Durability of Bridge Expansion Joints with Perforated Dowels Under Traffic Impact Loading

In design phases, expansion joints are required to have movement capacity, bearing capacity for static and dynamic loading, watertight, low noise emission and traffic safety. On the basis of the fact that failure due to dynamic loading is the main reason for the observed damages, attention is focused on the bearing capacity for dynamic loading governed by impact, because it differs from the static loading. In this study, from the viewpoint of durability, experimental studies for dynamic behavior were conducted for aluminium alloy expansion joints with perforated dowels. The validity of the perforated dowels against traffic impact loading was confirmed by both experimental and numerical studies.     

Design of bridge expansion joints with perforated dowels under impact loading

The expansion joints are expected to have movement capacity, bearing capacity for static and dynamic loading, water-tightness, low noise emission and traffic safety. In particular, the failure due to impact loading is the main reason for the observed damages. The problem of dynamic behavior of the expansion joints is so complex that we shall focus our attention on the impact factor for vehicle load that is governed by traffic impact. In order to overcome this difficulty, the cantilever-toothed aluminum joint (finger joint) is one of the promising joints under impact loading. In this study, from the viewpoint of design methodology, numerical studies for impact behavior were conducted for aluminum alloy expansion joints with perforated dowels. The design impact factor for the expansion joints with the perforated dowels against traffic impact loading was examined by using numerical simulations.     

钢管搭接节点破坏过程分析

随着钢结构的发展,钢管搭接节点应用越来越广泛.钢结构中节点受力最复杂,目前对平面K型钢管搭接节点的静力研究有很好的基础.但是在低周往复荷载下节点滞回性能的分析还比较少.采用有限元法对平面K型圆钢管搭接节点在弦杆轴向荷载作用下节点的承载力进行研究,对比分析不同几何参数与节点焊接形式下的极限承载力和破坏形式.     

某空腹式双曲拱桥承载力现场测试与分析

为检验在役双曲拱桥的承载能力与动力特性,对某净跨为36 m空腹式双曲拱桥进行了静载试验、动载试验及空间有限元分析。测试结构的静态应变、动态应变、挠度、自振频率、振型及加速度等结构反应,计算得出冲击系数。将实测结果与有限元结果进行对比分析,结果表明:应变校验系数为0.5~0.9,结构具有较好承载力。实测的各阶频率及相应振型与有限元计算结果比较吻合,桥梁整体竖向刚度较好。     

基于边界摩擦的碟簧隔振器力学性能(英文)

为研究边界摩擦对碟簧隔振器力学性能的影响,基于能量守恒定律推导了在考虑边界摩擦时碟簧隔振器的载荷位移迟滞曲线公式.通过有限元分析与静载试验验证了该公式的正确性.在此基础上研究了边界摩擦对碟簧隔振器承载能力的影响,并通过动载试验研究了边界摩擦对碟簧隔振器的动态性能的影响.试验结果表明:边界摩擦可提供较大的阻尼,使得碟簧隔振器具有良好的阻尼特性,其阻尼比可达0.23;隔振器的耗能、动刚度和阻尼特性对加载幅值更为敏感,而对加载频率敏感度较小.该研究成果对碟簧隔振器设计具有重要的指导意义.     

五跨连续刚构桥承载力评定

为判断五跨连续刚构桥梁在试验荷载作用下的实际工作性能和承栽力,评价桥梁的施工质量,通过静载试验测定桥跨结构的静应变、静挠度等静力效应;通过动载试验测定桥跨结构的动应变、自振频率、冲击系数等动力性能,进而对桥梁结构的承载能力进行了综合评定。     

Numerical simulation on dynamic bending strength of three-graded concrete beam based on meso-mechanics

To study the bending strength of mass concrete under dynamic loading, the pure bending zone of three-graded concrete beam is considered as a three-phase composite composed of matrix, aggregate and interface between them on meso-level. Dynamic constitutive model considering strain-rate strengthening effect and damage softening effect is adopted to describe the cocrete and meso-element's damage. The failure mechanisms of beam under impact loading, triagle wave load, dynamic load coupling with initial static loading were simulated by using displacement-controlled FEM. Furthermore, stress-strain curve of the specimens and their dynamic bending strength were obtained. The results obtained from numerical simulation agreed well with experimental data.     

