UNREINFORCED MASONRY STRUCTURES -PART I - DEFINITIONS AND PROBLEMS UNDER LATERAL LOADS

Transcription

1 UNREINFORCED MASONRY STRUCTURES -PART I - DEFINITIONS AND PROBLEMS UNDER LATERAL LOADS

2 Some Definitions UnReinforced Masonry (URM): Defined as masonry that contains no reinforcing in it. Masonry Unit: Clay brick or natural stone element used to construct masonry. Mortar: Binding element being used to connect masonry units, typically composed of limeorcement,orboth,andsand.

3 Masonry Walls Wallsmostgenerallyaremadeof brick, hollow concrete blocks, hollow clay tiles??, stone and adobe, and are loadbearing. Solid clay-brick unit masonry is the most common type of masonry unit.

4 Typesof Masonry Wall Units

5 Masonry Walls A common type of unreinforced masonry wall in one- or two-story buildings is approximately a cm thick, and uses a pattern of brickwork. In this pattern, most of the bricks are laid running parallel with the wall (these are known as stretchers). Approximately every sixth horizontal row, there will be a row of bricks with their ends rather than their sides visible (these are known as headers), as illustrated in Figure 8.

6 Basic Brickwork Terminology Head Joint Bed Joint Course - horizontal layer of brick

7 A Patternof Brickwork Course: Continuous layer Wythe: Continuous vertical section

8 A TYPICAL MASONRY STRUCTURE MAIN COMPONENTS Main components of URM structures: Footing and/or foundation wall (concrete, masonry, or rock) Load bearing masonry exterior walls, Woodframefloor(s)(inmostofthecases), Roof system, At the interior, there is some type of bearing wall(s), normally URM or wood.

9 Foundation Walls Foundation walls for URM buildings may be either concrete, masonry, or rock, If the foundation wall is unreinforced masonry or rock, it can break apart at the mortar joints when seismic activity occurs, Many times, these walls have been badly deteriorated from moisture penetration over the life of the building, The mortar used in many older buildings contains very little cement andisnormallyverysoftandweak.

10 Load Bearing Walls A bearing wall is defined as a wall which supports any vertical load in a building/structure as well as its own weight. The distance between the wall units is sometimes larger to provide insulation. This type of wall configuration is called cavity walls. How to connect different wall layers (there is nomortar)?

11 Floor and Roof Diaphragms Three categories of diaphragms can be identified: rigid concrete slab diaphragms, flexible wood, metal diaphragms, Intermediate systems such as hollow concrete planks and brick spanning between beams also exist. In flexible diaphragms, excessive deflections can lead to out-ofplane?? wall damage. Flexible Wood Diaphragm Hollow Brick System Hollow brick/concrete systems may lack adequate interconnections to function as a continuous load path.

12 Floor and Roof Diaphragms An Intermediate Floor Diaphragm System

13 Wooden Joist System for Floors

14 A Typical Single Story URM Building System as a Whole

15 A Typical Multi-storyUnreinforced Masonry Building

16 What is Wrongwith URM Structures? Masonry is one of the oldest building materials and has been considered the most durable, It is behavior under vertical/gravity static loads is superb(under compressive forces), But earthquake (EQ) ground shaking has been found to be very damaging to URM buildings, Previous EQs have shown that masonry structures are the most vulnerable of all building types to the lateral(earthquake) forces.

17 Why Earthquake Loads are Damaging to URM? Masonry material performs well under compressive forces, EQ loads generates tensile as well as shear forces in the material which is intrinsically weak in tension, Lack of additional material (e.g., steel reinforcement) withstanding well to tension forces makes URM building very vulnerable for EQ loads.

18 ThenWhy URM Structures are Still Being Studied? In many modern building codes, it is prohibited to build URM building in high seismic regions, But in existing building stocks, URM structures DO exist, therefore identifying them in building inventories, assessing their earthquake performance, and retrofitting them are important and valid tasks.

19 A Recent Inventory Study Conducted in Balçova(2011) Entire Balçova area has been studied to characterize its building inventory, following figures were identified, Out of 7628 buildings 2660 many of them are URM buildings(35% of the total), Only %23 of them have projects, the remaining do not have projects(majority), It is estimated that 25-30% of Izmir s entire building stock is composed of URM buildings.

