Research Article Feasibility of Using Palmyrah Strips as ...downloads.hindawi.com/journals/jcen/2014/589646.pdf · Research Article Feasibility of Using Palmyrah Strips as Reinforcing

Research ArticleFeasibility of Using Palmyrah Strips as Reinforcing Material inCost Effective Houses

K Baskaran H E Mallikarachchi M J P L M Jayasekara and G A T Madushanka

Department of Civil Engineering University of Moratuwa Moratuwa Sri Lanka

Correspondence should be addressed to H E Mallikarachchi mhansinirocketmailcom

Received 17 December 2013 Revised 15 March 2014 Accepted 15 March 2014 Published 14 April 2014

Academic Editor F Pacheco-Torgal

Copyright copy 2014 K Baskaran et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Construction of cost effective houses is a dilemma among the impoverished population in developing countriesThe ever increasingprice of traditional building materials results in high capital investments for residential buildings Palmyrah is a significanteconomic resource widely spread all over the northeast region of Sri LankaThis research explores the technical feasibility of usingheartwood of Palmyrah as a reinforcing member in lightly loaded concrete elements Initially mechanical properties of Palmyrahwere examined through static bending tensile and compressive tests Percentages of water absorption dimensional stability andanchorage bond strength were investigated to envisage the suitability of Palmyrah as reinforcement Next several short span slabsand beams reinforced with Palmyrah strips were subjected to tests It was observed that Palmyrah reinforcement enhanced themoment capacity of the slabs and beams compared to unreinforced sections Experimental failure loads of slabs and beams werehigher than theoretically predicted values with Palmyrah reinforcement Further Palmyrah reinforced beams and slabs underwentflexural failures Thus it is concluded that heartwood of Palmyrah has the potential to be used as reinforcement in lightly loadedslabs and beams Further research is recommended to investigate the durability and serviceability issues

1 Introduction

The current energy crisis provoked by indiscriminate indus-trial development andpopulation growth has caused increas-ing concerns about managing the limited energy resourcesavailable todayThepursuit of sustainable development whileproviding shelter for the ever increasing world populationwithout causing environmental degradation has become ahuge challenge

Construction of cost effective houses is an ever-presentproblem all over the world The recent escalation of steelprices has created controversial economic problems in devel-oping countries like Sri Lanka where steel is imported Inaddition after 2004 Indian Ocean tsunami and thirty yearsof internal conflict the demand for cost effective houses hasincreased drastically in Sri Lanka Lack of reliable technicalinformation about local materials makes the consumersmainly depend on expensive industrialised materials forwhich the details are freely available

In this context there is an intense ongoing search fornonpolluting materials and manufacturing processes whichrequire less energy Emphasis is placed on innovative non-conventional materials and construction technologies Asa result the concept of timber reinforcement has recentlyemerged in the construction field

Timber is one of the sustainable building materials onearth which is naturally renewable and recyclable and leavesa lighter footprint than any other In its production theembodied energy in wood is a fraction of the energy requiredto produce almost any other buildingmaterialThere is ampleevidence to prove that our ancestors have used timber stripsto enhance the tensile strength of clay in daub houses

The Palmyrah tree flourishes in tropical and subtropicalclimates in South East Asia It is a cheap and replenishableagricultural resource which is abundantly available in the dryzone of Sri Lanka It is used in many structural applicationssuch as purlins and rafters of residential dwellings Althoughthere is a great deal of local field experience with Palmyrah

Hindawi Publishing CorporationJournal of Construction EngineeringVolume 2014 Article ID 589646 9 pageshttpdxdoiorg1011552014589646

2 Journal of Construction Engineering

as a structural member its feasibility to be substituted asreinforcement has not been searched yet

Thus as a preliminary step this investigation has exploredthe feasibility of using Palmyrah strips as reinforcementin lightly loaded and short span slabs and beams Initiallythe suitability of using Palmyrah strips as a reinforcingmaterial was examined through investigation of mechanicalproperties water absorption and bonding strengthThe loadbearing capacity of Palmyrah reinforced slabs and beams wasexperimented thereafter

2 Review of the Literature

21 Timber Reinforcement During the past few decadesthere has been a growing interest in substituting bamboo andBabadua strips for steel reinforcement in concrete

A series of research programmes have been conducted byGhavami [1 2] Ghavami andHombeek [3] andKankamet al[4] to assess the suitability of bamboo reinforced light weightconcrete elements for low stress applications It is noteworthyto state that Ghavami has revealed that the tensile strengthof bamboo is relatively high and can reach up to 370MPaThis makes bamboo an attractive alternative to steel in tensileloading applications [3]

The results of investigations conducted by Ghavamidemonstrated that for the bamboo reinforced lightweightconcrete beams the ultimate applied load can be increasedup to 400 as compared with the unreinforced concretebeams [2] Moreover further experiments concluded that 3of bamboo with respect to concrete section is the optimumrecommended value of reinforcement [2]

