Fem Analysis For Prestressed Anchorage System

Pre-stress method is widely used in engineering structures in which anchorage plays a very important role. Pre-stress concrete structures have a higher techno-economics index and wide-ranging practicability. The key of development of pre-stress techniques is pre-stress high strength steel products and anchorage. The design and selection of anchorage play an important part in the design of post-tensioned concrete structures. Bearing strength of anchorage will directly influence the result of pre-stress and security of structures. The stress of Anchors and concrete which bears huge pre-stress under anchors is relatively well-distributed or not, that is measure criterion of anchorage. Domestic theoretic research of anchorage is not enough, few documents in this field is reported, and research using FEM in this domain is even rarely seen in publication.The interaction in components of jaw vice anchorage is very complicated, mechanical and geometric characteristics of those under load effect are also complex. Analyzing those problems by using classical elastic-plastic theory will meet lots of difficulties, in other words, the success possibility will be very small. Otherwise, FEM can give effective results which can approach project practices. By using non-linear FEM, this thesis considers contact friction between anchor plate and clip-pieces, contact friction between anchor plate and under board, elastic-plastic nature of anchor plate material, establishes non-finite element models for mono-strand anchorage and multi-strand anchorage. The stress distribution and characteristics of deformation are analyzed particularly. In addition, considering anchor-region of pre-stress structure will endure huge part-stress under great pressure, so the thesis gives the general distribution regularity of stress of anchor-region by using FEM, and a qualitative analysis is presented.This thesis, firstly, presents the application of the parameterization design for the cone angle of anchors by using FEA. The influence of cone angle on the mechanics characteristics of the anchor is analyzed particularly. Synthetically considering limited cone angle, reasonable angle degrees of the model should 6.5~7.5. Secondly, this thesis presents the non-linear FEM analysis results of mono-strand anchor on contact friction problem. The influence of fraction coefficients on the mechanics characteristics of the anchor is analyzed particularly. The results show that: the degree of deformation and yield-region will decrease as the fraction coefficients increasing; the influence of fraction coefficient f1 between clip-pieces and anchor plate is more remarkable than f2 between anchor plate and under board, the influence of f2 can be negligible. Considering that multi-strand anchorage is widely used in civil engineering more and more, an FEM model for seven-strand anchorage has been established in this thesis, the Numerical results is presented, the internal force and deformation characteristic are analyzed in detail. Finally, this thesis gives a linear FEM analysis on the stress distribution in anchor region of pre-tress concrete structure. A qualitative comparison between two conditions whether the preset holes are considered is given in this thesis, and the shear-smash mechanism and reinforcing methods are discussed.