趙寶俊+謝路+朱郭瑞+孟江
摘要:為了研究拼接拓寬空心板橋梁荷載橫向傳遞及內(nèi)力變形規(guī)律,建立有限元模型,對(duì)橋梁新舊板剛接和鉸接連接形式下耦合受力情況進(jìn)行分析,研究不同連接形式對(duì)新舊板整體受力的影響。結(jié)果表明:采用不同連接形式拓寬后,舊橋各板的橫向分布系數(shù)均低于原板,即拓寬后舊空心板仍起控制作用,但其整體受力性能得到提高;拓寬后側(cè)邊板內(nèi)力和撓度比中板大,且新板內(nèi)力和撓度比舊板??;空心板橋梁采用剛接形式拓寬時(shí),結(jié)構(gòu)整體剛度的提升高于鉸接形式的;隨著耦合剛度增大,橋梁整體剛度增大,彎矩和撓度降低逐漸明顯,跨中頂緣壓應(yīng)力減小,底緣拉應(yīng)力增大;從結(jié)構(gòu)整體受力和結(jié)構(gòu)性能角度來(lái)看,剛接形式的新舊板頂緣壓應(yīng)力比鉸接形式的小,且完全剛接的連接方式受力更合理。
關(guān)鍵詞:橋梁工程;空心板橋;拓寬;耦合受力;連接形式
中圖分類號(hào):U443.3文獻(xiàn)標(biāo)志碼:A
Analysis on Coupling Force of New and Old Beams After Widening
Hollow Slab BridgeZHAO Baojun1,2, XIE Lu2, ZHU Guorui2, MENG Jiang1
(1. Post Doctoral Research Station of Transportation Engineering, Changan University, Xian 710064, Shaanxi,
China; 2. Shaanxi Provincial Communication Construction Group, Xian 710075, Shaanxi, China)Abstract: In order to study the effect of lateral load transfer and deformation rules of widening hollow slab bridge, the finite element model was established to analyze the new and old connection coupling force in different ways (hinged or rigid), and the influences of different connections on the force of the new and old boards were studied. The results show that after using different connection form to widen, old bridge transverse distribution coefficient of each plate is lower than that of the original plate, it is showed that old plate still plays a controlling role after widening, but the overall mechanical performance is improved. The force and deflection of side plate is larger than that of the internal plate, and the force and deflection of new internal plate is smaller than that of the old one after widening. When hollow slab bridge is widened using rigid connection, the rise of the overall rigidity of the bridge is larger than that using hinged connection. With the increase of coupling stiffness, the overall rigidity of the bridge increases, bending moment and deflection decrease clearly, the top edge compressive stress decreases, and bottom flange tensile stress increases. In the view of structure stress and the overall structure properties, the compressive stress of the top edge is smaller than that using rigid connection, and fully rigid connection form of stress is more reasonable.
