Research On Damping Property Of Recycled Aggregate Concretes

With the double-quick urbanization course, the urban renovation, construction industry and infrastructure construction are developing rapidly. At the same time, the study of recycled aggregate concrete becomes a hot research subject in academic circle, but the study of the damping properties of recycled aggregate concrete is still a rarity. Currently, the analysis of wind-induced vibration elastic-plastic seismic response become more widely available, and it is especially important to appropriately grasp material and structural damping.In order to accelerate the course that recycled aggregate concrete can be used as structural material, this thesis study the damping properties of recycled aggregate concrete through both theoretical and experimental analyses.First, the physical and mechanical performance of recycled coarse aggregate, natural aggregate and recycled aggregate concrete was tested. Tests showed that, relative to natural aggregate, the apparent density and bulk density of recycled aggregate were both smaller, and the water absorption and water content was notably higher. Besides, the strength of recycled aggregate concrete decreased with the replacement ratio of recycled aggregate increasing.Second, the damping properties of recycled aggregate material was tested through large-size damping tester with three point bending and damped method with cantilever beam free vibrating. In this case the relations among replacement ratios of different recycled aggregate, gradation of different recycled aggregate, damping properties and working frequency of different modified recycled aggregate concrete materials, and working stress were obtained. Lab studies showed that the replacement ratios and particle sizes of different recycled aggregate, the frequency and the amplitude of exciting force, and mixing modified materials all have different effect on the damping properties of recycled aggregate concrete.Third, the relation between the loss factors of concrete materials and the equivalent loss factors of components and the relation between the loss factors of concrete materials and equivalent loss factors of materials were tested. The result showed that, to the complex damping models which vibrate in single degree of freedom bearing, the equivalent loss factors of concrete materials, the equivalent loss factors of components and the loss factors of materials are all the same.Fourth, several important parameters of the damping properties of describe concrete materials were obtained according to the relation between dissipating energy of materials and working stress which was proposed by Lazan, the relation between theoretically derivational damping energy dissipation of constructional element and the working stress, and the comparative analysis of the result of experiments. The result shows that the loss factors of material not only relate to the damping properties of materials themselves, but also relate to the section format of elements, load types, element constraints, and the amplitude of the outer loading.At last, the damping ratio of the elements of recycled aggregate concrete in non-elastic stage was tested by damped method with cantilever beam free vibrating and obtained the relations among the damping properties of the elements of recycled aggregate concrete, crack, and damage evolution.