This paper presents a study of rubberized concretes designed by replacing coarse aggregate in normal concrete with ground and crushed scrap tire rubber in various volume ratios. The objective of the study was to investigate the effect of rubber types and rubber content on strength and deformation properties. The compressive strength, static, and dynamic modulus of elasticity of rubberized concrete were tested and studied. The stress-strain hysteresis loops were obtained by loading, unloading, and reloading on specimens. Brittleness index values were calculated based on the hysteretic loops. The experiments revealed that strength and modulus elasticity of rubberized concrete decreased with the increasing amount of rubber content. Compressive strength and modulus of elasticity of crushed rubberized concrete were lower than that of ground rubberized concrete. An American Concrete Institute equation could reasonably predict modulus of elasticity of rubberized concrete. Brittleness index values of rubberized concrete were lower than that of normal concrete, which means that rubberized concrete had higher ductility performance than that of normal concrete.

Fragility analysis constitutes the basis in seismic risk assessment and performance-based earthquake engineering during which the probability of a structure response exceeding a certain limit state at a given seismic intensity is sought to relate seismic intensity and structural vulnerability. In this article, the seismic vulnerability assessment of a subway station structure is investigated using a probabilistic method. The Daikai subway station was selected as an example structure and its seismic responses are modeled according to the nonlinear incremental dynamic analysis procedure. The limit states are defined in terms of the deformation and waterproof performance of the subway station structure based on the central column drift angle and the structural tension damage distribution obtained from the incremental dynamic analysis. Fragility curves were developed at those limit states and the probability of exceedance at the limit states of operational, slight damage, life safety, and collapse prevention was determined for the two seismic hazard levels. Results reveal that the proposed fragility analysis implementation procedure to the subway station structure provides an effective and reliable seismic vulnerability analysis method, which is essential for these underground structural systems considering their high potential risk during seismic events.

Self-compacting concrete (SCC) is being used in high-rise buildings and industrial structures which may be subjected to high temperatures during operation or in case of an accidental fire. The proper understanding of the effects of elevated temperatures on the properties of SCC is necessary. This paper reports the results of laboratory investigations carried out to study the effects of high temperatures ranging from room temperature to 800°C on the compressive strength of different water-cement ratio SCC and high-strength concrete. It is found that the hot compressive strength of SCC decreases with increasing temperature. Compared with normal-strength SCC, high-strength SCC possesses a larger compressive strength exposed to high temperature. Another result of tests is that addition of polypropylene fibers decreased the strength and probability of explosive spalling.