Interactive structural design with computer graphical output

A study has been made of cost patterns of precast concrete portal framed buildings. Studies carried out into fabrication, haulage, foundations, cladding and erection have been used to develop a Cost Model Computer Program. Data describing the structure is input into this Cost Model and the resulting overall cost is used to generate cost contour maps for precast concrete portal framed buildings. The Cost Model program is interfaced with a computer graphical system which enables engineering drawings and bar bending schedules to be output interactively.     

Automatic Design of Cable-Tensioned Glass Shells

We propose an optimization algorithm for the design of post-tensioned architectural shell structures, composed of triangular glass panels, in which glass has a load-bearing function. Due to its brittle nature, glass can fail when it is subject to tensile forces. Hence, we enrich the structure with a cable net, which is specifically designed to post-tension the shell, relieving the underlying glass structure from tension. We automatically derive an optimized cable layout, together with the appropriate pre-load of each cable. The method is driven by a physically based static analysis of the shell subject to its service load. We assess our approach by applying non-linear finite element analysis to several real-scale application scenarios. Such a method of cable tensioning produces glass shells that are optimized from the material usage viewpoint since they exploit the high compression strength of glass. As a result, they are lightweight and robust. Both aesthetic and static qualities are improved with respect to grid shell competitors.     

Cladding-network interaction in pretensioned cable roofs, studied by dynamic relaxation

Current methods of analysis and design of pretensioned cable roofs disregard the cladding contribution to the overall stiffness of the structure, and therefore full-scale constructions suffer from excessive pretensioning of the cables. This paper investigates cladding stiffening effects in pretensioned cable roof models, using a dynamic relaxation algorithm. A mathematical model of cladding-network interaction in combined response to static external loads is presented, developed on the assumption of a discrete membrane surface of the cladding attached to the cable network. Detailed results are presented for a partially and fully clad hyperbolic paraboloid model. Comparisons are made between the results from the analysis of the composite structure clad with panels of varying stiffness and the corresponding “bare” network analysis. Results show that the cladding makes a substantial contribution to the stiffness of the composite structure, and suggest that future design of foundations for the cable anchorage should take this into account.     

Nonlinear finite element analysis of concrete structures using new constitutive models

Nonlinear finite element analysis was applied to various types of reinforced concrete structures using a new set of constitutive models established in the fixed-angle softened-truss model (FA-STM). A computer code FEAPRC was developed specifically for application to reinforced concrete structures by modifying the general-purpose program FEAP. FEAPRC can take care of the four important characteristics of cracked reinforced concrete: (1) the softening effect of concrete in compression, (2) the tension-stiffening effect by concrete in tension, (3) the average (or smeared) stress–strain curve of steel bars embedded in concrete, and (4) the new, rational shear modulus of concrete. The predictions made by FEAPRC are in good agreement with the experimental results of beams, panels, and framed shear walls.     

