目录

• Understanding Rebar Development Length in Pad Footings
• 压缩展开长度
• 张力发展长度
• SkyCiv 基础设计模块

This documentation explores the significance of rebar development length in concrete footings and its role in ensuring structural integrity. You can gain insights into design code requirements, factors that influence development length, and practical approaches for incorporating them into your footing designs. 加, discover how the SkyCiv Foundation Design module simplifies the process of verifying rebar development length for your projects.

Understanding Rebar Development Length in Pad Footings

Proper anchorage and reinforcement are essential for the stability and longevity of concrete structures, especially in pad footings. Development length is the minimum length of rebar embedded in the concrete necessary to achieve the required bond strength between steel and concrete. A development length check ensures that reinforcement is adequately embedded to resist loads without slipping, maintaining structural integrity and enabling safe load transfer to the ground. Verifying development length is a key part of footing design, assuring performance under static and dynamic loads and safeguarding overall structure stability.

Different design standards provide specific guidelines for determining these lengths to ensure that reinforcing bars are securely anchored within the concrete. This article provides an overview of the footing development length requirements as specified by various design standards, 包括ACI 318-14 (美国混凝土研究所), 如 3600 (澳大利亚标准), CSA (加拿大标准协会), 和EN (欧洲规范). By examining the distinct approaches and criteria set forth by each standard, engineers can better understand how to apply these guidelines effectively in practice, ensuring robust and compliant structural designs.

压缩展开长度

The compression development length of a footing is a crucial factor in determining its required thickness to ensure proper anchorage of reinforcing bars. This length is calculated based on the need to embed the bars sufficiently within the concrete to achieve adequate bond strength and prevent slippage under compressive loads. Incorporating the correct development length allows engineers to design footings with optimal thickness for reinforcement, ensuring structural stability and durability and enhancing overall safety.

美国混凝土研究所 (ACI 318 部分 25.4.9)

公制:

\(由使用公式计算的最小值控制{直流} = max left[ \压裂{0.24 F_{和} \psi_{[R}}{\lambda sqrt{F'_{C}}} \d_{b}, 0.042 F_{和} \psi_{[R} d_{b}, 200MM 对]\)英制:

\(由使用公式计算的最小值控制{直流} = max left[ \压裂{F_{和} \psi_{[R}}{50 \λ sqrt{F'_{C}}} \d_{b}, 0.0003 F_{和} \psi_{[R} d_{b}, 8英寸右]\)在哪里:

F_和 =钢筋屈服强度 (兆帕, 压力)
F’_C =具体强度 (兆帕, 压力)
d_b =销杆直径 (毫米, 在)
ѱ _[R = Confinement reinforcement factor (桌子 25.4.9.3)
ƛ = Concrete type factor (桌子 25.4.9.3)

澳大利亚标准 (如 3600 部分 13.1.5)

基本发展长度:

\(由使用公式计算的最小值控制{他的,CB} = max left[ \压裂{0.22 F_{他的}}{ \sqrt{F_{C}’}} \d_{b}, 0.0435 F_{他的} d_{b}, 200MM 对]\)在哪里:

F_他的 =钢筋屈服强度 (兆帕)
F_C‘ =具体强度
d_b =启动杆直径 (毫米)

加拿大标准协会 (CSA部分 12.3)

\(由使用公式计算的最小值控制{D b} = max left[ \压裂{0.24 F_{和}}{ \sqrt{F_{C}’}} \d_{b}, 0.045 F_{和} d_{b}, 200MM 对]\)在哪里:

F_和 =钢筋屈服强度 (兆帕)
F_C‘ =具体强度
d_b =销杆直径 (毫米)

欧洲规范 (在节中 8.4)

基本的锚固长度 (8.4.3)

\(由使用公式计算的最小值控制{b,RQD} = frac{\φ}{4} \时代 frac{\sigma_{SD}}{F_{BD}} \)在哪里:

F_和 =钢筋屈服强度 (兆帕)
F_BD =最终键应力 (兆帕)
σ_SD =杆的设计应力，位于从锚定的位置测量的位置 (兆帕)
ɸ = Dowel bar diameter (毫米)

设计锚固长度 (8.4.4)

\(由使用公式计算的最小值控制{BD} =\alpha_{1} \α_{2} \α_{3} \α_{4} 由使用公式计算的最小值控制{b,RQD} \)在哪里:

一种₁, 一种₂, 一种₃, 一种₄ = 1.0 for Compression (桌子 8.2)

Minimum anchorage length (8.4.4)

\(由使用公式计算的最小值控制{b, 分} =MAX \left[ 0.6 由使用公式计算的最小值控制{b,RQD}, 10ɸ, 100MM 对]\)Anchorage length in compression

\(由使用公式计算的最小值控制{BD,压缩} =MAX\left[ 由使用公式计算的最小值控制{b, 分}, 由使用公式计算的最小值控制{BD}\对]\)

张力发展长度

The tension development length is key to ensuring that a footing’s dimensions are adequate to anchor reinforcement against tensile forces. This length, calculated to achieve the necessary bond strength between concrete and rebar, directly impacts the footing’s size and design. Properly determining the tension development length allows engineers to design footings capable of securely anchoring the reinforcement, enabling the structure to withstand tensile stresses and maintain stability and performance.

