News / Articles TERIMA KASIH DAVYSUKAMTA & PARTNERS, Structural Engineers

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1 Jakarta, the Capital of Indonesia News / Articles TERIMA KASIH Principal, DS&P Complex Basement Construction in Very Congested Urban Environtment DEEP BASEMENT IN DENSE URBAN CONDITION Design Consideration: Complex Basement Construction in Very Congested Urban Environtment - Depth of Excavation - Type of Soil - Water Table - Adjacent Structure / Site Constraints - Sequence of Works - Excavation Methodology - Construction Details Use of RC Slab as Struts SUPPORT Use of RC slab as strut gives the required rigid support for the diaphragm wall GROUND ANCHOR STRUT : Steel or RC slab (top down) Top-Down Construction TDC enables the superstructure and the underground structure to be built simultaneously Semi Top-Down Construction Semi TDC makes use of the stiff RC slab as struts, starting the construction from the ground to the bottom Work progressed simultaneously for the basement and the super-structure, saving construction time Design MUST reflect the actual sequence of work. DETAILING is tedious and complex 1

2 Top-Down Construction The Key Component Construction Method Choice of King-Post Sequence of Work LL for Working Platform Depends on Equipment And Method of Work Where to install the 1 st slab Load Path Strutting System Installing the Kingpost Casting Concrete under the Slab Connect RC Slab to Kingpost Steel Rebar Passing Through Kingpost Soil Removal: Skip Floor or Not? Construction Holes? Soil Removal Soil Removal Mosque WTC-2 5-level basement Dense urban location Wisma Metropolitan 1 + WTC-2 + Mosque are close to the basement Depth of excavation 16 M Semi Top-Down Construction WM-1 Basement is located very close to adjacent WTC-2, Wisma Metropolitan 1, Mosque and future WTC-4. Excavation reached 15.8 meters Deformation of the retaining structure must be minimized to avoid damaging adjacent structures Not possible to install ground anchors Limited access and space for work 2

3 WM piles φ15mm with kingpost Bored-piles φ12 mm without kingpost WTC-2 Strutting the Hole Temporary Ramp for Construction Stress S22 Diagram: Effect of soil pressure and openings on RC slab Check the Stress in the Slab Due to Soil Pressure and Construction Opening COMPRESSION TENSION 3

4 The Details Connection Detail: Kingpost to Slab Use of CAD/CAM to help the Design Process Work on Progress: Preparation Work for B-1 Slab (Working Platform) Welding Quality Inspection Shear Stud Quality Assurance Case Study No.2: Plaza Indonesia Extension 48-story + 5-level basement, 22, sq.m, completed in 29 Basement is located very close to adjacent Grand Hyatt hotel, e-x center and Japanese Embassy, and excavation reached 17 meters Project Location High water table, meters below the surface Deformation of the retaining structure must be minimized to avoid damaging adjacent structures Limited Construction time and space for work 4

5 -Use RC slab as strut -Work simultaneously upwards and downwards Top-Down Construction The Ground floor was designed for LL = 2kg/sq.m (2kPa) to take construction load Use of RC slab as strut gives the required rigid support for the diaphragm wall Work progressed simultaneously for the basement and the super-structure, saving 11 month s construction time On completion of B level, work on superstructure had reached level-11 Use of metal formwork for precision and speed of construction Holes for steel rebar Use of weldable coupler Dye Penetrant Test to Check Weld Quality 5

6 Foundation of Tower Crane Pipes for concrete casting Analysis and design of D-wall, king-posts and supporting bored-piles must follow construction sequence High capacity king-post and bored pile is required to take the construction load before the RC mat is poured and steel king-post encased in concrete Horizontal Deflection Bending Moment Shear Force Horizontal Deflection Bending Moment Shear Force "A"-side : Adjacent to Existing Plaza Indonesia (Without Temporary Strut) Excav. To 3.7m (EL. -.35m) Bending Moment B1 and Excav. To 6.7m (-3.35m) Min ton.m/m Max 64. ton.m/m B2 and Excav. To 9.7m (-6.35m) B3 and Excav. To 12.7m (-9.35m) B4 and Excav. To 14.2m (.85m) Horizontal Deflection (mm) 5 1 Bending Moment (ton.m /m ) 25 5 Shear Force (ton/m) Horizontal Deflection (mm) 5 1 Bending Moment (ton.m /m) 25 5 Shear Force (ton/m ) Excav. To 15.85m (-12.5m) Mat (t=2.5m) Excav. To 3.7m (EL. -.35m) B1 and Excav. To 6.7m (-3.35m) Excav. To 3.7m (EL. -.35m) B1 and Excav. To 6.7m (-3.35m) Excav. To 3.7m (EL. -.35m) B1 and Excav. To 6.7m (-3.35m) Excav. To 15.85m (-12.5m) Mat (t=2.5m) Excav. To 15.85m (-12.5m) Mat (t=2.5m) Excav. To 15.85m (-12.5m) Mat (t=2.5m) GWL Recovery D-Wall Bending Moment (ton.m/m ) 6

7 Site Condition Oct.26 Adjacent to Existing Plaza Indonesia [Excavation depth = 16m] Adjacent to Exist. Plz. Indo. 1st Step Final Step D-Wall Horz. Deflection (mm ) Envelope of D-Wall Bending Moment (ton.m/m) Adjacent to Jln. Thamrin [Excavation Depth = 14.5m] Adjacent to Jln. Thamrin 1st Step Final Step IA-1 IB Envelope of D-Wall Bending Moment (ton.m/m ) D-Wall Horz. Deflection (mm) 7

8 Jan28 8

9 Case Study No.3 MENARA BANK MEGA JAKARTA 26-story, 4-level basement Semi Top-Down Construction Skip-floor method Completed in 26 Construction of Secant Pile, Bored-Pile and Kingpost Installation of King-Post TAHAP 1 9

10 Construction of Level B-1/ Working Platform Use Level B-1 as Working Platform TAHAP 2 Excavation under B-1 Slab Excavation to B-3 Level: Skip Floor Method TAHAP 3 Work on Level B-3 Starter Bars 1

11 Steel Ramp for Access Strutting the Hole Completion of B-4 level TAHAP 4 Excavation Work Under B-3 B 3 Slab 11

12 Use of Chemical Anchors as Dowels Transfer of Force by Shear-Friction Galian Tanah P3 Galian Tanah P3 dan Opening LG+P2 Casting of mat foundation m 3 in 36 hours Constructing the B-2 Level: Inserting the RC Slab Preparation for mat Foundation TAHAP 5 12

13 Constructing the B-2 Slab Use of Chemical Anchors as Dowels Transfer of Force by Shear-Friction Soil Excavation Under LG (B-1) = 16, m 3 Completed in 76 Days Main Issue: Exercise care for Kingpost Excavation LG-P2 (B-1 to B-3) = 25,2 m 3 Completed in 48 Days Excavation P2-P3 (B-3 s/d B-4) dan Mat Foundation Completed in 65 Days Final Work by Manual Excavation Completed Project, 26 13