Shape optimization of cold-formed steel beam-columns with practical and manufacturing constraints

Peer reviewedPostprin

Design of Cold-Formed Steel Beams with Holes and Transverse Stiffeners in Shear

This thesis presents a comprehensive study on shear buckling and shear strength of high strength G450 and G500 cold-formed steel sections with web holes and/or with intermediate transverse web stiffeners. The primary aim is to develop a Direct Strength Method (DSM) of design to predict the capacity of such sections. The study also suggests a new structural application, the cold-formed steel girder, which could be potentially used as heavily loaded cold-formed member such as a transfer beam. The research involved the development of two new testing apparatuses that enable the experimental shear study of cold-formed beams with an aspect ratio (shear span / web depth) greater than 1:0. The first uses a single actuator similar to that used by Basler in the 1960s. The second uses dual actuators and a sophisticated control system. The test rigs were designed in such a way that they could minimize the bending moments applied to the shear span, thus allowing shear strength close to pure shear to be achieved for shear panels with an aspect ratio of 2:0. Three test series including thirteen tests on channel sections and SupaCee® sections were conducted to validate the new test rig designs. The experimental results were also used to validate the existing Direct Strength Method (DSM) of design for shear which was derived from shear tests on beams with an aspect ratio of 1:0. It was found that the new test rigs, which generated minimal moments in the shear span, significantly enhanced the shear strength of relatively long shear panels. Further, close agreement between the DSM prediction and the experimental shear strength confirmed the viability of the DSM for shear for structures with an aspect ratio up to 2:0. A test series including twelve tests on channel sections with various circular and square holes was carried out using the dual actuator rig to study the shear strength reduction due to the occurrence of the web holes. Another six tests on channel sections with intermediate transverse web stiffeners were conducted to investigate the shear strength of transversely stiffened sections as well as the cross-section requirement of the stiffeners. The finite element package Abaqus was employed to simulate the tests. The FE models were calibrated against the experiments prior to being used to perform parametric studies. The FE analyses extended the experimental database and provided insights into the stress development and the full displacement fields. The numerical study was also used to study the influence of such factors as flange restraints and moment to shear ratios on the shear strength of cold-formed sections. The experimental and numerical results were subsequently used to validate DSM shear proposals to design beams with web holes and with intermediate transverse web stiffeners. The proposal was first developed and validated by the tests on beams with web holes with an aspect ratio of 1:0. It made use of the existing DSM design rules and introduced modifications of the shear buckling load (Vcrh) and the shear yield load (Vyh) to account for the inclusion of the web holes. The Vcrh was determined via non-dimensionalised graphs or from a simple expression derived by an artificial neural network. A practical model on the basis of a Vierendeel plastic mechanism to determine Vyh was introduced. The validation extends the applicability of the DSM proposal to perforated members with aspect ratios up to 2:0

