Experimental study on joint of spliced steel-PSC hybrid girder, Part I: Proposed parallel-perfobond-rib-type joint

The object of this study is to determine and propose a suitable joint type for spliced hybrid I-girder bridges consisting of steel girders at the mid-span and PSC (prestressed concrete) girders at the supports. Three joint types are experimentally tested on small-scale steel-PSC hybrid beams to determine the type offering the best combination of structural capacity and constructional convenience. One joint type, first suggested and trialed in the present study, is composed of multiple perfobond rib connectors attached in parallel to upper and lower plates located between the steel girder and the PSC girder. The two other types incorporate the stud connectors, which are widely used in connecting steel and concrete, but differ in the amount of reinforcement. The test results reveal that a joint consisting of parallel perfobond ribs and a joint consisting of studs with sufficient reinforcement show the similar beam strength and failure modes resulting from the failure of the PSC components. Notably, beams of the proposed joint type consisting of perfobond ribs, compared to those with studs, show higher stiffness and strength prior to reaching their ultimate strength, as well as lower strains in the joint. Indeed, with the parallel-perfobond-rib-type joint, advances in constructional convenience as well as structural capacity can be anticipated. Thus, it is concluded that the proposed joint type is a more suitable system for spliced steel-PSC hybrid girder bridges.     

钢-预应力混凝土混合梁节点的试验研究(第1部分:建议采用开孔板连接件的节点形式)

旨在为跨中采用钢梁、两端采用预应力混凝土梁的Ⅰ型混合桥梁选用一种适当的节点形式。分别对采用3种类型的节点的钢-预应力混凝土混合梁进行缩尺模型试验,以分析哪种节点形式的结构性能最好且便于施工。目前,研究中首先采用的一种节点形式,是位于钢梁和混凝土梁之间的顶底板上的多个开孔板连接组成。另2种节点形式结合了广泛应用于钢结构和混凝土结构之间的螺栓连接,而区别在于加强措施的数量。试验结果显示:从预应力混凝土构件的破坏模式看,采用开孔板连接件和采用有足够加强措施的螺栓连接有近似的梁的强度和破坏模式。显而易见,采用被建议的开孔连接板与采用螺栓连接相比,在达到梁极限承载力之前有更高的刚度、强度及更小的应变。可以肯定的是采用开孔板连接件,更便于施工且结构性能好。因此,可以得出文中建议的节点形式更适合于钢-预应力混凝土混合梁桥梁的结论。     

Experimental evaluation of joints consisting of parallel perfobond ribs in steel-PSC hybrid beams

The objective of this paper is to estimate the structural capacity and application feasibility of joints with parallel perfobond ribs in steel-PSC (prestressed concrete) hybrid beams. In order to investigate the joints, two steel-PSC hybrid beams of 8 m length are fabricated, and experimental tests are performed. The hybrid beams consist of a steel beam in the center, PSC beams at both ends, and joints connecting the steel beam and the PSC beams. In the joints, perfobond ribs are used as shear connectors in place of studs which are generally used. The parallel perfobond ribs are attached to the steel plates horizontally and vertically to assess joint performance under both flexural moments and shear forces. The test results reveal that the failure of hybrid beams occurs at the PSC region near the interface between the PSC component and the joint. No joint failure is observed in the test beams up to the fracture load stage. In addition, the test beams show sufficient ductility by virtue of the arrangement of adequate reinforcements, even though perfobond ribs are considered to be stiff shear connectors. Therefore, it is concluded that the joint with parallel perfobond ribs is an applicable system to utilize in steel-PSC hybrid beams. In addition, the perfobond ribs can be an alternative to stud shear connectors in joints of hybrid beams.     

