distribution to different levels along the height of the building and to various lateral load resisting elements for the following buildings:

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1 Day 29 DYNAMIC ANALYSIS USING RESPONSE SPECTRUM METHOD Dynamic Analysis shall be performed to obtain the design Seismic force, and its distribution to different levels along the height of the building and to various lateral load resisting elements for the following buildings: (a) Regular Buildings: Height > 90m in zones II & III. >40m in zones IV & V (b) Irregular Buildings: All framed buildings Height > 40m in zones II & III. >12m in zones IV & V Types of Dynamic Analysis: Dynamic Analysis may be performed by 1. Response Spectrum Method 2. Time History Method Response Spectrum Method: Qik =Ak ⱷik Pk Wi. User will provide Ak and Wi. In these Ak can be provided by specifying Seismic parameter configuration. Wi can be provided by specifying Selfweight contribution in X, Y, Z direction with factor 1 and dead load and appropriate live load in all three direction. Response Spectrum Method of analysis shall be performed using the Design Spectrum Ah= Z I Sa 2 R g STAAD utilizes following procedure to generate the lateral seismic loads: User provides the value of Z I as factors for input spectrum. 2 R Program calculates time periods for first 15 modes or as specified by the user. (earlier 6 modes)

2 Program calculates Sa/g for each mode utilizing time period & damping for each mode. The program calculates design horizontal acceleration spectrum Ak for different modes. The program then calculates mode participation factor for different modes. The Peak lateral seismic force at each floor in each mode is calculated. All response quantities for each mode are calculated. The peak response quantities are then combined as per method (CQC or SRSS or ABS or TEN or CSM) as defined by the user to get the final results. The design base shear VB (Calculated from the Response Spectrum Method) is compared with the base shear Vb (Calculated by empirical formula for the fundamental time period). If VB is less than Vb, all of the response quantities are multiplied by Vb/VB as per clause Rules for Spectrum Load in STAAD Response spectrum Load definition you have to define within Seismic Load definition. If you have to define all other load cases before defining this definition. Design of seismic shear (VB) Total design seismic base shear VB also any principal direction is given by VB= Ah W Ah= Design horizontal acceleration spectrum value Ah= (Z/2) (I/R) (Sa/g) W= Seismic weight of building = Dead load + appropriate amount of imposed load. Note: 1. Live load upto and including 3.0 KN/m 2 =25% of imposed load. 2. Live load > 3.0KN/m 2 = 50% of imposed load.

3 3. For calculating design seismic forces imposed load on roof need not be considered. PROBLEM: Data: Length of building : 6 bays 4m each=24m Height of building: 7 bays 3.0m each = 21.0m Width of building : 6 bays 4m each =24m. Zone V Medium Soil ; RF=5 I=1.0 Floor Loads: Dead Load for Floor slab: 4 KN/m 2 and Roof slab: 5 KN/m 2 Live Load for Floor slab: 2 KN/m 2 and Roof slab: 1.50KN/m BEAMS ARE OF SIZE 0.3 X PLAN COLUMN ARE OF SIZE 0.4 X.40

4 21.00 BEAMS ARE OF SIZE 0.3 X COLUMN ARE OF SIZE 0.4 X ELEVATION 1. Geometry Creation : New Project Select Space Length =meters; Force=KN; File Name=Dynamic Response Spectrum method Next Select Open Structure Wizard Finish. Change to Frame models from Truss models Select Bay Frame and double click on it. Length X=24.0m No. of Bays =6 Each Bay =4.0m Height Y=21.0m No. of Bays=7 Each Bay =3.0m Width Z=24.0m No. of Bays=6 Each bay =4.0m Apply Transfer Model YesOk. Go to front view.

5 2. Member Property : Click General Property Define Rectangle YD=0.40 ZD=0.40m Add YD=0.30 ZD=0.30AddClose. Highlight YD=0.40 ZD=0.40 Main menu Select Beam parallel to Y Assign to selected beam Assign Yes. Highlight YD=0.30 ZD=0.30. Main menu Select Beam parallel to X axis and Select Beam parallel to Z Assign to selected beam Assign Yes Close. Deselect the member. 3. Supports : Go to front view. Click Support Create Fixed Add. Highlight support 2 and select bottom support nodes of column by windowing using node cursor Assign to selected nodes Assign Yes Close De select the nodes and change to beam cursor. 4. Loading : Following Load shall be considered for Response Spectrum Method: 1.Define Seismic Parameter Configuration. 2. Load case 1: DL+LL 3. Load case 2: Seismic loading-response Spectrum. Page Control Click Load & Definitions Definitions Seismic Definitions Add. Seismic parameter screen will appear. Select Type: IS Click GenerateAdd. Select city or Zone: (Table 2 of IS ) say zone V Z=0.36 Response Reduction Factor(RF): (Table 7 of IS ) : 5 for SMRF (Special Moment Resisting Frame) Important Factor (I) : (Table 6 of IS ): 1 ( for Ordinary building) Rock or Soil sites factor (SS): (Clause of IS ): 2 ( for Medium soil) Type of structure(st)(optional) (Clause 7.6 of IS ): 1 ( for RCC Frame building) Damping ratio (DM): (Table 3 of IS ) DM= 0.05 (for concrete). Px =Period in X direction: (Optional)

