No abstract

Recently, strong earthquakes are continuously occurring all over the world regarding, repair and strengthening of non-seismically designed structures. Presently, fiber-reinforced polymer (FRP) surface-bonding method is used as a quick and easy way to retrofit and strengthen damaged columns and walls. However, the inherent problems of the FRP surface-bonding method of bond degradation are adhesive interfaces and FRP sheet aging during service-life still. In order to overcome these problems, it is necessary to develop new materials and techniques that can induce monolithic behavior between the structural member and retrofit material by eliminating the bonding interface. One solution is to use repair and strengthening using stiff-type polyurea (STPU) developed as a seismic retrofitting material which can be applied by spraying method. In order to investigate the retrofitting effect of STPU, pseudo-dynamic push–pull test and dynamic shaking table tests are performed. The novelty of the study is that the RC columns strengthened with a newly developed STPU are tested for pseudo-dynamic (i.e., also represents the static behavior) and dynamic behavior. From the test results, overall strengthening effect of the STPU for both static and dynamic loading conditions can be understood, which can be used for retrofitting of concrete structures all over the world. The study results are discussed in detail in the paper.

In the construction of concrete bridges, the lighter dead load of decks can significantly reduce the number or size of substructure members, such as girders, piers and foundations. Although, the arch decks (ADs) ensure superior load carrying capacity and can have longer span length than flat decks (FDs), relatively minute number of studies was performed on longer span decks manufactured as arch shape to maximize the performance. In the previous study, a precast reinforced concrete (RC) AD with enhanced width of 2.5 m was developed. In this study, the behavior of precast RC AD under punching shear load was studied. Three real-scale AD specimens were tested and analyzed to understand its performance under punching shear loading. Different sizes of the ADs were manufactured to evaluate the punching shear capacity. The punching shear capacity and failure mode were obtained from the test, and the results were then compared to various design provisions. Finite Element Analyses (FEAs) were conducted to validate the experiment results and to verify the arching action of the AD with various thicknesses. The study results clearly verified that the AD had a higher or similar load-carrying capacity than the FD due to the arching action caused by the lateral restraint and arch shape, despite of thinner thickness of AD than FD. An analytical and prediction model for the punching shear behavior of ADs was developed and calibrated. The resulting models are described in a code-friendly formulation.