EVALUATION OF STRESS REDUCTION FACTORS BASED ON TESTS ON AXIALLY AND ECCENTRICALLY LOADED WALLS KRISHNA KUMAR S 1BM08CCT07...
<ul><li>INTRODUCTION </li></ul><ul><li>LITERATURE REVIEW </li></ul><ul><li>INITIAL TESTS </li></ul><ul><li>EXPERIMENTAL ST...
<ul><li>The International Building Code (IBC 2000) defines Masonry as &quot;a built-up construction or combination of buil...
<ul><li>Began as low walls of stones or caked mud </li></ul><ul><li>Sun-dried bricks and with the availability of fire bec...
 
20 th  Century Developments <ul><li>Steel Reinforced Masonry </li></ul><ul><li>High Strength Mortars </li></ul><ul><li>Hig...
 
GREAT WALL OF CHINA
Bonds in Masonry <ul><li>Bond is the interlacement of bricks, formed when they lay those immediately below or above them. ...
Mortar   <ul><li>In masonry construction, mortars constitute only a small proportion (approximately 7%) of the total wall ...
<ul><li>The basic advantages of masonry constn. is that the same element can perform a variety of functions such as sub-di...
<ul><li>A wall can be defined as an upright member, the width of which exceeds four times its thickness. If this ratio is ...
Cavity wall Solid wall Panel wall
Types of loading in Walls <ul><li>Primarily walls are subjected to compression. But however when walls are loaded eccentri...
Objective of Present study <ul><li>To study the behaviour of full scale masonry wall under axial and eccentric loading wit...
Factors affecting Compressive strength of masonry <ul><li>Mortar strength </li></ul><ul><li>Unit strength </li></ul><ul><l...
Literature Review
Compressive strength of bricks ***Gumaste(2004 )
Earlier studies on Full scale Masonry walls in India <ul><li>Raghunath et al 2003 ,carried   out tests on un- reinforced a...
<ul><li>Gumaste 2004, </li></ul><ul><li>had carried out compression tests on 3, storey height walls. The walls were of fol...
<ul><li>Jolad 2008, </li></ul><ul><li>had carried out compression tests on 2 walls. The walls were of following dimensions...
Details of tests carried on full scale walls
Behaviour of Masonry under Compression <ul><li>Masonry loaded in uniform compression will either fail by the development o...
Design of Masonry Wall for Vertical Load (IS 1905) Factors: Slenderness Ratio Stress reduction factors  Effective length E...
Masonry Walls: Slenderness and Eccentricity Stocky wall,  central  load Slender wall,  central load 100%  strength Reduced...
Masonry Walls: Slenderness and Eccentricity Stocky wall, eccentric load Slender wall, eccentric load Reduced strength Redu...
Effect of slenderness and eccentricity
Masonry Walls: Slenderness   and Eccentricity IS 1905 1987  Slenderness Ratio = Effective Height/Effective Thickness (or) ...
Masonry Walls: Slenderness   and Eccentricity IS 1905 - 1987 Effective Height = Actual Height * a number from 0.75 to 1.5,...
Masonry Walls: Slenderness  and Eccentricity IS 1905 – 1987 Effective Length = Actual Length * a number from 0.80 to 2.0 d...
Eccentricity depends on various factors ! <ul><li>Extent of bearing </li></ul><ul><li>Magnitude of loads </li></ul><ul><li...
<ul><li>Eccentricity of vertical loading at a  particular junction in a masonry wall shall depends on factors, such  as ex...
VAULT PITHCED ROOF
EXPERIMENTAL PROGRAMME <ul><li>Basic Tests on bricks </li></ul><ul><li>Tests on Mortar </li></ul><ul><li>Tests on Masonry ...
