空心玻璃微珠-氧化石墨烯协同增强聚氨酯泡沫的制备与压缩性能

为提高粒子增强体对聚氨酯泡沫的增强效率,将空心玻璃微珠及氧化石墨烯分别进行表面改性,并反应制备成协同增强体。该增强体可以借助空心玻璃微珠良好的分散性,带动表面接枝氧化石墨烯在机械搅拌下实现有效分散。实验表明,协同增强体中空心玻璃微珠与氧化石墨烯的比例满足阈值要求时,其对聚氨酯泡沫的压缩性能明显提升。其中,空心玻璃微珠与氧化石墨烯质量比为30∶1的协同增强体添加量为9.3份时,压缩性能提升最佳,压缩强度较未增强泡沫提高了30.5%,压缩模量提高了23.77%,优于单一增强体的增强效果。     

浅谈被忽视的房屋建筑结构施工质量问题

提出了房屋建筑中一个广泛被忽视的质量问题,即框架剪力墙结构中边板负弯矩钢筋锚固长度不足及墙体分布钢筋应作为连梁的腰筋在连梁范围内拉通连续配置问题,通过成因分析,提出了合理建议,以保证工程质量。     

Energy absorption potential of concrete floors containing secondary (shrinkage and temperature) reinforcements

This paper experimentally investigates the energy absorption potential of two types of concrete floors, namely, normal density concrete and structural low-density concrete, containing secondary (shrinkage and temperature) reinforcements. The test program considered the following secondary reinforcements: 1) traditional welded-wire steel mesh, 2) steel fiber and 3) poly composite fiber. To estimate the extent to which crushing of floor slab materials would help absorb energy, a series of concrete penetration tests employing patch loading was undertaken on scaled down model slabs. Each concrete-secondary reinforcement combination considered slabs of 50 mm in depth with square plan dimensions ranging from 50 to 500 mm, resulting in a total of 30 test specimens. The first part of the paper discusses the test specimens, the test setup, and the test procedure. The second part of the paper presents the experimental results and establishes the energy absorption of different concrete-secondary reinforcement combinations. Sieve analysis results of the crushed specimens were used to derive a “work index” value that relates the pulverized particle size distributions to energy inputs. The work index values of concrete-secondary reinforcement systems can be used to assess the energy dissipation potential associated with such floor slabs in buildings undergoing progressive collapse. The results indicate that floors with secondary reinforcements could play an important role in helping arrest global progressive collapse.     

不同埋深的植筋群锚连接受拉试验研究

进行了埋深为10d和15d(d为钢筋直径)两种情况下植筋群受拉试验。研究结果表明,植筋群埋深15d时的屈服荷载较10d时的提高约22.5%,极限承载力提高约6.3%。破坏时二者的钢筋均达到屈服,为钢筋受拉破坏。埋深10d破坏时基材混凝土表面开裂严重,表现出锥体破坏的趋势;埋深15d破坏时为钢筋拉断,钢筋周围有混凝土小锥体破坏。建议工程应用中最小埋置深度取15d,并提出植筋群受拉承载力计算式。     

土工合成材料加筋土地基承载性能数值分析

对土工合成材料加筋地基进行了数值模拟, 旨在研究加筋材料布置方式对加筋地基承载性能的影响及其变化规律。在已有加筋土地基模型试验结果的基础上, 建立了加筋土地基数值模型, 针对不同的加筋材料布置方式, 进行有限元计算并对结果进行了系统分析。分析结果表明:①随首层筋材埋深的增大, 承载力提高系数先增大后减小, 存在峰值;②加筋土地基承载力提高系数随加筋层数的增加而增大, 但不宜超过3层;③承载力提高系数随加筋层间距的减小而增大, 但存在一个合理的布筋间距;④随加筋长度增加, 地基承载力提高而基础沉降减小, 但加筋长度增加不宜超过3倍基础宽度。所得出的结论是, 基础下存在一个合理的布筋范围, 超过此范围, 加筋对提高地基承载力作用不大。分析成果可为土工合成材料加筋土地基的工程应用提供借鉴。     

