Monday, April 7, 2008

WMS Structure Concrete

WORKS METHOD STATEMENT

STRUCTURAL REINFORCED CONCRETE


TABLE OF CONTENTS


1.0 WORK ORGANISATION
2.0 DESIGN CONSTRAINTS AND COORDINATION
3.0 CONTRACTING METHODS
4.0 PROCUREMENT METHODS
5.0 RESOURCE PROVISIONS
6.0 LOGISTICS PROVISIONS
7.0 MATERIAL MANAGEMENT SYSTEMS
8.0 CONSTRUCTION METHODS AND TECHNOLOGY
9.0 CONSTRUCTION PHASING AND WORKFLOW
10.0 TRAFFIC MANAGEMENT AND MONITORING
11.0 SAFETY PROGRAMME
12.0 QUALITY ASSURANCE AND CONTROL PROGRAMMES
13.0 INDUSTRIAL RELATIONS POLICIES
14.0 ENVIRONMENTAL MONITORING PROGRAMMES
15.0 APPENDICES


1.0 INTRODUCTION

This Work Method Statement shall outline the construction of Structural Reinforced Concrete at Private Hospital, Jalan Tun Razak project.

2.0 DESIGN CONSTRAINTS AND COORDINATION

Not Applicable.

3.0 CONTRACTING METHODS

Since PCSB is liable for the performance of any Sub-contractor, it is vital that only companies with proven track records in the relevant activity will be engaged as Sub -contractors.

It is acknowledged that before any part of the works can be sublet, the approval of the Employer’s Representative is required.

The Conditions of Contract have been reviewed by PCSB and particularly those conditions in respect of Sub-contractors. The conditions are bespoke for this project and therefore be required to be reflected in any form of Sub-contract utilized on the project.

Please refer to PHOS-CN-010 to PHOS-CN-030 for the Contract Procedures.

4.0 PROCUREMENT METHODS

Please refer to PHOS-PR-010 to PHOS-PR-030 for the procurement procedures.
5.0 RESOURCE PROVISIONS

5.1 Manpower/Labour

The number of manpower/labour to be used during the earthworks activities have been identified in the Manpower Histogram.

5.2 Plant Equipment

Typical plant equipment to be used shall consist of:

~ Vibrators
~ Trowelling Machine
~ Hand tools
~ Cranes
~ Skips
~ Lighting towers



6.0 LOGISTICS PROVISIONS

The logistic control shall be in accordance with the approved Site Logistic Plan and includes wheel wash facilities and traffic management.

7.0 MATERIAL MANAGEMENT SYSTEMS

Please refer to PHOS-CP-040 for the Material Control Procedure.

8.0 CONSTRUCTION METHODS AND TECHNOLOGY

8.1 Design Mix

The design mix shall be proportioned in accordance with BS 5328 and approved by construction drawings and shall be reviewed / approved by Consultant prior to any concrete work being undertaken.

Concrete shall be supplied, sampled and tested by ready-mix approved supplier. All batching, sampling and testing shall be completed in accordance with supplier procedure and specifications.

A monitoring station shall be set up where all incoming / outgoing concrete trucks shall pass and will be manned by Peremba personnel when delivery is due. Delivery orders shall be checked for grade of concrete, time of batching and number filed accordingly. A daily record of temperatures shall be taken showing the maximum / minimum temperature and also the average shade temperature.

Testing schedule – Nine test specimens shall be made from each batch. Three specimens shall be tested at 7 days and three at 28 days. The remaining three specimens shall be tested at 90 days unless otherwise directed by the Employer’s Representative. The trial mix proportions shall be approved if all three individual cube results tested at 28 days exceed the characteristic strength by the current margin less than 3.5N/mm2, subject to satisfactory strength increments recorded in tests at 7 and 90 days.

Samples shall be taken at the slump station area. As for the bigger pour, samples shall be taken at the site itself. Concrete shall be transported from the batching plant to its placing point without any segregation or loss of any ingredients.


8.2 Formwork

Formwork shall generally be Peri Hory Proprietary Formwork. (See attached Method Statements). All formwork shall be designed and signed off by a Professional Engineer.


Formwork shall generally be fabricated in the formwork fabrication area and shall be transported to the work area for installation. Once formwork has been used, they shall be stored in designated areas for later use or returned to the fabrication area for dismantling. In general, no redundant formwork shall be left in / around the work areas.

