This paper describes the investigation and examination of damage conditions of a reinforced concrete school building with three stories which was constructed on a soft stratum in 1966. In this study, the self-strain stresses due to the differential settlement and concrete drying shrinkage were evaluated with the related damage, and the influence of such damage on the structural performance was discussed. The following findings were obtained from this study:
(1)A part of the structural frames has been reached to yield conditions due to remarkable differential settlement and, as a result, the apparent rigidity of the structure was estimated as to be about 1/3 of the elastic rigidity.
(2)The magnitude of differential settlement was significantly influenced by the structural rigidity as well as the soil condition.This was confirmed by the theoretical values of the differential settlement which was almost corresponded to the measured one.
(3)Based on the measured concrete drying shrinkage strain, the average strain of main beams in the statically indeterminate rigid frames was estimated as about 150×10 -6 , and that of each of the slab and the sub-beam was to be about 200×10 -6.