E 9=2kN. m ↓4 p=8kM 例1、三铰拱及其所受荷载如 图所示拱的轴线为抛物线方程 myx0=)计算反力并绘 制内力图 7kM H=7. 5KM Ix,=3m 6m (1)计算支座反力 V likE =P2×6×9+8×31kN 12 12=12=262+832=98 (2)内力计算以截面2为例 H=MC=116-2×6×3 7.5kM 4 4f 4×4 3(12-3)=3m 12 M2=M212=(1×3-2×3×15)-75×3 =15kN·m d4/,2x)14×4(,2×3 tg 2 dx x=3 12 Q2=cog2-Hsin2=(1-2×3)×0832 =0667 75×0555=-00025kN≈-0003kN 02=334,sm0.2055c0920832Sm2=Hcos2=(1-2×3)×055 75×0.832=-90l5kNx q=2kN .m P=8kN 3m x2=3m 7.5kN VA H VB 2 y2 y 0 1 2 3 4 5 6 7 8 A B 例 1、三铰拱及其所受荷载如 图所示拱的轴线为抛物线方程 y ( ) f l = x l − x 4 2 计算反力并绘 制内力图。 (1)计算支座反力 VA =VA = kN + = 2 6 9 8 3 12 11 VB =VB = kN + = 2 6 3 8 9 12 9 H M f kN C = = − = 11 6 2 6 3 4 7.5 (2)内力计算 y ( ) ( ) f l 2 2 x l x 2 m 4 4 4 12 = − = 3 12 3 3 − = tg dy dx f l x l 2 x 3 x 3 4 1 2 4 4 12 1 2 3 12 0 667 = = − = − = = = . 2 = 33 41 2 = 0555 2 = 0832 ,sin . ,cos . M M Hy ( ) kN m 2 2 2 11 3 2 3 15 7 5 3 15 = − = − − = . . . Q Q H ( ) kN kN 2 2 2 2 11 2 3 0832 7 5 0555 0 0025 0 003 = − = − − = − − cos sin . . . . . ( ) k N N Q H 7.5 0.832 9.015 2 2 sin 2 cos 2 11 2 3 0.555 − = − = − − = − − 6m 6m f=4m =11kN = 9kN = 7.5kN 以截面2为例