The purpose of this procedure is to describe the Erection procedure of a span by using the span by span method. This document describes 2 methods of erection: Segments delivery from ground level Segments delivery from rear of LG over completed viaduct
1.2 SCOPE OF WORK
This procedure is developed for application in the scope of works and applies to all the spans composing the spans of the viaduct superstructure of the HCMC Line 1 Metro Project and erected by launching gantries using the span by span method. It also describes the tools, plant, equipment, materials and labour which will be used for this activity together with a risk analysis of the operations.
LG Launching Gantry SB Spreader Beam MG Main Girder FH Front Head FS Front Support RH Rear Head RS Rear Support HS Hanging System AS Auxiliary Support CG Centre of Gravity WT Winch Trolley PS Pier Segment PT Post Tensioning
2. RELEVANT SPECIFICATIONS, STANDARDS AND DOCUMENTS
• Kinematic drawings erection from ground FVR-TEC-DWG-3240-016 • Kinematic drawings erection from rear FVR-TEC-DWG-3240-020 • Method Statement for Permanent PT FVR-TEC-MST-3430-001
3. SEGMENT DELIVERY & LIFTING SEGMENTS
The segments are transported from the pre-cast yard and delivered to the erection site by truck and trailer. In the typical situation the segments are required to be delivered at the ground level under the gantry such that the lifting point is within +/- 550 mm from the neutral position of the winch trolley. The trailer is parked at the required position at the appropriate span.
The spreader beam is used for lifting the segment by engaging the hydraulically operated adjustable arms of the beam to the underside of the segment top flange. Timber shims placed on the bearing area at the contact point ensure that no hard points occur. The spreader beam is aligned with centre of gravity before being lifted to height. Once the spreader beam is engaged, the segment can be hoisted and moved to the required position on the Launching Gantry using the winch trolley. The segment is prevented from rotating while lifting by the use of rotation lock mechanism in the spreader beam.
3.1 SEGMENT POSITIONING AND HANGING
After being lifted by the spreader beam, the segment is required to be positioned in the correct location in the span. After all the segments are suspended and hung in this manner, the segment alignment, gluing and temporary PT procedure can commence. The main hanging components are the two types of hanger bars and the two types of connection systems for the interface of the segment to the hangers. The two types of hanger bars are the main hanger bars (Ø40 PT bars, yield load = 1358 kN) and the secondary hanger bars (2 nos Ø32 PT bars, yield load = 869 kN). Refer to Attachment #2 for technical information. Wire rope sling Ø32 has a minimum breaking load (MBL) 976 kN (2 nos for each segment = 1592 kN). Refer to Attachment #3 for technical information. The main hanger bars are linked to the secondary hanger bars by means of a wire rope and a transfer beam. The transfer beam is attached to the segment using the Ø32 secondary bars while the wire rope is attached to the main hanger bars.
Max segment weight = 412 kN
Master Slave (only for PS near RS) Of the two types of suspension systems, the master system comprises main hanger bars, wire rope sling and two secondary Ø32 bars. The slave system comprises the same components as the master system except that it has only one secondary Ø32 bar.
3.2 POSITIONING AND HANGING PROCEDURE FOR ERECTION FROM GROUND LEVEL
The segments are first positioned at the correct location while the segment is still supported by the winch trolley after the segment has been lifted. The weight of the segment is transferred to the hanger bars from the spreader beam supported by the winch trolley in the following manner : a. Preparatory works Temporary bearings have to be positioned at correct location before positioning PS. b. 1st Pier Segment (PS) The 1st Pier Segment, at the pier closest to the Rear Support (RS) of the LG, is positioned after being lifted and brought to the pier location by the winch trolley. The segment is surveyed and adjusted in the longitudinal and transverse direction with respect to the line and level and the required erection coordinates. The procedure for the transfer of the load is as follows: The segment is brought up to the position with winch trolley, hold it by 2nos single hangar bars and surveyed, adjust using the winch trolley and spreader beam as necessary. Set first segment in its approximate final position approximate 10~20mm above temporary bearing. The load from the winch trolley is then released slowly such that the load is transferred to the 2nos single hanger bars. 2nos single hanger bars are necessary to level the PS. The 1st PS is the most important for the span levelling. All remaining segments position will be determined by the alignment of 1st PS. c. 2nd Pier segment After hanging the 1st pier segment, the 2nd PS near FS is then positioned as per sketch and suspended using 1no master hanger bar (as opposed to the case of the 1st PS). One master hanger bar is sufficient in this case as the segment is to be glued and joined to the previous segment. d. 1st Typical Segment The first TS will be placed above the PS near FS legs, as per drawing, following similar load transfer procedure from winch trolley to hanger bars. The TS adjacent the PS is stacked temporarily in a high position to accommodate the accumulated gaps between the remaining TS as they are lifted and hung from the LG. e. Other Typical segments Then the remaining field segments will be suspended from the gantry on 2 bars in the correct order to ensure the connection faces are matched. Note : The gap between hung TS/TS should be around 100mm (or 200mm between PS/TS) as per drawing.
