自由曲面网格结构的力学性能研究

首先介绍了自由曲面网格结构网格划分方法的研究现状。其次,基于浙江大学空间结构研究中心自主研发的自由曲面网格划分专用软件ZD-Mesher,选取曲面展开和引导线法结合的网格划分方法,对同一曲面划分不同走向的网格。最后,根据自由曲面的网格,建立有限元分析模型,分析并比较同一曲面不同走向网格的力学性能。结果表明,由此得到的自由曲面网格,基本实现了美学与力学的兼顾统一。     

基于自定义单元法的自由曲面网格划分研究北大核心CSCD

为实现对任意自由曲面的建筑网格划分,采用自定义单元法,以网格节点为对象,以"代"为整体进行节点推进。首先,根据节点的演化规律进行网格单元自定义。其次,在节点推进过程中,根据曲面特征进行单元选择生成下代节点,自适应曲面尺寸变化,将每一推进步单元"组装",建立网格拓扑的参数化表达;采用黎曼度量表征单元节点参数距离,考虑适应曲面曲率特征,确定节点参数坐标。最后,参数网格映射到自由曲面形成空间网格结构。结果表明,自定义单元法能够通过参数选择实现对网格规模和形式的量化控制,为自由曲面提供多样化网格划分方案,生成的网格杆件均匀、线条流畅、形式多样。     

自由形态B样条曲面网格生成的参数化方法研究(英文)

研究了自由曲面上网格的参数化生成方法.该方法利用了张量积曲面的特性,通过在曲面上提取等参线并等分等参线来生成网格.阐述了在B样条曲面上提取等参线(实质是B样条曲线)的原理,并给出了等参线等分以及由等参数生成网格的算法步骤.列举三个不同类型曲面上网格生成的例子,通过这些算例进一步介绍该方法的使用范围和使用策略.最后通过在实际工程中的应用案例表明该法的实用性及有效性.这一新网格生成技术能够划分出既均匀又美观的网格,可以广泛应用于自由曲面空间网格结构.     

自由曲面单层网格的智能布局设计研究

单层网格结构的网格划分标准不同于有限元网格的划分,它更侧重于以定性要求为标准的网格质量评价。为满足自由曲面单层网格杆件长度尽量一致、分布尽量均匀、过渡尽量流畅的要求,以自由曲面优化找形为前提,基于网格形状和单元长度的网格质量衡量标准,编制智能化网格设计程序。在整个布局设计过程中,首先通过拓扑不变的原则将空间问题转化为平面问题。其次,利用空间映射原理将在平面参考域上布置好的网格映射回三维空间曲面。最后,通过对初始拓扑网格进行智能化的修正和优化,保证所有杆件长度一致、网格布置美观的效果。通过在上海世博轴阳光谷工程中的实际应用证明,该方法操作简单,效果理想。且若采用不同拓扑关系布置的网格可以生成同样要求的最终杆件布置效果,供建筑师设计选用。     

剪力墙结构的自由网格划分

本文针对剪力墙结构提出了一种新的自由网格划分方案,使得剪力墙结构的有限元离散模型更加合理,从而提高有限元分析的精确性和可靠性。该方案以铺砌法自由网格算法为核心并联合几何拆分法和映射网格法,兼顾自由网格的通用性和映射网格的高效性,既满足各种复杂结构模型的要求,又提高网格划分的质量,并同时确保网格划分的速度,从而节省结构分析的总时间。     

自由曲面索支撑空间网格结构形态优化

索支撑空间网格结构是一种新型的单层网壳形式,主要应用于玻璃采光顶结构中。由于目前对自由曲面索支撑空间网格结构形态方面的研究国内外还相对较少,为此提出了一套适用于该类结构的形态优化方法。该优化方法采用结构整体应变能为优化目标、结构高度为优化变量、共轭梯度法为优化算法。根据索支撑空间网格结构的建模方法,将优化结构整个曲面转化为优化结构的准线和母线。采用该方法对自由曲面索支撑空间网格结构进行形态优化研究,得到结论如下:首先,采用本文形态优化方法,收敛速度快,形态优化后结构的力学性能提高很大;其次,形态优化过程中平面四边形网格属性不变,优化变量少;最后,对优化后的离散网格重新进行拟合生成曲面,对该曲面重新划分网格,保证网格长度相等。重新划分网格为结构构件加工和施工提供了便利,而且结构力学性能削弱不大。     

