Analysis of the stress-strain state of foundation slabs on soils subject to seismic effects

Abstract

The foothills of Caucasus are characterized by considerable areas comprised of soils prone to slump-type settlement, and elevated seismic activity; this should be considered when analyzing and constructing the foundations of buildings. As we know, prior to their wetting, soils prone to slump-type settlement will behave as normal soils, the deformation properties of which correspond to their physicomechanical characteristics in the unwetted state.When buildings are designed for installation in seismically active areas comprised of soils prone to slump-type settlement, three analytical situations should be considered.1. The initial period of a building's occupancy when wetting of the bed has not yet occurred. As for conventional soils, buildings and foundations should be analyzed for seismic effects. 2. Wetting of bed soils prone to slump-type settlement has occurred during the building's occupancy. The building will function, sustaining damages only due to slump-type settlement of the soils.3. Seismic action will affect a building with a wetted bed prone to slump-type settlement. This paper investigates the stress-strain state (SSS) of the foundation slab of a nine-story brick building with a basement as applies to the situations described. A monolithic 800-mm-thick reinforcedconcrete slab formed from Class V20 concrete reinforced with Class A-III deformed bars was selected for investigation. Figure 1 shows the dimensions of the slab and the location of columns and stiffening diaphragms. The section of the columns is 40 40 cm, their spacing is 6 m in the longitudinal and transverse directions, and the number of spans is two and 10 in the transverse and longitudinal directions, respectively. The columns are the bearing components of the building, and the stiffening diaphragms and floors are composed of monolithic reinforced concrete.Class V30, V20, and V35 concrete was specified for the columns, stiffening diaphragms, and floor slabs, respectively. The superstructures are reinforced with Class A-III deformed bars.The slab with the frame placed on it was analyzed using the LIRA 9.4 software package. In the analytical model of the building, the slab was partitioned into triangular and tetragonal finite elements Results of analysis are presented for a foundation slab of a brick building subject to seismic effects on land with soils prone to slump-type settlement. The effect of the wetting of this soil on the stress-strain state of the foundation slab is evaluated.