20 Other URM Components Non-wall Components In URM structures there are other components called non-wall component. In many cases, especially under earthquakes, their response becomes important, and damage to these components may occur before damage on the walls becomes significant. Below, common behavior modes of non-wall components are discussed.

21 Non-wall URM Components Parapets These short extensions of walls above the roof typically occur at the perimeter of the buildings and are primarily present for aesthetic reasons. As originally constructed, they are not braced back to the roof and are thus susceptible to brittle flexural out-of-plane failure. Building Itself From Adjacent Building

22 Parapets (Are they just simple extensions?)

23 This category includes veneer, cornices, brackets, statuary, and any minor masonry feature that is susceptible to falling, Damage may result from excessive accelerations of appendages and deformations that cause connection failures between the appendage and the structure, Delamination of veneer can result from missing or inadequate ties, Pounding against adjacent buildings can lead to localized falling hazards. Non-wall URM Components Appendages

24 Canopy Failure Are they just shades and shelters?

25 Generally limited to low-strength tension connections in which one endofasteelbarisembeddedone wytheinfromtheouterfaceofthe wall and the other end is hammered into the side of a wood joist. Non-wall Components Wall-Diaphragm Ties Wall-diaphragm separation due to inadequate or missing tension ties can lead to out-of-plane failures of walls; Missing shear ties can lead to the diaphragm sliding along the inplane walls and then pushing against the walls perpendicular to the movement, resulting in corner damage to the walls. Tension Ties Missing shear ties! In-plane walls

26 URM Components More Details on Wall Components URM wall elements can be subdivided into five component types based on the mode of inelastic behavior. The majority of modes relate to in-plane damage, but out-of-plane damage can occur as well in each of the systems, often in combination with in-plane damage. The five component types are described below.

27 In-Plane and Out-of-Plane (OOP) Damage in URM building In-plane Wall Damage OOP Wall Damage

28 Wall Components Solid Cantilever Wall (URM1) Typical Inelastic/Failure Behavior URM1: Such walls are typically found adjacent to other buildings or on alleys, and they act as cantilevers up from the foundation.

29 Overview of In-plane Failure Modeson a SolidMasonry Wall

30 Wall Components Weak Pier inperforated Wall (URM2 and URM4) URM2: This component is a weakpierinaperforatedwall.in this system, inelastic deformation occurs in the piers. Typical Inelastic/Failure Behavior URM4: This component is a strong spandrel in a weak pierstrong spandrel mechanism. Strong spandrels do not experience damage.

31 Wall Components Weak Spandrel in Perforated Wall (URM3) URM3: This component is a weak spandrel in a perforated wall. Inelastic deformation occurs first in the spandrels then leading to inelastic deformation and damage in the piers. Typical Inelastic/Failure Behavior

32 Wall Components Weak Joints in Perforated Walls (URM5) URM5: Perforated wall with panel zone weak joints. Inelastic deformation occurs in the region where the pier and spandrel intersect. Typical Inelastic/Failure Behavior Such damage is not observed generally in experimental tests, nor is it seen in actual earthquakes, except at outer piers of upper stories.

33 Understanding the Response of Structural Componentsin URM Buildings under EQ Loads

34 What Makes URM Buildings Weak Under EQ Forces(Lateral Forces)? The walls are weak in resisting horizontal forces (and they lack ductility), The walls are heavy (they have high mass, leading to high inertial forces), Diaphragms are excessively flexible (insufficient lateral support for the walls), Diaphragm-to-wall connections are either absent or weak, Parapets and ornamentation are common (and made of masonry).

35 An Intrinsic Problem Brittle Material Masonry materials are intrinsically strong when compressed under the gravity loads but are weak in resisting earthquake forces, which make materials flex and also shear, When an earthquake shakes an unreinforced masonry building, it causes the building s walls to flex out-of-plane and to shear in-plane, Unreinforced masonry is weak in resisting both of those types of forces. Mortar is the glue that holds the masonry units together; however, when it eventually cracks, it does so in a brittle manner, similar to thewaythatthebrickscrack.

