（1）可以通過粘貼鋼板和粘貼纖維復(fù)合材料，或者通過增加截面方法來增加鋪路層的厚度并增加厚度，來增強(qiáng)梁底部的彎曲裂紋和沿預(yù)應(yīng)力筋的縱向裂紋。該部分的壓縮區(qū)域。該區(qū)域有利于增加彎曲強(qiáng)度和剛度，但是高度的增加受到限制，同時自重也增加了。如果梁底部的高度增加，則加固實(shí)際上會增加；

 

（2）對于腹板上的傾斜裂紋，可將鋼板或纖維復(fù)合材料粘貼在與裂紋相反的方向上，并與水平線成大約45°角，即與傾斜裂紋大致正交的方向。光束高度低，并且將鋼板或纖維錨固。當(dāng)長度不足時，可以以U形箍和壓條的形式粘貼。

 

（3）對于腹板上的收縮裂縫和錨固區(qū)域的裂縫，根據(jù)接縫的寬度，使用環(huán)氧膠堵住或填充接縫；

 

（5）對于因力引起的上述各種疾病，可以采用外部預(yù)應(yīng)力加強(qiáng)方法。有許多特定的方法。該方法的設(shè)計(jì)和構(gòu)造復(fù)雜，但效果較好。

 

（6）對于病多，重的單根梁，在條件允許的情況下，可通過剪斷橫梁來代替剛度更高的新梁，同時減少其他梁的載荷分布。如圖所示，在大多數(shù)情況下，邊緣光束嚴(yán)重病變。

 

5.鋼筋混凝土和預(yù)應(yīng)力混凝土連續(xù)梁和懸臂梁橋

 

連續(xù)梁橋和懸臂梁橋的橫截面通常為T形，I形和箱形。 30米以上的大多數(shù)跨度是箱形的，并且使用了可變高度的不等跨度的梁。通常使用等高鋼筋混凝土連續(xù)梁。跨度小于30米的鋼筋混凝土連續(xù)梁或懸臂梁的跨度通常小于50米。這種使用大跨度鋼筋混凝土材料的橋梁價格昂貴，橋面的負(fù)彎矩區(qū)域也很容易。出現(xiàn)橫向裂縫。高度恒定的預(yù)應(yīng)力混凝土連續(xù)梁的跨度通常在60米以下，而高度可變的預(yù)應(yīng)力混凝土懸臂梁通常在100米以下，但100米以上是常見的，連續(xù)梁通常在200米以下。 ，但200多米也很常見。這種類型的橋梁通常用于穿越障礙物或城市立交橋，并且無論跨度大小如何，都容易出現(xiàn)各種疾病。

 

常見的問題是：

 

（1）懸臂梁牛腿的撓度太大，墩頂?shù)臉蛎姘褰?jīng)常開裂。主要是由于懸臂剛度不足，體積小，車輛超重的影響，縱向預(yù)應(yīng)力損失大，施工質(zhì)量差等原因造成的；

 

（2）如下圖所示，懸臂梁的局部裂縫主要是由于鋼筋不足，高度低，溫度影響或懸梁與梁之間的連接不良所致，導(dǎo)致汽車跳動和局部過大。影響;

 

（3）如果懸臂梁的錨孔跨度太大，則當(dāng)其尺寸太小或鋼筋不足時，很可能在翼展的底部出現(xiàn)中跨撓度或垂直裂縫。中跨梁

 

（4）將預(yù)應(yīng)力筋錨固到齒形板上后出現(xiàn)傾斜裂紋。對于所有預(yù)應(yīng)力箱形梁，這都是一種可能的疾病。如下圖所示，主要原因是齒板附近的應(yīng)力集中太大，普通鋼筋的構(gòu)形太小，預(yù)應(yīng)力鋼絞線被錨固。集中過多引起的。

 

（5）箱形梁頂部和底部的縱向裂縫，如下圖所示，主要是由于頂板和底板的橫向彎曲力矩過大，無橫向預(yù)應(yīng)力，箱形梁橫向彎曲的空間效應(yīng)所致；板厚薄，橫向鋼筋不足，箱形梁的內(nèi)外。溫差過大會引起溫度應(yīng)力等原因；

 

（6）箱形梁頂部和底部的縱向裂縫。在箱形梁的頂部和底部，大量的預(yù)應(yīng)力縱向鋼絞線穿過，局部應(yīng)力過大，或者認(rèn)為箱形梁的正剪力滯后效應(yīng)還不夠。或者是由于偏心荷載作用下箱形梁的變形和扭轉(zhuǎn)而引起的腹板下端過大的局部應(yīng)力所致；

