1、固端弯矩计算将框架梁视为两端固定梁计算固端弯矩,计算结果见表315表315 固端弯矩计算 AB跨BC跨简图固端弯矩M0MJ(KN/m)简图固端弯矩MJ=MK(KN/m)23.69KN/m23.696.6284.5421.84KN/m21.842.4210.4832.94KN/m32.946.62119.5716.98KN/m16.982.428.155.4KN/m 5.46.6219.605.4KN/m5.42.422.597.2KN/m7.26.6226.147.2KN/m7.22.423.46分配系数计算考虑框架对称性,取半框架计算,半框架的梁柱线刚度如下图3-10所示。切断的横梁线刚度为
2、原来的一倍,分配系数按与节点连接的各杆的转动刚度比值计算。例:A柱顶层节点:下柱=0.537梁=0.463其他节点的分配系数图见图311及图312。传递系数: 远端固定,传递系数为 远端滑动铰质,传递系数为1。弯矩分配:恒载作用下,框架的弯矩分配计算见图311,框架的弯矩见图313;活载作用下,框架的弯矩分配计算见图312,框架的弯矩见图314。在竖向荷载作用下,考虑框架梁端的塑性内力分布,取弯矩调幅系数为0.8,调幅后,恒载及活载弯矩图见恒载作用下框架弯矩图及活载用框架弯矩图括号内数值。梁端剪力及柱轴力计算梁端剪力 V=VqVm式中:Vq梁上均布荷载引起的剪力,Vqql;Vm梁端弯矩引起的剪
3、力,Vm 柱轴力 N=V+P式中:V梁端剪力; P节点集中力及柱自重。图311 恒载弯矩分配图 (KN/m)以AB跨六、七层梁在恒载作用下,梁端剪力及柱轴力计算为例。由图3-9,查得梁上均布荷载为:第六层:q32.94 KN/m集中荷载:98.32 KN柱自重: 26.24KN第七层:q23.29 KN/m由图3-13,查得:六层梁端弯矩: ML= 103.64(82.91) KNm Mr = 108.23(86.58) KNm七层梁端弯矩: ML=60.76(48.61) KNm Mr =72.41(57.93) KNm括号内为调幅后得数值续图311 活载弯矩分配图 (KN/m)七层梁端剪力
4、 VqDVqJql23.296.676.86 KN调幅前: VmDVmJ=-1.77 KNVDVqDVmD76.861.7775.09 KNVJVqJVmJ76.861.7778.63 KN调幅后: VmDVmJ=1.41 KN VDVqDVmD76.861.4175.45 KN VJVqJVmJ76.861.41=78.27 KN 图312 活载弯矩分配图 (KN/m)同理第六层梁端剪力:调幅前: VD32.946.6108.01 KN VJ32.946.6109.40 KN调幅后: VD32.946.6+108.14 KN VJ32.946.6109.26KN第七层A柱柱顶及柱底轴力:N顶
5、VP73.45075.45 KNN底75.4526.24102.69 KN第六层A柱柱顶及柱底轴力N顶75.45108.1498.32281.91 KNN底281.9126.24=308.15 KN其它梁端剪力及柱轴力计算见表16,活载作用下梁端剪力及柱轴力见表表3-16恒载作用下梁端剪力及柱轴力(KN)层 数荷载引起剪力弯矩引起剪力总剪力柱轴力AB跨BC跨AB跨BC跨AB跨BC跨A柱B柱VqAVqBVqAVqBVmAVmBVmBVmC VmAVmBVAVBVBVCN顶N底N顶N底776.8626.21-1.77(-1.41)075.0(75.45)78.63(78.27)26.2175.45
6、102.69104.48130.726108.7020.38-0.70(-0.56)0108.00(108.1)109.40(109.26)20.38281.91308.15332.44358.685108.720.38-0.88(-0.70)0107.82(108.0)109.58(109.40)20.38488.23514.47560.54586.784108.7020.38-0.86(-0.69)0107.84(108.0)109.56(109.39)20.38694.56720.8788.63814.873108.7020.38-0.87(-0.70)0107.83(108.0)109
7、.57(109.4)20.38900.88927.121016.731042.972108.7020.38-0.75(-0.60)0107.95(108.1)109.45(109.3)20.381107.31133.541244.731270.971108.7020.38-0.95(-0.76)0107.75(107.9)109.65(109.46)20.381317.471352.831476.81512.06注:括号内为调幅后的剪力值。表3-17活荷载作用下梁端剪力及柱轴力(KN) 层 数荷载引起剪力弯矩引起剪力总剪力柱轴力AB跨BC跨AB跨BC跨AB跨BC跨A柱B柱VqAVqBVqAVq
