Ultimate Strength of Annular Reinforced Concrete Members Under Combined Actions

Annular reinforced concrete(RC) members are commonly used in bridge structures and offshore platforms. These RC members often fail under the combined actions of axial force, bending moment, shear force and torsion load in hazards of earthquake and wind. It is very important to study the failure mechanism of annular RC members under combined actions. This study proposes a model to analyze the ultimate strength of annular RC members under combined actions using limit failure theory. A new method is established to determine the geometric parameters of the warped failure surface, and the new calculation model for the ultimate strength is obtained using the equilibrium conditions based on the geometric parameters and the stress distribution on the failure surface. The proposed model calculations are compared with a series of experimental results of annular RC members, and they correspond well with the experimental results. The proposed model is feasible for engineering application.     

3D Nonlinear Numerical Simulation of Intact and Debonded Reinforced Concrete Beams

To study the behaviour of reinforced concrete (RC) structures with sections of concrete removed and the reinforcement exposed, 3D nonlinear numerical analysis was performed upon both intact and debonded RC beams by using finite element techniques. The deformational characteristics and the ultimate loads were obtained through numerical models, as well as crack and stress distributions. The failure modes can also be deduced from computational results. Compared with intact beams, the normal assumptions of plane section behaviour is not hold true and the patterns of stress and strain are different in debonded RC beams. The numerical results show good consistency with experimental data. This kind of numerical simulation is a supplement to existing codes.     

FRP加固钢筋混凝土梁非线性有限元分析

在GFRP布加固钢筋混凝土梁受弯试验的基础上,考虑钢筋、混凝土的材料非线性行为,采用有限元法对FRP加固钢筋混凝土梁的受弯力学性能进行了数值模拟和分析,并与试验结果进行了比较.根据计算结果,分析了FRP加固钢筋混凝土梁的极限荷载、剥离荷载、FRP的应变分布、FRP端部区应力分布情况及受力机理.分析结果表明,非线性有限元法可以很好地模拟FRP加固钢筋混凝土梁的受力性能,并能预测FRP加固钢筋混凝土梁发生剥离破坏的荷载.     

基于弹性模量缩减法的随机极限承载力分析

为确定工程结构的随机极限承载力,结合弹性模量调整策略和摄动随机有限元法,提出一种基于弹性模量缩减法的随机极限承载力分析方法.首先利用摄动随机有限元法计算结构的随机响应量和单元可靠指标,并定义单元可靠指标均匀度和基准可靠指标,进而论证随机极限分析的比例加载条件及随机响应量的比例关系;然后通过有策略地缩减低可靠度单元的弹性模量,以模拟结构的失效演化历程,形成一系列静力容许应力场,进而根据塑性极限分析理论确定结构的失效模式及其对应的随机极限承载力.算例分析结果表明,该方法通常只需要迭代15步左右即可收敛,与蒙特卡洛法（抽样50万次）的相对误差在0.5%以内.      

碳纤维加固预应力钢筋混凝梁抗弯试验研究

为进一步了解加固预应力梁的受力性能,通过试验研究了碳纤维布加固预应力钢筋混凝土梁的抗弯性能,量测了各试验梁的钢筋、碳纤维和跨中截面混凝土表面的应变、梁的变形曲线、裂缝的形态和发展及正截面受弯破坏形态等;得出了试验梁的跨中荷载-挠度曲线,并且对试验结果进行了分析.试验结果表明,粘贴碳纤维布可以明显提高梁抗弯承载力,粘贴一、两层纤维布的完好梁承载力提高幅度分别为44.73%和55.81%;初始微裂缝对碳纤维布加固预应力混凝土梁的影响较小.     

拉弯扭共同作用下RC构件极限扭矩试验研究

根据８根钢筋混凝土拉弯构件扭强度的试验结果,对拉弯扭构件的破坏形态,纵筋及箍筋的应力应变规律等问题进行了分析研究。论文以变角桁架理论为基础,推导出拉弯扭构件相关方程,提出了在较大轴拉力情况下的计算拉弯扭构件极限扭矩的实用公式。     

Analytical Solutions to Strain Rates of Reinforced Concrete Simply Supported Slabs under Blast Loads

Based on the Duhamel integral, a couple of analytical solutions are derived to predict the strain rates of concrete and steel reinforcement in reinforced concrete slabs under blast loads and to estimate their variation over depth of a cross-section along the entire length of the member. The analytical approach utilizes the single-degree-of-freedom mode for the analysis of reinforced concrete simply supported one-way panels subjected to blast loads. These analytical solutions can give the strain rate profile for any cross-section at any time and permit variations of strain rate in each time step of numerical iteration method, thus making it possible to directly incorporate strain rate effects into non-linear dynamic response analysis of structural members subjected to blast loads.     

