钢-混凝土组合梁在负弯矩作用下抗剪性能的试验研究

通过3根钢-混凝土组合梁在负弯矩作用下的试验,研究了其变形发展及破坏过程,得到了组合梁的跨中剪力-挠度曲线、交界面滑移曲线和沿截面高度分布的应变变化曲线,分析了剪切连接程度、截面尺寸、剪跨比、材料强度、钢筋配置等因素对组合梁承载力和延性的影响。对钢梁进行了塑性分析,得出在负弯矩作用下钢-混凝土组合梁抗剪承载力的提高不是由于钢梁腹板的硬化效应所致,而是由于混凝土翼板的贡献,并提出了考虑混凝土翼板影响的组合梁在负弯矩作用下抗剪承载力计算公式。将计算结果与实测结果进行了比较,二者吻合良好。     

负弯矩区部分充填混凝土对窄幅钢箱-混凝土组合梁受力性能影响试验研究

为了研究充填混凝土对窄幅钢箱-混凝土组合梁负弯矩区的荷载-挠度特征、截面应变分布、抗弯刚度、钢箱梁的约束机理以及承载能力的影响,对5根部分充填混凝土窄幅钢箱-混凝土简支组合梁试件和1根全充填混凝土试件进行了静力加载试验。试验结果表明：在负弯矩作用下,配筋率和剪力连接程度对窄幅钢箱-混凝土组合梁的受力性能影响显著,配筋率从1%增加到2%,承载力提高22%;剪力连接度从0.75增加到1.25,承载力提高13%。半充填和全充填混凝土对窄幅钢箱-混凝土组合梁试件的承载力和刚度影响很小。充填混凝土对钢箱梁的屈曲约束作用明显,所有试件最终破坏时均未发生内凹屈曲。由于充填混凝土有效地限制钢箱变形,从而提高了组合梁的承载力和结构的稳定性。基于简化塑性理论提出了部分充填混凝土窄幅钢箱-混凝土组合梁的承载力计算方法,且计算值与试验值吻合较好。     

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 inelastic mechanical behaviour of composite girders under hogging moment

Negative bending moments acting on the support regions of continuous composite girders generate tensile stresses in the concrete slab and compressive stresses in the lower steel profile. As a result, the mechanical behaviour of these girders becomes strongly nonlinear, which needs special study. In this paper, static experimental tests on four half-scale models of steel and concrete composite girders with different shear connectors such as studs and Perfo-Bond Strips (PBLs) under hogging moments are cautiously conducted in order to investigate the reduction of flexural stiffness and the inelastic behaviour after cracking. In the test results, crack development, crack widths and strains of the composite section before and after cracking were observed. The crack width evaluation methods based on design codes for steel and concrete composite girders under negative bending moment were compared. Crack widths should be controlled appropriately within an allowable value in the slab under service load. The strains in reinforcing bars obtained through the static tests agreed well with the values calculated through the application of the existing tension stiffening theory. The test specimens could be assumed to be a full composite section until the ultimate state on the basis of load and slip relationship results of shear connectors. It follows that analytical and experimental studies can be served as a basis for the design of continuous composite bridges.     

Experimental study on double composite action in the negative flexural region of two-span continuous composite box girder

In the negative flexural region of continuous composite girder, cracking of concrete slab results in a reduction in the sectional stiffness and may affect the durability of reinforcement. Double composite action defined as attaching additional concrete to steel bottom flange to improve local buckling strength can be a way to increase the sectional stiffness. It has many advantages for construction while disadvantages also exist. In this case, two continuous composite girders, both of which had two 9 m long spans with 300 mm extension at each edge support and were 0.55 m high, were designed to study the mechanical properties in concrete crack, formation of sectional plastic hinge, load-carrying capacity, etc. One was a conventional composite girder named CCG and the other one was designed with double composite action in the negative flexural region named DCG. Moreover, evaluations of concrete crack width, based on different design codes, and cracking moment were compared with test results and agreed with each other. It indicated double composite action made concrete crack development slower in service load stage. The evaluation of sectional bending-carrying capacity of CCG in the negative flexural region based on the mechanical model with full plastic section of Euro Code 4 and an analogous method was found to evaluate that of DCG. The evaluation results coincided with test results proved the summation which can be drawn from test results.     

