BAB VANALISIS DAN DISAIN PONDASI

5.1. Umum

Laporan “Design Pondasi” ini merupakan bagian yang tidak terpisahkan

dengan laporan Detail Desain Perencanaan Gedung ………………….. yang berisi

uraian tentang konsep, rumusan kriteria design serta pemilihan type dan jenis

pondasi yang akan di gunakan sesuai dengan hasil perhitungan.

5.2. Desain Pondasi

Perhitungan beban yang direncanakan akan diterima pondasi telah

dilakukan oleh tim perencanaan stuktur atas (upper structure). Data beban yang

diterima oleh pondasi dapat dilihat sebagai berikut.

Computer Program SANSPRO V.4.91Structural Analysis and Design(C) Nathan Madutujuh, ESRC, 2008

Licensee : Ir. Rani Hendrikus, MS, UNIKA WIDYA MANDIRA, KUPANGProject : Model File : D:\Proyek 2011\Mido Sekolah\Escola_Str.MDLDate : 28\06\2011Output : Support Reactions

Load Combination : Using Automatic (Computer generated) Load CombinationsLoad Factor : No (Unfactored Output)Ductility, Rx : 8.50Ductility, Rz : 8.50EQ Load Multiplier : NO (OmgX = 1.0, OmgZ = 1.0)Use LLRF1 : NO (LLRF1 = 1.0, No Axial Reduction for Story Effects)Use LLRF2 : NO (LLRF2 = 1.0, No Live Load Reduction for Earthquake)

SUPPORT REACTIONS:-------------------------------------------------------------------------------------------------------------------------------------Floor Node Nmin Nmax Vx,max Vz,max Mx,min Mx,max Mz,min Mz,max Id (kg) (kg) (kg) (kg) (kg.cm) (kg.cm) (kg.cm) (kg.cm)------------------------------------------------------------------------------------------------------------------------------------- 0 14 -9666.8 36849.1 2239.5 2839.3 -547621.9 554255.8 -513316.6 509047.7 0 27 6523.4 38385.1 2225.6 3971.6 -622407.2 631865.8 -514538.6 514389.7 0 40 13551.3 38596.6 2349.2 3087.2 -557742.9 572910.8 -527189.7 518556.2 0 53 7220.0 34475.3 2284.2 1844.9 -480384.4 489954.9 -527406.9 525777.5 0 15 -2051.5 41283.3 3315.5 2841.9 -545612.9 549034.4 -585046.8 580433.8 0 28 16697.7 49594.1 3309.7 3935.0 -618269.0 627246.1 -586810.3 584973.6 0 41 29103.0 53640.7 2916.6 3160.6 -560001.4 575622.4 -565011.1 552415.9 0 54 18959.4 43474.1 3390.6 1858.7 -478680.3 483171.4 -601163.7 598658.3 0 16 -471.2 41600.6 2941.2 2915.3 -546105.6 544488.5 -560092.4 559517.4 0 29 19896.8 59874.0 3072.5 3559.3 -590524.7 573843.7 -571000.3 569288.5 0 55 28027.4 44450.4 3139.9 1157.0 -419599.5 437627.9 -584449.8 582937.7 0 17 175.4 42613.4 2948.3 2806.0 -537213.5 539610.8 -559868.6 560564.8 0 30 20626.9 52267.0 2947.1 3868.1 -608210.2 616120.9 -561962.1 562635.5 0 43 41985.9 56423.2 1809.9 3202.7 -556641.7 572616.8 -490433.7 491225.9 0 56 23206.6 45449.8 3009.3 1829.4 -470817.6 474285.2 -575699.2 575741.3 0 6 1332.1 41613.7 1503.3 2540.4 -513953.1 521582.1 -461824.7 443483.4 0 19 22397.4 37096.2 2694.8 4501.3 -644567.1 648456.2 -543667.2 510216.3 0 32 22806.2 57468.7 2788.8 3863.4 -597587.8 610941.7 -552083.4 503983.5 0 45 29549.3 43065.8 2819.2 3162.0 -546650.1 564175.4 -558521.5 475921.5 0 58 19673.4 39609.1 3076.0 1789.9 -461236.3 472629.4 -580188.5 573465.9 0 18 -419.0 39801.1 2991.4 2886.0 -538362.4 536326.4 -563439.1 559479.6 0 31 19337.5 58594.0 3093.0 3481.0 -579495.7 565378.6 -572360.0 570926.6 0 57 27945.9 44286.1 3149.8 1135.6 -415284.5 430315.8 -582870.5 585109.6 0 59 19275.5 23835.0 3171.0 2330.1 -406250.6 506961.2 -586522.1 586522.1 0 8 1255.0 41690.8 1503.9 2542.5 -514764.4 522393.4 -443523.5 461864.8 0 21 22422.4 37071.0 2694.6 4506.6 -645585.1 649474.3 -510204.7 543655.3 0 34 22754.0 57520.6 2789.3 3870.0 -598685.5 612039.4 -504017.6 552117.3 0 47 29564.0 43051.0 2821.9 3168.4 -547740.7 565265.9 -476105.8 558705.8 0 60 19655.7 39626.8 3076.0 1793.3 -462123.4 473516.5 -573470.5 580193.0 0 22 -468.0 39850.0 2991.2 2891.7 -539427.4 537391.3 -559464.6 563423.8 0 35 19349.5 58582.0 3092.9 3485.7 -580496.7 566379.5 -570923.4 572356.5 0 61 27957.5 44274.5 3149.8 1139.0 -416240.5 431271.8 -585109.1 582870.0

