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Παρασκευή, 21 Ιανουαρίου 2022

Ενας ενδιαφέρων, πλήρως εικονογραφημένος πρακτικός οδηγός που επεξεργάσθηκε η Γαλλική Εταιρεία Αντισεισμικής Μηχανικής (Association Française du Génie Parasismique, AFPS) για την ασφαλή ανακατασκευή των κατοικιών στην ύπαιθρο του Νεπάλ, μετά τους καταστροφικούς σεισμούς που έπληξαν την χώρα.

Manual for post-Earthquake r e b u i l d i n g i n Ne p a l E S E V ALL E Y Swww.facebook.com/rebuildingnepal http://afps-seisme.org “Earthquakes don’t kill people… Improperly design buildings do !” When the shaking from the Himalayan earthquake occurred just before noon on April 25, most of the victims were within buildings hastily constructed and poorly built. This earthquake may have caught Nepal by off guard, but that doesn’t mean it came as  a surprise. In fact Nepal is located on a well-known tectonic plate boundary where Indian Plate goes beneath Asia forming the Himalayan mountain range. This plate collision gives raise to frequent earthquakes, some of them being particularly strong with return period of few centuries. And the resulting devastation came as no surprise, because buildings in cities and in villages of high Nepalese valleys are not constructed to stand up to a quake. Since it’s impossible to predict an earthquake with reliability, the most efficient preventive action is to (re) build with earthquake-resistant principles. This pedagogic document, prepared by the French Association for Earthquake Engineering, aims at applying these simple but efficient earthquake resistant principles to one storey traditional houses in Nepalese valley villages using available materials at those isolated places.Thierry WINTER and colleagues who worked on this guide2 SUMMARY1 Whybuildings collapseduring an earthquake?2 Wellimplantbuildings3 Welldesignbuildings45(Re)buildBuildearthquake-resistantearthquake-resistanttraditional buildingsbag-buildings3 1 Whybuildings collapse during an earthquake?4 Effectsof earthquake on masonry buildings (bricks,before quakerubble stones)f o r e - b ac kDuring an earthquake, the building is shaking at its bottom in all directions. left-rightdu r i n g q u a k eu p - do w n after quake5 Effectsof earthquake on masonry buildings If the walls are not connected at their own junctions and with the roof, cracks appears at the junctions and the walls could collapse under earthquake.(bricks,rubble stones)Total collapse The main damages of masonry buildings under earthquake are in particular : - The failure of the junctions between wall elements with the separation’s walls and walls at the corner of masonry buildings - Bulging delamination and collapse of stone masonry buildings.StoneCollapse of large part of wall in the middle long walls or delamination (No lateral connections)wa l l de l am i n a t i o n wi t h b u c k l e d w a l l sGable collapse (no reinforcement vertical and horizontal band between walls) Walls going out of plumb (bad connection between roof and walls)Collapse of corner (no reinforcement band between walls) 6 Fora good seismic behavior and avoid the collapse, make a monolith building as a gift packageRoof band vertical reinforcement Lintel bandPlinth bandFoundationEssential internal elements i n b u i l di n g s f o r e a r t h q u a k e s a f e t y 7 2 Wellimplant buildings8 Don’tdo it!Do not build at the edge of a cliff or close to a river/stream.no!no!Do not build under a cliff.Do not build under rocky blocks.no!9 Doyes!Loose fill slopes must be stabilized.!no!!Foundation of buildings must be in firm soil.Keep distances from landslide and rock fall hazard.10 m [33’]1m [40”]yesnoit!10 m [33’]yes! 10 3 Welldesign buildings11 Welldesign buildingsNo irregular shapes.no!no!no!Do not stack buildings. No piles for accommodating slope.no! no! 12 Preparation 0,50 m [20”]Retaining wall, about 1 m [40”] height