Benoit P. Gilbert

Net Section Tension Capacity of Bolted Connections in Cold-Reduced Steel Sheets

This paper examines the accuracy of design equations specified in the North American, European and Australasian codes for cold-formed steel structures in determining the net section tension capacity of bolted connections in flat steel sheets. It points out that the shear lag factors embedded in the code equations either yield “anomalous” results or become irrelevant when they exceed unity. The “anomaly” was demonstrated through laboratory tests and is explained by using simple calculus. The configurations of specimens tested in the laboratory include single shear- and double-shear connections, with single or double bolts in a line parallel or perpendicular to the force. A proper mathematical expression for the in-plane shear lag factor, which does not suffer from the anomaly of the code equations and never implies shear lag factors greater than unity for any configuration, is presented and shown to yield improved results compared to the current specifications. The resistance factor of 0.8 for the proposed...

Drive-in Steel Storage Racks I: Stiffness Tests and 3D Load Transfer Mechanisms

Steel storage racks, made of cold-formed steel, are used extensively in industry for storing goods. Two main racking systems prevail, referred to as selective racks and drive-in racks. International racking design codes deal mainly with selective racks, but limited design guidelines are available for drive-in racks. Drive-in racks require minimum floor space by storing pallets one after the other with no space between them. The forklift truck drives into the rack to store the pallets on the first-in, last-out principle. To allow forklift passage, drive-in racks can be braced only at the back (spine bracing) and at the top (plan bracing) in the down-aisle direction, resulting in a complex slender structure with poorly understood three-dimensional (3D) behavior and increased risk of collapse. Tests on drive-in rack systems to accurately capture their 3D behavior have not previously been available in the literature. This paper presents experimental results from full-scale tests conducted on a complete drive-...

Analysis-based design provisions for steel storage racks

AbstractThe paper summarizes the main new design provisions included in the recently revised Australian standard for steel storage racks. The standard features multitiered analysis provisions ranging from basic linear-elastic analysis-based provisions to highly advanced integrated design-analysis [geometric and material nonlinear analysis with imperfections (GMNIA)] provisions that allow the analysis and design to be completed in one step. The GMNIA provisions distinguish between beam element–based and shell element–based analysis according to cross section slenderness and provide rules for the imperfections to use for the two types of analysis, including imperfections in the local and distortional buckling modes for the shell element–based analysis. The selection of the system-based reliability (resistance) factor (ϕs) is discussed. The standard is seen as the most advanced design code of its type currently available for frame-type steel structures. The paper also provides an in-depth discussion about th...

Structural Veneer Based Composite Products from Hardwood Thinning – Part I: Background and Manufacturing

In Australia, plantation forests have increased in area by around 50% in the last 10 years. While this expansion has seen a modest 8% increase for softwoods, hardwood plantations have dramatically increased by over 150%. Hardwood plantations grown for high quality sawn timber are slow to mature, with a crop rotation time potentially reaching 35 years. With this long lead-time, each year the risk from fire, pests and adverse weather events dramatically increases, while not translating into substantially higher financial returns to the grower. To justify continued expansion of Australia’s current hardwood plantation estate, it is becoming necessary to develop higher value end-uses for both pulpwood and smaller ‘sawlog’ resources. The use of the low commercial value stems currently culled during thinning appears to be a necessary option to improve the industry profitability and win new markets. This paper provides background information on Australian forests and plantations and gives an overview of potential uses of Australian hardwood plantation thinning logs, as their mechanical properties. More specifically, this paper reports on the development of structural Veneer Based Composite (VBC) products from hardwood plantation thinning logs, taking advantage of a recent technology developed to optimise the processing of this resource. The process used to manufacture a range of hollow-form veneer laminated structural products is presented and the mechanical characteristics of these products are investigated in the companion paper. The market applications and future opportunities for the proposed products are also discussed, as potential benefits to the timber industry.

Net Section Tension Capacity of Cold-Reduced Sheet Steel Channel Braces Bolted at the Web

This paper examines the accuracy of equations specified by the North American and Australasian steel structures codes for deter- mining the net section tension capacity of a channel brace. It points out that there are three distinct factors affecting the net section efficiency of a cold-formedsteel channelbraceboltedat theweb. Thesefactors include(1) thein-plane shearlagassociatedwith stressconcentration around aboltholethatisalsopresentin flatsheets,(2)theout-of-planeshearlagthatisalsopresentinanI-sectionboltedatthe flangesonly,and(3)the bending moment arising from the connection eccentricity with respect to the neutral axis. Each of the relevant factors is explicitly incorporated into the equation proposed in this paper for determining the net section tension capacity of a cold-formed steel channel brace bolted at the web. The proposed equation is demonstrated through laboratory tests on low-ductility channel braces having practical aspect ratios that were bolted onto flexible plates, to be more reliable than the code equations and those existing in the literature. DOI: 10.1061/(ASCE)ST.1943- 541X.0000650.

