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Domain |
Explanation |
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Speaker |
Er. Heng Hua Jee is the Senior Principal Project Manager of HDB. He joined HDB in 1980 as a Structural Engineer and later as one of the pioneers in the Building & Project Management Department (BPMD) in 1990. He graduated from the University of Singapore in 1978 and obtained MSc (Civil Engineering) from National University of Singapore in 1985.
Er. Heng has vast experience in the design, supervision and project management of HDB's building projects. He involved in developing various project management systems and had contributed to the successful implementation of ISO 9002 certification for the Department's Project Management services. He is currently heading a unit besides handling HDB housing projects, also managing some other non-standard projects.
- Structural engineer, project development
- Head of project management, non-standardised projects; design & supervision
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Abstract |
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Toa Payoh HDB HUB |
- Toa Payoh: 1st satellite town estate
- RC with precast components building
- Development as part of estate renewal strategy
- Integrated centre, bus interchange & MRT for seamless movement
- Design & development:
- Contract: Jun 1998
- Ground-breaking: 30 Sep 1998
- Construction: 3.5yr
- Top-up: 5 Jun 2001
- TOP (temporary operation permit): Sep 2001
- Open to public: Jun 2002
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TOC |
- Outline
- Design
- Advanced construction technologies
- Project management
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Outline |
- Contractor: Shimizu Corporation
- RSP Architect & Planners
- S$450m, 42months
- 250, 000 m2 floor area
- Organization:
- Client: HDB
- Superintendent officer (SO) representative
- D&B design consultants
- Supervising consultants
- Challenges:
- MRT: operational, tunnels running straight through under site à need to control settlement à within code of practice controlled 1st, 2nd & 3rd reserves
- 3-6m spacing between tunnel & edge of site wall
- Deep basement construction: >10m
- Existing buildings & shops: downtime, vibration, noises, dust, mosquitoes
- Commuters & pedestrians movement: public safety access (allow safe passage); carpark; public transport (buses, MRT)
- Architectural layout:
- Tall building
- Lower offices & eateries
- Tunnels & 2 underground carparks (North & South entrances)
- Intelligent & friendly building:
- More energy conservation & efficiency
- More security, communications
- Higher quality: customer management, structured cabling, smart card, e-Queue (which carpark lot to go)
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Construction overview |
- Foundation: Bored & barrette piles, prefound columns, diaphragm walls, verticality control
- Props: kingposts, chicken-feet à shear studs
- Walls: edge panel à panel-by-panel
- Soil improvement: chemical piling (increase foundation stiffness)
- E-splice: end-to-end rebar connections
- Large pilecap: mass-concreting à needs monitoring & careful control of cracks due to thermal restraints
- Ground anchor-strutting: prestressed struts
- Semi-top-down construction
- Basement-superstructure construction
- Design, procurement, preparation, testing, monitoring, construction
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Construction |
- Geology:
- Soil investigation: 22 boreholes, distribution
- Groundwater: <1.2m from ground à basement: flooded à needs water-separation
- Ground condition: Bukit Timah Granite & Kallang Formation
- Ground profile: Fill (organic, marine clay) à Alluvium (Boulders) à Granite: 13-26m
- Needs to dump clay: approval from MPA (Maritime Port Authority)
- Existing MRT safety zones:
- 1st, 2nd and 3rd reserves: approval & restrictions
- Works required: tunnels, utilities, bus
- Protect MRT station & tunnels
- Excavation
- Diaphragm: de-bonding
- Break-through existing walls: ensure sufficient supports, strength & stiffness (less deformations)
- Criteria to satisfy:
- Pressure soil: max.
- Differential settlement: <15mm
- Peak particle velocities
- Design of construction:
- Movement criteria
- Sequence of construction
- Instrumentation:
- Monitoring to avoid & minimize criteria
- Japanese: uses many advanced construction technologies
- Using:
- Systems: Watcher, 4-sight, smart system, superwing, semi-top-down, GPCF (granite precast concrete formwork)
- Instruments: tiltmeters, inclinometers, vibration sensors, etc.
