Lesson learnt from Nepal Earthquake

Transcription

1 Post-earthquake School Reconstruction Project Workshop on Earthquake Resilient Construction for School Buildings Day-1 Session 2 Lesson learnt from Nepal Earthquake Chandani Chandra Neupane

2 Gorkha Earthquake 2015 Gorkha Earthquake 2015 is followed by 465 numbers of aftershocks with local magnitude 4 until 07 July

3 Impacts of Nepal Earthquake Barpak Village Bhaktapur Kathmandu Gorkha Sindhupalchowk Dhading 3

4 Impacts of Nepal Earthquake Nuwakot Kavrepalanchowk Rasuwa Dolkha Makwanpur Sindhuli 4

5 Affected Area (31 districts) 14 districts D. Gautam & H. Chaulagain (2016) 5

6 Loss: Gorkha Earthquake ,000 schools estimated destroyed Deaths 8,686 Injured 16,808 Government Houses Fully Destroyed: 978 Partial Destroyed: 3,021 Public Houses Fully Destroyed: 500,223 Partial Destroyed: 269,156 6

7 Is damages/causalities less? Both earthquakes occurred on a non-school day. Time of Earthquake (Mid day) : 11:56 am (NST), 12:50 pm (NST) Less no of tall buildings Less population density in epicenter and severely hit region. 7

8 Lesson Learnt Approach for the better seismic performance of buildings needs to take into account from grass-root realities. Must create awareness that leads to increased demand for safer buildings and skills. Must strengthen capabilities at all levels. 8

9 Lesson learnt from Nepal Earthquake 9

10 Lesson learnt from Nepal Earthquake Other Measures Nonengineered Construction Construction Technology Transfer of Lessons Lesson Learnt Construction Material Appropriate Planning Training of Masons Site Consideration Legal Enforcement and Awareness 10

11 Lesson 1: Non-engineered Construction 90% Construction = Nonengineered (No engineers & professionals are involved in survey, design, construction & supervision) Destruction of non-engineered structures during earthquake 11

12 Lesson 1: Non-engineered Construction COUNTERMEASURE 1 New construction (non-engineered) needs to stop increasing risk Larger needs for retrofitting and strengthening of existing buildings for decreasing unacceptable risks. Non-engineered Construction in Nepal 12

13 Lesson 1: Non-engineered Construction COUNTERMEASURE 1 Emphasis on retrofitting, because; a) it creates awareness, and b) it is actually feasible in public institutions such as public schools. It is much easier to intervene in residential buildings for new seismic-resistant construction. Retrofitting Process 13

14 Lesson 2: Construction Technology Building Typology found in Nepal 1. Adobe or earth construction 2. Stone in mud mortar 3. Brick, Block or Stone in cement mortar 4. RC framed construction with masonry infill 5. Timber/bamboo framed construction 6. Steel framed buildings 14

15 Lesson 2: Construction Technology Poor Construction technology/skill The prevailing construction practice does not incorporate earthquake resistant components and the existing housing stock is highly vulnerable to earthquakes. Only RC structure might not be disaster resilient, if it is constructed without proper foundation, seismic bands, in good soil and following correct construction techniques. 15

16 Lesson 2: Construction Technology COUNTERMEASURE 2 Appropriate technology should be developed or transferred. For example, instead of changing very high strength construction material or applying higher technology in construction, stitching the walls, providing bands, tying roofs and floors and vertical rods at corners etc. in case of masonry buildings, and improving ductile detailing, and workmanship in case of RC buildings are important than adopting new construction material. 16

17 Brick Masonry Vertical reinforcement in T & L joints. Horizontal Bands of at least 2 ft. Mortar joints should be properly arranged & vertical joints must not be in straight line. long in each side in each (24-36 inch height). Sill & Lintel Bands Properly designed Roof Beams Brick Masonry in C/S Mortar: 3 Story Building -At least 14 thk. wall in ground floor 17 and 9 thk. wall in upper floors; 2 story building 9 thk wall for all floors.

