Interlocking Compressed Earth
Interlocking Compressed Earth
Block Walls: Out-Of-Plane
Block Walls: Out-Of-Plane
Structural Response
Structural Response
N.A. Herskedal & P.T. Laursen N.A. Herskedal & P.T. Laursen
Dept. Of Architectural Engineering, California Polytechnic State University, Dept. Of Architectural Engineering, California Polytechnic State University,
San Luis Obispo, California, USA. San Luis Obispo, California, USA. D.C Jansen & B. Qu
D.C Jansen & B. Qu
Dept. of Civil and Environmental Engineering, California Polytechnic State University, Dept. of Civil and Environmental Engineering, California Polytechnic State University,
San Luis Obispo, California, USA. San Luis Obispo, California, USA.
SUMMARY: SUMMARY:
Interlocking compressed earth blocks (ICEBs) are cement stabilized soil blocks that allow for dry stacked Interlocking compressed earth blocks (ICEBs) are cement stabilized soil blocks that allow for dry stacked construction.
construction. The incomplete understandiThe incomplete understanding of the inelastic performance of ICEB building systems limits wideng of the inelastic performance of ICEB building systems limits wide spread acceptance of this structural form in earthquake prone areas. This paper presents results from an spread acceptance of this structural form in earthquake prone areas. This paper presents results from an experimental program designed to explore the behaviour of ICEB walls built according to current
experimental program designed to explore the behaviour of ICEB walls built according to current design practicedesign practice in Indonesia and Thailand, and subjected to out-of-plane loading. A total of five reinforced and grouted walls in Indonesia and Thailand, and subjected to out-of-plane loading. A total of five reinforced and grouted walls were constructed and tested.
were constructed and tested. Results from experimentatResults from experimentation show that the current masonry design coion show that the current masonry design code in thede in the U.S. can adequately predict the yiel
U.S. can adequately predict the yield strength of these walls. d strength of these walls. However, the masonry code grossly over-predictsHowever, the masonry code grossly over-predicts the actual wall stiffness.
the actual wall stiffness. Furthermore, a brittle failure was observed in one walFurthermore, a brittle failure was observed in one wall before reaching the predicted l before reaching the predicted flexural strength.
flexural strength. The testing results provide useful data for develoThe testing results provide useful data for developing analytical modeping analytical models that predicts thels that predicts the seismic behaviour of ICEB walls
seismic behaviour of ICEB walls under out-of-plane loading.under out-of-plane loading.
Keywords: Compressed Earth Block Wall, Out-of-Plane Loading, Inter
Keywords: Compressed Earth Block Wall, Out-of-Plane Loading, Inter locking Masonry, Dry Stack locking Masonry, Dry Stack
1. INTRODUCTION 1. INTRODUCTION
Interlocking compressed earth block (ICEB) masonry is a cost effective and sustainable construction Interlocking compressed earth block (ICEB) masonry is a cost effective and sustainable construction material.
material. ICEB construction has ICEB construction has the potential to bring the potential to bring durable and affordurable and affordable homes to dable homes to developingdeveloping countries around
countries around the world. the world. Today, ICEB Today, ICEB construction is construction is becoming increasingly becoming increasingly popular inpopular in developing countries.
developing countries. Compressed earth blocks Compressed earth blocks are energy efficient; they requirare energy efficient; they require anywhere from e anywhere from 1/51/5 to 1/15 of the energy to make when compared to fired bricks and concrete masonry units (Maini to 1/15 of the energy to make when compared to fired bricks and concrete masonry units (Maini 2010).
2010). Since indigenous soil is the main ingredient in ICEBSince indigenous soil is the main ingredient in ICEBs construction, there is a large reduction ins construction, there is a large reduction in purchased materials
purchased materials (Maini 2010). (Maini 2010). Traditional masonry Traditional masonry relies heavily relies heavily on skillon skilled labor ed labor and expensiveand expensive materials.
materials. The interlocking nature of ICEThe interlocking nature of ICEBs allows for Bs allows for dry stacked, mortar-dry stacked, mortar-less construction, whichless construction, which reduces the need for skilled labor and sho
reduces the need for skilled labor and shortens construction time. rtens construction time. These reductions lower the cosThese reductions lower the cost of t of labor by as much as
labor by as much as 80% (Anand and Ramamur80% (Anand and Ramamurthy 2005). thy 2005). These advantages make ICEBs These advantages make ICEBs a practicala practical and preferred construction form.
and preferred construction form.
Presently, the understanding of the behaviour of ICEB walls is incomplete. While research and testing Presently, the understanding of the behaviour of ICEB walls is incomplete. While research and testing results have been presented on material properties (Bales
results have been presented on material properties (Baleset al.et al. 2009; Perera and Jayasinghe 2003; Bei2009; Perera and Jayasinghe 2003; Bei and Papayianni 2003; Bryan 1988; Heathcote 1991; Reddy
and Papayianni 2003; Bryan 1988; Heathcote 1991; Reddyet al.et al. 2007; Burroughs 2006; Jayasinghe2007; Burroughs 2006; Jayasinghe and Mallawaarachchi 2009), little effort has been made to quantify and analyze strength and and Mallawaarachchi 2009), little effort has been made to quantify and analyze strength and performance
performance of of ICEB ICEB walls. walls. From From previous previous experiments experiments with with ICEB ICEB walls, walls, it it is is clear clear that that using using thethe current U.S. masonry code (ACI 530) to calculate shear strength and displacement response is current U.S. masonry code (ACI 530) to calculate shear strength and displacement response is inaccurate (Bland
inaccurate (Bland et al.et al. 2011; Stirling 2011). 2011; Stirling 2011). In regions with In regions with seismic activity, it is seismic activity, it is imperative thatimperative that these design inaccuracies be addressed through experimentation
these design inaccuracies be addressed through experimentation
It is the goal of this paper to present preliminary results from testing of ICEB walls under out-of-plane It is the goal of this paper to present preliminary results from testing of ICEB walls under out-of-plane loading.
