STUDY OF THE STRESS-STRAIN STATE OF A REINFORCED CONCRETE SLAB USING HYDROSTATIC METHOD

Abstract

The scientific article is devoted to a complex study of the stress-strain state of a monolithic slab, implemented using the author’s method of hydrostatic loading, which involves setting the load by the weight of water and regulating its value by the height of the water column. To implement the given procedure, we used a tank-shaped facility for field tests of structures for vertical short-term and long-term loads. To determine the deflections of the loaded slab system, we installed mechanical deflection gauges of the 6PAO brand under the slab at pre-planned places. The short-term loading of the selected section of the monolithic reinforced concrete slab involved three stages. The first two stages of loading were carried out step by step, with a load step of 1–2 kN/m2 and a time delay until the arrows of the deflection gauges stopped. The maximum load on the slab was 5 kN/m2. The maximum deflection was recorded for point 2 (conventional centre of the tank) and was equal to 1.27 mm. The third stage of slab loading proceeded by analogy with the previous two. The maximum load on the slab was 8 kN/m2. The maximum deflection was recorded for point 2 and equalled 1.57 mm. After completing the stepped loading, the water tank was left on the slab to track vertical deflections for 32 days. The study experimentally established that the displacement of the examined slab in the span and support zones under increased load did not exceed the normative values. We carried out numerical verification using finite-element modelling followed by calculations in a linear and non-linear model. The theoretical and experimental calculation results showed a qualitative and quantitative data match (the difference did not exceed 15–20%). The nature of the change in the deflections remained practically linear and closely correlated with the experimental data (the values of the maximum deflections were equal to 1.16 and 1.57 mm, respectively, which was less than the maximum allowable deflection of 30 mm). Based on the results of the comprehensive study, we have made proposals for further safe operation of the investigated slab system through the use of lightweight floor elements (lighter filling, reduction of screed thickness, and others) to limit the total load on the overlapping to 10 kN/m2 (taking into account dead weight of the slab, load from floor structure and partitions, load from people and various types of construction and other equipment). Keywords: hydrostatic loading, testing, concrete, calculation, deflection, modelling.