Slow-bonded low-retraction prestressed short cable system and its calculation and tensioning methods

Abstract

An anchoring system for slow-bonded low-retraction prestressed short cables, including: a clip-type anchor, an anchor cup, a support nut, a first backing plate, and a slow-bonded prestressed tendon, and a clip-type anchor is used at the tension end The clip of the tool combines the slow-bonding prestressed tendons and the anchor cup together, and then transmits the tensioned prestress to the first backing plate through the threaded engagement between the support nut and the anchor cup. It also provides a design calculation method and a stretching method of the system, which can reduce the anchoring retraction loss and solve the problem of grouting quality.

Description

technical field [0001] The invention relates to the technical field of civil engineering design and construction, in particular to the lateral and vertical prestressing of prestressed concrete bridges. Background technique [0002] The web cracks of prestressed concrete bridges are concentrated between 25° and 45°, which are structural main tensile stress cracks, which mainly appear in the cast-in-place section of the side hole of the continuous box girder bridge, near the L / 4 section or the thickness of the beam web change section. The oblique cracks in the web develop continuously from the vicinity of the support to the compression zone with the passage of time, the number of cracks continues to increase, and the crack area gradually expands to the mid-span direction. Judging from the overall distribution characteristics of cracks, such cracks are mostly in the direction perpendicular to the main tensile stress in the web, which can basically be determined as the cracking...

AI Technical Summary

Problems solved by technology

[0010] (2) Insufficient quality of vertical grouting

Using movable struts and pouring mortar in the casing may cause strength problems caused by the retraction caused by the pitch of the rebar

However, in the tensioning method, movable struts, sleeves, and reinforcing rings are set, which makes the construction difficult and the process complicated

[0020] Chinese patent CN103726447A discloses a method and system for vertically prestressed steel strands in a secondary tension low-retraction anchorage system, which only relies on secondary tension to solve the problem of low retraction, but does not solve the problem of insufficient grouting quality, steel bars Bonding with concrete slurry causes problems such as stress concentration; in addition, the parameters in the tensioning method are determined by experience, and the range value is too large to make accurate adjustments according to the actual situation

[0021] Chinese patent CN205531024U discloses a prestressed anchorage system for low-retraction fine-rolled threaded steel bars, using threaded steel bars and secondary tensioning technology, the problems of retraction and tensioning accuracy caused by the pitch cannot be solved

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