How to calculate steel beams
As a common load-bearing component in building structures, the calculation process of steel beams involves multiple parameters and specification requirements. This article will combine the hot topics and hot content on the Internet in the past 10 days, introduce the calculation method of steel beams in a structured way, and provide relevant data tables for reference.
1. Basic principles of steel beam calculations
The calculation of steel beams is mainly based on mechanical principles and steel structure design specifications, including verification of strength, stiffness, stability and other aspects. The following are the parameters to focus on when calculating steel beams:
| Parameter name | symbol | unit | illustrate |
|---|---|---|---|
| Cross-sectional area | A | mm² | The total area of the steel beam cross-section |
| Sectional moment of inertia | I | mm⁴ | Index reflecting the bending resistance of a section |
| Section modulus | W | mm³ | Index reflecting the flexural strength of the section |
| Yield strength of steel | fy | MPa | The stress value at which plastic deformation begins in steel |
| elastic modulus | E | MPa | Elastic deformation ability of steel |
2. Calculation of steel beam strength
The strength calculation of steel beams mainly includes the calculation of normal stress, shear stress and local compressive stress. Here is the formula for strength calculation:
| Calculate content | Calculation formula | illustrate |
|---|---|---|
| Normal stress calculation | σ = M/W ≤ fy/γm | M is the bending moment, γm is the material partial coefficient |
| Shear stress calculation | τ = V·S/(I·tw) ≤ fv/γm | V is shear force, S is static moment, tw is web thickness |
| Local compressive stress calculation | σc = F/(tw·lz) ≤ fy/γm | F is the concentrated load, lz is the load distribution length |
3. Calculation of steel beam stiffness
The stiffness calculation of steel beams mainly considers the deflection limit to ensure that the deformation of the structure in use is within the allowable range. The common deflection calculation formula is as follows:
| Load type | Maximum deflection formula | Allowed deflection |
|---|---|---|
| Simply supported beam with uniformly distributed load | δ = 5qL⁴/(384EI) | L/250～L/400 |
| Concentrated load simply supported beam | δ = PL³/(48EI) | L/300～L/500 |
| Cantilever beam end load | δ = PL³/(3EI) | L/200～L/300 |
4. Calculation of steel beam stability
The stability calculation of steel beams includes two aspects: overall stability and local stability. The overall stability check is particularly important, especially when the free length of the compression flange is large.
| stability type | Calculation method | Key parameters |
|---|---|---|
| Overall stable | M/(φb·W) ≤ fy/γm | φb is the overall stability coefficient |
| Web locally stabilized | hw/tw ≤ limit value | hw is the web height, tw is the web thickness |
| flange local stability | b/t ≤ limit value | b is the flange width, t is the flange thickness |
5. Parameter reference of popular steel models
According to recent industry hot spots, the following are the parameters of several commonly used hot-rolled H-shaped steels (GB/T 11263-2017 standard):
| model | HeightH(mm) | WidthB(mm) | Web thickness tw (mm) | Flange thickness t(mm) | Theoretical weight (kg/m) |
|---|---|---|---|---|---|
| HN400×200 | 400 | 200 | 8 | 13 | 66.0 |
| HN500×200 | 500 | 200 | 10 | 16 | 89.6 |
| HN600×200 | 600 | 200 | 11 | 17 | 106.0 |
6. Recommended steel beam calculation software
According to recent engineering software usage trends, the following are several popular steel beam calculation tools:
| Software name | Developer | Main functions | Applicable standards |
|---|---|---|---|
| STAAD.Pro | Bentley | Comprehensive Structural Analysis and Design | International multi-national standards |
| ETABS | CSI | Building Structural Analysis and Design | Internationally applicable |
| Midas Gen | Midas IT | Steel structure analysis and design | GB 50017 etc. |
7. Answers to frequently asked questions about steel beam calculations
Based on the recent popular discussions on the engineer forum, the following common questions are summarized:
1.How to choose steel beam section?Standard profiles should be given priority based on comprehensive considerations such as load size, span, support conditions and other factors.
2.Why do we need to check stability?Steel has high strength but a relatively slender cross-section and is prone to instability under pressure, so stability checks must be performed.
3.What should I do if the deflection of the steel beam is too large?Measures such as increasing the section height, setting up intermediate supports, or using prestressing can be used to improve stiffness.
4.How to design steel beam connection nodes?The node design should ensure clear force transmission and avoid stress concentration. Welding, high-strength bolt connection, etc. can be used.
Through the above structured data and content, I believe readers can have a comprehensive understanding of the calculation methods of steel beams. In actual projects, it is recommended to perform calculations based on specific project conditions and relevant specification requirements, and consult a professional structural engineer when necessary.
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