According toKankamwhen bamboo reinforced two-wayslabs have been subjected to concentrated central loadingexperimental cracking loads were found to be on average42 of the experimental ultimate loads and 15 greaterthan theoretical punching loads Since punching failurealways followed the full development of the flexural collapsemechanism there is no fear of sudden shear failure [5]

Since themodulus of elasticity of bamboo is not as high asconcrete bamboo does notmake a significant contribution tothe flexural stiffness of bamboo reinforced concrete sections[1 2] As discussed by Ghavami other main shortcoming ofbamboo is dimensional variation of bamboo strips withinconcrete due to moisture and temperature effects which leadto cracking of concrete during service life [1 2]

Laboratory tests were carried out by Kankam on one-wayand two-way concrete slabs reinforced with Babadua barsExperimental failure loads of one way slabs were found tobe on average 300 and 175 of the theoretically predictedvalues for unreinforced section and Babadua reinforcedsection respectively [6] On average monotonic and cyclicfailure loads of two-way slabs were approximately 330and 270 greater than the theoretical flexural strength ofunreinforced concrete section respectively They were also170 and 200 higher than the theoretical flexural strengthincluding Babadua bars [5]

The above studies have depicted that strips of someecological materials satisfy fundamental requirements to be

used as reinforcing bars in concrete elements After waterrepellent treatments they have shown no decay in concretemedium However swelling and shrinkage of timber andlow bonding strength between timber and concrete are stillcritical issues which limit their applications in composites

3 Methodology

The experimental procedure comprised two main sectionsInitially eligibility of Palmyrah as a reinforcing materialwas scrutinized by determining mechanical and physicalproperties of Palmyrah Then Palmyrah reinforced concretebeams and slabs were cast and tested to find the ultimatecarrying capacity

31 Testing of Palmyrah Strips Tests were conducted incompliance with BS 3731957 to determine the mechanicalproperties of Palmyrah from various regions in the country[7] Static bending test and compressive test were done usinga Universal Timber Testing Machine whereas tensile test wasperformed by tensometer as demonstrated in Figures 1(a)1(b) and 1(c)

Bending strength modulus of elasticity and tensile andcompressive strength parallel to grain were determined andthe characteristic values have been derived by statisticalanalysis Characteristic values were taken as lower fifthpercentile value of the distribution

32 Water Absorption Test Eight samples were subjected towater absorption test of which four were coatedwith varnishThey were immersed in water after measuring their initialweights Weights of water absorbed samples were measuredwith timeDimensions of all the samples weremeasured priorto the test and after 24 hours of water absorption Thenthey were oven-dried for 24 hours under normal atmospherictemperature and dimensions were taken again

33 Pullout Test Four treated and untreated Palmyrah stripsof 10mm times 10mm cross-section were used for the pullouttest In treated samples varnish was applied to reduce waterabsorption and sand was pressed to increase the bondwith concrete 12 cmndash14 cm length of strips was anchored in150mm times 150mm times 150mm concrete cubes Verticality ofPalmyrah strip had to be maintained in the process After28 days pullout forces of each sample were measured inan Amsler Testing Machine Anchorage bond strength wasderived from (1) Consider

Bond Strength = 119865119871 times 119878

(1)

34 Testing Palmyrah Reinforced Slabs and Beams

341 Preparing Samples 12m long Palmyrah strips whichhad two types of cross-sectional dimensions (10mmtimes 10mmand 20mm times 20mm) were cut and planed All strips werepainted with varnish sand pressed and dried for 24 hours asa water treatment Grade 20 concrete was utilized for castingslabs and beams

Journal of Construction Engineering 3

(a) (b)

(c)

Figure 1 (a) Static bending test (b) compressive test and (c) tensile test

Dimensions of the slab were 1200mm times 1200mm times60mm whereas dimensions of the beams were 1200mm times150mmtimes 150mmReinforcementmesh of slabswas preparedwith Palmyrah strips of 10mm times 10mm in both longitudinaland transverse directions Cover blocks of 15mm thicknesswere tied to the net Reinforcement details of slabs are givenin Table 1 Figures 2(a) and 2(b)

In beams Palmyrah strips were used as top and bottomlongitudinal reinforcement and mild steel shear links wereused at 80mm spacing along the total beam length Beam 1was cast without any reinforcement for comparison purposeand other beams had increasing percentage of reinforcementArrangement of beam reinforcement is given in Table 2 andFigures 3(a) and 3(b)

342 Testing of Slabs and Beams After 28 days from castingthe slabs and beamswere coatedwithwhite limeThis processis essential because it will give a better view of crack shapesand mode of failure during the test

The slab was supported on two I beams with 50mmbearing on either side A dial gauge was arranged to measurethe central deflection of the slab After taking the initial dialgauge readings line load was applied at the centre by meansof a hydraulic jack placed on an I beam as shown in Figures4(a) and 4(b) The test procedure included crack monitoringand central deflection measurements

The beams were also simply supported with 50mmbearing on either side A dial gauge was arranged to measure

