ahmed abdelrahman , ph.d .
Lecturer - Assistant Professor at Structural engineering department, Faculty of Engineering, Mansoura University
Structural engineering department, Faculty of Engineering, Mansoura University
Al Manşūrah, Ad Daqahliyah, Egypt
Lecturer - Assistant Professor
Doctor of Philosophy - PhD
Structural Engineering 
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The Hong Kong Polytechnic University
https://eg.linkedin.com/school/hong-kong-polytechnic-university/
Non-degree, Visiting Scholar
Thin-walled structures group - Professor Benjamin Schafer
Structural Engineering
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Johns Hopkins Whiting School of Engineering
https://eg.linkedin.com/school/johns-hopkins-whiting-school-of-engineering/
Master of Science - MS
Structural Engineering
Faculty of Engineering, Mansoura University
Bachelor's degree
Civil Engineering
Faculty of Engineering, Mansoura University
The main objective of this paper is to validate a finite-element (FE) modeling protocol to simulate thin-walled members for static and dynamic analyses. Arbitrary-shaped cross-sections, including open, closed, and multicellular sections can be efficiently modeled for further advanced study. The framework is thoroughly validated and verified using the existing analytical and closed-form solutions, as well as experimental results available in literature. This work is motivated by the higher accuracy of the shell FE-based modeling to capture the local and global complex behaviors of thin-walled members with asymmetric sections. Higher computational expenses, however, are required for such sophisticated shell finite element models (SFEM). Accordingly, a framework hosted in MATLAB and implementing the python scripting technique in ABAQUS, is developed, which includes eigen buckling, static nonlinear, modal frequency and dynamic time-history analyses. For a more modeling convenience, various parameters are incorporated such as imperfections, residual stresses, material definitions, element choice, meshing control, and boundary conditions. Several examples are provided to illustrate the application of the proposed framework, and to prove the robustness and accuracy of the generated FE models. This paper concludes with the efficiency of implementing SFEMs for simulating thin-walled members; thereby, establishing a more accurate and advanced structural analysis.
Simulation of Thin-Walled Members with Arbitrary-Shaped Cross-Sections for Static and Dynamic Analyses
International Journal of Structural Stability and Dynamics / World Scientific
https://www.worldscientific.com/doi/abs/10.1142/S021945542050128X#
Latticed structures are commonly used in transmission towers due to lightweight, fast fabrication, and easy installation, but they generally experience more complicated structural behaviors. The full-scale tests on transmission towers have revealed large discrepancies between the numerical simulation and experimental results because the significant joint slip effects have not well considered in the former. The existing joint slip models were so simple that many key parameters had not been taken into account. Thus, a comprehensive joint slip model is proposed in this article for better prediction and design of tower structures. First, a full-detailed finite element model based on ABAQUS incorporating more realistic parameters for a typical joint is developed and calibrated by the experimental data from the literature. Furthermore, the proposed FE model is used for parametric study of joint behaviors with considerations of bolt pretension, friction at contact face, angle sizes and plate thickness, steel and bolt grades, number of bolts, and hole tolerance. Finally, an advanced joint slip model is provided for further incorporation in the second-order direct analysis of transmission towers. This work is limited in the literature and will significantly improve safety and enhance the cost-efficiency of tower design. The proposed model shows high accuracy and can be simply determined by joint details in line with the component method specified in Eurocode 3-1-8.
Advanced joint slip model for single-angle bolted connections considering various effects
Advances in Structural Engineering
https://doi.org/10.1177/1369433220906226
Single angle members are widely used in lightweight transmission line towers. However, angle members may experience complex behaviors such as flexural, flexural-torsional or lateral-torsional buckling due to unsymmetrical section and eccentric loading. The current design practice is generally based on the effective length method, in which semi-empirical formulas should be used to account for the actual end conditions and member initial imperfections. In contrast, advanced beam-column elements or finite shell elements should be used when using second-order direct analysis method without the need of effective length assumption. Direct model of the failure modes of angle members is still a challenging task, especially for unequal angle members. This paper proposes an effective stress-strain relationship representing the typical failure modes and initial imperfections, which has been calibrated by extensive finite element analysis and experimental results, for the direct analysis such that the steel structures made of angle sections can be safely designed avoiding the use of effective length method. The proposed method is so simple that it can be incorporated into any conventional beam-column elements to implement the direct analysis of angle structures. The examples show that the proposed method is on the conservative side and therefore it can be employed in the practical design of angle structures.