箱梁施工中负弯矩施工质量的控制

根据多年的工作经验,针对箱梁施工中存在的负弯矩波纹管定位、漏浆严重、压浆不饱满、张拉槽口后期封堵,以及锚垫板加强筋处理等问题,提出了相应的预防和处理措施,解决了箱梁施工的质量问题。     

部分剪力连接预应力组合箱梁受弯性能试验研究

为研究剪力连接程度对预应力钢与混凝土组合箱梁的界面相对滑移、挠度及受弯承载力的影响,设计制作了4根不同剪力连接程度预应力钢与混凝土组合箱梁模型试件,采用三分点对称加载,对其进行了受弯性能试验研究。研究表明,随着剪力连接程度的降低,变形及界面滑移明显增大,承载能力有所降低,但并不与剪力连接程度成正比关系,连接程度为0.5的组合箱梁承载力较完全连接组合箱梁降低不到30%。结合国内外7根部分剪力连接组合梁试验资料, 运用最小二乘法,对欧洲规范EC4中关于部分剪力连接组合梁承载力计算公式进行了修正。结果表明,修正值与实测值吻合良好,满足工程精度要求。     

负弯矩作用下钢-混凝土组合梁受力性能试验研究

通过8根跨度为3.0m和4.2m的钢-混凝土组合梁在负弯矩作用下的受力性能试验,研究了端部弯矩、跨度、H形钢的腹板高厚比、抗剪连接栓钉数量、设置横向加劲肋等因素对组合梁失稳破坏模式、受弯承载力及转动能力的影响。试验结果表明：对两端部作用数值相等的负弯矩工况,组合梁发生畸变失稳,其受弯承载力小于组合梁全截面塑性弯矩,转动能力偏小,而对其他接近实际结构的负弯矩工况,组合梁发生局部失稳或局部与畸变耦合失稳,其受弯承载力大于组合梁全截面塑性弯矩,转动能力较大;随着腹板高厚比减小或者在腹板上设置横向加劲肋,组合梁的受弯承载力和转动能力都有明显提高。     

单箱双室箱梁对称弯曲时的局部扭转效应

为研究单箱双室箱梁在对称竖向荷载作用下的受力特征,基于横截面的荷载等效原理与荷载分解,分析了单箱双室箱梁对称弯曲时的局部扭转效应。基于截面的剪力流平衡和箱室受力分解,得到了局部扭转的等效荷载及应力计算式。通过与有机玻璃模型试验和有限元模拟结果的对比,验证了局部扭转效应计算式的正确性,并获得了单箱双室简支箱梁的局部扭转效应下的应力分布规律。研究表明,单箱双室箱梁在仅中腹板作用竖向荷载及两边腹板作用相等竖向荷载时,均存在纵向弯曲和局部扭转的组合变形模式。局部扭转由约束扭转、畸变和横向弯曲效应组成,在截面引起纵向应力和横向应力。局部扭转效应的理论计算结果与模型试验和板壳有限元分析结果吻合良好,表明基于截面剪力流等效的局部扭转荷载求解方法对双室箱梁是适用的;单箱双室箱梁的局部扭转效应在荷载作用点附近截面最为突出,截面上、下缘纵向应力和横向应力以中腹板为拐点呈折线分布,其应力分布和大小与荷载在横截面上作用的部位紧密关联;对算例箱梁,局部扭转效应产生的纵向应力可达初等梁弯曲应力的25%。     

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。     

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.     

Experimental study on shear behavior of box section bamboo-steel composite beams

为研究以冷弯薄壁型钢和竹材人造板通过结构胶复合而成的箱形截面钢-竹组合梁的受剪性能,以梁截面的翼缘及腹板竹胶板厚度、型钢翼缘宽度和剪跨比等为主要参数,对6根钢-竹组合箱形梁进行受剪试验,观察各级荷载作用下组合梁的应变和挠度发展,分析其破坏过程和破坏机理,研究组合梁受剪性能的影响因素,探讨钢-竹组合箱形梁的受剪承载力及变形计算方法。研究结果表明：钢-竹组合箱形梁整体工作性能优良且组合效应显著,其受力过程经历弹性和弹塑性两个阶段,具有良好的延性和安全储备;增加翼缘和腹板处竹胶板厚度可提高组合梁的受剪承载力,减小剪跨比可有效提高组合梁的受剪能力,同时适当减小型钢翼缘宽度能使梁的受剪性能进一步增强;采用所提出的组合梁的跨中挠度计算公式得到的计算值与试验值吻合较好,组合梁受剪承载力的计算公式所得结果偏于保守。     