loading. Experimental values of Experimental values of strength and stiffnesstrength and stiffness are compared s are compared to ACI 530 to ACI 530 calculations tocalculations to provide
provide a a better better perspective perspective of of performance for performance for ICEB ICEB walls. walls. In-plane seismic In-plane seismic performance of performance of ICEBICEB shear walls was investigated concurrently and presented elsewhere (Qu
Figure 2.1:
Figure 2.1:Variations of Rhino Blocks (Source: Variations of Rhino Blocks (Source: Wheeler, 2005)Wheeler, 2005)
2. MATERIAL PROPERTIES 2. MATERIAL PROPERTIES
The ICEB used
The ICEB used for this experimental prfor this experimental program was ogram was the Rhino Block. the Rhino Block. The block and press The block and press werewere developed by the Centre f
developed by the Centre for Vocational Building Technology (CVBTor Vocational Building Technology (CVBT). ). These blocks allow for These blocks allow for dry- dry-stacking and have holes for grout
stacking and have holes for grout and reinforcement. and reinforcement. A total of nine differA total of nine different varieties of these blocksent varieties of these blocks can be made on the same press
can be made on the same press by removing or adding inserts. by removing or adding inserts. Varieties include channel blocks for Varieties include channel blocks for horizontal reinforcement, pillar blocks with no grout cores at the ends, and half blocks of each type. horizontal reinforcement, pillar blocks with no grout cores at the ends, and half blocks of each type. Some varieties (dimensions in centimetres) are shown in Fig. 2.1.
Some varieties (dimensions in centimetres) are shown in Fig. 2.1.
The mixture used in the making of the blocks w
The mixture used in the making of the blocks was chosen to balance economy and stras chosen to balance economy and strength. ength. The soil,The soil, free of organic matter, consisted of 18% clay (particles finer than 0.002 mm) and was dried and free of organic matter, consisted of 18% clay (particles finer than 0.002 mm) and was dried and pulverized
pulverized into into a a fine fine consistency. consistency. A A mixture mixture of of 74.3% 74.3% soil, soil, 10% 10% sand, sand, 6.2% 6.2% portland portland cement cement and and 9.5% water by weight was used (Proto
9.5% water by weight was used (Proto et al.et al. 2010). 2010). Water was Water was added to the dry added to the dry components slowly,components slowly, until a specific consisten
until a specific consistency was achieved. cy was achieved. Blocks were Blocks were pressed manually wpressed manually with each type of ith each type of block block containing set amounts of the mixture.
containing set amounts of the mixture. Blocks were then allowed Blocks were then allowed to cure for a mto cure for a minimum of 7 days ininimum of 7 days in humid conditions before
humid conditions before wall construction began. wall construction began. Individual blocks were Individual blocks were tested for tested for compressivecompressive strength in order to guarantee the blocks
strength in order to guarantee the blocks were formed with consistency (Table 2.1).were formed with consistency (Table 2.1).
Grouted ICEB prisms were tested for com
Grouted ICEB prisms were tested for compressive strength for each wall built, see Fig. 2.2. pressive strength for each wall built, see Fig. 2.2. Stacks of Stacks of three blocks were us
three blocks were used with a 2:1 height ed with a 2:1 height to thickness ratio. to thickness ratio. Prisms and test unPrisms and test units were grouted its were grouted simultaneously as construction progressed to ensure accurate values for masonry strength (f’
simultaneously as construction progressed to ensure accurate values for masonry strength (f’mm). Table). Table
2.1 shows average prism strength of 2.81 MPa, a
2.1 shows average prism strength of 2.81 MPa, a value considerably lower than 10.3 value considerably lower than 10.3 MPa used for lowMPa used for low strength concrete masonry
strength concrete masonry units. units. The coefficient of The coefficient of variation (COV) wvariation (COV) was high compared to curas high compared to currentrent masonry standards, indicative of the variation in mixture
masonry standards, indicative of the variation in mixture batches and curing conditions.batches and curing conditions.
Figure 2.2:
Table 2.1:
Table 2.1:Compressive Test ResultsCompressive Test Results Material Type
Material Type Number of Sam Number of Samplesples CompressiveCompressive Strength, MPa Strength, MPa Coefficient of Coefficient of Variation Variation Individual ICEB Individual ICEB 22 22 7.76 7.76 13.5 13.5 %%
Grouted ICEB Prisms
Grouted ICEB Prisms 12 12 2.81 2.81 10.7 10.7 %%
Grout Cylinders (Cured in ICEB)
Grout Cylinders (Cured in ICEB) 19 19 9.19 9.19 16.4 16.4 %%
Soil-Cemen
Soil-Cement t Plaster CylindersPlaster Cylinders 3 3 0.85 0.85 13.3 13.3 %%
Based on stress and strain measurements during the prism tests, an average modulus of elasticity of Based on stress and strain measurements during the prism tests, an average modulus of elasticity of 350 MPa w
350 MPa was calculated. as calculated. This modulus equals This modulus equals 125 f’125 f’mm, which is much lower than the ACI 530 values, which is much lower than the ACI 530 values
of 700 f’
of 700 f’mmfor clay masonry and 900 f’for clay masonry and 900 f’mmfor concrete mfor concrete masonry. asonry. The relatively high The relatively high flexibility of theflexibility of the
prisms is particularly caused by the gaps inherent in dry stacked masonry. prisms is particularly caused by the gaps inherent in dry stacked masonry.
