跨度 24m梯形钢屋架设计

24m钢结构开始设计1、设计资料1）某厂房跨度为24m，总长90m，柱距6m，屋架下弦标高为18m。2）屋架铰支于钢筋混凝土柱顶，上45柱截面400×400，混凝土强度等级为C30。3）屋面采用1.5×6m的预应力钢筋混凝土大型屋面板。（屋面板不考虑作为支撑用）。4）该车间所属地区为北京市5）采用梯形钢屋架考虑静载：①预应力钢筋混凝土屋面板（包括嵌缝）、②二毡三油加绿豆沙、③找平层2cm厚、④支撑重量考虑活载：活载（雪荷载）积灰荷载6）钢材选用Q345钢，焊条为E50型。2、屋架形式和几何尺寸屋面材料为大型屋面板，故采用无檩体系平破梯形屋架。屋面坡度i=（3040－1990）/10500=1/10；屋架计算跨度L0＝24000－300＝23700mm；端部高度取H=1990mm，中部高度取H=3190mm（约1/7。4）。屋架几何尺寸如图1所示：1990135022902590289031902608285931193370253528593129339615091508150AacegIBCDFGHI15008=12000×150815081508150815081508起拱50图1：24米跨屋架几何尺寸3、支撑布置由于房屋长度有90米，故在房屋两端及中间设置上、下横向水平支撑和屋架两端及跨中三处设置垂直支撑。其他屋架则在垂直支撑处分别于上、下弦设置三道系杆，其中屋脊和两支座处为刚性系杆，其余三道为柔性系杆。（如图2所示）上弦平面支撑布置屋架和下弦平面支撑布置垂直支撑布置4、屋架节点荷载屋面坡度较小，故对所有荷载均按水平投影面计算：荷载计算表荷载名称标准值(KN/m^2)预应力钢筋混泥土屋面板1.4二毡三油加绿豆沙0.4找平层２cm厚0.4屋架及支撑重量0.12+0.011×24=0.384永久荷载总和2.58屋面活载（大于雪荷载）0.7可变荷载总和0.7计算屋架时考虑下列三种荷载组合情况1)满载（全跨静荷载加全跨活荷载）节点荷载①由可变荷载效应控制的组合计算：取永久荷载γG＝1.2，屋面活荷载γQ1＝1.4，屋面集灰荷载γQ2＝1.4，ψ2＝0.9，则节点荷载设计值为F＝（1.2×2.584+1.4×0.70+1.4×0.9×0.80）×1.5×6＝45.7992kN②由永久荷载效应控制的组合计算：取永久荷载γG＝1.35，屋面活荷载γQ1＝1.4、ψ1＝0.7，屋面集灰荷载γQ2＝1.4，ψ2＝0.9，则节点荷载设计值为F＝（1.35×2.584+1.4×0.7×0.70+1.4×0.9×0.80）×1.5×60＝46.593kN2)全跨静荷载和（左）半跨活荷①由可变荷载效应控制的组合计算：取永久荷载γG＝1.2，屋面活荷载γQ1＝1.4，屋面集灰荷载γQ2＝1.4，ψ2＝0.9全垮节点永久荷载F1=（1.2×2.584）×1.5×6＝27.9072kN半垮节点可变荷载F2＝（1.4×0.70+1.4×0.9×0.80）×1.5×6＝17.892kN②由永久荷载效应控制的组合计算：取永久荷载γG＝1.35，屋面活荷载γQ1＝1.4、ψ1＝0.7，屋面集灰荷载γQ2＝1.4，ψ2＝0.9全垮节点永久荷载F1=（1.35×2.55）×1.5×6＝31.347kN半垮节点可变荷载F2＝（1.4×0.7×0.70+1.4×0.9×0.80）×1.5×6＝31.347kN故应取P＝46.23kN3)全跨屋架和支撑自重、（左）半跨屋面板荷载、（左）半跨活荷载+集灰荷载①由可变荷载效应控制的组合计算：取永久荷载γG＝1.2，屋面活荷载γQ1＝1.4，屋面集灰荷载γQ2＝1.4，ψ2＝0.9全跨屋架和支撑自重F3=1.2×0.384×1.5×6＝4.4172Kn半跨屋面板自重及半跨活荷载F4＝（1.2×1.4+0.7×1.4）×1.5×6＝23.94kN②由永久荷载效应控制的组合计算：取永久荷载γG＝1.35，屋面活荷载γQ1＝1.4、ψ1＝0.7，屋面集灰荷载γQ2＝1.4，ψ2＝0.9全跨屋架和支撑自重F3＝1.35×0.384×1.5×6＝4.617kN半跨屋面板自重及半跨活荷载F4＝（1.35×1.4+1.4×0.7×0.7）×1.5×6＝23.184kN5﹑屋架杆件内力计算见附表16﹑选择杆件截面按腹杆最大内力Nab=-413.28KN,查表7.6，选中间节点板厚度为8mm，支座节点板厚度10mm。1）上弦杆整个上弦杆采用等截面，按最大内力NFH=-711.01KN计算在屋架平面内：为节间轴线长度，即lox=l。=150.8cm,loy=301.6cm＝0.659Areq＝N/f＝711010/(0.659×310×100)=34.803cm2假定＝70ixreq=lox/＝150.8/70＝2.54cmiyreq＝loy/＝301.6/70＝5.08cm由附表9选2125×80×10，短肢相并，如下图所示，A＝2×19.71＝39.42cm2、ix=2.26cm、iy=6.04cm截面验算：x＝lox/ix＝150.8/2.26=66.7［］＝150(满足)y＝loy/iy=301.6/6.04=49.9［］＝150(满足)双角钢T形截面绕对称轴（y轴）应按弯扭屈曲计算长细比yzb1/t=12.5/1.0=12.50.56loy/b1=0.56×301.6/12.5=13.51,则：yz＝3.7*b1/t（1+l2oy2t/52.7b12）=3.7×14（1+301.62×0.82/52.7×12.54）=54.1〈x故由max＝x＝66.7查附表1.2得＝0.686由N/A=711.01×1000/(0.686×39.42×100)＝262.93N/2mmf(满足)故上弦杆采用2125×80×10截面形式2）下弦杆整个下弦杆采用等截面，按最大内力Ngi=706.82KN计算lox＝300cmloy=2370/2=1185cm,Anreq=N/f=706.82×1000/(310×100)=22.80cm2由附表9选2125×80×7短肢相并A＝2×14.1＝28.2cm2，ix＝2.3cm，iy＝5.97cmnA/N＝=706.82×103/(28.2×102)=250.65N/2mmf(满足)x＝lox/ix＝300/2.3=130.43［］＝350(满足)y＝loy/iy=1185/5.97=198.49［］＝350(满足)故下弦杆采用2125×80×7短肢相并3）腹杆①、aB杆NaB＝－413.28KN，loy=lox＝l=253.5cm选用2110×70×8长肢相并查附表9得：A＝2×13.94=27.88cm2,ix＝3.51cm，iy＝2.85cmx＝lox/ix＝253.5/3.51=72.2［］＝150(满足)y＝loy/iy=253.5/2.85=88.9［］＝150(满足)因为b2/t=7/0.8=8.750.48loy/b2=0.48*253.5/7=17.38按式yz＝y［1＋（1.09b42）/（l2oy2t）]＝88.9×［1＋1.09×74/(253.52×0.82)]=94yzx,由yz查附表1.2得x＝0.472则A/N413.28×1000/(0.472*27.88*100)=314.058N/2mmf(满足)故Ab杆采用2110×70×8长肢相并②、Bc杆NcB＝320.56KN,lox=0.8L＝0.8*260.8=208.6cm,loy=L=260.8cm选用275×8A＝2×11.5＝23cm2，ix＝2.28cm，iy＝3.42cmx＝lox/ix＝208.6/2.28=91.51［］＝350(满足)y＝loy/iy=260.8/3.42=76.26［］＝350(满足)nA/N＝=320.56×1000/(23×100)=139.37N/2mmf(满足)③、cD杆NcB＝－253.47KN,lox=0.8L＝0.8×285.9=228.72cm,loy=L=285.9cm选用275×8A＝2×11.5＝23cm2，ix＝2.28cm，iy＝3.42cmx＝lox/ix＝228.72/2.28=100.32［］＝150(满足)y＝loy/iy=285.9/3.42=83.60［］＝150(满足)因为b/t=75/8=9.3750.58loy/b=0.58×285.9/7.5=22.11,则yz=y（1+0.475b4/l2oy2t）=83.6×(1+0.475×7.54/285.92×0.82)=86由于xyz,则由x查附表1.2得=0.430nA/N＝=253.47×1000/(0.411*23×100)=268.14N/2mmf(满足)④、De杆NeD＝172.39KN,lox=0.8L＝0.8*285.9=228.72cm,loy=L=285.9cm选用256*5A＝2×5.42＝10.84cm2，ix＝1.72cm，iy＝2.62cmx＝lox/ix＝228.7/1.72=132.98［］＝350(满足)y＝loy/iy=285.9/2.62=109.12［］＝350(满足)nA/N＝=172.39×1000/(10.84×100)=159.03N/2mmf(满足)⑤、eF杆-114.62NeF＝按压杆进行计算：5.1lox=0.8L＝0.8×312.9=250.3cm,loy=L=312.9cm选用275×8A＝2×11.5＝23cm2，ix＝2.28cm，iy＝3.42cmx＝lox/ix＝250.3/2.28=109.79［］＝150(满足)y＝loy/iy=312.9/3.42=91.49［］＝150(满足)因为b/t=75/8=9.3750.58loy/b=0.58×285.9/7.5=22.11,则yz=y（1+0.475b4/l2oy2t）=91.49×(1+0.475×7.54/312.92×0.82)=93.68由于xyz,则由x查附表1.2得=0.375nA/N＝=114.62×103/(0.375×23×102)=132.89N/2mmf(满足)nA/N＝=5.1×103/(23×102)=2.22N/2mmf(满足)⑥、Fg杆+58.58KN按压杆进行计算：NgF＝lox=0.8L＝0.8×311.9=249.5cm,loy=L=311.9cm-5.31KN选用256×5A＝2×5.42＝10.84cm2，ix＝1.72cm，iy＝2.62cmx＝lox/ix＝249.5/1.72=145.1［］＝150(满足)y＝loy/iy=311.9/2.62=119.05［］＝150(满足)因为b/t=5.6/0.5=11.20.58loy/b=0.58×311.9/5.6=32.3,则yz=y（1+0.475b4/l2oy2t）=119.05×(1+0.475×5.64/311.92×0.52)=121.34由于由于xyz,则由x查附表1.2得=0.235nA/N＝拉=58.58×1000/(10.84×100)=54.04N/2mmf(满足)nA/N‘压＝=5.31×1000/(0.235*10.84×100)=20.84N/2mmf(满足)⑦、gH杆+36.03KN按压杆进行计算：NgH＝lox=0.8L＝0.8×339.6=271.7cm,loy=L=339.6cm-35.38KN选用263×5A＝2×6.14＝12.28cm2，ix＝1.94cm，iy＝2.89cmx＝lox/ix＝271.7/1.94=140.1［］＝150(满足)y＝loy/iy=339.6/2.89=117.51［］＝150(满足)因为b/t=6.3/0.5=12.60.58loy/b=0.58×339.6/6.3