薄壁不锈钢压弯构件的耦合失稳性能及设计方法研究

Stainless steel sees increasingly wide-spread use in modern structural applications, which poses an urgent demand for the corresponding research into the structural behavior and design methods. While the special behavior of stainless steel members under axial compression or uniaxial bending were investigated extensively, the experimental and analytical data about the beam-column behavior were rare. On the other hand, there have been new developments in the structural design theory during last two decades, which has the potential of considerably simplifying the design of thin-walled members. However, some further research is still necessary to fully implement the new design theory into design codes. Under such backgrounds, the current project aims at investigating the actual bearing capacity of thin-walled stainless steel beam-columns under the effect of coupled instability, and further exploring suitable design formulae for them adopting the latest design theory. The work will include: (i) carrying out a full series of experiments of thin-walled stainless beam-columns undergoing sectional-global interaction buckling, which reflects the key factors such as material properties, sectional slenderness, loading eccentricity and etc., (ii) developing and calibrating a detailed numerical model with the finite element method, and then running a parametric study with the model, (iii) developing a database comprising the experimental and analytical data from the aforementioned research and those from literature, and (iv) exploring some suitable format of design formula which reflects the key affecting factors in coupled instability behavior of beam-columns, and finally derive design equations from reliability study on the basis of existing strength database.

不锈钢结构应用的日趋广泛驱动着相关研究和设计规范的发展完善，然而有关此类构件特殊失稳行为的研究多针对轴压、单轴弯曲等简单加载条件，对于实际结构中普遍存在的压弯构件，其实际承载力性能的实验及分析较为有限。另一方面，近年来薄壁结构设计理论取得了新进展，可在简化设计过程的同时实现与传统方法相近乃至更优的精度，而将这一理论进展真正纳入设计规范尚需一定针对性的研究工作。在此理论和实践背景下，本课题重点研究薄壁不锈钢压弯构件的耦合稳定承载力及基于最新设计理论的设计方法：（1）展开系列的不锈钢压弯构件实验，反映截面-整体耦合失稳性能并体现材料特性、截面柔度、加载偏心等关键因素的影响；（2）建立、校准精细化有限元模型，并进行参数分析以在更大关键参数变化范围内考察构件行为；（3）综合本课题基础研究数据并整合文献中既有成果形成具有代表性的承载力数据库；（4）探究适应薄壁构件截面特征的准确可靠压弯构件设计公式。

薄壁不锈钢结构构件应用日趋广泛，然而针对其各类失稳性能的研究尚不完善。薄壁构件的设计理论近年来也取得了新进展。本课题工作重点为薄壁不锈钢压弯构件的耦合稳定承载力及基于新设计理论的设计方法研究，作为相关的基础性研究工作还涵盖了不锈钢受弯构件纯畸变失稳破坏及设计方法、空翼缘构件整体-畸变耦合失稳性能研究。. 开展了卷边C型不锈钢截面仅受畸变失稳控制时的破坏性能研究，进行了冷轧板材材性测试、几何缺陷高精度测量、侧向限位弯曲试验。基于ABAQUS开发了精细化数值模型、以试验数据进行校准并展开参数分析。结合试验及模拟数据总结畸变失稳承载力随材性、截面形式、截面柔度的变化规律，探讨了以受压翼缘与腹板交界处的应变监测判断畸变失稳点的实用方法。以直接强度法拟合得到了适用于C型和Z型不锈钢构件畸变失稳承载力的设计公式。相关成果已发表国际会议论文一篇，另有两篇期刊文章已完稿。以上述精细化模型为基础进行拓展参数分析，研究不锈钢空翼缘截面畸变-整体耦合失稳性能，探讨该类构件耦合失稳的设计方法，相关成果已发表国际会议论文一篇。. 不锈钢压弯构件耦合失稳研究包括系列精细化试验、数值建模及参数分析、设计理论及方法研究。试验选取卷边C形、I型及矩形截面构件，分别反映局部-整体、畸变-整体耦合失稳效应。试验中引入钢材材性、截面柔度、构件柔度、等效加载偏心等变化因素。受国内市场供应情况限制，前期规划的低镍双相体S32101不锈钢小批量采购始终未能实现，只得采用双向体S32205板材替代。试验所用的专用加载、缺陷测量装置均有较高精度要求、需专门加工。上述工作过程中若干非预期因素造成试验研究进度滞后于计划，当前有一部分构件试验仍在进行中。数值建模和设计理论研究也同步进行，已梳理压弯构件设计理论框架及两种具体设计思路。相关成果目前已申请发明专利一件，一篇期刊文章撰稿中，后续研究成果还将有2~3篇论文发表。