地下结构抗震分析的反应位移法研究

基于地下结构的震动特性,比较反应位移法在地下结构抗震分析中计算地震荷载作用下结构相对位移的三种方法。结合工程实例,分别应用三种求解方法计算地震荷载作用下的土层相对位移及作用在结构上的等效荷载,建立有限元模型分别计算结构各点的相对位移,并与时程分析法计算结果比较。结果表明:(1)不同求解方法计算得到的结构相对位移有很大的差异,由此导致结构地震响应差别显著;(2)不同计算公式有其相应的适用性,研究成果可为地下结构抗震设计提供参考。     

求解饱和土固结方程的增维精细积分法

采用增维精细积分法对饱和土固结方程进行了求解,详细推导出了以位移表示的状态方程、求解位移及孔隙流体压力的计算公式。一维固结沉降的计算结果表明,该方法的计算精度和计算效率均很高。     

文克勒地基上板的有限条法

本文探讨了用有限条法求解文克勒地基上的弹性薄板问题,研究了在不同荷载、不同约束条件下的弹性地基板的内力、位移等。计算结果表明,该方法计算简便,精度高,是求解弹性地基板的一种有效方法。     

钢-混凝土组合框架抗震目标位移的计算方法分析

在已有的钢管混凝土柱和钢-混凝土组合梁抗震性能分析理论基础上,探讨了在地震作用下钢-混凝土组合框架结构的屈服目标位移和极限目标位移的主要影响因素,提出了相应的计算方法.通过钢-混凝土组合框架结构层间屈服位移和结构侧移曲线的求解来确定结构的屈服位移,避免了侧移曲线中各种参数的不确定性带来直接求解侧移的困难.本文提出的方法同时解决了塑性极限状态的位移求解,具有简单有效的特点,可用于组合框架结构基于位移抗震设计中的目标位移计算.     

空间框架结构矩阵位移法分析

本文应用矩阵位移法对空间框架结构进行了有限元分析,并通过Fortran语言编制出相关计算程序,进而对三层框架算例进行了数值求解。通过对计算结果分析可知,该方法在求解空间框架结构的内力与位移方面具备结果准确性高、求解速度快的优点,能有效避免人为错误的产生。     

计算多自由度弹性体系的最大地震反应

简要介绍了计算多自由度弹性体系最大地震反应的振型分解法及底部剪力法的理论基础,着重对这两种方法求解框架的最大底部剪力和最大顶点的位移过程进行了探讨,得出了一些有意义的结论。     

刚性桩复合路基沉降计算数值解法

本文基于桩身压缩量法,提出了一种求解刚性桩复合路基桩-土相对位移的数值计算方法。该方法根据对称面剪应力等于零的力学原理,将桩网路基分割为单桩独立柱体模型,通过编制计算机程序求解桩身零摩阻区或中性点,以及桩顶、桩端刺入量,进而计算出桩侧摩阻力、桩体轴力及路基沉降。通过工程实例进行比较,表明该计算方法具有较好的精度。     

隧道横断面反应位移法基本原理及其应用

我国大量的隧道工程位于高地震烈度区,隧道作为国家生命线工程的主体结构之一,必须对其抗震计算方法给予高度重视。基于隧道的振动特性,从地下结构与周围地层的整体运动微分方程出发,总结归纳隧道横断面反应位移法的基本原理及计算模型,得到均质半无限地层和非均匀成层地层在地震荷载作用下地层位移的求解方法,并通过反应位移法和时程法的计算和比较分析,对反应位移法的适应性进行探讨,研究结果表明：反应位移法理论清晰,反映地震响应主要由地层相对位移控制的土层或软弱岩层隧道的振动特性,在具备工程场地位移或速度反应谱的条件下,计算较方便快捷,不失为该类隧道的一种较好的抗震计算方法。     

工业厂房框-剪结构弹塑性简化计算研究

结合拟动力试验所得结构与剪力墙的刚度退化规律,推导出弹塑性阶段框架-剪力墙刚度比特征值及顶层位移的计算方法;并根据剪力墙底率先出现塑性铰的试验事实,提出了通过释放“多余弯矩”求解工业厂房框-剪结构在弹塑性阶段位移的简化计算方法及计算模型,可供第二阶段设计参考。     

平板网架结构的半解析半数值解

本文采用综合离散化分析方法分析平板网架。该方法既采用了有限元法处理离散体结构的便利,能真实反映不等高网架、变截面网架和其它结构情况,又通过力学途径用一组满足边界条件的位移函数来描述网架结构位移场,使得由求解节点位移变成求解位移函数中的待定参数,以达到减少所需求解未知量的目的。计算结果表明,本文方法具有相当的计算精度,并有未知量少(一般不超过30个),工作量省,可在微机或袖珍机上计算等许多半解析半数值方法的特点。     

基于土钉支护结构水平位移的灰色预测

针对土钉设计方法在位移计算方面的不足,引入了灰色理论来预测基坑开挖过程中的水平位移,以此来适应复杂基坑开挖的水平位移预测,经工程实例验证了三种方法预测基坑位移的可行性。     

复杂地下洞室群开挖方案优化

某地下洞室群,主洞室断面很大,支洞较多,距离较近,且断面变化复杂.考虑到支洞室开挖对主洞室围岩位移、结构受力的影响,特选择三种支洞开挖顺序用FLAC进行数值模拟.对比分析了三种开挖方法时引起的主洞室围岩周边位移、围岩塑性破坏区和主支洞交接处应力的变化特点,比选出较为有利的开挖方法,并得出了一些有意义的结论,可供类似复杂洞室群的开挖方案参考.     

大跨度钢结构屋盖落架分析方法

首先对大跨度钢结构屋盖的落架过程进行了简单分析,给出了落架应遵循的基本原则,并提出了“同步协调”和“分组分步”2种落架方式;其次,介绍了落架过程数值模拟的3种计算方法:支座位移法、等效杆端位移法和千斤顶单元法,并详细论述了各自的计算原理及特点;最后,基于ANSYS有限元软件,应用3种落架计算方法对3点支撑悬臂梁及国家体育场进行了落架过程模拟。结果表明,等效杆端位移法和千斤顶单元法是2种合理有效的方法,并可以方便地应用于工程实际中。     

Evaluation of interpretation criteria for drilled shafts with tip post-grouting

This paper evaluates the effects of tip post-grouting on various capacity interpretation criteria for drilled shafts under compression loading. A wide array of load test data for drilled shafts constructed using three post-grouting methods, including tube-a-manchette, flat jack, and jet grouting, is utilized for the analysis. The load tests were divided based on the different tip post-grouting methods, then they were further divided based on the soil conditions (undrained or drained). The interpreted capacity and displacement at the interpreted capacity are examined for each interpretation criterion. Furthermore, the interpreted results were compared with current studies on drilled shafts that are not subjected to tip post-grouting techniques to determine the effects of post-grouting methods. Based on these analyses, the normalized load–displacement curves and the relationships between various interpretation criteria for drilled shafts with tip post-grouting are established. The drilled shafts subjected to any post-grouting method produced higher capacity and yield larger displacement with the same amount of normalized capacities for undrained and drained soils compared to drilled shafts not subjected to any post grouting procedures. Among the three grouting methods studied, the jet grouting method can produce a greater capacity than the other methods, especially for drained soil conditions. Finally, specific recommendations to guide the design of drilled shafts with tip post-grouting are provided.     

国家体育馆屋盖滑移支撑转换变形分析

国家体育馆在滑移施工过程中一个非常关键的步骤是七点支撑转变为三点支撑,文章给出两种转换方案,分析此过程中结构的位移、支撑架反力、杆件应力的变化情况。     

高层建筑中地基处理设计应用探讨

采用高置换率CFG桩的地基处理方法解决了一个高层建筑地基基础设计,对CFG桩的单桩承载力计算公式进行了探讨,获得考虑群桩效应的CFG桩单桩承载力公式,并对比了几种变形计算方法。     

Research on the Compression Behavior of Steel Reinforced Concrete Columns With Built-in Steel Tubes

In order to study the compression behavior of rectangular steel reinforced concrete columns with built-in steel tubes under different eccentric loads, three 1/10 scale specimens were designed and monotonic loading tests were carried out on them. The dimensions, steel bars and steel tube of the three specimens were the same except for the location of the loading point. The eccentricity ratios of the three specimens were 0, 0.25 and 0.5, respectively. The failure modes, load-bearing capacity and displacement characteristics of the test specimens were analyzed. According to the Chinese code, the load-bearing capacity calculation principles and methods of steel reinforced concrete columns with built-in steel tube were investigated for the comparison. The study shows that the peak vertical loads of specimens decrease and the corresponding vertical and horizontal peak displacement increase as the eccentricity increases. The load-bearing capacity calculation results from Chinese code are slightly smaller than the test result because of the unconsidered sleeve effect of the internal steel tube. The errors between them are small, and the calculation methods are beneficial to ensure the structural safety.

     

考虑位移协调的上埋式圆管涵设计方法

埋入式圆形涵管上的填土不但是荷载,也是涵管与土发生作用的介质,这种特性决定了圆管涵的工作性质。本文考虑了涵管结构与土的位移协调,提出了相应的涵管设计方法。结合现有规范方法和试验结果的比较分析,证实了本文方法的合理性。     

通风效率的规律性问题

按照不同的通风方法,讨论了三个有关通风效率规律性的问题：用通风效率检验混合通风的实际性能;置换通风通风效率的分析与应用;我国暖通规范自然通风热分布系数更新的必要与可能性。     

Structural Displacement Measurement Using an Unmanned Aerial System

Vibration‐based Structural Health Monitoring (SHM) is one of the most popular solutions to assess the safety of civil infrastructure. SHM applications all begin with measuring the dynamic response of structures, but displacement measurement has been limited by the difficulty in requiring a fixed reference point, high cost, and/or low accuracy. Recently, researchers have conducted studies on vision‐based structural health monitoring, which provides noncontact and efficient measurement. However, these approaches have been limited to stationary cameras, which have the challenge of finding a location to deploy the cameras with appropriate line‐of‐sight, especially to monitor critical civil infrastructures such as bridges. The Unmanned Aerial System (UAS) can potentially overcome the limitation of finding optimal locations to deploy the camera, but existing vision‐based displacement measurement methods rely on the assumption that the camera is stationary. The displacements obtained by such methods will be a relative displacement of a structure to the camera motion, not an absolute displacement. Therefore, this article presents a framework to achieve absolute displacement of a structure from a video taken from an UAS using the following phased approach. First, a target‐free method is implemented to extract the relative structural displacement from the video. Next, the 6 degree‐of‐freedom camera motion (three translations and three rotations) is estimated by tracking the background feature points. Finally, the absolute structural displacement is recovered by combining the relative structural displacement and the camera motion. The performance of the proposed system has been validated in the laboratory using a commercial UAS. Displacement of a pinned‐connected railroad truss bridge in Rockford, IL subjected to revenue‐service traffic loading was reproduced on a hydraulic simulator, while the UAS was flown from a distance of 4.6 m (simulating the track clearance required by the Federal Railroad Administration), resulting in estimated displacements with an RMS error of 2.14 mm.