浅淡砌体结构顶层墙体的温度裂缝

砖混结构房屋墙体经常出现裂缝，形成裂缝的原因很多，本文仅对房屋墙体在温度应力作用下产生的裂缝现象以及原因作了扼要分析，并结合砌体结构形式以及设计中的一些问题，提出了设计中应遵循的防止裂缝的原则和施工中应采取的防治措施。     

谐波热作用下墙体温度场的解析解

超长结构设计时应分析墙体温度场变化产生的温度应力,以控制温度作用墙体产生裂缝.针对谐波热作用下的单层墙,采取变量分离法求解第一类边界条件下的热传导微分方程,得到单层墙温度场的解析表达式.以此为基础,采用两层墙接触面处温度和热流相等的基本假设,推导了谐波热作用下第一类和第三类边界条件时多层墙温度场的解析解,为墙体温度应力分析和裂缝控制提供了理论基础.利用推导的墙体温度场计算公式,对外墙外保温墙体的温度场进行了分析和研究.     

砌体结构裂缝的控制措施的探析

温度的变化会引起材料的热胀、冷缩,当约束条件下温度变形引起的温度应力足够大时,墙体就会产生温度裂缝在总结分析砌体裂缝的性质、控制原则和措施的基础上,提出了防止墙体开裂的具体构造措施建议为科学施工提供依据。     

浅谈砖砌体墙体裂缝与防治

在砌体结构中墙体裂缝是常见的质量问题.建筑砖砌体裂缝不仅种类繁多,形态各异.而且较普遍,轻微者影响建筑物的美观,造成渗漏水,严重者降低建筑结构的承载力、刚度、稳定性和整体性、耐久性,甚至还会导致建(构)筑物整体倒塌的重大质量事故,因此,正确分析原因,切实加以防治十分必要.引起砌体结构,墙体裂缝的因素很多,即有地基、温度、也有设计卜的疏忽,施工质量、材料不合格等因素.根据工程实践和统计资料这类裂缝几乎占全部可遇裂缝的80%以上.而最为常见的裂缝有两类,一是温度裂缝,二是干燥收缩裂缝,简称千缩裂缝,以及由温度和干缩共同产生的裂缝.     

混凝土温度控制

在建筑施工过程中，我们经常会遇到基础底板体积及截面大（特厚、超长），混凝土标号高，一次性浇筑混凝土量大，往往还工期很紧，作业温度高等施工情况。这样水泥水化过程中将释放出大量的水化热，在混凝土内部产生很大的水化热升温。此期间，当基础受到外部地基的约束作用或内外较大的温度变化，会产生较大的温度应力，有可能导致箱形基础产生深进或贯穿性裂缝，影响基础结构的整体性、持久强度和防水性能。     

关于砌体结构裂缝控制措施的建议

引起砌体结构墙体裂缝的因素很多,既有地基、温度、干缩,也有设计上的疏忽、施工质量、材料不合格及缺乏经验等。根据工程实践和统计资料数据分析这类裂缝几乎占全部可遇裂缝的80%以上。而最为常见的裂缝有两大类,一是温度裂缝,二是干燥收缩裂缝,以及由温度和干缩共同产生的裂缝。     

CFRP加固砌体结构的力学性能分析

在分析碳纤维加固的砖砌体在水平周期反复荷载作用下试验结果的基础上,研究了碳纤维加固砖砌体的约束及抗倒塌机理;建立了墙体侧向位移与碳纤维应变、碳纤维应变与墙体抗震剪切强度的关系;讨论了不同加固方式、碳纤维面积百分率等在墙体不同受力阶段对墙体抗剪承载能力和变形性能的作用与影响;提出了计算碳纤维加固墙体承载能力和变形的计算方法。计算方法考虑了不同粘贴碳纤维角度、碳纤维面积百分率等对墙体承载能力和变形性能的影响;推导了最优粘贴加固角;提出了改进的粘贴加固方法以提高加固效果。     

砌体结构偻、屋面板考虑温度应力和混凝土收缩时裂缝分析与对策

对一批已建和在建砌体结构工程中,由于温度应力、混凝土的收缩徐变、施工期间养护不当、构造柱圈梁过分约束、基础不均匀沉降等原因造成楼面板屋面板开裂进行了调查研究。通过理论分析及具体实际概述了砌体结构中砼构件在砼固收缩以及温度变化时结构内部产生的及其影响。找出产生裂缝的原因,提出在设计和施工中应注意的一些新的看法。     

