Modelling of beam-to-column connections at elevated temperature using the component method

B.A. Izzuddin,N.H. Ramli Sulong,A.Y. Elghazouli,N. Ajit 국제구조공학회 2006 Steel and Composite Structures, An International J Vol.6 No.1

In this paper, a nonlinear model is developed using the component method in order to represent the response of steel connections under various loading conditions and temperature variations. The model is capable of depicting the behaviour of a number of typical connection types including endplate forms (extended and flush) and angle configurations (double web, top and seat, and combined top-seat-web) in both steel and composite framed structures. The implementation is undertaken within the finite element program ADAPTIC, which accounts for material and geometric nonlinearities. Verification of the proposed connection model is carried out by comparing analytical simulations with available results of isolated joint tests for the ambient case, and isolated joint as well as sub-frame tests for elevated temperature conditions. The findings illustrate the reliability and efficiency of the proposed model in capturing the stiffness and strength properties of connections, hence highlighting the adequacy of the component approach in simulating the overall joint behaviour at elevated temperature.

Rate-sensitive analysis of framed structures Part I: model formulation and verification

Izzuddin, B.A.,Fang, Q. Techno-Press 1997 Structural Engineering and Mechanics, An Int'l Jou Vol.5 No.3

This paper presents a new uniaxial material model for rate-sensitive analysis addressing both the transient and steady-state responses. The new model adopts visco-plastic theory for the rate-sensitive response, and employs a three-parameter representation of the overstress as a function of the strain-rate. The third parameter is introduced in the new model to control its transient response characteristics, and to provide flexibility in fitting test data on the variation of overstress with strain-rate. Since the governing visco-plastic differential equation cannot be integrated analytically due to its inherent nonlinearity, a new single-step numerical integration procedure is proposed, which leads to high levels of accuracy almost independent of the size of the integration time-step. The new model is implemented within the nonlinear analysis program ADAPTIC, which is used to provide several verification examples and comparison with other experimental and numerical results. The companion paper extends the three-parameter model to trilinear static stress-strain relationships for steel and concrete, and presents application examples of the proposed models.

A Simplified Model for Axially Restrained Beams Subject to Extreme Loading

B. A. Izzuddin 한국강구조학회 2005 International Journal of Steel Structures Vol.5 No.5

This paper presents a simplified explicit model for axially restrained beams subject to extreme transverse loading, focussingto midspan point loading as wel as uniformly distributed loading, alowing for a plastic hinge at the beam midspan. For theambient case, the proposed model expresses the load-deflection response directly, accounting for elasto-plastic bending andplastic tensile catenary action. On the other hand, for the elevated-temperature case, the model enables the determination of thetemperature-deflection response under constant transverse loading, further allowing for compresive catenary action that arisesegod accuracy with simplicity, thus offering a practical tol for the design of beams under extreme loading.

Rate-sensitive analysis of framed structures part II: implementation and application to steel and R/C frames

Fang, Q.,Izzuddin, B.A. Techno-Press 1997 Structural Engineering and Mechanics, An Int'l Jou Vol.5 No.3

The companion paper presents a new three-parameter model for the uniaxial rate-sensitive material response, which is based on a bilinear static stress-strain relationship with kinematic strain-hardening. This paper extends the proposed model to trilinear static stress-strain relationships for steel and concrete, and discusses the implementation of the new models within an incremental-iterative solution procedure. For steel, the three-parameter rate-function is employed with a trilinear static stress-strain relationship, which allows the utilisation of different levels of rate-sensitivity for the plastic plateau and strain-hardening ranges. For concrete, on the other hand, two trilinear stress-strain relationships are used for tension and compression, where rate-sensitivity is accounted for in the strain-softening range. Both models have been implemented within the nonlinear analysis program ADAPTIC, which is used herein to provide verification for the models, and to demonstrate their applicability to the rate-sensitive analysis of steel and reinforced concrete structures.

