METHOD FOR PRESTRESSING OF MULTIPLE-SPAN UNSPLITTABLE REINFORCED CONCRETE SLAB-TYPE SUPERSTRUCTURES OF BRIDGES Russian patent published in 2000 - IPC

FIELD: bridge-building industry. SUBSTANCE: according to method, following operations are performed: placing of concrete mix into shuttering, creation of temperature difference in separate components of lateral cross-sections of structure with retention of neutral internal stressed state, fixing of aforesaid components with difference of their temperature into single integrally working lateral cross-section and keeping concreted structure during required period of time until reaching temperature which corresponds to real operating conditions. Prior to placing concrete mix, shuttering is coated underneath with thermal-insulating material such as foam plastic, wood chips, etc. located at both sides of each intermediate support on sections of length "a". Upper surface of structure being concreted is covered with layer of film. For remaining part of bridge superstructure, except sections of length "a", created are heat-exchanging conditions which are similar for upper and lower surfaces so as to prevent temperature differential over cross-section. Operation for creating temperature difference in separate components of lateral cross-section with retention of neutral internal stressed condition is carried out during period when concrete acquires strength due to difference of thermal resistance of thermal insulation located in upper and lower surfaces of concreted structure at both sides of each intermediate support of bridge in sections of length "a". Operation for fixing components of cross-section at their different temperature into single integrally working lateral cross-section is performed during period from moment of start of acquiring hardness to moment when required hardness is reached which is equal to (0,25÷0,30)R₂₈. This is achieved by provision of calculated temperature conditions during keeping of produced superstructure at given values S of thermal resistance of superstructure slab. Length of section "a" is determined from relation brought forth in description of invention. Application of aforesaid method allows for reduction of labour intensity and simplification of working process. EFFECT: higher efficiency. 1 cl, 6 dwg