Findings and Proposals/Recommendations

Transcription

1 For Resilient Infrastructures Development in Nepal Findings and Proposals/Recommendations 1. Sustainable Infrastructures and Key Recommendation 2. Vulnerability Study for Roads & Bridges in Kathmandu Metropolitan Area 3. Development of Nepal Own Seismic Design Code 4. Improvement of Roads in Rural/Mountain Areas Shigeki UNJOH, Dr. Eng., PE PWRI, MLIT, JAPAN 1

2 Sustainability of Infrastructures -Roads and Bridges- Planning and Structural Design Necessary Requirement and Function Seismic Design For Sustainable Infrastructures Construction Quality Control Materials Construction Technology Maintenance Operation Inspection (Ordinary, Emergency) Rating Repair Works Seismic Retrofit Issues for Consistency 1. Policies and Codes Development 2. Technology Development/Accumulation and Dissemination/Education System of Engineers (Government, Academia, and related Organizations) 2

3 Key Recommendation: Establishment of Technology Development Group/Committee/ Organization in Nepal (For Ex. Bridges) Gov. of Nepal NPC MOPIT DOR MOFALD DOLIAAR MOUD KVDA MOI DWIDP Government Academia Technology Development Committee -Bridge Committee- Theory and Real Practice New Technology, Information Sharing, Education, Code Development and Dissemination (Design, Construction, Maintenance) Engineering Association Construction Companies Consulting Firms Bridge Makers Bearing Makers /////// Supporting and Advising International Community 3

4 For Resilient Infrastructures Development in Nepal Findings and Proposals/Recommendations 2. Vulnerability Study for Roads & Bridges in Kathmandu Metropolitan Area 4

5 Objectives of Vulnerability Study for Road and Bridges in Kathmandu Proposal of Urban Recovery Planning in Kathmandu Metropolitan Area based on BBB Concept Long-term comprehensive urban recovery planning in Kathmandu metropolitan area, based on the future population forecast, future urban structure, land use plan, transportation plan, risk assessment, etc. Vulnerability Study for Roads and Bridges As a basis for Urban Recovery Planning in Kathmandu To Prepare Next Possible Earthquakes in Future Next Earthquake M8 class EQ near in Kathamndu Damage to be prevented and Expected Performance No Collapse, No Unseating, and Quick Recovery of Road Function 5

6 Damage to Bridge Weak and Nonductile Stopper Lifeline: Water Pipes 6

7 Vulnerability Study of Bridges Simplified Evaluation Method for Seismic Performance Start Design Drawings, Current Condition Data, Soil Condition, etc. Superstructure Substructure (Pier and Abutment) Unseating 1)Bearing Supports (Stiff/Weak) 2) Stopper (Stiff/Weak) 3) Support Length (Small/Long) Foundation 1) Material (Brick/Wood/RC) 2) Stiff/Soft (Liquefaction/Soft Soil) 3) Scour (Serious/Light) Column 1) Material (Brick/Wood/RC) 2) Type of Section (Wall/Single) 3) Shear Failure Abutment 1) Material (Brick/Wood/ RC) Key Issues: Hazard/Importance/Vulnerability Vulnerability: Design Standard Applied is also essential issue. Vulnerability Ranking on Possibility of Serious Damage (Tentative) Rank A: High Possibility Rank B: Medium Possibility Rank C: Low Possibility 7

8 Analysis of Current Status of Roads and Bridges Yearly Construction of Bridges Total Road Length = 12,500km (approx) Number of bridges(1,709 bridges, data available for 558 bridges) 3 Year Program: 400 Bridge Constructions (Road: 3,000km) Weak Shear Strength and Low Ductility Design After Kobe Data of 558/1709 *) The data is from Web-based Nepal Bridge Management System. 8

9 Seismic Retrofit Improved Seismic Performance Damage 1982 Urakawa-oki EQ Increase of Design Acceleration Improvement of Ductility 1995 Kobe EQ 2011 Great East Japan EQ C o d e LESSONS Research Projects Experimental Researches for Seismic Retrofit R e v i s i o n Unretrofitted Bridges Repeated Similar Damage Observed in Past EQs Retrofit Retrofitted Bridges Suffered Minor Damage except a Few Bridges 9

