Static Seismic Loads

1. Model the structure. The structure must be modeled so that the gravity acts in the direction opposite to the GCS Z-direction.

2. Convert the self-weight of the structure included in the modeling into mass data, if the self-weight is to be considered for the equivalent static seismic load calculation. Use "Converting Type of Model weight to Masses" in Structure Type to assign the directions to be considered for the mass components and enter the value in the "Gravity Acceleration" field.

The procedure of converting the self-weight of the model into mass data by stories to calculate the equivalent static seismic load is as follows :

Calculate the self-weight of the members. Divide and assign the self-weight equally to the connection nodes, which then become the story mass data when the connection nodes are on a story plane (refer to step 4). If the connection nodes fall in between the stories, the nodal masses are considered to exist at the upper story.

3. Use Building > Control Data to enter the position of the ground level in GCS Z-axis coordinate.

Once the ground level is entered, the base shear is calculated at the ground level. The parts below this level are considered as underground floors. All the entered mass data are neglected in the equivalent static seismic load calculation. If the ground level is not defined, the lowest part of the structural model is assumed to be the ground level by default.

1. 4. Use Story to define stories and their floor rigid diaphragm characteristics. Enter the eccentricities to consider the accidental eccentricity moments at each story. Use to auto-generate the data necessary for the stories and the application of seismic loading.

Once the floor diaphragm is defined in Story, the X-, Y-displacement degrees-of-freedom and the rotational degree-of-freedom about the Z-axis between all the nodes on the plane (plane parallel to the GCS X-Y plane) are constrained.

In addition, a part or all of constrained nodes can be separated from the floor rigid diaphragm using Floor Diaphragm Disconnect.

Note
If, at a specific story, Story Diaphragm is released, the Story Force at the corresponding story is considered to be zero.  Even if the user specifies Additional Seismic Loads, the program considers the Story Force to be zero.  

1. 5. Use Nodal Masses, Floor Diaphragm Masses or Load to Masses to enter the mass components not included in the model.

   6. Use Static Seismic Loads to select the desired standards and enter the data for the calculation of equivalent static seismic loads.

[Built-in standards for the calculation of equivalent static seismic loads]

Equivalent static seismic load generation

Seismic Load Parameters

Short Period Site Coefficient (Fa)

Spectral Response Acceleration Parameter (Sds)

Long Period Site Coefficient ( Fu)

Occupancy Category

Period Coefficient

Approximate Period

Risk Category

Site Class

Mapped Spectral Response Acceleration at Short Periods (Ss)

Mapped Spectral Response Acceleration at 1 Second Periods (S1)

Importance Factor

Seismic Load Parameters

Short Period Site Coefficient (Fa)

Spectral Response Acceleration Parameter (Sds)

Long Period Site Coefficient ( Fu)

Occupancy Category

Period Coefficient

Approximate Period

Site Class

Mapped Spectral Response Acceleration at Short Periods (Ss)

Mapped Spectral Response Acceleration at 1 Second Periods (S1)

Importance Factor

Seismic Design Categories

Site Class

Mapped Spectral Response Acceleration at Short Periods (Ss)

Mapped Spectral Response Acceleration at 1 Second Periods (S1)

Importance Factor

Soil Profile Type

Seismic Zone Factor

Seismic Source Type

Closest Distance to Known Seismic Source: Distance to the verified epicenter

Importance Factor

Soil Profile Type

Zone Factor

Importance Factor

Soil Profile Coefficient

Effective Peak Velocity

Zonal Velocity Ratio (v): The specified zonal horizontal ground  velocity expressed as a ratio to 1 m/s

Acceleration Zone (Za): Acceleration-related seismic zone

Velocity Zone (Zv): Velocity-related seismic zone

Importance Factor (I)

Foundation Factor (F)

Seismic Load Parameters:

(1) Spectrum parameters

     Clause 3.2 Seismic Action

     Table 3-2  Topographic categories : T1, T2, T3, T4

(2) Spectral Parameters (Tc*, ag , F0 )

