Tousignant, Kyle
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Item Open Access Reliability Assessment of Concrete-Filled RHS Beam-Column Design Provisions (Preprint)(Springer, 2023-08-01) Rahbarimanesh, F; Tousignant, KRevisions were recently proposed to the way in which concrete-filled hollow structural section members are handled in CSA S16. These revisions were based on previous research, comparisons to experiments, and an approximate first-order reliability method analysis of the new and existing provisions. Herein, this topic is further expanded by using Monte Carlo simulations (MCS) to evaluate the reliability of design rules for concrete-filled rectangular hollow section (RHS) beam-columns. A representative set of ten concrete-filled RHS members is analysed with variations in wall slenderness, effective length, and loading eccentricity. Using MCS, reliability indices (β+) are determined over a range of live-to-dead load ratios. The β+ values are compared to the code-specified target of β+ = 3.0 in Annex B of CSA S16.Item Open Access Design of Single-Sided Fillet Welds under Transverse Load (Postprint)(American Society of Civil Engineers, 2022-09-01) Thomas, JH; Tousignant, KIn North American steel design specifications, a directional strength-enhancement factor is used to increase the predicted strength of fillet welds subjected to transverse loading (i.e., loading at 90° to the weld axis). Committees have expressed concerns about this factor being unsafe for single-sided fillet welds; however, due to a lack of testing, only cautionary statements have been made in most specifications to address this. An experimental program was hence developed to test 40 transversely loaded single-sided fillet welds in cruciform connections subjected to branch axial tension. The connections varied weld size, branch-plate thickness, and loading eccentricity to investigate the effects of these parameters on fillet-weld strength. Results of this program are presented herein, and a first-order reliability method (FORM) analysis was performed. It is shown that current fillet-weld design provisions meet/exceed code-specified target safety indices provided that (1) the directional strength-enhancement factor is not used, and (2) stresses that result in opening of the weld root notch are avoided.Item Open Access Experimental tests on fillet and PJP welds in CHS moment T-connections (Postprint)(Elsevier, 2022-09-01) Yang, Z; Tousignant, KAn experimental program was developed at Dalhousie University to test various unreinforced circular hollow section (CHS)-to-CHS 90° T-connections subjected to branch in-plane bending moment with the objective of determining the effective section properties of the welded joints. Eleven specimens were designed to be weld-critical (i.e., to fail by weld rupture), and tested by applying a single quasi-static point load, laterally, to the top of each branch. An equation for the weld effective section modulus for CHS-to-CHS moment T-connections is developed, and various design formulae are assessed through a first-order reliability method analysis. The scope of this research covers fillet and partial-joint-penetration groove welded connections with 0.31 ≤ branch-to-chord width ratio ≤ 0.91, 31 ≤ chord wall slenderness ≤ 46, and 0.75 ≤ branch-to-chord thickness ratio ≤ 1.00. Recommendations are made for weld design using the “effective length approach” in AISC 360.Item Open Access Chord-end RHS-to-RHS and CHS-to-CHS X-connections with rigid cap plates: Stress concentration factors (Postprint)(Elsevier, 2021-04-01) Sun, M; Tousignant, K; Nejad, AZ; Daneshvar, SFor rectangular hollow section (RHS)-to-RHS and circular hollow section (CHS)-to-CHS connections situated near a truss/girder end, reinforcement using a chord-end cap plate is common; however, for fatigue design, formulae in current design guidelines [for calculation of stress concentration factors (SCFs)] cater to: (i) unreinforced connections, with (ii) sufficient chord continuity beyond the connection on both sides. To develop definitive design guidelines for end connections with rigid cap plates, previous full-scale connection test results have been used to validate a finite element (FE) modelling approach, and a total of 496 FE models with different chord end distance-to-width (or diameter) (e/b0 or e/d0), branch-to-chord width (β), branch-to-chord thickness (τ), and chord slenderness (2γ) ratios have been modelled and analyzed. Existing SCF formulae in CIDECT Design Guide 8 are shown to be inaccurate if applied to cap plate-reinforced end connections. SCF correction factors (ψ), and parametric formulae to estimate ψ based on e/b0 (or e/d0), β, τ and 2γ, are derived.Item Open Access Circular hollow section X-connections near an open chord end: stress concentration factors (Postprint)(Elsevier, 2021-02-01) Nejad, AZ; Sun, M; Tousignant, KThis paper presents a numerical finite element (FE) investigation to determine stress concentration factors (SCFs) for circular hollow section (CHS)-to-CHS X-connections near an open chord end. Previous large-scale experiments are used to validate FE models, and a parametric study is performed. The parametric study consists of 240 models with variations in chord slenderness (2γ), branch-to-chord diameter