Comparison of dynamic properties of spliced and monolithic prestressed concrete box railway girders

Longitudinal splicing of precast prestressed concrete (PSC) girders has recently gained increasing support as an effective method to accelerate bridge construction. The presence of the joints in the spliced girder may alter the dynamic properties of the system. In this study, a 20 m long full-scale spliced PSC girder was fabricated and tested to identify its dynamic characteristics against a monolithically fabricated girder (monolithic girder) with the same dimensions. The experimental program involved two phases. First, the dynamic properties of the test girders were identified from a modal test. Numerical modal analyses based on three-dimensional finite element models were also performed, and the calculated modal parameters were compared with the test results. The second phase involved a characteristic decrease of the natural frequency due to the damage to each girder after the load test. This study shows that the spliced girder provides a dynamic performance comparable to that of a monolithic girder in both the uncracked and cracked states.     

波形或桁架式钢腹板的预应力钢混组合桥主梁的安全性能和使用性能评估

在许多国家,预应力混凝土箱梁被认为是中等跨径(30～50m)混凝土梁最有效的结构形式。但是当混凝土梁的单跨长度超过50m时,相对钢梁,混凝土箱梁自重问题成为其最大约束。因此,在韩国,中等跨径桥梁主要采用钢箱梁。在20世纪,研究者们多次尝试提高预应力混凝土箱梁结构的有效性,最终采用混凝土-钢混合梁以减轻结构自重。但是,混合桥采用不同类型钢腹板及不同连接形式,会引起结构安全性能和使用性能的变化。为了全面了解钢腹板梁及钢腹板连接形式的性能,对5根带腹板的预应力混凝土梁进行静力荷载试验。这5根试件中,有2根混合梁采用波形钢腹板,而另3根采用桁架式钢腹板。结果显示:通过加强钢腹板与预应力筋的连接节点,可以改善使用性能相关问题(开裂荷载和挠度)及安全性能相关问题(刚度和极限承载力)。     

预制装配式混合框架屈曲约束狗骨式节点抗震性能试验研究

为充分发挥装配式混凝土结构施工便捷的特性及钢结构中狗骨式钢梁的抗震性能优势,提出了预制装配式混合框架屈曲约束狗骨式节点。该混合框架节点由预制钢筋混凝土柱和预制钢-混凝土混合梁通过高强螺栓连接而成,其中混合梁由屈曲约束狗骨式钢梁段与混凝土梁段采用高强螺栓连接。完成了2个框架中节点及2个框架边节点的低周往复加载试验。通过对节点的破坏形态、滞回曲线、骨架曲线、耗能能力及变形能力、承载力及刚度退化的研究,对节点类型及梁内是否布置预应力筋对该节点抗震性能的影响进行了分析。研究结果表明：该节点的拼装方式采用全螺栓连接,施工便捷;节点的破坏主要集中于钢梁段,达到了塑性铰外移的目的;节点梁内布置预应力筋能明显提高混凝土梁段的抗裂性能及节点整体抗震能力;提出了该节点中梁端受弯承载力计算方法,试验值与计算值吻合较好。     

用连续振动阻抗法进行预应力钢筋混凝土梁桥的混合健康监测

提出连续振动阻抗法,对预应力钢筋混凝土桥梁的两种破坏形式(即预应力筋破坏或梁破坏)进行混合健康监测。监测包括3个步骤:第一步,通过监测加速信号的变化,对整体破坏进行预警。第二步,通过振动和阻抗识别模式,将破坏类型分为预应力筋破坏或梁破坏。第三,基于形状模式和频率方法,通过测量试验室中几个预应力筋和梁的加速响应和电子-机械阻抗,对所提系统的可行性进行评估。     

PC箱梁与钢桁架组合加劲梁斜拉桥的刚度与稳定分析

探讨预应力混凝土箱梁与钢桁架组合式加劲梁高速铁路斜拉桥的刚度与稳定 ,与无钢桁架PC钢箱梁相比 ,跨径 488m大跨度铁路斜拉桥的活载挠度与跨径之比从 1/4 2 6降低到 1/777,最小整体弹性稳定系数为 11 9。PC钢箱梁与钢桁架组合式加劲梁有效地提高了斜拉桥的刚度和稳定性 ,是大跨度铁路和公铁两用斜拉桥的合理结构形式。     

