Built in the late 1960s in the collegiate "bunker" architecture of the Vietnam War Era, the administration building on my campus has weathered decades of anti-war and other student protests. Inside the building, however, several of the original polymer-based staircases betray 50+ years of continuous footfalls. Notice that the "swayback" steps in the above photos are predominantly on the right side as you're looking down the staircase (on the left side as you're looking up). You keep to your right when descending or ascending. The disproportionate sway on one side, then, must reflect your greater foot impact on steps as you descend. The difference in impact is a factor of two, observes a professor of civil engineering at my university. (See the footnote below for his explanation, which I could not fathom.)*
|Resilient scholastic bunker architecture|
Staircase design is serious business. The height of risers and depth of treads are standardized in state and local building codes. Nothing jolts your hard-wired sensory-motor expectations like missing a step, or on the upside, encountering one that is unexpectedly high or diminutive. Thirty years ago, arriving in the dark from Canada at the two-story rental where my partner and I occupied the second floor, my suitcase and I went flying when my foot encountered an unexpected supersized first-step riser on the stoop of my building. While I was out of town a handyman had replaced the old stoop with a one-piece modular version. Unfortunately for me, he had failed to sufficiently sink the bottom riser, which was twice the height of the others, into the ground.
|Stooping to be conquered?|
*Descending, think of sudden loading: use a dynamic load factor of two (on the weight only independent of any factors of safety,etc.). Ascending : first thought is to consider a ramp loading. However, since we might run up the stairs, think of sudden loading again and use DLF of 2 again. So I would use 2 times as the factor.