36 Other Problems Maintaining Integrity Furthermore a number of common failure modes of URM buildings related to maintaining integrity have repeatedly been observed in earthquakes. These modes can be grouped in the following categories: Lack of anchorage, Anchorfailure, In-planefailures, Out-of-planefailure, Combined in-plane and out-of-plane effects, Diaphragm-relatedfailures.

37 FourRecognized In-planeFailure Modes

38 Foundation Rocking Mode 1 Rocking of a wall and its foundation on the supporting soil has been observed in the field. Though recognized as a potentially favorable mode of nonlinear response and a source of damping rather than significant damage, Excessive rocking could theoretically lead to some instability and nonstructural damage in the superstructure, Several technologies being used to encourage rocking

39 Wall-Pier Rocking Mode 1 In the wall-pier rocking behavior mode, after flexural cracking develops at the heel, the wall or pier acts as a rigid body rotating about the toe.

40 Toe Crushing Mode 2 Characteristics of toe crushing Lossofmaterialattoeofpier Vertical load carrying capacity generally maintained Notreallyafailure

41 Bed Joint Sliding Mode 3 In this type of behavior sliding occurs on bed joints. Commonly observed both in the field and in experimental tests, There are two basic forms: sliding on a horizontal plane, and a stairstepped diagonal crack where the head joints open and close to due to movement on the bed joints.

42 Bed Joint Sliding Mode 3 Stair-step Type

43 Bed Joint Sliding Mode 3 Horizontal Type Characteristics of bed joint sliding Governed by friction, Consumesenergy, Pseudo ductility source, Vertical load carrying capacity generally maintained Not really a failure Horizontal Sliding

44 Diagonal Tension Failure Mode 4 Characteristics of diagonal tension failure Governed due to tension stresses (shear forces lead to tension stresses), that is why also called shear failure, No bed joint sliding, Observable in both piers and spandrels. Tension Cracks on a Pier and Spandrels Tension Cracks on a Pier

45 Diagonal Tension Failure Mode 4 Spandrel Failure Pier Failure

46 Out-of-plane (OOP) Failure Modes TherearethreetypesofOOPdamage: One-way bending between vertical supports, Two-way bending, end walls represent either 3 or 4 boundary conditions, Corner failure.

47 Out-of-plane Failure One-way Bending

48 Out-of-plane Failure Two-way Bending

49 Out-of-plane Failure Two-way Bending

50 Spalled corner Out-of-plane Failure Two-way Bending

51 Out-of-plane Failure Cantilever Action Complete collapse of a gable by cantilever action (lack of anchorage) Diaphragm is visible

52 Out-of-plane Failure Corner Damage

53 Out-of-plane Failure Mixed Mode Failure (In-plane, out-of-plane and corner effects) Very common type of damage (heavy roof usually the culprit)

54 UNREINFORCED MASONRY STRUCTURES -PART I - DEFINITIONS AND PROBLEMS UNDER LATERAL LOADS

55 Some Definitions UnReinforced Masonry (URM): Defined as masonry that contains no reinforcing in it. Masonry Unit: Clay brick or natural stone element used to construct masonry. Mortar: Binding element being used to connect masonry units, typically composed of limeorcement,orboth,andsand.

56 Masonry Walls Wallsmostgenerallyaremadeof brick, hollow concrete blocks, hollow clay tiles??, stone and adobe, and are loadbearing. Solid clay-brick unit masonry is the most common type of masonry unit.

57 Typesof Masonry Wall Units

58 Masonry Walls A common type of unreinforced masonry wall in one- or two-story buildings is approximately a cm thick, and uses a pattern of brickwork. In this pattern, most of the bricks are laid running parallel with the wall (these are known as stretchers). Approximately every sixth horizontal row, there will be a row of bricks with their ends rather than their sides visible (these are known as headers), as illustrated in Figure 8.