钢桁腹预应力混凝土箱梁桥的设计应用

钢桁腹预应力混凝土箱梁桥是采用桁式钢腹杆代替混凝土箱梁中混凝土腹板而形成的一种新型组合结构桥梁。介绍了这种桥型的发展、应用、结构特点及节点构造,并举例介绍了国内第1座钢桁腹预应力混凝土连续箱梁桥的设计情况,供工程设计人员参考。     

波形钢腹板体外预应力箱梁的工程应用

将波形钢腹板应用在无背索斜拉桥中,是波形钢腹板体外预应力箱梁应用领域的又一次新的突破。本文结合亚洲最大的无背索斜拉桥—新密溱水路大桥,阐述了波形钢腹板体外预应力混凝土组合箱梁的优点,具体介绍了该桥波形钢腹板的构造以及体外预应力体系的设计,为该组合箱梁结构在我国的推广应用奠定了基础。     

部分预应力混凝土梁正截面疲劳性能及计算方法

本文通过16根出现裂缝的先张法部分预应力混凝土试验梁及3根试验吊车梁的静力和疲劳试验,较系统地研究了此类梁的疲劳性能。文中剖析了在重复荷载作用下裂缝截面处钢筋应力的变化规律以及垂直裂缝的开展与闭合;提出了预应力钢筋应力的计算方法和裂缝的控制条件。     

预应力SRC梁式转换结构研究与展望

阐述了预应力型钢混凝土梁是在普通型钢混凝土梁的基础上采用预应力技术的一种新型组合构件，它兼有型钢混凝土结构和预应力结构的特点，就PSRC梁的受力性能、设计理论、抗震性能进行了综述分析，指出PSRC梁将以其优良的性能而具有广阔的应用前景。     

跨径30m箱梁的预制

介绍了桥孔跨径为30 m的标准预应力混凝土箱梁预制的主要过程,从梁场建设,门吊选型,普通钢筋和预应力钢绞线制安,后张法施加预应力施工等方面进行了详细论述,提供了此类箱梁的施工方法和技术支持,对保障箱梁预制质量、降低成本、提高效率具有重要意义。     

新型装配式钢管混凝土柱-钢筋混凝土梁框撑体系振动台试验研究

结合装配式建筑和钢管混凝土柱-钢筋混凝土梁组合框架结构的优点,提出新型装配式方钢管混凝土柱-钢筋混凝土梁组合框撑体系。为研究该类新型体系的整体抗震性能,设计制作了缩尺比为1/3的6层整体模型,对该模型输入了《建筑抗震设计规范》(GB 50011—2010)所建议的多种烈度下的地震激励,获得了其在相应地震激励作用下的结构响应及破坏形态,分析研究了其整体抗震性能、结构失效路径以及连接节点的可靠性。研究表明：①该类结构体系具有“强钢管混凝土柱-弱钢筋混凝土梁”及“强节点-弱构件”的理想失效路径;②梁的破坏点位于工字型钢接头梁段与钢筋混凝土梁段交界位置,距梁柱节点核心区域有一定距离,从而保证了节点核心区域的完整性;③结构部分楼层在强震下会因斜撑失效而形成薄弱层,造成结构响应的放大。     

Static and seismic studies on steel/concrete hybrid towers for multi-span cable-stayed bridges