2.1 Grout 2.1 Grout
Grout mixtures for ICEB construction must be workable enough to pour into the small holes of the Grout mixtures for ICEB construction must be workable enough to pour into the small holes of the ICEB block.
ICEB block. Therefore, a grTherefore, a grout mixture with fine out mixture with fine sands and a versands and a very high slump was y high slump was used. used. An effortAn effort was also made to create a grout that would closely match the compressive strength of the ICEBs. was also made to create a grout that would closely match the compressive strength of the ICEBs. Previous testing had shown that brittle failure occurs in prisms where the grout has a significantly Previous testing had shown that brittle failure occurs in prisms where the grout has a significantly higher compressive strength
higher compressive strength than the ICEBs (Bthan the ICEBs (Bales et al., 2009). ales et al., 2009). The grout mixture chThe grout mixture chosen consisted osen consisted of approximately 1:0.4:2.6:4.2 parts of Portland cement to lime to water to sand; all measured by dry of approximately 1:0.4:2.6:4.2 parts of Portland cement to lime to water to sand; all measured by dry volume.
volume. Preparation of Preparation of the grout consisted the grout consisted of dry mof dry mixing the ingredients ixing the ingredients in 15 liter in 15 liter batches. batches. The dryThe dry mixture was then added slowly to a portion of the water and mixed until a homogeneous mixture was mixture was then added slowly to a portion of the water and mixed until a homogeneous mixture was obtained.
obtained. Water was Water was then slowly added until a highly workable grout then slowly added until a highly workable grout was achieved.was achieved.
Grout samples w
Grout samples were tested for ere tested for each batch of grout each batch of grout poured. poured. Due to the IDue to the ICEB’s inherent wCEB’s inherent water ater absorbing properties, it was decided to
absorbing properties, it was decided to test grout samples that had beetest grout samples that had been poured into the blocks. n poured into the blocks. GroutGrout cylinders were c
cylinders were carefully extracted from arefully extracted from the blocks before the blocks before testing. testing. Compressive test resCompressive test results in Tableults in Table 2.1 show the grout strength to be comparable to the ICEB block strength and about three times as high 2.1 show the grout strength to be comparable to the ICEB block strength and about three times as high as the masonry prism strength.
as the masonry prism strength.
2.2 Soil-Cement Plaster 2.2 Soil-Cement Plaster A plaster was
A plaster was to be applied to one wato be applied to one wall for testing. ll for testing. A sustainable and cost A sustainable and cost effective mixture usingeffective mixture using materials that would already be on site during construction was pref
materials that would already be on site during construction was preferred. erred. A suitable mixture of soil,A suitable mixture of soil, sand, and cement was deemed
sand, and cement was deemed to be the best option for this experiment. to be the best option for this experiment. Iterations of different plastersIterations of different plasters were made in order to find a mixture that would not crack once dried, and had a compressive strength were made in order to find a mixture that would not crack once dried, and had a compressive strength that would be compatible with the stiffness of the IC
that would be compatible with the stiffness of the ICEB wall. EB wall. The final mixture consisted of 1:6:0.25The final mixture consisted of 1:6:0.25 parts of soil to sand to Portland cement.
parts of soil to sand to Portland cement.
For compressive tests, the soil-ceme
For compressive tests, the soil-cement mixture was formed in 76 mm diameter plant mixture was formed in 76 mm diameter plastic cylinders. stic cylinders. OnceOnce the mixture had surface hardened, it was removed from the form in order to allow the mixture to air the mixture had surface hardened, it was removed from the form in order to allow the mixture to air dry.
dry. The compressive streThe compressive strength of the plaster was ngth of the plaster was low, see Table 2.1, partially attributed to low, see Table 2.1, partially attributed to initialinitial curing under conditions not representing the
curing under conditions not representing the actual porosity of the ICEB.actual porosity of the ICEB.
3. TEST SETUPS AND PROCEDURES 3. TEST SETUPS AND PROCEDURES A total of five w
A total of five walls were built for alls were built for this testing program. this testing program. Three 1100 mm tall cantilever Three 1100 mm tall cantilever walls werewalls were built
built to to explore explore general general flexural flexural response, response, lap lap splicing splicing and and plaster plaster surface surface coating. coating. These These cantilever cantilever walls were used to provide a basis for testing the larger wa
walls were used to provide a basis for testing the larger walls. lls. Two full scale walls were built to studyTwo full scale walls were built to study the ICEB out-of-plane b
Grade 40 (276 MPa) D10 (9.53 mm diameter) steel reinforcement with measured average yield Grade 40 (276 MPa) D10 (9.53 mm diameter) steel reinforcement with measured average yield strength of 338 MPa.
strength of 338 MPa.
3.1 Cantilever Walls 3.1 Cantilever Walls All cantilever walls
All cantilever walls had identical block layouts. had identical block layouts. One D10 rebar One D10 rebar was inserted into a was inserted into a concrete footingconcrete footing using an anchoring adhesive.
using an anchoring adhesive. The concrete footing wThe concrete footing was clamped to as clamped to the testing facility strong fthe testing facility strong floor.loor. The first layer of IC
The first layer of ICEBs was laid level on a 20 mEBs was laid level on a 20 mm thick cement mortar base. m thick cement mortar base. Each wall was 1.5Each wall was 1.5 blocks
blocks (450 (450 mm) mm) wide wide and and 11 11 blocks blocks (1100 (1100 mm) mm) tall. tall. At At the the first, first, fifth, fifth, ninth, ninth, and and eleventh eleventh layer,layer, channel blocks allowed fo
channel blocks allowed for one D10 r one D10 steel rebar to steel rebar to be laid horizontally. be laid horizontally. After every After every channel block channel block layer was placed, grout was poured into all
layer was placed, grout was poured into all holes and allowed to cure.holes and allowed to cure.
