手风琴效应对预应力波纹腹板钢-混凝土组合梁抗火性能影响研究

由于预应力波纹腹板组合梁的腹板存在显著的手风琴效应,使其受力性能不同于普通平腹板组合梁。为了研究手风琴效应对预应力波纹腹板组合梁抗火性能的影响,采用ABAQUS有限元软件建立了考虑端部约束的预应力波纹腹板组合梁在火灾下的数值模型,分析了预应力波纹腹板组合梁在高温下的破坏形式、跨中挠度、拉索张力及组合梁轴力等随温度变化的特点。结果表明： 高温下波角30°腹板的局部失稳区域大于波角45°和60°组合梁的失稳区域;波高50 mm的组合梁跨中挠度值最小;波高越大,临界状态时腹板局部失稳区域越大;平直段长度50 mm组合梁跨中挠度最小,轴向刚度更大;腹板厚度对波纹腹板组合梁跨中挠度的影响最为显著;轴向约束作用下的组合梁典型破坏形态是梁端负弯矩区腹板和下翼缘发生局部屈曲;不同轴向约束比下,梁的轴向力从压力转变为拉力时温度为691 ℃;转角约束比对组合梁的影响主要集中在473 ℃至临界温度阶段;不同转角约束比下,组合梁轴向压力转变为轴向拉力的温度为677 ℃。     

Accordion effect of prestressed steel beams with corrugated webs

Various types of composite members have been developed to utilize the combined advantages of existing reinforced concrete and steel structures, and to actively improve ductility and serviceability of structural members. One of them is the hybrid-type steel beam, in which the prestressing method is applied to a steel beam. Introducing prestress to the existing I-shaped steel beam, however, results in a very low prestress efficiency due to the large axial stiffness of the section. On the other hand, if corrugated webs are used, the prestress introduced to the main flexural-resistant elements—the upper and lower flanges—gets larger due to the accordion effect, so that it is very advantageous not only in terms of serviceability, but also of achieving the improved flexural strength. Most previous studies on steel members with corrugated webs, however, have focused on the shear buckling strength of the corrugated webs, and few studies have been conducted on the accordion effect of the corrugated webbed beam to which prestress is introduced. Therefore, this research proposed two rational and theoretical models to quantitatively estimate the accordion effect, which is induced by the introduction of prestress to corrugated webbed steel beams, and performed experiments on two steel beams with corrugated webs and one with typical wide flange section. The experimental results showed that the prestressing efficiency of steel beams with corrugated webs increased more significantly than that of the steel beam with a typical web, and it is verified that the proposed methods are very simple and provide good agreements with the experimental results.     

初始残余应力对预应力钢-混凝土连续组合梁抗火性能影响

为研究钢梁残余应力对预应力连续组合梁抗火性能的影响,建立了预应力连续组合梁在高温下非线性升温过程受力行为的有限元模型。通过考察梁的破坏形式、跨中挠度、预应力拉索张力、截面弯矩以及梁的曲率等关键参数随温度的变化,得到不同残余应力模式对组合梁抗火性能的影响机理。分析结果表明：残余应力的分布并不总是对预应力钢-混凝土组合梁的高温性能产生不利影响,腹板具有初始残余拉应力分布模式的预应力钢-混凝土组合梁高温下的挠度相对最小;残余应力主要通过影响截面正应力分布来影响钢梁的截面刚度;在临界状态时,残余应力对组合梁截面刚度的影响不明显;不同残余应力模式对高温下预应力钢-混凝土组合梁的截面抗弯刚度影响不同;当预应力钢-混凝土组合梁的初始残余应力模式以腹板全截面拉应力为主时,预应力钢-混凝土组合梁跨中截面抗弯刚度最大;当残余应力对组合梁跨中截面抗弯刚度有利时,梁跨中截面处中和轴位置比无残余应力影响时较高。     

