Investigation of Effect of Steps in Inelastic-Buckling Strength of I-Beams Subjected to Two Concentrated Loads Using Experimental Tests, Finite Element Analysis and Proposed Equations

Surla, Albert S,박종섭 한국방재학회 2015 한국방재학회논문집 Vol.15 No.5

This paper is focused on the analysis of results obtained in the experimental tests on singly symmetric doubly stepped I-beams. Specifically, two point load tests were conducted on the beams having non-compact flange sections. The tests were conducted to investigate the inelastic buckling behavior of the stepped beams. For every specimen, the main parameters are the unbraced length and the stepped beam parameters. Four short span specimens were tested and the monosymmetric ratio of all the beams was fixed at 0.7. The unbraced lengths were 3 meters and 4 meters. Furthermore, the buckling capacity of the stepped beams were investigated by using finite element analyses. The results were also compared to equations proposed by different researchers which determine the buckling capacity of stepped beams. Also, values recommended by various codes of practice on prismatic beams were used as a reference to determine the accuracy of the finite element models. Results showed that the values yielded by FEA had a good correlation with the values obtained from the tests. Meanwhile, the equations used to determine the strengths of the stepped beams yielded over conservative and unconservative results. The significant effect of steps in increasing the capacity of the beams was also observed.

Investigation of Lateral-Torsional Buckling Strength Trends in Monosymmetric Stepped I-Beams Subjected to Several Loading Conditions

Surla, Albert S,박종섭 한국방재학회 2014 한국방재학회논문집 Vol.14 No.4

It has been proven in recent studies that for monosymmetric I-section beams, in considering bending moment diagrams caused by anycombination of applied end moments and transverse loads acting at the shear centre, the lowest critical lateral torsional bucklingmoment does not necessarily correspond to uniform bending. This finding is different from the intuitive expectation that researchershave that for lateral torsional buckling of thin walled beams, the lowest critical lateral torsional buckling moment always correspondsto a uniform bending moment diagram. To determine the applicability of the findings stated, considering stepped beams, this studywill be focusing on the comparison of the lateral torsional buckling strength trends in monosymmetric I-beams having doubly steppedand compact cross section. Several loading conditions will be applied to see the effect of different moment diagrams having differentinflection points on the lateral torsional buckling strength of stepped beams. The study will be made using the finite element program,ABAQUS. The study will investigate stepped beams having monosymmetric ratios ranging from 0.5 to 0.9. These ratios correspond tovarying bottom flange width while keeping the top flange width unchanged. Unbraced length to height ratio of the beam to be analyzedis 20. Finally, the findings for this study will be shown using illustrative figures and conclusions will be made.

A Study on Inelastic Lateral Torsional Buckling of Singly Symmetric and Singly Stepped I-beams Subjected to Basic Loading Condition

Albert Surla,Kathleen Mae Gelera,Jong Sup Park,Gyu Sei Yi 한국복합신소재구조학회 2013 복합신소재구조학회 학술발표회 Vol.2013 No.04

This study is all about the presentation of the results of the analyses made to determine the inelastic lateral torsional buckling strength of singly symmetric singly stepped I-beam with constant depth subjected to basic loading condition. A finite element program ABAQUS and a regression program MINITAB are used to analyze the simply supported singly symmetric singly stepped I-beams having singly symmetric ratio, ρ, of 0.1 to 0.9 and a Lb/h ratio of 4.5. Using the results of the analyses made, a design equation is suggested that can easily calculate the stepped beam correction factor Cist which then can be used to determine the inelastic lateral torsional buckling strength of singly symmetric singly stepped I-beams subjected to pure bending moment. Then, the results from the equation proposed are compared with the results obtained from the finite element analysis. The results obtained show acceptable results for singly stepped beams having a ρ of 0.3 to 0.9 and a very conservative result for a ρ of 0.1.

