Post-fire behaviour of concrete-filled steel tubular column to axially and rotationally restrained steel beam joint

This paper presents a numerical investigation on the post-fire behaviour of concrete filled steel tubular (CFST) column to restrained steel beam joint. An entire loading and fire phase, including ambient loading, heating with constant loads, cooling with constant loads and post-fire loading, was employed in the numerical analysis, and a finite element analysis (FEA) model was built to simulate the behaviour of CFST column to axially and rotationally restrained steel beam joints with external diaphragm connections under the entire loading and fire phase. For validation, the proposed modelling method was used to predict the test results of CFST columns and joints in fire and post-fire. The comparison demonstrates that the accuracy of the proposed FEA model is acceptable. Afterwards, the FEA model was used to analyse the mechanics characteristics of CFST column to restrained steel beam joints in the entire loading and fire phase. Based on the numerical analysis, the joint moment versus relative rotation angle relationship in the entire loading and fire phase was addressed, and the residual joint strength index and stiffness index were defined to evaluate the post-fire performance of joints. Finally, simplified calculating formulas were proposed to calculate the two indexes, which provide a simply and feasible method to evaluate the post-fire performance of external diaphragm joints in the CFST column-steel beam framed structure

Entire loading procedure analysis of concrete-filled steel tube column to steel beam joints under fire

This paper presents a finite element analysis (FEA) model to study the mechanical performance of circular concrete-filled steel tube (CFST) column-steel beam joints with reinforced concrete (RC) slab under combined temperature and load. Tests on this kind of joint exposed to ISO-834 standard fire are carried out to verify the FEA model. The accuracy of the predicted result is generally acceptable. Based on the FEA model, the moment versus relative rotation between column and beam curve in the full range including ambient, heating, cooling and post-fire phases is calculated, and the stress distributions of core concrete and steel beam in joint zone at different feature time points during the above four phases are analyzed

(Some new developments of the fire performance research on composite structures)

The research on fire-endurance performance and fire-resistance design of composite structures is one of the hot topics in structural engineering. This paper briefly summarizes and reviews some of the recent progress on the fire performance of composite slabs, composite beams, composite columns, beam-column connections, frames and structural system. Finally, A number of issues need to be addressed on the fire performance of composite structures are identified and discussed

Finite element analysis on the temperature field of steel-concrete composite joints under fire

A finite element analysis (FEA) modeling is established and introduced in this paper to calculate the temperature field of steel-concrete composite joints under the IS0-834 fire including a cooling phase. Two types of joints, steel beam to concrete filled steel tubular (CFST) column joints and steel reinforced concrete (SRC) beam to steel reinforced concrete (SRC) column joints were simulated. Testing results were used to verify the feasibility of the FEA modeling. The FEA modeling was then used to analyze the temperature distributions of the composite joints during fire

Post-fire behaviour of concrete-filled steel tubular column to axially and rotationally restrained steel beam joint

This paper presents a numerical investigation on the post-fire behaviour of concrete filled steel tubular (CFST) column to restrained steel beam joint. An entire loading and fire phase, including ambient loading, heating with constant loads, cooling with constant loads and post-fire loading, was employed in the numerical analysis, and a finite element analysis (FEA) model was built to simulate the behaviour of CFST column to axially and rotationally restrained steel beam joints with external diaphragm connections under the entire loading and fire phase. For validation, the proposed modelling method was used to predict the test results of CFST columns and joints in fire and post-fire. The comparison demonstrates that the accuracy of the proposed FEA model is acceptable. Afterwards, the FEA model was used to analyse the mechanics characteristics of CFST column to restrained steel beam joints in the entire loading and fire phase. Based on the numerical analysis, the joint moment versus relative rotation angle relationship in the entire loading and fire phase was addressed, and the residual joint strength index and stiffness index were defined to evaluate the post-fire performance of joints. Finally, simplified calculating formulas were proposed to calculate the two indexes, which provide a simply and feasible method to evaluate the post-fire performance of external diaphragm joints in the CFST column-steel beam framed structure

Simulation model for ultra-high strength concrete filled composite column under static loads

Previous experimental research at National University of Singapore on ultra-high strength concrete (UHSC) filled composite columns exhibits that the brittleness of UHSC of compressive strength up to 200MPa can be overcome due to the passively confinement supplied by steel tube. Therefore, how to consider the confinement effect reasonably is the key issue of simulating the behavior of UHSC filled composite column under static loads. In this paper, based on existing stress-strain relation for normal strength concrete, a UHSC stress-strain relation model is proposed, which is confinement-dependent and fits for the Concrete Damaged Plasticity Model (CDPM) in ABAQUS. The suggested stress-strain relation model is adopted to establish finite element analysis models of UHSC filled composite circular columns subjected to vertical load or bending. The FEA models are validated to be reasonable compared with existing experimental results, and the limitation of the models which leads to inaccurate predicted results is also discussed in the end of the paper. Based on the FEA models, the mechanical performance analysis and systematic parameter analysis can be carried out to UHSC filled composite columns in the oncoming research

Temperature field analysis of SRC-column to SRC-beam joints subjected to simulated fire including cooling phase

Three tests were performed on steel reinforced concrete (SRC) column to SRC beam joints subjected to fire scenarios including heating and cooling phases, and this paper reports the thermal part of the test results as well as the spalling observations. As these joints were designed to investigate the behaviour of a big joint zone including part of the beams and columns connected, temperatures in the junction and areas certain distance away from the junction were measured during both the heating and cooling phases. The three tests tested the influence of heating time on the temperature distributions at various sections of the specimen. A three-dimensional finite element analysis (FEA) model is developed to calculate the temperature field of the SRC column to SRC beam joints. The predicted temperatures show good comparison with the test results. Based on the finite element analysis, the differences of the temperature distributions in the joint zone and the non-joint zone are analyzed and its influence to the structural fire safety design is illustrated. One important conclusion from this study is the necessity to include cooling phase in structural safety design because it is in the cooling phase that the majority of the specimen materials reached their peak temperature

(Analytical behaviour of concrete filled steel tubular column-reinforced concrete beam planar frames subjected to fire)

This paper develops a finite element analysis (FEA) model for concrete filled steel tubular column - reinforced concrete beam planar frames under coupled loading and fire with heating and cooling phase. The modeling is validated against existing test data. Based on the FEA model, the mechanical behavior of the composite frame under ISO-834 standard heating and cooling fire is analyzed, and the influences of beam load ratio, column load ratio, and heating time ratio are investigated. The results indicate that the composite frame will fail in both the heating and cooling phases. Whether or not the composite frame reaches its failure in cooling phase is related to beam load ratio, column load ratio, and heating time ratio

(Analysis on fire performance of concrete-filled steel tubular (CFST) trimple-limb laced columns)

A finite element analysis (FEA) model is established to study the fire performance of concrete-filled steel tubular (CFST) triple-limb laced columns subjected to ISO834 standard fire including heating and cooling phases. Some key issues regarding the fire performance of CFST triple-limb laced columns, including the failure mode, the axial deformation and load distribution on each CFST chord are studied when the columns reach a limit state, based on the FEA model. Besides, the influence of the load ratio and heating time ratio on whether the CFST triple-limb laced columns would reach a limit state in the cooling phase of fire is discussed. It can be found that the column could reach a limit state both in a heating phase and a cooling phase of fire. With the increase of a heating time ratio at an identical load ratio, or with the increase of a load ratio at an identical heating time ratio, the possibility of the column reaching the limit state in a cooling phase increased, and the failure time in the cooling phase decreased