钢筋混凝土圆环形受压构件正截面承载力数值算法

根据规范中截面应变计算假定、正截面承载力极限状态下的截面应变特征以及数值积分法计算正截面内力的公式,构建了基于极限状态下截面应变分布逆向计算正截面承载力的方法,通过构造程序算法指导电算程序编写,从而减轻了按规范公式手算承载力的工作量。     

混凝土结构设计(二)——承载能力极限状态计算

<正> 三、承载能力极限状态计算承载能力极限状态计算包括正截面、斜截面、扭曲截面承载力,受冲切承载力和局部受压承载力计算以及疲劳强度验算。(一)正截面承载力计算原规范的正截面承载力计算是以极限平衡理论为基础,辅以经验公式为主体的设计方法,其基本假     

混凝土构件正截面受弯承载力计算方法的比较

以单筋矩形截面受弯承载力计算为题,根据规范就构件正截面承载力计算所遵循的计算假定条件,计算出构件正截面受弯承载力的理论解,并以此为根据,通过分析规范正文中的正截面承载力计算公式和规范附录F的计算公式对单筋矩形截面受弯承载力计算的配筋结果,阐明用规范附录F计算方法计算的配筋结果的安全性。     

混凝土梯形构件正截面受弯承载力计算方法

根据文献 [1]矩形构件正截面受弯承载力计算公式及其纵向受拉钢筋截面面积计算方法 ,推导出了混凝土梯形构件正截面受弯承载力计算公式及其纵向受拉钢筋截面面积计算方法 ,并将其受弯承载力计算系数制成了表格 ,可供大家设计梯形梁时使用     

钢管混凝土的截面形式及其承载力分析

针对钢管混凝土快速发展的现状,介绍了钢管混凝土的圆形截面、矩形截面、中空夹层截面和实心双层截面等形式及受力特点。为了能方便地分析各种截面形式的承载力性能,对几种截面形式的轴心受压极限承载力用大型有限元软件ANSYS,加入不同的混凝土本构关系进行了承载力分析计算,得到了这些截面形式的钢管混凝土的承载力-位移关系曲线以及应力云图;并同已有的试验或计算结果进行了比较,其结果较为吻合。对于钢管混凝土的截面选择和极限承载力的计算有一定的参考意义。     

锥形、阶梯形截面的正截面受弯承载力计算

分析了锥形、阶梯形截面的受弯承载力计算原理,并依据混凝土构件正截面承载力计算的基本假定,推导出适用于锥形或阶梯形基础与承台的正截面受弯承载力精确计算的理论公式。     

异形截面多腔钢管混凝土柱轴压承载力计算方法研究

异形截面多腔钢管混凝土柱截面形状不规则,受力复杂,其承载力不能按常规钢管混凝土柱计算方法计算。基于已有的6个两类截面的异形截面多腔钢管混凝土巨型柱轴压承载力试验结果,在分析评价国内外规范或规程承载力计算方法基础上,对异形截面多腔钢管混凝土柱轴压承载力计算方法进行研究。结果表明：相关规范或规程中按非圆形截面钢管混凝土柱计算公式所得轴压承载力大多低于试验值,偏于安全;基于Mander约束混凝土模型,将混凝土划分为有效和非有效约束区,提出了考虑折减约束效应的承载力计算式,计算所得承载力值略高于实测值,但相对差值在5%以内。     

L形、Z形截面压弯承载力实用计算方法

本文从工程人员常用的简化方法入手,采用非线性分析程序分析了大量算例,建立了Ｌ形、Ｚ形截面承载力与腹板矩形承载力之间的关系,将复杂的异形截面承载力计算转化为简单的矩形截面承载力计算,提出了一种既能定性又能定量的实用计算方法。     

异形柱截面抗弯承载力分析

异形柱截面的抗弯承载力不同于矩形截面,需对不同荷载角下的承载力分别计算。分析了异形柱截面抗弯承载力在不同荷载角下的特点,并给出了简化计算的公式,为在实际工程应用中提供参考。     

采用钢筋混凝土本构关系计算构件正截面承载力

采用双模量弹性理论研究了钢筋混凝土构件正截面承载力的计算。利用钢筋混凝土构件受压应力与应变本构关系,由截面静力平衡条件推导出了采用钢筋混凝土本构关系计算构件正截面承载力的方法,并将该方法应用于受弯构件和短柱的正截面承载力的计算。最后通过算例将该方法的计算结果与相关规范方法的计算结果进行比较。     

混杂纤维增强应变硬化水泥基复合材料的弯曲性能预测

基于混凝土断裂力学与细观力学理论,同时考虑钢纤维(SF)/聚乙烯醇(PVA)混杂纤维对应变硬化水泥基复合材料(SHCC)弯曲性能的影响,提出了一种适用于SF/PVA纤维混杂SHCC(SF-PVA/SHCC)弯曲性能的预测方法.开展了SF-PVA/SHCC弯曲性能试验,分析了纤维种类和掺量对SHCC抗弯强度、极限弯曲挠度及弯曲荷载挠度曲线的影响.结果表明所提出的弯曲性能计算方法可以较好地预测SF-PVA/SHCC的抗弯强度和极限弯曲挠度.     