Tests on Bricks
Avg. Dry density C.O.V Range 1.75 g/cc 1.70% 1.6-1.95g/cc ****
Water  Absorption(%) (Avg) C.O.V Range 13.90 2.06% ≤ 20%**
***Sarangpani 1998 I.R.A  kg/m 2/ min C.O.V Range kg/m 2/ min 2.815  8.55% 1.35-3.53**
***Sarangpani1998, Raghunath 2003  for  T.M.B of Bangalore Compressive Strength = Ultimate Load  MPa. Area of Loading Comp...
E = 752.6 MPa  from the Graph
TESTS ON MORTAR <ul><li>Compressive strength of mortar </li></ul><ul><ul><ul><ul><li>Tests were carried out as per IS 2250...
<ul><li>Flow is defined as the resulting increase in the base diameter of mortar mass expressed as a percentage of origina...
Mortar cone before and after applying jolts Conical mould Rigid frame Brass plate-circular
Tests on Masonry Prisms <ul><li>Objective  </li></ul><ul><ul><ul><li>To evaluate  basic properties such as compressive str...
225 mm masonry prism and stack bonded prism before testing
Stress strain curve for prisms
Modes of failure <ul><li>Failure of brick-mortar bond was often noticed. </li></ul><ul><li>crushing of the brick was also ...
 
<ul><li>To investigate stress reduction factor of walls, </li></ul><ul><li>for slenderness ratio= 6.0  for  axial loading ...
EXPERIMENTAL PROGRAM <ul><li>I n the present project, full scale brick wall have been constructed for both axial and eccen...
4 legged loading frame-reaction type Courtesy-RVCE
 
1.55m 0.95m 0.225m
Arrangement for Ecc.loading 0.5m 1.3m 1.0m DIAL GAUGE POSITION
Plan of Eccentric loading arrangement-1 Plan of Eccentric loading arrangement-2
Test Set-up details
WALL1- Front face and Rear face after testing Crushing of brick vertical splitting
WALL2- Front face and Rear face after testing Spalling   Vertical cracks
Comments on failure of axial loaded walls <ul><li>Vertical splitting crack observed in the wall specimen after failure. </...
Eccentric  loading  before and after failure
CRACK PATTERN-ECCENTRICALLY LOADED Separation of 2 leaves of wall
Comments <ul><li>Global failure of wall specimen was observed i.e. all courses from top to the bottom participated in sust...
Wall1
Wall2
Wall3
wall4 WALL 4(ECC2)
SUMMARY OF WALL TESTED
Evaluation of stress reduction factors <ul><li>It is virtually impossible to apply an axial compressive load to a wall or ...
<ul><li>The additional moment can be allowed in 2 ways </li></ul><ul><li>The stresses due to the equivalent axial loads an...
Where σ max  from  experiment  on walls ‘ E’ VALUE from prism experiment (e/t)= eccentricity ratio (l/t)= slenderness ratio
 
(P/A) values
Stress reduction factor obtained
 
Comparison with different codes of masonry <ul><li>In present study, In the present study, stress reduction factors comput...
Graph showing stress reduction factors for varying  eccentricites  and slenderness ratio as per  Euro-code (ENV 1996-1-1-1...
<ul><li>As per BS 5628 (code of practice for masonry in Britain), Stress reduction factor is denoted by “β”. In the presen...
 
Conclusion <ul><li>The  analytical approach  using secant formula was adopted to evolve the  stress reduction factor  whic...
Scope for Further Study <ul><li>In the present case, experiments on full scale walls were carried out for slenderness rati...
References <ul><li>AVINASH A.C. (2006) “A Comprehensive study on Masonry units”, M.Tech Thesis, Department of civil Engine...
<ul><li>JAGADISH .K.S, “Alternative Building Materials”, Indian Institute of Science, 2005, New Age International Publishe...
