Roger A. LaBoube

Behavior of low ductility steels in Cold-Formed Steel connections

Abstract Accepted design approaches for the strength of a steel connection rely on adequate ductility of the connected parts. In cold formed steel connection design, adequate ductility is defined by the Specification for the Design of Cold-Formed Steel Members. To assess the influence of low ductility steels, i.e. steels not meeting the specification ductility requirements, single lap bolted connections were studied. The experimental study reflected key connection strength parameters: edge distance, sheet thickness, sheet width, bolt pattern, F u F y , and percentage elongation. Test results indicate that failure modes in low ductility steels are inconsistent with observed failure modes in adequate ductility steels. It has also been determined that specification connection strength equations will provide reasonable estimates of the connection load capacity for low ductility steels.

Cold-formed steel webs with openings: Summary report

Abstract Based on a 3-year study that focused on the behavior of cold-formed steel beams with web openings, researchers at the University of Missouri Rolla have developed simple, easy, to apply design recommendations. The design recommendations address the limit states of web buckling resulting from bending, shear, web crippling, combined bending and shear, and combined bending and web crippling. The recommendations were developed based on the results of experimental and analytical studies of C-section beams. The C-sections, which are commonly used for wall studs and floor joists, are manufactured with web openings. Common web opening sizes are 38 × 102 mm and 19 × 51 mm. All web openings are located at mid-depth of the web and spaced 61 cm on center along the length of the C-section.

Local buckling flexural strength of webs with openings

Abstract One phase of an ongoing research study of the behaviour of web elements in flexural members is summarized. The unique aspect of this study is the focus on the influence of web openings on the structural behaviour. Flexure, shear, web crippling, and combinations thereof are being studied, this paper concentrates on the flexural behaviour. A test program, which concentrated on industry standard sections, was conducted. The results are presented, along with the correlation of tested moment capacity and computed moment capacity. The computed capacities were determined using recognized US design practices. Suggested refinements to the design practices are also discussed.

Recent research and developments in cold-formed steel framing

Recent research studies at the University of Missouri-Rolla (UMR) have focused on developing a better understanding of the behavior of cold-formed steel members and truss assemblies. This research was initiated by the more widespread use of cold-formed steel in the residential construction market, and the need to provide structurally reliable, as well as highly economical design solutions. Steel trusses are commonly assembled using C-shaped sections and self-drilling screws. Based on UMR findings, appropriate design recommendations have been proposed for the web and chord members of a truss. Also of concern is the introduction of large holes in the webs of floor joists. To assess the effect of the web opening, a multi-phased research effort has recently been concluded. This paper summarizes the UMR studies, and the suggested design recommendations.

Web crippling and combined bending and web crippling of cold-formed steel beam headers

Beam headers are commonly used in walls framed with cold-formed steel studs to span openings in bearing walls. This paper presents the results of an experimental study conducted at the University of Missouri-Rolla to establish the web crippling strength of both box- and I-beam headers for an interior-one-flange (IOF) loading condition. The beam header specimens were tested as a system consisting of two C-sections together with top and bottom track sections. The header configuration used in this study are defined in the Standard for Cold-Formed Steel Framing, Header Design (2000). Tested as a system, it was found that the web crippling strength was greater than that for two independent, single web C-sections. Based on the results of this study design recommendations are proposed.

Web crippling behaviour of nested Z-purlins

Abstract The findings of three research projects that focused on the web crippling behaviour of nested Z-sections are summarized. The nested Z-section is utilized by the metal building industry in the USA for continuous span roof purlin systems. Present design provisions in the USA, do not specifically address this configuration. Experimental studies addressed what is commonly considered to be pure web crippling, as well as the combination of web crippling and bending. The experimental results are compared with established design practice in the USA. Suggested design modifications are also presented.

Web crippling of cold-formed steel beams at end supports

This investigation focused on the effects of overhang length on the web crippling capacity of cold-formed steel members. The current design recommendations in North America do not provide for an increase in web crippling capacity for end-one-flange loading when an overhang is present beyond the end support. The test specimens used for the investigation were single web C-sections and Z-sections. The current design requirements for end-one-flange web crippling capacity were found to be conservative for overhang lengths ranging from 0.5 h to 1.5 h, where h is the web depth. However, the design practice that permits the application of the interior-one-flange loading condition for overhangs equal to or greater was discovered to be unconservative. Test results allowed for the formulation of a modification factor to the end-one-flange loading condition based.

University of Missouri-Rolla research on cold-formed steel structures

Abstract During the past 27 years, numerous research projects have been conducted at the University of Missouri-Rolla (UMR) under the sponsorships of the American Iron and Steel Institute, National Science Foundation, American Society of Civil Engineers, Metal Building Manufacturers Association, Steel Deck Institute, Metal/Lath Steel Framing Association, Chromium Center, Nickel Development Institute, and several steel companies located in the USA, Canada, and South Africa. The purpose of these investigations has been to study the structural strength of cold-formed steel members, connections, and structural systems. Some of the research findings have been used in the development of the AISI Specification for the Design of Cold-Formed Steel Structural Members, the AISI Automotive Design Manual, and the ASCE Standard Specification for the Design of Cold-Formed Stainless Steel Structural Members. This paper reviews the research work and other related activities on cold formed steel structures conducted at UMR.

Serviceability limit state for cold-formed steel bolted connections

Publisher Summary This chapter investigates the tensile capacity, bearing capacity and the interaction of tension and bearing capacities of flat sheet cold-formed steel bolted connections. The influence of bolt hole deformation is also investigated. In the experimental investigation, single shear flat sheet connections are examined for single bolt and multiple bolt configurations. The intent of this investigation is to compare the current design equations for the nominal bearing and tensile capacities and to develop appropriate serviceability design criteria. The focus of this chapter is the development of a serviceability limit for the nominal bearing capacity of cold-formed steel flat sheet connections.

Rubble Pile Characterization Model

Rubble piles created following the collapse of a building in a combat situation can significantly impact mission accomplishment, particularly in the area of movement and maneuver. Rubble characteristics must be known, for example, in order to predict the ability of a vehicle to override the collateral damage from weapon effects in urban areas. Two types of models are developed: a first-order model and a first-principles-based model. In both models, we assume complete rubblization of the building and develop a rubble profile model using the size and composition of the collapsed structure to predict the rubble volume. In both cases, this profile model includes the size of the footprint area surrounding the original building assuming that the rubble is free to expand horizontally as well as the resulting height of such a rubble pile. Empirical data is now needed to verify the predictive capabilities of these models.