--- type: Skill name: concrete-column-design description: "This skill should be used when an architect or structural designer needs to verify PDF-backed concrete column requirements such as longitudinal reinforcement ratio, minimum longitudinal-bar count, minimum shear reinforcement, and column splice rules 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 Column Design ## Overview Design requirements for reinforced concrete columns in Taiwan, limited here to items directly verified against the uploaded PDF: longitudinal reinforcement ratio, minimum longitudinal-bar count, minimum shear reinforcement, and column splice rules. Seismic confinement details that were not fully transcribed remain chapter references only. For cover and splice fundamentals, see [concrete-general-requirements](../../混凝土通用規定/concrete-general-requirements/). --- ## Section 1: Column Classification ### 1.1 By Cross-Section Shape | Type | Section | Reinforcement Type | |---|---|---| | Rectangular column (矩形柱) | Square or rectangle | Ties (繫筋) | | Circular column (圓柱) | Circle | Spirals (螺旋筋) or circular ties | | L-shaped / irregular | Composite shapes | Combined tie arrangement | ### 1.2 By Primary Loading | Type | Characteristics | Design Consideration | |---|---|---| | Axially loaded | Gravity load dominant | ρg within limits; tie spacing | | Eccentrically loaded | Combined axial + bending | Interaction diagram (P-M curve) | | Short column | Slenderness ratio < limit | Direct strength calculation | | Slender column | Slenderness ratio ≥ limit | Moment magnification required | --- ## Section 2: Main Bar Requirements (主筋) ### 2.1 Gross Reinforcement Ratio (ρg) $$\rho_g = \frac{A_{st}}{A_g}$$ Where: - Ast = total area of longitudinal steel - Ag = gross cross-sectional area of column | Limit | Value | Reason | |---|---|---| | Minimum | **1.0% (0.01)** | Below this, column cannot resist minimum bending; creep becomes excessive | | Maximum | **8.0% (0.08)** | Above this, bar congestion at splices and joints prevents proper concrete casting | | Practical note from commentary | Reinforcement ratio is generally not preferred above 4% when all lap splices occur at one location | Constructability warning only | > **Design Check**: ρg < 1% → ERROR. ρg > 8% → ERROR. Source: 10.6.1.1 and its commentary. ### 2.2 Minimum Number of Main Bars | Column Shape | Minimum Bars | |---|---| | Rectangular ties | 4 bars (one at each corner) | | Circular spirals | 6 bars | | Triangular ties | 3 bars | Source: 10.7.3.1. ### 2.3 Source-Control Note Bar-size limits, bundling, and development-length effects must be resolved from Chapter 25 when needed. This skill does not preserve unverified bar-size assumptions. --- ## Section 3: Transverse Reinforcement Clauses The following clauses were verified in the PDF and should be used instead of inferred detailing rules: | Topic | Governing Clause | |---|---| | Minimum shear reinforcement trigger | 10.6.2.1 | | Minimum shear reinforcement formula | 10.6.2.2 | | Minimum bar spacing reference | 10.7.2.1 → Chapter 25.2 | | Minimum longitudinal-bar count | 10.7.3.1 | | Tie / spiral / closed-tie detailing | 10.7.6.1.2 → Chapter 25.7 | Do not infer tie-spacing rules beyond what has been directly transcribed from the PDF. --- ## Section 4: Minimum Shear Reinforcement When shear reinforcement is required, the PDF gives: $$A_{v,min} = \max\left(0.062\frac{\sqrt{f'_c}}{f_{yt}}b_ws,\ 0.35\frac{b_ws}{f_{yt}}\right)$$ This reflects clause 10.6.2.2. Source: 10.6.2.2. --- ## Section 5: Column Splice Rules Verified from the PDF ### 5.1 Compression Lap Splices If column bars are in compression, compression lap splices may be used. Clause 10.7.5.2.1 allows reduction of lap length, but not below 30 cm: - tied columns: multiply by 0.83 when the tie confinement requirement inside the splice zone is met - spiral columns: multiply by 0.75 when the spiral confinement requirement inside the splice zone is met ### 5.2 Tension Lap Splices Clause 10.7.5.2.2 gives the verified classification: | Bar Stress Under Factored Load | Detail Condition | Splice Type | |---|---|---| | ≤ 0.5fy | at any section, spliced bars ≤ 50% and splice locations staggered by at least ψgld | Class A | | ≤ 0.5fy | all other cases | Class B | | > 0.5fy | all cases | Class B | Source: 10.7.5.2.2, Table 10.7.5.2.2. ### 5.3 Seismic Restrictions Special seismic column confinement and splice-location restrictions must be checked directly against Chapter 18. This skill does not restate unverified hinge-zone dimensions. --- ## Section 6: Placement and Support Details Verified from the PDF - bottom tie or closed tie in a story must be placed no farther than one-half tie spacing above the footing or slab top: 10.7.6.2.1 - top tie or closed tie in a story must be placed no farther than one-half tie spacing below the lowest horizontal reinforcement of the slab / capital / drop panel; with beams or brackets on all four sides, not farther than 7.5 cm below the lowest beam or bracket reinforcement: 10.7.6.2.2 - if anchors or precast connectors are placed at a column end, transverse reinforcement must be provided within 12.5 cm of the end: 10.7.6.1.5, 10.7.6.1.6 --- ## Section 7: AI Design Check Table — Column | Check | Condition | AI Action | |---|---|---| | ρg minimum | ρg < 1% | ERROR: Insufficient longitudinal reinforcement. Column cannot resist minimum moment. | | ρg maximum | ρg > 8% | ERROR: Excessive reinforcement — casting impossible at splices. | | Compression splice reduction | 0.83 or 0.75 reduction applied without clause 10.7.5.2.1 confinement condition | ERROR: Splice reduction not justified. | | Tension splice class | Class A used when stress/detail condition in 10.7.5.2.2 is not met | ERROR: Upgrade to Class B. | | Seismic splice location | Column is part of seismic system and Chapter 18 location check not performed | WARNING: Verify Chapter 18 splice restrictions before approval. | | Min bars (rectangular) | < 4 main bars | ERROR: Minimum 4 bars required for rectangular tied column. | --- ## Section 8: MCP Tool Examples ```python # Search for column reinforcement ratio requirements taiwan-building-code_search_building_code(query="柱 縱向鋼筋比 ρg 最小 最大", limit=10) # Search for tie spacing requirements taiwan-building-code_search_building_code(query="柱 繫筋間距 橫向鋼筋", limit=10) # Search for seismic column requirements taiwan-building-code_search_building_code(query="柱 耐震 特殊圍束筋 塑鉸區 lo", limit=10) # Search for splice location in columns taiwan-building-code_search_building_code(query="柱 搭接位置 塑鉸區 禁止", limit=10) # Official interpretations taiwan-building-code_search_building_interpretations(query="柱 繫筋 圍束 計算方式") ``` --- ## Additional Resources - General requirements (cover, development length): [concrete-general-requirements](../../混凝土通用規定/concrete-general-requirements/) - Beam design: [concrete-beam-design](../../混凝土梁設計/concrete-beam-design/)