Seismic Building Design¶

The Seismic Building Design tab describes the building and calculates its seismic forces by the equivalent lateral force procedure of Section 12.8. You enter the levels with their elevations and seismic weights, and one or more seismic force-resisting systems from Table 12.2-1. For each system, Prose reports the approximate period, the seismic response coefficient, the base shear, and the forces at every level.

ASCE 7-22 renumbered several Section 12.8 equations, so the equation numbers below are given for each edition.

Key Features¶

• Any number of building levels, each with an elevation and a seismic weight
• The total seismic weight W summed for you
• The complete Table 12.2-1 library of seismic force-resisting systems, by category
• R, Ω0, Cd, and the system limitations, including height limits, for Seismic Design Categories B through F shown for the chosen system
• Approximate period Ta per Section 12.8.2.1, with Ct and x for the system type
• Seismic response coefficient Cs with the Section 12.8.1.1 limits, and the base shear V
• Vertical distribution of forces Fx and diaphragm forces Fpx at each level
• Several systems side by side, for example one per direction

Building Levels¶

The Levels table holds one row per level above the base. A new module starts with two placeholder rows.

• Add Level adds a row
• The three-dot menu (⋮) at the end of a row deletes it
• Seismic Weight, W below the table is the sum of the level weights

Drag rows by their handle to reorder them. Values commit when you leave the field.

Seismic Force-Resisting Systems¶

Each system card describes one seismic force-resisting system.

Choosing a system fills in its design coefficients from Table 12.2-1: the response modification coefficient R, the overstrength factor Ω0, and the deflection amplification factor Cd, with the system limitations, including height limits, for seismic design categories B through F. A limit shown as NL means not limited; NP means the system is not permitted in that category.

Several Systems¶

• + Add System adds an empty system card
• The three-dot menu (⋮) on a system's header offers Duplicate, which copies the system with its selections, and Delete, which asks you to confirm

Use one system per direction when the building resists seismic forces differently in each, and name them for the direction. Each system gets its own period, base shear, and distribution.

Base Shear and Force Distribution¶

Under each system, Prose writes out the equivalent lateral force calculation:

On ASCE 7-16 projects on Site Class E with Ss of 1.0 or more or S1 of 0.2 or more, where the tabulated site coefficients are used, Section 11.4.8 as revised by Supplement 3 takes Cs from Equation 12.8-2 for all periods, so the upper limits do not apply. On Site Class D with S1 of 0.2 or more, SM1 is increased by 50% instead (see Design Criteria).

The chart marks the system's period on the design response spectrum. The Distribution of Forces table lists Cvx, Fx, and Fpx for every level.

Summary View¶

The summary on the right lists the building information, then for each system its design details: the system coefficients, the period, the base shear with every limit checked, and the force distributions. The outline button at the top jumps to a system.

Code Reference¶