COMPARATIVE STRENGTH CALCULATION OF VERTICAL JOINTS OF PREFABRICATED WALL ELEMENTS

Abstract

Finland's progressive method of creation keyed joints of prefabricated wall elements on flexible loops instead of rigid joints significantly improves manufacturing technology. It allows to use the wall panel formwork repeatedly, individually change the step and keys arrangement and simplifies the wall elements installation. For its introduction in the construction industry of Ukraine it is necessary to develop an appropriate regulatory framework. Comparative theoretical strength calculation of such 46 joints, determined according to Eurocode, norms of Ukraine and Russia, with experimental data was performed. The joints parameters the varied widely: the number of boxes (keys) varied from 2 to 4, boxes were used with sizes 35x160, 35x180, 50x160, 80x120 mm with one or two loops in each, the wall panels thickness was taken 120 and 150 mm, the joint width was 80, 90 and 100 mm, compressive strength of grouting concrete was within f_{c, prizm} = 23,5 - 40 MPa. The analysis results indicates a significant overestimation of the theoretical strength, inconsistency to the accepted calculation schemes of the joint destruction character. This is explained by not taking into account the specifics of the joints structural solution of wall elements on flexible loops by the existing regulatory documents. Suggestions for improvement of the normative calculation by specifying the influence degree of the main determining factors are given: concrete tensile and compressive strength and stress values in flexible loops in the failure stage. The method required accuracy can only be guaranteed in the presence of an experimental data large sample. An alternative may be the use of a general method of calculating reinforced concrete elements under the shear action based on the plasticity theory mathematical apparatus using a variational method developed at PoltNTU.