Performance of Exterior Precast Concrete Cladding Panels in NEES-TIPS/E~Defense Tests on a Full-Scale 5-Story Building

Two full-scale architectural precast concrete cladding panels were tested in 2011 on a full-scale five-story steel frame building at the E~Defense shake table facility at Miki. Japan. Two full-height column cover panels were tested: a return cover 3D shape, and the matching half-width flat panel. The cladding specimens represented one type of standard U.S. cladding façade design where cladding is designed to accommodate inter-story drift though racking of individual panels. A 50 mm vertical seismic joint was installed between the two panels. The panels and connections were designed according to common U.S. practice and the connection hardware was fabricated in the U.S. as a subcontract to a California precast fabrication company. Due to the expense of shipping full concrete panels, the panels were cast in Japan with final installation overseen by U.S. personnel. Two issues evaluated during the experiments were: (1) the effect of three-directional ground acceleration on the cladding panels, and (2) the effectiveness of the current slotted-bolt sliding connection to allow for inter-story earthquake motion. Instrumentation measured the acceleration of the panels and the movement of the slotted connections. The panels were mounted on the 4^th floor of the steel frame structure, which was then shaken at the foundation with both fixed-base connections between the structure and foundation and two alternative isolation systems. The primary findings was that slotted connections were able to slide while being accelerated in a full scale 3D seismic motion and no damage was seen in the panels at inter-story drift ratios as high as 0.0075 radians. Detailed study of the panel performance for the fixed-base experiments is reported in the paper. Torsional twist of the structure was found to be significant thus drift of the panels was determined using the displacement of the floor plates at the perimeter of the structure rather than considering the panel drift to be equivalent to the drift of the center of mass of each story. Review of the accelerations recorded on the panels was inconclusive. High-frequency vibration resulted in spikes of acceleration well above the value expected to cause damage. Additional study is required to correlate the acceleration readings with panel performance. The results of the experiments indicate that modern detailing and construction practice should produce facade systems which will perform suitably in future earthquakes.