Structural Engineering & Statics
where the load goes
Concept

Restraint — where it appears

Anything preventing a movement a structure would otherwise make, which converts that movement into a force nobody applied.

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

1 d10 d100 d2.7 yr27 yr0246810time since the strain was imposedstress, N/mm²E × strain: 9.6tensile strength: 3.5what is left: 2.32the one-line shortcut at χ = 0.8: 3.31

The strain that was imposed, and the stress that leaked away

Multiply a restrained shrinkage strain by the modulus and the answer is three times the tensile strength — which predicts that every restrained concrete member ever cast has cracked. Most have not, and the reason is that the material creeps while it is being stressed.

materials · relaxation 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

Named alongside it

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

Ageing coefficientBucklingCrackingCreepExpansion jointImposed deformationIndeterminacyPrestressRelaxationSelf stressServiceabilityShrinkage

All concepts