混泥土結(jié)構(gòu)(第四版)第五章答案

1、第5章受壓構(gòu)件的截面承載力已知某多層四跨現(xiàn)澆框架結(jié)構(gòu)的第二層內(nèi)柱，軸心壓力設(shè)計(jì)值N1100kN,樓層高H6m,混凝土強(qiáng)度等級(jí)為C20,采用H級(jí)鋼筋(HRB335ffi筋)。柱截面尺寸為350mm350mm,求所需縱筋面積。解：根據(jù)混凝土結(jié)構(gòu)設(shè)計(jì)規(guī)范規(guī)定：l01.25H1.2567.5m則：r端021.43查表61得:0.714由N0.9fcAfyAs得:fy0.9fcA30031100109.63500.90.71423501786mm選取42521964mmAsA1.6%350350min0.6%,可以截面每一側(cè)配筋率：0.2% ,可以19640.5TZTTZT0.8%min350350已知

2、圓形截面現(xiàn)澆鋼筋混凝土柱,直徑不超過350mm,承受軸心壓力設(shè)計(jì)值N1900kN,計(jì)算長(zhǎng)度I。4m,混凝土強(qiáng)度等級(jí)為C25,柱中縱筋采用HRB400鋼筋，箍筋用I級(jí)鋼筋。試設(shè)計(jì)該柱截面。解：柱子直徑取為350mm(1)先按普通縱筋和箍筋柱計(jì)算104ml0d400035011.43,查表得:0.9311 Nf 0.9y12122A-d2-35mm244由N0.9fcAfyAs得：,119000002fcA11.996162.53120mm3600.90.931-3.2%A96162.5選取822As3041mm2(2)按采用螺旋箍筋柱計(jì)算，假定3%得：As2A2885m

3、m選取6125As22945mm混凝土的保護(hù)層取30mm,則:dcor30235060290mmd2dcor66018.5mm20.9fcAcor2fyAssofyAs混凝土強(qiáng)度等級(jí)為C25,1.0A-N0.9fcAcorfyAs2fy19000000.911.966018.53602368mm其中：AssodcorAss1取螺旋箍筋直徑2d10mm,則Assi78.5mmdA-corss1sAsso3.1429078.5194mm368取s50mm,以滿足不小于40mm,并不大于80mm及0.2dcor的要求。所以：柱中縱筋選取625,As22945mm箍筋采用螺旋箍筋,s50mm,d10m

4、m驗(yàn)算：AssodcorAss13.1429078.521429.6mm50Asso0.25As20.252945736.25mm2,可以N0.9fcAcor2fyAssofyAs0.911.966018.521.03601429.636029452587.6kNN 0.9fcAfy As0.9 0.93111.9 96162.5 360 30411876.1kN1.5 1876.1kN 2814.2kN2587.6kN所以該柱的軸心受壓承載力設(shè)計(jì)值為2587.6kN 1900kN ,故滿足要求。已知柱的軸向力設(shè)計(jì)值N 800kN ,彎矩M 160kNm ；截面尺寸b 300mm ,h 500

5、mm, as as45mm ;混凝土強(qiáng)度等級(jí)為C30,采用HRB400級(jí)車岡筋;計(jì)算長(zhǎng)度l0 3.5m 0求鋼筋截面面積As 及 As。解：e0M160 1033N800 100.2m 200mm20mm , h0as 455mme0ea20020 220mmfcA0.5 c 0.514.3 300 5008001031.341,ei3.50.515,取1.01400ei/h0 h11400 220455235001 1 1.075001.07 220 235.4mm0.3h0136.5mm可以按大偏心受壓計(jì)算:he ei-asi2 s235.4 等 45440.4mmNe 1 fcbx h0

6、fy As hoas,取b 0.5182Nefcbhcb10.5bfyhgas800103440.41.014.330045520.51810.50.51836045545rr 277mm minbh-20.002 300 500 300mm取As300mm21 fcbx fy AsfyAsAs1fcb bh0 NfyAsfy3601.014.33000.5184558001033002886mm受拉鋼筋選用2 25, As2982mm ；受壓鋼筋選用 2 16, As2402mm。N fy AsfyAsx 1 fcb800 103 360 402 360 982 ” 235mm1.0 14.

7、3300x 2350.517h04550.518故假定為大偏心受壓是正確的。 垂直于彎矩作用平面的驗(yàn)算：I03535 11.67,查表得0.30.955Nu0.9fcAfyAsfyAs0.9 0.955 14.3300500 360 402360 9822271864 N 800103 N滿足要求。已知柱的軸向力設(shè)計(jì)值N 550kN ,彎矩 M450kN m ;截面尺寸 b 300mm ,h600mm,aa45mm；混凝土強(qiáng)度等級(jí)為C35,采用in級(jí)鋼筋；計(jì)算長(zhǎng)度I。7.2m 0求鋼筋截面面積As及As。幗e0M45U030.818m818mme20mm,h0ha555mm81820838mm

8、fcA0.5c-N0.516.73006005501032.7311.0l0h7.20.612151.01400ei/h02l0h1838140055572001.068838895mm0.3h0166.5mm600111.068可以按大偏心受壓計(jì)算:Nehei21 fcbxh。89560045 1150mmfyAs h0b 0.518Ne1 fcbh： b0.5 bfyh0as550 1 03 1150 1.0 1 6.7 30025552 0.5181 0.5 0.518360555452263mm min bh0.2% 300 600 360mm2取As2360mm1 fcbx fy A

