Effect Of Semi-rigid Connections Research Articles

Static Stability of Beam-Columns under Combined Conservative and Nonconservative End Forces: Effects of Semirigid Connections

Stability criteria that evaluate the effects of combined conservative and nonconservative end axial forces on the elastic divergence buckling load of prismatic beam-columns with semirigid connections is presented using the classic static equilibrium method. The proposed method and stability equations follow the same format and classification of ideal beam-columns under gravity loads presented previously by Aristizabal-Ochoa in 1996 and 1997. Criterion is also given to determine the minimum lateral bracing required by beam-columns with semirigid connections to achieve buckling ~i.e., with sidesway inhibited!. Analytical results obtained from three cases of cantilever columns presented in this paper indicate that: ~1! the proposed method captures the limit on the range of applicability of the Euler's method in the stability analysis of beam-columns subjected to simultaneous combinations of conservative and nonconservative loads. The static method as proposed herein can give the correct solution to the stability of beam-columns within a wide range of combinations of conservative and nonconservative axial loads without the need to investigate their small oscillation behavior about the equilibrium position; and ~2! dynamic instability or flutter starts to take place when the static critical loads corresponding to the first and second mode of buckling of the column become identical to each other. Flutter in these examples is caused by the presence of nonconservative axial forces ~tension or compression! and the softening of both the flexural restraints and the lateral bracing. In addition, the transition from static instability ~with sidesway and critical zero frequency! to dynamic instability ~with no sidesway or purely imaginary sidesway frequencies! was determined using static equilibrium. It was found also that the static critical load under braced conditions ~i.e., with sidesway inhibited! is the upper bound of the dynamic buckling load of a cantilever column under nonconservative compressive forces. Analytical studies indicate the buckling load of a beam-column is not only a function of the degrees of fixity ~ra and rb!, but also of the types and relative intensities of the applied end forces ~Pci and P fj !, their application parameters ~ci, hj, and jj!, and the lateral bracing provided by other members sSDd. DOI: 10.1061/~ASCE!0733-9399~2005!131:5~473! CE Database subject headings: Buckling; Building codes; Beam columns; Flutter; Structural stability; Frames; Connections, semi-rigid.

Joint characteristics of traditional Chinese wooden frames

The wooden frames of the remains of traditional Chinese architecture were built up using plug-slot type of beam-to-column connections without using any metal nails or bolts. One type of these connections commonly found in primary frames has been studied. Three different types of artificially degraded connections that imitate those deteriorated conditions naturally were investigated experimentally. The behaviour of these connections is found to be semirigid. They can be simulated by a three-parameter connection model. The effects of semirigid connections on frames were also studied through tests and the second-order elastic analysis by the Newton-Raphson method. It is shown that the behaviour of the frame is dominated by the characteristics of the connections. The proposed numerical method can accurately predict the response of the partially restrained wooden frame.

Seismic behaviour of semi-rigid steel frames

Abstract This paper deals with aspects of the performance and design of steel frames with semi-rigid connections under earthquake loading conditions. Current evidence on the feasibility of this type of structure for seismic design is discussed. This is followed by a description of a testing programme on two-storey frames with rigid and semi-rigid beam-to-column connections. A brief account of the results from five monotonic, cyclic and pseudo-dynamic tests is presented. An analytical component-based model is verified in comparison with the tests; static and dynamic response comparisons are undertaken. The model is used to investigate further the effect of semi-rigid connections on the member as well as the frame behaviour. It is shown from both the experimental and analytical investigations that semi-rigid frames exhibit ductile and stable hysteretic behaviour and may be used effectively in earthquake-resistant design.

Ultimate strength analysis of three-dimensional column subassemblages with flexible connections

Abstract The effect of semi-rigid connections on the behaviour and strength of three-dimensional column subassemblages has been investigated using a finite element method. The connection is modelled as an element with its force-deformation characteristics being represented by a piecewise linear curve. The analysis allows for the effect of initial deflection, residual stress and plastic action. It also includes the unloading of connections. The validity of the program has been verified by comparisons against available experimental work. A limited parametric study has been conducted to evaluate the influence of connection flexibility. These results have been assessed against the predictions of the UK Steelwork Code and it has been concluded that it is possible to incorporate an allowance for connection flexibility in the column design procedure of the code.

Effects of semi-rigid connections on steel column strength

Effects of semi-rigid connections on steel column strength

Effect of semi-rigid connections on steel column strength

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 column's 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.