This paper presents the development and experimental validation of a multizard bridge pier concept, i.e., a bridge pier system capable of providing an adequate level of protection against collapse under seismic and blast loading ͑but not acting simultaneously͒. A multicolumn pier-bent with concrete-filled steel tube ͑CFST͒ columns is the proposed concept, and the adequacy of this system is experimentally investigated under blast loading. This paper describes simplified blast analysis, multihazard design of bridge piers, and blast experimental program and results. Additionally, the results from the blast experiments are compared with the results from the simplified method of analysis considering an equivalent single degree of freedom system having an elastic-perfectly plastic behavior. It is found that prototype bridge CFST columns can be designed to provide both satisfactory seismic performance and adequate blast resistance. It is also shown that the CFST columns exhibited a ductile behavior under blast load in a series of tests at 1 / 4 scale. Maximum deformation of the columns could be calculated using simplified analysis considering a factor to account for the reduction of pressures on the circular column and determined from this experimental program.
Research was conducted to analytically investigate the blast-response and behavior of multihazard-resistant bridge piers having circular-shaped, concrete-filled steel tube (CFST) columns. Two different analysis methods, namely a single-degree-of-freedom (SDOF) dynamic analysis and a fiber-based dynamic analysis, were used for this purpose and calibrated with the maximum residual deformations obtained from 1=4 scale blast tests of CFST columns. It was noted that the structural response of SDOF dynamic analyses is sensitive to assumptions made in the load-mass factors needed to model structural components as an equivalent SDOF system. Fiber-based dynamic analyses showed that high-frequency modes of vibration have some influence on the structural response when subjected to blast loading. This study shows that different values of the shape factors, β (which reduces blast pressures when applied to a circular column), must be used with different analytical methods, along with assumptions and conditions behind these different analytical methods.
<p>The 2016 Kumamoto Earthquake occurred in central Kyushu, Japan, on April 14th with Mw 6.2 followed by the Mw 7.0 mainshock on April 16th. These earthquakes were mainly caused by the Futagawa fault and Hinagu fault where surface ruptures extended about 34 km long. Some of the bridges located in mountain area and close to the fault were damaged due to these near‐field earthquakes. Oginosaka Bridge is one of them and is a horizontally curved bridge with longitudinal and transverse slope, which is a feature of the bridges located in mountain area. The superstructure was rotated on plan and displaced transversely at both abutments to the opposite side, and there was an evidence of the deck‐abutment pounding in longitudinal direction. In order to investigate the seismic behavior of the curved bridge, nonlinear time‐history analyses including a deck‐abutment pounding interaction were carried out. The deck‐abutment pounding interaction considered in the analyses could capture the post‐impact response of the superstructure. The near‐field ground motions were used for the analyses. The analytical results showed that the curved bridge is susceptible to the deck rotation caused by pounding in longitudinal direction at the deck end under earthquake loading.</p>
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