Who said 桩是承压构件，设计中一般不考虑受拉的?

I am a geotechnical engineer. My daily job is doing foundation design, including shallow foundation (e.g., spread footing) and deep foundation (e.g., piles). I don't do the structure design, but I know the piles have be structurally designed for compression, tension, shear, and bending.
The pictures clearly shows the piles failed due to their structural capacity. I have to say most of 飘兄's comments are wrong. 龙坡居士兄's observation and conclusion basically are very correct.

工字钢梁can not be 用在楼房的基础上? They can be. They are just way more expensive compared to concrete piles. Depending on site conditions, sometimes steel pipe piles or H piles ( 工字钢梁), instead of concrete piles, have to be used due to hard driving is anticipated.