V. UBC 1994 Static Seismic
Calculation of base shear and its distribution along the height for equivalent lateral force method in UBC 1994.
Problem
- Zone = 0.4
- Site coefficient, S = 1
- Building period coefficient, CT = 0.0731
- Importance factor = 1.0 (I 1.0)
- Response modification factor X = 3 (RX 3)
- Response modification factor Z = 3 (RX 3)
The seismic weight for each floor is assumed as 200 kN applied as joint weight of 50kN to nodes 2 3 5 6 8 9 11 To 20. Seismic Load as per UBC 1994 specifications are generated along horizontal direction global X. The base shear and its distribution along height reported by STAAD.Pro is verified against hand calculation.
Calculations
Structure period calculation:
- Height = hn = 16m, Ta = CT × hnx = 0.0731 × 160.75 = 0.585,
- Tb (from output file) = 1.286
Tused = 0.585
C = 1.25× S /(T2/3) = 1.25 × 1 / (0.5852/3) = 1.787
Design base shear calculation:
V = (Z × I × C / Rwx) × W= (0.4 × 1 × 1.787 / 3 ) × (200 × 4) = 0.2383 × 800 = 190.62 kN
Lateral seismic force Fx = (Wx × hx / ∑ Wi × hi) × (V - Ft)
Since T = 0.585 < 0.7 sec, Ft = 0STAAD Input
The file C:\Users\Public\Public Documents\STAAD.Pro CONNECT Edition\Samples\ Verification Models\06 Loading\UBC\UBC 1994 Static Seismic.STD is typically installed with the program.
STAAD SPACE
START JOB INFORMATION
ENGINEER DATE 18-May-15
END JOB INFORMATION
INPUT WIDTH 79
UNIT METER KN
JOINT COORDINATES
1 0 0 0; 2 0 4 0; 3 4 4 0; 4 4 0 0; 5 0 8 0; 6 4 8 0; 7 0 0 5; 8 0 4 5;
9 4 4 5; 10 4 0 5; 11 0 8 5; 12 4 8 5; 13 0 12 0; 14 4 12 0; 15 0 12 5;
16 4 12 5; 17 0 16 0; 18 4 16 0; 19 0 16 5; 20 4 16 5;
MEMBER INCIDENCES
1 1 2; 2 2 3; 3 3 4; 4 2 5; 5 5 6; 6 6 3; 7 2 8; 8 3 9; 9 5 11; 10 6 12;
11 7 8; 12 8 9; 13 9 10; 14 8 11; 15 11 12; 16 12 9; 17 5 13; 18 6 14;
19 11 15; 20 12 16; 21 13 14; 22 13 15; 23 14 16; 24 15 16; 25 13 17; 26 14 18;
27 15 19; 28 16 20; 29 17 18; 30 17 19; 31 18 20; 32 19 20;
DEFINE MATERIAL START
ISOTROPIC CONCRETE
E 2.17185e+07
POISSON 0.17
DENSITY 23.5616
ALPHA 1e-05
DAMP 0.05
TYPE CONCRETE
STRENGTH FCU 27579
END DEFINE MATERIAL
MEMBER PROPERTY AMERICAN
1 3 4 6 11 13 14 16 TO 20 25 TO 28 PRIS YD 0.3 ZD 0.3
2 5 7 TO 10 12 15 21 TO 24 29 TO 32 PRIS YD 0.3 ZD 0.25
CONSTANTS
MATERIAL CONCRETE ALL
SUPPORTS
1 4 7 10 FIXED
DEFINE UBC LOAD
ZONE 0.4 I 1 RWX 3 RWZ 3 CT 0.0731 S 1
JOINT WEIGHT
2 3 5 6 8 9 11 TO 20 WEIGHT 50
*SELFWEIGHT 1
*MEMBER WEIGHT
*2 5 7 TO 10 12 15 UNI 10
LOAD 1 LOADTYPE Seismic TITLE EL-X DIR
UBC LOAD X 1
PERFORM ANALYSIS PRINT LOAD DATA
PRINT ANALYSIS RESULTS
FINISH
STAAD Output
LOADING 1 LOADTYPE SEISMIC TITLE EL-X DIR ----------- *********************************************************** * * * X DIRECTION : Ta = 0.585 Tb = 1.286 Tuser = 0.000 * * C = 1.7875, LOAD FACTOR = 1.000 * * UBC TYPE = 94 * * UBC FACTOR V = 0.2383 x 800.00 = 190.67 KN * * * *********************************************************** JOINT LATERAL TORSIONAL LOAD - 1 LOAD (KN ) MOMENT (KN -METE) FACTOR - 1.000 ----- ------- --------- 2 FX 4.767 MY 0.000 3 FX 4.767 MY 0.000 8 FX 4.767 MY 0.000 9 FX 4.767 MY 0.000 ----------- ----------- TOTAL = 19.067 0.000 AT LEVEL 4.000 METE 5 FX 9.533 MY 0.000 6 FX 9.533 MY 0.000 11 FX 9.533 MY 0.000 12 FX 9.533 MY 0.000 ----------- ----------- TOTAL = 38.133 0.000 AT LEVEL 8.000 METE 13 FX 14.300 MY 0.000 14 FX 14.300 MY 0.000 15 FX 14.300 MY 0.000 16 FX 14.300 MY 0.000 ----------- ----------- TOTAL = 57.200 0.000 AT LEVEL 12.000 METE 17 FX 19.067 MY 0.000 18 FX 19.067 MY 0.000 19 FX 19.067 MY 0.000 20 FX 19.067 MY 0.000 ----------- ----------- TOTAL = 76.267 0.000 AT LEVEL 16.000 METE