现浇钢筋混凝土板裂缝产生的原因及其防治

针对建筑工程中现浇钢筋混凝土板出现裂缝相当普遍这一现象，主要从施工和设计方面分析了其产生的原因，同时提出了几条预防的措施及出现裂缝后的主要处理方法。     

CRTS Ⅲ型板式无砟轨道新型压板工装及配套设施的应用

自密实混凝土填充层灌注是CRTSⅢ型板式无砟轨道施工的关键环节。为保证轨道板在自密实混凝土灌注过程中不出现上浮现象，需在轨道板精调完成后安装抗上浮装置。由于普通压杆无法实时显示压力，本文研发了一种具有监测功能的轨道板灌注用扣压装置及监测方法，拉力及上浮量可直接显示并自动记录。     

Drying of in situ cast concrete ground slabs and covering criteria

The main objective of this paper was to examine the overall moisture behaviour of an in situ cast concrete ground slab during the initial drying period of the fresh concrete from casting to flooring. This article describes and evaluates various methods to measure moisture levels in concrete slabs in order to decide if flooring can be attached. The most accurate method is verified against measurements and compared with calculations. Many of the methods only consider the surface moisture content of the slab and do not consider the moisture condition deep in the slab. According to performed laboratory tests and FE modelling, moisture content of the slab surface is not a reliable indicator of the overall moisture conditions of the slab. Residual moisture deep in the slab has a major effect on the moisture distribution at the slab cross-section after flooring. The only reliable method to determine the moisture conditions in a new concrete ground slab before flooring is to measure the moisture content at the equivalent depth of the slab. It reliably predicts the ultimate moisture content at slab/flooring interface after flooring. A ground slab is drying in two directions: towards the indoor air by evaporation from the slab surface, and towards the cooler subsoil layers by diffusion. The significance of drying downwards increases after the flooring assembly.     

GFRP筋地下连续墙混凝土板受弯性能试验研究及有限元分析

为了解GFRP筋地下连续墙的受弯性能,通过GFRP筋混凝土板和钢筋混凝土板的对比受弯试验,分析了两者的受力-变形过程和破坏形态,对比了两者的挠度、开裂荷载、极限荷载以及混凝土应变。结果表明：GFRP筋混凝土板的受力-变形曲线大致可划分为开裂前和开裂后两个阶段,其破坏表现为脆性;混凝土开裂前两种板的截面应变变化规律均基本符合平截面假定,但开裂后GFRP筋混凝土板的挠度增长速率远大于钢筋混凝土板,且该速率基本不变;两种板的开裂荷载较为接近,而GFRP筋混凝土板的极限荷载为钢筋混凝土板的1.2倍。在试验基础上,建立了GFRP筋混凝土板的有限元模型,通过参数分析表明,GFRP筋混凝土板的抗弯刚度在开裂后随配筋率的增大而增大。图13表6参8     

压型钢板-组合楼板耐火试验和破坏模式的探讨

在标准升温条件下,对闭口式压型钢板组合楼板进行了耐火试验,并测试了不同部位的升温情况。试验表明,被混凝土包裹的部分升温要比直接受火面慢,但由于热传导,升温122MIN时被混凝土包裹的部分最低温度也超过了600℃;无论是火灾前期还是后期,板的混凝土厚度都是影响组合楼板耐火性能的重要参数。在此基础上,分析了高温状态下组合楼板的试验现象,定性地分析了各影响参数,并探讨了组合楼板在耐火极限状态下的破坏模式。由于影响组合楼板耐火性能的参数多而复杂,因此,建议防火设计时必须保证一定的混凝土厚度,确保火灾下组合楼板的安全。     

Crushing and flexural strength of slab-column joints

In multi-storey buildings, columns are usually not continuous through the slabs to enhance ease of construction. Consequently, in slab-column joints, slabs have to carry column loads in addition to the shear and bending moments due to loads applied to the slab. In most cases, when high strength concrete is used for the columns and normal strength concrete for the slabs, compression stresses at the support areas of the inner columns exceed the uniaxial compressive strength of the concrete of the slab. Due to this reason, most current details for such regions reinforce the concrete of the slab between columns to ensure load transfer. Typically, this is achieved by linking top and bottom columns with reinforcement. Sometimes, it is also needed to incorporate special load transfer devices. This latter solution is however relatively complicated and expensive.In this paper, the crushing and flexural strength of slab-column joints is investigated accounting for an increase of the compressive strength of the failure region (concrete between columns) due to confinement stresses provided by the flexural reinforcement of the slab. The results of an experimental programme on 6 full-scale slabs (250 mm thick) are presented showing that flexural reinforcement of a slab significantly increases the crushing strength of slab-column joints. This allows ensuring load transfer without incorporating special devices or even without linking top and bottom column reinforcement for a wide range of cases leading potentially to more economic designs. An analytical approach, grounded on the theory of plasticity, is also presented allowing one to determine a failure criterion for such regions. This approach, which can also be used for design purposes, leads to an excellent correlation with test results.     

