安全護(hù)欄抗沖擊能力分析
特種安全護(hù)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(hù)欄的抗沖擊能力能夠有效減少交通事故中的財(cái)產(chǎn)損失,保護(hù)交通參與者的人身安全;同時(shí)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(hù)目標(biāo)之外。
(1)對護(hù)欄的抗沖擊性能進(jìn)行了理論分析。利用無回彈型車輛與護(hù)欄碰撞簡化力學(xué)模型,推導(dǎo)出了最大橫向撞擊力計(jì)算公式,并按照設(shè)計(jì)的安全防護(hù)等級,對護(hù)欄結(jié)構(gòu)的連接強(qiáng)度進(jìn)行了校核。參照公路交通安全設(shè)施設(shè)計(jì)規(guī)范,計(jì)算了護(hù)欄的加權(quán)平均高度,分析了其抗大型車輛傾覆的能力。計(jì)算結(jié)果表明,護(hù)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(hù)的抗沖擊性能要求,且具有較高的安全系數(shù);護(hù)欄框架的焊接強(qiáng)度在理想狀態(tài)下剛好滿足A級防護(hù)的抗沖擊性能要求,但安全系數(shù)僅為1.17;護(hù)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(hù)等級要求。
(2)對護(hù)欄的抗沖擊性能進(jìn)行了仿真分析。構(gòu)建了“車輛—護(hù)欄”碰撞仿真模型,參照城市道路交通設(shè)施設(shè)計(jì)規(guī)范中規(guī)定的碰撞條件和實(shí)際應(yīng)用中擬面對的正面撞擊極限工況進(jìn)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(hù)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(hù)欄對車輛起到了有效的攔阻作用,但護(hù)欄框架被突破,出現(xiàn)了車輛穿越護(hù)欄的現(xiàn)象,因此該型護(hù)欄的抗沖擊性能仍有較大的提高空間。
(3)對護(hù)欄進(jìn)行了水平靜力加載試驗(yàn)。試驗(yàn)由梁式和板式載荷分配器模擬小型車輛和大型車輛與護(hù)欄碰撞的接觸面,并通過螺旋千斤頂對護(hù)欄施加載荷力,觀測護(hù)欄的結(jié)構(gòu)變形情況。試驗(yàn)結(jié)果表明,護(hù)欄框架上下梁與框架邊柱焊接連接處為護(hù)欄結(jié)構(gòu)的薄弱環(huán)節(jié)。若采取提高護(hù)欄框架連接強(qiáng)度的改進(jìn)措施,則會使護(hù)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(hù)欄的抗沖擊性能。
(4)提出了護(hù)欄結(jié)構(gòu)優(yōu)化設(shè)計(jì)方案。以提高護(hù)欄框架焊接強(qiáng)度,避免或延緩護(hù)欄框架焊接處失效現(xiàn)象的發(fā)生為優(yōu)化目標(biāo),對護(hù)欄進(jìn)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(jìn),并對結(jié)構(gòu)優(yōu)化后的護(hù)欄進(jìn)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(hù)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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