and 50 cms [20”] thick, made of rocky blocks greater than 30-40 cms [12-16”], with, at its base, a draining ditch made of pebbles about 4-10 cm [2-4”] in diameter.1mSlope 45% Slope 33%NON-Slope 18%+Slope 10%++Slopes greater than 33% are forbidden. Prefer slopes lower than 18% (1 to 3), maximum handmade slope.0,50 m[40”]of horizontal platforms[20”]Excavate wide platforms of 8 m [26’], with a 1 m [40”] high retaining wall in-between.8m [26’]8m8m[26’][26’]13 Evacuationof rainwatersPlatform organization has to take into account run off water evacuation through a dedicated ditches network.By the way, drinking water and wastewater networks must be also implemented far from foundations of buildings . Walls of hole made by stones cemented or by stones alone if thick wall.G ro u n d le v e l ( u p p e r p la te fo rm )Slope lower than 3%G r o u n d le vel ( lo w e r p la teform)Vertical holeV ertical section of ditch between two plateformsSlope lower than 3%14 4 (R e ) build earthquake - resistant traditional buildings15 Howto build earthquake-resistant t r a d i t i o n a l s t o n e h o u s e ( o n e s t o r e y ) ? Roof bandSeismic bands hold the walls together and ensure integral Box actionvertical reinforcement Lintel bandPlinth bandFoundation16 Seismicresistant layout4m [13’] 0,40 m [16”]0,40 m [16”]1,50 m [5’] 1,50 m [5’]4m [13’]1,50 m [5’] W=4m [13’]1 m [40”]H = 2, [8’]4mFundamental ratios between wall thickness, maximum length, width and height of the walls must be respected. a. Wall thickness (e) greater than 40 cm [16”]. b. Wall width (W) lower than half of wall length (L). c. Maximum wall height lower than 6 times the wall thickness. d. Maximum sub-length between cross-walls lower than 10 times the wall thickness and lower than 3 m [10’]. e. Wall length greater than 1.2 m [4’] must be preserved on each side from door and windows. f. Window and door width lower than 1.2 m [4’]. An example is given on the drawingL=8m [26’]Foundations 17 BuildingmaterialsMud mutar As much as possible, it is better to use cement mortar (Cement 1; sand 3; water 1/3,) instead of mud mortar.Bamboo Matured bamboo ≥ 3 years old to soak the bamboo in running water ≥ 3 weeksRoofing sheetsnailsRubble stones / Broken stones Thickness ≥ 50 mm [2”] With, lenghth ≥ 150 mm [6”] size as uniform as possibleanchor steelTimber, Dry, straight, no cracks and no notchScrew for roof 18 Foundations Protection of vertical wood reinforcement from moisture : - applying a protective coating (bitume or melted paraffin wax) - or layer of polyethylene around wood pillar.Rubble stones foundation with mud mortar40 cm [16”]Dig a trench under the future walls to perform the building foundations and add an outside rainwater drainage network.INSIDEOUTSIDE vertical reinforcement [timber or bamboo] timber plinth band rubble stones with mud mortar40 cm [16”]90 cm40 cm[35”]dry gravels[16”] gravel [loose stone] 20 cm [8”] thick sand : 10 cm [4”] thick 70 cm [28”]rainwater drainage19 Wallsin rubble stones with mud mortarThrough stones or wood pieces 120 cm [4’]60 cm [24”]60 [2460 cm [24”]cm ”] 120cm[4’]To avoid stone wall delamination, put regularly spaced through stones or wood pieces across the wall thickness.60 cm [24”]60 cm [24”]20 Detailof seismic bands withRoof bandAs previously mentioned, Lintel band seismic bands hold the walls together Plinth band and ensure integral Box action. If these seismic bands (plinth, lintel and roof) are made with WOOD, apply the present design.WOODsectionb50 cm [20”] 7,5 cm50 cm [20”][3”] 3,8 cm [2”]50 cm [20”]5,0 cm [2”] 3,0 cm [2”]2 sawn lumbers horizontal renforcement50 cmmud mortar50 cm50 cm[20”][20”][20”]nails [minimu 4]loose small stones rubble stones [mud mortar]vertical confining [timber or bamboo] 21 Detailof seismic bands with 15 cm [6”]Roff band Lintel bandBAMBOOcorner post bamboo plinth band10 cm [4”]small stones mud mortarPlinth