The most important is considering the tower structures\' P-△effect under two-dimensional earthquake effect,and this article has done some contrast studies on the result which is obtained by the effect of geometry nonlinearity and linearity.

And power series solutions,with well consideration to P-△ effect,are derived respectively for displacement and stress calculation of the pile section above the ground and that of pile section in a homogeneous layer of soil.

With the development of high buildings, the influence of gravity second-order effect (gravity P-△ effect) is attached more and more importance to, especially the areas in which the wind load or earthquake action is very great.

Estimation of P-Δ effect on constant-ductility inelastic displacement ratio spectra;

Dynamic P-Δ effects on seismic force modification factors;

Design methods of reinforced concrete frame column considering P-δ effect;

Based on D value method,a simplified computational method is proposed for semi-rigidly mul ti-sto-ry and high-rise steel frames,which takes into consideration P-Δeffect,flexibilities of connections and initial out-of-plumb ness.

P-δeffects,P-Δeffects and second order effects have been distinguished in the definition at first,cantilever columns set as examples to explain the difference.