Structural System - Special Concentrically Braced Frame (SCBF)
Frame type - Centralized-core SCBF: chevron (inverted-V) braced bays on the interior core lines, per the LFRS bay layout below
Number of stories - 5
Story heights - First story 15 ft (ground-floor lobby + MEP main distribution); typical upper stories (2-5) 12 ft 6 in to 13 ft; total height ~65 to 67 ft
Analysis procedure - Equivalent Lateral Force (ELF); SDC D (high seismic)
Design standards - AISC 360, AISC 341, ASCE 7

## Material Properties
- Structural steel (W-shapes): **ASTM A992**, **Fy = 50 ksi**
- Braces (HSS): **ASTM A500 Grade C**, **Fy = 50 ksi**
- Gusset plates: **ASTM A572 Grade 50**
- Floor system: composite - 3 1/4 in. lightweight concrete on 3 in. composite steel deck

## Gravity Loads
| Load Type | Magnitude |
|------------|-----------|
| Dead Load | 75 psf (composite floor: slab, deck, framing, superimposed MEP/ceiling/finishes) |
| Cladding Load | 15 psf (perimeter facade - glass/metal curtain wall) |
| Floor Live Load | 50 psf (office) + 15 psf partition allowance (ASCE 7-22 Table 4.3-1); reducible per Sec. 4.7 |
| Roof Live Load | 20 psf (Lr, ordinary roof; reducible per Sec. 4.8) |

### Additional Notes
- Wind loads - V = 110 mph (ASCE 7-22), Exposure B; MWFRS per Ch. 26-27. Verify wind vs seismic per direction - seismic expected to govern in SDC D.
- Composite gravity beams designed per AISC 360; infill beams spaced at 10 ft o.c.

## Column Design Requirements
- Column splices at two-story intervals, located ~4 ft above finished floor
- Column sizes in lower stories never smaller than stories above
- Unbraced length of columns = clear story height (floor framing braces both axes at each level)

## Building Plan Geometry
  - Footprint: 90'-0" (Transverse/Y-axis) × 150'-0" (Longitudinal/X-axis).
  - Story Heights:
      - Level 1: 15'-0" (Floor-to-Floor)
      - Levels 2–5: 13'-0" (Floor-to-Floor, typical)
      - Total Height: 67'-0" (to roof parapet)
  - Column Grid Coordinates:
      - Transverse (Y-Axis): Grid Lines A to D (3 bays @ 30'-0" o.c.).
      - Longitudinal (X-Axis): Grid Lines 1 to 6 (5 bays @ 30'-0" o.c.).
LFRS System Classification
  - System Type: Special Concentrically Braced Frames (SCBF) conforming to
    AISC 341 (Seismic Design Category D).
  - Brace Configuration: Chevron (Inverted-V) configuration within designated
    bays.
LFRS Bay Locations (1-Bay Widths, Centralized Core Layout)
To concentrate the lateral system within a central service/circulation core and
preserve a fully glazed exterior perimeter, LFRS bays are located as follows:
Transverse Direction (Y-Axis LFRS):
  - Frame 1 (Interior Core Line): Located on Grid Line 2, between Grid Lines B
    and C (Bay Width: 30'-0").
  - Frame 2 (Interior Core Line): Located on Grid Line 5, between Grid Lines B
    and C (Bay Width: 30'-0").
Longitudinal Direction (X-Axis LFRS):
  - Frame 3 (Interior Core Line): Located on Grid Line B, between Grid Lines 3
    and 4 (Bay Width: 30'-0").
  - Frame 4 (Interior Core Line): Located on Grid Line C, between Grid Lines 3
    and 4 (Bay Width: 30'-0").
Critical Design Provisions (AISC 341 & AISC 360)
  - Member Slenderness: All bracing members must satisfy highly ductile member
    limits (\lambda_{hd}) per AISC 341 Table D1.1 (e.g., b/t limits for HSS
    sections).
  - Connection Design:
      - Brace-to-gusset connections must utilize the Uniform Force Method (UFM)
        for force distribution.
      - Gusset plates must incorporate a continuous "2t" plastic hinge fold-line
        clearance to accommodate out-of-plane buckling rotation.
- All columns will vary in size every 2 storeys
- All beams on a storey are the same size, every storey may have a different beam size
- Column splices at two-story intervals; column unbraced length = clear story height.
- Base fixity - all pinned
- framing connections - pinned

## Brace Connections (SCBF, per AISC 341)
- Brace-to-frame connections: gusset plates, **3/4 in. to 1 in. thick (ASTM A572 Gr. 50)**.
- Provide a **"2t" linear fold-line clearance** (t = gusset thickness) to permit the brace to form an out-of-plane plastic hinge during buckling.
- Gusset-to-beam and gusset-to-column welds designed by the **Uniform Force Method (UFM)**.
- Brace width-to-thickness ratios: **highly ductile** limits per AISC 341 Table D1.1.
