i
 STABILITY OF DRY- STACK MASONRY        
by      
Joseph Vincent Ngowi   
A thesis submitted to the Faculty of Engineering, University of the 
Witwatersrand, in the fulfilment of the requirements for the degree of Doctor of 
Philosophy in Engineering.      
Johannesburg, 2005  
 
ii
 DECLARATION      
I declare that this thesis is my own, unaided work.  It is being submitted in the 
Faculty of Engineering at the University of the Witwatersrand, for the degree of 
Doctor of Philosophy in Engineering. It has not been submitted before for any 
degree or examination in any other University    
(Signature of candidate)     
..   day of    year    
      
 
iii
 ABSTRACT   
This thesis presents the findings on empirical study of dry-stack masonry.        
Dry-stack masonry refers to a method of building masonry walls, where most of 
the masonry units are laid without mortar in the joints. Of late (since mid eighties) 
in modern construction, dry-stacking or mortarless technology is increasingly 
becoming popular because of its advantages. The construction industry is 
acknowledging the need to accelerate the masonry construction process, as the 
traditional method is labour intensive and hence slower due to the presence of a 
large number of mortar joints. Early attempts were made to increase the size of 
masonry units (block instead of brick), thereby reducing the number of mortar 
joints, wherein the use of bedding mortar imposed constraints on the number of 
courses to be constructed in a day. Elimination of bedding mortar accelerates 
construction; thereby reducing cost, variation due to workmanship and generally 
small pool of skilled labour is required in dry stacking. Dry-stack masonry is a 
relatively new technology not yet regulated in the code of practice and therefore 
very limited information on the structural behaviour of the masonry is available. 
This project is based on the investigation of the HYDRAFORM dry-stack system, 
which utilises compressed soil-cement interlocking, blocks. The system is now 
widely used in Africa, Asia and South America. The main objective of the project 
was to establish through physical testing the capacity of the system to resist lateral 
load (e.g. wind load), vertical load and dynamic load such as earthquake loading.   
In the first phase of the project investigations were conducted under static loading 
where series of full-scale wall panels were constructed in the laboratory and tested 
under lateral loading, and others were tested under vertical loading to establish the 
mode of failure and load capacity of the system. Series of control tests were also 
conducted by testing series of wallettes to establish failure mechanism of the units 
and to establish the flexural strength of the system. Finally the test results were 
used for modelling, where load prediction models for the system under vertical 
loading and under lateral loading were developed. The theoretical load prediction 
models were tested against the test results and show good agreement. After the 
 
iv
 load capacity was established the next step in the study was to further improve the 
system for increased capacity particularly under dynamic loading. The normal 
Hydraform system was modified by introducing a conduit, which allows 
introduction of reinforcements. Series of dry-stack seismic systems were 
constructed and initially tested under static lateral loading to establish the lateral 
load capacity.  
The second Phase of the project was to investigate the structural behaviour and 
performance of the Hydraform system under seismic loading. A shaking table of 
20 tonnes payload, (4m x 4m) in plan was designed and fabricated. A full-scale 
plain dry-stack masonry house was constructed on the shaking table and subjected 
to seismic base motions. The shaking table test was performed using sine wave 
signals excitations starting from low to very severe intensity. A conventional 
masonry test structure of similar parameters was also constructed on the table and 
tested in a similar manner for comparison. The tests were conducted using a 
frequency range of 1Hz to 12Hz and the specimens were monitored for peak 
accelerations and displacements. For both specimens the initial base motion was 
0.05g.   
The study established the mode of failure of the system; the structural weak points 
of unreinforced dry-stack masonry, the general structural response of the system 
under seismic condition and the failure load. The plain dry-stack masonry failed at 
0.3g and the conventional masonry failed at 0.6g. Finally recommendations for 
further strengthening of system to improve its lateral capacity were proposed.        
 
