1 GSA Training Miscellaneous Slides

Axis set definitions

Beam element axes: non-vertical

Beam element axes: vertical

Beam element orientation: default Orientation angle = 0° No orientation node

Beam element orientation: by node Orientation angle = 0° Orientation node

Beam element orientation: by node & angle Orientation angle = 90° Orientation node

Element releases OK: GSA automatically removes rotational freedom No good: GSA is fooled into allowing nodes to rotate about longitudinal axis

Element offsets: Beam between columns

Element offsets: Edge beam Note: Element offsets are specified in global directions. Element axes are with respect to the flexible part of the element.

Constraints Constraints are where a condition is applied to a degree of freedom in the model: Restraints Settlements Joints Rigid constraints These constraints can all be represented as constraints equations. u i = f(u j,u k,…)

Simple constraints Restraints u i = 0 Settlements u i = settlement

Joints Two degrees of freedom in the model are linked in a given direction u si = u mi Joints relate the displacement/force at the slave degree of freedom s to the master degree of freedom m. Joints are an “artificial” feature and can be misused. Joints may not give an equilibrium condition Master Slave moment lost F F

Rigid constraints Rigid constraints are a set of constraint equations that maintain equilibrium For a rigid constraint in the x-y plane the equations are u sx = u mx - u mθz. x u sy = u my + u mθz. y u sθz = u mθz Slave M = F x F F x Master

Grid load Load applied to a position on a grid plane. Load is not applied directly to elements. Load is distributed to the elements surrounding the load depending on the span type: One way Two way – for simple load conditions Multi way – for general load conditions Distributed load is in equilibrium with applied load

Grid load – one way spanning span direction

Grid load – multi way spanning

Error norm The error norm is a measure of the accuracy of the solution Static analysis Solve for uf = K u Calculate residual r = f – K u Solve for ũ r = K ũ Calculate error norme = || ũ || / ||u|| Modal analysis Solve K φ – λ M φ = 0 Calculate error norme = || K φ – λ M φ || / || K φ ||

Cursor modes in Graphic Views RotateZoomVolumeSelectPolylineSculpt Geometry Click -zoom in & pan delete last volume clear & select picked item start or finish line create node if necessary, add node to topology list Drag rotatezoom boxnew inclusive volume clear & select items drag existing vertex drag existing node on grid plane Ctrl+ Click pick object point pan-toggle picked item -as Click but use node as start of next element Ctrl+ Drag Vert.: zoom Horz.: distance -new exclusive volume toggle items-- Shift+ Click reset object point zoom out & pan delete all volumes select picked item - Shift+ Drag pan--select items-- Ctrl+ Shift+ Click re-scale