Moment Redistribution Effect of the Continuous Glass Fiber Reinforced Polymer-Concrete Composite Slabs Based on Static Loading Experiment

This study aimed to investigate the moment redistribution in continuous glass fiber reinforced polymer(GFRP)-concrete composite slabs caused by concrete cracking and steel bar yielding in the negative bending moment zone.An experimental bending moment redistribution test was conducted on continuous GFRP-concrete composite slabs,and a calculation method based on the conjugate beam method was proposed.The composite slabs were formed by combining GFRP profiles with a concrete layer and supported on steel beams to create two-span continuous composite slab specimens.Two methods,epoxy resin bonding,and stud connection,were used to connect the composite slabs with the steel beams.The experimental findings showed that the specimen connected with epoxy resin exhibited two moments redistribution phenomena during the loading process:concrete cracking and steel bar yielding at the internal support.In contrast,the composite slab connected with steel beams by studs exhibited only one-moment redistribution phenomenon throughout the loading process.As the concrete at the internal support cracked,the bending moment decreased in the internal support section and increased in the midspan section.When the steel bars yielded,the bending moment further decreased in the internal support section and increased in the mid-span section.Since GFRP profiles do not experience cracking,there was no significant decrease in the bending moment of the mid-span section.All test specimens experienced compressive failure of concrete at the mid-span section.Calculation results showed good agreement between the calculated and experimental values of bending moments in the mid-span section and internal support section.The proposed model can effectively predict the moment redistribution behavior of continuous GFRP-concrete composite slabs.

Numerical investigation of temperature gradient-induced thermal stress for steel–concrete composite bridge deck in suspension bridges

A3D finite element model(FEM)with realistic field measurements of temperature distributions is proposed to investigate the thermal stress variation in the steel–concrete composite bridge deck system.First,a brief literaturereview indicates that traditional thermal stress calculation in suspension bridges is based on the2D plane structure with simplified temperature profiles on bridges.Thus,a3D FEM is proposed for accurate stress analysis.The focus is on the incorporation of full field arbitrary temperature profile for the stress analysis.Following this,the effect of realistic temperature distribution on the structure is investigated in detail and an example using field measurements of Aizhai Bridge is integrated with the proposed3D FEM model.Parametric studies are used to illustrate the effect of different parameters on the thermal stress distribution in the bridge structure.Next,the discussion and comparison of the proposed methodology and simplified calculation method in the standard is given.The calculation difference and their potential impact on the structure are shown in detail.Finally,some conclusions and recommendations for future bridge analysis and design are given based on the proposed study.

Design methods of headed studs for composite decks of through steel bridges in high-speed railway

Aimed at two typical composite floor systems of through steel bridges in high speed railway,design methods of headed studs were put forward for different composite members through comparing and analyzing the structure,mechanical characteristics and transmission routes of deck loads.The simplified calculation models were brought out for the stud design of the longitudinal girders and transverse girders in the composite floor system of Nanjing Dashengguan Yangtze River Bridge (NDB).Studs were designed and arranged by taking the middle panel of 336 m main span for example.The results show that under deck loads,the longitudinal girders in the composite floor system of through steel bridges are in tension-bending state,longitudinal shear force on the interface is caused by both longitudinal force of "The first mechanical system" and vertical bending of "The second mechanical system",and studs can be arranged with equal space in terms of the shear force in range of 0.2d (where d is the panel length) on the top ends.Transverse girders in steel longitudinal and transverse girders-concrete slab composite deck are in compound-bending state,and out-of-plane bending has to be taken into account in the stud design.In orthotropic integral steel deck-concrete slab composite deck,out-of-plane bending of transverse girders is very small so that it can be neglected,and studs on the orthotropic integral steel deck can be arranged according to the structural requirements.The above design methods and simplified calculation models have been applied in the stud design of NDB.

