Papers by Alireza Sabbagh
Journal of Cultural Management, Jul 23, 2018
Restrained shrinkage is an important issue in design of concrete industrial ground floors, althou... more Restrained shrinkage is an important issue in design of concrete industrial ground floors, although it is often overlooked. This paper studies shrinkage behaviour of a SFRC floor subjected to static racking load, through FE simulation. The ultimate load bearing capacity and cracking of the floor is assessed. It is shown that shortly-spaced surface micro-cracks are formed due to shrinkage. These cracks are not initially visible, but get longer and wider after loading. As a result, the load-carrying capacity of the floor reduces significantly, and the equivalent crack opening increases by up to10 times.
Journal of Constructional Steel Research, Sep 1, 2013
In this paper monotonic and cyclic finite element (FE) analyses are presented for the development... more In this paper monotonic and cyclic finite element (FE) analyses are presented for the development of an I-beam-to-CHS column steel moment joint for seismic actions. The development process for the final joint details includes: (1) eliminating two identified structural deficiencies of distortion in column web panel and strain concentrations in the external diaphragms; (2) creating a multi-fuse energy dissipation mechanism; (3) devising a joint to delay onset of beam yielding. Two external diaphragm collar plates are welded to the circumference of the CHS column for connection to beam flanges. Various collar ring widths are examined for these horizontal diaphragms and a width (based on achieving full strength of the beam flanges) is found to produce an acceptable web panel performance. Different types of stiffener geometries in the connection region are then trialed to eliminate strain concentrations in the diaphragms. Two pairs of triangular diaphragm stiffeners are found to provide the desired performance. In order to produce a multi-fuse energy dissipation mechanism, tapered cover plates (TCPs) equipped with vertical stiffeners (VSs) are integrated into the joint. Oversized web holes of 4-10 mm are required to enable inelastic deformation for an overall joint rotation of 60-100 mrad, without undesirable web distortion. Further FE analyses are used to design the TCPs and VSs so they can be replaceable link post-seismic actions. For the final joint detailing it is shown that 6 mm oversized holes for the TCPs will delay the occurrence of yielding in the beam until the joint rotation is 70 mrad.
Proceedings of the International Conference on Civil, Structural and Transportation Engineering, Jun 1, 2022
In this research, with the use of cold-formed steel (CFS) sections in-filled with rubberized conc... more In this research, with the use of cold-formed steel (CFS) sections in-filled with rubberized concrete (RuC), a new low-carbon construction system is developed and assessed for its structural resilience and environmental impact compared to the current conventional earthquake-proof construction. First, connection level moment-rotation responses of the new form of CFS-RuC framed structure are validated against the results obtained from detailed finite element analyses. Next, nonlinear pushover analyses are undertaken on the CFS-RuC framed system in conjunction with conventional hot-rolled steel and reinforced-concrete (RC) frames for a case study selected in Istanbul. Lastly, economic and environmental impact analyses are conducted on the frame systems. The results show that the new CFS-RuC composite system offers both structural and environmental advantages compared to conventional systems. In terms of seismic performance of multi-storey buildings, it is shown that the ductility capacity of the CFS-RuC system can be improved by increasing the number of stories.
Engineering Structures, Feb 1, 2021
Flexibility in the manufacturing of cold-formed steel (CFS) cross-sectional shapes provides a uni... more Flexibility in the manufacturing of cold-formed steel (CFS) cross-sectional shapes provides a unique opportunity to improve the load-carrying capacity of these elements, leading to more efficient and economic structural systems. This paper presents a practical constrained optimization methodology for pin-ended anti-symmetric CFS beam-columns members with different lengths subjected to various combinations of axial compression and bending moment. The optimization process is carried out using a Genetic Algorithm (GA) with respect to buckling resistance of CFS elements determined according to the Direct Strength Method (DSM). In total, 132 CFS beam-columns with three different lengths (1000, 2000 and 3000 mm) and eleven different cross-sections are optimized under concentrically compressive loads with different levels of eccentricities varying from 0 to 30 mm. Each cross-section is formed using a certain number of fold-lines of steel plate, while the length and angle of the constituent elements of the cross-section are considered as the main design variables. To provide more practical beam-column elements, end-use constraints as well as a range of practical manufacturing and construction limitations are imposed on the selected cross-sections during the optimization process. A standard commercially available anti-symmetric Z section is taken as a starting point of optimization and used to assess the efficiency of the optimized sections. The results show that, for the given plate width and thickness, the adopted optimization process can significantly increase the strength of beam-column members on average 62%, 92%, and 188% for the short, medium and long length elements, respectively, compared to those with the standard section. It is also demonstrated that using more complex cross-sectional shapes does not necessarily provide higher strength for beam-column members. Finally, to verify the efficiency of the optimized sections, detailed nonlinear finite element models are developed using ABAQUS software. The developed models should prove useful for the efficient design of CFS beam-column elements in practice.
