WAC 51-50-480506   Section 506 -- Structural.  


506.1.1.2 IBC level seismic forces. When seismic forces are required to meet the International Building Code level, they shall be one of the following:

     1. One hundred percent of the values in the International Building Code. The R-factor used for analysis in accordance with Chapter 16 of the International Building Code shall be the R-factor specified for structural systems classified as "ordinary" in accordance with Table 12.2.1 of ASCE 7, unless it can be demonstrated that the structural system satisfies the proportioning and detailing requirements for systems classified as "intermediate" or "special."

     2. Those associated with the BSE-1 and BSE-2 Earthquake Hazard Levels defined in ASCE 41. Where ASCE 41 is used, the corresponding performance levels shall be those shown in Table 506.1.1.2.

TABLE 506.1.1.2

     ASCE 41 AND ASCE 31 PERFORMANCE LEVELS

OCCUPANCY CATEGORY (BASED ON IBC TABLE 1604.5)	PERFORMANCE LEVEL FOR USE WITH ASCE 31 AND WITH ASCE 41 BSE-1 EARTHQUAKE HAZARD LEVEL	PERFORMANCE LEVEL FOR USE WITH ASCE 41 BSE-2 EARTHQUAKE HAZARD LEVEL
I	Life Safety (LS)	Collapse Prevention (CP)
II	Life Safety (LS)	Collapse Prevention (CP)
III	Note a	Note a
IV	Immediate Occupancy (IO)	Life Safety (LS)

a.

Performance levels for Occupancy Category III shall be taken as halfway between the performance levels specified for Occupancy Category II and IV. Where seismic forces are permitted to meet reduced International Building Code levels, the performance level for Occupancy Category III shall be Life Safety (LS). Where seismic forces are required to meet the International Building Code levels, performance levels for Occupancy Category III shall be taken as follows: Acceptance criteria shall be taken as twenty-five percent more restrictive than the acceptance criteria specified for Occupancy Category II performance levels, but need not be more restrictive than the acceptance criteria specified for Occupancy Category IV performance levels.

506.1.1.3 Reduced IBC level seismic forces. When seismic forces are permitted to meet reduced International Building Code levels, they shall be one of the following:

     1. Seventy-five percent of the forces prescribed in the International Building Code. The R-factor used for analysis in accordance with Chapter 16 of the International Building Code shall be the R-factor as specified in Section 506.1.1.2 of this code.

     2. In accordance with the applicable chapters in Appendix A of this code as specified in Items 2.1 through 2.5 below. Structures or portions of structures that comply with the requirements of the applicable chapter in Appendix A shall be deemed to comply with the requirements for reduced International Building Code force levels.

     2.1. The seismic evaluation and design of unreinforced masonry bearing wall buildings in Occupancy Category I or II are permitted to be based on the procedures specified in Appendix Chapter A1.

     2.2. Seismic evaluation and design of the wall anchorage system in reinforced concrete and reinforced masonry wall buildings with flexible diaphragms in Occupancy Category I or II are permitted to be based on the procedures specified in Appendix Chapter A2.

     2.3. Seismic evaluation and design of cripple walls and sill plate anchorage in residential buildings of light-frame wood construction in Occupancy Category I or II are permitted to be based on the procedures specified in Appendix Chapter A3.

     2.4. Seismic evaluation and design of soft, weak or open-front wall conditions in multiunit residential buildings of wood construction in Occupancy Category I or II are permitted to be based on the procedures specified in Appendix Chapter A4.

     2.5. Seismic evaluation and design of concrete buildings and concrete with masonry infill buildings in all occupancy categories are permitted to be based on the procedures specified in Appendix Chapter A5.

     3. In accordance with ASCE 31 based on the applicable performance level as shown in Table 506.1.1.2.

     4. Those associated with the BSE-1 Earthquake Hazard Level defined in ASCE 41 and the performance level as shown in Table 506.1.1.2. Where ASCE 41 is used, the design spectral response acceleration parameters S_XS and S_X1 shall not be taken less than seventy-five percent of the respective design spectral response acceleration parameters S_DS and S_D1 defined by the International Building Code and its reference standards.



[Statutory Authority: RCW 19.27.074, 19.27.020, and chapters 70.92, 19.27, and 34.05 RCW. 07-01-091, § 51-50-480506, filed 12/19/06, effective 7/1/07.]