This study aims to investigate the effects of very high strain rate on low-cycle fatigue behavior of structural steel under large plastic strain with strain rate order of 1.0 s-1 as expected during earthquakes. Low-cycle fatigue tests were conducted using compact-tension specimens at various strain rate levels. Fatigue life based on crack size indicated that the higher strain rate caused lower fatigue life in large plastic strain region. The energy approach was employed to clarify the low-cycle fatigue mechanism in this region. Finally, a prediction method for fatigue life regarding high strain rate effect in large plastic strain region is proposed in this study.

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According to visual inspection on the bridge site, the target bridge has major cracks in RC deck in the center span. This certain type of damage could affect structural performance and should be monitored. The structural health monitoring system was set up on the target bridge and the strain-based evaluation could be used to quantitatively determine bridge condition. The FE model of the bridge was modeled with various types of RC cracking pattern to represent the severity of bridge damage. The relationship between damage level and strain measurement is generated, As a result, Bridge monitoring curve based on strain index has been established.

This paper presents a simple numerical procedure based upon the projected gradient descent (PGD) and finite element method (FEM) for the shape optimization of laterally restrained columns to attain the maximum elastic buckling load under the specified volumetric constraint. The analysis of the buckling load is achieved via the formulation based on Euler-Bernoulli beam theory, the discretization by the standard finite element technique, and the determination of the least eigenvalue and the corresponding eigenvector via the power method with Rayleigh quotient. In the optimization, the profile of the cross-sectional area of the column is represented by piecewise polynomial interpolation functions. The gradient information and the projection operator required in PGD iterations are obtained explicitly in a closed form. A selected set of results is reported to demonstrate not only the good convergence behavior and accuracy of numerical solutions, but also the capability of the proposed technique to attain the optimal shape of columns for various scenarios.