 

（7）箱形梁腹板中間的垂直裂縫通常在脫模后的2至3天內(nèi)發(fā)生，并且不會向上和向下延伸。預(yù)應(yīng)力后，大多數(shù)將關(guān)閉。這主要是由于混凝土的收縮或箱形梁的內(nèi)外之間的溫度差或腹板的水平加強(qiáng)。不足或與混凝土混合物的質(zhì)量有關(guān)；

 

（8）箱梁腹板上的斜裂縫如下圖所示，通常出現(xiàn)在橋墩支點(diǎn)與倒置點(diǎn)之間的梁段中。這是一個剪切裂縫，其原因更加復(fù)雜，主要是縱向或垂直預(yù)應(yīng)力。損失不足或過多，箱梁內(nèi)部和外部之間的溫差過大，箱梁的彎曲或扭轉(zhuǎn)剛度不足，在偏心載荷下箱梁的變形應(yīng)力過大，腹板厚度小，剪切滯后效應(yīng)的影響，無-預(yù)應(yīng)力鋼筋配置不足，混凝土混合物和添加劑的影響，施工不當(dāng)，縱向預(yù)應(yīng)力梁的線性布置以及跨距布置不合理。

 

（9）箱形梁腹板上的水平裂縫，如下圖所示，主要是由于箱形梁橫向彎曲的空間效應(yīng)和內(nèi)外溫差應(yīng)力所致，從而在箱梁上產(chǎn)生較大的豎向應(yīng)力。腹板的內(nèi)部或外部，箱形梁的橫向剛度不足以及變形應(yīng)力。 ，是由于垂直預(yù)應(yīng)力不足等原因引起的。

 

（10）在懸臂施工過程中，每個節(jié)段的連接處或封閉截面的連接處都有裂縫，這主要是由于施工縫的處理不善造成的，這些連接處變成薄弱的部分，在縱向彎矩，混凝土收縮或收縮的作用下開裂。溫差應(yīng)力大，或由于預(yù)制接頭不致密。橋面開裂后，接縫會滲水，鋼材也會被腐蝕。

 

（11）當(dāng)箱形梁較寬時，橫向隔板或橫梁中可能會出現(xiàn)垂直裂縫，如下圖所示。這主要是因?yàn)槭┘釉跈M隔板或橫梁上的橫向預(yù)應(yīng)力不足或損失太大，或者是由于梁的抗扭性差而引起的箱形。

 

2）鋼筋混凝土和預(yù)應(yīng)力混凝土連續(xù)梁

 

中跨向下過度彎曲通常伴隨著中跨梁底部的橫向裂縫，橋墩頂部的橋面板上的裂縫或傾斜的腹板裂縫。主要原因是彎曲剛度不足，例如梁高低，腹板薄和縱向預(yù)應(yīng)力。由壓力不足或過度損失引起。

 

其他疾病與鋼筋混凝土和預(yù)應(yīng)力混凝土懸臂梁相同。上述疾病的可選增強(qiáng)方法是：

 

（1）對于懸臂梁的牛腿端的偏斜，**的方法是增加預(yù)應(yīng)力。利用可變高度梁的特性，將全長無粘結(jié)預(yù)應(yīng)力電纜布置在路面層中，并錨定到牛腿上。如圖1所示，應(yīng)通過植入大量的錨桿，在橋面的預(yù)應(yīng)力在人行道層和箱梁的頂部平板之間轉(zhuǎn)移，如圖1所示。當(dāng)一個具有多個腔室且箱體高度足夠的單個箱體的橫截面時，全長的外部主體可以布置在中間腹板頂部的兩側(cè)。束固定在腹板上，如下圖2所示，但要注意對錨固孔的影響。

 

（2）為防止托梁出現(xiàn)裂縫，通常在兩側(cè)粘貼塊狀鋼板或鋼帶，如圖3所示。如果盒內(nèi)的托梁可以由人操作，請考慮從外部鉆一個斜孔，然后如圖4所示，通過預(yù)應(yīng)力筋將其張緊并錨固。

 

