2016年廣播電視大學《混凝土結構設計原理》作業(yè)參考答案小抄.doc
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電大混凝土結構設計原理作業(yè)1、2、3、4參考答案作業(yè)1說明:本次作業(yè)對應于文字教材1至3章,應按相應教學進度完成。一、選擇題1下列關于鋼筋混凝土結構的說法錯誤的是( A )。A鋼筋混凝土結構自重大,有利于大跨度結構、高層建筑結構及抗震B(yǎng)取材較方便、承載力高、耐久性佳、整體性強C施工需要大量模板、工序復雜、周期較長、受季節(jié)氣候影響大D耐火性優(yōu)、可模性好、節(jié)約鋼材、抗裂性差2我國混凝土結構設計規(guī)范規(guī)定:混凝土強度等級依據(jù)( D )確定。A圓柱體抗壓強度標準 B軸心抗壓強度標準值C棱柱體抗壓強度標準值D立方體抗壓強度標準值3混凝土的彈性系數(shù)反映了混凝土的彈塑性性質,定義( A )為彈性系數(shù)。A彈性應變與總應變的比值B塑性應變與總應變的比值C彈性應變與塑性應變的比值D塑性應變與彈應變的比值4混凝土的變形模量等于(D )。A應力與彈性應變的比值B應力應變曲線原點切線的曲率C應力應變曲線切線的斜率D彈性系數(shù)與彈性模量之乘積5我國混凝土結構設計規(guī)范規(guī)定:對無明顯流幅的鋼筋,在構件承載力設計時,取極限抗拉強度的( C )作為條件屈服點。A75%B80%C85%D70%6結構的功能要求不包括( D )A 安全性B 適用性C 耐久性D 經(jīng)濟性7結構上的作用可分為直接作用和間接作用兩種,下列不屬于間接作用的是( B )。A 地震B(yǎng) 風荷載C 地基不均勻沉降D 溫度變化8( A )是結構按極限狀態(tài)設計時采用的荷載基本代表值,是現(xiàn)行國家標準建筑結構荷載規(guī)范(GB 50009-2001)中對各類荷載規(guī)定的設計取值。A 荷載標準值B 組合值C 頻遇值D 準永久值二、判斷題1通常所說的混凝土結構是指素混凝土結構,而不是指鋼筋混凝土結構。( )2混凝土結構是以混凝土為主要材料,并根據(jù)需要配置鋼筋、預應力筋、型鋼等,組成承力構件的結構。( )3 我國混凝土規(guī)范規(guī)定:鋼筋混凝土構件的混凝土強度等級不應低于C10。( )4 鋼筋的伸長率越小,表明鋼筋的塑性和變形能力越好。( )5鋼筋的疲勞破壞不屬于脆性破壞。( )6粘結和錨固是鋼筋和混凝土形成整體、共同工作的基礎。( )7只存在結構承載能力的極限狀態(tài),結構的正常使用不存在極限狀態(tài)。( )8一般來說,設計使用年限長,設計基準期可能短一些;設計使用年限短,設計基準期可能長一些。( )9鋼筋和混凝土的強度標準值是鋼筋混凝土結構按極限狀態(tài)設計時采用的材料強度基本代表值。( )10荷載設計值等于荷載標準值乘以荷載分項系數(shù),材料強度設計值等于材料強度標準值乘以材料分項系數(shù)。( )三、簡答題1鋼筋和混凝土這兩種物理和力學性能不同的材料,之所以能夠有效地結合在一起而共同工作,其主要原因是什么?答:3提示答案:1)鋼筋和混凝土之間良好的黏結力;2)接近的溫度線膨脹系數(shù);3)混凝土對鋼筋的保護作用。2試分析素混凝土梁與鋼筋混凝土梁在承載力和受力性能方面的差異。答:提示答案:素混凝土梁承載力很低,受拉區(qū)混凝土一開裂,裂縫迅速發(fā)展,梁在瞬間驟然脆裂斷開,變形發(fā)展不充分,屬脆性破壞,梁中混凝土的抗壓能力未能充分利用。鋼筋混凝土梁承載力比素混凝土梁有很大提高,受拉區(qū)混凝土開裂后,鋼筋可以代替受拉區(qū)混凝土承受拉力,裂縫不會迅速發(fā)展,直到鋼筋應力達到屈服強度,隨后荷載略有增加,致使受壓區(qū)混凝土被壓碎。梁破壞前,其裂縫充分發(fā)展,變形明顯增大,有明顯的破壞預兆,結構的受力特性得到明顯改善。同時,混凝土的抗壓能力和鋼筋的抗拉能力得到充分利用。3鋼筋混凝土結構設計中選用鋼筋的原則是什么?答:提示答案:1)較高的強度和合適的屈強比;2)足夠的塑性;3)可焊性;4)耐久性和耐火性5)與混凝土具有良好的黏結力。4什么是結構的極限狀態(tài)?結構的極限狀態(tài)分為幾類,其含義是什么?答:提示答案:整個結構或結構的一部分超過某一特定狀態(tài)就不能滿足設計指定的某一功能要求,這個特定狀態(tài)稱為該功能的極限狀態(tài)。結構的極限狀態(tài)可分為承載能力極限狀態(tài)和正常使用極限狀態(tài)兩類。結構或構件達到最大承載能力、疲勞破壞或者達到不適于繼續(xù)承載的變形時的狀態(tài),稱為承載能力極限狀態(tài)。結構或構件達到正常使用或耐久性能的某項規(guī)定限值的狀態(tài),稱為正常使用極限狀態(tài)。5什么是結構上的作用?結構上的作用分為哪兩種?荷載屬于哪種作用?答:提示答案:答:結構上的作用是指施加在結構或構件上的力,以及引起結構變形和產(chǎn)生內力的原因。結構上的作用又分為直接作用和間接作用。荷載屬于直接作用。6什么叫做作用效應?什么叫做結構抗力?答:提示答案:直接作用和間接作用施加在結構構件上,由此在結構內產(chǎn)生內力和變形,稱為作用效應。結構抗力R是指整個結構或構件承受作用效應(即內力和變形)的能力,如構件的承載力和剛度等。作業(yè)2說明:本次作業(yè)對應于文字教材4至5章,應按相應教學進度完成。一、選擇題1受彎構件抗裂度計算的依據(jù)是適筋梁正截面( A )的截面受力狀態(tài)。A第I階段末B第II階段末C第III階段末2受彎構件正截面極限狀態(tài)承載力計算的依據(jù)是適筋梁正截面( C )的截面受力狀態(tài)。