安全護欄抗沖擊能力分析
特種安全護欄是保障道路交通安全的重要設(shè)施,也是保衛(wèi)重要場所安全的第一道屏障。提高護欄的抗沖擊能力能夠有效減少交通事故中的財產(chǎn)損失,保護交通參與者的人身安全;同時也能夠更好的應(yīng)對突發(fā)事件,將不安全因素阻隔在被保護目標(biāo)之外。
(1)對護欄的抗沖擊性能進行了理論分析。利用無回彈型車輛與護欄碰撞簡化力學(xué)模型,推導(dǎo)出了最大橫向撞擊力計算公式,并按照設(shè)計的安全防護等級,對護欄結(jié)構(gòu)的連接強度進行了校核。參照公路交通安全設(shè)施設(shè)計規(guī)范,計算了護欄的加權(quán)平均高度,分析了其抗大型車輛傾覆的能力。計算結(jié)果表明,護欄框架與半月柱之間采用5.8級及以上等級的M16螺栓連接能夠滿足A級防護的抗沖擊性能要求,且具有較高的安全系數(shù);護欄框架的焊接強度在理想狀態(tài)下剛好滿足A級防護的抗沖擊性能要求,但安全系數(shù)僅為1.17;護欄的加權(quán)平均高度為1.88 m,滿足A級抗大型車輛傾覆的防護等級要求。
(2)對護欄的抗沖擊性能進行了仿真分析。構(gòu)建了“車輛—護欄”碰撞仿真模型,參照城市道路交通設(shè)施設(shè)計規(guī)范中規(guī)定的碰撞條件和實際應(yīng)用中擬面對的正面撞擊極限工況進行了模擬仿真。仿真結(jié)果表明,在標(biāo)準(zhǔn)工況下,車輛與該新型特種安全護欄的碰撞過程中出現(xiàn)了“絆阻現(xiàn)象”;在正面撞擊極限工況下,該型護欄對車輛起到了有效的攔阻作用,但護欄框架被突破,出現(xiàn)了車輛穿越護欄的現(xiàn)象,因此該型護欄的抗沖擊性能仍有較大的提高空間。
(3)對護欄進行了水平靜力加載試驗。試驗由梁式和板式載荷分配器模擬小型車輛和大型車輛與護欄碰撞的接觸面,并通過螺旋千斤頂對護欄施加載荷力,觀測護欄的結(jié)構(gòu)變形情況。試驗結(jié)果表明,護欄框架上下梁與框架邊柱焊接連接處為護欄結(jié)構(gòu)的薄弱環(huán)節(jié)。若采取提高護欄框架連接強度的改進措施,則會使護欄結(jié)構(gòu)充分利用其自身塑性變形吸收更多的碰撞沖擊能量,提高護欄的抗沖擊性能。
(4)提出了護欄結(jié)構(gòu)優(yōu)化設(shè)計方案。以提高護欄框架焊接強度,避免或延緩護欄框架焊接處失效現(xiàn)象的發(fā)生為優(yōu)化目標(biāo),對護欄進行了增設(shè)加固角碼和提高底座凸臺高度的結(jié)構(gòu)優(yōu)化改進,并對結(jié)構(gòu)優(yōu)化后的護欄進行了抗沖擊性能仿真分析。結(jié)果表明,結(jié)構(gòu)優(yōu)化后的護欄對沖擊能量的吸收提升了20.5%,且具備較好的多道布置攔停車輛的能力。
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