The main objective of this research is to extend the “Direct strength method” for determining the web crippling strength of cold-formed steel C and Z sections subjected to End one flange loading and Interior one flange loading conditions. Direct strength method is applied for designing the columns and beams earlier. The existing specifications equation for calculating the web crippling strength of cold-formed steels designed by American Institute of Iron and Steel is very old method and it is based on the extensive experimental investigations conducted at different universities. Calculating the web crippling strength of cold-formed steels using direct strength method is a new technique. In the present research the web crippling strength of cold-formed steels were calculated using Direct Strength Method. The experimental data is collected from the tests that were conducted at different universities. The critical buckling strength of the members were calculated using Abaqus. Microsoft excel is used to generate the equations. The safety and resistance factors for the designed equations were calculated using “Load and resistance factor design” and “Allowable strength design” from North American Cold-Formed Steel Specification, 2012 edition book.

This thesis presents experiments and numerical analysis of the cold-formed steel clip angle in three different limit states which are shear, compression, and combination of the screw connection. A previous cold-formed steel clip angle test program (which is Phase 1) developed design methods for clip angle. Therefore, the object of this thesis is to further investigate the behavior and design methods of loading-bearing cold-formed steel clip angles under different screw pattern. For each limit state, a test program was conducted to investigate the behavior, strength, and deflection of the clip angle. The test result were compared with previous CFS clip angle design method. Amending existing CFS clip angle method were developed by each of the four limit states studied in this project.

No description available.

This thesis presents a research project aimed at advancing the treatment of cold-formed steel (CFS) structural reliability in roof trusses. Structural design today relies almost exclusively on component-level design, so structural safety is assured by limiting the probability of failure of individual components. Reliability of the entire system is typically not assessed, so in a worst-case scenario the system reliability may be less than the component reliability, or in a best-case scenario the system reliability may be much greater than the component reliability. A roof truss itself, is a subsystem with several possible failure modes that are being studied in this test program. These trusses are constructed of CFS members that nest with one another at the truss nodes and are connected by drilling fasteners through the mated surfaces, as well as having steel sheathing fastened to the top chords for lateral bracing. Presented in this paper is a series of full-scale static tests on single cold-formed steel roof trusses with a unique experimental setup. The test specimens were carefully monitored to address multiple failure modes: buckling of the top chord, buckling of the truss webs, and any connection failures. This research includes the experimental results, the computed system reliability of the trusses as well as their relationship between the components reliability.

M.Ing. / During all manufacturing processes it is crucial to use certain design criteria and guidelines. Special care should be exercised when the final product of a manufacturing process is used in the automotive industry, because the failure of such a component may have tragic consequences. The failure of a bus chassis in the public transport sector is an example of a case where the failure of a product can have serious consequences. In recent years it has become common practice to use corrosion-resisting steel in the manufacture of these vehicles. The reason for this is the corrosion caused by a prolonged service life and adverse conditions such as salted road surfaces (The salt is used to melt the ice that forms on roads, particularly in European countries). These bus structures consist of tubes of varying size and geometry, and the manufacturing process of these tubes is considered in the present investigation. In a tube manufacturing process the design criteria may consist of such properties as the tube size and geometry, the thickness of the sheet that is used and the radius of the corners of the tube. Design criterion is also dependent upon the material that is used. The change in mechanical properties of the material during a manufacturing process is an important consideration during the establishment of design guidelines. The purpose of this investigation is to study the effects of particularly the cold forming manufacturing process on the mechanical properties of the material. The material used is 3CR12 corrosion resisting steel, a proprietary alloy also known as Type 1.4003, that was developed by Columbus joint venture as a cheaper alternative to stainless steels. 3CR12 is not a substitute for stainless steel but it is an alternative to treated mild steel, providing a cost-effective solution to corrosion. An experimental investigation is conducted into the forming of 40mm 3CR12 square tubes and normal plate bending of 3CR12. Various different wall thicknesses and bend radiuses are considered. A numerical investigation consisted of simulating the above-mentioned manufacturing processes using non-linear finite element analysis and then comparing its results to the experimental investigation. The experimental investigation showed that substantial work hardening occurred in the corner regions of the tube during forming. A loss of up to 70% of 3CR12's ductility may result in the corner regions. The work hardening at the inside of the tube was found to be higher than at the outside. A region of very little work hardening near the middle of the tube wall thickness was also identified (neutral axis). This neutral axis also seems to shift slightly more to the inside of the tube with thicker wall sections. The numerical analysis confirmed the experimental observations. An excellent correlation between the experimental and numerical results was achieved.

In this research, monotonic and cyclic tests on cold-formed steel shear walls sheathed with steel sheets on one side were conducted to (1) verify the published nominal shear strength for 18-mil and 27-mil steel sheets; and (2) investigate the behavior of 6-ft. wide shear walls with multiple steel sheets. In objective 1: this research confirms the discrepancy existed in the published nominal strength of 27-mil sheets discovered by the previous project and verified the published nominal strength of 18 mil sheet for the wind design in AISI S213. The project also finds disagreement on the nominal strength of 18-mil sheets for seismic design, which is 29.0% higher than the published values. The research investigated 6-ft. wide shear wall with four framing and sheathing configurations. Configuration C, which used detailing, could provide the highest shear strength, compared to Configurations A and B. Meanwhile, the shear strength and stiffness of 2-ft. wide and 4-ft. wide wall can be improved by using the seismic detailing.

