Abstract
AbstractThis paper presents the shake table test results of a novel system for the design of precast reinforced concrete bridges. The specimen comprises a slab and four precast columns. The connections are dry and the columns are connected to the slab by an ungrouted tendon. One of the tendon ends is anchored above the slab, in series with a stack of washer springs, while the other end is anchored at the bottom of the column. The addition of such a flexible restraining system increases the stability of the system, while keeping it relatively flexible allowing it to experience negative post‐uplift stiffness. It is a form of seismic isolation. Anchoring the tendon within the column, caps the design moment of the foundation, and reduces its size. One hundred and eighty‐one shake table tests were performed. The first 180 caused negligible damage to the specimen, mainly abrasion at the perimeter of the column top ends. Hence, the system proved resilient. The 181stexcitation caused collapse, because the tendons unexpectedly failed at a load less than 50% of their capacity (provided by the manufacturer), due to the failure of their end socket. This highlights the importance of properly designing the tendons. The tests were used to statistically validate a rigid body model. The model performed reasonably well never underestimating the median displacement response of the center of mass of the slab by more than 30%. However, the model cannot predict the torsion rotation of the slab that was observed in the tests and is due to imperfections.
Highlights
Modern bridge design should fulfill a number of requirements
This paper presents the shake table test results of a novel system for the design of precast reinforced concrete bridges
Different names have been used for similar concepts: damage avoidance design,[5] controlled rocking,[6,7,8,9,10,11,12,13] self-centering system,[14,15,16,17,18,19,20,21,22,23,24] precast hybrid systems,[25,26,27,28,29] hybrid sliding–rocking system,[30,31,32,33] pre- or posttensioned rocking,[34,35,36] and it has recently found its way to practice in New Zealand[37] and China.[38]
Summary
Modern bridge design should fulfill a number of requirements. Modern bridges should often (a) be constructed quickly; (b) be resilient, that is, avoid collapse, and suffer minimal or no damage under the design (or even a larger) earthquake. The above concept is based on the early work of Priestley and Tao,[1] Stanton et al.,[2] and the PREcast Seismic Structural Systems (PRESSS) project.[3,4] Different names have been used for similar concepts: damage avoidance design,[5] controlled rocking,[6,7,8,9,10,11,12,13] self-centering system,[14,15,16,17,18,19,20,21,22,23,24] precast hybrid systems,[25,26,27,28,29] hybrid sliding–rocking system,[30,31,32,33] pre- or posttensioned rocking,[34,35,36] and it has recently found its way to practice in New Zealand[37] and China.[38]. This paper claims that this dogma is not necessary, it results in unnecessarily large pile foundations It presents shake table tests of a slab supported on four precast columns. A detailed cost/performance comparison of conventional seismic isolation (i.e., spherical sliding or rubber bearings, which reduce the design shear and moment of bridge piers) and the suggested approach lies beyond the scope of this paper
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