# Applied P-Delta Methods in the Design Office

*by*Horatio Allison, Allison, McCormac & Nickolaus, Rockville, MD, USA,

**Abstract:**At first glance some axioms of a P-Delta analysis appear to be paradoxical. First, the P-Delta effects are a direct function of the depth of the structure parallel to the wind direction. The P-Delta effects are inversely proportional to the design wind load. The required P-Delta stabilizing forces are the same for a given frame deflection. Thus, the P-Delta effect is greater with the wind force applied to the narrow side as when applied to the long side. When wind loads are increased, the required stabilizing forces remain constant for any given frame deflection. Thus, for higher wind loads, P-Delta affects are less critical than for lower wind loads.

**Subject Headings:**Wind loads | Load factors | Frames | Wind forces | Displacement (mechanics) | Critical loads | Building design

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