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【五層】5100平米左右框架結(jié)構(gòu)局部六層大學(xué)教學(xué)樓(開題報告、任務(wù)書、計算書、設(shè)計圖),【溫馨提示】壓縮包內(nèi)含CAD圖有預(yù)覽點開可看。打包內(nèi)容里dwg后綴的文件為CAD圖,可編輯,無水印,高清圖,壓縮包內(nèi)文檔可直接點開預(yù)覽,需要原稿請自助充值下載,所見才能所得,請細(xì)心查看有疑問可以咨詢QQ:11970985或197216396
單位代碼
學(xué) 號
分 類 號
密 級
畢業(yè)設(shè)計
文獻(xiàn)綜述
院(系)名稱
工學(xué)院建筑系
專業(yè)名稱
土木工程
學(xué)生姓名
指導(dǎo)教師
2013年3月3日
xx科技學(xué)院畢業(yè)設(shè)計(文獻(xiàn)綜述) 第 4 頁
文獻(xiàn)綜述
本項目為鄭州大學(xué)電氣工程學(xué)院教學(xué)樓方案二。采用鋼筋混凝土框架結(jié)構(gòu)體系,建筑結(jié)構(gòu)的類別為二類,使用年限為50年,總建筑面積為5100平方米。
框架結(jié)構(gòu)體系是由鋼筋混凝土梁、柱節(jié)點及基礎(chǔ)為主框架,加上樓板、填充墻、屋蓋組成的結(jié)構(gòu)形式??蚣苄纬煽伸`活布置的建筑空間,使用較方便。但是隨著建筑高度的增加,水平作用使得框架底部梁柱構(gòu)件的彎矩和剪力顯著增加,從而導(dǎo)致梁柱截面尺寸和配筋量增加,到一定程度,將給建筑平面布置和空間處理帶來困難,影響建筑空間的正常使用,在材料用量和造價方面也趨于不合理,因此在使用上層數(shù)受到限制。正是因為如此原因,框架結(jié)構(gòu)適用于辦公樓、教學(xué)樓、商場、住宅等建筑。本設(shè)計的是多層建筑,所以選用框架結(jié)構(gòu)體系較為合理。
混凝土結(jié)構(gòu)設(shè)計中指出在框架結(jié)構(gòu)中,框架是由梁、柱構(gòu)件通過節(jié)點連接形成的骨架結(jié)構(gòu)。框架結(jié)構(gòu)的特點是由梁、柱承受豎向和水平荷載,墻僅起維護(hù)作用,其整體性和抗震性均好于混合結(jié)構(gòu),且平面布置靈活,可提供較大的使用空間,也可構(gòu)成豐富多變的立面造型。國外多用鋼為框架材料,而國內(nèi)主要為鋼筋混凝土框架,因為鋼筋混凝土結(jié)構(gòu)有以下的一些優(yōu)點:
第一:合理的利用了鋼筋和混凝土兩種材料的受力性能特點,可以形成強度較高、剛度較大的結(jié)構(gòu)構(gòu)件。這些構(gòu)件在有些情況下可以用來代替鋼構(gòu)件,因而能夠節(jié)約鋼材,降低造價。
第二:耐久性和耐火性較好,維護(hù)費用低。
第三:可模性好,結(jié)構(gòu)造型靈活,可以根據(jù)使用需要澆注成各種形狀的結(jié)構(gòu)。
第四:現(xiàn)澆鋼筋混凝土結(jié)構(gòu)的整體性好,可通過合理的設(shè)計,使之具有良好的延性,成為“延性框架”,在地震作用下,這種延性框架具有良好的抗震性能;同時它的防震性和防輻射性也好,亦適于用作防護(hù)結(jié)構(gòu)。
第五:混凝土中占比例較大的砂、石材料便于就地取材。
因為鋼筋混凝土具有這些特點,所以在建筑結(jié)構(gòu)、地下結(jié)構(gòu)、橋梁、隧道、鐵路等土木工程中得到廣泛應(yīng)用?;炷烈猿蔀楫?dāng)今世界上用量最大的建筑材料。但是,鋼筋混凝土也存在一些缺點,如自重過大,抗裂性能較差,隔熱隔聲性能不好,澆注混凝土?xí)r需要模板和支撐,戶外施工受到季節(jié)條件限制,補強修復(fù)比較困難。這些缺點在一定程度上限制了鋼筋混凝土的應(yīng)用范圍。隨著科學(xué)技術(shù)的發(fā)展,鋼筋混凝土的這些缺點正在逐步的得到克服和改善。
鋼筋混凝土多層框架結(jié)構(gòu)作為一種常用的結(jié)構(gòu)形式, 具有如下優(yōu)點:
(1) 建筑平面布置靈活,分割方便。
(2) 整體性、抗震性能好。
(3) 傳力路線明確。
(4) 墻體采用輕質(zhì)填充材料時,結(jié)構(gòu)自重小。
(5) 承重構(gòu)件與圍護(hù)構(gòu)件有明確分工。
目前混凝土框架結(jié)構(gòu)已被廣泛地應(yīng)用于各類多層的工業(yè)與民用建筑中。但是, 在框架結(jié)構(gòu)仍有一些缺點:如側(cè)向剛度較低、對于較高建筑需要截面尺寸較大的梁、柱才能滿足受力和變形的要求。近年來, 隨著計算機(jī)技術(shù)的不斷發(fā)展, 框架結(jié)構(gòu)的計算精度日益提高, 設(shè)計人員的工作強度逐漸降低。在框架結(jié)構(gòu)的設(shè)計中, 仍然存在著一些概念性和實際性的問題需要設(shè)計人員予以重視, 以確保設(shè)計質(zhì)量的提高。所以,本次設(shè)計仍以手工計算為主,電算校核的方法,以提高基本概念的應(yīng)用能力,這對于以后的實際工程有現(xiàn)實意義。
