Performance and Capacity Assessment of Concrete Barriers Subject to Lateral Loading

Current specifications for concrete barrier design (AASHTO-LRFD Section 13) indicate that the yield line method (YLM) should be used to ensure that a barrier has the adequate flexural capacity to resist the demand imposed by the truck impact. However, ensuring appropriate shear behavior of the parapet is not clearly addressed. Two recent experimental studies suggested that punching shear, rather than flexural yielding, can be the dominant failure mode of concrete barriers subjected to lateral loading. These studies employed idealized static loading setups in the laboratory, which are not necessarily accurate representations of truck impact loading on a barrier. The objective of this study is to use computational simulation to systematically investigate the failure pattern of concrete barriers subjected to lateral truck impact and assess their behavior in both flexure and shear. A set of pushover tests on half-scale concrete walls are selected from the literature and the failure modes of the tested parapets are simulated and analyzed in detail. Static loading demands from the tests are compared with those from impact loading as computed from high fidelity truck impact simulations and the results used to assess the potential for punching shear failure. A punching shear model is proposed. It is shown that the punching shear capacity of the MASH concrete barrier considered, which has standard details, is substantially larger than its flexural capacity. Therefore, it is conservative to continue to design barriers for flexural capacity as is the current practice.