LAPORAN STRUKTUR V - 1

0 23 138.7 42650.1 2948.2 2811.2 -538248.9 540646.1 -560563.4 559866.8 0 36 20604.3 52289.6 2947.1 3875.3 -609384.3 617295.0 -562635.8 561962.2 0 49 41982.6 56426.5 1809.8 3208.6 -557724.0 573699.1 -491224.3 490432.2 0 62 23192.5 45463.9 3009.3 1832.8 -471731.2 475198.7 -575741.2 575699.1 0 25 -1980.8 41212.9 3315.5 2847.1 -546649.2 550070.7 -580433.9 585046.8 0 38 16647.8 49644.2 3309.7 3942.3 -619442.3 628419.4 -584969.9 586806.5 0 51 29112.8 53630.9 2916.8 3166.4 -561077.5 576698.4 -552429.4 565024.5 0 64 18925.1 43508.4 3390.7 1862.1 -479598.6 484089.6 -598661.2 601166.6 0 26 -9749.7 36931.9 2239.5 2844.5 -548660.7 555294.6 -509047.5 513316.5 0 39 6575.0 38333.6 2225.6 3978.9 -623589.6 633048.2 -514389.4 514538.3 0 52 13544.2 38603.6 2349.3 3092.8 -558808.2 573976.0 -518559.5 527193.0 0 65 7342.9 34352.4 2284.2 1848.3 -481300.2 490870.7 -525778.6 527408.1 0 24 -509.0 41638.4 2941.2 2920.5 -547146.9 545529.8 -559517.7 560092.4 0 37 19868.9 59901.8 3072.5 3565.9 -591657.4 574976.4 -569288.5 570999.9 0 63 28020.9 44456.9 3139.9 1158.4 -420383.7 438412.0 -582938.5 584450.5-------------------------------------------------------------------------------------------------------------------------------------REACTIONS FROM SPRING ELEMENT:-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------Load Sum,Rx Sum,Ry Sum,Rz Sum,Mx Sum,My Sum,MzComb (kg) (kg) (kg) (kg.cm) (kg.cm) (kg.cm)---------------------------------------------------------------------------------------------------------- 1 0.0 1563633.1 0.0 240887.1 0.0 -1.6 2 38730.7 2075670.1 131273.9 25690593.3 24131.0 7780006.4 3 -37413.4 1975913.1 124044.9 24291493.2 -24130.9 -7692195.4 4 37413.4 1151353.1 -124044.9 -23809719.0 24131.0 7692192.3 5 -38730.7 1051596.1 -131273.9 -25208819.0 -24130.9 -7780009.5 6 127104.4 1868542.2 50346.1 9997767.3 80436.5 25800173.6 7 -126709.3 1536019.1 26249.6 5334100.6 -80436.4 -25773832.5 8 126709.3 1591247.1 -26249.6 -4852326.4 80436.5 25773829.4 9 -127104.4 1258724.0 -50346.1 -9515993.1 -80436.4 -25800176.7 -------------------------------------------------------------------------------------------------------------------------------------

Dari data beban tekan yang bekerja pada pondasi terlihat bahwa nilai

beban < 60 ton. Pondasi bangunan direncanakan menggunakan pondasi telapak

bujur sangkar beton bertulang yang diletakkan pada kedalaman 2.0 m. Penggalian

dapat dilakukan dengan cara manual oleh manusia atau menggunakan excavator.