Key words: bridge engineering; hollow slab bridge; widening; coupling force; connection form
0引言
加寬后橋梁橫向主梁數(shù)量增多,改變了原橋橫向荷載傳遞規(guī)律,新舊主梁剛接和鉸接的不同連接方式對(duì)荷載的橫向分布有較大的影響,使單梁內(nèi)力發(fā)生較大變化[12]。本文以不同拼接構(gòu)造的簡(jiǎn)支空心板橋?yàn)槔?,?duì)荷載橫向傳遞規(guī)律及內(nèi)力變形定量分析[3],研究不同連接方式對(duì)新舊簡(jiǎn)支空心板梁整體受力的影響。新舊板連接后會(huì)在連接處產(chǎn)生相同的變形,因此,荷載作用后可以看作新舊板為耦合受力[45]。
1空心板梁橋拼接構(gòu)造
依托工程為13 m預(yù)應(yīng)力混凝土空心板橋,交角為90°,現(xiàn)舊橋加寬,在原橋外側(cè)加寬8.25 m。新舊橋梁連接有鉸接和剛接2種方式[67]。
1.1鉸接
新舊橋連接時(shí)將舊橋邊梁懸臂部分的混凝土鑿除一部分,露出鋼筋或者在懸臂邊緣植筋,新橋邊板在預(yù)制時(shí)板內(nèi)預(yù)埋鋼筋。連接時(shí)將新舊橋邊板懸臂的鋼筋進(jìn)行焊接,然后澆注混凝土,使新舊橋形成整體[圖1(a)][8]。
1.2剛接
剛接連接采取的措施是在縱向接縫處每隔2 m設(shè)置一道寬40 cm的橫隔梁。在橫梁處舊橋邊板植筋,新橋邊板預(yù)埋鋼筋。新橋梁板架設(shè)后放置3個(gè)月,待收縮徐變和基礎(chǔ)不均勻沉降初值消除后焊接鋼筋,澆注混凝土形成橫梁[圖1(b)][9]。
圖1空心板拓寬構(gòu)造(單位:cm)
Fig.1Structure of Widening Hollow Slab (Unit:cm)2荷載橫向傳遞規(guī)律分析
采用鉸接板法計(jì)算分析不同連接形式下結(jié)構(gòu)整體的荷載橫向傳遞規(guī)律,計(jì)算得每片梁的橫向分布系數(shù),直觀反映出單片梁承受荷載大小[1011]。在結(jié)構(gòu)抵抗能力一定的情況下,單片梁的橫向分布系數(shù)越小,則該結(jié)構(gòu)的通行能力越高[1213]。在上部結(jié)構(gòu)相連接的橋梁拓寬中,舊橋主梁所承擔(dān)的力被新建橋梁分擔(dān)一部分,因此,其橫向分布系數(shù)會(huì)相應(yīng)降低[1415]。
對(duì)舊橋鉸接拓寬、剛接拓寬模型分別進(jìn)行計(jì)算,得舊橋主梁的橫向影響線,根據(jù)影響線得到荷載的最不利布置情況下舊橋主梁的橫向分布系數(shù),如圖2所示。
圖2不同拓寬方式下舊橋橫向分布系數(shù)比較
Fig.2Comparison of Transverse Distribution
Coefficients of Old Bridge Under Different
Widening Modes由圖2可知:采用不同連接方式拓寬改建后,舊橋各梁的橫向分布系數(shù)均明顯低于拓寬前舊橋中各梁的橫向分布系數(shù),表明拓寬后新橋承擔(dān)了部分活荷載,減輕了舊橋主梁所承擔(dān)的荷載,拓寬后結(jié)構(gòu)的整體工作性能得到了改善;拓寬后,不論采用剛接還是鉸接,舊橋靠近加寬側(cè)橫向分布系數(shù)減小均較多,表明舊橋靠近加寬側(cè)的梁板比拓寬前更多地承擔(dān)了荷載,梁板的承載能力得以充分發(fā)揮;拓寬后舊橋各梁的橫向分布系數(shù)大于新橋的橫向分布系數(shù),說(shuō)明拓寬后起控制作用的仍然是舊橋部分的梁。3新舊梁耦合受力計(jì)算分析
3.1有限元數(shù)值模擬
采用有限元程序ANSYS對(duì)新舊橋梁進(jìn)行建模,并模擬兩者間不同的連接方式。在建模過(guò)程中采用約束方程和耦合連接形式來(lái)建立自由度和節(jié)點(diǎn)的關(guān)系,完成節(jié)點(diǎn)自由度耦合,達(dá)到準(zhǔn)確模擬新舊板梁之間的不同連接形式[16]。本文中采用共節(jié)點(diǎn)的耦合方法,由于連接段尺寸較小,將其視為一個(gè)整體與新舊橋相耦合,通過(guò)改變連接段的剛度來(lái)實(shí)現(xiàn)不同耦合受力剛度的計(jì)算分析[1718]。
3.2有限元模型的建立
