Lessons · Engineering · Following a load to the ground
Every load reaches the ground or the building falls down
A load path is the continuous route a force takes from where it is applied to the foundation: slab to beam to column to pad to soil. Every element on the route carries everything above it. A path that stops somewhere is not a design, it is a collapse waiting for the load.
Hone is a place to practise a career, one idea a day. This is one of its lessons, written out in full and free to read without an account.
In beta. This lesson was written for Hone and has not yet been checked by a licensed engineer. Practice material, not professional advice. What that means.
What it is for
The commonest serious error in a small structure is not a miscalculated member. It is a beam that lands on nothing -- supported by a wall that was removed, or by a slab that was never designed to take a point load -- because nobody traced the route all the way down.
How to think about it
Start at the load and walk down, naming every element in turn and saying what it hands the load to next. Stop only at soil. If you cannot name the next element, you have found the problem, and you have found it on paper.
Worked example
Load on slab.Distributed over an area.
Slab spans to beams.Now a line load on each beam.
Beams land on columns.Now a point load at each column head.
Columns to pads, pads to soil.Spread until the pressure is one the soil will take.
Your turn
Name the last thing in any complete load path.
A load path ends only at the
Solve one, graded on the server
The trap
Checking members one at a time without tracing the route. Each can be adequate while the route between two of them does not exist.