TR.31.2.8 Colombian NSR-10 SeismicLoad
The seismic load generator can be used to generate lateral loads in the X & Z directions for Y up or X & Y for Z up. Y up or Z up is the vertical axis and the direction of gravity loads (See the
SET Z UP
command in
TR.5 Set Command Specification). All vertical coordinates of the floors above the base must be positive and the vertical axis must be perpendicular to the floors.
General Format
DEFINE COLOMBIAN 2010 (ACCIDENTAL) LOAD
AA f1 AV f2 FA f3 FV f4 I f5 ( CT f6) ( PX f7) ( PZ f8) ( ALPHA f9 )
weight-data
Refer to Common Weight Data for information on how to specify structure weight for seismic loads.
Where:
Parameter | Definition |
---|---|
AA f1 | A coefficient representing effective peak horizontal acceleration for design (Table A.2.4-3 NSR-10). Must be within the range of 0 to 0.5 (inclusive) or the output will indicate an error. |
AV f2 | A coefficient representing the effective peak horizontal velocity for design (Table A.2.4-4 NSR-10). Must be within the range of 0 to 0.5 (inclusive) or the output will indicate an error. |
FA f3 | The dimensionless amplification factor that affects the acceleration in the short periods due to the effects site (Table A.2.4-3 NSR-10). Must be within the range of 0 to 3.5 (inclusive) or the output will indicate an error. |
FV f4 | The dimensionless amplification factor that affects the acceleration in the intermediate periods due to site effects (Table A.2.4-4 NSR-10). Must be within the range of 0 to 3.5 (inclusive) or the output will indicate an error. |
I f5 | The importance factor (Table A.2.5-1 NSR-10). Must be within the range of 1 to 1.5 (inclusive) or the output will indicate an error. |
CT f6 | Optional CT value to calculate time period. (Table A.4.2-1 NSR-10) |
PX f7 | Optional Period of structure (in sec) in X-direction to be in lieu of fundamental period of the structure |
PZ f8 | Optional Period of structure (in sec) in Z-direction to be in lieu of fundamental period of the structure |
ALPHA f9 | Exponent used in calculating the approximate period, Ta (Table A.4.2-1 NSR-10). |
Generation of NSR Seismic Load
General format to provide Colombian Seismic load in any load case:
LOAD i
COLOMBIAN LOAD {X | Y | Z} (f10) (ACCIDENTAL f11)
Where:
Parameter | Definition |
---|---|
LOAD i | load case number |
COLOMBIAN LOAD { X | Y | Z } f10 | factor to multiply horizontal seismic load |
ACCIDENTAL f11 | multiplying factor for Accidental Torsion, to be used to multiply the accidental torsion load (default = 1.0). May be negative (otherwise, the default sign for MY is used based on the direction of the generated lateral forces). |
If the ACCIDENTAL
option is specified, the accidental torsion will be calculated per the specifications. The value of the accidental torsion is based on the center of mass for each level. The center of mass is calculated from the SELFWEIGHT
, JOINT WEIGHT
, and MEMBER WEIGHT
commands specified for this load definition.
Example
Using NSR-10:
DEFINE COLOMBIAN 2010 LOAD
AA 0.2 AV 0.15 FA 0.85 FV 1.01 I 1.12
JOINT WEIGHT
6 TO 15 21 TO 30 36 TO 45 WEIGHT 10
LOAD 1
COLOMBIAN LOAD X 1.2
Methodology for NSR-10
The time period, T, is determined using the Rayleigh method (see
section TR.34.1 Rayleigh Frequency Calculation) or
specified directly in the X and Z directions with the optional
parameters PX
and PZ
, is used to
calculate spectral coefficient, Sa
, as
(refer to Fig. A.2.6-1 in the code):
Base Shear, Vs is calculated as
The horizontal seismic force, Fx , at any level x is calculated by the program as: