Research On The Design Method Of PC Structure Under Hyperstatic Restraint

The main characteristic of modern PC structure has transformed into complex structure (usually statically indeterminate structure) form simple one (usually simply supported member). There are great changes in design method and construction, and the following work is done in this paper:Influence factor of restraint. The influence of lateral restraints on the PC structure has been discussed in many papers and main factors including structure system, stiffness ratio of column to beam and construction sequence are considered. The results of the instances demonstrated that the distribution of effective prestress and shape of prestressing tendon should also be considered in the calculation of lateral restraint. Then, the influence of the time effect and patch effect of construction is discussed.Calculation method of secondary shear force. By comparing several common computational methods of secondary interior force both domestic and international, the method of Secondary Interior Force under Restraint should be more convenient.Based on the analysis of design standards and research works, a suggestion of the combination of load effects in PC structure both in serviceability limit states and ultimate bearing limit states is summarized, and the design formula under restraint in the above-mentioned two-stages is proposed in this paper.Exploration of essence of restraint. By analyzing the formula and examples, it is proved that the essence of restraint is secondary interior force in the structure rather than prestress loss. Thus the restraint must be considered in the design procedure, and secondary axial force besides secondary bending moment should be under consideration in the flexural structure.Study on the rational utilization of secondary interior force. The design suggestions are proposed based on the analysis of the influence factors of secondary interior force.