【作者】 彭伟贤；

【导师】 高博青；

【作者基本信息】 浙江大学 ， 结构工程， 2005， 硕士

【摘要】 荷载缓和体系(Load Relieving System)是一种新颖的概念，通过在结构中引入一种可动装置，达到自我调节和自我保护的目的。其受力不同于一般的刚性结构，也不同于通常的柔性结构。本文主要以总结已有荷载缓和体系的研究成果为基础，结合机械学的理论，对实现荷载缓和的装置进行了创新研究，并发展了荷载缓和体系的计算方法，拓展了荷载缓和体系理论的外延。 本文在综述现有荷载缓和体系的形式、理论及其计算方法的基础上，结合机械学中的经典机械模型，对荷载缓和体系的荷载缓和装置进行了创新研究：同时对荷载缓和体系的计算方法，主要是力密度法和多次加载非线性有限元法进行了研究和算例验证。主要包括的内容如下： 提出了实现荷载缓和的几种装置形式：四连杆装置、螺旋压榨装置、弹簧装置、结构体装置和智能材料SMA装置等形式。并对其中的弹簧装置进行了弹簧杆结构和弹簧铰结构以及弹簧—四连杆结构的算例分析。 力密度法是在离散后结构各杆件的几何拓扑、设定的力密度值和边界节点坐标基础上，建立关于节点坐标的线性方程组，然后进行迭代计算求解。算例表明该方法计算速度快，同时可以人为控制计算收敛精度，但该法对于复杂荷载缓和体系前期处理工作量仍较大。 本文提出基于通用有限元程序的多次加载非线性有限元法。通过对单元参数的修改，多次分步加载并修正结构几何模型，以求得最终结构形状。多次加载非线性有限元法只要保证所考虑的索单元内力恒定，则有理由确信结构只发生了刚体位移，实现了单元内力不变而自由伸长这一特性，因此也就实现了对荷载缓和体系的受力分析。算例表明，多次加载非线性有限元法能够有效解决荷载缓和体系的计算，但是其中的参数处理、准确性的界定等问题仍需完善。 本文详细阐述了弹簧这种材料特性，讲述了其在荷载缓和体系中的三种应用(弹簧杆结构、弹簧铰结构和弹簧—四连杆结构)，并对其中的弹簧杆结构和弹簧—四连杆结构进行了受力及性能分析。计算结果表明：弹簧杆结构进行了向下荷载作用下各单元内力变化与刚性杆基本相同(有时还略大)：在向上荷载作用时结构中虽然发生了很大的位移，但是其内力基本变化不大。因此说明弹簧杆结构在向上荷载时，具有很好的荷载缓和功能。 针对弹簧杆结构内力分析的结果，本文提出弹簧杆结构应用的前提条件：当假设外荷载所对应的虚位移发生时，相应的结构应更有利于承担原来的外荷载。 弹簧—四连杆结构是机械学与结构静力学的综合应用，其运动分析可以参照机械学中机构分析方法，静力分析可以采用静力平衡关系进行分析。经本文参数分析，在转角仇=1300时，结构具有较大的外荷载调节范围，相应的k取100kN/弧度。 论文最后对上述研究内容及成果作了简单的总结，并展望进一步研究的方向和需要进行的工作。关键词:荷载缓和体系;缓和装置;力密度法;非线性有限元法;弹簧杆结构:弹簧铰结构;弹簧一四连杆结构么更多还原

【Abstract】 Load Relieving System was a new type of structure, which was put forward by a British scholar in 1980’s. Its basic conception is that the structure achieves the goal of self-adjustment and self-protection by introducing some kind of movable device. Load Relieving System is different from the general rigid structure and the flexible structure.Firstly, the up-to-date researches in domestics and international were summarized, some types of load-relieving device was innovated, and then two kinds of analysis methods were developed - force density method and non-linear finite element method. The main content included as follows:On one hand, several kinds of devices had been brought forward: four-bar-linkage structure, spiral pressing structure, spring structure, structure body device and shape memory alloy device. And then, spring bar structure, spring ream structure and spring four-bar-linkage structure are further studied the effects of load relieving.On the other hand, the analysis method was discussed:Force density method was based on the relationship of geometry, the force density value of each element and each node coordinate, then the linear equations about the nodal coordinate was set up and solved. Practice showed that force density method was highly efficient and could control the precision of convergence arbitrary.The steps of non-linear finite element method were to adopt the virtual material parameters, split the outside loads to a comparable small increment, and revise the geometry model every time to get the final shape. The key of this method was to keep the invariance of each element force in the whole process. Example showed that this method can analyze the Load Relieving System efficiently, but there were some problems need to be solved.The characteristic of spring was explained in details, and there were three kinds of applications in Load Relieving System: spring bar structure, spring ream structure and spring four-bar-linkage structure. Research showed: although very great displacement took place in spring bar structure, each element force did not change much with the increase of external force. But the precondition using spring bar structure was: when the dummy displacement was corresponded to the outside load directions, the newly structure should be propitious to bear the increased external loads. Spring four-bar-linkage structure was also studied in this paper.In the end, some conclusions were summarized and the problems that should be studied further were put forward.更多还原