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Beam deflection & bending calculator

Engineering calculators (Beta)

Choose supports and load to calculate deflection, reactions and bending stress.

Inputs

Choose units and enter numbers. Full-width digits and fractions such as 1/8 or 1 3/8 are accepted. Changing a unit converts the entered value.

Results

Reference calculation only. Results do not certify suitability for an actual design or its safety.

Diagram

Inputs: select a blue symbol to edit Results: red-orange values and lines

Formula and applicability

σmax = |M|max / Zmin

Displayed values are rounded. Diagrams illustrate the calculation conditions. Initial material and fluid properties are examples; replace them with values for the actual material, temperature and conditions.

Reference
Using this information as a reference

Equations assume particular loads, supports and deformation ranges. Check inputs, units and the applicability of each equation. Diagrams explain conditions; they are not manufacturing drawings or proof of safety.

Material values are typical values or reference ranges, not certified product properties or ready-to-use design allowables. They vary with standards, product form, dimensions, temper and temperature. Check the specifications and inspection certificates for the actual product.

Displayed safety factors and checks apply only to the supplied inputs and calculation model. They do not automatically establish the safety of a complete design, including code compliance, service life, fatigue or joints. For actual design, manufacture and use, separately verify applicable regulations and standards, product specifications, and the necessary tests and engineering review.

この計算で求められること

支点と荷重を選び、たわみ・反力・曲げ応力を確認します。

入力・結果・適用条件を確認する

選択した形状・計算方法により、使う項目は変わります。実際の計算は上の図と入力欄で行えます。

主な入力

  • 梁の長さ L (mm / cm / m)
  • ヤング率 E(入力例) (GPa / MPa / Pa)
  • 曲げ軸の I (mm⁴ / cm⁴ / m⁴)
  • 曲げ軸の最小 Z (mm³ / cm³ / m³)
  • 集中荷重 F (N / kN / mN)
  • 等分布荷重 q (N/m / N/mm / kN/m)
  • 左支点から荷重点 a (mm / cm / m)

得られる結果

  • 最大たわみ δmax (mm)
  • 最大たわみの位置 x (mm)
  • 最大曲げ応力の絶対値 (MPa)
  • 最大曲げモーメントの絶対値 (N·m)
  • 最大せん断力の絶対値 (N)
  • 左側の鉛直反力 RA (N)
  • 右側の鉛直反力 RB (N)
  • 左固定端の反力モーメント(反時計回りが正) (N·m)
  • 右固定端の反力モーメント(反時計回りが正) (N·m)
  • 左端のたわみ角(下向き変位の勾配) (°)
  • 右端のたわみ角(下向き変位の勾配) (°)
  • 最大たわみ角の絶対値 (°)

計算式の概要

σmax = |M|max / Zmin

一定断面・均質・線形弾性・小変形のEuler–Bernoulli梁です。荷重は下向き。上向き反力、正曲げモーメント、下向きたわみを正とします。せん断変形・自重・応力集中・座屈・疲労は含みません。IとZは同じ主軸まわりの値を使用します。図の変形は拡大表示です。

現在選択中の方法には、操作欄の「計算式・適用条件」を使ってください。参考計算であり、設計全体の安全性を保証するものではありません。

関連する計算

What this calculator does

Choose supports and load to calculate deflection, reactions and bending stress.

Inputs, outputs and applicability

The selected model determines which of these inputs and outputs apply. Use the working diagram and input panel above to calculate.

