Single-box single-chamber box girder and its design method for continuous rigid-frame aqueduct with variable box and variable cross-section

Abstract

The invention provides a variable box variable cross section continuous rigid frame aqueduct single-box single-chamber box girder and a design method thereof. According to the method, in the process of casting the variable cross section single-box single-chamber box girder, with the gradual increase of the cross section, an arched curve is formed at the lower edge of the bottom plate of the single-box single-chamber box girder; the change rules the same as that those of the curve of the lower edge are adopted for the upper edge of the bottom plate, so that the bottom plate forms an arched curve whole with identical thickness; gradual change space is formed between the upper edge of the bottom plate and box inside water body space of concrete of the single-box single-chamber box girder; the gradual change space is filled with cushion layers so that the upper surface of the gradual change space is smooth. According to the invention, the problems caused by sudden increase of the thickness of the bottom plate of a conventional box girder are solved, the prestressing effect of longitudinal prestressed rebars is improved, and the problem in the arrangement of box girder bottom plate longitudinal prestressed steel bundle anchoring toothed plates is solved, and the additional temperature gradient effect of the bottom plate of the single-box single-chamber box girder is reduced; the self-weight of a midspan area of a continuous rigid frame aqueduct is reduced, the overall deformation of the structure is improved, and the economical efficiency is great.

Description

technical field [0001] The invention relates to a single-box single-chamber box girder of a variable-box variable-section continuous rigid-frame aqueduct and a design method thereof, belonging to the technical field of water conservancy engineering. Background technique [0002] With the rapid development of China's water conservancy projects, the application of large-span continuous rigid-frame aqueducts for drainage and drainage is becoming more and more extensive. etc.; at the same time, in order to ensure smooth water flow in the tank body and smooth connection with the two boxes with variable cross-section box girders, the upper edge of the bottom plate of the single-box single-chamber box girder generally adopts a straight line with a longitudinal slope of 1 / 1000 to 1 / 3000, and the single-box single-chamber box During the transition of the beam to the cross-section of the two-box variable cross-section box girder, the thickness of the bottom plate increased sharply, re...

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Problems solved by technology

[0002] With the rapid development of China's water conservancy projects, the application of large-span continuous rigid-frame aqueducts for drainage and drainage is becoming more and more extensive. etc.; at the same time, in order to ensure smooth water flow in the tank body and smooth connection with the two boxes with variable cross-section box girders, the upper edge of the bottom plate of the single-box single-chamber box girder generally adopts a straight line with a longitudinal slope of 1 / 1000 to 1 / 3000, and the single-box single-chamber box During the transition of the beam to the cross-section of the two-box variable cross-section box girder, the thickness of the bottom plate increased sharply, resulting in an increase in the cross-sectional area and moment of inertia of the single-box single-chamber box girder, which greatly reduced the core position of the cross-section. Weakened the prestressing effect (see CN202450427U for details) of the longitudinal prestressing reinforcement of the bottom plate of the single box single chamber box girder area, increased the usage of the bottom plate longitudinal prestressing reinforcement of the whole continuous rigid structure aqueduct, meanwhile, the single box single chamber box girder needs Only a distance of 15-20m can be used to transition to the cross-section of two boxes of variable-section box girders, which makes it difficult to arrange the longitudinal prestressed steel anchor tooth plate of the bottom plate. Not only that, but the contact between the concrete of the bottom plate structure and the water body will cause two unfavorable factors: ①Single box and single box The bottom plate of the chamber box girder will generate an additional temperature gradient effect, the maximum positive temperature difference is 14°C, and the maximum negative temperature difference is -6.5°C. Adding a positive tensile stress of about -2MPa to the bottom slab is seriously detrimental to the structural stress, and further increases the use of longitudinal prestressed steel bars on the bottom slab; ②The water body will directly erode the structural concrete and surface steel bars of the bottom slab, affecting the durability of the structure

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