This paper aims to evaluate the modal frequencies, damping ratios and mode shapes of an asymmetric building, modeled as general torsionally coupled buildings using a modified random decrement method together with the Ibrahim time domain technique based only on few floor acceleration response records from earthquakes. It is not necessary to measure earthquake excitation input. The general relationship between the reduced random decrement signature and the true free vibration response is derived analytically. Because only partial floor response measurements are used, a mode shape interpolation technique is developed to estimate the mode shape values for the locations without measurement, such that all floor responses can be obtained. The results were obtained from simulation data from a five-story building under the 1940 El Centro earthquake and actual records from a seven-story RC school building in northeastern Taiwan, due to an earthquake near the building site. The results show that the proposed system identification technique is capable of identifying structural dominant modal parameters and responses accurately even with highly coupled modes and high levels of noise contamination.

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Self-consolidating lightweight aggregate concrete (SCLC) is a highly flowable and lightweight concrete. In this study, the properties of SCLC and prestressed SCLC members were tested and compared with those made of normal-weight self-consolidating concrete (SCC). The test results show that SCLC can be used for prestressed concrete members. The use of lightweight aggregates with a particle density larger than 1100 kg/m 3 can avoid the serious segregation of fresh concrete. In addition, the SCLC designed in this study can meet most of the SCC Rank 2 test standards, except for the V-funnel test. The water contained in the lightweight aggregates supplied sustained curing, so the level of drying shrinkage of the SCLC was lower than that of the conventional SCC. However, the level of creep of the SCLC was higher than that of the conventional SCC, because normal-weight aggregates are more able to inhibit the change of the concrete's volume. On-site test results show that after 180 days of prestressing, the prestress loss was about 5.35-6.83% for the full-size SCLC members, which was smaller than that for the conventional SCC members (about 8.19-9.06% loss).