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Influence of mechanical and geometrical properties of embedded long-gauge strain sensors to the accuracy of the strain measurement

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The response of bridges subject to fire is an under researched topic despite the number of bridge failures caused by fire. Since available data shows that steel girder bridges are especially vulnerable to fire, this papers delves into their fire response by analyzing with a 3D numerical model the response of a typical bridge of 12.20 m. span length. A parametric study is performed considering: (1) two possibilities for the axial restraint of the bridge deck, (2) four types of structural steel for the girders (carbon steel and stainless steel grades 1.4301, 1.4401, and 1.4462), (3) three different constitutive models for carbon steel, (4) four live loads, and (5) two alternative fire loads (the hydrocarbon fire defined by Eurocode 1 and a fire corresponding to a real fire event). Results show that restraint to deck expansion coming from an adjacent span or abutment should be considered in the numerical model. In addition, times to collapse are very small when the bridge girders are built with carbon steel (between 8.5 and 18 minutes) but they can almost double if stainless steel is used for the girders. Therefore, stainless steel is a material to consider for steel girder bridges in a high fire risk situation, especially if the bridge is located in a corrosive environment and its aesthetics deserves special attention. The methodology developed in this paper and the results obtained are useful for researchers and practitioners interested in developing and applying a performance-based approach for the design of bridges against fire.

ElsevierPaya-Zaforteza, I.; Garlock, ME.; Loma-Ossorio, E.; Hospitaler Pérez, A. (2014). Analysis of a bridge failure due to fire using computational fluid dynamics and finite element models. Engineering Structures. 68:96-110. doi:10.1016Structures. 68:96-110. doi:10. /j.engstruct.2014 Please, cite this paper as:Alos-Moya, J., Paya-Zaforteza, I., Garlock, M.E.M., Loma-Ossorio, E., Schiffner, D., Hospitaler, A. Analysis of a bridge failure due to fire using computational fluid dynamics and finite element models (2014) Engineering Structures, 68: 96-110. DOI: 10.1016/j.engstruct.2014 Please, cite this paper as:Alos-Moya, J., Paya-Zaforteza, I., Garlock, M.E.M., Loma-Ossorio, E., Schiffner, D., Hospitaler, A. Analysis of a bridge failure due to fire using computational fluid dynamics and finite element models (2014 AbstractBridge fires are a major concern because of the consequences that these kind of events have and because they are a real threat. However, bridge fire response is under researched and not covered in the codes. This paper studies the capabilities of numerical models to predict the fire response of a bridge and provides modeling guidelines useful for improving bridge design. To reach this goal, a numerical analysis of the fire of the I-65 overpass in Birmingham, Alabama, USA in 2002 is carried out. The analyses are based on computational fluid dynamics (CFD) for creating the fire model, and finite element (FE) software for obtaining the thermomechanical response of the bridge. The models are validated with parametric studies that consider heat release rate of the spilled fuel, discretization of the fire temperature in the transition from CFD to FE modeling, and boundary conditions. The validated model is used in a study to evaluate the influence of fire scenario (CFD versus standard fires), and live load. Results show that numerical models are able to simulate the response of the bridge and can be used as a basis for a performance-based approach for the design of bridges under fire.Additionally, it is found that applying the Eurocode standard and hydrocarbon fires along the full length of the bridge does not adequately represent a real bridge fire response for medium-long span bridges such as this case study. The study also shows that live loads essentially do not influence the response of the bridge.Keywords: fire, bridge, CFD, steel girder bridge, I-65 overpass, performance-based design.Please, cite this paper as:Alos-Moya, J., Paya-Zaforteza, I., Garlock, M.E.M., Loma-Ossorio, E., Schiffner, D., Hospitaler, A. Analysis of a bridge failure due to fire using computational fluid dynamics and finite element models (2014) Engineering Structures, 68: 96-110.

Although bridge fires pose a real threat, the topic is not covered in current design codes. This paper analyses information related to 154 cases of bridge fires, proposes classifying the damage levels suffered by a bridge during a fire, and establishes the main factors involved in bridge fire damage, which include: type of vehicle involved in the fire and its position, vertical clearance of the bridge, and the type of material composing the deck. The analysis shows that wooden bridges are the most vulnerable and that a tanker carrying gasoline under the bridge, or that is on the bridge and causes a serious spill under the bridge, is responsible for most of the fires that result in the collapse or demolition of the bridge.

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