01-27-2008, 04:47 AM
Bullwinkle is correct that unreinforced masonry is unsafe and that steel is absolutely necessary. He is also correct on the lifespan of stick built builings here as being about 30 years (33 years by some federal statistics I've read, 40 years by others).
I sell and use a hybrid concrete system called Rastra. It was developed in Germany about 1970. I participated in a pentagon funded study with Naval engineering in which the Navy engineers explained that concrete is generally accepted as a 100 yr. material. Because of the permanent insulating form used in the Rastra system they gave it a 200+ year projected lifespan.
Steel: Concrete has massive compressive strength. Steel rebar provides tensile strength. Steel can rust (the 100 yr. life span) and can be acquired with coatings to extend the lifespan.
Bad workmanship in either wood, steel or concrete constuction is the biggist risk in the projected safety and lifespan. Steel can and will rust. Wood can and will rot faster than steel can and will rust.
As for seismic (earthquake) considerations.... U.C. Irvine has a seismic rack which simulates earthquake forces. At the tests I was involved in they were looking to establish the level of force to compromise wood frame (2x4 w/ plywood shearwall) and the Ratsra concrete system. They were also looking to determine if, at failure, the two systems failed catastrophically or gradually. Gradual failure implies you might have time to evacuate the building.
Wood frame experienced a catastrophic failure at 9 kps of lateral force. Rastra experienced a gradual failure at 84 kps of lateral force.
Dollar for dollar, as a master carpenter myself, I came to the determination that wood frame provides the least value for the construction dollar. The systems I sell, while superior, are still man made and eventually nature will always reign supreme.
Everyone makes their own choices. Thanks for asking.
I sell and use a hybrid concrete system called Rastra. It was developed in Germany about 1970. I participated in a pentagon funded study with Naval engineering in which the Navy engineers explained that concrete is generally accepted as a 100 yr. material. Because of the permanent insulating form used in the Rastra system they gave it a 200+ year projected lifespan.
Steel: Concrete has massive compressive strength. Steel rebar provides tensile strength. Steel can rust (the 100 yr. life span) and can be acquired with coatings to extend the lifespan.
Bad workmanship in either wood, steel or concrete constuction is the biggist risk in the projected safety and lifespan. Steel can and will rust. Wood can and will rot faster than steel can and will rust.
As for seismic (earthquake) considerations.... U.C. Irvine has a seismic rack which simulates earthquake forces. At the tests I was involved in they were looking to establish the level of force to compromise wood frame (2x4 w/ plywood shearwall) and the Ratsra concrete system. They were also looking to determine if, at failure, the two systems failed catastrophically or gradually. Gradual failure implies you might have time to evacuate the building.
Wood frame experienced a catastrophic failure at 9 kps of lateral force. Rastra experienced a gradual failure at 84 kps of lateral force.
Dollar for dollar, as a master carpenter myself, I came to the determination that wood frame provides the least value for the construction dollar. The systems I sell, while superior, are still man made and eventually nature will always reign supreme.
Everyone makes their own choices. Thanks for asking.
Assume the best and ask questions.
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