The first wall was the referen
The first wall was the reference wall. ce wall. The second wall contained a 460 mm lap splice at the base of The second wall contained a 460 mm lap splice at the base of the wall in
the wall in accordance with ACI accordance with ACI 530. 530. The third wall wThe third wall was constructed exactly like as constructed exactly like the first wathe first wall.ll. However, once finished, a 20 mm thick soil-cement plaster finish was app
However, once finished, a 20 mm thick soil-cement plaster finish was app lied to both sides of lied to both sides of the wall.the wall. The plaster was applied in two coats and allowed to cure.
The plaster was applied in two coats and allowed to cure. During the application, the wet plaster wasDuring the application, the wet plaster was forced into the cracks between layers of the dry-stacked blocks, ensuring that none of the inherent forced into the cracks between layers of the dry-stacked blocks, ensuring that none of the inherent gaps were left unfilled.
gaps were left unfilled.
The cantilever walls
The cantilever walls were loaded cyclically using a hydraulic jack as were loaded cyclically using a hydraulic jack as suggested in Fig. 3.1. suggested in Fig. 3.1. A loadingA loading sequence was selected to best observe the cracking and yielding behaviour, as well as the performance sequence was selected to best observe the cracking and yielding behaviour, as well as the performance past yield.
past yield. Each target load or displacement was achieved twice in both the push and pull direction.Each target load or displacement was achieved twice in both the push and pull direction.
Fig. 3.1 shows the cantilever wall test setup.
Fig. 3.1 shows the cantilever wall test setup. At three heights, vertical displacements were mAt three heights, vertical displacements were measured easured on both sides of the walls in order to determine the cu
on both sides of the walls in order to determine the curvature along the wall. rvature along the wall. A strain gauge was alsoA strain gauge was also applied to each bar 40 mm above
applied to each bar 40 mm above the concrete footing. the concrete footing. For the lap splice, an additional strain gaugeFor the lap splice, an additional strain gauge was added to the midpoint of the splice.
was added to the midpoint of the splice.
3.2 Full Scale Walls 3.2 Full Scale Walls
Layouts for the full scale walls were determined to best represent a typical ICEB structure in Thailand. Layouts for the full scale walls were determined to best represent a typical ICEB structure in Thailand. Fig. 3.2 shows the w
Fig. 3.2 shows the wall cross sections and Dall cross sections and D10 reinforcement layout of 10 reinforcement layout of each wall. each wall. The difference inThe difference in width of each wall was to provide sy
width of each wall was to provide sy mmetry to each wall.mmetry to each wall.
Figure 3.1:
Figure 3.1:Cantilever Wall Test SetupCantilever Wall Test Setup
Figure 3.2:
Figure 3.3:
Figure 3.3:Full Scale Wall Test SetupFull Scale Wall Test Setup
Each wall was
Each wall was 22 blocks tall, with a pin to pin he22 blocks tall, with a pin to pin height of 2.4 meters (Fig. 3.3). ight of 2.4 meters (Fig. 3.3). The first course wThe first course wasas made from channel blocks
made from channel blocks and placed on a mortar and placed on a mortar base. base. Every fourth layer was Every fourth layer was made from channelmade from channel blocks and included
blocks and included a horizontal D10 a horizontal D10 rebar. A concrete beam rebar. A concrete beam was cast in was cast in place at the place at the top of each top of each wallwall in order to tra
in order to transfer the load from nsfer the load from the pinned connection to the wall. the pinned connection to the wall. The top pin connection wasThe top pin connection was achieved using two steel pipes that
achieved using two steel pipes that transferred the load back into the reaction transferred the load back into the reaction frame.frame.
ICEB structures in Thailand and Indonesia contain shear
ICEB structures in Thailand and Indonesia contain shear reinforcement in pilasters and columns. reinforcement in pilasters and columns. For For this experiment, ties we
this experiment, ties were installed at every four blocks wre installed at every four blocks with the channel block layers. ith the channel block layers. Smooth 6 mmSmooth 6 mm diameter Gr. 60 (414 MPa) pencil rod bars with measured average yield strength of 435 MPa were diameter Gr. 60 (414 MPa) pencil rod bars with measured average yield strength of 435 MPa were used.
used. A masonry saw was used to cut openings to fit the ties and a layer of grout, see Fig. 3.4.A masonry saw was used to cut openings to fit the ties and a layer of grout, see Fig. 3.4.
Both full scale walls were loaded cyclically (push only) using a hydraulic jack and a load spreader Both full scale walls were loaded cyclically (push only) using a hydraulic jack and a load spreader simulating seismic
simulating seismic loading with four loading with four equal and equally spaced equal and equally spaced loads. loads. A loading sequence A loading sequence waswas determined for
determined for each wall to best each wall to best observe the cracking, observe the cracking, yielding, and post yield performance. yielding, and post yield performance. TwoTwo cycles of each target load or displacement was achieved.
cycles of each target load or displacement was achieved. The pilaster wall was loaded on the flat side.The pilaster wall was loaded on the flat side.
Figure 3.4:
Figure 3.4:Pilaster Tie PlacementPilaster Tie Placement
6 mm Pencil Rod 6 mm Pencil Rod
D10 D10
A single load cell attached to the hydraulic jack m
A single load cell attached to the hydraulic jack measured the total load applied to each wall. easured the total load applied to each wall. A totalA total of ten displacement transducer
of ten displacement transducers were used fs were used for each wall or each wall as shown in Fig. 3as shown in Fig. 3.3. .3. Strain gauges wereStrain gauges were placed in each
placed in each wall at mid-height. wall at mid-height. The flat wall had The flat wall had one strain gauge one strain gauge on each vertical on each vertical rebar, while therebar, while the pilaster wall had one on a tension rebar and another on a compression rebar.
pilaster wall had one on a tension rebar and another on a compression rebar.
