Improving the crack resistance of inclined cross-sections of reinforced concrete containment shells in areas of emergency loads of pushing

Abstract

The object of this research was the crack resistance of inclined sections of concrete and reinforced concrete fragments of protective structures under the action of emergency dynamic loads. The characteristics of dangerous emergency dynamic loads on protective structures (seismic, aircraft attack), the experience of increasing the crack resistance of inclined sections with various materials and design measures under static effects have been described. Areas of influence of dynamic loads on reinforced concrete structures reinforced with horizontal grids near the upper and lower faces need to increase crack resistance and eliminate the risk of splitting in the mesh plane. Comparison of the results of experimental studies of inclined sections of protective structures in the area of influence of local emergency load showed the feasibility of such structural measures. Additional horizontal reinforcement near the pushing face increases crack resistance by 55–65 %. When using the developed theoretical dependences, the error in determining the cracking forces and pushing strength does not exceed 20.7 %. Increased crack resistance is ensured by limiting the maximum diameters of the rods of horizontal grids and their pitch. Especially important is the arrangement of additional reinforcement in the middle zone, taking into account the actual tensile strength of concrete in the calculated dependences. Complete elimination of the danger of splitting in areas of probable action of emergency dynamic load in protective structures in the planes of the grids is recommended through the use of concrete of class not lower than C16/20, the use of reinforcement Ø12–14 mm. The optimal pitch of the rods is 50–125 mm. This makes it possible to increase the reliability of the design and operation of protective structures in case of emergency impacts, to reduce the cost of their repair after such impacts.