Post Tension Procedures And Requirements

The steps of tensioning should conform to the design regulations. The tensioning method generally adopts two-end tensioning. When the channel is short, single-ended tensioning can be used. When the conditions do not allow two-end tensioning, single-ended tensioning can also be used. However, the stress loss of prestressed anchorage is relatively large when single-ended tensioning, and measures to reduce stress loss must be adopted. For example, in the Qianqiu Bridge construction, the main span is a three-hole 60m reinforced concrete prestressed tied arch, only the first hole can be tensioned at both ends, and the remaining two holes can only be tensioned at one end, but due to the long channel, single-ended tensioning has a large frictional resistance, and whether the stress can be smoothly transmitted to the other end and how much can be transmitted. This has no successful precedent nationwide. In order to obtain scientific data, under the condition of a hole with two ends of tension, a single-ended tension test is adopted, and the channel friction test is mainly carried out. It is concluded that without any measures, the tensile force transmission of one end tensioned linear beam is 73.34%, and the curve beam tensile force is 52.4%, which is far from the tensile stress requirements. After the test of adding soapy water to reduce the friction resistance of the tunnel, it is concluded that the stress transmission is 83.85%, which is an increase of 16.48%, which can basically meet the tensile requirements. Because the single-ended tension test of the first hole provides scientific data, the last two single-ended holes use soapy water to reduce the friction resistance of the tunnel, and the tension and elongation meet the requirements, and the single-ended tension is solved. In the contradiction of the transmission of pulling force, the tension is successful at one time.