3.2.1拓寬結(jié)構(gòu)的幾何特征
依托工程舊橋中梁和邊梁截面尺寸、舊橋典型橫截面、拓寬后橋梁整體橫截面布置見圖3。
圖3拓寬結(jié)構(gòu)的幾何特征(單位:cm)
Fig.3Geometrical Features of Widening
Structure (Unit:cm)3.2.2材料特性
材料特性如表1所示。
表1材料特性
Tab.1Characteristic of MaterialsMPa位置舊橋接縫處新梁混凝土標(biāo)號(hào)C45C50C45設(shè)計(jì)強(qiáng)度軸心抗壓19.723.120.5軸心抗拉1.711.891.74標(biāo)準(zhǔn)強(qiáng)度軸心抗壓28.532.429.6軸心抗拉2.472.642.51彈性模量33 10034 50033 5003.2.3建立有限元模型
采用Solid65單元分別對(duì)舊橋、鉸接加寬橋梁、剛接加寬橋梁建立有限元模型(圖4)。舊橋模型節(jié)點(diǎn)數(shù)為31 443,單元數(shù)為23 736;鉸接加寬模型節(jié)點(diǎn)數(shù)為52 781,單元數(shù)為39 790;剛接加寬模型節(jié)點(diǎn)數(shù)為53 074,單元數(shù)為40 048。
圖4鉸接和剛接加寬模型下表面
Fig.4Lower Surface of Hinged and
Rigid Broadening Models3.3計(jì)算工況選取
按照不同連接方式選取計(jì)算工況。為明確鉸接連接和剛接連接更細(xì)致的區(qū)別,增加從鉸接到剛接的過(guò)渡分析,將連接段混凝土剛接部分采用不同的耦合剛度進(jìn)行計(jì)算[19]。連接部耦合剛度的擬合單獨(dú)建模型進(jìn)行計(jì)算[20]。為得到更為普遍的新舊板梁耦合受力整體變化規(guī)律,按照標(biāo)準(zhǔn)圖集中13 m簡(jiǎn)支空心板梁橋計(jì)算分析,結(jié)構(gòu)形式與示例相同??紤]到預(yù)應(yīng)力筋具有離散性,而本文研究重點(diǎn)針對(duì)整體結(jié)構(gòu)的性能,故計(jì)算荷載只考慮恒活載(含二期鋪裝)[2122]。計(jì)算工況見表2。
3.413 m簡(jiǎn)支空心板梁橋計(jì)算分析
3.4.1變形對(duì)比分析
不同連接形式的空心板梁位移云圖見圖5。計(jì)算表明,不論新舊橋以何種形式連接,橫橋向和豎向的變形趨勢(shì)基本一致。簡(jiǎn)支板縱橋向頂緣受壓,在混凝土泊松比的影響下頂緣混凝土在橫橋向向兩側(cè)延伸,且兩邊梁橫橋向位移最大。鉸接連接時(shí),左邊
表2計(jì)算工況
Tab.2Calculation Cases工況編號(hào)新舊板梁連接情況耦合剛度1舊橋,11片板梁2鉸接連接3剛接連接0.25EI4剛接連接0.50EI5剛接連接0.75EI6剛接連接EI注:EI為完全剛接時(shí)的剛度。
圖5工況1~6下板梁位移云圖(單位:m)
Fig.5Displacement Nephogram of Beam
Under Conditions 16 (Unit:m)板的橫橋向最大位移由原來(lái)舊橋工況下的0.11 mm變?yōu)?.14 mm,而當(dāng)以不同的耦合剛度剛接時(shí),左邊板的橫橋向最大位移由0.25EI剛接后的0.13 mm變?yōu)橐訣I剛接(完全剛接)后的0.12 mm,隨著耦合剛度增大,橫橋向位移變小。豎向位移都是跨中截面處最大,且兩邊板較中板更大。當(dāng)以鉸接方式連接時(shí),連接段混凝土跨中也會(huì)產(chǎn)生較大的豎向位移。采用剛接后,連接段混凝土跨中豎向位移明顯減小,且隨著耦合剛度的增大而減小,而向兩側(cè)延伸影響越小。兩邊板豎向位移基本不隨耦合剛度變化。相比舊橋而言,由于縱向跨度不變,不論采用何種方式連接,空心板梁的豎向位移最大值也基本保持不變。表明新舊橋連接形式對(duì)連接段混凝土及鄰近板梁有明顯影響,而對(duì)兩邊板附近板梁影響較小。
3.4.2應(yīng)力對(duì)比分析
不同連接形式空心板梁的應(yīng)力云圖見圖6。計(jì)算表明,不論新舊橋以哪種形式連接,橫橋向和縱橋向的應(yīng)力分布特點(diǎn)基本一致,在拼接處應(yīng)力突變最大,板梁橫橋向中心受壓,且跨中截面頂緣壓應(yīng)力最大。隨著新舊板梁連接剛度增大,橫橋向壓應(yīng)力的范圍也逐漸增大;以鉸接形式連接時(shí),連接段混凝土頂緣的壓應(yīng)力最大,達(dá)到2.3 MPa;以剛接形式連接時(shí),連接段混凝土頂緣的壓應(yīng)力減小,與板梁過(guò)渡均勻,且隨著耦合剛度的變化,頂緣壓應(yīng)力的范圍仍基本保持不變,最大壓應(yīng)力不超過(guò)1 MPa;從縱橋向應(yīng)力云圖來(lái)看,板梁的應(yīng)力變化較小,均是跨中壓應(yīng)力最大,向兩端遞減。
