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

FIELD: bridge-building industry. SUBSTANCE: method implies following operations: placing concrete mix into shuttering, creating difference of temperature of separate components of lateral cross-section of structure with retention of neutral internal stressed condition, fastening of components at their different temperature in united commonly operating lateral cross-section, and keeping concreted structure during period until its temperature corresponds to operating conditions. Prior to placing concrete, shuttering at both sides from lateral axis of bridge superstructure at sections of length "a" is lagged atop for warmth-keeping with thermal insulation material such as foam plastic, wood saw-dust, etc. Underneath surface of structure being concreted is covered with layer of film. For remaining part of superstructure except sections of length "a", created are conditions of heat exchanging which are similar for upper surface and lower surface so as to prevent temperature differential over cross-section. Operation for creating difference of temperature of separate components of lateral cross-section with retaining neutral internal stressed condition is effected during period of acquiring strength of concrete due to difference of thermal resistance of thermal insulation located on lower and upper surfaces of structure being concreted at both sides from lateral axis of bridge superstructure on sections of length "a". Operation of fastening cross-section components at their different temperature into united commonly operating lateral cross-section is carried out during period from moment of initial hardening of concrete to moment when concrete acquires preset hardness which is equal to (0.25-0.30)R28. This is obtained by ensuring preset temperature condition of keeping manufactured structure at design value of thermal resistance "S" of slab in span-piece of bridge superstructure. Length of section "a" is determined from relation given in description of invention. Application of method allows for reduction of labour intensity and for simplification of construction process. EFFECT: higher efficiency. 1 cl, 6 dwg