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The design and detailing of the components of the seismic-force-resisting system for structures designed using the simplified analysis procedure in Section 1617.5 shall comply with the requirements of this section in addition to the nonseismic requirements of this code. Buildings shall not exceed the limitations of Section 1616.6.1.

Exception: Structures assigned to Seismic Design Category B (see Section 1616) shall conform to Sections 1620.2.1 through 1620.2.10.
1620.2.1 Second-Order Load Effects
Where è exceeds 0.10 as determined in Section in ASCE 7, second-order load effects shall be included in the evaluation of component and connection strengths.
UpCodes note: There seems to be no "è" in ASCE 7-02 Section P-Delta Effects. The stability coefficient is indicated by "θ".
1620.2.2 Openings
Where openings occur in shear walls, diaphragms or other plate-type elements, reinforcement at the edges of the openings shall be designed to transfer the stresses into the structure. The edge reinforcement shall extend into the body of the wall or diaphragm a distance sufficient to develop the force in the reinforcement.
1620.2.3 Discontinuities in Vertical System
Structures with a discontinuity in lateral capacity, vertical irregularity Type 5, as defined in Table 1616.5.1.2, shall not be over two stories or 30 feet (9144 mm) in height where the "weak" story has a calculated strength of less than 65 percent of the story above.

Exception: Where the "weak" story is capable of resisting a total seismic force equal to the over-strength factor, Ωo, as given in Table 1617.6.2, multiplied by the design force prescribed in Section 1617.5, the height limitation does not apply.
1620.2.4 Connections
All parts of the structure, except at separation joints, shall be interconnected and the connections shall be designed to resist the seismic force, Fp, induced by the parts being connected. Any smaller portion of the structure shall be tied to the remainder of the structure for the greater of:

Fp = 0.133 SDSwp          (Equation 16-58)


Fp = 0.05 wp                   (Equation 16-59)

SDS = The design, 5-percent damped, spectral response acceleration at short periods as defined in Section 1615.
wp = The weight of the smaller portion.

A positive connection for resisting a horizontal force acting parallel to the member shall be provided for each beam, girder or truss to its support for a force not less than 5 percent of the dead plus live load reaction.
1620.2.5 Diaphragms
Permissible deflection shall be that deflection up to which the diaphragm and any attached distributing or resisting element will maintain its structural integrity under design load conditions, such that the resisting element will continue to support design loads without danger to occupants of the structure.

Floor and roof diaphragms shall be designed to resist Fp as follows:

F p = 0.2 IESDSw p + Vpx             (Equation 16-60)


Fp = The seismic force induced by the parts.
IE = Occupancy importance factor (Table 1604.5).
SDS = The short-period site design spectral response acceleration coefficient (Section 1615).
wp = The weight of the diaphragm and other elements of the structure attached to the diaphragm.
V px = The portion of the seismic shear force at the level of the diaphragm, required to be transferred to the components of the vertical seismic-force-resisting system because of the offsets or changes in stiffness of the vertical components above or below the diaphragm.

Diaphragms shall provide for both shear and bending stresses resulting from these forces. Diaphragms shall have ties or struts to distribute the wall anchorage forces into the diaphragm. Diaphragm connections shall be positive, mechanical or welded-type connections.
1620.2.6 Collector Elements
Collector elements shall be provided that are capable of transferring the seismic forces originating in other portions of the structure to the element providing the resistance to those forces. Collector elements, splices and their connections to resisting elements shall have the design strength to resist the special load combinations of Section 1605.4.

Exception: In structures or portions thereof braced entirely by light-framed shear walls, collector elements, splices and connections to resisting elements need only have the strength to resist the load combinations of Section 1605.2 or 1605.3.
1620.2.7 Bearing Walls and Shear Walls
Bearing walls and shear walls and their anchorage shall be designed for an out-of-plane force, Fp that is the greater of 10 percent of the weight of the wall, or the quantity given by Equation 16-61:

Fp = 0.40 IESDSww                 (Equation 16-61)


IE = Occupancy importance factor (Table 1604.5).
SDS = The short-period site design spectral response acceleration coefficient (Section 1615.1.3 or 1615.2.5).
ww = The weight of the wall.

In addition, concrete and masonry walls shall be anchored to the roof and floors and members that provide lateral support for the wall or that are supported by the wall. The anchorage shall provide a direct connection between the wall and the supporting construction capable of resisting the greater of the force, Fp as given by Equation 16-6 1 or(400 SDS IE) pounds per linear foot of wall. For SI: 5838 SDSIEN/m. Walls shall be designed to resist bending between anchors where the anchor spacing exceeds 4 feet (1219 mm). Parapets shall conform to the requirements of Section of ASCE 7.
1620.2.8 Inverted Pendulum-Type Structures
Supporting columns or piers of inverted pendulum-type structures shall be designed for the bending moment calculated at the base determined using the procedures given in Section 1617.4 and varying uniformly to a moment at the top equal to one-half the calculated bending moment at the base.
1620.2.9 Elements Supporting Discontinuous Walls or Frames
Columns or other elements subject to vertical reactions from discontinuous walls or frames of structures having plan irregularity Type 4 of Table 1616.5.1.1 or vertical irregularity Type 4 of Table 1616.5.1.2 shall have the design strength to resist special seismic load combinations of Section 1605.4. The connections from the discontinuous walls or frames to the supporting elements need not have the design strength to resist the special seismic load combinations of Section 1605.4.


  1. The quantity, Em, in Section 1617.1.1.2 need not exceed the maximum force that can be transmitted to the element by the lateral-force-resisting system at yield.
  2. Concrete slabs supporting light-framed walls.
1620.2.10 Direction of Seismic Load
The direction of application of seismic forces used in design shall be that which will produce the most critical load effect in each component. The requirement will be deemed satisfied if the design seismic forces are applied separately and independently in each of the two orthogonal directions.

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