beam1, beam1t

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beam1, beam1t

Purpose

Element function for a 12 DOF beam element. beam1t is a 2 node beam with pretension available for non-linear cable statics and dynamics.

Description

beam1

In a model description matrix, element property rows for beam1 elements follow the format

 [n1 n2 MatID ProID nR 0 0 EltID p1 p2 x1 y1 z1 x2 y2 z2]

where

n1,n2	node numbers of the nodes connected
MatID	material property identification number
ProID	element section property identification number
nr 0 0	number of node not in the beam direction defining bending plane 1 in this case {v} is the vector going from n1 to nr. If nr is undefined it is assumed to be located at position [1.5 1.5 1.5].
vx vy vz	alternate method for defining the bending plane 1 by giving the components of a vector in the plane but not collinear to the beam axis. If vy and vz are zero, vx must not be an integer. MAP=beam1t('map',model) returns a normal vector MAP giving the vector used for bending plane 1. This can be used to check your model.
p1,p2	pin flags. These give a list of DOFs to be released (condensed before assembly). For example, 456 will release all rotation degrees of freedom. Note that the DOFS are defined in the local element coordinate system.
x1,...	optional components in global coordinate system of offset vector at node 1 (default is no offset)
x2,...	optional components of offset vector at node 2

Isotropic elastic materials are the only supported (see m_elastic). p_beam describes the section property format and associated formulations.

beam1t

This element has an internal state where each colum of Case.GroupInfo{5} gives the local basis, element length and tension [bas(:);L;T].

This is a sample example how to impose a pre-tension :

 model=femesh('testbeam1 divide 10');
 model=fe_case(model,'fixdof','clamp',[1;2;.04;.02;.01;.05]);
 model.Elt=feutil('set group 1 name  beam1t',model);
 [Case,model.DOF]=fe_mknl('init',model); 
 m=fe_mknl('assemble',model,Case,2);
 k=fe_mknl('assemble',model,Case,1);
 f1=fe_eig(m,k,[5 10]);
 Case.GroupInfo{1,5}(11,:)=1.5e6; % tension
 k1=fe_mknl('assemble',model,Case,1);
 f1=[f1 fe_eig(m,k1,[5 10])]  % Note the evolution of frequencies