SEISMIC ANALYSIS USING LUMPED MASS METHOD

STEPS INVOLVED:

1. Creation of Geometry

2. Giving Member Property

3. Support Condition

4. Giving Loads :

Load 1 Dead Load

Load 2 Live Load

5. Specifying Analysis Type

6. Post Analysis Print

7. Design

8. Analysis.

(1) In this complete steps 1 to 6. Then follow the further steps for Lumped

Mass.

There are two parts.

Part 1 : Finding Joint Loads for Earth quake analysis.

Part 2: Applying Earthquake analysis.

Before Proceeding take a copy of Model created from step 1 to 6.

Part 1: To find Joint Loads:

1.To give pinned supports at column nodes except base nodes:

Main menu Select Beams parallel to Y

Main menu View View selected objects only.

Main menuCommands Support specifications Pinned Assign.

2. Apply Load:

(1) In Seismic Load for finding joint load we have to consider the following

Load case as per Table 8 (Clause 7.3.1 )of IS 1893-2002.

1.0DL+0.25LL (If LL<3KN/m2)

1.0DL+0.50LL (If LL>3KN/m2)

Main menu Edit Edit input command file

In Load case below Live Load type the following:

Load Combination 3

1 1 2 0.25

Perform Analysis

Load List 3

Print Support Reaction

(2) Main Menu Analysis Run Analysis Done.

(3) Main Menu View Tables □ Support Reaction.

From support reaction Select only Joint No. and Force FY.

Copy and Paste the Joint No. and vertical reaction at the pinned supports

in a separate file named as “Joint Load “file.

Type Weight in between Joint No. and Force Fy as below:

16 WEIGHT 81.47

Close the File.

Part 2 : Applying Earthquake Analysis:

Go to original file of Model created from step 1 to 6. Then follow the steps

below:

DEFINING SEISMIC LOAD:

1. Main menu CommandsLoading DefinitionsSeismic Load IS1893-

2002

2.Seismic Parameter screen will appear. Select type:IS1893-2002.

□ Include Accidental Load

□ Generate .

3. IS1893-2002 Seismic Parameter screen will appear.

Select city or Zone. For Zone III Z=0.16 (Table 2 IS1893-2002)

Response Reduction Factor (RF) : (Table 7 IS1893-2002)

: 5 for SMRF

: 3 for OMRF

Importance Factor (I) : (Table 6 IS1893-2002)

: 1 for Ordinary Residential Building

: 1.5 for Important Building

Other Factors:

Rock or Soil sites Factor (SS) : (Clause 6.4.5 of IS1893-2002)

: 1 for hard soil (N>30)

: 2 for medium soil (10≤ N ≤ 30) for all soils.

: 3 for soft soils (N< 10)

Type of Structure (ST) (Optional) : (Clause 7.6 IS1893-2002)

=1 for RC Frame Building

= 2 for Steel Frame Building

= 3 for all other Building

Damping Ratio (DM) (Table 3 IS1893-2002): 0.05%

PX =Period in X Direction (Optional):

PZ =Period in Z Direction (Optional):

□ Generate Add Close.

4. Go to “ Joint Load” file .Copy the Joint Weight and apply them as

Seismic Weights. For this go to

Main menu Edit Edit Input Command file.

Below the Zone factor, copy and paste the JOINT WEIGHT as in the Joint Load

file.

1. Edit the Load case No.1 (Dead Load) and 2(Live Load) as Load case No. 5 &

6.

2. APPLYING SEISMIC LOAD:

(1) Click Load case details in the Data Area Add.

Number: 1 Loading Type: Seismic

Tittle : Seismic X +ve Add.

Click Load Case 1 Add

Seismic Load X Direction. Factor 1 Add. Close.

(2) Click Load case details in the Data Area Add.

Number: 2 Loading Type: Seismic

Tittle : Seismic X -ve Add.

Click Load Case 2 Add

Seismic Load X Direction. Factor:- 1 Add. Close.

(3) Click Load case details in the Data Area Add.

Number: 3 Loading Type: Seismic

Tittle : Seismic Z +ve Add.

