考虑累积损伤的坞式船闸裂缝扩展及钢筋锚固改进研究

坞式船闸受力复杂,河侧闸墙倒角附近易开裂,钢筋锚固长度设计为现行水工行业规范最小值时,裂缝扩展路径可能绕过锚固延长段,甚至引发倒塌事故。采用扩展有限元方法(XFEM)建立仿真模型,研究考虑累积损伤下的坞式船闸裂缝扩展规律,并对钢筋锚固提出改进措施。结果表明:考虑累积损伤的钢筋混凝土闸室裂缝扩展路径,均在相同荷载作用下素混凝土状态闸室的拉应力区内部或附近;倒角附近钢筋锚固长度取规范最小长度时,部分损伤情形中荷载作用下裂缝扩展路径会绕过闸室倒角附近钢筋锚固延长段,导致结构极限承载能力无法满足要求;将钢筋锚固段延长,使穿出素混凝土状态闸室拉应力区的钢筋长度等于规范最小锚固长度,可使锚固延长段穿过裂缝扩展路径,并减小裂缝扩展长度和钢筋最大拉应力,使结构满足极限承载能力要求。研究结果可为船闸工程事故防治和相关设计规范进一步修订提供依据。

Crack extension of dock-typed navigation-locks and improvement of reinforcing bar anchorages considering cumulative damages

The structure of dock-typed navigation-locks is under complex loads and is prone to cracks near the chamfering of the riverside lock wall. When the anchorage length of reinforcing bars is designed to be the minimum value according to the current hydraulic industry code, the crack propagation path may bypass the anchorage extension sections and even cause collapse accidents. Here, a simulation model of the navigation-lock structure was established using the extended finite element model (XFEM) to study the cracking law of dock-typed navigation-locks with the consideration of cumulative damages, and the improvement measures for the anchoring of reinforcing bars were put forward. The results show that considering cumulative damages, the crack propagation paths of the reinforced concrete lock chambers are all in or near the tensile stress area of the plain concrete lock chamber under the same loads. When the anchorage lengths of the reinforcing bars near the chamfering are designed to be the minimum value of the code, the crack propagation paths in some damage situations under the loads would bypass the anchorage extension sections of reinforcing bars near the chamfering of the lock chamber, resulting in the failure of meeting the requirements of the ultimate bearing capacity of the structure. When the lengths of the anchorage extension sections of reinforcing bars are stretched beyond the tensile stress area of the plain concrete lock chamber, and the exceeding parts are equal to the minimum value of the code, the anchorage extension sections can be made to pass through the crack propagation path, and the crack extension length and the maximum tensile stress of the reinforcing bars can be reduced to meet the requirements of the ultimate bearing capacity. The study results can provide a basis for the accident prevention and control of the navigation-lock structure, and for the further revisions of relevant design codes.