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Effect of eccentricity on masonry walls

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Krishna final overall ppt (2) eccentrically loaded masonry walls

  1. 1. EVALUATION OF STRESS REDUCTION FACTORS BASED ON TESTS ON AXIALLY AND ECCENTRICALLY LOADED WALLS KRISHNA KUMAR S 1BM08CCT07 GUIDED BY Smt MANGALA KESHAVA Assistant Professor, Dept of Civil Engineering, BMSCE B’lore BY
  2. 2. <ul><li>INTRODUCTION </li></ul><ul><li>LITERATURE REVIEW </li></ul><ul><li>INITIAL TESTS </li></ul><ul><li>EXPERIMENTAL STUDIES ON WALLS </li></ul><ul><li>ANALYTICAL STUDIES </li></ul><ul><li>COMPARISON OF RESULTS </li></ul><ul><li>DISCUSSION AND CONCLUSION </li></ul><ul><li>SCOPE FOR FURTHER STUDIES </li></ul><ul><li>REFERENCES </li></ul>
  3. 3. <ul><li>The International Building Code (IBC 2000) defines Masonry as &quot;a built-up construction or combination of building units or materials of clay, Shale, concrete, glass, gypsum, stone or other approved units bonded together with or without mortar or grout or other accepted methods of joining” </li></ul><ul><li>Masonry practically considered as the art of shaping and uniting masonry units made of either Natural i.e., Adobe, Granite e.t.c Artificial i.e., Clay blocks , Bricks ,Concrete masonry units, Hollow blocks with aid of cement or iron cramps and lead. It therefore includes cutting ,facing, placing of masonry units into particular forms required to perform operations which needs practical dexterity with some skill in geometry and mechanics </li></ul>
  4. 4. <ul><li>Began as low walls of stones or caked mud </li></ul><ul><li>Sun-dried bricks and with the availability of fire became burnt bricks </li></ul><ul><li>The first sun-dried bricks were made in Mesopotamia (what is now Iraq), in the ancient city in about 4000 BC. </li></ul><ul><li>The description of the building skills of early Romans can be found in the four books of Vitruvius, the famous mason who lived in the first century B.C. </li></ul><ul><li>The earliest evidence of masonry construction is the arches found in the excavations at Ur in the Middle East. These ruins have been dated at 4000 B.C. Arch structures dating la 3000 B.C. have been found in Egypt. </li></ul><ul><li>The pyramid of Khufu in Egypt built about 2700 B.C remains one of the largest single stone masonry structure built by humans even though its original height of 147 m (482 ft.) is now reduced to 137m. </li></ul>
  5. 6. 20 th Century Developments <ul><li>Steel Reinforced Masonry </li></ul><ul><li>High Strength Mortars </li></ul><ul><li>High Strength Masonry Units </li></ul><ul><li>Pre-stressed Masonry </li></ul>
  6. 8. GREAT WALL OF CHINA
  7. 9. Bonds in Masonry <ul><li>Bond is the interlacement of bricks, formed when they lay those immediately below or above them. </li></ul><ul><li>It is the method of arranging the bricks in courses so that individual units are tied together and the vertical joints of successive courses do not lie in the same vertical line. </li></ul>
  8. 10. Mortar <ul><li>In masonry construction, mortars constitute only a small proportion (approximately 7%) of the total wall area, but its influence on the performance of the wall is significant. </li></ul><ul><li>The primary purpose of mortar in masonry is to bind masonry units into an assemblage that acts as an integral element having desired functional characteristics. </li></ul><ul><li>Bond masonry units together into an integral structural assembly </li></ul><ul><li>Seals joints against penetration by air and water </li></ul><ul><li>Accommodates small movements within a wall </li></ul><ul><li>Bonds to joint reinforcement to assist in resisting shrinkage and tension </li></ul>Functions
