Abstract
Soil underneath a structure might affect the behavior and the overall response of the structure in seismic events. The role of loose soil conditions and the inclusion of soil-structure interaction (SSI) in the analysis are important issues that need to be addressed. Since steel structures are light, two configurations designed as spatial and perimeter are considered to study the effect of soil on the steel structural frames for the same building. The paper provides a parametric analysis on the influence of SSI on the overall performance of MRFs (Moment Resisting Frames) according to the provisions of Saudi Building Code (SBC) [1]. A case study has been developed in which spatial and perimeter moment resisting frames of 12, 6 and 3 stories residential buildings are designed using Saudi Building Code (SBC) prescriptions. A modal response spectrum analysis has been carried out to see the influence of SSI on the fundamental period of vibration, top story displacement and inter-story drift limitations. Moreover, a static non-linear analysis has been performed to investigate the performance of frames, thus allowing to identify the influence of SSI on the structural design of steel MRFs.
Highlights
The earth is an internally active planet and the increase and decrease in seismic activity for a certain region is a normal phenomenon
The fundamental period obtained from the codified formulation for 12, 6 and 3 stories are found to be 1.44 sec, 0.83 sec and 0.47 sec, respectively, which is lower than the one obtained by modal analysis (See Table 6); in this circumstance the code specifies that scaling factors for the design forces and drift must be applied
It is obvious that the fundamental period of vibration and the top displacement are higher when soil-structure interaction (SSI) was considered
Summary
The earth is an internally active planet and the increase and decrease in seismic activity for a certain region is a normal phenomenon. The fulfilment of the damageability criteria (inter-story drifts) would be difficult to achieve as the structure flexibility will be higher for higher fundamental periods To this end, satisfying drift limitations will enhance the member profiles drastically, especially beam sections, compared to column profiles, which will disturb the capacity design rules of the code or otherwise will lead to uneconomical design solutions. As per Eurocode 8 [6], the following conditions are believed to have strong influence and need to be incorporated in the design: 1) Structure where second order effects play a dominant role 2) Structures with massive or deep-seated foundations, such as bridge piers, offshore caissons and silos 3) Slender tall structures, such as towers and chimneys 4) Structures supported on very soft soils, with average shear wave velocity less than 100 m/s, such as clayey soils
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