Shuichi Fujikura

Experimental Investigation of Seismically Resistant Bridge Piers under Blast Loading

This paper reports the findings of research examining the blast resistance of bridge piers that are designed in accordance with current knowledge and specifications to ensure ductile seismic performance. Blast testing was conducted on 1/4 scale ductile RC columns, and nonductile RC columns retrofitted with steel jacketing. The seismically designed RC and steel jacketed RC columns did not exhibit a ductile behavior under blast loading and failed in shear at their base rather than flexural yielding. A moment-direct shear interaction model was proposed to account for the reduction of direct shear resistance on cross sections when large moments are simultaneously applied. This made it possible to match and explain the experimentally obtained behavior when direct shear strength was compared with the shear demand obtained from plastic analysis.

Dynamic Analysis of Multihazard-Resistant Bridge Piers Having Concrete-Filled Steel Tube under Blast Loading

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. DOI: 10.1061/(ASCE)BE .1943-5592.0000270.

Multihazard-Resistant Highway Bridge Bent

There are some similarities between seismic and blast effects on bridge structures: both major earthquakes and terrorist attacks/accidental explosions are rare events that can induce large inelastic deformations in the key structural components of bridges. Since many bridges are (or will be) located in areas of moderate or high seismic activity, and because many bridges are potential terrorist targets, there is a need to develop structural systems capable of performing equally well under both events. This paper presents the findings of research to establish a multi-hazard bridge pier concept capable of providing an adequate level of protection against collapse under both seismic and blast loading, and whose members’ dimensions are not very different from those currently found in typical highway bridges. A series of experiments on 1/4 scale multi-hazard bridge piers was performed. Piers were concrete-filled steel tube columns (CFST columns) with different diameters (D = 4”, 5” and 6”), connected to a steel beams embedded in the cap-beam and a foundation beam. Fiber reinforced concrete was used for the cap-beam and the foundation beam to control cracking, which was deemed desirable against spalling of the concrete. The CFST column exhibited a ductile behavior under blast load, and no significant damage was suffered by the fiber reinforced concrete cap-beam as a result of the blast pressures.