3.3 POSITIONING AND HANGING PROCEDURE FOR ERECTION FROM REAR OF LG
In case of the delivery from ground is an issue, it is possible to deliver from rear of LG, using the method called “Back feeding”. The segment will be delivered by a segment transporter running on the erected viaduct between a designated collection point of the location of the LG. Then, the WT lifts up the segment off the transporter. Note : Segments have to be lifted as per drawing such as it can go through AS & RS. The handrail of the AS & RS have to be removed to give enough space for segments. First Pier Segment arrives by transporter. Transporter has to park near AS, as per drawing.
First Pier Segment in position as shown below. It is surveyed and adjusted in the longitudinal and transverse direction with respect to the line and level and the required erection coordinates.
Second Pier Segment in position as shown below.
Typical segments: ERECTION OF 27 METER-LONG SPAN:
ERECTION OF 30 METER-LONG SPAN:
ERECTION OF 31.25 METER-LONG SPAN:
ERECTION OF 32 METER-LONG SPAN:
ERECTION OF 35 METER-LONG SPAN:
ERECTION OF 37 METER-LONG SPAN:
4. RELOCATION, EPOXY & TEMPORARY PT
4.1 RELOCATION OF SEGMENTS
Once all segments are lifted, suspended and the deflection induced in the main girder, one by one the segments can be assembled to form the span. The relocation of segment is realizing thanks to the winch trolley. Install steel brackets for temporary PT on segments (see 4.3 sketches). Note : - Steel brackets will come from previous erected span to be reused. - Take up the slack in the hanging system (bars & wire rope), by applying hydraulic jacking on top of hanging system, before releasing segment from spreader beam to minimize the movement of segments as the load is transferred during alignment.
4.2 APPLY OF EPOXY
A two component epoxy structural adhesive is used for the segment gluing and it is formulated as per the requirement of the specifications of the project;
1. Pot life – Time before which the mixed epoxy must be applied on match cast surface which is generally limited to 45 minutes
2. To prevent the ingress of epoxy into the prestressing ducts, ‘O-Rings’ are used. The ‘O-Rings’ are to be made of an elastomeric foam material and are to be installed before the epoxy application works commence.
3. Each segment is to be lifted by the winch trolley and slowly brought up into contact against the previous segment to ‘dry match’ to check the alignment of the segments.
4. During this dry run, the joint under consideration is to be closed as best as possible.
5. The leading segment is then to be brought back about 200 mm.
6. The time at the start of the mixing operations and the time taken for the mixing shall be recorded. 7. The prepared epoxy is to be removed from the container and applied to the concrete surface within the pot life of the epoxy. 8. The application is to be done by hand using rubber gloves. 9. The epoxy is applied by hand, using gloves, to the entire surface of one of the match cast surfaces forming the joint. Note : For each match cast joint, the corresponding volume of epoxy (segment face area with an estimated average thickness of 2mm) shall be pre-prepared for efficient application of product. 10. Special care is to be taken in ensuring the even application of epoxy in the following zones: a. At the lower surface of the male shear keys. b. At the outer tip of the top flanges. c. In those areas where many ducts are present at close intervals. 11. After the application of the epoxy is completed the leading segment is attached to the previous segment by moving it means of the winch trolley until the segment shear keys are engaged and the joint closed a much as is practical.