10 Seismic Retrofit Program in US for Older Bridges By Caltrans (refer to 10

11 Provision of Current Condition Data for Bridges 11

12 Vulnerability Study of Bridges Simplified Evaluation Method #1 (Materials) RC, Steel (Stable) Multi span + Pier Start Material Spans Masonry, Wood (Unstable) Rank A Single span + Abutment Rank C Check Superstructure And Substructure Rank A: Detailed Study including Capacity/Demand Ratio Analysis including Construction Condition of Masonry. 12

13 Vulnerability Study of Bridges Simplified Evaluation Method #2 (Support Length) Start Superstructure Unseating Prevention Support Length SE<40cm: Rank A 70cm>SE>40cm: Rank B (AASHTO Code) SE>70cm: Rank C (JRA Code) If the following devices are provided, 1) Bearing Supports Design Force >IRC Code: Stiff, or 2) Additional Stopper Design Force > IRC Code: Stiff Rank B to Rank C Rank A to Rank B Rank A: Detailed Study including Capacity/Demand Ratio Analysis Installation of Stoppers or Widening of Seat Width 13

14 Vulnerability Study of Bridges Simplified Evaluation Method #3 (Shear of Column) Width(TR): b Width(LG): a Start Substructure (Column) Rank A: Detailed Study including Capacity/Demand Ratio Analysis Good Rank C Wall (b/a>3) Rank B Bending Failure (h/d>3) Confinement Re-bar Poor Rank B *) This is a case for columns without design information including drawings. If there is, the check can be made based on them. Section Type Possible Shear Failure Shear Re-bar Rank A Single(b/a<3) or Multi Column (Circular) Shear Failure (h/d<3) Poor Steel/Fiber/RC Jacketing Of Columns Good Rank B Height: h Width: D *) If TR direction of multi-columns is considered, h shall be h/2 because of bending moment. 14

15 Vulnerability Study of Bridges Simplified Evaluation Method #4 (Foundation Stability) Start Substructure(Foundation) 1. Current/Previous River Area, Reclaimed area, Embankment on Water Area, Low Ground Area between Sand Hills Rank A Low Ground Area other than 1. Check Soil Type Others and Underground Water Level Saturated Sandy Soil Topographical Classification Rank B Layer, No Information Highland, Hill, Mountain Area Rank C Rank A: Detailed Study including FL/PL Values and Thickness of Liquefiable Layers Check Scour Effect Significant Rank A Rank C Not Significant 15

16 Emergency Transport Routes: Bridges on Ring Road and Arniko Highway 8 MLIT Support Team Kathmandu 2 3 Vulnerability Ranking on Possibility of Serious Damage (Tentative, need Detailed Study) A: High Possibility B: Medium Possibility C: Low Possibility *)Check Points 1)Connection of Girder (Stiff or Weak) 2)Seat Width (Small or Large) 3)Columns (Shear Failure, Need Check Re-bar Arrangement) 4)Foundations (Stiff or Soft, Scour) 5)Others (Deterioration) c OpenStreetMap contributors 16

17 Emergency Transport Routes: Bridges inside Ring Road Vulnerability Ranking on Possibility of Serious Damage (Tentative, need Detailed Study) A: High Possibility B: Medium Possibility C: Low Possibility *)Check Points 1)Connection of Girder (Stiff or Weak) 2)Seat Width (Small or Large) 3)Columns (Shear Failure, Need Check Re-bar Arrangement) 4)Foundations (Stiff or Soft, Scour) 5)Others (Deterioration) c OpenStreetMap contributors 17