  9. 11. <ul><li>The basic advantages of masonry constn. is that the same element can perform a variety of functions such as sub-division of space, thermal and acoustic insulation, fire and weather protection, energy efficient </li></ul><ul><li>In the first half of the present century, masonry construction for multi-storied buildings was very largely replaced by steel and R.C .structure due to excessively thick walls wasteful in terms of space and material </li></ul><ul><li>Hence code of practice came into existence through research and experience providing sufficient basis for design of masonry structures. </li></ul>Development of load bearing masonry
  10. 12. <ul><li>A wall can be defined as an upright member, the width of which exceeds four times its thickness. If this ratio is less than four, the wall is considered as column. </li></ul><ul><li>Mainly classified into 2 types </li></ul><ul><li>Load bearing type </li></ul><ul><li>Non load bearing type </li></ul>Definition Classification Walls
  11. 13. Cavity wall Solid wall Panel wall
  12. 14. Types of loading in Walls <ul><li>Primarily walls are subjected to compression. But however when walls are loaded eccentrically, they will be subjected to flexure in addition to compression. </li></ul>
  13. 15. Objective of Present study <ul><li>To study the behaviour of full scale masonry wall under axial and eccentric loading with S.R=6.0 and (e/t=0.25) </li></ul><ul><li>To compute Stress reduction factor by an Analytical approach. Secant formula has been used for computing stress reduction factors for varying slenderness ratio and eccentricities </li></ul><ul><li>To compare the stress reduction factor obtained from experimental investigation and Secant formula with BS code (BS 5628), Euro code (ENV-1995-1-1-1996) Indian code (IS-1905-1987) </li></ul>
  14. 16. Factors affecting Compressive strength of masonry <ul><li>Mortar strength </li></ul><ul><li>Unit strength </li></ul><ul><li>Relative values of unit and mortar strength </li></ul><ul><li>Ratio of the units (ratio of height to least horizontal dimension) </li></ul><ul><li>Orientation of the units in relation to the direction of the applied load </li></ul><ul><li>Bed-joint thickness </li></ul><ul><li>Workmanship (Hendry,1998) </li></ul><ul><li>Type of bond </li></ul>
  15. 17. Literature Review
  16. 18. Compressive strength of bricks ***Gumaste(2004 )
  17. 19. Earlier studies on Full scale Masonry walls in India <ul><li>Raghunath et al 2003 ,carried out tests on un- reinforced and reinforced walls for Axial and eccentric load Eccentric load on 1-brick un-reinforced masonry walls ( 3 Specimens) </li></ul><ul><li>Eccentric load test on 1-brick masonry walls with containment reinforcement ( 3 Specimens) </li></ul><ul><li>It was not possible to sustain the applied load after the observation of the first crack in the entire un-reinforced specimen. These un-reinforced specimen started to rotate as soon as the cracks formed, leading to the failure of wall, which broke into two parts. </li></ul>
  18. 20. <ul><li>Gumaste 2004, </li></ul><ul><li>had carried out compression tests on 3, storey height walls. The walls were of following dimensions; </li></ul><ul><li>Wall No 1. 720 x 105 x 2770mm(TMB)-1:0:6 mix </li></ul><ul><li>Wall No 2. 970 x 230 x 2770mm(TMB), 1:0:6 mix </li></ul><ul><li>Wall No 3. 750 x 115 x 2770mm(WCB),1:1:6 mix </li></ul><ul><li>The half brick thick stretcher walls failed due to material crushing where as the failure of one brick thick English bonded wall was due to a combination of splitting of bricks, bond failure and diagonal shear failure </li></ul><ul><li>Stress reduction factors from IS code( 0.54,0.67) were on conservative side as compared to experimental values(0.91,0.83) </li></ul>