Table 1 Reinforcement details of slabs

Cross-section ofPalmyrah stripsmm timesmm

Spacingmm

Reinforcementpercentage

Covermm

Slab 1 10 times 10 300 07 15Slab 2 10 times 10 100 18 15

the central deflection of the beam After taking the initial dialgauge readings two-point loading was applied as shown inFigures 5(a) and 5(b) Dial gauge readings were taken for eachload increment Failure loads as well as initial crack loadswere observed for each beam

4 Results and Discussion

41 Suitability of Palmyrah as a Reinforcing Material Theproperties of Palmyrah determined from machine testingare summarised in Table 3 It is concluded that only theheartwood part of Palmyrah trunk in which tensile strengthcan reach up to 170 Nmm2 is suitable for reinforcing [8]

The cumulative water absorption of Palmyrah strips withtime is plotted in Figure 6 During the 50 hours of thetest Palmyrah absorbed water continuously even if theabsorption rate has been reduced with time Water absorp-tion of Palmyrah after 24 hours was lower than that of bam-boo when compared with previously published results [1]


(a) (b)

Figure 2 Bottom reinforcement of slabs (a) 300mm spacing and (b) 100mm spacing

Palmyrah reinforcement-Stirrups-R6 at

1200mm

15mm

150mm

150mm

80mm 10mm times 10mm

(a) (b)

Figure 3 (a) and (b) Arrangement of beam reinforcement

(a)

600mm 600mm

50mm 50mm

(b)

Figure 4 (a) and (b) Testing of slabs

Table 2 Reinforcement details of beams

Area of bottomreinforcement

number timesmm timesmm

Area of topreinforcement



Covermm

Beam 1 (without rf)Beam 2 4 times 10 times 10 2 times 10 times 10 267 15Beam 3 6 times 10 times 10 2 times 10 times 10 35 15Beam 4 2 times 20 times 20 2 times 10 times 10 44 15


(a)

450mm 450mm200mm

50mm 50mm

(b)

Figure 5 (a) and (b) Testing of beams

Table 3 Mechanical properties of Palmyrah

Mechanical properties Characteristicvalue Minimum value Average value Standard deviation

Bending strength (Nmm2) 119891119898119896 803 489 1383 294

Modulus of elasticityobtained from bendingtest (Nmm2)

119864bt 98564 8787 131182 26224

Tensile strength parallel tograin (Nmm2) 119891

1199050119896 44 43 877 418

Compressive strengthparallel to grain (Nmm2) 119891

1198880119896 518 371 727 148

Moisture content 126 12 15 21Density (kgm3) 8153 681 9897 1045

000

200

400

600

800

1000

1200

1400

0 10 20 30 40 50 60Hours

UntreatedTreated

()

Figure 6 Cumulative water absorption of Palmyrah strips

Also it is evident that applying varnish has reduced thewater absorption initially But its effectiveness diminishedafterwards

The volumetric stability incorporates both cross-sectionalarea and length changes which are critical when Palmyrahis to be used as a reinforcing material embedded in con-crete During casting and curing water will be absorbed byPalmyrah from concrete When Palmyrah strips are embed-ded in concrete swells it will generate cracks in concrete

After sometime it will shrink back leaving voids so that thebond with concrete is reduced

Average variations of lengths and cross-sections ofPalmyrah samples after swelling by water absorption andshrinkage by subsequent drying are tabulated in Table 4 Theplus mark reflects increase in the dimensions and the minusmark shows decrease in dimensions from previous stageAverage bond strengths calculated from pullout test withstandard deviation in brackets are summarized in Table 5

Although Palmyrah is not fully dimensionally stable assteel it has low variation in dimensions compared withother timber reinforcements [1] Bond strength of Palmyrahis lower than that of bamboo obtained from similar pull-out tests (with treatment 155Nmm2 without treatment12 Nmm2) when compared with values published previ-ously by Ghavami [1]

42 Palmyrah Reinforced Slabs and Beams The experimentalfailure loads and crack initiation loads of slabs and beams aretabulated in Table 6 The experimental mean cube strengthswere 215Nmm2 and 244Nmm2 for slabs and beamsrespectively

Table 6 depicts that experimental collapse loads of bothslabs and beams have increased with reinforcement percent-age Both slabs exhibited flexural failures and collapsewas dueto fracture of Palmyrah reinforcement Slab 1 failed in almost


Table 4 Dimensional variations of Palmyrah

SampleDimensional variation

After 24 hr water absorption After 24 hr dryingCross-section Length Cross-section Length

Untreated set +256 +0027 minus113 0Treated set +24 +0013 minus11 0

Table 5 Bond strength and anchorage lengths of Palmyrah

Sample Anchorage length(mm)

Bond strength(Nmm2)

With treatment 131 (11) 1445 (01)Without treatment 125 (125) 1315 (006)

Table 6 Experimental failure loads and crack initiation loads

Percentage ofreinforcement

Crackinitiation

load 119875cr (kN)