6 Pz=Period in Z directionoptional) Depth of foundation (DT):( For under ground structures): Click Generate Add. Self weightselfweight Factor :1Add. Floor weights Load pressure: 4KN/m 2 (Dead load) Define Y range Minimum =3.0m Maximum= 18m Add. Load pressure: 5 KN/m 2 (Dead load) Define Y range Minimum =18 m Maximum= 21.0 Add Load pressure : 0.25KN/m 2 (25% of LL 2.0 KN/m 2 ) Define Y range Minimum =3.0m Maximum= 18m Add *Load pressure : 0.38 KN/m 2 (25% of LL 1.5 KN/m 2 ) Define Y range Minimum =18m Maximum= 21.0m Add Close. Note: As per IS Live load on Roof need not be considered for seismic analysis. Load case 1 (DL+LL): Click Load case details Add. Number 1: Loading type: None Title: Dead Load+Live Load Add Close. Click Load case 1Add. Selfweight Selfweight Y Factor: -1 Add. Floor Load (Dead Load of Floor slab except top roof) Pressure:-4 KN/m 2 Global Y Define Y range Mini.= 3.0m Max.=18.0m Add Floor Load (Dead Load of Roof slab ) Pressure:-5 KN/m 2 Define Y range Mini.= 18.0m Max.=21.0m Add Floor Load (Live Load of Floor slab except top roof slab) Pressure:-2 KN/m 2 Define Y range Mini.= 3.0m Max.=18.0m Add Floor Load (Live Load of Roof slab ) Pressure:-1.50 KN/m 2 Define Y range Mini.= 18.0m Max.=21.0m AddClose. Highlight Selfweight Y -1 Assign to view Assign Yes.

7 Load case 2 (Response Spectrum Load) Click Load case details Add. Number 2: Loading type: Seismic Title: Response spectrum Add Close. Click Load case 2 Add. Click Selfweight Direction X Factor: 1 Add. Selfweight Direction Y Factor: 1 Add. Selfweight Direction Z Factor: 1 Add. Floor Load (Dead Load of Floor slab except top roof) Pressure:4 KN/m 2 Define Y range Mini.= 3.0m Max.=18.0m Direction X Add Direction Y Add. Direction Z Add Floor Load (Dead Load of Roof slab ) Pressure:5 KN/m 2 Define Y range Mini.= 18.0m Max.=21.0m Direction X Add Direction Y Add. Direction Z Add. Floor Load (Live Load of Floor slab except top roof slab) Pressure: 0.50 KN/m 2 (25% of LL=2.0 KN/m 2 ) Define Y range Mini.= 3.0m Max.=18.0m Direction X Add Direction Y Add. Direction Z Add *Floor Load (Live Load of Roof slab ) Pressure: 0.38KN/m 2 (25% of LL= 1.50 KN/m 2 ). Define Y range Mini.= 18.0m Max.=21.0m Direction X Add Direction Y Add. Direction Z Add Close. Highlight Selfweight X Assign to view Assign Yes. Highlight Selfweight Y Assign to view Assign Yes. Highlight Selfweight Z Assign to view Assign Yes. Click Seismic Loading Add. Response spectra Select Code: IS1893 Combination Method: SRSS Sub soil class: Medium soil DM=0.05 Include Torsion IS 1893

8 X= Z I =0.36 x 1 = R 2 5 Scale: 1 Add Close. 5. Analysis Type : Page control Click Analysis/print Mode Shapes Add Close. Click post print Define commands Analysis resultsadd Storey Drift Allowable Drift factor =0.005 Add Close. Note: Save the File and Run the Program. 6. Analysis : From Main Menu ` Analysis Run Analysis View output file Done. 7. Results : Go to post processing mode. Results Eigen solution -Fundamental frequency Response Spectrum Load Peak Storey Shear Peak Storey Shear Torsion Modal base actions Mass Participation factors in percent Analysis Results Joint Nodal Displacement Member forces Reactions forces Storey Drift. By reviewing the results, if the modes are very close, change the SRSS Method to CQC method. Also see whether the mass participation factor is more than 90% as per code. Check whether Missing weight is Dynamic Weight Modal Weight. Also check the design base shear VB is compared with the base shear Vb.

9 If VB is less than Vb, multiply the value of X by (0.036) x Vb/VB as per clause and again Run the analysis once again to get accurate results.