Experimental studies of the elements of a joint-monolithic flat plate system floor

Abstract

The paper describes a full-scale tests of the floor fragment were performed during the construction of a three-section multi-apartment residential building. The purpose of the tests was a comprehensive check of frame members and connection joints for strength, stiffness and crack resistance requirements.

The structural basis of the residential building is a precast monolithic spatial frame without beams and capitals. The frame is assembled from factory products, with the subsequent monolithing of the joints. The main load-bearing members of the frame are columns with and floor slabs, the thickness of the slabs is 160 mm. The grid of columns has a step of 6 m and 3 m, the height of the floors is 3.0 m. The columns are continuous three- and two-story. Floor slabs are divided into overcolumned, intercolumned and middle. The reinforcement lugs are arranged in the form of a loop at the ends of the slabs. This design ensures a monolithic connection of adjacentslabs. Floor slabs are installed using temporary mounting supports. The reinforcement lugs on the ends of adjacent plates intersect in such a way that a closed space is formed.  After installing the reinforcement, the joints of the slabs are concreted with fine-grained concrete.

The fragment of the overlapping above the basement of the erected house was selected for the test. The load value was calculated for individual sections of the overlap. This load was the sum of dead and live load. The loading was carried out in stages according to norms. The wall blocks made of aerated concrete were used for creating the load. These blocks were used for the construction of external and internal walls after the tests.

The work presents the results of the performed tests. The value of slab deflections was obtained, which did not exceed the deflections got from the calculation. The devices that were responsible for recording the vertical movements of the slabs relative to the columns did not record such movements. No normal cracks were found in factory-made slabs. Cracks were found in monolithic loop joints between adjacent slabs. The opening width of such cracks did not exceed the limit values. The results of the conducted tests confirmed the accepted prerequisites for the calculation and construction of the members of the precast monolithic flat plate frame. Theoretical calculations with sufficient probability reflect the adopted design model.