Experimental study on seismic behaviors of steel-concrete composite frames

Steel-concrete composite frames are seeing increased use in earthquake region because of their excellent structural characteristics, including high strength, stiffness, and good ductility. However, there exist gaps in the knowledge of seismic behavior and the design provisions for these structures. In order to better understand the seismic behaviors of composite frame systems, eight steel-concrete composite frames were designed. These composite frames were composed of steel-concrete composite beams and concrete filled steel tube columns. The axial compression ratio of column, slenderness ratio and linear stiffness ratio of beam to column were selected as main design parameters. The low reversed cyclic loading tests of composite frame system were carried out. Based on test results, the seismic behaviors of composite frames such as failure mode, hysteresis curve, strength degradation, rigidity degradation, ductility and energy dissipation were studied. Known from the test phenomenon, the main cause of damage is the out-of-plane deformation of steel beam and the yielding destruction of column heel. The hysteretic loops of composite frame appear a spindle shape and no obvious pinch phenomenon. The results demonstrate that this type of composite frame has favorable seismic behaviors. Furthermore, the effects of design parameters on seismic behaviors were also discussed. The results of the experiment show that the different design parameter has different influence rule on seismic behaviors of composite frame.

Internal Force Distribution in Steel-Concrete Composite Structure for Pylon of Cable-Stayed Bridge

Adopting a steel-anchor beam and steel corbel composite structure in the anchor zone on pylon is one of the key techniques for the design of Jintang bridge, a cable-stayed bridge in Zhoushan, China. In order to ensure the safety of the steel-concrete composite structure, a stud connector model for the joint section was put forward. Experiments were conducted to obtain the relation between load and slip of specimen, the failure pattern of stud connector, the yield bearing capacity and ultimate bearing capacity of a single stud, etc. The whole process of the structural behavior of the specimen was comprehensively analyzed. The features of the internal force distribution in the steel-concrete composite structure and the strain distribution of stud connector under different loads were emphatically studied. The test results show that the stud connector is applicable for the steel-concrete composite structure for pylon of Jintang bridge. The stud has a good ductility performance and a obvious yield process before its destruction. The stud connector basically works in a state of elasticity under a load less than the yield load.

Mechanical performance of shear studs and application in steel-concrete composite beams

This work experimentally investigates the effects of shear stud characteristics on the interface slippage of steel-concrete composite push-out specimens. ABAQUS is used to establish a detailed 3D finite element(FE) model and analyze the behavior of push-out specimens. The modeling results are in good agreement with the experimental results. Based on parametrical analysis using the validated FE approaches, the effects of important design parameters, such as the diameter, number, length to diameter ratio, and yield strength of studs, concrete strength and steel transverse reinforcement ratio, on the load-slip relationship at the interface of composite beams are discussed. In addition, a simplified approach to model studs is developed using virtual springs with an equivalent stiffness. This approach is demonstrated to be able to predict the load-displacement response and ultimate bearing capacity of steel-concrete composite beams. The predicted results show satisfactory agreement with experimental results from the literature.

Static behavior of semi-rigid thin-walled steel-concrete composite beam-to-column joints with bolted partial-depth flush end plate:experimental study

A new type of semi-rigid thin-walled steel-concrete composite beam-to-column joint has been proposed in this paper.Five semi-rigid composite beam-to-column joint specimens subjected to hogging moments under monotonic loading were tested to study the static behavior of this new type of joint.The main variable parameters for the five joint specimens were the longitudinal reinforcement ratio and the joint type.The experimental results designated that the magnitude of extension of the longitudinal reinforcement is the most important factor that influenced the moment-rotation characteristic of the new type of joint.The concrete slabs could resist 3.8%-19.1% of the total shear load applied to the cross-sections near the beam-to-column connection.The edge stiffened elements,such as the flange of the lipped I-section thin-walled steel beam,were capable of having considerable inelastic deformation capacity although they had comparatively large width-to-thickness ratios.The shear failure of the concrete cantilever edge strip must be taken into account in practical design because it has significant influence on the anchorage of the longitudinal reinforcement in the new type of external joints.