18 Lesson 2: Construction Technology COUNTERMEASURE 2 In Rural areas, intention should be made to incorporate earthquake resistant elements in brick or stone masonry in mud/cement. This acceptance on the technology and availability of the skilled human resources will certainly result in better sustainability of the technology. 18

19 Stone Masonry Small/Boulder stone should be avoided. Vertical Joints shouldn t be in same line. Lintel Bands of RC. Rods must be carefully bent in the corners. Vertical Reinforcement at T & L joints. T & L bands should be provided in each 2m height. Through stone or steel bar at every 2 ft. height and every 3 m length-wise. Properly designed Roof Beams 19

20 RC Framed Structure 60Ф No. of story and distance At least 3 stirrups between 2 columns decides the column dimension ft. Foundation Beam & Tie Beam. Width of column > width of beam by 3. Distance between columns should be properly designed and in same line. STIRRUPS Rod of Beam 60Ф ft. Ld 60Ф Beam Column Joint Illustration Rod of column All the Splicing shouldn t be placed at same position. Stirrups at 4 distance in splicing area and in column-beam joints at least up to 2ft. distance. Arrangement of reinforcements at sill and lintel in the column as shown in the figure to connect column with the wall. 20

21 Lesson 3: Construction Materials Inherently weak materials and its improper use; for example; mud, boulder stone, low-quality sand, etc. It is difficult to change the construction scenario at once. Forgone Face: Buildings continue to be constructed by using locally available construction materials. 21

22 Lesson 3: Construction Materials Adobe or earth construction and Stone in mud mortar are most vulnerable during an earthquake. Roof materials like tiles, jhingati and stone slate are also vulnerable form seismic consideration. 22

23 Lesson 3: Construction Materials COUNTERMEASURE 3 In urban areas retrofit masonry buildings and construct earthquake resistant RC buildings: Trend shows that adobe and mud-based construction in urban area is significantly reduced and there is a remarkable growth in brick-in-cement and Reinforced Concrete (RC) frame constructions. To stop increasing risk in RC construction, it is necessary to create a condition of enforcing the building code requirements. For decreasing existing risk, existing masonry (brick in mud, and brick in cement) structures should be encouraged for retrofitting. 23

24 Lesson 4: Training of Masons Technicians and engineers have little control over the construction In technological aspects, the local craftsmen play pivotal role. Proper training of craftsman can built his confidence, in using the technology and skill to construct safer buildings. 24

25 Lesson 4: Training of Masons Positive impact of the Mason Training observed at 3 levels: in the community, in the attitude of the masons trained in the construction quality and safety level of the buildings reconstructed. 25

26 Lesson 4: Training of Masons COUNTERMEASURE 4 Trained manpower required for earthquake resistant construction technology Increased awareness and enhanced capacity of masons help implementing building code effectively and practically 26

27 Lesson 4: Training of Masons COUNTERMEASURE 4 Making decision at the top level alone is not sufficient for the challenge of implementation Bottom-up approach is powerful for effective building code implementation 27

28 Lesson 4: Training of Masons COUNTERMEASURE 4: Technology Transfer though Training Training forms a crucial part of Capacity Building. First step is to transfer the disaster resistant technologies to the building artisans & petty contractors, engineers and building owners. Equally important is to make available the necessary material and equipment to the communities. 28

29 Lesson 4: Training of Masons COUNTERMEASURE 4: Technology Transfer though Training Consists of some theory through specially developed communication tools, and extensive hands-on training at an actual construction site in disaster-resistant new construction as well as retrofitting of existing structures. 29

30 Lesson 4: Training of Masons COUNTERMEASURE 4: Technology Transfer though Training Training of engineers is equally important since they could effectively promote the concepts of improved technology and retrofitting. Unfortunately, most engineers lack the know how vernacular structures (built with local materials) behave in an earthquake and what makes them disaster resistant. Hence, this forms the basis for their training coupled with the site visits that would enable them to relate theory with practice. 30

31 Lesson 5: Legal Enforcement & Awareness Most municipalities have a system of building permits. But there is no provision in the process to check the submitted plans against the strength criteria. 31

32 Lesson 5: Legal Enforcement & Awareness COUNTERMEASURE 5 Only one approach may not work Seismic safety of buildings can be improved by legal enforcement and awareness The approach of creating building act and laws can provide legal environment where as awareness at community level or training to masons transfer the ownership of knowledge and the process leading to a desired level of sustainability. 32

33 Lesson 6: Site Consideration During earthquake, the construction works at steep & unstable slopes, landslide areas, landfill areas, river banks and water logged areas had found to be destroyed more than areas with good and stable soil. Choice of site: Slope stability Flood Hazard Liquefaction Hazard Ground Topography Fault Rupture Hazard 33

34 Lesson 6: Site Consideration COUNTERMEASURE 6 Construction site should be selected properly. i. Compact soil & stable ground ii. Nearly flat terrain or ground with low slopes iii. Far from river iv. Far from big trees v. Far from geological fault & ruptured area vi. Far from unstable & steep slope vii. Far from landslide & rock fall 34

