Fundamentals
Tributary area vs influence area
Tributary area is the floor that loads a member; influence area is the larger area whose load affects it. Here is the difference, the K_LL factor, and why it drives live load reduction.
Sam Rivera··4 min
Fundamentals
How loads transfer from a slab to beams
A slab hands its load to the beams that support it, as a uniform strip in one-way action or as triangles and trapezoids in two-way action. Here is how, with the load shapes.
Sam Rivera··5 min
Fundamentals
Area load vs line load vs point load
Loads come in three forms: area loads on slabs, line loads on walls and beams, and point loads at columns. Here is what each means, its units, and how they convert.
Sam Rivera··4 min
Load paths
Column load takedown by hand, step by step
How to take one column down by hand: tributary area per floor, load per floor, accumulate down the building, then factor. A full worked example with numbers.
Sam Rivera··5 min
Workflow & tools
Free tributary area calculator (online)
Need tributary areas without the sketch and spreadsheet? StructLoads is a free browser tool that computes them from a plan you draw, exactly and instantly.
Elena Marchetti··4 min
Fundamentals
Tributary area: edge column vs corner column
An edge column carries about half a bay; a corner column about a quarter. Here is why, with the geometry, the load ratios, and a worked comparison.
Sam Rivera··5 min
Fundamentals
How to calculate tributary area for a column
A column's tributary area is the floor region nearest to it. Here is the half-bay method, the interior, edge and corner cases, and a worked example.
Sam Rivera··5 min
Load paths
Load takedown, floor by floor: a worked example
A column reaction is just every floor above it, added up in the right order. Here is a full three-storey gravity takedown worked by hand, from slab pressures to a factored foundation load.
Elena Marchetti··8 min
Fundamentals
Dead load and live load calculator (free)
Need to turn floor build-ups and occupancy into dead and live loads fast? StructLoads is a free tool that computes them and carries them through a full load takedown.
Elena Marchetti··4 min
Load paths
Interior vs edge vs corner column loads
An interior column carries about twice an edge column and four times a corner. Here is why, the load ratios, and a worked comparison you can use as a sanity check.
Elena Marchetti··4 min
Codes & standards
LRFD vs ASD load combinations, explained
LRFD factors the loads up and the strength down; ASD keeps loads near service and limits the stress. Here is the difference, the ASCE 7 gravity sets, and a worked example.
Sam Rivera··4 min
Fundamentals
Dead load vs live load, explained
Dead load is the permanent weight of the structure; live load is the movable weight it carries. Here is the difference, typical values, and how each is factored.
Elena Marchetti··4 min