1设计某厂房钢屋架一、设计资料梯形屋架跨度24m,物价间距6m,厂房长度120m。屋架支撑于钢筋混凝土柱子上,节点采用焊接方式连接,,其混凝土强度C25,柱顶截面尺寸400mm×400mm。屋面用预应力钢筋混凝土大型屋面板。上弦平面侧向支撑间距为两倍节间长度,下弦平面在柱顶和跨中各设一道纵向系杆。屋面坡度i=1/10。刚材采用Q235B钢,焊条E43××系列,手工焊。二、屋架形式和几何尺寸屋架的计算跨度l0=L-300=24000-300=21000mm,端部高度取H0=2000mm,跨中高度H=3200mm三、屋盖支撑布置(见图1)四、荷载计算⒈永久荷载:预应力钢筋混凝土屋面板(包括嵌缝)1.40KN/m2防水层(三毡四油上铺小石子)0.35KN/m2找平层(20mm厚水泥砂浆)0.02×20=0.40KN/m2保温层(泡沫混凝土)厚40mm0.25KN/m2钢屋架及支撑重0.12+0.011×24=0.384KN/m2合计2.784KN/m2⒉可变荷载:屋面荷载0.5KN/m2雪荷载0.6KN/m2由于可变荷载和雪荷载不能同时达到最大,因此去他们中的较大值。取0.6KN/m2五、屋架杆件内力计算与组合永久荷载分项系数1.2,可变荷载分项系数1.4.⒈荷载组合:⑴全跨恒载+全跨活载⑵全跨恒载+半跨活载⑶全跨屋架,支撑自重+半跨屋面板重+半跨活载⒉节点荷载:永久荷载F1=1.2×2.784×1.5×6=30.07KN2可变荷载F2=1.4×0.6×1.5×6=7.56KN⒊屋架杆件内力计算表一屋架构件内力组合表(单位:KN)见表1六、屋架杆件设计支座斜杆的最大内力设计值为-333.40KN,查表9.1,中间节点板厚度选用10mm,支座节点板厚度选用12mm。⒈上弦杆上弦采用等截面,按N=-572.28KN,FG杆件的最大设计内力设计。上弦杆计算长度:平面内:lox=lo=1507mm;在屋架平面外,根据支撑和内力变化情况,取loy=2×l0=3014mm。假设λx=λy=120,查表得φ=0.437。取强度设计值f=215N/mm2,则需要的截面面积:A=N∕φf=572280∕0.751×215=3544mm2=35.44cm2需要回转半径:ix=lox∕λ=1507∕70=21.5mmiy=loy∕λ=1507×2∕70=43mm根据需要的A、ix,查角钢型钢表,3选用2∟125×80×10,A=39.4cm2,ix=2.26,iy=6.11,a=10mm。按所选角钢进行验算:λx=lox∕ix=1507∕(2.26×10)=66.7<[λ]=150λy=loy∕iy=3014∕(6.11×10)=49.3<[λ]=150满足长细比要求。σ=N/A=572280∕(39.4×102)=145.2N/mm2﹤f=215N/mm2,满足截面要求。⒉下弦杆:下弦采用等截面,按de杆件的最大设计内力值,N=568.97KN;下弦杆计算长度:平面内:lox=lo=3000mm;在屋架平面外,根据支撑和内力变化情况,loy=l0=6000mm,根据屋架平面外上弦杆的计算长度,需要的截面:A=N/f=568.97×103/215=26.46cm2,选用2∟125×80×7,A=28.2cm2,ix=2.30cm,iy=6.04cm。λx=lox∕ix=300∕2.3=130.4﹤[λ]=350λy=loy∕iy=600∕6.04=99.3﹤[λ]=350满足长细比要求。σ=N/Aφ=201.8N/mm2﹤f=215N/mm2满足截面要求。⒊端斜杆:因屋架对称结构以下只设计了左半跨的杆件,右半跨的杆件与左半跨的相同。⑴Ba杆杆件轴力N=-333.40KN,lox=253.9cm,loy=l=253.9cm需要的截面积:A=N/f=35.49cm24查角钢型钢表,选用2∟100×10:A=38.6cm2>35.49cm2,ix=3.05cm,iy=4.52cm。