Experimentalfailure load119875119890(kN) 119875cr119875119890

Slab 1 07 664Slab 2 18 104 1648 063

Beam 1 0 883Beam 2 267 745 2413 031Beam 3 35 883 2472 036Beam 4 44 981 3002 033

brittle manner with little warning so that crack initiation loadwas indistinguishable But with increase in an amount ofreinforcement from 07 to 18 collapse of the slab becameremarkably gradual

Collapse of beams with Palmyrah reinforcement (Beams2 3 and 4) was gradual while collapse of the unreinforcedbeam was so sudden Difference between crack load and fail-ure loads was indistinguishable in Beam 1 The unreinforcedbeam had a diagonal shear failure at one of the loading pointswhereas other beams experienced flexural failures Failuremodes and crack propagation of both slabs and beams areshown in Figures 7(a) and 7(b) respectively It is evident thatcrack load of beams averages to one third of failure load

Load deflection curves of the two slabs and the fourbeams are plotted in Figures 8(a) and 8(b) respectively

The gradients of the load deflection curve of test slabswere relatively high until the appearance of the first crackin the central region of the bottom of the slab Immediatelyfollowing this first crack there was a noticeable flatteningof the deflection curve as the line of crack at the bottomwidened Large deflectionwithoutwarning is due to low valueof modulus of elasticity of Palmyrah

In a beam subjected to two-point loading the cen-tral region between two loads undergoes maximum bend-ing moment and zero shear while the remaining sectionsexperience maximum shear force and varying bendingmoment The largest flexural strains therefore occur withinthis middle span and consequently cracking is initiated at

the bottom of this region All the cracks formed withinthe short constant moment span of approximately 200mmand this implies that the beams have developed adequateresistance against diagonal shear Also Beams 2 3 and 4developed multiple cracks indicating good bond betweenthe reinforcing Palmyrah bars and surrounding concreteFigure 8(b) shows that up to the appearance of the firsttension crack in the central zone all the beams showed thesame rigidity and a linear behaviour After that there wasa noticeable increase of deflection in Beams 2 3 and 4Beam 1 which was without reinforcement showed the higheststiffness

43 Moment Capacity of Slabs and Beams Based on thefailure loads in Table 6 experimental moment capacitiesof slabs and beams were calculated For the determinationof theoretical moment capacity experimental propertiesof concrete derived from cube strength minimum tensilestrength and elastic modulus of Palmyrah reinforcementbars determined from mechanical testing were used Tensilestrength of concrete was derived from equations in BS 81101997 using cube strengthThe theoretical moment capacity ofunreinforced section was derived from (2) as given below

theoreticalmoment capacity of unreinforced section

Mt119888=

119891119888119905times 119887 times ℎ

2

6

(2)

The theoretical moment capacity considering the con-tribution of Palmyrah reinforcement was calculated by trialand error process using fundamental concepts such as straincompatibility force equilibrium and moment equilibrium

The stress strain diagrams in Figure 9 were assumed at thefailure for calculation purposes Since both slabs and beamscollapsed by fracture of Palmyrah bars strain of Palmyrah isassumed to reach its breaking strain before concrete reachedits ultimate strain

Table 7 depicts that Palmyrah reinforcement hasenhanced the moment capacity of Slab 1 by 23 and Slab 2by 193 compared with an unreinforced slab Experimentalmoment capacities are 74 and 71 higher than theoreticallypredicted value with Palmyrah reinforcement for Slabs 1 and2 respectively The reason for this difference may be that thetheoretical value is based on minimum tensile strength ofPalmyrah

The actual moment capacities of Beams 2 3 and 4 areupgraded by 328 345 and 440 using Palmyrah rein-forcement compared with theoretically unreinforced beamsExperimental moment capacities of Beams 2 3 and 4 are


(a) (b)

Figure 7 Crack propagation in (a) a beam and (b) a slab

0

2

4

6

8

10

12

0 05 1 15 2 25 3

Load

(kN

)

Deflection (mm)

Slab 1Slab 2

(a)

0

5

10

15

20

25

30

0 1 2 3 4 5 6 7

Load

(kN

)

Deflection (mm)

Beam 1Beam 2

Beam 3Beam 4

(b)

Figure 8 Load deflection curves of (a) slabs and (b) beams

Strain distribution

Stress at failure

Z

Cross-section

d

Strain at failure

h

X

fc lt fcu

fps = fy

ℰc ℰc lt ℰcu

ℰps ℰps = ℰy

Figure 9 Stress and strain distribution of composite slabs and beams


Table 7 Calculated moment capacities of slabs and beams

Experimentalmoment capacity

(kNm)Me

Theoretical moment capacity (kNm)Mt MeMt

119888MeMt

119901

Based on concretesection alone Mt

119888

Including Palmyrah barsin tension Mt

119901

Slab 1 1826 149 17 1225 1074Slab 2 453 1546 265 293 1709

Beam 1 2 13 mdashBeam 2 543 127 258 4275 21Beam 3 556 125 379 4448 1467Beam 4 675 125 5 54 135

