This simulator follows vertical load and overturning moment from a column through a spread footing into a compression-only soil interface, letting you explore load eccentricity, loss of soil contact and a simplified elastic Winkler soil-spring response in real time.
• A real-time 3D cutaway workbench with a column pier and load head, a rigid spread footing with sectioned reinforcement, a layered soil cutaway with independent vertical Winkler springs, bearing-pressure contact strips, a load-resultant and middle-third reference marker, settlement/rotation gauges, and a horizontal-demand versus friction-capacity comparison, with home view, focus-selected-part, toggleable full enclosure, exploded view, auto-rotate, expand and show/hide labels controls. • Adjustable footing width across eccentricity (1.5-4 m), footing length perpendicular to section (2-5 m), column vertical load (200-2000 kN), centered footing/dead load (50-300 kN), column-load offset from base center (-0.6 to +0.6 m), horizontal force at the column head (-300 to +300 kN), horizontal-force height above base (2-6 m), illustrative Winkler spring modulus (10-100 MN/m³), selected pressure comparison threshold (100-500 kPa), and illustrative base friction coefficient (0.2-0.8). • Loading actions: ramp applied loads, apply full loads, and release applied loads. • A Curves & measurements tab with contact-pressure-history and compression-contact-history charts, the underlying model equations (N, M, eccentricity e, full-contact and partial-contact pressure formulas, Winkler spring relation and friction comparison) and snapshot readouts (total vertical load, moment about base center, resultant eccentricity, middle-third boundary, compression contact width/percentage, mean and peak/minimum contact pressure, peak spring compression, center settlement, footing rotation, bearing ratio, horizontal demand, friction capacity, sliding ratio). • An Experiments tab with four guided fixtures (centered column load, partial contact, reversed moment, resultant beyond the base) 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 combining vertical load and moment, using the middle third correctly, distinguishing contact from bearing capacity, and interpreting the spring-bed motion, a knowledge-check quiz with reset, and a written model-scope statement with a technical reference link.
The resultant eccentricity is e = M/N, where M combines the column-load offset and any horizontal-force overturning moment. When |e| stays within the middle third (|e| ≤ B/6), the model predicts a full-contact linear trapezoidal pressure distribution, q(x) = N/(BL)[1 + 12ex/B²]. Once |e| exceeds B/6 but stays below B/2, the soil can no longer carry tension, so the simulator switches to a shorter triangular compression block of width c = 3(B/2 − |e|) with qmax = 2N/(Lc).
If the eccentricity reaches or exceeds B/2, no compression-only equilibrium exists at all, and the simulator reports no pressure or settlement result — a clear signal that the load path has moved entirely off the footing.
A pressure distribution that satisfies equilibrium does not by itself prove the soil or footing has adequate bearing capacity — the selected pressure threshold in this lab is only an educational comparison input, not a geotechnical design result. Likewise, the illustrative friction bound |H| ≤ μN flags whether horizontal demand may exceed a simple friction estimate, without modeling sliding displacement, passive soil resistance or anchorage.
This is a rigid rectangular footing model with one-axis eccentricity, linear pressure blocks and independent compression-only Winkler springs. It excludes ultimate geotechnical bearing capacity calculations, consolidation, soil continuum interaction, structural footing/rebar design, groundwater effects, passive resistance and sliding dynamics; ramp and release actions scale the column and horizontal loads while the centered dead load stays constant.
No. The foundation model uses compression-only vertical contact — if the full-contact equation would predict a negative pressure anywhere, the simulator instead switches to a partial-contact calculation with soil separation over part of the base.
The middle third is the region |e| ≤ B/6 around the footing center. Inside it, the full base stays in compression with a linear pressure distribution; outside it, the soil separates over part of the footing and a shorter triangular compression block develops instead.
No. The lab omits ultimate bearing-capacity factors, structural footing and reinforcement design, site characterization and several settlement mechanisms. The selected threshold is only an educational comparison input.
At or beyond half the footing width, no compression-only equilibrium is mathematically available, so the simulator reports no valid pressure or settlement result — the resultant has effectively moved off the footing base.