v
 STATEMENT OF ACHIEVEMENT   
I believe that the work reported in this thesis has made a contribution to the field 
of dry-stack masonry. The following technical papers were derived from this 
investigation:  
1. Uzoegbo, H; Ngowi J.V;(2004) Lateral Strength of Dry-stack Wall 
System , International Journal of British Masonry Society  Vol.17,No.3 
Dec. 2004, pp 122-128.  
2. Uzoegbo, H; Ngowi J.V;(2005)  Empirical Studies of Flexural Strength 
for Interlocking Masonry , Botswana Journal of Technology (in press).   
3. Uzoegbo H; Ngowi J.V;  Structural Behaviour of Dry-stack Interlocking 
block Walling Systems subjected to In-Plane Loading Journal of the 
Concrete Society of the Southern Africa.  Issue No 103, May 2003          
pp. 8-13.  
4. Uzoegbo H; Ngowi J.V;   Structural Behaviour of Dry-stack Interlocking 
block walling systems . Proceedings of the Sixth International Masonry 
Conference, British Masonry Society, London, 4th 6th     Nov. 2002.       
pp. 498-502,  
5. Uzoegbo H; Ngowi J.V; Load prediction Model for Laterally Loaded 
Dry-stack Masonry , International Conference on Structural and Road 
Transportation (START), 3rd 5th Jan. 2005 INDIA   
6. Uzoegbo H; Ngowi J.V; Senthivel R.;(2004) Load Capacity of Dry-stack 
Masonry walls The Masonry Society Journal USA (under review)    
 
vi
 DEDICATION   
For my family, my wife Magdalena and my two sons   
Nelson and Imani Ngowi           
By the way the African pyramids are dry-stacked
        
 
vii
 ACKNOWLEDGEMENTS   
Completing a PhD is an arduous task. The author wishes to thank the following 
people and organisations for the contributions they made to make this research a 
success.  
Prof. H.C Uzoegbo my supervisor, Mr A. Hofmeyr and J. Meyer for showing me 
how to use some of the instruments reported in this research.  
The government of Tanzania for sponsoring my studies.  
HYDRAFORM (Pty) Ltd for sponsoring the project and technical advice.   
MEGMET (Pty) Ltd for their involvement in the design and fabrication of 
affordable Shaking Table.   
SPOORNET for permission to use their Laboratory.   
Mi TeK South Africa (Pty) Ltd for supply of some of roof materials.  
Members of staff from WITS and SPOORNET laboratories for their support.   
Finally, my sincere thanks to my wife, Magdalena and my sons for being 
encouraging and understanding during my study period away from home.       
 
viii
 CONTENTS 
                                                                                           Page  
DECLARATION  ii 
ABSTRACT . iii 
STATEMENT OF ACHIEVEMENT .. iv 
ACKNOWLEDGMENTS .. .vii 
CONTENTS .. viii 
LIST OF FIGURES  xvi 
LIST OF TABLES     xxiii 
LIST OF SYMBOLS   xxvi   
CHAPTER 1  
INTRODUCTION  
1.1      General .1-1 
1.2      Problem Statement 1-2 
1.3      Objective and Scope .1-3 
1.4      Outline of the Thesis 1-4  
CHAPTER 2  
EVALUATION OF THE EXISTING INTERLOCKING DRY-STACK 
MASONRY SYSTEMS    
2.1 Introduction 2-1 
2.2 Hollow interlocking dry-stack masonry wall systems . ..2-1 
2.3 Solid interlocking dry-stack masonry wall systems ..2-2 
2.4 General Advantages and Disadvantages of Interlocking  
Dry-stack Masonry System . ..2-2 
2.4.1 Advantages ...2-2 
 