band keys If these seismic bands (plinth, lintel and roof) are made with BAMBOO, apply the present design. Note spacing of vertical bamboo reinforcement.bamboo plinth bandsectioncorner post keys plancorner post HHvertical renforced bambooHsmall stones H mud mortarrubble stones [mud mortar]bamboo planth band22 Connection 7 cm7 cm[3”][3”]between transverse walls To further strengthen transverse walls (corner) horizontal timber stiches may be used. Minimum length in each wall is 1.20 m [4’]. They are placed in every 60 cm [24”] in height.plan 40 cm60 cm[16”][24”]40 cm40 cm[16”][16”]60 cm6 cm[24”][3”]3,8 cm [2”]5 cm 40 cm[2”][16”]3 cm [1”]Wood dowel at corner of wallReinforce wall corners with 3 vertical timber or bamboo wood dowel greater than 7 cm [3”] in diameter.3 wooden vertical reinforcement1,20 m [4’] 0,60 m [24”] 0,60 m [24”]1,20 m [4’]0,40 m [16”]23 Connection 7 cm [3”]7 cm60 cm40 cm60 cm[3”][24”][16”]between transverse walls[24”] 40 cm [16”] 60 cm [24”]6 cm [3”] 3,8 cm [2”]40 cm5 cm[16”][2”]plan3 cm [1”]Wood dowel at T junction wallTo further strengthen transverse walls (corner) horizontal timber stiches may be used. Minimum length in each wall is 1.20 m [4’]. They are placed in every 60 cm [24”] in height. Reinforce wall corners with 3 vertical timber or bamboo wood dowel greater than 7 cm [3”] in diameter.wooden vertical reinforcementT junction stiches0,40 m [16”]m 1,200.60 m [24”] 1,20 m0.60 m [24”][4’]24 Timbervertical reinforcement 40 cm [16”]40 cm [16”]wooden seismic band40 cmTimber vertical reinforcement for each corner[16”]Timber vertical reinforcement for T-junctionPut vertical reinforcement at each junction between walls (corner and T-junction) on the height from foundation to roof. 25 Timber Rafter Cross-bracing in plane of roofCollar tieroof Roofs have two main parts: structure and cover. Roofing structure must be light, well connected and adequately tied to the walls. Do not charge an attic with heavy load. purlinRoofband6x12 cm [2x5”] 8x 12 cm [3 x5 ”]Roof band and rafters tied together with wire8x12 cmwooden roof band Steel anchor must be placed during the construction of stone wall. It is threated for fixing the roof with a bolt.[3x5”]loose stone with mud mutarSteel anchor Stone wall 26 Timber 6x 6xpurlin12cm[2x512cm[2x5”]wooden pin min. Ø 10 mm”]2 8x18x12 cm [3x5”]12 8xm [3x5”]iron sheet 4,40 mm [0,2”] plank 20x100 mm [1x4”] bolt min. Ø 10 mm Ø [4”]cm[3x5”]6x12x512[3Ø [4”]All pieces forming the roof structure ( planks, rafters, collar ties, purlin,…) must be tightly connected using wooden pins, metallic sheets and bolts.”]cm[8xcmcm8x 12 cm [3 x5 ”]12[3x5”]8x12 c8xroof”] 3x58x12c3x m[5”]bolt min. Øcm [2x5”]cleat 12 8x[1x4”][0,2”]”]6x12 cm8x110 mmiron sheet 4,40 mmx5purlinØ [4”]plank 20x100 mmcm[32cm[3x5[2x5”]”]bolt min. Ø 10 m Ø [4”]27 RoofRidge coveriron panelridge 6x12 cm [2x5”]Purlin 6x12 cmScrew[2x5”]Galvanized iron sheet roofcleat1 Roof truss 8x12 cm [3x5”]Screw20 [8”cm]Galvanized iron sheet roofPurlin 6x12 cm [2x5”]Galvanized metallic panels are fixed on the wooden roof structure using screws. Overlapping of galvanized metallic panels must be of 30 cm [12”] on large side and 10 cm [4”] along short side. Use a minimum of 8 screws by panel.1cleat2Roof truss 8x12 cm [3x5”] Galvanized iron sheet roofPurlin 6x12 cm23Screw[2x5”]cleatRoof truss 8x12 cm [3x5”]Fascia beam 2x25 cm [1x10”]Screw for roof328 5 Build earthquake-resistant bag-buildings29 Buildingmaterials x8 BAMBOOS5,810 cm [4”]5,00 m10 cmx8 BAMBOOS’] 0 m [19 [16’]x10 WOOD PURLINS[4”] 10 cm [4”]from 3,20to 3, m [11’]x4 WOOD POLES12’] 70 m [6,5 m[22’]6 cm [3”]10 cm250 Nails[4”]2,50 m [8’]x202 cm0,80 m[1”][31”]Broken stones for ballasting roof galvanized metallic panels10 cm [4”]Nylon yarn[7’]RopePeak of cut bamboo2mPVC rice bagsx100,80 m [31”]30 galvanized metallic panelsStraw 30 Preparationof bags0,60 m [24”]0,12 m [5”]0,40 m0,60 m [24”]0,12 m[16”][5”]Example of a 30 cm [12”] bag filled at the good level within the template.0,30 m [12”] 0,40 m 0,40 m [16”][16”]0,12 m [5”]0,30 m [12”]clay0,40 m [16”]0,40 m [16”]0,30 m [12”]0,45 m [18”]0,30 m [12”]stone0,12 m [5”]0,12 m [5”]0,45 m [18”]Construct 4 wooden templates to fill bags at adequate level.Bags must be filled as above shown : stone in the center part to increase the friction between bags ; and clay at the bottom and the top respectively to facilitate the insertion of the peaks of bamboo.31 Minimumtools required 8.1. 