     Tc*: Period of commencement of the tract at a constant speed in the horizontal acceleration of the

             Spectrum

       ag : maximum horizontal acceleration at the site

       F0 : maximum value of the amplification factor of the spectrum in the horizontal acceleration       

Seismic Load Parameters:

(1) Spectrum parameters

     Clause 3.2 Seismic Action

     Table 3-2  Topographic categories : T1, T2, T3, T4

(2) Spectral Parameters (Tc*, ag , F0 )

     Tc*: Period of commencement of the tract at a constant speed in the horizontal acceleration of the

             Spectrum

       ag : maximum horizontal acceleration at the site

       F0 : maximum value of the amplification factor of the spectrum in the horizontal acceleration       

Ground Type: Soil type (A, B, C, D, E, S1 and S2)

Soil Factor (S): Soil factor (range: S > 0)

Spectrum Parameters

Tb: Lower limit of the period of the constant spectrum acceleration branch

Tc: Upper limit of the period of the constant spectrum acceleration branch

Td: Value defining the beginning of the constant displacement response range of the spectrum

Design ground acceleration (Ag): Design ground acceleration (range: Ag > 0)

Behavior factor (q): Behavior factor (range: q> 0)

Lower bound factor (b): Lower bound factor for the design spectrum (range: b> 0)

Importance Factor (I): Importance factor (range: I > 0)

Soil Class

Basic Behavior Factor (q0)

Ductility Class (Kd)

Elevation Regularity (Kr)

Failure Mode Factor (Kw)

Ratio of Design ground acceleration to gravity acceleration (alpha)

IS1893 (2002)

Seismic Zone Factor (Z)

Soil Type

Importance Factor(I)

Damping (%)

Damping Multiplying Factor:

Damping Multiplying Factor is automatically calculated by linear interpolation based on the table shown below.

Seismic Zone (Z)

Seismic Zone Related Data

General Zone

Horizontal Spectral Accel.  

Short Period (Ss): Horizontal Spectral Acceleration at short periods

1 Sec Period (S1): Horizontal Spectral Acceleration at 1 second periods

Site Magnify Factor

Soil Type

Short Period (Fa): Site Magnify Factor at short periods

1 Sec Period (Fv): Site Magnify Factor at 1 second periods

Near Fault Zone

Horizontal Spectral Accel.  

Short Period (Ss): Horizontal Spectral Acceleration at short periods

1 Sec Period (S1): Horizontal Spectral Acceleration at 1 second periods

Near Source Factor  

Short Period (Na): Near Source Factor at short periods

1 Sec Period (Nv): Near Source Factor at 1 second periods

Site Magnify Factor

Soil Type

Short Period (Fa): Site Magnify Factor at short periods

1 Sec Period (Fv): Site Magnify Factor at 1 second periods

Taipei Basin  

Sub Zone

Horizontal Spectral Accel.  

Short Period (Ss): Horizontal Spectral Acceleration at short periods

Trans. Period: Transfer period

T0: S1/Ss

Importance Factor(I)

Seismic Magnify Factor

Seismic Zone (Z)

Soil Type

Importance Factor (I)

Seismic Magnifying Factor

Design Spectral Response Acceleration

Site Class

Effective Peak Acc. (Aa)

Effective Peak Vel. (Av)

Site Coeff. at Short Period (Fa)

Site Coeff. at 1sec. Period (Fv)

Period Coef. (Cu)

Importance Factor (I)

Seismic Zone Factor (Z)

Soil Period (Tc)

Std. Base Shear Factor (C0)

Seismic Base Shear Distribution Factor (Ai)

Note
Ai is automatically calculated or entered by the user.

