An experimental study of the long-term behaviour of reinforced concrete flat slabls under s ustained service loads

摘要

An experimental program of long-term testing of large-scale reinforced concrete flat slab structures is described and the results form the first series of tests on two continuous flat slab specimens are presented. Each specimen was subjected to sutained serivce lads for periods up to 220 days and the deflection, exten of cracking and olumn loads wee monitored througgout. The measured long-term deflection is many times the initial short-term deflection, due primarily to the loss of stiffness associated with time-dependent cracking under the combined influences of transverse load and drying shrinkage. This effect is not accouhndted for in the current code approaches for deflection caluclation and control, and the test results will be used to suggest improvements to the current design proedures for the serviceability of flat slabs.