ОСЛІДЖЕННЯ НАПРУЖЕНО-ДЕФОРМОВАНОГО СТАНУ ЗАЛІЗОБЕТОННОЇ МОНОЛІТНОЇ ПРОГОНОВОЇ БУДОВИ МОСТУ ПІСЛЯ ТРИВАЛОЇ ЕКСПЛУАТАЦІЇ

Abstract

Introduction. The vast majority of reinforced concrete bridges built in Ukraine until the 1950s were mostly monolithic. Spans were built of monolithic concrete with a length of 2, ..., 6 m and ribbed structures with a length of 8, ..., 15 m. Monolithic spans were provided with good spatial work and considerable durability. Problems Statement. The main disadvantage of reinforced concrete monolithic spans of bridges built before the 50s of the last century was the low design strength of concrete, which over time led to defects and thus reduce their durability. In addition, the vast majority of such bridges with monolithic spans were built according to technical standards of 1962 and earlier, and at this time the load capacity does not meet the requirements of modern regulations. The need to study the stress-strain state, to determine the bearing capacity of the spans of bridges after long-term operation, given the above, is an important factor in deciding on the feasibility of their repair. Purpose. Research of the stress-strain state of the structures of the monolithic spans of the bridge after its long operation. Materials and Methods. A survey of the monolithic reinforced concrete span of the bridge, built in 1940, was carried out. It was established that the span of the bridge, in accordance with the identified defects, is in a limited working condition (condition 4). And given the low load capacity of the span, condition 5 (inoperable) was finally adopted. The main defects found during the inspections of the span significantly reduce its durability and bearing capacity. Destruction of the protective layer of beams of the span with exposure and intensive corrosion of reinforcement with weakening of the area by more than 10% was revealed. Based on the data from the inspection of the bridge, it was decided to conduct additional tests to determine the stress-strain state of the spans, the availability of strength reserves and the possibility of strengthening them or the need for replacement. Results. Based on the test of the bridge, the parameters of spatial work and stress-strain state of the span were determined by measuring the absolute deformations (deflections) under the action of static load. According to the test results, the value of the design coefficient k, which is in the range of 0.1… 0.79, was determined. The values of the transverse distribution coefficients (CRC) for each beam were experimentally determined and the numerical analysis of the field and analytical spatial work of the span of the bridge on the transverse distribution coefficients was performed. Conclusion. The results of the analysis of experimentally and analytically obtained test data of the bridge indicate the normal spatial operation of the bridge spans, which corresponds to the nature of the idealized finite element scheme, good spatial rigidity and the presence of strength reserves in the bridge spans. Key words: bridges, span, tests, deformability, technical condition.