Used in the following article: Naser MZ. Fire resistance evaluation through artificial intelligence-A case for timber structures. Fire Safety Journal. 2019 Apr 1;105:1-8. https://doi.org/10.1016/j.firesaf.2019.02.002
This paper presents the development of a simplified approach for classification of bridges based on fire hazard. Statistical data from recent fires in bridges is utilized to quantify the probable risk of fire in bridges and also probability of fire-induced collapse of structural members in bridges. An importance factor is derived for identifying the vulnerability of bridges to fire hazard. The proposed importance factor, developed using weighted factor approach, takes into account the degree of vulnerability of different bridge components, critical nature of a bridge from traffic functionality point and fire mitigation strategies present in a specific bridge. The proposed importance factor for fire design, which is similar to the one currently used for evaluating wind, and snow loading in buildings, is validated against previous bridge fire incidents. It is shown through this validation that the proposed method for importance factor can be used as a practical tool for identifying critical bridges from the point of fire hazard.
Fire resistance of flexural members is derived based on flexural limiting criterion with no consideration to shear failure. However, under certain conditions, shear capacity can degrade at a higher rate than moment capacity in steel beams exposed to fire and this can lead to early failure of beams. This paper discusses the effect of shear on fire resistance of steel beams. For studying this phenomenon, a three-dimensional nonlinear finite element model capable of predicting fire response of steel beams is developed using the finite element package ANSYS. This model is capable of predicting fire response of steel beams under different conditions such as loading pattern, web slenderness and fire insulation. The finite element model is applied to evaluate fire response of beams with different geometrical configurations. It is shown that shear capacity can degrade at a higher rate than flexural capacity in certain scenarios and hence, shear limiting state can be a dominant failure mode in such flexural members.
Fire represents a significant hazard to civil infrastructure, including bridges. However, fire hazard is still not accounted for in conventional bridge design. This paper presents an approach for developing an importance factor for overcoming fire hazard in bridges. The importance factor takes into account the degree of vulnerability of a bridge to fire and also the critical nature of a bridge from the point of traffic functionality. The importance factor is derived by assigning weightage factors to key characteristics of bridges, i.e. bridge’s geometrical features, material properties and design characteristics, traffic demand, hazard (risk) likelihood, expected environmental damage, and economic consequences resulting from a fire incident. The proposed importance factor for fire design, which is similar to the one currently used for evaluating wind, and snow loading in buildings, is validated for a number of bridges where fire incidents occurred previously. It is shown through this validation that the proposed method for importance factor can be used as a practical tool for identifying critical bridges from the point of fire hazard and also for developing relevant design strategies for mitigating fire hazard in bridges.
This paper aims to develop a 3D nonlinear finite element (FE) model that is capable of accurately predicting the performance of reinforced concrete (RC) beams reinforced with internal Glass Fiber-Reinforced Polymer (GFRP) bars when exposed to fire loading. The developed FE model is based on tested experimental data collected from the open literature. The model accounts for the variation in the thermal and mechanical constituent materials with temperature associated with the RC beam. To study the heat transfer mechanism and mechanical behavior of the RC beam, transient thermal-stress finite element analysis is performed using the ANSYS. It was shown that the FE predicted temperature and mid-span deflection results are in a good agreement with that of the measured experimental data. The validated FE model is used to conduct a parametric study to investigate the effect of the different parameters on the flexural performance of the reinforced beam specimens. The parametric study consisted of varying the concrete cover thickness as well as exposing the FE model to different fire curves. It is concluded that successful FE modeling of this structure would provide an economical and alternative solution to expensive and time consuming experimental testing. Other observations and recommendations are also discussed.
This paper presents results from numerical studies on the behavior of fire exposed steel beams by taking into consideration temperature-induced sectional instabilities. A three-dimensional nonlinear finite element model is developed to evaluate the response of fire exposed steel beams under both flexural and shear effects. This model is applied to investigate the effect of sectional slenderness on the onset of local instability and capacity degradation in steel beams exposed to fire. Results from finite element analyses are utilized to evaluate failure of beams under different limit states including flexure, shear, sectional instability and deflection criteria. These results show that under certain loading scenarios and sectional configurations, shear capacity in steel beams can degrade at a higher pace than that of moment capacity. In addition, results from numerical studies infer that room temperature classification of steel beams based on local stability, can change with fire exposure time; a compact section at ambient conditions can transform to a non-compact/slender section under high temperature effects. This can induce temperature-induced local buckling in steel sections and lead to failure prior to attainment of failure under flexural yield and/or shear limit state.
Contributors:M. Tanarslan, R.A. Hawileh, G. Sakar, J.A. Abdalla, M.Z. Naser
The aim of this investigation is to evaluate experimentally and numerically the cyclic loading response of reinforced concrete (RC) beams strengthened in shear with Glass Fiber Reinforced Polymer (GFRP) rods using the near surface mounted (NSM) technique. The experimental results indicated that the use of GFRP rods as NSM strengthening systems can significantly enhance the overall capacity and ductility of shear deficient RC members when subjected to cyclic loading. In particular, the increase in the load-carrying capacity of the strengthened specimens over the unstrengthened control specimen was in the range of 49–66%. Furthermore, the increase in the displacement over the control specimen ranged between 112% and 172%. A 3D finite element (FE) model was also developed to simulate the response of the tested specimens. The developed FE model integrates multiple simulation techniques, nonlinear material properties and corresponding constitutive laws. The models incorporate concrete cracking, yielding of steel reinforcement, bond–slip behavior between NSM reinforcement and adhesive material and between steel reinforcement and adjacent concrete material, respectively. The load–deflection response envelopes and the load–deflection hysteresis loops of the experimentally tested beams and those simulated by the FE models were compared. Good matching was observed between the predicted and measured results at all stages of cyclic loading.