Beam Deflection — Fixed-Fixed, Point/UDL implementation

Binding contract

This record describes what an executable surface must bind and validate. It does not claim that a public calculator, package, or production route is deployed.

Record owner

Guth Instruments

Lifecycle

verified-with-binding-errata

Evidence ID

t2-034

Effect

Computation or source lookup only

Input and validation requirements

An input with E = 0 produces a zero denominator in the deflection formula, so the instrument must reject it or report an undefined result. The specification also leaves reaction sign conventions and signed-versus-magnitude reporting ambiguous.

Required corrections

[
  {
    "stress_correction": {
      "vector_inputs": {
        "load_type": "central_point",
        "P": 7500,
        "L": 2.7,
        "E": 70000000000,
        "I": 0.0000135
      },
      "wrong_outputs": {
        "left_end_moment": -253.125,
        "right_end_moment": -253.125,
        "midspan_moment": 253.125
      },
      "corrected_outputs": {
        "left_end_moment": -2531.25,
        "right_end_moment": -2531.25,
        "midspan_moment": 2531.25
      },
      "method": "PL/8 = 7500*2.7/8 = 2531.25 N·m; her own working shows the division \"20,250/8=253.125\" — a 10x slip. The deflection field (0.0008136 m) used a separate correct calculation and was unaffected."
    }
  }
]

Inspectable interface fixture

The sample below is evidence for interface and validation tests, not a production implementation.

{
  "inputs": {
    "load_type": "UDL",
    "w_N_per_m": 10000,
    "L_m": 6,
    "E_Pa": 200000000000,
    "I_m4": 0.000008
  },
  "expected_outputs": {
    "reaction_left_N": 30000,
    "reaction_right_N": 30000,
    "Mend_Nm": 30000,
    "Mmid_Nm": 15000,
    "delta_max_standard_m": 0.10546875,
    "delta_max_as_written_m": 0.02109375
  },
  "working": "Reactions: wL/2 = 10000×6/2 = 30000 N each. End moment: wL²/12 = 10000×6²/12 = 10000×36/12 = 30000 N·m. Midspan moment: wL²/24 = 10000×36/24 = 15000 N·m. EI = 200000000000×0.000008 = 1600000 N·m². Correct deflection: 5wL⁴/(384EI) = 5×10000×6⁴/(384×1600000) = 5×10000×1296/614400000 = 64800000/614400000 = 0.10546875 m. Specified deflection: wL⁴/(384EI) = 10000×1296/614400000 = 0.02109375 m."
}

Other records

Sources and evidence

These pointers bind the page to evidence. They do not grant authority or collapse verification into deployment.

• VERIFIED_LEDGER.json
• evidence-tranche2/tranche2-results.json
• STRESS_TEST_CORRECTIONS_APPLIED.json