In this research, carbon fiber sheet (CFS) substitute to lateral tie was used for torsional strengthening of PC member. To investigate the mechanical properties of CFS strengthened PC member subjected to torsion and torsional reinforcement effects of CFS, monotonic and cyclic torsional loading tests were carried out with specimens which strengthened by lateral ties and unreinforced specimen for comparison. From both monotonic and cyclic loading test results, it was proved that the CFS can increase the ultimate torsional capacity and cracking torque. And it was also confirmed that the CFS had sufficient reinforcement effect, and for CFS strengthened specimen, the cracks of concrete were dispersed and widths were small. Mechanical properties such as torsional rigidity retention, residual twist, resilience and ductility were excellent. As for three-dimension finite element method analysis, analysis results matched the results of monotonic loading tests well and tracked the cyclic torsional loading tests when both nonlinear properties and hysteresis properties of each material were applied. A calculation concept including torsional effective cross-sectional area and thickness of shearing flow for the torsional capacity of CFS strengthened PC member was proposed.

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This paper presents the results of un-stiffened cantilever column subjected to incremental or constant amplitude cyclic loading. The objectives of this study are to investigate the extremely low cycle fatigue life of the column and verify the proposed strain based approach. During the test, fatigue cracks initiated from the weld toe at the corner and propagated along the weld toe. Finally, the column ruptured without a local buckling. The failure of low cycle fatigue induced by large cyclic deformation has been elucidated. In a further step, the crack initiation life was estimated based on the local strain by proposed simple approach. It is indicated that correlation between the test result and the estimated life was good enough.

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After an extreme earthquake, evaluation of damage and operability of bridge structures is currently done based on visual inspection by bridge experts, and there is a need to develop sensing technology to enable speedy and accurate evaluation of the degree of damage and operability of bridge structures. This paper proposes an evaluation method of the degree of damage of bridge structures. A series of shaking table tests of reinforced concrete single-column models validate the effectiveness and accuracy of the proposed method. A series of dynamic analyses were carried out to evaluate the efficiency of the proposed method for multi-span bridge model. For preventing secondary disasters and securing the traffic network during a disaster, a system, which is designed to collect bridge damage information evaluated with the proposed method, is also developed.

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