# shell_angle#

EQ =shell_angle{1 | 2} {Galerkin_wt} {SH_ANG1 | SH_ANG2} {Interpol_fnc}


## Description / Usage#

This card provides information for solving a definition equation for the surface orientation angle in a 2-dimensional bar element. It applies only to shell element blocks. Note that this equation is available in three-dimensional problems but is in fact untested at this time.. The shell angle equation(s) determine the components of the normal vector to the shell surface; since its magnitude is 1 by definition, one less degree of freedom is required tha the number of coordinates. The Galerkin weight and the interpolation function must be the same for the code to work properly.

 shell_angle{1|2} Name of the equation to be solved. {Galerkin_wt} Two- or four-character value that defines the type of weighting function for this equation, where: Q1-Linear Q2-Quadratic SH_ANG{1|2} SH_ANG{1|2} Name of the variable associated with the shell angle equation. {Interpol_fnc} Two- or four-character value that defines the interpolation function used to represent the variable SH_ANG where: Q1-Linear Continuous Q2-Quadratic Continuous

This equation requires no equation term multiplier entries.

## Examples#

The following are sample cards that use linear continuous curvature interpolation and weight function:

EQ = shell_angle1 Q1 SH_ANG1 Q1

EQ = shell_angle2 Q1 SH_ANG2 Q2


The second card applies only to 3D problems.

## Technical Discussion#

For 2D problems, the defining equation is: $$\Theta$$ = atan[ $$n_x$$, $$n_y$$] where Q is shell_angle1 and $$n_x$$ and $$n_y$$ are the components of the normal vector to the shell surface. There is an analogous definition for shell_angle2.