2.5.4.7.6.3.For the platforms preparation and excavations : 1, 2, 3 For the construction : 4, 5, 6, 7, 8 32 Foundations Map0,25 m [10”]view of the dimensions of the projected building0,25 m [10”] 2,50 m [8’]Map 2,00 m [7’]0,30 m [12”] 2,50 m [8’]view of pole location and the trenchto be excavated for the building foundations 6,40 m2,80 m [9’][21’]3,00 m [10’]1,60 m [5’]2,50 m [8’]0,80 m [31”]1,80 m0,10 m [4”][6’] 7,10 m [23’]The dimension of the projected building is directly derived from the number and sizes of galvanized metallic panels, by considering an overlap of 10 cm [4”] and 30 cm [12”] for the short and large sides respectively. Here, it has been considered 10 and 20 units of 80x200 cm [31”x7’] and 80x250 cm [31”x8’] galvanized metallic panels respectively.2,50 m 1,60 m[8’][5’]2,05 m1,70 m2,05 m[7’][6’][7’]33 Foundations 0,60 m 0,60 m [24”]0,20 mFoundations and pole anchoring[0,7”] 0,60 m 0,60 m [24”]TrenchDig a trench under the future walls to perform the building foundations.Foundations has to rise from 10 to 20 cms [4” to 8”] above ground level at the base of opposite walls.Foundations and pole anchoring must be performed as in the “(Re)build earthquake-resistant traditional buildings” chapter (plate 19)0,10 m [4”]34 Plinthseismic band implementation and connections with foundationsAs previously mentioned, seismic bands hold the walls together and ensure integral Box action. This plinth seismic band is made of double bamboo, 10 cm [4”] in diameter, at the base of each wall.PlinthInfillingof the plinth seismic bandInfill the space between bamboo with small stones and mud mortar.seismic band at the base of each wall0,10 m [4”] 0,10 m [4”]0,20 mAt each wall corner, bamboo are closely connected (i) some with the others and (ii) with vertical poles by means of cleats.[8”]35 Constructionabove foundations and plinth seismic bandPlace 60 cm [24”], 40 cm [16”] and 30 cm [12”] long bags on the lower part of the plinth seismic band in order to reach a global horizontal plane above the seismic band as shown on the drawing.Place 60 cm [24”] long bags at the base of the vertical poles up to the height of the plinth seismic band.36 Construction 1stbag layerPlace the various size bags (various colors) above the seismic band to achieve the 1st layer.Watch out ! Bag tongues pass over the “full” bags. Crash the peaks of cut bamboo cut in bags for linking filled bags. 37 Construction 1stof wallsbag layerComplete the 1st layer by respecting the distribution of various bag sizes (colors). Do not forget the internal and outer strengthening along vertical poles.1stWatch out ! Bag tongues pass over the “full” bags. Crash the peaks of cut bamboo cut across upper tongues and lower bags for linking filled bags.b ag l a y e r s e e n f r o m a b o v e38 Construction Secondof wallsbag layerStart again by bags against poles and respect as well the sense of bag arrangement. Don’t forget to crash the peaks of cut bamboo.Secondb ag l a y e r s e e n f r o m a b o v eStuff spaces around posts with small stones and mud mortar. 