35 Lesson 6: Site Consideration COUNTERMEASURE 6 Improving site is an expensive option Saturation of foundation soil is dangerous from liquefaction and landslide, so site should be kept drained. In the area where it is impossible to avoid selection of a site with saturated soil, pile foundations going to depths of 8 to 10 m will generally be adequate. 35

36 Lesson 7: Appropriate Planning Disproportionately tall building Pounding between two close buildings Sudden deviation in load transfer path 36

37 Lesson 7: Appropriate Planning COUNTERMEASURE 7 Plan of Building Source: EERC 37

38 Lesson 7: Appropriate Planning COUNTERMEASURE 7 Shape of Building Source: EERC 38

39 Lesson 7: Appropriate Planning COUNTERMEASURE 7 Projection and Overhangs Avoid heavy mass at top Source: EERC 39

40 Lesson 7: Appropriate Planning COUNTERMEASURE 7 Open Ground Story Separation Joint Source: EERC 40

41 Lesson 8: Transfer of Lessons COUNTERMEASURE 7 Dangers of earthquakes Necessity for engineers to design structures for earthquake-prone areas that are able to withstand the forces of seismic waves. A properly engineered structure does not necessarily have to be extremely strong or expensive; it has to be properly designed to withstand the seismic forces while sustaining an acceptable level of damage. 41

42 Lesson 8: Transfer of Lessons COUNTERMEASURE 8 Programs like School Earthquake Safety Program (SESP) should be promoted & continued In all the villages where SESP has conducted, local people have been replicating the construction methods employed in school building to construct other buildings too. Except some minor features, newly constructed houses adopt all basic earthquake resistant construction technology like bands, wall stitching, vertical tensile reds etc. 42

43 Lesson 8: Transfer of Lessons COUNTERMEASURE 8 It shows higher level of perception on what masons are trained. Obviously, it can be said that the process of replication would multiply in future to set a new technological culture in construction. In this aspect, the retrofitting project of school has much higher social value compared to other risk reduction programs that hardly are able to translate technology in real ground in root level. 43

44 Lesson 8: Transfer of Lessons COUNTERMEASURE 8 Institutionalization is long-term process To achieve better seismic performance of buildings the approach and processes should address the needs at more than one level and take into account the grass-root realities. It must create an awareness that leads to increased demand for safer buildings and skills. 44

45 Lesson 8: Transfer of Lessons COUNTERMEASURE 8 Institutionalization is long-term process It must strengthen capabilities at all levels. It should allow some flexibility in how the various levels of safety norms/standards are adopted. 45

46 Lesson 9: Other Measures Non Structural Measures Early Warnings & Communication How communities & the private sector saved lives and assets Relocation and new regulations Emergency Response Prompt Rehabilitation of infrastructure Governance in time of emergency Partnerships to facilitate emergency operations Evacuation centers and temporary housing New crowd-sourced information and the use of social media and FM radio 46

47 Lesson 9: Other Measures Reconstruction Planning A new law for reconstruction Hastening recovery and reconstruction through cooperation between communities and local and national government Debris and Waste Management Livelihood and Job Creation Hazard and Risk Information and Decision Making Economics of disaster risk, risk management and risk financing Prompt Government intervention to keep damage from spreading across sectors & countries 47

48 Lesson 9: Other Measures Recovery and relocation Relocation and new regulations of land use in at-risk areas Relative merits of self-reconstruction and public housing in post-disaster reconstruction Preserving cultural heritages Recovering from damage 48

49 Reference Amod M. Dixit, 2004, 13th World Conference on Earthquake Engineering, Vancouver, B.C., Canada, Promoting Safer Building Construction in Nepal UNDP. A Global Report, Reducing Disaster Risk, A Challenge for Development GESI. Global Earthquake Safety Initiative, Pilot Project, Final report. Geo Hazards International and United Nations Center for Regional Development, NSET. Kathmandu Valley Earthquake Risk Management Action Plan. NSET and GHI, V. Suresh, Promoting Safer Building Construction, Regional Workshop on Best Practices in Disaster Mitigation. Learning from Mega-disasters: Lessons from the great East Japan Earthquake National Center for Peoples Action in Disaster Preparedness Center for Eco-centric Development and Peoples Action Protection of Educational Buildings Against Earthquake: A Manual for Designers and Builders. Nepal Earthquake Response: Lessons for operational agencies 49

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