# Abnormal deformation of link180 element

**1**

hello everyone.

l m running a static analysis on a simply-supported prestress beam in APDL. l used solid65 to model concrete, beam188 to model reinforcing steels and link180 to model the prestressing strands. prestress was applied by defining thermal expansion for the prestessing strand material. l defined 3 different load steps. load 1 ( the prestressing), load step 2 for self-weight and load step 3 for applied external force. l got convergence problem after a very small part of the external force was applied. l realize that the link element has an abnormal large deformation at mid span (see attached files). l have no idea of what could be inducing this problem. can you help me resolve this?

## Answers

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1Memberhello everyone.

l m running a static analysis on a simply-supported prestress beam in APDL. l used solid65 to model concrete, beam188 to model reinforcing steels and link180 to model the prestressing strands. prestress was applied by defining thermal expansion for the prestessing strand material. l defined 3 different load steps. load 1 ( the prestressing), load step 2 for self-weight and load step 3 for applied external force. l got convergence problem after a very small part of the external force was applied. l realize that the link element has an abnormal large deformation at mid span (see attached files). l have no idea of what could be inducing this problem. can you help me resolve this?

as l said, l used

solid65 to model the concrete

beam 188 (with beam section defined) for reinforcing steels

link180 (with link section defined) for prestressing strand

l used real constant of the concrete for the link180 as could not define real constant for the link element element (l m using GUI method). is this the problem?

multilinear material for the concrete, bilinear material for other materials. thermal expansion was defined for the link element to apply the prestressing force

l define beam188 and the link180 element on line. later l merged nodes of the beam element with that of the concrete. for the link180 element a used combin 39 element with degree of freedom in x direction. in y and z directions nodes of the link180 was coupled with nodes of concrete at the same location. l get deformation as shown in the attached pictures for the link180 elements during analysis, before the concrete reaches it . l dont really know what could be a the origin of this as l m newbie in ansys. thank you again for your help.