110 47 and 35higher than theoretically predicted valueswith Palmyrah reinforcement Furthermore experimentalmoment capacities of Palmyrah reinforced beams are sub-stantially higher than moment capacity of the unreinforcedbeam (Beam 1)

Although Palmyrah has not fully satisfied the eligibilitycriteria of a prospective reinforcing element such as dura-bility and ductility heartwood of Palmyrah has a potentialto replace steel reinforcement with some remedial actions tominimize undesirable characteristics Change in dimensionsof cross-section and length by water absorption and subse-quent drying should be decreased as possible Therefore abetter water repellent method than varnish should be usedfor this purpose

Increase of the percentage of Palmyrah reinforcementresults in increase of moment capacities of both slabs andbeams Compared to steel reinforced sections these slabs andbeams showed low stiffness in the postcracking region due tolow modulus of elasticity of Palmyrah

Since crushing of concrete did not occur until reinforce-ment percentage of 44 from cross-section it can be con-cluded that there is a higher margin for over reinforcementof Palmyrah compared to steel

Since slabs are short span they are suggested to be usedas precast slabs with secondary beams Design calculationsindicated that Palmyrah reinforced beams have sufficientmoment capacity to be used as lintels of doors and windowsof single storey or two-storeymasonry wallsTherefore whenmaterial safety factor of 3 is introduced for Palmyrah andsafety factor of 15 is used for concrete safe design canbe achieved for floor slabs and lintel beams of residentialbuildings

44 Economical and Environmental Feasibility Palmyrah isabundantly available in Jaffna Peninsula which is in theNorthern part of Sri Lanka Since Sri Lanka is a smallisland of 65 610 square kilometres transport distance toworking sites is limited Price of 1m of 210158401015840 times 110158401015840 piece isRs165 including transport sawing splicing of bars andwater treatment Maximum of 6 numbers of 10mm times 10mmstrips and 2 of 10mm times 10mm strips can be cut from210158401015840times 110158401015840 piece Compared to steel Palmyrah reinforcement

can reduce the cost of 12m2 panel nearly by 40 and cost

of 12m beam by 36 Heartwood ratio of a bottom partof a matured Palmyrah trunk is about 13 which varieswith origin of the tree However it is an eternal truth thatthere are repercussions of cutting down trees If continuousplantation programmes are implemented to replenish loggedtrees probable environmental impacts can be minimized

5 Conclusions and Recommendations forFuture Studies

The following conclusions were drawn from the conductedresearch

(i) 10mm square Palmyrah bars with anchorage lengthof 12ndash14 cm had bond strength about 13-14Nmm2in grade 20 concrete

(ii) Introducing Palmyrah strips into unreinforced con-crete elements enhanced their moment capacity

(iii) With increase of amount of reinforcement collapseload as well as moment capacities of beams and slabshas increased

(iv) Collapse mechanisms of Palmyrah reinforced slabsand beams were flexural failures by fracture ofPalmyrah bars

(v) Poor volumetric stability under absorption of waterand low modulus of elasticity are major drawbackswhen Palmyrah is utilized as a reinforcing material

It should be noted that the above conclusions are basedon limited number of test specimens and further specimensshould be tested prior to extensive use of Palmyrah asan alternative to steel reinforcement Moreover durabilityof Palmyrah reinforcement on the long term has to bescrutinised in detail in future as they have not been discussedwithin this research Better water repellent methods andsurface treatments to reduce water absorption and increasebond have to be further investigated In addition service-ability criteria such as deflection and crack width should beprobed in detail andmore specimens should be tested varyingsection thickness and reinforcement percentage to determineminimum optimum reinforcement


List of Notations

119891119898119896

Bending strength of Palmyrah119864119887119905 Modulus of elasticity of Palmyrah1198911199050119896

Tensile strength of Palmyrah parallel tograin

119891119888119905 Tensile strength of concrete119887 Width of slab or beamℎ Depth of slab or beam119889 Effective depth of slab or beam119865 Pull-out force119871 Anchorage length119878 Perimeter of Palmyrah bar119875119888119903 Crack initiation load119875119890 Experimental failure load

Me Experimental moment capacityMt119888 Theoretical moment capacity ofunreinforced section

Mt119901 Theoretical moment capacity withPalmyrah reinforcement

119891119901119904 Stress of Palmyrah119891119910 Breaking stress of Palmyrah119891119888 Stress of concrete119891119888119906 Ultimate stress of concrete

E119901119904 Strain of Palmyrah

E119910 Breaking strain of Palmyrah

E119888 Strain of concrete

E119888119906 Ultimate strain of concrete119883 Depth to neutral axis119885 Lever arm

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

The authors would like to acknowledge the staff of Depart-ment of Civil Engineering inUniversity ofMoratuwa for theirassistance in carrying out the testing The authors are alsograteful towards Mr Ravindraraja and Mr Sarangan whosupported purchasing and delivery of Palmyrah

References

[1] K Ghavami ldquoBamboo as reinforcement in structural concreteelementsrdquo Journal of Cement and Concrete Composites vol 27no 6 pp 637ndash649 2005

[2] K Ghavami ldquoUltimate load behaviour of bamboo-reinforcedlightweight concrete beamsrdquo Journal of Cement and ConcreteComposites vol 17 no 4 pp 281ndash288 1995

[3] K Ghavami and R V Hombeeck ldquoApplication of bamboo as aconstruction material Part I mechanical properties and waterrepellent treatment of bamboo Part II bamboo reinforcedconcrete beamsrdquo in Proceedings of the Latin American Sympo-sium on Rational Organization of Building Applied to Low CostHousing pp 49ndash66 CIB Sao Paulo Brazil October 1981

[4] J A Kankam M Ben-George and S H Perry ldquoBamboo-reinforced concrete two-way slabs subjected to concentratedloadingrdquoThe Structural Engineer B RampDQuarterly vol 64 no4 pp 85ndash92 1986

[5] C K Kankam and B Odum-Ewuakye ldquoBabadua reinforcedconcrete two-way slabs subjected to concentrated loadingrdquoConstruction and Building Materials vol 20 no 5 pp 279ndash2852006

[6] C K Kankam and B Odum-Ewuakye ldquoFlexural behaviourof babadua reinforced one-way slabs subjected to third-pointloadingrdquo Construction and Building Materials vol 15 no 1 pp27ndash33 2001

[7] British Standard Institute ldquoMethod of testing small clear speci-mens of timberrdquo Tech Rep BS 373 BSI London UK 1957

[8] H E Mallikarachchi K Baskaran M J P L M Jayasekaraand G A T Madushanka ldquoA study on palmyrah as a materialof constructionrdquo in Proceedings of the 2nd Annual Sessionsof Society of Structural Engineers-Sri Lanka vol 2 pp 7ndash16September 2012

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as a structural member its feasibility to be substituted asreinforcement has not been searched yet

Thus as a preliminary step this investigation has exploredthe feasibility of using Palmyrah strips as reinforcementin lightly loaded and short span slabs and beams Initiallythe suitability of using Palmyrah strips as a reinforcingmaterial was examined through investigation of mechanicalproperties water absorption and bonding strengthThe loadbearing capacity of Palmyrah reinforced slabs and beams wasexperimented thereafter

2 Review of the Literature

21 Timber Reinforcement During the past few decadesthere has been a growing interest in substituting bamboo andBabadua strips for steel reinforcement in concrete

A series of research programmes have been conducted byGhavami [1 2] Ghavami andHombeek [3] andKankamet al[4] to assess the suitability of bamboo reinforced light weightconcrete elements for low stress applications It is noteworthyto state that Ghavami has revealed that the tensile strengthof bamboo is relatively high and can reach up to 370MPaThis makes bamboo an attractive alternative to steel in tensileloading applications [3]

The results of investigations conducted by Ghavamidemonstrated that for the bamboo reinforced lightweightconcrete beams the ultimate applied load can be increasedup to 400 as compared with the unreinforced concretebeams [2] Moreover further experiments concluded that 3of bamboo with respect to concrete section is the optimumrecommended value of reinforcement [2]

According toKankamwhen bamboo reinforced two-wayslabs have been subjected to concentrated central loadingexperimental cracking loads were found to be on average42 of the experimental ultimate loads and 15 greaterthan theoretical punching loads Since punching failurealways followed the full development of the flexural collapsemechanism there is no fear of sudden shear failure [5]

Since themodulus of elasticity of bamboo is not as high asconcrete bamboo does notmake a significant contribution tothe flexural stiffness of bamboo reinforced concrete sections[1 2] As discussed by Ghavami other main shortcoming ofbamboo is dimensional variation of bamboo strips withinconcrete due to moisture and temperature effects which leadto cracking of concrete during service life [1 2]

Laboratory tests were carried out by Kankam on one-wayand two-way concrete slabs reinforced with Babadua barsExperimental failure loads of one way slabs were found tobe on average 300 and 175 of the theoretically predictedvalues for unreinforced section and Babadua reinforcedsection respectively [6] On average monotonic and cyclicfailure loads of two-way slabs were approximately 330and 270 greater than the theoretical flexural strength ofunreinforced concrete section respectively They were also170 and 200 higher than the theoretical flexural strengthincluding Babadua bars [5]

The above studies have depicted that strips of someecological materials satisfy fundamental requirements to be

used as reinforcing bars in concrete elements After waterrepellent treatments they have shown no decay in concretemedium However swelling and shrinkage of timber andlow bonding strength between timber and concrete are stillcritical issues which limit their applications in composites

3 Methodology

The experimental procedure comprised two main sectionsInitially eligibility of Palmyrah as a reinforcing materialwas scrutinized by determining mechanical and physicalproperties of Palmyrah Then Palmyrah reinforced concretebeams and slabs were cast and tested to find the ultimatecarrying capacity