The analysis of nonlinear cable net systems and their supporting structures

The analysis of large cable net systems is feasible only with the aid of high speed digital computers. However, even computerized design of cable nets requires careful formulation and the selection of efficient solution techniques. This paper describes the solution of a general integrated structural system which includes three-dimensional beam members and cable elements that is useful to the design engineer. This solution is used to analyze an example prestressed cable structure, and results are presented to demonstrate the efficiency and accuracy of different solution techniques and to illustrate the effect of variation of important parameters.NET 3 is the general solution program. Input includes: (1) cable sizes, weights, and stress-strain characteristics; (2) initial coordinate points and cable forces due to prestressing; (3) support conditions for the cable net; (4) applied loads; and (5) data for supporting structure. The initial shape and cable forces are computed with the aid of an auxilliary program, SHAPE, given the coordinates of the cable end points, the initial prestressing forces, and an initial interior coordinate. The cable stress-strain characteristics may be linear or nonlinear. The supporting structure may be replaced with equivalent spring stiffnesses or actual three-dimensional elements.The assumptions used in the solution are: (1) cable elements are straight between nodal points and have no flexural stiffnesses; (2) the roofing and decking provide no stiffness; (3) all loads are applied at the nodal points; and (4) all supporting structural elements are elastic. It should be noted that no displacements of the cable nodal points are neglected. Even at boundaries, the elastic stiffness can be considered. Temperature changes can be analyzed to determine their effect upon the structure.Cable net structures usually have many elements and require relatively large amounts of computer time. In addition many loading and geometric conditions must be considered. To be useful as a practical design tool, it was essential that the program be as efficient as possible and require a minimum of storage. The solution utilizes a variation of the Newton-Raphson method. Initially the tangent-modulus stiffness is used. At each iteration the change in the element force is compared with the change in element force for the previous iteration to determine if the convergence rate is within a prescribed value. If it is acceptable, the stiffness for the previous iteration is used; if unacceptable for any element, tangent stiffnesses for all elements are recalculated. This technique attempts to combine the best features of the Newton-Raphson and the modified Newton-Raphson methods by increasing convergence probability and decreasing solution time.To minimize storage requirements, NET 3 has the capability of utilizing tapes in the problem solution. The storage requirements are determined internally before the solution is initiated. If the required storage exceeds that alloted for the system of equations, the solution is effected through the use of tapes.Output for the cables includes nodal point displacements, nodal point forces, and element forces; for beam elements, forces and moments are given. The solution has been verified by comparison with results by other investigators.An elliptical shaped structure, 220 by 240 ft, has been analyzed with the program to investigate the influence of several parameters. The short direction cables were prestressed, and a uniform load of 40 psf was assumed. The variables investigated include: (1) initial prestress force; (2) degree of stiffness of supporting structure; (3) cable sizes; (4) sag-span ratio; and (5) temperature change.     

Interactive microcomputer-aided design of circular suspension cable roofs

This paper presents interactive computer-aided design of circular suspension cable roofs. A microcomputer program developed in Advanced BASIC and according to the principles of structured programming is presented. The program can display/plot the plan of cable roof, the elevation of the structure including the loading on the cables and the cross-section of the reinforced concrete compression ring. The interactive program helps the user to explore many design alternatives rapidly and arrive at a practically optimum design.     

装配式混凝土构件设计软件

针对当前装配式混凝土结构发展迅速而相应的设计软件严重缺乏的现状，研发装配式混凝土构件设计软件PCMSD。该软件具有叠合梁端结合面、预制柱底施工缝、桁架钢筋混凝土叠合楼板、预制外挂墙板、叠合梁与预制柱节点、主次梁牛担板连接节点和主次梁缺口连接节点等设计功能。PCMSD在紧扣国家结构设计标准的基础上，结合工程实际，针对设计人员在装配式结构设计中急需解决的问题提供相应的解决方案。通过采用OpenXML标准和C++托管技术实现Word计算书的输出，其中包含构件设计的详细过程、公式和数据代入过程，便于设计人员检查校核。     

Bifurcation, pre- and post-buckling analysis of frame structures

A procedure is developed for investigating the stability of complex structures that consist of an assembly of stiffened rectangular panels and three-dimensional beam elements. Such panels often form one of the basic structural components of an aircraft or ship structure. In the present study, the stiffeners are treated as beam elements, and the panels between them as thin rectangular plate elements, which may be subject to membrane and/or bending and twisting actions.

The main objective of the study is the determination of the critical buckling loads and the generation of the complete force-deformation behavior of such structures within a specified load range, based on the use of a computer program developed for this purpose. The present formulation can trace through the postbuckling or post limit behavior whether it is of an ascending or descending type. A limit load extrapolation technique is automatically initiated within the computer program, when the stability analysis of an imperfect or laterally loaded structure is being carried out.

The general approach to the solution of the problem is based on the finite element method and incremental numerical solution techniques. Initially, nonlinear strain-displacement relations together with the assumed displacement functions are utilized to generate the geometric stiffness matrices for the beam and plate elements. Based on energy methods and variational principles, the basic expressions governing the behavior of the structure are then obtained. In the incremental solution process, the stiffness properties of the structure are continuously updated in order to properly account for large changes in the geometry of the structure.

The computer program developed during the course of this study is referred at as GWU-SAP, or the George Washington University Stability Analysis Program.     