体外预应力加固钢筋混凝土空心板的试验研究

体外预应力加固技术施工方便、经济可靠,能有效地提高现有桥梁承载能力、改善结构性能,因而在既有加固梁桥中应用较多,但应用到钢筋混凝土空心板桥中还很少,因此其适用性还有待研究.在完成2片1∶1足尺空心板的制作、加固前后测试的基础上,对比分析了普通钢筋混凝土空心板用纵向体外预应力技术加固增强前后的挠度、应变、裂缝开展情况和极...     

Punching Shear Behavior of RC Slab-Column Connections with Nonrectangular Columns

This paper present an experimental study on the RC slab-colunm connections with nonrectangular colunms, namely cross-shaped column, T-shaped column and L-shaped column. The punching shear deformation and strength characteristics of slab-column connections with nonrectangular columns under punching shear load are investigated. Nine specimens with the three kinds of nonrectangular columns and two reference specimens with square columns are tested. The tested ultimate loads, deformations, and failur emodes of specimens are presented and discussed. Test results reveal that the punching shear strength and ductility of the connections with nonrectangular columns are higher than those of the corresponding connections with square columns, and also prove that the application of nonrectangular columns to flat-plate structure was feasible. Based on the test results, one method of calculating punching shear strength of connections with nonrectangular columns is proposed, which conforms with the current design practice of China. The test results on the punching shear strength are compared with the predictions of the formulas proposed by codes of several different countrie; and the predictions given by ACI code and China code are found to be conservative as the reinforcement ratio is increased.     

沉入式大圆筒防波堤稳定性分析的有限元强度折减法

沉入式大圆筒结构的抗滑、抗倾稳定性是靠地基土的嵌固作用来维持的,可通过弱化土体强度来实现对结构极限破坏状态的模拟.在该假设的基础上,建立了沉入式大圆筒防波堤稳定性分析的有限元强度折减法.结合某工程实例,利用有限元强度折减法,分析了沉入式大圆筒防波堤结构的稳定性,并与加载系数法计算结果进行了比较.分析结果表明:用强度折减...     

桥梁结构爆炸分析特点综述

笔者在文中论述了爆炸荷载的特点和冲击波超压 时间曲线,这是模拟爆炸荷载对桥梁结构作用的基础.爆炸荷载作用下,公路梁桥以局部破坏形式为主.进行爆炸效应的数值模拟时应注意到爆炸荷载对梁桥的作用效应为有限的区域,而不能简单地用均布荷载施加于桥面上.并介绍了爆炸模拟的原则和特点.     

矩形混凝土空心墩延性抗震性能试验研究

为深入认识混凝土空心墩地震损伤机理并评估其延性能力,对不同剪跨比、纵筋率及配箍率的方形和矩形空心墩试件开展拟静力加载试验. 观测各墩裂缝分布和损伤情况,分析桥墩的滞回性能、曲率及位移延性,并结合文献试验数据探讨既有塑性铰公式对空心墩顶部位移能力计算的适用性. 研究结果表明:各空心墩试件呈弯曲破坏特征,延性系数均在5.0以上,抗震性能良好;相同剪跨比下空心墩抗剪性能弱于相同外尺寸实心墩;增加纵向率能够适当提升空心墩侧向承载力和极限位移;在低轴压比下,纵筋率和箍筋用量对空心墩位移延性系数的影响规律不明显;空心墩塑性铰长度随剪跨比、纵筋强度或直径、轴压比的增加而提高,随混凝土强度的增加而降低,而配箍率的影响不显著;Mander、孙治国和JRA塑性铰模型预测值与试验值误差不超过5%,其中Mander公式计算效果最佳,可用于评估空心墩等效塑性铰长度;规范中较多采用的Paulay-Priestley模型高估了空心墩塑性铰长度,会使得桥墩抗震设计偏于不安全.      

临坡条形基础极限承载力上限计算

利用极限分析中的机动法,构建临近边坡条形基础承受极限承载力的二维机动许可破坏模式．根据外力功率与内部耗能相等获得极限承载力的目标表达式,并把其转化成了一个求含有非线性约束的极限承载力上限解最小值问题计算模型．通过编制和调用计算程序,对建立的计算模型采用序列二次规划法（SQP）进行了优化求解．研究结果表明：边坡倾斜程度δ和岩土体内摩擦角φ对临坡条形基础地基承载力影响较大;边坡坡角δ的增加将使地基破坏区域发生显著变化,使各分项系数Nr,Nc,Nq迅速减小;而内摩擦角φ增加对Nr、Nc、Nq的影响则相反．     

组合结构箱梁扭转极限承载力计算方法研究

对受扭组合结构箱梁进行理论分析,提出了配筋率与混凝土破坏模态和钢筋屈服模态之间的相互关系.提出了组合结构箱梁的扭转极限承载力计算方法.通过与实验结果进行比较,验证了所提出计算方法的正确性.     