A Study on the Effects of Load Height on the Inelastic Lateral Torsional Buckling Strength of Doubly Stepped I-Beams Using Finite Element Analysis

Albert Surla,Jong Sup Park 한국방재학회 2015 한국방재학회 학술발표대회논문집 Vol.14 No.-

This study focuses on the effects of load height on the inelastic lateral buckling of doubly stepped I-beams. The effects of having compact and non-compact flanges are also covered by this study. Two sections are analyzed: one having compact flanges and web while the other section has a compact web and non-compact flanges. The loadings are limited to those having an inflection point of zero. Also, the three main locations for the loads analyzed would be at the top of the flange, at the shear and at the bottom flange. The nonlinear analysis is done using the finite element program, ABAQUS. Also, to take into consideration the effect of inelastic buckling, residual stresses and geometric imperfections are applied to the models made. The results of the analysis would then determine if the location of the loads has significant effects on the buckling strength of the stepped beams. Also, the results are compared to the results of previous studies involving the effects of load-height on prismatic beams. The final results are tabulated and conclusions and new design methods are provided.

An Experimental Study on Inelastic Lateral-Torsional Buckling Strength of Singly Symmetric Stepped I-Beams Having Compact and Non-Compact Flange Sections

Albert Surla,Jong Sup Park 한국방재학회 2015 한국방재학회 학술발표대회논문집 Vol.14 No.-

Recently, as the level of market competition in the structural engineering field continues to rise, structural designers are finding other ways to make their designs stand out. One way of doing that is to make the designs more economical without sacrificing efficiency. As a result, the use of stepped beams and the studies involving it has become more common. Stepped beams are beams that have a sudden increase in cross section along its length. The change in cross section is made by increasing the width and/or the thickness of the flanges along a certain length while maintaining the dimensions of the web. Most of the studies involving lateral torsional buckling of stepped beams are focused on developing equations and studying the effects of symmetry. However, the studies involving actual test experiments are still very limited. Thus, this study has three main objectives. The first objective of this study is to give a brief historical overview on the series of studies involving the lateral torsional buckling capacity of stepped beams and give an idea on its current state of the art. The second objective is to determine if the intuitive expectation that the lowest critical moment always corresponds to uniform bending moment holds true for stepped beams. The degree of symmetry is varied and several loading conditions are observed. The third objective of this study is to determine the actual inelastic lateral torsional buckling capacity of doubly stepped singly symmetric I-beams having compact and non-compact flange sections subjected to two point loading condition and to use the results obtained to determine the applicability of previously proposed equations in predicting the buckling strength of stepped beams. The results are obtained by conducting actual destructive tests on doubly stepped I-beams using a universal testing machine and running simulation tests using the finite element program, ABAQUS. The main factors that are considered for the experimental and finite element analysis are the degree of beam symmetry, the loading condition, the supports, the stepped beam factors and the unsupported length. The degree of symmetry of all the stepped beams analyzed is fixed at 0.7. The unsupported lengths of the beams analyzed are 3 meters and 4 meters. The results obtained from the analysis are compared with the results from design specifications to determine the effects of steps and from proposed design equations to determine the equations’ applicability and safety. Finally, the results revealed that the stepped beams did have an increase in lateral torsional buckling capacity in comparison with the prismatic beams and that the proposed equations are suitable to be used in predicting the strength of stepped beams having compact flanges under the observed loading condition. However, for beams having non-compact flanges, the previously proposed equations produced over conservative results. Further study can also be made on stepped beams with varying degree of symmetries, loading conditions, boundary conditions and stepped beam parameters.

A Comparison Study on Lateral Torsional Buckling of Monosymmetric Stepped I-beams Using Finite Element Method, AISC, AS4100 and EC3

Albert S. Surla,Kang, Sung Yong(강성용),Jerome V. San Juan,Park, Jong Sup(박종섭) 대한토목학회 2013 대한토목학회 학술대회 Vol.2013 No.10

Experimental and Numerical Investigation on LTB Strengths of Monosymmetric Compact I-Beams with Thickness-Stepped-Flanges

Albert S. Surla,박종섭 한국강구조학회 2015 International Journal of Steel Structures Vol.15 No.4

This paper investigates the inelastic lateral torsional buckling, LTB, of doubly stepped singly symmetric compact I-beams under two concentrated loads. The results are obtained by conducting actual destructive tests on the beams using a testing machine and running simulation tests using the finite element program, ABAQUS. The main factors that are considered for the analyses are the degree of symmetry, the loading and supports, the stepped beam factors and the length. For this study, the beams have simple supports. The monosymmetric ratio of all the beams analyzed is fixed at 0.7. The unbraced lengths of the beams are 3 meters and 4 meters. The results obtained from ABAQUS are compared with the results from design specifications to determine the effects of steps and from proposed design equations to determine the equations’ applicability and safety. The results revealed that the stepped beams did have an increase in capacity in comparison with the prismatic beams and that the proposed equations are suitable to be used in predicting the strength of stepped beams under the observed loading condition.

