Description

A full-scale buckling-restrained brace (BRB) under a standard qualification cyclic loading protocol.

Reference

Xu (2016), full-scale BRB component test 7.

Model

vfopro's buckling-restrained brace element, sized to the specimen's core cross-sectional area, with its steel hardening and strength-adjustment parameters calibrated to the specimen's measured hysteresis, connecting two nodes along the brace's work-point length. The brace is driven through the specimen's own qualification cyclic protocol under displacement control.

Loading protocol applied

Response comparison

Full loading history, physical test vs. vfopro simulation.

Comparison

Conclusion

All four checks are within the 10% criterion: elastic stiffness is about 6% low, while peak tension, peak compression and the cumulative dissipated energy over the full loading history are each within about 1.5% of the test. Compared band by band, the peak tension is within about 5% of the test at every displacement level and the peak compression within about 4%. The chart shows the main features of the test reproduced: the compression force keeps rising with deformation (about 490 kip at small amplitudes to about 566 kip at the largest) and the loops match in width and shape. The brace material’s hardening parameters and its yield strength and strength-adjustment factors (ω and β, listed above) were calibrated together to this specimen’s measured hysteresis. The calibrated yield strength (about 45 ksi) is higher than the coupon value reported for the specimen (40.2 ksi), so it should be read as an effective value that absorbs the material’s overstrength. The stiffness difference reflects the assumed effective length of the yielding core. The protocol above is the one actually recorded in the test: two cycles at each amplitude. Other brace specimens will need their own values.