汽车荷载对滑坡稳定性的影响分析

当前滑坡防治工程设计中,没有考虑汽车荷载对滑坡稳定性影响。将汽车荷载简化为移动恒载和汽车动力荷载,其中移动恒载量值介于2.34~6.41 kPa之间,并以冲击系数表征汽车动力荷载,冲击系数μ介于0.1~0.4之间。并采用工程界常用的多种稳定性分析方法,结合算例,通过不考虑同考虑汽车移动恒载载、汽车动力荷载的滑坡稳定性分析对比,发现对于公路从滑坡下滑段通过的浅层滑坡(8m以内),不考虑汽车荷载同考虑汽车移动恒载相比,稳定性系数要高4.3%~11%,不考虑汽车荷载比同时考虑汽车动荷载时稳定性系数要高5.8%~12.1%,即不考虑汽车移动恒载、汽车动力荷载的影响会人为提高滑坡的稳定性系数,且量值不可忽略。对于中厚层滑坡或公路从滑坡抗滑段通过情况,汽车荷载对滑坡稳定影响微弱,可以不予考虑。     

车辆荷载对基坑支护结构影响分析

目前的基坑支护设计规范并未明确说明是否考虑以及如何考虑车辆荷载,将车辆简化为等效静荷载及移动恒载+冲击荷载,并通过具体的基坑实例加以计算分析。结果表明,车辆荷载对基坑有一定的影响,将车辆荷载简化为等效静荷载对基坑的影响小于将车辆荷载简化为移动恒载+冲击荷载。     

新建重载铁路桥梁设计荷载标准的研究

对国内外荷载标准与列车运营模式间的关系进行研究分析,探讨设计活载标准的合理储备,分析国内重载铁路发展的情况,制定重载运营车辆检算模式。基于修正后中-活载(2005)中的ZH图式,从静活载储备、考虑恒载和相关设计参数后储备两方面,对重载列车作用下桥梁结构设计荷载系数的取值进行研究,提出适用于新建重载铁路设计的荷载系数。研究成果可为重载铁路标准规范提供依据。     

轻型门式刚架钢结构荷载取值审查常见问题剖析

本文对轻型门式刚架钢结构设计中常见的荷载问题进行了归纳整理,分析了恒载、活载、风载、雪载及吊车荷载取值对主次结构的影响,强调设计人员应重视与荷载有关的参数取值及荷载简图的复核,可供设计和审查人员参考。     

楼梯荷载输入方法分析

楼梯设计是结构设计中一个必不可少的重要部分。设计中常有设计师对楼梯设计荷载取法较为混乱或人云亦云的输入荷载值。更有甚者,只要是梯间,无论什么样的楼梯,对楼梯荷载通通按恒载8.0kN/m2,活载2.0kN/m2。论文通过对典型双跑楼梯、单跑楼梯、剪刀楼梯等的受力进行举例分析比较,总结出通常做法的谬误之处,提出了合适的楼梯荷载输入法,希望对设计师在设计有所帮助。     

履带历桥梁度验荷载车

履带式桥梁试验荷载车是徐工研究院和内蒙古车辆设计研究院共同研制的一种主要用于桥梁通载性能试验的特种车辆，本产品采用的履带战车底盘，是一种高可靠性和高性能的国内首创桥梁试验产品，外形尺见图1     

单轴拉伸荷载对混凝土渗透性的影响规律研究

研究了拉伸荷载下混凝土渗透性测试方法的可靠性。单轴拉伸荷载通过碟簧及应力传愂器迚行恒载控制，开发出了在荷载状态下测试混凝土中氯离子扩散系数的装置。将加载一定荷载的混凝土试件采用“NEL法”迚行在线渗透性测试，实现了持续荷载下混凝土渗透性的测试。     

公路桥梁荷载试验浅析

我国是一个桥梁大国，新建和巳建桥梁众多，保证桥梁结构的施工质量与运营安全至关重要。桥梁荷载试验可以直接测试结构特性，为判定桥梁承载力性能提供评价指标。本文通过对新旧公路桥梁规范中汽车荷载及冲击力规定的分析，明确了新规范的合理性。同时，对结构分析与试验方案的要点进行了讨论。最后，对荷载试验效率和结构校验系数进行了探讨，并展望了荷载试验的发展方向。     

