Section 1905A — California Building Code (Title 24, Part 2)

MODIFICATIONS TO ACI 318

1905 A .1 General. The text of ACI 318 shall be modified as indicated in Sections 1905 A.1.1 through 1905A.1.15.

1905A.1.1 ACI 318 Section 4.12.2.2. Modify ACI 318, Section 4.12.2.2 by adding the following:

Where prestressed concrete elements are restrained from movement, an analysis of the stresses in the pre- stressed elements and loads in the adjoining structural sys- tem induced by the above-described effects shall be made in accordance with PCI Design Handbook.

1905A.1.2 ACI 318, Section 4.12.2.3. Modify ACI 318 Section 4.12.2.3 by adding the following:

For prestressed concrete members with recessed or dapped ends, an analysis of the connections shall be made in accordance with procedures given in PCI Design Handbook.

1905A.1.3 ACI 318, Section 9.6.1.3. Modify ACI 318, Sec- tion 9.6.1.3 by adding the following:

This section shall not be used for members that resist seismic loads, except that reinforcement provided for foun- dation elements for one-story wood-frame or one-story light steel buildings need not be more than one-third greater than that required by analysis for all loading conditions.

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1905A.1.4 ACI 318, Section 11.2.4.1. Replace ACI 318, Section 11.2.4.1 as follows:

11.2.4.1 – Walls shall be anchored to intersecting ele- ments such as floors or roofs; or to columns, pilasters, buttresses, of intersecting walls and footings with rein- forcement at least equivalent to No. 4 bars at 12 inches (305 mm) on center for each layer of reinforcement.

1905A.1.5 ACI 318 Section 11.7. Add Section 11.7.6 to ACI 318.1 as follows:

11.7.6 – Reinforcement. Perimeters of precast walls shall be reinforced continuously with a minimum of one No. 5 bar extending the full height and width of the wall panel. Where wall panels do not connect to columns or other wall panels to develop at least 75 percent of the horizontal wall steel as noted below, vertical perimeter bars shall be retained by hooked wall bars.

of precast walls_ shall be reinforced continuously with a minimum of one No. 5 bar extending the full height and width of the wall panel. Where wall panels do not connect to columns or other wall panels to develop at least 75 percent of the horizontal wall steel as noted below, vertical perimeter bars shall be retained by hooked wall bars.

A continuous tie or bond beam shall be provided at the roof line either as a part of the roof structure or part of the wall panels as described in the next para- graph below. This tie may be designed as the edge member of the roof diaphragm but, in any case, shall not be less than equivalent to two No. 6 bars continu- ous. A continuous tie equivalent to two No. 5 bars mini- mum shall also be provided either in the footing or with an enlarged section of the floor slab.

Wall panels of shear wall buildings shall be con- nected to columns or to each other in such a manner as to develop at least 75 percent of the horizontal wall steel. No more than half of this continuous horizontal reinforcing shall be concentrated in bond or tie beams at the top and bottom of the walls and at points of inter- mediate lateral support. If possible, cast-in-place joints with reinforcing bars extending from the panels into the joint a sufficient distance to meet the splice require- ments of ACI 318, Section 25.5.2, for Class A shall be used. The reinforcing bars or welded tie details shall not be spaced over eight times the wall thickness verti- cally nor fewer than four used in the wall panel height. Where wall panels are designed for their respective overturning forces, the panel connections need not comply with the requirements of this paragraph.

Exception: Nonbearing, nonshear panels such as nonstructural architectural cladding panels or col- umn covers are not required to meet the provisions of this section.

1905A.1.6 ACI 318, Section 11.9. Modify ACI 318 by adding Section 11.9 as follows:

11.9 – Foundation walls. Horizontal reinforcing of concrete foundation walls for wood-frame or light-steel buildings shall consist of the equivalent of not less than one No. 5 bar located at the top and bottom of the wall. Where such walls exceed 3 feet (914 mm) in height, intermediate horizontal reinforcing shall be provided at spacing not to exceed 2 feet (610 mm) on center. Minimum vertical reinforcing shall consist of No. 3 bars at 24 inches (610 mm) on center.

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Where concrete foundation walls or curbs extend above the floor line and support wood-frame or light- steel exterior, bearing or shear walls, they shall be doweled to the foundation wall below with a minimum of No. 3 bars at 24 inches (610 mm) on center. Where the height of the wall above the floor line exceeds 18 inches (457 mm), the wall above and below the floor line shall meet the requirements of ACI 318, Section 11.6 and 11.7.

1905A.1.7 ACI 318, Section 12.7.3. Add Section 12.7.3.4 to ACI 318 as follows:

12.7.3.4 – At least two No. 5 bars in diaphragms having two layers of reinforcement in both directions and one No. 5 bar in diaphragms having a single layer of rein- forcement in both directions shall be provided around openings larger than 12 inches in any dimension in addition to the minimum reinforcement required by Section 12.6.

1905A.1.8 ACI 318, Section 17.2.3. Modify ACI 318, Sections 17.2.3.4.2, 17.2.3.4.3(d) and 17.2.3.5.2, to read as follows:

17.2.3.4.2 – Where the tensile component of the strengthlevel earthquake force applied to anchors exceeds 20 percent of the total factored anchor tensile force associated with the same load combination, anchors and their attachments shall be designed in accordance with 17.2.3.4.3. The anchor design tensile strength shall be determined in accordance with Section 17.2.3.4.4.

