RESPONSE OF REPAIRED FUSE BEAMS TO DYNAMIC TESTING

Abstract eng:
Controlled energy distribution is desirable for structures subjected to severe earthquakes. EC8[1] prescribes (for steel structures) that reduced beam sections may behave like a fuse that protects beam-to-column connections against early fracture (cl. B.S.3.), provided that they can develop the minimum rotations specified. Unlike common steel structures, innovative types of seismic resistant steel frames have been proposed, with dissipative fuses, where only damage will occur. Fuses are designed to be easily replaced. They usually consist of steel hollow sections. In the present paper, used hollow beams, that had suffered strength degradation of more than 50% were filled with cement based repair mortar (fcd =35 MPa), forming concrete filled composite beams (CFCBs) and were retested, without any other kind of repair. CFCBs are reported to have demonstrated higher axial load capacity, better ductility performance, larger energy absorption capacity and lower strength degradation than conventional reinforced concrete and steel hollow section columns. This became apparent by the results or the tests achieved by the experiments; bearing capacity of fuse beam was practically restored to its initial value when the damaged side of the initial beam was subjected to tension, while it increased to about 2.5 times its initial value, when the damaged side is subjected to compression. Increase of energy dissipation per loading cycle was also remarkable (increase about 150%). Calculation of the stiffness of the fuse beam is performed, as it varies with the imposed displacement. Its effect on the eigenperiod of the main structure is discussed. The deformation limits that the cement based repair mortar has reached are calculated. Ideas for further research on the subject are proposed.

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