39 Thirdbag layerConstructionof wallsForth layer similar to the second one BUT by inverting the sense of bag/tongue arrangement.ForthForthlayer from abovebag layerThird layer similar to the first one BUT by inverting the sense of bag/tongue arrangement.Thirdlayer from above40 Construction Nextof wallsbag layersLintelLayers 5, 9 and 13 similar to the first layer Layers 6, 10 and 14 similar to the second layer Layers 7, 11 and 15 similar to the third layer Layers 8, 12 and 16 similar to the forth layerseismic band implementationAs previously mentioned, seismic bands hold the walls together and ensure integral Box action. As for the plinth band (plate 35), this lintel seismic band is made of double bamboo, 10 cm [4”] in diameter, at the top of each wall. Start with two opposite walls.Placingof the flueAttention not to leave the flue against PVC bags: keep it away using with stones or/and clay.41 Construction Lintelof wallsseismic band implementationwallsReach a global horizontal plane before placing bamboo on the two remaining opposite walls. Before placing the seismic band bamboo on the two other opposite walls, arrange 40 cm [16”], 45 cm [18”] and 60 cm [24”] long bags on the top of the walls as shown on the drawing.CompleteAt each wall corner, bamboo are closely are closely connected (i) some with the others and (ii) with vertical poles by means of cleats.the lintel seismic band42 ConstructionInfillthe space between bamboo with small stones and mud mortarof walls and connections for roofReacha global horizontal planeBefore placing the seismic band bamboo on the two other opposite walls, arrange 30 cm [12”], 40 cm [16”] and 60 cm [24”] long bags on the top of the walls similarly to first bag layer (as shown on the drawing).43 Constructionof walls and connections for roof Bag 2.90 m [10’7”]layers above the lintel seismic band 2.75 m [9’]2.55 m [8’4”] 2.40 m [8’]Placethe roof frameworkBags filled with strawPlace bags up to 10 cm [4”] from the top of poles. Respect the same arrangement than for first, then second, then third, then forth layers.Lay down the 4 (or plus) wood purlins lintels (according to snow effects): be care that the two central one are located at the center beneath the overlapping of the galvanized metallic panels.Connect the purlins to the poles with cleats and/or wedge them with bags of adequate sizes. Isolate and seal with bags filled with straw.44 Construction Roofof roof InsulationimplementationFix the galvanized metallic panels to the wood purlins by means of 8 nails by metallic panels, 4 at the top and 4 the base of the metallic panel overlapping.of the roofInsulate the roof with wisps of straw and fix them with rope set on the wood purlins.RoofstabilizationStones are added stabilize roof against wind.45 Constructionof current slabInside the house, settle a mud floor about 10 cm [4”] thick.To protect PVC bags from the sun and guarantee the building durability, it is recommended to implement an outside facing on facades using : - Either “dry” stones and not connected to the building façade - Braided bamboo : but avoid the mixture clay / straw mixture which remains fragile facing rains46 P repared by 1. E arthquake - resistant traditional buildings Marc BOUCHON : AFPS Expert (Civil Engineer) Youssef JARADEH : ARCADIS Expert (Civil Engineer) – AFPS member Caterina NEGULESCU : BRGM Expert (Civil Engineer) – AFPS member Jean PICCHIOTTINO : AFPS Expert (Civil Engineer) 2. E arthquake - resistant bag - buildings Eric PASQUIER : Head of the Société d’Aménagement de la Savoie and « Soutiens d’Avenirs » (NGO) president Georges RENAUD : CEO of STEBAT group (Civil Engineer) Pierre RIEGEL : Head of EQUATERRE (Engineering Geologist) 3. N etwork diffusion Samuel AUCLAIR : BRGM Engineer (Seismologist) – AFPS member Ghislaine VERRHIEST : Ecology French Ministry (Risk Expert) – AFPS member Richard GUILLANDE : SIGNALERT CEO – AFPS member 4. D rawings and final design Marie Gabrielle BERLAND : Independent worker – www.mgberland.com 5. G lobal conception and coordination Thierry WINTER : BRGM Public Policy Deputy Director (Natural risk expert) AFPS member47
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