畢業(yè)設(shè)計是對四年專業(yè)知識的一次綜合應(yīng)用、擴(kuò)充和深化,也是對我們理論運用于實際設(shè)計的一次鍛煉。通過畢業(yè)設(shè)計,不僅可以溫習(xí)以前在課堂上學(xué)習(xí)的專業(yè)知識,同時也將學(xué)習(xí)和體會到建筑結(jié)構(gòu)設(shè)計的基本技能和思想。
在設(shè)計之前必須先充分理解建筑設(shè)計的內(nèi)容,并收集相關(guān)的資料如建筑圖集、結(jié)構(gòu)計算手冊及相關(guān)國標(biāo)規(guī)范等,做好準(zhǔn)備工作。
讀懂建筑設(shè)計中的建筑圖,如底層及標(biāo)準(zhǔn)層平面圖、頂層平面圖、主要立面圖、剖面圖,根據(jù)實際情況所選擇的建筑方案,滿足相關(guān)規(guī)范的要求考慮到實用、美觀、符合教學(xué)目的等等各方面要求。
結(jié)構(gòu)設(shè)計中根據(jù)承重框架布置方向的不同,框架的結(jié)構(gòu)布置方案有橫向框架承重、豎向框架承重、縱橫向框架承重。多層框架是超靜定結(jié)構(gòu),在計算內(nèi)力之前,必須先確定桿件的截面形狀、尺寸和慣性矩。為此,查閱了許多文獻(xiàn)資料,包括標(biāo)準(zhǔn)、規(guī)范、手冊、圖集,以及國內(nèi)外相關(guān)書籍、論文,明確了設(shè)計路線。
結(jié)構(gòu)設(shè)計包括結(jié)構(gòu)計算和繪制結(jié)構(gòu)圖兩方面。結(jié)構(gòu)計算又需完成基礎(chǔ)設(shè)計、縱橫向平面框架結(jié)構(gòu)設(shè)計、樓蓋設(shè)計、樓梯、陽臺、雨蓬等結(jié)構(gòu)設(shè)計,其中縱橫向平面框架結(jié)構(gòu)設(shè)計是最重要的,也是最難的??v橫向平面框架結(jié)構(gòu)設(shè)計又涉及到框架梁、柱、節(jié)點設(shè)計,要滿足“強柱弱梁,強剪弱彎,強節(jié)點弱構(gòu)件”的設(shè)計原則。在本次畢業(yè)設(shè)計中采用手算和電算兩種方法,手算采用力矩分配法和D值法(計算豎向荷載采用力矩分配法法,計算水平荷載采用D值法)來完成,電算采用PKPM結(jié)構(gòu)計算軟件。最后,將手算與電算的結(jié)果比較,相互檢驗,以提高結(jié)構(gòu)計算的精確度。
框架結(jié)構(gòu)房屋的布置應(yīng)對稱、均勻,減小抗側(cè)剛度中與水平荷載合力作用線的距離,減小結(jié)構(gòu)重心和剛度中心之間的距離,以減小結(jié)構(gòu)發(fā)生的扭轉(zhuǎn)。由于框架構(gòu)件截面較小,抗側(cè)剛度較小,在強震作用下結(jié)構(gòu)整體位移和層間位移都較大,容易產(chǎn)生震害。此外,非結(jié)構(gòu)性破壞如填充墻、建筑裝修和設(shè)備管道等破壞較嚴(yán)重。因而其主要適用于非抗震區(qū)和層數(shù)較少的建筑,抗震設(shè)計的框架結(jié)構(gòu)除需加強梁、柱和節(jié)點的抗震措施外,還需注意填充墻的材料以及填充墻與框架的連接方式等,以避免框架變形過大時填充墻的破壞。
畢業(yè)設(shè)計是集理論與實踐為一體,在設(shè)計之前作為設(shè)計者必須深入實際,調(diào)查研究,是大學(xué)四年里最重要的實踐環(huán)節(jié)。通過一個完整的畢業(yè)設(shè)計,在資料查閱,文獻(xiàn)綜述與閱讀,設(shè)計思路與方案的確定等方面有了較大的提高,對于相關(guān)設(shè)計規(guī)范、手冊、標(biāo)準(zhǔn)圖以及工程實踐中常用的方法有較系統(tǒng)地認(rèn)識了解。
參考文獻(xiàn)
1.《建筑結(jié)構(gòu)制圖標(biāo)準(zhǔn)》GB/T50105-2001
2.《建筑結(jié)構(gòu)荷載規(guī)范》GB5009-2006
3.《混凝土結(jié)構(gòu)設(shè)計規(guī)范》GB50010-2010
4.《建筑地基基礎(chǔ)設(shè)計規(guī)范》GB5007-2002
5.《砌體結(jié)構(gòu)設(shè)計規(guī)范》GB5003-2001
6.《建筑抗震設(shè)計規(guī)范》GB5011-2010
7.《結(jié)構(gòu)力學(xué)》,高等教育出版社,1998
8.《建筑結(jié)構(gòu)構(gòu)造資料》(合訂本),中國建筑工業(yè)出版社,1988年。
9.《混凝土結(jié)構(gòu)構(gòu)造手冊》,中國建筑工業(yè)出版社,2002年。
