This simulator runs two identical beam benches side by side under the same centered point load and uniform load, changing only the end restraint, so you can watch end rotation, hogging support moments and midspan deflection diverge as fixity increases.
• A real-time 3D cutaway workbench with a front simply-supported beam (pin and roller), a rear beam with fixed-end blocks or rotational-spring cartridges, shared central point-load and full-span uniform-load hardware, end-angle indicators, aligned inspection slices on both beams, and a dual displacement-gauge comparison console, with home view, focus-selected-part, toggleable full enclosure, exploded view, auto-rotate, expand and show/hide labels controls. • Adjustable common span (2-10 m), centered point load (0-100 kN), uniform load (0-20 kN/m), section width (100-400 mm) and depth (150-600 mm), elastic modulus (70-210 GPa), rear-bench end restraint (ideal fixed-fixed or equal rotational springs), rotational spring stiffness at each end (0.1-100 MN·m/rad), and a common inspection coordinate (0-100% of span). • Loading actions: ramp applied loads, apply full loads, and release applied loads. • A Curves & measurements tab with bending-moment-comparison and midpoint-deflection-history charts, the underlying model equations (reactions, ideal fixed-end moment, rotational-spring fixity fraction, restrained moment/deflection formulas and standard ratios) and snapshot readouts (reaction, simple and restrained midspan moment, restrained end moment, simple and restrained midpoint deflection, deflection reduction percentage, simple and restrained end rotation, fixity fraction, rear-bench section moment and shear). • An Experiments tab with four guided fixtures (uniform loading only, centered point load only, flexible end connections, increased section depth) and a model verification bench that runs independent deterministic checks against a fresh model without disturbing your live trial, plus a timestamped event log and a copyable trial report. • A Learn & assess tab with guided lessons on controlled comparison, tracking redistributed moment, comparing deflection versus connection demand, and relaxing the restraint, a knowledge-check quiz with reset, and a written model-scope statement with a technical reference link.
Both beams share identical span, EI and applied loads, so any difference you see comes purely from end restraint. Fixing the ends develops negative (hogging) support moments that reduce the positive midspan moment: under a uniform load, the peak midspan moment drops from wL²/8 (simply supported) to wL²/24 (ideal fixed-fixed), and the ideal fixed-fixed midpoint deflection is one-fifth of the simply-supported value for a uniform load, and one-quarter for a centered point load.
The equal rotational-spring option models an intermediate condition using a fixity fraction f = β/(1+β) where β = kθL/(2EI) — as spring stiffness increases toward rigid, the rear beam's response approaches the ideal fixed-fixed case; as it decreases, the response approaches the simply-supported case.
A common misconception the lab is built to correct: fixing the ends does not eliminate bending moment in the beam — it redistributes part of it into support (hogging) moments that the connections must now carry. The two beams in this comparison always show equal vertical reactions because the loading and support geometry are symmetric, which is a property of this specific case, not a general rule for asymmetric fixed-beam loading.
This is a symmetric, linear-elastic, small-deformation Euler-Bernoulli model applied to two identical prismatic beams with zero support settlement. It excludes asymmetric load solutions, plastic hinges, shear deformation and connection capacity design; the rotational springs are linear and equal at both ends, and both beams use a common displayed deformation gain for a fair visual comparison.
No — fixed supports create support (hogging) moments and redistribute bending rather than eliminating it. The beam still bends; the negative moment at the fixed ends simply reduces the positive moment at midspan compared with a simply supported beam.
For the ideal fixed-fixed case, the midpoint deflection is one-fifth of the simply supported value under a uniform load, and one-quarter of the simply supported value under a centered point load — with identical span, EI and applied load in both cases.
Because the loading and support geometry in this comparison are symmetric — both beams share the same span, the same centered point load and the same full-span uniform load. This is a property of the symmetric case shown here, not a general rule that holds for asymmetric fixed-beam loading.
Only in the limit of very high spring stiffness. The lab models the spring case with a fixity fraction f = β/(1+β); as stiffness kθ increases, β grows and f approaches 1 (the ideal fixed value), but a finite spring always sits between the simply supported and ideal fixed responses.