公路桥梁荷载试验的荷载组合问题探讨

桥梁荷载试验是评价桥梁结构承载能力和动力特性的重要方式之一,荷载组合的选择直接影响试验检验结果的合理性与准确性。针对规范中公路桥梁荷载试验控制荷载的荷载组合问题,基于对规范相关内容进行梳理与研究,给出了桥梁静载试验中控制荷载的建议荷载组合,研究讨论了3种典型桥梁下桥梁静载试验荷载组合的选择,并计算了标准组合与频遇组合下桥梁静载主要测试截面的荷载效率。研究结果表明,桥梁静载试验中控制荷载的建议荷载组合,原则上应遵循“老桥按老标准,新桥按新标准”理念,特殊情况下荷载组合可根据桥梁设计年代以及实际情况选择标准组合或频遇组合。     

荷载分项系数调整对钢筋混凝土梁可靠性的影响分析

为明确新版《建筑结构可靠性设计统一标准》(GB 50068-2018)中的荷载分项系数调整对钢筋混凝土梁设计安全性的影响,参考已有统计参数模型,采用蒙特卡罗法对钢筋混凝土梁进行可靠指标计算。考虑抗弯和抗剪两种破坏模式、四种常用荷载组合等情形,分别计算了荷载分项系数调整后钢筋混凝土梁可靠指标的变化。结果表明：荷载分项系数调整后,对于办公楼活荷载、风荷载、雪荷载分别与恒载组合以及办公楼活荷载和风荷载与恒载联合组合的四种情况,钢筋混凝土梁的抗弯可靠指标提高了约9.7%～16.9%,基本满足目标可靠指标3.2的要求;当抗力分项系数在1.5～2.2范围变化时,钢筋混凝土梁的抗剪可靠指标增加较小,增幅仅约为0.05～0.20;当抗力分项系数取2.2时,钢筋混凝土梁的抗剪可靠指标基本满足目标可靠指标3.7的要求。     

Proof load testing for bridge assessment and upgrading

Bridge deterioration with time and ever increasing traffic loads raise concerns about reliability of aging bridges. One of the ways to check reliability of aging bridges is proof load testing. A successful proof load test demonstrates immediately that the resistance of a bridge is greater than the proof load. This reduces uncertainty in the bridge resistance and so increases the bridge reliability. The paper considers a reliability-based calibration of intensities of proof loads for aging bridges to verify either an existing or increased load rating taking into account possible bridge deterioration. Intensities of proof loads are calibrated based on a consistent target reliability index. The influence of test risk, dead to live load ratio, and uncertainties associated with dead and live loads and bridge resistance is considered. The results presented in the paper relate to short and medium span bridges.     

Structural adequacy assessment of a disused flat bottom rail wagon as road bridge deck

This paper presents half of a full scale experimental testing technique for assessing the structural adequacy of a disused flat bottom rail wagon (FBW) for low volume, heavy axle load road bridge applications. The aim of this ongoing research project is to develop sufficient knowledge required for achieving significant economy and safety of the heavy axle transportation system in regional government council roads. In the absence of such knowledge, the viability of replacing/rehabilitating the ageing bridges could not be economically justified, mainly due to low volume traffic and the costs of alternate solutions using new materials for heavy axle load demands.This study describes a comprehensive laboratory testing of half of a single lane, single span bridge deck and an associated three dimensional finite element modeling. The novel idea in the paper is to enforce the transverse continuity conditions along the longitudinal edge of the half of full scale bridge so that the single FBW tested will mimic the behaviour of a double FBW deck for a single lane road bridge under heavy axle design loads. Several serviceability and ultimate load tests, conforming to the Australian bridge design traffic loads applied at critical locations of the FBW system are reported in the paper. The test results demonstrate that the FBW possesses sufficient structural strength and can service the required design traffic loads.     

浅谈城市桥梁设计汽车荷载标准

对《城市桥梁设计荷载标准》和《公路桥涵设计通用规范》规定的汽车荷载计算参数和荷载效应值进行了对比,同时比较了国外桥梁设计荷载规范,结合我国城市桥梁荷载特点,提出了目前阶段城市桥梁设计荷载的取值标准,并对制定中的城市桥梁设计通用规范提出建议,以指导桥梁设计。     

移动荷载作用下大跨度铁路斜拉桥纵向共振机理

列车荷载作用下铁路斜拉桥将在不同方向上发生振动,列车竖向荷载作用下导致的主梁纵向振动将影响道床稳定性和伸缩装置的使用,甚至影响行车安全性和舒适性。采用等效纵向荷载研究移动荷载作用下斜拉桥纵向振动机理,推导纵向共振速度估算公式。以一大跨度铁路斜拉桥为实例,分析了不同速度的移动荷载作用下结构动力响应。结果表明,当移动荷载速度与估算纵向共振速度接近时,移动荷载通过桥梁时的纵向加载频率与桥梁一阶纵向振动频率接近,斜拉桥发生纵向共振现象,主梁和桥塔动力响应显著增大。     

