Method for measuring effective pre-stress of finish rolling deformed steel bar under anchor

Abstract

The invention discloses a method for measuring effective pre-stress under a finish rolling deformed steel bar anchor. The method comprises the following steps: firstly, fixing an acceleration sensor on one side of an exposed end of the finish rolling deformed steel bar through a magnetic clamping seat; then knocking the other side of the exposed end of the finish rolling deformed steel bar through an excitation hammer; then, vibration signals generated in the process that the finish rolling deformed steel bar is knocked are collected through the acceleration sensor, and a first curvilinear equation is determined based on the vibration signals; on-site deformed steel bars are tensioned to 20%, 40%, 60%, 80% and 100% of design values in a grading mode for parameter calibration, and a second curvilinear equation and key parameters of the second curvilinear equation are determined after calibration is completed; and finally, substituting the key parameters into the first curvilinear equation to determine the effective pre-stress of the finish-rolled deformed steel bar, thereby realizing rapid and accurate detection of the vertical pre-stress of the finish-rolled deformed steel bar.

Description

technical field [0001] The invention belongs to the technical field of prestress detection of finish-rolled threaded steel, and particularly relates to a method for measuring the effective prestress under an anchor of finish-rolled threaded steel. Background technique [0002] Long-span prestressed concrete box girders are more and more widely used in domestic bridges, and the disease detection reports related to this type of beams also tend to increase. The appearance of diseases seriously reduces the overall service life of the bridge, causing unnecessary Economic losses. The main reason for the cracking of the bridge web is that the vertical prestress of the rebar of the beam body is insufficient or under tension. [0003] At present, the detection methods for vertical prestressing of rebar mainly include non-destructive testing and reverse pull testing. The reverse pulling method requires equipment such as oil pumps, jacks and reaction frames. It is very troublesome to ...

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Problems solved by technology

[0003] At present, the detection methods for the vertical prestress of rebar mainly include non-destructive testing and reverse pull detection. The reverse pull method requires the use of equipment such as oil pumps, jacks and counter force frames. During the detection process, the handling and movement are particularly troublesome, which affects the detection progress, and The detection time is relatively long, and the average prestressing detection time of a single rebar requires at least 20 minutes. However, most of the vertical prestressing detection sites of fine-rolled rebars require full inspection, and the detection task is heavy. The detection efficiency is likely to affect the construction progress of the entire project. The detection efficiency of the detection method is higher than that of the reverse pull method. At present, there is a detection method on the market by fitting the relationship between the vibration frequency of the rebar end and the tension force, but the detection accuracy is very low.

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