Study On Shear Behavior Of Reinforced Concrete Continuous Beams Under Different Fire Conditions

Under fire conditions,the thermal and mechanical properties of steel bar and concrete materials decrease sharply due to the increase of temperature.The ultimate shear and bending capacity of reinforced concrete continuous beams decrease sharply,which is lower than the inherent load value of the beams at a certain time,leading to the destruction of the members.It is of great significance to study the shear fire resistance limit of continuous beams under fire conditions for structural design and rescue work under fire conditions.Six fire conditions of reinforced concrete continuous beams are studied and designed,which are single-span beam three-way fire,two-span beam three-way fire,twospan beam three-way fire,three-side fire,three-span beam three-way fire,three-span beam three-way fire,three-span beam three-way fire and three-span three-way fire.The shear performance simulation of beams is carried out in ABAQUS software.The main contents are as follows:1)The temperature field model of reinforced concrete beams is established according to the material thermal performance parameters of different specifications at home and abroad.The accuracy of the model is verified by comparing with the experimental data.The correction coefficient between the simulated data and the experimental data is 1.12.2)The heat conduction equation of materials is deduced,and the stress measurement of the indeterminate structure is described.The internal deformation of the indeterminate structure is analyzed at high temperature,and several hypotheses of the temperature field simulation model of the reinforced concrete beam are established.3)The thermo-mechanical coupling model of temperature field under six fire conditions is established.The shear failure time of continuous beam is studied by analyzing the time-temperature curves and time-stress curves of stirrups,longitudinal bars and concrete.The ultimate fire-resistant limit of the beam is 2194 s,2122s,2087 s,2096s,2060 s and 2024 s.Figure 65;Table 15;Reference 49...