Numerical investigation of cold formed steel sleeve connection for channel sections subjected to combined bending and shear Surya Chandan Bondapalli, Vijayakumar Natesan, Mahendrakumar Madhavan Journal of Constructional Steel Research, 2024 This study focuses on the behaviour of the sleeve connection to ensure proper distribution of moment at the location of discontinuity between two channel sections subjected to combined bending and shear using finite element (FE) modelling. The FE model was validated with the experimental data from previous authors studies and was found. A total of 180 simulations were carried out as part of the parametric study , by varying the depth, thickness, length of sleeve connector, length of the test specimen, and bolt configuration. Two modes of failure were identified based on sleeve length (L s ) and combination of sleeve length and channel thicknesses. The L s /D ratios were suggested to achieve a similar strength and stiffness of sleeve specimen when compared with control specimen. The influence of sleeve length on the ultimate moment resistance was studied for combination of sleeve length and channel thickness. The increase in the channel thickness from 2 mm to 2.5 mm led to as significant increase in the ultimate moment resistance. An equation was proposed to calculate the nominal moment capacity of sleeved specimens and reliability analysis of this equation was carried out. The conservativeness of the proposed design procedure was checked by comparing it with the AISI S100 [ 1 ] interaction curve.
Effect of staggered bolted connections on CFS channel sections Bharath Shanmugasundaram, Vijayakumar Natesan, Mahendrakumar Madhavan Journal of Constructional Steel Research, 2020 This research focuses on the effect of staggered bolted connections on the ultimate tensile capacity and failure modes of the cold-formed steel channel sections connected to the gusset plates. The test program includes two series of 113 channel specimens tested under axial tension with one series containing 52 two-bolted specimens and the other with 61 three-bolted specimens. All the specimens were bolted in the web in a staggered fashion, and the main parameters being investigated are different channel dimensions, staggered and gauge distances, and bolt hole diameter. The test results indicate that the tensile resistance of the two-bolt staggered connection is usually bearing controlled and that of the three-bolt staggered connection is net-section rupture. In addition, the original formula s2/(4g + 2dh) proposed by Cochrane is used to calculate the net section area, instead of simplified s2/4g, which could overestimate the net section area upto 10%. Furthermore, the net-section efficiency factor proposed in codes such as EN-1993-1-3, AS/NZS 4600: 2018, and literature to account for in-plane and out-of-plane shear lag, and bending moment due to the eccentricity in loading is evaluated with the test results from three-bolt configurations obtained from this study. It was observed that the current code provisions (EN-1993-1-3:2004, AS/NZS 4600:2018) for staggered bolt configuration yield non-conservative estimates of the ultimate tensile strength. However, the latest equation proposed by Teh and Gilbert [1] (also adopted in AISI 2016), which accounts for all the sources of capacity reduction factors mentioned above, predicted the net section tension capacity accurately. Through the reliability analysis of the equation by Teh and Gilbert [1] based on the present test results, the resistance factor of 0.75 for LRFD and safety factor of 2.05 for ASD design philosophies are suggested.
Experimental study of clip angle bolted connection between two cold-formed steel channels Vijayakumar Natesan, Mahendrakumar Madhavan Proceedings of the Institution of Civil Engineers Structures and Buildings, 2020 An experimental investigation was conducted to study the load–deflection relationships, ultimate load and behaviour of beam-to-beam cold-formed steel (CFS) channels connected with clip angles using...
Comparative experimental studies on the web cleat bolted CFS beam-to-column connection Vijayakumar Natesan, Bharath Shanmugasundaram, Mahendrakumar Madhavan Journal of Constructional Steel Research, 2020 Cold-formed steel (CFS) clip angles/web cleats are widely used as connectors between two CFS members. This study aims to determine the efficiency of a three bolted web cleat over a two-bolted web cleat joint between the beam-column predominantly subjected to a shear load. A total of 26 specimens were studied to investigate the three bolted web cleat configuration by considering two different parameters: (i) thickness of the web cleat (TC) and (ii) the aspect ratio (L/B) of the web cleat leg attached to the column. The experimental results show that the ultimate load increases with a decrease in the aspect ratio of the web cleat leg attached to the column. In addition, the experimental loads of three-bolted configuration were 13 to 95% higher than the corresponding two-bolted configuration. Two types of failure modes were observed: (i) local buckling and (ii) bearing failure of CFS beam under the loading points. The lateral deflection of the column, relative rotation of the connections, and vertical deflection under the loading points were measured and analysed. The nominal shear values calculated from available equations in the past studies are over-conservative when compared to the observed experimental shear values. Hence, a new design equation is suggested for the design of three-bolted web cleat configuration with some specified limits. Besides, reliability studies were performed for the existing and proposed equations for the design of web cleat with three-bolt configuration.
