Blast Loading and Blast Effects on Rc Frame Buildings
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2011-03
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Addis Ababa University
Abstract
This thesis deals with the nature of blast loading and its effects on reinforced concrete frame structures, designed to withstand normal gravity and earthquake loads. Three dimensional and single degree of freedom (SDOF) nonlinear analysis programs have been used to determine the dynamic behavior of reinforced concrete elements under external blast loading. Section design property has been employed to model reinforced concrete structural elements in SAP2000. Moments M3 and M2 are considered to cause plastic hinges in flexural members and the axial-moment interaction (P-M2-M3) is considered to cause plastic hinge in columns. Equations of dynamic equilibrium have been solved using direct integration time history analysis. The solution algorithms are applied by utilizing Newmark’s Average Acceleration Method with one millisecond time step size. Numerical study has been carried out based on Unified Facility Criteria (UFC 2005) guideline from the US Department of Defense (DoD) to evaluate the performance of a building in resisting progressive collapse. It has been found that building designed according to the (EBCS) guidelines did not satisfied (UFC 2005) requirements to mitigate progressive collapse, and building designed according to the (UFC 2005) requirements could withstand blast loads result from detonation of 250 lbs (113.5 kg) at 10m standoff distance. The dynamic response of typical RC column subjected to lateral blast loading has been examined by performing nonlinear SDOF blast analysis. It has been found that the maximum displacement result using SDOF approximation method is comparable with SAP2000 result for 250 lbs (113.5 kg) charge weight at 10m and 7m standoff distances. But the maximum displacement difference ratio of this analysis model increases as the standoff distance decreases. Finally, it is recommended that guidelines on abnormal load cases and provisions on progressive collapse prevention should be included in the current Ethiopian Building Code Standard at least for special and important buildings.
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Civil Engineering