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。     

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.     

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。     

基于频率退化的砌体房屋结构抗震性能评价

为研究双向地震作用下预制板砖砌体房屋结构的抗震性能评价方法,进行1∶2比例模型的双向拟动力试验。通过介绍试验中结构刚度和频率的变化,提出基于频率变化的抗震性能评价方法,评价结果与基于刚度退化的方法接近,但计算过程更加简捷。基于频率的评价结果与实际破坏状态也较吻合,说明该方法可以应用于预制板砖砌体房屋结构的抗震性能评价。     

水垫塘底板稳定研究

 通过对水垫塘底板不计止水、抽排和锚固等作用的20多种组合工况的试验研究 获得了板块开始失稳时的水流条件和动水压力的试验成果；分析了单宽流量和板块大小对板块稳定的影响；导出了板块稳定的必要条件；并应用所得成果对某工程水垫塘底板的稳定性作了分析，初步验证表明本研究成果具有实用性。     

预应力砼空心板标准图设计探讨

论述了冷轧带肋钢筋、冷拔钢丝预应力砼空心板标准图编制中荷载标准值的计算——图解法,以供大家参考.     

镶嵌铰链混凝土板式护坡加固长江干堤研究

由于石料缺乏,长江干堤护坡型式常采用预制混凝土和现浇混凝土板两种形式.在综合上述两种护坡形式优点的基础上,设计出一种新的护坡形式-镶嵌铰链混凝土板护坡.镶嵌铰链混凝土板为小单元、大整体结构.小单元结构为一端带有两个母榫,另端带有两个公榫,两边带有企口的长方形薄边,板厚t根据不同工况确定,板的平面尺寸为0.45～0.7 m左右.将其应用在江南垸1 km长的堤防护坡中进行应用研究.经过一年多的洪水考验,护坡效果良好.对铰链混凝土护坡的设计过程作了详细介绍,可供类似工程参考.     

Mechanisms for the intermetallic formation during the Sn-20In-2.8Ag/Ni soldering reactions

The morphology and growth kinetics of intermetallic compounds formed during the interfacial reactions between liquid Sn-20In-2.8Ag solder and Ni substrates are investigated. Energy-dispersive x-ray (EDX) analysis identifies the composition of the interfacial intermetallics as Ni₃(In_0.99In_0.01)₄. The soldering reactions at lower temperatures (225–275°C) result in the predominant formation of a homogeneous intermetallic layer whose growth is diffusion controlled. At higher soldering temperatures (300–350°C), the interfacial intermetallics appear to be long needlelike crystals, and the grooves in between the intermetallics provide fast-diffusion paths for Ni atoms to react with Sn atoms at the intermetallic front, which leads to interface-controlled growth kinetics. The intermetallic needles turned out to be flat slablike after selective etching of the unreacted solder. Kinetics analysis showed that they not only lengthened in the longitudinal direction, but also coarsened transversely by the Ostwald ripening mechanism.     

FRP筋混凝土板冲切承载力计算方法

基于临界剪切裂缝理论,提出FRP筋混凝土板冲切承载力的计算方法. 该方法考虑拉伸刚化效应的混凝土拉伸应力-应变关系,利用截面分析法确定FRP筋受弯构件的弯矩-曲率关系. 根据混凝土板的变形假定、弯矩-曲率关系以及板的平衡方程,确定FRP筋混凝土板的需求曲线. 收集文献中试验数据对该计算方法进行验证,并将其与其他计算模型进行比较分析. 参数分析结果表明：随着混凝土强度与柱头尺寸的增加,FRP筋板承载力名义应力相应降低,混凝土板的延性呈现增长趋势;随着配筋率与厚度的增加,板冲切承载力的名义应力增大,配筋率与厚度的增加会导致板延性降低,因此在设计中应充分考虑板厚与配筋率对FRP筋混凝土板延性的影响.     

组合楼板的破坏模式及承载能力试验研究

根据组合楼板可能发生的主要破坏模式,研究组合楼板的承载能力,并通过对承载能力影响因素的分析,为设计人员合理选择组合楼板参数提供一定的参考和依据,进一步完善组合楼板的承载力计算方法。