密实截面组合梁的竖向抗剪强度Ⅱ:受负弯矩作用的组合梁

在负弯矩区段,虽存在严重的混凝土开裂,但组合梁的竖向抗剪承载力仍远大于钢梁腹板抗剪名义值.采用通用有限元程序ABAQUS 6.5,对密实截面组合梁负弯矩区的弯剪强度问题进行研究.分析结果表明,提出的有限元分析方法可以准确预测组合梁的弯剪强度,同时对组合梁的变形刚度也可以较准确地模拟.在此基础上,利用有限元方法,对剪力连接程度、混凝土强度、力比、混凝土翼板截面尺寸、剪跨长度等参数进行计算分析,回归得到组合梁负弯矩区截面考虑力比影响的竖向抗剪强度公式.研究发现,在负弯矩区段,组合梁竖向抗剪强度的提高,只来源于混凝土翼板的抗剪作用,组合作用的贡献可以忽略;采用建议的抗剪强度公式可以不考虑组合梁负弯矩区截面弯矩与剪力的相互影响.     

密实截面组合梁的竖向抗剪强度Ⅰ:受正弯矩作用的组合梁

挖掘混凝土翼板的抗剪潜力,充分利用钢-混凝土组合梁的组合抗剪作用,有利于进一步提高组合梁的经济效益.采用通用有限元程序ABAQUS 6.5,对密实截面组合梁正弯矩区的弯剪强度问题进行研究.分析结果表明,提出的有限元分析方法,特别是钢-混凝土的界面模型,可以准确预测组合梁的弯剪强度,同时对组合梁的变形刚度也可以较准确地模拟.在此基础上,利用有限元方法,对混凝土翼板截面尺寸、剪力连接程度、剪跨比等参数进行计算分析,回归得到考虑剪力连接程度影响的组合梁竖向抗剪强度计算公式.研究发现,在正弯矩区段,组合梁抗剪强度相对于钢梁腹板抗剪名义值的提高,不仅来源于混凝土翼板的抗剪作用,组合作用的贡献也很显著;采用建议的抗剪强度公式,可以不考虑简支组合梁弯矩与剪力的相互影响.     

负弯矩作用下腹板开洞组合梁受力性能试验与有限元分析

为了研究负弯矩作用下腹板开洞钢-混凝土组合梁的极限承载力及相关受力性能,对4根组合梁试件进行了试验研究和有限元分析。结果表明,负弯矩作用下的组合梁腹板开洞后,其刚度和承载力明显降低,洞口区域应变不再符合平截面假定;通过增加混凝土板厚度可以提高其承载力;混凝土翼板对负弯矩区腹板开洞组合梁的抗剪承载力有很大的贡献;洞口形状对其受力性能有较大的影响。     

钢-混凝土组合梁截面组合抗剪性能的试验研究

对4根密实截面钢-混凝土组合梁的组合抗剪性能进行了试验研究。试件全部采用简支,跨中两点对称单调静力加载,考虑抗剪连接程度及正负弯矩的影响。试验结果表明,组合梁负弯矩区的界面滑移规律与正弯矩区的不同,其大小对组合梁的抗剪承载能力影响较小。不论混凝土翼板是处于组合梁截面的受压区还是受拉区,其对组合梁截面的抗剪承载能力均有明显的贡献,目前规范仅计算钢梁腹板的抗剪作用偏于保守。按叠加法建立了计算组合梁抗剪承载能力的计算式,计算值与实测值吻合良好。     

钢-砼组合梁竖向抗剪承载力研究

在6根钢-火山渣砼简支组合梁和6根钢-火山渣砼连续组合梁试验的基础上,探讨影响组合梁竖向抗剪承载力的主要因素:混凝土翼板、名义剪跨比和力比等。试验与计算结果表明,在计算组合梁竖向抗剪承载力时,如果不考虑混凝土翼板的作用,计算结果将趋于保守,对于连续组合梁还应该考虑弯矩比的影响。     

钢-砼组合梁竖向抗剪承载力研究

在6根钢-火山渣砼简支组合梁和6根钢-火山渣砼连续组合梁试验的基础上，探讨影响组合梁竖向抗剪承载力的主要因素：混凝土翼板、名义剪跨比和力比等。试验与计算结果表明，在计算组合梁竖向抗剪承载力时，如果不考虑混凝土翼板的作用，计算结果将趋于保守，对于连续组合粱还应该考虑弯矩比的影响。     

