Chuyên đề Sự làm việc vấn đề mô hình hóa và thiết kế của hệ khung vách chịu cắt

Shear Wall Behavior, Modeling, Analysis and Design AIT - Thailand ACECOMSSự làm việc của vách và khung giằng... Shear Wall Behavior, Modeling, Analysis and Design AIT - Thailand ACECOMST

Trang 2

Bài toán cơ bản

• Bài toán mô hình hoá và phân tích

– Truyền tải trọng cho vách chịu cắt – Mô hình hoá vách chịu cắt ở 2D – Mô hình hoá vách chịu cắt ở 3D – Tương tác giữa vách chịu cắt và hệ khung

• Bài toán thiết kế và bố trí cốt thép

– Tính toán cốt thép chịu uốn – Tính toán cốt thép chịu cắt – Bố trí cốt thép ở các lỗ mở và góc – Thiết kế và chi tiết liên kết ở các vách chịu cắt dạng ô

Trang 3

Shear Wall Behavior, Modeling, Analysis and Design AIT - Thailand ACECOMS

Vách chịu cắt-Một số quan niệm sai lầm

 Due to misleading name “Shear Wall”

– (lí do do sai lầm trong đặt tên “shear wall”)

 The dominant mode of failure is shear

 Strength is controlled by shear

 Designed is governed primarily by shear

 Force distribution can be based on relative stiffness

Trang 4

Vách chịu cắt hay cột

Trang 5

Vách chịu cắt hay khung

Trang 6

Sự làm việc của khung và vách

Trang 7

Sự làm việc của vách và khung giằng

Trang 8

Vách và khung

Sự làm việc của vách Sự làm việc của khung

Trang 9

Tương tác giữa khung và vách

Interactionforces

Trang 10

A-1 A-2 A-3 B-4 B-1 B-2 B-3 B-4

Khung và hệ khung-vách

Trang 11

Tương tác giữa vách và khung

• Biến dạng của khung

– Biến dạng chủ yếu là biến dạng cắt – Nguồn gốc của độ cứng ngang là độ cứng của nút khung (cột-dầm- sàn)

• Biến dạng của vách

– Biến dạng chủ yếu là uốn

– Biến dạng cắt tương đối nhỏ – Chỉ có những vách rất thấp mới bị phá hoại do cắt – Làm việc giống như một côn xôn mảnh

– Được thiết kế để chống lại tác động của cả lực dọc, mômen uốn

và lực cắt

Trang 12

S làm vi c c a ự ệ ủ

Trang 13

Với mỗi toà nhà 10,20,30 tầng

Chỉ có vách ( 3 trường hợp )

Chỉ có khung ( 3 trường hợp ) Khung vách ( 3 trường hợp )

