Sag control method for small-sag datum strand

Abstract

The invention discloses a sag control method for a small-sag datum strand, inn order to solve the problems that the adjustment amount of the present cable length is too large in error under a small sag, or inconvenient to programme on the spot. The sag control method for the small-sag datum strand comprises the following steps of: acquiring the relationship between the adjustment amount of the cable length of a suspension cable and the change amount of a sag via a simplified adjustment cable formula based on parabola theory, and the unstressed length S0 of the simplified suspension cable; then calculating the adjustment amount Delta S needing to be adjusted, of the cable length after knowing a sag difference Delta f; and finally lengthening or shortening the Delta S at one end of a flexible cable, anchoring, and detecting that a mid-span elevation achieves a target elevation. Compared with a determination method for the adjustment amount of the cable length based on catenary theory and quasi-catenary theory, a computer is not needed in the sag control method disclosed by the invention; and compared with the traditional simplified adjustment cable formula obtained based on parabola theory, the adaptive sag-to-span ratio does not have the lower limit range, and enough engineering accuracy is provided for the mid-spans and the side-spans of all the suspension-cable bridges in the sag control method disclosed by the invention.

Description

technical field [0001] The invention relates to a method for controlling the sag of a small sag reference cable strand. Background technique [0002] Before the alignment of the reference strands is accurately controlled, the strands are usually tightened at the anchorages on both sides of the bank, so that the strands have a certain amount of upward lift relative to the design position, the middle span is raised by 200-300mm, and the side span is about 100mm [1] . The precise control of the alignment of the reference strands is a key link in the construction control of the suspension bridge, and the precise control of the sag of the load-bearing cables of the catwalk is related to the convenience of subsequent construction and the stress of the bridge tower during the construction stage. The core of both is to calculate the cable length adjustment ΔS (that is, the amount of relaxation or tightening) according to the sag amount Δf that needs to be adjusted, and the key is t...

AI Technical Summary

Problems solved by technology

Although the traditional cable length adjustment calculation formula based on the parabolic theory is convenient and does not require programming, it does not consider the influence of elastic elongation on the unstressed cable length of the strands, and the calculation deviation of the adjustment amount is large when the sag is small [1] , according to the determined cable length adjustment amount, carry out fine adjustment construction of small sag suspension cable, if the line shape (sag) cannot reach the target, the cable length adjustment must be repeated, which increases the workload of fine adjustment construction and calculation

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