Structural Performance of Light Weight Multicellular FRP Composite Bridge Deck Using Finite Element Analysis

Fiber reinforced polymer （FRP） composite materials having advantages such as higher strength to weight than conventional engineering materials, non-corrosiveness and modularization, which should help engineers to obtain more efficient and cost effective structural materials and systems. Currently, FRP composites are becoming more popular in civil engineering applications. The objectives of this research are to study performance and behavior of light weight multi-cellular FRP composite bridge decks （both module and system levels） under various loading conditions through finite element modeling, and to validate analytical response of FRP composite bridge decks with data from laboratory evaluations. The relative deflection, equivalent flexural rigidity, failure load （mode） and load distribution factors （LDF） based on FE results have been compared with experimental data and discussed in detail. The finite element results showing good correlations with experimental data are presented in this work.

Experimental Study on Shear Behavior of New-Type Steel-Concrete Composite Bridge Deck

To alleviate deck fatigue failure and regular pavement damage,which are congenital deficiencies of highway steel bridge deck structure,this paper proposes a newtype of composite bridge deck,consisting of steel tubular connectors and steel-reactive powder concrete (RPC). Push-out tests were conducted to study the newdeck's shear performance. During the experimental process,specimens were divided into two groups which are composed of steel tubular connectors with or without penetrative bars set in. Then,researchers analyzed destroyed models and mechanisms of the composite structure under shear forces. Results showed that test models in two groups,once destroyed,displayed similar shear fracture,which appeared on the lower margin of the steel tubular wall along the welds. Meanwhile,RPC under the connector,for varied tests,was crushed at the same stage,although the large shear and bending deformation just occurred on connectors with penetrative bars. Additionally,shear capacity of specimens with penetrative bars,compared with the ones without bars,unexpectedly decreased by 20%,but the structural ductility was 1.75 times as much,and the ductility coefficients of specimens were all larger than 3.5,demonstrating certain deformation capacity.

Bridge Structures with GFRP Composite Deck

In this paper, author’s first part of research of GFRP bridge deck (using ASSET fiber line composite modular system) took part at AGH University of Science and Technology Laboratory of Glass Technology and Amorphous Coatings Department. The analysis consisted spectrometer analysis of chemical constitution of glass fiber, identification of material according to Fourier spectroscopy, electronic scan microscopy (SEM/EDAX) and DTA analysis. The modal FEM analysis of chosen footbridge with light GFRP deck has been presented in the paper.

Fatigue Performance of Precast FRP-Concrete Composite Deck with Long Span

The fatigue performance of precast FRP-concrete composite (PFC) deck is evaluated. This type of deck enables a reduction of the weight by 30% compared to conventional reinforced concrete decks owing to the composition of a hollow FRP panel with concrete. Therefore, the application of such deck in cable-stayed bridge will reduce effectively the weight of the superstructure leading also to substantial savings in the materials required for the superstructure and substructure and, therefore, achieve significant improvement of the economic efficiency. Static, pulsating fatigue and rolling fatigue tests were carried out on 4 m × 4 m precast FRP-concrete composite decks. All the specimens did not fail even after 2 million fatigue cycles, and the subsequent static tests conducted on these specimens verified that all the design criteria were satisfied. These experimental results demonstrated that the PFC deck developed in this research secures sufficient performances for future applications for cable-stayed bridges.

Shear Behavior of Open Steel Tube Connectors in Steel⁃UHPC Composite Decks

Steel and ultra⁃high performance concrete(UHPC)composite decks are effective at reducing fatigue cracking and asphalt pavement damage.The shear behavior of innovative open steel tube(OST)connectors in steel⁃UHPC composite decks was investigated by conducting push⁃out tests.The test parameter is the presence of reinforcement in the deck.The load⁃slip curves and shear behavior of the push⁃out specimens were obtained and discussed.The test results indicate that as compared with plain concrete specimens,the limit slip of reinforced specimens decreased by 32%and the shear stiffness increased by 10%,but the ultimate shear capacity was almost the same.The use of UHPC influenced the failure process as it was observed that the OST connector was sheared off at its lower semi⁃tube,followed by the pull⁃out failure of the upper semi⁃tube.A finite element model was verified by tests and was then used to analyze the deformation and failure behaviors of the composite deck with open tubes.The model demonstrates that there is a stress concentration zone at the connector root,and the lower semi⁃tube is the main component that is subject to loads.