  19. 21. <ul><li>Jolad 2008, </li></ul><ul><li>had carried out compression tests on 2 walls. The walls were of following dimensions; </li></ul><ul><li>Wall No1. 1050 x 230 x 2430mm(TMB)-1:0:6 mix axial loaded, S.R=10.57 </li></ul><ul><li>Wall No 2. 1050 x 230 x 2430mm(TMB )1:0:6 mix, eccentric loading (e/t=(1/6)), S.R=10.57 </li></ul><ul><li>The axially loaded wall exhibited typical compression type failure i.e. crushing of bricks, spalling, vertical cracks. Whereas wall with ecc. loading collapsed and typical flexure failure was noticed </li></ul><ul><li>Stress reduction factors from IS code were ( 0.88,0.83-(e)) whereas from experiments it was (0.925,0.370) </li></ul>
  20. 22. Details of tests carried on full scale walls
  21. 23. Behaviour of Masonry under Compression <ul><li>Masonry loaded in uniform compression will either fail by the development of tensile cracks parallel to the axis of loading or by kind of failure along the lines of weakness </li></ul><ul><li>A number of studies have been carried out on full-scale masonry walls however there is little data which is available for masonry using moderate strength bricks in India & in particular, south Indian bricks </li></ul><ul><li>In this present experimental investigation an attempt has been made to determine the strength, elasticity and stress reduction factor(K s ) of a masonry wall for SR=6.0 for axial and eccentric and comparing the results obtained with codal provisions of different countries. </li></ul>
  22. 24. Design of Masonry Wall for Vertical Load (IS 1905) Factors: Slenderness Ratio Stress reduction factors Effective length Effective thickness Effective height Eccentricity of load Thickness of wall Eccentricity ratio
  23. 25. Masonry Walls: Slenderness and Eccentricity Stocky wall, central load Slender wall, central load 100% strength Reduced strength
  24. 26. Masonry Walls: Slenderness and Eccentricity Stocky wall, eccentric load Slender wall, eccentric load Reduced strength Reduced strength e e
  25. 27. Effect of slenderness and eccentricity
  26. 28. Masonry Walls: Slenderness and Eccentricity IS 1905 1987 Slenderness Ratio = Effective Height/Effective Thickness (or) = Effective Length/Effective Thickness *** whichever is least
  27. 29. Masonry Walls: Slenderness and Eccentricity IS 1905 - 1987 Effective Height = Actual Height * a number from 0.75 to 1.5, depending on the end fixity ***In the present study depending on boundary condition provided it was considered 0.85 H as per IS 1905 - 1987
  28. 30. Masonry Walls: Slenderness and Eccentricity IS 1905 – 1987 Effective Length = Actual Length * a number from 0.80 to 2.0 depending on the end fixity
  29. 31. Eccentricity depends on various factors ! <ul><li>Extent of bearing </li></ul><ul><li>Magnitude of loads </li></ul><ul><li>Unequal span lengths of the slabs </li></ul><ul><li>Degree of fixity at the support </li></ul><ul><li>Moment at floor/roof – wall junction </li></ul><ul><li>Pitched roofs </li></ul><ul><li>Walls of varying thickness </li></ul>
  30. 32. <ul><li>Eccentricity of vertical loading at a particular junction in a masonry wall shall depends on factors, such as extent of bearing, magnitude of loads, stiffness of slab or beam, fixity at the support and constructional details at junctions. </li></ul><ul><li>No exact calculations are possible to make accurate assessment of eccentricity. Extent of eccentricity under any particular circumstances has, therefore, to be decided according to the best judgment of the designer. Some guidelines for assessment of eccentricity are given in Appendix A. of IS 1905 - 1987 </li></ul><ul><li>Arches, vaults and pillars generally experience eccentric force </li></ul>
