PUBLICATIONS -- ABSTRACTS

M.Sc. Thesis Completed:

Cold Formed Steel Hat Sections in Bending with Multiple Intermediate Longitudinal Stiffeners

by V.V. Acharya

It is well known that hat sections with multiple intermediate stiffeners can fail either in a local sub-element buckling mode or alternatively, can experience an overall plate buckling mode of failure. Although both failure modes were examined, the main objective was to develop a consistently accurate and practical method of predicting the ultimate bending strength of sections which failed in overall plate buckling.
94 tests were carried out, encompassing a range of section dimensions and material properties. All test specimens were simply supported and subjected to uniformly distributed vacuum loading. The test program consisted of hat sections that failed primarily in overall plate buckling and in a few cases also in local sub-element buckling of the compression flange. Based on the work by Lind, which is shown to adequately predict the strength of sections that experience overall plate buckling, an alternate design method for strength determination is presented.

Optimal Design of Cold-Formed Steel Roof Trusses

by H. Min

A computer-based system is developed for the optimal design of cold-formed steel roof truss subject to member resistance and deflection criteria with the consideration of current design practice. CSA136-94 (CSA, 1994) and the Cold-formed Steel Truss Design Guides (CSSBI, 1997, AISI, 1999) are incorporated in the computer-based system. A non-penalty genetic algorithm (GA) is employed to search for the optimal truss type, panel number, panel point coordinate and member sizes. The two types of design variables used in the optimization process are the variables associated with truss configuration and the variables associated with truss member sizes. All the design variables have discrete values. The functions implemented in the cold-formed steel truss design computer program include structure analysis, design verification, topology design optimization, shape design optimization, panel point coordinate optimization and member size design optimization.

Vibrations of Floor Supported by Cold-Formed Steel Joists

by W. Liu

In this study, floor vibration in residential buildings supported by cold-formed steel joists is studied by experimental testing, finite element analysis, and the equivalent plate method. Several full-scale floor systems with different details are tested. Two models are employed in the finite element study. An equivalent plate method for rib-stiffened plates is proposed to determine the frequencies and the deflections of the floor system. To determine which one best predicts the deflections and frequencies of such floor system, the test results were compared with that determined from the following methods: the finite element method, the CWC and ATC design criteria, and the equivalent plate method.

M.Sc. Projects Completed:

Yield Strength Increase of Cold Formed Sections Due to Cold Work of Forming

P.A, Sloof

The design approach in predicting the increase in yield strength due to cold work of forming in the AISI 1996 Cold-Formed Specification is different from the approach used in the CSA S136-94 Standard on the design of Cold Formed Steel Structural Members. The AISI approach is based on the experimental work completed principally by Karren and Winter, while the S136 approach is based on the theoretical work by Lind and Schroff. Twelve different sections were tested as part of the test program. Strength data was collected on virgin material, on full sections and on the flat section elements, thus providing comparisons to be made using only experimental data. The main purpose for this investigation was to help answer two questions, i.e., 1) should the average yield strength in the flats after forming be allowed in either approach? and 2) is there a simplified expression, such as a modified S136 approach, that would produce similar results with fewer inputs.

Web Crippling of Single Web Cold Formed Steel Members Subjected to End One-Flange Loading

R.R. Gerges

The focus of this study was devoted to the web crippling behavior of cold formed steel C-sections subjected to end one-flange (EOF) loading, with particular emphasis on large inside bend radius to thickness ratios. Seventy-two C-sections with R values ranging between 5 and 10 were tested. Comparing the experimental results with predictions using the 1996 edition of the AISI Specification for the design of cold formed steel structural members, considerable underestimation was observed in web crippling strength. Using the test data and the web crippling method contained in the Canadian Standard (S136-94), new coefficients for the EOF design expression of single web members have been developed. Also, calibrations were carried out for the safety requirements of both the Canadian Standard (S136-94) and the AISI-96 Specification.

Web Crippling of Single Web Cold Formed Steel Members Subjected to End and Interior Two Flange Loading

B. Beshara

The primary objective of this study was to carry out an experimental investigation of cold formed steel stiffened C-and Z sections subjected to web crippling. Two different loading conditions were investigated, i.e., 1) end two flange (ETF) loading and 2) interior two flange (ITF) loading. Particular emphasis was placed on large inside bend radius to thickness ratios, R, (up to 12) with the specimens being fastened to the support during testing. There is no experimental data available in the literature regarding the web crippling resistance of such members that are fastened to the support and have inside bend radius to thickness ratios greater than 2.7. A total of 72 tests were conducted on C-and Z sections. The test results were compared to the predicted values of the AISI-96 and the S136-94 web crippling design equations. Using the same model of the web crippling design expression currently used in S136-94, new web crippling coefficients for the ETF and ITF loading conditions for both C and Z-sections were established. Calibrations were also carried out for the safety requirements of both the Canadian Standard (S136-94) and the AISI-96 Specification.

Evaluation of Different Floor Vibration Criteria for Cold-Formed Steel Residential Construction

by U. Rizwan

This project provides a comparative study of the following four design methods for the control of vibration in cold-formed steel residential floor construction: a) Applied Technology Council (ATC) design method; b) Canadian Wood Council (CWC) design method; c) Ohlsson design method; and d) Smith and Chui design method. The results of experimental tests conducted at the Virginia Polytechnic Institute and State University and at the University of Waterloo were used to evaluate the performance of these design methods. The frequency and deflection of the floors, tested at the two universities, were computed by these design methods and compared with the actual test results. The limitations associated with the application of these design methods to cold-formed steel joists supported floors are highlighted.

Semi-Rigid Connection in Cold-Formed Steel Truss

by Z. Wu

Current design practice idealized web-to-chord connections of cold-formed steel truss as pinned connections. With this adoption of such idealized connection behaviour, the analysis and design process of truss is highly simplified. However, most connections used in practice transmit some moment and experience some deformation upon loading. The recent revision on AISI Cold-Formed Steel Truss Design Guide permits connection flexibility to be taken into account in the analysis and design of truss. But no specific guideline on how to incorporate the connection flexibility into the process of truss analysis and design were provided primarily due to the lack of information on the behaviour of such connection. Experimental tests on C-shape web-to-chord connection were conducted, the nonlinear moment-rotation behaviour of the connection was determined. A mathematical model is developed to represent such connection behaviour. The generated model gives a close representation of the experimentally obtained moment-rotation relationship for the connections investigated.

M.Sc. Thesis in Progress:

A Design Procedure for Floors Supported by Cold Formed Steel Joists

by F.M. Tangorra

At present, various design methods exist to predict the deflection and frequency of a floor system. However, most of them are based on experiments done on wood floor systems. Presented in this thesis will be a new design method to evaluate the fitness of a residential lightweight floor system (i.e.: supported by cold formed steel joists) in order to prevent harmful and uncomfortable vibrations. The design method will be based on an analytical analysis and several full-scale laboratory and field tests.

Web Crippling of Multi-web Deck Sections Subjected to End One Flange Loading

by J. Wallace

Currently almost no data exists in the published literature regarding web crippling of multi-web deck sections subjected to end one flange loading. The object of this research is to establish the required data for this geometric section type and load condition. Using this data, the appropriate web crippling coefficients will be determined in accordance with the web crippling expression developed by Prabakaran at the University of Waterloo. The necessary calibrations will also be carried out to establish the resistance factors and respective factors of safety to be used in the North American Cold Formed Steel Design Standard.
This research is jointly sponsored by the Canadian Sheet Steel Building Institute and the Steel Deck Institute.