Pushover Analysis as Per EC8

GenV741 Training Series Pushover Analysis as per EC8:2004

Pushover Analysis of RC structurePushover Analysis of RC structurePushover Analysis of RC structure Pushover Analysis of RC structure as per EC8:2004 as per EC8:2004

DL SD NC

Program Version V7.4.1

MIDAS Information Technology Co., Ltd.

Program Version V7.4.1

Program License Registered, Trial

Revision Date 2008.07. 30


Pushover Analysis ProcedurePushover Analysis ProcedureOverviewOverview

Pushover analysis is one of the performance-based design

methods, recently attracting practicing structural engineers

engaged in the field of seismic design. The objective of a

The pushover analysis procedure is as follows:

performance-based design is achieved after the user and the

designer collectively select a target performance for the

structure in question. The engineer carries out the conventional

design and subsequently performs a pushover (elasto-plastic)

Modeling & Design

- Details of Building

- Perform analysis

- Check assigned rebar data

analysis to evaluate if the selected performance objective has

been met.

In midas Gen V741, pushover analysis as per EN1998:2004

Pushover Analysis

- Pushover Global Control

- Pushover Load Casesis newly added and analysis performance & usability are

significantly improved. This tutorial explains the method and

procedure for pushover analysis of 2-dimensional RC structural

as per EN1998:2004. For this reason, the procedure for

- Define Hinge Properties

- Assign Hinge Properties

- Perform Pushover Analysis

- Pushover Curvemodeling and analysis were not explained in detail. For the

users who are not familiar with the basic functions for modeling

and analysis, it is recommended to review “Application 1”

tutorial before following this tutorial.

- Pushover Hinge Status Results

- Safety Verification Table

MIDAS Information Technology Co., Ltd.2


Details of the example structure

C1 C1

G1 LB1 G1

15@

3,00

0 =

45,

000

unit : mm

Figure 2. Cross sectionFigure 1. Two-dimensional building model

9000 9000

27200

4000 40001200

Designation Story Section Number Column Dimension

12~15F8~11F

104103

600 x 600700 x 700

Designation Section Number Section Dimension

G1 21 350 x 650

Column section Beam section


C1 8~11F4~7F1~3F

103102101

700 x 700800 x 800900 x 900

G1 21 350 x 650

LBl 31 200 x 400


Applied Design Code

Materials (Eurocode4:2004)

•Eurocode

•Column: C30/37•Beam: C25/30

Applied Loads

•Wall: C30/37

Gravity loads•unit: kN/m2

•Use : Residential

Static Wind Loads

Load Name Details

Unit Load Cases

Static Wind Loads•Applied code: Eurocode1:2005•Terrain Category : II• Fundamental Basic Wind Velocity (Vb,o) : 26m/s Static

LoadCases

1 DL Dead Load

2 LL Live Load

Wind LoadStatic Seismic Loads

•Applied code: Eurocode8:2004•Ground Type: B•Design Ground Acceleration: 0.08g•Behavior Factor (q): 1 5

Cases 3 WX Wind Load(X-direction in the global coordinates)

4 XY Wind Load(Y-direction in the global coordinates)


Behavior Factor (q): 1.5•Lower Bound Factor (b): 0.2•Importance Factor (I) : 1


Step 1 Open the model file and perform analysisStep 1. Open the model file and perform analysis

1. Open “Pushover_2D RC structure.mgb”

2. Click icon to perform analysis.

Pushover analysis is carried out in the post-processing mode

after completing elastic analysis.

2



Step 2: Check assigned rebar data

1. Design > Concrete Design Parameter > Modify Beam Section Data2. Check on the section ID 21. 3. Check rebar data for Beam.4. Design > Concrete Design Parameter > Modify Column Section Data5. Check on the section ID 101. 6. Check rebar data for column.

`

In order to calculate the yield

strength for each member in

pushover analysis rebar must be


pushover analysis, rebar must be

assigned.


Step 3: Check Concrete Design Code

1. Design > Concrete Design Parameter > Design Code2. Specify the code as ‘Eurocode2:04’.3. Check [OK] button.

Design Code specified in the Concrete Design Code dialog is

applied to calculate the capacity of members in pushover

analysis.



Step 4: Pushover Global Control

1. Design > Pushover analysis > Pushover Global Control2. Select DL in the combo box and click [Add] button.3. Select LL in the combo box and enter the Scale Factor as 0.4.4. Click [Add] button.5. Click [OK] button.5. Click [OK] button.

