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Fig. 1 Structural Cofiguration
The lateral force resisting system chosen for the building is a five story reinforced concrete moment resisting system (Fig. 1). Such a configuration is commonly found in California. Connection details will be selected in consultation with Industry partners supporting the building construction efforts led by Englekirk Partners –the Carpenters/contractors cooperation committee. Candidate frame beam details include the innovative framing configurations tested in previous years at UCSD. These systems, which included use of high strength concrete, precast assemblies adapting ductile insert concepts and high strength steels, demonstrated superior performance over conventional special moment resisting frame connections.
The number of floors in this building requires a full-height elevator in the prototype building. The plan geometry of the typical floor was conceived to optimize the use of the LHPOST footprint of 40’x25’ (Fig. 2). This building will be rather flexible, which is suitable for the testing of displacement-sensitive NCSs. To stiffen the lower floors, it may be feasible to provide supplemental bracing to the building, thereby increasing the potential for large accelerations and supporting investigations of the response of forcesensitive NCSs – this option will be assessed once all NCSs are selected. We note that the diaphragm is discontinuous due to the current implementation of the stair and elevator opening – this is recognized as a realistic configuration in a building structure that one needs to address during design. The staircase, an important element of fire egress, will provide evidence of the interaction with rather flexible structural systems. Stairs will be provided with and without slip joints to accommodate the imposed drift. It is anticipated that stairs at those floors without a joint may attract significant story shear, which will likely damage the stairs and cause torsion in the building response. A shaft for an operating elevator will also be included in the building model.
Fig. 2 Conceptual Plan Layout at Lower Floors and Upper Floors
The building design lateral forces will be obtained using displacement-based design methodologies that were used in the design of the UCSD 7-story building test. Preliminary design indicates an effective first modal mass of 215 Tons at an effective height of 42 ft. from the base of the LHPOST platen. The base-shear seismic coefficient at overstrength for the building, including dynamic effects, has been estimated at 40% of the total building weight. This shear force is much less than the horizontal force capacity of the LHPOST of 1465 kip. Likewise, calculations show that the maximum overturning moment for the building system is well within the limiting overturning moment of 14,800 kip-ft for the bare table.
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