HUYS ADVIESGALVANISED WIRE REINFORCEMENT(GWR) TECHNOLOGYEarthquake Reinforcement forNon-Engineered Stone and Earth ConstructionsEngineer Sjoerd NienhuysJaffna, Sri LankaFebruary 2006 (Update of July 2004)

AbstractGalvanised Wire Reinforcement (GWR) can be used as earthquake reinforcement for non-engineerddressed and semi-dressed stone walls, adobe, soil block and rammed earth building constructions. Inremote mountain areas masonry with cement mortar is only marginally done (or not done at all) due tothe high cost of the cement, sand and aggregates. Traditional 18" (45cm) thick stone walls have avery loose internal structure horizontally (lengthwise and across) and vertically. While in the pasthardwood tie-beams were used to provide bonding, durable wood has become scarce and expensive.The GWR provides reinforcement both lengthwise and crosswise within the wall thickness andvertically along the borders of all openings. L-shaped and C-shaped cement blocks provide space forthe vertical reinforcement, facilitating construction and providing an aesthetic architectural design.GWR is simple to apply and low cost in material and transport. Several GWR strips can be used forlintel reinforcement. GWR with three length wires is used to make thermally insulating cavity walls.Table of Contents1.INTRODUCTION . 12.EARTHQUAKE REINFORCEMENT TECHNOLOGY. 23.TRADITIONAL DRY STONE CONSTRUCTION. 74.GALVANISED WIRE REINFORCEMENT . 125.GWR TECHNIQUE . 146.BUILDING A HOUSE . 177.CONSTRUCTION DETAILS . 208.RESUME . 27GWR Technology – February 2006 (Update July 2004)

AcknowledgementDuring the development of this technology in 1999-2001, Sjoerd Nienhuys was Technical andProgramme Director of the Building and Construction Improvement Programme (BACIP). He wasassisted by Ahmed Saeed Shaikh, Deputy Director, and Qayum Ali Shah, Manager Field Operations,who built his own house using this technology.BACIP is a project of the Aga Khan Planning and Building Services, Pakistan. The programme wasfinanced by PAK-SID, a collaborative venture between the Canadian International Development Aid(CIDA) and the Aga Khan Development Network. In addition, the cost of the Programme Directorwas financed by The Netherlands Directorate General for International Cooperation (DGIS).Edited by: Doreen NienhuysDrawings, sketches and photographs by:Mubarak Ahmed (BACIP) sketches on pages 11, 21, 22a and 23.Indian Earthquake Research Institute documents (1976) sketches on pages 2- 4.Sjoerd Nienhuys all other drawings, sketches and photographs*********Aga Khan Planning and Building Service, Pakistan (AKPBS,P)300/2 Garden East, Behind Ismaili Garden JamatkhanaKarachi 74550, NienhuysCaritas-Hudec14 Mathew’s Road, Deogu StreetJaffna, Sri [email protected]*********The views expressed in this report are those of the author and not necessarily shared by theAga Khan Planning and Building Services, Pakistan.This report may be copied and/or reproduced, giving due acknowledgement to the author.GWR Technology – February 2006 (Update July 2004)