自由曲面空间网格建筑形态获取与模型实现

随着结构设计手段、施工技术及材料的发展和应用,现代建筑的外观追求以"曲"为特征的连续、平滑的形态,和柔和的艺术美感。文章提出并实践了自由曲面网格建筑外形的一种逆向设计方案,包括从物理模型到数字模型的三维信息输入,和从数字模型到物理模型的实物展示。引入三维扫描与三维打印技术,追求精确和便捷的一体化研究,达到曲面网格建筑美感和结构性设计的统一。     

Rock failure and its jointed surrounding rocks: A multi-scale grid meshing method for DDARF

DDARF (Discontinuous Deformation Analysis for Rock Failure) is an improved method of DDA (Discontinuous Deformation Analysis method), while there are only uniform grids in the original DDARF, and multi-scale grid meshing method cannot be realized. A multi-scale grid meshing method for DDARF is proposed to rock failure analysis, which balances off between the calculation accuracy and computation time. Simulations with multi-scale grid model and uniform grid model are established respectively, and compared with the laboratory tests; this multi-scale grid meshing method is applied to progressive failure process for jointed surrounding rock, and influence on crack propagation by the different lateral pressure coefficients K₀ of in situ stress is analyzed. It is concluded that this multi-scale grid meshing method for DDARF is feasible and the calculation accuracy can be improved with the same grid number. The proposed method is able to increase the computation efficiency by reducing the computation time when simulating underground cavern excavations, at the same time maintain the calculation accuracy. With increase of the lateral pressure coefficient K₀ of in situ stress, the main cracks propagating zones are moved gradually from both sidewalls of the cavern to the arch crown and floor. This method improves the DDARF to large projects, and it can analyze the progressive failure process of rock more effectively.     

正方形边界悬垂织物自由形态的逆向实现

以正方形边界悬垂织物模型的逆向实验为例,研究自由形态的逆向实现技术,将正方形边界悬垂织物模型经三维扫描,得到表征自由形态特征的点云数据,基于逆向软件处理点云数据,得到重构曲面并生成初始网格,引进条带化旋转展开技术,进一步综合运用三维造型软件与三维打印技术,设计自由形态空间网格结构并可将其快速打印成型,验证了逆向实现技术的可行性。     

基于网格划分的全空间块体识别方法及其工程应用

为了解决复杂几何边界条件下有限结构面的全空间块体识别问题,提出有向面单元的几何建模概念,并将网格划分思想引入块体理论中。首先利用空间正交网格将岩体离散为若干个小单元块体,然后依次添加结构面,对单元进行接触性判断及切割,最后去除网格合并单元,形成独立的空间块体。针对块体的切割,给出了平面对任意形态块体的切割方法。针对单元块体的合并,提出了以有向边合并为基础的块体合并方法,将同向面、异向面合并方法统一。研究表明该方法具有可动态添加有限结构面、建立复杂几何模型、识别块体的形态数量不受限制、编程简单等优点。结合辽宁某隧道工程实例,利用本研究成果识别出全空间内所有独立块体,并进一步提供围岩周围关键块体的基本信息,证明了其应用于复杂岩石块体识别的有效性和优越性,为确保岩体工程的安全生产提供技术支持。     

某海螺形自由曲面单层网壳结构形态构建和整体稳定分析

通过三维建模软件Rhinoceros及其可视化编程插件Grasshopper,参数化建模出一种海螺形自由曲面网壳结构.采用ANSYS软件对该结构进行几何非线性分析,研究不对称荷载和初始几何缺陷对结构整体稳定性的影响.采用本文的自由曲面建模方法可以方便、快捷、参数化地设计出建筑师想要的不规则曲面建筑.分析表明:该结构对不...     

Meshing and integrated optimisation for free-form reticulated shells

Presented herein is a study on the meshing and the integrated optimisation technique combined with configuration and mechanical behaviour for free-form reticulated shells. It focuses on the realisation of the practical layouts of meshes and improves the evaluation criteria for grid quality. For the preparation for the integrated optimisation, the bicubic quasi-uniform B-spline surface is applied to describe the free-form surface, and the energy method is introduced to smooth free-form reticulated shell through fairing factors. In order to perform optimisation automatically, a novel integrated optimisation system is established including fairing, finite element analysis (FEA) and optimisation programme modules. Based on the relationship between the fairing factors and the structural configuration, the zoned fairing factors are chosen as design variables (DVs). The FEA module is introduced to analyse and calculate the total structural strain energy of the structural components. By using the optimisation module, the optimum structural configuration can be found when the total structural strain energy reaches the minimum. Numerical results demonstrate that the proposed optimisation technique is convenient and feasible.     

