What's new
Essays arrive in groups rather than one at a time, and a group usually opens up a subject the collection had not covered before. Between one group and the next nothing changes, so a reader who has seen the most recent group has seen everything.
13 August 2026
15 essays onconnections — a subject new to the collection
The connection is not a point, and every diagram on this site says it is
Every free body drawn here has joined its members at points. Real structures fail at the joints far more often than in the members, and the reason is that a joint is exactly the region the theory behind every other page explicitly excludes.
ConnectionsThe bolt that carries more than its share
Six bolts, one hundred kilonewtons, and a worst bolt carrying fifty. The load is shared equally and the torque is not, and the second one is invisible on any drawing where the connection is a point.
ConnectionsThe force the bolt never saw applied
Pull a tee stub with a hundred kilonewtons and its bolt carries a hundred and fifty. The extra comes from the flange bending and pressing its own edge against the thing it is bolted to, and no free body of the connection as a point contains it.
ConnectionsThe metal between the holes, which comes out as a block
A bolted end connection can fail without a single bolt breaking and without the plate reaching its tensile strength anywhere. A block of metal simply comes out, bounded by two surfaces with two different strengths on them.
ConnectionsThe tear that goes diagonally, and the correction that has no derivation
Stagger the holes so that no straight line crosses more than one and the plate does not get its strength back. The tear runs at an angle instead, and the arithmetic that makes it come out right is a century-old piece of curve-fitting nobody has improved on.
ConnectionsThe hole that goes oval, and the one that tears to the edge
A bolt pressing on the side of its hole either crushes the plate in front of it or shoves a channel of metal out to the end. Which one happens is decided entirely by a distance that is usually set by a minimum in a table.
ConnectionsThe weld that is stronger across than along
The same fillet weld, the same size, the same steel, carries twenty-two per cent more when the load runs across it than along it. The factor is exactly the square root of three over the square root of two, and it comes out of the yield criterion rather than out of a test.
ConnectionsThe corner that is not the worst point
Check the point furthest from the centroid. It is the standard rule for a weld group under an eccentric load, it is exactly right for some shapes, and for others it misses the peak by sixteen per cent — or picks one of four points it cannot tell apart whose stresses differ by two thirds.
ConnectionsThe joint that carries nothing until it slips
Tighten the bolts hard enough and the plates are clamped together with a force nothing applied. The joint then carries shear by friction, the bolts are in tension and not in shear at all, and the load path has nothing in common with the joint it looks identical to.
ConnectionsThe angle that uses half of itself
Bolt an angle through one leg and the other leg is not fully working. The correction is one over a length — both halves of it are geometry, neither involves a material, and a two-bolt connection throws away a quarter of the section.
ConnectionsNeither pinned nor rigid, which is every real connection
Frame analysis offers two options for a joint and reality supplies a continuum between them. Worse, the boundaries are not properties of the connection at all — the same end plate is rigid on a short stiff beam and semi-rigid on a long slender one.
ConnectionsA joint made of springs in series
A connection's stiffness is not a property of the connection. It is the series combination of the flexibilities of everything the force passes through — so the softest component decides, and stiffening any of the others changes almost nothing.
ConnectionsThe redistribution nobody chose
A beam designed as simply supported, on connections that are not pins, has end moments the analysis never predicted and a mid-span moment smaller than it was sized for. Usually that is safe. It is never intentional, and there is one direction in which it is not safe at all.
ConnectionsMaking a moment cross a gap
A moment is not a thing that can be handed across a joint. It has to be turned into a pair of forces, carried separately, and reassembled — and the whole design is a question of how the tension is shared between bolt rows that are not equally able to take it.
ConnectionsWhere the structure meets the ground, and when the bolts start working
Push a base plate off its middle third and it lifts off the foundation. The holding-down bolts then carry exactly nothing, and go on carrying nothing until the plate has crushed the concrete underneath it.
Before that
Everything published earlier, newest first. Titles only — the cards are on the full listing.
11 August 2026
15 essays onmaterials
- The stress at which nothing in particular happens — materials
- The one number a stronger steel does not change — materials
- The property that appears in none of the equations — materials
- The section that yields from the outside in — materials
- The stress that was there before the load — materials
- Two ways to fail, and the curve between them — materials
- The section that cannot reach its own strength — materials
- What is left when the load comes off — materials
- The structure that settles down, and the one that walks — materials
- The deflection that arrives three years late — materials
- The strain that was imposed, and the stress that leaked away — materials
- The flaw that sets the strength — materials
- The hole that multiplies the stress by three — materials
- The load that never came near failing anything — materials
- The hour that is really a temperature — materials
10 August 2026
12 essays onstability and deflection
- The load that makes itself worse — stability
- The beam that fails sideways — stability
- The plate that ripples, and the width that is left — stability
- The column that was never straight — stability
- The brace that need not be strong — stability
- Stiffness is not strength, and usually it is the one that governs — deflection
- Span to the fourth, which is why spans are short — deflection
- One support too many, and what it costs to know — deflection
- One deflection, without solving everything — deflection
- The theorem that swaps the question round — deflection
- The support that moved — deflection
- The water that will not run off — deflection
7 August 2026
15 essays oninternal forces, sections and stress and stability
- After the first yield, which is not the end — internal forces
- The moment over the support, and what it buys — internal forces
- The worst place to stand — internal forces
- The moment that will not lie flat — internal forces
- The train that is worse than its heaviest axle — internal forces
- The material far from the middle does nearly all the work — sections and stress
- Bending is a pair of forces, pushing and pulling — sections and stress
- The same steel in a different shape, and a factor of forty — sections and stress
- Plane sections stay plane, and what the assumption costs — sections and stress
- The shear nobody draws — sections and stress
- The point that is not in the section — sections and stress
- When half the section has given up — sections and stress
- The section made of pieces — sections and stress
- Strong enough and still falls over — stability
- The ends decide the length that matters — stability
3 August 2026
19 essays onequilibrium, structural form and internal forces
- Everything adds to nothing, and that is the whole of statics — equilibrium
- The free body is a choice, and choosing it well is the whole skill — equilibrium
- Three forces must meet at a point, and a drawing can find it — equilibrium
- Counting the unknowns, and finding out whether statics can answer — equilibrium
- Answering one question without solving the rest — equilibrium
- The load that is spread out, and the force that replaces it — equilibrium
- The equation that is not new, and the three that are — equilibrium
- The count that does not see it — equilibrium
- The triangle that cannot fold, and everything built out of it — structural form
- The shape that carries itself, and the arch that is its reflection — structural form
- Depth is the cheapest strength there is — structural form
- The polygon that finds the shape — structural form
- The hinge put in on purpose — structural form
- The frame that leans, and what stops it — structural form
- The line that must stay inside — structural form
- The joint that is not a pin — structural form
- What a cut reveals, and why it was there all along — internal forces
- The diagram is an integral, and that is why it can be drawn by eye — internal forces
- Where to put the supports, which is not at the ends — internal forces