CALCULATION METHOD OF THIN LAYER PLASTIC CONCRETE COATING ON REINFORCED CONCRETE SLAB OF ROADWAY SECTION OF HIGHWAY BRIDGES FOR DURABILITY

Summary. The paper examines the basic principles of calculating the durability of thin-layer plastic concrete covering on reinforced concrete slabs of roadways of highway bridges, taking into account domestic and European experience and countries of the world. The proposed methodology for calculating thin-layer coating on bridges takes into account the thermorheological properties of aerated concrete, using the provisions of the kinetic theory of the strength of solid bodies and based on the principles of Palgren-Miner and Bailey about the superposition of damage to the structure of aerated concrete during the period of operation under the negative joint action of the most influential factors, this made it possible to develop a limit state criterion thin-layer coating based on plastic concrete. Analytical calculations are given to determine the horizontal normal stresses that arise in the thin-layer concrete coating on bridges due to the effect of concrete shrinkage, changes in (seasonal, annual and daily) temperatures and the action of pneumatic wheels of vehicles. Analytical dependences are given for the components of the limit state criterion and the estimation of the service life of the thin-layer coating on bridges, namely: the measure of exhaustion of the durability of the thin-layer plastic concrete coating from shrinkage (МУс); the measure of exhaustion of the durability of thin-layer plastic concrete coating from the action of the load of pneumatic wheels of vehicles (МТр); a measure of exhaustion of the durability of a thin-layer plastic concrete coating from a change in the temperature of the corresponding season (МТ)). These analytical solutions made it possible to estimate the estimated (expected) service life (Троз) of thin-layer aerated concrete covering on reinforced concrete road bridges, namely: the service life (Троз) is the ratio of the maximum permissible value of the indicator of the degree of durability depletion (МВД=1) to the sum of the degree of exhaustion of thin-layer coating from the joint effect of plastic concrete shrinkage, temperature changes and the action of the load of pneumatic wheels of vehicles, which in turn is greater than or equal to the standard service life (Тн=15 years) of thin-layer plastic concrete coating on road bridges. Keywords: highway bridge, thin-layer coating; plastic concrete, coating, durability, shrinkage, temperature, load, degree of exhaustion.