10.《地基基礎(chǔ)設(shè)計手冊》,上??萍汲霭嫔?,1998年。
11.《混凝土結(jié)構(gòu)設(shè)計手冊》,中國建筑工業(yè)出版社,2002年。
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單位代碼
學(xué) 號
分 類 號
密 級
畢業(yè)設(shè)計
文獻(xiàn)翻譯
院(系)名稱
工學(xué)院建筑系
專業(yè)名稱
土木工程
學(xué)生姓名
指導(dǎo)教師
2013年3月3日
畢業(yè)設(shè)計
外文資料翻譯
原文題目:Reinforcement of concrete beam–column connections with hybrid FRP sheet
譯文題目:具有混合纖維增強塑料片的混凝土梁–柱聯(lián)接部位的加固
院系名稱: 工學(xué)院建筑系 專業(yè)班級: 土木工程2班
學(xué)生姓名: 學(xué) 號:
指導(dǎo)教師:
附 件: 1.外文資料翻譯譯文;2.外文原文。
附件1:外文資料翻譯譯文
摘要
本篇文章描述了對加固后標(biāo)準(zhǔn)尺寸混凝土結(jié)構(gòu)試件進(jìn)行試驗的結(jié)果,該試件代表平面框架結(jié)構(gòu)中的梁–柱聯(lián)接部位。設(shè)計試驗的目的是為了研究在靜載條件下纖維增強塑料被應(yīng)用到梁–柱聯(lián)接部位外表面附近時對所測試件的影響。特別令人感興趣的是在靜載條件下應(yīng)用纖維增強塑料對增強梁–柱聯(lián)接部位所起的作用。作為研究的關(guān)鍵,為了從外部對混凝土的連接部分進(jìn)行加固,設(shè)計了帶有E玻璃無捻粗紗布和碳布的混合纖維增強塑料復(fù)合物,并且該復(fù)合物結(jié)合了短貼原絲氈和帶有乙烯基酯樹脂的玻璃纖維帶。結(jié)果顯示,對于應(yīng)用纖維增強塑料改進(jìn)過的混凝土結(jié)構(gòu)的關(guān)鍵部分能夠?qū)炷两Y(jié)構(gòu)的強度和硬度起到增強的作用,同時也能夠起到在不同類型荷載條件下增強它們的效果。同時,本篇文章也討論了為改進(jìn)和增強混凝土結(jié)構(gòu)的強度和硬度而如何選擇纖維增強塑料和結(jié)構(gòu)類型。
關(guān)鍵詞:混凝土結(jié)構(gòu);加固;修復(fù);混合纖維增強塑料;繞接技術(shù)
1.引言
為了對混凝土結(jié)構(gòu)進(jìn)行改進(jìn),一個被廣泛采用的技術(shù)是使用鋼外套管放置于現(xiàn)有混凝土柱的周圍,這種使混凝土產(chǎn)生側(cè)向限制的技術(shù)已經(jīng)被廣泛的研究[1,2];而且已經(jīng)顯示重縮載重承載量和混凝土柱的延性增加。然而,這一個技術(shù)的缺點是它在實際的應(yīng)用受到來自腐蝕和固有的缺點。
另一方面,纖維增強塑料日益被采用來加固混凝土,磚石和木結(jié)構(gòu)。通過關(guān)鍵部分的外表面采用纖維增強塑料來加固結(jié)構(gòu),能夠很明顯提高結(jié)構(gòu)的載重量和結(jié)構(gòu)的效用。最近幾年,纖維增強塑料的材料類型更加的廣泛,有玻璃纖維、碳纖維等。它們提供給設(shè)計者一個使用的、有效的構(gòu)造材料,這些材料具有范圍很廣的模數(shù)和強度的特性。和傳統(tǒng)的加固技術(shù)相比,纖維增強塑料復(fù)合物具有特別高的強度和硬度,以及設(shè)計上的靈活性、在不利的環(huán)境中的可替代性、較強的韌性等優(yōu)點。通過優(yōu)化材料組成和結(jié)構(gòu),使得纖維增強塑料達(dá)到最好的加固效果是可能的,同時也是必要的。為了在實際的加固過程中充分利用纖維增強塑料的優(yōu)點,優(yōu)化組成材料和結(jié)構(gòu)是非常必要的。研究表明,正方形混凝土柱周圍的碳纖維/ 環(huán)氧基樹脂能夠使其負(fù)載能力增加8%—22%,而這種能力的增強是依賴于大量纖維的使用以及對基層表面的處理。樹脂注入技術(shù)的使用表明其對繞接效果的改進(jìn)起了非常重要的作用,研究表明,當(dāng)使用玻璃無捻粗紗布來增強繞接效果時,不僅能顯著提高混凝土的負(fù)載能力同時也能夠增加混凝土短支柱的變形抵抗能力。此外,通過使用帶有環(huán)氧樹脂的玻璃/ 碳混合增強材料來加固混凝土,當(dāng)對混凝土柱進(jìn)行反復(fù)的試驗來檢測它的最初性能時,發(fā)現(xiàn)它的負(fù)載能力進(jìn)一步的提高了。根據(jù)復(fù)合物彎曲的方位和厚度,表明在套箍位置處進(jìn)行加固會產(chǎn)生更好的效果。盡管已經(jīng)進(jìn)行了大量的研究,但是大多數(shù)研究中都存在一個不足之處,即他們所做的試驗僅限于形狀較小較簡單的結(jié)構(gòu),如混凝土圓柱體,而不是真正的結(jié)構(gòu)。此外,有必要根據(jù)成本其中包括材料和處理方法來研究使組合結(jié)構(gòu)達(dá)到最優(yōu)化。這就表明,當(dāng)使用纖維增強塑料來進(jìn)行基礎(chǔ)加固時,應(yīng)該使用各種材料的優(yōu)點,不僅僅是帶有環(huán)氧樹脂的碳纖維,同時也應(yīng)該包括玻璃纖維或帶有其它聚合樹脂的碳/玻璃纖維的復(fù)合物,在這個試驗中為了加固一個典型的建筑部分,即梁–柱聯(lián)接部位,設(shè)計了一個帶有乙烯基酯樹脂的碳/E玻璃復(fù)合物。為了研究帖有纖維增強塑料對構(gòu)件的影響,在靜載條件下,分別對通過纖維增強塑料加固后的試件和沒有加固的試件進(jìn)行了大量的試驗。
