平行弦 meaning in English
parallel chords
Examples
- The optimized section area considering reliability is in some degree different from that without it , which can be applied in practice . the examples of three bar truss and parallel chord truss with biggish span are analyzed on the conditions of reliability or not , the results of which prove the model and method proposed in this paper are feasible
本文分别从考虑可靠度约束和不考虑可靠度约束的情况下对三杆桁架，和跨度较大的平行弦桁架进行算例分析；并将两种算法结果进行比较，结果证明本文模型与方法是可行的和现实的。 - The main work of this paper was as fellows : ( 1 ) generalized the development of pre - stressed steel structure in our nation and abroad , and pointed out the main problem in practice ; ( 2 ) presented the mechanism of pre - stressed steel structure and revealed its applicable range ; ( 3 ) established the optimization design model for pre - stressed steel structure , which accounts for constraints on stresses and displacements of structure ; ( 4 ) brought forward the optimization design method , which combined linear programming and the principle of full restriction , through which we can obtain the magnitude of each time pre - stress and the optimized sections of each members of structure ; ( 5 ) analyzed the best times of pre - stress and pointed out that 2 ~ 3 times is preferable ; ( 6 ) conducted optimization design on large - space steel roof , horizontal parallel steel truss with local cables , horizontal parallel steel truss with global cable , and ultra - static steel truss , the result of which indicated that the multiple pre - stress structure is very economic ; ( 7 ) compared different schemes of cable placement for horizontal parallel steel truss , and the results showed that the local cable only unloaded the second girders , but had no response on the first girders and stomach poles , while global cable could unload the second girders and the stomach poles outside of turning point of cable , thus proving that global cable is more economic than local - cable
本文的主要工作是：对国内外预应力钢结构的发展历史及现状作了综述和总结，指出当前预应力钢结构工程实践中存在的主要问题；阐述了预应力钢结构的受力机理，并指出预应力钢结构的适用范围和特点；在考虑结构应力和变位约束的条件下，建立预应力钢结构优化设计模型；提出多次预应力钢结构优化设计方法和步骤，采用线性规划和满约束准则相结合的优化方法，可优化设计出施加的每一级预应力的大小，并得到结构各部分的优化截面；对多次预应力最佳的施加次数作了分析，并建议以2 3次为宜；为验证文中理论和方法，分别对大跨多次预应力钢屋架、局部布索的水平平行弦钢桁架、整体布索的水平平行弦钢桁架和局部布索的超静定钢桁架等算例进行了优化设计，经济效益明显；对水平平行弦钢桁架的几种施加预应力的方案进行比较，对于局部布索，预应力只对下弦起到卸载作用，对上弦和腹杆基本不起作用；而整体布索预应力除对下弦卸载外，对索折点以外部分腹杆也起到卸载作用，经济效益好于局部布索。