Journal of Constructional Steel Research, Apr 1, 2019
This study aims to present a practical method for optimization of symmetric cold-formed steel (CF... more This study aims to present a practical method for optimization of symmetric cold-formed steel (CFS) beam-column members using Genetic Algorithm (GA). To eliminate impractical crosssection shapes from the optimization results, a range of manufacturing and construction constraints are incorporated into the optimization process. Axial forces are applied with different eccentricities (0 to 30 mm) to cover the full spectrum of beam-column actions from pure axial compression to pure bending. The effect of element length on the optimization results is investigated by using short, intermediate and long beam-column members. A total of 132 beam-columns with different cross section shape complexity (4 to 12 rollers/nodes and 1 to 3 lips) are optimized. The compression and bending moment strengths are obtained based on direct strength method (DSM) using CUFSM software by accounting for local, distortional and global buckling modes. The results show that using more complex shapes does not necessarily lead to better design solutions. Increasing the eccentricity generally leads to more spread optimum sections particularly when distortional buckling is the predominant mode in short and intermediate-length beam-columns. In cases where local and global buckling modes govern the design, however, less spread sections with higher turn angles generally provide higher strength capacities. With the variation of eccentricity, the ultimate strength of optimum beam-column sections normalised by the strength of a reference lippedchannel are in the range of 110-163%, 128-194% and 160-222% for short, medium and long members, respectively. The results of this study, should prove useful in more efficient design of CFS beam-column elements in practice.
Thin-walled Structures, Mar 1, 2021
This paper presents the development of side-framed lightweight steel (SFLS) structures featuring ... more This paper presents the development of side-framed lightweight steel (SFLS) structures featuring semi-rigid floor-to-wall connections. Initially, the effect of variation of connection rotational stiffness on the design of a two-storey frame is investigated considering different construction methods. The results revealed a considerable effect of the connection rotational stiffness on the design of the joists and studs. A semi-rigid connection is then developed using validated finite element analyses. The developed SFLS system enables more efficient designs addressing the predominant limit states of the conventional designs with fewer and lighter flooring members and connections.
Proceedings of the 7th International Conference on Civil, Structural and Transportation Engineering (ICCSTE'22)
In this research, with the use of cold-formed steel (CFS) sections in-filled with rubberized conc... more In this research, with the use of cold-formed steel (CFS) sections in-filled with rubberized concrete (RuC), a new low-carbon construction system is developed and assessed for its structural resilience and environmental impact compared to the current conventional earthquake-proof construction. First, connection level moment-rotation responses of the new form of CFS-RuC framed structure are validated against the results obtained from detailed finite element analyses. Next, nonlinear pushover analyses are undertaken on the CFS-RuC framed system in conjunction with conventional hot-rolled steel and reinforced-concrete (RC) frames for a case study selected in Istanbul. Lastly, economic and environmental impact analyses are conducted on the frame systems. The results show that the new CFS-RuC composite system offers both structural and environmental advantages compared to conventional systems. In terms of seismic performance of multi-storey buildings, it is shown that the ductility capacity of the CFS-RuC system can be improved by increasing the number of stories.