This thesis presents two major sections with the objective of introducing a new cold-formed steel (CFS) shear wall system with corrugated steel sheathings. The work shown herein includes the development of an optimal shear wall system as well as an optimal slit configuration for the CFS corrugated sheathings which result in a CFS shear wall with high ductility, high strength, high stiffness and overall high performance. The conclusion is based on the results of 36 full-scale shear wall tests performed in the structural laboratory of the University of North Texas. A variety of shear walls were the subject of this research to make further discussions and conclusions based on different sheathing materials, slit configurations, wall configurations, sheathing connection methods, wall dimensions, shear wall member thicknesses, and etc. The walls were subject to cyclic (CUREE protocol) lateral loading to study their deformations and structural performances. The optimal sit configuration for CFS shear walls with corrugated steel sheathings was found to be 12×2 in. vertical slits in 6 rows. The failure mode observed in this shear wall system was the connection failure between the sheathing and the framing members. Also, most of the shear walls tested displayed local buckling of the chord framing members located above the hold-down locations. The second section includes details of developing a Finite Element Model (FEM) in ABAQUS software to analyze the lateral response of the new shear wall systems. Different modeling techniques were used to define each element of the CFS shear wall and are reported herein. Material properties from coupon test results are applied. Connection tests are performed to define pinching paths to model fasteners with hysteretic user-defined elements. Element interactions, boundary conditions and loading applications are consistent with full scale tests. CFS members and corrugated sheathings are modeled with shell elements, sheathing-to-frame fasteners are modeled using nonlinear springs (SPRING2 elements) for monotonic models and a general user defined element (user subroutine UEL) for cyclic models. Hold-downs are defined by boundary conditions. A total of three models were developed and validated by comparing ABAQUS results to full scale test results.

This thesis presents a research effort aimed at developing a stronger, lighter, and more economic shelter using rigid wall panels. Reported herein is insulation research, wall and roof panel design and testing, floor section modeling and strength calculations, and cost and weight calculations. Beginning stages focus on developing solid wall and roof panels using cold-formed steel corrugated sheathing and members, as well as polyurethane spray foam for insulation. This research includes calculating uniform load density, to determine the overall strength of the panel. The next stage focuses on the flexural strength of the wall and roof panels, as well as finalizing the floor design for the shelter. This includes determining maximum flexural strength required to meet the standards set by the project goal. Direct strength method determined the correct thickness of members to use based on the dimension selected for the design. All Phases incorporated different connection methods, with varied stud spacing, to determine the safest design for the new shelters. Previous research has shown that cold-formed steel corrugated sheathing performs better than thicker flat sheathing of various construction materials, with screw and spot weld connections. Full scale shear wall tests on this type of shear wall system have been conducted, and it was found that the corrugated sheathing had rigid board behavior before it failed in shear buckling in sheathing and sometimes simultaneously in screw connection failures. Another aspect of the research is on the insulation of the wall panels. Research was conducted on many different insulation options for the mobile facilities. Specifically, insulation made of lightweight material, is non-combustible, added rigidity to the structure, and has high thermal properties. Closed cell polyurethane spray foam was selected for full-scale testing in this research. Closed cell polyurethane adds extra rigidity, is lighter than common honeycomb insulation, and has a higher R-value. Several polyurethane foam companies were studied for this research, and promising products were identified. The research focuses on the impacts of the polyurethane foam to the structural performance of the wall panels. Both shear and 4-point bending tests were completed to investigate the strength and behavior of the cold-formed steel framed wall panels with polyurethane foam insulation. Comparing the cost and weight of the current shelter, and the new design is reported herein. The material studies, specimen details, and test results are reported in this thesis.

University of Macau / Faculty of Science and Technology / Department of Civil and Environmental Engineering

The research was focused on the three major structural elements of a typical cold-formed steel building - shear wall, floor joist, and column. Part 1 of the thesis explored wider options in the steel sheet sheathing for shear walls. An experimental research was conducted on 0.030 in and 0.033 in. (2:1 and 4:1 aspect ratios) and 0.027 in. (2:1 aspect ratio) steel sheet shear walls and the results provided nominal shear strengths for the American Iron and Steel Institute Lateral Design Standard. Part 2 of this thesis optimized the web hole profile for a new generation C-joist, and the web crippling strength was analyzed by finite element analysis. The results indicated an average 43% increase of web crippling strength for the new C-joist compared to the normal C-joist without web hole. To improve the structural efficiency of a cold-formed steel column, a new generation sigma (NGS) shaped column section was developed in Part 3 of this thesis. The geometry of NGS was optimized by the elastic and inelastic analysis using finite strip and finite element analysis. The results showed an average increment in axial compression strength for a single NGS section over a C-section was 117% for a 2 ft. long section and 135% for an 8 ft. long section; and for a double NGS section over a C-section was 75% for a 2 ft. long section and 103% for an 8 ft. long section.