浅议砌体结构常见裂缝的原因及防治

引起砌体结构墙体裂缝的因素很多,大体上有:地基的不均匀沉降,收缩和温度的变化,设计上对房屋的构造处理不当,施工质量不合格,使用的建筑材料不合格等。本文主要对以上几点进行分析     

建筑施工裂缝分析

结构中墙体裂缝的质量问题,引起裂缝的原因有地基不均匀沉降,温度应力、地震力、膨胀力、冻胀力、荷载和施工质量等,现对地基不均匀沉降和温度应力引起墙体裂缝特征进行分析。因此,也要求我们不断的学习,掌握和发展该技术,并应用到实际工作中,充分发挥科学技术带来的社会效益和经济效益。     

Development of digital image correlation method to analyse crack variations of masonry wall

The detection of crack development in a masonry wall forms an important study for investigating the earthquake resistance capability of the masonry structures. Traditionally, inspecting the structure and documenting the findings were done manually. The procedures are time-consuming, and the results are sometimes inaccurate. Therefore, the digital image correlation (DIC) technique is developed to identify the strain and crack variations. This technique is non-destructive for inspecting the whole displacement and strain field. Tests on two masonry wall samples were performed to verify the performance of the digital image correlation method. The phenomena of micro cracks, strain concentration situation and nonuniform deformation distribution which could not have been observed preciously by manual inspection are successfully identified using DIC. The crack formation tendencies on masonry wall can be observed at an earlier stage by this proposed method. These results show a great application potential of the DIC technique for various situations such as inspecting shrinkage-induced cracks in fresh concrete, masonry and reinforced concrete structures, and safety of bridges.     

高延性混凝土加固无筋砖墙抗震性能试验研究与承载力分析

为研究高延性混凝土(HDC)加固无筋砖墙的抗震性能,设计制作了3片HDC面层加固砖墙、1片钢筋网水泥砂浆面层加固砖墙和1片作为对比试件的未加固砖墙,通过拟静力试验,研究了HDC面层加固砖墙的破坏形态、滞回性能及耗能能力。试验结果表明:HDC面层可对墙体形成约束作用,延缓墙体开裂并改变墙体的破坏模式,提高墙体的承载力和延性;与钢筋网水泥砂浆面层加固相比,单面HDC加固的墙体开裂荷载与耗能能力明显提高,承载力下降缓慢。针对试件的破坏形态,考虑未开裂区加固面层对墙体水平承载力的贡献,提出了加固墙体的承载力计算方法,并根据试验结果进行了验证。     

砖墙抗爆炸冲击震动效应模型试验研究

为研究砖墙在爆炸冲击震动作用下的破坏模式及阈值,据工程内砖墙实际情况建立简化的底部固定、周边无约束砖墙模型,在模拟爆炸震动冲击试验台上进行三方向单独作用的冲击试验,研究砖墙模型的动态响应及破坏时加速度峰值、作用时间。结果表明,遭水平向冲击时模型均表现为水平通缝破坏。破坏主要由受拉而非剪切所致。通过对试验结果分析,获得三个冲击方向独立作用下的破坏阈值。     

砌体墙的破坏准则及剪压复合作用下抗剪承载力

砌体墙在竖向压力和平面内水平剪力复合作用下的破坏准则是确定砌体抗剪承载力的重要依据。通过对比分析, 推导出基于最大主应力理论、剪摩理论、Mohr 理论和变形能理论的适合于砌体在剪压复合作用下的破坏准则。考虑到微元体与宏观墙模型的差别, 建立了相应于各种破坏准则的砌体抗剪承载力计算公式。并将公式的计算结果与收集的111 片普通粘土砖砌体墙片的试验结果进行了对比分析, 得到了常用多层砌体房屋墙的抗剪承载力计算公式。     

Limitation of cracking in AAC masonry under the window zone

The article describes the results of tests on the impact of reinforcement on the appearance of cracks and on the manner of damage to masonry under the window zone. Masonry made of Autoclaved Aerated Concrete units with thin layer mortar was tested. Eight unreinforced test specimens (two series) and four series of test specimens (12 specimens) with reinforcement in the bed joints were subject to testing. Two types of reinforcement were used in the tests. It is demonstrated that the reinforcement has a significant impact on the level of cracking stress and propagation of cracks. It was found that when a pillar is correctly designed, cracks should not occur in the masonry under the window zone.     

