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当前位置:首页 > 建筑/环境 > 工程监理 > 荷载内力计算和杆件截面选择计算
(1)设计资料昆明地区某工厂金工车间,屋架跨度为24m,屋架端部高度2m,长度90m,柱距6m,车间内设有两台30/5t中级工作制桥式吊车,屋面采用1.5×6m预应力钢筋混凝土大型屋面板。20mm厚水泥砂浆找平层,三毡四油防水层,屋面坡度i1/10。屋架两端铰支于钢筋混凝土柱上,上柱截面400×400mm,混凝土C20,屋面活荷载0.50kN/m2,屋面积灰荷载0.75kN/m2,保温层自重0.4kN/m2。(2)钢材和焊条的选用屋架钢材选用Q235,焊条选用E43型,手工焊。(3)屋架形式,尺寸及支撑布置采用无檩屋盖方案,屋面坡度10/1i,由于采用1.5m6m预应力钢筋混凝土大型屋面板和卷材屋面,故选用平坡型屋架,屋架尺寸如下:屋架计算跨度:mmLL23700300240003000屋架端部高度取:oH2000mm跨中高度:mmiLHH319031851012237002000200屋架高跨比:4.712370031900LH为使屋架节点受荷,配合屋面板1.5m宽,腹杆体系大部分采用下弦节间为3m的人字形式,仅在跨中考虑腹杆的适宜倾角,采用再分式杆系,屋架跨中起拱48mm,几何尺寸如图所示:根据车间长度,跨度及荷载情况,设置三道上,下弦横向水平支撑,因车间两端为山墙,故横向水平支撑设在第二柱间;在第一柱间的上弦平面设置刚性系杆保证安装时上弦的稳定,下弦平面的第一柱间也设置刚性系杆传递山墙的风荷载;在设置横向水平支撑的同一柱间,设置竖向支撑三道,分别设在屋架的两端和跨中,屋脊节点及屋架支座处沿厂房设置通长刚性系杆,屋架下弦跨中设置一道通长柔性系杆,凡与横向支撑连接的屋架编号为GWJ-2,不与横向支撑连接的屋架编号为GWJ屋架竖向支撑(3)荷载和内力计算1)荷载计算永久荷载标准值:预应力钢筋混凝土大型屋面板(包括灌缝):24.1mkN防水层(三毡四油,上铺小石子):24.0mkN找平层(20mm厚水泥砂浆):24.0mkN屋架和支撑自重(按经验公式估算):238.024011.012.0011.012.0mkNL保温层:24.0mkN可变荷载标准值:屋面活荷载:25.0mkN屋面积灰荷载:275.0mkN2)节点荷载计算(1)当基本组合由可变荷载效应控制时,上弦节点荷载设计值为:kNSP21.47507.1675.09.05.04.1507.164.04.038.04.04.12.1(2)当基本组合由永久荷载效应控制时,上弦节点荷载设计值为:kNSP35.49507.1675.09.05.07.04.1507.164.04.038.04.04.135.1由以上可知,本工程屋面荷载组合由永久荷载效应控制,节点集中力设计值取:kNP35.493)屋架节点荷载计算。计算屋架时应考虑下列三种荷载组合情况:(1)全跨永久荷载+全跨可变荷载;(2)全跨永久荷载+(左)半跨可变荷载;(3)屋架和支撑自重+(左)半跨屋面板重+(左)半跨施工荷载。设:1P——由永久荷载换算得的节点集中荷载;2P——由可变荷载换算得的节点集中荷载;3P——由部分永久荷载换算得的节点集中荷载;4P——由部分永久荷载和可变荷载换算得的节点集中荷载。则:kNP38.36507.164.04.038.04.04.135.11kNP98.1275.09.05.07.04.12kNP64.46507.138.035.13kNP39.21507.165.07.04.14.135.144)内力计算用图解法或结构力学求解器先求出全跨和半跨单位节点荷载作用下的杆件内力系数,然后乘以实际的节点荷载,即得杆件内力。屋架在上述第一种荷载组合作用下,屋架的弦杆,竖杆和靠近两端的斜腹杆,内力均达到最大,在第二种和第三种荷载作用下,靠跨中的斜腹杆的内力可能达到最大或发生变号。因此,在全跨荷载作用下所有杆件的内力均应计算,而在半跨荷载作用下仅需计算跨中的斜腹杆内力。计算结果如下表:屋架杆件内力计算(kN)名称杆件编号杆力系数杆力计算杆力(KN)P=1第一组组合第二组组合第三组组合左右全(P1+P2)③P1③+P2①P3③+P4①①②③④⑤⑥上弦AB0000000BD-6.26-2.48-8.74-431.41-399.22-174.46-431.41DF-9.05-4.49-13.54-668.33-610.05-256.41-668.33FG-9.17-6.09-15.26-753.23-674.19-266.95-753.23GI-9.55-5.59-15.50-765.08-687.85-276.19-765.08下弦ab+3.49+1.25+4.74233.97217.7496.64233.97bc+8.01+3.53+11.54569.61523.80224.88569.61cd+9.35+5.31+14.66723.62654.69268.02723.62de+7.47+7.47+14.93736.94640.11229.06736.94斜腹杆aB-6.53-2.34-8.87-437.82-407.45-180.83-437.82Bb+4.77+2.12+6.88339.60312.21133.95339.60bD-3.40-2.03-5.55-268.02-241.68-97.92-268.02Dc+1.90+1.79+3