（3）對于連續(xù)梁中跨和懸臂梁錨固孔，底部撓度太大。**的方法是外部預(yù)應(yīng)力加固。利用可變高度梁的特性，線形或虛線形的主體被布置在盒子中的腹板的兩側(cè)。如圖1和圖2所示，外部預(yù)應(yīng)力梁得到了加固，同等高度的連續(xù)梁應(yīng)通過折線布梁進(jìn)行加固，如圖3所示。

 

（4）預(yù)應(yīng)力錨固齒板附近的裂縫一般在填充接頭后用薄鋼板或碳纖維等復(fù)合材料加固；

 

（5）對于墩頂頂部橋面的橫向裂縫，可以去除路面層的混凝土，并可以在平板頂部表面添加普通的抗拉鋼筋或未粘結(jié)的預(yù)應(yīng)力筋。如圖1所示，將預(yù)應(yīng)力鋼絞線錨固在現(xiàn)澆層中?；蛟诤凶又懈拱鍍蓚?cè)的重心軸橫截面上方設(shè)置外部預(yù)應(yīng)力電纜加強(qiáng)筋，如圖2所示。 。

 

（6）對于連續(xù)梁底部的橫向裂縫或分段節(jié)理處的橫向裂縫，常采用縱向粘結(jié)鋼板或碳纖維等復(fù)合材料加固；或使用外部預(yù)應(yīng)力電纜進(jìn)行加固。對于分段節(jié)中的裂縫，如果是非應(yīng)力引起的，則只需用膠水填充即可；

 

（7）對于箱形梁頂部和底部的縱向裂縫，通常采用橫向粘貼鋼板或其他纖維復(fù)合材料或增加橫向連接的方法來對其進(jìn)行加固。如果頂板的底面縱向開裂，則主要是由于頂板的水平跨度太大而未設(shè)置橫向預(yù)應(yīng)力所致。您可以考慮在頂部平板上方的路面層上添加橫向預(yù)應(yīng)力筋，如下圖所示，然后連接路面層和屋頂板。在它們之間植入了大量的錨桿，以傳遞橋面板的預(yù)應(yīng)力。

 

（8）對于箱形梁頂部和底部的縱向裂縫和腹板的豎向裂縫，可通過密封，灌漿或粘貼纖維復(fù)合材料進(jìn)行加固；

 

（9）對于腹板上的傾斜裂縫，可以將鋼板或纖維復(fù)合材料粘貼到腹板上，類似于下圖?；蜻m當(dāng)增加腹板的厚度，或縱向或垂直施加預(yù)應(yīng)力以加強(qiáng)腹板；

 

（10）對于腹板上的水平裂縫，可在腹板上粘貼垂直鋼板或纖維復(fù)合材料，或增加水平連接，例如增加橫向隔板或施加垂直預(yù)應(yīng)力加強(qiáng)；

 

（11）對于箱形橫梁中橫隔板或橫梁的豎向裂縫，可以在橫隔板的兩側(cè)施加橫向外部預(yù)應(yīng)力，并通過箱壁錨固，如下圖所示?；蛱砑訖M向擋板以增強(qiáng)抵抗橫向彎曲和扭曲的能力。

 

6.預(yù)應(yīng)力混凝土T形剛性框架橋

 

T形剛性框架橋包括具有懸掛梁或鉸鏈的T形剛性框架以及連續(xù)的剛性框架。其主要特征是梁和墩固結(jié)在一起，但前者的上部結(jié)構(gòu)類似于懸臂梁橋，后者的上部結(jié)構(gòu)類似于連續(xù)梁橋，不同之處在于墩必須承受較大的荷載?？v向彎矩。當(dāng)然，仍然存在力的差異，并且跨度也增加了很多。連續(xù)的剛性框架（如雙薄壁墩）已達(dá)到約300米。預(yù)應(yīng)力T形剛性框架橋，無論是帶有吊梁的T形剛性框架，還是連續(xù)的剛性框架，通常使用高度可變的箱形梁，預(yù)應(yīng)力懸臂梁和連續(xù)梁橋。他們也可能有問題。 ，可選的加固方法也相同。

 

區(qū)別在于帶有懸掛梁的T形剛性框架具有較長的懸臂。如果施工或設(shè)計(jì)質(zhì)量不佳，尤其是施工質(zhì)量較差，將導(dǎo)致很大的預(yù)應(yīng)力損失和懸臂的抗彎剛度不足。牛腿很容易出現(xiàn)。過度偏斜和其他疾病。當(dāng)使用外部預(yù)應(yīng)力電纜進(jìn)行加固時，可以將未粘結(jié)的鋼絞線布置在箱形梁頂面上的路面層中，并固定在兩端的牛腿上。在新舊混凝土之間植入了大量的錨桿，以轉(zhuǎn)移橋面。壓力，如圖所示：

