Dear users,
I am trying to analyze a 3D model of a beam-column joint with opensees1.5.exe (tcl/tk 8.4.4). My approach is to separate elements of concrete from these of steel reinforcement and to connect them with zero length elements of bond stress material. So, I used:
a) 20-Node or 8-Node Standard Brick Elements of 3D-Material for Concrete.
b) Truss Elements of Uniaxial Elastic or Plastic Material for Reinforcement.
c) Zero Length Elements with Bond02 Material for bond modeling.
I tried static analysis with linear pattern load (10steps) and load control intergrator.
Questions:
1. Has the counting of nodes and elements to be continuous?
2. Do I have to enter different nodes with the same coordinates to be able to attach the zero strength elements?
3. What kind of 3D Material can be used for 20-node brick elements of concrete? ElasticIsotropic Material was not accepted by the program. However I couldn't manage to enter neither a J2Plasticity Material nor a Template Elasto-Plastic Material. I tried also to use 8-node standard brick elements with no results.
4. How can I use 6 degrees of freedom for the model. When I enter ndf=6 I cannot run my input files.
5. When using 8 node brick elements the analysis always stops with error in convergence (even if tollerance is 0.1).
I managed only to get results when I used only one 8-node brick element under static loading without connection with reinforcement.
I would be very glad if somebody could help me. Thanks in advance.
Warm Regards
Questions on beam-column joint analysis
Moderators: silvia, selimgunay, Moderators
Questions on beam-column joint analysis
Timosidis Dimitris
Phd student
Department of Civil Engineering
Democritus University of Thrace, Greece
Phd student
Department of Civil Engineering
Democritus University of Thrace, Greece
ansewrs to your questions:
1. nodes and elements DO NOT have to be continuous.
2. you just have to enter 2 DIFFERENT nodes, remember the material for the ZeroLength
will define the force-deformation and not stress-strain relationship. the 'strain' sent to the material at each step will be the difference in displacements for the specified dirn.
3. the 'stdBrick' (brick) and 'bbarBrick' elements only work at present with the ElasticIsotropic and J2Plasticity nD materials. the brick8N and brick20N elements will work with the Template materials. hopefully someone (Jeehoe where is your model!) will provide us with a nD concrete model at present we only have uniaxial concrete models. you can post the request for the concrete nD model on the future directions board.
4. the 3d brick elements have only 3dof at the nodes (translation only), you can mix 3 and 6 dof
models only by creating duplicate nodes where elements meet and connecting them together with the equaldDOF command or some stiff elements. it doesn't sound like you have any elements that require the 6dof anyway!
5. you have a problem with your model!!
good luck.
1. nodes and elements DO NOT have to be continuous.
2. you just have to enter 2 DIFFERENT nodes, remember the material for the ZeroLength
will define the force-deformation and not stress-strain relationship. the 'strain' sent to the material at each step will be the difference in displacements for the specified dirn.
3. the 'stdBrick' (brick) and 'bbarBrick' elements only work at present with the ElasticIsotropic and J2Plasticity nD materials. the brick8N and brick20N elements will work with the Template materials. hopefully someone (Jeehoe where is your model!) will provide us with a nD concrete model at present we only have uniaxial concrete models. you can post the request for the concrete nD model on the future directions board.
4. the 3d brick elements have only 3dof at the nodes (translation only), you can mix 3 and 6 dof
models only by creating duplicate nodes where elements meet and connecting them together with the equaldDOF command or some stiff elements. it doesn't sound like you have any elements that require the 6dof anyway!
5. you have a problem with your model!!
good luck.