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The behavior of lightweight reinforced concrete deep beams (LRCDBs) under fire conditions is investigated in this study, with a specific focus on the effect of varying transverse reinforcement spacing. Four LRCDB specimens with transverse reinforcement intervals of 60 mm and 150 mm are constructed and subjected to four-point bending tests at both normal and elevated temperatures. The ultimate load-bearing capacity of the specimens is increased by 6.9% when the spacing of transverse reinforcements is reduced from 150 mm to 60 mm. Additionally, the load-bearing capacity of the specimens with 60 mm and 150 mm stirrup spacing is reduced after exposure to fire, with reductions of 16.8% and 23.6% respectively. The ultimate deflection of the mid-span of the beam is also diminished by the heat from the fire. The analysis of the specimens is performed using Abaqus software and the Finite Element Method. The obtained results exhibit a strong agreement with the experimental data, providing valuable insights into the behavior of LRCDBs during fire conditions. These insights highlight the critical importance of designing appropriate transverse reinforcement.

Sinusoidal corrugated web girders, which are in the focus of the current paper, have been increasingly used in the past years in civil engineering applications due to economical design. Recently, a number of experiments dealing with the particular behaviour of this girder type have been carried out at room temperature, while the structural behaviour at elevated temperature has not been widely analysed and requires further investigation and clarification. The current paper deals with the improved geometrically and materially nonlinear analysis with imperfections (GMNIA) of sinusoidal corrugated web girders under fire conditions. The developed finite element model, which is validated based on previous measurements during fire tests found in the international literature, is capable of modelling the specialties, e.g., the so‐called 'accordion effect', of corrugated web girders. The applicability of design formulae is also illustrated in the paper while an extensive numerical parametric study is also carried out to demonstrate the impact of different parameters on the stability behaviour and failure mode of corrugated web girders at elevated temperature. [ABSTRACT FROM AUTHOR]

Air-supported structures are widely used as public buildings. Air-supported structures are soft and most traditional fire-fighting installations cannot be used in them. Existing design specifications only specify the fire resistance of the materials to be used for air-supported structures and there is no fire resistance design method for air-supported structures. The destruction process of air-supported structures can be divided into three stages: pre-fracture, leakage, and collapse. Theorical and numerical models were used to research the time span of all those stages. A framework to estimate the collapse and evacuation time was proposed in this paper. Air-supported structures with different spans were researched in this paper, and we found that the height of a structure has a significant influence on its fire resistance. The evacuation time increased by more than 52 times when the structure's span increased from 20 m to 80 m. The pre-fracture stage contributed to more than 90% of the evacuation time when the span of structure was larger than 80 m. [ABSTRACT FROM AUTHOR]

In recent decades, reinforced-concrete bridges have experienced premature deterioration and other problems during service due to severe environmental effects such as fire and corrosion. Previous studies have shown that the use of ultra-high-performance concrete (UHPC) can improve the durability of bridge structures. In this study, four-point bending tests were conducted on twelve UHPC–NC laminated beams with different UHPC-layer heights and at different temperatures in order to evaluate their flexural performance under fire conditions. The test variables were the UHPC heights (20 mm, 50 mm, 80 mm) and temperatures (20 °C, 200 °C, 400 °C, 600 °C), and the effects on the flexural load capacity of UHPC–NC laminated beams under the influence of these factors were investigated. The test results show that the increase in temperature causes the concrete color to change from grayish blue to white and leads to a significant decrease in the flexural load capacity of the stacked beams. The height of the UHPC layer has an important effect on the stiffness of the stacked beams and delays the formation of local cracks, thus improving the durability of the stacked beams. [ABSTRACT FROM AUTHOR]

• Mechanical response characteristics of beam-column substructures exposed to fire are analyzed. • Explicit calculation formulas for determining the collapse resistance are derived in detail. • Proposed theoretical calculated formulas agree well with these from numerical simulations. • Error analysis is conducted to reveal deviation reasons between theoretical model and numerical simulations. This paper provides a simplified analytical model for the restrained steel beam-column substructure under a fire-induced progressive collapse scenario, which is applied to predict the collapse resistance of substructures under fire. The simplified model is formulated for axially and rotationally restrained two-span steel beam-column substructures under column-loss scenarios and involves rigid and semi-rigid connections. The response characteristics of restrained substructures exposed to fire under column-loss scenarios in each response stage are elaborately analyzed. A "negative" catenary stage, in consideration of the unique negative axial force effects induced by the temperature thermal expansion, was first introduced in the five-stage simplified model for restrained substructures exposed to fire against progressive collapse. Subsequently, the explicit calculation formulas for determining the vertical loads and deflection of both rigid and semi-rigid joint substructures exposed to fire were derived in a quantified way, based on rigid-plastic mechanisms and restraint coefficient methods. In addition, the corresponding numerical simulation analysis on a restrained two-span steel beam-column substructure with different end constraints and fire conditions was carried out to verify the applicability and reliability of established theoretical formulas. Comparisons of vertical load-deflection relationships between the calculation formulas and corresponding numerical simulation shows good accuracy. For more accurate prediction results, the error analysis was further conducted, and several theoretical formulas were modified, which were verified to be accurate and reliable after correction. With derived resistance functions, the resistance of steel beam-column substructures in fire-induced progressive collapse scenarios can be predicted. [ABSTRACT FROM AUTHOR]