Behavior of Pultruded Fiber-Reinforced Polymer Beams Subjected to Concentrated Loads in the Plane of the Web

Results of the behavior of pultruded fiber-reinforced polymer (FRP) I-shaped beams subjected to concentrated loads in the plane of the web are presented. Twenty beams with nominal depths from 152.4 to 304.8?mm were tested in three-point bending with a span-to-depth ratio of four. Load was applied to the top flange directly above the web—12 without bearing plates and 8 with bearing plates of varying width and thickness. All test specimens failed with a wedgelike shear failure at the upper web-flange junction. Finite-element results support experimental findings from strain gauge and digital image correlation data. Bearing plates increased beam capacity by 35% or more as a function of bearing plate width and thickness. Bearing plates increased average shear stress in the web at failure from 17.4 to 27.2?MPa—below the accepted value of in-plane shear strength (69?MPa). A design equation is presented, and predicted capacities are compared with experimental results. The average value of experimental capacity to predicted capacity is 1.12 with a standard deviation of 0.11 and coefficient of variation (COV) of 0.10 for sections up to 304.8?mm deep.     

Contribution to Shear Wrinkling of GFRP Webs in Cell-Core Sandwiches

Glass-fiber-reinforced polymer (GFRP) cell-core sandwiches are composed of outer GFRP face sheets, a foam core, and a grid of GFRP webs integrated into the core to reinforce the shear load capacity. One of the critical failure modes of cell-core sandwich structures is shear wrinkling, a local buckling failure in the sandwich webs because of shear loading. The shear wrinkling behavior of GFRP laminates with different laminate sequences, stabilized by a polyurethane foam core, was experimentally and numerically investigated. Shear wrinkling was simulated by a biaxial compression–tension setup. The results show that an increasing transverse tension load significantly decreases the wrinkling load. The decreasing effect of tension is explained by the lateral contraction because of Poisson’s effect, which causes an increase in the initial imperfections and subsequent accelerated bending.     

Elsevier和ISI网页浏览器

信息是当今社会最重要的资源之一,如何开发、利用在Internet网上的信息资源,是科学研究工作者应该解决的基本问题之一;本文简单介绍了在Internet网上的两个网页浏览器：Elsevier和ISI网页浏览器。     

Local buckling and slenderness limits for steel webs under combined bending, compression and shear at elevated temperatures

At elevated temperatures induced by fire loading, the I-section beam and column elements in a steel framed building experience combinations of axial, bending and shearing actions that may precipitate local buckling of the steel element. Under this loading regime, the Young's modulus, shear modulus and uniaxial yield strength may vary through the section depth because of the temperature gradient, and as a result predicting the local buckling capacity and the critical geometrical slenderness for coincident elastic local buckling and yielding are not straightforward. This paper presents an analysis of the elastic local buckling of the web of an I-section beam, by modifying a spline finite strip method of local buckling analysis to include the variation of material properties through the web. Necessarily, the method must also include the variation of mechanical strains through the web depth, in order that the limiting depth to thickness ratio that delineates yielding and elastic buckling (and hence the cross-section classification) can be prescribed. Under the combined loading, it is shown how the elastic local buckling coefficient and the web slenderness limit that classifies a non-compact section are dependent on the thermal gradient, the depth of the compression zone in the representation of the mechanical strain, and on the values of the shear strain. Graphical results are presented for the elastic local buckling coefficients as a function of the temperature and of the temperature gradient in a web with idealised edge restraint conditions. Since the local buckling response is crucial in establishing the formation hinges in flexural elements in the initial stages of thermal loading prior to the subsequent development of catenary action, the results are valuable for undertaking a rational fire engineering design of the steel elements exposed to a compartment fire, and they lend themselves to a codified approach for the structural behaviour.     

A rational design model for transverse web stiffeners

Existing design methods for web stiffeners differ widely in concept and in the stiffener size which results. An investigation has been conducted to provide a rational, usable and validated design method for transverse stiffeners. The proposed design method takes account of the axial compression in stiffeners caused by tension field action and external forces, the transverse forces on the stiffeners required to enforce effective division of the web plate, and the tendency for the stiffened plate to buckle overall. Design criteria are established to ensure that the resulting stiffeners do not yield before plate failure, and that the plating is effectively divided into panels. The transverse stiffener dimensions required by the proposed design model have been validated against finite element results for plates subjected to pure shear, and to combined shear and direct in-plane loading. Finally, the stiffener sizes are compared with those required by the existing methods.     

Number of Singularities of a Generic Web on the Complex Projective Plane

Given a generic d-web W_d of degree n in ², we associate with it a triple (S_Wd, |S_Wd, F_Wd), where S_Wd is a surface in T*², the projective cotangent bundle of ², |S_Wd is the restriction of the natural projection T*^{2 2} to S_Wd and F_Wd is a foliation on S_Wd given by a special meromorphic 1-form. The main objective of this article is to calculate the total number of singularities and the sum of the indices of Baum–Bott for the foliation F_Wd in terms of d and n. These results are compared with the case d = 1 (foliation in ²). We also calculate the total number of nodes and cusps of the projection |S_Wd in terms of d and n.2000 Mathematics Subject Classification. Primary: 37F75, Secondary: 34M45.     

Behavior of Corrugated Web I-Girders under In-Plane Loads

A theoretical formulation of the linear elastic in-plane and torsional behavior of corrugated web I-girders under in-plane loads is presented. A typical corrugated web steel I-girder consists of two steel flanges welded to a corrugated steel web. Under a set of simplifying assumptions, the equilibrium of an infinitesimal length of a corrugated web I-girder is studied, and the cross-sectional stresses and stress resultants due to primary bending moment and shear are deduced. The analysis shows that a corrugated web I-girder will twist out-of-plane simultaneously as it deflects in-plane under the action of in-plane loads. In the paper, the in-plane bending behavior is analyzed using conventional beam theory, whereas the out-of-plane torsional behavior is analyzed as a flange transverse bending problem. The results for a simply supported span subjected to a uniformly distributed load are presented. Finally, finite element analysis results are presented and compared to the theoretical results for validation.     

横向腹板加劲肋的合理设计模型

腹板加劲肋的现行设计方法在概念和加劲肋尺寸上有很大差异。为了给横向加劲肋提出一个合理、适用的有效设计方法，考虑了加劲肋上由拉力和外力作用产生的轴向压力，加劲肋上有效分隔腹板所必需的横向力和加劲板的整体屈曲趋势。为保证加劲肋的屈服不会在板屈服前发生，建立了相应的设计标准。     

基于B/S模式的社区电子政务系统设计

通过对上海市某街道社区内部办公业务流程的分析研究，设计了一个基于B／S结构的电子政务系统。论述了在当前信息发展状况下社区内部系统开发的背景、目标及具体的系统设计，并阐述了在当今“三网通”技术下的电子政务普及方式。