Bài toán

Tổng 3x3 = 9 Trường hợp

Trang 14

Vách 10 tầng ∆ = 26.73 cm

Chiều dày vách = 15 cm

Trường hợp 1

Trang 15

Khung 10 tầng

Dầm = 60 cm x 30 cm Cột = 50 cm x 50 cm

Trường hợp 2

Trang 16

Hệ khung-vách 10 tầng ∆ = 5.14 cm

Dày vách = 15 cm Dầm = 60 cm x 30 cm Cột = 50 cm x 50 cm

Trang 17

Dày vách = 20 cm

Trang 18

Khung 20 tầng ∆ = 27.35 cm

Dầm = 60 cm x 30 cm Cột = 75 cm x 75 cm

Trang 19

Dày vách = 20 cm Dầm = 60 cm x 30 cm Cột = 75 cm x 75 cm

Trang 20

Vách 30 tầng ∆ = 355.04 cm

Dày vách = 30 cm

Trường hợp7

Trang 21

Dầm = 60 cm x 30 cm Cột = 100 cm x 100 cm

Trang 22

Khung-vách 30 tầng ∆ = 20.87 cm

Dày vách = 30 cm Dầm = 60 cm x 30 cm Cột = 100 cm x 100 cm

Trang 23

Tương tác khung-vách

Trang 24

Trang 25

Trang 26

Trang 27

Trang 28

Shear Wall Moments

for the Coupled System

Change in Shear Wall Moments

Interaction forces

Trang 29

Interaction forces

Coupling Element Moments

Trang 30

Shear Wall-Frame Load Distribution Curves

Trang 31

Deflected Shape of Shear Wall-Frame Interactive System

Khan-Sbarounis

Curves

Trang 32

Comparison of Shears and Moments in the Core wall

4 Different Layouts for Same Function Requirements

CL

2 1

12 in

in thick flat plate

CL

2 1

12 in

in thick flat plate

12 in

in thick flat plate

10 in

18-story high shear walls

CL

2 1

12 in

in thick flat plate

10 in

18-story high shear walls

Type D

Trang 33

12 in

in thick flat plate

Typical Floor Plan- Structure Type A

1 2 3 4 5 6 7 8 28 29 30 31 32 33 34 35 36

8' clear height between floors

Trang 34

12 in

in thick flat plate

Typical Floor Plan- Structure Type B

1 2 3 4 5 6 7 8 28 29 30 31 32 33 34 35 36

12 in

in thick flat plate

Trang 35

12 in

in thick flat plate

Typical Floor Plan- Structure Type C

1 2 3 4 5 6 7 8 28 29 30 31 32 33 34 35 36

12 in

in thick flat plate

12 in

in thick flat plate

Comparison of… : Type C

Trang 36

Typical Floor Plan- Structure Type D

1 2 3 4 5 6 7 8 28 29 30 31 32 33 34 35 36

12 in

in thick flat plate

Comparison of… : Type D

Trang 37

Comparison of Shears and Moments in the Core wall

Trang 38

Tương tác khung-vách-Kết luận

– Vách biến dạng chủ yếu do uốn

– Giả thuyết phổ biến bỏ qua khả năng chịu lực ngang của khung có thể

Trang 39

Các dạng cơ bản của vách

Trang 40

Các dạng cơ bản của vách

Trang 41

Các tuỳ chọn cho việc

mô hình hoá vách cứng

Trang 42

Sử dụng cấu kiện 1 D

L

t x h L

Trang 43

Mô hình khung cho vách phẳng

Vùng c ng ứ

• Đặc biệt thích hợp cho H/B lớn hơn 5

• Thay thế vách bằng một “cột” có tiết diện “B x t”

• Các dầm bên ngoài mép vách xem như dầm thông thường

• “Cột” được liên kết với dầm qua vùng cứng hay có tiết diện ngang rất lớn

B H

t

Trang 44

Mô hình khung cho lõi

Trang 45

Trang 46

Modeling Walls Using Membrane

DOFs: 2 DOFs /Node Ux and Uy

2-Translation Dimension: 2 dimension element Shape: Regular / Irregular Properties: Modulus of Elasticity(E),

Poisson ratio(v), Thickness( t )

This “Incomplete” Panel or Membrane Element

does not connect with Beams completely and

rotation DOF of beams and the ends are “Orphaned”

The Incomplete Membrane Element

Trang 47

Modeling Walls using Shell Elements

DOFs: 3 DOFs /Node Ux and Uy and Rz

2 Translation, 1 rotation Dimension: 2 dimension element

Shape: Regular / Irregular

Properties: Modulus of Elasticity(E),

Poisson ratio(v), Thickness( t )

Trang 48

Using Incomplete Membrane Elements

Multiple elements greater accuracy in determination of stress distribution and allow easy modeling of openings

Using Incomplete Membrane only

(No Moment continuity with Beams)

Using with Beams and or Columns are Required

(Full Moment continuity with Beams and Columns)

Trang 49

Using Complete Membrane Elements

Multiple elements greater accuracy in determination of stress distribution and allow easy modeling of openings

Using Complete Membrane only

(Moment continuity with Beams automatically provided)

Using with Beams, Columns

is NOT Required

(Full Moment continuity with Beams and Columns)

Trang 50

Connecting Walls to Slab

In general the mesh in the slab should match with mesh in the wall to

establish connection

Some software automatically establishes connectivity by using constraints or “Zipper” elements

“Zipper”

Trang 51

Using Trusses to Model Shear Walls

αππροξιµατεδ βψ τρυσσ µοδελσ:

– The vertical elements provide the axial-flexural resistance

– The diagonal elements provide the shear resistance

ωηερε αλλ τενσιον ισ τακεν βψ τιεσ ανδ χοµπρεσσιον βψ χονχρετε

Trang 52

2 5

10

Truss Model for Shear Walls

Comparing Deformation and Deflections of Shell Model with Truss Model

Trang 53

Truss Model for Shear Walls

2 5

10

Comparing Deformation and Deflections of Shell Model with Truss Model

Trang 54

2 5

10

Truss Models for Shear Walls

Comparing Axial Stress and Axial Force Patterns

Trang 55

2 5

10

Truss Models for Shear Walls

Trang 56

How to Construct Truss Models

• Φορ τηε πυρποσε οφ αναλψσισ, ασσυµε τηε µαιν τρυσσ λαψουτ βασεδ

• Γενεραλλψ σινγλε διαγοναλ ισ συφφιχιεντ φορ µοδελινγ βυτ δουβλε διαγοναλ µαψ βε υσεδ φορ εασιερ ιντερπρετατιον οφ ρεσυλτσ

• Τηε φλοορ βεαµσ ανδ σλαβσ χαν βε χοννεχτεδ διρεχτλψ το τρυσσ

ελεµεντσ

C

t B

t x 2t

t x t

Trang 57

Very Large Openings may convert the Wall

Spandrel

Column Beam

Wall

Trang 58

Openings in Shear Walls - Cellular

2 5

Trang 59

Openings in Shear Walls - Planer

Trang 60

Modeling Walls with Opening

Trang 61

Frame Model of Shear Walls

3 DOF per rigid zone

Rigid Zones Beams Columns

A: Shear Wall with Line Loads B: Finite Element Model

C: Define Beams & Columns D: Beam-Column Model

Based on Concept proposed by E.L Wilson

Trang 62

Using Beam-Column to Model Shear Walls

– 4-Node plane element may not accurately capture the linear

bending, because constant shear distribution is assumed in formulation but actually shear stress distribution is parabolic

– Since the basic philosophy of RC design is based on cracked

sections, it is not possible to use the finite elements results directly for design

– Very simple model (beam-column) which can also captures the

behavior of the structure, The results can be used directly to design the concrete elements.

