连梁拉杆装置是防止强震下RC梁式桥纵向落梁的有效措施,需要对其合理刚度取值进行研究.以典型的铁路RC简支梁桥为对象,采用基于FEMA440性能点轨迹法的能力谱分析方法,以现行《铁路工程抗震设计规范》设计谱及汶川地震动为需求,讨论了不同的场地类型和设防烈度下连梁拉杆的最优刚度分布.研究表明,场地类型对连梁装置刚度取值无显著影响,在8度罕遇烈度设防的四种场地下,连梁装置的刚度均可在0.05～0.15倍的梁体线刚度范围内取值,可有效抑制墩、梁相对位移及桥梁整体地震响应.设防烈度对刚度取值有显著影响,当PGA(peak ground acceleration)不超过0.2g时,可不予设置；当PGA为0.4g和0.6g时,连梁拉杆的合理刚度可分别取为0.1倍和0.2倍的梁体线刚度.采用非线性动力时程方法验证了上述结论的合理可靠性,可供桥梁抗震设计及规范修编参考.%Unseating prevention device is an effective measure to forefend beams from falling from a RC girder bridge, so it is necessary to study thoroughly the, reasonable range of the stiffness of this rubber-tie bar device. Based on the capacity spectra method of FEMA440, a typical railway RC simply supported girder bridge was taken to discuss the stiffness distribution of the device for different site soils and fortification intensities under the aseismic demand of current design spectra and Wenchuan Earthquake. It was indicated that the site soil has no obvious influence on the stiffness of the unseating prevention device, and the rational stiffness ratio is between 0. 05 ~0. 15 times of the linear stiffness of the adjacent beams for 8 degrees of high-level fortification intensity, under which the relative displacement between the piers and beams as well as the overall structural response can be effectively repressed; however, the fortification intensity has remarkable influence on the stiffness of the device; when peak ground acceleration (PGA) is less than 0. 2g, it is not essential to install the unseating prevention device, and when PGA is 0. 4g and 0. 6g, the reasonable stiffness ratio may be 0. 1 and 0. 2, respectively. The rationality and reliability of the above conclusions was validated with nonlinear time history analysis. The study results could provide a reference for seismic design of RC bridges and the revision of related seismic design codes.
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