ix
 2.4.2 Disadvantages 2-3 
2.5 Evaluation Criteria for Dry-stack Masonry System 2-3 
2.5.1 Aesthetic ..2-4 
2.5.2 Social and political ..2-4 
2.5.3 Nominal dimensions and tolerance . 2-5 
2.6 Ancient dry-stack masonry in Africa ..2-5 
2.6.1 Structural problems in ancient walls 2-6 
2.7 Concrete Dry-stack Masonry systems ..2-7 
2.7.1 Introduction . .2-7 
2.7.2 Azar dry-stack system Canada .2-7  
2.7.3 Spurlock dry-stack system  Canada ..2-9 
2.7.4 Haener dry-stack system   USA ..2-10 
2.7.5 Linkblock dry stack system - South Africa 2-11 
2.7.6 The Baker system ..2-13 
2.7.7 The German KLB system ..2-13 
2.7.8 Sparfill system ...2-14 
2.7.9 The Sinustat system 2-14 
2.7.10 The Whelan-Hatznikolas-Drexel (WHD) . .2-15 
2.7.11 Smart dry-stack system Australia 2-15 
2.7.12 The modified H-Block system ..2-16 
2.7.13 The Stepoc building system ..2-17 
2.7.14 Jordanian interlocking system ..2-18 
2.7.15 The Mecano system ..2-19 
2.7.16 Barlock interlocking system .2-19 
2.7.17 Whelan interlocking masonry ...2-20 
2.7.18 McIBS, Inc. mortarlesss interlocking system ...2-21 
2.7.19 The Etherington building system ..2-21 
2.7.20 The ACECOMS dry-stack system Thailand 2-22 
2.8 Soil-Cement Dry-stack Masonry Systems  2-24 
2.8.1 Introduction . 2-24 
2.8.2 The Unique dry-stack building system - South Africa ...  2-24 
2.8.3 IPI   dry-stack system Tanzania ...  2-25 
 
x
 2.8.4 Hydraform dry-stack building system South Africa ..2-27 
2.8.4.1 Construction details of Hydraform building system and use 
limitations ..2-28 
2.8.4.2 Manufacture of Hydraform Blocks ...2-31   
CHAPTER 3  
DEVELOPMENT OF LOAD PREDICTION MODEL FOR DRY-STACK 
WALL PANELS UNDER STATIC VERTICAL LOAD 
3.1 Introduction .3-1 
3.2 Materials ....3-1 
3.3 Experimental Procedures 3-2 
3.4. Test results .3-5 
3.4.1 Wall Panel Tests ..3-5 
3.4.2 Prism test results ..3-7 
3.4.3 Test on conventional wall panel ..3-8 
3.5 Discussions and Conclusions ...3-10 
3.5.1 Relationship between wall panel capacity and masonry unit strength ..3-10 
3.5.2 Relationship between the strengths of masonry unit, prism and 
wall panel 3-11 
3.5.3 Comparison with Conventional masonry . .3-12 
3.5.4 Conclusion . 3-14   
CHAPTER 4  
LATERAL STRENGTH OF DRY-STACK MASONRY WALL SYSTEMS 
WITHOUT PRECOMPRESSION 
4.1 Introduction ..4-1 
4.2 Materials ...4-1 
4.3 Experiment procedures . 4-2 
4.3.1  General . 4-2 
 
xi
 4.4 Effect of span on lateral strength on dry-stack masonry wall panel . 4-3 
4.4.1 Introduction ..4-3 
4.4.2 Testing of the Short Span wall .4-4 
4.4.3 Testing of the Medium Span wall 4-5 
4.4.4 Testing of the Long Span wall .4-6 
4.4.5 Testing of the Medium Span- Standard Conventional masonry for  
Comparisons .4.7 
4.4.6 Discussions . .4-9 
4.5 Effect of Block unit Strength on Lateral strength on Dry-stack 
masonry ..4-11 
4.5.1 General ..4-11 
4.5.2 Testing of the low unit strength wall panel ...4-11 
4.5.3 Testing of the medium unit strength wall panel 4-13 
4.5.4 Testing of the high unit strength wall panel ..4-14 
4.5.5 Discussions 4-15 
4.6 Effect of degree of Interlocking mechanism on lateral strength 4-16 
4.6.1 General 4-16 
4.6.2 Testing of the wall of shallow interlocking mechanism 4-17 
4.6.3 Testing of the wall of deep interlocking mechanism .4-18 
4.6.4 Discussions .4-19 
4.7 Effect of Everbond on the lateral strength on dry-stack masonry wall  
panel partially bonded 4-20 
4.7.1 General 4-20 
4.7.2 Testing of the wall with Everbond after every three courses .4-20 
4.7.3 Testing of the wall with Everbond every course ....4-21 
4.7.4 Discussions 4-22 
4.8 Effect of plaster on the lateral strength on dry-stack masonry wall 
panel ...4-23 
4.8.1 General ...4-23 
4.8.2 Test results and Discussions ...4.24 
4.9 Conclusions and Recommendations for Future Study 4-26  
 