Research on an innovative structure of an open-ribbed steel-ultra-high performance concrete composite bridge deck

To completely solve the problem of fatigue cracking issue of orthotropic steel bridge decks(OSDs),the authors proposed a steel–ultra-high performance concrete(UHPC)lightweight composite deck(LWCD)with closed ribs in 2010.Based on the successful application of that LWCD,an adaptation incorporating an innovative composite deck structure,i.e.,the hot-rolled section steel–UHPC composite deck with open ribs(SSD)is proposed in this paper,aiming to simplify the fabrication process as well as to reduce the cost of LWCD.Based on a long-span cable-stayed bridge,a design scheme is proposed and is compared with the conventional OSD scheme.Further,a finite element(FE)calculation is conducted to reflect both the global and local behavior of the SSD scheme,and it is found that the peaked stresses in the SSD components are less than the corresponding allowable values.A static test is performed for an SSD strip specimen to understand the anti-cracking behavior of the UHPC layer under negative bending moments.The static test results indicate that the UHPC layer exhibited a satisfactory tensile toughness,the UHPC tensile strength obtained from the test is 1.8 times the calculated stress by the FE model of the real bridge.In addition,the fatigue stresses of typical fatigue-prone details in the SSD are calculated and evaluated,and the influences of key design parameters on the fatigue performance of the SSD are analyzed.According to the fatigue results,the peaked stress ranges for all of the 10 fatigue-prone details are within the corresponding constant amplitude fatigue limits.Then a fatigue test is carried out for another SSD strip specimen to explore the fatigue behavior of the fillet weld between the longitudinal and transverse ribs.The specimen failed at the fillet weld after equivalent 47.5 million cycles of loading under the design fatigue stress range,indicating that the fatigue performance of the SSD could meet the fatigue design requirement.Theoretical calculations and experiments provide a basis for the promotion and application of this structure in bridge engineering.

型钢-UHPC轻型组合桥面板及其抗弯性能研究

正交异性钢桥面是目前800m以上国内外特大跨径钢桥的唯一选择,主因是自重轻、强度高、架设方便。但其存在疲劳开裂风险大、运维成本高的缺点。随着高性能材料UHPC的研发和应用,为构建自重轻、病害少、经济性好的桥面新结构提供了可能性。经过多年研究,作者提出一种新型桥面板结构——型钢-UHPC轻型组合桥面结构,将型钢、钢板条与UHPC组合,桥面板的形成无任何板件焊接,因而具有高抗疲劳性,且与传统钢桥面相比,自重持平、造价减半,可作为除“正交异性钢桥面”外的“第二种”大跨径钢桥的桥面结构方案。该文研究这种轻型组合桥面板预制板及横向接缝的抗弯性能,制作4个条带模型(包括2个预制板试件和2个接缝试件),开展三点弯曲的横向接缝负弯矩试验和预制板正弯矩试验,并对试验结果进行分析;基于“条带法”建立预制板试件极限承载力计算模型,提出接缝试件的UHPC开裂名义拉应力计算方法;基于某斜拉桥应用实例,进行整体计算和局部计算,验证新型组合桥面结构在实桥上应用的可行性。研究结果表明:(1)型钢与UHPC间在极限状态前相对滑移非常小,具有良好的协同受力性能;(2)预制板试件的正弯矩极限承载力以型钢屈服控制,而接缝试件负弯矩极限承载力以UHPC开裂和加密钢筋断裂控制;(3)接缝试件的“T形”接缝、加密钢筋、燕尾形的企口、交错式切割型钢钢条等构造设计对接缝整体抗弯拉性能有很好的提高效果;(4)预制板试件极限承载力计算模型所得计算值与试验值吻合良好,该模型搭配名义拉应力计算方法,可帮助工程实际问题的设计与应用;(5)试验结果与实桥的有限元计算值相比,新型桥面结构均有1.3倍以上的安全系数,新型组合桥面应用于实桥具有可行性。

钢-UHPC组合桥面板横向负弯矩区受弯性能研究

为明确横向负弯矩作用下,剪力键形式、接缝设置情形、配筋率和钢混界面黏结状态等参数对钢-超高性能混凝土(ultra-high-performance concrete,UHPC)组合板受力性能的影响,完成了8块组合板局部足尺模型静力弯曲试验及有限元参数分析。试验结果表明:开孔板(perfobond leiste,PBL)试件的名义开裂强度(对应最大裂缝宽度为0.05 mm)较栓钉试件提高16.8%;矩形齿缝试件的名义开裂强度较整浇试件降低16%~23%;UHPC层钢筋配筋率从1.96%增加到2.82%时,名义开裂强度提高16.2%;钢板-UHPC界面涂油除黏PBL试件的初裂强度和名义开裂强度较界面黏结试件分别降低10.1%和5.8%。数值分析结果表明:PBL贯穿钢筋的存在、PBL和栓钉间距的减小能有效提高组合板的开裂后刚度;PBL开孔钢板上的孔径和孔间距对组合板的受力性能影响较小。

平钢板-UHPC组合桥面板纵向抗负弯性能试验研究

某大桥次边跨及中跨主梁为钢-UHPC组合梁,钢-UHPC组合梁的桥面板首次采用一种通过PBL剪力键将8 mm平钢板与15 cm的UHPC层连接起来的新型组合桥面体系。为了探究该桥新型钢-UHPC组合桥面板抗负弯矩性能与安全性,完成了2块足尺模型的静力性能试验,进行了桥梁整体受力和桥面板局部受力计算,以及桥面板抗负弯矩极限承载力构成分析。结果表明:UHPC名义开裂强度达8.90 MPa以上,其值远大于实桥荷载作用下UHPC层上缘的纵桥向最大拉应力,组合桥面板负弯矩抗裂性能良好,能满足工程需求;组合桥面板抗负弯承载力的计算,UHPC受拉本构宜采用三折线模型,抗负弯承载力简化计算的UHPC受拉区等效均布应力折减系数可取0.76,抗负弯承载力状态的受压钢板受力仍处于线弹性阶段,抗负弯破坏模式与抗正弯明显不同,为受拉钢筋拉断;PBL剪力键能保证了钢板与UHPC板整体共同受力;组合桥面板在负弯矩作用下的延性良好,裂宽增长缓慢,UHPC的名义极限强度达名义开裂强度的4.1倍以上,到达极限荷载后,组合板承载力没有明显下降。

组合桥面板切应力分布规律及横向剪力钉布置

根据组合桥面板截面的切应力、剪力流分布规律,在混凝土板和钢顶板完全连接的条件下,理论推导出混凝土板和钢顶板的剪力流承担比例,证明组合桥面板层间纵向剪力小于采用组合梁公式得到的计算值.层间完全连接和通过弹簧单元模拟剪力钉离散连接开展的有限元计算均支持这一观点,验证了组合桥面板截面的竖向剪力主要由腹板承担的观点的正确性.探究横向上剪力钉的布置方式.结果表明,组合桥面板应沿横向全宽布置剪力钉,在腹板两侧进行加密,腹板正上方不宜布设剪力钉.

