Concentrated static and step loading were applied to circular arches with geometric parameters 7 < γ < 20. The static equilibrium path and the dynamic response at the loading position were recorded. Dynamic buckling is distinct. Supercritical and subcritical response were separated by 0.5 percent of the total load. The sensitivity of the arch to off set loading was studied. The effect was pronounced in the static tests but moderate in the dynamic case. An energy approach was used to determine the lower, and upper bound for the critical step load. The lower bound agrees well with the experimental results.