港口大型圆形地下连续墙施工技术

日照港石臼港区东煤南移项目翻车机房围护结构采用圆形地下连续墙。文章阐述了在吹填地层港口环境下,针对圆形地连墙厚砂层坍塌、内径小且弧度大、圆弧形钢筋笼、偏槽等难点问题,采取了场地加固、设置导墙外扩角、改进开挖方法、特制加工平台、多方法纠偏等处理措施,取得了较好的效果,为类似工程提供一定的参考。     

SMW工法桩在荆州基坑支护中的设计与应用

介绍荆州市恒大翡翠华庭项目基坑支护体系设计方案选型思路。本项目地质条件差,周边环境极为复杂,通过弹性抗力法计算模型,运用天汉软件对支护结构内力和变形进行计算,以及基坑抗隆起、抗倾覆、整体稳定性等验算,选择采用SMW工法。计算结果与基坑监测资料对比分析结果显示,应用SWM工法桩作为支护结构,达到设计合理、经济适用的效果,保证了基坑及周边建筑的安全。本工程是SWM工法桩在荆州市基坑支护工程中的首次应用,同时获得了显著的社会效益。     

大径高隧道变形监测方法及分析

我国隧道建设工程的日益增加,为隧道变形监测提出了新的要求,为适应大径高隧道变形监测的高新要求,本文在分析了传统监测方法的基础上,探讨了一种利用铟钢丝进行隧道变形监测的新方法,详细阐述了该方法的特点、实施过程和要求,结合工程实例验证了这种方法的有效性和高精度。     

采用非线性纤维梁单元法的钢管混凝土组合框架动力响应分析

钢管混凝土结构已经广泛应用于我国高层和超高层建筑中,为研究该类结构的抗震性能,分别采用分离模量法和统一模量法对某13层钢管混凝土框架结构进行抗震性能分析,研究不同地震波作用下组合框架的模态和多遇地震下的弹性动力时程,对比组合框架顶点位移反应、加速度反应、层间侧移及动力放大系数等。研究结果表明,分离模量法和统一模量法建模方法在分析钢管混凝土框架抗震动力特性上总体相差不大,但前者可以考虑材料弹塑性,从而对结构弹塑性进行分析,而后者在弹塑性阶段需要用全曲线表达式,尚需进一步的研究。     

铁路大跨度简支钢桁梁桥车-桥耦合振动研究

桥梁作为线路工程中不可或缺的重要枢纽,对列车通过桥梁时,桥梁和车辆之间相互作用的问题迫切需要做出解答,特别是针对铁路钢桁梁,并考虑大跨度简支特性的车-桥耦合振动问题研究更具有一定的理论与实际意义。以黄韩侯铁路新黄河特大桥156 m简支钢桁梁桥作为工程背景,建立车辆动力模型、桥梁有限元模型并考虑轮轨关系,以蛇形运动和轨道不平顺作为系统的自激激励源,利用大型有限元软件ANSYS以及UM(Universal Mechanism)动力学分析软件联合进行仿真分析,实现单个机车、编组客车和编组货车以设计时速通过桥梁时对大跨度简支钢桁梁桥车-桥耦合振动的研究。经过计算分析得出:大跨度钢桁梁桥的横向刚度相对较小;不同编组情况以设计时速通过桥梁时,车辆和桥梁的各项动力响应参数均在规范允许的范围之内;编组货车通过桥梁时,桥梁跨中横向、竖向加速度较之其他编组情况要大。     

Earthquake‐induced loss assessment of steel frame buildings with special moment frames designed in highly seismic regions

This paper discusses an analytical study that quantifies the expected earthquake‐induced losses in typical office steel frame buildings designed with perimeter special moment frames in highly seismic regions. It is shown that for seismic events associated with low probabilities of occurrence, losses due to demolition and collapse may be significantly overestimated when the expected loss computations are based on analytical models that ignore the composite beam effects and the interior gravity framing system of a steel frame building. For frequently occurring seismic events building losses are dominated by non‐structural content repairs. In this case, the choice of the analytical model representation of the steel frame building becomes less important. Losses due to demolition and collapse in steel frame buildings with special moment frames designed with strong‐column/weak‐beam ratio larger than 2.0 are reduced by a factor of two compared with those in the same frames designed with a strong‐column/weak‐beam ratio larger than 1.0 as recommended in ANSI/AISC‐341‐10. The expected annual losses (EALs) of steel frame buildings with SMFs vary from 0.38% to 0.74% over the building life expectancy. The EALs are dominated by repairs of acceleration‐sensitive non‐structural content followed by repairs of drift‐sensitive non‐structural components. It is found that the effect of strong‐column/weak‐beam ratio on EALs is negligible. This is not the case when the present value of life‐cycle costs is selected as a loss‐metric. It is advisable to employ a combination of loss‐metrics to assess the earthquake‐induced losses in steel frame buildings with special moment frames depending on the seismic performance level of interest. Copyright © 2017 John Wiley & Sons, Ltd.     

