*E*, for use in Equations 16-5, 16-10 and 16-17, shall be defined by Equation 16-50:

*E*=

*ρQ*+ 0.2

_{E}*S*

_{DS}D**(Equation 16-50)**

where:

D |
= | The effect of dead load. |

E |
= | The combined effect of horizontal and vertical earthquake-induced forces. |

r |
= | A redundancy coefficient obtained in accordance with Section 1617.2. |

Q_{E} |
= | The effect of horizontal seismic forces. |

S_{DS} |
= | The design spectral response acceleration at short periods obtained from Section 1615.1.3 or 1615.2.5. |

Where the effects of gravity and seismic ground motion counteract, the seismic load, E, for usein Equations 16-6, 16-12 and 16-18 shall be defined by Equation 16-51.

*E*=

*ρQ*- 0.2

_{E}*S*

_{DS}D**(Equation 16-51)**

Design shall use the load combinations prescribed in Section 1605.2 for strength or load and resistance factor design methodologies or Section 1605.3 for allowable stress design methods.