T梁张拉伸长量计算值(示例).doc
30m、40mT梁张拉伸长量计算值(示例)
(按μ=0.17,k=0.0015计算)
5弹性模量Ep=1.95×10MPa
根据后张预应力筋理论伸长值及预应力筋平均张拉力的计算式:
-(kx-Ep)P×L ) P(1-×eP
ΔL= P= P
A×E Kx+μθ PP
式中: ?L—预应力筋理论伸长值:cm;
P—预应力筋的平均张拉力,N;
x—从张拉端至计算截面孔道长度,cm;
2 Ap—预应力筋截面面积,mm;
Ep—预应力筋的弹性模量,Mpa;
p—预应力筋张拉端的张拉力,N;
θ—从张拉端至计算截面曲线孔道部分切线的夹角之和,rad;
k—孔道每米局部偏差对摩擦的影响系数,0.0015;
μ—预应力筋与孔道避的摩擦系数,0.17 ;
中主梁(以30m中梁为例)
1.N1(1*6)
预应力筋截面面积Ap=140*6=840mm2
b锚下控制应力σcon=0.72Ry=0.72*1860=1339.20MPa
起始端头张拉力p=σcon*Ap=1339.2*840=1124.928KN 1
由图纸说明:θ=4.46?*3.14/180?=0.078rad
L=31.6806-2*1=29.6806m
L弯=5*2=10m
L直=(29.6806-10)/2=19.6806/2 =9.8403m
μ=0.17,K=0.0015,
由张拉力的计算公式:
0.0015*5+0.23*0.078)[1-e-(kx+μθ)] e-( 1- P=P× =1124.928*
0.0015*5+0.23*0.078 kx+μθ
=1110.739KN
曲线段末端(直线段起始点)张拉力:
p2=2P-P1=1110.739*2-1124.928=1096.55KN
,×, 35?L = =1110.739*10*5*100/(840*1.95*10 )
,y×Eg
=3.39cm
55 ?L直=P21096.55*9.8403*10/840/1.95*10=6.59cm ×L/Ap×E=
L=(3.39+6.59)*2=19.96cm 千斤顶工作长度的伸长量计算:
5ΔL=PL/ApEy=σk*Ap*L/ApEy=σk*L/Ey=1124.928*1/840*1.95*10
=0.68cm
边跨边梁(以40m边梁为例)
1.N1(1*8)
2预应力筋截面面积Ap=139×8=1112mm
b锚下控制应力σcon=0.68Ry=0.68*1860=1264.8MPa
起始端头张拉力p1=σcon*Ap=1264.8*1120=1416.58KN
由图纸说明:θ=2.23?*3.14/180?=0.039rad
L=36.6654-2*1=34.6654m
L弯=4.5*2=9m
L直=(34.6654-9)/2=25.6654/2 =12.8327m
μ=0.23,R=0.0015,
由张拉力的计算公式:
0.0015*4.5+0.23*0.039)[1-e-(kx+μθ)] e-( 1- P=P× =1416.58*
0.0015*4.5+0.23*0.039 kx+μθ
=1405.5KN
曲线段末端(直线段起始点)张拉力:p2=2P-P1=1405.5*2-1416.58=1394.42KN
,×, 35?L = =1405.5*10*4.5*100/(1120*1.95*10 )
,y×Eg
=2.90cm
55 ?L直=P21394.42*12.8327*10/1120/1.95*10=8.19cm ×L/Ap×E=
L=(2.9+8.19)*2=22.18cm
千斤顶工作长度的伸长量计算:
5ΔL=PL/ApEy=σk*Ap*L/ApEy=σk*L/Ey=1124.928*1/840*1.95*10
=0.68cm