钢筋混凝土叠合板组合模具研究现状及分析

目前,我国装配式建筑中叠合板是使用频率最高的预制构件,叠合板模具的设计、制作直接影响工程造价及工期.研究目前市场上各企业叠合板模具现状,叠合板模具类型可分为分离式组合模具、拼装式组合模具、调节式组合模具,列举各类型模具设计实例,分析该种类型的优缺点.     

考虑楼板不同刚度时跳层空腹网架结构的受力性能分析

跳层空腹网架在利用网架的空腹部分做楼层使用时，网架的上、下弦杆均与楼板浇注成为一个整体，以往对跳层空腹网架结构的力学性能分析均未考虑楼板刚度的影响．本对普通型跳层空腹网架结构在竖向荷载作用下考虑楼板不同刚度和不考虑楼板刚度进行了比较分析，揭示了楼板对空腹网架受力性能的影响规律．本的结论可为跳层空腹网架结构的工程设计提供参考．     

Theoretical investigations on load‐bearing capacity of RC flat‐plate framed structures subject to middle column loss

This paper presents theoretical studies on load‐bearing capacity of reinforced concrete flat‐plate framed structures. The existing methods for determining load‐bearing capacity of simply supported slabs are first reviewed, and their limitations are presented. An energy‐based refined method is then proposed to enhance the accuracy of the existing methods by considering the contributions to internal energy dissipation due to the extension of reinforcing bars along yield lines, the additional resultant bending moment from membrane forces, and the sectional bending moment along yield lines of slabs. The refined method for simply supported slabs is extended for fixed supported slabs, and thus, the load‐bearing capacity of reinforced concrete flat‐plate structures subject to a middle column loss is analytically determined. The performance of the proposed method is validated against test results and also verified against finite element analyses. Parametric studies are conducted to investigate the effect of reinforcement ratio, slab thickness and aspect ratio on the stiffness, and yield‐line resistance of structures. It is found that for the fixed supported slabs, it is reasonable to assume negative yield lines along the slab edges to consider the effect of obvious concrete crushing along the edge. Square slabs have higher ultimate loads than rectangular slabs, due to a longer horizontal yield line in the middle in the rectangular slab, which has detrimental effect on the sectional ultimate bending moment. The numerical results show that the reinforcement ratio has little effect on the initial bending stiffness and yield‐line resistance of slabs for a given slab thickness and aspect ratio. The initial stiffness and yield‐line resistance increase as the slab thickness increases. For the same reinforcement ratio and slab thickness, a larger aspect ratio leads to a lower initial bending stiffness, yield‐line resistance, and stiffness in tensile membrane action stage, due to a longer yield line along which tensile membrane forces have a detrimental effect on the sectional bending moment.     

Towards standardisation of proof load testing: pilot test on viaduct Zijlweg

Proof load tests of bridges can be very useful for structures with a lack of information, or for structures of which the effect of material degradation is difficult to assess. Contrary to diagnostic load testing, proof load testing is not well-defined in current standards in terms of required load and analysis of measurements. The risk related to the high loads used in proof load testing requires standardisation for these tests. The paper highlights important considerations for proof load testing that may lead to the development of guidelines in the Netherlands, by illustrating a pilot study on the viaduct Zijlweg in the Netherlands. This reinforced concrete bridge rates too low in shear. Topics of interest are the required load that the bridge has to withstand to be approved by the load test and the interpretation of the measurements during the test to avoid permanent damage to the structure. These measurements were compared to the stop criteria from existing codes for buildings, to examine if recommendations for the use with bridges can be formulated. The final result of the test on this case study is that the capacity of the viaduct is proven to be sufficient for shear and bending moment.     

