STM Design Steps

The design process using STM involves five major steps described below. These steps are illustrated in Figure 1 using the design example of a dapped-ended beam.

1.	Define the boundaries of the D-Region and determine the boundary forces (the ultimate design forces) from the imposed local and sectional forces.
2.	Sketch the truss, determine the equivalent boundary forces, and solve for the truss member forces.
3.	Select reinforcing or prestressing steel to provide the necessary tie capacity and ensure that this reinforcement is properly anchored in the nodes.
4.	Evaluate the dimensions of the struts and nodes such that the capacity of all struts and nodes is sufficient to carry the truss member forces.
5.	Provide distributed reinforcement to ensure ductile behavior of the D-Region.

Since equilibrium of the truss with the boundary forces must be satisfied (step 2) and stresses everywhere must be below the limits (step 3 and 4), one can see that the STM is a lower-bound (static or equilibrium) method of limit analysis.

                                     Figure 1   The Major Steps in STM Design Process
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