Impact of Beam Strength on Seismic Performance of Chevron Concentrically Braced Frames
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Special concentrically braced frames (SCBFs) are a popular choice for lateral force resisting systems in regions of high seismicity. SCBFs with braces oriented in a chevron (or inverted V) configuration are often preferred for their architectural advantages. Current design provisions require the beam in chevron SCBFs to develop the unbalanced load resulting from one brace at its maximum tensile capacity and the other brace at a significantly degraded compressive capacity. This results in large, expensive beam sections in chevron SCBFs and as a result the popularity of this system has declined. Very little research has been done to support the current beam strength provisions, and several studies have indicated that beams that do not meet this requirement still allow the system to achieve adequate strength and ductility. The objective of this research is to systematically evaluate the effect of beam strength on the seismic performance of chevron SCBFs. Three full-scale frames were tested under a quasi-static cyclic displacement history to achieve this objective – one with a beam that met current strength provisions and two with beams weaker than currently required. The results show that chevron SCBFs with yielding beams achieve somewhat smaller lateral resistance but increased ductility and energy dissipation compared to frames that meet current beam strength requirements.
- Civil engineering