Similitude Law Considering the Variation of Strain Ratio for Dynamic Test using Scaled Model with Composite Material

Abstract

It is required to evaluate an exact dynamic response of a reinforced concrete column to prevent seismic failure of reinforced concrete structures. Considering limitations from available capacity of test equipment and expensive cost for making and experimenting specimens, a dynamic test using real scale specimen is not generally recommended. In this case, a test using small scale model specimens is an economic alternative. To design the scaled model, it is important to decide which material is used for model material. For a scaled model of reinforced concrete structures, it is necessary to use model concrete such as micro-concrete, gypsum concrete and mortar whose aggregate size is smaller than ordinary concrete of real scale specimen(=prototype). This implies the material characteristics of prototype and model concrete are different. However the material characteristics of prototype and model reinforcement are typically not different because steel is used for both prototype and model reinforcements. For this reason, strain distortion which implies that strain ratio of concrete and steel are different and become not unity is occurred. In addition, from nonlinear material characteristics of concrete, the strain ratio is not constant but variable during the model test. In this thesis a new similitude law which reasonably considers the effect of the strain distortion and the variation of strain ratio, which is caused by the difference of characteristics between prototype and model materials especially for scale model of composite material, was developed. Furthermore an iterative method for estimating strain ratio was also suggested. Numerical verifications of dynamic analysis of reinforced concrete cantilever column with rectangular section were conducted. Results indicate that prediction by the developed similitude law shows higher accuracy of prediction for the response of prototype than those by similitude laws of previous studies. After the numerical verifications, experimental verifications were conducted. Both shaking table test and pseudo dynamic test were used. Tests using prototype and scaled model applying similitude laws of previous studies and the developed similitude law were conducted. By comparing responses of prototype with predictions from the response of model by applying the similitude laws, the validation of the developed similitude law were verified experimentally.