Dalam desain ini ukuran pondasi telapak dibuat bujur sangkar yaitu 1.50 m

dengan mengambil beban sebesar 60 ton

Perhitungan daya dukung pondasi telapak bujur sangkar dilakukan dengan

Metode Terzaghi (1943). Menurut teori ini pondasi dangkal ialah pondasi yang

diletakkan pada kedalaman (Df) kurang atau sama dengan lebar pondasi. Namun

pada perkembangannya pondasi dengan Df sama dengan 3 sampai 4 kali dari

lebar pondasi masih didefinisikan sebagai pondasi dangkal. Jadi analisis pondasi

untuk bangunan ini memenuhi persyaratan rumusan pondasi dangkal Terzaghi.

Untuk pondasi pada tanah kering dan berbentuk bujursangkar yang menunjukkan

kondisi general shear failure, Terzaghi menyarankan rumus sebagai berikut :

qu = 1,3 cNc + q Nq + 0,4 B N

Kapasitas dukung ultimit tersebut dibagi faktor keamanan sebesar 4

menghasilkan kapasitas dukung aman terhadap beban tekan yang bekerja.

Disain pondasi dilakukan dengan menggunakan prorgam komputer Spread

Footing Design For Windows 1.0 yang merupakan salah satu program

LAPORAN STRUKTUR V - 2

pelengkap dari Sans For Windows V.4.76. Data gaya pondasi diperoleh dari

analisis gaya yang dihasilkan oleh program Sans For Windows V.4.76 dan

beberapa data-data tambahan yaitu :

Mutu beton (fc’) : 20 Mpa Mutu baja (fy) : 2400 Kedalaman pondasi dari muka tanah : 2,00 m Berat jenis tanah : 1800 kg/m3

Desain pondasi dilakukan berdasarkan besaran beban yang dipikul oleh pondasi.

Besaran beban merupakan output dari program Sans. Secara terperinci dapat

dilihat pada lampiran IV-02, sedangkan posisi dan type pondasi dapat dilihat pada

gambar kerja.

5.3. Resume Desain Pondasi TYPE F1

FOOT - Spread Footing Design V.1.0 (C) Nathan Madutujuh, 1999 Engineering Software Research Center Licensee : Seminar SANS for Windows 1999, UNWIRA, Kupang, NTT Project : Job Name : SPREAD FOOTING DESIGN Foundation Type : Spread Footing, 1-way Design Code : PBI-91 Factor for Dead Load = 1.20 Factor for Live Load = 1.60 Strength Reduction for Moment = 0.80 Strength Reduction for Shear = 0.70 Footing Width, By = W = 150.00 cm Footing Length, Bx = 150.00 cm Footing Slab Thickness, Tp = 35.00 cm Column Wall Thickness, T1 = 35.00 cm Depth of Slab Base, Ht = 200.00 cm Column/Wall Eccentricity, ex = 0.00 cm Concrete Unit Weight, Gm = 2400.00 kg/m3 Concrete Compr. Strength, fc1 = 275.00 kg/cm2 Concrete Cover, cv = 5.00 cm Rebar Yield Strength, fy = 3200.00 kg/cm2 Rebar Diameter, db = 1.60 cm Allowable Soil Stress, qa = 2.50 kg/cm2 Factored Axial Load, Nu = 59901.80000 kg Factored Moment, Mux = 574976.40000 kg.cm Factored Shear, Vux = 3072.50000 kg.cm COLUMN/WALL DESIGN:

LAPORAN STRUKTUR V - 3

Factored Axial Load, Nw = 60386.90000 kg Factored Moment, Mwx = 68013.90000 kg.cm Factored Shear, Vwx = 3072.50000 kg.cm -> USE COLUMN DESIGN PROGRAM TO FIND COLUMN REBAR SOIL PRESSURE: (1-way and 2-way action) Allowable soil stress, qa = 2.500 kg/cm2 Maximum soil stress, q_max = 2.094 kg/cm2 -> OK Minimum soil stress, q_min = 1.921 kg/cm2 Soil stress at left, q_left = 2.094 kg/cm2 -> OK Soil stress at right, q_right = 1.921 kg/cm2 -> OK CONCRETE SLAB DESIGN: Note: One-way action is assumed. SHEAR CHECKING : (one-way action) Concrete Allowable Shear Stress, vc1 = 6.155 kg/cm2 Critical section, at left, x1 = 22.500 cm Critical section, at right, x2 = 127.500 cm Shear stress, left side = 1.873 kg/cm2 -> OK Shear stress, right side = 1.740 kg/cm2 -> OK SHEAR CHECKING : (punching shear action) Allowable Punching Shear Stress, vc2 = 18.466 kg/cm2 Perimeter of Critical Section SC = 280.000 cm Punching Shear Stress = 6.452 kg/cm2 -> OK MOMENT CHECKING : (one-way action) Critical section, at left, x1 = 57.500 cm Critical section, at right, x2 = 92.500 cm Soil Stress, at left side, fx1 = 2.027 kg/cm2 Shear Force, at left side, Vsx = 24880.103 kg Location of Resultant, xs = 28.904 cm Moment Force, Msx = 719134.093 kg.cm Bending Rebar = d16-17.5 cm Soil Stress, at right side, fx2 = 1.987 kg/cm2 Shear Force, at right side, Vsx = 23593.884 kg Location of Resultant, xs = 28.588 cm Moment Force, Msx = 674493.043 kg.cm Bending Rebar = d16-15.0 cm

