科研之友
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摘要
Precast concrete frames can sustain earthquakes with little damage, if their beams are not monolithically connected to strong columns but via: (a) unbonded post-tensioned cables, continuous and concentric along all beam spans in the frame, and (b) top and bottom bars which cross the joint unbonded while being well anchored in the beam at both sides of the joint. Such a frame can sway thanks to intermittent opening and closing of the dry interfaces between the beam ends and the columns, instead of plastic hinging and damage at the ends of the beams. A pocket in the foundation typically allows the precast column to sway, without plastic hinging at the base. As this detail is inefficient and increases the vulnerability of the column to blast or impact, it is replaced in the paper with monolithic connection of the column to an isolated footing, which is free to rock and uplift, unrestrained by tie-beams. The lateral load response of such a rocking type frame with two stories and two bays was compared to that of a fixed-base frame. The latter suffered heavy damage at the base of the columns and at weak links along the beam spans, whereas the former confirmed the ability of a dry-jointed rocking frame to significantly reduce structural damage. Certain yielding at the top of the ground-story columns in the rocking frame was due to the artificially low column axial loads, lower than those found in practice even in low-rise buildings. An analysis model appropriately accounting for the flexibility due to the opening of the dry joints and for uplifting (modeled by a pair of no-tension springs under each footing) was found to give good agreement with test results.
- 出版日期2017-11
