Research On The Application Of Yield Strength Coefficient In The Seismic Appraisal Of R.C.Frame Structures

This paper reflects on the development of China’s seismic appraisals in different historical periods and methods widely adopted at home and abroad, analyzes the calculations on the yield strength coefficient ofξy, tries to provide the range of story compound seismic capacity index of β under varied structural damages and the variation of P under different requests on earthquake-resistant capabilities based ongenerated through shaking table tests for reinforced concrete frame structure models, categorizes integral modification factor of Ψ1and attempts to propose improvement suggestion for the Standard for Seismic Appraisal of Buildings. Major contents of this paper are as follows:1. Clarifying the definition and usage of story yield strength coefficient stated in the Code for Seismic Design of Buildings GB50011-2010and the Standard for Seismic Appraisal of Buildings GB50023-2009(Hereinafter refers to as the Standard), discussing the advantages and problems of the Standard’s using yield strength coefficient to appraise compound seismic capacity, analyzing the calculations on the story lateral shear capacity and seismic action of story responding to earthquake.2. Analyzing the story yield strength coefficient based on data gathered from shaking table tests for reinforced concrete frame structure models. Selecting a particular part from a school building damaged during the Wenchuan Earthquake in2008as the Prototype1and using the2005version of PKPM to design the Prototype2. Making Models1and2that are five times larger of the two prototypes and placing them on the same platform in the shaking table tests. The calculation and tests show that it is feasible to apply β, which is made out of the modification of ξy, in assessing the damage of frame structures under varied magnitude. Engineers can set a reasonable goal for the structure’s earthquake-resistant capacity according to the categorization of β in different state of damage.3. Making Models3,4and5based on simulative structures with different height of their ground floor and making sure the models are10times larger than the structures. Further proving previous conclusion by calculation and tests, deducing irregularity lateral stiffness’s impact on integral modification factor.4. Calculating the seismic peak ground acceleration Amax and the maximum earthquake affecting coefficient αmax of different seismic intensity region during the continuous seismic service life. Calculating the adjustment coefficient of ground shaking parameter of earthquake during the continuous seismic service life. Providing the relationship between the seismic damage andβ of R.C. frame structures. According to performance-based seismic appraisal, generalizing performance objective of R.C. frame structures under earthquake and giving out quantitative indicators ofβ. The author designed two frame structures according to the basic detailing requirements of type A and type B reinforced concrete frames, and compared the β of the two structures with the findings of model tests in terms of continuous seismic service life. Testing the β of Model6that was made by reinforcing the test-damaged Model2and confirmating performance objective requirements.5. Designing8simulative structures with different height of their ground floor and using Etabs’pushover to analyze the possible damage of each structure in frequently and seldom occurred earthquakes, calculating their responding β. The conclusion can be reached that irregularity in lateral stiffness has very little effect on β if a frame structure remain intact after an earthquake, but has significant impact on β in collapse stage. Providing the relationship between the story’s minimum stifness ratio and adjustment coefficient. To get Ψ(?) of frame structure, we can multiply adjustment coefficient and other coefficients given by the Standard.