第六章截面设计6.1框架梁以第一层AB框架梁的计算为例，说明计算方法和步骤。6.1.1梁的最不利内力组合根据第五章的计算，梁的最不利内力如下：跨间：Mmax=54.80KN m支座 A: Mmax=-234.6KN m支座 B: Mmax=-184.56KN mV=96.83KN (调整后)6.1.2梁的正截面受弯承载力计算抗震设计中，对于楼面现浇的框架结构，梁支座负弯矩按矩形截面计 算纵筋数量，跨中正弯矩按T形截面计算纵筋数量。跨中截面的计算弯矩， 应取该跨的跨间最大弯矩或支座弯矩与1/2简支梁弯矩之中的较大者，依据上述理论，得：(1) 考虑跨间最大弯矩处按T形截面设计，翼缘计算宽度 气按跨度考虑，b尸/3=2000mm ；按 翼缘厚度考虑时，b =b=300mm。所以b可取2000mm。h =100mm。fff办公楼属一类环境，梁保护层厚度 c=20mm，a = M =54.80 x 106=0 006s a fb h2 一1.0x 14.3 x 2000 x 5602 =.1 c f 054.80 x106Y = 0.5(1 + J1 - 2a )=0.5 X( 1+0.994 ) =0.997=327.17mm 2Y fh0 0.997 x 300 x 560实配钢筋2A =402mm 2。402P =300 x 600=0.2214 3,，一一 .x143 = 2%，满足要求。300 P mi=0.45 f / f =0.45 X 1.43/300=0.215 % ,且 t yp va= = 1.0 x 0.576梁端截面受压区相对高度：& = fyAs =300 x 402=0.075 V & b =0.576a fb h 1.0 x 14.3 x 200 x 5601 c f 0满足抗震设计要求。(2) 考虑两支座处A支座负弯矩比较大，可将下部跨间截面的 2 16钢筋伸入支座， 作为支座负弯矩作用下的受压钢筋， A；=402mm2，再计算相应的受拉钢筋 A，B支座负弯矩较小，可不必伸入。1)支座A上部：1x14 3 x 300 x 5602M ff A (h a) 234.6 x106 300 x 402 x(560 40) s0=0.127实配钢筋：422, A=1520mm2。1520=0.84 % Pmi=0.45 f / f =0.45 X 1.43/300=0.215 % ,且t yP =300 x 600pa& f = 1.0 x 0.576 x143 = 2%，满足要求。1 b f300y2)支座B上部：Ma =s a f b h21 c f 0184.56 x106=0.1391x14.3 x 300 x 5602Y = 0.5(1 + pm i =0.45 f / f =0.45 X 1.43/300=0.215 % ,且300 x 600t Sp 96.83kN故可按构造要求配置箍筋：加密区配置2。8100 ,非加密区配置 2。8200。加密区长度取 1.5h=900mm。(3) 梁斜截面受剪承载力计算P = =2 X 50.3/ ( 300 X 200 ) =0.17 %sv bs P min=0.24f =0.24 X 1.43/270=0.13 %yv满足构造要求。其他各梁斜截面受弯承载力计算见表6-2。表6-2中1层BC跨需按计算配筋(只配箍筋)，计算过程如下：A = k -a f?h = 83.33x 103 - 0.7 x 1.43x 200x 360 = 0 116秫心 /mmTfV 0270 x 360. mm mmA取101mm即配置双肢4 8的箍筋，间距可取100mm。其他各层框架梁配筋见表6-1和表6-2。表6-1框架梁纵筋配筋表楼层截面M(kN- m)r小、 a fbh h - r c f f 02V)M&=1-J1 - 气A(mm2)As(mm2)实配钢筋(mm2)配筋率(%)a =s a J bfh025A支座-57.200.0430.043348.012 16(4020.22AB跨间64.331515.80 M0.0070.007384.292 16(402)0.22B支座左-49.890.0370.038302.712 16(4020.22B支座右-22.570.0610.063215.722 12(2260.28BC跨间-10.46377.52 M0.0070.00797.202 14(308)0.394A支座-123.650.0920.097773.333 IS(76.3)0.42AB跨间90.861515.80 M0.0100.010543.603 16(603)0.34B支座左-111.590.0830.087694.293 18(763)0.42B支座右-47.090.1270.136467.892 18(509)0.64BC跨间-12.87377.52 M0.0090.009119.652 12(226)0.283A支座-143.010.1060.113902.033 20(9240.51AB跨间45.211573.00 M0.0050.005269.792 16(402)0.22B支座左-123.020.0910.096769.193 18(763)0.42B支座右-57.060.1540.168576.793 16(603)0.75BC跨间-8.18400.40 M0.0060.00675.912 12(226)0.282A支座-179.480.1330.1441151.083 22(1140)0.63AB跨间45.031573.00 M0.0050.005268.722 16(402)0.22B支座左-150.920.1120.119955.283 20(942)0.52B支座右-69.880.1890.211723.273 18(7630.95BC跨间-5.09400.40 M0.0030.00347.212 12(226)0.281A支座-234.610.1280.1371500.544 22(1520)0.84AB跨间54.801573.00 M0.0060.006327.212 16(4020.22B支座左-186.540.1390.1501200.354 20(1256)0.70B支座右-88.850.2400.278955.763 20(924)1.18BC跨间-6.45400.400 M0.0040.00459.832 16(402)0.50表6-2框架梁箍筋计算表6.2框架柱6.2.1柱截面尺寸验算根据抗震规范，对于三级抗震等级，剪跨比宜大于 2，轴压比小 于0.85，表6-3给出了框架柱各层剪跨比和轴压比计算结果。注意：表中 的Mc、Vc和N都不应考虑抗震调整系数，由表可见，各柱的剪跨比和轴 压比均满足规范要求。表6-3边柱的剪跨比和轴压比验算柱号楼层B(mm)h 0 (mm)Fc(N/mm 2)M c(kN- m)Vc(kN)N (kN)力RcA柱550047014.393.2710.04437.0119.760.12450047014.392.1430.07924.656.520.26350047014.3117.1648.491357.965.140.38250047014.3138.2454.921792.335.350.50150047014.3223.7967.982225.047.000.62B柱550047014.394.0121.36454.699.370.13450047014.3131.8850.401041.185.570.29350047014.3135.5475.641575.293.810.44250047014.3160.7486.042108.483.970.59150047014.3246.06102.682641.305.100.74第六章截面设计即：450/30=15mm，故取 20mm轴向力对截面重心的偏心距 e =M/N=232.75x 106/ ( 1328.19x 103) =175.24mm初始偏心距：e= e + e =175.24+20=195.24mm。l =H=4.75m ,柱的计算长度，根据规范，对于现浇楼盖的底层柱其它层取 l =1.25H=1.25 X 3.2=4m匚 c=0.5 f A/N=0.5x 14.3x4502/ ( 1328.19x 103) =1.09 1.0，取匚 c=1.02匚=1+(4750/450) 2x1.0/ (1300x 195.24/410 ) =1.181nr1300 eh0C = 0.7 + 0.3也=0.7+0.3 X 186.8