- Foundation:
- Bored piles
- Barrette piles
- Prefound columns
- Diaphragm walls
- Using separation from water, soils, earth-retaining
- Reverse drilling
- De-bonding: to separate the differential movement between piles & soils
- Soil-structure-interaction:
- To satisfy construction criteria, strength & stiffness over time & locations
- External consultants using FEM: CRISP
- Examine 2 critical sections of MRT
- Ground anchor system:
- Tie up walls to outside soil: more interior workspace
- 173 anchors used: must install
- Must remove: to clear underground obstacles
- Tall building:
- 145m
- Purpose: study effects of wind, façade design, effects of surroundings, human activities, M&E services
- Using wind tunnel 1998
- Bored, barrette piles: prestressed beams, struts
- Cast in-situ: walls, columns
- Perimeter beams: precast
- Column: G50; beam: G40; LL: 5kN/m2
- Semi-top-down:
- Top-down construction: cast diaphragm walls to seal up
- But cast ground slab: stiff workspace, coordinate simultaneous superstructure & substructure constructions; protect from weather; increase productivity
- Basement construction sequence: basement 3 à 2 à 1
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Advanced construction technologies |
- Watcher system:
- Online monitoring of MRT tunnels through connected sensors & instrumentation into database (3 times per day, 8-hour cycle)
- Max deflection during construction: 8mm <15 mm (ok, using de-bonding, construction sequence & technique), minimize movement
- Plots:
- Deflection profile
- Settlement profile
- Plan profile
- Location profile
- 4-sight simulation:
- Due to complexity of construction sequence à needs to plan way ahead & visualize the sequence using simulations
- Due to coordination of 4-5 separate management teams
- Visual 3-D & time-dimension: 4-D perspective
- View 3-D simulation in stages: ease planning
- SMART system:
- Originally invented for steel structures, now for RC HDB HUB
- Integration of vertical & horizontal hoisting system
- Maximise use of precast components
- 3-tier jack-up sequence
- 8-day construction cycle: for each floor
- Hence, one jack-up per 24 days
- Adv.: roof, no weather, protection & more efficiency
- Superwing system:
- 3 long steel trusses with prestressing to span across MRT tunnels
- MRT route: reduce load across MRT
- Prestressing strands at bottom chords of trusses: effective prestressing = 1700kN
- Stressing sequence
- Monitoring mid-point deflection
- Sequence: erection à Bondeck slab à prestressing à anchor & lock à jacking: pulling à fire protection: vermiculite spraying (tennis courts)
- GPCF:
- Granite precast concrete formwork: stairs core-wall
- Curtain wall
- Coating: hydrotherm for water-proofing & weathering
- Higher quality, higher efficiency, higher safety
- Curtain wall:
- Aluminum framing with vision panels (glass windows)
- Safety measures: barricades, nets & hazard measures to catch falling objects
- Mock-up test: to test curtain walls for air leakage, water penetration & structural performance
- Test on-site
- Top tracing system:
- Anti-crane-collision system at the same system: due to overlapping reaches of the crane
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Project management |
- Software aspect
- HDB:
- HDB: D&B with contractor: Shimizu
- Consultants: supervising
- Coordination:
- Client requirements
- Resolve problems: operational, managerial
- Progress review
- Scheduling:
- Equipment
- Labour
- Materials
- 5 focal points:
- Higher quality:
- Durability:
- Materials: quality
- Work method: technique & methodology
- Workmanship: skilled
- Material management:
- Delivery
- Storage: reduced deterioration
- Testing: to ensure materials meet specifications
- Tests: fire rating, water-proofing
- Work demonstration:
- Do it right first time
- Manage production
- Set standards
- Worker training
- Supervisor training
- On-time:
- Within budget:
in-process audit process: checking while doing
- Public relations:
- Management, control & understanding of surrounding people
- Pre-emptive management
- Analyse: historical collapse cases
- Safety:
- Safety management: supervisor & employment
- Morning exercises: daily constant tireless reminder & revision of safety measures & steps
- Box meetings: remind & ensure anchorage
- Weekly mass house-keeping
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