Q460高强度钢材混合截面钢梁延性与承载性能研究

发布时间：2018-07-23 20:02

【摘要】：受弯构件的抗弯性能参数主要包括抗弯强度和转动能力。现行抗震设计方法实际上允许构件在强震作用下产生非弹性变形,以满足设计经济性的需求。事实上,延性是评估结构非弹性的参数。影响构件延性的因素主要包括截面尺寸、支撑条件、荷载类型、加工偏差(初始缺陷和残余应力)及材料性能。本研究旨在考察高强钢工字型截面受弯构件的延性和承载力。共进行了6个高强钢工字型截面梁绕强轴弯曲的足尺试验,其中3个构件采用翼缘为高强钢、腹板为普通钢的混合截面,3个构件采用纯Q345钢截面。同时建立了钢梁的三维有限元模型,并用试验结果进行验证。验证时考虑了材料非线性和加工初始缺陷的影响,并引入实测的应力-应变关系。结果表明,试验和有限元分析得到的弯矩-转角曲线和极限承载力均十分一致。基于此,选取荷载工况、材料特性、截面类型、截面几何尺寸和侧向支撑情况等参数,开展了全面的参数分析。为了确保钢梁能够合理承载,规范中通常要求采用紧实截面,并对梁的侧向支撑条件进行了规定。现有研究表明规范中的宽厚比限值对于高强钢梁而言是不合理的。因此,本文尝试研究翼缘、腹板宽厚比和侧向支撑间距对于钢梁(包括混合截面梁和纯高强钢截面梁)延性的影响。本文基于等效塑性弯矩指标提出了一个新的计算构件在纯弯作用下转动能力的理论方法,并用数值方法对所提的理论方法进行了验证,以确保该方法的准确性。现行规范中截面分类考虑了截面对于局部失稳的敏感性,对于受弯构件设计而言至关重要。事实上,在众多现行规范中,对由翼缘或腹板失稳控制的截面,延性概念已经应用其中,但翼缘和腹板的限值是独立的。这种假设是不合理的,因为翼缘和腹板相互具有约束作用,这种相互作用必须考虑。因此,构件性能分级应该取代上述的截面性能分级。在构件层面上,现有研究提出了一种基于构件转动能力的受弯构件分类方法,这种方法考虑了局部失稳和相关失稳模式的相互影响,并收录到中国钢结构设计规范最新版之中。根据上述参数分析的结果,本文还提出了一种确定工型梁抗弯承载力的新方法,这种方法基于在设计过程中与截面分类独立的长细比参数,并考虑了局部与整体相互作用的不稳定性。事实上,本方法旨在简化现行的受弯构件设计流程。最后,开展了本方法与EC3和AISC的对比研究,结果表明本方法与现行EC3的结果十分一致。
[Abstract]:The bending performance parameters of bending members mainly include bending strength and rotation ability. The current seismic design method actually allows the inelastic deformation of the member under strong earthquake to meet the demand of design economy. In fact, ductility is a parameter to evaluate the inelasticity of a structure. The main factors affecting the ductility of the members include section size, supporting conditions, load types, machining deviations (initial defects and residual stresses) and material properties. The purpose of this study is to investigate the ductility and bearing capacity of high-strength steel I-section flexural members. Six I-section beams of high strength steel were subjected to full-scale bending tests around the strong axis. Among them, three members were made of high strength steel with flange, the web was a mixed section of ordinary steel, and three members were made of pure Q345 steel section. At the same time, the three-dimensional finite element model of steel beam is established and verified by test results. The effects of material nonlinearity and initial defects are considered, and the measured stress-strain relationship is introduced. The results show that the bending moment-angle curve and ultimate bearing capacity obtained from the test and finite element analysis are in good agreement. Based on this, the parameters such as load condition, material characteristics, cross-section type, cross-section geometry and lateral bracing are selected, and a comprehensive parameter analysis is carried out. In order to ensure that the steel beam can carry load reasonably, the compacted section is usually required in the code, and the lateral bracing condition of the beam is stipulated. Current studies show that the width-thickness ratio limit in the code is unreasonable for high-strength steel beams. Therefore, the effects of flange, web width to thickness ratio and lateral bracing spacing on the ductility of steel beams (including mixed section beams and pure high strength steel section beams) are studied in this paper. Based on the equivalent plastic moment index, a new theoretical method for calculating the rotation capacity of members under pure bending is proposed in this paper. The proposed method is verified by numerical method to ensure the accuracy of the method. The section classification in current codes takes into account the sensitivity of section to local instability, which is very important for the design of flexural members. In fact, the concept of ductility has been applied to the section controlled by flange or web instability, but the limit of flange and web is independent. This assumption is unreasonable because the flange and web are bound by each other and this interaction must be taken into account. Therefore, the component performance classification should replace the section performance classification mentioned above. At the component level, a classification method of bending members based on the rotation ability of members is proposed. This method takes into account the interaction between local instability and related instability modes, and is included in the latest edition of the Code for Design of Steel structures in China. Based on the results of the above parameter analysis, a new method for determining the flexural bearing capacity of beams is proposed. This method is based on the slenderness ratio parameters, which are independent of the section classification in the design process. The instability of local and global interaction is considered. In fact, this method aims to simplify the current design process of bending members. Finally, a comparative study of this method with EC3 and AISC is carried out. The results show that the method is in good agreement with the current EC3 results.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU391

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