4. RESULTS 4. RESULTS
4.1 Cantilever Walls 4.1 Cantilever Walls All tests were ca
All tests were carried out successfully. rried out successfully. However, the maximum sHowever, the maximum stroke of the hydraulic jack hindered troke of the hydraulic jack hindered the test from
the test from continuing cyclically. continuing cyclically. Once the jack Once the jack could not be extended any could not be extended any further, the jack further, the jack waswas repositioned closer to the wall, but subsequently could only load the wall in the push direction.
repositioned closer to the wall, but subsequently could only load the wall in the push direction.
The hysteretic behaviour
The hysteretic behaviour of the cantilever of the cantilever walls is presenwalls is presented in Fig. 4.1. ted in Fig. 4.1. VVnn corresponds to thecorresponds to the
predicted
predicted nominal nominal flexural flexural strength strength per per ACI ACI 530. 530. It It can can be be seen seen that that each each wall wall exhibited exhibited stablestable hysteretic behaviour, large displacement capacities and show large amounts of pinching throughout hysteretic behaviour, large displacement capacities and show large amounts of pinching throughout the tests.
the tests. These results show These results show flexure-dominated behaviour for Iflexure-dominated behaviour for ICEB walls under out-of-plane loading.CEB walls under out-of-plane loading. On each hysteresis loop there are also distinct points of initial stiffness loss due to cracking and On each hysteresis loop there are also distinct points of initial stiffness loss due to cracking and significant stiffness
significant stiffness loss due to loss due to yielding. yielding. These points These points were used were used to create pieceto create piecewise linear wise linear approximations to be used for comparing the
approximations to be used for comparing the walls (Envelope Comparison in Fig. 4.1).walls (Envelope Comparison in Fig. 4.1).
The comparison shows a slight increase of initial stiffness in the lap splice wall compared to the The comparison shows a slight increase of initial stiffness in the lap splice wall compared to the reference wall.
reference wall. Despite the difference in stifDespite the difference in stiffness, the flexural strength was fness, the flexural strength was similar to the referencesimilar to the reference wall.
wall. Compared to the reference Compared to the reference wall, the plastered wwall, the plastered wall results showed a all results showed a significant increase insignificant increase in stiffness, due to the plaster filling the cracks between the dry stacked blocks, and flexural capacity, stiffness, due to the plaster filling the cracks between the dry stacked blocks, and flexural capacity, due to the increased wall thickness
due to the increased wall thickness. . The plaster wall also The plaster wall also showed a drop in flexural sshowed a drop in flexural strength pasttrength past being pushed 50 mm that coincided with the plaster spalling from the ICEB wall.
being pushed 50 mm that coincided with the plaster spalling from the ICEB wall.
Figure 4.1:
Figure 4.2:
Figure 4.2:Common Flexural CrackingCommon Flexural Cracking
Table 4.1:
Table 4.1:Cantilever Wall Summary of Test Cantilever Wall Summary of Test ResultsResults Wall
Wall Type Type Nominal Nominal Flexural Flexural Strength Strength Initial Initial Wall Wall StiffnessStiffness ACI
ACI Actual Actual ACI ACI ActualActual 1:
1: Basic Basic 1528 1528 N N 1720 1720 N N 96.1 96.1 N/mm N/mm 19.3 19.3 N/mmN/mm 2:
2: Lap Lap Splice Splice 1528 1528 N N 1660 1660 N N 96.1 96.1 N/mm N/mm 16.7 16.7 N/mmN/mm 3:
3: Plastered Plastered 2013 2013 N N 2215 2215 N N 216.5 216.5 N/mm N/mm 87.2 87.2 N/mmN/mm
Horizontal cracking in the grout cores initiated under low force levels at dry-stacked joints, see Fig. Horizontal cracking in the grout cores initiated under low force levels at dry-stacked joints, see Fig. 4.2.
4.2. The cracks were observeThe cracks were observed starting above the base layer of d starting above the base layer of ICEBs and slowly progrICEBs and slowly progressing up theessing up the wall above each layer of blocks.
wall above each layer of blocks. On the plastered wall, cracks appeared On the plastered wall, cracks appeared in the plaster on each face of in the plaster on each face of the wall
the wall in various locations, in various locations, and not alwand not always at the ays at the dry-stack joints. dry-stack joints. The plastered The plastered wall had wall had significantly more rotation at the base than the other cantilever walls.
significantly more rotation at the base than the other cantilever walls.
ACI 530 does require minimum properties for proper use of the design methods, some of which were ACI 530 does require minimum properties for proper use of the design methods, some of which were not met with these ICEBs.
not met with these ICEBs. These include a minimum cThese include a minimum compressive strength of 10.34 MPompressive strength of 10.34 MPa, a minimuma, a minimum vertical reinforcing ratio of 0.002, and although it is not ever explicitly stated in the ACI code, design vertical reinforcing ratio of 0.002, and although it is not ever explicitly stated in the ACI code, design options do not include dry-stacked m
options do not include dry-stacked masonry. asonry. Nevertheless, the cracking and Nevertheless, the cracking and nominal flexural strengthnominal flexural strength and stiffness values were calculated with this code.
and stiffness values were calculated with this code.