LAPORAN STRUKTUR V - 4

TYPE F2

FOOT - Spread Footing Design V.1.0 (C) Nathan Madutujuh, 1999 Engineering Software Research Center Licensee : Seminar SANS for Windows 1999, UNWIRA, Kupang, NTT Project : Job Name : SPREAD FOOTING DESIGN Foundation Type : Spread Footing, 1-way Design Code : PBI-91 Factor for Dead Load = 1.20 Factor for Live Load = 1.60 Strength Reduction for Moment = 0.80 Strength Reduction for Shear = 0.70 Footing Width, By = W = 120.00 cm Footing Length, Bx = 120.00 cm Footing Slab Thickness, Tp = 30.00 cm Column Wall Thickness, T1 = 30.00 cm Depth of Slab Base, Ht = 200.00 cm Column/Wall Eccentricity, ex = 0.00 cm Concrete Unit Weight, Gm = 2400.00 kg/m3 Concrete Compr. Strength, fc1 = 275.00 kg/cm2 Concrete Cover, cv = 5.00 cm Rebar Yield Strength, fy = 3200.00 kg/cm2 Rebar Diameter, db = 1.60 cm Allowable Soil Stress, qa = 2.50 kg/cm2 Factored Axial Load, Nu = 39850.00000 kg Factored Moment, Mux = 537391.30000 kg.cm Factored Shear, Vux = 2991.20000 kg.cm COLUMN/WALL DESIGN: Factored Axial Load, Nw = 40217.20000 kg Factored Moment, Mwx = 28887.30000 kg.cm Factored Shear, Vwx = 2991.20000 kg.cm -> USE COLUMN DESIGN PROGRAM TO FIND COLUMN REBAR SOIL PRESSURE: (1-way and 2-way action) Allowable soil stress, qa = 2.500 kg/cm2 Maximum soil stress, q_max = 2.146 kg/cm2 -> OK Minimum soil stress, q_min = 2.003 kg/cm2 Soil stress at left, q_left = 2.146 kg/cm2 -> OK Soil stress at right, q_right = 2.003 kg/cm2 -> OK CONCRETE SLAB DESIGN: Note: One-way action is assumed. SHEAR CHECKING : (one-way action) Concrete Allowable Shear Stress, vc1 = 6.155 kg/cm2 Critical section, at left, x1 = 15.000 cm Critical section, at right, x2 = 105.000 cm Shear stress, left side = 1.496 kg/cm2 -> OK Shear stress, right side = 1.408 kg/cm2 -> OK SHEAR CHECKING : (punching shear action) Allowable Punching Shear Stress, vc2 = 18.466 kg/cm2

LAPORAN STRUKTUR V - 5

Perimeter of Critical Section SC = 240.000 cm Punching Shear Stress = 5.808 kg/cm2 -> OK MOMENT CHECKING : (one-way action) Critical section, at left, x1 = 45.000 cm Critical section, at right, x2 = 75.000 cm Soil Stress, at left side, fx1 = 2.092 kg/cm2 Shear Force, at left side, Vsx = 16019.373 kg Location of Resultant, xs = 22.595 cm Moment Force, Msx = 361959.247 kg.cm Bending Rebar = d16-25.0 cm Soil Stress, at right side, fx2 = 2.056 kg/cm2 Shear Force, at right side, Vsx = 15342.327 kg Location of Resultant, xs = 22.401 cm Moment Force, Msx = 343679.003 kg.cm Bending Rebar = d16-25.0 cm

LAPORAN STRUKTUR V - 6