钢—混凝土组合节点在正弯矩作用下的试验研究

针对钢—混凝土组合柱组合节点在正弯矩下受力性能进行了试验研究,并探讨了混凝土组合柱对组合节点受力性能的影响。试验结果表明：组合节点在正弯矩作用下,受拉部件主要为中和轴下面的螺栓,受压部件主要为混凝土板。其他条件相同时,柱翼缘内填充混凝土的组合节点,在节点延性略有减小的同时,初始强度得到提高。     

Influence of group studs layout style on static behavior of steel-concrete composite small box girder models

设计制作4片具有不同栓钉布置方式的钢-混凝土组合小箱梁模型进行试验研究,并进一步采用有限元法,考虑组合梁材料的本构关系和接触问题等,对其从弹性荷载至极限荷载下的受力行为进行分析,得到从开始加载至极限荷载下各模型梁的荷载-挠度曲线、跨中钢梁底板应变随荷载的变化曲线和弹性阶段钢梁与混凝土板相对滑移的分布,以及组合梁的屈服荷载、极限荷载和破坏时混凝土板的应力云图等。与试验测试结果的对比表明,采用群钉布置的快速施工组合梁达到完全抗剪要求时,组合梁承载能力与焊钉数量和布置型式关系不大,按照文中建立的有限元模型能较好地分析预测快速施工不同群钉设计参数下钢-混组合梁的屈服荷载和极限荷载。     

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。     

负弯矩区腹板开洞钢-混凝土组合梁承载力试验研究与理论分析

通过外挑钢-混凝土组合梁的单调加载试验和有限元分析,研究负弯矩区腹板开洞对其受力性能的影响,并基于弯剪承载力相互作用的准则,提出承载力理论计算方法。结果表明：截面开洞显著降低了组合梁的承载能力和刚度;最终破坏形式为洞口上方混凝土板的剪切破坏;组合梁承载能力随着截面削弱的加大而降低;洞口补强板可减轻洞口区域应力集中,进而提高组合梁的承载力;承载力随着洞口中心线与支座距离减小（即弯剪比的增大）而减小。应用建议的负弯矩区腹板开洞组合梁承载力计算方法得到的承载力计算结果与试验及有限元分析结果吻合较好。     

基于碳化的预应力组合箱梁桥可靠性分析

为了研究预应力混凝土结构在混凝土碳化后,结构在服役期间的可靠度,分析讨论了混凝土碳化及其影响因素.将混凝土强度、保护层厚度、计算模式不确定性系数以及荷载增长系数作为随机变量,以混凝土的碳化深度作为一个随时间变化的随机过程,建立了一般大气环境下,混凝土碳化的时变概率随机模型.在此基础上,对五跨预应力组合箱梁进行了研究,从可靠度方面给出了在服役期间结构的可靠度水平.     

Behavior of steel-concrete composite cantilever beams with web openings under negative moment

The effect of web openings on the mechanical behavior of composite beams under negative moment was studied through monotonically loading tests. Nonlinear finite element method based analysis was also conducted for cantilever composite beams. The test and the finite element analysis results indicated that the initial cracking loads of composite beams with web opening are lower than that without web opening. The first crack initiated from the concrete slab on the top of the opening. The beams with web opening failed due to shear failure of concrete slab upon the opening. It was also found that the load carrying capacity of beam decreases with the increase of the moment-to-shear ratio at the central line of the opening and the mechanical behavior of beam can be improved significantly by applying stiffening steel plates around the opening. To quantify the reduction of load carrying capacity, a method for calculating the load carrying capacity of beams with web openings under negative moment was derived with consideration of the interaction between moment and shear. Good consistency was obtained between the proposed method, the finite element method and the test results.     

组合式钢桥弧形箱梁跨铁路安装施工工艺

介绍了遥控液压调平技术的特点及使用范围,以阳煤集团棚户区改造工程麻地巷组合钢箱梁桥安装工程为依托,对组合式钢桥弧形箱梁跨铁路安装施工工艺流程及操作要点进行了阐述,指出应用该工艺取得了良好的社会和经济效益。