A第I階段末B第II階段末C第III階段末3梁的破壞形式為受拉鋼筋的屈服與受壓區(qū)混凝土破壞同時發(fā)生,則這種梁稱為( C )。A少筋梁B適筋梁C平衡配筋梁D超筋梁4雙筋矩形截面梁正截面承載力計算基本公式的第二個適用條件的物理意義是( C )。A防止出現(xiàn)超筋破壞 B防止出現(xiàn)少筋破壞C保證受壓鋼筋屈服 D保證受拉鋼筋屈服5受彎構件斜截面承載力計算公式是以( D )為依據(jù)的。A斜拉破壞B斜彎破壞C斜壓破壞D剪壓破壞二、判斷題1混凝土強度等級的選用須注意與鋼筋強度的匹配,當采用HRB335、HRB400鋼筋時,為了保證必要的粘結力,混凝土強度等級不應低于C25;當采用新HRB400鋼筋時,混凝土強度等級不應低于C30。( )2一般現(xiàn)澆梁板常用的鋼筋強度等級為HPB235、HRB335鋼筋。( )3混凝土保護層應從受力縱筋的內邊緣起算。( )4鋼筋混凝土受彎構件正截面承載力計算公式中考慮了受拉區(qū)混凝土的抗拉強度。( )5鋼筋混凝土梁斜截面破壞的三種形式是斜壓破壞、剪壓破壞和斜拉破壞。( )6鋼筋混凝土無腹筋梁發(fā)生斜拉破壞時,梁的抗剪強度取決于混凝土的抗拉強度,剪壓破壞也基本取決于混凝土的抗拉強度,而發(fā)生斜壓破壞時,梁的抗剪強度取決于混凝土的抗壓強度。( )7剪跨比不是影響集中荷載作用下無腹筋梁受剪承載力的主要因素。( )8鋼筋混凝土梁沿斜截面的破壞形態(tài)均屬于脆性破壞。( )三、簡答題1鋼筋混凝土受彎構件正截面的有效高度是指什么?答:計算梁、板承載力時,因為混凝土開裂后,拉力完全由鋼筋承擔,力偶力臂的形成只與受壓混凝土邊緣至受拉鋼筋截面重心的距離有關,這一距離稱為截面有效高度。2根據(jù)配筋率不同,簡述鋼筋混凝土梁的三種破壞形式及其破壞特點? 答:1)適筋破壞;適筋梁的破壞特點是:受拉鋼筋首先達到屈服強度,經(jīng)過一定的塑性變形,受壓區(qū)混凝土被壓碎,屬延性破壞。2)超筋破壞;超筋梁的破壞特點是:受拉鋼筋屈服前,受壓區(qū)混凝土已先被壓碎,致使結構破壞,屬脆性破壞。3)少筋破壞;少筋梁的破壞特點是:一裂即壞,即混凝土一旦開裂受拉鋼筋馬上屈服,形成臨界斜裂縫,屬脆性破壞。3在受彎構件正截面承載力計算中,的含義及其在計算中的作用是什么?答:是超筋梁和適筋梁的界限,表示當發(fā)生界限破壞即受拉區(qū)鋼筋屈服與受壓區(qū)砼外邊緣達到極限壓應變同時發(fā)生時,受壓區(qū)高度與梁截面的有效高度之比。其作用是,在計算中,用來判定梁是否為超筋梁。4什么情況下采用雙筋截面梁?答:對于給定截面彎矩當按單筋截面梁設計時,若給定彎矩設計值過大,截面設計不能滿足適筋梁的適用條件(),且由于使用要求截面高度受到限制又不能增大,同時混凝土強度等級因條件限制不能再提高時,可采用雙筋截面。即在截面的受壓區(qū)配置縱向鋼筋以補充混凝土受壓能力的不足。5有腹筋梁斜截面剪切破壞形態(tài)有哪幾種?各在什么情況下產(chǎn)生? 答:受彎構件斜截面剪切破壞的主要形態(tài)有斜壓、剪壓和斜拉三種。當剪力相比彎矩較大時,主壓應力起主導作用易發(fā)生斜壓破壞,其特點是混凝土被斜向壓壞,箍筋應力達不到屈服強度。當彎剪區(qū)彎矩相比剪力較大時,主拉應力起主導作用易發(fā)生斜拉破壞,破壞時箍筋應力在混凝土開裂后急劇增加并被拉斷,梁被斜向拉裂成兩部分,破壞過程快速突然。剪壓破壞時箍筋在混凝土開裂后首先達到屈服,然后剪壓區(qū)混凝土被壓壞,破壞時鋼筋和混凝土的強度均有較充分利用。6影響有腹筋梁斜截面受剪承載力的主要因素有哪些?答:配有腹筋的混凝土梁,其斜截面受剪承載力的影響因素有剪跨比、混凝土強度、縱向鋼筋的銷栓作用、箍筋的配筋率及其強度、彎起鋼筋的配置數(shù)量等。四、計算題1已知鋼筋混凝土矩形梁,一類環(huán)境,其截面尺寸,承受彎矩設計值,采用C30 混凝土和HRB335 級鋼筋。試配置截面鋼筋。解:解:, 滿足要求,取選配鋼筋3 25(2已知矩形截面梁,已配縱向受拉鋼筋4根22mm 的HRB400級鋼筋,按下列條件計算此梁所能承受的彎矩設計值。 混凝土強度等級為C25; 若由于施工原因,混凝土強度等級僅達到C20級。解: 查教材附錄知:對于一類環(huán)境,可取梁的保護層厚度mm,HRB400級鋼筋,C25級混凝土,。 當混凝土強度等級為C25,梁所能承受的彎矩設計值為。 若由于施工原因,混凝土強度等級僅達到C20級,C20級混凝土。 若由于施工原因,混凝土強度等級僅達到C20級,梁所能承受的彎矩設計值為。3一鋼筋混凝土矩形截面簡支梁,處于一類環(huán)境,安全等級二級,混凝土強度等級為C25,梁的截面尺寸為,縱向鋼筋采用HRB335級鋼筋,箍筋采用HPB235級鋼筋,均布荷載在梁支座邊緣產(chǎn)生的最大剪力設計值為250kN。正截面強度計算已配置425 的縱筋,求所需的箍筋。解:(1)確定計算參數(shù) , (2)驗算截面尺寸,屬一般梁 截面符合要求。(3)驗算是否需要計算配置箍筋 故需進行計算配置箍筋。 (4)求箍筋數(shù)量并驗算最小配筋率選雙肢箍8(,)代入上式可得:取,可得:滿足要求4. 承受均布荷載設計值作用下的矩形截面簡支梁,安全等級二級,處于一類環(huán)境,截面尺寸,混凝土為C30級,箍筋采用HPB235級鋼筋。梁凈跨度。梁中已配有雙肢 200箍筋,試求:梁在正常使用期間按斜截面承載力要求所能承擔的荷載設計值。解:(1)確定計算參數(shù), (1)求荷載設計值 作業(yè)3說明:本次作業(yè)對應于文字教材6至9章,應按相應教學進度完成。一、選擇題1螺旋箍筋柱較普通箍筋柱承載力提高的原因是( C )。