研究報告是一個合作研究項目的一個組成部分,該項目是有悉尼理工大學(xué)、高級材料技術(shù)中心和悉尼大學(xué)共同合作研究的關(guān)于應(yīng)用高級纖維復(fù)合物來增大混凝土的強度和硬度,由此來對混凝土結(jié)構(gòu)進(jìn)行加固。
1、 實驗程序
為了這一項目設(shè)計了三個標(biāo)準(zhǔn)尺寸加固混凝土結(jié)構(gòu)試件,它們代表了典型的梁–柱聯(lián)接部位。圖一表示了局部帶有纖維增強塑料構(gòu)件的幾何形狀。在這三個試件中,其中兩個試件相當(dāng)于混凝土梁–柱聯(lián)接類型(非加固試件),另一個是在梁–柱聯(lián)接部位周圍用碳纖維和玻璃纖維復(fù)合物加固的試件(加固試件)。這三個試件都使用標(biāo)準(zhǔn)商品混凝土,其強度等級為C40。在圖一中也顯示了混凝土試件的配筋情況。為了測定混凝土的彈性模量和抗壓強度,進(jìn)行了混凝土抗壓試驗,該實驗是根據(jù)AS 1012–1986標(biāo)準(zhǔn)進(jìn)行的。
圖1 試件的幾何細(xì)節(jié)(沒按比例確定)
2.1 復(fù)合式結(jié)構(gòu)
三個混凝土結(jié)構(gòu)試件中的一個用復(fù)合物進(jìn)行加固,該復(fù)合物由四個部分組成,包括E玻璃無捻粗紗布(WR-600g/ m2)、短貼原絲氈(CSM-300g/m2)、碳布(200g/ m2)和玻璃纖維布(GFT-250g/ m2)詳細(xì)見表格1和圖2,平面詳圖見圖3。雙軸平面布置不僅對軸向方向提供了相當(dāng)?shù)膹姸?,而且對箍部位也起到了同樣的作用。而玻璃無捻粗紗布和碳布的使用對于雙軸平面布置起到多方位的加固作用,在這個復(fù)合式結(jié)構(gòu)中它們都起到了基本的加固作用。把玻璃纖維帶應(yīng)用到箍部位能夠提供非常好的限制作用,同時也能夠增強結(jié)構(gòu)的完整性。樹脂修復(fù)系統(tǒng)的選擇主要與樹脂膠性時間有關(guān)。一般來說,當(dāng)采用濕鋪法,可以使用冷環(huán)繞樹脂系統(tǒng)。對于本次研究所描述的環(huán)繞方法沒有可采用濕鋪機(jī)器,所以采用人工方式。在室溫下,乙烯基酯樹脂和Dastar-R/VERPVE/SW/TP被混合并且混合有1.5%的MEKP,0.4%的CONAP和0.5%的DMA。在室溫條件下加工處理樹脂。對于玻璃無捻粗紗布/短貼原絲氈層,樹脂和纖維的比率是1:1.5,對于碳布比率是1:0.8。混凝土構(gòu)件被一層lames-wool和一層加固層所包裹。在放置第一層纖維層之前,應(yīng)使用丙酮來清理混凝土的表面,然后采用樹脂涂層去密封混凝土表面上的小洞。然而,當(dāng)進(jìn)行進(jìn)一步的表面處理時,應(yīng)該有意識的去避免沙粒被暴露在外面。為了確使結(jié)構(gòu)完全加固,每一個復(fù)合層都應(yīng)該用樹脂潤濕并且卷在混凝土結(jié)構(gòu)之上。
表1
圖2
圖3
2.2靜載試驗設(shè)計
在水平面上設(shè)計混凝土結(jié)構(gòu)試件的靜載試驗,三個混凝土框架支撐是卷筒狀的,如圖4。被加載構(gòu)件末端也是卷筒類型的支撐。然而,其水平運動沒有被明顯的限制。為了在沒個構(gòu)件末端能夠提供理想的卷筒類型邊界條件,設(shè)計了一個專門的裝置,該裝置在加載點配有滾筒和一個軸承,如圖5。在試驗中,使用了4個1000KN的千斤頂。在它們之中唯一一個活動的是那個放在加載構(gòu)件出的,而其它的幾個只簡單的起到提供支座反力的作用。
圖4
圖5
2.3儀表使用和數(shù)據(jù)記錄
使用4個千斤頂?shù)难b載單元放置在每個支撐物和加載點上,測出所家荷載和反作用力的大小。為了獲得混凝土框架試件準(zhǔn)確的偏差撓曲線。使用12個可變位移傳感器,該傳感器測量范圍為±2.5mm到±50mm,把它們放在重要位置上來測量撓度偏差。為了使試驗更加地規(guī)范并對沒有經(jīng)過使用纖維增強塑料加固的混凝土結(jié)構(gòu)試件的變形有更準(zhǔn)確的了解,設(shè)計了大量應(yīng)變計來獲取所測試試件的壓力分布。每一個試件使用56個應(yīng)變計,其中有28個應(yīng)變計放置在試件的鋼筋處,另外28個30mm的應(yīng)變計放置在混凝土結(jié)構(gòu)試件的外表面處。按順序排列應(yīng)變計以便能夠測出連接部分大量的點。對于大部分被測試的連接部分,一個典型的排列方式如圖6。應(yīng)變計在這些部分內(nèi)部的排列方式如圖7。