Design Spectral Response Acceleration

Seismic Zone

Site Class

Sds: Spectral response acceleration at short periods

Sd1: Spectral response acceleration at a period of 1 sec

Seis. Use Group

City Plan Region

Importance(Ie)

Seis. Design Category

Soil Profile Type

Earthquake Zone

Importance Factor

Soil Profile Type

Earthquake Zone

Importance Factor

Seis. Fortification Intensity

Site Class

Structure Type

Damping ratio

Frequent Earthquake

Scarce Earthquake

Masonry Multistory, Framed 1st Story, Interior Frame - Exterior Masonry Structure

Near Source Category

Seis. Fortification Intensity

Site Class

Structure Type

Damping Ratio

Frequent Earthquake

Scarce Earthquake

Masonry Multistory, Framed 1st Story, Interior Frame - Exterior Masonry Structure

Period (Analysis): Obtained by eigenvalue analysis

Approximate Period: Obtained by the Code method

Response Modification Coefficient (R)

Period (Analysis): Obtained by eigenvalue analysis

Approximate Period: Obtained by the Code method

Response Modification Coefficient (R)

Period (Analysis): Obtained by eigenvalue analysis

Period (Code): Obtained by the Code method

Response Modification Coefficient (R)

Period: Periods of the structure calculated from the equation in the code

Ductility Coefficient (R): Numerical coefficients representative of the inherent overstrength and global ductility capacity of a lateral force resisting system

Period (Analysis): Natural periods of the structure from eigenvalue analysis

Period (Code): Natural periods of the structure calculated from the equations in the code

Ductility Coefficient (Rw): Numerical coefficients representative of the inherent overstrength and global ductility capacity of a lateral force resisting system

Period (Analysis): Natural periods of the structure from eigenvalue analysis

Period (Code): Natural periods of the structure calculated from the equations in the code

Response Modification Coeff.

Period (Analysis): Natural periods of the structure from eigenvalue analysis

Period (Code): Natural periods of the structure calculated from the equations in the code

Response Modification Factor (R)

: Auto-calculation of periods from the code equations

N: Number of Stories

H: Height of the building

Ds: Length of the wall or braced frame which constitutes the main lateral-force-resisting system in the direction parallel to the

applied forces

Note
If the main lateral-force-resisting system does not have a well-defined length then D Shall be used in lieu of Ds
D: Length of  the building in a direction parallel to the applied  forces

Fundamental Period

: Auto-calculation of periods from the code equations

H: Height of the building

Ac: Combined effective area of the shear walls in the first story of building

d: lateral displacement if the top of the building due to the gravity loads applied horizontally

Fundamental Period

: Auto-calculation of periods from the code equations

h: Height of the building (unit: m)

d: Width of the building in a direction parallel to the seismic load at the 1st floor

Response Reduction Factor

Analytical Period: Natural periods of the structure from Eigenvalue analysis

Approximate Period: Natural periods of the structure calculated from the equations in the code

Fundamental Period

Response Modification Factor

Analytical Period: Natural periods of the structure from Eigenvalue analysis

Approximate Period: Natural periods of the structure calculated from the equations in the code

Response Modification Factor

Period (Analysis): Obtained by eigenvalue analysis

Approximate Period: Obtained by the Code method

Response Modification Coefficient (R)

Period (T)

Period Calculator

Analytical Period: Natural periods of the structure from Eigenvalue analysis

Approximate Period: Natural periods of the structure calculated from the equations in the code

 : Auto-calculation of periods from the code equations

Fundamental Period

Response Modification Factor

Period (Analysis): Natural periods of the structure from eigenvalue analysis

Period (Code): Natural periods of the structure calculated from the equations in the code

: Auto-calculation of periods from the code equations

Response Modification Coeff.

Period (Analysis): Natural periods of the structure from eigenvalue analysis

Period (Code): Natural periods of the structure calculated from the equations in the code

: Auto-calculation of periods from the code equations

Response Modification Coeff.

Fundamental Period

 : Auto-calculation of periods from the code equations

H: Height of the building

Bx: Width of building subjected to seismic load in the Global X-axis direction

By: Width of building subjected to seismic load in the Global Y-axis direction

n: Number of Stories

Fundamental Period

: Auto-calculation of periods from the code equations

H: Height of the building

Bx: Width of building subjected to seismic load in the Global X-axis direction

By: Width of building subjected to seismic load in the Global Y-axis direction

n: Number of Stories