Early crack control method for prestressed concrete cast-in-place continuous box girder

Abstract

The invention relates to an early crack control method for a prestressed concrete cast-in-place continuous box girder. An early hydration heat temperature field value and early strain value of the continuous box girder are monitored; when the prestressed concrete cast-in-place continuous box girder is subjected to full framing secondary pouring, the pouring time for pouring a bottom plate and a web plate and the pouring time for pouring a top plate and a flange plate are obtained in sequence, the time difference value of the two kinds of pouring time serves as a layered pouring age difference,the optimal layered pouring age difference suitable for the current continuous box girder is obtained, a finite element model of the prestressed concrete continuous box girder is established, and a temperature load curve is fitted; the finite element model which is verified to be correct is utilized, the cast-in-place construction process of the continuous box girder is simulated, the influence of different initial tensioning time and initial tensioning control stress on the early cracking of the top plate of the box girder is evaluated, an optimized initial tensioning construction process with a good control effect on early cracking of the top plate of the continuous box girder is obtained, and the optimized initial tensioning construction process is used for guiding subsequent construction of the continuous box girder.

Description

technical field [0001] The invention relates to the field of crack control of concrete structures, in particular to a method for controlling early cracks of prestressed concrete cast-in-place continuous box girders. Background technique [0002] Currently, prestressed concrete continuous box girders are widely used in bridge engineering. In the construction, the construction technology of secondary pouring of the full hall support is often used. Specifically, the bottom plate and web are poured for the first time, and the top plate and flange plates are poured for the second time. [0003] In related actual projects, after the formwork was removed, the construction personnel found that there were a large number of cracks along the direction of the transverse bridge and the direction of the longitudinal bridge on the roof of the box girder, among which there were more cracks along the direction of the transverse bridge. These early cracks in the cast-in-place continuous box...

AI Technical Summary

Problems solved by technology

These cracks that appear in the early stage of the cast-in-place continuous box girder roof will seriously affect the durability of the bridge structure and the safety of operation

However, at present, the control methods for the early cracks of the cast-in-place continuous box girder roof are mostly to optimize the concrete mix ratio, optimize the concrete production, or maintain the concrete for heat preservation, moisture retention, etc., but the prevention and control effects on cracks are not satisfactory.

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