 

當(dāng)箱形梁是具有多個腔室的單個箱形梁時，可以在中間腹板的兩側(cè)布置全長的外部預(yù)應(yīng)力電纜以進(jìn)行加固，然后在墩頂上鉆穿兩個橫向隔板，然后將其錨固到腹板兩側(cè)的錨固座上方，如圖所示：

 

7.鋼筋混凝土平板拱，肋拱和箱形拱橋

 

所謂的平板拱，肋拱和箱形拱主要是根據(jù)主拱環(huán)的截面形式來劃分的，這里主要是指甲板拱橋，其跨度可以小也可以大，小則大于10米，大的可以達(dá)到箱形肋拱。它長420米，具有各種結(jié)構(gòu)和樣式，但許多疾病大致相同。

 

常見的問題是：

 

（1）主弓環(huán)的下邊緣和側(cè)面的橫向裂紋以及弓形腳的上邊緣和側(cè)面的橫向裂紋，如下圖所示。這主要是由于這兩個部分的抗彎強(qiáng)度不足。原因有很多，例如尺寸小，加固不充分，拱軸不合理，橋墩沉降不均勻或向路堤滑動或旋轉(zhuǎn)，車輛超重的影響，完整性差和施工質(zhì)量差所致。如果裂紋的上下邊緣的位置與上述相反，則通常是墩沿橋孔的方向滑動或旋轉(zhuǎn)。

 

（2）在主弓形環(huán)（平板弓形環(huán)）或腹弓形環(huán)中出現(xiàn)縱向裂紋，如下圖所示。它通常伴隨著墩，平臺帽或帽梁的縱向裂縫。如果裂縫大致位于中間，則可能是橋墩和平臺基礎(chǔ)的上，下游沉降不均勻造成的。如果僅僅是側(cè)拱盒的接縫處的裂縫，那么接縫通常是不連接的。良好，完整性差，這是由于偏心載荷下側(cè)拱盒的更大力和變形所致；

 

（3）混凝土的碎裂和脫落發(fā)生在主拱環(huán)的局部，通常發(fā)生在具有高壓縮應(yīng)力的地方，例如拐角，等截面拱形拱的拱腳附近等?？箟簭?qiáng)度材料不足，導(dǎo)致分裂或壓碎，或內(nèi)部鋼筋生銹和膨脹；

 

（4）主拱圈拱趾處的徑向裂紋主要是由于材料的抗剪強(qiáng)度不足引起的；

 

（5）雙曲拱橋的拱形波峰上出現(xiàn)縱向裂紋，或在拱肋和拱波的連接處出現(xiàn)圓形裂紋，這主要是由于肋骨之間的橫向連接薄弱，完整性差，截面組合不合理以及不均勻造成的。墩臺的橫向沉降等等

 

（6）拱的彎曲的框架，梁和柱破裂，特別是短柱的短端被破裂和壓碎，墩，基臺或?qū)嵭母拱褰孛娴母构h(huán)的拱腳和拱頂穿過側(cè)壁到橋面板的裂縫，以及側(cè)壁。側(cè)壁與拱形環(huán)之間的連接以及側(cè)壁中的其他裂縫如下圖所示。主要原因是短柱和腹弓環(huán)上沒有鉸鏈，相應(yīng)位置的側(cè)壁和橋面板上沒有變形縫，主弓環(huán)變形或墩臺位移and abutment pull and crack;

 

(7) Longitudinal cracks on the bridge deck are often accompanied by vertical cracks in the transverse connection, especially the severe cracks in the mid-span transverse connection, indicating that the horizontal integrity of the bridge is poor and the lateral load distribution is not good;

 

(8) When the main arch ring is assembled by segmented prefabrication, cracks may also appear at the joints;

 

(9) When steel tube concrete is used for arch ribs, there may be shrinkage folds on the surface of the steel tube, or there may be cavities and segregation in the tube. The thickness of the steel tube is often insufficient, the hoop effect is partially lost, and the steel tube lattice structure is unreasonably arranged, and the tube wall stiffening ribs Insufficiency and so on.

