Hi! My name is Daniela and I'm a Civil Engineering student in Brazil. My graduation is almost over and I'm writing my final essay to get my degree. I want to write about american/international structure designs, because here in Brazil we build houses in a different way. So, I wanted your help. I'm sorry in advance for any typos, but I'll try to explain what I'm thinking so you guys can help me. I've done some research and I've found out that most of the houses there are build in wood frame, but I've searched some YouTube videos (like this one: https://www.youtube.com/watch?v=1TXpiv4XWME&t=...) and they show two-storey houses with 2 different structure design: the first floor is made of concrete blocks and the second is all wood frame. What I wanted to know, if any of you can please please answer me: why does the bottom storey is made of concrete? Is it because of earthquakes? Is there a name for those mixed structure designs? Is there a book or any article about the calculation of these structures made of concrete and wood? Because my idea is to show how to calculate a structure like that. Anyways, I hope you can help me! Thanks in advance! :)