Study On Influences To Seismic Safety Assessment Of Intake Tower Caused By Current Seismic Specifications

In the west of China,there are rich hydropower resources but with frequent strong earthquakes.Due to that intake tower,as the first building of water drainage and supply systems in hydropower engineering hub,could have severe impacts on power stations’ operation and even bring threats to the whole project hub once damaged during earthquakes,it has always been our key point and difficult point to research intake towers’ seismic safety of hydrop ower projects.After Wenchuan Earthquake in China and on basis of long-term experience accumulation,a profound understanding is achieved regarding movement characteristics of ground motion as well as damage mechanism and models of hydraulic structure during earthquakes.Revisions were made to DL 5073-2000 Seismic Design Specifications of Hydraulic Structure(previous specifications),and in 2015,NB 35047-2015 Seismic Design Specifications of Hydraulic Structure for Hydropower Engineering(new current specifications)was issued,where great adjustments were made to seismic safety assessment of intake tower.One of the key and imp erative subjects for us designers and researchers to do is study influences to seismic safety assessment of intake owers built or being built caused by previous and current specifications.In terms of influences to seismic safety assessment of intake towers built or being built caused by previous and current seismic specifications of hydraulic structure,the paper includes several aspects:firstly,the paper discusses about intake tower’s dynamic characteristics,site conditions and effects to total input energy caused by characteristic index of design response spectrum through total input energy formula of response spectrum theory,combined with values analysis of finite element.Secondly,the paper talks about effects to intake tower displacement and stress response caused by the index of descending part of response spectrum,site characteristic period,damping ratio,dynamic concrete modulus of elasticity as well as deformation modulus of foundation rock by way of model super-position response spectrum.In accordance with differences between previous and current specifications,this paper studies intake tower’s seismic responses in both specifications,and then has an assessment of seismic capability of intake tower designed in compliance with previous specifications.Thirdly,the capability of intake tower designed in compliance with previous specifications.Thirdly,the paper presents that ground motion can be produced artificially in compliance with design response spectra of previous and current specifications and then a study can be carried out of intake tower’s linear elasticity and non-linear seismic response with the adoption of dynamic time-history method.The paper,by analyzing intake tower’s seismic safety under previous and current specifications,shows that current specifications have caused some influence to intake tower’s seismic response(either displacement or internal force)by putting higher requirements on intake tower’s seismic capability.Thus it is necessary to carry out seismic safety review of high intake towers built or located in high intensity areas.