xii
 CHAPTER 5   
INVESTIGATION OF FLEXURAL STRENGTH FOR  
DRY-STACK MASONRY  
5.1 Introduction ..5-1 
5.2 Flexural Test of the Specimens under Vertical Bending ..5-2 
5.2.1 Introduction .. 5-2 
5.2.2 Testing of 9 MPa specimens all joints dry-stack . 5-3 
5.2.3 Testing of 16 MPa specimens all joints dry-stack 5-5 
5.2.4 Testing of 9 MPa specimens with horizontal joints laid in mortar  
and vertical joints dry-stack .5-5 
5.2.5 Testing of 16 MPa specimens with horizontal joints laid in mortar 
 and vertical joints dry-stack 5-6 
5.3 Flexural Test of Specimens under Horizontal Bending .. 5-7 
5.3.1 Introduction ..5-7 
5.3.2 Testing of 9 MPa specimens all joints dry-stack .5-7 
5.3.3 Testing of 16 MPa specimens all joints dry-stack 5-8 
5.3.4 Testing of 9 MPa specimen with horizontal joints laid in mortar 
 and vertical Joints dry-stacked 5-9 
5.3.5 Testing of 16 MPa specimen with horizontal joints laid in  
mortar and vertical Joints dry-stacked 5-10 
5.4 Flexural tests results discussion . 5-10 
5.4.1 Introduction ... 5-10 
5.5 Orthogonal ratio ..5-12 
5.6 Discussions .5-13 
5.7 Conclusions .5-15      
 
xiii
 CHAPTER 6  
DEVELOPMENT OF LOAD PREDICTION MODEL FOR DRY-STACK 
MASONRY LATERALY LOADED  
6.1 Introduction ..6-1 
6.2 The lateral strength of dry-stack wall panel .6-1 
6.3 Discussions and conclusions 6-5  
CHAPTER 7  
DEVELOPMENT OF DRY-STACK WALL SYSTEM FOR SEISMIC 
CONSTRUCTION USING HYDRAFORM BLOCKS  
7.1 Introduction ..7-1 
7.2 Study of the seismic motarless blocks .7-2 
7.3 Wall system with reinforcements anchored to the returns ...7-4 
7.4 Wall system with corner columns .7-5 
7.5 Discussions and recommendation .7-9 
7.6 Recommendations for further study . 7-11  
CHAPTER 8  
SHAKING TABLE STUDY OF A SINGLE STORY DRY-STACK 
MASONRY HOUSE 
8.1 Introduction .8-1 
8.2 Object and Scope ..8-4 
8.3 Description of the Test Structures 8-4 
8.3.1 House 1  Plain Dry-Stack Masonry ...8-4 
8.3.1.1 Wall construction details ..8-4 
8.3.1.2 Roof structure and dead load 8-7 
8.3.2 House 2 - Standard Conventional masonry House for comparisons 8-8 
 