59 Basic Brickwork Terminology Head Joint Bed Joint Course - horizontal layer of brick

60 A Patternof Brickwork Course: Continuous layer Wythe: Continuous vertical section

61 A TYPICAL MASONRY STRUCTURE MAIN COMPONENTS Main components of URM structures: Footing and/or foundation wall (concrete, masonry, or rock) Load bearing masonry exterior walls, Woodframefloor(s)(inmostofthecases), Roof system, At the interior, there is some type of bearing wall(s), normally URM or wood.

62 Foundation Walls Foundation walls for URM buildings may be either concrete, masonry, or rock, If the foundation wall is unreinforced masonry or rock, it can break apart at the mortar joints when seismic activity occurs, Many times, these walls have been badly deteriorated from moisture penetration over the life of the building, The mortar used in many older buildings contains very little cement andisnormallyverysoftandweak.

63 Load Bearing Walls A bearing wall is defined as a wall which supports any vertical load in a building/structure as well as its own weight. The distance between the wall units is sometimes larger to provide insulation. This type of wall configuration is called cavity walls. How to connect different wall layers (there is nomortar)?

64 Floor and Roof Diaphragms Three categories of diaphragms can be identified: rigid concrete slab diaphragms, flexible wood, metal diaphragms, Intermediate systems such as hollow concrete planks and brick spanning between beams also exist. In flexible diaphragms, excessive deflections can lead to out-ofplane?? wall damage. Flexible Wood Diaphragm Hollow Brick System Hollow brick/concrete systems may lack adequate interconnections to function as a continuous load path.

65 Floor and Roof Diaphragms An Intermediate Floor Diaphragm System

66 Wooden Joist System for Floors

67 A Typical Single Story URM Building System as a Whole

68 A Typical Multi-storyUnreinforced Masonry Building

69 What is Wrongwith URM Structures? Masonry is one of the oldest building materials and has been considered the most durable, It is behavior under vertical/gravity static loads is superb(under compressive forces), But earthquake (EQ) ground shaking has been found to be very damaging to URM buildings, Previous EQs have shown that masonry structures are the most vulnerable of all building types to the lateral(earthquake) forces.

70 Why Earthquake Loads are Damaging to URM? Masonry material performs well under compressive forces, EQ loads generates tensile as well as shear forces in the material which is intrinsically weak in tension, Lack of additional material (e.g., steel reinforcement) withstanding well to tension forces makes URM building very vulnerable for EQ loads.

71 ThenWhy URM Structures are Still Being Studied? In many modern building codes, it is prohibited to build URM building in high seismic regions, But in existing building stocks, URM structures DO exist, therefore identifying them in building inventories, assessing their earthquake performance, and retrofitting them are important and valid tasks.

72 A Recent Inventory Study Conducted in Balçova(2011) Entire Balçova area has been studied to characterize its building inventory, following figures were identified, Out of 7628 buildings 2660 many of them are URM buildings(35% of the total), Only %23 of them have projects, the remaining do not have projects(majority), It is estimated that 25-30% of Izmir s entire building stock is composed of URM buildings.

73 Other URM Components Non-wall Components In URM structures there are other components called non-wall component. In many cases, especially under earthquakes, their response becomes important, and damage to these components may occur before damage on the walls becomes significant. Below, common behavior modes of non-wall components are discussed.

74 Non-wall URM Components Parapets These short extensions of walls above the roof typically occur at the perimeter of the buildings and are primarily present for aesthetic reasons. As originally constructed, they are not braced back to the roof and are thus susceptible to brittle flexural out-of-plane failure. Building Itself From Adjacent Building

75 Parapets (Are they just simple extensions?)

76 This category includes veneer, cornices, brackets, statuary, and any minor masonry feature that is susceptible to falling, Damage may result from excessive accelerations of appendages and deformations that cause connection failures between the appendage and the structure, Delamination of veneer can result from missing or inadequate ties, Pounding against adjacent buildings can lead to localized falling hazards. Non-wall URM Components Appendages

77 Canopy Failure Are they just shades and shelters?

78 Generally limited to low-strength tension connections in which one endofasteelbarisembeddedone wytheinfromtheouterfaceofthe wall and the other end is hammered into the side of a wood joist. Non-wall Components Wall-Diaphragm Ties Wall-diaphragm separation due to inadequate or missing tension ties can lead to out-of-plane failures of walls; Missing shear ties can lead to the diaphragm sliding along the inplane walls and then pushing against the walls perpendicular to the movement, resulting in corner damage to the walls. Tension Ties Missing shear ties! In-plane walls

79 URM Components More Details on Wall Components URM wall elements can be subdivided into five component types based on the mode of inelastic behavior. The majority of modes relate to in-plane damage, but out-of-plane damage can occur as well in each of the systems, often in combination with in-plane damage. The five component types are described below.

