DAYA DUKUNG DINAMIK YZ
Dynamic Formulas To predict static load capacity based on the foundation’s response to dynamic loads This technique probably harkens back to when people first began driving piles Based upon pile set (per blow) information obtained during driving Engineers tried to base on energy concepts equating hammer kinetic energy to resistance of pile penetration (difficult and easy to drive)
Dynamic Formulas Basic Equation: where: W = ram weight h = ram stroke R = soil resistance sb = pile set per blow (diperoleh di lapangan) Due to simplicity, widely used Variations exist which consider pile weight, energy losses, etc.
Rumus Janbu (Janbu formula)(1953) . Dimana Qu = daya dukung batas L = panjang tiang A = luas penampang tiang E = modulus elastisitas tiang η = faktor efisiensi W = berat hammer Wp =berat tiang s = final set (penurunan/per pukulan)
Faktor effisiensi () tergantung pada peralatan pemancangan tiang, prosedur pemancangan, tipe tiang dan kondisi lapangan. = 0.7 untuk kondisi pemancangan yang baik -=0.55 untuk kondisi pemancangan normal = 0.4 untuk kondisi pemacangan sulit atau jelek
Rumus Hiley (Hiley formula)(1925) dimana Qu= daya dukung batas, h = efisiensi pukulan hammer, k= koef. Hammer, W=berat hammer, h=tinggi jatuh hammer, s= penurunan tiang per pukulan, c= cp+cc+cq
Koefisien K Hammer K Drop hammer, which operated 0.8 Drop hammer, trigger release 1.0 Single acting hammer 0.9 BSP, double acting hammer McKiernan=terry diesel hammer
Modified Engineering News Formula (1961) dimana Qa = daya dukung ijin E = energi per pukulan Wp = berat tiang e = koefisien restitusi