NUMERCIAL MODELS OF FIRE INDUCED PROGRESSIVE COLLAPSE ANALYSIS FOR REINFORCED CONCRETE FRAME STRUCTURES

Progressive collapse is the global behavior of the whole structural system. In order to investigate the fire induced progressive collapse of reinforced concrete (RC) frame structures, a fiber beam model for RC beam and column and a multilayer shell model for RC slab are established. In elemental-scale, the sections at integration points are divided into some fibers or layers. Different material properties are assigned with various fibers and layers to consider the contribution of steel reinforcement and concrete. The relationship between the deformations of elements and the strains of fibers or layers is defined according to the assumption that plane section remains plane. For materials, temperature-stress loading path is discretized into sub-increments. The various strains of fibers or layers, induced by coupled actions of temperature and stresses, are calculated within each sub-increment. The accuracy and efficiency of the models in simulating the behaviors of RC beams, columns and slabs in fire are validated through a series of fire tests. In order to simulate the discontinuous displacement field during the procedure of structure collapse, the failure criterion and the deactivation of the structural elements are introduced to the model. Therefore, the influence of internal force redistribution induced by element failure on the mechanical response of the whole structure is taken into consideration. At last, a frame structure is analyzed to study the failure mechanism of its fire induced collapse via the proposed numerical models.