Mechanical Characteristics of Radial Magnetic Bearing

1 IntroductionThe great majority of docUments about magneticbearings dealt only with the characteristics when thejournal was concentric with the radial magnetic bearing inthe past, and few research involved the ones when thejournal was eccotic with the radial magnetic bearing.For example, the bulk of documents suPPosed thecomponents Fx and F. of magnetic force depended onlyon the cUrred in x and y direchons respeGtively, bac theair gap thickness and the curvatUre of suiface shape werenot co…     

径向磁轴承的力学特性

This paper is based on the example of a radial magnetic bearing possessed of eight-pole, and derives the calculation formulas of static and dynamic mechanical characteristics of the bearing, in which the shape and curvature of surface, eccentricity and tilt of the journal are taken into account. Variations of the static and dynamic characteristics of the radial magnetic bearing versus static tilt parameters of journal are discussed. The outcomes show that the static tilt of the journal has influence on the mechanical characteristics of radial magnetic bearing, and change the static load capacity between two radial magnetic bearings and exert coupling effect between them. To study the dynamics of a practical rotor-magnetic bearing system, at least six stiffness coefficients in each radial magnetic bearing must be considered in ideal case, and twelve stiffness coefficients must be considered in general case of tilting journal. Such a find can be used for the coupled electromechanical dynamics analysis of rotor system equipped with magnetic bearings.     

Seismic behavior of specially shaped column joints with X-shaped reinforcement

To investigate the seismic behavior of specially shaped column joints with X-shaped reinforcement,two groups of specimens with or without X-shaped reinforcement in joint core region were tested under constant axial compression load and low reversed cyclic loading,which imitated low to moderate earthquake force.The seismic behavior of specially shaped column joints with X-shaped reinforcement in terms of bearing capacity,displacement,ductility,hysteretic curve,stiffness degradation and energy dissipation was studied and compared to that without Xshaped reinforcement in joint core region.With the damage estimation model,the accumulated damage was analyzed.The shearing capacity formula of specially shaped column joints reinforced by X-shaped reinforcement was proposed with a simple form.The test results show that X-shaped reinforcement is an effective measure for improving the seismic behavior of specially shaped column joints including deformation behavior,ductility and hysteretic characteristic.All specimens were damaged with gradual stiffness degeneration.In addition,X-shaped reinforcement in the joint core region is an effective way to lighten the degree of cumulated damage.The good seismic performance obtained from the specially shaped column joint with X-shaped reinforcement can be used in engineering applications.The test value is higher than the calculated value,which indicates that the formula is safe for the design of specially shaped column joints.     

某大楼人工挖孔桩荷载传递及承载性状试验研究

根据某大楼2根无扩底人工挖孔桩灌注的静载试验,通过埋设在桩中不同土层位置的混凝土应变传感器在各级加载下所测得的数据,分析了桩端阻力、桩侧摩阻力的发挥规律和桩的变形规律,研究了人工挖孔桩的承载特性和荷载传递机理.试验结果表明,对嵌入软质岩有一定深度的人工挖孔桩,其桩的荷载传递性状呈现为摩擦桩的特点.根据这一特点,建议在人工挖孔桩设计前应对桩进行承载力试验,当桩端嵌入岩层一定深度时可不设计扩大头.     

钢管混凝土柱-环扁梁中节点静载试验研究

介绍了钢管混凝土柱-钢筋混凝土环扁梁中节点的构造和基本受力机理,以及环梁、环扁粱节点的静载试验结果.试验结果表明,通过合理设计,环梁、环扁梁节点能有效地传递框架梁、扁梁梁端的剪力和弯矩,具有良好的变形能力.     

