Optimization Design Of Nonlinear Steel Frame Based On Reliability

The steel frame has the extensive application in many high public building and various industry building structures (include the ocean terrace structure, the power station boiler the structure to prop up, the mineral mountain opencast well etc.).Compared with the common reinforced- concrete frame, the steel frame structure has the weight light, the strength is high, the ductility is big, anti- earthquake function is good, construction speed quick, the piece of cuts is small etc. advantage, therefore, along with our country the economic power strengthened and technique level raised, the steel frame structure will more and more extensively applied ,and become our country one of the main structure systems .this text mainly studies optimized design method of the nonlinear steel frame structure, include: the internal force analytical, the calculation of the reliability index, Genetic Algorithm applies in the nonlinear steel frame under the reliability control.In the conventional design of a steel frame, the first step is to determine the internal forces and moments by using global analysis based on first order theory. Second order effects are reflected indirectly by the factors of effective length and the factors of equivalent moment during the design of members in succession Unfortunately, it is difficult to obtain the accurate effective length of columns ,which may bring on incorrect results sometimes especially for a sway frame. At this time, second order analysis for the whole frame is necessary. In order to avoid complex analysis ,a approximate method is proposed to calculate P-Δeffects. This method considers the effects of deflection by using imaginary horizontal loads and imperfections are taken into account.This text introduced the basic theories of the structure system reliability, adopts the bound criterion and algorithms on the base of system's critical strength, .and introduces the soft self-adaptation control Bound into the identification of dominant failure modes; at the same time, with the incremental load method and differential equalized recursive method, computes the limit-state function of failure mode and probability index precisely under no leaking the dominant failure modes.This text is turned the structure credibility is analytical and excellent to design the theories to gather in integral whole, introduced the basic principle of the heredity calculate way first and in summary in the text, carried on the detailed research to the heredity calculate way concept, operation process, characteristics and the progress circumstance, then, design a kind of heredity calculate way for improvion, Select the improved heredity and lead into the mechanics standard to raise the searching efficiency, and pass to carry on the restrict the processing and can make calculated method apply in nonlinear steel frame design deduce and build up nonlinear steel frame structure beam, pillar according to credibility of excellent turn to design mathematics model, The reliability index is replaced by Subentry coefficient in optimal model restrict equation ,and deal with corresponding restrict conditions with applied expressions carry out the unify of safety and economy of the structure design .This text gives finally not the line steel frame is excellent to turn on the whole example and the result analysis. Pass the analysis and comparisons of calculate the examples, prove the enunciation originally the text put forward of method is right and viable.