Structural Engineering & Statics
where the load goes
Concept

Storey drift — where it appears

2 essays name this object, across one field. What follows is each of them, and the objects they name alongside it.
wall 146 mmframe 140 mmtogether 58 mm20 storeys at 3.5 m · 40 kN per floor

How a tall building stands still

A shear wall bends and a framed tube shears, and the two deflected shapes are the wrong way up for each other. Tie them together at every floor and the pair is stiffer than the sum of their stiffnesses — because near the base the wall holds the frame back and near the top the frame holds the wall.

structures · lateral system centre of masscentre of rigidity1000 kNwest wall500 kN direct+ 39 torsional= 539 kNeast wall500 kN direct+ 39 torsional= 539 kNsouth wall0 kN direct− 19 torsional= 19 kNnorth wall0 kN direct+ 19 torsional= 19 kNcentre of rigidity at x = 15.00 m, y = 9.00 mtorsional radius r = 17.02 m against a plan radius of 10.10 mtorsionally stiff by the usual criterion

The corner that moves most

A lateral force is shared out in proportion to stiffness only if it passes through the centre of rigidity, which is not the centre of the plan and not the centre of mass. The distance between the two is a torque, and the wall that pays for it is the one furthest away and carrying least.

structures · plan torsion

Named alongside it

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

Lateral systemShear wallAccidental eccentricityCentre of rigidityDiaphragmEccentricityIndeterminacyInstantaneous centreInteractionLoad sharingOutriggerPlan torsion

All concepts