31 Testing of Palmyrah Strips Tests were conducted incompliance with BS 3731957 to determine the mechanicalproperties of Palmyrah from various regions in the country[7] Static bending test and compressive test were done usinga Universal Timber Testing Machine whereas tensile test wasperformed by tensometer as demonstrated in Figures 1(a)1(b) and 1(c)

Bending strength modulus of elasticity and tensile andcompressive strength parallel to grain were determined andthe characteristic values have been derived by statisticalanalysis Characteristic values were taken as lower fifthpercentile value of the distribution

32 Water Absorption Test Eight samples were subjected towater absorption test of which four were coatedwith varnishThey were immersed in water after measuring their initialweights Weights of water absorbed samples were measuredwith timeDimensions of all the samples weremeasured priorto the test and after 24 hours of water absorption Thenthey were oven-dried for 24 hours under normal atmospherictemperature and dimensions were taken again

33 Pullout Test Four treated and untreated Palmyrah stripsof 10mm times 10mm cross-section were used for the pullouttest In treated samples varnish was applied to reduce waterabsorption and sand was pressed to increase the bondwith concrete 12 cmndash14 cm length of strips was anchored in150mm times 150mm times 150mm concrete cubes Verticality ofPalmyrah strip had to be maintained in the process After28 days pullout forces of each sample were measured inan Amsler Testing Machine Anchorage bond strength wasderived from (1) Consider

Bond Strength = 119865119871 times 119878

(1)

34 Testing Palmyrah Reinforced Slabs and Beams

341 Preparing Samples 12m long Palmyrah strips whichhad two types of cross-sectional dimensions (10mmtimes 10mmand 20mm times 20mm) were cut and planed All strips werepainted with varnish sand pressed and dried for 24 hours asa water treatment Grade 20 concrete was utilized for castingslabs and beams


(a) (b)

(c)









Spacingmm


Covermm







(a) (b)



1200mm

15mm

150mm

150mm


(a) (b)


(a)

600mm 600mm

50mm 50mm

(b)








Covermm



(a)

450mm 450mm200mm

50mm 50mm

(b)






119864bt 98564 8787 131182 26224


1199050119896 44 43 877 418


1198880119896 518 371 727 148


000

200

400

600

800

1000

1200

1400

0 10 20 30 40 50 60Hours

UntreatedTreated

()
















Bond strength(Nmm2)




Crackinitiation

load 119875cr (kN)


Slab 1 07 664Slab 2 18 104 1648 063










Mt119888=

119891119888119905times 119887 times ℎ

2

6

(2)






(a) (b)


0

2

4

6

8

10

12

0 05 1 15 2 25 3

Load

(kN

)

Deflection (mm)

Slab 1Slab 2

(a)

0

5

10

15

20

25

30

0 1 2 3 4 5 6 7

Load

(kN

)

Deflection (mm)

Beam 1Beam 2

Beam 3Beam 4

(b)


Strain distribution

Stress at failure

Z

Cross-section

d

Strain at failure

h

X

fc lt fcu

fps = fy

ℰc ℰc lt ℰcu

ℰps ℰps = ℰy





(kNm)Me


119888MeMt

119901


119888


119901

Slab 1 1826 149 17 1225 1074Slab 2 453 1546 265 293 1709



















List of Notations

119891119898119896













Acknowledgments


References











RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










(a) (b)

(c)









Spacingmm


Covermm







(a) (b)



1200mm

15mm

150mm

150mm


(a) (b)


(a)

600mm 600mm

50mm 50mm

(b)








Covermm



(a)

450mm 450mm200mm

50mm 50mm

(b)






119864bt 98564 8787 131182 26224


1199050119896 44 43 877 418


1198880119896 518 371 727 148


000

200

400

600

800

1000

1200

1400

0 10 20 30 40 50 60Hours

UntreatedTreated

()
















Bond strength(Nmm2)




Crackinitiation

load 119875cr (kN)


Slab 1 07 664Slab 2 18 104 1648 063










Mt119888=

119891119888119905times 119887 times ℎ

2

6

(2)






(a) (b)


0

2

4

6

8

10

12

0 05 1 15 2 25 3

Load

(kN

)

Deflection (mm)

Slab 1Slab 2

(a)

0

5

10

15

20

25

30

0 1 2 3 4 5 6 7

Load

(kN

)

Deflection (mm)

Beam 1Beam 2

Beam 3Beam 4

(b)


Strain distribution

Stress at failure

Z

Cross-section

d

Strain at failure

h

X

fc lt fcu

fps = fy

ℰc ℰc lt ℰcu

ℰps ℰps = ℰy





(kNm)Me


119888MeMt

119901


119888


119901

Slab 1 1826 149 17 1225 1074Slab 2 453 1546 265 293 1709



















List of Notations

119891119898119896













Acknowledgments


References











RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










(a) (b)