一类新复合形法及其在临界滑动面搜索中的应用

针对广泛采用的基本复合形法存在着搜索不完全、映射系数取值不灵活、复形多样性保持差等缺陷,提出了相应的改进措施,如动态全域映射收缩算子以及最大冗余点映射准则,形成了一类新型的复合形法。在确定冗余点时综合考虑了距离空间和目标函数值两方面的信息。通过对某复杂土坡的最危险滑动面的搜索表明,新型复合形法的寻优成功率比基本复合形法大大提高。     

Discrete singular convolution method for buckling analysis of rectangular Mindlin plates

The discrete singular convolution (DSC) method is proposed for solving the elastic buckling problem of thick rectangular plates under a uniaxial compressive loading. To allow for the effect of transverse shear deformation in thick plates, the Mindlin plate theory has been adopted. The numerical results are checked against available analytical and other numerical solutions. It is found that the convergence of the DSC approach is very good and the results agree well with those obtained by other researchers.     

距离势离散单元法

 势函数离散单元法在接触力计算中存在势函数物理意义不明确、接触力计算与客观实际不符等重大缺陷。在已有研究的基础上,提出一种新型任意形状块体距离势离散单元法。该方法将势函数定义为接触体间归一化的距离函数,可以客观衡量单元间的嵌入程度,具有明确的物理意义,真实反映单元的接触刚度,使法向接触力计算更为合理。此外,新方法重新定义了切向方向矢量,提出切向接触力计算方法。新方法保留原势函数法所有优点,同时完善接触力计算受单元形式影响的不足,并突破三角形单元的限制,能够应用于任意凸多边形单元。通过若干算例说明新方法的正确性和有效性,可用于精确描述复杂非连续介质的运动过程。     

Shape optimization method of free-form cable-braced grid shells based on the translational surfaces technique

Cable-braced grid shells, being a new type of single-layer reticulated shell, are widely used in glass roofs. However, research on the shape optimization of free-form cable-braced grid shells is relatively lacking. This paper describes a shape optimization method for cable-braced free-form grid shells, with strain energy used as the optimization object, structural height used as the optimization variable, and the conjugate gradient method used as the optimization algorithm. According to the shape forming method for grid shells, their shape optimization can be realized only by adjusting the generatrix and directrix, not by optimizing the whole surface. The B-spline curve method is used to model the generatrix and directrix and maintain an optimized surface fairing. The following conclusions can be drawn from this study. First, the structural mechanical behavior of grid shells can be significantly improved with rapid convergence using the proposed shape optimization method. Second, the plane quadrilateral mesh is maintained and fewer optimization variables are needed during the proposed shape optimization method. Finally, the optimized surface is fairing and the mechanical properties of the optimized surface are somewhat decreased when using the B-spline curve method.     

Planning algorithms for in-situ production of free-form concrete panels

Various materials are used when fabricating free-form panels, including glass, aluminum, titanium, and glass fiber reinforced concrete (GFRC), in addition to steel and concrete. Concrete has excellent structural stability, constructability, and economic efficiency, as well as the advantages of shape, thickness, forming of the finished surface and homogeneity of material. As a result, fast, low-cost technology has been developed to ensure the quality of free-form concrete panels (FCPs). FCPs, like precast concrete members, are generally constructed during in-plant production, on-site transportation, and installation. However, if FCPs are produced in site, cost savings of approximately 20% can be achieved due to savings in transportation and overhead at plants. In order to produce and install FCPs in site with restricted time and area, it is necessary to analyze and systematically link the related processes and influence factors. The purpose of this study is to develop planning algorithms for the in-situ production of free-form concrete panels. For this study, the relationship between the factors affecting the production plan of FCPs was mathematically established. The algorithms proposed in this study support the quick and easy establishment of in-situ production plans, contributing to cost reduction, according to various influencing factors such as the number of CNC machines, number of production cycles, production time, production area, and lead time.