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RISS 인기검색어
- 검색키워드
- 저자 : Antoine Gergess (검색결과 4 건)
- 무료
- 기관 내 무료
- 유료
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Antoine N. Gergess,Rajan Sen 국제구조공학회 2014 Steel and Composite Structures, An International J Vol.17 No.6
Point bending is commonly used for cambering and curving steel girders to large radii. In this system, a hydraulic ram or press is used to apply concentrated loads at selected points to obtain the required vertical (cambering) or horizontal (curving) curved profile from induced permanent deformations. This paper derives closed form solutions that relate loads to permanent deformations for horizontally curving wide flange steel beams based on their post-yield response. These solutions are presented in a parametric form to identify the relationship between key variables and their impact on the accuracy of the curving operation. It is shown that point bending could yield parabolic curved profiles that are within 1% of a desired circular curve if the span length to radius of curvature ratio (L / R) is less than 1.5 and the point loads are spaced at one third the beam length. Safe limits are then established on loads, strains and curvatures to avoid damaging the steel section. This leads to optimization of the point bending operation for inducing a circular profile in wide flange steel beams of any size.
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Numerical analysis of heat-curved I-girders
Antoine Gergess,Rajan Sen 한국CDE학회 2017 Journal of computational design and engineering Vol.4 No.4
Heat curving is a practical and economical process used by steel fabricators for curving structural steel. In this method, the flange edges of a fabricated straight girder are asymmetrically heated to induce residual curvature on cooling. Available analytical methods for predicting the resulting residual stress, strain and curvature are complex and iterative because of the need to account for material and geometric nonlinearity. This paper presents a single-step, non-iterative, numerical procedure for determining the effects of heat-curving on residual stress and strain based on a previously developed simplified analysis. Thermal equilibrium equations for idealized heating profiles are first recast in a general parametric form and then solved numerically for standard heating width and temperature using modern technical computing. The resulting solutions are expressed as polynomial functions to allow the solution space for the residual curvature to be graphically represented. Curvature predictions using this simplified approach are shown to be within 11% of measured values and within 5% of values obtained using more rigorous numerical methods.
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Finite Element Modeling of Cold Curved Steel Rolled Beams Under Service Loads
Najib G. Saliba,Dola F. Nehmeh,Antoine H. Helal,Antoine N. Gergess 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.2
Cold bending is an effi cient method recommended by steel fabricators for curving structural steel beams. It relies solely on mechanical forces to curve the beam into the required shapes without heating. While extensive research has been conducted on fabrication processes, data on the structural performance of cold bent steel girders in service is scarce which limits its use specifi cally in bridge structure applications. This paper investigates the eff ects of cold bending on the service load capacity of steel rolled shapes. An experimental and analytical program was developed for this purpose. The experimental program consists of cold curving a rolled IPE section about its weak axis and then bending it about its strong axis by applying vertical static loads that simulate service loads. Numerically, fi nite element analysis was conducted and validated based on experimental results. A parametric study was then conducted to identify structural parameters that can adversely aff ect the resistance capacity of cold bent steel rolled beams. Results show that the reduction in resistance capacity of the cold curved steel beam depends on the confi guration of the applied loads and that its structural behavior can be improved by adding stiff eners, bearing plates, modifying the end boundary conditions and introducing load eccentricities. Recommendations are fi nally made to improve the effi ciency of cold curved steel beams in service.
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Finite element modeling of rolled steel shapes subjected to weak axis bending
Najib G. Saliba,Issam Tawk,Antoine N. Gergess 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.29 No.2
Point bending is often used for cambering and curving structural steel girders. An analytical solution, applicable in the elasto-plastic range only, that relates applied loads to the desired curve was recently developed for inducing horizontal curves using four-point bending. This solution does not account for initial residual stresses and geometric imperfections built-in hotrolled sections. This paper presents results from a full-scale test on a hot-rolled steel section curved using four-point bending. In parallel, a numerical analysis, accounting for both initial geometric imperfections and initial residual stresses, was carried out. The models were validated against the experimental results and a good agreement for lateral offset and for strain in the elastoplastic and post-plastic ranges was achieved. The results show that the effect of initial residual stresses on deformation and strain is minimal. Finally, residual stresses due to cold bending calculated from the numerical analysis were assessed and a revised stress value for the service load design of the curved girder is proposed.
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