非连续增强铜基复合材料的研究现状

非连续增强铜基复合材料具有很高的导电、导热性能,以及优异的摩擦磨损特性和较高的高温力学性能,是导电、导热、耐磨、减摩等领域的理想材料。本文综述了非连续增强铜基复合材料的研究现状,介绍了该类材料的设计原理以及力学、摩擦磨损、导电导热等性能,回顾了材料的制备工艺,指出了各种工艺的优缺点,最后阐述了非连续增强铜基复合材料的发展方向。     

Mechanical behaviour of diamond reinforced metals

Diamond reinforced metals with a diamond content of 55–60 vol.% were made by gas driven liquid metal infiltration. They were characterized with regard to their stiffness, strength and fracture toughness as a function of diamond particle size and matrix alloy by means of tensile and Chevron notch tests, respectively. The choice of the metal matrix, i.e. pure Al, Al–Cu, Cu–B and Ag–Si alloys was made in view of their application in thermal management where high thermal conductivity is important. For undamaged material Young's moduli, measured in unloading–reloading cycles necessary to measure static Young's modulus, of 250 GPa for Al-based and 300 GPa for Ag-based composites were obtained. The copper-based composites exhibited much lower values indicating that the small deformation necessary to measure Young's modulus induced already considerable damage. Strain to fracture of the composites was found to be a few tenth of a percent. An ultimate tensile strength of approximately 300 MPa was reached for the silver-based composites compared with roughly 150 MPa for the Al-based and below 50 MPa for the Cu-based composites. The size of the diamond particles had little influence on stiffness and strength of the composites but fracture toughness increased with increasing particle size. The differences in the mechanical behaviour of the configurations investigated can be rationalized by observations made during fractographic investigations by scanning electron microscopy. Additionally, the damage evolution in the composites was observed by the repeated determination of the specimen's stiffness during the tensile tests.     

FRP网格加固桥梁水下结构技术研究与应用

桥梁水下结构在我国桥梁结构的工程实践中普遍存在,桥梁水下结构常常需要面临加固需要,传统的水下结构加固技术具有造价高、工期长的缺点。以某桥梁的水下桩基础加固工程为背景,对比分析了3种不同的水下结构加固方案,通过工程实践应用,论证了纤维网格(FRP网格)加固桥梁水下结构技术的可行性,提出了FRP网格加固桥梁水下结构的施工工艺,其以水下无排水施工为指导思想,将高强轻质的FRP网格作为增强材料,以水下不分散材料为黏结材料,实现对桥梁水下结构的快速加固修复。FRP网格加固桥梁水下结构技术是一种新的有效技术,尤其在无法或难于修筑围堰的情况下,具有广阔的应用前景。     

深基坑开挖坑底隆起影响因素有限元分析

深基坑工程中由于土体开挖卸荷,导致基坑坑底隆起,其隆起量的大小直接关系到基坑安全和稳定,已越来越受到重视。系统地研究基坑坑底隆起的影响因素并对其进行有限元分析尚不多见。利用有限元软件ABAQUS建立有限元模型,研究坑底工程桩、坑底被动区加固、地下连续墙插入深度和坑底软土层厚度等对坑底隆起变形的影响,并探讨各隆起变形控制措施的控制效果。最后通过南京某隧道基坑的实测数据,验证了坑底设置工程桩对坑底隆起的控制效果。     

钢筋混凝土结构平法配筋的辅助表格

施工图平面整体表示方法极大地简化了钢筋混凝土结构构件的设计表达 ,如果辅以文中所提供的几个配筋表格 ,加上两个常用的钢筋表格 ,可以使结构设计者更加方便自如地表达钢筋混凝土结构的设计意图