1.INTRODUCTIONEarthquakes and Remote Mountain AreasThe western wing of the Karakorum Range of the Pakistan Himalayas, comprising the Northern Areasand Chitral, is under the influence of plate tectonics that culminate beneath Afghanistan. Earthquakemovements are frequently registered in the entire area. A very large earthquake occurred in October2005, leaving 75,000 people dead and destroying more than 100,000 houses. Building to withstandthese tremors is therefore extremely important in saving human lives and minimising economicdisaster. Road access to remote villages is by donkey trail. Bringing cement, long concretereinforcement bars sand or aggregate is extremely difficult and expensive.Lack of natural resources, such as timber, have affected the building practices over the last generation.This aspect, combined with rapid population growth, has resulted in a severe deterioration of buildingquality, especially in areas where no alternatives to traditional stone constructions have beendeveloped. BACIP has introduced the Galvanised Wire Reinforcement (GWR), providing aneconomically feasible and technically sound method to reinforce traditional dressed stone, semidressed stone and soil block constructions in remote mountain villages.Non-Masoned Semi-Dressed Stone and Rammed Earth ConstructionGalvanised barbed wire was first used in 1970 with the reconstruction of low-cost bahareque houses(timber frame, bamboo mats and soil plaster construction) in Guatemala by CARE. The use of wiremesh in stone masonry was used by the author in the earthquake reconstruction programme after thedevastating earthquake of 1982 in Dhamar, Yemen Arab Republic1. The galvanised wire-meshtechnology was particularly suited for the horizontal reinforcement of 18" wide dressed stone walls.In the Dhamar reconstruction project, rolls of pre-manufactured double galvanised cattle fencing wereused for rapid application. The openings in this wire-mesh ranged from 6cm to 20cm.The central plateau of Yemen has good quality clays. Two to four-storey houses are traditionallybuilt from rammed earth, having 2-3 ft. thick walls. Before casting and compacting a higher layer oframmed earth between a wooden formwork, a new strip of the cattle wire-mesh is laid from corner tocorner. By doing so, a horizontal reinforcement is realized at 1 ft. vertical intervals, providing aneven distribution of reinforcement throughout the walls. With the slimming of the walls, the wiremesh is cut in narrower strips, keeping the length wires along the sides of the wall about one inchfrom the external face.Plaster or Cavity WallA GWR strip can be made with three length wires. Two wires consist of the main wall reinforcement,while the third external wire is used to create a cavity wall. Cavity walls create thermal insulationwhereby comfort is enhanced and firewood savings realised. Especially in the desert climates andhigh altitudes, such as on the Yemen plateau, Pakistan, North India, Nepal, Tibet, China andMongolia, cavity walls are economically and thermally efficient.1Project financed by the Netherlands Directorate for International Cooperation (DGIS) and DHV ConsultingEngineers, The Netherlands. The use of wire-mesh is common in reinforced masonry designs (burned brick).GWR Technology – February 2006 (Update July 2004)1

2.EARTHQUAKE REINFORCEMENT TECHNOLOGYThe objective of the GWR is to provide internal stress resistance to walls lacking sufficient naturalbonding to function as shear walls, or when the bonding is exceeded by an earthquake jolt. Stressresistance is traditionally obtained with wooden tie-beams laid in the walls. In modern buildingtechnology, iron reinforcement bars are applied by imbedding them in a layer of concrete. This"modern" building technique has a number of serious disadvantages when applied in remote mountainareas because the correct sand and stone aggregates are unavailable, cement is very expensive, andmixture and curing processes are often deficient. Improperly realised concrete constructions becomean additional earthquake hazard in themselves due to their massive weight.The amount of reinforcement required is determined by the expected earthquake forces; these aredirectly related to the mass of the construction (weight). The expected horizontal forces caused by anearthquake can be derived from a standard earthquake code2. This force varies from 20-30% of themass of the construction. For public buildings a multiplier of 1.25 or 1.5 is used, depending on itsimportance. These values are used for low-rise buildings up to four storeys.Well masoned houses with tie-beams, floor diaphragms and consisting of no more than two storeyswith proper distribution of doors and windows are usually strong enough to withstand minorearthquakes. In general, these houses are non-engineered, meaning that no special calculations aremade.Non-masoned and non-reinforced houses will fail in any major earthquake and cause numerouscasualties, as well as great economic loss. For non-masoned (non-bonded masonry) houses to beearthquake resistant, the following is required:a.b.c.d.e.Rectangular cut stones that are fully supported by lower stones.Minimal one through-stone per square meter of wall.Floors and roof beams anchored into the walls in two directions, making diaphragms.Oenings that are at least one meter away from the junctions of the walls.Short freestanding wall lengths (without cross walls) and low unsupported walls.The diagram below shows the effect of an earthquake on a room made in masonry that does not haveany stress capacity3.23The American ACI 318 and the Indian Earthquake code are rather similar in their calculation methods.Sketches on pages 2-4 are copied from Indian Earthquake Research Institute documents, 1976.GWR Technology – February 2006 (Update July 2004)2