8、BVmAVmBVmAVmCVAVBVAVBN顶N底N顶N底717.826.48-0.40(-0.32)017.42(17.5)18.22(18.14)6.4817.524.7623.768.64-4.56(-1.17)023.52(17.5)24(23.95)8.6441.0757.34523.768.64-1.49(-1.20)023.5(23.55)24.02(23.97)8.6464.6290423.768.64-1.33(-1.08)023.5(23.55)24.02(23.97)8.6488.17122.66323.768.64-1.19(-1.00)023.5(23.55)24.0
9、2(23.97)8.64111.72155.32223.768.64-1.28(-1.02)023.69(23.7)23.83(23.82)8.64135.42187.79123.768.64-0.87(-0.70)022.7(22.92)24.82(24.6)8.64158.34221.25注:括号内为调幅后的剪力值。3.2.6 内力组合(1) 框架梁内力组合在恒载和活载作用下,跨间Mvmax可近似取跨中的M代表。 Mvmaxql2 式中:M左、M右梁左、右端弯矩,见图13、14括号内的数值。跨中M若小于 ql2,应取M ql2。在竖向荷载与地震力组合时,跨间最大弯矩MGE采用数值法计算,如
10、图3-15所示。图中 MGA、MGB重力荷载作用下梁端的弯矩;MGA、MEB水平地震作用下梁端弯矩;RA、RB竖向荷载与地震荷载共同作用下梁端反力。对RB作用点取矩: RA(MGBMGAMEAMEB)x处截面弯矩为:MRAxMGAMEA 由0,可求得跨间Mmax的位置为x1 将x1代入任一截面x处的弯矩表达式,可是跨间最大弯矩为:MmaxMGEMGAMEAMGAMEA当右震时,公式中的MEA、MEB反号。MEA及x1的具体数值见表18,表中RA、x1 、MGE均有两组数值。梁内力组合见表19。表中恒载和活载的组合,梁端弯矩取调幅后的数值(图13、14括号中数值),剪力取调幅前后的较大值,如图1
11、6所示,图中M左、M右为调幅前弯矩值。M左、M右为调幅后弯矩值。剪力值应取V左、V右,具体见表3-16、表3-17。表3-18 MGE及X值计算 1.2(恒0.5活)1.3地震qKN/mMGA(KNm)MGB(KNm)MEA(KNm)MEB(KNm)AB跨765.2677.7244.6233.0231.196110.69115.8688.3770.5943.855109.04115.43120.7799.454109.14115.39158.08131.563109.00115.32173.75139.752110.94115.48199.49161.331100.78110.12218.73
12、190.19BC跨724.2224.2226.1826.1829.45620.0520.0556.1756.1724.70520.2320.2379.0779.07420.3420.34104.62104.62320.3820.38111.15111.15220.1720.17128.25.128.25.124.1124.11151.26151.26项目层次跨L(m)RA(KN)x1(m)MGE(KNm)AB跨76.689.28/112.802.86/3.62106.92/94.486119.84/168.012.73/3.83141.08/122.565110.37/177.102.52/4
13、.04150.96/128.04499.87/187.642.28/4.28162.91/134.41398.25/191.252.19/4.36169.26/134.04289.35/198.692.04/4.53179.79/139.49181.33/205.251.85/4.68192.99/160.70BC跨72.413.52/57.160.46/1.305.08/-25.516-36.25/95.53-1.47/3.8736.12/36.125-57.54/116.82-2.33/4.7358.84/58.844-62.99/122.27-2.55/4.9584.28/84.283-
14、63.39/125.60-2.57/5.0890.77/90.772-77.24/136.52-3.13/5.53108.08/108.081-96.41/155.69-3.90/6.30127.15/127.15注:当x1l或x120计算截面以上各楼层活荷载总和的折减系数1.00(0.9)0.850.700.650.600.55表3-20 A柱内力组合表 层次位置内力荷载类型竖向荷载组合竖向荷载与地震力组合恒载活载地震荷载1.21.41.2(0.5)1.37柱顶M60.7614.7334.3293.1136.95126.19N75.4517.59.04115.0489.29112.79柱底M
15、-54.21-12.0218.48-81.88-48.24-96.29N102.6917.59.04147.73121.98145.486柱顶M49.4311.3149.575.151.75130.45N281.9141.0727.56395.79327.11398.76柱底M-50.86-11.5633-77.22-25.07-110.87N308.1541.0727.56427.28358.59430.255柱顶M51.1811.5659.977.6-9.52146.22V488.2364.6253.23676.34555.45693.85柱底M-51.06-11.5649-77.46-4