推出试验中摩擦接触效应的数值分析

建立精确有效的2D非线性有限元模型,以研究组合桥梁中预制混凝土板和钢梁间抗剪连接件的力学性质。考虑材料非线性本构关系,采用4节点平面单元,该模型还对大梁翼缘与混凝土板以及混凝土板底部双头螺柱与混凝土之间的摩擦接触面进行了有限元分析。将数值分析结果与试验结果进行比较。每个试件中含有4个或9个双头螺柱。首先,给出能够精确模拟经典3D实际问题的2D数值分析法:等值法。然后,进行数值计算,研究摩擦系数对试件加载滑动性能的影响以及试件的内部变形与内力分布情况。最后,利用参数研究法和实际经验更好地进行连接件设计。     

某住宅墙、楼板工程质量问题的分析与处理

对某住宅墙、楼板开裂状况进行了检测和分析 ,提出了处理意见 ,处理后的效果较好。     

砖混住宅楼混凝土条形基础的加固

针对某住宅楼条形基础混凝土强度等级远低于设计强度的现状,提出在原基础上重新浇筑混凝土条形基础的加固方案,加固处理后效果良好。     

Curved structures in waffle slab construction

Horizontally-curved concrete waffle slab structures are sometimes used as superstructures of bridges and as floor slabs in large exhibition halls. The idealization of a horizontally-curved wide structure as a curved beam or an assemblage of curved beams leads to inaccurate results. Although the finite element technique can be used to analyse the structural response of horizontally-curved structures, trial solutions have shown that the finite difference method is a more attractive alternative since it requires fewer equations. In using this latter method accurate estimates of the structure's orthotropic rigidities are required. An analytical study is undertaken to investigate the structural efficiency of a curved waffle slab system in comparison with conventional alternatives, such as the solid slab and girder-slab systems. The feasibility of using an equivalent orthotropic plate system to predict the elastic behaviour of curved concrete waffle slab structures is examined. The analytical results are verified and substantiated by tests on horizontally curved concrete waffle slab models subjected to concentrated and uniformly distributed loads.     

自燃煤矸石砂轻混凝土单向叠合板的受弯性能

以混凝土组合形式及预制底板自燃煤矸石砂轻混凝土(SSC)的强度等级为变量,制作了5块SSC单向叠合板,通过静力加载试验,对其变形特征、破坏形态和裂缝开展情况进行了分析.结果 表明:5块单向叠合板表现出相似的变形特征;分形维数分析表明,适当提高预制底板SSC的强度等级,保证了叠合面不出现滑移;合理设计的半普通混凝土-半SSC和全SSC单向叠合板,均具有良好的整体性和较高的极限荷载,能够作为楼板使用.     

GFRP筋加固混凝土板的试验分析

本文介绍了GFRP筋混凝土板和钢筋混凝土板的试验室抗弯试验,描述了试件的受力～变形过程和破坏形态,对两种混凝土板的开裂荷载和极限荷载、挠度以及混凝土的应变进行了对比和分析。同时,对不同配筋率GFRP筋混凝土板进行了有限元模拟试验,探讨了配筋率对GFRP筋混凝土板刚度的影响,给出了GFRP筋混凝土板开裂后抗弯刚度的计算公式。     

预应力混凝土圆孔板中的剪力研究

预应力圆孔板是被广泛采用的一种楼面构件。关于它的抗剪强度计算问题,以前很少研究,在国内外规范中,一般都没有具体的规定。本文通过理论分析,对照试验结果,提出了计算各种预应力圆孔板的抗剪强度的计算公式。通过大量试验,综合了截面形式、预应力、纵向钢筋配筋率等因素,建议采用最小肋宽乘增大系数γ_ρ值的方法以简化计算。     

收缩对混凝土组合板长期应力与变形的影响

混凝土板和钢面板组合而成的单向板常作为永久模板在建筑结构中得到广泛应用。钢面板在浇筑混凝土时作为模板,待混凝土凝固后作为外部加固构件。这类板的使用性能具有时间依赖性,目前对其研究较少,在计算长期变形时为结构工程师提供的指导也较少。众所周知,板底部的不透水钢面板对沿组合板板厚分布的混凝土干燥收缩特性有着重要影响,但该影响尚未被量化。通过试验测定了沿组合板板厚非均匀分布的收缩特性,考虑了该结果对这类板长期变形的影响。组合板的应力与变形随时间变化而变化,该文描述了确定组合板应力和变形的分析过程,通过所测量的收缩特性,给出几种常见板型的分析结果。     

