## 4 Pseudo-Dynamic Test Overview and Result Analysis
### Overview of the Existing Seismic Test Method  
In the event of an earthquake, its influence on a structure depends on the characteristics of the ground acceleration as well as the type, weight, and stiffness of the structure. The shear force in the vertical members that support the building caused by the horizontal seismic acceleration generates relative lateral motion in the building. In general, in the event of an earthquake, structures should withstand large deformations without collapse and absorb energy through inelastic behavior. In other words, while seismic loads are transmitted to a structure in the event of an earthquake, considerable seismic input energy is absorbed by the inelastic behavior of the structure because materials locally reach yield points and plastic deformation occurs in the structural system. However, it is extremely difficult or impossible to evaluate such inelastic behavior using theoretical methods, despite the development of computer software.  
The experimental methods generally used to predict the inelastic seismic responses of structures can be classified into shaking-table, quasi-static, and pseudo-dynamic tests. A shaking-table test is the most effective for examining the seismic behavior of a structure. However, scale models are mostly used because the weight and size of specimens are significantly limited by the size and capacity of the shaking table, which causes a similarity problem with the actual structure. Due to these constraints, a quasi-static test that controls the displacement or load of the structure has commonly been used to evaluate the inelastic behavior of a real-size structure.  
The pseudo-dynamic test, which combines the benefits of the shaking and quasi-static tests [36], is a composite experimental method that combines an experiment with numerical analysis. The pseudo-dynamic test consists of a numerical calculation by a computer and an experiment in which the specimen is loaded. In the numerical calculation, the equation of motion is calculated using numerical integration based on the response of the specimen to specific deformation, the input seismic acceleration, and the response of the current step measured in the experiment. In addition, the response deformation for the next step is calculated. In the loading experiment, the response deformation is applied to the specimen using loading devices such as actuators, and the resulting displacement history is measured. By repeating the above manipulations, the seismic response of the target structure is calculated, while a response deformation similar to that in the event of an earthquake is applied to the specimen, with the seismic response calculated using a computer.  
The pseudo-dynamic test is similar to the quasi-static test except that the displacement to be applied to the structure is determined by numerical analysis during the test. In general, it is necessary to assume hysteretic characteristics when predicting the seismic response using numerical dynamic analysis. However, the pseudo-dynamic test can obtain an effect similar to the actual seismic response by directly measuring such information from the specimen, and it is used in several studies to evaluate the seismic performance of buildings [37; 38; 39; 40].