Formwork shall be installed in compliance with BS 5975 and the formwork design drawings. Formwork shall be constructed to the exact sizes, shapes, lines and dimensions shown on the drawings and as required to obtain accurate alignment, location, grades, level and plumb of the finished structures in accordance with the schedule of the tolerances.

Formwork shall be deemed to include all formers of openings recesses, keyways, moulding, chamfers etc. Formwork shall be cleaned and coated with an approved release agent (oil) prior to erection and installation of reinforcement.

Formwork used to form construction joints shall be coated with an approved retarder or release agent in accordance with the manufacturers recommendations.

8.2.1 Falsework

Falsework shall be erected to give sufficient support and bracing and allow for any necessary adjustment for positioning and striking. Wedges, jacks or camber strips to be provided to facilitate vertical adjustments. After concrete placement operations, the falsework and formwork shall be inspected to determine abnormal deflection or any signs of failure.

8.2.2 Pre-pour Inspection

The following shall be checked prior to placement of concrete :

- Line, plumbness and level
- Shoring and ties
- Joints sealed
- Cleanliness and application of release agent and retarder (where required)
- Joint formers, chamfers, mouldings, etc.
- Pour level strips (if applicable)
- Waterproofing system where applicable.

8.2.3 Formwork Removal

Formwork shall be removed in accordance with the most stringent requirements of BS 8110, contract specifications or as allowed by the Resident Engineer.





Table 1
Element Stripping Time
Column forms and beam sides 24 hrs
Suspended slabs and beam soffits 25 Mpa
Wall forms 16 hrs
Slab and pile cap edge forms 16 hrs
Construction joints to be green cut Within 6 hrs after initial set
Mould, keyways, chamfers, etc. 16 hrs

Additional cubes (2 minimum) shall be taken where suspended elements are to be stripped between 48 and 72 hours.

Back props will be provided for all suspended elements where required and as shown on shop drawings.

8.3 Reinforcement

Delivery of reinforcement

Reinforcement, once cut and bent, shall be stored in the lay down area or on off ground supports and shall only be transported to the work area when required. All bars will be tagged as per the bending schedule.

All scrapped or unused reinforcement shall be stored in a central area before being removed from site. In general, no loose or scrap reinforcement shall be left in / around the work areas.

The Contractor shall receive and verify the material and type according to the purchase order. He will submit the Mill Certificate to the QA/QC Manager to review chemical analysis, tensile and bend tests as performed by the manufacturer and approved by the Employer’s Representative. The Subcontractor shall ensure that the reinforcement is stored correctly to avoid any adverse effects from the environment.

All delivery shall be filed with the relevant Mill certificates and for each delivery, the following information shall be gathered :

~ Delivery dates
~ Heat Number
~ Transportation (vehicle) number
~ Number of bundles
~ Total weight
~ Delivery order number
~ Type of rebar

Peremba supplier is to ensure the following Quality Assurance is in place and that the steel delivered conforms to BS 4449/78 standards.

Tensile and rebend tests are to be carried out from samples taken at side as required by the specifications and as instructed by the R.E.

Concrete spacer blocks or steel chair shall be used to support the bottom layers of reinforcement and to space reinforcement from edgeforms. Plastic PVC spacer may be used to space reinforcement from edgeforms if approved by the R.E.

The spacer block shall be selected to provide the correct cover to the bottom reinforcement layer and shall be of adequate strength to support the load.

Where required, steel chairs shall be scheduled and fabricated to support intermediate and top layers of reinforcement. Reinforcement shall be installed once the blinding, soffit formwork or preparation of the supporting / adjacent concrete element has been inspected and signed off as per ITP.

Cleanliness during fixing of the reinforcement is a priority. Any rubbish or loose particles are not to be dropped in the pour area. The pour area will be blown clear before concrete placement.

Where reinforcement is used to secure formwork or cast – in items and the welding may be detrimental to the reinforcement bar, a dummy reinforcement bar shall be fixed.

The starter bar positions are critical and must be checked.

The following checks shall be conducted prior to placement of concrete:-

• Ensure correct cover is provided
• Reinforcement fixing shall be in accordance with the drawings
• Starter bars, trimmer bars, etc are fixed in correct locations.
• Top level of reinforcement is correct
• Reinforcement shall be clean
• Stop ends fixed correctly.
• Cast in items are correctly placed and securely fixed.

8.4 Concrete Placement

Pre – Pour Works

The client shall be notified 24 hours prior to placing of concrete for inspection of formwork and concrete reinforcement

The interior of forms shall be cleaned thoroughly. The surface and reinforcement shall be sprayed with clean water prior to concrete pouring.