 

The optional reinforcement methods are:

 

(1) Because the main arch ring is an eccentric compression member, if the dome or arch foot transversely cracks or is partially crushed, it is best to use the method of increasing the section from the soffit surface or the back of the arch to reinforce it, such as chiseling the original concrete surface, Concrete or sprayed concrete is poured after planting and laying of reinforcements, especially for cracks at the arch foot, it is necessary to implant steel bars in the pier cap, and then increase the cross section of the arch foot, as shown in the following figure:

 

Secondly, it can be pasted with steel plate or fiber composite material, but it should be noted that the soffit pasting material is too long, and the problem of radial tearing after bending. In the medium and small span arch bridges, external prestressed reinforcement can also be considered, but the impact on other parts should be considered. It is also possible to reduce the self-weight of the building on the arch, such as replacing the filler, or digging out the filler and changing the side wall to a full open-web beam web hole to reduce the burden on the main arch ring, as shown in the figure below, but the main arch axis shape is somewhat different Change, pay attention to checking calculations. If the disease is caused by the displacement of the pier and abutment is still developing, the pier and abutment should be strengthened first to eliminate the cause of the disease.

 

(2) For the longitudinal cracks in the main arch ring or abdominal arch ring, the longitudinal cracks of the pier and platform cap and the vertical cracks of the pier and platform body, if the cracks continue to develop, the foundation and other substructures must be reinforced first. The arch ring cracks should be Depending on the width of the seam, grouting is used to block the cross section, and steel plate or fiber composite material is pasted horizontally. Or add multiple steel hoops, and try to make them into block hoops, or use steel tie rods, apply transverse prestress and other methods to reinforce, as shown in the figure below.

 

(3) For double-curved arch bridges, the longitudinal cracks at the top of the arch or the joint between the arch rib and the arch wave should be strengthened or added to the transverse connection, the arch rib or arch slab section or the number of arch ribs should be increased, and the weight of the building on the arch should be reduced, such as Replace the filler of the belly arch and solid web section, change the horizontal wall type web hole pier to the column type web hole pier, and change the arch type web hole to the beam-slab web hole, etc., as shown in the figure below. If the crack is caused by the uneven lateral settlement of the pier and platform, the foundation should be reinforced first.

 

(4) For the cracks at the upper and lower ends of the low column on the arch, it is best to change the neck hinge to allow it to rotate properly, as shown in the figure below. For the arch toe or vault crack near the pier and the solid web, if the crack is wide enough to break or there is a significant difference in height on both sides, it should be considered to be dismantled and rebuilt into a three-hinged or two-reamed web hole, otherwise Don't care about it for the time being, but the deformation joints of the side walls and bridge decks at the corresponding positions should be set up, otherwise there will be water leakage;

 

(5) For the longitudinal cracks of the bridge deck and the vertical cracks of the transverse connection, the transverse integrity of the structure should be strengthened, such as increasing or adding beams, combined with the refurbishment of the bridge deck, appropriately thickening the thickness of the concrete paving layer, increasing the markings, and strengthening the bridge deck For arch bridges with transverse reinforcement and fillers, the fillers will be excavated and replaced with cast-in-situ concrete for reinforcement;

 

(6) The cracks that are not good at the main arch ring joints can be strengthened by means of grouting, planting bar connection or repair welding connection;

 

(7) For the wrinkles on the surface of the concrete-filled steel tube, it is best to use a layer of reinforced concrete to increase the section, or to densify the slab between the lattice structures, or to increase the tube wall stiffener. For the voids in the pipes, drill holes should be filled with epoxy glue or cement slurry;

 

(8) For arch bridges with excessive deflection of the vault and lateral cracks on the bottom surface, external prestressed cables can be used to set anchors on the arch back below the elastic center of the arch ring to make the vault produce negative bending moments and inverted arches. As shown in the figure below, but the arch foot also produces a negative bending moment, the cross section of the arch foot section should be increased to deal with it. The specific position of the external cable and the tensile force should be tested repeatedly according to the changes in the internal force of the arch ring (mainly bending moment) Confirm after calculation;

 

(9) For rib arches, double-curved arches, etc., due to excessive deformation and cracking of the main arch ring due to the horizontal displacement and subsidence of the arch foot, and the arch axis and the pressure line are seriously deviated, the arch foot can be used when it is difficult to use other reinforcement measures. The method of pushing and restoring to adjust the arch axis improves the force of the arch ring, but this method has complex technology, high risk, and low cost, so it is rarely used.

