that defined and characterized the building. As part of the renovation, the public spaces have been reclaimed, the original ornamentation has been revealed, colors have been restored, and the building has been brought closer to its original configuration than it has been for more than 80 years.

Reclamation of the original space meant the total count of offices in the building had to return to the original number. To facilitate this, the 90-year-old vision of developing a full capitol campus became a reality. Site plans and other drawings from that period depicted a quad-style configuration of buildings on Capitol Hill that included three other buildings. These were to be subordinate to the capitol and were to be constructed in a symmetrical arrangement that would allow for landscaping and other features that would make the site truly distinctive.

This vision of three subordinate buildings became a reality as a result of the renovation. Two new annex buildings were added at the east and west just north of the capitol and were designed to complement the State Office Building, which had been added to the site decades before. The annex buildings help to complete the original vision of Capitol Hill and provide the overflow space that made it possible for the capitol to be returned to its original configuration. Architecturally similar to the capitol, the annex buildings were detailed as subordinate structures. Their construction provided not only the badly needed overflow space but also a temporary home for the bodies of state government, thus enabling the capitol renovation to proceed unencumbered by building occupation.

Addition of the terrace structure along the perimeter of the capitol also helped realize the original vision for Capitol Hill. Renderings from that period clearly depict the terrace structure skirting the entire building. This structure was not built, probably for financial reasons. However, as part of the renovation design the original scheme has now become a reality. Not only does the terrace structure provide housing for mechanical and electrical equipment; it also provides other areas that make it possible to reclaim spaces within the capitol that were part of its original makeup. Furthermore, it provides for an assembly to mask the moat space—the 24 in. (609.6 mm) of void along the perimeter of the existing building where the base isolation system allows displacement. The terrace also implements a safety measure that could not possibly have been considered by those envisioning Capitol Hill 90 years ago: it provides a physical barrier that separates the capitol from an individual on the outside with nefarious intentions and a load of explosive cargo.

t is the very nature of construction to be disruptive and at times chaotic. Of considerable concern during this project was the protection of delicate finishes and spaces while the renovation work proceeded. One of the first undertakings of the contractor upon occupying the building was to protect these features. Marble surfaces and stairs were covered with protective wood sheathing. All paintings were covered throughout most of the project; they were uncovered only as part of the artistic restoration process. Such spaces as the State Reception Room (often referred to as the Gold Room) were closed and protected to the highest degree possible. In fact, spaces such as this were deemed of such value that the retrofit solution sought to preserve the original finishes to the fullest extent possible. The addition of new shear walls in abandoned ventilation shafts at the perimeter of the structure required the complete removal and replacement of existing finishes. Fortunately, the shear walls were not required along the entire perimeter. Thus such spaces as the Gold Room were avoided. Furthermore, since symmetry of form is not unrelated to structural behavior, dispensing with shear walls at certain locations, for example, the Gold Room, could be repeated in symmetrical fashion throughout the building. In essence the structural solution embodies a symmetry that not only pays homage to such spaces as the Gold Room but also optimizes structural performance.

Renovation projects and projects carried out for reasons of historic preservation are often bedeviled by unforeseen conditions whose effects on the schedule and budget are by no means benign. Although the Utah State Capitol renovation had its share of unforeseen issues, to a great extent they were accounted for through the creative management and project development structure mandated by Hart. Design of the project began in the fall of 2002 but construction did not commence until the fall of 2004. Nevertheless, a contingent of the construction management team, including cost estimators, was required to mobilize and occupy site construction trailers jointly with the project designers. The construction management contingent also included skilled carpenters and tradespeople capable of investigating the structure, sometimes with limited demolition, to truly understand the nature of the assemblies and materials that would be encountered during construction. As questions arose during two years of design regarding the nature of existing assemblies or conditions, the construction manager simply assigned various people to investigate the condition, clarify mysteries, and document the actual materials and configurations at hand.

All members of the design team, including all the engineering subconsultants, took advantage of this team structure during design. The result was simple, and the benefits were clear once construction began. The entire team had an incredibly distinct picture of the existing building. Many potential problems were anticipated and addressed and then incorporated into the cost model before construction even began. The final result was a project delivered on time and within budget. The premium for this was earlier mobilization by the construction manger and general contractor and perhaps a longer design period, a premium believed to be a mere fraction of the cost overruns that could have accompanied a more conventional approach.

The careful planning and management of this important project resulted in a virtually unprecedented outcome for a project of this scope and nature. The project was completed on time and within budget. From the early days of scheduling the project, Hart worked tirelessly and thoughtfully with Jacobsen Hunt to ensure that the project would be completed on time and within budget. The capitol was reopened with great fanfare this year on January 4, the day that commemorates Utah’s statehood. Thus the members of Utah’s legislature could convene at their true home. Legislators felt privileged to return to Utah’s formal statehouse and to find it so splendidly restored. They were also gratified to have access to state-of-the-art telecommunications systems rivaled only by those of statehouses designed from the outset to incorporate such technology.

The total cost of the project was approximately $212 million, funded directly as a special allocation from the state legislature and proportioned over the years of the project duration. Such a figure often prompts inquiries regarding a simple demolition and replacement of the building, a possibility considered here but abandoned when it became clear that the cost of a facility of similar magnitude and stature would have been four times as great. Moreover, there is the intrinsic value of this stately edifice, a building constructed at great sacrifice by Utah’s earlier residents. The record is clear in this regard. The capitol was built as a gift to Utah’s future, a structure that was to be handed down from one generation to the next and to be cared for, protected, and preserved in a manner consistent with the traditions and values of Utah’s citizens.  

Jerod G. Johnson, S.E., LEED AP, is a principal of Reaveley Engineers + Associates, of Salt Lake City. René Vignos, S.E., is a senior associate of Forell/Elsesser Engineers, Inc., of San Francisco.

Project Credits
Owner: State of Utah
Owner’s representative: David H. Hart, AIA, architect of the capitol
Architectural team: Capitol Restoration Group, Salt Lake City; Valentiner Crane Brunjes Onyon Architects, Salt Lake City; Max J. Smith Architects, Salt Lake City; and Schooley Caldwell Associates, Columbus, Ohio
Structural team: Reaveley Engineers + Associates, Salt Lake City, and Forell/Elsesser Engineers, Inc., San Francisco
Construction manager and general contractor: Jacobsen Hunt, Salt Lake City
Geotechnical engineer: AMEC, Salt Lake City
Geoseismic engineer: AMEC, Riverside, California, and Geomatrix, Oakland, California