| Steel shell concrete immersed tube is made of steel shell concrete plate splicing,which has good tensility,impact resistance,antiseepage and anti-seismic abilities,and can achieve industrialized manufacturing.In recent years,the demand for river crossing in urban central area is increasing,and small section steel shell concrete immersed tube tunnel will be more widely used.Based on the small section steel shell concrete immersed tunnel,this thesis studied the temperature distribution of small section tunnel fire by literature research,theoretical analysis and numerical simulation.The refined heat transfer analysis model of the steel shell concrete immersed tube was established to study the fire temperature distribution and parameter analysis of steel shell concrete structure.A fire protection design method for the steel shell concrete immersed tube structure was proposed.The main research contents and conclusions were as follows:(1)The real fire scene in the small section tunnel is simulated by using FDS.Considering heat release rate,number and location of vehicles on fire,natural ignition and forced ignition,the temperature field of the small section tunnel fire is analyzed.The results show that the maximum temperature below the ceiling of the small section tunnel is relatively low and is about 700 ℃.The horizontal temperature difference below the ceiling is small,and the spread distance of high temperature region in longitudinal direction is short.There is a significant difference between the fire temperature rise curve of the small section tunnel and the standard fire temperature rise curve of RABT and HC.(2)The temperature distribution law of the steel shell concrete immersed tunnel segment under fire is studied.Refined heat transfer model of the steel shell concrete immersed tunnel segment is established by ABAQUS to study the temperature distribution of the immersed tunnel segment.Based on the heat transfer analysis model,the effects of fire heating curve,the steel panel thickness,the rib spacing and the rib thickness on structural temperature are investigated.The results show that the complex internal structure of the steel shell concrete slab breaks the one-dimensional heat transfer mode of the traditional concrete slab.Fin and partition can transfer high temperature to the depth of structure more quickly,so that the phenomenon of low temperature in the center and high temperature around the compartment appears inside the structure.Fire heating curve has great influence on the structure temperature,and the steel panel thickness,the fin spacing and the fin thickness,which are commonly used in engineering,have little influence on the structure temperature.(3)The calculation formula of equivalent thermal resistance of fire protection layer is proposed.The temperature field of the steel shell concrete slab with fire protection is simulated,which is based on the refined heat transfer analysis model.The relationship between the temperature of the steel panel and the equivalent thermal resistance of the fire protection layer under the action of HC and RABT standard fire heating curves was obtained by simulation.The calculation formula of equivalent thermal resistance under different fire endurance and different limited temperature is proposed.The formula can be easily applied to practical projects.In this paper,the fire temperature field in small section steel shell concrete immersed tube tunnel and the temperature distribution law of the steel shell concrete immersed section are studied.A fire protection design method of the steel shell concrete immersed tube tunnel.The conclusions in this paper can promote the application of the small section steel shell concrete immersed tunnel.There are 82 figures,16 tables and 75 references in this dissertation. |
