CivilLab
Interactive simulators for civil engineering fundamentals. Move a load, rotate a stress state, and watch the theory answer. Built for the University of Moratuwa syllabus, Semesters 1 to 7, as a companion suite to Water Lab.
Live now
Beam SFD & BMD Studio
Drag point loads, UDLs and applied moments along a beam. Reactions, the shear force diagram and the bending moment diagram redraw as you move.
OpenMohr's Circle for Stress
Set a plane stress state and rotate the cutting plane. The element and the circle move together, with the 2θ rule shown live.
OpenBending Stress Explorer
Build a section, apply a moment, and watch the linear stress distribution with the neutral axis, section modulus and fibre stresses.
OpenShear Stress Distribution
τ = VQ/(Ib) through the depth of any section. See why the web carries the shear and where the profile jumps.
OpenTorsion Simulator
Solid, hollow and tapered circular shafts. Twist, the radial stress distribution, and why hollow shafts are efficient.
OpenBeam Deflection Visualiser
The deflected shape by double integration of M/EI. Drag loads, change EI, and hover for slope and deflection at any section.
OpenColumn Buckling & Struts
Euler buckling with all four end conditions, the mode shape, and the stress against slenderness design curve.
OpenTruss Solver
Pratt, Howe and Warren trusses solved by the method of joints. Members coloured by tension or compression, click a node to load it.
OpenInfluence Lines
A unit load moves; the section stays. Watch the influence line for reactions, shear or moment build, with overhangs showing negative regions.
OpenSoil Phase Diagram
The three phase block to scale. Slide e, w and Gs and watch every unit weight and Se = wGs update together.
OpenMoment Distribution
Continuous beams solved by Hardy Cross. Step through each balance and carry over, watch the table build row by row and the bending moment diagram settle as it converges.
OpenPlastic Collapse Mechanisms
Plastic hinges form and the mechanism rotates. Six cases from a simply supported beam to a portal frame, with the work equation and the governing load factor.
OpenStructural Dynamics
A mass on a spring vibrating in real time with its decay envelope, or a shear building with its mode shapes animated side by side.
OpenParticle Size & Classification
Drag the grading curve or type the sieve results straight in. D10, D30 and D60 are read off the curve, the sample moves on the Casagrande chart, and the Unified group symbol is worked out step by step.
OpenMohr-Coulomb Shear Strength
Load a triaxial specimen until it shears. The total and effective circles grow towards the failure envelope, pore pressure slides them apart, and the specimen splits along the plane at 45 + φ/2. Drained, undrained and UU tests side by side.
OpenFlow Nets & Seepage
A real flow net, solved rather than sketched. Drag the cutoff deeper and watch every flow path lengthen, the discharge fall and the exit gradient ease. Uplift under a dam is drawn on its base, and the net you draw is checked against the solved field.
OpenConsolidation over Time
Watch the pore water carry the load and then hand it to the soil. Press play and the isochrones collapse as the settlement curve fills in, with t50 and t90 marked. Change the drainage and the same job takes four times as long.
OpenSlope Stability · Method of Slices
Drag the slip circle anywhere on the slope and watch the factor of safety follow. Every slice is tabulated, one has its force polygon drawn, and a search button hunts down the circle that actually governs.
OpenEarth Pressure & Retaining Wall
Build a gravity retaining wall and watch the active pressure diagram grow with depth. Add a surcharge, raise the water table, switch to Coulomb, and the three stability checks, sliding, overturning and bearing, update live with utilisation bars.
OpenShallow Foundation Bearing Capacity
Terzaghi or the general method with Hansen shape and depth factors. The Prandtl failure wedge is drawn to scale, the three capacity terms are broken down with their factor chains, and a Boussinesq profile shows how the stress decays with depth.
OpenActions & Load Combinations
Set the characteristic permanent, imposed and wind actions. See Eq 6.10 beside 6.10a and 6.10b with the three SLS combinations and the BS comparison, all from the same inputs. The psi factors update with the building category.
OpenRC Beam Designer
Design a reinforced concrete beam through four tabs: flexure with the EC2 stress block drawn to scale, variable strut angle shear, span to depth deflection check, and crack width. The BS 8110 comparison runs alongside.
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