Introduction. In Ukraine, reinforced concrete monolithic span structures using post-tensioned systems are becoming more and more popular. According to the results of recent studies and existing experience in the use of post-tensioning in bridge construction, the main advantages of such solutions compared to prefabricated pre-stressed structures can be identified, namely, an increase in the length of spans and a decrease in the cost of materials for their installation.
Problems Statement. To achieve greater efficiency of post-tensioned span structures that would last the designed term, using all their advantages, it is important to obtain comprehensive information about the structure, its technical condition. Recent studies of such span structures conducted in Ukraine do not allow for a more qualitative assessment of the operation of these structures as a whole without a detailed study of their characteristics under dynamic loads.
Therefore, the issue of studying the dynamic impact on monolithic reinforced concrete span structures arranged with the use of post-tensioned systems is relevant and requires additional research in order to improve and rationalize such structural solutions.
Purpose. Research of dynamic characteristics (natural frequencies, oscillation decrement and dynamic coefficient) of a monolithic continuous prestressed span bridge structure with tension on concrete (post-tensioned system).
Materials and Methods. When writing the article, the materials of the tests of the reinforced concrete span structure of the bridge across the Desna River on the public highway of state importance M-01 Kyiv - Chernihiv - Novi Yarylovychi (to the city of Gomel), the southern entrance to the city of Chernihiv at km 11+414 were used.
The following research methods were used: information analysis, mathematical modeling, methods of full-scale and theoretical research.
Results. Based on the conducted study of the bridge span structure, four vibration forms and frequencies under the action of dynamic loading were established. The least stable vibrations occur according to the first form. Vibrations according to this form are excited by the fast movement of transport and quickly fade away. The largest stable vibrations of the span structure (the decrement of vibrations according to this form does not exceed 0.04) have the fourth vibration form with a frequency of 5.91 Hz - this vibration form is almost insensitive to the conditions of mobility at the ends of the span structure and therefore the damping of vibrations occurs very slowly.
The results of determining the dynamic coefficient at different speed modes of movement of single cars are presented. At car speeds from 10 to 50 km/h, the value of the coefficient increases and ranges from 1.07 to 1.23.
Conclusion. According to the results of the analysis of the obtained data from the dynamic tests of the reinforced concrete monolithic prestressed (post-stressed system) continuous span structure of the bridge, the frequencies of the main forms of natural vibrations and the values of dynamic coefficients for the most stressed structural elements of the span structure were established. It was established that the values of dynamic coefficients increase with increasing speed and do not exceed the standard values.