按所选角钢进行验算:λx=lox∕ix=83.2<[λ]=350λy=loy∕iy=56.2<[λ]-350σ=N/Aφx=19.8N/mm2﹤f=215N/mm2满足截面要求。⑵He杆杆件轴力N=-115.65KN,lox=271.92KN,loy=339.9KN。查角钢型钢表,选用2∟63×6:A=12.28cm2,ix=1.94cm,iy=2.97cm。按所选角钢进行验算:λx=lox∕ix=118.5﹤[λ]=150λy=loy∕iy=96.7﹤[λ]=150满足长细比要求。σ=N/Aφx=20.13N/mm2﹤f=215N/mm2满足截面要求。⒋再分式腹无。屋架杆件截面选用表杆件计算内力(KN)截面规格截面积A(cm2)计算长度(cm)回转半径(cm)长细比容许长细比名称编号lox(cm)loy(cm)ixiyλxλy[λ]上弦杆所有-572.282∟125×80×1039.40150.7301.42.266.1166.749.3150下弦杆所有568.972∟125×80×728.20300.0600.02.306.04130.499.3350斜腹杆支座处Ba-333.402∟100×1038.60253.90253.903.054.5283.256.2150其他Bb258.522∟63×612.28209.76262.201.942.97108.188.3350Db-204.412∟100×1038.60229.84287.303.054.5275.463.6150Dc139.532∟63×612.28229.84287.301.942.97118.596.7350Fc-92.572∟100×1038.60250.56313.203.054.5282.269.3150Fd63.722∟63×612.28250.56313.201.942.97129.2105.5350Hd70.092∟63×612.28271.92339.901.942.97140.2114.4350He-115.652∟100×1038.60271.92339.903.054.5289.275.2150竖杆支座处Aa20.522∟30×33.50200.00200.000.911.63219.8122.7350其他Ie72.332∟30×33.50256.00320.000.911.63281.3196.3350Cb-41.042∟45×46.98184.00230.001.382.24133.3102.71505Ec-49.342∟45×46.98208.00260.001.382.24150.7116.1150Gd-49.342∟45×46.98232.00290.001.382.24168.1129.5150七、填板设计填板厚度等于节点板厚度等于10mm,用填板连接的双角钢构件,可按实腹式构件进行计算,但填板间的距离不应超过受拉杆件80i受压杆件40iT形截面i为单个角钢对与填板平行的形心轴的回转半径,十字形截面i为单个角钢的回转半径iv。填板尺寸:厚度=10mm(节点板厚度),宽度b=50~80mm,保证b≥8hf+2hf(最小焊缝长度),hf可按构造要求选用。高度T形截面,h=角钢连接边宽度+2(10~15)mm,即填板伸出角钢连接边10~15mm,受压构件除了满足l1≤40i,在构建两个侧向支撑点间的填板数不应小于2个。