Exception: Anchors designed to resist wall out-of- plane forces with design strengths equal to or greater than the force determined in accordance with ASCE 7, Equation 12.11-1 or 12.14-10, and Section 1604A.8.2 of this code shall be deemed to satisfy Section 17.2.3.4.3(d).

17.2.3.4.3(d) – The anchor or group of anchors shall be designed for the maximum tension obtained from design load combinations that include E, with E increased by Ω0. The anchor design tensile strength shall be calculated from 17.2.3.4.4.

17.2.3.5.2 – Where the shear component of the strength-level earthquake force applied to anchors exceeds 20 percent of the total factored anchor shear force associated with the same load combination, anchors and their attachments shall be designed in accordance with 17.2.3.5.3. The anchor design shear strength for resisting earthquake forces shall be determined in accordance with 17.5.

Exceptions:

1. For the calculation of the in-plane shear strength of anchor bolts attaching wood sill plates of bearing or nonbearing walls of light- frame wood structures to foundations or foun- dation stem walls, the in-plane design shear strength in accordance with 17.5.2 and 17.5.3 need not be computed and 17.2.3.5.3 shall be

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deemed to be satisfied, provided all of the fol- lowing are met:

1.1. The allowable in-plane shear strength of the anchor is determined in accordance with AWC NDS Table 12E for lateral design values parallel to grain.

1.2. The maximum anchor nominal diameter is ⁵ /8 inch (16 mm).

1.3. Anchor bolts are embedded into concrete a minimum of 7 inches (178 mm).

1.4. Anchor bolts are located a minimum of 1 ³ /4 inches (45 mm) from the edge of the concrete parallel to the length of the wood sill plate.

1.5. Anchor bolts are located a minimum of 15 anchor diameters from the edge of the concrete perpendicular to the length of the wood sill plate.

1.6. The sill plate is 2-inch or 3-inch nominal thickness.

2. For the calculation of the in-plane shear strength of anchor bolts attaching cold- formed steel track of bearing or nonbearing walls of anchor bolts attaching cold-formed steel track of bearing or nonbearing walls of light-frame construction to foundations or foundation stem walls the in-plane design shear strength in accordance with 17.5.2 and 17.5.3 need not be computed and 17.2.3.5.3 shall be deemed to be satisfied, provided all of the following are met:

2.1. The maximum anchor nominal diameter is ⁵ /8 inch (16 mm).

2.2. Anchors are embedded into concrete a minimum of 7 inches (178 mm).

2.3. Anchors are located a minimum of 1 ³ /4 inches (45 mm) from the edge of the con- crete parallel to the length of the track.

2.4. Anchors are located a minimum of 15 anchor diameters from the edge of the concrete perpendicular to the length of the track.

2.5. The track is 33 to 68 mil designation thickness.

Allowable in-plane shear strength of exempt anchors, parallel to the edge of concrete shall be permitted to be determined in accordance with AISI S100, Section J3.3.1.

3. In light-frame construction, bearing or non- bearing walls, shear strength of concrete anchors less than or equal to 1 inch (16 mm) in diameter of sill plate or track to foundation or foundation stem wall need not satisfy 17.2.3.5.3 (a) through (c) when the design strength of the anchors is determined in accordance with 17.5.2.1(c).

1905A.1.9 ACI 318, Table 19.2.1.1. Modify ACI 318, Table 19.2.1.1 as follows:

For concrete designed and constructed in accordance with this chapter, f 'c, shall not be less than 3,000 psi (20.7 MPa). Reinforced normal weight concrete with specified compressive strength higher than 8,000 psi (55 MPa) shall require prior approval of structural design method and acceptance criteria by the enforcement agency.

1905A.1.10 ACI 318, Section 18.5. [DSA-SS] Modify ACI 318, Section 18.5, by replacing Section 18.5.2.1, add- ing new Section 18.5.2.2 and renumbering existing Sec- tions 18.5.2.2 and 18.5.2.3 to become 18.5.2.3 and 18.5.2.4, respectively:

18.5.2.1 – In connections between wall panels, yielding shall be restricted to steel elements or reinforcement. In connections between wall panels and the foundation, they shall be designed per Section 1617A.1.16.

18.5.2.2 – Connections that are designed to yield shall be capable of maintaining 80 percent of their design strength at deformation induced by the design displace- ment or shall use type 2 mechanical splices.

18.5.2.3 - Elements of the connection that are not designed to yeild shall develop at least 1.5 Sy .

18.5.2.4 - In structures assigned to SDC D, E or F, wall piers shall be designed in accordance with 18.10.8 or 18.14 in ACI 318.

1905A.1.11 ACI 318, Section 18.10.6.5. Modify ACI 318, Section 18.10.6.5 by adding the following:

(c) Where boundary members are not required by ACI 318 Section 18.10.6.2 or 18.10.6.3 minimum reinforce- ment parallel to the edges of all structural walls and the boundaries of all openings shall consist of twice the cross-sectional area of the minimum shear reinforce- ment required per lineal foot of wall. Horizontal extent of boundary element shall be in accordance with ACI 318 Section 18.10.6.4 (a), (b) and (c).

1905A.1.12 ACI 318, Section 18.12.6. Add Section 18.12.6.2 to ACI 318 as follows:

18.12.6.2 – Collector and boundary elements in top- ping slabs placed over precast floor and roof elements shall not be less than 3 inches (76 mm) or 6 d b thick,

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