ll_dlg.dcl — Lintel/Ledger Configuration

File: ll_dlg.dcl
Version: v3.60
Category: Dialog Definitions
Size: 6.1 KB (185 lines)

Note

Lintel and Ledger Details

Configure structural lintels above openings and ledgers for support conditions with engineering capacity checks and reinforcement detailing.

Functional Purpose

Lintel/Ledger Configuration - Designs and details structural support elements including lintels over openings and ledgers at bearing conditions with capacity verification.

Key Functions:

  1. Lintel design (beams above door/window openings)

  2. Ledger specification (support strips, bearing pads)

  3. Load calculations (loads above opening, beam reactions)

  4. Reinforcement sizing (bars required for capacity)

  5. Bearing checks (support adequacy verification)

  6. Detail generation (lintel sections, schedules)

User Need

  • Lintel design (support loads above openings)

  • Code compliance (adequate support per ACI)

  • Optimization (minimum reinforcement for capacity)

  • Detailing (bar placement, bearing details)

  • Documentation (lintel schedules, capacity reports)

Typical Workflow

1. User has window/door opening in panel
2. User opens ll_dlg for opening
3. System calculates loads:
   • Tributary width: 6' (opening width)
   • Height above: 4' (to panel top)
   • Load: 6'×4'×100 PSF = 2,400 lbs
4. User specifies lintel:
   • Depth: 12" (adequate for span)
   • Width: 6" (panel thickness)
   • Reinforcement: 3-#5 bars bottom (tension)
5. System checks capacity:
   • Required: 2.4 kips
   • Capacity: 5.2 kips
   • Status: ? OK (SF = 2.2)
6. Detail generated: Section showing lintel bars
7. Lintel added to schedule

Control Semantics

Opening Selection

Target Opening:

  • opening_id - Opening dropdown (from wall panel openings)

  • Loads calculated from:

    • Opening width (span)

    • Height above opening (tributary)

    • Applied loads (gravity, lateral if applicable)

Lintel Dimensions

Geometry:

  • lintel_depth - Depth (vertical dimension):

    • Minimum: Span/12 (rule of thumb)

    • Typical: 12”-18” for 4’-6’ openings

    • Maximum: Constrained by panel geometry

  • lintel_width - Width (into panel):

    • Typically = panel thickness

    • Can be wider (corbel effect)

  • lintel_bearing - Bearing length beyond opening:

    • Minimum: 8” (code)

    • Typical: 12”-24”

    • Ensures adequate support at ends

Reinforcement

Lintel Bars:

  • lintel_bars - Bottom bars (tension):

    • Number: 2-6 bars typical

    • Size: #4, #5, #6 most common

    • Based on capacity calculations

  • lintel_stirrups - Shear reinforcement:

    • Size: #3 or #4

    • Spacing: 6”-12” o.c.

    • At ends and throughout if high shear

Additional Bars:

  • top_bars - Top bars (compression, skin):

    • Typically 2-#3 or 2-#4

    • Minimum requirement

  • side_bars - Side face bars:

    • For deep lintels (>18”)

    • Control cracking

Load Case

Load Calculation:

  • load_type - Load source:

    • Gravity (typical - wall above)

    • Lateral (wind, seismic)

    • Combined (factored combinations)

  • trib_width - Tributary width:

    • Auto-calculated OR

    • User override

  • trib_height - Height above opening:

    • To panel top OR

    • To next opening/relief

  • unit_load - Load intensity (PSF)

Engineering Calculations

Lintel Capacity

Load Calculation:

Given:
Opening: 6' wide × 7' tall (door)
Height above: 3' (to panel top)
Wall load: 100 PSF (dead + live equivalent)

Tributary load:
P = Width × Height × Load
P = 6' × 3' × 100 PSF = 1,800 lbs

Concentrated load at opening center (worst case):
Or uniform load on lintel (more realistic)