圖6
圖7
2.4 試驗程序程
表2給出了所測試試件的名稱和一個簡單的描述。在正式運行負(fù)載進(jìn)行試驗之前,首先對非加固試件進(jìn)行一系列研究試驗,主要是加載40KN,其中一個加到超過50KN。其次,對非加固試件和加固試件不家任何負(fù)載,直到達(dá)到先前使用負(fù)載水平。在每一個試件受到大約100次的加載后,處理所有最終負(fù)載試驗。
表2
3.結(jié)果和分析
為了決定纖維增強塑料對加固結(jié)構(gòu)試件的影響,處理了在3個試件上進(jìn)行的5個試驗,其中包括以運行負(fù)載進(jìn)行試驗的三個試驗和以最終負(fù)載進(jìn)行試驗的兩個試驗。對于每個試驗,都進(jìn)行了四個負(fù)載記錄,十二個撓度記錄和 56 或 64個應(yīng)變的數(shù)據(jù)記錄。
3.1靜載試驗的確定
為了使所做的靜載試驗得到證實,依次列出了每次試驗的靜力平衡,如下:
外部荷載的平衡:由于在設(shè)計這些試驗中避免了多余約束的存在,而且把加載裝置布置于加載點和反力點,這使得通過使用簡單的靜力學(xué)來檢驗加載點和反力點的靜力平衡變的很方便。表2顯示的外部負(fù)載平衡令人很滿意。
斷面上力的平衡和力矩的平衡:為了準(zhǔn)確地計算內(nèi)部力和部分力矩,需要在指定的區(qū)間內(nèi)使用應(yīng)變計。為了處理在一個給定的斷面上的標(biāo)準(zhǔn)應(yīng)變, 做了下列的假設(shè):截面上的應(yīng)變沿線性變化,換句話說就是在被給定的一個斷面上的應(yīng)變可以用一條應(yīng)變線表示。在這一假設(shè)條件下,采用具有兩個解釋變量的最小二乘法來獲得平面應(yīng)變,對于每個被給定的區(qū)間使用6個平面應(yīng)變值。圖8表示把所測得的平面應(yīng)變數(shù)值與用最小二乘法擬合所計算的數(shù)值做了比較。通過計算平面應(yīng)變可以獲得應(yīng)變值,這些數(shù)值將用于隨后的計算。對于確定一個被給定的斷面內(nèi)部的平衡,力的計算是通過結(jié)合在拉力段和壓縮段中所分別測得的數(shù)值而完成的。假設(shè)混凝土只受壓力和受拉區(qū)的力主要有鋼筋(一些表面帶有纖維增強塑料 )來承擔(dān)。平衡狀態(tài)即受壓區(qū)的合力與受拉區(qū)的合力相等。被給定斷面上的力矩應(yīng)該通過這個斷面上所受的壓力來計算。把它們與通過所測荷載來計算的數(shù)值做對比。這些計算的詳細(xì)公式如附錄 A,表3和表 4 表示靜載試驗的確定。
圖8
表3
表4
3.2負(fù)荷–凸形豎曲線
圖9和圖10中顯示了加固試件的負(fù)荷–凸形豎曲線和非加固試件的對比情況,其中既包括在使用載荷條件下,又包括在極限載重條件下。結(jié)果顯示,由于使用了纖維增強塑料,使混凝土的硬度增加了大約45%(使用載荷條件下)。試驗表明,在極限載重條件下使用纖維增強塑料加固混凝土結(jié)構(gòu)試件能夠使其負(fù)載能力提高大約30%。
圖9
圖10
3.3 應(yīng)變結(jié)果的分析
由于纖維增強塑料具有加固作用,所以為了估計鋼筋處的應(yīng)變變化,定義了一個參數(shù),即“平面應(yīng)變約數(shù)”。定義如下:在相同的負(fù)載條件下,P代表兩個非加固試件中最大區(qū)間內(nèi)的平均應(yīng)變值,R代表兩個加固試件中最大區(qū)間內(nèi)的平均應(yīng)變值。表5和表6對非加固試件和加固試件的最大/最小應(yīng)變值進(jìn)行了典型的對比以及在相同荷載條件下不同斷面的平均應(yīng)變約數(shù)的對比情況(同見圖11)。如果對所有梁部分采用平均應(yīng)力約數(shù)的方法,它將產(chǎn)生 51% 的應(yīng)變縮減因子。以相同的方式, 對于柱部分將產(chǎn)生55% 的應(yīng)變縮減因子。平面應(yīng)變約數(shù)可以用以衡量外部使用纖維增強塑料加固的效果。
表5
表6
圖11
3.4 對應(yīng)用復(fù)合物建筑的討論
