An experimental investigation into the moment-rotation response of cold-formed steel (CFS) welded clip-angle beam-to-column joint was conducted through a series of 34 laboratory connection tests. The web, top flange, and bottom flange sections of both the beam and column were fastened using a welded clip-angle (CA), a bolted top flange cleat (FC), and a bolted bottom flange cleat (FC) in that order. The assessed connection exhibited several modes of failure, including (i) distortional buckling of the welded CA, (ii) local buckling of the welded CA, (iii) pull through failure of the top FC and (iv) bearing failure of the bottom FC. The analysis revealed that the design variables of the welded CA, namely thickness, width, and depth, significantly impact the failure modes, ultimate moment capacity, and initial rotational stiffness of the connections under examination. Classifying connections is essential for accurate analysis, effective design, and safe, economical structural performance. However, current design codes lack guidelines for CFS connections; this research aims to address that gap. The moment-rotation properties of the CFS beam were experimentally evaluated and used as a reference for the categorization of the tested cold-formed steel (CFS) connections. A new classification framework for the CFS beam-to-column welded CA connections was developed by employing the aggregated data from 97 laboratory tests, which includes both prior literature and current test series. Based on their relative strength and stiffness in relation to the connected beam, the CFS connections were divided into three distinct categories: rigid, semi-rigid, and flexible. Design guidelines have also been suggested to achieve the required degree of connection rigidity and most of the tested connections exhibited semi-rigid properties.

The present research work evaluates the ultimate shear capacity of a beam-to-beam moment connection comprising a 2-bolted clip-angle with a flange strip with 44 laboratory tests. The ultimate shear capacity of the 2BM connection was investigated by varying the clip-angle design parameters such as (i) thickness and (ii) aspect ratio (L/D). The governing failure modes observed in the 2BM connection are (i) tearing failure and (ii) shear local buckling based on the L/D ratio of the clip-angle. Following the conventional approach, an empirical shear strength equation for the chosen 2-bolted moment connection (2BM) is proposed (Method-1). In addition, a new design method is introduced (Method-2), and the increase in shear strength of the 2-bolted moment connection over the 2-bolted shear connection is evaluated with a rigidity factor. The shear performance of the 2BM connection is 2.37 times that of the 2BS connection due to adding a flange strip. Design factors for the Load and Resistance Factor Design (LRFD), Limit State Design (LSD), and Allowable Strength Design (ASD) methods are produced by conducting the reliability analysis on the experimental data.

A comprehensive experimental study was conducted on cold-formed steel (CFS) beam-to-column connections, which included a configuration featuring a 3-bolted clip-angle (CA) connecting the web portions and two flange-cleats (FC) linking the top and bottom flange sections of both the beam and column. A total of 22 laboratory tests were performed. An in-depth parametric analysis of the moment-rotation behaviour was carried out and design guidelines were suggested for the optimum design of the chosen connection. The observed failure modes in the tested specimens are local buckling and distortional buckling of the clip-angle connector, pull through and bearing failure in the top and bottom FC respectively. Most of these connections attain at least 80 % of the plastic moment capacities of the associated beam. A new classification system has been suggested for the CFS beam-to-column connections from the 108 collated test data of CFS connections with only web portions connected (Type 1), with web and top flange portions connected (Type 2) and web, top and bottom flange portions connected (Type 3). The CFS connections are classified into rigid, semi-rigid, and flexible types, depending on their strength and stiffness characteristics in relation to the properties of the connected CFS beam.

In the present study, the shear performance of a cold-formed steel (CFS) 2-bolted beam-to-column moment connection (2BM) is investigated through 39 laboratory connection tests. The chosen design parameters of the test specimen are the thickness, width and depth of the clip-angle. The effect of the design parameters on the ultimate shear strength, initial stiffness and failure modes of the 2BM connection was analysed and design recommendations were proposed. The test results showed that clip angles with aspect ratio (L/D) ≤ 0.36 are prone to tearing failure, while the failure is due to shear local buckling for L/D > 0.36 in a 2BM connection. Two design methods, namely Method-1: empirical design approach and Method-2: generic design approach, are developed to predict the ultimate shear capacity of the 2BM connection. Both Method-1 and Method-2 yielded equal ultimate shear strength, but Method-2 was preferred as it accounts for the change in design variable of the clip-angle and flange-cleat. The design factors were evaluated for Methods 1 and 2 through reliability analysis. The shear strength increment in a 2-bolted moment connection over a 2-bolted shear connection is quantified, and a parametric study is conducted. The relative shear performance of the present 2-bolted moment connection and the existing 3-bolted moment connection is evaluated, and design recommendations are suggested to facilitate the connection selection process. Practical application: A standard 2-bolt clip-angle shear connection allows for basic load transfer with minimal material and fabrication needs. Adding a flange cleat transforms it into a 2-bolt moment connection, increasing ultimate strength by 85 %. Introducing a third bolt creates a 3-bolt moment connection, providing an additional 16 % strength boost over the 2-bolt moment connection while maintaining similar stiffness and ductility. Although the strength gain is slight, it enhances redundancy and durability. However, the costs of adding bolts across a structure, covering material, fabrication, and erection must be considered. A balanced design strategy should use 2-bolt shear connections where appropriate, upgrade to 2-bolt moment connections for added strength, and selectively apply 3-bolt moment connections for enhanced capacity and redundancy, promoting structural efficiency and cost-effectiveness.

