POST FOUNDATION DESIGN EQUATIONS: VALIDATION AND SENSITIVITY ANALYSIS

The equations developed in Riskowski and Friday (1991) and included in ASAE EP 486 (ASAE, 1991) were used to evaluate the sensitivity of post foundation strengths to various combinations of embedment depths, post sizes, collar and footing sizes, and soil strengths. These equations were also used to compare predicted lateral and vertical load resistances of post foundations to field research results. Moment capacity of nonconstrained post foundations was found to be sensitive to changes in lateral shear. Collars and attached footings significantly increased lateral strength and vertical uplift resistance of post foundations. Predictions were conservative relative to field test values for the nonconstrained post-only, nonconstrained bottom collared posts with rock and gravel backfill, and con-strained bottom collared posts. The predicted values for nonconstrained bottom collared posts with soil backfill were significantly under field test values. All predicted uplift resistances were much lower than field test values.