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Lecture 9: Flexibility Method – Grids
Washkewicz College of Engineering
Introduction - Grids
A grid is a structure on which loads are applied perpendicular to the plane of the structure, as
opposed to frames where loads are applied in the plane of the structure. Both torsional and
bending moments can exist in a grid structure and both types of moments can be carried
through a joint.
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Lecture 9: Flexibility Method – Grids
Washkewicz College of Engineering
A schematic of a typical grid structure is depicted below.
T2
T3
T1
Typically the points of application of forces or moments become nodes in a grid structure.
Analyzing a grid structure using flexibility methods proceeds in a manner that is quite
similar to frames. However, an additional action-displacement relationship is necessary, i.e.,
the torsion-rotation relationship identified in example 4.9
GJ
T 
L
In order to compute the torsional stresses generated by torques applied to the components of
a grid structure the student is referred to AISC’s Design Guide 9 entitled “Torsional
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Analysis of Structural Steel Members.”
Lecture 9: Flexibility Method – Grids
Washkewicz College of Engineering
Example 9.1
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