基于性能的偏心支撑钢框架抗震设计方法研究

偏心支撑钢框架的理想失效模式为每层耗能连梁均屈服,底层柱脚形成塑性铰,传统设计方法基于强度设计理论,很难保证结构的弹塑性受力状态。该文提出了偏心支撑钢框架基于性能的抗震设计方法(PBSD),该方法以结构的目标侧移和失效模式来预测和控制结构的非弹性变形状态,保证偏心支撑钢框架在大震作用下各层连梁均参与耗能,而其他构件仍保持弹性,即偏心支撑钢框架的层间侧移趋于均匀,避免结构薄弱层的出现,便于偏心支撑钢框架的震后修复。依据PBSD方法分别设计了10层K形和Y形偏心支撑钢框架算例,采用静力推覆分析和非线性时程分析验证该设计方法的合理性,分析结果表明：依据PBSD方法设计的偏心支撑钢框架的极限状态接近于理想整体失效模式,即结构非弹性变形主要集中在耗能连梁中发生,且各层连梁均参与耗能,没有薄弱层出现。该方法为偏心支撑钢框架的工程优化设计提供了参考依据。

A PERFORMANCE-BASED SEISMIC DESIGN METHOD FOR ECCENTRICALLY BRACED STEEL FRAMES

The ideal failure mode of eccentrically braced steel frames is associated with the yield of interstory links and the formation of plastic hinges at the column base of the bottom story. Traditional design methods are based on the strength design theory and can hardly represent the inelastic behavior of structures. In this study, a performance-based seismic design (PBSD) method for eccentrically braced frames was proposed. The inelastic deformation was governed by the target drift and failure modes of structures. All links dissipated energy under excessive seismic loading, while other members remained elastic. That is, the interstory drift was uniform along the height of the steel frame, and no weak layers occurred for post-seismic recovery of the structure. The validity and credibility of the proposed method was demonstrated by ten-story K-shaped and Y-shaped braced frame buildings, applying pushover analysis and dynamic elastic-plastic analysis. Results show that the ultimate state of the designed frames approached the desired ideal failure mode. The inelastic deformation mainly occurred at interstory links. All links were involved in energy dissipation and no weak layers appeared. The proposed PBSD method is expected to offer engineering design reference for eccentrically braced steel frames.