开孔冷弯薄壁型钢压弯构件在多种屈曲模态和约束作用下的破坏机理与承载力预测

Light steel prefabricated buildings are widely used in construction industry in recent years and this type of building also meets the medium and long-term development proposal in China. Cold-formed steel section members are usually employed as main structural members in the load-bearing wall system of light steel prefabricated buildings. Due to the serviceability of electric wires and pipelines, the perforations are necessarily located at the web of members. The influences of perforations on the stability and strength of cold-formed steel member have been investigated by researchers, but a definitive analytical solution and the influence mechanism of stability for perforated members have not yet been properly established. This project will provide an investigation into the structural behaviour of cold-formed steel perforated section members when subjected to combined compression and bending, detailed comparisons will be made in three stages, which are the characteristic of cross-section investigation stage, the structural behaviour of member investigation stage and the cold-formed steel load-bearing wall system investigation stage. By means of experimental investigation, analytical method and numerical simulation method, the influences of perforations on the bearing capacity and stability behaviour of shear bucking will be demonstrated, the influence mechanism of perforations on the stability of member will be revealed, the interactions of distortional buckling and global bucking will be investigated, and the design curves and design formulae of cold-formed steel composite wall systems will be proposed by large data results obtained from numerical method. The research results will provide theoretical support for the investigations of cold-formed steel perforated section members, and also provide technical support for the design code of cold-formed steel perforated section members. Moreover, the results will be significance for extensive application of the cold-formed steel load-bearing wall systems of light steel prefabricated buildings.

本项目以组合墙体中常用的开孔冷弯薄壁型钢C形压弯构件作为研究对象，结合结构工程、材料学、计算力学等学科的基本理论：在截面特性方面，利用试验手段对比研究有孔和无孔构件，并针对孔洞的几何特性进行参数分析，阐明孔洞对压弯构件截面承载力的影响机制，揭示开孔压弯构件腹板剪切屈曲的失稳机理；在构件结构性能方面，通过对开孔构件进行压弯试验并结合数值模拟分析主要影响参数，明确构件畸变与整体屈曲相关作用的失稳和破坏机理，并提出其承载力设计方法；在整体结构体系方面，构建在墙面板约束作用下开孔压弯构件的理论简化模型，结合开孔构件与墙面板体系的整体压弯试验和数值模拟结果，揭示在墙面板约束作用下开孔压弯构件的失稳和破坏机理，并提出在墙面板约束下开孔压弯构件承载力设计方法。本项目的研究成果将为开孔冷弯薄壁型钢构件的设计提供理论支撑，为相关设计规范的制定提供技术支持，从而进一步推广冷弯薄壁型钢组合墙体在工程中的应用。

近年来，轻钢装配式建筑因为其具有的绿色环保、轻质高强、施工速度快、劳动力需求小、环境污染少等优点正在被国内外广泛推广采用。以冷弯薄壁型钢构件作为主要受力构件的建筑是轻钢装配式建筑的主要形式。其中，冷弯薄壁型钢制成的组合墙体是其重要的竖向承重单元。为方便管线等设施通过，墙架柱的腹板处通常会设置等距连续或者单独零散的孔洞。.孔洞尺寸、位置和形式对构件的承载力和稳定性都有着重要的影响，无孔构件的设计方法不适用于开孔构件的设计。澳洲、北美冷弯薄壁型钢结构技术规范已对腹板开孔构件的设计做出相应规定，但我国的《冷弯薄壁型钢结构技术规范》并没有对腹板开孔构件提出具体的设计规定。因此，明确孔洞尺寸、位置和形式三者对冷弯薄壁型钢C形截面压弯构件截面承载力的影响机制；明确开孔压弯构件畸变与整体屈曲相关作用的失稳机理和破坏机理，并提出开孔压弯构件畸变与整体屈曲相关作用的承载力设计曲线和设计公式；即将完成开孔冷弯薄壁型钢C形压弯构件在受墙面板约束作用下的试验分析并明确开孔压弯构件在受墙面板约束作用下的失稳机理和破坏机理，并提出基于墙面板约束作用下开孔压弯构件的承载力设计曲线和设计公式。通过本项目研究发现，对于腹板开孔压弯构件，孔洞对于构件的承载力有明显削弱并且影响构件的破坏模式，畸变与整体屈曲相关作用较易发生。此外，进一步研究截面形式、孔洞率、偏心距离对立柱承载力的影响，丰富腹板开孔立柱的试验研究数据库，进一步优化直接强度法的设计曲线；在组合墙体中，开孔立柱构件受到墙面板的约束作用，故后续进行受墙面板约束开孔立柱的承载力试验并进一步对组合墙体进行研究。