Recent Research and Developments in Cold-formed Steel Design and Construction

Golden Anniversary of the AISI Specification - The 1996 AISI Specification - A New AISI Cold-Formed Steel Design Manual - Design of Cold-Formed Steel Stiffened Elements with Multiple Longitudinal Intermediate Stiffeners - A Probablistic Examination of the Ultimate Strength of Cold-Formed Steel Elements - Effective Width of a Simple Edge-Stiffener Subjected to Stress Gradient - The Effects of Perforation Length on the Behaviour of Perforated Elements in Compression - Interaction of Flangel/Edge-Stiffened Cold-Formed Steel C-Sections - Cold-Formed Steel Flat Width Ratio Limits, d/t and d/w - Comparison of the Distortional Buckling Method for Flexural Members with Tests - Design of Thin-Walled Beams for Distortional Buckling - Comparison of Tests of Purlins With and Without Cleats - Determination of Purlin R-Factors Using a Non-Linear Analysis - Deflection Design of Cold-Formed RHS Steel Beams - Finite Element Analysis of Hollow Flange Beams with Web Stiffeners - Buckling Experiments on Hollow Flange Beams with Web Stiffeners - Flexural Strength of Cold-Formed Steel Panels Using Structural Grade 80 of A653 Steel - Experimental Research on the Behaviour of Combined Web Crippling and Bending of Steel Deck Sections - Design Models of Continuous Sandwich Panels - Structural Detailing of Openings in Sandwich Panels - Non-Linear Buckling Analysis of Thin-Walled Metal Columns - Effect of Bracing Stiffness on Buckling Strength of Cold-Formed Steel Columns - Structural Design Study on a Light- Gauge Steel Portal Frame with Cold-Formed Sigma Sections - Lower Cost Lightweight Cold-Formed Portal Frames - Strength and Stiffness Calculation Procedures for Composite Slabs - Strength of Headed Shear Studs in Cold-Formed Steel Deck - Towards a Numerical Procedure for Composite Slab Assessment - Moment Rotation Behavior for Concrete Filled SHS Column to Composite Beam Connection - Stability of Standing Seam Roof-Purlin Systems - Modeling of Cold-Formed Purlin-Sheeting Systems - Dynamic Performance of Light Gauge Steel Framed Shear Walls - Steel - The Clear Cut Alternative - Residential Applications of Cold-Formed Structural Members in Australia - A Study of the Effect of Cold Forming on the Yield Strength of Stainless Steel Type 304 - Hardness Test Approach - An Explicit Approach to Design of Stainless Steel Columns - The Strength of Partially Stiffened Stainless Steel Compression Members - Burst Strength of Type 304L Stainless Steel Tubes Subjected to Internal Pressure and External Forces - Additional Design Considerations for Bolted Connections - Shear Behavior of Self Drilling Screws Used in Low Ductility Steel - Performance of Self-Tapping Screws in Lap-Shear Metal-to-Metal Connections - Evaluation and Modelling of the Material Properties for Analysis of Cold-Formed Steel Sections - The Modulus of Elasticity of Steel Is it 200 GPa? - Geometric Imperfections and Residual Stresses for Use in the Analytical Modeling of Cold-Formed Steel Members - Cold-Formed Steel Sections Experimental Data Base - Cold-Formed Steel Design by Spreadsheet Progra

Recent Research and Developments in Cold-formed Steel Design and Construction

Unstiffened Elements - Some Interesting Features - Tests of Profiled Steel Decks with V-Stiffeners - Bending Strength of Beams with Non-Linear Analysis - Local and Distortional Buckling of Thin-Walled Beams - Design of C-Sections Against Deformational Lip Buckling - Lateral Buckling of Singly Symmetric Beams - Flexural Capacity of Discretely Braced C\u27s and Z\u27s - The Buckling Behaviour of Hollow Flange Beams - Experimental Investigations of I-Beams - Tests of Continuous Purlins Under Downwards Loading - Tests of Full-Scale Roofing Systems - Profiled Sheet Behaviour Under Concentrated Load - On Design of Profiled Sheets with Varying Cross Sections - Properties for Cellular Decks in Negative Bending - Contrasting Behaviour of Thin Steel Roof Claddings Under Simulated Cyclonic Wind Loading - New ASCE Standards for Cold-Formed Steel Deck Slabs - Composite Slabs Analyzed by Block Bending Test - Repeated Point Loading Tests on Composite Slabs - Thermal Shielding Near Intermediate Supports of Continuous Span Composite Slabs - Design of Channels Against Distortional Buckling - Distortional Buckling of Cold-Formed Steel Z-Section Columns - Shah Alam Sports Complex: Design and Construction of Unistrut Space-Frame Roof Structure - Flexibly Connected Thin-Walled Space Frame Stability - Test of a Full Scale Roof Truss - Down-Aisle Stability of Rack Structures - Racking Performance of Plasterboard-Clad Steel Stud Walls - An Experimental Study of Shear Wall Units - Some Applications of Generalized Beam Theory - Calibration of a Bending Model for Cold-Formed Sections - Recent Development in Cold-Formed Steel - The 1989 Edition ofthe Canadian Cold-Formed Steel Design Standard - Observations and Comments Pertaining to CAN/CSA-S136-M89 - Prediction of Corner Mechanical Properties for Stainless Steels Due to Cold Forming - Stainless Steel Tubular Beams - Tests and Design - The Lateral Torsional Buckling Strength of Cold-Formed Stainless Steel Lipped Channel Beams - Testing and Design of Bolted Connections in Cold-Formed Steel Sections - Behavior of Arc Spot Weld Connections in Tension - The Bi-Axial Behaviour of Shear Connectors in Composite Slabs and Beams - Influence of Deformed Metal Decking Composite Floors to Beam-Column Connections - Education in Cold-Formed Steel Structures - Lifelong Learning - Activities of the Center for Cold-Formed Steel Structure