Modelling of beam-to-column connections at elevated temperature using the component method

N.H. Ramli Sulong,A.Y. Elghazouli,B.A. Izzuddin,N. Ajit 국제구조공학회 2010 Steel and Composite Structures, An International J Vol.10 No.1

In this paper, a nonlinear model is developed using the component method in order to represent the response of steel connections under various loading conditions and temperature variations. The model is capable of depicting the behaviour of a number of typical connection types including endplate forms (extended and flush) and angle configurations (double web, top and seat, and combined top-seat-web) in both steel and composite framed structures. The implementation is undertaken within the finite element program ADAPTIC, which accounts for material and geometric nonlinearities. Verification of the proposed connection model is carried out by comparing analytical simulations with available results of isolated joint tests for the ambient case, and isolated joint as well as sub-frame tests for elevated temperature conditions. The findings illustrate the reliability and efficiency of the proposed model in capturing the stiffness and strength properties of connections, hence highlighting the adequacy of the component approach in simulating the overall joint behaviour at elevated temperature.

Partitioned analysis of nonlinear soil-structure interaction using iterative coupling

Jahromi, H. Zolghadr,Izzuddin, B.A.,Zdravkovic, L. Techno-Press 2008 Interaction and multiscale mechanics Vol.1 No.1

This paper investigates the modelling of coupled soil-structure interaction problems by domain decomposition techniques. It is assumed that the soil-structure system is physically partitioned into soil and structure subdomains, which are independently modelled. Coupling of the separately modelled partitioned subdomains is undertaken with various algorithms based on the sequential iterative Dirichlet-Neumann sub-structuring method, which ensures compatibility and equilibrium at the interface boundaries of the subdomains. A number of mathematical and computational characteristics of the coupling algorithms, including the convergence conditions and choice of algorithmic parameters leading to enhanced convergence of the iterative method, are discussed. Based on the presented coupling algorithms a simulation environment, utilizing discipline-oriented solvers for nonlinear structural and geotechnical analysis, is developed which is used here to demonstrate the performance characteristics and benefits of various algorithms. Finally, the developed tool is used in a case study involving nonlinear soil-structure interaction analysis between a plane frame and soil subjected to ground excavation. This study highlights the relative performance of the various considered coupling algorithms in modelling real soil-structure interaction problems, in which nonlinearity arises in both the structure and the soil, and leads to important conclusions regarding their adequacy for such problems as well as the prospects for further enhancements.

An Analytical Model for Evaluating Axial Boundary Stiffness of Steel Beam Restrained by Neighboring Floor Systems

K. Q. Wang,C. Fang,G. Q. Li,B. A. Izzuddin 한국강구조학회 2011 International Journal of Steel Structures Vol.11 No.4

Extreme loading such as blast and impact usually lead to a disastrous damage on targeted columns, such that the column can be seen as completely removed. Under this circumstance, the ‘double-span’ beam system bridging over the removed column can deflect greatly, and catenary action of the beam plays an important role in enhancing its resistance. In this context, a reliable evaluation of the boundary axial stiffness is crucial in predicting the actual response of axially restrained beams. Although a considerable number of factors affecting the boundary restraints of the beam in a frame have been investigated, the influences of planar stiffness offered by surrounding slabs systems have hardly been addressed. This paper proposes a design-oriented procedure for evaluating the boundary axial stiffness provided by adjacent slab systems. Firstly, three components that contribute to the axial restrain stiffness are identified, namely, slabs, steel beams and studs. Then nonlinear deformation functions of the components are proposed, from which the axial restraining stiffness formulas are derived. Due to the fact that only a part of slab length is attributed to resisting the external force if a sufficient slab length is allowed, an ‘effective length’has to be considered. The axial stiffness formulas are then modified on the basis of the effective length. Subsequently, the reliability of the proposed formulas is validated against a case study of twenty FE examples, and good correlations are observed. Finally, additional stiffness offered by the minor axis bending of the steel beams perpendicular to the restrained beam is investigated, and it is found that the influence is relatively small, and thus can be ignored.