A螺旋筋使縱筋難以被壓屈B螺旋筋的存在增加了總的配筋率C螺旋筋約束了混凝土的橫向變形D螺旋筋的彈簧作用2大偏心和小偏心受壓破壞的本質區(qū)別在于( B )。A受拉區(qū)的混凝土是否破壞B受拉區(qū)的鋼筋是否屈服C受壓區(qū)的鋼筋是否屈服D受壓區(qū)的混凝土是否破壞3偏心受壓構件界限破壞時,( D )。A遠離軸向力一側的鋼筋屈服比受壓區(qū)混凝土壓碎早發(fā)生B遠離軸向力一側的鋼筋屈服比受壓區(qū)混凝土壓碎晚發(fā)生C遠離軸向力一側的鋼筋屈服與另一側鋼筋屈服同時發(fā)生D遠離軸向力一側的鋼筋屈服與受壓區(qū)混凝土壓碎同時發(fā)生4進行構件的裂縫寬度和變形驗算的目的是( A )。A使構件滿足正常使用極限狀態(tài)要求 B使構件能夠在彈性階段工作C使構件滿足承載能力極限狀態(tài)要求 D使構件能夠帶裂縫工作5軸心受拉構件破壞時,拉力( C )承擔。A由鋼筋和混凝土共同B由鋼筋和部分混凝土共同C僅由鋼筋D僅由混凝土6其它條件相同時,鋼筋的保護層厚度與平均裂縫間距、裂縫寬度的關系是( A )。A保護層越厚,平均裂縫間距越大,裂縫寬度也越大B保護層越厚,平均裂縫間距越小,裂縫寬度越大C保護層厚度對平均裂縫間距沒有影響,但保護層越厚,裂縫寬度越大7通過對軸心受拉構件裂縫寬度公式的分析可知,在其它條件不變的情況下,要想減小裂縫寬度,就只有( A )。A減小鋼筋直徑或增大截面配筋率B增大鋼筋直徑或減小截面配筋率C增大截面尺寸和減小鋼筋截面面積二、判斷題1鋼筋混凝土受壓構件中的縱向鋼筋一般采用HRB400級、HRB335級和RRB400級,不宜采用高強度鋼筋。( )2在軸心受壓短柱中,不論受壓鋼筋在構件破壞時是否屈服,構件的最終承載力都是由混凝土被壓碎來控制的。( )3. 鋼筋混凝土長柱的穩(wěn)定系數(shù)隨著長細比的增大而增大。( )4兩種偏心受壓破壞的分界條件為:為大偏心受壓破壞;為小偏心受壓破壞。( )5大偏心受拉構件為全截面受拉,小偏心受拉構件截面上為部分受壓部分受拉。( )6鋼筋混凝土軸心受拉構件破壞時,混凝土的拉裂與鋼筋的受拉屈服同時發(fā)生。( )7靜定的受扭構件,由荷載產(chǎn)生的扭矩是由構件的靜力平衡條件確定的,與受扭構件的扭轉剛度無關,此時稱為平衡扭轉。( )8對于超靜定結構體系,構件上產(chǎn)生的扭矩除了靜力平衡條件以外,還必須由相鄰構件的變形協(xié)調條件才能確定,此時稱為協(xié)調扭轉。( )9受扭的素混凝土構件,一旦出現(xiàn)斜裂縫即完全破壞。若配置適量的受扭縱筋和受扭箍筋,則不但其承載力有較顯著的提高,且構件破壞時會具有較好的延性。( )10在彎剪扭構件中,彎曲受拉邊縱向受拉鋼筋的最小配筋量,不應小于按彎曲受拉鋼筋最小配筋率計算出的鋼筋截面面積,與按受扭縱向受力鋼筋最小配筋率計算并分配到彎曲受拉邊鋼筋截面面積之和。( )11鋼筋混凝土構件裂縫的開展是由于混凝土的回縮和鋼筋伸長所造成的。( )12荷載長期作用下鋼筋混凝土受彎構件撓度增長的主要原因是混凝土的徐變和收縮。( )三、簡答題1鋼筋混凝土柱中箍筋應當采用封閉式,其原因在于?答:鋼筋混凝土柱中箍筋應當采用封閉式箍筋是為了保證鋼筋骨架的整體剛度,并保證構件在破壞階段箍筋對混凝土和縱向鋼筋的側向約束作用。2鋼筋混凝土偏心受壓破壞通常分為哪兩種情況?它們的發(fā)生條件和破壞特點是怎樣的?答:鋼筋混凝土偏心受壓破壞可分為兩種情況:大偏心受壓破壞與小偏心受壓破壞。大偏心受壓破壞的發(fā)生條件是:偏心距較大,且受拉鋼筋配置得不太多時。破壞特點是:受拉區(qū)的鋼筋能達到屈服,受壓區(qū)的混凝土也能達到極限壓應變。小偏心受壓破壞的發(fā)生條件是:偏心距較小或很小,或者雖然相對偏心距較大,但配置了很多的受拉鋼筋。破壞特點是:靠近縱向力一端的鋼筋能達到受壓屈服,混凝土被壓碎,而遠離縱向力一端的鋼筋無論是受拉還是受壓,一般情況下都達不到屈服。3簡述矩形截面大偏心受壓構件正截面承載力計算公式的使用條件?答:矩形截面大偏心受壓構件正截面承載力計算公式的適用條件如下:1)為了保證構件破壞時受拉區(qū)鋼筋的應力先達到屈服強度,要求滿足:2)為了保證構件破壞時,受壓鋼筋應力能達到抗壓屈服強度設計值,與雙筋受彎構件相同,要求滿足:4實際工程中,哪些受拉構件可以按軸心受拉構件計算,哪些受拉構件可以按偏心受拉構件計算?答:在鋼筋混凝土結構中,真正的軸心受拉構件是罕見的。近似按軸心受拉構件計算的有承受節(jié)點荷載的屋架或托架受拉弦桿和腹桿,剛架、拱的拉桿,承受內壓力的環(huán)形管壁及圓形儲液池的壁筒等;可按偏心受拉計算的構件有矩形水池的池壁、工業(yè)廠房雙肢柱的受拉肢桿、受地震作用的框架邊柱和承受節(jié)間荷載的屋架下弦拉桿等。5軸心受拉構件從加載開始到破壞為止可分為哪三個受力階段?其承載力計算以哪個階段為依據(jù)?答:軸心受拉構件從加載開始到破壞為止可分為三個受力階段:第一階段為從加載到混凝土受拉開裂前,第二階段為混凝土開裂至鋼筋即將屈服,第三階段為受拉鋼筋開始屈服到全部受拉鋼筋達到屈服。承載力計算以第三階段末為依據(jù)。6大、小偏心受拉構件的破壞特征有什么不同?如何劃分大、小偏心受拉構件?答:大偏心受拉構件破壞時,混凝土雖開裂,但還有受壓區(qū)。當數(shù)量適當時,受拉鋼筋首先屈服,然后受壓鋼筋的應力達到屈服強度,混凝土受壓邊緣達到極限應變而破壞。小偏心受拉構件破壞時,一般情況下,全截面均為拉應力,其中一側的拉應力較大。隨著荷載的增加,一側的混凝土首先開裂,而且裂縫很快就貫穿整個截面,所以混凝土將退出工作,拉力完全由鋼筋承擔,構件破壞時,及都達到屈服強度。