The slender high rise buildings are wide spreading in Egypt and no probabilistic assessment procedures have been proposed or developed for seismic risk evaluation of these special buildings. So, the objective of this study is to numerically investigate the role of both edge shear walls and raft foundation projection out of the boundary of building in the seismic resistant of such structures. Several three-dimension models were developed including the subgrade modulus as a variable and the multipurpose commercial finite element program SAP2000 [6] was utilized for all runs in the current study. The loading is considered using acceleration time history with a peak ground acceleration of 0.25g provided in the new Egyptian code (ECOL2008)[2] for seismic loads on structures and building works. The results conclude that the slender high rise buildings provided with edge shear walls and raft projection insure significant improvement in the induced base shear and internal forces in the raft foundation. On the contrary, the study shows the large values of base shear in the corner columns under seismic loads in a projected raft foundation building. The results give a wide vision that can be used as an aid to the engineer for dealing with such slender high buildings.
The elevated cylindrical storage silos are lifeline structures and strategically very important, since they have vital use in industries. Silos are special structures subjected to many different unconventional loading conditions, which result in unusual failure modes. In addition silos are cantilever structures with the material stacked up very high vertically. The earthquake response of silo structures for the storage of bulk solids differs for elevated silos and silos supported directly on the ground. The walls of different type of silos are subject to earthquake loads from the stored mass, and these may substantially exceed the pressures from filling and discharge. The assessment of horizontal action of ensiled material due to seismic vent seems to be particular interest. This paper is concerned with the earthquake response of these structures, which has received little attention to date. A cylindrical silo wall and bulk solid is modeled by three dimensional finite solid l elements. The interaction effect between the silo wall and bulk solid is taking account by using the nonlinear approach proposed by Duncan and Chang. A then interface layer proposed by Desia is applied to describe the phenomena taking place on the surface between the granular material and silo wall. Coulomb's friction low was used for modeling of wall friction. An incremental iterative finite element technique is applied for dynamic analysis of wheat silos using SAP2000 structural software package. In this research seven reinforced concrete silo models with different height to diameter ratios were studied and analyzed in time history by using earthquake acceleration 0.5g applied to silos models. The resulting finite element silo pressures as the silo is full with and without earthquake excitation are compared with theoretical filling and discharging pressure. The result obtained revealed that the elevated silos response is highly influenced by the earthquake characteristics and is depending on the height to diameter ratio. Also the findings indicate that the squat silo (large diameter and height) are more resistance to the earthquake and more economical. The seismic responses of the elevated wheat silo such as top displacement, normal forces, shearing forces and bending moments in silo support have been assessed for earthquake records.
Executions of the shear walls along the exterior perimeter of slender high rise buildings enhance the efficiency of such buildings to resist the seismic forces. But uncertainties in the locations of shear walls are very high because of the demandable architectural openings (windowsdoors) in the exterior views of such buildings. So, this study presents a considerable interest in establishing design guide lines for numerical investigation of seismic response of shear walls taking into account such openings and their locations. Five three dimensional models of different configurations of the openings are chosen and compared to figure out the best installation of openings having more efficiency on the performance of shear walls under earthquake excitation. Computer generated models are analyzed by SAP2000 program[11] and the loading is considered using acceleration time history with a peak ground acceleration 0.25g provided in the new Egyptian code (ECOL2008)[13] for seismic loads on structures and building works. The comparative results showed that the top displacement, base shears and stress distributions around the openings depend on the openings arrangement system. The results of staggered opening system in the shear walls (spatial arrangement) are very much close to those resulted in the shear walls without openings than the other opening arrangement cases. Finally the staggered arrangement of openings between the stories in shear walls are suggested to be applied in engineering practice since it satisfies both the architectural and seismic requirements.
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