在使用載荷和極限載重條件下,對混凝土結(jié)構(gòu)試件進(jìn)行試驗,從所得到的結(jié)果可以發(fā)現(xiàn),采用纖維增強塑料來加固建筑物,能夠成功地提高結(jié)構(gòu)的硬度和負(fù)載能力。令人感興趣的是發(fā)現(xiàn)雖然纖維增強塑料的彈性模量僅僅大約是混凝土的一半,但是在增強混凝土的硬度和負(fù)載能力方面卻扮演非常重要的角色。在應(yīng)用纖維增強塑料來加固混凝土結(jié)構(gòu)試件之前,雖然沒有采取專門的表面處理,但是復(fù)合物與混凝土表面之間的連接卻沒有失敗。這可能是由于復(fù)合物具有較小的彈性模量。有跡象表明,由于混凝土具有較低抗拉強度,所以彈性模量較小的纖維增強塑料可能對混凝土結(jié)構(gòu)起到更好的加固作用。在采用鋪法設(shè)計中,厚度的逐漸變化是必要的。這樣可以降低在纖維增強塑料中可能產(chǎn)生的應(yīng)力集中,這些應(yīng)力集中能夠引起混凝土的裂縫。然而,有必要指出,由于僅僅對一些受到限制的試件進(jìn)行研究,所以這些結(jié)論可能有一定的偏差。建議做更多的試驗來證明這些結(jié)論。
4.結(jié)論
作為研究的結(jié)果,列出了以下結(jié)論:
1.對加固后標(biāo)準(zhǔn)尺寸混凝土結(jié)構(gòu)試件進(jìn)行試驗已經(jīng)被成功地處理,所設(shè)計的試件代表了平面框架結(jié)構(gòu)中的梁–柱聯(lián)接部位。通過平衡校核證明了由該試驗所得出的結(jié)論。
2. 由無捻粗紗布、碳布、短貼原絲氈和玻璃纖維帶組成的復(fù)合物有效地證明了纖維增強塑料對混凝土結(jié)構(gòu)試件的加固效果。試驗的結(jié)果表明由于使用了纖維增強塑料復(fù)合物使得混凝土的硬度和負(fù)載能力有了明顯的提高。結(jié)果也表明用較低的成本加強混凝土結(jié)構(gòu)并且使其達(dá)到較好的效果,使結(jié)構(gòu)達(dá)到最優(yōu)化是很重要的。
3. 靜載試驗的結(jié)果也表明具有較低彈性模量的混合碳/ E玻璃纖維復(fù)合物可能會提供更好的連接。然而,這需要被更多的試驗證明。
4.研究也表明應(yīng)該進(jìn)行進(jìn)一步的研究,其中包括加固被破壞的混凝土結(jié)構(gòu)試件,循環(huán)荷載和使用不同的結(jié)構(gòu)類型。
附錄 A
假定梁/柱上一個被給定的斷面的應(yīng)變分布是線性的。對于給定的區(qū)間,應(yīng)變能夠被表達(dá)為
公式(A.1)
其中a,b,c是常數(shù)。
考慮兩個解釋變量的反映模型
Yi=0+1xi1+2xi2+ei, (A.2)
附件2:外文原文
Abstract The paper describes the results of tests on prototype size reinforced concrete frame specimens which were designed to represent the column–beam connections in plane frames. The tests were devised to investigate the influence of fibre reinforced plastic (FRP) reinforcement applied to external surfaces adjacent to the beam–column connection on the behaviour of the test specimens under static loading. Of particular interest under static loading was the influence of FRP reinforcement on the strength and stiffness of beam–column connection. As a key to the study, the hybrid FRP composites of E-glass woven roving (WR) and plain carbon cloth, combined with chopped strand mat (CSM), glass fiber tape (GFT) with a vinyl-ester resin were designed to externally reinforce the joint of the concrete frame. The results show that retrofitting critical sections of concrete frames with FRP reinforcement can provide signification strengthening and stiffening to concrete frames and improve their behaviour under different types of loading. The selections of types of FRP and the architecture of composites in order to improve the bonding and strength of the retro-fitting were also discussed.