  31. 33. VAULT PITHCED ROOF
  32. 34. EXPERIMENTAL PROGRAMME <ul><li>Basic Tests on bricks </li></ul><ul><li>Tests on Mortar </li></ul><ul><li>Tests on Masonry prisms </li></ul><ul><li>Full Scale Tests on Masonry walls </li></ul>
  33. 35. Tests on Bricks
  34. 36. Avg. Dry density C.O.V Range 1.75 g/cc 1.70% 1.6-1.95g/cc ****
  35. 37. Water Absorption(%) (Avg) C.O.V Range 13.90 2.06% ≤ 20%**
  36. 38. ***Sarangpani 1998 I.R.A kg/m 2/ min C.O.V Range kg/m 2/ min 2.815 8.55% 1.35-3.53**
  37. 39. ***Sarangpani1998, Raghunath 2003 for T.M.B of Bangalore Compressive Strength = Ultimate Load MPa. Area of Loading Compr . Strength (MPa) C.O.V Range (MPa) 5.32 2.56% 3-11***
  38. 40. E = 752.6 MPa from the Graph
  39. 41. TESTS ON MORTAR <ul><li>Compressive strength of mortar </li></ul><ul><ul><ul><ul><li>Tests were carried out as per IS 2250-1981 </li></ul></ul></ul></ul><ul><ul><ul><ul><li>1:6 ratio was chosen and hence mortar cubes were cast measuring 70.6 mm*70.6mm*70.6mm </li></ul></ul></ul></ul>** As per IS-1905-1987 Compr strength (MPa) C.O.V Range (MPa) 10.03 3.87% min3.0**
  40. 42. <ul><li>Flow is defined as the resulting increase in the base diameter of mortar mass expressed as a percentage of original base diameter </li></ul><ul><li>This test is useful in determining the optimum water cement ratio for a particular mortar mix </li></ul>As per IS-2250-1981, Flow value shall be b/w 100-115%
  41. 43. Mortar cone before and after applying jolts Conical mould Rigid frame Brass plate-circular
  42. 44. Tests on Masonry Prisms <ul><li>Objective </li></ul><ul><ul><ul><li>To evaluate basic properties such as compressive strength, elastic modulus, stress-strain relationship </li></ul></ul></ul><ul><ul><ul><li>Presently behaviour of stack bonded prism and 225 mm thick masonry prisms have been studied </li></ul></ul></ul><ul><ul><ul><li>Prisms have been cast using 1:6 mix cement sand mortar 1.2 water cement ratio and table moulded bricks </li></ul></ul></ul><ul><ul><ul><li>An average thickness of 10-12mm was maintained for mortar joints and the prisms were cured for 14 days and tested under compression in Universal testing machine </li></ul></ul></ul>
  43. 45. 225 mm masonry prism and stack bonded prism before testing
  44. 46. Stress strain curve for prisms
  45. 47. Modes of failure <ul><li>Failure of brick-mortar bond was often noticed. </li></ul><ul><li>crushing of the brick was also seen in prisms </li></ul><ul><li>Tensile splitting of the brick was also noticed in the prism </li></ul>
  46. 49. <ul><li>To investigate stress reduction factor of walls, </li></ul><ul><li>for slenderness ratio= 6.0 for axial loading and eccentric loading(e/t=0.25) </li></ul>Need for present investigation
  47. 50. EXPERIMENTAL PROGRAM <ul><li>I n the present project, full scale brick wall have been constructed for both axial and eccentric loading(e/t=0.25) for a slenderness ratio =6 </li></ul><ul><li>Number of test specimens </li></ul><ul><ul><ul><ul><ul><li>For axial loading – 2 Nos </li></ul></ul></ul></ul></ul><ul><ul><ul><ul><ul><li>For eccentric loading -- 2 Nos </li></ul></ul></ul></ul></ul><ul><li>In this experiment an attempt has been made to compare the values obtained by experiments, with actual stress reduction factor in Table9, IS-1905-1987. </li></ul>
  48. 51. 4 legged loading frame-reaction type Courtesy-RVCE
  49. 53. 1.55m 0.95m 0.225m
  50. 54. Arrangement for Ecc.loading 0.5m 1.3m 1.0m DIAL GAUGE POSITION
  51. 55. Plan of Eccentric loading arrangement-1 Plan of Eccentric loading arrangement-2
  52. 56. Test Set-up details
  53. 57. WALL1- Front face and Rear face after testing Crushing of brick vertical splitting