平行螺旋传输线用于岩土形变分布式测量的机理研究

提出了一种平行螺旋传输线作为传感电缆用于岩土形变位移的分布式测量,基于建立的拉伸分布参数模型,推导了传感电缆特性阻抗与岩土拉伸量的关系并给出了拟合函数。根据编写的上位机程序计算出其特性阻抗的变化从而实现了岩土拉伸位置的定位测量,再利用拟合函数,确定拉伸量的大小,最终求得岩土形变的拉伸总量。为了验证理论分析的正确性,设计了基于时域反射技术的形变测量系统,对平行螺旋传输线进行了局部多点拉伸的定位及形变测量实验,实验测量结果和理论计算结果吻合度很好,为平行螺旋传输线在岩土形变分布式测量的应用提供了有力的理论分析和实验验证。     

Further comparison of the numerical and experimental buckling behaviors of composite panels

Experimental buckling behaviors for fiber-reinforced, circular cylindrical panels under prescribed uniform end-displacement are compared with numerical buckling behaviors computed from an energy-based, finite-difference computer program.Buckling behaviors were obtained for five test panels with simply-supported straight edges and clamped curved edges, and for five test panels with unsupported straight edges.Numerical buckling behaviors were obtained for one panel from each of the two groups using measured initial transverse imperfections.Experimental buckling loads for test panels with simply-supported straight edges ranged from 4600 to 5775 lb. This range of experimental buckling loads was due principally to an inability to impose circumferential displacements precisely, and to differences between distributions of initial transverse imperfections for various test panels. Numerical computations using measured initial transverse imperfections and boundary conditions along the straight edges that allowed circumferential displacements to either occur freely or to be completely restrained tend to confirm these assertions. Favorable agreement was observed, since the experimental buckling loads were included between the two limiting numerical buckling loads (4505 and 6106 lb).Experimental buckling loads for test panels with unsupported straight edges ranged from 2165 to 2715 lb. This range of experimental buckling loads was due principally to differences between distributions of initial transverse imperfections for various test panels, and, possibly, small initial stresses that accompany installation of a test panel in the testing device. Numerical computations indicate that the experimental buckling loads are associated with a limit point that correspond to equilibrium configurations remote from the equilibrium configuration corresponding to buckling of the straight edges. The computed buckling load (2500 lb) compared favorably with the experimental buckling (2715 lb) corresponding to the initial imperfections used to calculate the numerical buckling load.     

一种矿用锚杆(索)长度无损测量方法

针对现有锚杆(索)长度检测方法操作复杂、检测精度低等问题,提出了一种基于磁致伸缩导波技术的矿用锚杆(索)长度无损测量方法,介绍了锚杆(索)长度测量原理、测量系统的设计方案以及测量操作方法,在实验室环境下完成了系统速度标定以及混凝土结构中的锚杆长度测量。实验结果表明,该方法的最大测量误差为2.66%,平均测量误差为0.33%,满足现有煤矿锚杆(索)长度测量应用要求。     

Bond between prestressed steel and concrete—computer analysis using ADINA

A comprehensive test series was carried out to study the load carrying behaviour of pretensioned hollow-core slabs, which are not in accordance with the German building codes because of their geometry and the lack of conventional reinforcement. It was found that a number of problems concerning the end anchorage zones of the slab cannot be simply solved by experimental means with reasonable expense.

Therefore a finite element analysis using the ADINA program was carried out. The intent of this contribution is to show that the modular structure of the ADINA program is extremely suitable for modification by the user for the analysis of structures whose load carrying behaviour cannot be reproduced adequately by the original version of the program.

A contact element with a nonlinear bond-slip-relation is presented and added to the program, maintaining completely its modular structure.

Special attention is paid to the derivation of the bond stiffness, which is of special influence on the numerical results. The validity of the computer analysis is judged by comparing test measurements of bending tests and analytical results.

Although this study is restricted to a 2D representation of the real three-dimensional reinforced concrete structure with a varying cross-section (and is intended to be a preliminary study), the results are excellent and can be used to draw conclusions for the design problem.     