80 In-Plane and Out-of-Plane (OOP) Damage in URM building In-plane Wall Damage OOP Wall Damage

81 Wall Components Solid Cantilever Wall (URM1) Typical Inelastic/Failure Behavior URM1: Such walls are typically found adjacent to other buildings or on alleys, and they act as cantilevers up from the foundation.

82 Overview of In-plane Failure Modeson a SolidMasonry Wall

83 Wall Components Weak Pier inperforated Wall (URM2 and URM4) URM2: This component is a weakpierinaperforatedwall.in this system, inelastic deformation occurs in the piers. Typical Inelastic/Failure Behavior URM4: This component is a strong spandrel in a weak pierstrong spandrel mechanism. Strong spandrels do not experience damage.

84 Wall Components Weak Spandrel in Perforated Wall (URM3) URM3: This component is a weak spandrel in a perforated wall. Inelastic deformation occurs first in the spandrels then leading to inelastic deformation and damage in the piers. Typical Inelastic/Failure Behavior

85 Wall Components Weak Joints in Perforated Walls (URM5) URM5: Perforated wall with panel zone weak joints. Inelastic deformation occurs in the region where the pier and spandrel intersect. Typical Inelastic/Failure Behavior Such damage is not observed generally in experimental tests, nor is it seen in actual earthquakes, except at outer piers of upper stories.

86 Understanding the Response of Structural Componentsin URM Buildings under EQ Loads

87 What Makes URM Buildings Weak Under EQ Forces(Lateral Forces)? The walls are weak in resisting horizontal forces (and they lack ductility), The walls are heavy (they have high mass, leading to high inertial forces), Diaphragms are excessively flexible (insufficient lateral support for the walls), Diaphragm-to-wall connections are either absent or weak, Parapets and ornamentation are common (and made of masonry).

88 An Intrinsic Problem Brittle Material Masonry materials are intrinsically strong when compressed under the gravity loads but are weak in resisting earthquake forces, which make materials flex and also shear, When an earthquake shakes an unreinforced masonry building, it causes the building s walls to flex out-of-plane and to shear in-plane, Unreinforced masonry is weak in resisting both of those types of forces. Mortar is the glue that holds the masonry units together; however, when it eventually cracks, it does so in a brittle manner, similar to thewaythatthebrickscrack.

89 Other Problems Maintaining Integrity Furthermore a number of common failure modes of URM buildings related to maintaining integrity have repeatedly been observed in earthquakes. These modes can be grouped in the following categories: Lack of anchorage, Anchorfailure, In-planefailures, Out-of-planefailure, Combined in-plane and out-of-plane effects, Diaphragm-relatedfailures.

90 FourRecognized In-planeFailure Modes

91 Foundation Rocking Mode 1 Rocking of a wall and its foundation on the supporting soil has been observed in the field. Though recognized as a potentially favorable mode of nonlinear response and a source of damping rather than significant damage, Excessive rocking could theoretically lead to some instability and nonstructural damage in the superstructure, Several technologies being used to encourage rocking

92 Wall-Pier Rocking Mode 1 In the wall-pier rocking behavior mode, after flexural cracking develops at the heel, the wall or pier acts as a rigid body rotating about the toe.

93 Toe Crushing Mode 2 Characteristics of toe crushing Lossofmaterialattoeofpier Vertical load carrying capacity generally maintained Notreallyafailure

94 Bed Joint Sliding Mode 3 In this type of behavior sliding occurs on bed joints. Commonly observed both in the field and in experimental tests, There are two basic forms: sliding on a horizontal plane, and a stairstepped diagonal crack where the head joints open and close to due to movement on the bed joints.

