简介:Long-periodpulsesinnear-fieldearthquakesleadtolargedisplacementsinthebaseofisolatedstructures.Todissipateenergyinisolatedstructuresusingsemi-activecontrol,piezoelectricfrictiondampers(PFD)canbeemployed.TheperformanceofaPFDishighlydependentonthestrategyappliedtoadjustitscontactforce.Inthispaper,theseismiccontrolofabenchmarkisolatedbuildingequippedwithPFDusingPD/PIDcontrollersisdeveloped.Usinggeneticalgorithms,thesecontrollersareoptimizedtocreateabalancebetweentheperformanceandrobustnessoftheclosed-loopstructuralsystem.Oneadvantageofthistechniqueisthatthecontrollerforcescaneasilybeestimated.Inaddition,thestructureisequippedwithonlyasinglesensoratthebasefloortomeasurethebasedisplacement.Consideringsevenpairsofearthquakesandnineperformanceindices,theperformanceoftheclosed-loopsystemisevaluated.Then,theresultsarecomparedwiththosegivenbytwowell-knownmethods:themaximumpossiveoperationofpiezoelectricfrictiondampersandLQGcontrollers.Thesimulationresultsshowthattheproposedcontrollersperformbetterthantheothersintermsofsimultaneousreductionofflooraccelerationandmaximumdisplacementoftheisolator.Moreover,theyareabletoreducethedisplacementoftheisolatorsystemsfordifferentearthquakeswithoutlosingtheadvantagesofisolation.
简介:随着大庆油田气井深入开发,积液井数逐年增多稳产难度增大,但常规柱塞排水工艺需关井等待柱塞下落,关井时间长,影响气井产量,同时井筒中的液体灌入地层,造成近井地层气相渗透率下降,形成“水锁”,影响气藏采收率。为此,设计了连续排水型柱塞,采用分体式结构,柱塞与密封件井底吸合组成密封柱塞上行举液,到达井口时柱塞与密封件分离,实现柱塞套与钢球分别先后下落,且下落过程中井筒中的气液两相流可通过钢球周围和有中心通道的柱塞套向上流动,减少柱塞下落阻力,提高下落速度,以缩短关井时间;同时利用数值模拟技术与室内试验相结合的方式对柱塞的内外部结构进行优化,提高了柱塞密封性。改进后的连续排水型柱塞可实现不关井连续排水,柱塞密封性良好,可延长气井生产寿命、改善气田开发效果。