Hello Everyone!
For an anchored sheet pile wall (say 9m height), prestresses strands with a preload of 15T were recommended to limit deflection. Bridge abutment behind the sheet pile wall.
However, during execution, contractor has replaced strands with micropiles (fy 500 to 600 MPa). We've been asked to carry out the validation. It was conveyed to them that if the anchors are not prestressed, deflection criteria will not be met.
We have been informed that they have applied some preload. Data supplied was Torque and pressure cell calibration certificate for hydraulic set up used for the head connection.
Question is whether the torque applied to tighten the bolt head be considered as pretension??
We've been asked to assume a pretension of around 40T (bar capacity is 85T). Calculation was not provided. When I checked the torque to axial tension relation (T=KDF/1000) applied for usual bolt tightening, the force is found to be of the order of 40T. However, is it even correct to consider the tightening torque as preload for ground anchors? Normal bolts will be of say 1-2m length, with clamping arrangements.
The overall length of these anchors is around 10m. Basically hollow bars filled (core filled with concrete) and grouted around.
For an anchored sheet pile wall (say 9m height), prestresses strands with a preload of 15T were recommended to limit deflection. Bridge abutment behind the sheet pile wall.
However, during execution, contractor has replaced strands with micropiles (fy 500 to 600 MPa). We've been asked to carry out the validation. It was conveyed to them that if the anchors are not prestressed, deflection criteria will not be met.
We have been informed that they have applied some preload. Data supplied was Torque and pressure cell calibration certificate for hydraulic set up used for the head connection.
Question is whether the torque applied to tighten the bolt head be considered as pretension??
We've been asked to assume a pretension of around 40T (bar capacity is 85T). Calculation was not provided. When I checked the torque to axial tension relation (T=KDF/1000) applied for usual bolt tightening, the force is found to be of the order of 40T. However, is it even correct to consider the tightening torque as preload for ground anchors? Normal bolts will be of say 1-2m length, with clamping arrangements.
The overall length of these anchors is around 10m. Basically hollow bars filled (core filled with concrete) and grouted around.