Kaplin R. Multi-criteria rationalization of structural parameters of steelreinforced concrete bridge spans during reconstruction

The thesis is devoted to the rationalization of the design parameters of steelreinforced concrete bridge spans, including perforated metal box-section blocks and an effective reinforced concrete slab of the roadway. The dissertation deals with the issues of improving the design of steel-reinforced concrete spans of an auto-road bridge and its numerical and experimental research, as well as methods for rationalizing and controlling its characteristics. For the proposed systems, rationalization criteria are justified and internal and external control parameters are determined. The classification, general characteristics and design features of the most common reinforced concrete girder structures of bridges are considered. The main advantages and disadvantages of these systems, as well as design features of the details of the combination of metal and reinforced concrete part of the structure are considered. The experience of application of lightweight effective metal and reinforced concrete elements in the form of perforated beams and reinforced concrete slab with hollow formers is also analyzed. On the basis of the obtained theoretical data, a new structural solution of the span was formed, in which the compressed part is presented in the form of a lightweight reinforced concrete slab, and the stretched part is presented in the form of a metal spatial part, which consists of perforated plates with an irregular topology of holes. The configuration of the perforated metal element under the conditions of multicriteria is obtained. A method of manufacturing of perforated elements with irregular topology and steps of holes is proposed. To determine the efficiency of the reinforced concrete slab, an algorithm for determining the optimal height of the cross section of the girder and the impact of the reinforced concrete slab on the height of the metal part of the structure is proposed within the framework of the specified design solution. A theoretical calculation model of the proposed reinforced concrete span structure is constructed, on the basis of which an analysis of the stress-strain state is performed. The theoretical study was carried out according to two calculation schemes of span structures, consisting of three blocks connected by high-strength bolts and a single reinforced concrete slab. The first considered model is a span structure with metal perforated blocks having a regular pitch and width of holes. The second is represented by a span structure, with metal perforated blocks, have an irregular pitch and width of holes. In general, the analysis allows us to judge the positive impact of the use of perforated elements with irregular pitch and hole width, as it reduces the deflections of the structure, as well as minimize the values arising in the belts and elements, forces and stresses up to 40%. Full-scale experimental studies of the steel-reinforced concrete block of the superstructure have been carried out. During the experiment, the fact of reliable joint operation of the reinforced concrete slab with the metal part of the model was confirmed. The analysis of the obtained results allows one to judge the high rigidity of the system and testifies to the elastic work of materials. It should be noted that the nature of the deformation of the system confirms the correctness of the compiled theoretical model, and the obtained experimental data coincide with the theoretical ones, while the discrepancy does not exceed 15%.