| As a cross water conveyance structure used for cross regional water diversion in water conservancy project,aqueduct plays an irreplaceable role in the whole field of water conservancy project.Once a sudden accident occurs in the aqueduct,it will cause serious damage to the country ’s property safety and the people ’s water problems.China is a country with frequent earthquake disasters.Aftershocks often occur after the main shock,and aftershocks will cause secondary damage to the aqueduct,and even lead to the risk of overall instability of the aqueduct.At present,the research on the seismic performance of the aqueduct mainly focuses on the influence of a single main shock on the aqueduct,and rarely involves the study of the dynamic damage and vulnerability of the aqueduct under the action of the main shock and aftershock.In particular,the masonry aqueduct,which has been built for a long time,often does not take into account the influence of the main shock and aftershock on the performance of the aqueduct,which is obviously unfavorable for the aqueduct to maintain a high safety margin.Therefore,how to ensure the safety of masonry aqueduct under the action of main aftershocks and reasonably evaluate the seismic performance of the aqueduct is an urgent scientific research problem to be solved.In this thesis,the Koyna gravity dam is used to verify the applicability of the main aftershock sequence tectonic earthquake motion,and its construction method is applied to the masonry aqueduct project without local real sequence earthquake to study the dynamic damage behavior of the aqueduct under the action of the main aftershock sequence.Finally,the seismic performance of the aqueduct is reasonably evaluated by performance-based incremental dynamic analysis(IDA)vulnerability analysis.The main research contents of this thesis are as follows :(1)The nonlinear time history analysis of Koyna gravity dam under different tectonic mainshock-aftershock sequences is carried out,and the residual displacement response under different tectonic earthquake sequences is obtained.Through the statistics of residual displacement under the action of seven groups of tectonic seismic sequences,the error values of tectonic seismic sequences with different factors are calculated,and the calculation results under the action of real seismic sequences are compared and analyzed to verify the rationality and applicability of tectonic seismic sequences.(2)According to the above theory of tectonic earthquake,by selecting seven natural mainshock-aftershock sequence of ground motion data,the mainshock-aftershock ground motion in line with the local natural resource conditions is constructed,and the dynamic damage analysis of the aqueduct-foundation model is carried out.At the same time,the influence of strong aftershocks on the damaged structure of the aqueduct and the influence of different characteristic periods of aftershocks on the seismic performance of the aqueduct are analyzed.The results show that the application of aftershocks increases the risk of damage to the aqueduct structure,and the secondary incremental damage caused by aftershocks is not only related to the intensity of aftershocks,but also affected by the initial damage from the main shock.Compared with short-period aftershocks,long-period aftershock ground motions will significantly increase the cumulative damage level of the aqueduct.(3)Based on the dynamic analysis of the aqueduct,the incremental dynamic analysis and vulnerability analysis of the aqueduct under the action of the main aftershock sequence are carried out.The results show that the vulnerability curve of the mainshockaftershock sequence is located above the single mainshock.Under the action of 0.3 g ground motion,the exceeding probability of the aqueduct to achieve moderate damage and severe damage is 38.52 % and 12.08 % higher than that of the single mainshock,respectively,indicating that the aftershock ground motion has a significant impact on the vulnerability curve of the aqueduct.In the seismic safety assessment of the aqueduct,the influence of the aftershock ground motion cannot be ignored. |
