Jeffrey Chan, PE, Shamil Lallani, And Florian Meier, PE 2024-03-02 12:19:24
Dramatic steel cantilevers and an innovative façade design help an energy research laboratory save energy.
THE UNIVERSITY OF PENNSYLVANIA is expanding its facilities dedicated to energy research with the new Vagelos Laboratory for Energy Science and Technology (VLEST). The new building, located on the east side of campus near downtown Philadelphia, will house current and future energy research programs and laboratory spaces shared between the School of Arts and Sciences and the School of Engineering and Applied Science.
The 112,000-sq. Ft VLEST has a 1,600-ton structural steel frame and includes seven floors of research laboratories, workstations, collaborative spaces, and faculty offices. It sits on a former parking lot between the David Rittenhouse Laboratory building to the west and South 32nd Street to the east, aligning with the street and creating a new landscaped quad with the neighboring campus buildings.
A lowered Philadelphia SEPTA train line runs on the other side of 32nd Street, and nearby train traffic made noise and vibration key considerations when designing the lab spaces and supporting structure. On-site vibration studies informed the strategic location of the more sensitive laboratory equipment.
The design team initially considered both concrete and steel structural systems, but chose steel because it achieved the building’s cantilevering form and local steel bidders were more plentiful.
Building Form and Structure
The building’s unique architecture is a result of Behnisch Architekten’s early collaboration with engineers and consultants to integrate sustainable ideas and energy efficiency, aligning with the research institute’s core mission. The building’s form responds to the complex site and incorporates passive, low-energy strategies in its massing and façade design, which are informed by sun path and orientation.
The typical building floorplans are organized as parallel bars, with laboratory space on the east side and collaborative spaces, offices, and interconnecting stairs on the west. While there are no repeating floorplates, the common overlapping areas of the varying floors are an approximately 170-ft by 82-ft parallelogram. The architectural design rotates and extends half of the floorplate in two-story packages, creating angular, dynamic cantilevered volumes on the north and west sides of the building.
The shifted floorplates are achieved with cantilevered wide flange sections of the floor framing, which cantilever up to 25 ft. The cantilevered floor beam solution allows for a simplified structure with interior spaces unobstructed by diagonals had trusses been used, while also reducing fabrication costs. Steel wide flange columns are arranged on a 22-ft by 28-ft grid, taking lead from 11-ft-wide laboratory modules.
Most primary structural columns are continuous from foundation to roof, except for some columns on the east and north sides that are transferred at Levels 2 and 3. The structure and column layout were coordinated and optimized to maintain as many continuous columns as possible, achieving the complex architectural form while simplifying the structure and keeping structural costs down.
At the northwest corner of Level 7, a pair of heavy W36~487 girders cantilever west and create a 25-ft overhang. The backspan of one girder meets at an acute angle with another cantilever spandrel beam at a common column.
Structural engineer knippershelbig and fabricator Berlin Steel decided the two backspan pieces would be fabricated and lifted together. The resulting 21,400-lb joined peace was the heaviest pick on the project. From Level 7, exposed rectangular hollow structural system (HSS) hangers suspend the Level 5 floor structure below, resulting in a doubleheight space and a dramatic overhanging volume on the buildingfs west side.
Aligning building movements with the facade is always critical to a successful building project, and the VLEST is no exception. The buildingfs large cantilevers and associated de ections were carefully coordinated for compatibility with facade joints and have up to 5.8 in. Of anticipated movement after facade installation.
To meet the acoustic transmission targets of the laboratory spaces, Vulcraft 3VLPA acoustic metal deck was used as part of a 7-in. Composite deck floor system on the east portions of the floorplans over the laboratories. The remainder of the typical floors consist of conventional 4-in. Lightweight concrete slab over 3-in. Metal deck. Radiant heated floors were used in the shared and collaboration spaces in isolated areas on occupied floors.