波形钢腹板体外预应力组合梁正截面承载力及应力分布特征研究

为研究预应力状态下波形钢腹板组合梁的截面应力分布特征,设计制作2根波形钢腹板组合梁,在预应力筋张拉过程中研究了预应力对组合梁受弯截面应力分布特征的影响,通过正截面受弯试验对试件塑性承载力先进行测定;对体外预应力组合梁正截面承载力进行了理论分析;利用有限元分析软件,对与试件同类型的波形钢腹板体外预应力组合梁的塑性受弯承载力进行了参数分析,研究了腹板高度和混凝土强度对正截面承载力的影响。结果表明：预应力对此类构件的翼缘应变变化量影响较波形钢腹板的大约2~3倍;预应力损失对截面中性轴位置变化影响可忽略不计;施加预应力将使波形钢腹板组合梁的受弯承载力提高约30%,腹板高度等参数与此类结构跨中截面承载力呈线性关系;理论值与有限元模拟结果吻合良好,验证了所提出正截面承载力理论的准确性。     

预应力钢-混凝土连续组合梁的变形分析

对预应力钢-混凝土连续组合梁在正常使用极限状态下的变形计算进行分析。分析考虑钢与混凝土之间的滑移效应,建立简化计算模型,并在此基础上,提出混凝土支座开裂区长度以及预应力筋内力增量的计算公式,给出两跨预应力连续组合梁跨中挠度的计算图表。分析结果表明,两跨预应力连续组合梁变形计算公式计算正常使用极限状态预应力筋的内力值精度较高,不考虑预应力筋内力增量的变形计算值较试验值偏大,考虑预应力筋内力增量的变形计算值精度有明显提高,与试验结果吻合较好,可供工程设计参考。最后在两跨预应力连续组合梁变形计算公式的基础上提出预应力连续组合梁变形计算的通用方法。     

装配式波形钢腹板工字型组合梁试设计

结合工程实例,对一种新型的波形钢腹板工字型组合梁结构进行了分析,提出了改善组合结构墩顶负弯矩区混凝土桥面板受力性能的方法,并简要介绍了装配式波形钢腹板工字型组合梁的施工过程,指出了装配式波形钢腹板工字型组合梁在实际应用中的优势。     

预应力钢-混凝土连续组合梁的非线性有限元分析

以六根两跨预应力钢-混凝土连续组合梁的系列试验结果为基础,以通用有限元程序MSC.MARC(2005r2)为平台,提出了用于模拟预应力连续组合梁非线性全过程受力行为的精细有限元模型,并给出了单元选取、材料建模以及整体组装的详细过程。有限元分析基于弹塑性本构模型,能充分考虑材料非线性和几何非线性,反映结构受力全过程中预应力筋内力变化、滑移效应、内力重分布、应力分布、曲率分布以及塑性铰形成等复杂特性,深入揭示了预应力连续组合梁的受力机理和特点。模型计算结果和实测结果以及理论分析结果吻合良好,表现出良好的数值特性。文中模型对于预应力连续组合梁的精细化分析具有较高的精度和广泛的适用性,为研究预应力连续组合梁受力性能提供了强有力的工具。     

谈钢—混凝土组合结构耐火性

简要介绍了钢—混凝土组合结构的形式、优势及其抗火性能,运用ANSYS软件,分析了钢管混凝土的截面温度场分布,体现了其优越性,并总结了常见的耐火保护方法,以供参考。     

Numerical analysis on mechanical behavior of steel-concrete composite beams under fire

This paper investigated the fire behavior of steel-concrete composite beams (SCB) and partially encased steel-concrete composite beams (PEB) through numerical analysis. The numerical models established by the software ABAQUS were verified against experimental results. Parametric studies were performed to study the influences of load ratio, strength of concrete and steel, width of concrete slab, size of steel beam, fire protection layer, and degree of shear connection on the fire behavior of SCB and PEB. The analysis results show that the deformation stages of SCB and PEB under fire both go through four stages: elastic, elastic–plastic, plastic small deformation, and plastic large deformation. The web of SCB experiences a tension–compression–tension process under fire, and the bottom flange of PEB may even change from tension to compression at a lower load ratio. The failure mode of PEB, whether the concrete is crushed, depends on the load ratio. When SCB fails, the concrete is crushed and only the bottom flange of the steel beam yields. Under various parameters, the fire resistance of SCB is about 22 min, while the fire resistance of PEB is 82–93 min under a load of 0.4. When the load ratio increases from 0.2 to 0.6, the fire resistance of SCB decreases by 8 min, while that of PEB decreases by 110 min. To meet class I fire resistance rating under a normal service load ratio of 0.4, additional measures for PEB are still required, and at least 15 mm of fire protection layer is required for the steel beam of SCB. Finally, considering the temperature internal fore, a coefficient related to the fire time was introduced to modify the formula of ultimate flexural capacity of SCB and PEB, which showed good accuracy.     

