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Montclair State University, located in Montclair, N.J., is ready to accept students into its new 2,000-bed dormitory, less than 21 months after design started on the project. This is one of the first public/private partnership (P3) projects authorized by the State of New Jersey, where a private developer, in this case, Capstone Companies, of Birmingham, Ala., builds and operates a project on public land. Capstone Companies hired Terminal Construction Corporation, of Wood Ridge, N.J., as their design/build contractor, with Paulus, Sokolowski and Sartor Engineering, P.C. (PS&S), of Warren, N.J., as the architect/engineer.
The project consists of a 2,000-bed residence hall built on an abandoned rock quarry on the summit of the first ridge of the Watchung Mountains, with magnificent views of the New York City skyline. The project consists of two buildings, each with four wings and a central core area. The wings vary in height from six to eight stories, with footprints ranging from 7,500 square feet to 9,500 square feet. A 600-seat full service cafeteria is located on the ground floor of one of the wings. The total building area is approximately 550,000 square feet and the construction budget is in excess of $100 million. The project is seeking LEED Silver certification.
PS&S is the structural engineer of record on the project as well as its architect of record, site civil engineer, and MEP engineer. Since all major disciplines were in-house at PS&S, the company was able to efficiently use 3D BIM technology to design and document the project. Indeed, the design was completed in less than four months, with advance design packages for foundations, precast concrete superstructure, structural steel, and major mechanical equipment. The advance design packages also facilitated the code review by the State of New Jersey.
The foundation for the buildings was complicated due to the topography of the quarry site. In order to minimize rock excavation, the buildings were laid out to follow the site topography as much as possible. Nevertheless, there were instances where adjacent footings could be bearing at vastly differing elevations, separated by a high vertical rock wall. Extensive retaining walls were required for site features and roads around the buildings. Revit was used to accurately model these features, and the model was used to convey to the architect the layout of foundation walls and footings. In some cases grade differentials of up to two stories, or 26 feet, occur across the width of a wing. In this case the high side was filled while the low side was excavated, requiring a two-story-high center bearing/retaining wall running the full length of the building. This was accomplished through the use of buttress walls oriented perpendicular to the center wall, which was designed to engage sufficient dead load to resist the overturning forces. In addition, the slab-on-grade on the high side was designed as a diaphragm to transfer the lateral earth pressures to shear walls located along the end walls of the wing. This allowed the precast framing to be simplified without requiring special design to resist the unbalanced earth pressures. The varying rock elevations also resulted in top of rock elevations that were well below the floor slab elevation, in some cases by as much as 20 feet. Isolated spread footings with piers and deep grade beams were used to support the exterior precast bearing walls.
Site conditions also played a large and somewhat surprising role in the lateral analysis of the buildings. Normally, with heavy precast buildings it is expected seismic forces would exceed forces due to wind. However, due to the location, atop a ridge approximately 150 feet above the base of the ridge, the often overlooked topographic factor known as Kzt resulted in an 80 percent increase in wind pressures and caused wind to be the controlling load case for lateral design in the short direction of the buildings.
The building wings and the core areas were modeled in Revit Structures based on the architectural Revit layouts. Major floor and wall openings were imported from the architectural and MEP Revit models. This geometry was then exported and used to describe the buildings in RAM for analysis and design of the framing components. The wings are framed with 8 inch interior load bearing precast concrete walls with 8 inch concrete hollow-core plank floors and roof. Exterior walls consist of 11 inch composite insulated sandwich precast concrete panels. The core areas are framed primarily in structural steel with a light weight concrete topping over composite metal deck. Due to the relatively low floor-to-floor heights, beam depths were generally limited to W8s or W10s to allow for MEP systems to traverse through the core and run from one wing to the next. The cores were considered a hub for the operations of the buildings, and considerable coordination, facilitated by Revit, was paramount to the success of the project.
Each building includes two mid-rise cores that match the story height of the individual wings and a low-rise core that interconnects and allows communication between all four wings. The mid-rise cores are attached to a precast wing on one side and separated from the adjacent wing by an expansion joint. The cores are laterally stabilized by the main wing precast concrete shear walls and other core walls that provide support for elevator banks and stair towers. The lateral seismic and wind story shears associated with the cores were determined and provided to the precaster for inclusion into the design of the precast buildings. The steel framing was modeled and designed using RAM system, and the results were transferred back to the Revit Structures model with sections and details produced within Revit Structures.
The Revit Structures models were utilized by the structural steel fabricator and the precast concrete fabricator to produce shop drawings with a resulting schedule savings.
Navisworks was used to facilitate quality control, checking and clash detection between the difficult design disciplines. The various models were overlaid within Navisworks and a listing of coordination issues was produced. This listing was then utilized to make any necessary changes to eliminate the conflicts. On the Montclair State University project, the change order rate due to drawing issues was less than one third of 1 percent of the cost.
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PS&S has been using Revit Structures for virtually all of its work for more than 5 years. It has significantly enhanced productivity and improved quality and has been particularly useful with multi-discipline projects. These include a 50-story hotel tower and low-rise spa for Harrahs in Atlantic City, N.J., and the Red Bull Soccer Stadium in Harrison, N.J.
As most recently demonstrated with the Montclair State University project, this technology allows PS&S to significantly accelerate the design and construction of complex projects, while at the same time dramatically reducing the number and cost of change orders.
Todd R. Heacock, P.E., SECB, is senior vice president, and Glenn Kustera, P.E., S.E., is associate principal, PS&S, a design and engineering firm based in Warren, N.J. Contact them at theacock@psands.com and gkustera@psands.com. Learn more about the firm at www.PS&S.com.
