钢与混凝土组合梁的可靠度分析

建立了对桥梁中钢与钢筋混凝土组合梁可靠度分析的半随机过程模型,研究了考虑车辆荷载（包括活载和冲击荷载）与恒载组合作用于下组合梁的可靠度评估．TR荷载组合规则被用来考虑荷载效应之间的关系．运用系统可靠度评估的方法,组合梁被模型化为由混凝土板、剪力传递器和钢梁串联而成的结构系统．     

考虑土壤-结构共同作用影响的双曲冷却塔可靠度

本文建立了对风荷载、自重和温度荷载组合作用下的双曲冷却塔结构进行可靠度分析的半随机过程模型,研究了考虑土壤-结构共同作用、塔底用连续弹性支承和离散支柱所造成的可靠度评估差异.运用等效静态的方法,考虑湍流动态风荷载响应.将动态随机过程模型转化为静态随机变量模型.TR荷载组合规则被用来考虑各荷载效应之间的关系.以广东茂名90米双曲冷却塔作为算例,数值结果表明不考虑共同作用的设计是保守的.     

钢结构吊车梁疲劳动态可靠度研究

本文视吊车荷载与疲劳强度为随机过程 ,建立了基于极限应力模式的钢结构吊车梁疲劳动态可靠度分析模型 ,提出了对吊车荷载效应与构件疲劳强度进行统计分析的方法。并结合某工程现场实测荷载数据与模型疲劳试验 ,对某工业厂房吊车梁圆弧端进行了疲劳可靠度评估 ,结果表明本文建立的疲劳动态可靠度分析模型能很好对吊车梁圆弧端的破坏情况进行概率解释。     

采用国外木结构持续荷载效应系数时需注意的问题与探讨

基于加拿大的累积损伤模型,考虑欧美等国与我国地理环境、荷载分项系数等参数的取值不同。在考虑组合荷载为简化的恒载和雪荷载之后,进而采用蒙特卡洛仿真方法基于matlab得到给定木材构件在长期荷载作用下的可靠度指标进而得到持续荷载效应系数(DOL),并提出有关问题进行探讨。     

环境作用下侧面内嵌碳纤维增强复材加固混凝土梁抗剪可靠度分析

为了评估环境作用对侧面内嵌碳纤维增强复材(CFRP)加固钢筋混凝土梁抗剪可靠度的影响,在考虑环境作用的情况下建立了加固梁极限状态抗剪承载力功能函数时变模型;基于当量正态化法(JC法)计算不同恒载标准值与活载标准值比值下混凝土梁加固前后的时变抗剪可靠度,继而评估加固梁的服役年限。结果表明:混凝土梁抗剪可靠度随服役时间在早期呈现缓慢下降,而后期呈线性快速下降的趋势;加固梁相比未加固梁,可靠度有一定程度的提高。抗剪梁在达到80%的服役基准期之后,采用侧面内嵌CFRP技术进行加固,可以延长梁体的抗剪服役寿命,约为服役基准期的8%。     

荷载分项系数调整对钢筋混凝土梁可靠性的影响分析

为明确新版《建筑结构可靠性设计统一标准》(GB 50068-2018)中的荷载分项系数调整对钢筋混凝土梁设计安全性的影响,参考已有统计参数模型,采用蒙特卡罗法对钢筋混凝土梁进行可靠指标计算。考虑抗弯和抗剪两种破坏模式、四种常用荷载组合等情形,分别计算了荷载分项系数调整后钢筋混凝土梁可靠指标的变化。结果表明：荷载分项系数调整后,对于办公楼活荷载、风荷载、雪荷载分别与恒载组合以及办公楼活荷载和风荷载与恒载联合组合的四种情况,钢筋混凝土梁的抗弯可靠指标提高了约9.7%～16.9%,基本满足目标可靠指标3.2的要求;当抗力分项系数在1.5～2.2范围变化时,钢筋混凝土梁的抗剪可靠指标增加较小,增幅仅约为0.05～0.20;当抗力分项系数取2.2时,钢筋混凝土梁的抗剪可靠指标基本满足目标可靠指标3.7的要求。     

