P.A. Kirby

THE ANALYSIS OF FRAMES WITH SEMI-RIGID CONNECTIONS - A STATE-OF-THE- ART REPORT

Abstract The history of research into the behaviour of steel beam-to-column connections is traced starting from early developments in 1917. Attention is focussed on moment-rotation characteristics as this is the most important influence on the response of either individual members or complete frames. The nonlinear nature of this characteristic is identified and methods of representing moment-rotation curves for subsequent use in analytical procedures are discussed. A review is made of all available test data; this may be used as a starting point for both further studies of connection behaviour and as the basis for investigations of the effects of semi-rigid connections on structural response.

Rotational stiffness characteristics of steel beam-to-column connections

Abstract A series of tests on a variety of beam-to-column connections suitable for rectangular frames using I-section members has been conducted. The principal objective was the provision of moment-rotation data so that a comparative assessment of the performance of the different types, in terms of connection stiffness and moment capacity, could be undertaken. Thus all tests employed similar beam and column sizes, test apparatus, instrumentation and test procedures. The connections studied were (in ascending order of stiffness and strength): web cleats, flange cleats, combined seating cleat and web cleats, flash end plate and extended end plate. Connections to the column flanges and the column web were included. Major sources of connection flexibility have been identified and the results prepared for subsequent use in assessments of semi-rigid joint action in steel frames.

Strength and rotational stiffness of simple connections to tubular columns using flowdrill connectors

Abstract A new thermal drilling technique (the flowdrill process) has made it possible to use ordinary bolts in tapped holes in relatively thin-walled tubes. This in turn has opened the opportunity for traditional partial depth and flush endplate connections to be used to join open section beams to tubular columns in simply designed braced steel frames. The experimental work reported concerns a series of tests conducted to investigate the moment capacity and rotational stiffness of simple joints bolted to tubular columns using flowdrill connectors. Tests show the connections to behave in a manner suitable for use as either pinned or partial strength connections for simply designed braced steel frames. This paper is one of a series; the others deal with moment-resisting connections and the influence of filling the tubes with concrete.

Moment-capacity and rotational stiffness of endplate connections to concrete-filled tubular columns with flowdrilled connectors

A test programme to obtain experimental data on the behaviour of endplate beam to column connections has been conducted. The reported tests concern joints made between universal beams and tubular columns using endplates bolted directly to the column face with ordinary bolts screwed into threaded holes formed using the flowdrill process. Results obtained from tests are presented in a series of three papers; this final paper reports tests conducted with concrete-filled tubes and the results are compared with those from a parallel series of tests in which the tubes were unfilled. Significant differences in strength and stiffness were observed.

Strength and rotational response of moment connections to tubular columns using flowdrill connectors

Abstract Using the flowdrill process it is possible to form threaded holes in steel tubes even with wall thicknesses less than 12 mm. Ordinary bolts may then be used to secure endplate beam connections to tubular columns. A series of tests was conducted to investigate the strength and rotational stiffness characteristics of joints made in this way. The results of the tests described on both thick flush endplates and extended endplates show that strengths approaching the plastic capacity of the supported beam and large rotational capacities can be obtained. Deformation of the tube face gives excellent ductility but the joints have relatively low stiffness for a nominally rigid joint. Connections of this type are ideally suited for use in semi-rigid design methods.

Effect of semi-rigid connections on steel column strength

Abstract A review has been made of all available experimental data relating to the moment versus in-plane rotational behaviour of practical beam-to-column connection types as used in steel frames. This has clearly shown that all forms of connection possess some stiffness which will act as partial restraint to the columns ends. Moreover this restraint has been found to be a non-linear function of connection deformation. Methods of mathematically describing connection data have been reviewed and an improved representation based on the use of cubic B-splines proposed. This possesses the advantage that it will not give an (incorrect) negative connection stiffness. Using this technique to model connection behaviour a computer program for the maximum strength analysis of steel columns has been written. This is based on a Newton-Raphson incremental finite element approach and incorporates features such as initial lack of straightness and spread of yield through the cross-section including the effects of residual stresses. The results of some preliminary analyses, which demonstrate the increases in column strength and reduction in column deformation that result from a consideration of actual joint behaviour, are presented.

Experimental behaviour of 3-D column subassemblages with semi-rigid joints

Abstract Preliminary results are presented for a series of full-scale subassemblage tests designed to illustrate the beneficial effects of semirigid joint action on the three-dimensional response of nonsway steel columns. The experimental arrangement, including the specially devised instrumentation systems, is described, the generally observed behaviour is discussed and the use of the tests to verify a parallel theoretical study is cited.

Effect of lack of fit on connection restraint

Abstract A series of eight tests on different popular types of beam-to-column connection incorporating various forms of lack of fit is reported. The presence of either oversize holes in cleated connections or distortion in end plates has been considered. For the former, additional slip of the bolts permits larger rotations than would occur in equivalent ‘perfect’ connections. The performance of end plate connections appears to be virtually unaffected, even when the bolts have not been tightened sufficiently to remove the gap.

Semi-rigid design of partially restrained columns in non-sway steel frames

Abstract This paper proposes a method for column design in non-sway bare steel structures which takes into account the semi-rigid action of the beam to column connections when estimating the effective length ratio. The simple design method ignores column head moments arising from connection eccentricity for the design of columns in non-sway steel frame. This new method predicts safe column capacities compared with experimental results, analysis and values determined from the UK code BS 5950.

Maximum connection rotations in non-sway semi-rigid frames

Abstract In research into the behaviour of semi-rigidly connected steel frames, the connections moment-rotation relationship is a vital parameter. In the absence of definitive knowledge about the range of moment-rotation data that is required in frame analysis, undue concentration has been given to levels of connection rotation far beyond those likely to be experienced in non-sway frames. This paper is directed towards the establishment of a reasonable maximum value which should enable researchers to concentrate on the part of the M-O curve that is of most relevance.