Design-truck ultimate limit states of buried modular polymer stormwater collection structures

Modular polymer stormwater structures are a relatively new class of buried structure with two horizonal platens supported by vertical columns. While structural demand at design truck loads has been quantified, the ultimate limit state to design tuck loading is unknown. Full-scale physical experiments were conducted to quantify the applied load and identify the mode(s) of failure at the ultimate limit state of three types of modular structures when buried (with 0.6 m soil cover) and subject to static design truck loading. All three module types tested reached an ultimate limit state at applied loads around 3 times the nominal design load, but had different modes of failure. The ultimate resistance for the module with columns having the lowest moment of inertia relative to length squared was caused by column buckling and top platen rupture, while the two modules with nearly twice the moment of inertia relative to length squared failed by top platen rupture and their column forces at most were 70% to 75% of their short-term single column buckling resistance. The results provide new data to allow independent load rating of the buried structure, support continued assessment of column buckling, and identify the need to limit platen bending deflections.