HomeCalculatorsMechanicalBeams & DeflectionMidspan Load at a Station Calculator
Mechanical calculator

Midspan Load at a Station Calculator

Deflection at station x when the load is at midspan. δ = P c (3 L² − 4 c²) / (48 E I). Runs locally.

Instant result
Result
—

Enter values to calculate.

Inputs—
Mode—
Formula—
Trust summary CVP VERIFIED · production STALE · CVP protocol 1.0.0-proposed · Engineering assurance · midspan point load at station δ = P c(3L²−4c²)/(48 E I); + O3 mpmath tabulated δ.
Input interpretation
Enter values to calculate.
Result
—
Verified scope
midspan point load at station δ = P c(3L²−4c²)/(48 E I); + O3 mpmath tabulated δ.
Assurance
Engineering
Declared partition coverage
PASS · 5/5 declared partitions (main, alias, signed, awkward, invalid-domain) · Matrix
Deferred
Not midspan tip-only under the same load, and not a cantilever.
Numerical scope
O2: delta vs a separate-module identity (≤2 ULP). Not midspan tip-only under the same load, and not a cantilever. ≤2 ULP vs O3 applies only to the published tabulated beam-deflection-at vectors.
Known limitations
  • Core CVP does not include live graph, viewport, or pointer interaction.
Model
Deflection at a stated station on a simply supported span with one midspan load.
Scope
Calculation runs locally in the browser; values are not uploaded.
Verification
Engine tested · Source checked · v1.0.0 · CVP VERIFIED · production STALE · CVP protocol 1.0.0-proposed · Engineering assurance · midspan point load at station δ = P c(3L²−4c²)/(48 E I); + O3 mpmath tabulated δ.· View Manifest · CVP overview · Specification
Versions
Calculation 1.0.0 · CVP protocol 1.0.0-proposed · Evidence 2026-09-27.o2-o3
Verification revision
2026-09-27.o2-o3 · 1/1 property · digest 7cd4cb567491
Legacy regression
3/3 tests · Production surface contract 6/6
Trust layers
Verification VERIFIED · Production STALE · overall VERIFIED_STALE
CVP status
STALE · Capability production binding: STALE · Site report: STALE · Evidence changed after the last successful production attestation. Re-attestation required.
Reference
O1 model · O3 expected_values · O3 numerical_behavior · O2 expected_values · O2 numerical_behavior
Interfaces
PASS · UI (SSR) / REST / MCP — ui-ssr is query-result HTML, not a live browser session. Error-path engine·REST·MCP 1/1 (status, code, calculation_version). SSR compared on URL-canonical requested calculations; empty query is idle (not an error) and JSON-typed object/array inputs are REST/MCP-only.
Supplemental domain review
Not performed
Named expert review
Not performed
CVP suite
4/4 golden · 1/1 CVP boundary · 3/3 invalid · 1/1 property · 1/1 metamorphic · 8/8 O3 · 2/2 cross-interface · 6/6 CVP contract · Manifest
Sources
  • Hibbeler, Mechanics of Materials — Deflection of beams — concentrated load at midspan
  • Gere and Goodno, Mechanics of Materials — Deflection of beams — reciprocity
Sources
Evidence
2 legacy golden · 1 legacy boundary · legacy regression suite · 4/4 oracle-backed golden · 3/3 invalid · Artifact integrity PASS
STALE · Build schema 1.0.0 ready · Semantic contract ✓ · Last attestation PASS · current evidence changed · re-attestation required · CVP STALE · attestation STALE — Production CURRENT withheld
Semantic contract
PASS
Full verification

Manifest identity, reference classes, interfaces, suite, and production records.

Formulas

Core equations used by this calculator.

Deflection at xδ = P c (3 L² − 4 c²) / (48 E I)
ix = L/2 is the midspan point-load page. By reciprocity, the quarter-span value equals the midspan value of a load at the quarter point.

How to use

1

Enter the load, the station, the span, the modulus, and the area moment

x must lie strictly between the supports.

2

Read the deflection at that station

x and L − x give the same number.

Example calculations

Common configurations with formula and result.