混凝土铺装层开裂对正交异性钢桥面疲劳性能劣化作用研究

为合理评估混凝土铺装层开裂对正交异性钢桥面板疲劳性能劣化的影响,开展足尺模型疲劳试验并进行数值仿真分析,得到铺装层开裂后钢桥面板典型易损细节疲劳应力,并提出疲劳应力增大系数量化分析裂缝尺寸对各细节疲劳应力的影响效应。结果表明:混凝土裂缝深度不超过其厚度20%时,正交异性钢桥面典型细节疲劳应力增幅很小;混凝土层正下方的横隔板-U肋-顶板及横隔板-U肋细节疲劳应力对混凝土裂缝长度、深度变化较敏感,混凝土开裂对横隔板弧形开口处及U肋圆弧处的影响较小;纵桥向裂缝对疲劳应力的影响比横桥向裂缝显著,且多裂缝会明显增大疲劳细节处应力水平,会加速桥面结构疲劳性能劣化,因此须设钢筋网阻滞裂缝扩展。

日本UFC桥面板和UFC组合桥面板的研发与应用

日本较早期建设的城市高速公路桥梁中主要采用钢桥面板和混凝土桥面板。针对钢桥面板的焊缝疲劳开裂和混凝土桥面板的老化现象,研发了超高强度纤维增强混凝土桥面板(UFC桥面板)及UFC组合桥面板,具有高强度、高耐久性。UFC桥面板分为平板型和方格肋型2种类型,可应用于既有公路桥梁的桥面板更换以及新建公路桥梁的桥面板。UFC组合桥面板为在预制PC桥面板顶面设UFC层作为防水层,可省去预制PC桥面板防水层施工,提高施工效率。UFC桥面板和UFC组合桥面板在预制场预制、现场安装,施工便捷,已实际应用在阪神高速公路15号堺线玉出匝道桥桥面板更换工程、阪神高速公路1号环线信浓桥匝道桥新建桥梁工程、东北高速公路宫城白石川桥上行线既有桥面板更换等工程上,可提高桥梁结构的耐久性、减少桥梁养护工作量、降低养护成本。

温度作用下钢-UHPC轻型组合桥面疲劳性能研究

文中以宜昌长江大桥钢桥面加固改造工程为背景,通过有限元计算,分析不同温度作用下组合桥面疲劳易损细节的应力变化规律.结果表明:相比传统沥青钢桥面,钢-UHPC轻型组合桥面能够在不增加桥梁恒载情况下,降低疲劳细节应力幅值,改善钢桥面抗疲劳性能;不同温度作用下,相比传统沥青钢桥面,钢-UHPC轻型组合桥面各疲劳易损细节应力的降幅达15%~46%.

钢-薄层UHPC组合桥面结构中PBL剪力键抗剪性能试验

为探究钢-超高性能混凝土(UHPC)组合桥面结构中PBL剪力键的抗剪性能,以抗剪钢板尺寸、贯穿钢筋设置和端部承压状态为试验参数,完成了16个PBL试件的推出试验。结果表明:(1)随着抗剪钢板尺寸的增加,试件由UHPC榫无明显损伤时的钢板剪断破坏转变为UHPC榫局部压碎或整体压碎后的钢板剪断破坏,PBL的极限承载力随之相应提高,但其延性系数无明显变化;(2)贯穿钢筋对PBL承载能力的影响与UHPC榫的损伤状态密切相关,其对PBL抗剪承载能力的提高由榫无明显损伤时的5.3%增加到榫局部压碎时的9.7%和榫整体压碎时的14.9%;(3)对于钢-UHPC组合桥面结构中平行阵列布置的多列PBL,当列间距不小于10倍贯穿钢筋直径或12倍抗剪钢板厚度时,相邻列剪力键间相互作用的影响较小。基于试验结果,提出了适用于组合桥面结构中PBL剪力键的抗剪承载力计算公式,并以本文及其它文献的试验结果验证了其适用性。