 

(10) Among the above various reinforcement methods, if the building on the arch is modified or the section of the main arch ring is enlarged, attention should be paid to the balanced symmetry between the single hole and the multi-hole during the unloading and loading process to ensure the arch ring and pier The stability of the station.

 

8. Middle and through arch bridges

 

Middle and through arch bridges are ribbed arches, and the arch ribs are often reinforced concrete rectangular, I-shaped or box-shaped (the latter are more). Steel pipe or concrete-filled steel tube, or their combination is also commonly used. In terms of the force system, there are ordinary arches (that is, thrust arches) and tied arches (ie, no thrust arches). The main components of deck arch bridges are different from suspenders and suspender beams (some also have longitudinal beams). ,Tie. The boom has rigid boom and flexible boom, the latter is more used.

 

Tie rods are also divided into rigidity and flexibility. Mid-bearing (flying swallow) tie-bar arches usually use flexible high-strength steel wires as tie rods. Down-bearing tie-bar arches include flexible tie rod rigid arches, rigid tie rod rigid arches and rigid tie rod arches. The first two are more common in the difference of rod flexible arch. In addition to the diseases similar to deck arch bridges, there may also be the following diseases:

 

(1) The anchor head of the boom is loose, rusted, or the steel wire is corroded or sheared. The anchor head under the bridge deck and the anchor heads at both ends of the short boom are easy to appear;

 

(2) The suspender beam is used as a simply supported beam or a double cantilever simply supported beam. Reinforced concrete or prestressed concrete is commonly used. There may be vertical bending cracks at the bottom of the mid-span beam, and oblique cracks appear on the webs on both sides of the lifting point. In addition, longitudinal cracks may appear on the top surface of the beam at the lifting point, as shown in the figure below. The bridge deck with longitudinal beams between the suspenders and beams may crack near the nodes of the longitudinal and transverse beams and the nodes of the arch ribs and rigid tie rods;

 

(3) Looseness or corrosion of the anchor head of the tie rod, or corrosion or broken wire of the steel wire. Rigid tie rods are similar to elastically supported continuous beams because they have to withstand axial force and local bending moments, and they also have common problems with bending members.

 

The optional reinforcement methods are:

 

(1) If the anchor head of the suspender or tie rod is loose or individual slips, when conditions permit, the anchor head should be tightened to adjust the internal force or elevation of the loose tie rod or suspender. Most of the flexible suspenders use piers. The head anchor can be tightened by adding a steel spacer. If the tie rod uses a clip anchor, the heavy anchor should be supplemented. For booms or tie rods that are severely corroded, broken wires, or unconditionally tensioned and tightened, the cables should be replaced through reserved holes. If there are no reserved holes, other measures should be taken to temporarily unload the replaced booms or tie rods. Change the rope.

 

(2) The various cracks that appear in the boom beams, longitudinal beams or rigid tie rods can be reinforced like the reinforced concrete or prestressed concrete simple beams, continuous beams and cantilever beams in the previous sections of this chapter, such as external prestressing method , Pasting steel plate or fiber composite material method, etc.

 

(3) For the cracks of the longitudinal and transverse beam nodes and the arch foot nodes, the simple method is to paste the block steel plate or fiber composite material, as shown in the figure below.

 

9. Reinforced concrete rigid frame arch bridge

 

Under normal circumstances, the most common diseases of long-span rigid-framed arches are the cracks at the chords and rigid joints. As long as the rigid-framed arch bridges with diseases, most of them have such cracks, but for reinforced concrete members, as long as the crack width does not exceed The allowable value is also a normal use. Although there are many owners who are opposed to building a new rigid-frame arch bridge, through analysis of the causes of its diseases, the problems of its bearing capacity and performance should be treated correctly.

 

Alternative reinforcement methods for rigid frame arch bridges

 

The rigid frame arch bridge is mainly composed of outer chords, inner chords, solid webs, arch legs (main arch legs), diagonal braces (secondary arch legs), transverse connections, bridge decks and bridge deck pavement, as shown in the following figure. The following will discuss each component's disease phenomenon, its causes, and the reinforcement methods currently used one by one.

