Anti-progressive collapse performance of prefabricated RC column-steel beam substructure with unbounded prestressed tendons

The anti-progressive collapse experiment on the prefabricated reinforced concrete column-steel beam (short title: PRCS) substructure with top-seat angles was conducted using the quasi-static loading method. Experimental results showed that the top-seat angle started the first yield and was followed by fractures, and the test finally ended with the tearing of the web at the connection part. The top-seat angle is the weakest and earliest plastic-damage part. On this basis, unbonded prestressed tendons were used instead of top-seat angles to enhance the anti-progressive collapse performance. The finite element modeling method verified by the experimental results was to analyze the anti-progressive collapse performance of the PRCS substructure with unbonded prestressed tendons (short title: UPT-PRCS). The results showed that the use of unbonded prestressed tendons instead of top-seat angles can effectively enhance the initial resistance and the ultimate bearing capacity, prolong the catenary action, and enhance the anti-progressive collapse performance. In addition, the load-bearing mechanism of the UPT-PRCS beam–column substructure was analyzed theoretically, and a load bearing capacity calculation formula suitable for progressive collapse was deduced. The theoretically calculated load-bearing capacities were compared with those computed from the finite element method, with the largest difference of 3.7%.