  54. 58. WALL2- Front face and Rear face after testing Spalling Vertical cracks
  55. 59. Comments on failure of axial loaded walls <ul><li>Vertical splitting crack observed in the wall specimen after failure. </li></ul><ul><li> Crushing of bricks also observed as seen in the figure </li></ul><ul><li> De-lamination of brick due to crushing also observed </li></ul><ul><li> The vertical cracks were distributed from top of the specimen to the bottom course </li></ul><ul><li> Diagonal shear cracks were also observed in the wall specimen </li></ul>
  56. 60. Eccentric loading before and after failure
  57. 61. CRACK PATTERN-ECCENTRICALLY LOADED Separation of 2 leaves of wall
  58. 62. Comments <ul><li>Global failure of wall specimen was observed i.e. all courses from top to the bottom participated in sustaining load </li></ul><ul><li>Mainly, horizontal cracks induced due to flexure were observed in this specimen </li></ul><ul><li>Vertical cracks along the side face of the specimen were also observed i.e., separation of two leaves of wall </li></ul>
  59. 63. Wall1
  60. 64. Wall2
  61. 65. Wall3
  62. 66. wall4 WALL 4(ECC2)
  63. 67. SUMMARY OF WALL TESTED
  64. 68. Evaluation of stress reduction factors <ul><li>It is virtually impossible to apply an axial compressive load to a wall or column since this would require a perfect unit with no fabrication errors </li></ul><ul><li>The vertical load will, in general, be eccentric to the central axis and this will produce a bending moment in the member </li></ul>
  65. 69. <ul><li>The additional moment can be allowed in 2 ways </li></ul><ul><li>The stresses due to the equivalent axial loads and bending moments can be added using the formula below </li></ul><ul><li>Total stress= P/A±M/Z </li></ul><ul><li> (or) </li></ul><ul><li>Reducing the axial load-carrying capacity, of the wall, by a </li></ul><ul><li>suitable factor known as “Stress reduction factor” in </li></ul><ul><li>IS-1905-1987 </li></ul><ul><li>The problem of column buckling has been </li></ul><ul><li>approached in a different way, by observing that </li></ul><ul><li>load P applied to a column is never perfectly centric </li></ul><ul><li>Due to eccentricity, moment is induced in column </li></ul><ul><li>which induces bending </li></ul>Formulation of Secant formula
  66. 70. Where σ max from experiment on walls ‘ E’ VALUE from prism experiment (e/t)= eccentricity ratio (l/t)= slenderness ratio
  67. 72. (P/A) values
  68. 73. Stress reduction factor obtained
  69. 75. Comparison with different codes of masonry <ul><li>In present study, In the present study, stress reduction factors computed from various codes have been compared with the present stress reduction factor obtained from Secant formula for slenderness ratio = 6.0 and eccentricity ratio = 0.25 </li></ul><ul><li>As per ENV 1996-1-1-1995(code of practice for masonry in Europe), Stress reduction factor is denoted by “øm”. In the present study, the stress reduction factor for slenderness ratio = 6.0 and eccentricity ratio =0.25, is equal to 0.48. </li></ul>Euro-code (ENV 1996-1-1-1995)
  70. 76. Graph showing stress reduction factors for varying eccentricites and slenderness ratio as per Euro-code (ENV 1996-1-1-1995) 0.48
  71. 77. <ul><li>As per BS 5628 (code of practice for masonry in Britain), Stress reduction factor is denoted by “β”. In the present study, the stress reduction factor for slenderness ratio = 6.0 and eccentricity ratio =0.25, is equal to 0.55 </li></ul>British code (BS 5628) 0.55
