结构工程
现浇混凝土空心楼板现浇混凝土空心楼板
    现浇混凝土空心楼板是一种在大跨度现浇混凝土厚板中埋入永久性内部空腔以减轻结构自重的新型结构体系，它适用于荷载和跨度较大的建筑。应用于一般民用建筑和工业建筑，可以节约楼层净高，降低工程综合造价，具有良好的使用功能和经济效益。现浇混凝土空心楼板已经用于建造多跨连续整体浇筑的超长无缝大型结构，试点工程实例显示这种结构具有很好的抗裂特性。空心楼盖最突出的问题是在荷载作用下内力的分布规律，目前国内的研究主要是少数破坏性试验和简化的数值模拟，通过这些试验和模拟对空心楼板的受力性能有了一定的了解，但对空心板的内力分布规律还不明确，本文在总结其他科研单位的成果的基础上，利用有限元软件进一步细化分析，揭示了混凝土空心楼板在荷载作用下的应力分布、截面剪应力分布及变形规律。超长混凝土结构的关键问题就是如何控制结构在非荷载作用下的开裂，引起结构裂缝产生的主要非荷载作用主要有：混凝土水化温升引起的温度应力、混凝土的收缩应力及外界气候变化引起的温度应力等。本文通过试验对现浇混凝土空心楼板的早期水化热、收缩及钢筋的应变进行研究。利用有限元软件对现浇混凝土空心楼板的温度场进行了数值模拟，并把试验结果和有限元模拟理论计算结果进行比较，验证了有限元模拟方法的可行性。最后，本文总结了现浇混凝土空心板的早期温度场分布规律及影响水化温升的主要因素，提出了控制现浇混凝土空心板内部温度场和减小结构内外温差的措施。总结了混凝土收缩的规律，针对如何减小混凝土的收缩和防止结构裂缝产生这一关键问题，从材料、设计和施工等几方面给出了建议。 [英文摘要]：     Cast-in-situ hollow floor is a new type of long-span structure system, which can reduce the self-weight of the structure by embedding permanent cavities in thick plank. It is applicable to buildings with greater loads and span. It can economize the storey height; reduce the total cost of the project. So it is a type of floor with good application function and economy benefit. Cast-in-situ hollow floor has been applied to build great multiple-bay structures which are continuously cast without construction joints. The pilot projects indicate that the structure has good crack resistance. The key problem of hollow floor is the law of stress distribution under loads action. Presently, most researches on cast-in-situ hollow floor are fewness experiments and simple numerical simulation. People can know the mechanics capability of the hollow floor to a certain extent through these researches, but it is not very clear yet. The paper utilizes FEM software to analyze the hollow floor accurately basing the conclusions of other research departments; it reveals the laws of stress distribution, shear stress distribution in the section and laws of deformation of the cast-in-situ hollow floor. 
    The key problem of super-long concrete structure is how to control the crack under non-load factors. The main non-load factors are: thermal stress caused by temperature rise due to hydration heat, shrinkage of concrete and the thermal stress due to variation of ambient temperature. The paper studied the hydration at early ages, shrinkage and the strain of steel bar through experiments. It utilized FEM software to simulate the temperature field of cast-in-situ hollow floor and compared the computation results with the experiment results. It indicated that it was feasible to analyze the temperature field through FEM. At last, the paper summarized the laws of distribution of the temperature field and the main factors influencing the temperature rise due to hydration and put forward some measures to control the temperature field of concrete hollow floor and minimize the inside and outside temperature difference; summarized the law of concrete shrinkage and put forward some advice on material, design and construction aiming at the key problem, which is how to minimize the shrinkage of concrete and prevent the structure from cracking.