 

(1) Bridge decks: The decks of rigid frame arch bridges are commonly used in two types: less ribbed haunches or slightly curved plates. A few of them use rectangular solid or hollow slabs. The first two are optimized on the basis of rectangular slabs. The amount of steel and concrete is small and the weight is light. Especially the rib and haunches are hollowed out at the cost of complex construction. The less-reinforced rib axillary plate and micro-bend plate not only have less reinforcement, but also have a small thickness. They will definitely be no problem under short-term design loads. Under the condition of long-term overload, the actual bridge disease shows that the direction of the bottom of the ribbed plate is not correct. Regular cracks, severely exposed ribs and leaking water. If it is a micro-bending plate, the bottom surface of the stiffening rib of the micro-bending plate has a number of vertical cracks extending upward, some of which can extend to the top of the plate, causing the top of the plate to crack longitudinally.

 

The optional reinforcement methods for the above diseases are:

 

For the micro-bent slab with cracked stiffeners, a U-shaped unidirectional carbon fiber sheet with vertical cracks is used. It is more convenient to stick to the bottom of the rib than to stick the steel plate. The longitudinal cracks on the top of the micro-bent slab are filled and sealed depending on the width.

 

In combination with the reconstruction of the bridge deck, the thickness and strength of the cast-in-situ layer are increased, and the reinforcement in the cast-in-situ layer is strengthened to improve the stress condition of the bridge deck.

 

(2) Inner and outer chords and solid webs: chords and solid webs often use rectangular, I-shaped, box-shaped sections, the outer chords are bending members, and the inner chords and solid webs are bent (eccentrically). Compressed) components. Generally, the cracks produced by the arches often appear on the outer chord, followed by the inner chord and the solid web. Vertical cracks in the outer chord and oblique cracks on both sides of the large and small nodes are common, but the degree is different. Of course, if the crack width is within the allowable range, it also meets the design requirements or is not at the point where it must be reinforced. But for rigid frame arch bridges with serious diseases, there are many and wide cracks in the tension zone at the bottom of the mid-span of the outer chord and the solid web, and the inner chord has more cracks, some have penetrated in the horizontal direction, and cracked to the top in the vertical direction, especially the nodes. The diagonal cracks on both sides are wider, and some have penetrated.

 

The optional reinforcement methods are:

 

① For the reinforcement of the bending member of the outer chord of the rigid frame arch, if the chord is not a super-reinforced beam, the U-shaped fiber sheet or the steel plate can be pasted in the tension zone of the bottom surface or the section height and reinforcement can be increased. For super-reinforced beams, it is best to increase the section height and reinforcement, or to paste U-shaped fiber sheets or steel plates in the tension zone on the bottom surface, and increase the thickness of the cast-in-situ layer on the bridge deck.

 

② The inner chord is an eccentric compression member and can be reinforced by the same method as the outer chord.

 

③ The oblique cracks on both sides of the large and small nodes can be reinforced with steel plates or fiber sheets on the crack surfaces to withstand the main tensile stress. Increasing the height of the chord section can also reduce the main tensile stress.

 

④ U-shaped carbon fiber sheet can be pasted on the slightly arc-shaped bottom surface of the solid web in the mid-span to withstand the bending tensile stress and radial tearing force, or the method of increasing the section height and reinforcement can be adopted.

 

⑤ For the cracks in the chord and other parts of the solid abdomen, the cracks can be filled and sealed.

 

(3) Lateral connection: The lateral connection of a rigid frame arch bridge. There is one line between the chords and solid webs about 3 meters, and the nodes are strengthened. On the arch legs and diagonal braces, there are one or more channels according to the size of the span. The situation is relatively intact. However, rigid frame arches with integral damage are quite different. Most of the diaphragms of the solid web and chord sections have vertical cracks that penetrate up and down. The hollowed diaphragms are more serious than the solid diaphragms, especially There are many cracks in the transverse diaphragm of the solid web, and some of them are almost broken into only steel bars. The transverse connections on the arch legs and diagonal braces are generally intact. However, rigid frame arch bridges with gravity piers and abutments have few problems in the lateral connection, indicating that flexible piers should not be used for light arch bridges with low rigidity.