Trang 63

Shear Wall Design –Meshing

• Shell Deformations:

– Three types of deformation that a single shell element

could experience

– A single shell element in the program captures shear

and axial deformations well

– But a single shell element is unable to capture bending

deformation.

Trang 64

Modeling Shear Walls Using Shell Elements

A-1 Plates with Columns

and Beams

A-2 Plates with Beams

A-3 Plates with Columns

A-4 Plates Only

Trang 65

Modeling Shear Walls Using Beam Elements

B-1 Single Bracing Double Bracing B-2 Column with B-3

Rigid Zones

B-4 Columns with Flexible Zones

Trang 66

Comparison of Behavior

Trang 67

Comparison of Behavior (5 Floors)

B4

B1

A1 A1

B1

Trang 68

B4

B1

A1 A1

B1

Trang 69

B4

B1

A1 A1

B1

Trang 70

Effect of Shear Wall Location

Trang 71

Modeling of Shear Walls

In ETABS

Trang 72

Shear Wall Design – Using ETABS

• Simplified Section (C, T or Linear)

• Uniform reinforcing section

• General Sections

Special Considerations/Concepts:

Trang 73

• Wall Meshing and Load Transfer:

– Appropriate Meshing and labeling of Shear Walls is the key to

proper modeling and design of walls

– No automatic meshing is available for walls (only manual) – Loads are only transferred to walls at the corner points of the

area objects that make up the wall

– Generally the Membrane or Shell type Elements should be used

to model walls

Trang 74

Wall Meshing:

– Piers and spandrels where bending deformations are

significant (slender piers and spandrels), need to mesh the pier or spandrel into several elements

– If the aspect ratio of a pier or spandrel one shell

element is worse than 3 to 1, consider additional meshing

of the element to adequately capture the bending deformation

Trang 75

Shear Wall Design – Pier Zones

– Pier labels are assigned to vertical area

objects (walls) and to vertical line objects (columns)

– Objects that are associated with the same

story level and have the same pier label are considered to be part of the same pier.

you can get output forces for the element or before you can design the element.

Pier Zone Labeling (Naming/Grouping)

Trang 76

– A single wall pier cannot extend over

multiple stories

– Wall pier forces are output at the top and

bottom of wall pier elements

– Wall pier design is only performed at

stations located at the top and bottom of wall pier elements.

Trang 77

Piers Labeling Examples

Trang 78

General Comments on Case d:

– All of the area objects given the same

label P1

– Design is performed across the entire

wall at each story level

– Wall forces would be provided for the

entire wall at each story level

– Combined reinforcement is reported at

the top and bottom of each floor (3-5 area objects)

Section for Design

at II Floor Top

Trang 79

General Comments on Case a:

– Common way to label piers – At the upper level, Pier P1 is defined to

extend all the way across the wall above the openings

– Pier P2 makes up the wall pier to the

left of the door opening

– Pier P3 occurs between the door and

window openings

– Pier P4 occurs between the window

opening and the edge of the wall

– Pier P5 occurs below the window

opening between the door and the edge of the wall A similar labeling of piers occurs at the

– lower level.

Trang 80

General Comments on Case a (Common Way):

– At the upper level, Pier P1 is defined to

extend all the way across the wall above the openings

– Pier P2 makes up the wall pier to the left of

the door opening.

– Pier P3 occurs between the door and

window openings

– Pier P4 occurs between the window

opening and the edge of the wall

– Pier P5 occurs below the window opening

between the door and the edge of the wall

– A similar labeling of piers occurs at the

lower level.

Trang 81

General Comments on Case a (Common Way):

Design pier –

1

Design pier –2 Design pier –3 Design pier –4 Output for Each Pier

Sections

Trang 82

Shear Wall Design – Spandrel Zones

– Spandrel labels are assigned to vertical area

objects (walls) and to horizontal line objects (beams)

– Unlike pier elements, a single wall spandrel

element can be made up of objects from two (or more) adjacent story levels

can get output forces for the element or before you can design the element

Spandrel Zone Labeling (Naming/Grouping)

Trang 83

Trang 84

– Wall spandrel forces are output at the left and

right ends of wall spandrel Elements

– Wall spandrel design is only performed at

stations located at the left and right ends of wall spandrel elements

– Multiple wall spandrel labels cannot be assigned

to a single area object.

Spandrels or Headers

Trang 85

Examples: Spandrel Labeling

Định dạng
Số trang	150
Dung lượng	2,81 MB