Ultimate compressive strength design methods of aluminum welded stiffened panel structures for aerospace, marine and land-based applications: A benchmark study

The high strength-to-weight advantage of aluminum alloys has made it the material of choice for building airplanes and sometimes for the construction of land-based structures. For marine applications, the use of high-strength, weldable and corrosion resistant aluminum alloys have made it the material of choice for weight sensitive applications such as fast ferries, military patrol craft, luxury yachts and to lighten the top-sides of offshore structures and cruise ships. And while, over the last two decades, the ultimate limit state (ULS) design approach has been widely adopted in the design of aerospace and land-based (steel) structures, it is just recently being considered as a basis for the structural design and strength assessment of ships and offshore structures. Practical ULS methods or design codes are available in the aerospace and civil engineering industries, but they are just now being developed for use by the marine industry. The present paper compares some useful ULS methods adopted for the design of aerospace, marine and land-based aluminum structures. A common practice for aerospace, marine and civil engineering welded stiffened panel applications is discussed.     

Optimum design of steel frames using Cuckoo Search algorithm with Lévy flights

In the last two decades, many researchers have implemented various kinds of meta‐heuristic algorithms in order to overcome the complex nature of the optimum design of structures. In this paper, the optimum design of two‐dimensional steel frames for discrete variables based on the Cuckoo Search (CS) algorithm is developed. The CS is one of the recently developed population‐based algorithms inspired by the behavior of some cuckoo species in combination with the Lévy flight behavior of some birds and insects. The design algorithm is supposed to obtain minimum weight frame through suitable selection of sections from a standard set of steel sections such as the American Institute of Steel Construction (AISC) wide‐flange (W) shapes. Strength constraints of AISC load and resistance factor design specification and displacement constraints are imposed on frames. In order to demonstrate the effectiveness and robustness of the CS, low‐weight design and performance comparisons are made between the CS and other algorithms for some benchmark frames. Copyright © 2011 John Wiley & Sons, Ltd.     

Empirical formulation for estimating the fundamental frequency of historical stone mosques with masonry domes

Historical stone mosques with masonry dome are complex structures due to their different structural elements, material properties, boundary conditions, connections, etc. It is very difficult to develop the numerical models representing the real behaviour of these structures. Therefore, their numerical models should be checked with ambient vibration tests for the reliable safety evaluations before the restoration applications. However, it is known that the ambient vibration tests of historical mosques are very difficult and costly and need permissions from the owners and relevant government agencies. The paper aims to develop an empirical formulation for estimating the fundamental frequency of historical stone mosques with masonry dome to check the initial finite element models. Nine stone mosques with masonry dome in different dimensions in the eastern Black Sea Region of Turkey were selected as examples for this purpose. By performing ambient vibration tests of the selected mosques, experimental natural frequencies, mode shapes, and damping ratios have been determined and evaluated together. An empirical formulation for the fundamental frequency and coefficients for the second and third frequencies of stone mosques with masonry dome based on vibration data are obtained by using the statistical regression analysis and verified with the control data. The comparative results confirm that the proposed formulation has a reliable predictive performance.     

Minimum‐weight design of high‐rise structures subjected to flexural vibration at a desired natural frequency

In this paper, a parametric approach for design of high‐rise structures subjected to flexural vibration is proposed. The optimization problem is formed based on a preselected value for the fundamental natural frequency, and it is formulated for minimum structural weight. In a two‐step approach, first, an alternative formulation aimed at maximizing structural stiffness that in turn maximizes structure's fundamental frequency is introduced. Then, optimized results are used in obtaining a closed‐form solution of the actual problem. Because the resulting equations are rather complicated, approximate forms are developed in order to simplify the design process. In all relations, contributions from shear forces to lateral displacement are assumed to be negligible; hence, bending resistance is the only design variable, and its optimal value is computable using simple relations. Two numerical examples are presented in order to illustrate the efficiency of this method in practice.     

AFRP筋体外预应力混凝土梁的自振频率分析

分析了考虑应力增量时AFRP筋体外预应力梁的自振频率计算方法，并根据自编的MathCAD程序，对AFRP筋与高强钢丝分别作为体外筋材时梁的自振频率理论计算值进行了对比。     

四边支承矩形薄板自振频率计算

从弹性薄板的基本振动微分方程出发,利用可以满足各边边界条件的振型函数,根据能量法推导出四边支承六种不同边界条件的矩形薄板的最低自振频率计算公式,为楼板结构的自振频率计算和舒适性设计提供了指导。     

通用频率指纹库在固接梁损伤定位中的应用

从理论上推导了基于梁的自振频率数据进行损伤定位的基本原理，得出了一些梁的基于频率数据定义的动力参数（任意两阶频率变化比）仅是损伤位置的函数，而与损伤的程度无关的结论。随后在理论推导的基础上，重点研究了利用任意两阶频率变化比作为损伤定位的参数，建立了两端固接梁损伤定位通用频率指纹库，建立的过程中还考虑了损伤程度对指纹库的影响。最后通过两个数值算例，验证了该指纹库用于固接梁损伤定位的有效性和通用性，从而为工程中任意固接梁的损伤定位找到了一个标尺。     

半刚性节点单层球面网壳结构的抗震性能及其设计方法

由单根或多根螺栓现场拼装而成的半刚性节点单层球面网壳逐渐受到工程设计人员及一些学者的关注。这种节点具有一定的弯曲刚度和扭转刚度,是介于刚接和铰接节点之间的一种半刚性节点。利用文献中的弯矩-转角曲线对凯威特型半刚性螺栓球节点单层球面网壳的抗震性能进行了较为系统的分析,包括其自振特性及杆件地震内力系数随矢跨比、跨度、屋面质量、杆件截面、地震动、节点弯曲刚度等参数的变化规律;通过大规模参数分析,采用基于包络响应的地震内力系数统计方法,给出凯威特型半刚性节点单层球面网壳考虑杆件弯矩影响的地震内力系数取值;提出基于地震内力调整系数的凯威特型半刚性节点单层球面网壳的实用抗震设计方法,可为工程设计提供参考。