Journal of Constructional Steel Research
Structures
This paper presents the development of a composite cold-formed steel (CFS)-rubberised concrete (R... more This paper presents the development of a composite cold-formed steel (CFS)-rubberised concrete (RuC) semi-rigid moment-resisting connection suitable for framed building structures. The connection comprises built-up tubular cold-formed steel beam and column sections connected using side-plate screwed fasteners and infilled with rubberised concrete. A detailed finite element analysis validated against physical tests is employed to model both bare steel and composite beam-tocolumn connections subjected to lateral and gravity loadings. The governing design limit states are characterized as local buckling in bare steel beams, connection screw shear failure, and side plate plasticity. It is shown that the strength and ductility capacity of composite connections could be increased by up to 1.44 and 3.46 times, respectively, compared with those of the bare steel connections. The connection rigidity of both bare steel and composite connections can be classified as a semi-rigid joint.
This paper presents investigation on cold-formed steel (CFS) beam-to-column moment-resisting (MR)... more This paper presents investigation on cold-formed steel (CFS) beam-to-column moment-resisting (MR) bolted connections with high energy dissipation capacity suitable for seismic areas. Bolting friction-slip mechanism of the introduced CFS MR connection is developed as its main seismic energy dissipation fuse aiming to postpone or eliminate local buckling and yielding in the CFS MR connections. Finite Element (FE) modelling techniques are employed to effectively simulate the connections with an activated friction-slip mechanism. Hysteretic energy dissipation response of the connections with circular bolting (CB) arrangement designed to slip at 0.5M p are presented. Based on the obtained FE results, fullscale physical tests on the CB connections have been performed under cyclic loading. Both the FE and the test CB connections comprised double back-to-back segmental-flange beams of 2, 4 and 6mm thicknesses. The results show that the bolting friction-slip mechanism developed for the CB connections can effectively delay local buckling and yielding in the CFS beams of as thin as 2 mm.
Restrained shrinkage is an important issue in design of concrete industrial ground floors, althou... more Restrained shrinkage is an important issue in design of concrete industrial ground floors, although it is often overlooked. This paper studies shrinkage behaviour of a SFRC floor subjected to static racking load, through FE simulation. The ultimate load bearing capacity and cracking of the floor is assessed. It is shown that shortly-spaced surface micro-cracks are formed due to shrinkage. These cracks are not initially visible, but get longer and wider after loading. As a result, the load-carrying capacity of the floor reduces significantly, and the equivalent crack opening by up to 10 times.
Engineering Structures, 2021
Flexibility in the manufacturing of cold-formed steel (CFS) cross-sectional shapes provides a uni... more Flexibility in the manufacturing of cold-formed steel (CFS) cross-sectional shapes provides a unique opportunity to improve the load-carrying capacity of these elements, leading to more efficient and economic structural systems. This paper presents a practical constrained optimization methodology for pin-ended anti-symmetric CFS beam-columns members with different lengths subjected to various combinations of axial compression and bending moment. The optimization process is carried out using a Genetic Algorithm (GA) with respect to buckling resistance of CFS elements determined according to the Direct Strength Method (DSM). In total, 132 CFS beam-columns with three different lengths (1000, 2000 and 3000 mm) and eleven different cross-sections are optimized under concentrically compressive loads with different levels of eccentricities varying from 0 to 30 mm. Each cross-section is formed using a certain number of fold-lines of steel plate, while the length and angle of the constituent elements of the cross-section are considered as the main design variables. To provide more practical beam-column elements, end-use constraints as well as a range of practical manufacturing and construction limitations are imposed on the selected cross-sections during the optimization process. A standard commercially available anti-symmetric Z section is taken as a starting point of optimization and used to assess the efficiency of the optimized sections. The results show that, for the given plate width and thickness, the adopted optimization process can significantly increase the strength of beam-column members on average 62%, 92%, and 188% for the short, medium and long length elements, respectively, compared to those with the standard section. It is also demonstrated that using more complex cross-sectional shapes does not necessarily provide higher strength for beam-column members. Finally, to verify the efficiency of the optimized sections, detailed nonlinear finite element models are developed using ABAQUS software. The developed models should prove useful for the efficient design of CFS beam-column elements in practice.