2,3

2 42,4


5


Step 4: Pushover Global Control‘Reference Design code (Eurocode 8:2004)’ option is displayed whenReference Design code (Eurocode 8:2004) option is displayed when

the design code (in the main menu, Design > Concrete Design

Parameter or Steel Design Parameter > Design code) is specified as

Eurocode and Design code in preferences (in the main menu, Tools >

Preferences…) is specified as Eurocode.f ) p

Scale Factor for Ultimate Rotation

1) Wall : In calculating the total chord rotation capacity at ultimate , θu, for wall , the value isdivided by 1.6 as per EN1998-3:2004 A.3.1.1.

2) Cold-worked brittle steel : If cold-worked brittle steel is used the total chord rotation capacity isdivided by 1.6 as per EN1998-3:2004 A.3.1.1.

3) Without Detailing for earthquake resistance : In members without detailing for earthquakeresistance the total chord rotation capacity is multiplied by 0.85 as per EN1998-3:2004 .

4) Smooth longitudinal bars : in members with smooth (plain) longitudinal bars without lapping in


the vicinity of the end region where yielding is expected, the total chord rotation capacity may bemultiplied by 0.575 as per EN1998-3:2004.


Step 4: Pushover Global Control

Secondary Seismic Elements

In order to calculate the total chord rotation capacity at ultimate, θu, the factor ‘γel’ is used. Since γel is differently applied for primary and

secondary seismic element (γel = 1.5 for primary seismic elements, γel = 1.0 for secondary seismic elements As per EN1998-3:2004seco d y se s c e e e (γel . o p y se s c e e e s, γel . o seco d y se s c e e e s s pe 99 :

A.3.1.1), the user can define Secondary Seismic Elements group. If Secondary Seismic Elements are not defined, all the elements are

considered as Primary Seismic Elements.

In this tutorial, Secondary Seismic Elements are not defined since pushover hinge properties are assigned to primary elements only.



Step 4: Pushover Load Case22

1. Design > Pushover analysis > Pushover Load Cases2. Click [Add] button.3. Enter the pushover load case name as ‘PL’.4. Enter the Increment Steps as ‘20’.5. Check on ‘Use Initial Load’ option.6 Ch k ‘C id P D lt Eff t’ ti

3

5

6. Check on ‘Consider P-Delta Effect’ option.7. Select ‘Displacement Control’ in the Increment Method.8. Select ‘Mater Node’ option.9. Click the entry field and click the node no. 93 with the

mouse in the model view.10. Enter the Max. Displacement as 0.12m. 4

56

7

8

9

11. Specify the Load Case as ‘EX’ in the combo box and click [Add] button.

12. Click [OK] button.

8

10

11

11


12


Step 5: Define Pushover Hinge Properties – Moment Hinge 2

1. Design > Pushover analysis > Define Pushover Hinge Properties2. Click [Add] button.3. Enter the pushover hinge properties name as ‘Beam’.4. Check on ‘Fz’ & ‘My’ component.5. Click [Apply] button.

In order to check or modify the hinge properties, click [Properties…]

3

button of the desired component.

4


5


Step 6: Define Pushover Hinge Properties – PMM (Axial-Moment interaction) Hinge for Column

1. Enter the pushover hinge properties name as ‘Column’.2. Select ‘P-M-M in Status Determination’ option for Interaction

Type.

Coupled axial force-biaxial moment behavior is reflected by

calculating the flexural yield strength of a hinge considering the

ff f i l f3. Check on ‘Fz’ & ‘My’ component.4. Click [Apply] button.

effect of axial force.

1

2

3


4


Step 7: Define Pushover Hinge Properties – PMM (Axial-Moment interaction) Hinge for Wall

1. Enter the pushover hinge properties name as ‘Wall’.2. Select the Element Type as ‘Wall(CRB)’.3. Select the Interaction Type as ‘P-M-M in Status Determination’.4 Check on ‘Fz’ & ‘My’ component4. Check on Fz & My component.5. Click [Apply] button.6. Click [Close] button.

