Numerical analysis of tilted angle shear connectors in steel-concrete composite systems

Koosha Khorramian,Shervin Maleki,Mahdi Shariati,Abdolrahim Jalali,M.M. Tahir 국제구조공학회 2017 Steel and Composite Structures, An International J Vol.23 No.1

This study investigates numerically the behavior of tilted angle shear connectors embedded in solid concrete slabs. Two different tilted angle connectors were used, titled angle with 112.5 and 135 degrees between the angle leg and steel beam flange. A nonlinear finite element model was developed to simulate and validate the experimental push-out tests. Parametric studies were performed to investigate the variations in concrete strength and connector's dimensions. The results indicate that the ultimate strength of a tilted angle shear connector is directly related to the square root of the concrete compressive strength. The effects of variations in the geometry of tilted angle connectors on the shear capacity are discussed in details. Based on the numerical analyses, two equations are proposed to estimate the ultimate capacity of tilted angle shear connectors of 112.5 and 135 degrees in the defined range of parameters.

Investigation of shear lag effect on tension members fillet-welded connections consisting of single and double channel sections

Moien Barkhori,Shervin Maleki,Masoud Mirtaheri,Meissam Nazeryan,S.Mahdi S.Kolbadi 국제구조공학회 2020 Structural Engineering and Mechanics, An Int'l Jou Vol.74 No.3

Shear lag phenomenon has long been taken into consideration in various structural codes; however, the AISC provisions have not proposed any specific equation to calculate the shear lag ratio in some cases such as fillet-welded connections of front-to-front double channel sections. Moreover, those equations and formulas proposed by structural codes are based on the studies that were conducted on riveted and bolted connections, and can be applied to single channel sections whilst using them for fillet-welded double channels would be extremely conservative due to the symmetrical shape and the fact that bending moments will not develop in the gusset plate, resulting in less stress concentration. Numerical models are used in the present study to focus on parametric investigation of the shear lag effect on fillet-welded tension connection of double channel section to a gusset plate. The connection length, the eccentricity of axial load, the free length and the thickness of gusset plate are considered as the key factors in this study. The results are then compared to the estimates driven from the AISC-LRFD provisions and alternative equations are proposed.

Investigation of pipe shear connectors using push out test

Saeed Nasrollahi,Shervin Maleki,Mahdi Shariati,Aminaton Marto,Majid Khorami 국제구조공학회 2018 Steel and Composite Structures, An International J Vol.27 No.5

Mechanical shear connectors are commonly used to transfer longitudinal shear forces across the steel-concrete interface in composite beams. Steel pipe as a new shear connector is proposed in this research and its performance to achieve composite strength is investigated. Experimental monotonic push-out tests were carried out for this connector. Then, a nonlinear finite element model of the push-out specimens is developed and verified against test results. Further, the finite element model is used to investigate the effects of pipe thickness, length and diameter on the shear strength of the connectors. The ultimate strengths of these connectors are reported and their respective failure modes are discussed. This paper comprises of the push-out tests of ten specimens on this shear connector in both the vertical and horizontal positions in different reinforced concretes. The results of experimental tests are given as load-deformation plots. It is concluded that the use of these connectors is very effective and economical in the medium shear demand range of 150-350 KN. The dominant failure modes observed were either failure of concrete block (crushing and splitting) or shear failure of pipe connector. It is shown that the horizontal pipe is not as effective as vertical pipe shear connector and is not recommended for practical use. It is shown that pipe connectors are more effective in transferring shear forces than channel and stud connectors. Moreover, based on the parametric study, a formula is presented to predict the pipe shear connectors' capacity.

Live Load Distribution Factor for Tank Loading on Slab-Girder Bridges

Bahareh Miranbeigi,Shervin Maleki 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.8

The aim of this research is to obtain the bending moment and shear live load distribution factors (LLDFs) for interior girders of simply supported slab-girder bridges subjected to continuous loading, such as military tanks. The effective parameters considered in calculating the live load distribution factor were: Girders’ number and spacing, span length, slab thickness and the longitudinal to transverse ratio of deck stiffness. Over fifty 3D finite element models were created based on the existing information of bridges in the USA. An equation was obtained for the distribution factor and its validity was assessed against the numerical results. The proposed equation was compared with the AASHTO-LRFD equation for one lane of standard truck loading and also with the equation proposed by the US army corps of engineers for military vehicles. The accuracy of the equation was also verified by performing several sensitivity analyses for the parameters involved. It is concluded that the proposed LLDF equation predicts the distribution factor more accurately than the above mentioned specifications.

Evaluation of seismic performance factors for tension-only braced frames

Mahdi Shariati,Majid Lagzian,Shervin Maleki,Ali Shariati,Nguyen Thoi Trung 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.35 No.4

The tension-only braced frames (TOBFs) are widely used as a lateral force resisting system (LFRS) in low-rise steel buildings due to their simplicity and economic advantage. However, the system has poor seismic energy dissipation capacity and pinched hysteresis behavior caused by early buckling of slender bracing members. The main concern in utilizing the TOBF system is the determination of appropriate performance factors for seismic design. A formalized approach to quantify the seismic performance factor (SPF) based on determining an acceptable margin of safety against collapse is introduced by FEMA P695. The methodology is applied in this paper to assess the SPFs of the TOBF systems. For this purpose, a trial value of the R factor was first employed to design and model a set of TOBF archetype structures. Afterwards, the level of safety against collapse provided by the assumed R factor was investigated by using the non-linear analysis procedure of FEMA P695 comprising incremental dynamic analysis (IDA) under a set of prescribed ground motions. It was found that the R factor of 3.0 is appropriate for safe design of TOBFs. Also, the system overstrength factor (Ω0) was estimated as 2.0 by performing non-linear static analyses.

Numerical Study of Load Eccentricity Effects on Block Shear Rupture of Welded Gusset Plates

Majid Ghaderi-Garekani,Shervin Maleki 한국강구조학회 2023 International Journal of Steel Structures Vol.23 No.4

Block shear rupture is a potential failure mode in welded steel gusset plates. The research on this failure mode in welded connections is scarce, and in available few studies, only concentric loading condition has been considered. Nevertheless, gusset plates are often loaded eccentrically, either in-plane or out-of-plane, depending on the connection. This paper examines the block shear failure in welded gusset plates under eccentric loading. First, an advanced nonlinear finite element model with ductile fracture prediction capability was developed and verified in detail against the authors’ experiment. Then, a comprehensive parametric study consisting of 260 connections was performed. Based on the results, the eccentricity of the applied load made the tensile and shear stress distributions on the failure planes uneven. The ratio of the eccentricity to the connection length was the main parameter that affected block shear strength under eccentric loads. In out-of-plane eccentric cases, gusset plate thickness was also a significant factor. Moreover, the findings implied that current block shear strength equations suggested for welded gusset plates did not take into account load eccentricity-induced effects and overestimates the connection capacity. Accordingly, modified design equations are proposed that predict the block shear strength under eccentric loading with greater accuracy.