Table 4.1 shows a
Table 4.1 shows a comparison between comparison between the experimental values and the the experimental values and the code estimations. code estimations. InitialInitial stiffness was defined for both the ACI code predictions and the experiments by the slope of the line stiffness was defined for both the ACI code predictions and the experiments by the slope of the line from zero to
from zero to the displacement at flexural the displacement at flexural strength. strength. Note how the ANote how the ACI values for nomCI values for nominal flexuralinal flexural strength were achieved and slightly surpassed by each test, but also that all stiffness estimations were strength were achieved and slightly surpassed by each test, but also that all stiffness estimations were significantly higher than actual.
significantly higher than actual. This indicates that the strength This indicates that the strength design methods translate wedesign methods translate well to ICEBll to ICEB design, but that the inherent gaps between the ICEB courses creates a behaviour that allows for more design, but that the inherent gaps between the ICEB courses creates a behaviour that allows for more rotation and therefore less stiffness than traditional masonry.
rotation and therefore less stiffness than traditional masonry.
4.2 Full Scale Walls 4.2 Full Scale Walls
The hysteretic behaviours of the two full scale
The hysteretic behaviours of the two full scale walls are shown in Fig. 4.3. walls are shown in Fig. 4.3. Dramatic differences inDramatic differences in stiffness and strength are evident.
stiffness and strength are evident. As predicted from the outcomAs predicted from the outcome of the cantilever wall tests, the flate of the cantilever wall tests, the flat wall was found
wall was found to be very flexible. to be very flexible. The pilaster waThe pilaster wall was observed ll was observed to have an overall sto have an overall stiffness,tiffness, calculated from zero load until significant strength degradation was observed, that was about 17 times calculated from zero load until significant strength degradation was observed, that was about 17 times greater than that of the flat
greater than that of the flat wall. wall. Table 4.2 shows a comparison of Table 4.2 shows a comparison of actual values versus ACI 530actual values versus ACI 530 expected values for nominal strength and stiffness.
Figure 4.3:
Figure 4.3:Hysteretic Curves for Full Scale WallsHysteretic Curves for Full Scale Walls
similar fashion to the cantilever walls.
similar fashion to the cantilever walls. For these two walls, the predicted flexural strengths wFor these two walls, the predicted flexural strengths were notere not achieved.
achieved. Uneven load distribution from the Uneven load distribution from the load spreader could have contributed to load spreader could have contributed to this.this.
The flat wall proved
The flat wall proved to be flexure controlled, simto be flexure controlled, similar to the cantilever walls. ilar to the cantilever walls. The wall had The wall had crackingcracking that was similar to
that was similar to the cantilever walls. the cantilever walls. Horizontal cracks began at Horizontal cracks began at the wall mid-height and continued the wall mid-height and continued both
both above above and and below mid-height below mid-height at that the dry-stacked e dry-stacked joints. joints. After yielding After yielding in in the the steel steel reinforcementreinforcement had occurred, a large crack started to form
had occurred, a large crack started to form four courses of blocks from the basfour courses of blocks from the base. e. Further push cyclesFurther push cycles made this crack grow to the point where the wall was able to slide away from the base layers of blocks made this crack grow to the point where the wall was able to slide away from the base layers of blocks and create instability.
and create instability. The two strain gauges sThe two strain gauges showed steel yielding prior to thhowed steel yielding prior to this instability.is instability.
The pilaster wall exhibited signs of shear dominated behaviour before any significant yielding could The pilaster wall exhibited signs of shear dominated behaviour before any significant yielding could be observed
be observed by tby the strain he strain gauges. gauges. The shear The shear cracking started cracking started to to form at form at a shear a shear force of force of 8.7 kN, 8.7 kN, at at aa displacement of 10.9 mm
displacement of 10.9 mm. . Fig. 4.4 shows craFig. 4.4 shows cracks forming in cks forming in the bottom few layers othe bottom few layers of the pilaster. f the pilaster. TheThe cracks were predominantly vertical a
cracks were predominantly vertical along the lines of the reinforcement holes. long the lines of the reinforcement holes. These cracks are mosThese cracks are mostt likely caused by inadequate tie
likely caused by inadequate tie spacing. spacing. More ties, spaced More ties, spaced closer together, would likecloser together, would likely mitigate thisly mitigate this issue.
issue.
Table 4.2:
Table 4.2:Full Scale Wall Summary of Test ResultsFull Scale Wall Summary of Test Results Wall
Wall Type Type Nominal Nominal Strength Strength Initial Initial Wall Wall StiffnessStiffness ACI
ACI Actual Actual ACI ACI ActualActual Flat Flat 8720 8720 N N 8166 8166 N N 352 352 N/mm N/mm 75.6 75.6 N/mmN/mm Pilaster: Flexure Pilaster: Flexure 29100 29100 N N - - 3307 3307 N/mm N/mm 1265 1265 N/mmN/mm Pilaster: Shear Pilaster: Shear 31038 31038 N N 26940 26940 N N - - --Figure 4.4:
Along with the shear
Along with the shear cracks, uplift began betwecracks, uplift began between the first and secen the first and second block layers. ond block layers. The verticalThe vertical reinforcement and sur
reinforcement and surrounding grout began to separate from rounding grout began to separate from the first layer of ICEBthe first layer of ICEBs. s. This upliftThis uplift shows that the construction technique used at the base could have been improved by restraining the shows that the construction technique used at the base could have been improved by restraining the rebar from lifting aw
rebar from lifting away from the base. ay from the base. A detail of the base as built, with a A detail of the base as built, with a bent D10 U-bar connectingbent D10 U-bar connecting two vertical D10 bars
two vertical D10 bars, is included in Fig. 3.3. , is included in Fig. 3.3. Note that the reinforcemenNote that the reinforcement ends at the first courst ends at the first course of e of blocks.
blocks.