The effect of simple stress reinforcement in the higherparts of the wall is illustrated right.The better the stress reinforcement is embedded in thewall and distributed over the higher part of the wall, theless cracks will appear in the unsupported central part.GWR or reinforced concrete tie-beams provide such adistributed stress reinforcement in semi-dressed stoneor soil block constructions.The four diagrams below give an idea of the shear forces in small wall sections, such as those betweendoors and windows. With the occurrence of an earthquake, diagonal cracks will appear in the walls asindicated in the first diagram. To withstand the horizontal forces, stress reinforcement should bebrought into the wall in several layers, crossing the diagonal line of failure (second diagram). Thethird diagram shows the overturning of a narrow wall section. Here stress reinforcement needs to beplaced vertically as indicated in the last diagram. C-shaped and L-shaped cement blocks at wallendings and corners provide room for placing such vertical reinforcement.LOCATION OF HORIZONTAL AND VERTICAL SHEAR REINFORCEMENTThe combination of the above two principles of wall reinforcement requires that narrow wall sectionsneed to be fully framed along their outside borders. With the use of L-shaped and C-shaped blocks,slender stiffener columns can be integrated with the extremities of the walls, connecting thefoundation to the upper tie-beams.The schematic presentation of such a reinforcement pattern is present in the sketches below.GWR Technology – February 2006 (Update July 2004)3

When the above reinforcement pattern is combined with a tie-beam reinforcement in the top of thewall, it will provide an overall reinforcement pattern as indicated in the sketch below.The stability of a house not only depends on the reinforcement of individual wall sections, but on theoverall coherence of the construction as well. Long walls need to be supported with either reinforcedbuttresses or anchored cross walls. All floor and roof beams need to be properly anchored into thewall tie-beams to create floor/roof diaphragms that function in all horizontal directions. In addition,all inside walls need to be anchored into this floor/roof diaphragm.The method of reinforcement described can be used for one or two-storey buildings without loadbearing reinforced concrete columns. However, the higher the building, the greater the amount ofreinforcement required in the lower walls. For buildings with a few storeys, the strength of the shearwalls in the lowest part of the building should be more than in the top floors.The window and door openings should be distributed in the façade in such a way that sufficient wallsegments or piers remain to form shear wall sections. For non-engineered constructions, the totalsection of piers in the lower floor walls should increase with the height of the building. When a twostorey building is planned, but will be built in stages, the amount of piers and internal wallreinforcement should conform to that higher design of the future.GWR Technology – February 2006 (Update July 2004)4

Earthquake disasters occur when a storey is added on top of a ground floorconstruction that was not designed for additional floors. This is aggravatedwhen shear walls on the ground floor are eliminated to make room for shops.The quality control of house construction in villages depends entirely on the knowledge of the houseowner. Building advice should give general rule-of-thumb guidelines to ensure sufficient safety towithstand earthquakes. These guidelines must be understood by both the house owner and the locallyavailable skilled labourers. Some guidelines found in earthquake building codes are: No window or door opening should be made within one meter of the corners of the building. When the width of a wall section between openings is smaller than its height (piers), the verticalsides of these wall sections need to be reinforced. The piers next to a door or window opening should have a minimum width equal to half theheight of that opening. For example, if the door opening is two meters high (6 ft.), the pier shouldbe minimum one meter (3 ft.) in width. When numerous window openings are required, it is better to make one large opening with astrong shear wall, rather than several small openings with many piers. Depending on the design,reinforced columns can be considered instead of several piers. For the top floor, where there will be no future construction above, the cross section of the shearwalls should be a minimum of 40% of the original wall section (without the openings). For the floor where there will be only one floor constructed above, the cross section of the shearwalls should be a minimum of 50% of the original wall section (without the openings). For the floor where there will be two floors constructed above, the cross section of the shear wallsshould be a minimum of 60% of the original wall section (without the openings). When the openings in the lowest floor of a three-storey building consist of more than 30% of theoriginal wall construction, then reinforced column constructions need to be realised. For those buildings that are higher than three storeys, engineering calculations should be made. The above-indicated percentages can be taken over the entire wall section of the floor only whereboth the inner and outside walls have a fully integrated network of linked up tie-beams, floor androof diaphragms. When horizontal or vertical loads are applied on walls, good bonding from face to face of the wallshould avoid internal separation.In traditionally built houses without the traditional wood framing, the above-indicated conditionsseldom exist.The following drawing gives a schematic presentation of the information provided above.GWR Technology – February 2006 (Update July 2004)5