xiv
 8.3.2.1 Wall construction details ..8-8 
8.3.2.2 Roof structure .8-10 
8.4 Test Facility .8-11 
8.4.1 Earthquake Simulator 8-11 
8.4.1.1 Introduction    8-11 
8.4.1.2 Shaking Table specifications . 8-12 
8.4.1.3 Design of the Table    8-12 
8.4.2 Data acquisition      8-16 
8.4.3 Reference frame ..8-18 
8.5 Test Results .8.21 
8.5.1 Introduction 8-21 
8.5.2 Response of House 1 ..8-22 
8.5.2.1 Input data ...8-22 
8.5.2.2 Response of the test structure .8-24 
8.5.2.3 Performance of the roof structure .8-29 
8.5.3 Natural frequency of the test structure - House 1 ..8-33 
8.5.4 Discussions 8-36 
8.6 Response of House 2  8-53 
8.6.1 In put data ...8-53 
8.6.2 Response of the test structure .8-53 
8.6.3 Performance of the roof structure ..8-60 
8.6.4 Natural frequency of the test structure - House 2 ...8-64 
8.6.5 General discussion ..8-78 
8.6.6 Major observations from the study 8-82 
8.6.7 Recommendations  8-84        
 
xv
 REFERENCEs ..9-1  
APPENDIX A            DRY-STACK MASONRY HYDRAFORM  
                                     STYTEM ..A-1  
APPENDIX B             MODE OF FAILURE AND LATERAL                                          
DEFLECTIONS .B-1  
APPENDIX C             FLEXURAL STRENGTH TEST RESULTS AND  
                                     CALCULATIONS ..C-1  
APPENDIX D            HYDRAFORM BLOCKS ..D-1  
APPENDIX E            FAILURE OF THE TEST STRUCTURES .E-1                   
 
xvi
 LIST OF FIGURES  
Page 
CHAPTER 2  
2.1 Zimbabwe Ruins .2-5 
2.2 Azar System ...2-8 
2.3 Spurlock dry-stack System ..2-10 
2.4 Block and stacking of the original Haener System ...2-11 
2.5 Linkblock System .2-12 
2.6 Baker System 2-13 
2.7 KLB block 2-13 
2.8 Sparfill Block ...2-14 
2.9 Sinustat System 2-14 
2.10 Whelan Masonry System ..2-15 
2.11 Smart Masonry System 2-16 
2.12 Modified H-Block System .2-17 
2.13 Stepoc System ...2-18 
2.14. Jordanian System ..2-18 
2.15 Mecano System .2-19 
2.16 Barlock Interlocking System ..2-20 
2.17 Whelan Interlocking System ..2-20 
2.18 McIBS Masonry System 2-21 
2.19. Etherington System (1979) .2-22 
2.20 ACECOM Dry-stack blocks ...2-23 
2.21 Unique system .2-25 
2.22 IPI dry-stack system 2-26 
2.23 Ordinary dry-stack block 2-27 
2.24 Partition block 2-28 
2.25 Ordinary corner block 2-28 
2.26(a) Dry-stacking Stretcher bond ..2-29. 
 
xvii
 2.26(b) Dry-stacking the mid courses .2-29 
2.26(c) Wall construction details 2-30 
2.27 Production of Hydraform interlocking blocks 2-33 
2.28 Block curing  .2-34 
2.29 Delivering of the blocks in pallets ..2-34   
CHAPTER 3  
3.1 Normal Hydraform interlocking block .3-2 
3.2 Wall panel construction details and strain gauge positions ..3-3 
3.3 Setting out the starter course on machine platen ..3-4 
3.4 Specimen under vertical load ..3-4 
3.5 Sketch of the dry-stack prism test set up .3-4 
3.6 Testing bonded prism   3-4 
3.7 Front view of wall panel showing failure line .3-5 
3.8 Side view of cracks at top 3-5 
3.9 Side view, crushing of the top courses (5 MPa specimen) ..3-6 
3.10 Panel load vs unit strength 3-7 
3.11 Four-unit dry-stack prism 3-7 
3.12 Four-unit prism bonded with mortar 3-7 
3.13 Mode of failure conventional panel . .3-9 
3.14 Panels of similar units strength 3-9 
3.15 Panel load vs unit strength ..3-10 
3.16 Wall strength  vs masonry unit strength .3-11   
CHAPTER 4  
4.1 Hydraform Interlocking block .4-2 
4.2 Full-scale one-room structure in the laboratory ...4-3 
4.3 Testing rig and Position of dial gauges on the wall .4-3 
 