95 Bed Joint Sliding Mode 3 Stair-step Type

96 Bed Joint Sliding Mode 3 Horizontal Type Characteristics of bed joint sliding Governed by friction, Consumesenergy, Pseudo ductility source, Vertical load carrying capacity generally maintained Not really a failure Horizontal Sliding

97 Diagonal Tension Failure Mode 4 Characteristics of diagonal tension failure Governed due to tension stresses (shear forces lead to tension stresses), that is why also called shear failure, No bed joint sliding, Observable in both piers and spandrels. Tension Cracks on a Pier and Spandrels Tension Cracks on a Pier

98 Diagonal Tension Failure Mode 4 Spandrel Failure Pier Failure

99 Out-of-plane (OOP) Failure Modes TherearethreetypesofOOPdamage: One-way bending between vertical supports, Two-way bending, end walls represent either 3 or 4 boundary conditions, Corner failure.

100 Out-of-plane Failure One-way Bending

101 Out-of-plane Failure Two-way Bending

102 Out-of-plane Failure Two-way Bending

103 Spalled corner Out-of-plane Failure Two-way Bending

104 Out-of-plane Failure Cantilever Action Complete collapse of a gable by cantilever action (lack of anchorage) Diaphragm is visible

105 Out-of-plane Failure Corner Damage

106 Out-of-plane Failure Mixed Mode Failure (In-plane, out-of-plane and corner effects) Very common type of damage (heavy roof usually the culprit)

107 UNREINFORCED MASONRY STRUCTURES -PART I - DEFINITIONS AND PROBLEMS UNDER LATERAL LOADS

108 Some Definitions UnReinforced Masonry (URM): Defined as masonry that contains no reinforcing in it. Masonry Unit: Clay brick or natural stone element used to construct masonry. Mortar: Binding element being used to connect masonry units, typically composed of limeorcement,orboth,andsand.

109 Masonry Walls Wallsmostgenerallyaremadeof brick, hollow concrete blocks, hollow clay tiles??, stone and adobe, and are loadbearing. Solid clay-brick unit masonry is the most common type of masonry unit.

110 Typesof Masonry Wall Units

111 Masonry Walls A common type of unreinforced masonry wall in one- or two-story buildings is approximately a cm thick, and uses a pattern of brickwork. In this pattern, most of the bricks are laid running parallel with the wall (these are known as stretchers). Approximately every sixth horizontal row, there will be a row of bricks with their ends rather than their sides visible (these are known as headers), as illustrated in Figure 8.

112 Basic Brickwork Terminology Head Joint Bed Joint Course - horizontal layer of brick

113 A Patternof Brickwork Course: Continuous layer Wythe: Continuous vertical section

114 A TYPICAL MASONRY STRUCTURE MAIN COMPONENTS Main components of URM structures: Footing and/or foundation wall (concrete, masonry, or rock) Load bearing masonry exterior walls, Woodframefloor(s)(inmostofthecases), Roof system, At the interior, there is some type of bearing wall(s), normally URM or wood.

115 Foundation Walls Foundation walls for URM buildings may be either concrete, masonry, or rock, If the foundation wall is unreinforced masonry or rock, it can break apart at the mortar joints when seismic activity occurs, Many times, these walls have been badly deteriorated from moisture penetration over the life of the building, The mortar used in many older buildings contains very little cement andisnormallyverysoftandweak.

116 Load Bearing Walls A bearing wall is defined as a wall which supports any vertical load in a building/structure as well as its own weight. The distance between the wall units is sometimes larger to provide insulation. This type of wall configuration is called cavity walls. How to connect different wall layers (there is nomortar)?

117 Floor and Roof Diaphragms Three categories of diaphragms can be identified: rigid concrete slab diaphragms, flexible wood, metal diaphragms, Intermediate systems such as hollow concrete planks and brick spanning between beams also exist. In flexible diaphragms, excessive deflections can lead to out-ofplane?? wall damage. Flexible Wood Diaphragm Hollow Brick System Hollow brick/concrete systems may lack adequate interconnections to function as a continuous load path.