钢-ECC组合梁负弯矩区受弯性能试验研究

纤维增强水泥基复合材料（Engineered Cementitious Composite,ECC）具有高延展性以及受拉刚化特点,应用于组合梁桥的负弯矩区时可有效减少桥面板的受拉开裂。完成了2根钢-ECC组合梁和1根钢-混凝土组合梁对比构件在负弯矩作用下的静力加载试验,通过试验研究了不同配筋率的ECC对结构受力性能特别是抗裂性的影响。试验研究表明：在负弯矩作用下,钢-ECC组合梁的刚度较钢-混凝土组合梁明显提高|由于ECC翼板的抗拉作用导致截面中和轴上升,钢梁受压区增大,构件延性有所降低|钢-ECC组合梁可有效提高结构的开裂荷载并减小裂缝宽度,提高配筋率有利于进一步减少ECC翼板的裂缝宽度。提出了钢-ECC组合梁的承载力与开裂荷载的计算方法,提供了挠度分析的方法和裂缝宽度的基本模型。     

钢砼组合梁竖向抗剪承载力的试验研究

在６根钢－火山渣砼简支组合梁和６根钢－火山渣砼连续组合梁试验的基础上，探讨影响组合梁竖向抗剪承载力的主要因素：混凝土翼板、名义剪跨比和力比等．试验与计算结果表明，在计算组合梁竖向抗剪承载力时，如果不考虑混凝土翼板的作用计算结果将趋于保守，对于连续组合梁还应该考虑弯矩比的影响。     

负弯矩作用下腹板开洞组合梁极限承载力有限元分析

通过有限元软件ANSYS建立了非线性有限元模型,对负弯矩作用下腹板开洞钢-混凝土组合梁的极限承载力进行了分析计算。将有限元结果与试验结果进行了对比,吻合良好,验证了有限元模型的准确性和可靠性。分析表明:负弯矩作用下的组合梁腹板开洞后,其刚度和承载力降低很大,通过增加混凝土板厚度可以显著提高其承载力,而增加混凝土板配筋率能有效提高其变形能力;混凝土翼板对负弯矩区腹板开洞组合梁的抗剪承载力有很大的贡献。     

被动式节能钢-混凝土组合梁结构的受力性能研究

设计了4组外包花纹钢-混凝土组合梁,研究了组合梁的荷载-挠度、荷载-应变和应变沿截面高度的分布曲线,并进行了相应地受力分析。结果表明,4组外包花纹钢-混凝土组合梁的破坏形式都为受弯破坏,梁端未见明显滑移;CACC-1、CACC-2、CACC-3和CACC-4组合梁混凝土翼板中钢筋屈服载荷作用时的实测挠度与组合梁极限载荷时的实测挠度的比值δ_(ut)/δ_(yt)分别为1.698、1.819、2.275和3.208,在负弯矩作用下,CACC-4组合梁的延性相对较差;同一截面不同位置的荷载-应变曲线可以较好的吻合,表明加载过程中钢梁底板不同位置的受力分布较为均匀;4种组合梁在有效宽度范围内的剪力滞后现象并没有影响到混凝土翼板中受力钢筋的共同作用效果;组合梁中配筋率的增加对开裂载荷不会造成明显影响,但是在相同载荷条件下,配筋率的变化会影响裂缝的产生和发展,组合梁混凝土翼板中配筋率愈大则对跨中裂缝的束缚作用愈强。     

爆炸荷载作用下钢-混凝土组合梁的动力响应及破坏形态分析

本文利用LS-DYNA软件对同冲量不同超压峰值不同时间的三种荷载工况下钢-混凝土组合梁的动力响应及破坏模式进行了研究对比,并对梁的变形过程、关键位置点的位移、速度、支座剪力和跨中弯矩进行了详细的分析。结果表明,在爆炸冲击波下,开始阶段混凝土板对钢梁有很好的保护作用,但混凝土易于破碎,钢-混凝土组合梁容易丧失共同工作的能力,剪切破坏是钢-混凝土组合梁的一种重要破坏形式。     

钢-压型钢板混凝土组合梁的极限负弯矩强度

组合梁的抗剪连接程度是影响组合梁极限承载能力的重要因素。为此 ,推导了压型钢板混凝土组合梁负弯矩强度计算公式 ,讨论了采用线性内插法的简化计算方法 ,分析了影响负弯矩强度计算的剪力连接程度     

钢-混凝土组合梁的简化非线性模拟

建立有效的宏观模拟方法,研究钢-混凝土组合梁的非线性性能,考虑了材料非线性和混凝土板与钢梁之间的表面滑移。通过组合梁宏观模拟和试验的对比,分析了这种方法的有效性。对单调正、反弯曲下的4根足尺组合梁进行了试验研究。结果表明:通过宏观模型能获得组合梁的非线性荷载-位移性能的重要特征。宏观模拟方法对简化形式和准确度做了权衡,是进行有限元分析的可行方法。采用数值宏观模型,进行负弯矩下钢-混凝土组合梁的参数研究,包含:混凝土板的受压强度、型钢翼缘和腹板的屈服强度、剪切连接程度。最后,对加载过程中的滑移和其对组合梁性能的影响进行了分析。     