18 Bridge #1 (Rank A, Deterioration) 18

19 Bridge #7 (Rank A) 19

20 Vulnerability Study of Bridges Simplified Evaluation Method for Deterioration Start Superstructure Substructure (Pier and Abutment) Girder Slab Bearing Ex. Joint Foundation (Scour) Column Abutment Deterioration Evaluation (Tentative) Rank A: Need Urgent Treatment (Unsafe Situation) (Need Detailed Study) Rank B: Need Repair and Replacement in early time Rank C: Continuous Monitoring Rank D: Fair Standardized Evaluation Method of Rank A to D (Photos and Sketches) 20

21 Deterioration (1) Slab and Joints Handrail Rank A: Joint and Slab Pedestrian Deck 21

22 Deterioration (2): Scour of Foundation Bridge closed with large Inclination Rank B: caused by Backfill Soil Scouring Effect (Settlement) Rank A: Scour Rank A: Scour 22

23 Vulnerability Study of Pedestrian Bridges Kathmandu Vulnerability Ranking on Possibility of Serious Damage (Tentative, need Detailed Study) A: High Possibility B: Medium Possibility C: Low Possibility *)Check Points 1)Connection of Girder (Stiff or Weak) 2)Seat Width (Small or Large) 3)Columns (Need Check Re-bar Arrangement (Shear)) 4)Others (Deterioration) c OpenStreetMap contributors 23

24 Damage to Pedestrian Bridge Residual Displacement at Bearing: 46cm No Offset Tilted Column Tilted Column 24

25 Vulnerable Pedestrian Bridges Damaged Bridge Rank A: Seat Width Rank A: Skewed Girder Rank A: Column: Need to Check Re-bar 25

26 Damage to Earth Structures: Soft Soil, Sliding, Settlement, Drainage (Need Detailed Study) Large Slide and Cracks: Need Detailed Study of Soil Foundation 26

27 Embankment Section New Cracks in Retaining Wall (Need Detailed Study) c OpenStreetMap contributors Water Drainage is not enough. 27

28 Road Function and Bottleneck Issues: Bridge Width and Footways Bottlenecked Section of Width Narrow Width and No Footway 28

29 Structures to Reduce River Section Significantly 29

30 Japanese Practice: Bridge Design Plan minimizing the Effect on River Flooding The level of lower bottom of bridge girder shall be higher than planed HWL plus specified additional space. For the river with width of 50m or more, abutment shall not be placed in the lower level than HWL. 50m or more Less than 50m Specified Rules for Location of Bridge Abutment Minimizing the effect on river flooding, appropriate regulation and coordination between river and structures administrations are essential. 30

31 Results of Vulnerability Study for M/P km National Institute for Land and Infrastructure Management A:Vulnerable Pier Narrow Width No footway Narrow Width A:Vulnerable Pier Lifeline Damage Vulnerability Ranking on Possibility of Serious Damage Rank A: High Possibility Rank B: Medium Possibility Rank C: Low Possibility (Tentative, Need Detailed Evaluation) Ministry of Land, Infrastructure, Transport and Tourism JAPAN A:Vulnerable Pier A:Soil Section 32

32 For Resilient Infrastructures Development in Nepal Findings and Proposals/Recommendations 3. Development of Nepal Own Seismic Design Code 33

33 Nepal Bridge Standards-2067 Design Standard Applied The design standards for bridges had not been developed, but it is concluded that 2010 Nepal Bridge Standards specified to use the Indian Road Congress (IRC) Code. It is specified that IRC code or AASHTO Code is to be applied for loading issues, and that IRC code is to be applied for the design. 34

34 Nepal Bridge Standards-2067 Recommendation: It is strongly recommended to develop the original code applicable and suitable for the earthquake situation in Nepal. If we do not have own original code, 1) the information of code is not enough and the understanding of the back-data of each specified article becomes unclear. 2) no technology accumulation since the code shows a measure of current standard technology. 3) no interaction between research and practices 4) no education for engineers since to learn the development/revision of codes is a good opportunity for training for engineers. 35

35 Damage to Bridge Weak and Nonductile Stopper Lifeline: Water Pipes 35

36 IRC: Section Recommended Provision Non-ductile Damage In 2015 Nepal EQ By IRC Code Discussion: It is recommended the design details of blocks should be modified including design force (to be primary) and bending/shear design. By IRC Code 36

