Bolted connections in cold-formed steel structures

INTRODUCTION A. Purpose of Investigation. The design of bolted connections in cold-formed steel structures is based on the present AISI Specification for the Design of Cold-Formed Steel Structural Members. 1 Prior to the development of the design criteria, bolted connections were tested at University of Michigan 2 in the 1940\u27s and then at Cornell University 3,4 in the 1950\u27s. The present design provisions were developed primarily on the basis of the tests conducted by George Winter and his associates at Cornell University. Additional tests were recently made by Popowich 5 on multi-bolt connections and by Dhalla 6 on connections with low ductility steels. In these tests, the specimens were tightened to specified torques, and washers were placed under the head and nut of each bolt. During recent years, bolted connections without washers have often been used in numerous instances. In some cases, the washers were used in the connections, but the bolts may not have been tightened according to the torques previously used in the Cornell tests. In order to study the effect of washers on connection strengths, Chong and Matlock 7 have conducted connection tests with and without washers. It was found that the bearing strengths of the connections were reduced considerably when the washers were eliminated. In addition, the parameters used by Chong and Matlock for evaluation of the tensile strength of bolted connections were slightly different from those used in the AISI Specification. It is the purpose of this investigation to review the available test data first and then to study the applicability of the present design formulas to the connections that do not have washers and/or have improper torques. Thin sheets will be used to make an additional study of the connection strength affected by the pretension of bolts and the behavior of bolted connections. In the study carried out to date, additional parameters, such as d/t and Fu/Fy ratios, have been considered for the evaluation of the connection strength. B. Scope of Investigation The present research project consists of an investigation of the structural behavior of bolted connections, a review of the current design criteria, and the conduct of additional tests to provide new design information if necessary. The following items have been planned for inclusion in this study: 20 1) Analysis of available data 2) Effect of torque or pretension in bolts on bearing strength 3) Tensile strength of connections 4) Effect of d/t ratio on bearing strength, longitudinal shearing strength,and tensile strength of steel sheets 5) Difference between single shear and double shear conditions. In order to achieve the objectives of the investigation, the planned research work includes the following three phases: 20 1) Analysis of available data 2) Analytical and experimental investigation 3) Preparation of recommendations Phase 1 of the investigation was initiated in February 1976. It was carried out by Randall L. Mosby, Research Assistant, and directed by Dr. Wei-Wen Yu, Professor of Civil Engineering at the University of Missouri-Rolla. Phases 2 and 3 will be conducted in future studies. This progress report contains the results obtained from the analysis of the available data. It also includes the plans for future analytical and experimental investigations. The research project was sponsored by American Iron and Steel Institute. The technical guidance provided by the AISI Task Group on Bolted Connections (L.W. Ife, T.J. Jones, R.B. Matlock, and D.S. Wolford, members) and the AISI Staff (A.L. Johnson and D.P. Cassidy) is gratefully acknowledged. Thanks are also due to J.H. Senne, Chairman of the Department of Civil Engineering,for his advice. Acknowledgment is also due to E.B. Gibson, past Chairman of the AlSI Task Group, for his technical guidance

Critical phenomena and thermodynamic geometry of charged Gauss-Bonnet AdS black holes

In this paper, we study the phase structure and equilibrium state space geometry of charged topological Gauss-Bonnet black holes in $d$-dimensional anti-de Sitter spacetime. Several critical points are obtained in the canonical ensemble, and the critical phenomena and critical exponents near them are examined. We find that the phase structures and critical phenomena drastically depend on the cosmological constant $\Lambda$ and dimensionality $d$. The result also shows that there exists an analogy between the black hole and the van der Waals liquid gas system. Moreover, we explore the phase transition and possible property of the microstructure using the state space geometry. It is found that the Ruppeiner curvature diverges exactly at the points where the heat capacity at constant charge of the black hole diverges. This black hole is also found to be a multiple system, i.e., it is similar to the ideal gas of fermions in some range of the parameters, while to the ideal gas of bosons in another range.Comment: 17 pages, 8 figures, 3 table