一种面向目标识别的分布式临时簇构建算法

利用无线传感器网络进行目标识别可以提供更可靠的识别结果,为了满足网络的无中心、自组织、自恢复、低能耗等特性,采用了一种分布式的方法来进行目标识别;其基本方式是从感知到目标出现的节点中选择合适的节点,由它构建临时的簇,由临时簇中的节点进行目标识别;提出了一种分布式的临时簇构建算法(DTCA),DTCA通过节点之间的信息交互动态产生簇头并且构建簇,通过分析可知,DTCA算法的通信复杂度为O(N);实验表明,DTCA算法能够有效平衡能耗,延长系统的生命期。     

动态海缆机械性能有限元分析

为探究动态海缆在剧烈交变环境载荷下的疲劳寿命,基于环境载荷响应,开展动态海缆系统的整体分析。基于有限元方法,研究海水中悬浮的动态海缆在服役过程中承受的极端载荷,分析破断力和侧压力工况,提取关键部位的应力、应变分布并进行校核。研究结果可为动态海缆材料选型、结构优化以及疲劳分析和测试提供理论依据。     

基于分布式光纤技术的煤矿巷道顶板监测系统

当前巷道顶板变形监测方式为基于井下工业环网的在线实时监测,采用电子式和光纤光栅式的位移传感器并以无线方式连接,存在有较多监测盲点、误差较大、依靠连续供电等问题。针对上述问题,设计了一种基于分布式光纤技术的煤矿巷道顶板监测系统。该系统以布里渊光时域反射计(BOTDR)作为数据采集和分析的核心监测工具,采用5 mm钢绞线光纤作为感测光纤,以锚杆、锚索为固定点布设光缆,通过顶板光纤的应变变化来监测顶板变形状况,实现了对煤矿巷道顶板的实时在线分布式监测。现场应用结果表明,光纤应变变化能够实时准确地反映顶板变形情况,基于光纤应变的顶板监测结果与顶板离层仪监测结果、十字法观测结果一致。用光纤应变表征顶板变形程度消除了人为因素和断电等影响,保证了监测结果的客观性,这种长距离、耐腐蚀、抗干扰、无需供电的分布式光纤应变监测方式为煤矿提供了一种全新的巷道监测手段。     

Inelastic dynamic response of reinforced concrete infilled frames

An inelastic finite element model to simulate the behaviour of reinforced concrete frames infilled with masonry panels subjected to static load and earthquake excitation has been presented. Under the loads, the mortar may crack causing sliding and separation at the interface between the frame and the infill. Further, the infill may get cracked and/or crushed which changes its structural behaviour and may render the infill ineffective, leaving the bare frame to take all the load which may lead to the failure of the framing system itself. In this study, a mathematical model to incorporate this behaviour has been presented.     

Dynamic response analysis of nonlinear structures using step-by-step integration techniques

The paper describes step-by-step integration techniques to predict the dynamic response of nonlinear tension structures. The analytical procedure and the mathematical formulation of selected potential algorithms used for the solution of the equation of motion are presented. Methods of introducing the wind and earthquake loading into the step-by-step method are described. The response analysis of vibrations of a flat pretensioned cable net excited by simple harmonic loading and by a falling load are also presented, followed by a numerical example of an experimental portal frame solved by the linear acceleration method.     

飞机作动器连杆光纤光栅载荷校准方法

结构状态评估技术可为飞机活动面载荷试飞提供监测手段,以验证载荷设计方法和分析数据是否有效,并可为活动面安全性确认和结构设计优化提供最直接的数据参考。传统的应变片测量方法在低温环境下的测试不稳定性可能会导致采集数据异常,使飞行载荷实时监测及精度保证成为型号试飞的一个难题。本文利用光纤传感器低温测试性能较稳定特性,结合理论分析、有限元仿真计算及试验验证,建立连杆结构在拉、压载荷工况下的应变-载荷关系模型,并提出一种基于光纤光栅传感器的作动器连杆应变-载荷校准方法。同时,针对作动器连杆结构典型承载形式与载荷辨识工况,给出光纤光栅传感器优化布局方法。研究结果表明,本文中建立的基于光纤光栅传感器的应变-载荷反演方法有效,能够满足民用飞机典型作动器连杆结构应变监测及载荷反演需求。