Activity 2.1.7 Truss Force Study
This calculator supports activity 2.1.7 style truss work. It treats each joint as a particle in static equilibrium. Every connected member is assumed to carry only axial force. A positive value means tension. A negative value means compression. The page also finds support reactions when the structure is statically determinate. Save exports when documenting classwork, lab notes, or review evidence. They help compare revised models and trials.
Why truss force calculation matters
Trusses appear in bridges, roof frames, towers, and classroom models. Their strength depends on how loads move through straight members. A small downward load may create large internal force in a diagonal member. This tool helps students test that idea without losing the calculation steps. It also gives checks for unknown count, equation count, and residual error.
What the inputs mean
Joint data defines the geometry. Each row needs a joint name, x coordinate, y coordinate, support type, and applied loads. Member data defines which joints are connected. Units can be pounds, newtons, inches, feet, or meters, but they must stay consistent. The solver uses angles from the joint coordinates, so member direction is calculated automatically.
How the solver works
The method is based on two equations at every joint. The sum of horizontal forces must be zero. The sum of vertical forces must also be zero. Unknown member forces and reaction components are assembled into one linear system. The page solves that system with Gaussian elimination. Then it reports each member sign, magnitude, length, and direction angle.
Reading the result
Start with the status message. If the truss is not determinate, the answer may be unstable or incomplete. Next, inspect reactions. They should balance the entered loads. Then review member forces. Tension pulls away from a joint. Compression pushes toward a joint. The largest force often controls design decisions, material choice, and safety review.
Good practice
Use simple labels for joints, such as A, B, and C. Keep all coordinates in one unit. Enter downward loads as negative vertical forces. Check that each support type matches the real model. A pin support adds horizontal and vertical reactions. A roller adds one vertical reaction. Recalculate after changing any load, geometry, or member connection.