⒈上弦杆AB(零杆)设置两块填板BC(压杆)la=150.7cm∕2=75.35<40i=90.4设置两块填板CD(压杆)la=150.7cm∕2=75.35<40i=90.4设置两块填板DE(压杆)la=150.7cm∕2=75.35<40i=90.4设置两块填板EF(压杆)la=150.7cm∕2=75.35<40i=90.4设置两块填板FG(压杆)la=150.7cm∕2=75.35<40i=90.4设置两块填板GH(压杆)la=150.7cm∕2=75.35<40i=90.4设置两块填板HI(压杆)la=150.7cm∕2=75.35<40i=90.4设置两块填板⒉下弦杆ab(拉杆)la=285cm∕2=142.5<80i=186.3设置两块填板bc(拉杆)la=285cm∕2=142.5<80i=186.3设置两块填板cd(拉杆)la=285cm∕2=142.5<80i=186.3设置两块填板de(拉杆)la=285cm∕2=142.5<80i=186.3设置两块填板⒊斜腹杆Bala=253.9cm∕3=84.640i=122设置两块填板Bbla=262.2cm∕3=87.480i=155.2设置两块填板Dbla=287.3cm∕3=95.740i=122设置两块填板Dcla=287.3cm∕3=95.780i=155.2设置两块填板Fcla=313.2cm∕3=104.440i=122设置两块填板Fdla=313.2cm∕3=104.480i=155.2设置两块填板Hdla=339.9cm∕3=113.80i=155.2设置两块填板Hela=339.9cm∕3=113.340i=122设置两块填板八、屋架节点设计刚材采用Q235B钢,焊条E43,fwf=160,手工焊。t1角钢厚度,t2节点板厚度。6对上弦杆和竖杆,厚度为12mm,节点板厚度为10mm,则肢背焊缝hf1≥1.5√t2=1.5√10=4.74mmhf1≤t1-(1~2)=12-(1~2)=11~10mm取8mmhf2≥1.5√t2=1.5√10=4.74mm肢尖焊缝hf2≤1.2t1=1.2×12=14.4mm取6mm对其他杆件,厚度为12mm,节点板厚度为10mm,则肢背焊缝hf1≥1.5√t2=1.5√10=4.74mmhf1≤1.2t1=1.2×12=14.4mm取6mmhf2≥1.5√t2=1.5√10=4.74mm肢尖焊缝hf2≤t1=12mm取6mm⒈下弦节点1)设ab杆件的肢背和肢尖焊缝hf=8mm和6mm,内力分配系数0.7,0.3,则所需焊缝长度为肢背:lw1=lw+2hf=0.75N/2×0.7hf1fwf+2hf=0.75×177240/(2×0.7×8×160)+2×8=90.17mm取95mm肢尖:lw2=lw+2hf=0.25N/2×0.7hf1fwf+2hf=0.25×177240/(2×0.77×6×160)+2×6=45mm取50mm2)设bc杆件的肢背和肢尖焊缝hf=8mm和6mm,内力分配系数0.7,0.3,则所需焊缝长度为肢背:lw1=lw+2hf=0.75N/2×0.7hf1fwf+2hf=0.7×431.99/(2×0.7×8×160)+2×8=196.8mm取200mm肢尖:lw2=lw+2hf=0.25N/2×0.7hf1fwf+2hf=0.3×431.99/(2×0.7×6×160)+2×6=92.35mm取95mm3)Cb杆件的内力较小,肢背和肢尖焊缝均按构造要求取值hf=6mm。4)设Bb杆件的肢背和肢尖焊缝hf=8mm和6mm,内力分配系数0.7,0.3,则所需焊缝长度为肢背:lw1=lw+2hf=0.7N/2×0.7hf1fwf+2hf=0.7×258.52/(2×0.7×8×160)+2×8=117mm取120mm肢尖:lw2=lw+2hf=0.3N/2×0.7hf1fwf+2hf=0.3×258.52/(2×0.7×6×160)+2×6=69.7mm取70mm5)设Db杆件的肢背和肢尖焊缝hf=8mm和6mm,内力分配系数0.7,0.3,则所需焊缝长度为肢背:lw1=lw+2hf=0.7N/2×0.7hf1fwf+2hf=0.7×204.41/(2×0.7×8×160)+2×8=95.8mm取120mm肢尖:lw2=lw+2hf=0.3N/2×0.7hf1fwf+2hf=0.3×204.41/(2×0.7×6×160)+2×6=57.6mm取60mm验算下弦杆与节点板的连接焊缝,内力差,ΔN=Nbc-N