Applied moment (simple span):
M = PL/4 (concentrated at center)
M = 1,800 × 6 / 4 / 12 = 225 lb-ft = 0.225 kip-ft

OR (uniform load):
M = wL²/8
w = 1,800 / 6 = 300 lb/ft
M = 300 × 6² / 8 / 12 = 337.5 lb-ft = 0.34 kip-ft
Use 0.34 kip-ft (slightly higher, conservative)

Reinforcement Required:

M = 0.34 kip-ft = 4,080 lb-in

Required As:
As = M / (? × fy × 0.9d)

Assume:
? = 0.9 (flexure)
fy = 60,000 PSI
d = 12" - 2" (cover/stirrup) = 10"

As = 4,080 / (0.9 × 60,000 × 0.9 × 10)
As = 4,080 / 486,000
As = 0.008 sq in (very small!)

Use minimum: 2-#4 bars (As = 0.40 sq in) ?
Large safety factor for small opening

Bearing Capacity

End Bearing Check:

Reaction at each end:
R = Total load / 2
R = 1,800 / 2 = 900 lbs

Bearing area (each end):
12" bearing × 6" width = 72 sq in

Bearing stress:
fb = 900 / 72 = 12.5 PSI

Allowable:
0.85 × f'c = 0.85 × 5000 = 4,250 PSI

12.5 < 4,250 ? OK (huge margin)

Ledger Design

Ledger Bearing Strips:

When ledger mode selected (vs lintel):

Purpose:

  • Support for roof/floor beams

  • Continuous bearing strip

  • Alternative to beam pockets

Configuration:

  • ledger_width - Strip width: 6”-12” typical

  • ledger_projection - From panel face: 0”-4”

  • ledger_height - Strip height: 8”-12”

  • ledger_bars - Reinforcement: 2-#4 continuous

Capacity:

Bearing capacity (same as lintel bearing)
Check: Beam reaction / Bearing area < 0.85f'c

Integration

Called By:

  • wall_dlg ? Lintel button (per opening)

  • Opening schedule ? Engineering check

Generates:

  • Lintel section details

  • Reinforcement bar lists

  • Capacity reports

  • Lintel schedule

Variables:

  • Linked to opening_id

  • Saved with panel data

  • Used in drawing generation

User Example

Scenario: 5’ wide door opening, 4’ above to panel top

1. Opening: 5'W × 7'H door
2. Load above: 5' × 4' × 100 PSF = 2,000 lbs
3. Lintel design:
   • Span: 5' (opening width)
   • Depth: 12" (5'/12 = 0.42', adequate)
   • Width: 6" (panel thickness)
   • Bearing: 12" each end
4. Reinforcement:
   • Bottom: 3-#4 bars (As = 0.60 sq in)
   • Top: 2-#3 bars (minimum)
   • Stirrups: #3 @ 8" o.c.
5. Capacity check:
   • Applied: 0.5 kip-ft
   • Capacity: 2.8 kip-ft
   • Ratio: 5.6 ? OK
6. Detail generated showing lintel bars
7. Added to project lintel schedule

Best Practices

Lintel Sizing:

  • ? Depth ? Span/12 (minimum)

  • ? Bearing ? 12” each end (typical)

  • ? Check both flexure AND shear

  • ? Use stirrups for deep lintels (>12”)

Reinforcement:

  • ? Minimum 2 bars bottom (even if calculations show less)

  • ? Always include top bars (compression, crack control)

  • ? Extend bars 24” beyond opening (development)

  • ? Add stirrups at ends (high shear)

Common Mistakes:

  • ? Insufficient bearing length (<8” - code violation)

  • ? Forgetting stirrups (shear failure risk)

  • ? No top bars (cracking, spalling)

  • ? Bars too short (inadequate development)

Documentation Metadata

Enhancement Status: ? COMPREHENSIVE - ENHANCED [6/23 v3.60 remaining]

End of Document