Structural Engineering & Statics
where the load goes
Concept

Expansion joint — where it appears

A deliberate discontinuity provided so that a structure can change length without generating force. It converts an imposed deformation into a movement, which is the only way of dealing with one that does not involve strength.

Named by 2 essays across one field — each of them below, with the objects they name alongside it.

free at one end10.8 mmno stressheld at both ends75.6 MPaheld by a spring of 100 kN/mm53.2 MPaE·α·ΔT = 210000 × 12×10⁻⁶ × 30 = 75.6 MPa, at every length

The movement nobody applied

A temperature change is the only load in this collection that a structure can decline. Let it move and it produces a movement with no stress; hold it and it produces a stress with no movement — and that stress contains no length, no area and no second moment, so a bracket and a bridge girder carry exactly the same one.

deflection · thermal movement 012345678-0.03-0.02-0.0100.010.020.03along the span (m)deflection, each scaled to the same mid-span drop3.20 · a uniform load3.00 · a load at mid-span2.99 · a triangular load3.60 · a load on half the spanθ = C · δ/L, and the same δ gives 1.21× the rotation across these

The angle nobody limits

Every serviceability rule in this collection limits a displacement. What a bearing, a joint and a cladding gap actually have to accommodate is an angle — and the angle is locked to the displacement by a coefficient that contains no material, no section and no span.

deflection · end rotation

Named alongside it

The objects these essays reach for when they reach for this one.

RestraintServiceabilityBearingBucklingCladdingCompatibilityCurvatureDeflectionEnd rotationImposed deformationIndeterminacyJoint stiffness

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