.79182.14158.9057.76182.14cF-0.71-1.75-2.34-120.93-98.35-26.55-120.93Fd-0.45+1.56+0.9454.7934.54-4.4854.79(-4.48)df+2.43-2.05+0.7318.2645.0053.6953.69fI+2.95-2.21+1.4836.5365.2166.5366.53Gf+0.52-0.17+0.6816.7819.1212.7019.12竖腹杆Aa-0.500-0.50-24.68-24.68-13.02-24.68Cb-1.000-1.00-49.36-49.36-26.03-49.36Ec-0.98+0.02-1.00-49.36-49.36-26.03-49.36Gd-1.37+0.13-1.24-61.21-62.89-35.06-62.89Hf-0.68+0.20-0.49-24.19-26.65-16.82-26.65Ie0000000杆件截面选择1)上弦杆GI。整个上弦不改变截面,按最大内力计算,kNNGI08.765,cmlox8.150,cmloy5.301,截面宜选用两个不等边角钢,短肢相并。根据腹杆的最大内力KNNBb60.339,查表2.8节点板t=10mm,支座节点板厚t=12mm。假定60,对x轴和y轴均属于b类截面,查表得807.0。cmlicmlicmfNAoyyoxx03.5605.301,51.2608.150,096.44215807.01008.76523选用10901402L短肢相并;cmicmicmAyx77.6,56.2,522.442。验算:1509.5856.28.150xoxxil;1505.4477.65.301yoyyil;6.12140301556.056.0141014011bltboy则1501.541407.521030151101407.37.5217.322241221btltboyyz满足刚度要求由9.58maxx,查表得814.0x2232151.2112.4452814.01008.765mmNmmNAN满足强度和稳定性要求2)下弦杆de。整个下弦杆采用等截面,按下弦杆的最大内力kNNde94.736计算,cmlox0.300,cmloy0.1185所需要面积23276.342151094.736cmfNAden,选用10801002L,短肢相并,22276.34334.34cmcmA,cmix35.2,cmiy78.4验算:3507.12735.2300xoxxil,3509.24778.41185yoyyil64.6100118556.056.0101010011bltboy则,3500.381007.521011851101007.37.5217.342241221btltboyyz满足刚度要求2232156.2144.34331094.736mmNfmmNAN满足强度要求3)斜端杆Ba。cmllkNNoyoxBa1.253,82.437假定75,对x轴和y轴均属于b类截面,查表得720.0。cmliicmfNAoxyx37.3751.253,283.28215720.01082.43723选用10801002L,长肢相并;cmicmicmAyx53.3,12.3,334.342。验算:1507.7153.31.253,1501.8112.31.253yoyyxoxxilil19.1580253148.048.08108022bltboy则,1507.761025318009.117.7109.112242242tlboyyyz满足刚度要求取1.81maxx,查表的680.0x2232155.1874.3433680.01082.437mmNfmmNAN满足强度和稳定性要求4)斜腹杆Bb。cmlcmlkNNoyoxBb5.260,4.2085.2608.0,60.339。所需面积23795.152151060.339cmfNAn选用cmicmicmALyx69.3,44.2,606.24;88022。验算:3506.7069.35.260,3504.8544.24.208yoyyxoxxilil89.1880260558.058.00.10880bltboy则,35076.738260580475.016.70475.01224224tlboyyyz满足刚度要求2232150.1386.24601060.339mmNfmmNAN满足强度要求5)斜腹杆fdIf。此杆是再分式桁架的斜腹杆,在f节点处不断开,两段杆内力不同:最大拉力kNNNkNNNdffI69.53,53.6621,在桁架平面内的计算长度cmlox0.220,在桁架平面外的计算长度cmlcmNNlloy4.2195.06.41753.6669.5325.075.08.43825.075.0112123094.32151053.66cmfNAn选用cmicmicmALyx26.2,37.1,584.8;54522验算:3508.18426.26.417,3506.16037.10.220yoyyxoxxilil8.5345417658.058.09545bltboy则,3501.1864417645475.018.184475.01224224tlboyyyz满
本文标题:荷载内力计算和杆件截面选择计算
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