某大橋現(xiàn)澆m跨連續(xù)箱梁預(yù)應(yīng)力混凝土鋼桁架梁與鋼支墩力學(xué)計(jì)算

PAGEPAGE6XX大橋B標(biāo)段現(xiàn)澆30m跨連續(xù)箱梁預(yù)應(yīng)力砼鋼桁架梁與鋼支墩力學(xué)計(jì)算(內(nèi)部資料)鋼桁架與鋼支墩力學(xué)計(jì)算本橋擬采用裝配式公路鋼橋桁架節(jié)（貝雷）拼裝成桁架梁，用于水上現(xiàn)澆連續(xù)箱梁砼施工。桁架梁與梁之間用鋼支撐片進(jìn)行橫向聯(lián)結(jié)，以保證桁架梁的穩(wěn)定。由于單孔橋梁跨度較大，擬在L=30m跨中設(shè)置一個(gè)臨時(shí)鋼支墩，以改善桁架梁的受力狀況，減少鋼桁架的布置數(shù)量?；举Y料現(xiàn)取F線第二聯(lián)（F6～F10）4×30m為例（詳見(jiàn)《鋼桁架與鋼支墩布置簡(jiǎn)圖》）F匝道橋第二聯(lián)：C50砼763m3，鋼筋135.87t，鋼絞線25.50t，預(yù)應(yīng)力砼密度v==2.61t/m3（不含錨具等）二、橋面恒載取順橋向1.0米作為計(jì)算單元砼重量：=19.91t（按20%加載考慮）施工荷載：=4.50t模板重量：=1.00t貝雷重量：=1.0t合計(jì)：q=26.41t桁架梁布置1、強(qiáng)度驗(yàn)算按均布荷載簡(jiǎn)支梁計(jì)算彎矩M===515.82t·m鋼桁架布置n==折減系數(shù)：0.9；[M]=78.82t·m=7.27（實(shí)際布置12排）剪力Q==0.5×26.41×12.5[Q]=24.52t=165.06n===7.48排1、撓度計(jì)算f===0.015＜=0.031m可鋼支墩設(shè)計(jì)1、鋼橫梁（3I32a）計(jì)算按一端懸臂梁承受集中荷載P的最不利情況驗(yàn)算P===13.76t=692.5cm3M=13.76×1.0=13.76t·m（設(shè)斜撐）σ===662.3＜1700kg/㎡可τ===12.75kg/cm2＜100kg/cm2可f===0.07＜=0.25cm可2、鋼立柱計(jì)算①φ60cm，δ=0.8cm鋼管樁（一排4根）P=Q/4==41.26t；A=π（302-29.22）=148.72強(qiáng)度σ===277.43kg/cm2＜1400kg/cm2可i==20.93λ===47.8查得，φ=0.896穩(wěn)定性σφ==309.5＜1400kg/cm2可②φ40cm，δ=0.8cm鋼管樁（一排5根）A=л（202-19.22）=98.52cm2P=Q/5==31.21t強(qiáng)度σ===316.79kg/cm2＜1400kg/cm2可i==13.86λ===72.15查得，φ=0.778穩(wěn)定性σφ==407.18＜1400kg/cm2可開(kāi)口鋼管樁計(jì)算由于現(xiàn)行橋規(guī)中沒(méi)有開(kāi)口鋼管樁的設(shè)計(jì)及相關(guān)條文規(guī)定，一般按照閉口鋼管樁計(jì)算，然后乘以系數(shù)，以考慮擠土效應(yīng)。（參看《橋梁建設(shè)》總第165期）樁的總豎向承載力等于樁側(cè)壓力加樁端阻力即[P]=假設(shè)按鋼管樁平均打入中砂層l=25m,樁端進(jìn)入全風(fēng)化花崗巖層計(jì)算，查鉆探資料：中砂τi=45kPa.全風(fēng)化花崗巖σR=260kPa(持力層)。取αi=0.7；α=0.9；折減系數(shù)0.7；A=л×0.32=0.283m2鋼管樁豎向承載力：[P]==541kN單樁豎向荷載P=412.6kN（上部荷載）+4kN（鋼橫梁重）+46.8kN（鋼管樁重）=463.4kN＜541kN可注：根據(jù)《港口工程樁基規(guī)范》要求，開(kāi)口鋼管樁樁端按進(jìn)入持力層＞5D（5×60=3.0m）控制。計(jì)算：復(fù)核：審核：目錄一、基本資料··········································1二、橋面恒載··········································1三、桁架梁布置········································1四、鋼支墩計(jì)算········································21、鋼橫梁計(jì)算······································22、鋼立柱計(jì)算·································