While placing concrete, objects such as anchor bolts, reinforcing bars and other fixtures shall be monitored for movement.

The concrete slump shall be such that it can be easily placed without segregation. If the concrete is acceptable, it will continue to be discharged. Slump test shall be taken at every load of concrete. The load shall be accepted if the concrete slump at the point of discharge is within tolerance for the design mix ordered. If the slump is below tolerance, the load shall be rejected.

The concrete is to be agitated continuously by rotation of the mixer drum during transport to the Site and while waiting discharge. Concrete shall be discharge from the delivery vehicle within 2 hours after the time of loading.

Vibrators or other suitable tools shall be used to ensure the required compaction is achieved. Vibrators shall be inserted and vertically and not used to move concrete at least one spare vibrator will be available at all times.

Concrete shall be deposited as quickly as practicable in its final position to avoid segregation and cold joints.

Concrete that has partially hardened or been contaminated with foreign materials shall not be deposited in the structure.

Chutes should preferably be of rounded cross section to avoid the accumulation of concrete in corners.

Concrete shall be poured in alternate panels if construction joints are required in concrete slab pours. The positions and pouring sequence will be approved by the Client prior to casting or shall be as per schedule or the programme.

In the event of rain occurring during a pour, the live faces of the layers of concrete will be kept as close as possible to minimize the exposed horizontal concrete to the rain. Where possible the pour rate will be slowed, particularly considering the life of the concrete should increase due to the moisture in the air. Where the pour rate is slowed, additional retarder (which has been approved by the Client and the complied with the contract specification requirement) may be added to the mix to keep the concrete live longer. Generally free water in forms will be blown to the edge of the pours and removed.


8.5 Construction Joints

Construction joints shall be permitted only where indicated on approved construction
drawings.

The surface for all construction joints shall be horizontal and vertical. Irregular
construction joints shall not be permitted.

When water tight construction is required, a water stop shall be set in position, as detailed and fixed securely so that the water – srop will not move or be damaged when concreting.

If a surface is cast against another surface which has hardened, the existing surface shall be roughened until the aggregate over the whole surface is exposed, cleaned, thoroughly wetted and covered with specified bonding compound as stated in the Contract Document.


8.6 Finishing

When the concrete is poured to level, the surface will be finished generally. Areas of specialized finishes will be treated separately.

Holes left by the withdrawal of the tie rods shall be filled solidly with non – shrink mortar (as approved) and finished to match the surrounding surface.

All exposed concrete shall be free from bulges, honeycomb, fins and other similar surface defects.

When the concrete has stiffened sufficiently, the surface shall be bowelled by hand or by machine sufficiently to produce a uniform surface free from screed marks and to ensure that the surface of the concrete is within tolerance.

8.7 Post – Pour Works

Concrete Curing

Concrete placed shall be cured as required in the specification using approved curing compound and or wetting method as described below.

• Cover all exposed concrete surfaces with canvas, straw, gunnysack or similar material, which shall be wetted with flushing or sprinkling water.
• Spray curing compound onto the entire exposed concrete surface.

Removed of slop ends will be stripped as soon as the concrete has hardened. The joint will be green cut by jet washing or mechanical method.

Surveys shall be completed within 48 hours following pour completion. A post pour inspection will be carried out to highlight any areas for repair.










9.0 CONSTRUCTION PHASING AND WORKFLOW

Following basement slab formatting superstructure will commence moving from grids 27/H towards 1/A, rising vertically in 4 zones.

10.0 TRAFFIC MANAGEMENT AND MONITORING

The Logistic Manager and the traffic management contractor shall be responsible for the management and control of the traffic in and out from the construction site.


11.0 SAFETY PROGRAMME

Please refer to PHOS-HS-010 Health and Safety Plan and Job Safety Analysis.


12.0 QUALITY ASSURANCE AND CONTROL PROGRAMMES

Please refer to Appendix 15.2 for the Inspection and Test Plan and Appendix 15.3 for the Checklist.


13.0 INDUSTRIAL RELATIONS POLICIES

Not Applicable


14.0 ENVIRONMENTAL MONITORING PROGRAMMES

Please refer to PHOS-EMP-001 Environmental Management Plan


15.0 APPENDICES

15.1 Peri Formwork Method Statement

15.2 Inspection and Test Plan – Structural Reinforced Concrete
15.3 Checklist
15.4 Job Safety Analysis.

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