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3.TRADITIONAL DRY STONE CONSTRUCTIONTraditional houses in the Northern Areas of Pakistan use four to seven heavy wooden columns in thecentre of the room, supporting massive roof beams and having in-filled stone walls on the periphery.These dry stone (non-cemented) exterior walls often have internal wooden posts supporting the heavyroof construction. The roof consists of tree trunks, branches, twigs, grass, birch bark and variouslayers of clay soil. Adjacent to the central living area, various stores are built having a solid wallconstruction (no window openings). The only light comes through a central opening in the roof,doubling in function as a smoke outlet.In the event of a major earthquake, the pillared construction would remain standing, but peripherynon-masoned walls would eventually fall out of their framing. If the walls of the adjacent rooms(stores) fail to withstand the earthquake, the pillars would topple sideways causing the whole massiveroof to collapse, burying the inhabitants under the heavy roof and rubble.LAYOUT OF THE TRADITIONAL HOUSE IN THE NORTHERN AREAS OF PAKISTANGWR Technology – February 2006 (Update July 2004)7

TRADITIONAL HOUSE COLUMNS JUST MANAGE TO KEEP THE HEAVY ROOF UP.WITHOUT THE REMAINING BRACING WALLS, THE STRUCTURE WILL COLLAPSE FURTHER.In the past, a wooden tie-beam constructionwas made in the length of the wallconsisting of two parallel (fruit tree) woodsections connected to each other with shortsleepers. In some cases, these lengthwisewooden strips have been applied in thecorners of the walls only.The population growth has created a highdemand for new construction and this hasled to an over-exploitation of availableforests for building materials and firewood.The result is the non-availability of fruittrees for construction and scarcity ofquality wood for the traditional housedesign with the central columns. Thelimited hardwood available in the market isunaffordable for wall reinforcement. In theabsence of an alternative, villagers areconstructingwallswithoutanyreinforcement. This makes all such houseshighly vulnerable to earthquake jolts anddoes not allow for the building of twostorey houses.The GWR replaces the traditional woodreinforcement in dry wall stone masonry.OLD BUILDING WITH TRADITIONAL WOODEN TIE-BEAMSGWR Technology – February 2006 (Update July 2004)8

LATERAL WALL REINFORCEMENT TRADITIONAL METHOD AND NEW GWR SOLUTIONModern dressed and semi-dressed stone constructions have particular disadvantages in relation toearthquake movements. The worst are stone constructions with nicely cut-face stonework.a. Earthquake forces are directly related to the mass of the construction. Traditional 18-20"(46-50cm) dressed stone walls generate tremendous earthquake forces that can only be resistedwith either very strong or very stable constructions. Non-masoned stone construction has neitherof those two characteristics.b. Traditional stone walls are composed of two lines of semi-dressed stones (inner and outer faces).Small pointer stones are used throughout the construction (both on the inside and outside faces) tobalance the stones vertically in the façade of the wall. When some of these pointer stones fall outdue to erosion or vibration, the wall becomes unstable and eventually will bulge and collapse.PHOTO LEFT: CROSS-SECTION OF TRADITIONAL WALL SHOWING LACK OF BONDING BETWEEN FACES,BUT WITH THE USE OF A LARGE AMOUNT OF CEMENT MORTAR AND PLASTER.PHOTO RIGHT: TRADITIONAL WALL, THE TOP IS HELD IN PLACE BY THE ROOF.GWR Technology – February 2006 (Update July 2004)9

c. For a straight uniform finish of thefaçade, the stones are dressed to evenheight and size. The stones are cutbackwards from the cut-face into aconical shape so they can be easilyaligned.The façade stones aresupported inside the same wall withroughly cut stones, rubble and clay.Cut-faced stones will resist somevertical vibrations, but the inside of thewall is compressible. The result willbe a rotation of the cut-face stones,breaking them loose from the innerwall. This will cause the cut-face stonewall to fall away in an earthquake.d. To provide binding between the inner and outer wall faces, through-stones need to be placed atintervals of minimum one meter every other layer, thus providing about one tie per square meterwall. This is still insufficient to withstand many tremors over a long period of time. These walls,if not masoned with cement mortar, will come apart.e. In many government buildings (schools, police posts) the cut-face stone walls are additionallybeautified with raised cement joints. The amount of work and cement of these building is veryhigh, while technically these constructions are potential death traps during an earthquake.EXAMPLE OF POLICE POST WITH CUT-FACE STONE WALLS AFTER AN EARTHQUAKEf.When the 18" two-stone wall is masoned with cement mortar for additional strength and bondingbetween the two faces, large amounts of mortar are required (30% of wall volume). When steelreinforcement bars are masoned into this cement work, the quality of the cement mortar coveringGWR Technology – February 2006 (Update July 2004)10