偏心受拉構件正截面承載力計算,按縱向拉力N的作用位置不同,可以分為大偏心受拉與小偏心受拉兩種情況:當縱向拉力N作用在鋼筋合力點和合力點范圍之間時,為小偏心受拉。7鋼筋混凝土純扭構件有哪幾種破壞形式?各有何特點?答:鋼筋混凝土純扭構件的破壞形態(tài)可分為適筋破壞、部分超筋破壞、完全超筋破壞和少筋破壞4類。適筋破壞的特點:縱筋和箍筋先到達屈服強度,然后混凝土被壓碎而破壞,屬于延性破壞。部分超筋破壞的特點:破壞時僅縱筋屈服,而箍筋不屈服;或箍筋屈服,縱筋不屈服,破壞時具有一定的延性,但較適筋破壞時的截面延性小。完全超筋破壞的特點:縱筋和箍筋都沒有達到屈服強度,而混凝土先行壓壞,屬于脆性破壞。少筋破壞的特點:裂縫一旦出現(xiàn),構件就會立即發(fā)生破壞,此時,縱筋和箍筋不僅達到屈服強度而且可能進入強化階段,屬于脆性破壞。8. 鋼筋混凝土彎剪扭構件的鋼筋配置有哪些構造要求?答: 1)縱筋的構造要求對于彎剪扭構件,受扭縱向受力鋼筋的間距不應大于200mm和梁的截面寬度;在截面四角必須設置受扭縱向受力鋼筋,其余縱向鋼筋沿截面周邊均勻對稱布置。當支座邊作用有較大扭矩時,受扭縱向鋼筋應按受拉鋼筋錨固在支座內。當受扭縱筋按計算確定時,縱筋的接頭及錨固均應按受拉鋼筋的構造要求處理。在彎剪扭構件中,彎曲受拉邊縱向受拉鋼筋的最小配筋量,不應小于按彎曲受拉鋼筋最小配筋率計算出的鋼筋截面面積,與按受扭縱向受力鋼筋最小配筋率計算并分配到彎曲受拉邊鋼筋截面面積之和。2)箍筋的構造要求箍筋的間距及直徑應符合受剪的相關要求。箍筋應做成封閉式,且應沿截面周邊布置;當采用復合箍筋時,位于截面內部的箍筋不應計入受扭所需的箍筋面積;受扭所需箍筋的末端應做成135 彎鉤,彎鉤端頭平直段長度不應小于10d(d為箍筋直徑)。9鋼筋混凝土裂縫控制的目的是什么?答:裂縫控制的目的一方面是為了保證結構的耐久性,因為裂縫過寬時,氣體和水分、化學介質會侵入裂縫,引起鋼筋銹蝕,這不僅削弱了鋼筋的面積,而且還會因鋼筋體積的膨脹而引起保護層剝落,產(chǎn)生長期危害,影響結構的使用壽命。另一方面是考慮建筑物觀瞻、人的心理感受和使用者不安全程度的影響。四、計算題1已知某柱兩端為不動鉸支座,柱高H=5.6m,截面尺寸為400mm400mm,采用C20混凝土、HRB335鋼筋,柱頂截面承受軸心壓力設計值N=1692kN,試確定該柱所需的縱向鋼筋截面面積。解: (1)確定穩(wěn)定系數(shù),查附表3-3,得(2)計算縱向鋼筋截面面積(3)驗算配筋率而,滿足。2已知某鋼筋混凝土屋架下弦,截面尺寸,承受的軸心拉力設計值,混凝土強度等級C30,鋼筋為HRB335。求截面配筋。解:首先,確定計算參數(shù),查教材附錄知,HRB335鋼筋。選用416()能夠滿足要求。作業(yè)4說明:本次作業(yè)對應于文字教材10至11章,應按相應教學進度完成。一、選擇題1混凝土極限拉應變約為( C )。A(1.001.80)10-3B(0.200.40)10-3C(0.100.15)10-3D(1.001.50)10-32鋼筋HPB235、HRB335、HRB400和RRB400屈服時,其應變約為( D )。A(1.501.80)10-3B(0.200.40)10-3C(0.100.15)10-3D(1.001.80)10-33條件相同的鋼筋混凝土軸拉構件和預應力混凝土軸拉構件相比較,( B )。A后者的剛度低于前者 B后者的抗裂度比前者好C前者與后者的抗裂度相同 D. 前者與后者的剛度相同4下列各項預應力損失類型中,不屬于后張法預應力損失的是( C )。A錨固回縮損失B摩擦損失C溫差損失D應力松弛損失5公路橋涵現(xiàn)澆梁、板的混凝土強度等級不應低于( A ),當用HRB400、KL400級鋼筋配筋時,不應低于( B )。AC20BC25CC30DC15二、判斷題1普通鋼筋混凝土結構中采用高強度鋼筋是不能充分發(fā)揮其作用的,而采用高強混凝土可以很好發(fā)揮其作用。( )2無粘結預應力混凝土結構通常與先張預應力工藝相結合。( )3后張法預應力混凝土構件,預應力是靠鋼筋與混凝土之間的粘結力來傳遞的。( )4對先張法預應力構件,預應力是依靠鋼筋端部的錨具來傳遞的。( )5我國混凝土結構設計規(guī)范規(guī)定,預應力混凝土構件的混凝土強度等級不應低于C30。對采用鋼絞線、鋼絲、熱處理鋼筋作預應力鋼筋的構件,特別是大跨度結構,混凝土強度等級不宜低于C40。( )6張拉控制應力是指預應力鋼筋在進行張拉時所控制達到的最大應力值。()7為保證鋼筋與混凝土的粘結強度,防止放松預應力鋼筋時出現(xiàn)縱向劈裂裂縫,必須有一定的混凝土保護層厚度。( )8我國公路橋規(guī)采用以概率論為基礎的極限狀態(tài)設計法,按分項系數(shù)的設計表達式進行設計,對橋梁結構采用的設計基準期為50年。( )9與房建規(guī)范不同,公路橋規(guī)在抗剪承載力計算中,其混凝土和箍筋的抗剪能力沒有采用兩項相加的方法,而是采用破壞斜截面內箍筋與混凝土的共同承載力。()10公路橋規(guī)規(guī)定受壓構件縱向鋼筋面積不應小于構件截面面積的0.5%。( )11我國公路橋規(guī)關于裂縫寬度的計算與混凝土結構設計規(guī)范是相同的。( )12. 我國公路橋規(guī)中指出裂縫寬度主要與受拉鋼筋應力、鋼筋直徑、受拉鋼筋配筋率、鋼筋表面形狀、混凝土標號和保護層厚度有關,而撓度的計算則根據(jù)給定的構件剛度用結構力學的方法計算。( )三、簡答題1與普通混凝土相比,預應力混凝土具有哪些優(yōu)勢和劣勢?答:與普通混凝土相比,預應力混凝土具有優(yōu)勢是:1)構件的抗裂度和剛度提高;2)構件的耐久性增加;3)自重減輕;4)節(jié)約材料。