1

22

36

4


5


Yield strength of RC structuresPushover Hinge Properties

FlexuralHinge

M={As2*fsc*(d-d2)}+M’Where, As2= area of compression steel

M’=K’bd2fck

fsc=700(xu-d2)/xu ≤ fyd

d2=effective depth to compression steelxu=(δ-0.4)dfyd=design yield strength of reinforcement

Shear strength of reinforcement, VRd,S is the smaller value of:

Eurocode2:2004, Equation(6.8) and (6.9)

ShearHinge

Shear strength of concrete, VRd,C is given by:

Eurocode2:2004, Equation(6.2a) and (6.2b)

Therefore, Shear strength, VRd is FY = max (VRd,s ; VRd,c)

Where, αcw=1.0 fcd=αcc fck/γC

αcc =1.0 γC=1.0

Flexural

DYEurocode8-3:2004, Equation(A.10b)

RC structures (Eurocode8-3:2004, Annex A.3.1)


Hinge

DUEurocode8-3:2004, Equation(A.1)


Step 8: Assign Pushover Hinge Properties for Beams

1. Select Girder members (Section ID 21:G1) from the Tree Menu.2. Design > Pushover analysis > Assign Pushover Hinge Properties3. Select Hinge Properties Type as ‘Beam’ in the combo box. 4. Click [Apply] button.5 Click [Close] button5. Click [Close] button.

1 Right-click

3


4 5


Step 9: Assign Pushover Hinge Properties for Columns

1. Select column members from the Tree Menu.2. Drag and drop the ‘Column’ hinge property from the Tree Menu to

the Model Window .

Pushover hinge properties can be simply assigned to the

selected elements by Drag & Drop.

Right-click1

2


2


Step 10: Assign Pushover Hinge Properties for Walls

1. Select column members from the Tree Menu.2. Drag and drop the ‘Wall’ hinge property from the Tree Menu to the

Model Window .

Pushover hinge properties can be simply assigned to the

selected elements by Drag & Drop.

Right click1

Right-click


2


Step 11: Perform pushover analysis

1. Click ‘Task Pane’.2. Click ‘▼’ icon and select ‘Analysis’.3. Click ‘Perform Pushover Analysis’.

Task Pane displays work procedure for

advanced analysis functions and

description on input items so as to enable

2

p p

the user to work more easily.

midas program provides 4 types of

advanced analysis features - Pushover

Analysis, Nonlinear Time History

3

y , y

Analysis, Time History Analysis and

Material Nonlinear Analysis.

In addition, Task Pane data can be

saved in html format in the User Folder,saved in html format in the User Folder,

so that the user can directly write or add

the required input items for analysis.

1



Step 12: Pushover Curve

1. Click ‘Pushover Curve’ in the Task Pane.2. Select ‘For Target Displacement

(EC2/Masonry)’.3. Enter the Design Ground Acc. (Ag) as ‘0.15’.3. Enter the Design Ground Acc. (Ag) as 0.15 .4. Click [Draw] button.

2

1 3

4

For the detailed formula of the Target Displacement, refer to ‘ANNEX B DETERMINATION OF THE

TARGET DISPLACEMENT FOR NONLINEAR STATIC (PUSHOVER) ANALYSIS, EN 1998-1:2004’. The

target displacement, which is obtained from the above, corresponds to the seismic demand of the Limit State of

Significant Damage (SD). Target displacement of the Limit State of Near Collapse (NC) is taken equal to that

f SD lti li d b 1 5 T t di l t f th Li it St t f D Li it ti (DL) i t k l tof SD multiplied by 1.5. Target displacement of the Limit State of Damage Limitation (DL) is taken equal to

that of SD divided by 2.5.



Step 13: Hinge Status Results

1. Click ‘Hinge Status Results’ in the Task Pane.2. Select ‘Status of Yielding (EC8:2004)’.3. Select the Components as ‘Ry’.4. Check on ‘Legend’ and ‘Deform’.

5Clicking and scrolling

g5. Specify the desire step in the combo box.

The user can also check hinge status results for

each step by clicking on the step box and scroll

Clicking on the graph

2

3

or clicking on the pushover graph which is

displayed in the black background.

1

3

4



Step 13: Safety Verification Table

1. Click ‘Safety Verification Table’ in the Task Pane.2. Select ‘Show All Elements’.3. Click [OK] button.4. Select ‘Significant Damage (SD)’.5 Ch k ‘M ’ d ‘F ’5. Check on ‘My’ and ‘Fz’.6. Click [OK] button.

2

3

4

5

Safety Verification Table displays the comparison results between the demand and

capacities of the elements as per EN1998-3:2004 Table 4.3. Safety verification shall be

conducted of both ductile and brittle elements respectively. For ductile elements,

verification will be conducted in terms of deformation using mean values of properties

divided by CF For brittle elements verification shall be conducted in terms of strength


6

divided by CF. For brittle elements, verification shall be conducted in terms of strength

using mean values of properties divided by CF and by partial factor.


Capacity of RC structures for assessment in the Safety Verification Table (Eurocode8-3:2004, Annex A.3.1)


*For ductile elements, mean values of properties divided by CF are used. For brittle members, mean values of properties divided by CF and by partial factor.

Documents

Pushover Analysis as Per EC8