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This paper presents a detailed investigation in to fire resistance along with failure mode in continuous steel-concrete composite twin I-shaped bridge girders under different localized fire through considering fire severity and fire exposure positions namely; mid-span zone in one of the two span, hogging moment zone and side-support zone. A 3-D finite element (FE) model, built utilizing the computer program ANSYS, is used to track structural fire performance in a typical two span of continuous composite twin I-shaped bridge girders (fabricated with twin I-shaped plates supporting a concrete slab) dependent on thermomechanical coupled analysis. The model validation is undertook through comparison of temperature and deflection response attained from a scaled composite single I-shaped girder tested exposed to ISO834 fire. The numerical analysis results show that the developed model can be favorably used to analyze the behavior and failure mode of continuous steel-concrete composite twin I-shaped bridge girders during entire range of fire exposure. Fire severity and fire exposure positions present critical influence in to the fire resistance of continuous composite bridge girders. Fire exposure prevention on hogging moment zone can significantly extend failure time of continuous girders, and further hold back progressive structural collapse. Web buckling based failure criterion can be applicable to calculate fire resistance of realistic continuous girders under simultaneous structural loading together with localized fire. Continuous composite bridge girders subjected to localized fire present highly significant local deformation response in the fire exposed bridge girder span.
The materials engineering trends put forward the development of efficient structural solutions1,2. As a result, there is a tendency to develop new structural materials to change traditionally used concrete and steel3. Fiber-reinforced polymers (FRP) define the promising alternative to steel, and carbon, glass, and aramid fiber-based composites are the most common FRPs on the market4,5. It is known that manufacturing technology affects the mechanical performance of FRP composites. Thus, this study focuses on the pultruded objects because of the ability of the pultrusion technologies to produce a large volume at low operating costs and high fabrication rate, fiber content, and geometry tolerances6,7.
The pultrusion direction and reinforcement filament distribution coincide, ensuring the mechanical performance of the structural FRP parts6,7,8,9. However, such components often face transverse loads regarding the pultrusion pathway; moreover, the pultruded details must resist bolt removal-induced local stresses4,5. Therefore, the smooth unidirectional roving and mats protect the longitudinal filaments, complicating the internal reinforcement structure of the FRP material6. At the same time, these additional protection means can be insufficient for developing FRP structures10,11,12. In addition, the relatively low deformation modulus of typical FRP materials raises the deformations of the structural components. Together with the self-weight reduction increasing the kinematic displacements13, the latter issue makes developing hybrid structures comprising compression-resistant concrete and high-performance in tension FRP profiles important.
Although hybrid composite systems are applicable for bridge engineering13,14,15, the uncertainty of the inter-component bonding properties complicates developing these innovative structures. The typical solution focuses on local bond improvement, employing FRP profile perforation and mechanical anchorage systems, e.g., Mendes et al.16 and Zhang et al.17. However, the design of such structures lies beyond the standard regulation field. At the same time, the bond problem complicates structural analysis and numerical modeling18,19. Still, studies9,20,21,22,23 describe the typical analysis examples, neglecting the bond problem.
In contrast, this study employs the stress-ribbon bridge solution to create the hybrid beam prototype, combining the polymeric fiber-reinforced concrete (PFRC) slab and pultruded FRP profile. However, the proposed structural system does not require massive supports typical for the stress-ribbon systems15 because of the combination of the concrete, resisting the compressive load induced by the glass-fiber-reinforced profile (GFRP) distributed in the tension zone of the flexural element. Furthermore, the reliable profile fixation to the supports ensures the composite behavior of the hybrid beam. In addition, it simplifies the corresponding finite element (FE) model, allowing the perfect bond assumption between the composite parts. Thus, this FE model describes the reference for developing the hybrid beam system. The bending tests substantiate the solution adequacy and exemplify the situation when the numerically predicted outcome determines the hybrid system efficiency and provides the designer with the structural reference.
This study presents a novel design concept of the hybrid beam system comprising the synthetic fiber-reinforced concrete slab and pultruded FRP profile fixed on the supports. Adapting the stress-ribbon structural approach15,30 allows for solving the bond issue and applying the simplified numerical model, assuming the perfect bond between the composite components. The considered case exemplifies the design of the hybrid systems (Fig. 1) when the FE modeling outcome (Fig. 6a) defines the objective reference for the design procedure describing the hybrid system efficiency and modifies the structural target (Fig. 3). Figure 10 schematizes the proposed concept.
Bridge structures are generally exposed to a harsh in-service environment, and the ultimate capacity, fatigue performance, stability, and durability behaviour are essential for construction materials in bridge engineering applications. There are a lot of high-performance construction materials used in bridge engineering, such as fiber-reinforced polymer (FRP), engineered cementitious composite (ECC), ultra-high-performance concrete (UHPC), and high strength steel (HSS) amongst others. Hence it is important to evaluate the integrity of high-performance as well as traditional construction materials used in innovative bridge structures/components to promote scientific issues associated with the design, safety, reliability, and integrity of construction materials. 2b1af7f3a8