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Seismic Provisions

The table below lists the implementation for each class of sheathing materials of following design code provisions from ASCE 7 Table 12.2-1 and SDPWS 4.3.7.

Allowable Seismic Design Categories

The categories are defined in ASCE 7 11.6, the permissible categories and building heights are given in in Table 12.2-1 for each seismic force resisting system. SDPWS 4.3.7 provides further guidance for specific sheathing materials.

Shearwalls restricts the program from designing with prohibited materials, and issues a warning in three places - the Materials table, the Seismic Information Table, and the Shear results table Shearwalls also imposes restrictions based on seismic irregularities from 12.3.3.

Response Modification Factor R

R is used in the generation of seismic loads in the denominator fo the equation for the seismic response cefiicient Cs in 12.8-2. that is directly proportional to the base shear V in equation 12.8-1, therefore a larger R represents lower seismic loads.

The value of R can be overridden in the Site Information dialog if you think a modified R is appropriate for your building system. Refer to that topic for more information.

Deflection Amplification Factor Cd

Used in the determination of design story drift. The value of Cd can be overridden in the Site Information dialog if you think a modified R is appropriate for your building system.

Overstrength Factor W0

This is used in the calculation of the diaphragm design force Fpx from 12.10.1.1 to factor the forces from discontinuous shear lines on the level above the diaphragm. The diaphragm design force is ultimately used to create shear line forces for drag strut calculations.

The value shown in the table is the one used by Shearwalls; it cannot be over-ridden in the Site Dialog input.

Seismic Provisions

 

Wood Structural Panels

Allowable Design Categories

ASCE-7 Table 12.2-1

65 Feet or less

All

Greater than 65 feet

A, B, C

Response modification factor R

ASCE-7 Table 12.2-1

R - bearing walls

6.5

R - building frames

7.0

Deflection amplification factor Cd

ASCE-7 Table 12.2-1

Cd - bearing walls

4.0

Cd - building frames

4.5

Overstrength Factor W0 *

ASCE-7 Table 12.2-1, inc. Note 2

W0- bearing walls, rigid diaphragms

3.0

W0- building frames, rigid diaphragms

2.5

W0 - bearing walls, flexible diaphragms

2.5

W0 - building frames, flexible diaphragms

2.0

 

Fiberboard, Lumber Siding, and Gypsum-based Materials

Response modification factor R

ASCE-7 Table 12.2-1, 12.8.1.1

R -bearing walls

2.0

R -building frames

2.5

Deflection amplification factor Cd

ASCE-7 Table 12.2-1,

12.8.6

Cd - bearing walls

2.0

Cd - building frames

2.5

Overstrength Factor W0*

ASCE-7 Table 12.2-1, inc. note b; 12.10.1.1.

W0 - bearing walls, rigid diaphragms

2.5

W0 - building frames, rigid diaphragms

2.5

W0 - bearing walls, flexible diaphragms

2.0

W0 - building frames, flexible diaphragms

2.0

 

Fiberboard

Allowable Design Categories

SDPWS 4.3.7.4

 

All structural Fiberboard

A, B, C

 

 

Lumber Siding

Allowable Design Categories

SDPWS 4.3.7.7-10

 

Horizontal or Vertical

A,B,C

Diagonal or Double Diagonal

A,B,C,D

 

Gypsum-based materials

Allowable Design Categories

SDPWS 4.3.7.5-6

ASCE-7 Table 12.2-1

35 feet or less

A, B, C, D

Greater than 35 feet

A, B, C

Design Results Output

Shear Walls Material Table

If one or more materials in the table are disqualified and shear capacity set to zero due to seismic design category restrictions, a Note 4 appears below the table, and the number 4 appears in the Apply notes column to the table. The SDPWS design clause is given for each material in the table that is disallowed. This note appears only if there are seismic loads on the structure.

Seismic Information Table

Under the Seismic Information table, in a section called Seismic Design Category Restrictions, a note gives the materials that have been disqualified due to seismic zone restrictions and directs you to the Sheathing Materials table for the specific wall groups.

Shear Results

If any of the wall groups listed in the table do not have shear resistance on at least one side due to seismic design category restrictions, a note under the Seismic Shear Results table informs you that shear capacity is zero, and directs you to Sheathing Materials table to find out which were the offending groups.

In This Section

Weak Story Check

See Also

Design Provisions

Implementation History

Provisions by Sheathing Material Type

Design Capacities

Wall Construction

Wall Materials in Shear Line