Coupled element and structural level optimisation framework for cold-formed steel frames

Optimisation of cold-formed steel (CFS) structures can be challenging due to the complex behaviour of thin-walled CFS sections affected by different buckling modes. In this paper, a coupled framework is presented for element and structural level optimisation of CFS portal frames, under serviceability limit state (SLS) and ultimate limit state (ULS) conditions, using Genetic Algorithm. First, CFS lipped-channel beam sections are optimised with respect to their flexural capacity determined in accordance with the effective width method specified in Eurocode 3 (EC3). The relative dimensions of the cross-section are considered as the main design variables, while the EC3 plate dimensions and slenderness limits and a number of manufacturing and end-use constraints are taken into account in the optimisation process. The results show that the optimum CFS sections exhibit significantly higher (up to 84%) ultimate capacity compared to the standard lipped channel sections with the same plate width and thickness. The structural level optimisation is then carried out to obtain the optimal design solution for a long-span CFS portal frame with knee braces under SLS and ULS conditions. Compared to conventional optimisation using standard cross-sections, it is shown that the proposed coupled framework leads to more cost-effective solutions (up to 20% less structural material) by using the more efficient CFS cross-sectional shapes optimised for generic applications. The results also indicate that optimising the frame geometry and knee brace configuration can noticeably improve the structural performance and reduce the required structural weight, especially when both ULS and SLS conditions are considered

Coupled element and structural level optimisation framework for cold-formed steel frames

Optimisation of cold-formed steel (CFS) structures can be challenging due to the complex behaviour of thin-walled CFS sections affected by different buckling modes. In this paper, a coupled framework is presented for element and structural level optimisation of CFS portal frames, under serviceability limit state (SLS) and ultimate limit state (ULS) conditions, using Genetic Algorithm. First, CFS lipped-channel beam sections are optimised with respect to their flexural capacity determined in accordance with the effective width method specified in Eurocode 3 (EC3). The relative dimensions of the cross-section are considered as the main design variables, while the EC3 plate dimensions and slenderness limits and a number of manufacturing and end-use constraints are taken into account in the optimisation process. The results show that the optimum CFS sections exhibit significantly higher (up to 84%) ultimate capacity compared to the standard lipped channel sections with the same plate width and thickness. The structural level optimisation is then carried out to obtain the optimal design solution for a long-span CFS portal frame with knee braces under SLS and ULS conditions. Compared to conventional optimisation using standard cross-sections, it is shown that the proposed coupled framework leads to more cost-effective solutions (up to 20% less structural material) by using the more efficient CFS cross-sectional shapes optimised for generic applications. The results also indicate that optimising the frame geometry and knee brace configuration can noticeably improve the structural performance and reduce the required structural weight, especially when both ULS and SLS conditions are considered

Long-span cold-formed steel single C-section portal frames

This thesis presents a comprehensive study of long-span cold-formed steel single C-section portal frames. The study includes the formulation of a nonlinear beam finite element for thin-walled sections, a series of full-scale frame tests and component tests, finite element modelling and advanced analysis followed by the formulation of design guidelines. The study was aimed at exploring the structural behaviour through experiment and numerical analysis towards developing provisions for the design of cold-formed steel portal frames using Advanced Analysis. A nonlinear thin-walled beam element for general open cross-sections was formulated, incorporating warping effect and non-coincident location of the shear centre and the centroid. It was successfully implemented in the geometric nonlinear analysis framework of the OpenSees finite element software. Towards investigating the behaviour and determining the ultimate strength, six full-scale tests on cold-formed steel single C-section portal frames were conducted. Separate tests were performed on frame connections, point-fastener connections and coupons to obtain the material parameters required for numerical modelling. Advanced shell finite element models of the full-scale frames and frame connections were created and validated against experimental results. The bolts and screws used for the connections between components were represented by point-based deformable fasteners. The force-deformation characteristics of the deformable fasteners were incorporated and successfully implemented in the Advanced Analysis. The strength of cold-formed steel single C-section portal frames determined by the Direct Strength Method and the Direct Design Method were compared. To account for inherent uncertainties in the strength of CFS portal frames, system resistance factors were derived. It was concluded that the Direct Design Method using Advanced Analysis is the likely future method for the design of cold-formed steel portal frames