美国混凝土研究所 (ACI 318 部分 25.4)

直条纹 (部分 25.4.2.3)

公制:

\(由使用公式计算的最小值控制{d} = max left[ \剩下( \压裂{F_{和}}{1.1 \λ sqrt{F'_{C}}} \时代 frac{\psi_{!} \psi_{2} \PSI_3}{\剩下(C_{b} + K_{tr} \对) / d_{b}} \对)\d_{b}, 300MM 对]\)英制:

\(由使用公式计算的最小值控制{d} = max left[ \剩下( \压裂{3 F_{和}}{40\λ sqrt{F'_{C}}} \时代 frac{\psi_{!} \psi_{2} \PSI_3}{\剩下(C_{b} + K_{tr} \对) / d_{b}} \对) \d_{b}, 12在右]\)

在哪里:

ѱ_Ť = Casting position factor (桌子 25.4.2.4)
ѱ_Ë = Bar coating factor (桌子 25.4.2.4)
ѱ_s = Bar size factor (桌子 25.4.2.4)
C_b =最小条形距离距离 (毫米, 在)
ķ_tr =横向加固指数 (毫米, 在)
(C_b + ķ_tr) / d_b ≤ 2.5

标准钩杆 (部分 25.4.3.1)

公制:

\(由使用公式计算的最小值控制{d} = max left[ \剩下( \压裂{0.24 F_{和} \psi_{Ë} \psi_{C} \psi_{[R}}{\λ sqrt{F'_{C}}} \对)\d_{b}, 8d_{b}, 150 MM 对]\)英制:

\(由使用公式计算的最小值控制{d} = max left[ \剩下( \压裂{F_{和} \psi_{Ë} \psi_{C} \psi_{[R}}{50 \λ sqrt{F'_{C}}} \对)\d_{b}, 8d_{b}, 6 在右]\)

在哪里:

ѱ_Ë = Bar coating factor (桌子 25.4.3.2)
ѱ_C = Bar concrete cover factor (桌子 25.4.3.2)
ѱ_[R = Confining reinforcement factor (桌子 25.4.3.2)

澳大利亚标准 (如 3600 部分 13.1.2.2)

基本发展长度:

\(由使用公式计算的最小值控制{他的,TB} = max left[ \压裂{0.5 钢底板设计欧洲规范{1} 钢底板设计欧洲规范{3} F_{和} d_{b}}{钢底板设计欧洲规范{2} \sqrt{F'_{C}}}, 0.058 F_{和} 钢底板设计欧洲规范{1} d_{b} \对]\)在哪里:

ķ₁ = 1.3 对于钢筋超过 300 MM混凝土铸件在杆下方 (1.0 否则)
ķ₂ = (132 – d_b)/100
ķ₃ = 1-[0.15(C_d – d_b)/d_b]
C_d =最小条形距离距离 (毫米)

直杆:

\(由使用公式计算的最小值控制{他的,Ť} = l_{他的,TB}\)

Standard hook or cog:

\(由使用公式计算的最小值控制{他的,Ť} =0.5 \times l_{他的,TB}\)

加拿大标准协会 (CSA部分 12)

直条纹 (部分 12.2.3)

\(由使用公式计算的最小值控制{d} = max left[ 0.45 钢底板设计欧洲规范{1} 钢底板设计欧洲规范{2} 钢底板设计欧洲规范{3} 钢底板设计欧洲规范{4} \压裂{F_{和}}{\sqrt{F'_{C}}} d_{b}, 300 MM 对]\)在哪里:

ķ₁ = Bar location factor (12.2.4)
ķ₂ = Coating factor (12.2.4)
ķ₃ = Concrete density factor (12.2.4)
ķ₄ = Bar size factor (12.2.4)

标准钩杆 (部分 12.5)

\(由使用公式计算的最小值控制{d} = max left[ \压裂{100 d_{b}}{\sqrt{F'_{C}}}\时代左(0.7 \压裂{F_{和}}{40}\对), 8 d_{b}, 150 MM 对]\)

欧洲规范 (在节中 8.4)

基本的锚固长度 (8.4.3)

\(由使用公式计算的最小值控制{b,RQD} = frac{\φ}{4} \时代 frac{\sigma_{SD}}{F_{BD}} \)设计锚固长度 (8.4.4)

\(由使用公式计算的最小值控制{BD} =\alpha_{1} \α_{2} \α_{3} \α_{4} 由使用公式计算的最小值控制{b,RQD} \)在哪里:

一种₁, 一种₂, 一种₃, 一种₄ = values shown in Table 8.2 for bars in tension

Minimum anchorage length (8.4.4)

\(由使用公式计算的最小值控制{b, 分} =MAX \left[ 0.3 由使用公式计算的最小值控制{b,RQD}, 10ɸ, 100MM 对]\)Anchorage length in compression

\(由使用公式计算的最小值控制{BD,紧张} =MAX\left[ 由使用公式计算的最小值控制{b, 分}, 由使用公式计算的最小值控制{BD}\对]\)

For a detailed guide on how the SkyCiv Design module verifies development length, refer to the following links:

• 美国混凝土研究所 (ACI 318)
• 澳大利亚标准 (如 3600)
• 加拿大标准协会 (CSA A23.3)
• 欧洲规范 (在 1992)

SkyCiv 基础设计模块

The latest update to the SkyCiv Foundation Design module enhances its functionality by introducing the ability to incorporate standard hooked reinforcements, enabling more precise and detailed development length checks. This new feature provides users with greater flexibility by allowing them to customize the reinforcement detailing at each end of the footing bars. Users can now specify reinforcement ends as straight bars, 90-degree hooks (齿轮), or 180-degree hooks, catering to various design requirements and standards.

The module also features updated graphics that visually aid in inspecting reinforcement detailing checks. Column dowel or starter bars are now also visible in the 3D graphics. With the newly added solver settings under the Miscellaneous tab, users can toggle to ignore specific design checks, such as development length checks and other advanced solving options.

 

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