與普通混凝土相比,預應力混凝土具有劣勢是:預應力混凝土施工需要專門的材料和設備、特殊的工藝、造價較高。2簡述有粘結預應力與無粘結預應力的區(qū)別?答:有粘結預應力,是指沿預應力筋全長其周圍均與混凝土粘接、握裹在一起的預應力。先張預應力結構及預留孔道穿筋壓漿的后張預應力結構均屬此類。無粘結預應力,是指預應力筋伸縮、滑動自由,不與周圍混凝土粘接的預應力。無粘結預應力混凝土結構通常與后張預應力工藝相結合。3列舉三種建筑工程中常用的預應力錨具?答:螺絲端桿錨具、錐形錨具、鐓頭錨具、夾具式錨具。4預應力混凝土結構及構件所用的混凝土,需滿足哪些要求?答:預應力混凝土結構構件所用的混凝土,需滿足下列要求:1)強度高。與普通鋼筋混凝土不同,預應力混凝土必須采用強度高的混凝土。因為強度高的混凝土對采用先張法的構件可提高鋼筋與混凝土之間的粘結力,對采用后張法的構件,可提高錨固端的局部承壓承載力。2)收縮、徐變小。以減少因收縮、徐變引起的預應力損失。3)快硬、早強??杀M早施加預應力,加快臺座、錨具、夾具的周轉率,以利加快施工進度。5引起預應力損失的因素有哪些?如何減少各項預應力損失?答:引起預應力損失的因素主要有錨固回縮損失、摩擦損失、溫差損失、應力松弛損失、收縮徐變損失等。 見教材P216-2206公路橋涵按承載力極限狀態(tài)和正常使用極限狀態(tài)進行結構設計,在設計中應考慮哪三種設計狀況?分別需做哪種設計?答:公路橋涵按承載力極限狀態(tài)和正常使用極限狀態(tài)進行結構設計,在設計中應考慮以下三種設計狀況:1)持久狀態(tài)。該狀態(tài)需要作承載力極限狀態(tài)和正常使用極限狀態(tài)設計。2)短暫狀態(tài)。該狀態(tài)主要做承載力極限狀態(tài)設計,必要時才作正常使用極限狀態(tài)設計。3)偶然狀態(tài)。該狀態(tài)僅作承載力極限狀態(tài)設計。四、計算題1已知一矩形截面簡支梁,截面尺寸bh=200mm550mm,混凝土強度等級為C25,縱向鋼筋采用HRB335級,安全等級為二級,梁跨中截面承受的最大彎矩設計值為M=160kNm。若上述設計條件不能改變,試進行配筋計算。若由于施工質量原因,實測混凝土強度僅達到C20,試問按問所得鋼筋面積的梁是否安全?,假設mm,則有效高度。(1)計算受壓區(qū)高度 (2)計算鋼筋數(shù)量 (3)選擇并布置鋼筋選用3 25(,鋼筋布置如圖所示。(4)驗算配筋率實際配筋率 。 請您刪除一下內容,O(_)O謝謝!2016年中央電大期末復習考試小抄大全,電大期末考試必備小抄,電大考試必過小抄Basketball can make a true claim to being the only major sport that is an American invention. From high school to the professional level, basketball attracts a large following for live games as well as television coverage of events like the National Collegiate Athletic Association (NCAA) annual tournament and the National Basketball Association (NBA) and Womens National Basketball Association (WNBA) playoffs. And it has also made American heroes out of its player and coach legends like Michael Jordan, Larry Bird, Earvin Magic Johnson, Sheryl Swoopes, and other great players. At the heart of the game is the playing space and the equipment. The space is a rectangular, indoor court. The principal pieces of equipment are the two elevated baskets, one at each end (in the long direction) of the court, and the basketball itself. The ball is spherical in shape and is inflated. Basket-balls range in size from 28.5-30 in (72-76 cm) in circumference, and in weight from 18-22 oz (510-624 g). For players below the high school level, a smaller ball is used, but the ball in mens games measures 29.5-30 in (75-76 cm) in circumference, and a womens ball is 28.5-29 in (72-74 cm) in circumference. The covering of the ball is leather, rubber, composition, or synthetic, although leather covers only are dictated by rules