EFFECTIVE STRESS-STRAIN RELATIONSHIP FOR ANALYSIS AND DESIGN OF SINGLE ANGLE MEMBERS
9th International Conference on Steel and Aluminium Structures (ICSAS19) Bradford, UK, 3-5, July 2019
ABSTRACT
Single angle members are widely used in transmission line towers due to light weight and easy installation. However, angle members may experience complex behaviors such as flexural, flexural-torsional or lateral-torsional buckling due to unsymmetrical section and eccentric loading. The current design practice is generally based on the effective length method, in which semi-empirical formulas should be used to account for the actual end conditions and member initial imperfections. In contrast, advanced beam-column elements or finite shell elements should be used when using second-order direct analysis method without the need of effective length assumption. Direct model of the failure modes (i.e. local and global failure modes) of angle members is still a challenging task. This paper firstly investigates the sensitivity of the flexural-torsional buckling of eccentrically loaded members compared to the assumed flexural buckling mode about the principal minor axis which is implemented in most of available beam-column elements. Moreover, an effective stress-strain relationship representing the typical failure modes and initial imperfections, which has been calibrated by extensive finite element analysis and experimental results, is developed for the direct analysis of steel structures made of angle sections without use of the effective length method. The proposed method is so simple that it can be incorporated into any conventional beam-column elements to implement the direct analysis of angle structures. The examples show that the proposed method is sufficiently accurate and therefore it can be employed in the practical design of angle structures.

Keywords: Single angle member, Angle structures, Effective stress-strain relationship, Direct analysis, Initial imperfections, Flexural-torsional buckling.
Stability design of single angle member using effective stress-strain method
Structures - Institution of Structural Engineers -  Elsevier Ltd
https://doi.org/10.1016/j.istruc.2019.04.013
Abstract: 
Single angle members are mostly subjected to eccentric forces due to the end connections at
their legs. Current design codes generally allow for considering the advantage of the plastic reserve of
single angle cross-sections. However, the available interaction equations to combine the effect of biaxial bending are linear which contradict the fact that the plastic surface of the single angle cross-sections is nonlinear as provided in the literature. In the current study, a reliable and efficient three-dimensional finite element model (FE) is provided to investigate the behavior of the member under eccentric forces. The well recognized residual stress distribution pattern together with the initial geometrical imperfections are incorporated in the current model. Based on the results of the FE model, the elastic flexural and flexural-torsional buckling loads for equal and unequal leg angle members are provided using a simplified equation rather than the complex ones available in current design codes. Finally, a new buckling curves taking the Eurocode design rules into account, are presented for single angle member subjected to eccentric load about both major and minor principal axes.
Keywords: Single angle, Plastic and compact cross-sections, Eccentric compression, Bi-axial bending, Plastic design.
DESIGN PROPOSALS FOR SINGLE ANGLE MEMBER UNDER ECCENTRIC COMPRESSION FORCE
Ninth International Conference on Advances in Steel Structures (ICASS’2018) - 5-7 December 2018 - Hong Kong, China
ABSTRACT
Practical single angle members are mostly subjected to eccentric forces due to the end connections to their legs. Plastic Class 1 and compact Class 2 angle cross-sections are allowed for using their plastic reserves. However, most of the interaction equations in the current design codes are linear whereas the nonlinear equations associated with plastic surface are provided in the literature. In this study, a new design method for single angle member to address the plastic failure as well as stability checks is proposed. The first yield moments at different critical points due to the interaction under the biaxial bending are provided. Moreover, the elastic flexural and flexural-torsional buckling loads for single angle member are calculated using a simplified equation rather than the complex design charts or series of equations in literature or design codes. New buckling curves, taking the Eurocode 3 design rules into account, are presented for single angle member subjected to eccentric load about both major and minor principal axes. A reliable and efficient finite element model is provided to verify the proposed equations and to investigate the different parameters affecting the buckling behavior. Finally, various initial geometric imperfections together with a residual stress distribution pattern are studied and provided in this paper.
