| Seismic design of buildings requires the use of design parameters that are specified in the codes. The R factor is one of these. Although these parameters have a great impact on the building designs, they were developed over time based on tradition, engineering judgment and observations of damage. Recently a rational method for assigning R values for new structural systems was proposed which utilizes subassembly and component tests, shake table tests and advanced analysis. The procedure results in a 90% confidence of satisfying the Collapse Prevention performance level for a seismic hazard of 2% probability of exceedance in 50 years. This thesis describes the application of this new rational procedure to cold-formed steel (CFS) braced frames that are popular for military barracks, low rise hotels and other structures.; Braced frame component tests and shake table tests of a full-scale two-story one bay structure were conducted at the U.S. Army Construction Engineering Research Lab in Champaign, Illinois. These tests were used to verify analytical modeling of the CFS braced frame system and to establish the maximum drift capacity based on brace fracture.; A series of 2-, 4- and 6-story buildings were designed and evaluated using the proposed method. It was found that 4- and 6-story buildings design and configured based on current provisions using an R factor of 4 did not satisfy the design objective. This resulted mainly from excessive drift demands in the top stories. The buildings were redesigned using an R of 3 and an R of 2, but the buildings were still inadequate. To reduce the excessive drift demand in the top story, the original buildings were reconfigured by using the same braces in even numbered stories that were used in the story below. This resulted in buildings that satisfied the design objective in all cases. Next, the original buildings were reconfigured by making only the top stories stiffer and stronger. These buildings also satisfied the design objectives. Major observations and conclusions are given. Recommendations for future research are presented. |
