Stephen Hicks

Safety factors for the resistance of steel sections

AbstractThe performance of the design equations given in the Australian Bridge and Steel Standards AS 5100.6 and AS 4100 have been evaluated when structural steel is used that conforms with the tolerances within the following overseas manufacturing standards: EN 10034, KS D 3502, JIS F 3192, JIS A 5526, ASTM A6/A6M-07 and AS/NZS 5100.6. From a consideration of the experimental results from full-scale bending tests, reliability analyses according to AS 5104:2005/IS0 2394:1998 and EN 1990 were conducted. From these analyses, a capacity factor of between 0.93 and 0.95 was determined for beams that have compact, not-compact and non-compact cross-sections when a target reliability index of 3.04 was used, based on the standardised FORM (first order reliability method) sensitivity factor for resistance given in AS 5104:2005/IS0 2394:1998. This finding demonstrates that the capacity factor of 0.90 given in AS 4100 and AS 5100.6 for beams in bending is on the conservative side for steel sections complying with ove...

Dynamic performance of a brick veneer house with steel framing

Abstract Brick veneer construction is a very common form for residential structures in Australia and is growing in popularity in New Zealand. The structural frame is made from steel or timber, and non-structural brick walls are attached to the frame via brick ties. Under earthquake loading there is a complex interaction between the frame and veneer walls, particularly in the out- of-plane direction, where there is risk of brick wall collapse. While there is a standard component test method for assessing the seismic capacity of brick ties, this method has been developed around brick veneer on timber studs. In order to realistically assess the overall performance of brick veneer construction with steel framing, a full scale one-room test structure “Test House” was tested on a shaking table. The Test House incorporated veneer walls with different geometries. It was subjected to varying levels of the El-Centro earthquake ranging from moderate serviceability limit state ground motion to well beyond the design maximum considered earthquake for New Zealand. These levels of shaking were selected in order to ascertain the response for specific limit states to the New Zealand Loading Standard and to compare against minimum performance requirements. Comprehensive measurements on the frame and veneer walls were taken, including acceleration, drift and differential movements between the frame and veneer. The Test House performed very well, with no brick loss up to 2.6 times El-Centro earthquake, which is well in excess of all performance requirements. This paper presents a summary of the outcomes from the experimental test program.

Against All Odds: The Birth of the Commonwealth Trans-Antarctic Expedition, 1955-1958

When the Commonwealth Trans-Antarctic Expedition 1955–1958 advance party sailed from the Millwall Docks in November 1955, bound for the Weddell Sea, their departure was the product of five years of intensive effort on the part of Vivian Fuchs to achieve the first overland crossing of the Antarctic continent. This paper investigates the many obstacles that had to be overcome leading up to Theron sailing and explains the manner in which they were overcome by the Fuchs-Wordie-Clifford triumvirate. The British Foreign Office was particularly opposed to the expedition with the offices focus on sovereignty rather than science while an alternative proposal from Duncan Carse raised a unique set of difficulties. The withdrawal from involvement by the Scott Polar Research Institute Director, Colin Bertram, indicated further disaffection. Most important, if political and financial goals were to be met, was the need for participation by several Commonwealth countries of which New Zealand was the essential partner. Fortunately, the vigorous efforts of a few Antarctic enthusiasts in New Zealand were successful in moving their government to assert its long dormant position in the Ross Dependency. New Zealands commitment turned the tide of commonwealth apathy towards the TAE. Although the TAE preceded the IGY, events, including the dominating IGY presence of the United States, caused the two projects to become tightly interwoven. For these reasons the years leading up to the departure of Theron were as intriguing as the crossing journey itself.

Fire Performance of an Office Building with Long-span Cellular Floor Beams—Britomart East, Auckland

Abstract This paper presents the application of a structural fire model to a twelve-storey office building in Auckland, which was one of the first projects in New Zealand to use long-span cellular floor beams. The structural fire model that was employed is known as the slab panel method (SPM), which is an extension of the Bailey tensile membrane model. Owing to the fact that the cellular beams had been optimised for structural efficiency, there was little reserve of strength in fire conditions, which resulted in the SPM predictions of peak deflection being supplemented by finite element simulations for a range of design fire severities. The simulations indicated that there was a tendency for the bottom flange of the asymmetric cellular beams to displace laterally, which resulted in the beams that form the slab panel supports requiring vertical stiffeners. Nevertheless, from these analyses it was demonstrated that the passive fire protection could be eliminated from the long-span secondary beams, with only the elements critical to the structural stability of the floor requiring applied fire protection. The resulting 80% reduction in the passive fire protection on the long-span cellular beams led to cost savings in excess of NZD 300 000 (EUR 189 000) to the client.

Analytical Methodology to Predict the Beam Overstrength Considering the Composite Slab Effects

The design strength of moment resisting steel frames in seismic regions around the world is generally calculated without considering strength enhancement caused by the slab. For column and panel zone design in New Zealand, the beam overstrength including the slab effect is considered. If the slab could be detailed to provide reliable lateral force resistance, then considering it directly in design would result in smaller beam sizes and more economical steel frames. In this paper, a simple analytical model (considering all key modes of failures) to predict the variation in strength due to the presence of the slab is proposed and validated with the experimental data. The proposed model to develop dependable slab contributions may change the design of steel moment frames around the world.

Short-term behaviour of reinforced and steel fibre–reinforced concrete composite slabs with steel decking under negative bending moment:

An experimental study was conducted on reinforced and steel fibre–reinforced concrete composite slabs with steel decking under negative bending moment to quantify the ultimate behaviour, loading capacity and crack width under short-term loading. Eight full-scale slab specimens were cast with different types and amounts of reinforcement in the concrete (e.g. mesh, steel fibre or normal reinforcing bars) but with the same type of steel decking. Each slab was simply supported and tested in four-point bending under increasing load until failure. The deflections at mid-span and under the applied point loads were monitored together with the end interface slip. The crack widths were obtained for each slab for different levels of applied load. It was found that the end slip was quite negligible and complete interaction on the steel decking–concrete slab interface existed at service loads and ultimate limit states. Compared to the slab with 20 kg/m3 steel fibre, the application of steel fibre in excess of 60 kg/m3 increased the rotational capacity and ultimate load by 60% and 80%, respectively. Moreover, the higher dosage of steel fibres resulted in improved crack control, as for the same level of applied load, the crack width was often reduced by 75%. However, the slabs with conventional high-strength ductile reinforcements had the greatest ultimate load and rotational capacity and exhibited the best degree of crack control with finer and more distributed cracks.

The new joint Australian and New Zealand Bridge Design Standard AS/NZS 5100 - part 6: steel and composite construction

This paper presents some of the innovations that will be included within the new joint Australian and New Zealand Bridge Design Standard for steel and composite construction AS/NZS 5100.6, which will be the first harmonized standard between Australia and New Zealand for the design of bridges. As Chairs of the Committees responsible for AS/NZS 5100.6 and AS/NZS 2327, the authors of this paper present the challenges faced from the introduction of concrete compressive strengths up to 100 MPa together with quenched and tempered steels with a yield strength up to 690 MPa. As well as introducing the structure of the new standard, an overview of the research work that was required to develop design rules to support the new material strengths will be given which, inter alia, includes: resistance of headed stud connectors; resistance and buckling strength of composite columns; and fatigue resistance. Perhaps one of the most innovative aspects of this standard is the introduction of an appendix that provides conformity assessment requirements for steel products that are not sourced from either Australia or New Zealand. This appendix is underpinned by rigorous structural reliability analyses undertaken by Australian and New Zealand researchers, which included the authors of this paper.