Case Study on the Design of Fastening of External Prestressing Anchorage
By: Saibabu, S
.
Contributor(s): Srinivasan, P.
Publisher: Thane ACC LTD 2020Edition: Vol.94(3), March.Description: 45-51p.Subject(s): Civil EngineeringOnline resources: Click here
In:
Indian Concrete JournalSummary: External post tensioning is a common technique to increase the structural member`s capacity due to its active strengthening systems. It induces external forces to the structural elements to counter act the external loads. A case study on the off shore structure has been undertaken in which girders shown distress due to corrosion of tendons. From the flexural analysis, it is found that the tensile stresses at the mid span exceeds permissible stresses. External post-tensioning, a best scheme to reduce the tensile stresses of the girder has been proposed as an immediate strengthening measure. Formula to find external prestressing force which is required to bring back the tensile stresses within the permissible stresses is predicted. Flexural stresses and deflections of the strengthened girders at mid span have been computed using the predicted external prestressing force and found to be within the corresponding permissble values. It is proposed to transfer the external prestressing force to the concrete principally by shear using the post-installed expansion type anchors. This method has advantage of not requiring lateral/transverse prestressing as necessary in case of conventional method and more suitable where ends of girders are not accessible for anchoring external prestressing. The bolts will not cause damage to the existing reinforcement at the anchor zone due to its smaller length. Design details for fastening of anchorage of external prestressing force using expansion type anchor bolts are presented in this paper.
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School of Engineering & Technology (PG) Archieval Section | Not for loan | 2021131 |
External post tensioning is a common technique to increase the structural member`s capacity due to its active strengthening systems. It induces external forces to the structural elements to counter act the external loads. A case study on the off shore structure has been undertaken in which girders shown distress due to corrosion of tendons. From the flexural analysis, it is found that the tensile stresses at the mid span exceeds permissible stresses. External post-tensioning, a best scheme to reduce the tensile stresses of the girder has been proposed as an immediate strengthening measure. Formula to find external prestressing force which is required to bring back the tensile stresses within the permissible stresses is predicted. Flexural stresses and deflections of the strengthened girders at mid span have been computed using the predicted external prestressing force and found to be within the corresponding permissble values. It is proposed to transfer the external prestressing force to the concrete principally by shear using the post-installed expansion type anchors. This method has advantage of not requiring lateral/transverse prestressing as necessary in case of conventional method and more suitable where ends of girders are not accessible for anchoring external prestressing. The bolts will not cause damage to the existing reinforcement at the anchor zone due to its smaller length. Design details for fastening of anchorage of external prestressing force using expansion type anchor bolts are presented in this paper.
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