The elevated stretch of Ho Chi Minh City Urban Railway Line 1 has mainly U girder shape structure to support track as superstructure. The typical U girder is 35m in span length (pier axis to pier axis) simply supported. The Effective span length from bearing axis to bearing axis is 33,6m. The purpose of this procedure is to describe the methodology for U-girder service load test.
######1.2 SCOPE OF WORK
- Service Load Test is conducted to ensure serviceability of typical U-girder 35m straight span and to confirm design results
- Service Load Test shall be conducted on standard structure which will be used during service
- The serviceability of structure is checked through verification of deflections of structure under service loads and comparison with design values
- Visual inspection of structure before and after loading, including crack inspection, shall also be carried out
2. RELEVANT SPECIFICATIONS, STANDARDS AND DOCUMENTS
Service load test shall be conducted in accordance with following guidelines: - Design Manual for viaduct and bridges - 22 TCN 272-05: Specification for Bridge Design - 22TCN-243-98: Provision for evaluation of road bridge; - 22TCN-170-87: Provision for load test of bridge; - Other specifications
3. PREPARATION WORKS
Before starting the load test, the current situation of the span should be inspected and recorded on the attached checklist to this MS. All important information facilitating the interpretation of results will be indicated: - Typical 35m span (in straight alignment) shall be tested after erection at site and after installation on permanent bearings and after grouting of PT tendons. Span shall be constructed, stored, transported and erected using the same method of construction and construction sequence time as any other standard typical span - Geometry of span after installation on permanent bearings shall be surveyed and recorded - Full inspection of structure shall be performed prior to testing to verify soundness of structure, including inspection of concrete (presence of cracks), inspection of segment joints, inspection of PT anchorage zone, inspection of elastomeric bearings and substructures - Actual material characteristics of each segment used in tested span shall be provided to Designer and Employer’s Representative prior to testing (concrete testing results from the precast yard will be attached to the load test report)
4. MEASUREMENT DEVICES
Instruments for survey reading (theodolite, precise level, survey stave) shall be calibrated and fit for this purpose. Official documents and calibration certificates are to be produced. - Longitudinal deflections shall be measured with an accuracy of +/-0.2 mm - Lateral deflections shall be measured with an accuracy of +/-0.3 mm - Control points for deflection on span shall be located on adjacent spans. In addition, the control point can be checked by reference point located on ground - Smooth steel plates or nails shall be fixed on structure as survey points. - Structure shall be checked through visual inspection and using magnifying glass if necessary
5. MEASUREMENT OF STRUCTURE
Service load test shall comprise: - Measurement of longitudinal profile & lateral profile of the built span subject to load test - Establishment of status of structures (cracks, pop-out of concrete…) - Measurement of concrete strength (samples from the precast yard or existing concrete testing results)
6. TEMPERATURE CORRECTION MEASURES
Service load test shall comprise: - Prior to load testing, deformation of structure under temperature effects shall be recorded - Deflections and temperature shall be recorded every 2 hours for 2 days prior to load testing - In addition, sun condition (clouded, sunny,…) shall also be recorded - During load test, at every step, temperature shall be recorded, and measured deflection value shall be corrected by temperature difference between current and previous measure
7. LOAD TEST PROCEDURE
- Uniform loading shall be applied as shown on drawings with a maximum loading of 30 kN/m2 (see attachment #3). So the total load on 35m span is 5863 kN ~ 598 ton
For this loading we can use concrete block 0.9m x 0.75m x 3.0m (or similar) which the weight is 5 ton: We can place the concrete blocks on three levels to have enough loads as per the sketch below:
The spread load on the deck of concrete blocks: 120 x 5.0T = 600 ton The spread load on the deck of timbers: 40 x 2.8 x 0.15 x 0.15 x 0.8 ton/m3 = 2.0 ton Total spread load on the deck: 600 + 2.0 = 602.0 ton > 598 ton (required value) - Loading shall be done by using increments 33% - 67% - 100% First we start with timbers and layer 1; then we start with layer 2 and final layer 3. - At each increment: deflection, environment temperature and visual inspection of the structure shall be measured. - When loading reaches 100%, load shall be sustained for 24 hours. - After 24 hours, all load shall be removed: layer 3 layer 2 layer 1 + timber: deflection, environment temperature and visual inspection of the structure shall be measured during unloading process. 8. LOAD TEST MEASUREMENT For the deflection measurement a total of 25 points will be controlled on the deck as below: 5 on the pier Pn line, 5 on 25% of the span length, 5 at mid span, 5 at 75% of the span length and 5 on the pier Pn+1 line. The points on the bottom slab are checked for the longitudinal deflection. The point on the top flange are checked for the lateral deflection.
If the distance of survey points is too far from the control point to enter into tolerance of instrument, we can add another control point on the other tip of the deck on the upcoming span.
9. POST TEST PROCEDURE
After completion of the load test, additional load will be removed from the deck as well as all the survey equipments and survey targets. A load test report with all the results and interpretative analysis, comparing to the theoretical study of the designer, will be submitted for approval.
10.1 EQUIPMENT TO BE USED
All survey instruments: - 1 theodolite for each line of lateral deflection control points - 1 precise level for each line of longitudinal deflection control points - Survey staves
10.2 MANPOWER TO BE DEPLOYED
Manpower to be deployed for the U-girder load test as per organization chart as below.
Note : - Number of manpower could be changed according to site condition.
11. INSPECTION TESTING PLAN
Inspection records will be kept for all critical activities particularly for the load test. Inspection sheets, test reports, material certificates and all the other documents to be collected are listed in the checklist.
12. 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 this load test. 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.
12.1 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 Ugirder load test and details the measures to be adopted to minimize or eliminate those risks identified. Attachment #1
12.2 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.
ATTACHMENT #1: HAZARD AND RISK ASSESSMENT (HRA) ATTACHMENT #2: LOAD TEST CHECKLIST ATTACHMENT #3: MOMENT COMPARISON FOR THE LOAD TEST ATTACHMENT #4: SKETCH FOR LIFITNG WORKS ATTACHMENT #5: MOBILE CRANE LOAD CHART