Method Statement for Precast Segment Production Short Line Typical Mould
1. INTRODUCTION
1.1 PURPOSE OF THE DOCUMENT
The purpose of this procedure is to define the sequence of operations to be carried out for the mould preparation & operation works of the Short Line Typical mould, including general arrangements, construction methodologies, technical solutions and other works, and ensures that all works will be conducted safely in accordance with the drawings and the project specifications.
1.2 PROJECT DESCRIPTION
Ho Chi Minh City Urban Railway Construction Project – Ben Thanh – Suoi Tien section (Line 1), contract Package 2 consists of approximately 12 km long of elevated viaduct structures, erected by span-by-span Method.
Figure 1: General layout - Precasting yard
1.3 SCOPE OF WORK
The purpose of this document is to clarify, step by step, the procedure for the mould preparations & operations, described in the casting sequence for Short Line Typical segments.
1.4 REFERENCES
All reference documents are intended to refer to the last issued revision. • Specifications - Clause 12.4 “Execution” Section 12-3 of 19 from Outline construction specification – Package 2: Civil (Elevated & Depot) - “Standard specifications for concrete structures – 2007, Materials and construction” from Japan Society of Civil Engineers, regarding the stripping strength required to reach. • Method Statement - HCMC-261-CSYD-CWS-MST-00012 “General precasting works at precasting yard” - HCMC-261-CSYD-CWS-MST-00042 “Geometry control for short line casting method” - HCMC-261-CSYD-CWS-MST-00017 “Casting sequence for Short Line Typical segments” - HCMC-261-CSYD-CWS-MST-00018 “Casting sequence for Short Line Pier segments” - HCMC-261-CSYD-CWS-MST-00019 “Casting sequence for Long Line Typical segments” - HCMC-261-CSYD-CWS-MST-00020 “Segment concreting works” - HCMC-261-CSYD-CWS-MST-00021 “Segment curing” - HCMC-261-CSYD-CWS-MST-00022 “Segment marking” - HCMC-261-CSYD-CWS-MST-00023 “Segment lifting & handling works” - HCMC-261-CSYD-CWS-MST-00015 “Precast segment production – Short Line Pier mould” - HCMC-261-CSYD-CWS-MST-00041 “Precast segment production – Long Line Typical mould” • Approval of materials - “Mould release Agent” (Reebol M1) - “Mould release Agent” (Rheofinish 225D) - “Mould release Agent” (Separol)
1.5 DEFINITIONS
All relevant definitions have been given in Section 1.5 “Definitions” of the Method Statement “General precasting works at precasting yard” HCMC-261-CSYD-CWS-MST- 00012 • Lifting frame for segment Also called “Spreader beam”, the lifting frame that is required for the lifting and transporting of the complete segment from the mould either to the finishing area or storage area. The lifting frame shall be designed so that there is no permanent distortion of the segment either during lifting, transport or placing on trailer prior to deliver on site. • Lifting frame for rebar cage Lifting frame that is required for the lifting and transporting of the fabricated rebar cage from the rebar jig area to the mould. The lifting frame shall be designed so that there is no permanent distortion of the rebar cage either during lifting, transport or placing. • Mould release agent Chemical product which provide quick, clean and easy stripping of moulds and formwork, and ensure high quality stain-free concrete. • Debonding agent Product which is applied on the match-cast segment face prior to cast the new segment.
2. SAFETY & ENVIRONMENTAL RISKS
2.1 HAZARD ANALYSIS & RISK ASSESSMENT
Hazards Analysis and Risks assessment are carried out and attached in each method statement. This document will identify all the hazards to ensure adequate control measures and strategies are in place to mitigate as much as possible the risks (Appendix A).
All personnel carrying out the work will be properly trained by experienced supervision. Besides, all personnel shall wear the appropriate PPE (Personal Protective Equipment), such as Safety shoes, safety helmet and safety harness if required.
2.2 TOOLS AND EQUIPMENT
All tools & equipment shall be in safe condition before utilisation and fit for its purpose.
2.3 EMERGENCY RESPONSE
In the event of an accident/incident, response will carried out in the appropriate procedure, such as: • Remedial Actions, proposing actions to ensure that the Accident/Incident will be fully fixed, as required, managed by the Responsible within a target date. • Preventive Actions, proposing actions to ensure that the Accident/Incident will never happen again, including for example: Toolbox Meeting (TBM) held by the Safety Officer to ensure that Site Team (Workers, Supervisors & Engineers) fully understand methods & risks. Prestart and TBM will reinforce safety requirements prior to commencement of the work.
3. CONSTRUCTION RESOURCES
In principle every type of work involves the following resources:
3.1 PERSONNEL
The personnel involved are such as: • Precasting yard Manager • Segment casting Superintendent • Site engineers • Quality engineers • Safety officers • Supervisors • Plant Operators (Tower cranes & Gantry Cranes) • Riggers • Workers
3.2 PLANT AND TOOLS
The following equipment shall be used for all precasting works: • Short Line Typical (SLT) mould • Gantry cranes 50 & 10T • Tower crane TC#1 (6.89ton – 50m) • Lifting frame for segment (also called “spreader beam”) • Lifting frame for rebar cage • Lifting frame for Stop-End • Electrical tools • Chains / slings / shackles • Chain blocks • Generator set • Air compressor & compressed air network Note that this list only provides a preliminary overview of resources which can be possibly used and does not necessarily prevent personnel to use other equipment plants and tools.
