装配式钢筋混凝土结构竖缝抗剪承载力研究及国内外规范的比较

分析比较了国内外建筑规范及专家学者提出的关于装配式钢筋混凝土结构竖向齿槽接缝的抗剪机理及抗剪承载力计算公式,指出各种计算公式的可取与不足之处,提出了符合我国国情的设计公式,从而加速我国建筑规范的发展,促进我国规范与国际规范的接轨。     

Seismic fracture evaluation of diaphragm joints in welded beam-to-box column moment connections

Steel box columns are widely used in steel building structures in Taiwan due to their dual strong axes. To transfer the beam-end moment to the column, diaphragm plates of the same thickness and elevations as the beam flanges are usually welded inside the box column. The electro-slag welding (ESW) process is widely used to connect the diaphragms to the column flanges in Taiwan because of its convenience and efficiency. However, ESW may increase the hardness of the welds and heat-affected zones (HAZs), while reducing the Charpy-V notch strength in the HAZ. This situation can cause premature fracture of the diaphragm-to-column flange welds before a large plastic rotation is developed in the beam-to-box column joints. To quantify the critical eccentricity and the effectiveness of fracture prediction, this study uses fracture prediction models and finite element model (FEM) analysis to correlate the test results. In this study, two beam-to-box column connection subassembly tests are conducted with different loading protocols and ESW chamber shapes. To implement a fracture prediction model, the material parameters are established from circumferential notched tensile tests and FEM analysis. Test results indicate that the fracture instances can be predicted on the basis of the cumulative plastic deformation in the HAZs. Analytical results indicate that fracture instances and locations are sensitive to the relative locations of the ESW joints and beam flange. Tests also confirm that the possible fracture of the diaphragm-to-column flange joints can be mitigated by enlarging the chamber of the ESW joint.     

地震作用下相邻地下结构与土相互作用特性研究

针对简单框架式地铁车站结构的抗震特性研究已取得一定成果,但对于结构形式较复杂或多个地下结构间相互作用等问题仍需进一步探究。本文利用现有地震分析方法中的动力时程分析法对两个地下结构间相互作用的影响进行系统对比分析,其中主体结构为三层三跨车站、附属结构为两层三跨车站。主要探讨附属结构与主体结构间距离的变化、两结构间连接形式对场地土以及主体结构地震响应特性的影响,分析比较场地土变形、主体结构变形、层间位移角以及内力在不同工况下的地震响应特性。结果表明:相邻地下结构与土相互作用形式较独立结构与土相互作用形式对场地土影响更加明显;当附属结构与主体结构间距离超过两倍结构宽度,附属结构对主体结构周围场地变形影响效应可基本忽略;同样当附属结构与主体结构间距离超过两倍的结构宽度,附属结构对主体结构的变形、内力基本已无影响,因此地震情况下相邻结构间相互作用影响范围基本为两倍结构宽度。与此同时,附属结构的存在对于主体结构抗震特性是不利的,不同连接形式中单层通道连接的形式变形以及内力方面均小于双层通道连接形式。     

考虑力组合效应的钢框架端板连接力学行为

为研究不同力组合效应对平齐端板连接力学行为的影响,采用ABAQUS程序建立不同受力情况下连接的非线性简化有限元模型,通过与国内外典型试验结果对比分析,验证了有限元模型的可靠性。基于此通过考虑8种力组合因素的影响,分析了2种不同钢等级的梁柱节点力学行为,进一步讨论了EC3 Part 1-8规范的适用性。结果表明:简化有限元模型在弯矩-转角曲线、破坏形态、初始刚度和塑性抗力等方面与试验结果吻合良好。框架梁轴力对节点的力学行为影响显著,当轴拉力为20%的框架梁轴向塑性抗力N_pl时,高强钢节点的刚度和强度分别降低68%和52%;当轴压力为-20%N_pl时,刚度和强度分别增加89%和42%。此外节点的滞回耗能能力、破坏模式以及分类属性与梁轴力水平密切相关。对于高强钢梁柱平齐端板节点,EC3规范对框架梁轴压力的限值仍过于保守。研究结果对于提高结构的抗倒塌能力和组合力作用下的理论研究具有重要参考价值。     

扩孔螺栓连接型消能梁段的力学模型及参数研究

当前国家对建筑结构的抗震性能和震后功能恢复能力提出了更高要求。基于短剪切型消能梁段的受剪屈服特性和剪切扩孔型螺栓连接的受剪滑移性能,提出一种新型扩孔螺栓连接型消能梁段,可有效增大消能梁段的延性和耗能能力并同时减小消能梁段的损伤,使带扩孔螺栓连接型消能梁段的新型Y形偏心支撑结构更好地适应当前要求。采用有限元方法详细分析扩孔螺栓连接型消能梁段的滞回性能、破坏模式和耗能机理,由此得到其骨架曲线和力学模型,并阐述其力学模型的影响参数,为相应偏心支撑结构的设计和分析提供理论依据。     