Effect Of Strain Rate On Cold-formed Steel Stub Columns

The material properties of steel and the strength of steel members are affected by strain rate to investigate this characteristic for compression members 49 stub columns fabricated from 35XF sheet steel and 48 stub columns fabricated from 50XF sheet steel are studied experimentally and analytically under different strain rates The strain rate ranged from 10-5 to 0.1. in./in./sec (10-5 to 0.1 mm/mm/s). The material properties of 35XF and 50XF sheet steels developed from previous tests are used for the evaluation of the test data obtained from the member tests using specimens fabricated from the same sheet steel. The results show that the strength of stub columns increased with the strain rate. The amount of increase is found to be dependent on the type of material the Fu/Fy ratio the width-to-thickness ratio (w/t) of the compression element and the strain rate used in the tests. The effective width approach included in the American Iron and Steel Institute (AISI) specification for cold-formed steel members and in the AISI Automotive Steel Design Manual is utilized for the evaluation of stub column strengths using static and dynamic yield stresses corresponding to the strain rates used in the tests It is found that better agreement can be achieved between the predicted and tested stub column strengths when using the dynamic yield stresses and considering the effect of cold work. © ASCE

Personalized content provision for virtual learning environments via the semantic web

In this paper we discuss how we may personalize e-learning along three distinct axes, namely: teaching and learning pedagogical philosophies, personalized educational processes to taste and the coordination of these processes during execution. In doing so we are concerned with supporting users' choices of educational options in course delivery via the Web services. In the work presented here, we assess the practical needs of learners and tutors and then the main research problems are analysed from a practical and pragmatic point of view. Following on from this the design of an intelligent virtual learning environment (VLE) is described to map a set of extensive didactic paradigms, which is represented by a system model and architecture. In this system, the semantic information of learning units and processes (e.g. the relationships among units) can be described and integrated in terms of various requirements of our users. As a result instructional materials with a wide variety of executional options and conditions can be built. Furthermore, through reassembling the semantics of learning content according to users' new demands, our target audience (both student and content deliverers) can change their particular educational experience dynamically. This VLE can provide high-powered pedagogy-layered personalization - thus enabling new managed e-learning Web services and applications

Spacing of Connections in Compression Flanges of Built-up Cold-formed Steel Beams

Built-up cold-formed steel sections may offer greater economy in building construction. Typical built-up sections are cellular decks or door and window header beams. A research project was initiated to determine if the current spacing criteria outlined in Section D1.2 of the AISI Specification accurately predicted the capacity of built-up sections with the cover plate in compression. This study showed that criteria No.2 of the AISI Design Specification spacing criteria is restrictive when applied to built-up cross sections in bending. All test sections continued to carry additional load after the cover plate buckled. The tests showed that as the spacing of connectors increased the moment capacity of the section decreased. An analytical procedure was developed to compute the nominal moment capacity for a range of connector spacings

Tensile and bearing capacities of bolted connections

PREFACE Experimental studies were preformed to investigate the tensile capacity, bearing capacity and the interaction of tension and bearing capacities of flat sheet cold-formed steel bolted connections. The effect of bolt hole deformation on the bearing capacity of bolted connections, was also investigated. In the experimental investigation, single shear flat sheet connections were investigated for single bolt and multiple bolt configurations. The intent of this investigation was to compare the current AISI and AISC Specifications for the nominal bearing and tensile capacities and to develop appropriate serviceability design criteria. A review and evaluation of past research on the tensile and bearing capacity of bolted flat sheet connections was performed and is discussed. The test results indicated that for connections failing in bearing, the AISI Specification correlated better with the test results than did the AISC Specification; for tension failure, both specifications correlated similarly to the test results. An analysis and discussion of the test results is included, as well as the development of a serviceability limit for nominal bearing capacity. This report is based on a thesis presented to the Faculty of the Graduate School of the University of Missouri-Rolla in partial fulfillment of the requirements for the degree of Master of Science. This investigation was sponsored by the American Iron and Steel Institute (AISI). The technical guidance provided by the AISI Connections Committee: M. Golovin (chairman), R. E. Albrecht, B. Bjorhovde, E. R. diGirolamo, D. S. Ellifritt, E. R. Estes Jr., W. B. Hall, M. A. Huizinga, A. L. Johnson, D. L. Johnson, W. E. Kile, R. A. LaBoube, L. D. Luttrell, W. McGuire, T. B. Pekoz, C. W. Pinkham, and W. W. Yu. Thanks are also extended to R. B. Haws, and K. L. Cole, AISI Staff, and J. N. Macadam, former chairman of the Subcommittee, for their assistance