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|Title:||ANALYTICAL AND EXPERIMENTAL ASSESSMENT OF REINFORCED CONCRETE BLOCK STRUCTURAL WALLS RESPONSE TO BLAST LOADS|
|Keywords:||Blast loads;Blast scaling;Experimental tests;Out-of-plane resistance;Probabilistic risk assessment;Reinforced concrete masonry;Risk;Site planning;Structural walls;Uncertainty|
|Abstract:||The current thesis focuses on estimating the damage levels and evaluating the out-of-plane behavior of fully-grouted reinforced masonry (RM) structural walls under blast loading, a load that they are typically not designed to resist. Twelve third-scale RM walls were constructed and tested under free-field blast tests. Three different reinforcement ratios and three different charge weights have been used on the walls, with scaled distances down to 1.7 m/kg1/3 and two different boundary conditions, to evaluate the walls’ performances. In general, the results show that the walls are capable of withstanding substantial blast load levels with different extents of damage depending on their vertical reinforcement ratio and scaled distance. It worth mention that the current definitions of damage states, specified in ASCE/SEI 59-11 (ASCE 2011) and CAN/CSA S850-12 (CSA 2012) standards, involve global response limits such as the component support rotations that are relatively simple to calculate. However, these quantitative damage state descriptors can be less relevant for cost–benefit analysis. Moreover, the reported experimental results showed that the use of quantitative versus qualitative damage descriptors specified by North American blast standards [ASCE 59-11 (ASCE 2011) and CSA S850-12 (CSA 2012)] can result in inconstancies in terms of damage state categorization. Therefore, revised damage states that are more suitable for a cost–benefit analysis, including repair technique and building downtime, were presented. These damage states are currently considered more meaningful and have been used to quantify the post-earthquake performance of buildings. In addition, a nonlinear single-degree-of-freedom (SDOF) model is developed to predict the out-of-plane behavior of RM structural walls under blast loading. The proposed SDOF model is first verified using quasi-static and free-field blast tests and then subsequently used to extend the results of the reported experimental test results with different design parameters such as threat level, reinforcement ratio, available block width, wall height, and material characteristics. In general, brittle behavior was observed in the walls with a reinforcement ratio higher than 0.6%. This is attributed to the fact that seismically detailed structural masonry walls designed to respond in a ductile manner under in-plane loads might develop brittle failure under out-of-plane loads because of their reduced reinforcement moment arm. In addition, increased ductility can be achieved by using two reinforcement layers instead of a single layer, even if the reinforcement ratio is reduced. Also, it is recommended to consider the use of larger concrete masonry blocks for the construction of RM structural walls that are expected to experience blast loads in order to reduce the slenderness ratio and for the placement of two reinforcement layers. Finally, a probabilistic risk assessment (PRA) framework is proposed in order to develop design basis threat (DBT) fragility curves for reinforced concrete block shear wall buildings, which can be utilized to meet different probabilities of failure targets. To illustrate the proposed methodology, an application is presented involving a medium–rise reinforced masonry building, under different DBT levels. The DBT fragility curves are obtained via Monte Carlo sampling of the random variables and are used to infer the locations, within the building premises, that are most suitable for the erection of barriers for blast hardening.|
|Appears in Collections:||Open Access Dissertations and Theses|
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|EL-SAYED_MOSTAFA_M_2014August_PHD.docx||Thesis||39.05 MB||Microsoft Word XML||View/Open|
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