118 Floor and Roof Diaphragms An Intermediate Floor Diaphragm System

119 Wooden Joist System for Floors

120 A Typical Single Story URM Building System as a Whole

121 A Typical Multi-storyUnreinforced Masonry Building

122 What is Wrongwith URM Structures? Masonry is one of the oldest building materials and has been considered the most durable, It is behavior under vertical/gravity static loads is superb(under compressive forces), But earthquake (EQ) ground shaking has been found to be very damaging to URM buildings, Previous EQs have shown that masonry structures are the most vulnerable of all building types to the lateral(earthquake) forces.

123 Why Earthquake Loads are Damaging to URM? Masonry material performs well under compressive forces, EQ loads generates tensile as well as shear forces in the material which is intrinsically weak in tension, Lack of additional material (e.g., steel reinforcement) withstanding well to tension forces makes URM building very vulnerable for EQ loads.

124 ThenWhy URM Structures are Still Being Studied? In many modern building codes, it is prohibited to build URM building in high seismic regions, But in existing building stocks, URM structures DO exist, therefore identifying them in building inventories, assessing their earthquake performance, and retrofitting them are important and valid tasks.

125 A Recent Inventory Study Conducted in Balçova(2011) Entire Balçova area has been studied to characterize its building inventory, following figures were identified, Out of 7628 buildings 2660 many of them are URM buildings(35% of the total), Only %23 of them have projects, the remaining do not have projects(majority), It is estimated that 25-30% of Izmir s entire building stock is composed of URM buildings.

126 Other URM Components Non-wall Components In URM structures there are other components called non-wall component. In many cases, especially under earthquakes, their response becomes important, and damage to these components may occur before damage on the walls becomes significant. Below, common behavior modes of non-wall components are discussed.

127 Non-wall URM Components Parapets These short extensions of walls above the roof typically occur at the perimeter of the buildings and are primarily present for aesthetic reasons. As originally constructed, they are not braced back to the roof and are thus susceptible to brittle flexural out-of-plane failure. Building Itself From Adjacent Building

128 Parapets (Are they just simple extensions?)

129 This category includes veneer, cornices, brackets, statuary, and any minor masonry feature that is susceptible to falling, Damage may result from excessive accelerations of appendages and deformations that cause connection failures between the appendage and the structure, Delamination of veneer can result from missing or inadequate ties, Pounding against adjacent buildings can lead to localized falling hazards. Non-wall URM Components Appendages

130 Canopy Failure Are they just shades and shelters?

131 Generally limited to low-strength tension connections in which one endofasteelbarisembeddedone wytheinfromtheouterfaceofthe wall and the other end is hammered into the side of a wood joist. Non-wall Components Wall-Diaphragm Ties Wall-diaphragm separation due to inadequate or missing tension ties can lead to out-of-plane failures of walls; Missing shear ties can lead to the diaphragm sliding along the inplane walls and then pushing against the walls perpendicular to the movement, resulting in corner damage to the walls. Tension Ties Missing shear ties! In-plane walls

132 URM Components More Details on Wall Components URM wall elements can be subdivided into five component types based on the mode of inelastic behavior. The majority of modes relate to in-plane damage, but out-of-plane damage can occur as well in each of the systems, often in combination with in-plane damage. The five component types are described below.

133 In-Plane and Out-of-Plane (OOP) Damage in URM building In-plane Wall Damage OOP Wall Damage

134 Wall Components Solid Cantilever Wall (URM1) Typical Inelastic/Failure Behavior URM1: Such walls are typically found adjacent to other buildings or on alleys, and they act as cantilevers up from the foundation.

135 Overview of In-plane Failure Modeson a SolidMasonry Wall

136 Wall Components Weak Pier inperforated Wall (URM2 and URM4) URM2: This component is a weakpierinaperforatedwall.in this system, inelastic deformation occurs in the piers. Typical Inelastic/Failure Behavior URM4: This component is a strong spandrel in a weak pierstrong spandrel mechanism. Strong spandrels do not experience damage.

