CSP00138[GEN-Tutorial]Pushover Analysis as Per Eurocode 8 2004

8/12/2019 CSP00138[GEN-Tutorial]Pushover Analysis as Per Eurocode 8 2004

1/24
http://www.cspfea.net/midas_gen.htmlhttp://www.cspfea.net/midas_gen.html


2/24

midas Gen tu torials Pushover Analysis as per EC8: 2004

MIDAS Information Technology Co., Ltd.

Program Version Gen 2010

Program License Registered, Trial

Revision Date 2010.07.14

Pushover Analysis of RC structure

as per EC8:2004

DL SD NC


3/24


MIDAS Information Technology Co., Ltd.2

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

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)

analysis to evaluate if the selected performance objective has

been met.

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

provided. 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 modeling 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.

The pushover analysis procedure is as follows:

Modeling & Design

- Details of Building

- Perform analysis

- Check assigned rebar data

Pushover Analysis

- Pushover Global Control

- Pushover Load Cases

- Define Hinge Properties

- Assign Hinge Properties

- Perform Pushover Analysis

- Pushover Curve

- Pushover Hinge Status Results

- Safety Verification Table

Pushover Analysis ProcedureOverview


4/24



Details of the example structure

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

15@3,000=45,000

9000 9000

27200

4000 40001200

unit : mm

C1 C1

G1 LB1 G1

Designation Story Section Number Column Dimension

C1

12~15F

8~11F

4~7F

1~3F

104

103

102

101

600 x 600

700 x 700

800 x 800

900 x 900

Designation Section Number Section Dimension

G1 21 350 x 650

LBl 31 200 x 400

Column section Beam section


5/24



Materials (Eurocode4:2004)

Eurocode

Gravity loads

unit: kN/m2

Use : Residential

Static Wind Loads

Applied code: Eurocode1:2005

Terrain Category : II

Fundamental Basic Wind Velocity (Vb,o) : 26m/s

Static Seismic Loads

Applied code: Eurocode8:2004

Ground Type: B

Design Ground Acceleration: 0.08g

Behavior Factor (q): 1.5

Lower Bound Factor (b): 0.2

Importance Factor (I) : 1

Applied Loads

Load Name Details

Static

Load

Cases

1 DL Dead Load

2 LL Live Load

3 WX Wind Load

(X-direction in the global coordinates)

4 XY Wind Load

(Y-direction in the global coordinates)

Unit Load Cases

Column: C30/37

Beam: C25/30

Wall: C30/37

Applied Design Code


6/24



Step 1. Open the model fi le and perf orm analysis

1. Open Pushover_2D RC structure.mgb

2. Click icon to perform analysis.

2

Pushover analysis is carried out in the post-processing mode

after completing elastic analysis.


7/24



Step 2: Check assigned rebar data

1. Design > Concrete Design Parameter > Modify Beam

Rebar Data

2. Check on the section ID 21.

3. Check rebar data for Beam.

4. Design > Concrete Design Parameter > Modify Column

Rebar Data

5. 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

assigned.

1

2

4

5


8/24



Step 3: Check Concrete Design Code

1. Design > Concrete Design Parameter > Design Code

2. Specify the code as Eurocode2:04.

3. Check [OK] button.

Design Code specified in the Concrete Design Codedialog is

applied to calculate the capacity of members in pushover

analysis.


9/24



Step 4: Pushover Global Control

1. Design > Pushover analysis > Pushover Global Control

2. Select DLin the combo box and click [Add] button.

3. Select LLin the combo box and enter the Scale Factoras 0.4.4. Click [Add] button.

5. Click [OK] button.

2

2 3

4

5


10/24



Step 4: Pushover Global ControlReference Design code (Eurocode 8:2004)option is displayed when

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

ParameterorSteel Design Parameter > Design code) is specified as

Eurocodeand Design code in preferences(in the main menu, Tools>

Preferences) is specified as Eurocode.

Scale Factor for Ultimate Rotation

1) Wall : In calculating the total chord rotation capacity at ultimate , u, for wall , the value is

divided by 1.6as perEN1998-3:2004A.3.1.1.

2) Cold-worked brittle steel: If cold-worked brittle steel is used the total chord rotation capacity is

divided by 1.6as perEN1998-3:2004A.3.1.1.

3) Without Detailing for earthquake resistance : In members without detailing for earthquake

resistance the total chord rotation capacity is multiplied by 0.85as perEN1998-3:2004.

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 be

multiplied by 0.575as perEN1998-3:2004.

Tools -> Preferences -> Select Design in the General


11/24



Secondary Seismic Elements

In order to calculate the total chord rotation capacity at ultimate, u, the factorelis used. Since elis differently applied for primary and

secondary seismic element (el= 1.5 for primary seismic elements, el= 1.0 for secondary seismic elements As per EN1998-3:2004

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 Global Control


12/24



Step 4: Pushover Load Case

3

56

7

8

9

10

13

12

21. Design > Pushover analysis > Pushover L oad Cases

2. 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. Check on Consider P-Delta Effect option.

7. Select Displacement Control in the I ncrement 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. Displacementas 0.12m.

