universal beams amp columns channels ub beam beamclamp mb 250x125x25 7 continental steel 250 ub31 steel south auckland north ub gb t 11263 2017 cross section h 250x125x29 6 jis g 3192 arbed h 250x125x29 6 jis g 3192 arbed ub gb t 11263 2017 cross section 250 ub column dimensions fast delivery