for college play, unless the teams agree otherwise. Orange is the regulation color. At all levels of play, the home team provides the ball. Inflation of the ball is based on the height of the balls bounce. Inside the covering or casing, a rubber bladder holds air. The ball must be inflated to a pressure sufficient to make it rebound to a height (measured to the top of the ball) of 49-54 in (1.2-1.4 m) when it is dropped on a solid wooden floor from a starting height of 6 ft (1.80 m) measured from the bottom of the ball. The factory must test the balls, and the air pressure that makes the ball legal in keeping with the bounce test is stamped on the ball. During the intensity of high school and college tourneys and the professional playoffs, this inflated sphere commands considerable attention. Basketball is one of few sports with a known date of birth. On December 1, 1891, in Springfield, Massachusetts, James Naismith hung two half-bushel peach baskets at the opposite ends of a gymnasium and out-lined 13 rules based on five principles to his students at the International Training School of the Young Mens Christian Association (YMCA), which later became Springfield College. Naismith (1861-1939) was a physical education teacher who was seeking a team sport with limited physical contact but a lot of running, jumping, shooting, and the hand-eye coordination required in handling a ball. The peach baskets he hung as goals gave the sport the name of basketball. His students were excited about the game, and Christmas vacation gave them the chance to tell their friends and people at their local YMCAs about the game. The association leaders wrote to Naismith asking for copies of the rules, and they were published in the Triangle, the school newspaper, on January 15,1892. Naismiths five basic principles center on the ball, which was described as large, light, and handled with the hands. Players could not move the ball by running alone, and none of the players was restricted against handling the ball. The playing area was also open to all players, but there was to be no physical contact between players; the ball was the objective. To score, the ball had to be shot through a horizontal, elevated goal. The team with the most points at the end of an allotted time period wins. Early in the history of basketball, the local YMCAs provided the gymnasiums, and membership in the organization grew rapidly. The