Mechanical Behaviors of Steel Reinforced ECC or ECC/Concrete Composite Beams under Reversed Cyclic Loading

摘要

Engineered cementitious composite (ECC) is a class of high performance cementitious composites with pseudo strain hardening behavior and excellent crack control. Substitution of concrete with ECC can avoid the cracking and durability problems associated with brittleness of concrete. In this paper, two series, totaling six steel reinforced beams with various transverse reinforcement ratios, ECC thicknesses, and shear span-depth ratios were tested under reversed cyclic loading. According to the test results, steel reinforced ECC beams show better seismic performance in terms of load carrying capacity, shear resistance, energy dissipation capacity, and damage tolerance compared with steel reinforced concrete beams. The extent of load capacity improvement strongly depended on the failure mode. Beams failed in shear showed more significant improvement than those failed in flexure. For the ECC/concrete composite beam, strategic application of ECC can lead to an increase of energy dissipation capacity. For the steel reinforced ECC beam without stirrups, final failure occurs in shear. However, the ultimate load capacity and deformation are comparable to the steel reinforced concrete beam with properly designed stirrups, and the failure process is ductile due to the strain hardening behavior of ECC materials.