Influence of deterioration modelling on the seismic response of steel moment frames designed to Eurocode 8

This paper assesses the influence of cyclic and in‐cycle degradation on seismic drift demands in moment‐resisting steel frames (MRF) designed to Eurocode 8. The structural characteristics, ground motion frequency content, and level of inelasticity are the primary parameters considered. A set of single‐degree‐of‐freedom (SDOF) systems, subjected to varying levels of inelastic demands, is initially investigated followed by an extensive study on multi‐storey frames. The latter comprises a large number of incremental dynamic analyses (IDA) on 12 frames modelled with or without consideration of degradation effects. A suite of 56 far‐field ground motion records, appropriately scaled to simulate 4 levels of inelastic demand, is employed for the IDA. Characteristic results from a detailed parametric investigation show that maximum response in terms of global and inter‐storey drifts is notably affected by degradation phenomena, in addition to the earthquake frequency content and the scaled inelastic demands. Consistently, both SDOF and frame systems with fundamental periods shorter than the mean period of ground motion can experience higher lateral strength demands and seismic drifts than those of non‐degrading counterparts in the same period range. Also, degrading multi‐storey frames can exhibit distinctly different plastic mechanisms with concentration of drifts at lower levels. Importantly, degrading systems might reach a “near‐collapse” limit state at ductility demand levels comparable to or lower than the assumed design behaviour factor, a result with direct consequences on optimised design situations where over‐strength would be minimal. Finally, the implications of the findings with respect to design‐level limit states are discussed.     

On‐line hybrid test method for evaluating the performance of structural details to failure

A test environment to evaluate the seismic performance of gusset plate connections intended for steel braced frames is proposed. The developed test method combines the substructuring techniques with finite element analysis methods in an on‐line hybrid scheme. Numerical substructure analysis is conducted on bracing members, while bracing connections are treated as experimental substructures. A force‐displacement combined control imposed with the aid of 2 jacks ensures physical continuity between the analysis and test. The rotational behavior of gusset plate connections subjected to large inelasticity and varying axial loading until fracture is investigated. Two gusset plate details were designed and tested to verify the efficiency of the proposed method. The test method is rational, and smooth operation is achieved. The test results revealed the advantage of the developed on‐line hybrid test method in exploring the ultimate capacity of bracing connections.     

A design procedure for suspended zipper‐braced frames in the framework of Eurocode 8

In the recent past, suspended zipper‐braced frames were proposed to avoid one‐storey collapse mechanisms and dynamic instability under severe ground motions. In this paper, the design procedure suggested by Yang et al. is first slightly modified to conform to the design approach and capacity design rules stipulated in Eurocode 8 for concentrically braced frames. The procedure is applied to a set of suspended zipper‐braced frames with different number of storeys and founded on either soft or rock soil. The structural response of these frames is analysed to highlight qualities and deficiencies and to assess the critics reported by other researchers with regard to the design procedure by Yang et al. Then, improvements are proposed to this procedure to enhance the energy dissipation of the chevron braces and the response of the structural system as well. The effectiveness of the design proposals is evaluated by incremental dynamic analysis on structures with different geometric properties, gravity loads and soil of foundation. Copyright © 2017 John Wiley & Sons, Ltd.     

Estimation of lateral force contribution of boundary elements in steel plate shear wall systems

Steel plate shear walls (SPSWs) are used as lateral force‐resisting systems in new and retrofitted structures in high‐seismic regions. Various international codes recommend the design of SPSWs assuming the entire lateral load to be resisted by the infill plates. Such a design procedure results in significant overstrength leading to uneconomical and inefficient use of materials. This study is focused on the estimation of contribution of boundary elements in resisting the lateral force considering their interaction with the web plates of SPSW systems. Initially, the relative contribution of web plates and boundary frames is computed for a single‐bay single‐story frame with varying rigidity and end connections of boundary elements. Nonlinear static analyses are carried out for the analytical models in OpenSees platform to quantify this contribution. Later, this study is extended to the code‐based designed three‐story, six‐story, and nine‐story SPSWs of varying aspect ratios. Based on the results obtained, a new design procedure is proposed taking the lateral strengths of the boundary frames into account. Nonlinear time‐history analyses are conducted for 40 recorded ground motions representing the design basis earthquake and maximum considered earthquake hazard levels to compare the interstory and residual drift response and yield mechanisms of SPSWs designed as per current practice and the proposed methodology. Finally, an expression has been proposed to predict the lateral force contribution of the infill plate and the boundary frame of SPSWs. Copyright © 2016 John Wiley & Sons, Ltd.