The radiant tubing was embedded directly within the structural 4-in. Concrete slab on 3-in. Metal deck. The embedded radiant tubing was coordinated to be above the 4-in. Tall studs within the concrete slab on deck, allowing for greater flexibility of tubing clear distances from studs without compromising composite action.
Limiting the floor structure’s vibration is essential for sensitive laboratory equipment to function properly. The steel floor structure is designed to limit the vibration velocity of specific floor areas with a mix of VC-A (less than 2000 mips) for laboratories on the elevated floors and VC-D (less than 250 mips) for high-performance labs on the ground floor.
A dynamic analysis was performed using finite element analysis methods of the critical floor areas to design the beams for vibration limits. Floor vibration analysis was performed according to AISC Design Guide 11: Vibrations of Steel-Framed Structural Systems Due to Human Activity, 2nd Edition.
Five monumental stairs join adjacent floors from Levels 1 through 6. The interconnecting stairs and the resulting double height atriums link the open collaboration spaces upwards between the floors. The stringers of all the stairs, including those with up to 127° turns at the landings, span from floor to floor without intermediate posts or hangers at the landings. Vibrations and vertical accelerations under descending occupants often control the stair design for turned stairs with floating landings. Stair dynamic analyses and floor framing stiffness and connectivity were coordinated with stair structure to meet Design Guide 11’s vertical acceleration criteria.
Steel ordinary concentric braced frames surround the building’s two stair cores and one elevator core, resisting the building’s lateral loads. The east-west lateral system is 11.3 ft, a short distance compared to the building’s 136- ft height. The slender braced frames resulted in significant column net uplift at the foundation under lateral loads.
Two mat slab foundations up to 42 in. Thick distribute the building’s overturning under lateral loads and eliminate the need for any foundation tension elements to resist net uplift. To resist concrete breakout of the mat foundation, the columns’ anchor rods with net uplift extend down near the bottom of the mat, and vertical reinforcement was added in the surrounding breakout zone.
Façade Sunshades
The striking building exterior features a curtainwall with a screen of 267 sunshades on the east and west elevations. The Ethylene Tetrafluoroethylene (ETFE) membrane shades lower the energy needed to cool the building and diffuse daylight to reduce glare.
Each shade consists of two ETFE panels heat-welded together—an upper 80% VLT light diffuser membrane and a lower 30% SHGC sunshade membrane—stretched across a 3-in. Diameter powder-coated steel tube frame with a perimeter keder rope clamped into aluminum extrusions.
Sunshade geometry was developed through multiple iterations of form-founding to achieve good double curvature for efficient membrane action while also optimizing solar coverage and direction and contributing to the building’s performance-driven architectural expression. The design team made a special effort to implement the shades modularly within a unitized curtainwall system for cost-efficiency and constructability.
Each shade frame connects to a curtainwall unit’s mullions at three points via stainless steel knife plates, which are flipped and offset between adjacent units to achieve continuous diagonal sightlines along the elevations—despite stack joint interruptions.
The aluminum curtainwall mullions are steel reinforced to carry extra loads from the shades, which extend 5 to 6 ft from the façade. Installing units below overhangs and cantilevers was considered, as were strategies for façade cleaning and maintenance. The steel tube frames arrived on site shop-attached to curtainwall units. They were lifted together and attached to the building at depressed curtainwall embeds at the edge of slab on deck.
Due to consistent coordination and collaboration between the design and construction teams, the VLEST is nearing an on-schedule end to construction and is scheduled to open in fall 2024 as a cutting-edge energy laboratory—in practice and design.
Owner
University of Pennsylvania
Architect
Behnisch Architekten
Structural Engineer, Façade Consultant
knippershelbig
General Contractor
LF Driscoll Co.
Steel Fabricator, Erector, and Detailer
Berlin Steel Construction Company
Jeffrey Chan (j.chan@knippershelbig.com) and Shamil Lallani (s.lallani@knippershelbig.com) are senior associates, and Florian Meier (f.meier@knippershelbig.com) is a director, all with knippershelbig.
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