the steel bars is often inadequate. Consequently, the steel reinforcement bars corrode and destroythe construction in the long term.g. Steel reinforcement bars embedded in natural stone masonry are always over-dimensioned inrelation to their adherence to the stones around them. Many thinner reinforcement wires or GWRprovide a better spreading of the stress resistance throughout the construction.The sketches below depict the above-indicated problems.GWR Technology – February 2006 (Update July 2004)11

4.GALVANISED WIRE REINFORCEMENTThe GWR technique provides a simple, cost-effective solution for making houses better resistant toearthquakes. Although binding of stone walls with cement mortar is the best method for making drystone masonry more earthquake resistant, the disadvantages of using cement mortar in the remotemountain villages outweigh the advantages for many inhabitants: Cement is costly, heavy and difficult to carry, making transport additionally expensive.For loose stone construction, a large quantity of cement mortar (30% of stone volume) isrequired.Reasonable sand quality is required for the cement mortar. Not all riverbeds have the qualityand quantity of sand required, and those that do often are located at considerable distancefrom the villages.Considering the above problems in the remote mountain villages, a reinforcement technique isrequired that can be applied in: stone masonry using stabilised mortar only.Construction of soil block walls.Adobe and rammed earth constructions.Masoned constructions in which stones, bricks or cement blocks are used.Steel bars used to reinforce masonry constructions require strong cement-sand mortar (minimum 1:4)or concrete (1:2:3). When the concrete or mortar quality is poor, steel reinforcement bars willeventually corrode and break the surrounding masonry.The GWR does not require masonry with strong cement-sand mortar (only 1:10) and can be used indry stone construction or adobe walls without the immediate danger of corrosion of the wires.Corrosion protection is adequate with double galvanisation, such as used for barbed wire and fencingwire.Good adherence between the wires and the wall is necessary. To achieve this adherence, a longladder-like strip is made from galvanised wire. The many cross wires grip the surrounding stoneconstruction or adobe masonry at regular intervals (1 ft.). To give the cross wires more grip, theextensions of the cross wires are wound over the length wire (see page 15).The amount of light sand-cement mortar required to fix the cross wires between the stones isconsiderably less in comparison to other masoned constructions. Less cement mortar results inconsiderable material and financial savings. Stabilised cement mortar is a large improvement overmud masonry and avoids wind and rain erosion in the joints.The GWR works best when the reinforcement is placed along the faces of each wall. Thick walls areheavier, but in a thicker wall, the distance between the wires is also increased and the increasedmoment-arm of the reinforcement will be more resistant to bending.An earthquake motion perpendicular to a wall will bend the wall between the supporting cross walls.With the GWR inside the outer faces of the wall, stress forces will be applied to the reinforcement,resisting the bending force. The alternating forces of an earthquake make the wires work in alteration.To improve resistance against compression, the open spaces between the stones of both faces need tobe pointed with cement mortar. Cement mortar is needed because the outside face is subject to windand rain erosion.GWR Technology – February 2006 (Update July 2004)12

WARNING:When the GWR is fitted into a poorly masoned wall construction or laid betweenimproperly cut or round stones that do not fit tightly around it, the GWR will not make thewall stronger.The GWR in itself does not make the wall earthquake resistant. It is only in combinationwith good masonry and/or stone cutting that it greatly enhances the earthquake resistance.The GWR resists only the stress forces and not the compression. The compression forcesneed to be taken care of by good quality stone work.A wall of rubble before an earthquake will be a pile of rubble after anearthquake – with GWR or not. GWR is no superglue.GWR Technology – February 2006 (Update July 2004)13