137 Wall Components Weak Spandrel in Perforated Wall (URM3) URM3: This component is a weak spandrel in a perforated wall. Inelastic deformation occurs first in the spandrels then leading to inelastic deformation and damage in the piers. Typical Inelastic/Failure Behavior

138 Wall Components Weak Joints in Perforated Walls (URM5) URM5: Perforated wall with panel zone weak joints. Inelastic deformation occurs in the region where the pier and spandrel intersect. Typical Inelastic/Failure Behavior Such damage is not observed generally in experimental tests, nor is it seen in actual earthquakes, except at outer piers of upper stories.

139 Understanding the Response of Structural Componentsin URM Buildings under EQ Loads

140 What Makes URM Buildings Weak Under EQ Forces(Lateral Forces)? The walls are weak in resisting horizontal forces (and they lack ductility), The walls are heavy (they have high mass, leading to high inertial forces), Diaphragms are excessively flexible (insufficient lateral support for the walls), Diaphragm-to-wall connections are either absent or weak, Parapets and ornamentation are common (and made of masonry).

141 An Intrinsic Problem Brittle Material Masonry materials are intrinsically strong when compressed under the gravity loads but are weak in resisting earthquake forces, which make materials flex and also shear, When an earthquake shakes an unreinforced masonry building, it causes the building s walls to flex out-of-plane and to shear in-plane, Unreinforced masonry is weak in resisting both of those types of forces. Mortar is the glue that holds the masonry units together; however, when it eventually cracks, it does so in a brittle manner, similar to thewaythatthebrickscrack.

142 Other Problems Maintaining Integrity Furthermore a number of common failure modes of URM buildings related to maintaining integrity have repeatedly been observed in earthquakes. These modes can be grouped in the following categories: Lack of anchorage, Anchorfailure, In-planefailures, Out-of-planefailure, Combined in-plane and out-of-plane effects, Diaphragm-relatedfailures.

143 FourRecognized In-planeFailure Modes

144 Foundation Rocking Mode 1 Rocking of a wall and its foundation on the supporting soil has been observed in the field. Though recognized as a potentially favorable mode of nonlinear response and a source of damping rather than significant damage, Excessive rocking could theoretically lead to some instability and nonstructural damage in the superstructure, Several technologies being used to encourage rocking

145 Wall-Pier Rocking Mode 1 In the wall-pier rocking behavior mode, after flexural cracking develops at the heel, the wall or pier acts as a rigid body rotating about the toe.

146 Toe Crushing Mode 2 Characteristics of toe crushing Lossofmaterialattoeofpier Vertical load carrying capacity generally maintained Notreallyafailure

147 Bed Joint Sliding Mode 3 In this type of behavior sliding occurs on bed joints. Commonly observed both in the field and in experimental tests, There are two basic forms: sliding on a horizontal plane, and a stairstepped diagonal crack where the head joints open and close to due to movement on the bed joints.

148 Bed Joint Sliding Mode 3 Stair-step Type

149 Bed Joint Sliding Mode 3 Horizontal Type Characteristics of bed joint sliding Governed by friction, Consumesenergy, Pseudo ductility source, Vertical load carrying capacity generally maintained Not really a failure Horizontal Sliding

150 Diagonal Tension Failure Mode 4 Characteristics of diagonal tension failure Governed due to tension stresses (shear forces lead to tension stresses), that is why also called shear failure, No bed joint sliding, Observable in both piers and spandrels. Tension Cracks on a Pier and Spandrels Tension Cracks on a Pier

151 Diagonal Tension Failure Mode 4 Spandrel Failure Pier Failure

152 Out-of-plane (OOP) Failure Modes TherearethreetypesofOOPdamage: One-way bending between vertical supports, Two-way bending, end walls represent either 3 or 4 boundary conditions, Corner failure.

153 Out-of-plane Failure One-way Bending

154 Out-of-plane Failure Two-way Bending

155 Out-of-plane Failure Two-way Bending

156 Spalled corner Out-of-plane Failure Two-way Bending

157 Out-of-plane Failure Cantilever Action Complete collapse of a gable by cantilever action (lack of anchorage) Diaphragm is visible

158 Out-of-plane Failure Corner Damage

159 Out-of-plane Failure Mixed Mode Failure (In-plane, out-of-plane and corner effects) Very common type of damage (heavy roof usually the culprit)