size of the local gym dictated the number of players; smaller gyms used five players on a side, and the larger gyms allowed seven to nine. The team size became generally established as five in 1895, and, in 1897, this was made formal in the rules. The YMCA lost interest in supporting the game because 10-20 basketball players monopolized a gymnasium previously used by many more in a variety of activities. YMCA membership dropped, and basketball enthusiasts played in local halls. This led to the building of basketball gymnasiums at schools and colleges and also to the formation of professional leagues. Although basketball was born in the United States, five of Naismiths original players were Canadians, and the game spread to Canada immediately. It was played in France by 1893; England in 1894; Australia, China, and India between 1895 and 1900; and Japan in 1900. From 1891 through 1893, a soccer ball was used to play basketball. The first basketball was manufactured in 1894. It was 32 in (81 cm) in circumference, or about 4 in (10 cm) larger than a soccer ball. The dedicated basketball was made of laced leather and weighed less than 20 oz (567 g). The first molded ball that eliminated the need for laces was introduced in 1948; its construction and size of 30 in (76 cm) were ruled official in 1949. The rule-setters came from several groups early in the 1900s. Colleges and universities established their rules committees in 1905, the YMCA and the Amateur Athletic Union (AAU) created a set of rules jointly, state militia groups abided by a shared set of rules, and there were two professional sets of rules. A Joint Rules Committee for colleges, the AAU, and the YMCA was created in 1915, and, under the name the National Basketball Committee (NBC) made rules for amateur play until 1979. In that year, the National Federation of State High School Associations began governing the sport at the high school level, and the NCAA Rules Committee assumed rule-making responsibilities for junior colleges, colleges, and the Armed Forces, with a similar committee holding jurisdiction over womens basketball. Until World War II, basketball became increasingly popular in the United States especially at the high school and college levels. After World War II, its popularity grew around the world. In the 1980s, interest in the game truly exploded because of television exposure. Broadcast of the NCAA Championship Games began