Behavior And Design Of Composite Beam In Fire With Considering Global Structure Effect

Behavior of element in the whole structure is much different from that of isolated element because real structure is highly redundant. This has been demonstrated in recent fire tests on the Cardington full scale test and observations from real fires. But the traditional fire design method neglected this important fact. The design method would lead to dangerous or uneconomical results. Fortunately, many scholars have studied the behavior of restrained steel beam in fire and gave some guide or design method on this. But for the composite beams, which have been popularized in construction, there is neither fire test nor fire design method been reported.The main objective of this dissertation is to study the behavior of restrained composite beam in fire according to fire test, and based on the comprehension on the behavior, to establish the temperature distribution model and the fire design method of restrained composite beam during the whole temperature elevating procedure. And thus the following work is demanded:1. Based upon the collection of papers about tests and models of materials, a serious of models fit for the study of this paper is selected.2. Composite beam, which is composed by concrete slab and steel beam, has a complex temperature distribution. Because there are many differences on thermal properties of concrete and steel. With the aid of FEM soft package -Ansys, the parametric analysis about the temperature distribution of the popularized composite beam(plat composite beam and deck composite beam) is conducted. The temperature distribution model, which is the base of analysis on fire-resistance capacity of composite beam, is established. The temperature distribution model can be easily determined by the simplified method proposed in this paper.3. Fire-resistance tests focus on two composite beams, of which axial restraint and flexure restraint comes from a restraining frame which remains room temperature during the whole temperature elevating procedure. The specimen and the restraining frame are designed based on the investigation and FEM model of real structures. With the investigation of the fire test, the characteristics of temperature distribution, load-bearing model and destruction procedure is summarized and studied. The test data including temperature distribution, deflection and displacement etc would give the verification for the fire-design method proposed in the following section in this paper.4. With some assumption, the bearing capacity calculation methods for restrained...