西安地区静压桩承载力可靠性统计分析

考虑与上部结构设计相匹配以及岩土工程学科自身发展的要求与趋势,利用可靠度方法来评价岩土工程的安全性,特别是桩基工程的安全性,是岩土工程可靠性理论领域研究的重点,且具有广阔的应用前景。本文在阐述岩土工程可靠性发展的基础上,进行了桩基可靠性基本原理研究。提出桩基一般要考虑承载能力极限状态和正常使用极限状态,并对极限状态方程的抗力和荷载进行讨论。利用中心点法,推导出桩基承载力可靠性指标计算公式。在收集和整理西安地区28个场地100组静压桩载荷试验数据的基础上,考虑三种基本荷载组合情况:恒载+办公楼面活载、恒载+住宅楼面活载、恒载+风荷载下,利用推导的可靠度公式计算西安地区静压桩可靠度指标,并对计算结果进行分析。     

轻钢结构承载能力设计中分项系数的确定

针对对可变荷载敏感的轻钢结构,应用现行规范中计算目标可靠度的校准法,主要考虑风荷载和雪荷载与恒荷载的简单组合,分别计算分析了轴心受拉、轴心受压和偏心受压三种构件的荷载和抗力分项系数,给出确保现行目标可靠度的分项系数的建议值,对轻钢结构的设计具有一定的指导意义。     

钢筋混凝土结构基于耐久性的可靠度设计方法

对处于氯盐环境中的混凝土结构,为使其在设计使用寿命期内具有合格的可靠度要求,基于结构抗力劣化过程的动态计算模型及动态可靠度分析,在我国 现行结构可靠度设计表达式基础上,引入结构耐久性系数γD来考虑抗力衰减对可靠指标的影响,并给出了耐久性系数的确定方法。针对50年设计使用年限 情况,考虑港口结构3种荷载组合以及5种可变荷载与恒载效应比影响,给出不同的环境条件、水灰比、保护层厚度下结构耐久性系数γD的取值。从而建立 了基于耐久性的可靠度设计实用方法。     

海洋大气环境下钢筋混凝土梁受弯时变可靠度分析

通过引入应力水平影响系数,建立考虑荷载影响的钢筋锈蚀速率时变模型。采用随机分析方法研究锈坑空间分布变异性对锈蚀钢筋混凝土梁可靠度的影响。通过把梁离散为许多小尺寸单元,将整个构件的失效概率转化为一系列单元的串联体系失效概率,采用蒙特卡罗法计算海洋大气环境下钢筋混凝土梁受弯时变可靠度。计算结果表明:对锈蚀钢筋混凝土梁进行时变可靠度分析时,考虑锈坑的空间变异性及荷载对结构劣化的影响十分必要。     

Behaviour of embedded steel plate in composite coupling beams

Plate-reinforced composite (PRC) coupling beam is fabricated by embedding a vertical steel plate into a conventional-reinforced concrete coupling beam to enhance its strength and ductility. Shear studs are welded on the steel plate surfaces to allow for proper load transfer between the concrete and steel plate. The present study focuses on the evaluation of internal load distributions and load sharing on the embedded steel plate as well as at the shear studs in composite coupling beams using the nonlinear finite element package ATENA. The proposed two-dimensional finite element model is able to simulate the overall load-deflection behaviour and internal load distributions of coupling beams subjected to bending and shear forces. The reliability of the model is demonstrated by comparisons with the available experimental results. This is followed by an extensive and carefully planned parametric study using the calibrated finite element model. Numerical results on the effects of steel plate geometry, span-depth ratio of beams and steel reinforcement ratios at beam spans and in wall regions are presented and discussed in this paper. The finite element model provides a better understanding of the behaviour of shear studs as well as plate anchorage in the wall regions and embedded beam region. Based on the numerical results, equations for quantifying the shear stud forces are established and a set of non-dimensional design charts for determining the internal forces of the embedded steel plates is constructed. Both of them are useful for engineers to design PRC coupling beams.     

初始挠曲对钢-混凝土连续组合梁受力性能的影响

讨论了钢材的初始挠曲对钢 混凝土连续组合梁的极限承载力与失稳屈曲临界荷载的影响。建立了钢 混凝土组合结构的非线性有限元分析模型 ,给出了初始挠曲的定量描述方法 ,分析了不同厚度腹板连续组合梁的失稳临界荷载 ,不同初始挠曲对相同厚度腹板的极限承载力和失稳临界荷载的影响 ,以及相同初始挠曲对不同厚度腹板的极限承载力和失稳临界荷载的影响     

基于Monte-Carlo法的钢-混凝土组合梁的可靠度

采用蒙特卡罗(Monte-Carlo)方法,对现行规范中简支组合梁的承载力计算公式进行了可靠度分析,研究了不同材料强度等级、不同荷载类型及不同抗剪连接件数量对组合梁可靠度的影响,得出了一些可供工程设计参考的重要结论.     