ratio (β), branch-to-chord thickness ratio (τ), and chord end distance (e) on one side of the of the connection. For each of the 240 models, SCFs are determined at the crown and saddle hot-spot stress locations. Extrapolating existing formulae to predict “end-distance effects” on SCFs at these locations in CHS-to-CHS X-connections, from CIDECT Design Guide 8 (DG8), is shown to be inaccurate. Hence, SCF correction coefficients (ψ) and parametric formulae to estimate ψ (based on e/d0, 2γ and β) are derived.Item Open Access Stress concentration factors for RHS-to-RHS X-connections near an open chord end(Elsevier, 2020) Daneshvar, Sara; Sun, Min; Tousignant, KyleThis paper presents an experimental and finite-element (FE) study to determine stress concentration factors (SCFs) for directly welded rectangular hollow section (RHS)-to-RHS axially loaded X-connections near an open chord end. Two-hundred and fifty-six FE models of RHS-to-RHS X-connections, with varied chord end distance-to-width (e/b0), branch-to-chord width (β), branch-to-chord thickness (τ), and chord slenderness (2γ) ratios were modelled and analyzed by using commercial software. The analysis was performed under quasi-static axial compression force(s) applied to the branch(es) and validated by comparison of strain concentration factors (SCNFs) to SCNFs obtained from two large-scale experimental tests. For all 256 connections, SCFs were determined at five critical hot spots on the side of the connection near the open chord end. The SCFs were found to vary as a function of e/b0, 2γ and β. Existing formulae in CIDECT DG8 to predict SCFs in directly welded RHS-to-RHS axially loaded X-connections are shown to be conservative when applied to a connection near an open chord end. SCF reduction factors (ψ), and a parametric formula to estimate ψ based on e/b0, 2γ and β, are derived.Item Open Access Design of fillet welds in RHS-to-RHS moment T-connections under branch in-plane bending(Elsevier, 2019) Yaghoubshahi, Mojgan; Sun, Min; Tousignant, KyleNon-linear finite element (FE) models were developed to assess the AISC 360-16 Chapter K design approach for fillet welds in rectangular hollow section (RHS) moment T-connections under branch in-plane bending. The FE models were validated by comparison of the weld fracture moments, load-deflection responses, and spot-strain measurements to results from six previous, large-scale, weld-critical experiments. Based on all available experimental and FE data, the AISC 360-16 design approach is shown to be over-conservative. A key reason for this is that it does not account for bearing between the branch and chord on the compression side of the connection. New design formulae that take bearing into account are hence proposed. These formulae are shown to provide more accurate predictions of fillet weld strength in RHS moment T-connections under branch in-plane bending, and yet still achieve a safety (reliability) index that meets the AISC's target value of 4.0 for connections. The scope of this paper covers connections with all-around fillet welds and branch-to-chord width ratios up to 0.85.Item Open Access Fillet weld effective lengths in CHS X-connections. I: Experimentation(Elsevier, 2017) Tousignant, Kyle; Packer, Jeffrey A.For the first time, an experimental test program was conducted to assess the strength of fillet welds in circular hollow section (CHS) connections. Six large-scale, fillet-welded CHS-to-CHS X-connections were designed with varied key parameters that affect the weld strength: branch-to-chord diameter ratio, chord wall slenderness, and branch inclination angle. By means of quasi-static tension applied to the branches, fracture of 12 test welds (two per connection) was obtained. Strain distributions measured adjacent to the welds indicated a weld effective length less than the total weld length, under pure axial load. Branch loads at rupture were also measured and used to determine the structural reliability of existing AWS provisions for weld effective lengths in CHS-to-CHS X-connections. For the range of parameters studied, the provisions are found to be very conservative. Hence, methods are assessed to accurately quantify the weld effective length. A parametric modelling study is presented in a companion paper to develop more liberal recommendations.Item Open Access Fillet weld effective lengths in CHS X-connections. II: Finite element modelling, parametric study and design(Elsevier, 2018) Tousignant, Kyle; Packer, Jeffrey A.Finite element (FE) modelling was performed to extend the results of a recently completed experimental test program to evaluate the static strength of fillet welds in X-connections between circular hollow sections (CHS). Non-linear FE models with weld fracture were validated by comparison of spot strains, load-deformation response, and fracture load with 12 experimental tests. Two hundred and fifty-six FE weld-critical CHS-to-CHS X-connections, with varied branch-to-chord diameter ratio, chord wall slenderness, branch inclination angle, and branch-to-chord thickness ratio, were analysed under quasi-static branch tension. The effect of these parameters on fillet weld strength is illustrated, and the structural reliability (or safety index) of North American specification provisions for