9、sfyAsAs1fcbbh0N受拉鋼筋選用232+228,As22841mm；受壓鋼筋選用216,As2402mm。N fy AsfyAs1 fcb550103fy1.0 16.7 300 0.518 555 550 1032360 2833mm4023602841237.5mm1.016.7360b 0.518x237.5八0.428h0555故假定為大偏心受壓是正確的。垂直于彎矩作用平面的驗(yàn)算：b 0.4l0b72-7224,查表得0.30.65Nu0.9fcAfyAsfyAs0.90.6516.730060036040236028413170kN,彎矩 M 83.6kN45mm ;混凝土

10、強(qiáng)度等級(jí)為m；截面尺寸 C35,采用田32441485.8N55010N滿足要求。已知荷載作用下柱的軸向力設(shè)計(jì)值b400mm,h600mm,a級(jí)鋼筋；計(jì)算長(zhǎng)度106.0m0求鋼筋截面面積As及As。解：e00.0264 m 26.4 mm3M83.610N317010320mm,h。555mmeie0ea26.42046.4mmfcA0.5c-N0.516.740060031701030.632l0h6.00.61015,1.01400e/h01.46.41400-555260000.63260011.544ei1.54446.471.4mm0.3h0166.5mm初步判定為小偏心受壓。0.8

11、,b0.518minbh_一20.002400600480mmfyhe-eia30071.445183.6mm2heeia71.430045326.4mm2Neifcbx-asAha,23X317010183.61.016.7400x4520.80.5180.8360解得x461mmxNe1fcbxh02fyAsh0aNe1fcbxh00.5xfyh0a46155523_317010326.41.016.7400461e。ea1fcbhh0fyh0as31701033004526.4201.016.740060055530036055545負(fù)數(shù)不會(huì)發(fā)生反向破壞。受拉鋼筋選用218,As509m

12、m360 555 452192 mm min bh 480mm為了防止反向破壞，對(duì)As進(jìn)行驗(yàn)算。；受壓鋼筋選用218,As509mm2。由N1fcbxfyAssAs和sLfyb1得x444mmbh00.518555287.5mm所以按小偏心受壓計(jì)算是正確的。驗(yàn)算垂直于彎矩作用方向的承載力：l06015,查表得0.895Nu0.9fcAfyAsfyAs0.90.89516.740060036050936050933523643.64N317010N滿足要求。已知軸向力設(shè)計(jì)值N7500kN,彎矩M1800kNm；截面尺寸b800mm,h1000mm,aa45mm；混凝土強(qiáng)度等級(jí)為C30,采用II級(jí)

13、鋼筋；計(jì)算長(zhǎng)度I。6m,采用對(duì)稱配筋（AsAs）;求鋼筋截面面積AsAs。解：N1fcbxfyAsfyAsN 1fcb37500 101.0 14.3 800655.6mm xbbh0 525.25mm按小偏心受壓計(jì)算。e0M 1800 0.24m 240mmN100075003033mm,h0 h as 955mme0ea24033 273mml0hCL fcA 0.5 N6000 人610000.514.3 800 10007500 1030.763ei15 ，取1400e /h01.068 273292mmei2按簡(jiǎn)化方法計(jì)算:292 5000.81.012731400 9550.3h0

14、286.5mm45 747mm2600010000.763 1 1.06837500 103 0.55 1 14.3 800 955327500 10 747 0.43 1 14.3 800 9550.8 0.55955 451 14.3 800 9550.55Ne0.43ifcbho0.8bhoa1.0 9.6 40033100 101.0 9.6 400x 360所以 x 610.5mm h取x h 600mm進(jìn)行計(jì)算。x1 fcbx h0fy As h0 ;2e N1.0 9.6 400 600 555 30033100 1019643600.8555-555 360 6030.518

15、0.81964555 450.645xh00.645955616mmNe1fcbh(210.5；Asfy%a_3_2_750010747114.3800955064510.50.645305.8mme-a305.86004550.8mm22取1.0則向50.8mme0eiea50.82030.8mmMuNe0 310010330.8 95.48kN m M 85kN m經(jīng)計(jì)算1.35與假定的1.0相矛盾重新選取1.4,則ei36.3mme0eiea36.32016.3mmM u Ne033100 1016.3 50.53kN m經(jīng)過計(jì)算1.4,可以。因MuM85kNm,故截面不安全。已知某單層

16、工業(yè)廠房的形截面邊柱，下柱高5.7m,柱截面控制內(nèi)力N870kN,M420kNm;截面尺寸b80mm,h700mm,bfbf350mm,hfhf112mm,aa45mm;混豌土強(qiáng)度等級(jí)為C35,采用HRB400鋼筋；對(duì)稱配筋。求鋼筋截面面積。解：e0420 1033870 100.483m 483mm7003023mm , h0h a 655mmeie0ea48323506mmCL 0.50.516.7 1164803870 101.17 1 ,取 11.0l01.0H5.7ml05700c.，8.14h7001400ei/h0l0h1c5061400-655570070021.01.01.06先按大偏心受壓計(jì)算。8701031fcbf1.0 16.7350149mm hf此時(shí)中和軸在腹板內(nèi)N 1 fchf bf b8703101.0 16.7 112350 801%b1.016.780273mm xb 0.55 655360mm按大偏心受壓公式計(jì)算鋼筋。ei1.06 506536mmheei2841mm由 Ne 1fc cbxbfb hfhffy Ash0 aNe1fcbxbf bhfhehffyha112112 655 23273870108411.016.780273655350802300655452109