ϟ

At midspan

P = 48, x = 2, L = 4, E = 1, I = 1

δ = P L³ / (48 E I)
δ = 64
ϟ

At a quarter point

P = 48, x = 1, L = 4, E = 1, I = 1

δ = 44
δ = 44

Midspan Load at a Station calculator specification

Version 1.0.0 · Engine tested

Calculation status

Review policy · Evidence

Definition
A simply supported span of length L carries one concentrated load P at midspan. c is the distance from station x to the nearer support. The deflection there is δ = P c (3 L² − 4 c²) / (48 E I).
What it calculates
Deflection at a stated station on a simply supported span with one midspan load.
Inputs
  • P
  • x
  • L
  • E
  • I
Outputs
  • delta
  • c
Formula
δ = P c (3 L² − 4 c²) / (48 E I).
Assumptions
  • Calculation runs locally in the browser; values are not uploaded.
  • Keep units consistent with the labels on each field.
  • x = L/2 is the midspan point-load page. By reciprocity, the quarter-span value equals the midspan value of a load at the quarter point.
Units
  • P, x, L, E, and I set the deflection unit.
Boundary conditions
  • missing P, x, L, E, or I → MISSING_REQUIRED_INPUT
  • L ≤ 0, E ≤ 0, or I ≤ 0 → VALUE_MUST_BE_POSITIVE
  • x ≤ 0 or x ≥ L → INVALID_INPUT
Example
P=48 x=1 L=4 E=1 I=1 → δ=44
Validation cases

3 published on this page · 3/3 tests · Production surface contract 6/6 · View evidence

  • P=48 x=2 L=4 E=1 I=1 → δ=64
  • P=48 x=1 L=4 E=1 I=1 → δ=44
  • x=4 L=4 → INVALID_INPUT
Sources
  • Hibbeler, Mechanics of Materials — Deflection of beams — concentrated load at midspan
    Supports: For x no farther than midspan, δ = P x (3 L² − 4 x²) / (48 E I).
  • Gere and Goodno, Mechanics of Materials — Deflection of beams — reciprocity
    Supports: Supports the symmetric form that uses the distance to the nearer support.
Calculation version
1.0.0

Background

Interpretation and common distinctions.

Find the deflection at a stated station when the concentrated load is at midspan.

Supported and not supported

Supported: δ = P c (3 L² − 4 c²) / (48 E I). x = L/2 is the midspan page.

Not supported: a load that is not at midspan. /calc/mechanical is not open.

Agent / API notes

Capability id: mechanical.statics.beam_deflection_at · tool id: beam-deflection-at · pin 1.0.0.

{ "P": 48, "x": 1, "L": 4, "E": 1, "I": 1 }

Other calculators in this family: Beam Deflection Calculator, Beam Moment Deflection Calculator, Beam Moment Maximum Deflection Calculator, Cantilever Deflection Calculator, Cantilever Intermediate Deflection Calculator, Cantilever Load at a Station Calculator, Cantilever Moment at the Couple Calculator, Cantilever Moment Deflection Calculator . Explore all Beams & Deflection.

→ Beam Deflection Calculator Midspan deflection of a simply supported span with one concentrated load. δ = P L³/(48 E I). I is an input. Runs locally. › → Beam Moment Deflection Calculator Midspan deflection of a simply supported span with one end moment. δ = M L²/(16 E I). I is an input. Runs locally. › → Beam Moment Maximum Deflection Calculator Largest deflection of a simply supported span with one end moment. δ = M L²/(9√3 E I) at x = L/√3. I is an input. Runs locally. › → Cantilever Deflection Calculator Free-end deflection of a cantilever with one concentrated load at the tip. δ = P L³/(3 E I). I is an input. Runs locally. › → Cantilever Intermediate Deflection Calculator Deflection at a concentrated load on a cantilever. δ = P a³ / (3 E I). a is measured from the fixed end. Runs locally. › → Cantilever Load at a Station Calculator Deflection at station x for a cantilever load at a. x = a is the load page. x = L is the free-end page. Runs locally. › → Cantilever Moment at the Couple Calculator Deflection at a concentrated moment on a cantilever. δ = M a² / (2 E I). a is measured from the fixed end. Runs locally. › → Cantilever Moment Deflection Calculator Free-end deflection of a cantilever with one concentrated moment. δ = M L²/(2 E I). I is an input. Runs locally. ›

Frequently asked questions

Key distinctions behind the calculation.

Why does the quarter point match the offset-load midspan page?

Maxwell reciprocity. A load at midspan, read at the quarter point, equals a load at the quarter point, read at midspan.