CSP轧机组主传动系统动力系统测试分析

在热连轧机组中,机械振动主要来源于主传动轴上的扭矩振动,通过CSP精轧机组设备主传动系统的承载能力、动态稳定性的测试分析,科学评估精轧机组设备状态,掌握机组的承载能力。     

标贯试验在膨胀土承载力分析中的应用研究

基于邢台市区膨胀土的主要性质,采用标准贯入试验进行了膨胀土承载力分析,并基于数据回归分析和工程经验,归结出了膨胀土承载力分析方法的适用范围。实践证明,在膨胀土承载力分析过程中,由于采用了将试验击数与载荷试验直接对比进行回归分析,具有相当的准确性和科学性。     

刚架综合实验平装置研制与应用

NHLX-G型刚架综合实验装置是为开展综合性、设计性的材料力学实验而研制的台式多功能组合实验装置。该装置的最大特点是可以用可装配杆件自主搭建各种不同的实验。在实验中通过改变不同支座,组成不同形式的约束、改变加载点或改变载荷的方向、选择不同的杆件或接头等,组建多种不同形式的刚架和桁架结构实验。该实验装置真正体现了综合性、设计性和研究性。学生在实验中灵活设计、自主实施,从而培养学生的综合素质和创新能力。     

不同场景中的视觉工作记忆

近年来,很多研究分别从动态场景中和静态场景中来研究视觉工作记忆。文章分别从研究范式、工作记忆的容量和存储方式的角度研究动态场景中的视觉工作记忆和静态场景中的视觉工作记忆的联系和区别。静态场景中的视觉工作记忆,大多使用变化觉察范式,主要在“强客体说”和“弱客体说”两种存储方式上存在较大的争议。动态场景中的视觉工作记忆,大多使用多客体追踪范式,强调“强客体说”的存储方式。     

不同加载角T形钢管混凝土压弯承载力研究

采用有限元软件ABAQUS建立了不同加载角T形带肋和多室钢管混凝土压弯构件的计算模型,数值计算结果与试验结果吻合良好。对影响T形钢管混凝土柱水平荷载P-水平位移Δ关系曲线的参数进行分析,结果表明:加载角为0°时,T形钢管混凝土构件的承载力最低,在67.5°负向加载时,构件的承载力最大,比0°加载角构件大13%左右,加载角为45°~90°间承载力总体上差别不大。随着钢管屈服强度、混凝土抗压强度、钢管长厚比、带肋和多室T形钢管混凝土构件在斜向加载的承载力增加,在传统钢管混凝土基础上,提出了适用于不同加载角带肋和多室T形钢管混凝土压弯构件的承载力设计方法,简化计算公式与有限元结果、试验结果均吻合较好。     

Ultimate Bearing Capacity of Hollow Spherical Joints Welded with Circular Pipes under Eccentric Loads

The National Swimming Center built for the 2008Beijing Olympic Games applies the polyhedron spatialframe structure, which is based on the foam physicstheory[1]. Its simple geometry is a square box of 170m×170 m×29 m. It can hold 17 000 people, theroof o…     

Bearing capacity and load transfer mechanism of a static drill rooted nodular pile in soft soil areas

The static drill rooted nodular pile is a new type of pile foundation consisting of precast nodular pile and the surrounding cemented soil. This composite pile has a relatively high bearing capacity and the mud pollution will be largely reduced during the construction process by using this type of pile. In order to investigate the bearing capacity and load transfer mechanism of this pile, a group of experiments were conducted to provide a comparison between this new pile and the bored pile. The axial force ofa precast nodular pile was also measured by the strain gauges installed on the pile to analyze the distribution of the axial force of the nodular pile and the skin friction supported by the surrounding soil, then 3D models were built by using the ABAQUS finite element program to investigate the load transfer mechanism of this composite pile in detail. By combining the results of field tests and the finite element method, the outcome showed that the bearing capacity of a static drill rooted nodular pile is higher than the bored pile, and that this composite pile will form a double stress dispersion system which will not only confirm the strength of the pile, but also make the skin friction to be fully mobilized. The settlement of this composite pile is mainly controlled by the precast nodular pile; meanwhile, the nodular pile and the surrounding cemented soil can be considered as deformation compatibility during the loading process. The nodes on the nodular pile play an important role during the load transfer process, the shear strength of the interface between the cemented soil and the soil of the static drill rooted pile is larger than that of the bored pile.     

考虑楼板作用的半刚性组合节点的有限元分析

文章通过SAP2000程序,建立了半刚性组合节点理论分析模型,采用转动弹簧单元来模拟实际中钢管柱与组合梁的半刚性连接。通过分析比较节点在低周反复荷载作用下的荷载(P)-位移(Δ)关系滞回曲得到,组合节点的承载力、刚度和耗能能力有所提高,耗能较好,但承载力相差不大,所以在正常的施工条件下,应优先选用方钢管。