I just read an article here about how the larger animal is, the smaller percent of its body mass it’s able to lift. It got me thinking… Exactly how strong would a 40 meter (130 ft) human be? (assuming of course a being like this could exist withous collapsing under its own weight or whatever) I’d imagine it would weigh around 80-100 tons, but the site doesn’t state the exact ratio of muscle area to force, and besides, numbers alone wouldn’t tell me much. So… would a 40 m tall human be able to lift a bus? Stop a F15? Push over an average skyscraper?
A simplistic way to estimate mass would be to take the cube of the height ratio. If we use as a prototype a man whose height is 2 meters and whose mass is 90kg, then your 40-meter giant is 20 times the height and thus 8000 times the mass: 720,000 kg (close to 800 tons). This is enormously more than bones could support.
I don’t know if you can really answer this question without assuming that his muscles and skeletal system are considerably stronger than ours. The reason is what you referred to, the cube-square law.
Assuming a 1.8m, 180 pound human male, a 40m giant would weigh about (40/1.8)^3 = 10,974 times more, roughly 988 tons. His bones however would only have about (40/1.8)^2 = 494 times the cross-sectional area - they’re carrying more than 22 times the stress that ours are, just from standing there.
Imagine loading 4000 pounds onto your shoulders and standing up, that’s the scale of the increased load you’re looking at. Something’s gonna break and it ain’t gonna be pretty.
Similar problems with muscles and ligaments and whatnot.
So if we want the giant up and about and able to perform feats of strength we have to assume that the materials making up his body are much stronger than ours, and I don’t know what guide we can use for that. Make everything 22 times stronger? A 100 times? A jillion?
So how did the largest dinosaurs carry all that weight without their skeletal systems collapsing?
The largest dinosaur was quite a bit smaller than our hypothetical giant - 18m high and with a mass of 60,000kg. But (as the link mentions) it certainly needed some serious bones.
And more importantly, they were built differently. Scale a human up to the size of an elephant and he’d collapse, but obviously it works for the elephants.
Here’s an interesting article on The Biology of B-Movie Monsters that discusses some of the considerations of scaling up (and down) in size.
Wow, the article was a great read. 
Unfortunately, it didn’t really answer my questions about strength. So, just for kicks - let’s say the giant is a large-scale version of the comic book Wolverine, and has metal-reinforced skeleton. What happens then (apart from dying of anemia)?
Real-life human giants can be surprisingly weak, often having trouble lifting their own weight. According to the IMDB )and other sources), giant Lock Martin, who played Gort in The Day the Earth Stood Still, couldn’t pick up Patricia Neal, and they had to use wires to hold her up:
They shoulda got Andre.
Yeah, well Andre was but a wee tyke of four when they made TDtESS, and he died of health problems associated with his size, nevertheless.
Let’s simplify calculations by assuming a baseline 2 meter tall human (6’7"), weighing 100 kilos (220 lb). A 40 m human would then have 20 times the linear dimensions, 400 times the strength (which depends on cross-sectional area of the muscles), and 8000 times the weight (800,000 kilos, or 800 metric tons) of the baseline human.
The world record in weight-lifting is about 470 kg. Therefore, a scaled up human could be expected to lift no more than 188,000 kg, or 188 metric tons. This would of course be moot, since such a creature would be completly unable to lift its own body weight, and could not even rise from the ground. It would also no doubt be unable to expand its lungs, and would die within a few minutes.
Yikes! So we’re talking about a 40m, 800-ton baby!?
Your explanation, Colibri, is the first time I’ve really understood the whole “collapse under their own weight” issue with giants.
Or let’s say a B-movie “Amazing Colossal Man” who was suddenly transformed from normal size to 40 m feet tall by eating radioactive broccoli (or something). As soon as he reached his giant size he would promptly die.
Radioactive? How 50’s. In this day and age it would be genetically engineered broccoli.
Genetically engineered? What is this, 2004? Clearly it would have something to do with nano technology. Nano robots would get in and replace the weak heavy mamal bones with super strong and light carbon nano tubes.
Remember to include the standard +2 ST adjustment per size class. So if you were originally an 20 Strength Medium-Sized Orc Barbarian that turned into a Giant Orc via a spell, you would become 26 Strength.
And remember too that while it might be wondrous to have a giant’s strength, 'tis monstrous to use it like a giant.