Spatial and Temporal Variability of Live Loads

A probabilistic model of sustained live occupancy loads on buildings is presented, compared with data, and analyzed to produce equivalent uniformly distributed loads (EUDLs) for structural load effects corresponding to a specified probability of being exceeded. The model of load intensity is a linear form including building, floor, and local spatial variation. The latter term is assumed to have exponentially decaying spatial correlation. Temporal variation is assumed to occur at random times associated with changes of one or more independent occupants. Influence surfaces permit translation to structural load effects. The model is compared and fitted to data from the English Building Research Station office loads survey. Results for sustained and maximum lifetime sustained load effects are shown. Figures compare 99% EUDLs for column axial forces and beam moments versus model U. S. and Canadian building codes.