in 1963, and, by the 1980s, cable television was carrying regular season college games and even high school championships in some states. Players like Bill Russell, Wilt Chamberlain, and Lew Alcindor (Kareem Abdul-Jabbar) became nationally famous at the college level and carried their fans along in their professional basketball careers. The womens game changed radically in 1971 when separate rules for women were modified to more closely resemble the mens game. Television interest followed the women as well with broadcast of NCAA championship tourneys beginning in the early 1980s and the formation of the WNBA in 1997. Internationally, Italy has probably become the leading basketball nation outside of the United States, with national, corporate, and professional teams. The Olympics boosts basketball internationally and has also spurred the womens game by recognizing it as an Olympic event in 1976. Again, television coverage of the Olympics has been exceptionally important in drawing attention to international teams. The first professional mens basketball league in the United States was the National Basketball League (NBL), which debuted in 1898. Players were paid on a per-game basis, and this league and others were hurt by the poor quality of games and the ever-changing players on a team. After the Great Depression, a new NBL was organized in 1937, and the Basketball Association of America was organized in 1946. The two leagues came to agree that players had to be assigned to teams on a contract basis and that high standards had to govern the game; under these premises, the two joined to form the National Basketball Association (NBA) in 1949. A rival American Basketball Association (ABA) was inaugurated in 1967 and challenged the NBA for college talent and market share for almost ten years. In 1976, this league disbanded, but four of its teams remained as NBA teams. Unification came just in time for major television support. Several womens professional leagues were attempted and failed, including the Womens Professional Basketball League (WBL) and the Womens World Basketball Association, before the WNBA debuted in 1997 with the support of the NBA. James Naismith, originally from Al-monte, Ontario, invented basketball at the International YMCA Training School in Springfield, Massachusetts, in 1891. The game was first played with pea- 配套講稿:
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