The Dynamic Response of Concrete Filled FRP Tubes Subjected to Blast and Impact Loading

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Qasrawi, Yazan
Concrete , FRP , Impact , CFFT , Blast
Blasts and impacts are two of the severest loads a structure can experience. Blast experimenters, however, have observed that the load imparted to a circular member was lower than the predicted design load. Additionally, numerous investigations have established the superiority of concrete filled FRP tubes (CFFTs) over conventional reinforced concrete members. These observations indicated CFFTs’ potential to resist dynamic blast and impact loads. The experimental and numerical investigations presented in this thesis aimed to demonstrate the suitability of CFFTs to resist blast and impact loads, to determine the parameters that influence their behaviour under such loads, and to develop a design procedure for resisting these loads. The initial numerical investigation determined the reflected blast loading parameters experienced by a circular cross section. The experimental phase consisted of testing twelve full scale specimens, two monotonically, four under impact loading, and six under close-in blast loading. The monotonically tested specimens acted as controls for the entire program. The results of the impact testing investigation were used to develop and validate a non-linear single degree of freedom (SDOF) model. This impact phase also led to the development of relatively simple procedures for designing CFFTs under impact loading using either SDOF modeling or the conservation of energy. Analysis of the blast testing results led to the development of numerical procedures for obtaining an equivalent close-in blast loading for SDOF analysis of CFFTs and Pressure-Impulse diagrams. The use of SDOF modeling and conservation of energy in blast design were also discussed. Finally, a non-linear explicit dynamic model of CFFTs was developed using the commercial software ANSYS Autodyn. This model was verified using the experimental impact and blast test results and used to conduct a parametric study. The results of these investigations indicated that CFFTs were particularly suitable for blast and impact resistant applications, as their geometry diffracted blast waves and the addition of the tube increased their energy absorbing capacity significantly giving them additional strength and ductility. The tube also confined and protected the concrete core and simplified construction.
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