A Parametric Study on the Elastic Lateral-Torsional-Vertical Buckling Capacity of Horizontally Curved Twin I-Girder Systems Considering the Effect of Curvature and Girder Spacing

Lay Allen Nicolas,Albert Surla,Jong Sup Park,Kee Se Lee,Young Jong Kang 한국방재학회 2015 한국방재학회 학술발표대회논문집 Vol.14 No.-

This parametric study investigates the effect of significant parameters on the elastic global lateral torsional buckling capacity of horizontally curved twin I-girder systems. Included are the effect of curvature and the effect of girder spacing. Twin I-girder systems analyzed in this study are those which are interconnected by intermediate cross frames and are subjected to uniform moment. The finite element analysis software, ABAQUS, is used to model the horizontally curved twin I-girder system and conduct the buckling analysis. To see the significant effect of curvature and girder spacing, the results from the finite element analysis of horizontally curved twin I-girder systems are compared to the results of a closed form solution for straight twin I-girder systems. The findings of this parametric study will be shown using illustrative figures and tabulated data and conclusions are made.

Investigation of Lateral-Torsional Buckling Strength Trends in Monosymmetric Stepped I-Beams Subjected to Several Loading Conditions

Park, Jong Sup,Surla, Albert,SanJuan, Jerome 한국방재학회 2014 한국방재학회 학술발표대회논문집 Vol.2014 No.-

It has been proven in recent studies that for monosymmetric I-section beams, in considering bending moment diagrams caused by any combination of applied end moments and transverse loads acting at the shear centre, the lowest critical lateral torsional buckling moment does not necessarily correspond to uniform bending. This finding is different from the intuitive expectation that researchers have that for lateral torsional buckling of thin walled beams, the lowest critical lateral torsional buckling moment always corresponds to a uniform bending moment diagram. To determine the applicability of the findings stated, considering stepped beams, this study will be focusing on the comparison of the lateral torsional buckling strength trends in monosymmetric I-beams having doubly stepped and compact cross section. Several loading conditions will be applied to see the effect of different moment diagrams having different inflection points on the lateral torsional buckling strength of stepped beams. The study will be made using the finite element program, ABAQUS. The study will investigate stepped beams having monosymmetric ratios ranging from 0.5 to 0.9. These ratios correspond to varying bottom flange width while keeping the top flange width unchanged. Both elastic and inelastic analysis will be carried out for this study. Finally, the findings for this study will be shown using illustrative figures and conclusions will be made.

State of the Art in Lateral Torsional Buckling Strength of Horizontally Curved I-Girder Bridge

Park, Jong Sup,Surla, Albert,Kang, Young Jong 한국방재학회 2014 한국방재학회 학술발표대회논문집 Vol.2014 No.-

Several studies concerning the lateral torsional buckling of horizontally curved I-beams have been made by different researchers. However, these studies are mostly limited to linear analysis and involving only single girders having single span. Nonlinear analysis of horizontally curved I-beams have been very limited or almost none. The aims of this study are to give a brief summary of the studies that have been made involving several factors concerning the lateral torsional buckling capacity of horizontally curved I-beams and to show several analyses that focused on determining the behavior of the horizontally curved I-beams that experience lateral torsional buckling failure. Subjects discussed in this study include: (1) different design provisions involving LTB of curved I-beams; (2) different equations that can be used concerning LTB of curved I-beams; (3) effect of cross frames; (4) effects of cross frame spacing; and (5) analysis results and trends comparing LTB strength of curved I-beams to straight beams. The summary of these studies will be essential in determining the future studies that has to be made involving the lateral torsional buckling of horizontally curved I-girder bridges which should cover single girder and multi girder systems as well as single span and multi span curved bridge systems.