Comportement sismique experimental et modelisation numerique des barrages-poids renforces par post-tension (French text).

摘要

Displacement controlled shear tests on post-tensioned concrete lift joint specimens with different surface roughness are conducted to develop a constitutive model for joints reinforced with ungrouted post-tension cables, and to determine the failure mechanisms. To validate the model and to study the rocking and sliding behaviors of post-tensioned dams, shake table tests are conducted on a 3.4m high plain concrete post-tensioned gravity dam model having a cold lift joint at about mid-height. Numerical simulations with the constitutive joint model are compared to the experimental results.; From the controlled shear tests, it is shown that the post-tension cable gives additional strength to the joint (i) by applying an additional normal load on the joint, and (ii) by the shear resistance that could be mobilized (cable dowel action). Tests performed on rough surface joints have demonstrated that the dilatancy phenomenon due to the asperities increases the post-tension force. A cable failure criterion is proposed from the combination of its axial and shear loads.; Dynamic tests on the 3.4m high dam model have shown that post-tension largely reduced the residual sliding displacements. This reduction is a function of the frequency content of the excitation. However, a single post-tension cable placed near the upstream face increases the upstream rocking response of the upper block, which is also a function of the frequency content of the excitation. Strong seismic excitation can induce cable failure at a lower value than the maximum tensile strength when significant shear displacements are taking place. The observed cable brittle failure results in sudden elastic strain energy release. Finally, the proposed post-tensioned joint model showed good agreement with the static and dynamic tests performed in evaluating the joint shear forces.