16、.51-131.91N514.4764.6253.23707.83586.94725.344柱顶M51.0611.5672.677.46-26.17162.59N694.5688.1786.99956.91773.29999.46柱底M-51.22-11.5659.4-77.658.82-145.62N720.8088.1786.99988.40804.781030.953柱顶M50.7611.5674.2577.10-28.68164.37N900.88111.72123.531237.46987.501308.68柱底M-48.72-11.3674.25-74.3731.25-161.81
17、N927.12111.72123.531268.951018.991340.172柱顶M55.1911.9479.2082.94-29.57176.35N1107.3135.42165.581518.351194.761625.27柱底M-63.26-11.7179.20-92.3120.02-185.90N 1133.54135.42165.581549.841226.251656.751柱顶M33.424.8689.0546.91-72.75158.79N1317.47158.34213.241802.641398.761953.18柱底M-16.71-2.43158.30-23.4518
18、4.28-227.3N1352.83158.34213.241845.071441.191995.61注:表中弯矩单位为KNm,轴力单位为KN。3.2.7 截面设计(1) 承载力抗力调整系数RE考虑地震作用时,结构构件的截面设计采用下面的表达式:S式中:RE承载力抗震调整系数,取值见表23;S地震作用效应或地震作用效应与其它荷载效应的基本组合; R结构构件的承载力。表3-21 B柱内力组合表层次位置内力荷载类型竖向荷载组合竖向荷载与地震力组合恒载活载地震荷载1.21.41.2(0.5)1.37柱顶M-49.88-11.745.54-76.24-126.08-7.67N104.4824.77.7
19、4159.96130.13150.26柱底M46.199.8630.3669.23100.8121.88N130.7224.77.74191.44161.62181.756柱顶M-43.88-9.5467.15-66.01-145.6828.92N332.4457.3425.23479.20400.53466.13柱底M44.659.6454.9567.08130.80-12.07N358.6857.3425.23510.69432.02497.625柱顶M-44.91-9.6482.37-67.39-167.1547.41V560.549050.24798.65661.34791.96柱底M
20、44.699.6476.0367.12158.25-39.43N586.789050.24830.14692.82823.454柱顶M-44.69-9.64105.65-67.12-196.7677.93N788.63122.6683.551118.08911.341128.57柱底M44.789.6485.7567.23170.99-51.96N814.87122.6683.551149.57942.831160.063柱顶M-44.48-9.64107.25-66.87-198.5980.27N1016.73155.32118.261437.521159.531467.01柱底M42.98
21、11.98107.2568.35198.19-80.66N1042.97155.32118.261469.011191.021498.532柱顶M-48.05-4.50115.50-63.96-210.5189.79N1244.73187.79158.421756.581400.401812.30柱底M54.7211.73115.5082.09222.85-77.45N 1270.97187.79158.421788.01431.891843.781柱顶M-27.25-5.54147.15-40.46-227.32155.27N1476.8221.25207.722081.911634.872
22、174.95柱底M13.632.77211.7520.23293.29-257.26N1512.06221.25207.722124.221677.192217.26注:表中弯矩单位为KNm,轴力单位为KN。注意:在截面配筋时,组合表中与地震力组合的内力均应乘以RE后再与静力组合的内力进行比较,挑选出最不利内力。 表3-23 承载力抗震调整系数RE 材料结构构件受力状态RE钢筋混凝土梁受弯0.75轴压比小于0.15的柱偏压0.75轴压比大于0.15的柱偏压0.80抗震墙偏压0.85各类构件受剪、偏拉0.85(2)横向框架梁截面设计以第一层梁为例,梁控制截面的内力如图17所示。图中M单位为KNm
