基于滑移连接的防屈曲支撑钢框架节点开合效应控制与设计方法

Buckling-restrained brace (BRB) is one type of bracing members that can work as both conventional braces and metallic yielding dampers. Design of corner gusset connection between BRB and structure is of crucial importance to the seismic performance of steel buckling-restrained braced frame (BRBF). Previous study showed that the opening and closing behavior of beam-column joint under seismic action would subject the welded corner gusset connection to combined brace action and frame action. Such complicated action would lead to undesirable failure of the gusset connection prior to fulfilling the structural fuse function of BRB. In this research, an innovative corner gusset connection that allows relative sliding deformation between gusset plate and framing members is proposed to reduce the negative frame action effects. Through numerical, experimental and theoretical studies, this research aims to investigate (1) the mechanical behavior of the proposed connection under individual brace action and frame action, (2) the effect of concrete slab on the frame action induced by the proposed connection, (3) the differences of structural behavior between the traditional and proposed connections, and (4) the effect of different gusset connections on the seismic performance and failure modes of BRBF. Theoretical models for prediction of the brace action and frame action forces on the proposed connection are to be established, and the design approach considering the combined action is to be presented. The constructional details of the framing members surrounding the proposed connection are to be determined. It is expected that this research could contribute to advancing the design standards from the current state of element based design to tomorrow’s state of considering brace-structure interaction, and therefore improving the seismic performance and seismic design methodology of dissipative braced frame structures.

防屈曲支撑是兼具普通支撑和金属阻尼器双重功能的支撑构件，而支撑节点的设计是影响支撑钢框架结构抗震性能的关键。然而大震中钢框架节点存在开合变形，使支撑节点处于支撑力效应和开合效应的复杂受力状态而先于支撑发生失效。本项目提出可允许支撑节点板与梁柱之间产生切向滑移的新型连接方法以减轻开合效应的不利作用。通过基于子结构模型的数值、试验和理论研究，采用先分解后合成的方法，揭示新型节点在支撑力和开合效应单独作用下的受力机制，明确楼板对新型节点开合效应的影响与作用，比较新型与传统节点的受力性能差异，探讨不同节点类型对支撑钢框架抗震性能与破坏模式的影响。以此为基础，建立新型节点在支撑力和开合效应单独作用下的计算方法，并提出考虑两种效应共同作用的新型节点设计方法，明确相应支撑钢框架的大震构造要求。预期成果有助于突破国内外现行抗震设计标准停留于独立构件的局限，为提升消能支撑结构大震性能与设计的科学性做出贡献。

防屈曲支撑是兼具普通支撑和金属阻尼器双重功能的支撑构件，而支撑节点的设计是影响支撑钢框架结构抗震性能的关键。然而大震下钢框架节点存在开合变形，使节点处于支撑力效应和开合效应的复杂受力状态而先于支撑发生失效，无法保证支撑与结构在强震下协同工作。. 本项目聚焦中心支撑框架结构开合效应引致节点断裂这一国际难题开展系统研究，提出可允许支撑节点板与梁柱之间产生切向滑移的新型连接方法以减轻开合效应的不利作用，并在“滑移节点的合理选型与抗震性能优化”、“考虑支撑力和开合效应综合作用的滑移节点设计方法”、“含滑移节点的防屈曲支撑钢框架子结构地震损伤控制方法”三方面取得了代表性成果：. 1）发现了节点开合效应由切向和法向约束两部分组成，在滑移节点释放切向约束的基础上，通过梁端加强和弹性节点域把梁端塑性铰转移至滑移节点区域外，可进一步减小节点区的法向约束，提高滑移节点的受力性能。. 2）滑移节点在支撑受拉、梁柱闭合状态下的界面力可简化为一对等效力，其作用点位置与有效传力区域内连接边中点到支撑轴线的距离相关，当滑移节点螺栓应力比控制在0.8及以下时，可保证螺栓处于弹性状态，此时由滑移产生的支撑变形损失可忽略不计。. 3）所提出的地震损伤控制方法可有效保证子结构塑性区在预设位置产生，配合基于能力的子结构构件承载力设计和滑移节点设计方法，以及基于布置横向加劲肋的延性增强策略，显著提高了子结构在超大震下的变形能力。. 上述成果解决了支撑力与开合效应在节点的耦合问题，发展了基于协同变形理念的防屈曲支撑钢框架结构地震损伤控制方法，实现了子结构与耗能支撑在强震下的变形协同，对提高建筑结构在强震下的安全性具有重要意义。. 成果在Engineering Structures、Structural Design of Tall and Special Buildings、建筑结构学报发表（含网上见刊）高水平论文6篇，授权美国专利1件、中国发明专利1件，并被省级地方标准和CECS标准采纳，作为主要成果之一获得2019年度河北省科技进步一等奖。