Kingstowne Section 36A (KT36A) is a 200,000 SF mixed use building currently being constructed in Fairfax County Virginia. When completed, the lower half of the building will serve as a parking garage serving the office tenants of the upper half of the building. The parking garage levels utilize flat slab concrete construction while the office levels use a composite steel construction. A more thorough description of the existing structure can be found in the first half of this report.
The purpose of Technical Report 3 is to analyze the lateral force resisting system found in KT36A based on ASCE 7-10 provisions for strength and serviceability requirements. For the purpose of this report, all lateral loads were viewed as being resisted by steel moment frames, steel braced frames, or concrete shear walls with no contribution from the gravity system in the structure. This is a conservative way for obtaining the loads on the lateral systems since in reality, the gravity system will see some small percentage of the lateral load, although usually not enough to impact the design of the gravity system. In order to efficiently achieve this for the entire building, a three-dimensional structural model was created using ETABS, a modeling and analysis software commonly used in the structural engineering profession for obtaining an accurate and realistic response of the structure. The uses of the model included:
– Finding the story shear resisted by each lateral element with a unit load applied and dividing this value by the story drift of the lateral element to obtain the relative stiffness of each element
– Obtaining the natural period of the building for different modes
– Determining the center of rigidity, center of mass, and center of pressure
– Finding the maximum design forces in members for different load combinations
– Determining maximum floor displacements and story drifts for the different load combinations
After conducting the analysis of the lateral system, different loading combinations were found to control in different directions of the building. All of the loading combinations analyzed also considered the lateral earth pressures acting on the first two and a half stories of the North face of the building. Considering story drifts, seismic loads control in the E-W direction while wind loads control in the N-S direction of the building. This makes sense considering the larger surface area for the wind to act on at the North and South faces of the building. Other controlling load combinations were also found to control the overturning moment of the building and the forces imparted upon certain lateral load resisting elements, all of which were found to be adequately resisted by the lateral system in the building.
|Title||Structural Design of Building – Concept and Option Report|
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