Proposed Design of a CFRP Flange-to-Flange Connection for Precast Prestressed Double Tee Systems

The current methods of connecting the flanges of precast double tee members, and their respective short comings in specific situations, are described. A new carbon fiber-reinforced polymer (CFRP) flange-to-flange connection is proposed to eliminate the problems associated with repair requirements for the current connections. Design expressions for the currently used mechanical anchorage and the proposed CFRP connection are presented. A comparative calculation for the two systems is given.     

大型法兰对接螺栓预紧力加载过程分析及处理措施

针对目前大型容器法兰接管对接时,螺栓预紧中,无法直接知道每个螺栓预紧力的大小,从而导致预紧力不能均匀的作用于密封垫,使密封垫产生不均匀变形,影响密封效果及产生泄漏。在工艺上,对法兰预紧螺栓的普遍要求是圆周逐步加载,使密封垫逐步均匀嵌入法兰密封槽,保证密封垫不发生局部变形,也就是法兰圆周均匀分布的许多螺栓加载过程要求变化梯度小、逐步均匀加载,最终各螺栓的预紧力达到规定值。设计一种在线监测仪器,此仪器能够在现场将每个螺栓的受力大小精确地反应出来,通过显示的数据来判断螺栓预紧顺序及加力大小。从而达到均匀逐步预紧,得到良好的密封效果。     

Cracking Mechanism and Simplified Design Method for Bottom Flange in Prestressed Concrete Box Girder Bridge

Serious cracking has occurred frequently in the bottom flange of box girders during construction in recent years. This paper aims at studying the cracking mechanism and countermeasures. The stress field in the bottom flange associated with the bottom continuity tendon is presented, and the propagation of cracks during tensioning is simulated by nonlinear analysis according to the actual construction sequence. A cracking mode, which is not easy to detect in field investigation, is illustrated through numerical and theoretical study. It is caused by the deficient shear strength of the bottom flange attributed to the void in tendon ducts. Based on numerical results and field investigation, four types of cracking in the bottom flange are proposed and discussed, and a simplified design method is recommended for control of cracking.     

Theoretical Evaluation of Flange Local Buckling for Horizontally Curved I-Girders

Curvature greatly complicates the behavior of horizontally curved steel plate girders used in bridge superstructures. The warping stress gradient across the width of I-girder flange plates reduces the vertical bending stress at which the flange plate buckles. The 2007 AASHTO Load and Resistance Factor Design Specifications eliminate the shortcomings of the 2003 AASHTO Guide Specifications for Horizontally Curved Bridges by unifying the flexural design of tangent and curved I-girder bridges. This paper evaluates flange local buckling resistance based upon theoretical and analytical models that consider the effect of stress gradient across the flange coupled with the influence of rotational resistance provided by the web. The developed equations are verified using the finite element method, and the potential impact is demonstrated using the design example presented in the Guide Specifications.     

GJF高压绝缘法兰有限元分析

高压绝缘法兰受力复杂，压力高已超过了现行规范设计范围。为了完成了ＧＪＦ高压绝缘法兰研究课题，采用了Ｓｕｐｅｒ ＳＡＰ有限单元分析系统，建立切合实际的力学模型，真实地模拟了高压绝缘法兰工况，计算结果令人满意，为评定高压绝缘法兰工作机理和优化设计打下了基础。     

Elastic buckling of I-beam flanges subjected to a linearly varying stress distribution

Lateral forces or torsion combined with major axis bending result in a stress gradient across the compression flanges of I-shaped flexural members. Sources that cause significant stress gradient include situations where unequal reactions come to opposite sides of a girder or beams that frame into one side of a girder, skewed bridge girder supports, wind loading on facia girders, curvature induced warping, etc. In this study, three sets of support conditions are considered for evaluating the elastic buckling capacity of flanges of I-shaped beams subjected to a stress gradient. This includes a Galerkin series solution that considers the full width of the flange plate with a variable rotational stiffness along the center of the plate. For a stress gradient leading to tension over part of the flange, equations for predicting the buckling capacity are developed using finite element analyses. Simplified equations are developed for I-shaped cross sections, and numerical examples are used to demonstrate the accuracy of the solution. A definition of the noncompact limit for flanges of I-shaped beams and girders subjected to stress gradient is presented.     

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.     

Degradation and collapse of square tubes under cyclic bending

This paper presents the results of an experimental investigation of the elastic–plastic degradation and collapse of steel tubes with square cross-section under cyclic pure bending in a curvature symmetric fashion. The results indicate that the structural performance of the tubes degrades due to the growth of periodic, transverse deflections in their flanges. The wavelength of these deflections is equal to the wavelength of the buckling mode of the tubes under monotonic pure bending. Persistent cycling induces localization of the amplitude of these deflections and leads to the formation of a kink in one of the flanges. This causes collapse of the tube.