xviii
 4.4 Load deflection behaviour for the short span ..4-4 
4.5 Mode of failure short span wall 4-5 
4.6 Load-deflection for the medium span wall ..4-6 
4.7 Mode of failure medium span wall ...4-6 
4.8 Load deflection behaviour long span wall 4-7 
4.9 Deflection and mode of failure of the long span wall ...4-7 
4.10 load-deflection behaviour standard conventional masonry wall . .4-8 
4.11 Mode of failure standard conventional masonry (medium span) .4-8 
4.12 load - deflection behaviour of different specimens 4-10 
4.13 Wall ultimate lateral load 4-10 
4.14 Interlocking block . ..4-11 
4.15 Test results low strength wall panel 4-12 
4.16 Load deflection for the medium units strength wall .4-13 
4.17 Mode of failure medium units strength wall ..4-13 
4.18 Load deflection high unit strength wall (23 MPa) .4-14 
4.19 Mode of failure high unit strength wall panel 4-15 
4.20 Wall ultimate lateral load ..4-16 
4.21 Load-deflection for the wall of shallow interlocking mechanism .4-17 
4.22 Mode of failure wall of shallow interlocking mechanism .4-17 
4.23 Load deflection wall with increased interlock ...4-18 
4.24 Mode of failure wall of deep interlocking units 4-18 
4.25 Load deflection wall with Everbond each 3rd course .4-21 
4.26 Mode of failure wall with Everbond each 3rd course .4-21 
4.27 Load - deflection wall with Everbond every course ...4-22 
4.28 Mode of failure wall with Everbond each course ...4-22 
4.29 Load - deflection for the plastered walls in comparison to dry-stack 
         and bonded walls 4-23 
4.30 Typical mode of failure - plastered wall .4-24 
4.31 Ultimate lateral load different walls . .4-25    
 
xix
 CHAPTER 5  
5.1 Wallette set up .5-3 
5.2 Interlocking Block ...5-3 
5.3 Typical mode of failure wallette format 1 . ..5-4 
5.4 Typical mode of failure 16 MPa specimens 5-5 
5.5 Typical mode of failure 9 MPa specimen in mortar 5-6 
5.6 Typical mode of failure 16 MPa specimens in mortar 5-6 
5.7 Wallette format 2 - set up 5-7 
5.8 Mode of failure wallette format 2 (9MPa) - under horizontal bending  
      after load removal 5-8 
5.9 Typical modes of failure 16 MPa specimens dry-stack ..5-9 
5.10 Typical mode of failure 9 MPa specimens laid in mortar ...5-9 
5.11 Mode of failure 16 MPa specimens in mortar 5-10 
5.12 Units - self-weight support by the interlocking mechanism ..5-15   
CHAPTER 6.  
6.1 Relationship of failing pressure to the length of dry-stack wall .6-2 
6.2 Comparison between analytical model and experimental results 6-4   
CHAPTER 7  
7.1 Conduit Block type I ..7-3 
7.2 Conduit Block type II 7-3 
7.3 Reinforcing details and mode of failure .7-4 
7.4 Load - deflection behaviour under lateral load ..7-4 
7.5 Wall cross-section details ..7-5 
7.6 Construction and mode of failure of the specimen 7-6 
7.7 Load - deflection behaviour under lateral load. 7-6 
 