Life Estimation of Reinforced Concrete Members after Fire

To solve the problem of life estimation of reinforced concrete （RC） members after fire, an analysis is made of the resistance of RC members after fire. On basis of the resistance, the life of RC members after fire is analyzed by using JC （Jukes and Cantor） method. Then the calculation models for the resistance and the life estimation of RC members after fire are put forward, and an example analysis proves their reliability and accuracy.     

组合结构箱梁扭转极限承载力计算方法研究

对受扭组合结构箱梁进行理论分析,提出了配筋率与混凝土破坏模态和钢筋屈服模态之间的相互关系。提出了组合结构箱梁的扭转极限承载力计算方法。通过与实验结果进行比较,验证了所提出计算方法的正确性。     

钢筋混凝土框架结构基于性能的塑性设计方法

为预测和控制钢筋混凝土框架结构在罕遇地震作用下的非弹性性能,基于功能平衡原理,提出了一种钢筋混凝土框架结构基于性能的塑性设计方法.该方法预先选定目标侧移和屈服机制,根据功能平衡方程即可得到结构的设计基底剪力;采用塑性设计法设计框架构件和节点,以达到预期的屈服机制和性能.采用此方法对一幢8层钢筋混凝土框架结构进行了设计,并采用动力时程分析法验证了该方法的可行性.研究结果表明,采用基于性能的塑性设计方法设计的钢筋混凝土框架结构最终呈现预期的屈服机构,非弹性性能沿结构高度分布均匀合理.      

受火后钢筋混凝土连续T形梁承载力试验研究

为探讨受火冷却作用对混凝土连续梁承载力的影响,对3根钢筋混凝土连续T形梁的承载力进行了试验研究,并用有限元法对试验结果进行了参数分析,提出了受火冷却后钢筋混凝土连续梁极限荷载的简化计算方法.结果表明:受火冷却后,钢筋混凝土连续T形梁的跨中屈服荷载、极限荷载和刚度均下降,承载力降幅明显低于刚度降幅;在受火120 min内,配筋率对受火冷却后钢筋混凝土连续T形梁的承载力有显著影响,而受火时间和混凝土强度的影响有限;按照简化计算方法计算的钢筋混凝土连续T形梁的极限荷载与试验值吻合较好.     

CFRP加固震损非延性RC框架抗震性能试验研究

为了研究碳纤维增强复合材料（CFRP）加固震损非延性钢筋混凝土（RC）框架抗震性能,制作并完成了1榀1/2缩尺两层两跨非延性RC框架子结构试件加固前后的拟静力试验. 将试件加载至峰值承载力,对采用外包CFRP法对震损节点处进行加固后的试件进行试验研究,获得了CFRP加固震损非延性RC框架的破坏形态与滞回曲线,分析了其刚度、强度、延性和耗能等抗震性能指标,并与完好结构进行对比. 分析结果表明:CFRP加固对提高震损非延性钢筋混凝土框架结构的最大水平承载力、初始刚度有限,对其耗能能力提升明显;加固结构的平均位移延性系数为2.81;当其最大层间位移角到达1/50时,加固结构依然具有较大的安全储备空间,加固后的震损非延性RC框架结构可以用于地震区.      

腹板开洞钢-混凝土连续组合梁受剪性能试验研究

为研究腹板开洞连续组合梁的受剪性能,以配筋率和混凝土板厚为变量参数,对5根腹板开洞连续组合梁进行了两点单调对称集中加载试验,采用剪力分离方法对应变试验数据进行计算,得到组合梁钢梁和混凝土板承担的剪力.试验结果表明:腹板开洞不仅降低了连续组合梁的刚度和承载能力,而且引起洞口区域混凝土板和钢梁截面的竖向剪力重分布,剪力主要通过洞口上方的混凝土板来承担,占到总剪力的 85%~90%;洞口区域不再符合平截面假定,最终连续组合梁洞口发生剪切破坏,组合梁丧失承载能力;增加混凝土板厚度和截面配筋率可以提高连续组合梁的承载和变形能力,并可以用来进行洞口区域的补强.