RPC混凝土力学性能的试验研究

以抗折强度和抗压强度为指标,研究活性混合材、钢纤维掺量、粗细集料类别及养护方式对RPC混凝土抗折强度和抗压强度的变化情况。结果表明,当硅灰和粉煤灰掺量相等时,RPC混凝土拌合物流动性好,抗压强度和抗折强度最高,分别达到124.2MPa和19.2MPa。钢纤维掺量的增加可有效提高RPC的抗折强度和抗压强度,但RPC混凝土抗压强度提高的幅度小于抗折强度。钢纤维体积掺量在1.0%-2.0%之间较合适。通过三种不同的养护制度发现,采用标准养护方式时,抗压强度值最小,采用高温养护方式时,抗压强度值最大,热水养护的抗压强度值介于二者之间。     

矿粉对混凝土弯拉破坏性能的影响分析

针对混凝土的抗裂性能,研究了混凝土弯拉强度与特征拉应变随龄期的发展趋势。根据实验所得的混凝土弯拉应力-弯拉应变关系,提出了确定混凝土弯拉初裂拉应变的新方法即曲率法,利用切线模量法确定混凝土的弯拉极限拉应变,结合弯拉试验方法,研究了矿粉对混凝土1~60d龄期的弯拉强度、弯拉初裂拉应变以及弯拉极限拉应变的影响。根据试验研究表明利用应变准则更能充分描述混凝土的开裂过程。     

焊接H型钢局部纵弯失稳下抗弯强度计算

对由厚度为6.0mm、名义屈服强度为315.0MPa的钢板制成的H型钢进行了一系列弯曲试验,研究焊接H型钢的抗弯强度。截面几何形状和侧向边界条件决定了薄壁受弯构件的屈曲形式(局部屈曲、侧向扭转屈曲或交互屈曲)。翼缘或腹板宽厚比较大的受弯构件最先出现局部屈曲,继而发生侧向扭转屈曲,在交互屈曲作用下材料最终破坏。侧向扭转屈曲下局部屈曲对抗弯强度有负面影响。计算薄壁抗弯构件名义屈服应力时应将该现象考虑在内。对翼缘和腹板宽厚比不同的焊接H型钢梁进行了试验。进行有限元分析时将局部和侧向扭转屈曲模态的初始缺陷及残余应力考虑在内。基于考虑焊接型材局部和侧向扭转屈曲相互作用的试验和有限元分析结果,给出直接强度法(DSM)计算抗弯强度的简化公式。计算强度曲线与AISC规范(2005),EC3(2003)及试验结果进行比较,验证了DSM方法所计算的强度曲线的准确性。通过试验得出薄壁焊接H型钢的抗弯强度和结构性能的有关结论。     

滑移效应对钢-混凝土组合梁弯曲强度的影响及其计算

在采用栓钉等柔性抗剪连接件的钢-混凝土组合梁的交界面上存在相对滑移变形,它不仅使梁的挠度增大,而且还使组合梁截面的弹性抗弯强度减小,现行换算截面法尚未考虑这一不利影响.本文通过滑移效应对组合梁抗弯强度影响的试验和分析,建立了考虑滑移效应的弹性和极限抗弯强度计算公式.结果表明,考虑滑移效应的弹性弯矩计算值与实测值吻合较好.考虑强度极限状态时钢梁部分截面进入强化阶段的有利影响,滑移对极限抗弯强度的影响可以忽略不计,对于完全剪力连接和横向配筋率不小于0.6%的组合梁,按照简化塑性理论的等效矩形应力模型得到的极限抗弯强度计算值与实测值吻合良好.     

Flexural strength–ductility performance of flanged beam sections cast of high‐strength concrete

Flanged sections are often used for long‐span concrete beams to maximize their structural efficiency. However, although for the same sectional area a flanged section could render a higher flexural strength, it would also lead to a lower flexural ductility, especially when heavily reinforced. Thus, when evaluating the flexural performance of a beam section, both the flexural strength and ductility need to be considered. In this study, the post‐peak flexural behaviour of flanged sections is evaluated by means of an analytical method that uses the actual stress–strain curves of the materials and takes into account strain reversal of the tension reinforcement. From the numerical results, the flexural strength–ductility performance of flanged sections is investigated by plotting the strength and ductility that could be simultaneously achieved in the form of design graphs. It is found that (1) at the same overall dimensions and with the same amount of reinforcement provided, a flanged section has lower flexural ductility than a rectangular section; (2) at the same overall dimensions, a flanged section has inferior strength–ductility performance compared to a rectangular section; and (3) at the same sectional area, a flanged section has better strength–ductility performance compared to a rectangular section. Copyright © 2003 John Wiley & Sons, Ltd.     