37 Performance-Based Design Concept Not specified Target Performance Indian Road Congress (IRC) Code is not performance-based. Discussion: It is recommended to use the performancebased design concept. TARGET SEISMIC PERFORMANCE (Japan) Importance Type of Ground Motion Medium EQ High Probability to Occur Type-A (Standard Br.) Type-B (Important Br.) SPL 1: Prevent Damage Large EQ Low Probability to Occur Type-I EQ Inter-plate EQs Type-II EQ Inland EQs SPL 3: Prevent Critical Damage (Non-Collapse) SPL 2: Limited Damage for Function Recovery 37

38 IRC: Section Z: Zone Factor By NBC Code By IRC Code Discussion: What zone value should be used for Nepal based on IRC code? 38

39 Earthquake Observation Data: Nepal Earthquake of 25 April Mw, 06:11:26 UTC, 28.15N 84.71E, Depth 15km Kanti Path,Kathmandu Distance 14km by CESMD (refer to 40

40 MLIT Support Team Future Anticipated Ground Motion (JICA2002 Study) Possible Scenario Earthquakes 1) Mid Nepal EQ (M8.0 2) North Bagmati EQ M6.0 3) Kathmandu Valley EQ M5.7 PGA: gal (Observation : PGA gal By JICA and MOHA 41

41 IRC: Section R: Response Reduction Factor? Discussion: The values for R without ductile detailing seems to be too large for substructures. Shear type failure is to be prevented. By IRC Code 41

42 Lateral Force MLIT Support Team Ductility Design and Engineering Limit States 耐震性能を満足するエリア 水平力 SPL1 耐震性能 1 SPL2 SPL3 耐震性能 2 耐震性能 3 水 水平変位 耐震性能 1 に対する限界状態 Limit state for SPL1 耐震性能 2 に対する限界状態 Limit state for SPL2 耐震性能 3 に対する限界状態 Limit state for SPL3 Note: The ductility design means the 42 consideration of damage. Lateral displacement 水平変位 42

43 Development of Standard Substructure Drawings for Road Bridges Recommendation: Coming 3 year DOR program: 1) New Road Construction: about 3000km 2) Upgrading of Roads 3) Bridge Construction: about 400 bridges Standard superstructure drawings for road bridges have been published. It is recommended to develop such standard drawings for Substructures considering the soil conditions and the effect of scouring. 43

44 For Resilient Infrastructures Development in Nepal Findings and Proposals/Recommendations 4. Improvement of Roads in Rural/Mountain Areas 45

45 Gorkha, Barpak Area: Countermeasures Countermeasures: Risk assessment, hazard mapping, preparation of heavy machines to reopen, Rangrung improvement River works with appropriate prioritization. 45

46 Roads in Mountain Areas: Ex. Road to Kulekhani: Slope Failure, Rockfalls 46

47 Temporary Repair for River Crossing Need Bridges River 47

48 Summary of Findings and Proposals/Recommendations Kathmandu Urban Area: Structures 1) Improvement of Functions (lanes and width) and Seismic Safety of Bridges on the Emergency Transport Routes to make Resilient the Urban Area. Bridge damage will be a bottleneck and cause the closure of Roads. Replacement to New Bridges, Seismic Design, Seismic Retrofit, 2) Provision of Maintenance Technology and System (Inspection and Repair of Bridges) Deterioration/Scouring might cause serious damage at next events. 3) Improvement of Earth Structures (Reclaimed River areas, Inadequate Drainage System) Countermeasures for Vulnerable Embankment Section 4) Pedestrian Bridges Replacement of Superstructures/Provision of Stopper/Connector Rural Areas and Mountain Areas 1) Improvement of Lifeline Routes to connect Villages to Cities 2) Urgent Countermeasure for Reliable Road Risk Assessment, Evaluation, Prioritized Improvement Works 48

49 Thank you very much Shigeki UNJOH, Dr. Eng., PE, PWRI, MLIT Visit PWRI web site: 49