Experimental study of prestressed steel-concrete composite beams with external tendons for negative moments

Four groups of prestressed steel-concrete composite beams with external tendons in negative moment regions were tested, and the cracking behaviours and the ultimate negative moment resistances of the composite beams were investigated experimentally. It is found that in hogging moment regions, on adding prestressing to the composite beams with external tendons, the cracking resistance of the beams can be effectively increased; however, the incremental internal tendon forces of the prestressed composite beams are rather small, and therefore can be neglected in the evaluation of the negative moment resistance of the beams. In hogging moment regions, the ultimate resistance of a composite beam prestressed with external tendons is governed by either distortional lateral buckling or local buckling, or an interactive mode composed of the two bucklings. For a beam with a compact section, the negative bending moment can reach the plastic moment when the steel section is fully plastic, and for a non-compact section, the negative bending moment is limited to the yield moment at which the compression steel flange initiates yield. The method for evaluating the buckling resistance of the composite beams is discussed, and a tentative design method based on BS5400: Part 3 is proposed to assess the buckling resistances of the prestressed composite beams.     

单箱单室波形钢腹板组合箱梁的扭转效应分析

依据乌氏第二理论,推导出波形钢腹板组合箱梁的扭转控制微分方程,采用初参数法,求解了两个截面的翘曲应力,研究表明,波形钢腹板按正交异性板考虑计算出跨中混凝土底板扭转翘曲正应力与弯曲正应力比值达33%,1/4跨波形钢腹板扭转翘曲剪应力与弯曲剪应力比值达47%。     

钢-混凝土组合梁抗裂性能的试验研究

为研究钢-混凝土连续组合梁的受力性能,特别是体外预应力对抗裂性能和刚度的影响,完成3根反向加载的简支组合梁和3根2跨连续组合梁的静力加载试验,其中包括2根在钢梁和混凝土板内折线布筋的体外预应力组合梁。试验表明:非预应力组合梁在负弯矩作用下的开裂荷载较低,连续梁在较低荷载下就会由于混凝土开裂而发生明显的内力重分布,且横向钢筋间距对裂缝间距具有一定影响;折线布筋的体外预应力组合梁开裂荷载增大,裂缝间距和裂缝宽度明显减小,且相同荷载下的挠度下降,说明体外预应力可有效改善组合梁的综合受力性能。此外,预应力作用对组合梁的滑移分布有较明显影响。     

Effective width of a concrete slab in steel-concrete composite beams prestressed with external tendons

The finite element method is applied to evaluate the effective width of a concrete slab in composite beams prestressed with external tendons. The beams studied are simply supported, with external prestressed strands straightly and draped arranged. The effective width for the prestressed composite beams evaluated based on the finite element parametric study is compared with that of plain composite beams without prestressing, and code provisions. The influence of the shear connections on the effective width and the shear slips along the beam span, as well as the incremental stresses developed in the prestressed strands, are analyzed. The behaviors of the external prestressed composite beams subject to the shrinkage and creep in the concrete slab are also discussed.     

某波形钢腹板预应力混凝土组合箱梁桥设计

结合太原市某高架桥工程,简要介绍了波形钢腹板预应力混凝土组合箱梁桥的构造特点、设计注意事项等,并采用桥梁博士软件对全桥进行了计算,为今后类似工程提供参考。     

Design of semi-continuous composite steel-concrete beams at the fire limit state

A two-dimensional temperature analysis procedure based on the finite element method (FEM) is described and applied to steel-concrete composite beams. A computer program developed for the analysis is detailed. A strategy is also proposed for incorporating the influence of the partial resistance of the composite connections in reducing the sagging moment at central regions of the beam spans when the beam is calculated as semi-continuous. Finally, an example problem is discussed, comparing the design uniformly distributed loads that can be supported by a composite beam calculated as semi-continuous and with simply supported spans. The temperature distribution due to fire at the central region of the spans is taken as in the simplified procedure proposed in European Prestandard ENV 1994-1-2 [ENV 1994-1-2. Eurocode 4, Design of composite steel and concrete structures — Structural fire design. Brussels: European Committee for Standardization (CEN); 1994] and then obtained with the more rigorous calculation using the described numerical algorithm. It will be assumed that no ultimate limit state will occur due to shear force (web buckling) or due to bending moment at the hogging moment regions of the beam (web and bottom flange buckling or distortional lateral buckling).     

