seismic analysis procedure

7/28/2019 Seismic Analysis Procedure

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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

Limped 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:

To give pinned supports at column nodes except base nodes:

Main menu select Beams parallel to Y


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Main menu View View selected objects only.


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Main menu Commands Support specifications Pinned Assign.


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(2)Apply Load:


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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 LL3KN/m 2 )

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.


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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


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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 Commands Loading Definitions Seismic Load

IS1893-2002

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


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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)


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: 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.


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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 :


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(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.




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Tittle : Seismic X -ve Add.


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



Tittle : Seismic Z +ve Add.


Seismic Load Z Direction. Factor 1 Add. Close.



Tittle : Seismic Z -ve Add.

Click Load Case 4 AddSeismic 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

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seismic analysis procedure

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