weld effective lengths is confirmed. An alternative method for estimating fillet weld strength, with specific weld effective lengths, is proposed. Recommendations for a new design approach that meets the minimum target safety index in North America are made.Item Open Access Investigation of weld effective length rules for CHS X-connections(Balkema, 2017) Tousignant, Kyle; Packer, J.A.A laboratory-based test program was conducted to assess the performance of fillet welds in X-connections between circular hollow sections (CHS). Six full-scale, fillet-welded CHS-to-CHS X-connections were designed to be weld-critical with varied key parameters that affect weld strength: branch-to-chord diam-eter ratio, chord wall slenderness, and branch inclination angle. By means of quasi-static tension applied to the ends of each branch, fracture of 12 test welds (two per connection) was obtained. Strain distributions ad-jacent to the weld and branch loads at rupture were measured. By using the carefully measured mechanical and geometrical properties of the fillet welds and CHS members, the structural reliability (or safety index) of the existing AWS specification provisions for weld effective lengths in CHS-to-CHS X-connections was de-termined. For the range of parameters studied, the existing AWS formulae were found to be very conserva-tive, hence a comprehensive parametric modelling study is planned to develop more liberal recommendations.Item Open Access Fillet welds around circular hollow sections(Springer, 2019) Tousignant, Kyle; Packer, Jeffrey A.A research program was conducted to evaluate the safety of design rules for fillet welds around the perimeter of steel circular hollow sections (CHS) in the current American Institute of Steel Construction (AISC) steel building specification, AISC 360. Specifically, the appropriateness of the fillet weld directional strength-enhancement factor was investigated for fillet welds to CHS branches, and the effect of non-uniform connection flexibility on fillet-weld strength in CHS-to-CHS connections was studied. A total of 24 large-scale, weld-critical experiments was tested and a further 290 nonlinear finite element models were used to parametrically expand the database. It was found that if the directional strength-enhancement factor is used the target reliability index prescribed by AISC for connectors is not achieved. A recommendation to prohibit this factor for fillet welds around the perimeter of CHS is made. With this restriction, it is shown that AISC 360-16 fillet weld design provisions meet the target safety index for welds in CHS-to-CHS X-connections, where a weld effective length phenomenon exists. It is therefore recommended that AISC advocate 100% weld effective lengths for fillet welds in CHS-to-CHS X-connections, provided that the directional strengthenhancement factor is not used.Item Open Access Experimental Evaluation of Design Procedures for Fillet Welds to Hollow Structural Sections(American Society of Civil Engineers, 2016) Packer, Jeffrey A.; Sun, Min; Tousignant, KyleThis paper discusses contemporary design procedures for fillet welds to Hollow Structural Sections (HSS) in several prominent design codes. The structural reliability associated with the "directional strength enhancement factor" contained in North American Specifications is examined, based on a set of laboratory tests on fillet-welded connections between HSS and rigid end-plates. A total of 33 connections, in which the welds had been designed to be the critical elements, were tested to failure by axial tension loading applied to the HSS members. The experimentally obtained weld strengths were compared to the predicted nominal strengths. The directional strength enhancement factor was found to lead to unsafe strength predictions, particularly for large weld sizes. Hence, a restriction on the use of this factor for fillet welds to HSS members, in North American steel design specifications, needs to be considered. The analysis also shows that Eurocode 3 fillet weld design provisions give conservative strength predictions.Item Open Access Numerical Investigation of Fillet Welds in HSS-to-Rigid End-Plate Connections(American Society of Civil Engineers, 2017) Tousignant, Kyle; Packer, Jeffrey A.This paper presents a finite element (FE) investigation on the behavior of fillet-welded hollow structural section (HSS) rigid end-plate connections, wherein the entire weld length is effective. The FE models are validated by comparison to 33 experimental tests and a parametric study is then performed with 73 numerical tests to evaluate the effect of weld size, HSS branch wall slenderness and branch inclination angle, on fillet weld strength. The inherent problem with one-sided fillet welds to a tension-loaded element is illustrated. A reliability analysis determined that the directional strengthincrease factor for fillet welds in North America leads to inadequate values of the safety index for joints to both circular and rectangular HSS, especially for connections with large welds. Hence, an alternative yet safe method for estimating the strength of fillet welds to HSS, based on weld size, is proposed. An expression for the fillet weld size required to develop the yield strength of a 90° HSS branch member is derived.