Click Load Case 1 Add

Seismic Load Z Direction. Factor 1 Add. Close.

(4) Click Load case details in the Data Area Add.

Number: 4 Loading Type: Seismic

Tittle : Seismic Z -ve Add.

Click Load Case 4 Add

Seismic Load Z Direction. Factor: - 1 Add. Close.

LOAD COMBINATION:

Main menu Load Combinations

Loading No.7

Name: 1.5(DL+LL) Default: 1.5

Available Load case Load

cases

Factor

1. EQX+ve

2. EQX-ve

3. EQZ+ve

4. EQZ-ve

5. DL

6. LL

>

>>

<

<<

5

6

1.5

1.5

Add

Loading No.8 Name: 1.5(DL+EQX+ve)

Default : 1.5

Available Load case Load

cases

Factor

1. EQX+ve

2. EQX-ve

3. EQZ+ve

4. EQZ-ve

5. DL

6. LL

>

>>

<

<<

5

1

1.5

1.5

Add

In the similar way add the following load combination.

Load case No. Load case Factor

9 5 1.5

2 1.5

10 5 1.5

3 1.5

11 5 1.5

4 1.5

12

5 1.2

6 1.2

1 1.2

13

5 1.2

6 1.2

2 1.2

14

5 1.2

6 1.2

3 1.2

15

5 1.2

6 1.2

4 1.2

16 5 0.9

1 1.5

17 5 0.9

2 1.5

18 5 0.9

3 1.5

19 5 0.9

4 1.5

Add Close.

(OR)

AUTO LOAD COMBINATION

Main menu Commands Loading Edit Auto Loads Select Indian

Code

Select : New category say EQ

No. of rule :4

Rule No. Dead Live Seismic

1 1.5 1.5 --

2 1.5 -- 1.5

3 1.2 1.2 1.2

4 0.9 --- 1.5

Click Update Table Close.

Click Load case details Add High light Auto Load Combination (in left

side).

Select : Indian code

Category: EQ Generate loadsAdd Close.

Main menuCommandsLoading Load List (selecting Design loads)

Load List.

Available Load Load list

1. EQ X+ve

2. EQ X-ve

3. EQ Z+ve

4. EQ Z-ve.

5.DL

6.LL

7. 1.5(DL+LL)

8. 1.5(DL+EQX+)

9. 1.5(DL-EQX-)

10. 1.5(DL+EQZ+)

11. 1.5(DL-EQZ-)

12. 1.2(DL+LL+EQX+)

13. 1.2(DL+LL+EQX-)

14. 1.2(DL+LL+EQZ+)

15. 1.2(DL+LL+EQZ-)

16. 0.9DL+1.5 EQX+

17. 0.9DL+1.5 EQX-

18. 0.9DL+1.5EQ Z+

19. 0.9DL+1.5EQ Z-

>

>>

<

<<

Load Comb

7 to 19

O.k. Close.

STEP 5 ( Analysis ):

From Main menu Commands – Analysis Perform Analysis No

print OK.

STEP 6 (Post Analysis Print):

From Main Menu Commands Post Analysis Print Support Reactions

To view OK.

STEP 7 ( Design) :

From Main menu Commands Design Concrete Design Current

code=IS 456 From Main menu Tools Set current input unit

Length =mm; Force = N OK.

Select all the member Define parameters

ELY =0.85 Assign

ELZ =0.85 Assign

FC =20 Assign

FYMAIN= 415 Assign

FYSEC =415 Assign

MAXMAIN =16 Assign

MAXSEC =8 Assign

MINMAIN =12 Assign

MINSEC =8 – Assign Close.

De select all members and select beams only (Main menu Select

Beams parallel to X and Beam parallel to Z axis) Commands (in

data area)

(Concrete Design) Design beam Assign Deselect all beams and

select columns only(Main menuSelect Beam parallel to Y axis)

Design column Assign Take off Assign Close.

Note: Save the File and Run the Program.

STEP 8 (Analysis):

From Main Menu ` Analysis Run Analysis Run Analysis Done.

Select the member and double click on it Shear bending Close.