Calculation of a monolithic plate Taking into account the rheological properties of reinforced concrete

Abstract

It is well known that the rheological properties of concrete are mainly due to its creep. Even if the load does not change much during the life cycle of the object, the increase in displacements over time due to the creep of concrete significantly affects the stress-strain state of the structure. Over time, it is possible to redistribute the effort between the loaded elements, between the reinforcement and concrete in the cross sections of the elements.

That is, the actual behavior of the structure during the life cycle may differ from that predicted in the design, taking into account only the elastic work of materials. The method of "engineering nonlinearity" used in the calculation makes it possible to determine the real stiffness characteristics of the section. They can be reduced due to plastic deformations of concrete and reinforcement, cracking, etc.

Using this technique, a monolithic reinforced concrete slab of the first floor of the shopping center was calculated for the current loads.

The main parameters of the stress-strain state of the structure of the investigated section of the floor slab in the elastic-linear calculation and calculation using the method of "engineering nonlinearity": moments in the first span, over the first support, in the second span, over the second support, displacement (deflection) in the first and the second span of the plate.

The analysis of the results showed that when applying the method of "engineering nonlinearity" there was some redistribution of forces in the elements of the plate (in the spans the moments increased by 30,8% and 6,1%, on the supports - decreased by 11,1% and 35,8%). Displacements (deflections) more than doubled: in the first span - by 57,6%, in the second - by 53,13%.

Due to the redistribution of forces in the spans, the reinforcement increased by 13,9% and 3,7%, and on the supports - decreased by 11,2% and 20,4%, respectively. The width of crack opening increased insignificantly - from 2,7% in the first span to 5,4% in the second support.