Bending Stiffness of Truss-Reinforced Steel-Concrete Composite Beams

This paper is concerned with a special steel-concrete composite beam in which the resisting system is a truss structure whose bottom chord is made of a steel plate supporting the precast floor system. This system works in two distinct phases with two different resisting mechanisms: during the construction phase, the truss structure bears the precast floor system and the resisting system is that of a simply supported steel truss;once the concrete has hardened, the truss structure becomes the reinforcing element of a steel-concrete composite beam, where it is also in a pre-stressed condition due to the loads carried before the hardening of concrete. Within this framework, the effects of the diagonal bars on the bending stiffness of this composite beam are investigated. First, a closed-form solution for the evaluation of the equivalent bending stiffness is derived. Subsequently, the influence of geometrical and mechanical characteristics of shear reinforcement is studied. Finally, results obtained from parametric and numerical analyses are discussed.

The Study of Force and the Mechanical Characteristic of Incremental Launching Construction Method on a Steel-Concrete Continuous Beam Bridge

The usage of steel-mixed composite beams is quite extensive today.During an event of constructing steel-mixed composite bridges,the incremental launching construction method is generally adopted.This paper mainly analyzes the force of incremental launching construction on a steel-concrete continuous beam bridge,the classification of incremental launching construction,the application of incremental launching construction in steel-mixed composite beams,the temporary facilities existing in incremental launching construction as well as their existing problems.Lastly,the analysis of the stress of composite beams in incremental launching construction is described by using the reference for the construction of mixed composite continuous beam bridges provided.

Research review on steel–concrete composite joint of railway hybrid girder cable-stayed bridges

Purpose–This study aims to research the development trend,research status,research results and existing problems of the steel–concrete composite joint of railway long-span hybrid girder cable-stayed bridge.Design/methodology/approach–Based on the investigation and analysis of the development history,structure form,structural parameters,stress characteristics,shear connector stress state,force transmission mechanism,and fatigue performance,aiming at the steel–concrete composite joint of railway long-span hybrid girder cable-stayed bridge,the development trend,research status,research results and existing problems are expounded.Findings–The shear-compression composite joint has become the main form in practice,featuring shortened length and simplified structure.The length of composite joints between 1.5 and 3.0 m has no significant effect on the stress and force transmission laws of the main girder.The reasonable thickness of the bearing plate is 40–70 mm.The calculation theory and simplified calculation formula of the overall bearing capacity,the nonuniformity and distribution laws of the shear connector,the force transferring ratio of steel and concrete components,the fatigue failure mechanism and structural parameters effects are the focus of the research study.Originality/value–This study puts forward some suggestions and prospects for the structural design and theoretical research of the steel–concrete composite joint of railway long-span hybrid girder cable-stayed bridge.

Flexural stiffness characterization of the corrugated steel-concrete composite structure for tunnel projects

Corrugated steel–concrete(CSC)composite structures are increasingly used in tunnel and culvert projects due to their good mechanical properties.The design of CSC composite structures is often governed by deflection limits in service,hence it becomes crucial to evaluate accurately their flexural stiffness.In this work,the deflection deformation mechanism of CSC composite structure is studied by experimental and numerical methods,and a simplified formula for calculating the flexural stiffness is established.In addition,the deflection results obtained by different methods are compared and analyzed.It is found that:(1)the flexural stiffness of the CSC composite structure is constant only when the load is small,and after the bending moment exceeds a certain value,the flexural stiffness will gradually become smaller as the bending moment increases.(2)The value of the bending moment corresponding to the end of the elastic stage of the bending moment-deflection curve increases with the increase of the axial force in the composite structure.(3)As the axial force of the composite structure increases,the flexural bearing capacity of the structure increases first and then decreases.

预制钢-混凝土组合楼梯抗弯性能与舒适度分析

为推进组合材料在建筑结构中的应用,对预制钢-混凝土组合楼梯踏步的抗弯性能和楼梯整体的舒适度进行研究。进行6个楼梯踏步试件的四点弯曲试验,主要探究抗剪件形式和踏步与梯梁的连接方式对楼梯踏步承载性能的影响。试验结果表明,相对于角钢和栓钉抗剪件,槽钢抗剪件对楼梯踏步的承载力提升更为显著。此外,焊接试件的承载力受抗剪件的影响较小,并且高于简支试件的承载力,在今后的工程应用中,焊接可以作为钢-混凝土组合楼梯踏步与梯梁连接的主要方式。为了更准确地研究楼梯踏步的力学行为,使用ABAQUS有限元软件对其进行建模,该有限元模型能够准确模拟楼梯踏步的力学行为。在验证模型准确性的基础上,对整体楼梯进行舒适度分析。结果表明,在规范限值范围内,楼梯的自振频率和人致激励下的加速度响应均满足行走的舒适度要求,使用过程中不会引起明显不适,符合人体工程学的要求。试验和建模分析证明,槽钢抗剪件对楼梯踏步的承载力提升效果更好,焊接可以作为楼梯踏步与梯梁的连接方式,并且楼梯的舒适度满足规范要求。

