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Experimental results of new precast concrete beam-column connections constructed by post-tensioning precast beams to precast columns using unbonded tendons are presented. The connections consist of precast beams which has steel cap at its ends and precast columns which has steel band at the connection region. The steel cap and steel band are used to reduce damage in the plastic hinge region of precast beams. Four test specimens were subjected to reversed cyclic loading and comparisons were made between the behavior of presented precast concrete specimens and conventional precast concrete specimen.

This paper presents a beam-end damper which is developed to improve energy dissipation capability of the unbonded post-tensioned concrete structure. To investigate the damper effects, a cantilever beam with dampers was tested under reversed cyclic loading. The experimental results indicate that a high energy dissipation unbonded post-tensioned concrete structure is readily achievable. And a method of modeling the damper for nonlinear analysis is also presented. This paper presents a beam-end damper which is developed to improve energy dissipation capability of the unbonded post-tensioned concrete structure. To investigate the damper effects, a cantilever beam with dampers was tested under reversed cyclic loading. The experimental results indicate that a high energy dissipation unbonded post-tensioned concrete structure is readily achievable. And a method of modeling the damper for nonlinear analysis is also presented. Comparisons of the experimental results and calculated results lead to confirm adequacy of proposed model.

The widespread use of seismic isolation has necessitated a better understanding of the more complex aspects of isolation device behavior. The properties of seismic isolation devices depend upon the interaction between horizontal and vertical forces acting on the isolator. The actual hysteretic behavior of an isolation bearing under a structure subjected to severe earthquake shaking is influenced by the variation of vertical load on the isolator due to overturning forces. To identify the mechanical characteristics of lead-rubber isolators, cyclic shear tests of isolators under varying vertical load were conducted. The authors propose an analytical model for predicting the behavior of isolators under varying vertical load conditions. The model can reflect the influence of varying vertical load on isolator properties, and this capability is confirmed by simulation analyses and comparison with the cyclic shear test results. The analytical model is also used to investigate the behavior of lead-rubber isolators under loadings more severe than typical design conditions.