Prediction of the flexural strengths of welded H-sections with local buckling

This paper describes the flexural strength of welded sections based on a series of flexural tests performed on H-sections fabricated from steel plates of thickness 6.0 mm with nominal yield stress of 315.0 MPa. Thin-walled flexural members undergo local, lateral-torsional or their interactive buckling according to the section geometries and lateral boundary conditions. Flexural members with the flanges or the web of large width-to-thickness ratios may undergo local buckling before lateral-torsional buckling and their interaction before the final collapse of the section. The local buckling has a negative effect on the flexural strength based on the lateral-torsional buckling. This phenomenon should be considered in the estimation of the nominal flexural strength of thin-walled flexural members. Welded H-section beams composed of the flanges and the web with various width-to-thickness ratios were tested to failure. The initial imperfections in local and lateral buckling mode, and residual stresses were included in the FE analyses. Simple design flexural strength formulas for the direct strength method (DSM) were proposed based on the test and FE results of welded sections to account for interaction between local and lateral-torsional buckling. The design strength curves were compared with the AISC specifications (2005), Eurocode3 (2003) and test results. The adequacy of the strength curve for the DSM was confirmed. A set of conclusions on the flexural strength and structural behavior of thin-walled welded H-sections was drawn from the experimental studies.     

基于细观本构模型的UHPC梁受弯全过程分析

为预测超高性能混凝土(UHPC)残余抗拉强度,通过细观力学分析,研究了纤维对UHPC残余抗拉强度贡献机理,提出了考虑纤维埋深、分布和取向的UHPC细观本构模型。基于UHPC细观本构、受力平衡方程和变形协调条件,建立了UHPC梁受弯分析模型和受弯承载力理论计算方法。经与8个UHPC梁试件受弯试验结果对比发现,文中提出的模型可以较好地预测UHPC梁受弯全过程响应和受弯承载力。基于基准试验梁的不同作用机制受弯贡献比例分析发现,纵筋配筋率从0增至2.5%时,受拉区混凝土对受弯承载力贡献从89.6%降至2.4%;纤维率从0增至3%时,受拉区混凝土对受弯承载力贡献从0增至22.1%。计算结果表明,对于低配筋UHPC结构,混凝土抗拉贡献应予以考虑。     

粗骨料UHPC的基本力学性能及弯曲韧性评价方法

为探究粗骨料UHPC的基本力学性能及自由收缩性能,进行基本力学性能试验及自由收缩试验,并与钢纤维混凝土、UHPC的性能进行对比。评议现有纤维混凝土弯曲韧性评价方法的优点和不足;提出可量化确定UHPC梁弯拉初裂点的偏移法;分别从能量和等效弯拉强度两个角度优化UHPC弯曲韧性的评价方法,并对3种混凝土的弯曲韧性进行评估。研究结果表明：相比于UHPC,粗骨料UHPC的弹性模量提高了10%,立方体抗压强度降低了15%,抗弯拉强度降低了6%;粗骨料UHPC的抗弯拉强度为钢纤维混凝土的1.8倍。0～91d 龄期范围内,粗骨料UHPC的自由收缩量与钢纤维混凝土基本相同;3d 和91d龄期的粗骨料UHPC的自由收缩量相比UHPC分别降低了63%和55%;通过添加粗骨料可降低UHPC早期收缩开裂的风险。提出的UHPC弯曲韧性评价新方法,克服了现有评价方法的不足,适用性强,可评价UHPC梁受荷全过程的弯曲韧性。粗骨料UHPC和UHPC的弯曲韧性明显优于钢纤维混凝土;相比UHPC,粗骨料UHPC的峰前弯曲韧性指数与峰前弯曲韧性比最大降幅分别为28%和22%;峰后弯曲韧性指数与峰后弯曲韧性比降幅均在11%以内。     

Flexural strength of a hybrid member for culverts consisting of mortar-filled steel tubes laterally connected by headed reinforcements

In this study, the temporary structural system for a trenchless method was developed. The developed structural system is a type of hybrid member consisting of mortar-filled steel tubes laterally connected by headed reinforcements. This lateral connection gives this system not only longitudinal but also lateral stiffness. Experimental studies were carried out to evaluate the flexural strength of the developed hybrid structural system. Behaviors of each component of this structural system, such as wing plate, connection plate and headed reinforcement were also studied. Experimental results showed that the developed system had superb flexural strength. The wing plate and connection plate had a positive effect on the flexural strength. Based on the experimental results, a simple design equation to evaluate the flexural strength of the developed structural system was suggested and compared with experimental results.