In the present research work, a series of 70 laboratory tests were carried out to investigate the shear characteristics of a CFS welded clip-angle (WS) connection. The WS connection primarily exhibits failure modes such as (i) local buckling and (ii) distortional buckling of the clip-angle, in addition to a CFS column bearing failure. The impact of column bearing failure on the ultimate shear strength of the WS connection is investigated. A detailed parametric study is undertaken to analyze the effects of design variables on the different failure modes and the ultimate strength of the WS connection. Following the conventional two-step process, a design approach for the WS connection is developed like (i) failure modes were classified using aspect ratio (width/depth) and (ii) a new design equation was developed to predict the ultimate shear strength. Nonetheless, it is important to note that these two design steps are not interrelated. Therefore, the present research introduces a unified design model to assess and relate the failure behaviour and ultimate strength using a failure index factor. Unlike conventional method that overlook thickness impact on failure mode categorization, the current failure index factor considers all relevant design variables. The suggested design methodology has been expanded to the CFS bolted connection and shows a good agreement with the literature data of 114 bolted CFS connection tests. A comparative study was executed on the welded and bolted CFS shear connection and design guidelines have been formulated. A reliability assessment of the developed design models for both welded and bolted CFS connections has been carried out. A design example is provided to elucidate the design methodology.

This paper reports on the shear performance of a cold-formed steel (CFS) beam-to-beam moment welded moment connection with 28 laboratory tests. The tested moment connection comprises a welded CFS 90° clip angle (CA) and a flat-shaped CFS flange strip (FS) that connects the web and flange portions of the beam members. The observed failure modes in the tested samples, namely, (1) tearing failure; and (2) local buckling of the welded CA are classified based on the aspect ratio of the CA. A detailed parametric study was conducted on the ultimate shear strength of the welded moment connection for the variation in the thickness, width, and depth of the CA. The effect of the FS in improving the shear strength of the chosen welded moment connection over the welded shear connection was quantified, and design guidelines were suggested. Two design methods, namely, (1) empirical approach, which is specific only for the chosen moment connection, and (2) generic design approach, which applies to shear and moment connections, have been proposed. In this study, CFS welded moment connections are compared with CFS welded shear connections, and design recommendations are suggested.

The present research work endeavours to study the shear performance of a 2-bolted clip-angle connector made of commonly available low-grade steel material (fy = 275-300 MPa) with 58 laboratory tests. The variability in the test specimens is achieved by varying the clip-angle thickness and its aspect ratio. The governing failure modes observed in the 2-bolted clip-angle are (i) Tearing failure for an aspect ratio (L/D) ≤ 0.23; (ii) Shear local buckling for an aspect ratio (L/D) > 0.23. An empirical shear equation for the 2-bolted clip-angle is developed by considering the present experimental data of low-grade steel material (fy = 275-300 MPa) and data in the literature for the high-grade (fy = 375-550 MPa) steel material. In addition, a new shear strength equation that applies to both 2-bolted and 3-bolted clip-angle of both high and low-grade steel strength is developed by the regression analysis of present 2-bolted and 3-bolted clip-angle experimental results from the literature. The proposed new shear strength equation is expressed as a function of L/D to represent the failure behavior of the bolted clip angles. Hence, the proposed new shear equation is applicable for all the bolted clip-angle connections under a shear load in a CFS beam-to-column connection and presents the corresponding failure mode as well. The design factors of Load and Resistance Factor Design (LRFD), Limit State Design (LSD) and Allowable Strength Design (ASD) methods were evaluated for the proposed shear equations by the reliability analysis.

In the current research work, the shear capacity of the cold-formed steel (CFS) three-bolted clip angle (CA) beam-to-column moment connection (3BM) is investigated with 45 laboratory test results. The 3BM connection comprises a three-bolted CA connector that connects the web portions and a bolted flange cleat (FC) that connects the flange portions of the beam and column; in comparison, the three-bolted shear connection (3BS) connects only the web portions of the beam and column. The presence of the FC improved the shear strength of the 3BM connection over the 3BS connection and it is quantified using a coefficient called the "rigidity factor (β)."A shift in the failure mode of CAs from shear local buckling in a 3BS connection to tearing failure in a 3BM connection was observed as the FC resists beam torsional deformation and delays the early local buckling of the CA. The existing design shear equation of the 3BS connection is improved by expressing it as a function of CA failure modes. Following the same trend, the existing design shear method for the CFS moment connection is improved by incorporating the failure modes of the CA boundary conditions along with the geometric and material properties of both the CA and FC for the present 3BM connection. In addition, an empirical shear design equation is suggested for the 3BM connection. The design factors of the proposed 3BM shear equations for load and resistance factor design, limit state design, and allowable strength design methods were evaluated from the reliability study.

