A prototype rigid wall relocatable shelter was designed and constructed using cold-formed steel (CFS) construction techniques including shear walls with corrugated sheathings. The design of the shelter was to be mechanically sound with adequate thermal performance and resistance to corrosion. Modeling of structural shear walls was performed using ABAQUS and verified with experimental results. At the project's conclusion, a completed full-scale prototype shelter was constructed.

The use of cold-formed steel (CFS) structures has become increasingly popular in different fields of building technology. For example, small housing systems using cold-formed steel for wall structures, framing systems and roof structures, including trusses and shielding materials, have been developed during recent years. The reasons behind the growing popularity of these products include their ease of fabrication, high strength/weight ratio and suitability for a wide range of applications. These advantages can result in more cost-effective designs, as compared with hot-rolled steel, especially in short-span applications. It has been common practice in cold-formed steel construction to cut openings in the web of beams for the passage of service ducts and piping. The provision of such openings reduces the story heights and consequently can result in saving of considerable amount of construction materials. On the other hand, the presence of a large web opening causes localized redistribution of stress around the opening region. The large opening causes loss of strength and changes the buckling characteristics of an entire member. It also affects the flexural stiffness, resulting in poor performance of member under serviceability. It is common practice to reinforce the opening of hot-rolled steel members, but proper reinforcement schemes for CFS perforated members has not been established yet. Various reinforcement schemes for cold-formed steel sections were investigated during this study. Two types of reinforcement schemes (for flexural zones and shear zones) were developed. Fifty-four flexural tests and 33 shear tests were conducted. Two types of sections (lipped channel joists with h/t ratio 180 and 118) were tested in flexure and one type of section (lipped channel joists with h/t ratio 180) was tested in shear. The study also included a finite element based numerical investigation, consisting of parametric studies on the size (web depth and thickness) of joists, size and shape of web openings, reinforcement and associated fastening schemes. It was observed that a 75 percent of opening in the web of CFS channel joist causes up to 25 percent reduction in flexural strength and up to 60 percent reduction in shear strength. Such reduced flexural and shear strengths were re-captured by providing proper reinforcement schemes. The flexural reinforcement schemes recommended by the current AISI Standard were found to be ineffective for the sections having low w /t ratios. Bridging channel reinforcement scheme was also considered in this study. Bridging channel reinforcement scheme was capable of restoring the flexural strength of cold formed steel joist having w /t ratios 118 and 180. Similarly, the reinforcement schemes recommended in AISI Standard were not adequate to restore the shear strength of joist sections. A newly developed Virendeel type reinforcement system was capable of restoring the original shear strength of a cold-formed steel joist section. / Thesis / Doctor of Philosophy (PhD)

Master of Science / Department of Architectural Engineering and Construction Sciences / Kimberly Waggle Kramer / Bill Zhang / Cold-formed steel members quickly are becoming a popular material for both commercial and residential construction around the world. Their high strength to weight ratio makes them a viable alternative to timber framing. In most cases cold-formed steel is used as a repetitive member in floor, wall, or roof assemblies. Structural sheathing is used in conjunction with the framing members in order to transfer loads between individual members. This sheathing is connected mechanically to the cold-formed steel through a variety of methods. The most common method uses screws spaced at close intervals, usually between 6 to 12 inches on center. When such assemblies are constructed, load is transferred from the sheathing through the connectors into the cold-formed steel, forming a composite assembly in which load is transferred and shared between two materials, providing a higher strength and stiffness over individual members themselves. The amount of load that can be transferred is dependent on the amount of slip that occurs when the assembly is loaded. This slip value describes the amount of composite action that takes place in the assembly. The amount of slip can be described by a value called the slip modulus. The composite, or effective, bending stiffness can be calculated using the slip modulus. In current design of cold-formed steel composite assemblies this composite action is not being taken into account due to a lack of research and understanding of the composite stiffness present in these assemblies. Taking composite action into account can lead to decreased member sizes or increased spacing of members, thereby economizing design. Furthermore, improved understanding of the effective stiffness can lead to more accurate design for vibrations in floor systems. This thesis tests cold-formed steel plywood composite members in an effort to verify previously established slip modulus values for varying steel thicknesses and establishes new values for varying fastener spacings. The slip modulus values obtained are used to calculate effective bending stiffness values in an effort to prove that composite action should be utilized in design of cold-formed steel composite assemblies.