3.3 MATERIALS
• Concrete (Provided by Sumitomo Corporation) • Rebar cage (equipped with corrugated PT duct and spacer blocks) • Mould release agent • Debonding agent
4. CONSTRUCTION SEQUENCE
4.1 INTRODUCTION
In the precasting yard, each span (straight or curved) is built by assembling differents segments of variable longitudinal lengths. More than 4,587 segments shall be manufactured by match-cast principle with combination of short line and long line casting method.
Straight spans will be cast with the long line casting method, via the Long Line Typical mould (LLT), while curved spans will be achieved using the short line casting method via the Short Line Typical mould (SLT). Casting of pier segments for straight & curved spans will be achived on dedicated Short Line Pier mould (SLP), using the short line casting method.
The segments are match-cast. It means that the previously Fresh-Cast (F/C) segment, after being cast, is defined as counter mould (Match-Cast M/C) segment; the new segment will be cast against, ensuring a perfect unique connection match cast face.
After the concrete has been poured, and the stripping concrete strenght required reached, the elements of the mould shall be stripped and shifted. The M/C segment is shifted on the rail track by means of manipulator and maintained aside for the requested curing time, prior to be transferred to finishing area the day after. In the same time, the F/C segment is also moved to the match-cast position, by means of manipulator; then a “free” space is created to start a new casting cycle with all succeeding segments cast against previously F/C segments.
Each typical segment shall be produced in accordance with all the relevant shop drawings issued for construction and the geometry control sheets.
4.2 DESCRIPTION
Listing of mould for the production of typical segments:
• Short Line Typical #1 (SLT #1)
• Short Line Typical #2 (SLT #2)
• Short Line Typical #3 (SLT #3)
4.3 COMPONENTS
The mould consists of different movable elements that can be joined together to compose the form of the segment, such as:
Figure 2: Short Line Typical mould - Transversal section
- Soffit tables 3 Nos
- Manipulator with 4 hydraulic vertical & horizontal jacks 1 Nos
- External side forms (left & right) 1 Set
- Inner forms (left & right) 1 Set
- Portal frame for inner form (including the roof) 1 Set
- Fixed bulkhead (with supports, Stairs & platforms) 1 Nos
- Stop-End #2 (Stop-End used to cast the 1st segment) 3 Nos for 9 formwork
- Hydraulic system (for inner forms) 1 Set
Figure 3: Short Line Typical mould – Longitudinal section
Figure 4: Short Line Typical view - Plan view
4.4 MOULD OPERATION CYCLE FOR SHORT LINE TYPICAL SEGMENT
• Survey of as-built geometry. • Remove inflatable tubes (also called “satujo”) after early concrete strength required reached • Strip inner forms • Shift on rail portal frame (with inner forms) behind the fixed bulkhead. • In parallel, marking of segment (ID number, No. span, date of casting & arrow) Refer to the method statement “Segment marking” HCMC-261-CSYD-CWS-MST-00022 • Shift and strip external side forms. • In parallel, clean inner forms & soffit table and apply the mould release agent. • Bond breaking between Fresh-Cast (F/C) segment and Match-Cast (M/C) segment (or remove stop-end if no M/C segment). • Detach F/C segment from fixed bulkhead and relocate to M/C position. • Apply the debonding agent to M/C segment joint surface. • Lift and position the soffit table to cast position. • Clean external sides forms and apply the mould release agent. • Position & pre-close the external side forms. • Rebar cage is store next to the casting location, completed and equiped with corrugated PT duct and spacer blocks. Place the pre-checked rebar cage in the mould. • Place and position the M/C segment (or stop-end if no segment). • Install and position “satujo” • Install inserts (CP3, temporaty PT, lifting holes, etc…) • SCC/GS inspection prior to formworks closure. • Shift on rail the portal frame (with inner forms) to casting position. • Final closing of inner forms & external side forms against fixed bulkhead and M/C segment (or Stop-end if no segment). • Final survey Refer to the method statement “Geometry control for short line casting method” HCMC-261-CSYD-CWS-MST-00016 • Infill completely “satujo” • Final inspection before casting • Cast short line typical segment & concrete finishing (floating) Refer to the method statement “Segment concreting works” HCMC-261-CSYD-CWS-MST-00020 • Cure segment Refer to the method statement “Curing of segments” HCMC-261-CSYD-CWS-MST-00021 • Transfer cured segment to finishing area, after lifting strength concrete required reached. Refer to the method statement “Segment lifting & handling works” HCMC-261-CSYD-CWS-MST-00023 • Segment finishing works Refer to the method statement “Segment finishing works” HCMC-261-CSYD-CWS-MST-00024 • Remedial works for segment (if needed) Refer to the method statement “Segment remedial works” HCMC-261-CSYD-CWS-MST-00025 • Storage of segment Refer to the method statement “Segment storage & ½ stacking” HCMC-261-CSYD-CWS-MST-00026 • Load segment on trailers for site delivery Refer to the method statement “Segment delivery and transportation” HCMC-261-CSYD-CWS-MST-00027
4.5 GENERAL ARRANGEMENT OF CASTING
For 35m curved span length, the first segment, from the middle of the span, is the segment “S6”.
Figure 5: 35m length curved span N – Longitudinal section – Typical
4.6 MOULD OPERATION CYCLE FOR SEGMENT “S6”
4.7 MOULD OPERATION CYCLE FOR SEGMENT “S5”
5. ACTIVITY HOLD POINTS
Hold points will be identified in the Inspection & test Plan. Refer to the ITP “Precast segment production”:
6. INSPECTION & RECORDS
All Inspection / check-lists & documents records will be identified in the Inspection & test Plan. Refer to the ITP “Precast segment production”:
