M.Z. Naser

Response of fire exposed composite girders under dominant flexural and shear loading

Purpose This paper aims to present results from numerical studies on the response of fire exposed composite girders subjected to dominant flexural and shear loading. A finite element-based numerical model was developed to trace the thermal and structural response of composite girders subjected to simultaneous structural loading and fire exposure. This model accounts for various critical parameters including material and geometrical nonlinearities, property degradation at elevated temperatures, shear effects, composite interaction between concrete slab and steel girder, as well as temperature-induced local buckling. To generate test data for validation of the model, three composite girders, each comprising of hot-rolled (standard) steel girder underneath a concrete slab, were tested under simultaneous fire and gravity loading. Design/methodology/approach The validated model was then applied to investigate the effect of initial geometric imperfections, load level, thickness of slab and stiffness of shear stud on fire response of composite girders. Findings Results from experimental and numerical analysis indicate that the composite girder subjected to flexural loading experience failure through flexural yielding mode, while the girders under shear loading fail through in shear web buckling mode. Further, results from parametric studies clearly infer that shear limit state can govern the response of fire exposed composite girders under certain loading configuration and fire scenario. Originality/value This paper presents results from numerical studies on the response of fire exposed composite girders subjected to dominant flexural and shear loading.

Effect of local instability on fire response of steel beams

Purpose This purpose of this paper is to quantify the effect of local instability arising from high shear loading on response of steel girders subjected to fire conditions. Design/methodology/approach A three-dimensional nonlinear finite element model able to evaluate behavior of fire-exposed steel girders is developed. This model, is capable of predicting fire response of steel girders taking into consideration flexural, shear and deflection limit states. Findings Results obtained from numerical studies show that shear capacity can degrade at a higher pace than flexural capacity under certain loading scenarios, and hence, failure can result from shear effects prior to attaining failure in flexural mode. Originality/value The developed model is unique and provides valuable insight (and information) to the fire response of typical hot-rolled steel girder subjected to high shear loading.

Emerging Construction Materials for Energy Infrastructure

This paper presents the role of emerging construction materials in the development of energy infrastructure. Recent advancements in construction materials is reviewed. Specific examples of application of high performance concretes, high performance steels, and wood composites in enhancing the efficiency of infra-structure needed for generating energy from conventional fuel sources is illustrated. In addition, application of specialized materials such as fiber reinforced composites, shape memory alloys and phase-change materials in energy installations for harnessing power from non-conventional energy sources is discussed.

Application of Importance Factor for Classification of Bridges for Mitigating Fire Hazard

This paper presents the application of a simplified approach for classification of bridges based on fire risk. An importance factor was developed for identifying the vulnerability of bridges to fire hazard. This 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. This importance factor is applied for evaluating vulnerability of a typical bridge to fire hazard. It is shown through two case studies that the proposed importance factor can be used as a practical tool for identifying critical bridges from the point of fire hazard.