Had a displacement limit of 2% been imposed on these walls, only a fraction of the flexural strength Had a displacement limit of 2% been imposed on these walls, only a fraction of the flexural strength could have been developed for
could have been developed for the flat wall (the flat wall (see Fig. 4.3). see Fig. 4.3). Conversely, a large amount of Conversely, a large amount of the pilaster the pilaster wall strength would be developed with the drift limit. The 2% limit was quasi-arbitrarily chosen to wall strength would be developed with the drift limit. The 2% limit was quasi-arbitrarily chosen to limit the P-delta eff
limit the P-delta effects and to reduce the ects and to reduce the non-structural damage. non-structural damage. Fig. 4.3 includes lines to illustrateFig. 4.3 includes lines to illustrate where this 2% limit would fall on th
where this 2% limit would fall on th e hysteresis curves.e hysteresis curves.
5. CONCLUSIONS 5. CONCLUSIONS
Three cantilever walls and two full scale walls were constructed and tested to explore the performance Three cantilever walls and two full scale walls were constructed and tested to explore the performance of ICEB
of ICEB walls under out-of-walls under out-of-plane loading. plane loading. The testing results The testing results provide useful data foprovide useful data for developingr developing analytical models that can predict the seismic performance of ICEB walls under out-of-plane loading. analytical models that can predict the seismic performance of ICEB walls under out-of-plane loading. All tests showed that current ACI 530 analysis techniques work reasonably well in determining the All tests showed that current ACI 530 analysis techniques work reasonably well in determining the nominal flexural strength of ICEB w
nominal flexural strength of ICEB walls. alls. However, the code proved to be unsatisfHowever, the code proved to be unsatisfactory at predictingactory at predicting stiffness for ICEB walls.
stiffness for ICEB walls.
A lap splice was found to have virtually no effect in the overall flexural strength of the wall, but did A lap splice was found to have virtually no effect in the overall flexural strength of the wall, but did affect the initial stiffness.
affect the initial stiffness. The comparison of the lap splice waThe comparison of the lap splice wall to the reference wall suggests thatll to the reference wall suggests that using the A
using the ACI 530 CI 530 to determine the to determine the necessary splice necessary splice length is acceptable. length is acceptable. The plaster The plaster coatingcoating increased the flexural str
increased the flexural strength, and was still accurately preength, and was still accurately predicted by code. dicted by code. Deflections measured inDeflections measured in the plaster wall
the plaster wall also showed more also showed more concentrated rotation at the concentrated rotation at the base. base. This can be attrThis can be attributed to theibuted to the application of the plaster into the gaps between the dry-stacked blocks, showing the plaster’s ability to application of the plaster into the gaps between the dry-stacked blocks, showing the plaster’s ability to control the rotations inherent in ICEB dry-stack joints.
control the rotations inherent in ICEB dry-stack joints.
Data from the vertical displacement measurements (see Fig. 3.1) can used to calculate the rotations Data from the vertical displacement measurements (see Fig. 3.1) can used to calculate the rotations and curvatures along the height of the cantilever walls.
and curvatures along the height of the cantilever walls. It is a goal of this research program It is a goal of this research program to developto develop a moment-curvature relationship that will allow for accurate prediction of displ
a moment-curvature relationship that will allow for accurate prediction of displ acements.acements.
The full scale walls were designed to investigate the strength and stiffness with and without stiffening The full scale walls were designed to investigate the strength and stiffness with and without stiffening elements (pilasters).
elements (pilasters). The pilaster increased the out-The pilaster increased the out-of-plane wall stiffness of-plane wall stiffness significantly and confirmssignificantly and confirms the beneficial effect of using pilasters to control out-of-plane displacement. The testing showed that the beneficial effect of using pilasters to control out-of-plane displacement. The testing showed that the pilaster decreased the ductility of
the pilaster decreased the ductility of the walls, leading to a non-ductile faithe walls, leading to a non-ductile failure. lure. Because the pilaster Because the pilaster wall failed in shear, the experiment also gave insight into the shear strength of ICEB pilasters and wall failed in shear, the experiment also gave insight into the shear strength of ICEB pilasters and columns.
columns. Comparing the experimental and AComparing the experimental and ACI 530 shear strengths, the ACI 530 shear strengths, the ACI code appears to over CI code appears to over predict the
predict the shear strength. shear strength. A smaller A smaller tie tie spacing and/or spacing and/or increased shear increased shear reinforcement area reinforcement area than used than used in the pilaster wall appears warranted, to minimize the
in the pilaster wall appears warranted, to minimize the risk of a brittle failure.risk of a brittle failure.
AKCNOWLEDGEMENT AKCNOWLEDGEMENT
The research reported in this paper was supported in part by the PDCI (California Polytechnic State University, The research reported in this paper was supported in part by the PDCI (California Polytechnic State University, San Luis Obispo) and the NCIIA through grant #8969-11.
REFERENCES REFERENCES
ACI 530 (2008). Building Code Requirements &
ACI 530 (2008). Building Code Requirements & Specification for Masonry Structures. American ConcreteSpecification for Masonry Structures. American Concrete Institute, Farmington Hills, MI 48331 U.S.A
Institute, Farmington Hills, MI 48331 U.S.A Anand, K.B., and Ramamurth
Anand, K.B., and Ramamurthy, K. (2005). y, K. (2005). Development and EvaluatiDevelopment and Evaluation of Hollow Concrete Interlocking Block on of Hollow Concrete Interlocking Block Masonry System.