Parametric study on contact sensors for MASW measurement-based interfacial debonding detection for SCCS

Steel-concrete composite structures(SCCS)have been widely used as primary load-bearing components in large-scale civil infrastructures.As the basis of the co-working ability of steel plate and concrete,the bonding status plays an essential role in guaranteeing the structural performance of SCCS.Accordingly,efficient non-destructive testing(NDT)on interfacial debondings in SCCS has become a prominent research area.Multi-channel analysis of surface waves(MASW)has been validated as an effective NDT technique for interfacial debonding detection for SCCS.However,the feasibility of MASW must be validated using experimental measurements.This study establishes a high-frequency data synchronous acquisition system with 32 channels to perform comparative verification experiments in depth.First,the current sensing approaches for high-frequency vibration and stress waves are summarized.Secondly,three types of contact sensors,namely,piezoelectric lead-zirconate-titanate(PZT)patches,accelerometers,and ultrasonic transducers,are selected for MASW measurement.Then,the selection and optimization of the force hammer head are performed.Comparative experiments are carried out for the optimal selection of ultrasonic transducers,PZT patches,and accelerometers for MASW measurement.In addition,the influence of different pasting methods on the output signal of the sensor array is discussed.Experimental results indicate that optimized PZT patches,acceleration sensors,and ultrasonic transducers can provide efficient data acquisition for MASW-based non-destructive experiments.The research findings in this study lay a solid foundation for analyzing the recognition accuracy of contact MASW measurement using different sensor arrays.

钢结构楼梯与PC叠合板在低层复杂结构体系中的应用研究

从施工角度出发,对钢结构楼梯、PC叠合板在低层复杂结构体系中的应用分别进行了深入研究。探讨了两种材料在实际施工中的优势和挑战,钢结构楼梯与PC叠合板在低层复杂结构体系中都具有独特的优势和应用价值,淮河行蓄洪区新建王截流和陈郢保庄圩居民迁入安置工程中,房屋快速安全成功建造的实践证明,两者结合运用将为建筑领域带来更多的可能性和创新,为建筑行业的发展贡献更多的智慧和力量。

Research on Concrete Preparation for the Steel-concrete Composite Segment of Jingyue Yangtze River Bridge

To improve the quality of the steel-concrete composite segment of the box girder,to ensure the compactness of concrete to avoid debonding and to enhance the fatigue strength of concrete are critical to the concrete preparation for such site. Furthermore,the coordination ability to deformation between steel and concrete is also important because of great difference of the elastic modulus between them. Concrete for the steel-concrete composite segment with high fluidity,excellent crack resistance and low shrinkage was prepared by adding efficient poly-carboxylic water-reducing agent,high quality fly ash and expansion agent to it. The quality of the concrete of the half partial testing block showed that the optimal mix proportion of polypropylene fiber reinforced concrete had achieved expected effect,ensured high quality,thus meeting the requirements of construction.

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.

Chemical Composition, Characterization and Factors Affecting Household Dust (<20 µm) in Greater Cairo, Egypt

Adverse health and environmental effects of household dust are derived from their chemical composition and properties. In this study, household, stairs and entryway dust (<20 μm) samples from homes located in urban, residential and residential near to industrial area in Greater Cairo during summer 2013 were collected to study their chemical composition, characterization and factors affecting them. Results indicate that the levels of measured anions and cations were higher in the household compared to stairs and entryway dust. The highest concentration of ?, , Cl-?,?, Na+, K+, Ca2+ and Mg2+ in the household and entryway dust was found in urban area. was abundant in household, entryway and stairs dust followed by Cl- and . Its average concentrations were 21.38, 14.57 and 15.83 mg/g, respectively. The household/entryway (I/O) concentration ratios of measured ion components indicate that these species might derive from indoor sources, although outdoor sources could be present as well. pH values of household, stairs and entryway dust ranged from 6.43 to 8.53, indicating that these dusts brought a large amount of crustal species, and might alleviate the tendency of acidification. The relationships between the concentrations of acidic components ( and ) and basic components (, Ca2+ and Mg2+) in household, stairs and entryway dust confirm that the acidity of dust is neutralized. Ca2+ and in household and stairs dust and Ca2+ and Mg2+ in entryway dust are the most dominant neutralization substances.