Author Keywords: Concrete structure; Strengthening; Rehabilitation; Hybrid FRP composite; Wrapping technique
1. Introduction
A widely adopted technique for retrofitting concrete structure is to use steel jackets placed around existing concrete columns [1 and 2]. The use of steel encasement to provide lateral confinement to the concrete in compression has been studied extensively [3 and 4], and has shown increase in the compression load carrying capacity and ductility of the concrete columns. However, the shortcomings of this technique are that it suffers from corrosions as well as inherent difficulties during practical applications. Fibre reinforced plastic (FRP), on the other hand, is increasingly being used to reinforce concrete, masonry and timber structures. The load carrying capacity and serviceability of existing structures can be significantly augmented through externally retrofitting critical sections with FRP sheeting. In recent years FRP materials with wide range of fibre types of glass, aramid or carbon provide designers with an adaptable and cost-effective construction material with a large range of modulus and strength characteristics. Comparing with traditional rehabilitation techniques, the FRP composites have high specific strength/stiffness, flexibility in design and replacement as well as robustness in unfriendly environments. With FRP composites it is possible and also necessary to achieve the best strengthening results by optimising the constitute materials and architecture. Optimisation of the constitute materials and architecture becomes essential in order to utilise the superiority of FRP composites in application of rehabilitation [5, 6, 7, 8 and 9]. It was found that winding of carbon fiber/epoxy composites around square concrete columns can increase the load carrying capacity by 8–22%, depending on the amount of fibres used and treatments of substrate surface [10]. The use of resin infusion technique was shown to contribute to substantial improvements in composite wrapping efficiency, and the use of woven glass roving, as the reinforcement in composites wrapping, was found to significantly increase both load carrying capacity and deformation resistance capacity of the concrete stubs [2]. Furthermore, through the use of glass/carbon hybrid reinforcements with an epoxy resin, replication of initial performance of concrete stubs subjected to deterioration was shown possible, with a simultaneous further improvement in load carrying capacity. In terms of the effects of orientation and thickness of the composites warps, it was found that the predominant use of reinforcements in the hoop direction would result in high efficiency [11]. Despite the large number of research carried out, one shortcoming of most studies has been that they were limited to simple small size components, such as concrete cylinders, rather than real structures. Furthermore, it is essential to study the optimisation of composites architectures in terms of cost effectiveness including materials and processing methods. This implies that the reinforcement of infrastructure with FRP composites should utilise the advantages of various materials, not only carbon fibers with epoxy resin, but also glass fiber or hybrid of carbon/glass fibres with other polymer resins. In this experimental investigation, a hybrid of carbon/E-glass with vinyl-ester resin composites jacket was designed to reinforce a typical building components, namely a column–beam connection. Static tests were then conducted on FRP reinforced and non-reinforced specimens with extensive instrumentation to study the influence of the designed composite reinforcement.
The investigation reported in the paper forms part of a collaborative research program between the University of Technology, Sydney and the Centre for Advanced Materials Technology, the University of Sydney in relation to application of advanced fibre composites to strengthen, stiffen and hence rehabilitate concrete structures.
2. Experimental procedures
Three prototype size reinforced concrete frame specimens, representing typical concrete column–beam connection, were designed for this study. Geometry of the specimens with location of FRP composite reinforcement is illustrated in Fig. 1. Among three specimens, two of them are as-is concrete beam–column connection type (none composites-reinforced (Non-CR) specimens) and one specimen was reinforced by the hybrid of carbon fiber and glass fibre composites around the column–beam joint (composites-reinforced (CR) specimen). All three specimens were pre-cast using standard commercial mix grade 40 concrete. The steel reinforcement of the concrete specimens are also shown in Fig. 1. Concrete compression tests based on the Australian Standard (AS 1012–1986) were conducted on the samples taken during the concrete pour in order to determine the modulus of elasticity and ultimate compression strength (UCS) of the concrete.
2.1. Composites architecture
One of the three concrete frame specimens was reinforced with hybrid composites. The hybrid composites consists of four basic architectures, namely E-glass woven roving (WR/600 g/m2), chopped strand mat (CSM-300 g/m2), carbon cloth (plain weave-200 g/m2) and glass fibre tape (GFT-250 g/mm2). The details of the composites architecture are shown in Table 1 and Fig. 2. Details of lay-up are illustrated in Fig. 3. WR and carbon cloth are a multi-directional reinforcement with biaxial plain weaving which provide equivalent strength in both axial and hoop directions. They play the basic reinforcement role in this composites architecture. GFT applying at hoop direction provides very good confinement and enhances structural integrity. The selection of resin curing systems is mainly concerned with the resin gel-time at ambient temperature, which is critical to wrapping process. In general, cold setting resin systems (ambient temperature curing) can be used when wet lay-up process is applied. Since no lay-up machine is available for the wrapping process described in this study, the hand lay-up method was used. The vinyl-ester resin, Dastar-R/VERPVE/SW/TP, was mixed with 1.5% of MEKP (methyl-ethyl-ketone-peroxide), 0.4% of CoNap (Cobalt napthenate), and 0.5% of DMA (Dimethylaniline) at ambient temperature. The resin cures at ambient temperature. The weight ratio between resin and fibre layers was 1:1.5 for WR/CSM layers and 1:0.8 for carbon cloth, respectively. The concrete frame was wrapped by a lames-wool roller and a consolidating roller. Before laying the first fibre layer, the concrete surfaces were cleaned up using acetone, and a thin resin coat was applied to seal micro holes on the surface of concrete columns. However, further surface treatment such as sanding surface to expose the aggregates was intentionally avoided. Each composite layer was wetted with the resin and rolled onto the concrete frame to ensure full consolidation.