xx
 7.8 Wall cross-section seismic block type II ..7-7 
7.9 Load-deflection different wall systems 7-8 
7.10 Load capacity of wall systems 7-8 
7.11 Corner blocks profile ..7-9 
7.12 Modified conduit blocks 7-11   
CHAPTER 8  
8.1 Earthquakes in Africa continent   8-2 
8.2: House 1 constructed on the shaking table .      8-4 
8.3 Blocks for House 1 ...8-5 
8.4 Brick force 8-6 
8.5 Starter course set-up on the Table 8-6 
8.6 Roof construction and dead load attachment ...8-8 
8.7 House 2 before test ...8-9 
8.8 Conventional bricks 8-9 
8.9 Starter course set-up 8-10 
8.10 Wall surface treatments .8-10 
8.11 Fabrication of the roof structure . 8-11 
8.12 Table construction ...8-13 
8.13 Vibration mode shape 8-14 
8.14 Stress distribution ...8-15 
8.15 Table response spectra 8-15 
8.16 Spoornet data acquisition system 8-16 
8.17 Monitoring Positions of the Test structures 8-17 
8.18 Reference frame ..8-19 
8.19 House 1 and 2 Parameters ..8-20 
8.20 Initial failure West wall at 2Hz [0.05g] ..8-24 
8.21 Initial failure at 4Hz [0.05g] ...8-24 
8.22 Failure pattern at 9Hz [0.1g] ...8-25 
8.23 North wall failure at 8Hz 8-26 
 
xxi
 8.24 Corner failure at 5Hz ..8-26 
8.25 East wall failure at 6Hz ..8-26 
8.26 Initial corner failure at 9Hz 8-27 
8.27 East wall deflection at 1Hz .8-27 
8.28 Bending of the door frame 2Hz ..8-27 
8.29 Typical diagonal failure of the walls ..8-28 
8.30 Collapse of out-of-plane walls at 1Hz [0.3g] ..8-28 
8.31  East wall failure details ..8-28 
8.32 West wall failure details .8-28 
8.33 Roof wire - mid trusses ...8-29 
8.34 Recorded max. accelerations at the roof and the supporting walls .8-30 
8.35 Roof response against the base and the supporting walls ...8-31 
8.36 Truss failure -House1 ..8-32 
8.37 Natural frequency House 1 at 0.05g ...8-34 
8.38 Natural frequency House 1 at 0.1g .8-35 
8.39 Natural frequency House 1 at 0.2g .8-36 
8.40 Sliding and opening of the perpend joints in the mid courses-House 1.8-37 
8.41 Typical corner failure House 1 [0.3g] ..8-38 
8.42 Measured response: house 1, test 2     [0.05g @2hz] ..8-42 
8.43 Measured response: house 1, test 4     [0.05g @4hz] ..8-44 
8.44 Measured response: house 1 test 12  [0.1g @ 9hz] .8-46 
8.45 Measured response: house 1, test 21 [0.2g@ 9hz] ..8-48 
8.46 Measured response: house 1, test 28  [0.2g @ 2hz] 8-50 
8.47 Measured response: house 1, test 30  [0.2g @ 1hz] 8-52 
8.48 Distribution of cracks: House 2 at 0.1g ..8-56 
8.49 Distribution of cracks on the walls: House 2 at 0.2g ..8-57 
8.50 Initial failure at lintel courses West wall [0.3g @ 9Hz] .8-57 
8.51 Diagonal failure East wall at 3Hz [0.4g] 8-58 
8.52 Diagonal failure at East wall [0.5g @ 5Hz] 8-58 
8.53 Collapse of the lintel courses East wall at 5Hz [0.6g] 8-59 
8.54 Window frame out of the structure .8-59 
8.55 Local failure of the rafter 8-60 
 
xxii
 8.56 Recorded max. accelerations at the roof and supporting walls ..8-61 
8.57  Natural frequency of the roof and supporting walls at 0.05g 8-61 
8.58  Natural frequencies House 2 at 0.05g 8-65 
8.59 Natural frequencies House 2 at 0.2g ...8-66 
8.60  Natural frequency House 2 at 0.3g 8-67 
8.61 Natural frequency House 2 at 0.4g .8-68 
8.62 Natural frequency House 2 at 0.6g .8-69 
8.63 Measured response: house 2, test 22 [0.2g@10hz] .8-71 
8.64 Measured response: house 2, test 32 [0.3g@9hz] ...8-73 
8.65 Measured response: house 2, test 37 [0.3g@ 4hz] ..8-75 
8.66 Measured response: house 2, test 47 [0.4g@ 3hz] ..8-77 
8.67 Response of out-of-plane walls ...8-80 
8.68 Roof response .8-80 
8.69 Horizontal Force Distributions ...8-89 
8.70 Introduction of lintel ring beam/band .8-89 
8.71 Dry-stack lintel beam .8-90 
8.72 Insitu side column ..8-90                
 