矩形钢管混凝土组合桁梁负弯矩区受力性能试验研究

矩形钢管混凝土组合桁梁由混凝土板和矩形钢管混凝土桁架组成,在竖向荷载作用下,其正弯矩区可充分发挥混凝土板和桁架的组合作用,但负弯矩区的力学性能较为薄弱且受拉混凝土板容易开裂。针对这一问题,提出了在负弯矩区混凝土板施加预应力以及布置局部释放剪切作用的剪力钉相结合的组合桁梁结构形式。采用跨中施加反向集中荷载模拟连续梁支点反力的方法,对2榀承受负弯矩的矩形钢管混凝土组合桁梁进行了静力加载试验,对其荷载-位移关系、裂缝发展规律、混凝土板应变分布、桁梁荷载-应变关系、钢与混凝土界面滑移及承载力进行了分析。还根据组合桁梁的简化力学模型对不同加载阶段的结构特征荷载进行了讨论。结果表明：采用局部释放剪切作用的剪力钉和混凝土板施加预应力的组合桁梁结构形式可有效提高其抗裂性能,但对受弯承载力影响较小;在加载过程中混凝土板的开裂和杆件的屈服导致结构塑性变形增大,最终节点处焊缝撕裂,组合桁梁丧失承载力;由简化力学模型计算得到的结构特征内力与实测值吻合较好,可为矩形钢管混凝土组合桁梁负弯矩区的设计和计算提供参考。     

设置垫板的梁柱T形件连接节点抗震性能试验研究

针对传统钢结构梁柱连接在地震中易脆性破坏,改进连接震后不易修复等问题,提出设置垫板的梁柱T形件连接构造措施。设计、制作3个不同形式的梁柱T形件连接试件,分别为未设置混凝土板的连接节点、设置混凝土板的连接节点和未设置混凝土板的传统梁柱T形件连接节点,对其进行往复荷载作用下的拟静力试验,研究试件的抗弯刚度、承载力、延性、滞回性能、耗能能力、破坏模式等。此外,更换梁下部翼缘处已破坏的T形件进行修复,并对修复后的试件进行拟静力试验。结果表明：设置垫板的T形件连接节点在往复荷载作用下具有稳定的滞回性能和良好的耗能能力;破坏试件的梁、柱均不发生屈服,转动中心位于梁端上部翼缘附近,能够保证在地震作用下梁端上部翼缘连接部位不发生破坏,并能够保护梁上混凝土楼板不发生较大的损坏;混凝土楼板的存在会提高节点正弯矩下的初始刚度和承载力,并使弯曲中性轴上移;更换梁下部翼缘处已破坏的T形件进行修复,修复后试件的滞回性能与原试件无明显差异。     

钢筋混凝土梁开裂有限元模拟及损伤分析

探讨了对钢筋混凝土梁自加载到开裂整个过程进行有限元模拟的方法，介绍了基于损伤梁单元的剩余寿命评估的原理，结合工程实例，基于ANSYS计算钢筋混凝土梁开裂后的损伤度以及剩余寿命，为既有桥梁寿命评估提供参考。     

锦屏一级水电站左岸深部卸荷裂隙的加固方案及数值模拟研究

锦屏一级水电站左岸边坡1650～1900m高程的岩体内存在着大量的卸荷裂隙。这些裂隙分布在50～300m深度范围内,数量多,规模大,延展长,走向基本平行于河道。水电站坝顶高程为1885m,正常蓄水位为1880m,大坝上游岩体的深度卸荷裂隙基本上位于正常蓄水位之下,而大坝下游的深度卸荷裂隙又受到水电站泄流导致的雾化雨的影响。这些深部卸荷裂隙在水的长期作用之下,工程性质进一步恶化,对大坝拱肩的安全性具有不利的影响,必须进行加固。采用通常的灌浆、锚索技术不能很好地予以加固。借助于现存的地质探洞,利用锚固洞技术、预应力锚梁技术予以加固可望取得较好的效果。选择左岸雾化区IV–IV剖面,用数值模拟方法,分别对锚固洞方案、预应力锚梁方案进行数值模拟计算。通过比较两种加固方案裂隙周围塑性区的分布状态发现,预应力锚梁技术对卸荷裂隙的加固效果较好。     

混凝土裂缝控制方法的探讨

本文简要分析了混凝土中的裂缝现象 ,对裂缝进行了分类 ,分析了裂缝产生的原因 ,探讨了裂缝控制的各种方法     

Experimental study of bonded steel concrete composite structures

This paper deals with the experimental analysis of the mechanical behaviour of bonded steel-concrete composite structures. The steel girder and the concrete slab are assembled by adhesives. The effect of the main parameters, such as the adhesive nature and the irregular thickness of the adhesive joint, on mechanical performance and ultimate load is studied. Two adhesives are used in this work. The results show that the connection between the steel girder and the concrete slab ensured by epoxy adhesive is perfect and without any slip in the steel-concrete interface. In the case of the composite beam interface ensured by polyurethane, the connection is flexible. The influence of the variation in adhesive thickness, 2 mm in the transverse direction and 4 mm in the longitudinal direction, on the mechanical behaviour and ultimate force is not important. The first cracks in the concrete slab appear in the transverse direction. The experimental results show that it is possible to realise a steel concrete composite structure bonded by adhesive.