机械连接预应力实心方桩承台节点抗震性能试验研究

预应力管桩在高烈度抗震设防地区已禁用,而普通钢筋混凝土方桩成本较高。首先针对卡扣式机械连接预应力混凝土实心方桩、PHC管桩和普通钢筋混凝土方桩与承台处的节点进行拟静力试验,并利用试验数据针对Park-Ang损伤模型进行了修正,进行了损伤指数分析。研究结果表明:预应力方桩比普通钢筋混凝土方桩的抗裂性能明显好,而预应力混凝土实心方桩承台节点耗能能力和延性低于预应力管桩和普通钢筋混凝土方桩;截桩施工导致桩端部损失部分预应力,相比较未截桩试件屈服荷载和极限荷载均减小,节点裂缝开展较早,损伤较未截桩试件严重;增配普通钢筋试件的滞回曲线比较饱满,水平承载能力和位移延性得到提升,节点抗震性能得到提升与改善;预应力混凝土实心方桩损伤前期较小,而一旦发生损伤后,损伤指数发展较快。     

基于小波变换和数学形态学的潮沟提取方法研究

潮沟是潮滩的主要地貌类型之一,潮沟信息的检测对湿地生态环境的监测和保护有着重要意义。本文以长江口九段沙下沙北部发育比较复杂的潮沟为研究对象,使用2016年1月26日Landsat8全色波段数据,采用了一种融合小波变换、最大类间方差法和数学形态学的方法对潮沟边缘信息进行了检测。小波变换中通过减小高层小波系数,达到弱化潮滩灰度变化的目的;通过增大低层小波系数,达到增强潮沟信息的目的;利用数学形态学和图像之间的几何(加减乘)运算,完成潮沟的提取;最后,分别在原始数据和检测结果相应的位置取样进行精度验证,样方潮沟面积一致性精度平均为92.1%。     

Effect of non‐moment braced frame seismic deformations on buckling‐restrained brace end connection behavior: Theoretical analysis and subassemblage tests

In‐plane buckling‐restrained brace (BRB) end rotation induced by frame action is a commonly observed phenomenon in buckling‐restrained braced frames (BRBFs). However, its effect on BRB end connection behavior has not yet been clear. In this study, four BRB end deformation modes for quick determination of end rotational demand are proposed for non‐moment BRBF considering different BRB arrangements, installing story of BRBs, and boundary condition of corner gussets connected with column base. Key factors affecting BRB end rotation and flexural moments are examined theoretically by parametric analysis. Subassemblage tests of seven BRB specimens under horizontal cyclic loading were conducted by adopting two loading frames to impose the expected BRB end deformations. It shows that BRB end rotation subjected BRB ends to significant flexural moments, leading to premature yielding of BRB ends or even tendency of end zone buckling. The deformation modes, the flexural rigidity of BRB ends, and the initial geometric imperfections of BRBs were found to have significant influence on BRB end connection behavior. The triggering moment induced by BRB end rotation was the main contributor to end flexural moment. However, the moment amplification effect induced by flexure of BRB end zones became prominent especially for small flexural rigidity of BRB ends. Implications and future research needs for design of BRB end connections are provided finally based on the theoretical and experimental results. Copyright © 2015 John Wiley & Sons, Ltd.     

Seismic performance and comparison of three different I beam to box column joints

Despite the inherently advantages of the box column, finding the best option for the I beam to the box column connection is the main challenge in using the box column as a structural member for special moment frames. In this paper, the seismic performance of unreinforced connection, weakened connection and strengthened connection was evaluated through a comprehensive experimental program. The seismic comparisons were fabricated by assessing the strength, ductility and energy dissipation in each configuration. Three full scale tests with several connections were carried out. All the specimens were subjected to cyclic loading and prior to failure by forming a plastic hinge in the beam, all the connections managed to reach an inelastic rotation of more than 6.0% rad. The experimental and analytical results showed that the seismic performance of the strengthened connection with flange and shear plates turned out to be the most effective in the beam to the box column connection. Moreover, the normalized stress distribution of the continuity plates revealed that the possibility of the weld fracture in unreinforced connection is more than other specimens.     

农村劳动力转移就业的时空路径——以安徽省4个样本村为例

借鉴时间地理学理论与方法,提出农村劳动力转移就业时空路径概念。以安徽省4个样本村为例,使用ArcGIS、SPSS等软件进行数据分析,得出农村劳动力转移就业时空路径的基本类型与特征:① 农村劳动力依据时空路径特征可分为稳定型、逐步稳定型、漂泊不定型、回流型、逐步开拓型、断续型六种类型;② 4个样本村劳动力打工时空路径演化有明显的地域差异;③ 21世纪初期是农村劳动力全面接受打工就业方式的时期,就业行业主要集中在建筑业、制造业、服务业,“老家亲戚、朋友”是最重要的打工媒介;④ 农村劳动力在打工地和家乡间的流动节律有“春节型”、“节假日型”、“休息日型”、“每日型”四种类型;⑤ 农村劳动力转移就业具有明显的空间指向和粘性特征,家乡是重要的结点空间,社会经济地理位置是地域差异形成的重要原因。