Master of Science / Civil Engineering / Hani G. Melhem / Bill Zhang / Composite action is the joint behavior of two elements connected or bonded together. It is a phenomenon that is utilized in several applications throughout engineering. Previous studies have shown that cold formed steel (CFS) sheathed with structural wood panels exhibits a degree of partial composite action behavior. However currently in the design process, CFS and wood sheathing systems are considered separately in a non-composite manner due to the absence of sufficient supporting data. These systems can include the floors, roofs, and walls of a building. In order to determine the level of composite action present, the slip modulus is needed. The slip modulus describes the relationship between the shear force and the displacement exhibited by two elements in a composite system. The scope of this research is to determine the influence of fastener spacing on the slip modulus and provide a foundation of information to fully define the composite action between CFS and wood sheathing.

In recent years, light gauge cold-formed steel members have been used extensively in low and mid- rise residential building construction. In cold-formed steel design there are several applications where built-up box girders are used to resist load induced in a structure when a single section is not sufficient to carry the design load. The cold-formed steel box girders may be subjected to eccentric loading when the web of one of the sections receives the load and transfers it through the connection to another section. There may be an unequal distribution of load in built-up girder assemblies loaded from one side. In the current North American Specification for the Design of Cold-Formed Steel Structural Members (CSA-S136-01, 2001), there is no guideline or design equation to calculate the flexural capacity of this type of section. AISI cold-formed steel framing design guide (2002) has recommended that the moment of resistance and inertia of the built-up section are the simple addition of the component parts, based on deflection compatibility of the two sections. However, this design approximation has not been justified by any experimental or numerical study. Very little information was found in literature about this topic. The objective of this study is the investigation of the flexural behaviour of built-up box girders assembled from cold-formed stud and track sections when subjected to eccentric loading. Finite element analysis is conducted for this purpose, being much more economical than expensive experimental testing. Detailed parametric studies are carried out to identify the factors affecting the flexural capacity of built-up cold-formed steel sections. The parametric results are used to develop a design equation for calculating the flexural capacity of built-up cold-formed steel sections.

Vibrations associated with lightweight floor systems, as a serviceability criterion, are not well addressed in current residential construction practice. Cold-formed steel floor systems are usually lighter and have less inherent damping. If designers are going to use the current span deflection criteria when designing residential floor systems, it is imperative to find the construction and design details that will limit these annoying vibrations in cold-formed steel floor systems. Presented in this seminar are the results from a recent laboratory study and field study on the vibration characteristics of cold-formed steel floors performed at the University of Waterloo. Several full-scale floor systems with varying construction and design details were constructed and tested, and several in situ floor systems were tested. The objectives of this research were: to evaluate the dynamic response of residential floor systems supported by cold-formed steel joists; to investigate the influence of span length, joist types, subfloor materials, toppings, ceilings, strongbacks, live loads and framing conditions on the vibration characteristics of cold-formed steel floor systems; to identify the critical construction details that will limit annoying floor vibrations; to compare the vibration characteristics of in situ floor systems and laboratory constructed floor systems; and to evaluate the vibration performance of laboratory and in situ floor systems based on current acceptability criteria.

Cold-formed steel structural members are used extensively in building construction, with a common application being wind load bearing steel studs. The studs frame into horizontal steel track members at the top and bottom of the wall assembly, with the stud-to-track connection typically being made with self-drilling screws or welds. The wall studs are designed to carry lateral loads only and must be checked for web crippling at the end reactions. While a design expression currently exists for the single stud-to-track connection, there is no similar design expression for multiple jamb stud members. An experimental investigation was carried out, consisting of 94 jamb stud assembly tests subjected to end-one-flange loading. The stud-to-track connections consisted of single C-section studs located at the end of a track simulating a door opening, and a built-up jamb made up of two studs simulating framing at either a window or door opening. The members were attached to the track with self-drilling screws. The research objective was to determine the failure modes and develop a design expression for these structural assemblies. The scope of the experimental investigation covered the following range of parameters: i) Stud and track depths of 92 mm and 152 mm; ii) Stud and track thickness (0.84 mm, 1.12 mm, 1.52 mm and 1.91 mm); iii) Configuration of jamb studs (back-to-back, toe-to-toe and single); iv) Location of jamb studs in the track (interior and end); v) Screw size (#8, #10 and #12); vi) Screw location (both flanges and single flange). Based on the findings of this investigation, design expressions are proposed to predict the capacity of this connection for two limit states: web crippling of the jamb stud; and, punch-through of the track. The web crippling design expression was taken from the North American Specification for the Design of Cold-Formed Steel Structural Members [AISI 2007a; CSA 2007] with new coefficients developed from the test data of the jamb stud-to-track assemblies. A new design expression is also proposed for the track punch-through failure mode, which differs from the approach currently used in the North American Standard for Cold-Formed Steel Framing – Wall Stud Design [AISI 2007b]. A proposal is also recommended to revise the wording in the North American Standard for Cold-Formed Steel Framing – Wall Stud Design [AISI 2007b] to include provisions for the design of jamb studs based on the results of this research.