xxiii
 LIST OF TABLES  
CHAPTER 2  
2.1 Physical properties of Azar Block ..2-9 
2.2 Basic requirements of Soil for CEB s production .2-31  
CHAPTER 3  
3.1 Basic requirements of Soil for CEB s production 3-2 
3.2. Wall panel tests results .3-6 
3.3 Prism compressive test results .3-8 
3.4 Relationship between block strength and prism strength ...3-11 
3.5 Relationship between dry -stack prism and dry-stack   
masonry wall panel .3-12 
3.6 Relationship between dry-stack masonry wall and unit strength ...3-12 
3.7 Effect of different joint materials on compression strength  
of brick couplets .3-13 
3.8 Effect of different joint materials on the compressive  
strength of prisms ..3-14   
CHAPTER 4  
4.1 Lateral load test results -walls of different units strength ...4-15 
4.2 Lateral load test results  specimens with different  
depth of interlock 4-19 
4.3 Tests results -load deflection different walls of same span ...4-25   
 
xxiv
 CHAPTER 5  
5.1 Flexural strength results for fully dry-stack specimens  5-11 
5.2 Flexural strength results for the specimens (partially dry-stack) bed joints 
in mortar and perpend joints dry stack 5-12 
5.3 Calculated Orthogonal ratio 5-13 
5.4 Comparison of Allowable Stress in Flexure ...5-14   
CHAPTER 6  
6.1 Lateral load test results 6-2 
6.2. Flexural strength results for fully dry-stack specimens 6-3   
CHAPTER 8  
8.1 Moderate earthquake occurred in 20th Century in South Africa ...8-3 
8.2 House 1 parameters ..8-5 
8.3 Analysis results ...8-13 
8.4 Sine wave signal input data ...8-22 
8.5 Test sequence House 1 .8-23 
8.6 House 1 Peak Acceleration and Displacements at the top of  
Out-of-plane walls and Roof Peak Acceleration 8-39 
8.7 House 1 Peak Acceleration and Displacements at the top of  In -plane 
walls and Roof Peak Acceleration ..8-40 
8.8 Test sequence House 2 conventional  masonry ...8-54 
8.9 House 2 peak acceleration and displacements at the top of out-of-plane  
walls and roof peak acceleration ...8-62 
8.10 House 2 peak acceleration and displacements at the top of in-plane  
walls and peak roof acceleration .8-63 
8.11 Structural damage of the walls at Total failure ..8-79 
 
xxv
 8.12 Response of the out-of-plane walls and the roof 8-80 
8.13 Performance of the Test Structures 8-81  
8.14 Recommendations to improve UDRM .. 8-88                              
 
xxvi
 LIST OF SYMBOLS  
fpanel              = average compressive strength of the dry-stack wall panel 
fcu                        = masonry unit cube strength 
f xdry          = flexural strength of the dry-stack masonry 
f drykxparal   = flexural strength of dry-stack masonry parallel to bed joint  
f drykxperp    = flexural strength of dry-stack masonry perpendicular to bed  joint 
h,                = height of the wall panel  
L                = length of the wall panel  
M cv          = vertical bending moment capacity  
M              = the bending moment 
P               = failing lateral pressure  
dry
          =  orthogonal ratio fully dry stack masonry 
pdry
        = orthogonal ratio partially dry-stack masonry 
k stackdry       = factor  varies with the block characteristics and the geometry of the  
                    interlocking mechanism 
Z             = gross-sectional modulus  
m
          =  safety factor on material