Civil Engineering Study 85-1
I. INTRODUCTION A. GENERAL In the past few years, a dramatic increase in the use of high strength sheet steels in automobiles has been brought about by the demand for improved fuel economy and safety of motor vehicles. Many of the automotive structural components, which are made of high strength sheet. steels, consists either partially or totally of curved elements. Therefore, it was decided to include an investigation into the structural behavior of curved elements as a part of a research project entitled, "Structural Design of Automotive Structural Components Using High Strength Sheet Steels." The research project began in early 1982 at the University of Missouri-Rolla (U~m) under the sponsorship of the American Iron and Steel Institute (AISI). However, work did not begin on the curved element investigation until the spring of 1983. In August, 1983, the Fourth Progress Report of the research project entitled, "Preliminary Study of Members Consisting of Flat and Curved Elements 1", was published. Included in this report was a review of all available literature on the behavior of curved elements as well as a tentative plan for an experimental investigation. The Sixth Progress Report of the research project entitled, "Status Report on the Study of Members Consisting of Flat and Curved Elements2" , was published 'in October, 1984. The Sixth Report contained an updated review of the literature along with a more definitive plan 2 for the experimental study. Particular emphasis was placed on the stub column testing, which had just begun at the time of printing. Since the publication of the Sixth Progress Report, all of the prop~sed stub column tests (36) have been performed. However, there have been a few changes in the originally proposed experimental program. After close examination of the first few stub column tests, it was observed that, in some cases, the web actually buckled before the curved flanges. In order to prevent premature web buckling, vertical bracing was added to the web of approximately half of the stub column specimens. Therefore, no web buckling could occur in these sections. Since an investigation of the case in which the web buckled early also seemed desirable, the web was left unbraced on the remainder of the specimens. Thus, two types of failure patterns were studied for the stub column tests. First, the originally planned case in which the curved flange failed initially was investigated. Also studied was the interaction between the web and the curved flanges when the web buckled before the flange. B. SCOPE OF INVESTIGATION The primary purpose of this report is to discuss the research work that has been done on the study of curved elements since the issuance of the Sixth Progress Report. Section II of the report summarizes the current status of the curved element research. Section III.A presents Redshaw's Equation (with some modification) and also an empirical equation determined by regression analysis of the stub column data. These equations are used to predict the local buckling strength of curved elements subjected to 3 uniform compression. Also discussed is an approximate procedure (Air Force Method) for predicting the total buckling load for sections consisting of flat and curved elements. Finally, a very brief discussion of the finite strip method, which might be useful for the prediction of curved element buckling, is presented. Section III.B.! describes the experimental program for the stub column specimens. In Section III.B.2, an evaluation of the stub column test results is given. An outline is proposed in Section IV for the design of cross-sections consisting of flat and unstiffened curved elements. Finally, a general summary of the curved element research is presented in Section V.
Civil, Architectural and Environmental Engineering
American Iron and Steel Institute
Wei-Wen Yu Center for Cold-Formed Steel Structures
Missouri University of Science and Technology
© 1985 Missouri University of Science and Technology, All rights reserved.
Report - Technical
Yu, Wei-wen and Parks, M. Brad, "Design of automotive structural components using high strength sheet steels - results and evaluation of stub column tests for unstiffened curved elements" (1985). Center for Cold-Formed Steel Structures Library. 189.