  72. 79. Conclusion <ul><li>The analytical approach using secant formula was adopted to evolve the stress reduction factor which gave a value of 0.40 for slenderness ratio of 6.0 and eccentricity ratio of 0.25 ( 1/4 ) </li></ul><ul><li>IS: 1905-1987 gives a value stress reduction factor of 1.0 for slenderness ratio of 6.0 for all eccentricity ratios ( 0 to 1/3 ). However the experiment has shown that there is a reduction in stress reduction factor value </li></ul><ul><li>The stress reduction factor value given in Eurocode(ENV-1996) and British code (BS 5628) also reveals the reduction in stress reduction factor for varying ( e/t ) ratios (eccentricities) against slenderness ratio of 6.0. Hence, the IS code value which is on higher side needs to investigated </li></ul>
  73. 80. Scope for Further Study <ul><li>In the present case, experiments on full scale walls were carried out for slenderness ratio of 6.0 and eccentricity ratio of 0.25. This can be extended for varying eccentricities such as (1/24), (1/12), (1/3), ETC AND FOR VARYING ECCENTRICITIES to find stress reduction factors as compared to axially loaded </li></ul>
  74. 81. References <ul><li>AVINASH A.C. (2006) “A Comprehensive study on Masonry units”, M.Tech Thesis, Department of civil Engineering, BMSCE, Bangalore, India. </li></ul><ul><li>BEER JOHNSTON DE WOLF, “Mechanics of Materials”,2004, Mc Graw Hill Publishers New York </li></ul><ul><li>BS 5628-1:1992,” Code of Practice for Structural use of Unreinforced Masonry” </li></ul><ul><li>DAYARATHNAM .P (1988),”Brick and Reinforced masonry Structures”, Oxford IBH </li></ul><ul><li>Publishing Company New Delhi </li></ul><ul><li>EUROCODE 6 ,“Design of masonry Structures”,(ENV 1996-1-1: 1995) </li></ul><ul><li>GUMASTE K.S. (2004), “Studies on the Strength and Elasticity of Brick masonry walls ”, Ph.D Thesis, Dept of Civil Engg, Indian Institute of Science, Bangalore </li></ul><ul><li>HENDRY A W, “Design of Structural Masonry”, 1998, Mc Millan Publishers London </li></ul><ul><li>HENDRY A W, B.P.SINHA ,S.R. DAVIES,” Design of Masonry Structures”, 2003, Chapman and Hall Publishers London </li></ul><ul><li>IS: 1905-1987, “Code of Practice for structural use of Unreinforced Masonry”, Bureau of Indian standards, New Delhi </li></ul><ul><li>IS: 2250-1981, “Code of practice for preparation and use of Masonry mortars”, (first revision), </li></ul>
  75. 82. <ul><li>JAGADISH .K.S, “Alternative Building Materials”, Indian Institute of Science, 2005, New Age International Publishers, Bangalore </li></ul><ul><li>MAC KENZIE ,”Design of Structural Masonry”, 2001,Palgrave Publishers, New York </li></ul><ul><li>MAURENBRECHER,1985,”Axial Compression Tests on Masonry Walls and Prisms”, National Research Institute of Canada </li></ul><ul><li>NARENDRA TALY, “Design of Reinforced Masonry structures”, 2002 Mc Graw Hill Publishers New York </li></ul><ul><li>NIKHIL JOLAD (2008),”Evaluation of Stress Reduction Factors through Experiments on Full Scale Brick Masonry Walls”, M.Tech Thesis. Department of Civil Engineering, BMSCE, Bangalore, India </li></ul><ul><li>RAGHUNATH (2003),”Static and Dynamic Behaviour of Brick masonry with Containment Reinforcement” Ph.D Thesis submitted to Department of Civil Engineering, Indian Institute of Science, Bangalore </li></ul><ul><li>SAHLIN SVEN, “Structural Masonry”, 1971, Prentice hall Publishers London </li></ul><ul><li>SARANGAPANI .G (1998), “Studies on the Strength of Brick Masonry” Ph.D thesis submittedto Dept. of Civil Engineering, Indian Institute of Science, Bangalore </li></ul><ul><li>SHWETHA( 2009), ”Stress Reduction Factors for Masonry an Analytical Approach”, M.TechThesis. Department of Civil Engineering, BMSCE, Bangalore, India </li></ul><ul><li>SP-20 (1991), “ Handbook on Masonry Design and Construction”, Bureau of Standards, New Delhi </li></ul>
  76. 83. THANK YOU THANK YOU

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