Linearity of deflections of long-term loaded slabs

Abstract

The effects of different long-term loading levels including those when cracks occur on the deflections of one-way reinforced slabs were investigated. Three series of slabs with different types of reinforcement were subjected to a sustained load at five levels over a period of about 800 days. The results have confirmed that a linear relationship between the initial and time-dependent deflections can be assumed up to a high loading level (0.8). Moreover, the effects of the age of concrete at the application of long-term load were studied. A series of 20 two-way slabs reinforced with welded deformed wire fabrics, made of concrete using river and crushed aggregate, were tested. Sustained load at the level of about 0.5 (with regard to the failure limit) was applied to slabs at the age of 7, 14, 28, 60 and 90 days and maintained for about 400 days. The results showed that the deflection surfaces at the two arbitrary time intervals were similar in spite of intensive crack development. The dependence of the deflection on the age of concrete at the time of load application was proved.