圖6工況1~6板梁應(yīng)力云圖(單位:Pa)
Fig.6Stress Nephogram of Beam Under
Conditions 16 (Unit:Pa)不同連接形式連接段混凝土的應(yīng)力云圖見圖7。計(jì)算表明,不論新舊橋以哪種形式連接,橫橋向和縱橋向的應(yīng)力分布特點(diǎn)基本一致,均是跨中頂緣壓應(yīng)力和底緣拉應(yīng)力最大。隨著耦合剛度增大,跨中頂緣壓應(yīng)力減小,底緣拉應(yīng)力增大,且剛接相比鉸接而言,底緣壓應(yīng)力較小,同一豎向高度處的拉應(yīng)力較大。
圖7工況2~6連接段應(yīng)力云圖(單位:Pa)
Fig.7Stress Nephogram of Connection Section
Under Conditions 26 (Unit:Pa)3.4.3跨中截面內(nèi)力和撓度對(duì)比分析
對(duì)有限元模型中跨中截面應(yīng)力進(jìn)行積分可得跨中截面內(nèi)力,位移根據(jù)節(jié)點(diǎn)提取,對(duì)比分析跨中截面的縱橋向彎矩和底緣撓度。
不同連接形式下19片板梁的跨中截面縱橋向彎矩見圖8。邊板跨中截面的縱橋向彎矩比中板大,最內(nèi)側(cè)中板彎矩最小。在舊橋拓寬后,原先的右邊板變?yōu)橹邪澹瑥澗匾惭杆贉p小,且離連接段越遠(yuǎn),內(nèi)力減小越少,左邊6塊板的彎矩基本不受橋梁拓寬的影響。新板梁側(cè)的邊板和中板的彎矩相比于舊板梁的邊板和中板都小一些。新舊板梁之間不論是鉸接,還是不同耦合剛度的剛接,除靠近連接段的兩相鄰板的彎矩發(fā)生明顯變化外,其余板的跨中截面彎矩基本不變化。隨著耦合剛度的增大,靠近連接段的兩相鄰板的彎矩減小得越多。完全剛接連接時(shí),靠近連接段的兩相鄰板的彎矩比其他中板還小,且新板梁側(cè)的更小。在新舊板梁連接后,新板梁的圖8工況1~6跨中截面縱橋向彎矩
Fig.8Longitudinal Bending Moments of Cross
Section at Midspan Under Conditions 16 右側(cè)板梁彎矩與舊橋的右側(cè)邊板彎矩基本相同。
不同連接形式下19片板梁的跨中截面底緣撓度見圖9。左右邊板跨中截面撓度比中板大,最內(nèi)側(cè)中板撓度最小。舊橋拓寬后,原先右邊板變?yōu)橹袌D9工況1~6跨中截面底緣撓度
Fig.9Bottom Edge Deflections of Cross Section at
Midspan Under Conditions 16板,撓度也迅速減小,且離連接段越遠(yuǎn),撓度減小得越少,左邊6塊板的撓度基本不受橋梁拓寬的影響。新板梁側(cè)的邊板和中板的撓度相比于舊板梁的邊板和中板都要小一些。剛接相對(duì)于鉸接而言,使得連接段附近的板梁撓度減小得更多。隨著耦合剛度的增大,連接段附近的板梁的撓度變得更小。完全剛接連接時(shí),連接段附近的板梁撓度基本與鄰近中板持平,變化不大。在新舊板梁連接后,新板梁的右側(cè)板梁撓度比舊橋的右側(cè)邊板撓度小。
4結(jié)語(yǔ)
(1)采用不同連接形式拓寬后舊橋各梁的橫向分布系數(shù)均明顯低于拓寬前舊橋中各梁的橫向分布系數(shù),表明拓寬后結(jié)構(gòu)承載能力得到提高。拓寬后各主梁的橫向分布系數(shù)均小于拓寬前舊橋各主梁的橫向分布系數(shù),起控制作用的仍然是舊橋的梁。
(2)對(duì)于靠近拓寬側(cè)的新橋左邊板而言,其橫橋向最大位移依工況排序?yàn)殂q接、0.25EI剛接、0.5EI剛接、0.75EI剛接、EI剛接,表明拓寬后橋梁整體剛度隨著耦合剛度的增大而增大。
(3)拓寬側(cè)邊板內(nèi)力和撓度比中板大,且拓寬后新板的內(nèi)力和撓度比舊板小。拓寬后舊橋板梁在恒活載作用下的內(nèi)力及撓度均降低,尤其靠近拓寬部分的板梁撓度及內(nèi)力降低較大。剛接比鉸接影響更大,且隨著耦合剛度的逐漸增大,彎矩和撓度減小得越多。
(4)新舊板梁橫橋向跨中截面頂緣壓應(yīng)力最大,剛接比鉸接頂緣的壓應(yīng)力小;對(duì)于連接段混凝土,跨中頂緣壓應(yīng)力和底緣拉應(yīng)力最大,隨著耦合剛度的增大,跨中頂緣壓應(yīng)力減小,底緣拉應(yīng)力增大。
(5)從結(jié)構(gòu)整體受力和結(jié)構(gòu)性能方面來(lái)看,完全剛接的連接形式更為合理。參考文獻(xiàn):
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