Seismic Loads — ASCE/SEI 7-22

1 · Input data

The seismic demand of a building to ASCE/SEI 7-22 Chapters 11, 12 and 13 — the design spectral accelerations and the Seismic Design Category, the equivalent lateral force procedure (C_s and the base shear V), the vertical distribution of the forces, the nonstructural component force F_p, and the drift and P-delta check. S_MS and S_M1 are INPUTS. §11.4.3 takes them from the USGS Seismic Design Geodatabase for the applicable site class; 7-22 prints no F_a or F_v table, so this page will not compute them from S_S and S₁ — it refuses that 7-16 chain. R, Ω₀ and C_d (Table 12.2-1), I_e (Table 1.5-2), T_L (Figures 22-14 to 22-17) and C_AR and R_po (Tables 13.5-1 and 13.6-1) are inputs too. Every parameter that needs a value is required, and a blank optional field is an answer, not an error: where the engine needs one after all it refuses, with the clause. Press Compute the seismic demand when the card is complete.

The site — the ground motion is an input, not a map reading

S_MS — the site-adjusted short-period MCE_R acceleration, g (§11.4.3)

S_M1 — the site-adjusted 1 s MCE_R acceleration, g (§11.4.3)

S_S — the Site Class BC short-period MCE_R acceleration, g — optional

S₁ — the Site Class BC 1 s MCE_R acceleration, g — optional

Site Class (§11.4.2) — optional

Risk Category (§1.5)

The seismic force-resisting system (Table 12.2-1) and the weight

R — the response modification coefficient (Table 12.2-1)

I_e — the seismic Importance Factor (Table 1.5-2)

Ω₀ — the overstrength factor (Table 12.2-1) — optional

C_d — the deflection amplification factor (Table 12.2-1) — optional

T_L — the long-period transition period, s (Figures 22-14 to 22-17) — optional

W — the effective seismic weight, kip (§12.7.2)

The period — C_t and x from Table 12.8-2, or the story count

C_t from Table 12.8-2 (§12.8.2.1) — optional

x from Table 12.8-2 (§12.8.2.1) — optional

Structural height h_n, ft (§11.2) — optional

Number of stories above the base, for (12.8-9) — optional

T — the fundamental period from the analysis, s (§12.8.2) — optional

The vertical distribution — the effective seismic weight at each level

Each row is one level: its effective seismic weight W_x and its height h_x above the base. The rows are used for (12.8-12) and (12.8-13). A row you leave completely blank is not used; a row with anything in it is a level, and the engine refuses it by name if a value it needs is missing.

The levels of the structure, one per row
Effective seismic weight W_x, kip	Height above the base h_x, ft	Remove

The 13.3.1 nonstructural component force — optional

Tick the box to compute F_p for a nonstructural component. C_AR and R_po come from Table 13.5-1 (architectural) or Table 13.6-1 (mechanical and electrical); this page does not transcribe those tables, so both are entered here.

Compute the nonstructural component force F_p (§13.3.1)

W_p — the component operating weight, lb (§13.1.3)

I_p — the component Importance Factor (§13.1.3)

z — the height of the point of attachment above the base, ft (§13.3.1.1)

h — the average roof height of the supporting structure, ft (§13.3.1.1)

C_AR — the component resonance ductility factor (Table 13.5-1 / 13.6-1)

R_po — the component strength factor (Table 13.5-1 / 13.6-1)

The component is at or below the grade plane (H_f = 1.0, R_mu = 1.0)

The 12.8.6 / 12.8.7 drift and P-delta card — optional

Tick the box to compute the amplified drift and the P-delta stability coefficient. The elastic displacements are required; P_x and h_sx turn on the stability check, which then needs V_x or the level number it is summed from.

Compute the drift and the P-delta stability coefficient (§12.8.6, §12.8.7)

δ_e at the top of the story, in. (§12.8.6.3)

δ_e at the bottom of the story, in. (§12.8.6.3)

δ_di — the diaphragm displacement, in. — optional

P_x — the total vertical design load at the story, kip (§12.8.7)

h_sx — the story height, in. (§12.8.7)

V_x — the seismic design shear at the story, kip (§12.8.4)

Level number for the story shear V_x (§12.8.4, (12.8-14))

β — the stability coefficient multiplier (§12.8.7) — optional

2 · Solution

No solution yet — complete the card above and press Compute the seismic demand. This card stays empty until a solution is computed, and it is emptied again the moment any input changes, so a displayed solution always belongs to the inputs on screen.