A new type of hybrid high tower is proposed and applied to a multi-span cable-stayed bridge. This is basically a sandwich type structure and consists of a steel double box section filled with concrete. The filled concrete increases its strength due to the confined effect and the steel plates increase the resistance against local buckling because the deformation is restricted by the filled concrete. Therefore, this hybrid tower is expected to have high bending and compressive strength, and also a good ductile property. First, static analysis is conducted for different live load intensity and distribution because the multi-span cable-stayed bridge is a new structure and its static behavior is not fully understood. The live loads distributed in alternate spans give larger bending moment of the towers than the live loads distributed in full spans. Towers with three different heights are also studied, showing that the higher tower produces smaller displacements and bending moments. Safety of the tower is checked by the limit states design method. Serviceability is not a major problem for the hybrid tower. Second, seismic analysis is carried out for a multi-span cable-stayed bridge subjected to the medium and ultra-strong seismic waves specified in Japanese Seismic Code for Highway Bridges. Three support conditions of the girder at the tower cross beams are compared: movable, connection with linear springs and bi-linear springs. Bi-linear springs are very effective in reducing the dynamic displacements and bending moments of the towers. Restorability of the composite tower is checked when an ultra-strong seismic wave hits the model bridge. This study shows that a new steel/concrete hybrid tower is feasible for multi-span cable-stayed bridges and most effective for seismic forces when the girder is connected with bi-linear springs.     

体内预应力组合梁混凝土预压应力分析

针对在混凝土翼板中设置后张预应力的连续组合梁,提出由分担预加轴力、主弯矩和次弯矩产生的混凝土法向应力计算公式,主要分析施加于混凝土翼板的预应力通过剪力键向钢梁传递的力学模型,建立混凝土翼板承担的预压力沿梁纵轴的分布函数和理论解,求得考虑剪力键柔性的混凝土法向应力计算公式,作为组合梁抗裂设计依据。     

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。     

高速铁路用HRBF500钢筋预应力混凝土梁疲劳性能试验研究

设计制作了2根配置500 MPa细晶粒(HRBF500)钢筋的预应力高强混凝土T形梁,通过实测预应力损失与理论计算比较,得出实测预应力损失大于理论计算值。基于疲劳荷载的试验,绘出HRBF500钢筋应力、钢绞线应力及梁跨中挠度曲线,分析配有细晶粒钢筋的预应力混凝土梁的疲劳性能。结果表明,在一定幅度的疲劳荷载(等幅)作用下,配有HRBF500钢筋的预应力高强混凝土梁,其钢筋、预应力钢绞线及跨中挠度均满足使用阶段规范的限值,即在HRBF500钢筋拉应力大于150 MPa条件下,经过250万次疲劳荷载作用后仍满足设计要求。     

Bending behavior of concrete-encased composite I-girder with corrugated steel web

A partially encased composite I-girder with flat or corrugated web has been proposed to improve the structural performance of continuous composite girder under hogging moment. The flexural behavior of such structure under two points symmetric loading has been experimentally and analytically investigated. Static flexural loading tests showed that the partially encased girder improved bending strength in comparison to steel I-girder, as local bucking of steel flange was restricted by encased concrete. Especially for the corrugated web girder, the ultimate bending strength was improved about 20%, and the ductility also increased about 3 times. In addition, the limitation of width-to-thickness ratios for steel and concrete-encased composite I-girders with corrugated web were suggested to prevent premature failure due to local buckling of compressive flange. Moreover, the analytical methods of flexural strength under service and ultimate state for partially encased composite girder were proposed and verified with experimental results. It was found that the analytical bending strengths agreed well with the experimental ones at both service and ultimate state, which means the proposed analytical equations can be applied in predicting flexural strength accurately for such encased composite girder with flat or corrugated web.     

预应力作用下组合梁混凝土法向应力分析

针对在混凝土翼板中设置后张预应力的连续组合梁,提出由分担预加轴力、主弯矩和次弯矩产生的混凝土法向应力计算公式,主要分析施加于混凝土翼板的预应力通过剪力键向钢梁传递的力学模型,建立混凝土翼板承担的预压力沿梁纵轴的分布函数和理论解,求得考虑剪力键柔性的混凝土法向应力计算公式,作为组合梁抗裂设计依据。