Numerical Analysis of a Moderate Fire inside a Segment of a Subway Station

Abstract

A 1:4 scaled fire test of a segment of a subway station is analyzed by means of three-dimensional Finite Element simulations. The first 30 min of the test are considered to be representative of a moderate fire. Numerical sensitivity analyses are performed. As regards the thermal boundary conditions, a spatially uniform surface temperature history and three different piecewise uniform surface temperature histories are used. As regards the material behavior of concrete, a temperature-independent linear-elastic model and a temperature-dependent elasto-plastic model are used. Heat transfer within the reinforced concrete structure is simulated first. The computed temperature evolutions serve as input for thermomechanical simulations of the fire test. Numerical results are compared with experimental measurements. It is concluded that three sources of uncertainties render the numerical simulation of fire tests challenging: possible damage of the structure prior to testing, the actual distribution of the surface temperature during the test and the time-dependent high-temperature behavior of concrete. In addition, the simulations underline that even a moderate fire represents a severe load case, threatening the integrity of the reinforced concrete structure. Tensile cracking is likely to happen at the inaccessible outer surface of the underground structure. Thus, careful inspection is recommended even after non-catastrophic fires.

Transient Nonlinear Heat Conduction in Concrete Structures: A Semi-Analytical Approach

“…The initial temperature is set equal to and the sudden temperature increase is set as , representing a moderate fire load [ 7 , 41 ]. As the investigated temperature is below , the dehydration process is not stimulated [ 5 , 8 ].…”

“…The solution was validated by numerical simulations and further applied to a scaled fire test, inspired by a three-span subway station [ 40 ]. The thermomechanical behavior of the model in the first 30 min of the test was analyzed by a three-dimensional Finite Element simulation, simulating a non-catastrophic fire event [ 41 ]. Notably, the thermophysical properties of concrete were assumed to be constant in simulating the temperature field.…”

Fire Resistance and Elevated Temperature in Reinforced Concrete Members: Research Needs for India

“…Studies employing numerical analysis of concrete members and structures subjected to fire or elevated temperature are plentiful in the literature. Researchers have investigated global structural response under fire [30,[64][65][66][67][68][69][70] and elevated temperature [71], local fire [72], hygrothermal response [73], restraint effect on structural members [74], structural response at member level [75,76], structural joints [77] and have performed nonlinear analysis [78] for response under fire, as well. There have been attempt to compare the results of numerical analysis with the provisions of the design code [79], as well as comparison of different codes [9,10] and such studies give better insight into the relevance of the code provisions for fire.…”

Transit-Based Evacuation for Urban Rail Transit Line Emergency

“…In other words, this constraint dictates the total number of evacuees that can be evacuated from station i to all temporary shelters at all time periods, which should be less than the entire population at station i. It is also worth noting that the capacity of vehicles is added to the right-hand side of the constraint to avoid leftover passengers when the passenger population is less than the capacity of the vehicle; Equation (12) implies that all vehicles must start from a station in each time window; Equation (13) restricts vehicles from starting their services from temporary shelters in the first time window; Equation 14defines the endpoint of vehicles in each time window; Equation (15) indicates that at the end of the final time window, vehicles can only finish their service at the designated temporary shelter; Equation (16) guarantees the continuous flow of vehicles by starting their next service from the last finished point; Equation (17) ensures the flow of the network is maintained within each time window, i.e., for each vehicle, the quantity that arrives at a node must be equal to the quantity that departs; Equation (18) guarantees that the number of times a vehicle travels from is an integer; the remaining Equations (19) and (20) specify the domain for binary variables.…”

“…An emergency is an abnormal and usually unplanned operational situation with rail stations or lines. The factors affecting emergency evacuation include occupant factors [13,14], building parameters [15,16], and environmental factors [17][18][19]. In this paper, pedestrian evacuation in rail stations is not a major concern, so we only focus on the evacuation outside rail stations while considering the urban rail transit line emergency.…”