Thin-Walled Structures, 2021
This paper presents the development of side-framed lightweight steel (SFLS) structures featuring ... more This paper presents the development of side-framed lightweight steel (SFLS) structures featuring semi-rigid floor-to-wall connections. Initially, the effect of variation of connection rotational stiffness on the design of a two-storey frame is investigated considering different construction methods. The results revealed a considerable effect of the connection rotational stiffness on the design of the joists and studs. A semi-rigid connection is then developed using validated finite element analyses. The developed SFLS system enables more efficient designs addressing the predominant limit states of the conventional designs with fewer and lighter flooring members and connections.
Thin-Walled Structures, 2019
This paper presents an investigation into a friction-slip mechanism in bolted joints in cold-form... more This paper presents an investigation into a friction-slip mechanism in bolted joints in cold-formed steel (CFS) moment-resisting connections suitable for seismic areas. The aim is to achieve higher ductility and energy dissipation capacity through an appropriately designed bolted connection, enabling activation of bolt slip, acting as a fuse mechanism, postponing the initiation of non-ductile local buckling in the CFS beams. By means of validated finite element analysis (FEA), both monotonic and cyclic performance of CFS connections comprising two types of square (SB) and circular (CB) bolt group arrangements, with four types of beam sections, are studied comparatively without and with slip at various levels. It is shown that the connections with slip provide higher energy dissipation capacity by up to 75% compared with that of the connections without slip. A design approach to predict an appropriate level for the connection slip moments to be initiated before the beam buckling moment is introduced using the direct strength method (DSM). On comparing the bolt forces obtained for the SB and CB groups, the CB connections produce a more uniform bolt-group force distribution which is closer to the idealised method; while the SB connection encounter a significant delay of up to 30% in activation of bolt group slip which could lead to unfavourable beam local buckling. Furthermore, to avoid an unfavourable hardening effect due to the bolts bearing action, slotted holes are used with a recommended length obtained for the cyclic movements of the bolts in the range of the designed connections. The instantaneous centre of rotation results show that the connections with slip have less deviation from the idealised centre of rotation than the connections without slip.
Journal of Constructional Steel Research, 2019
This study aims to present a practical method for optimization of symmetric cold-formed steel (CF... more This study aims to present a practical method for optimization of symmetric cold-formed steel (CFS) beam-column members using Genetic Algorithm (GA). To eliminate impractical crosssection shapes from the optimization results, a range of manufacturing and construction constraints are incorporated into the optimization process. Axial forces are applied with different eccentricities (0 to 30 mm) to cover the full spectrum of beam-column actions from pure axial compression to pure bending. The effect of element length on the optimization results is investigated by using short, intermediate and long beam-column members. A total of 132 beam-columns with different cross section shape complexity (4 to 12 rollers/nodes and 1 to 3 lips) are optimized. The compression and bending moment strengths are obtained based on direct strength method (DSM) using CUFSM software by accounting for local, distortional and global buckling modes. The results show that using more complex shapes does not necessarily lead to better design solutions. Increasing the eccentricity generally leads to more spread optimum sections particularly when distortional buckling is the predominant mode in short and intermediate-length beam-columns. In cases where local and global buckling modes govern the design, however, less spread sections with higher turn angles generally provide higher strength capacities. With the variation of eccentricity, the ultimate strength of optimum beam-column sections normalised by the strength of a reference lippedchannel are in the range of 110-163%, 128-194% and 160-222% for short, medium and long members, respectively. The results of this study, should prove useful in more efficient design of CFS beam-column elements in practice.
Thin-Walled Structures, 2016
In this paper experiments are presented to investigate the seismic response of steel sheathed col... more In this paper experiments are presented to investigate the seismic response of steel sheathed coldformed steel (CFS) shear walls using gypsum and fiber cement board claddings. Six steel sheathed wall specimens of various cladding configurations were tested under cyclic loading. The use of claddings at either or both sides of the walls results in an increase of their lateral stiffness, shear strength and energy dissipation capacity by up to 67, 80 and 76%, respectively. On the use of claddings connected to the CFS walls their effects on the shear strength must be incorporated into the current design specifications for an efficient and safe design.
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Papers by Alireza Sabbagh