5.GWR TECHNIQUEThe GWR technique is very simple and straightforward to apply in any wall construction, be it stone,cement blocks, adobe, compacted soil block or rammed earth walls. The GWR needs to be placed incourses from the foundation to the roof tie-beams. The GWR should be placed in alternating layers innon-masoned dressed stone walls to ensure that all stones are connected to the GWR.The GWR strips can be pre-manufactured, point-welded, double galvanised and supplied in rolls in afew standard sizes. Winding the cross-wire extensions can be done quickly on-site using a smallhollow tube tool.Width of GWRThe width of the GWR depends on the type of building materials, as follows: Adobe and Soil Block Walls: For 16-inch wide walls – 14-inch wide GWR. For 12-inch widewalls – 10-inch wide GWR. Semi-Dressed Stone Walls: Traditionally 18-inch wide – 16-inch GWR with light cement mortarin the joints (1:10). Cement Block Walls: Hollow 6-inch cement blocks are preferably used in light wallconstructions, providing stability and some thermal insulation. For the 6-inch hollow cementblock walls, 5-inch wide GWR is recommended.Factory-Produced Point-WeldedWhen the wire strips are factory point-welded, pre-manufactured rolls of 100-200m can be marketedin the same way as rolls of barbed wire. The cross wires should be thinner (2mm) than the lengthwires (2.5mm). The point-welding process needs to be carefully controlled so that the actual sectionof the length wire will not reduce to less than 2mm.Double Galvanisation after WeldingThe cross wires (2mm) are straight and stick 2 inches out from the length wires. After the weldingprocess, the wire strip needs to be double galvanised conform the treatment for good quality barbedwire. The GWR can be rolled to facilitate transport (200m 10 kg).Requirement for a Core HouseMinimal 400m (20 kg) is required for a 50-m2 core house. Each layer in a 50-m2 core house requires50m length of GWR. An earthquake-resistant ground-floor-only house requires six layers of GWR: 2x foundation, 1 x plinth, 1 x windowsill, 1 x lintel and 1 x roof tie. In addition, vertical reinforcementis recommended along all door and window frames, overlapping above the openings (see next page).On-Site ApplicationThe GWR is unrolled on the building site and cut to length. This length is longer than the wallsections to allow overlap and anchorage to the next section. The mason who applies the GWR in thewalls is required to wind the 2-inch extension twice around the main wire or to joining sections of theGWR. This winding will enhance the friction and adherence in adobe constructions; and with a littlecement mortar on the winding, it will greatly enhance the linkage with semi-dressed stoneconstructions. The metal winding tool is about the size of a thick ballpoint pen.GWR Technology – February 2006 (Update July 2004)14

As indicated in Chapter 2, shear wall reinforcement requires vertical reinforcement to be at the endsof the walls and along all window and door openings. The GWR needs to be folded upwards at thecorners of the walls and along the doors and windows. The upward folded GWR will meet otherGWR sections coming from lower layers. The overlapping strips of vertical GWR form the verticalwall reinforcement.GWR Technology – February 2006 (Update July 2004)15

L-shaped and C-shaped cement blocks have been designed for easy masonry work. These cementblocks are placed in the wall corners and along the sides of door and window openings. The cementblocks have three important advantages:1. With the placement of the cement blocks, straight vertical edges are first masoned upwards at allcorners and allow easy in-fill of the cut-stone masonry. A string is stretched between the raisedcorners. This saves substantial time in masonry work.2. The vertical GWR can be pulled upwards in the space between the cement blocks and the stonemasonry. The cement blocks will function as formwork allowing easy filling of the spacebetween the blocks and the stone wall with light mortar and small stones.3. The architecture obtained by the combination of the corner cement blocks and cut-stone in-fillwork is aesthetically very appealing (see sketch on the cover page).Various moulds can be used for making the C-shaped and L-shaped cement blocks. One manual typeof mould is described below – the rack mould. Large quantities of good quality cement blocks can berapidly made with this mould.The rack mould consists of a 2mm sheet metal mould (open at both the top and bottom) and a rackwith a compacting angle iron fitted to it. The mould is placed on a flat, sanded cement floor and filledto the rim with fairly dry aggregate cement mortar (8:1). The rack is then lifted over the mould andset down with force onto the mortar in the mould, compacting the mortar. An addi

Galvanised Wire Reinforcement (GWR) can be used as earthquake reinforcement for non-engineerd dressed and semi-dressed stone walls, adobe, soil block and rammed earth building constructions. In remote mountain areas masonry with cement mortar is only marginally done (or not done at all) due to the high cost of the cement, sand and aggregates.