Preliminarily Exploration The Theories Of Post-cracking Stiffness Of Rectangular Piers Considering The Tensile Strengh Of Concrete

The recent twenty years, many major earthquakes have occurred around the world, and they resulted in the heavy losses of life and property to people. Such as the United States's San Fernando earthquake in 1971 (M6.6), China's Tangshan earthquake in 1976 (M7.8), the United States's Loma Prieta in 1989 (M7.0) and Northridge earthquake (M6.7) in 1994, and Japan's Kobe earthquake in 1995 (M7.2). They respectively caused directly economic losses (in whichever currency at the time) were: 10 billion dollars, 10 billion dollars, 70 billion dollars, 20 billion REM and 1,000 billion dollars. Because of those earthquakes, many bridges were severely damaged and the traffic lifelines were cut off in the area of earthquakes, which caused the great difficulty to the relief work and resulted in huge economic losses. In order to guarantee the security and unblock of pavement, it becomes increasingly important to study the resisitant earthquake of the bridges engineering. Moreover, the moderate intensity earthquake also can severely cause the damaged of the bridge structure, which reflecting the seismic vulnerability of bridge structures.In the thesis, based on the basic mechanics concept of mechanics of materials, the two component rectangular reinforced concrete piers are studied in the elastic range, by initially discussing the degradation of the considering concrete tensile strength of the neutral axis of the distribution, power pier top displacement and the overall stiffness of concrete piers. In order to simplify the analysis model, the results are compared with the tests. Then the△P is introduced to the equivalent simplified model. The following works are mainly studied:①According to the mechanical concept, the formula of the neutral axis which considers the tensile strength of concrete is proposed, and the stiffness of components pier sections is obtained on this basis.②The cracking stiffness test of column are performed, and predictions of the model are compared and analyzed with experimental results. The variation trend of cracked stiffness of reinforce concrete column to make a cross-reference for the whole stiffness formula of column is summarized in the paper. ③Based on the three-phase simplified model, in order to provide a simplified formula of bending stiffness of the pier for cracking, the equivalent simplified of△P-type is introduced, and the correctness of the simplified formula is verified further.