1200mm

15mm

150mm

150mm


(a) (b)


(a)

600mm 600mm

50mm 50mm

(b)








Covermm



(a)

450mm 450mm200mm

50mm 50mm

(b)






119864bt 98564 8787 131182 26224


1199050119896 44 43 877 418


1198880119896 518 371 727 148


000

200

400

600

800

1000

1200

1400

0 10 20 30 40 50 60Hours

UntreatedTreated

()
















Bond strength(Nmm2)




Crackinitiation

load 119875cr (kN)


Slab 1 07 664Slab 2 18 104 1648 063










Mt119888=

119891119888119905times 119887 times ℎ

2

6

(2)






(a) (b)


0

2

4

6

8

10

12

0 05 1 15 2 25 3

Load

(kN

)

Deflection (mm)

Slab 1Slab 2

(a)

0

5

10

15

20

25

30

0 1 2 3 4 5 6 7

Load

(kN

)

Deflection (mm)

Beam 1Beam 2

Beam 3Beam 4

(b)


Strain distribution

Stress at failure

Z

Cross-section

d

Strain at failure

h

X

fc lt fcu

fps = fy

ℰc ℰc lt ℰcu

ℰps ℰps = ℰy





(kNm)Me


119888MeMt

119901


119888


119901

Slab 1 1826 149 17 1225 1074Slab 2 453 1546 265 293 1709



















List of Notations

119891119898119896













Acknowledgments


References











RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










(a)

450mm 450mm200mm

50mm 50mm

(b)






119864bt 98564 8787 131182 26224


1199050119896 44 43 877 418


1198880119896 518 371 727 148


000

200

400

600

800

1000

1200

1400

0 10 20 30 40 50 60Hours

UntreatedTreated

()
















Bond strength(Nmm2)




Crackinitiation

load 119875cr (kN)


Slab 1 07 664Slab 2 18 104 1648 063










Mt119888=

119891119888119905times 119887 times ℎ

2

6

(2)






(a) (b)


0

2

4

6

8

10

12

0 05 1 15 2 25 3

Load

(kN

)

Deflection (mm)

Slab 1Slab 2

(a)

0

5

10

15

20

25

30

0 1 2 3 4 5 6 7

Load

(kN

)

Deflection (mm)

Beam 1Beam 2

Beam 3Beam 4

(b)


Strain distribution

Stress at failure

Z

Cross-section

d

Strain at failure

h

X

fc lt fcu

fps = fy

ℰc ℰc lt ℰcu

ℰps ℰps = ℰy





(kNm)Me


119888MeMt

119901


119888


119901

Slab 1 1826 149 17 1225 1074Slab 2 453 1546 265 293 1709



















List of Notations

119891119898119896













Acknowledgments


References











RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation
















Bond strength(Nmm2)




Crackinitiation

load 119875cr (kN)


Slab 1 07 664Slab 2 18 104 1648 063










Mt119888=

119891119888119905times 119887 times ℎ

2

6

(2)






(a) (b)


0

2

4

6

8

10

12

0 05 1 15 2 25 3

Load

(kN

)

Deflection (mm)

Slab 1Slab 2

(a)

0

5

10

15

20

25

30

0 1 2 3 4 5 6 7

Load

(kN

)

Deflection (mm)

Beam 1Beam 2

Beam 3Beam 4

(b)


Strain distribution

Stress at failure

Z

Cross-section

d

Strain at failure

h

X

fc lt fcu

fps = fy

ℰc ℰc lt ℰcu

ℰps ℰps = ℰy





(kNm)Me


119888MeMt

119901


119888


119901

Slab 1 1826 149 17 1225 1074Slab 2 453 1546 265 293 1709



















List of Notations

119891119898119896













Acknowledgments


References











RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










(a) (b)


0

2

4

6

8

10

12

0 05 1 15 2 25 3

Load

(kN

)

Deflection (mm)

Slab 1Slab 2

(a)

0

5

10

15

20

25

30

0 1 2 3 4 5 6 7

Load

(kN

)

Deflection (mm)

Beam 1Beam 2

Beam 3Beam 4

(b)


Strain distribution

Stress at failure

Z

Cross-section

d

Strain at failure

h

X

fc lt fcu

fps = fy

ℰc ℰc lt ℰcu

ℰps ℰps = ℰy





(kNm)Me


119888MeMt

119901


119888


119901

Slab 1 1826 149 17 1225 1074Slab 2 453 1546 265 293 1709



















List of Notations

119891119898119896













Acknowledgments


References











RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation












(kNm)Me


119888MeMt

119901


119888


119901

Slab 1 1826 149 17 1225 1074Slab 2 453 1546 265 293 1709



















List of Notations

119891119898119896













Acknowledgments


References











RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation










List of Notations

119891119898119896













Acknowledgments


References











RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation











RoboticsJournal of





Journal of



RotatingMachinery





VLSI Design



Shock and Vibration







Journal of



Volume 2014


SensorsJournal of





Propagation









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