23、,V的单位为KN。图3-17 第一层梁内力示意 混凝土强度等级为C25(fcm13.5N/mm2,fc12.5N/mm2),纵筋为级(fy310 N/mm2),箍筋为级(fy210 N/mm2)。梁的正截面强度计算(见表24);梁的斜截面强度计算; 为了防止梁的弯曲屈服前先发生剪力破坏,截面设计时,对剪力设计值进行如下调整:(MbMbr)/LnVGb式中:剪力增大系数,对三级框架取1.0; Ln梁的净跨,对第一层梁LnAB6.1m,LnBC1.9m; VGb梁在重力荷载作用下,按简支梁分析的梁端截面剪力设计值。 VGb1.2(q恒0.5q活)LnMb、Mbr分别为梁的左右端顺时针方向或逆时针方
24、向截面组合的弯矩值。由表19得:AB跨:顺时针方向 Mb117.95 KNm ; Mbr-300.31 KNm逆时针方向 Mb319.50 KNm ;Mbr80.07KNmBC跨:顺时针方向 Mb127.15 KNm ; Mbr175.36KNm 逆时针方向 Mb127.15 KNm;Mbr175.36 KNm计算中MbMbr取顺时针方向荷逆时针方向中较大者。 剪力调整:AB跨:MbMbr117.95300.31=418.26 KNm 319.50+80.07=399.57 KNm VGb(32.94+0.57.2)1.26.1133.74 KNBC跨: MbMbr127.15175.36=3
25、02.51KNm VGb(16.980.57.2)1.21.923.46 KNm VA右VB左133.74205.74 KN VB右23.46190.66KN 考虑承载力抗震系数 RE0.85 RE VD右RE VJ左0.85205.74174.88 KN RE VJ右0.85190.66162.06 KN调整后的剪力值大于组合表中的静力组合剪力值,故按调整后的剪力值进行斜截面计算。 斜截面计算见表3-25表3-25 梁的斜截面强度计算 截面支座A右支座B左支座B右设计剪力V(KN)205.01208.30127.15RE V(KN)174.26177.06108.08调整后V(KN)205.
26、74205.74190.66RE V(KN)174.88174.88162.06bh0(mm)2505652505652505650.2fcbh0(KN)353.13V353.13V353.13V箍筋直径(mm)肢数(n)n2,8n2,8n2,8AsV1(mm)50.350.350.3箍筋间距S(mm)10010080Vcs0.056 fcbh0+1.2fyvh0242.11RE V242.11RE V179.54RE V ()0.4020.4020.503svmin0.03()0.1790.1790.179根据国内对低周反复荷载作用下钢筋混凝土连续梁荷悬臂梁受剪承载力试验,反复加载使梁的受剪
27、承载力降低,考虑地震作用的反复性,表中公式将静力荷载作用下梁的受剪承载力公式乘以0.8的降低系数。(3) 柱截面设计以第一、二层B柱为例,对图18中的-、-、-截面进行设计。混凝土为C25,fc12.5N/mm2,fcm=13.5 N/mm2,纵筋为级fy310 N/mm2,箍筋为级。轴压比验算表3-25 轴压比限值 类型抗震等级一二三框架柱0.70.80.9框支柱0.60.70.8由B柱内力组合表21查得: N-1=1843.78 KNc 0.590.9N-2174.95 KNc0.6960.9N-2217.26 KNc0.7090.9均满足轴压比限值得要求。正截面承载力得计算框架结构得变形
28、能力与框架得破坏机制密切相关,一般框架,梁的延性远大于柱子,梁先屈服可使整个框架由较大的内力重分布和能量消耗能力,极限层间位移增大,抗震性能较好。若柱形成了塑性铰,则会伴随产生极大的层间位移,危及结构承受垂直荷载的能力并可能使结构成为机动体系。因此,在框架设计中,应体现“强柱弱梁”三级框架:1.1 式中:节点下柱端顺时针或反时针截面组合底弯矩设计值之和; 节点左、右梁端反时针或顺时针方向截面组合底弯矩设计值之和。地震往复作用,两个方向的弯矩设计值均应满足要求,当柱子考虑顺时针弯矩之和时,梁应考虑反时针方向弯矩之和,反之亦然。若采用对称配筋,可取用两组中较大者计算配筋。由于框架结构的底层柱过早出
29、现塑性屈服,将影响整个结构的变形能力。同时,随着框架梁铰的出现,由于塑性内力重分布,底层柱的反弯点具有较大的不确定性。因此,对一、二、三级框架抗震规范规定:其底层柱下端截面的弯矩设计值,应乘以增大系数1.5。第一层梁与B柱节点的梁端弯矩值由美丽组合表19查得。:左震 300.31+127.15427.46 KNm 右震 80.07+175.36255.43 KNm 取427.46 KNm第一层梁与B柱节点得柱端弯矩值由内力组合表21查得。:左震 222.85+227.32=450.17 KNm 右震77.45+155.27232.72 KNm梁端取左震,也应取左震: 450.17 KNm1.11.1427.46=470.21 KNm 取470.21 KNm将与得差值按柱得弹性分析弯矩值之比分配给节点上下柱端(即