This paper presents an experimental investigation on the three-bolted clip-angle (CA) connector under direct shear load. A total of 48 clip-angle connection tests were carried out with 27 different clip-angle configurations by varying the thickness, width and depth of the clip-angle. The present experimental results and the data from literature indicates that the existing design methods for the service limit state design of the clip-angle are inefficient. The present investigation proposes a novel and efficient design method for the service limit state after calibration against test data, for the low-grade steel clip-angle (fy=271MPa to 307 MPa) from the present research work and for the higher grade steel (fy=375MPa to 550 MPa) from the literature data. Hence the proposed design method has wider steel grade application from fy=271MPa to 550 MPa. Parametric studies were performed to evaluate the influence of the geometric variables on the service shear strength of the three bolted clip-angle. The proposed design method was also applied to the welded clip-angle configuration in the literature and corresponding design equations were developed. In addition, a comparative study between the present three-bolted and most recent welded clip-angle connection was conducted which indicated that the three-bolted clip-angle configuration has higher stiffness than that of the welded configuration. Reliability studies were performed and relevant design factors were determined according to the LRFD, LSD and ASD methods.

The current research endeavours to evaluate the shear performance of the cold-formed steel (CFS) welded moment connection between beam-to-column with 36 laboratory tests. The web portions of the beam and column were connected by CFS welded clip-angle to form a CFS welded shear connection. Subsequently, it is converted into a welded moment connection by including a flange cleat between the flange portions. The shear capacity of the welded shear connection increases by an average of 67% after the inclusion of flange cleats, which is quantified using a performance ratio variable. This research presents two shear equations for the CFS welded moment connection (i) a new empirical shear equation; (ii) a new shear equation representing the shear strength of the moment connection as a function of the shear strength of the shear connection. The variability of the shear performance of welded moment and welded shear connections is expressed with force versus displacement plots and failure modes of the clip angles. The failure modes observed in the clip-angle in both welded moment and welded shear connections are (i) Local buckling and (ii) Distortional buckling. The shift in failure modes of some of the clip-angle in the WM connection (Local buckling) and the WS connection (Distortional buckling) indicates the effectiveness of flange-cleat in resisting due to free twisting of the beam because of load offset from the shear center. The design factors were also determined for the LRFD, LSD, and ASD methods by performing reliability studies.

In this paper, the ultimate shear capacity of the 3-bolt cold-formed steel clip-angle between the cold-formed steel (CFS) beam and column is evaluated through 54 laboratory tests. A series of experiments were conducted by varying (1) thickness, and (2) aspect ratio (L/D) of clip-angles for different depths (D) and widths (A). The experimental program consists of three phases of tests: (1) Phase-I: direct shear load tests on clip-angle attached to a CFS column through 4.6-grade bolts; (2) Phase-II: CFS column replaced with a hot-rolled steel (HRS) column, since the CFS column experienced bearing failure in Phase-I; and (3) Phase-III: 10.9-grade bolts used instead of 4.6, as the 4.6-grade bolts subjected to bolt shear failure in Phase-II. Failure modes observed in the test specimens are (1) shear local buckling of clip-angle; (2) column bearing failure; (3) bolt shear failure; and (4) tear failure in clip-angle. Design shear equations from the literature, for the bolted clip-angle, were found to be inefficient for the high-grade steel (fy=375 MPa to 550 MPa), and conservative for the commonly available low-grade steel (fy=275 MPa). Hence a new shear strength equation is suggested for the clip-angle from the collated data of the present study and past research work. A comparative study between 2-bolt and 3-bolt clip-angle configurations was conducted to evaluate the increase in shear strength. Reliability studies were conducted, and corresponding resistance and safety factors were suggested for the design shear strength calculation corresponding to load and resistance factor design (LRFD), limit state design (LSD), and allowable strength design (ASD) methods.

An experimental investigation on the fillet welded clip-angle connection between the cold-formed steel (CFS) beam and column was conducted under four-point bending. The purpose of the study was to investigate the shear strength of the fillet welded clip-angle between the CFS beam and column. To accomplish this objective, a total of 30 experiments with 27 clip-angle configurations and three repeat tests were carried out. The parameters studied include thickness and aspect ratio of the clip-angle. The clip-angles were found to fail in (i) distortional buckling for an aspect ratio (W/D) < 0.8 and (ii) local buckling for an aspect ratio (W/D) ≥ 0.8. The experimental outcomes of the welded clip-angles were summarized and compared with the design strength predictions for screwed and bolted connections in terms of design shear strength equations and behavior of the test specimens. The studies indicate that the welded connections exhibited higher stiffness with respect to the screwed and bolted connections resulting in lower serviceability limit requirements. Based on the test results, a new shear strength design equation for the fillet welded clip-angle is suggested. Further, the reliability analysis is conducted to evaluate the resistance and safety factors for the LRFD, LSD and ASD methods to determine the design shear capacities accordingly. The effectiveness of the proposed design method for the welded clip-angle between CFS beam and column is illustrated with the help of the design example in this paper.