Table 1. Details of five composite systems with a composite architectures
2.2. Design of static tests
The static tests of the concrete frame specimens were setup in a horizontal plane. The three supports of the concrete frame (no load applied) were roller type as shown in Fig. 4. The end at which load was applied was also a roller type support, however, horizontal movements were obviously not prevented. In order to provide the ideal roller type boundary conditions at each end as designed, a special setup was developed with combination of rollers and a swivel head at each supporting/loading point (Fig. 5). Four 1000-kN-hydraulic jacks were used in the tests. Among them, the only active jack was the jack that applied loads, while others were simply acting as adjustable packing to providing the reactions.
Fig. 4. Illustrative sketch of test set-up for static test.
Fig. 5. Set-up for static test of concrete frame.
2.3. Instrumentation and data logging
Applied load as well as reaction forces were measured using four 998.8 kN load cells located in each of four supporting/loading positions. In order to obtain detailed flexural deflection curves for the concrete frame specimens, twelve linear variable displacement transducers (LVDTs) with a range from ±2.5 to ±50 mm were used at strategic locations to measure the flexural deflections. Extensive strain gauging was designed to capture the stress distribution of the testing specimens in order to validate tests and gain an insight into the behaviour of the concrete frame with or without FRP reinforcement. The total number of strain gauges was 56 for each specimen, in which 28 strain gauges (5 mm) were located on steel rebars and the rest (30 mm strain gauges) were located on the external surface of the concrete frame specimens. Locations of the strain gauges were arranged so that the strains on various points of the cross sections could be captured. A typical strain gauge arrangement for most measured cross sections is shown in Fig. 6. Locations of strain gauges inside the section are shown in Fig. 7.
Fig. 6. Location of cross sections of the concrete frame for strain gauging.
2.4. Test procedure
Designations of test specimens and a brief description are given in Table 2. Prior to being formally tested at service load level, the first non-CR specimen was subjected to a series of investigative tests mostly loaded at the service load level of 40 kN with one single overload up to 50 kN. The second non-CR specimen and the CR specimens were not subjected to any loading until the initial service load level tests. All ultimate load tests were conducted after every specimen was exposed to about 100 cycles of cyclic loading at service load levels.
Table 2. Applied load and reactions for typical tests (unit: kN)
3. Results and analysis
In order to determine the influence of FRP composites, five sets of tests were conducted on the three specimens including three tests at service load levels and two at the ultimate load level. For every test, logged data consisted of four load records, twelve deflection records and 56 or 64 strain records.
3.1. Validation of the static tests
To validate the performed tests, the static equilibrium for each test was verified as follows:
Equilibrium of external loads: As redundancy was avoided in design of these tests and load cells were placed at each loading or reaction point, it was convenient to check equilibrium of the load/reaction forces through simple statics. Table 2 shows that the equilibrium of external loads was satisfied.
Equilibrium of forces and equilibrium of moment on cross sections: In order to calculate the internal forces and sectional moments, strains on the designated sections were required. To process the measured strains on a given cross section, the following assumption was made: the strains vary linearly through the cross sections. In other words the strains at a given cross section can be represented by a strain plane. Under this assumption, least square method with the two explanatory variables was adopted to obtain the strain plane for each given cross section using values of six measured strains. Fig. 8 shows comparison of the measured strain values and those calculated from the least square fitting. The strain values used in subsequence evaluations or calculations were obtained from calculated strain planes. For the validation of the equilibrium of internal forces in a given cross section, forces were calculated by integration of resulting stresses in tension and compression zones, respectively. The concrete was assumed to carry only compression loads and steel rebars (with FRP composites in some cases) were considered as the main load carriers in the tension zone. Equilibrium states that the resultant force in the compression zone should be equal to that in the tension zone. Moments at a given cross section were firstly calculated through integration of stresses in the section. They were compared to those calculated by using measured loads multiplied by the lever arms. Details of formulae pertained to these calculations are presented in Appendix A. As shown in Table 3 and Table 4, equilibrium is validated.
Fig. 8. Comparison of measured vs calculated strain values from least square fitting.
Table 3. List of calculated internal force and moments at section A-A of a non-CR specimen
Table 4. List of calculated internal force and moments at section A-A of a CR specimen
3.2. Load–deflection curves
Comparison of load–deflection curves for CR and non-CR specimens at both service load and ultimate load levels are shown in Fig. 9 and Fig. 10. About 45% increase in stiffness was observed due to the presence of FRP composites reinforcement (service load level). Results of the ultimate loading test indicated an increase in load carrying capacity of CR specimen of approximately 30% due to the presence of FRP composites.
3.3. Analysis of the strain results
To evaluate change of strain in steel rebars due to FRP reinforcement, a parameter was defined, n
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