正交异性钢-钢纤维混凝土组合桥面板疲劳极限状态研究

为了解正交异性钢-钢纤维混凝土(Steel Fiber Reinforced Concrete,SFRC)组合桥面板的疲劳性能及失效机理,以川南城际铁路临港长江大桥为背景,设计、制作正交异性钢-SFRC组合桥面板足尺模型进行疲劳试验,采用ANSYS软件建立试件有限元模型,研究关键细节的疲劳应力和开裂等情况。基于有限元模型,分析不同设计参数(钢顶板厚度、栓钉布置、SFRC抗拉强度及层厚)下组合桥面板疲劳极限状态的失效模式,并提出了主要控制参数取值建议。结果表明:200万次疲劳加载后足尺模型的实测最大裂缝宽度为0.136 mm,出现在SFRC层上缘,钢结构未开裂,组合桥面板疲劳性能良好;组合桥面板疲劳极限状态主要由SFRC层开裂控制,钢顶板厚度、栓钉布置对组合桥面板疲劳性能的影响较小,SFRC抗拉强度和层厚对组合桥面板疲劳性能影响较大,为主要控制参数;在常规正交异性钢桥面板上铺设薄层(厚度不超过50 mm)SFRC时,SFRC抗拉强度不应小于5 MPa,在常规正交异性钢桥面板上铺设普通SFRC(钢纤维体积含量不高于1%,抗拉强度不高于3 MPa)时,SFRC层厚不宜低于100 mm。

钢-混凝土组合简支桥面连续结构横向应力分析

针对钢-混组合简支梁桥的桥面连续结构开裂等病害,围绕桥面连接板的横桥向应力问题,采用线弹性理论和板的偏微分方程进行分析,得出了桥面连接板挠度和应力的分布函数,建立非线性有限元模型,并进行实桥荷载试验.通过比较理论解、有限元解和实测试验结果,证实了理论解和有限元的有效性.根据得到的分布函数,发现横桥向和纵桥向上的最大拉应力出现在钢梁端部位置的连接板的上缘.此外,还分析了连接板区域尺寸变化对横桥向应力峰值的影响,包括纵梁端部距支座的长度、纵梁的间距以及连接板区域整体尺寸变化.结果表明:较小的纵梁间距和较长的纵梁端部与支撑之间的距离会导致连接板中的横向拉应力峰值增加,并提高横向拉应力在总应力中的占比,从而导致桥面连接板早于设计荷载开裂.因此对于纵梁间距较小、梁端长度较长的钢-混组合简支梁桥桥面连续结构,仅计算其纵桥向受力性能会导致计算结果偏危险,建议按照本文方法考虑横桥向应力对桥面连接板的影响.

带钢筋桁架楼承板的PRC连梁抗震性能试验研究及数值分析

为适应超高层建筑以及现代工业化住宅建筑体系迅速发展的需要,提出了一种带钢筋桁架楼承板的新型钢板-混凝土组合(plate-reinforced composite,PRC)连梁。通过拟静力试验,分析了不考虑楼板作用、带普通钢筋混凝土(reinforced concrete,RC)楼板及带钢筋桁架楼承板PRC连梁的破坏形态、承载能力、变形能力和耗能能力等。在此基础上,采用ABAQUS软件分析在不同峰值荷载作用下钢筋桁架楼承板PRC连梁的混凝土、钢板和钢筋骨架的应力发展情况。研究结果表明:钢筋桁架楼承板的设置能显著提高小跨高比PRC连梁的受剪承载力、耗能能力和延性,设置楼板能显著提高连梁的峰值荷载,且带钢筋桁架楼承板对PRC连梁承载力的提升比带普通RC楼板更强,其连梁试件PRC-S3的正向峰值荷载比不带楼板连梁PRC-NS1和带普通RC楼板连梁PRC-S2分别提升了31%和18%,但带楼板连梁在梁板交界处产生通缝之后连梁的刚度退化较为严重;带钢筋桁架楼承板的PRC连梁具有优越的耗能能力,在连梁跨度范围内均出现了显著的对角压杆,主压杆及其衍生压杆共同构成桁架作用来承受剪力;楼承板桁架上下弦钢筋以及连梁纵筋均在连梁根部位置出现应力集中,且连梁试件PRC-S3破坏点对应的累积耗能是不带楼板试件PRC-NS1的1.39倍。