concrete-beam-design - SKILL.md Agent Skill

name: concrete-beam-design description: "This skill should be used when an architect or structural designer needs to verify PDF-backed concrete beam requirements such as minimum beam depth, T-beam effective flange width, minimum shear reinforcement, and the governing clause locations for beam detailing in Taiwan's concrete structure design code." user-invocable: true license: CC-BY-SA-4.0 compatibility: claude-code,opencode,agent-skills metadata: audience: architects region: taiwan class: C regulation: 建築物混凝土結構設計規範

Concrete Beam Design

Overview

Design requirements for reinforced concrete beams in Taiwan, limited to items directly verified against the uploaded PDF in this pass. This skill preserves the minimum beam-depth table, T-beam effective flange-width limits, and the verified clause references for beam reinforcement and detailing. For fundamental cover and splice concepts, see concrete-general-requirements.

Section 1: Beam Geometry and Effective Depth

1.1 Key Dimensions

┌─────────────────────────── b ───────────────────────────┐
│  ┌───────────────────────────────────────────────────┐  │
│  │  ← C → ┌─────────┐ stirrup ← sbar → ┌─────────┐  │  │
│  │         │ main bar│                  │ main bar│  │  │
│  │         └────┬────┘                  └────┬────┘  │  │
│  │              │← d (effective depth) ────→ ┤       │  │ h (total depth)
│  │              ↓                            ↓       │  │
│  │  ─────────────────────────────────────────────── │  │
│  └───────────────────────────────────────────────────┘  │
└─────────────────────────────────────────────────────────┘

h = total beam depth (全深度)
d = h − C − d_stirrup − d_main/2 (effective depth to main bar centroid)
b = beam web width (梁寬)
C = concrete cover (to stirrup face) — see concrete-general-requirements

1.2 Minimum Beam Depth (Non-Seismic, Simply Supported)

Support Condition	Minimum h (normal weight concrete, fy=420)
Simply supported	L/16
One end continuous	L/18.5
Both ends continuous	L/21
Cantilever	L/8

These are deflection-control minimums. Seismic design may govern a larger section.

Source: 9.3.1.1, Table 9.3.1.1.

Section 2: Reinforcement Limits and Detailing Clauses

The following beam clauses are relevant, but their full numerical expressions were not transcribed clause-by-clause in this pass:

Topic	Governing Clause
Minimum flexural reinforcement	9.6.1
Minimum shear reinforcement	9.6.3
Beam detailing and bar termination	9.7
Development length and splices	25.4, 25.5

If a numeric beam check depends on one of these clauses, the AI should resolve it from the PDF before issuing a pass/fail result.

Section 3: Beam Detailing Notes

Beam bar spacing, bundling, and related detailing must be checked against Chapter 25.2 and Chapter 9.7. This skill does not preserve unverified spacing formulas or example widths.

Section 4: Shear Reinforcement (Stirrups)

4.1 Stirrup Spacing

Beam stirrup spacing and seismic hinge-zone detailing must be checked directly from Chapter 9.7 and Chapter 18 when applicable. This skill intentionally avoids restating unverified spacing limits.

4.2 Minimum Shear Reinforcement

$$A_{v,min} = \max\left(\frac{0.062\sqrt{f'c}}{f{yt}} b_w s,\ \frac{0.35}{f_{yt}} b_w s\right)$$

This formula is taken from the PDF-backed beam clause for minimum shear reinforcement. Member-specific exceptions and exemptions must still be checked directly against the chapter text.

Source: 9.6.3.4, Table 9.6.3.4.

Section 5: T-Beam Effective Flange Width

When a beam is cast monolithically with a slab, it acts as a T-beam in positive moment regions. Effective flange width (bf) is the beam web width plus the effective overhang from the slab.

Flange Side Condition	Effective Overhang Limit
Flange on both sides	min(8h, sw/2, ln/8)
Flange on one side	min(6h, sw/2, ln/12)

Where h is slab thickness, sw is adjacent web clear spacing, and ln is clear span.

Source: 6.3.2.1, Table 6.3.2.1.

Section 6: AI Design Check Table — Beam

Check	Condition	AI Action
Min flexural steel	Numeric check needed under 9.6.1	WARNING: Resolve clause 9.6.1 from the PDF before checking.
Stirrup spacing	Numeric spacing check needed under 9.7 or Chapter 18	WARNING: Resolve the applicable clause from the PDF before checking.
Clear spacing	Spacing check required under Chapter 25.2	WARNING: Resolve Chapter 25.2 before checking.
Effective depth	d not calculated from C + stirrup + d_main/2	WARNING: Verify d calculation method.
Development at supports	Numeric ld-based support check needed	WARNING: Resolve Chapter 25.4 before checking.
Bar termination	Beam bar cut-off or support extension not checked to 9.7	WARNING: Resolve clause 9.7 from the PDF before checking.

Section 7: MCP Tool Examples

# Search for beam flexural reinforcement limits
taiwan-building-code_search_building_code(query="梁 最小鋼筋量 ρmin 彎矩", limit=10)

# Search for stirrup spacing requirements
taiwan-building-code_search_building_code(query="梁 箍筋間距 剪力鋼筋", limit=10)

# Search for seismic beam requirements
taiwan-building-code_search_building_code(query="特殊抗彎矩構架 梁 耐震", limit=10)

# Official interpretations
taiwan-building-code_search_building_interpretations(query="梁 鋼筋 最小量 計算")

Additional Resources

General requirements (cover, development length, splice): concrete-general-requirements
Column design: concrete-column-design