轮履式爬楼梯轮椅及轮履切换动力学分析

针对目前轮履复合式爬梯轮椅存在轮胎易干涉履带、爬梯时轮椅与顶端平台易发生碰撞等问题,设计了一种以关节型摆臂履带底盘为爬楼梯机构、新型轮履切换方式的轮履式爬楼梯轮椅。建立其数学模型,分析得出质心坐标、攀爬楼梯质心垂向位移曲线以及在轮履切换4个阶段时,摆臂电动机和电动推杆的动力学变化曲线;采用RecurDyn软件对轮椅的上下楼梯模式和轮履切换模式进行仿真,结果表明,轮椅在上下楼梯过程中平稳、安全,轮履切换4个阶段动力学的理论值与仿真情况相符。研究为该类爬梯轮椅的机械结构设计以及电动推杆选型、摆臂电动机选型提供了理论依据。

学校建筑叠合板及楼梯安装施工要点分析——以济阳第二实验中学迁建PPP项目为例

装配式建筑以其自身的优势在学校建设中得到了广泛应用。相比于传统钢筋混凝土现浇建筑,装配式建筑具有施工速度快、省去现场加工制作工序、质量控制效果等优势,工期较短,非常适合学校建筑应用。文章以济阳第二实验中学迁建PPP项目为工程案例,对其装配式建筑叠合板及楼梯安装施工要点进行分析。该项目工程规模比较大,叠合板及楼梯安装施工工程量大,为避免影响工期进度,在具体施工中,采用以4台QTZP125型塔式起重机作业为主、人工调整为辅的安装施工方法,取得了良好的效果,值得类似工程借鉴。

金鼎大厦结构设计中方案的比较及优化

金鼎大厦地上由2幢21层塔楼组成,地下共四层。设计中从结构合理、专业协调、便于施工并满足业主需求等角度全面进行了基础、地下室楼面、塔楼等的结构方案比较及优化,对塔楼标准层楼面进深梁、悬挑钢梯等构件也进行了优化。塔楼采用了钢框架-钢筋混凝土筒体结构体系,地下室楼面非预应力空心板采用了旋转布置形式,受力合理,对于其他工程结构设计的方案选择具有参考价值。

大跨度弧形悬吊楼梯的动力特性研究

大跨度悬吊楼梯的跨度大、约束少、整体刚度较柔，其结构的动力特性分析是寻求控制结构设计关键因素的重要途径。文中结合某大跨度弧形悬吊楼梯的结构特点，采用壳、空间曲梁及杆单元建立了有限元力学模型，并根据模态分析结果，得到楼梯结构的主要自振频率和振型分布。分析表明，其低阶自振频率避开了人步行频率范围1～3Hz，低阶振型主要为竖向弯曲和扭转形式。对该楼梯自振性能的分析为进一步优化结构设计提供了技术依据。

陡倾阶梯式复合建基面上进水塔的抗滑稳定分析

某高耸进水塔的建基面为陡倾阶梯式复合建基面,受力机理较为复杂。为验证其抗滑稳定性,借助ANSYS有限元分析软件,建立陡倾阶梯式复合建基面上进水塔的三维有限元模型,计算陡倾阶梯式复合建基面上的正应力和剪应力,并积分得到各平面的法向力和切向力,利用抗剪断强度公式计算进水塔的抗滑稳定性。结果表明,进水塔抗滑稳定性满足稳定要求;进水塔建基面上最大压应力不超过2.3 MPa,满足地基允许承载力要求;塔背撑墙与基岩交接面存在很大的顺水流向拉应力,需采取相应的工程措施。

Recent progress of seismic research on tall buildings in China Mainland

As a result of rapid economic growth and urbanization in the past two decades,many tall buildings have been constructed in China Mainland,offering researchers and practitioners an excellent opportunity for research and practice in the field of structural engineering. This paper reviews progress by researchers throughout China Mainland on the seismic research of tall buildings,focusing on three major topics that impact the seismic performance of tall buildings. These are:(1) new types of steel-concrete composite structural members such as steel-concrete composite shear walls and columns,(2) earthquake resilient shear wall structures such as shear walls with replaceable structural components,self-centering shear walls and rocking walls,and(3) performance-based seismic design,including seismic performance index,performance level and design method. The paper concludes by presenting future research needs and directions in this field.