Earthquake Tests of Reinforced Concrete Frames

The paper presents a series of shaking table experiments performed at the Structural Laboratory at Aalborg University, Denmark during the autumn of 1996. A brief description of the purpose and aim of the tests are given and some selected results are presented. The considered structure is a 2-bay, 6-story reinforced concrete frame in scale 1:5 with the outer measures 2.4 X 3.3 m. The test structure consists of two identical frames spaced 1000 mm on a shaking table. to the observed The dead-load of deck elements and pay load is modelled by 8 RC-beams placed on each storey in span between the two frames. One of the frames is instrumented with accelerometers at each storey and the shaking table is equipped with an accelerometer as well. Initially the modal parameters of the tests structure are determined from a free decay test, where the top storey is pulled approximately 5 mm out from the equilibrium state. Afterwards the test structure is subjected to the three strong ground motion oscillations where the two first sequences are followed by a free decay test. No free decay test was performed after the third earthquake due to collapse of the test structure during the third strong motion oscillation. After each of the strong motion sequences the structure is visually examined to reveal cracks etc., and this visual damage assessment is compared to the observed reduction in the two lowest eigenfrequencies of the structure which can be extracted from the measured top storey accelerations during the strong motion events