基于OMA隧道爆破振动下砌体结构的安全评价

以成渝客运专线新红岩隧道上方二层砌体结构为例,采用OMA(运行模态分析)方法研究了砌体结构在隧道爆破引起的地面振动作用下的安全性。结果表明:采用电子雷管爆破相比非电雷管能够有效降低地面振速,峰值振速最多降低约67%;二层砌体结构前4阶固有频率位于9~25Hz,有限元模型修正后其固有频率与实验值的误差明显减小,使其更加符合实际;非线性动力分析表明砌体结构门、窗的角部、砌体与混凝土材料的交界处及底层主应力集中程度高,但砌体的主压应力和主拉应力均小于规范值,表明砌体在爆破振动作用下是安全的,而且电子雷管更适用于结构安全性要求高的隧道爆破;现场调研发现砌体楼房在隧道爆破振动下没有发生损伤,表明基于OMA方法进行隧道爆破振动下砌体结构的安全评价是可行的。     

基于OMA隧道爆破振动下砌体结构的安全评价

以成渝客运专线新红岩隧道上方二层砌体结构为例,采用OMA(运行模态分析)方法研究了砌体结构在隧道爆破引起的地面振动作用下的安全性。结果表明:采用电子雷管爆破相比非电雷管能够有效降低地面振速,峰值振速最多降低约67%;二层砌体结构前4阶固有频率位于9²5Hz,有限元模型修正后其固有频率与实验值的误差明显减小,使其更加符合实际;非线性动力分析表明砌体结构门、窗的角部、砌体与混凝土材料的交界处及底层主应力集中程度高,但砌体的主压应力和主拉应力均小于规范值,表明砌体在爆破振动作用下是安全的,而且电子雷管更适用于结构安全性要求高的隧道爆破;现场调研发现砌体楼房在隧道爆破振动下没有发生损伤,表明基于OMA方法进行隧道爆破振动下砌体结构的安全评价是可行的。     

Shear effect on seismic behaviour of masonry walls

Firstly, a finite element numerical model for nonlinear dynamic analysis of masonry walls is briefly presented. The model can simulate the main nonlinear effects of masonry and reinforced concrete. It is simple and intended to the engineering application. A macro model of masonry is adopted for simulation its behaviour in compression and for cracks modelling in tension. Two constitutive models are implemented to describe the shear resistance of the masonry wall: One that does not take the effect of the shear failure of masonry (Model 1), and second which takes into account shear failure of masonry (Model 2). By using the numerical model, the shear effect of masonry on the behaviour of two‐storey unreinforced and confined masonry walls exposed to harmonic base acceleration was investigated. The height to length ratio of the walls and the quality of masonry are varied. Analysis results for Model 1 and Model 2 are significantly different. Model 1 gives a significantly higher load bearing capacities of masonry. It was concluded that the shear effect of masonry significantly depends on the type of the masonry walls (unreinforced, confined), the quality of the masonry and height to length ratio of masonry walls.     

Experimental study of dry stone masonry walls using digital reflection photoelasticity

Response of dry stack stone masonry walls under mechanical loading is complex and difficult to determine, mainly due to heterogeneous and discrete nature of the components of the stone wall. In this paper, reflection photoelasticity is used on scaled down models of stone masonry wall under uniaxial compression. Two walls are tested, and the methods to obtain near perfect dry stack masonry for reflection photoelastic studies are presented. Five-step phase-shifting methods are employed with TFP/RGB photoelasticity to quantitatively analyse the mechanical behaviour of the dry stack masonry walls. Isochromatics and isoclinic data are processed to obtain other whole field experimental stress data. Highly stressed zones are observed resulting in distinctive localised vertical failure in some of the stone units. In dry stack masonry construction, the failure mechanism is found to be dictated by the contact mechanics, which are governed by the non-uniformity of block geometry even in very regular dry stack masonry.     

Tube-Jack Testing for Irregular Masonry Walls: Regular Masonry Wall Testing

This paper presents the continued development of a novel non-destructive testing method termed tube-jack testing. The goal of the tube-jack system is to provide an enhanced and less destructive method than traditional flat-jack testing for determination of mechanical characteristics and local stress states in irregular masonry walls. Single tube-jack tests were performed, using previously developed rubber tube-jacks, in regular masonry walls of granite and cement-lime mortar. A traditional flat-jack test was also performed in the same masonry wall. Conclusions suggest that tube-jacks are successful in applying pressure to the masonry at low stress states.