Experimental study on ultimate strength of bolted L shaped sleeve joints between CFS lipped channel sections Vijayakumar Natesan, Mahendrakumar Madhavan Journal of Constructional Steel Research, 2020 This study aims to understand the behavior of bolted L shape sleeve joint connecting two Cold-Formed Steel (CFS) channel sections. A total of thirty-two specimens were experimentally tested under three-point bending. Three different series namely, (A) control specimen with two different span lengths, (B) sleeved specimen with the flange of sleeve connector capping the compression zone, and (C) sleeved specimen with the flange of sleeve connector capping the tension zone were tested. The parameters considered in this study include (i) the span length (Lt), (ii) sleeve length to section depth ratio (β), and (iii) thickness of sleeve connector (LS). The experimental results revealed that the ultimate moment resistance of specimens with a 2.5 mm thick sleeve connector was 19 to 73% higher than 2.0 mm thick sleeve specimens. The moment capacity of series C specimens was about 90–103% of that of the series B specimens. Based on the experimental results, design predictor equations were suggested to determine the moment resistance of sleeve specimens with respect to β. In addition, reliability studies were done for test series B to determine the safety and resistance factors for allowable strength design (ASD) method and load and resistance factor design (LRFD) method respectively. The equivalent and design uniformly distributed load (UDL) was determined based on the combined effect of shear and bending.
Structural performance on bolted sleeved connections between two CFS channel sections subjected to combined bending and shear Vijayakumar Natesan, Mahendrakumar Madhavan Structures, 2019 An experimental investigation was carried out to study the behavior of the sleeve connection between two cold-formed steel (CFS) channel sections subjected to combined bending and shear. A total of thirty-nine specimens including three control specimens were tested under three-point bending for different parameters such as three types of the span to section depth ratio, three different sleeve lengths, two sleeve thicknesses and two bolt configurations. Each tested specimen consisted of a pair of channel sections braced together using hot rolled angle sections along the length to ensure lateral stability. The test results indicate two different failure modes; local buckling due to combined bending and shear in the purlin section adjacent to sleeve end, and the other is shearing of the self-drilling screw at the tension zone. The moment resistance of the sleeve connection varied directly with the sleeve length to section depth ratio. The interaction study carried out between the proposed critical sleeve moment and shear capacity of the sleeve specimens is found to be conservative with respect to the AISI interaction equation. The resistance factor for load and resistance factor design (LRFD) method and safety factor for allowable strength design (ASD) method is proposed for the design of sleeve connection by considering it as a flexural member. The design uniformly distributed load (wD) of sleeve specimens having an average sleeve length to section depth ratio of 2.17, 3.51, and 4.85 are found to be 80, 103, and 125% the capacity corresponding to control specimen respectively. The proposed design method is also applicable to the design of continuous channel purlin/girt sections with 150 mm depth for any number of spans subjected to UDL.
Experimental study on beam-to-column clip angle bolted connection Vijayakumar Natesan, Mahendrakumar Madhavan Thin Walled Structures, 2019 The effectiveness of the clip angle bolted connection between CFS (Cold-formed steel) beam-to-column under shear is investigated in the present study. A total of thirty-one specimens were tested under four-point bending configuration to study the behavior of beam-to-column clip angle connection using bolts. The parameters considered in the experimental study are clip angle thickness and aspect ratio of the clip angle leg connected to the column. The test results indicate that the aspect ratio (L/B) of the clip angle leg plays a significant role in governing the ultimate strength, stiffness and failure mode of the connection. Two different failure modes were observed namely (i) local buckling failure at an aspect ratio (L/B) less than 0.8 and (ii) distortional buckling failure at an aspect ratio (L/B) greater than 0.8 in the clip angle leg connected to the column. An improved design equation for the clip angle bolted connection is proposed and validated with the previous studies from the literature. The proposed design equations for clip angle bolted connection were conservative compared with experimental test results. In addition, a shift in the anchor point (compact limit) i.e., reduction in the slenderness ratio (λ) is suggested for limiting the shear resistance of clip angle bolted connection. Further, reliability studies were carried out to determine the resistance and safety factors for the connections not listed in Table F1 of AISI S100-12 based on the current study and test results from the literature. The suggested design method will be applicable and conservative for the material yield strength up to 550 MPa.
