Research On The Design Method Of ?-? Effect In Code For Design Of Concrete Structures And Second-order Effect In Complex Frame Structure

Second-order effect is a widespread phenomenon in structure.The effect can't be ignored of second-order effect on the deformation and internal force during structural design. Strengthening theoretic recognition of second-order effect in RC structures has important practical significance in engineering structural design. Although study of the theory of second-order effect has been made a lot of progress recently, according to the characteristics of RC structures, there remains a series of problems needed to be clarified in this area, and looks forward to its research achievements can provide guidance and services for structural design.China Standard “Code for Design of Concrete Structure”has gradually established a complete theoretical system and engineering design in considering second-order effect from version 2002 to version 2010, its many research achievements sync with the latest developments worldwide. The author depth reflecting on the existing norms related content with the advance of the research team work, found in the Code is still worth studying issues related to the design method of second-order effect following aspects: 1) The Code is not comprehensive enough with ideas and methods to boundaries of need not consider ?-? effect in article 6.2.3; 2) The different ideas of additional eccentricity need to be unified for second-order internal forceanalysis and cross-sectional design to eccentric columns; 3) For practical engineering complex structures, such as staggered floor frame and structures containing the multiple-layer frame column, they still don't explicitly provide simple and effective method to calculate the second-order effect to the current specifications and commercial software(PKPM).Base on the above problems and insufficient consideration of existing norms of second-order effect, it is necessary to depth research to complete the specification method of second-order effect in RC structures and provide the basis for engineering design.The author has made some significance results through the systematic research of the above problems as follows:(1)Based on the depth comprehensive of ?-? effect and the idea of the method of m nsC-? to solve ?-? effect, and combined with the method of need not calculate ?-? effect boundaries in exiting norms, it pointed out the deficiencies in the determination of calculation boundary conditions. It has given the adjustment proposal to calculation boundary conditions through the results of series of example analysis. This part of the research can provide reference for the next round of revision of the specification.(2)Through combing related content of second-order effect in the exiting norms GB50010-2010, found different ideas while considering additional eccentricity when the Code analyze second-order internal force and design for cross-section to eccentric columns, they need to be unified. According to eccentric columns considering additional eccentricity, combined with comprehensive of the rules of second-order effect, we proposed an idea to uniformly consider additional eccentricity in internal force analysis. On this basis, we proposed reference advice for the next round of revision of the specification.(3)According to the method of analysis of independent member based on the actual state of the constraint by the team of Yang Guanglei, combined with series analysis case, it has been solved of length factor under the arbitrary constraints of the multiple-layer frame column for complex structures in practical engineering design. Based on traditional method of 0?-l, the simple method of second-order effect has been proposed to calculate complex the multiple-layer frame column, it can be referenced by engineering designers.(4)On the basis of second-order elastic analysis to staggered floor structure in different load case, the force characteristics and the basic rules of second-order effect have been recognized, and the method of definition of staggered floor column by one side of the floor based on horizontal load direction has been proposed. On the basis of analysis of independent member based on the actual state of the constraint and length factor of the multiple-layer frame column, practical calculation method has been proposed for second-order effect of staggered floor frame, it can be referenced by engineering designers.