Experimental and numerical study of hollow core slabs strengthened with mounted steel bars and prestressed steel wire ropes

Hollow core slabs are widely used in prefabricated buildings either as slab elements or bridge decks because of their economic benefits. However, little attention has been given to developing strengthening techniques that are especially suitable for hollow core slabs to recover or improve the original serviceability and load carrying capacity. In this study, two novel techniques for strengthening hollow core slabs with mounted steel bars and prestressed steel wire ropes (P-SWRs) were proposed. Six slab specimens were tested to failure under a four-point bending configuration, and the strengthening effects of the mounted steel bars and P-SWRs on the hollow core slab performance were studied. The experimental results indicated that the steel bars mounted in the cores were capable of enhancing the flexural performance of the hollow slabs. The prestressing technique and anchorages developed in this paper could be used to feasibly and easily prestress the steel wire ropes. P-SWRs were found to be more efficient in improving cracking load than mounted steel bars because of the prestress in P-SWRs. External P-SWRs were better at improving the cracking load, yield load and precracking stiffness compared with internal P-SWRs. The simultaneous use of both internal and external P-SWRs obtained the highest flexural capacity. A three-dimensional finite element (FE) model was developed incorporating the smeared-crack model for concrete and elastic-linear strain hardening model for steel. The validity of the FE model was verified through comparisons with experimental results. Thus, this study provides both experimental evidence and finite element model for the application of the proposed strengthening techniques for hollow core slabs.