复杂基础综合施工技术的研究与应用

萧山机场二期工程中,航站楼及穿主楼隧道基础部分施工存在标高种类多、当地土质粘聚性差等难点。工程应用复合土钉墙支护技术,在保证了特定土质下成孔的稳定性同时加快了施工速度;通过将连系梁底垫层混凝土变更为整体浇筑的方式,改善了基础防水层的薄弱点;拆撑阶段合理选用、安排机械,并利用专业计算软件对施工工序进行合理变更,提高了施工进度;采用创新的泥浆回填技术,合理利用当地资源解决了护坡桩间距过窄的问题。     

带约束预制混凝土叠合板受火后抗弯性能的试验研究

进行带约束预制混凝土叠合板常温和受火后受弯性能的对比试验,研究升降温过程中截面温度场变化和不同受火时间自然冷却后极限荷载、初始弯曲刚度和延性系数的变化规律。结果表明：未受火预制混凝土叠合板和不同受火时间自然冷却后预制混凝土叠合板均发生弯曲破坏。带约束预制混凝土叠合板升温阶段截面温度场呈受火面温度高、背火面温度低的层状分布,降温阶段温度场呈内部温度高、外部温度低的圈状分布;随着受火时间增加,极限荷载和初始弯曲刚度均呈抛物线型下降;受火自然冷却后的残余挠度也明显增大。理论分析表明,经典塑形铰线理论适用于预制混凝土叠合板未受火试件和受火后试件极限荷载的计算;截面温度场和受火后极限荷载数值模拟结果均与试验结果吻合较好,可为预制混凝土叠合板的防火设计和火灾后鉴定评估提供依据。     

某工程搁栅受弯试验研究

本文通过在三块楼板上施加均布荷载的试验,模拟某工程楼板改造后相应增设的矩形钢管搁栅及原有圆木搁栅在实际荷载作用下的受力情况。利用位移传感器测量的搁栅跨中挠度判断搁栅使用过程的安全可靠性,从而间接确定楼板改造方法的可行性。在试验基础上,回归出荷载-挠度曲线,回归曲线同试验曲线吻合良好。     

填充墙和现浇板对钢筋混凝土框架结构整体超强的影响研究

为充分实现框架结构的“强柱弱梁”耗能机制,需要考虑填充墙、现浇T形截面梁及其翼缘现浇板内与梁肋平行配置的钢筋对结构整体超强系数的影响。考虑抗震设防烈度、结构层数等因素,严格按我国抗震规范设计了15个典型钢筋混凝土框架结构,对结构进行Pushover 分析,得到了各种结构在非弹性阶段由于内力重分布而形成的超强性能。结果表明：结构设计考虑填充墙、现浇楼板的影响,会提高结构的整体超强能力,结构整体超强系数均随着抗震设防烈度的增高而减小,且先随结构层数的增大而减小,结构层数大于8层后,又随结构的层数的增大而增大。可以保守地认为,分别按抗震设防烈度6,7,8度设计的结构,同时考虑填充墙和现浇板影响时,结构整体超强系数分别至少要达到5.0,3.0,2.0。     

可拆装钢-混凝土组合楼板承载力试验与模拟分析

为掌握实际工程中预选用的组合楼板的承载性能,以钢框架-混凝土组合楼板为研究对象,进行静力加载试验,并利用通用有限元软件ANSYS对试验中组合楼板进行承载模拟计算,结果表明组合楼板的槽钢和压型钢板发生塑性变形前的模拟计算结果与试验得到的荷载-挠度曲线吻合很好,基于简化的材料应力-应变关系的有限元计算模型可用于钢框架-组合楼板弹性范围内的承载性能分析中。     

压型钢板对钢筋桁架楼板承载力影响的试验研究

为深入研究钢筋桁架楼板的受力性能,设计了足尺寸楼板试验。通过分析试验结果,得到底部压型钢板对钢筋桁架楼板承载力的影响。采用有效惯性矩法计算钢筋桁架楼板的正截面承载力的理论值,经与实测值比较,发现有效惯性矩法所算得的数值与试验值更为接近。提出可供参考的钢筋桁架楼板正截面受弯承载力计算公式,并给出相关修正系数。