A new type of steel–concrete composite channel girder and its preliminary experimental study

A new type of steel–concrete composite beam that is specifically applicable to railway bridges is presented. The beam is featured with a channel shaped section. For such a section, the U-section steel beam is prefabricated with steel plates and the interior side of the channel is cast with concrete. The steel plates and concrete are integrated through shear stud connectors and work together to distribute loads. This type of structure not only inherits the characteristics of traditional concrete channel beams but also possesses its own unique attributes, such as advantageous mechanical performances, facilitating construction process, and low maintenance cost etc. To develop a design method for this new type of structures, and based on some FEM analysis, a static test of four-point symmetric bending was designed on a simply supported steel–concrete composite channel beam model with 1/3 sectional scale and 1/4 length scale. Preliminary research was conducted on its bending capacity, stiffness, stress distribution, crack diagram etc. Experimental results revealed that the steel plates and the concrete slab integrated through shear stud connectors can work well together and the channel beam model presented a bending failure mode. The flexural load carrying capacities and deformations of the composite channel beam were also analyzed by the Section analysis method, and the results agreed well with those from the test.     

包头钢铁公司新建住宅楼加固设计

包头钢铁公司新建住宅楼为底层框架、上部5层砌体结构,因设计错误,致使整个结构可靠性严重不 足。针对其各部分可靠性的差异,分别采用增设混凝土剪力墙和型钢组合梁、外包钢加固柱、外包钢加固梁、 预应力螺杆加固梁及局部砖墙外包钢板组合柱等方法,对原结构进行了全面加固。     

矩形钢管混凝土组合桁梁负弯矩区受力性能试验研究

矩形钢管混凝土组合桁梁由混凝土板和矩形钢管混凝土桁架组成,在竖向荷载作用下,其正弯矩区可充分发挥混凝土板和桁架的组合作用,但负弯矩区的力学性能较为薄弱且受拉混凝土板容易开裂。针对这一问题,提出了在负弯矩区混凝土板施加预应力以及布置局部释放剪切作用的剪力钉相结合的组合桁梁结构形式。采用跨中施加反向集中荷载模拟连续梁支点反力的方法,对2榀承受负弯矩的矩形钢管混凝土组合桁梁进行了静力加载试验,对其荷载-位移关系、裂缝发展规律、混凝土板应变分布、桁梁荷载-应变关系、钢与混凝土界面滑移及承载力进行了分析。还根据组合桁梁的简化力学模型对不同加载阶段的结构特征荷载进行了讨论。结果表明：采用局部释放剪切作用的剪力钉和混凝土板施加预应力的组合桁梁结构形式可有效提高其抗裂性能,但对受弯承载力影响较小;在加载过程中混凝土板的开裂和杆件的屈服导致结构塑性变形增大,最终节点处焊缝撕裂,组合桁梁丧失承载力;由简化力学模型计算得到的结构特征内力与实测值吻合较好,可为矩形钢管混凝土组合桁梁负弯矩区的设计和计算提供参考。     

钢箱-混凝土组合梁弯曲性能试验研究

基于当前钢-混凝土组合结构和钢管(方)混凝土结构在用于梁类结构方面存在纵向滑移和受拉区混凝土增加了结构自重等问题,提出了钢箱-混凝土组合截面梁。并通过5根钢箱-混凝土组合梁及2根空钢箱对比梁的模型试验,研究其弯曲性能。试验研究表明:钢箱-混凝土组合梁具有良好的抗弯性能和延性,符合平截面假定,极限承载力提高显著,试验中测试还表明钢箱中的混凝土与钢箱在受弯过程中纵向有明显的相互剪切作用,有利于充分发挥钢与混凝土各自力学性能。     

Experimental study on curved composite beams subjected to combined flexure and torsion

There are situations in which a composite steel–concrete beam is subjected to torsion, such as members that are curved in plan or straight edge beams. The concrete slab and steel beam contribute to the torsional strength and stiffness of a composite steel–concrete beam, but this composite action is usually ignored in design codes of practice, which leads to conservative designs. Therefore, this paper investigates the ultimate strength of curved in place composite steel–concrete beams. Eight curved in plan composite steel–concrete beams have been tested under a single applied load at mid-span. Partial shear connection has also been considered in these tests. The composite steel–concrete beams have been designed with different span/radius of curvature ratios. This paper further supports the view that, in the presence of flexure, there will be an increase in the torsional moment capacity, but the flexural moment capacity does not greatly increase in the presence of torsion. A model has also been presented to represent the bending–torsion interaction for curved in plan composite steel–concrete beams with full and partial shear connection.