桥梁多灾害设计荷载系数确定方法探讨

目前美国的桥梁设计多采用荷载与抗力系数法规范(LRFD),其荷载系数和抗力系数是以概率为基础的极限状态方程的形式求得的。荷载与抗力系数规范(LRFD)主要标定常规荷载和单个极端荷载,没有考虑多个极端荷载的情况,而且LRFD对于单个极端荷载的考虑并没有基于概率基础。该文针对多种极端荷载下荷载系数设计存在的问题,将多种极端荷载视为随机过程,以失效概率为纽带,提出荷载系数设计的分项失效概率概念。基于LRFD极限状态方程的形式,提出解决多种极端荷载作用下的MH-LRFD荷载系数计算方法,并给出当仅有两种极端荷载下,桥梁结构多灾害设计荷载系数的一般计算步骤。     

浦阳江特大桥静动载试验及偏载效应分析

以浙赣线电气化提速改造工程浦阳江双线铁路连续梁桥为工程背景,分析了该桥动静载试验单线加载时偏载作用下箱梁的扭转效应.用ANSYS中的Beam4和Shell63单元分别建立了有限元模型,利用该模型计算了连续梁在偏载作用下的挠度和扭转角,计算结果与试验结果吻合,说明所提出的3种模型用于分析同类连续梁的扭转效应是可靠的。     

Effects of geometrical shape and incremental loads on scaffold systems

This paper investigates the influence of geometry-dependent loads and time-dependent incremental loads on the scaffolding systems with different configurations. The loading types considered are the uniform load, geometry-dependent load and incremental load. The geometry-dependent loads include the trapezoidal and triangular loads. Further, the mixed and bare scaffold systems with and without wooden posts at top are considered under the rectangle, L and U configurations on plan. It was found that the mixed scaffold system with wooden posts of typical length 1.7 m at top had a buckling resistance of only half of the bare scaffold system without wooden posts. Also, the largest deformation in the bare scaffold is found to be near the upper joint of the lowest scaffold layer and, in the mixed scaffolding system, the largest deflection occurs at the location between the bottom of the wooden post and top of the highest scaffold layer. Both systems buckle in the in-plane direction of the scaffolds. The critical load of a 3-bay 5-row 3-storey mixed scaffold system is considered under uniform load and its buckling resistance is found to be invariant under geometry-dependent loads and incremental loads. The buckling resistances of increasing the number of bays in the bare and mixed scaffold systems under the uniform load effect are much greater than choosing a particular geometrical L or U configuration.     

Live load factors for parking garage members

This paper proposes a simplified, but effective, algorithm to obtain critical design moments for clamped and/or elastically supported parking garage girders, beams and slabs. Maintaining the uniformly distributed load concept, the equivalent vehicle load factors which can simulate vehicle load effects without conducting additional sophisticated numerical analyses for the concentrated loads are introduced. After determining a standard design vehicle of 2.4 tons through an investigation of small to medium-sized vehicles made in Korea, finite element analyses for concentrated wheel loads were carried out by referring to the influence lines for the girders and beams and influence surfaces for the slabs. Based on the obtained member forces, we determined the equivalent vehicle load factors for the girders, beams and slabs which represent the ratios of member forces under vehicle loads to those under uniformly distributed loads. In addition, the relationships between the equivalent vehicle load factors and sectional dimensions were established by regression and used to obtain the design moments by vehicle loads. The member forces calculated by the proposed method are compared with the results of different approaches mentioned in current design codes with the objective of establishing the relative efficiencies of the proposed method.     

梁桥荷载试验评定结果的影响因素分析

桥梁荷载试验理论分析计算工作是根据桥梁的实际资料和有关数据,再参照原设计文件、施工文件及竣工文件,对桥梁结构进行设计荷载和试验荷载作用下的理论检算。该工作必须对实际结构进行简化,通常对截面以模型形式、约束条件、材料参数及荷载情况等在合理的条件下进行简化模拟,从而满足工程应用的需要,但也由此引入了一些误差。该文结合工程实例,具体对荷载试验结果评定的两大主要影响因素进行定量分析。结果表明,桥面铺装层对荷载试验结果评定的影响较大,荷载加载位置的影响较小。     

深圳特区公路简支梁桥设计荷载效应国内外规范比较研究

本文以英国、美国、香港规范和国内城A及汽 超 2 0荷载标准为基础 ,结合常用跨径的简支梁桥为例 ,以组合总效应相等的原则 ,进行影响线加载计算 ,得出各种荷载效应的相对系数 ,为特区该类型桥梁的设计提供参考