Inputs

  • Span L (mm / cm / m)
  • Young’s modulus E (example) (GPa / MPa / Pa)
  • I about bending axis (mm⁴ / cm⁴ / m⁴)
  • Smaller Z about bending axis (mm³ / cm³ / m³)
  • Point load F (N / kN / mN)
  • Uniform load q (N/m / N/mm / kN/m)
  • Load position a from left (mm / cm / m)

Calculated results

  • Maximum deflection (mm)
  • Position of maximum deflection (mm)
  • Maximum absolute bending stress (MPa)
  • Maximum absolute bending moment (N·m)
  • Maximum absolute shear force (N)
  • Left vertical reaction RA (N)
  • Right vertical reaction RB (N)
  • Left support moment (counterclockwise positive) (N·m)
  • Right support moment (counterclockwise positive) (N·m)
  • Left-end slope (downward displacement) (°)
  • Right-end slope (downward displacement) (°)
  • Maximum absolute slope (°)

Formula overview

σmax = |M|max / Zmin

Uniform homogeneous linear-elastic Euler–Bernoulli beam with small deflection. Loads act downward. Upward reactions, sagging moments and downward deflection are positive. Shear deformation, self-weight, stress concentrations, buckling and fatigue are excluded. I and Z must refer to the same principal bending axis. Deflection is exaggerated in the diagram.

The displayed formula and conditions in the working panel apply to the currently selected model. Reference calculation only; it does not certify a complete design.

Related tools

目的から順に確認する設計ガイド

図で条件を整理してから計算し、最後に実際の部品仕様を確認します。

Purpose-based design guides

Understand conditions with diagrams, calculate, then verify actual specifications.

数値の感覚を、図と動きで確かめる

説明用の別モデルです。適用条件を確認してください。数値は自動転記しません。

See the idea in diagrams and motion

A separate explanatory model. Check its assumptions; values are not transferred.

単純梁・両端支持梁・片持ち梁はどう選ぶ?

単純梁と両端支持梁の呼び方

この計算の「単純梁」は、両端をピンとローラーで支え、端の回転を拘束しないモデルです。「両端支持梁」と呼ばれることもあります。両端の回転も止める「両端固定梁」とは別の条件なので、実際の取付け方と図を合わせてください。

同じ梁・荷重で2つの代表条件を比べる

長さL = 500 mm、荷重F = 100 N、ヤング率E = 200,000 MPa、幅b = 40 mm・高さh = 20 mmの長方形断面を例にします。曲げる向きのI = bh³/12 = 26,666.666… mm⁴です。荷重点は、各代表モデルに合わせて自由端または中央に変わります。

支持・荷重点最大たわみの式この例の最大たわみ
片持ち梁・自由端にFFL³ / (3EI)0.78125 mm
単純梁/両端支持梁・中央にFFL³ / (48EI)0.048828125 mm

一様な線形弾性梁・小たわみ・1点荷重の例です。自重は含みません。この2条件での比較であり、どんな荷重点や支持条件でも同じ倍率になるわけではありません。

たわみが小さければ、壊れない?

たわみは変形量、曲げ応力は材料内部の負担です。必要な機能に対するたわみの上限と、材料・製品状態に対応する許容応力を分けて確認します。ヤング率だけで許容応力は決まりません。

梁のたわみと応力を図で確認する → · 断面二次モーメントIを計算する →

Choosing a simply supported or cantilever beam

What does simply supported mean here?

The simple-beam model uses a pin and a roller at the ends and allows end rotation. A fixed-fixed beam also restrains end rotation and is a different model. Match the support diagram to the actual connection.

Compare two standard support and load arrangements

Use L = 500 mm, F = 100 N, E = 200,000 MPa and a rectangular section of width b = 40 mm and height h = 20 mm. About the chosen bending axis, I = bh³/12 = 26,666.666… mm⁴. The point load is at the free end or the centre, as specified in each standard arrangement.

Support and load positionMaximum deflection formulaDeflection in this example
Cantilever, tip load FFL³ / (3EI)0.78125 mm
Simply supported, central point load FFL³ / (48EI)0.048828125 mm

These examples assume a uniform linear-elastic beam, small deflection and one point load, without self-weight. Their ratio does not apply to arbitrary support or load positions.

Does small deflection prove adequate strength?

Deflection measures displacement; bending stress measures internal material loading. Check the functional deflection limit separately from the allowable stress for the actual material and product condition. Young’s modulus alone does not determine allowable stress.

See beam deflection and stress with diagrams → · Calculate second moment of area I →