Final answer:
The internal forces in the web members of a parallel chord truss typically increase in tension or compression towards the center of the span, attributable to load distribution and bending moment effects.
Step-by-step explanation:
The internal forces in the web members of a parallel chord truss generally increase in tension or compression towards the center of the span. This is due to the nature of how load is distributed along the span of a truss. In the central region, forces typically peak due to bending moments being highest at the center of a simply supported beam, which is what a truss essentially acts as structurally.
Using the tension in a cable supporting weight as an analogy, the tension on either side of the weight has components that support the weight in the center. The forces are vectors and in the case of the truss, the structural members will either be compressed or under tension in a way that maintains the equilibrium of the entire structure.