509C.2 Selection of Procedure.

509C.2 Selection of Procedure. All buildings shall be analyzed by either the General Procedure of Section 510C or, when applicable, buildings may be analyzed by the Special Procedure of Section 511C.

EXCEPTIONS:

1. A building may be strengthened to the Bolts-plus level by complying only with the requirements for wall anchorage (tension bolts), diaphragm shear transfer (shear bolts) and out-of-plane wall and parapet and appendage bracing, provided the entire building complies with all of the following requirements:

(1) The building does not have any vertical irregularities of Types 1a or 1b (Soft Story), 4 (In-Plane Discontinuity) or 5a or 5b (Weak Story) as defined in ASCE 7-16 Table 12.3-2 or horizontal irregularities of Types 3 (Diaphragm Discontinuity) or 4 (Out-of-Plane Offset) as defined in ASCE 716 Table 12.3-1 or those irregularities are corrected.

(2) The building does not contain any Group A Occupancies with an occupant load of 300 or more, or Group E, Group I or Group H-1, H-2 or H-4 Occupancies.

(3) The building has a mortar shear strength, vt, as determined by Section 506C.3.3, of 30 psi (206.843 kPa) or more for all masonry classes.

(4) The building has wood or plywood diaphragms at all levels above the base of building.

(5) The building contains a maximum of six stories above the base of the building. The base shall be the ground level and basement or basements shall be excluded from the story count.

EXCEPTION: In an otherwise qualifying building of greater than six stories, a maximum of six of the uppermost contiguous stories may be retrofitted using the Bolts-Plus Procedure, providing the building is not located on poor soil as defined in Section 503B. The masonry walls required by Item 7 below shall occupy not less than 50 percent of the wall length in the lowest two of the uppermost six stories. Nonqualifying stories and stories below the uppermost six shall be retrofitted to any other procedure for which they qualify.

(6) The building has or will be provided with crosswalls as defined in Section 511C.3 at a spacing that does not exceed 40 feet (12.192 m) on center. Any story which does not have or is not provided with complying crosswalls and all stories below that story shall be analyzed using the General Procedure of Section 510C or, where applicable, the Special Procedure of Section 511C. The floor structure that separates the Bolts-Plus and General or Special Procedure stories shall be investigated for its adequacy to act as a diaphragm in accordance with Section 510C.1 or, where the Special Procedure is applicable, Section 511C.4.

all stories below that story shall be analyzed using the General Procedure of Section 510C or, where applicable, the Special Procedure of Section 511C. The floor structure that separates the Bolts-Plus and General or Special Procedure stories shall be investigated for its adequacy to act as a diaphragm in accordance with Section 510C.1 or, where the Special Procedure is applicable, Section 511C.4.

(7) The building has or will be provided with a minimum of two lines of vertical elements of the lateral force resisting system parallel to each axis. Masonry walls shall have wall piers with a height-to-width ratio that does not exceed 2 to 1 and shall occupy not less than 40 percent of the wall’s length in order to be considered as providing a line of resistance. Existing moment frames and other lines of resistance added or altered to comply with this requirement shall fully comply with Section 512C. At least one line in each direction shall be a masonry or concrete shear wall.

(8) In buildings containing one or more party walls, the Bolts-Plus Procedure shall not be used unless each building sharing a party wall individually complies with all of the limitations set forth above and the owner of each such building consents to the use of the procedure in writing.

When the Bolts-Plus Procedure is applicable, the forces to be used for diaphragm shear transfer and irregularity correction shall be those specified in Sections 511C.5 and 511C.6 and h/t ratios shall be evaluated in accordance with Section 511C.7. When the intersection of the diaphragm

span and demand capacity ratio falls outside the three regions of Figure 5C-1, the h/t ratios for “all other buildings” in Table 5C-B shall be used. The measures used to comply shall be part of, and be coordinated with, the complete strengthening scheme described in the engineering report required by Section 504B.2.3.

2. Buildings which are strengthened to conform to the requirements of SFEBC Section 304.4 in effect on or after May 21, 1973, are exempt from c om pliance with the provisions of this chapter.