4.3 TEMPORARY PT
The temporary prestressing is introduced into the joint after the epoxy is applied. The temporary PT system is reused for each span and it is made up of: • Steel brackets • Shear pin and inserts • 32 diameter high tension bar and relative accessories There are 4 PT bars to be stressed and these are positioned on the deck slab. At the start of the jointing of the segments, the bars in the initial two segments are stressed. Thereafter, the bars are coupled to the corresponding ones and the next joint stressed after installing the bracket (Steel brackets shall be installed before Epoxy applied). This procedure is repeated for each segment of the span. Note : Bars are coming from previous erected span once segment is Epoxy glued. Stressing requirement is 430 kN in each bar. The bars will be stressed simultaneously as per sketch below. The final alignment of span will be done at later stage during span alignment.
2 1 1 2
5. LOAD TRANSFER & PERMANENT PT
After segments are epoxy glued and temporary PT applied, activate the lowering jacks on the RS, FS to free the ringnut. Record the pressure reading on lowering jack. Reduce the value by 15 bar (= 100 kN for each 4 lowering jack of 1 support). This equates to approximately the weight of the Pier Segment. Stress the span with the permanent PT and complete the load transfer to temporary bearings in accordance with the FVR-TEC-MST-3430-001 method statement. • Once all the Permanent PT are been stressed, remove all the hangar bars. • Once all the hangar bars are been removed, prepare LG for launching (Refer to FVR-TEC-MST-3230-006 for 37m span ; FVR-TEC-MST-3230-013 for 35m span ; FVR-TEC-MST-3230-014 for 30m span). Note: Once all the Permanent PT are been stressed, Temporary PT may be removed either before or after LG launching.
6. RESOURCES TO BE USED
6.1 EQUIPMENT TO BE USED
Equipment to be deployed for the Erection, Epoxy and Temporary PT. No. Description Specification Quantity Unit 1 Setting-out instruments 1 set 2 Hand tools 1 set 3 Bar Jacks 60 T 2 U 4 Pump Y26 / SPX 554 2 U 5 Slings 1 set 6 Shackle 1 set 7 Safety signs 1 set 8 Hoisting equipment 1 set 9 Cherry picker 1 set 10 Mobile cranes 1 set 11 Launching Gantry 1 set 12 Generators 1 set 13 Spanners 1 set 14 Lever block 1 set Note : Above stated quantity of equipments could be changed if necessary.
6.2 MANPOWER TO BE DEPLOYED
Manpower to be deployed for the Erection works as per sections are listed below.
No. Description Detail Quantity 1 General superintendent of the 3 LG of project FVR 1 2 Supervisor of the concerned LG FVR 1 3 Site engineer FVR 1 4 Skilled workers FVR 13 Note : - Number of manpower could be changed according to site condition. - This manpower shall be deployed on site.
6.3 MATERIALS TO BE USED
Materials to be used for the Erection works as per sections are listed below. No. Description Quantity Unit Remarks 1 Epoxy 17.5 L Per TS match cast face 2 Epoxy 28.0 L Per PS match cast face Note : The material shall get approval from Employer’s Representative before commencement of gluing work.
7. INSPECTION TESTING PLAN
Inspection records will be kept for all critical activities particularly for the choosing at ground level of the segment, the positioning of the hung segments, the application of epoxy and the installation of temporary PT.
Inspection sheets, test reports, material certificates and all the other documents to be collected are listed in the specified ITP.
8. OCCUPATIONAL HEALTH AND SAFETY CONTROL
The Hazard and Risk Assessment (HRA) has been carried out in the form of the Job Safety Analysis (JSA) to include those activities which are specially associated with the erection of span using Launching Gantry. These are reviewed by the HSE Officer to ensure that all the hazards have been identified and adequate control measures are in place. All personnel shall wear the appropriate PPE at all times.
8.1 JOB SAFETY ANALYSIS (JSA) / HAZARD ANALYSIS & RISK ASSESSMENT (HRA) / SAFE WORK METHOD STATEMENT (SWMS)
The JSA has been completed by the Technical Department and has been reviewed by the HSE Department. It should also be reviewed by the work crew prior to activities being performed. The document has identified the hazards associated with the activities involved in the erection of span using launching gantry and details the measures to be adopted to minimize or eliminate those risks identified. Attachment #1
8.2 TOOLS AND EQUIPMENT
All tools and equipment for the task shall be in safe condition and fit for its purpose. Where applicable, registration papers, certifications shall be produced and tests certificates will be available for inspection.
At the start of each shift, equipment shall be visually checked for mechanical and structural soundness. All equipment shall be carefully examined and all hoses and couplings checked for the leaks and general condition.