Statistical evaluation of the lateral-torsional buckling resistance of steel I-beams, Part 1: Variability of the Eurocode 3 resistance model

The EN version of part 1-1 of EC3 introduces significant changes in the evaluation of the lateral-torsional buckling resistance of unrestrained beams, as well as alternative design procedures. Simultaneously, as a part of the preparation of the National Annexes of EC3 part 1-1 and the establishment of the corresponding NDP’s (Nationally Determined Parameters) it becomes necessary to define the partial safety coefficients for the bending resistance of beams when lateral-torsional buckling is a potential failure mode. In this paper the methodology for the resistance evaluation of beams subjected to instability is briefly described and the results are compared with FEM numerical results for the same elements. Subsequently, to assess the accuracy of the alternative design formulae, a statistical analysis of the results is performed on the basis of EN 1990-Annex D. A methodology is proposed for the evaluation of the design procedures allowing for the uncertainties in the resistance model. Results are presented for a wide set of beam geometries and loading cases and a proposal for the definition of the partial safety factor γ_rd is presented for the various methods, in line with the target failure probability of EN 1990.     

Eurocode 3, a basis for further development in joint design

This paper deals with the design aspects of joints based on Eurocode 3 and in particular on Part 1-8 “Design of Joints” and the possibilities for further developments. An overview is given of design philosophies named as “traditional” and “modern” design and the various design rules by which the structural behaviour in terms of stiffness, strength and deformation capacity can be predicted, with the aim of reducing the integral costs of steel structures.Emphasis is given on the need for reliable software tools to make the use of the Eurocode information easier for the designer. Possibilities for further development in joint design are discussed.     

Stability of curved panels under uniform axial compression

The use of curved panels for the construction of steel bridges becomes more and more popular. Their design is however made difficult by a lack of specifications, especially in European Standards. The present study aims thus at developing a method for predicting the ultimate strength of cylindrical unstiffened curved panels subjected to uniform axial compression. The methodology used in this study is based on the formal procedure recommended by Eurocode 3 for all types of stability verifications. A series of numerical simulations is first carried out to identify the fundamental characteristics of curved panels' elasto-plastic behaviour. Then on the basis of these numerical results, semi-empirical formulae for predicting the elastic buckling and ultimate strength are derived and illustrated on a practical example.     

Torsional and flexural torsional buckling — A study on laterally restrained I-sections

Torsional and torsional–flexural buckling of columns under axial compression–as defined in the Eurocode 3-1-1(2005)–may practically occur in axially compressed I-sections, which are laterally restrained so that weak axis flexural buckling is prevented and buckling is initiated by torsional deformation about the axis of lateral restraint. The present study is focussed on the development and representation of specific buckling curves for this type of buckling mode. This is based on numerical simulations taking into account material nonlinearities as well as geometric imperfections and residual stresses. The study not only illustrates the typical buckling curves for torsional buckling, but also the transition from torsional buckling to main axis flexural buckling when the column length increases. It also shows that the use of weak-axis buckling coefficients for torsional buckling–as given in the rules of Eurocode 3-1-1–may lead to rather conservative results in many cases.     

中欧钢结构规范螺栓连接承载力比较

根据欧洲钢结构设计规范的EN1993-1-8∶2005和GB50017-2003《钢结构设计规范》及JGJ82-2011《钢结构高强螺栓连接技术规程》对单个螺栓的设计承载力进行比较,包括抗剪连接、抗拉连接、剪拉连接和抗滑移连接的单栓承载力。比较分析可知:国标与欧标钢结构设计规范中的抗剪螺栓连接承载力二者基本一致;欧标的高强螺栓预拉力取值比中国的约高10%;抗拉螺栓连接与剪拉螺栓连接主要区别在于螺栓的抗拉承载力如何考虑撬力的影响。     

Schubversuche an simulierten Durchlaufbalken ohne Querkraftbewehrung

Shear test on simulated continuous beams without shear reinforcement This paper presents an experimental investigation on the shear behavior of continuous beams without shear reinforcement. A total of five rectangular 2‐span reinforced concrete beams under a uniform load were tested. In each beam the shear failure was arranged to take place in the main span, while the short span was highly reinforced by stirrups. The reaction at the end support of the short span was adjusted by different schemas during the test in order to obtain different M/V‐ratios at the main span. By this means significant differences in the failure location and thus the maximum shear force at failure between continuous beams have been observed. The experimental observations showed that the shear resistance is not a pure sectional property but it represents rather a structural character, which cannot be described by the model included in EC 2. The observations were interpreted using the proposed approach and generally could be well explained. Based on the knowledges obtained from this investigation and some other experimental programs, this paper suggests some remarks on the planning of test for continuous beams that conforms to the behavior of concrete structures in the practice.