Masonry System. The Masonry Society Journal.The Masonry Society Journal.23:123:1, 11-19., 11-19. Bales, C., Donahue, C., Fisher, M., Mellbom, A., and
Bales, C., Donahue, C., Fisher, M., Mellbom, A., and Pearson, T. (2009). Interlocking Compressed EarthPearson, T. (2009). Interlocking Compressed Earth Blocks: From Soil to Structure.
Blocks: From Soil to Structure. Senior Project Senior Project , California Polytechnic State University, San Luis Obispo,, California Polytechnic State University, San Luis Obispo, California.
California.
Bland, D.W., Jansen, D.C., Stirling, B.J., Qu, B., and Laursen,
Bland, D.W., Jansen, D.C., Stirling, B.J., Qu, B., and Laursen, P.T. (2011). In-Plane Cyclic Performance of P.T. (2011). In-Plane Cyclic Performance of Interlocking Compressed Earth Block Shear Walls.
Interlocking Compressed Earth Block Shear Walls. The 11th North American Masonry ConferenceThe 11th North American Masonry Conference.. Minneapoli
Minneapolis, Minnesota. June s, Minnesota. June 5-8, 2011.5-8, 2011. Bei, G., and Papayianni, I.
Bei, G., and Papayianni, I. (2003). Compressive Strength of Compressed Earth (2003). Compressive Strength of Compressed Earth Block Masonry.Block Masonry. StructuralStructural Studies, Repairs and Maintenance of Heritage Architecture
Studies, Repairs and Maintenance of Heritage Architecture.. VIIIVIII:367-75.:367-75. Bryan, A.J. (1988). Criteria for
Bryan, A.J. (1988). Criteria for the Suitability of Soil for the Suitability of Soil for Cement StabilizatCement Stabilization.ion. Building and Environment Building and Environment .. 23
23:309-19.:309-19.
Burroughs, S. (2006). Strength of
Burroughs, S. (2006). Strength of Compacted Earth: Linking Soil Properties to Stabilizers.Compacted Earth: Linking Soil Properties to Stabilizers. Building and Building and Research & Information
Research & Information.. 3434:55-65.:55-65.
Heathcote, K. (1991). Compressive Strength of Cement Stabilized Pressed Earth
Heathcote, K. (1991). Compressive Strength of Cement Stabilized Pressed Earth Blocks.Blocks. Building Research and Building Research and Information
Information.. 1919:101-5.:101-5. Jayasinghe, C., Mallawarachchi
Jayasinghe, C., Mallawarachchi, R.S. (2009). Flexural Strength , R.S. (2009). Flexural Strength of Compressed Stabilized Earth Masonryof Compressed Stabilized Earth Masonry Materials.
Materials. Materials and Design Materials and Design. 3859-68.. 3859-68. Maini, S. (2010). Earthen Architecture in the
Maini, S. (2010). Earthen Architecture in the World.World. Auroville Earth Institute. Auroville Earth Institute.Retrieved from Retrieved from http://wwhttp://wwwearth- wearth-aurovillecom
aurovillecom/?nav=menu&p/?nav=menu&pg=earthworld&g=earthworld&id1=26&lang_cid1=26&lang_code=en ode=en (Accessed September, 2011).(Accessed September, 2011). Perera, A., Jayasinghe, C. (2003).
Perera, A., Jayasinghe, C. (2003). Strength Characteristics and Structural Design Methods for Compressed EarthStrength Characteristics and Structural Design Methods for Compressed Earth Block Walls.
Block Walls. Masonry International Masonry International.. 1616:34-8.:34-8. Proto, C., Sanchez, D., Rowley, K., and
Proto, C., Sanchez, D., Rowley, K., and Thompson, R. (2010). ICEB: Design and Thompson, R. (2010). ICEB: Design and Construction Manual.Construction Manual. Senior Senior Project
Project , California Polytechnic State University, San Luis Obispo, California., California Polytechnic State University, San Luis Obispo, California. Qu, B., Stirling, B.J., Laursen, P.T., Jansen, D.C., and
Qu, B., Stirling, B.J., Laursen, P.T., Jansen, D.C., and Bland, D.W. (2012). Interlocking Compressed EarthBland, D.W. (2012). Interlocking Compressed Earth Block Walls: In-plane Structural Response of
Block Walls: In-plane Structural Response of Flexure-dominatFlexure-dominated Walls.ed Walls. 15th World Conference on15th World Conference on Earthquake Engineering
Earthquake Engineering. Lisbon, Portugal.. Lisbon, Portugal. Reddy, B.V., Lal, R., and Rao, K.S.
Reddy, B.V., Lal, R., and Rao, K.S. (2007). Optimum Soil Grading for the (2007). Optimum Soil Grading for the Soil-Cement Blocks.Soil-Cement Blocks. ASCE Journal ASCE Journal of Materials in Civil Engineering
of Materials in Civil Engineering.. 1919:139-48.:139-48. Stirling, B.J. (2011). Flexural Behavior of I
Stirling, B.J. (2011). Flexural Behavior of I nterlocking Compressed Earth Block Shear Walls Subjected to Interlocking Compressed Earth Block Shear Walls Subjected to I n- n-Plane Loading,
Plane Loading, M.S. Thesis M.S. Thesis. California Polytechnic State University, San Luis Obispo.. California Polytechnic State University, San Luis Obispo. The Center for Vocational Building Technology (CVBT).
The Center for Vocational Building Technology (CVBT). Accessed from: <www.cvbt-wAccessed from: <www.cvbt-web.org> (Accessed eb.org> (Accessed September, 2011).
September, 2011).
Wheeler, G. (2005). Manual of
Wheeler, G. (2005). Manual of Construction Interlocking Compressed Earth Blocks.Construction Interlocking Compressed Earth Blocks. Center for VocationalCenter for Vocational Building Technology
