Meaning and mechanism
We assume an ideal truss consists of members connected at joints, with loads applied at these joints. The members primarily experience forces along their axis.
The force exerted on the vertices is such that the sum of its horizontal and vertical components equals 0. By examining the signs of shear and compression, along with the reference, one can visualize the force transmission path.
Relationships and conditions
At each planar intersection, ΣFx=ΣFy=0 is used. m=2j−3 is a quantity used for determining the regularity of a typical, simple planar truss.
The mere fulfillment of the criteria for vacancy does not guarantee geometric stability. Actual deformation of the connection, yielding of the component, and material damage are effects outside of the assumed force model.
What to observe in the simulation
Tension and compression members together balance each joint.
A determinate pin-jointed truss assumes straight members and small deformation. Self-weight, buckling and joint failure are omitted. Capacity warning is not collapse dynamics. Do not test real bridge loads.
Key relationships and symbols
ΣFx = ΣFy = 0 · m = 2j − 3
| Symbol | Meaning | Unit |
|---|---|---|
| m | Number of members | items |
| j | Number of joints | items |
| Member force | Axial force in the member | N |
Worked example
What do blue and red members represent?
Tension and compression · Tension and compression members together balance each joint.
Common misconceptions
- It is not the case that all components of a truss equally share the load.