PSI - Issue 13

Mohammed A. Al-Shuwaili et al. / Procedia Structural Integrity 13 (2018) 2024–2029

2028

5

Mohammed Al-Shuwaili et al. / Structural Integrity Procedia 00 (2018) 000 – 000

In this comparison study, shown in Fig. 5(a), previous tests conducted by Costa-Neves et al. (2013) and Zheng et al. (2016), see Fig. 5(b,c); were selected for the following reasons: Costa-Neves et al. (2013) tested un-reinforced and reinforced PSCs which is similar to this testing campaign ; Costa-Neves et al. (2013) used the POT setup and the specimen was the EC-4 sample with two-holes rib while this research employed one-hole rib embedded in BS-5 sample which is the same as Zheng et al. (2016) who tested a rib with one circular hole of 60mm but cast into(460x460x400) mm concrete slabs; Costa-Neves et al. (2013) and Zheng et al. (2016) also compared their tests results to the equations shown in Table 1, which is useful to compare the results of this paper with them also. In these equations, is the estimated shear resistance of the PSC; ′ is the concrete compressive strength; D is the diameter of the hole; n is the number of the holes; ℎ , are the height of connector and its thickness; is the cross-sectional area of transverse rebars; is the yield strength of reinforcement. is the longitudinal slab area minus the connector area; b and h are the thickness of the concrete slab and the distance from the end of the rib to the bottom of the slab respectively. The average results of a set of three POTs conducted by Zheng et al. (2016) was 425 kN while the average of the predictions, is 568 kN which makes the percentage of the difference between the test result and the mean of the predictions is 25%. Costa-Neves et al. (2013) test result of a PSC with two holes of 30mm in diameter embedded in un-reinforced concrete slab was 280 kN. The average of the estimations is 258 kN and the percentage of difference between the test value and the average of estimation is 8.5%. The second test was for the same above sample but with transverse reinforcement embedded in the slab. The test result was 398 kN and the mean of the four predictions was 332 kN. The percentage of difference between the test value and the average of predictions s in this case is 17%, as shown in Fig. 5. In this study, the difference in results of OSPOT tests and the average of predications of the four equations are for P-ds10, P- ds8 and P is about 5% which is less than the average of the other researchers, see Fig. 5.

302 100 200 300 400 500 600 700 800 (Oguejiofor et al., 1997)(1) (Medberry et al, 2002)(2) (Veríssimo , et al., 2006)(3) P-ds8 P-ds10 P Zheng et al.(2016) Costa-Neves (2013)(un-rein) 251 247 305 254 249 233 183 200 728 406 539 236 186 296 339 288

Costa-Neves(2013)(rein)

626

388

314

313

288

275

184

Shear resistance (kN)

( Ahn, et al., 2010)(4)

Fig. 5. The estimated shear resistance and the test results

4 Conclusion

The results of the OSPOT identical twins were consistent, the difference is less than 5%, and this difference in results might be related the concrete mechanical properties, the vertical casting of the three layers of concrete for each slab and its vibration. The other results which are obtained from the OSPOTs are consistent also and have shown the effect of several design parameters. Further, according to Lorenc et al. (2010) (p.4) ‘ If the strength is reached due to shear of the steel connector, then the information about its load- bearing capacity and the ductility is given’, all the reinforced rib have shown this behaviour. Since all the reinforced PSCs have failed by the shearing of the connector. Also, the results of the comparison study have shown a better consistent between the OSPTs results and the estimations offered by several numerical expression which were originally derived from the regression analysis of the POT results. Hence, the OSPOT setup might consider a more economic option to investigate the structural behaviour of the PSCs as two results can be obtained from one POT specimen which reduces the cost and time significantly. The structural analysis of the load-slip curve from the OSPOT shows the elastic part of load-slip curve, i.e. the concrete dowel shear resistance, is coinciding with the same part of the reinforced PSC and they are identical if the other design parameters are kept constant. This confirms that the concrete dowel sustain the applied load first until the fracture of the concrete after that the rebar inside the hole starts to resist the applied load. Further, by comparing the results of the one-week samples with their counterparts of 28day samples, the increase in the overall shear resistance in the 28day sample is due to the increase in the concrete dowel shear resistance. Acknowledgements The first author thanks the University of Kufa, for financial support of his PhD stud y at Loughborough University, and to Roform Product Limited for their cooperation in the fabrication of the OSPOT specimens.