Influence of strain rates and load histories on the tensile damage behaviour of concrete

Abstract

Concrete structures are often subjected to dynamic loads, such as seismic, blast or impact loads. Under such loads, distinct changes may occur in the dynamic and damage behaviour of concrete. This paper presents the results of dynamic tensile tests of plain concrete specimens with axial strain rates ranging from 10−5/s to 10−1/s that were carried out on a servo-testing machine. Observed stages of damage evolution are divided into three phases: undeveloped, steadily developed and unsteadily developed. This study found that the stress threshold ratio of ultimate strength increases with strain rate, and that the initial tangent elastic modulus and Poisson's ratio are independent of the strain rate for the test specimens. Moreover, the tensile strength and critical strain of concrete increased approximately linearly with the logarithm of the strain rate, and an experimental relationship between strain rates and tensile strength, critical strain was established. Furthermore, dynamic tensile damage tests of concrete were carried out with axial strain rates ranging from 10−5/s to 10−2/s. The effects of loading histories on dynamic tensile strengths, dynamic stress–strain curves, and dynamic damage behaviour of concrete were studied. Results indicate that both dynamic tensile strengths and damage thresholds of concrete decreased while the given rated loading was applied compared with those samples that were not subjected to the load history. However, damage of concrete at the same stress ratio and strain ratio increased with the increasing load history.