G Davies

The influence of member orientation on the resistance of cross joints in square RHS construction

Abstract The diamond bird beak is a novel joint configuration for square RHS construction and is achieved by rotating the chord and brace of a traditional joint through 45° about their longitudinal axes. This paper describes a finite element examination of the resistance of welded diamond bird beak cross joints under axial brace compression. The effects of the joint parameters — brace/chord width ratio, wall slenderness, chord length to depth ratio, yield stress, and chord-end boundary restraint conditions, are considered. The chord length and the chord end boundary conditions are found to have a significant effect on the joint capacity and are considered in detail to develop an empirical equation for the joint resistance. Comparisons are also made with the resistance of conventional RHS cross-joints.

The strength of welded T-DT joints in rectangular and circular hollow section under variable axial loads

Abstract Finite element methods calibrated against experimental results from tests and data bases are used to obtain interaction diagrams for the strength of hollow section T-DT joints under three dimensional static brace loading. Suggestions are made for the use of modifying factors in conjunction with planar joint strength design recommendations.

Object-oriented fabrication cost model for the economic appraisal of tubular truss design

This paper is concerned with the development of a knowledge-based system for the economical design of tubular trusses using a fabrication-led approach. For this purpose the system employs a cost model for estimating the likely cost of fabrication for these trusses. The cost model, which was developed using the object-oriented methodology, is used for estimating the cost of fabrication of one or a number of trusses, joint detailing, members and individual fabrication operations. Therefore, the relative cost of one design option compared with its alternatives can be obtained. Using the model, the consequences of design decisions on the cost of fabrication can be appraised. This will assist in obtaining economical designs that take into account not only the cost of material but also that of fabrication.

A limit states design method for welded tension connections to I-section webs

Abstract Tension branch members welded orthogonally to the web of an I-section (wide flange member) often have a width which approaches that of the clear distance between the I-sections root fillets, especially if fillet welding of the branch member is involved. The strength of such connections has typically been determined by simple yield line analyses, with sometimes a uniform punching shear check also being incorporated. However, when the ratio, β′, of the branch member width (including welds) to the clear distance between the I-section root fillets approaches unity, connection strength estimates by both the classical yield line method and the punching shear model become extremely unsafe. This is demonstrated by 11 tension tests on such connections which are described in the paper. The actual failure mode for these connections having a high β′ value involves simultaneous flexure of the I-section web and shearing of the web material at the toes of the fillet welds adjacent to the I-section flunges. This action can be best represented by a combined flexural and punching shear yield line model which is proposed by the authors. By comparison with the test results this model is shown to provide a much better estimate of the connection ultimate strength than do either the simple yield line or the uniform punching shear models. Hence it is used as the basis for a limit states method which is described for these connections.

Torsional behaviour of rectangular hollow sections.

The results of a series of full-scale torsion tests on rectangular hollow sections (RHS) are presented and discussed. The observed torque–twist behaviour is compared to that predicted by an extended version of Marshall’s simplified thick wall torsion theory and finite element (FE) analysis, and significant differences are highlighted and examined. The behaviour predicted by the FE models is shown to be identical to that predicted by Marshall’s thick wall theory, which forms the basis of the British and European design procedures. However, even though the experimental measurements agree with the FE and theoretical predictions in the elastic range, the measurements of torsional capacity are significantly lower than those calculated, and this has important implications for design that may be wider than just torsion of RHS. A number of potential causes for this behaviour are examined, but it is yet to be fully explained. Evidence of similar behaviour in previous large-scale testing is highlighted and discussed.

A construction-led design process for tubular trusses

Abstract This paper describes a process for the design of tubular steel trusses using a construction-led approach. This process does not aim at automating the design of this type of structure, rather it aims at facilitating knowledge-aided design whereby the designer is fully in charge of design decisions aided by knowledge about the effect of these decisions on construction of a structure.

THE BEHAVIOUR OF FULL WIDTH RHS CROSS JOINTS

The compressive strength of orthogonal and oblique full width cross joints formed of Rectangular Hollow Section chords, with plate or RHS branches is examined on the basis of theory and test results. Joint parameters such as chord slenderness, bearing length, forming process and yield stress are considered and the relevant significance of sidewall bearing and buckling are discussed. Various estimates of strength including I.I.W. and ANSI/AWS are compared with methods being currently developed for I section beams.