考虑腹板剪切变形的波形钢腹板组合箱梁剪力滞效应分析

在波形钢腹板组合箱梁中,剪力主要由波形钢腹板承担。由于波形钢腹板的抗剪刚度比混凝土腹板有较大程度的降低,波形钢腹板会产生较大的竖向剪切变形。为此,基于能量变分法建立了考虑腹板剪切变形的波形钢腹板组合箱梁剪力滞效应分析方法。通过试验对该理论分析方法进行验证,并基于该理论分析方法研究波形钢腹板剪切变形对剪力滞效应的影响。同时,基于该分析方法提出了采用影响线最不利加载方式进行相关规范中规定的汽车荷载作用下的波形钢腹板组合箱梁桥剪力滞效应分析。结果表明：考虑腹板剪切变形的分析方法与试验结果吻合度良好;波形钢腹板的剪切变形有利于减轻三跨连续梁正弯矩区的剪力滞效应,即考虑腹板剪切变形后翼缘有效宽度系数值更接近于1。     

A comparative study of continuous steel-concrete composite beams prestressed with external tendons: Experimental investigation

A comparative study of prestressed continuous steel-concrete composite beams is carried out based on an experimental investigation. Four full-scale continuous composite beams were tested, among which two were two-span beams and two were three-span beams. One of the two-span beams was a conventional non-prestressed composite beam, and the other was a composite beam prestressed with external tendons in both the positive and negative moment regions. One of the three-span composite beams was non-prestressed, and the other was prestressed only in the negative moment regions with external high-strength tendons. The cracking behaviors, distortional lateral and local buckling as well as the load carrying capacity of the beams were investigated experimentally. Full plasticity was developed at the mid-span section of each beam; however, the maximum moments attained at the internal supports were governed by local buckling, which is related to the slenderness of the composite section. It is found that in hogging moment regions, the ultimate moment resistance of a composite beam prestressed with external tendons is governed by either distortional lateral buckling or local buckling, or an interactive mode composed of distortional lateral and local buckling. The results show that exerting prestressing on a continuous composite beam with external tendons increases the degree of the internal force and moment redistribution in the beam. A design proposal based on moment redistribution to evaluate the load carrying capacity of continuous composite beams with external tendons is proposed.     

预应力活性粉末混凝土梁抗火性能试验研究

活性粉末混凝土(RPC)是超高性能建筑材料,与高强预应力筋结合形成的预应力RPC梁具有显著的承载、变形和耐久性能优势,但预应力RPC梁的火灾安全性能是制约其广泛应用的关键问题之一。鉴于预应力RPC梁的火灾安全性亟待研究,以荷载水平、预应力筋保护层厚度、预应力筋类型、预应力度等为试验参数,设计制作了8个预应力RPC简支梁,开展了恒定荷载ISO 834标准升温条件下受火试验。获得了梁内温度变化、挠度-受火时间曲线、有效预应力、裂缝开展、爆裂分布及深度等试验数据,研究了火灾高温损伤演化规律和破坏模式。结果表明:干热养护可有效抑制RPC高温爆裂,受火试件保持了良好的完整性;荷载水平和预应力筋保护层厚度是影响预应力RPC梁抗火性能的关键因素,随荷载水平的减小和预应力筋保护层厚度的增大,耐火极限显著提高;荷载水平为0. 5、预应力筋保护层厚度不小于45 mm可满足2. 0 h的耐火极限要求;同等条件下有黏结预应力RPC梁的抗火性能优于无黏结预应力RPC梁;常温下按适筋梁设计的预应力RPC梁火灾下易发生少筋破坏。     

Patch loading resistance of girders with corrugated webs

The corrugated steel plate is a widely used structural element in many fields of application because of its favourable properties and has been applied since the 1920s. For the last 20 years it has been increasingly used in the web of steel and composite bridges. When such a bridge is incrementally launched, buckling of the thin steel web may occur. In this paper, a numerical model is developed on the basis of previous experiments. Numerical investigations are made for the determination of the patch loading resistance, and the geometric parameters which influence the patch loading resistance and the structural behaviour are determined and analysed. Existing design formulas from the literature are summarised from the point of view of bridges, and enhanced according to the numerical results and the existing and additional experiments.