Truss bridge design – bar forces and first failure

Design & TechnologyEngineering Drawing & DesignAges 15–16

A four-panel steel truss bridge with a pin support at one end and a roller support at the other. Students choose the truss type (Warren, Pratt, Howe), the material, the bar cross-section, and place a load on any node of the bottom chord by clicking it. The simulation solves the joint equilibrium equations to find the force in every bar, colouring tension bars red and compression bars blue, drawing bar thickness by force magnitude, computing stress σ = F/A and comparing it with the allowable stress. Click Ramp load to find the load at which the first bar fails.