Study of Steel Frame Bracing System with Indirect Connection on Seismic Retrofitting of RC Frame
Date Issued
2015
Date
2015
Author(s)
Jian, Qiao-Han
Abstract
Nowadays, Taiwan has been working on researches of seismic retrofitting on existing reinforced concrete buildings. This study focuses on the retrofitting method of using steel frame bracing system with indirect connection, and suggests an effective design procedure for engineers to use. It is expected that this retrofitting method can help existing RC buildings not only increasing vertical bearing capacity and lateral strength, but also developing good deformation ability which is defined as drift ratio develop higher than 2% when 80% of maximum lateral force happened. This study focuses on the design detailing of mortar connection between steel bracing system and RC frame. The strength of mortar connection is evaluated by using design equations of anchors from ACI 318-14 and HILTI design manual. The configuration of mortar connection refers to design manual of Japan. Gathering all the design requirements, we suggest a design procedure and design specimen M16 and M20 to check the usability of proposed design method. According to the observation from test results, at same drift ratio, mortar in the connection with spiral spalled dramatically while that with square stirrups remained well. Unfortunately, an unexpected failure, which is that studs in the connection had split at weld, made the stress concentration happened at corner mortar. To avoid this kind of failure mode, we suggest that the arrangement of studs needs to be improved. Specimens, M16 and M20, have developed good ductility due to brace buckling. Specimen M16’s deformation capacity is 3.7% with the retrofitting ratio of 5, while Specimen M20’s deformation capacity is 1.88% with the retrofitting ratio of 7. In conclusion, the proposed design method can not only help engineers effectively assess the retrofitting effectiveness of steel bracing system with indirect connection applied on RC frame, but also help reaching the target of deformation capacity.
Subjects
seismic retrofit
reinforced concrete frame
steel bracing system
gusset plate
mortar connection
deformation capacity
Type
thesis
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