In recent years, light gauge cold-formed steel members have been used extensively in low and mid- rise residential building construction. In cold-formed steel design there are several applications where built-up box girders are used to resist load induced in a structure when a single section is not sufficient to carry the design load. The cold-formed steel box girders may be subjected to eccentric loading when the web of one of the sections receives the load and transfers it through the connection to another section. There may be an unequal distribution of load in built-up girder assemblies loaded from one side. In the current North American Specification for the Design of Cold-Formed Steel Structural Members (CSA-S136-01, 2001), there is no guideline or design equation to calculate the flexural capacity of this type of section. AISI cold-formed steel framing design guide (2002) has recommended that the moment of resistance and inertia of the built-up section are the simple addition of the component parts, based on deflection compatibility of the two sections. However, this design approximation has not been justified by any experimental or numerical study. Very little information was found in literature about this topic. The objective of this study is the investigation of the flexural behaviour of built-up box girders assembled from cold-formed stud and track sections when subjected to eccentric loading. Finite element analysis is conducted for this purpose, being much more economical than expensive experimental testing. Detailed parametric studies are carried out to identify the factors affecting the flexural capacity of built-up cold-formed steel sections. The parametric results are used to develop a design equation for calculating the flexural capacity of built-up cold-formed steel sections.

Vibrations associated with lightweight floor systems, as a serviceability criterion, are not well addressed in current residential construction practice. Cold-formed steel floor systems are usually lighter and have less inherent damping. If designers are going to use the current span deflection criteria when designing residential floor systems, it is imperative to find the construction and design details that will limit these annoying vibrations in cold-formed steel floor systems. Presented in this seminar are the results from a recent laboratory study and field study on the vibration characteristics of cold-formed steel floors performed at the University of Waterloo. Several full-scale floor systems with varying construction and design details were constructed and tested, and several in situ floor systems were tested. The objectives of this research were: to evaluate the dynamic response of residential floor systems supported by cold-formed steel joists; to investigate the influence of span length, joist types, subfloor materials, toppings, ceilings, strongbacks, live loads and framing conditions on the vibration characteristics of cold-formed steel floor systems; to identify the critical construction details that will limit annoying floor vibrations; to compare the vibration characteristics of in situ floor systems and laboratory constructed floor systems; and to evaluate the vibration performance of laboratory and in situ floor systems based on current acceptability criteria.

Cold-formed steel structural members are used extensively in building construction, with a common application being wind load bearing steel studs. The studs frame into horizontal steel track members at the top and bottom of the wall assembly, with the stud-to-track connection typically being made with self-drilling screws or welds. The wall studs are designed to carry lateral loads only and must be checked for web crippling at the end reactions. While a design expression currently exists for the single stud-to-track connection, there is no similar design expression for multiple jamb stud members. An experimental investigation was carried out, consisting of 94 jamb stud assembly tests subjected to end-one-flange loading. The stud-to-track connections consisted of single C-section studs located at the end of a track simulating a door opening, and a built-up jamb made up of two studs simulating framing at either a window or door opening. The members were attached to the track with self-drilling screws. The research objective was to determine the failure modes and develop a design expression for these structural assemblies. The scope of the experimental investigation covered the following range of parameters: i) Stud and track depths of 92 mm and 152 mm; ii) Stud and track thickness (0.84 mm, 1.12 mm, 1.52 mm and 1.91 mm); iii) Configuration of jamb studs (back-to-back, toe-to-toe and single); iv) Location of jamb studs in the track (interior and end); v) Screw size (#8, #10 and #12); vi) Screw location (both flanges and single flange). Based on the findings of this investigation, design expressions are proposed to predict the capacity of this connection for two limit states: web crippling of the jamb stud; and, punch-through of the track. The web crippling design expression was taken from the North American Specification for the Design of Cold-Formed Steel Structural Members [AISI 2007a; CSA 2007] with new coefficients developed from the test data of the jamb stud-to-track assemblies. A new design expression is also proposed for the track punch-through failure mode, which differs from the approach currently used in the North American Standard for Cold-Formed Steel Framing – Wall Stud Design [AISI 2007b]. A proposal is also recommended to revise the wording in the North American Standard for Cold-Formed Steel Framing – Wall Stud Design [AISI 2007b] to include provisions for the design of jamb studs based on the results of this research.