U形肋正交异性组合桥面板力学性能

为验证桥面板在局部车轮荷载作用下的受力特性及桥面板在桥梁第二体系中的受力性能,提出新型U形肋正交异性组合桥面板系统,并区分其与常规桥面板的受力性能.设计制作了3个不同桥面板试件,其中包括1个混凝土桥面板,1个正交异性钢桥面板,1个带U形肋正交异性组合桥面板.通过静力试验测试了不同桥面板在荷载作用下负弯矩区混凝土开裂情况、桥面板不同部位的结构应变和变形等.试验结果表明:U形肋正交异性组合桥面板在车轮荷载作用下其局部应力水平显著低于正交异性钢桥面板,具有较强的抗疲劳性能;U形肋正交异性组合板在桥梁第二体系的承载能力分别是混凝土桥面板和钢桥面板的1.37倍和0.93倍.     

Object-level change detection based on full-scale image segmentation and its application to Wenchuan Earthquake

Aiming at object fragmentation and poor detection results caused by discontinuous segmentation scale in object-level change detection,a new object-level change detection method based on the full-scale object tree is presented in this paper.The core idea of this new algorithm is to establish the full-scale object tree based on convexity model theory and integrate full-scale image segmentation techniques and change detection into the whole process.Some Wenchuan Earthquake images are taken as an example to dis...     

Uplift behavior and load transfer mechanism of prestressed high-strength concrete piles

Prestressed high-strength-concrete (PHC) tube-shaped pile is one of the recently used foundations for soft soil. The research on uplift resistance of PHC pile is helpful to the design of pile foundations. A field-scale test program was conducted to study the uplift behavior and load transfer mechanism of PHC piles in soft soil. The pullout load tests were divided into two groups with different diameters, and there were three piles in each group. A detailed discussion of the axial load transfer and pile skin resistance distribution was also included. It is found from the tests that the uplift capacity increases with increasing the diameter of pile. When the diameter of piles increases from 500 to 600 mm, the uplift load is increased by 51.2%. According to the load-displacement (Q-S) curves, all the piles do not reach the ultimate state at the maximum load. The experimental results show that the piles still have uplift bearing capacity.     

Evaluation of the coefficient of friction of rail in the field and laboratory using several devices

ABSTRACT

Accurate friction measurement is vital to apply appropriate friction management techniques to the wheel/rail interface. This work analyses different friction measurement techniques under a variety of conditions in the laboratory and the field. Tests have been carried out using a pendulum tester, hand-push tribometer, twin-disc machine and full-scale rig in the UK and Colombia for a variety of interfacial conditions and rail hardness. The pendulum has been found to be more sensitive to different conditions than the hand-push tribometer. This is due to the area that the pendulum sweeps being smaller, and so it can be more carefully controlled and therefore measure the surface condition being tested. This is in contrast to the push tribometer which needs a long section of rail to take a measurement. Twin-disc and full-scale rig creep curves show good agreement between each other.     

Loading to failure and 3D nonlinear FE modelling of a strengthened RC bridge

A reinforced concrete railway trough bridge in Örnsköldsvik, Sweden, was strengthened in bending with rods of carbon-fibre-reinforced polymer and loaded to failure. The aim was to test and calibrate methods developed in the European Research Project ‘Sustainable Bridges’ regarding assessment and strengthening of existing bridges. A steel beam was placed in the middle of one of the two spans and was pulled downwards. Failure was reached at an applied load of 11.7 MN. It was initiated by a bond failure caused by a combined action of shear, torsion as well as bending after yielding in the longitudinal steel reinforcement and the stirrups. The bond failure led to a redistribution of the internal forces from the tensile reinforcement to the stirrups, causing the final failure. The computer models developed to simulate the loading process were improved step by step from linear shell models to more detailed models. The most developed model, a three-dimensional nonlinear finite element model with discrete reinforcement, gave accurate accounts of the response of the bridge.     

空间网架结构钢管混凝土柱节点力学性能足尺试验及分析

采用足尺试验与数值仿真相结合的方法研究空间网架结构中的钢管混凝土柱节点的受力及抗震性能。试验荷载逐级加载到设计荷载的1.6倍并观测柱节点的变形与应力。试验结果表明试验荷载下柱节点钢结构部分基本处于弹性状态,混凝土极小部分区域超出压应力极限,钢管与混凝土粘接良好。非线性有限元分析结果揭示了柱节点在低周往复荷载作用下的滞回耗能能力和破坏特征,指出了柱节点承载的薄弱位置,给出了柱节点的极限承载力。结果表明,足尺试验与数值计算相结合的方法可以全面揭示柱节点的受力特性及抗震性能。     

上海浦东国际机场候机楼R2钢屋架足尺试验研究

本文介绍了上海浦东国际机场候机楼张弦梁式钢屋架足尺模型在预应力张拉和加载两阶段的试验研究。与试验结果的比较表明,文中建立的张拉非线性分析模型和整体结构受力分析模型是适用的;试验结果和数值分析还表明,屋架在静力荷载作用下的结构分析可以采用线性理论。     

电网故障下全功率风电场内部机组的暂态稳定性分析

全功率风电场中机组并网运行的稳定性往往与网侧变流器的控制和并网阻抗有关,因而风电场中机组的失稳并不是同时发生的.为揭示风电场中机组的位置与其暂态稳定性的关系以及机组间稳定性的相互影响,建立了基于锁相环的多风电机组非线性降阶模型.基于等面积法的思想,分析了不同运行条件下风电场内部不同机组的暂态稳定裕度以及场内线路阻抗对稳...     

外挂微晶发泡板轻钢框架结构振动台试验

为研究外挂微晶发泡板轻钢框架结构在动力作用下的工作性能,进行了1个2层单跨轻钢框架外挂微晶发泡板足尺模型的振动台试验.试验选取了EL-Centro、Taft、张家口人工波3条地震波,地震加速度考虑8度多遇到9度罕遇.通过分析模型结构的自振周期、刚度、楼层加速度以及楼层位移,研究了外挂微晶发泡板轻钢框架结构的振动特性,对微晶发泡板的工程应用给出了建议.试验研究表明:在9度罕遇地震下,轻钢框架结构与外挂墙板龙骨基本无破坏,仅墙板表皮有脱落现象,部分墙板发生平面外扭转;采用微晶发泡板与框架间相对错动的装配连接方式,可一定程度上减小结构的层间位移;墙板开设较大门窗洞时,该方向刚度虽有较大退化,但在9度罕遇地震作用下无倒塌危险,能够满足大震不倒的抗震设防要求;相邻墙体之间的预留缝需要添加柔性材料改善相邻墙体间的撞击挤压现象.