Keywords: Single angle, Plastic and compact cross-sections, Eccentric compression, Bi-axial bending, Plastic design.
Finite Element Modeling and Design of Single Angle Member Under Bi-axial Bending
Structures - Institution of Structural Engineers -  Elsevier Ltd
https://doi.org/10.1016/j.istruc.2018.11.001
Awarded since May 2019 (3 reviews) in recognition of the review contributed to the journal
The Editors of Structures Journal - Elsevier
Certificate of Reviewing
The article below has been selected as the Editor-in-Chief’s Featured Article for the November 2018  issue of the journal Structures:
Finite Element Modeling  and Design of Single Angle Member Under Bi-Axial Bending, by A. Hussain, Yao-Peng Liu & Siu-Lai Chan, Structures, Volume 16, November 2018, Pages 373-389 https://doi.org/10.1016/j.istruc.2018.11.001
Elsevier - Structures - ISE
Editor-in-Chief’s Featured Article
Advanced steel structures
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Analysis of structures by computer
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Concrete structures - 2
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Concrete structures - 3
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Construction project management
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Design of irrigation works - 1
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Foundations
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Harbor engineering & Inland Navigation
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American Society of Civil Engineers
drive.google.com
11350832
Member, American Society of Civil Engineering, ASCE
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https://eg.linkedin.com/in/nagy-fouad-9a0996217
القاهرة
Nagy Fouad
Junior Civil Engineer
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دمياط
Mahmoud Hatab
General Manager at BADR for Engineering and Contracting
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مصر
khaled Reda
Senior Contract Engineer, Msc
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مصر
Abdelrahman Tahoon
Construction Engineer
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قسم أول مدينة نصر
Sayed Mostafa Abd El-Wareth
Civil Engineer Fresh Graduate
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دمياط
Amr elhadek
مهندس مدني.. اجيد تصميم و تنفيذ جميع المنشآت الخرسانية
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مصر
Mahmoud Amin
Technical Office Engineer at Orascom Construction PLC
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مصر
Ahmed Mohsen Geweda
Researcher at Mansoura University
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القاهرة
Mahmoud Elnakeeb
Site Engineer في الشركة الهندسية للإنشاءات العمرانية  
( IL Monte Galala Project )
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مصر
Nabil Mahmoud
--
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القاهرة
Rogina Samer
architectural engineer
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الجيزة
Mahmoud Fathy
CEO at Palmera landscape egypt
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السعودية
Haitham El-khawaga
Senior Site Engineer at Atrium Quality Contractors - TMG
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القاهرة, مصر
RD - Brand Management Decorative Glass
RD & Brand Management at Decorative Glass
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القاهرة
Ziad Yasser Fares
Student at Engineering
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القاهرة
Geo Art
Geotechnical Expert
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القاهرة, مصر
Ahmad Yasser
Road Engineer at Julfar Consultancy Services
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مصر
AKRAM ADEL
Senior Steel detailing engineer at Al Shafar Steel Engineering (Assent)
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مصر
Osama Emeira
Senior structural Engineer at Joint venture Cairo metro line-3(The arab contractors & Orascom construction)
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القاهرة
Mohamed Nagah
Technical Office Engineer at RFCO
https://www.linkedin.com/in/polymercoatings
Libertyville, IL
Ahmed Abdelrahman, Ph.D.
Senior Formulations Scientist
https://ca.linkedin.com/in/ahmed-s-abdelrahman-ph-d-8855074b
هاميلتون, ON
Ahmed S. Abdelrahman, Ph.D.
Principal Engineer at Enedym Inc.