 

The optional reinforcement methods are:

 

①  中斷交通施工時，橫隔板可采用混凝土加固，即在原橫隔板的基礎(chǔ)上，通過植筋加厚加高橫隔板。

 

不能中斷交通施工時，橫隔板只有采用施工快速、簡便的鋼結(jié)構(gòu)加固，如下圖。在原混凝土橫隔板的四個角，采用粘貼和螺栓固定四根角鋼，再用兩片鋼桁架夾住原混凝土橫隔板，施工時作好所有橫隔板加固準(zhǔn)備工作，并點(diǎn)焊固定位置后，臨時中斷交通，將各鋼構(gòu)件焊接完成后，再恢復(fù)交通。

 

（4）主拱腿及斜撐：主拱腿和斜撐為小偏心受壓構(gòu)件，在恒載及車輛作用下，一般不產(chǎn)生拉應(yīng)力，其內(nèi)主要按構(gòu)造配筋。但有的斜撐底部附近有較多由頂面而下的環(huán)形裂縫，有的開裂至截面高度一半左右。采用有限元計(jì)算分析可知，使用荷載下，構(gòu)件不產(chǎn)生拉應(yīng)力，但在墩、臺不均勻沉降時，斜撐底部的負(fù)彎矩就非常敏感，較小的不均勻下沉，在此處將產(chǎn)生較大的拉應(yīng)力。實(shí)橋觀察也說明斜撐底部有裂縫出現(xiàn)，極可能是墩、臺有不均勻沉降。此外，溫度下降時也容易產(chǎn)生斜撐底部的負(fù)彎矩。

 

可選的加固方法有：

 

對于斜撐根部的裂縫，可采用環(huán)形包裹粘貼纖維布，也可采用頂面粘貼鋼板或碳纖維條。也可考慮增大截面加固。

 

（5）橋面鋪裝層：橋面現(xiàn)澆層對采用預(yù)制拼裝施工的橋面板來說，尤為重要，以其它類型橋梁相比，剛架拱橋的混凝土鋪裝層是組合斷面的一部分，直接參與受力，更重要的是拱片大、小節(jié)點(diǎn)負(fù)彎矩區(qū)的受拉鋼筋都布置于現(xiàn)澆鋪裝層中。如果該位置所承受的拉應(yīng)力過大，將會導(dǎo)致橋面橫向貫通開裂，若橋梁整體性較差，還會引起橋面的拱片位置處縱向貫通開裂，這兩類裂縫均屬結(jié)構(gòu)受力性裂縫，必須盡快進(jìn)行加固。其他坑槽、網(wǎng)裂之類均屬鋪裝層本身局部病害。

 

可選的加固方法有：

 

①  鑿除橋面鋪裝，重新澆筑鋪裝層混凝土，按新規(guī)范要求提高混凝土標(biāo)號，加強(qiáng)橋面鋼筋網(wǎng)的配筋。并特別注意鋼筋網(wǎng)必須架起來。新澆鋪裝層的厚度，根據(jù)需要決定是否加厚。

 

②  進(jìn)一步加強(qiáng)負(fù)彎矩區(qū)的縱向鋼筋配置。

 

中等跨徑以下的桁架拱一般采用鋼筋混凝土，中等跨徑以上的桁架拱或桁式組合拱橋一般采用預(yù)應(yīng)力混凝土，它們均為組合體系拱，常采用預(yù)制拼裝施工。上弦桿及跨中實(shí)腹段除承受軸力外，還承受較大彎矩，下弦桿為偏心受壓構(gòu)件，腹桿有斜桿和豎桿，一般采用斜拉桿式腹桿，即斜桿為偏心受拉，豎桿為偏心受壓構(gòu)件。因此跨徑大時，需在上弦桿、斜桿及實(shí)腹段中施加預(yù)應(yīng)力。

 

常見問題有：

 

（1） 上弦桿及實(shí)腹段跨中附近底面及側(cè)面橫向開裂，或下?lián)线^大，表明桿件的**預(yù)加應(yīng)力不足，或截面高度偏小，普通鋼筋配置不足；

 

（2）斜桿開裂，說明拉力過大，預(yù)加應(yīng)力不足。

 

（3）下弦桿及豎桿沿桿長方向出現(xiàn)多條裂縫或局部壓碎，主要是桿件截面尺碼偏小。如果出現(xiàn)垂直于桿長方向的裂縫，說明桿件的長細(xì)比過大或桁架片變形較大引起較大偏心彎矩所致；

 

（4）各桿件節(jié)點(diǎn)附近開裂，由于各桿件軸線一般不會相交于一點(diǎn)，且受其他附加應(yīng)力影響使節(jié)點(diǎn)局部應(yīng)力過大引起開裂，如圖：

 

（5）橫向聯(lián)系（如橫隔板、橫系梁、剪刀撐等）中部出現(xiàn)豎向裂縫或其它裂縫，主要是桁片橫向整體性差，橫向聯(lián)系剛度不足、尺碼偏?。?/div>