11. Uncheck the L imit I nter-Story Deformation Angle in the

Anal ysis Stopping Conditi on12. Specify the Load Case as EXin the combo box and

click [Add] button.


4

11

12


13/24



Step 5: Defi ne Pushover H inge Propert iesMoment Hi nge

1. Design > Pushover analysis > Define Pushover H inge Properties

2. Click [Add] button.

3. Enter the pushover hinge properties name as Beam.

4. Check on Fz & My component.

5. Click [Apply] button.

2

5

4

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

button of the desired component.

3


14/24



Step 6: Defi ne Pushover H inge Propert iesPMM (Axial-M oment interaction) H inge for Column

1. Enter the pushover hinge properties name as Column.

2. Select P-M-M in Status Determination option for Interaction

Type.



4

3

Coupled axial force-biaxial moment behavior is reflected by

calculating the flexural yield strength of a hinge considering the

effect of axial force.

2

1


15/24



Step 7: Defi ne Pushover H inge Propert iesPMM (Axial-M oment interaction) H inge for Wall

1. Enter the pushover hinge properties name as Wall.

2. Select the Element Type as Wall(CRB).3. Select the I nteraction Type as P-M-M in Status Determination.



6. Click [Close] button.

5

4

3

1

2

6


16/24



Flexural

Hinge

M={As2*fsc*(d-d2)}+M

Where, As2= area of compression steel

M=Kbd2fck

fsc=700(xu-d2)/xu fydd2=effective depth to compression steel

xu=(-0.4)d

fyd=design yield strength of reinforcement

Shear

Hinge

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

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

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, cw=1.0 fcd=ccfck/Ccc =1.0 C=1.0

Yield strength of RC structures

Flexural

Hinge

DY

Eurocode8-3:2004, Equation(A.10b)

DU

Eurocode8-3:2004, Equation(A.1)

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

Pushover H inge Properti es


17/24



Step 8: Assign Pushover H inge Properti es for Beams

1. Select Girder members (Section ID 21:G1) from the Tree Menu.

2. Design > Pushover analysis > Assign Pushover H inge Properties

3. Select Hinge Properties Type as Beam in the combo box.4. Click [Apply] button.

5. Click [Close] button.

1

3

4 5

Right-click


18/24



Step 9: Assign Pushover H inge Properti es for Columns

1. Select column members from the Tree Menu.

2. Drag and drop the Columnhinge property from the Tree Menu to

the Model Window .

Right-click1

2

Pushover hinge properties can be simply assigned to the

selected elements by Drag & Drop.


19/24



Step 10: Assign Pushover H inge Propert ies 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 .

Right-click1

2

Pushover hinge properties can be simply assigned to the

selected elements by Drag & Drop.


20/24



Step 11: Perf orm pushover analysis

1. Click Task Pane.

2. Click icon and select Analysis.

3. Click Perform Pushover Analysis.

3

1

2

Task Panedisplays work procedure for

advanced analysis functions and

description on input items so as to enable

the user to work more easily.

midas program provides 4 types of

advanced analysis features - Pushover

Analysis, Nonlinear Time History

Analysis, Time History Analysis and

Material Nonlinear Analysis.

In addition, Task Pane data can be

saved in html format in the User Folder,

so that the user can directly write or add

the required input items for analysis.

P h A l i EC8 2004


21/24


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 ofNear Collapse (NC)is taken equal to that

of SD multiplied by 1.5. Target displacement of the Limit State ofDamage Limitation (DL)is taken equal to

that of SD divided by 2.5.


Step 12: Pushover Cur ve

1. Click Pushover Cur ve in the Task Pane.

2. Select For Target Di splacement

(EC2/Masonry).

3. Enter the Ref. Peak Ground Acc. (Ag) as 0.15.

4. Click [Draw]button.

1

2

4

3

id G i l P h A l i EC8 2004


22/24



Step 13: H inge Status Resul ts

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.

5. Specify the desire step in the combo box.

1

2

3

4

5

The user can also check hinge status results for

each step by clicking on thestep box and scrol l

or cl i ck ing on the pushover graph which is

displayed in the black background.

Clicking and scrolling

Clicking on the graph

id G t t i l P h A l i EC8 2004


23/24



Step 13: Safety Veri fi cation Table

1. Click Safety Verif ication Table in the Task Pane.

2. Select Show All Elements.

3. Click [OK] button.4. Select Signif icant Damage (SD).

5. Check on My and Fz.


2

3

4

5

6

Safety Veri f ication Table displays the comparison results between the demand and

capacities of the elements as perEN1998-3:2004 Table 4.3. Safety verification shall be

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

verification will be conducted in terms ofdeformationusing mean values of properties

divided by CF. Forbrittleelements, verification shall be conducted in terms ofstrength

using mean values of properties divided by CFand by partial factor.

id G t t i l P h A l i EC8 2004


24/24


MIDAS I f i T h l C L d23

*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.

Capacity of RC structu res for assessment in the Safety Veri fi cation Table (Eurocode8-3:2004, Annex A.3.1)

Documents

CSP00138[GEN-Tutorial]Pushover Analysis as Per Eurocode 8 2004