Net Section Tension Capacity of Cold-Reduced Sheet Steel Angle Braces Bolted at One Leg

This paper examines the accuracy of equations specified by the North American and Australasian steel structures codes for determining the net section tension capacity of a cold-formed steel angle brace bolted at one leg. The configurations tested in the laboratory include single equal angle, single unequal angle bolted at the wider leg, single unequal angle bolted at the narrow leg, double angles, and alternate angles. The steel materials used in the experiment are among those with the lowest ductility for which nominal tensile strength is permitted by cold-formed steel design codes to be fully utilized in structural design calculations. Based on a modification to the equation derived for channel braces bolted at the web, a design equation is proposed for determining the net section tension capacity of a cold-formed steel angle brace bolted at one leg. The proposed equation is demonstrated, through laboratory tests on 61 specimens composed of G450 sheet steel, to be more accurate than the code equations and those existing in the literature.

Mechanical Properties of Rotary Veneers Recovered from Early to Midrotation Subtropical-Hardwood Plantation Logs for Veneer-Based Composite Applications

AbstractThis paper experimentally investigates the mechanical properties of rotary veneers peeled from small-diameter hardwood plantation logs, recovered from early to midrotation subtropical hardw...

Structural Veneer Based Composite Products from Hardwood Thinning - Part II: Testing of Hollow Utility Poles

Australian utility pole network is aging and reaching its end of life, with 70% of the 5 million poles currently in-service nationally installed within the 20 years following the end of World War II. The estimated investment required for the replacement or remedial maintenance of the aging 3.5 millions poles is as high as 1.75 billion dollars. Additionally, an estimated 21,700 high-durability new poles are required each year, representing further investment of 13.5 million dollars per year. Yet, agreements which progressively phase out logging of native forests around Australia have been signed, giving the industry about 25 years to make the transition from Crown native forests to plantations and private forests. As utility poles were traditionally cut from native forest hardwood species, finding solutions to source new poles currently presents a challenge. This paper presents tests on Veneer Based Composite hardwood hollow utility poles manufactured from Gympie messmate (Eucalyptus cloeziana) plantation thinning. Small diameter poles of nominal 115 mm internal diameter and 15 mm wall-thickness were manufactured in two half-poles butt jointed together, using 9 veneers per halfpole. The poles were tested in bending and shear, and experimental test results are presented. The mechanical performance of the hollow poles is discussed and compared to hardwood poles cut from mature trees and of similar size. Future research and different options for improving the current concept are proposed in order to provide a more reliable and cost effective technical solution to the current shortage of utility poles.

Drive-In Steel Storage Racks. II: Reliability-Based Design for Forklift Truck Impact

Steel drive-in racks are susceptible to structural failure from accidental impact by operating forklift trucks. Under impact, the upright bends and the supported pallets may drop through the rack to cause structural collapse if the bay opening exceeds the pallet bearing width. This drop-through limit state has not been considered in existing rack design standards. This paper proposes a simple equation to calculate the equivalent static impact force based on recent tests and nonlinear dynamic analysis of drive-in steel racks. An impact load factor is developed on the basis of a structural reliability assessment, taking into account the uncertain nature of the impact force, structural resistance, and models used in structural analysis. In design practice, the bay opening is determined from factored impact loads and is not to exceed specified limits.

Senile coconut palm hierarchical structure as foundation for biomimetic applications

Superior to hardwood and softwood trees, coconut palms are able to withstand extreme weather conditions without failure. Previous studies have shown that the internal structure of coconut palm stems significantly differs from hardwood, softwood and even other palm stems, in terms of fibre orientation and density distribution, likely influencing the mechanical characteristics of the tree. This paper aims at quantifying the cocowood hierarchical structure at an integral level (stem structure). To achieved this, quantitative analysis of more than 40 senile coconut palms from Fiji and Samoa has been carried out. This paper defines and analyses the typical cocowood morphology (form-structure) in terms of such factors as characteristic radius, fibrovascular bundles orientation and density distribution. For the first time, the characteristic triple helix configuration traced out by the fibrovascular bundles within the cocowood structure is modelled for the whole coconut stem. Specific equations are proposed to determine these factors at any given position in the tree. Knowledge advanced from this study will provide a scientific basis for future cocowood biomechanics research, including finite element modelling and analysis for biomimetic engineering applications.