It introduces the group structure of steel-concrete,elaborates the design methods of twisted prestressing force steel-concrete group piles,analyses its advantages and using scopes so as to promote the application and development of twisted prestressing force steel-concrete group piles.

A method for calculating ultimate flexural strength of preflex composite beam with the elasto-plastic effect of steel;

Research on elastic-plastic ultimate capacity of preflex beam bridges;

This paper introduced the fundamental of preflexed beam; Aggregated the research development of preflexed beam at home and abroad in the past years; Discussed the material modeling and selected the stress-strain relationship of steel and concrete which is suitable for the nonlinear analysis of preflex beam; In.

Analytical theory and test study of longterm properties for the preflexed beam;

Based on the construction peculiarity of preflexed beam bridges,an analytical method is proposed for predicting properties of bridges structures.

Application and study on prestressed composite plate girders are presented in this article and its development in the future is pointed out as well.