Investigation tests of permanent prestressed strand ground anchors with varios designs of tendon bond length

A preparation of a practically feasible technological design of permanent prestressed strand ground anchors with a different concept of bond lengths, contained within joint polyethylene cover, is the main idea of this thesis. Anchors with increased stiffness of bond length (RCP/D-K), multiple anchors with staggered anchor units based on Barlay's anchors SBMA, only that all anchor units are placed within common polyethylene cover (RCP/D-Z) and anchors with variable stiffness of bond lengths after the patent of Škrabl (RCP/D-I) have been used. In the thesis description of testings, performed on the testing field of the retaining wall OZ-05, as well as descriptions of results of behaviour analysis of modified anchor types at investigation tests are given and compared with the behaviour of original RCP/D anchors. The software tool of open design for simultaneous evaluation of anchors' behaviour parameters at investigation tests has been prepared, whereat analysis of the whole anchor, anchor units as well as individual strands is feasible. The separation of pulled individual strand of an anchor is also possible. For each anchor competent interval creep displacement rates k_int were determined after four different methods. The pull-out resistance R_a of the anchor as a whole has been evaluated with averaging of displacements of all strands, and compared with the sum of pull-out resistances of individual strands of the anchor. Requirements for the definition of the common characteristic pull-out resistance of the productional anchor R_ak are not evidently defined in the valid regulation. Therefore different approaches has been used for the determination of R_ak values, whereat statistical methods and available historical data of numerous investigation tests, performed in the last decade, have been used. Admissible creep displacement rate k_adm for the retaining wall OZ-05 production anchors has been defined on the basis of the investigation tests. However, values of k_int for production anchors in practice are not always smaller than k_adm . With the anaylsis of investigation tests results of four anchored structures, carried out in practice, reasons for such behaviour of anchors has been found out.\ud \ud By means of the two types of laboratory testings reasons for high values of creep displacement rates at low force levels of investigation tests has been found out. Investigations of eccentric positions of ring load cell as for anchor tendon on measured forces, as well as investigations of the influence of isothermal relaxation on the behaviour of a strand, have been performed. In both cases of testings the procedure of an investigation test of prestressed ground anchors has been used. For this reason the results of laboratory testings can be directly compared with the results of investigation tests.\ud \ud Guidelines for effective realization of modified types of permanent prestressed strand anchors as well as the proposals for the performance and analysis of investigation tests are suggested in the conclusion of this thesis. This guidelines could be used for filling up gaps and vagueness of valid European regulation regarding execution and evaluation of investigation tests of prestressed strand anchors