Behavior of steel-concrete composite cantilever box beams under negative moment

Four steel-concrete composite cantilever beam specimens were tested to investigate their mechanical behavior under negative moment induced by concentrated loads at the ends of the beams. The failure modes, serviceability and ultimate bearing capacities of the composite beams with full shear connection were studied. The crack initiation and propagation were investigated with consideration of two types of shear connectors. Three kinds of longitudinal reinforcement ratios were also examined. The experimental results indicate that an increase in the reinforcement ratio is beneficial to the bearing capacity of the composite beams to some extent and that the shear stud connector is superior to the steel block connector with regards to the serviceability of the beams. Two numerical models, which were based on a concrete material model and an elasto-plastic material model, were employed to simulate the behavior of steel-concrete composite beams. The numerical calculation results show that the combination of the two models can be used to predict the longitudinal cracking load and ultimate bearing capacity of composite cantilever beams. Based on the experimental and numerical results, it was found that the ultimate bearing capacity of a steel-concrete composite beam under negative moment can be significantly affected by longitudinal cracks in the concrete slabs. An equation to predict the longitudinal cracking load of a composite cantilever beam under negative moment by concentrated load was proposed and found to have good accuracy.     

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.     

考虑剪力连接件刚度的钢-混凝土组合梁有限元分析

钢 -混凝土组合梁剪力连接程度是依据截面极限状态的抗弯强度定义的 ,即使是完全抗剪连接 ,组合梁的混凝土板与钢梁之间仍存在滑移。采用有限元分析 ,构造了混凝土板 -连接单元 -钢梁的组合梁有限元计算模型 ,推导了混凝土与钢梁界面有限元连接单元刚度系数 ,分析了不同剪力连接程度组合梁的受力与变形特性 ,研究了剪力连接程度对挠度和混凝土翼缘有效宽度的影响 ,并对照已有的试验数据和相关规范进行分析比较。     

体外索钢箱-混凝土组合连续梁非线性结构性能试验研究

钢箱-混凝土组合连续梁负弯矩区混凝土的开裂问题影响了这类组合结构向更大跨度的发展。针对这一问题,提出在钢箱-混凝土组合连续梁中施加体外索的新技术,研究施加体外索对增强钢箱-混凝土组合连续梁负弯矩区混凝土的抗裂能力,提高钢箱-混凝土组合连续梁弹塑性结构性能的有利作用。经对比试验表明,施加体外索后,钢箱-混凝土组合连续梁负弯矩区混凝土的开裂荷载提高2.8倍,组合连续梁的弹塑性抗弯刚度提高29.35%,承载力提高34.67%,结构性能显著提高。在试验研究基础上,分析钢箱-混凝土组合连续梁负弯矩区局部力学性能与整体非线性结构性能的关系,揭示体外索提高钢箱-混凝土组合连续梁弹塑性结构性能的力学实质,给出承载力计算建议。研究结果可作为体外索钢箱-混凝土组合连续梁工程应用和理论分析的参考。     

Field validation of UHPC layer in negative moment region of steel-concrete composite continuous girder bridge

Improving the cracking resistance of steel-normal concrete (NC) composite beams in the negative moment region is one of the main tasks in designing continuous composite beam (CCB) bridges due to the low tensile strength of the NC deck at pier supports. This study proposed an innovative structural configuration for the negative bending moment region in a steel-concrete CCB bridge with the aid of ultrahigh performance concrete (UHPC) layer. In order to investigate the feasibility and effectiveness of this new UHPC jointed structure in the negative bending moment region, field load testing was conducted on a newly built full-scale bridge. The newly designed structural configuration was described in detail regarding the structural characteristics (cracking resistance, economy, durability, and constructability). In the field investigation, strains on the surface of the concrete bridge deck, rebar, and steel beam in the negative bending moment region, as well as mid-span deflection, were measured under different load cases. Also, a finite element model for the four-span superstructure of the full-scale bridge was established and validated by the field test results. The simulated results in terms of strains and mid-span deflection showed moderate consistency with the test results. This field test and the finite element model results demonstrated that the new configuration with the UHPC layer provided an effective alternative for the negative bending moment region of the composite beam.     

Analysis of composite beams in the hogging moment regions using a mixed finite element formulation

Cracking of the concrete slab in the hogging moment region decreases the global stiffness of composite steel-concrete structures and also reduces the effect of continuity, thus making the structural behaviour highly nonlinear even for low stress levels. In this paper, the behaviour of continuous composite beams with discrete shear connection is investigated using a nonlinear mixed finite element model. The model includes appropriate nonlinear constitutive relationships for the concrete, the steel and tension stiffening effect. Furthermore, the discrete nature of the shear connection is embedded in the model and the tension stiffening effects are introduced in the analysis by using a concrete constitutive model proposed in the CEB-FIB Model Code 1990 which incorporates embedded steel. Special attention is paid to the hogging moment regions, where cracking occurs. Comparisons between the numerical analyses and experimental results in the current literature are undertaken to validate the accuracy of the model. Furthermore, a parametric study is carried out to study the influence of span length and degree of shear connection on the strength and ductility of continuous composite beams.