Experiment Study On Structural Performance Of Beam String Structure

Beam string structure, which is formed with arch and string with the connection of members in compression, is a new type space-structure. For beam string structure the horizontal forces of arch and string are equal to each other, so the structure is light and handy, and has good behavior under different load conditions. Since the 1990s, beam string structure has been widely used in many public buildings with long span. With the number of beam string structures increased, the performance of this structure need to identified more clearly. Now, with FEM method, researchers has made static analysis,dynamic analysis, got some useful conclusions. Although FEM method plays an important in research, bearing mechanism of beam string structure is not very clear, a simplified formula based on continuous hypothesis has not been derived yet. Without simplified formula, it is very hard to explain the conclusions got by FEM method theoretically. Meanwhile, in conceptual design, designers can not choose the structure parameters easily, or make judgments for some important behavior.This dissertation is devoted to the force mechanic of beam string structure. By theoretical analysis and modal experiment, we analyze the static behavior and the dynamic behavior systematically. For the problem raised in designing and construction, we also make some useful suggestion. This dissertation contains following parts:Generalize the developing process of beam string structure, classify different types of beam string structure by components geometry and mechanics characteristics, introduce research productions in related field, expound the meanings of research, and introduce some famous beam string structures.The main research work focus on the beam string structure. By making continuous hypothesis, beam string structure can be treated as a continuous system. We deduct the simplified formula to calculate displacement and force under uniformly distributing load and live load half span distribution; the simplified formula to calculate displacement and force corresponding the tensioning stage, and propose the reasonable value of prestress, rise span ratio, height span ratio and moment of inertia of arch. Design modal experiment to deep the understanding of beam string structure. The process of modal experiment contains follow parts: the displacement and force response in tensioning stage; the displacement and force response under uniformly distributing load; the displacement and force response under live load half span distribution; the ultimate bearing capacity experiments under uniformly distributing load. The purpose of these experiments is: compare different results(modal experiment,FEM method,simplified formula), conclude the suitability of FEM method and simplified formula; conclude the mechanics characteristic by analyzing the experiment result, and explain these conclusions by the simplified formula; analyze the failure mechanism and the ultimate bearing capacity of beam string structure.Based on the continuous hypothesis, deduct the simplified formula of the free vibration. Meanwhile, make modal experiment and test the former 4 orders natural frequency, compare different result(modal experiment,FEM method,simplified formula), conclude the suitability of FEM method and simplified formula. By analyze the experiment result, conclude the free vibration characteristics of beam string structure, explain and expand the conclusion by simplified formula.