# Flexural and Shear Performance of Prestressed Composite Slabs with Inverted Multi-Ribs
## 2 Experimental Program  
### Test Specimens  
Table 1 and Figure 2 show the details of the test specimens. A total of six specimens, one PC unit flexural specimen, one PC flexural specimen with cast-in-place concrete two PC unit shear specimens, and two PC shear specimens with cast-in-place concrete, were fabricated to evaluate the structural performance of the JAS. The width (\(b\)) and length (\(L\)) of all specimens were 1100 mm and 7200 mm, respectively, and six prestressing strands with a diameter of 15.2 mm were placed on the tension side of the specimens. In addition, the N-type lattice reinforcement with a diameter of 10 mm and a spacing of 200 mm was placed in inverted multi ribs. The PC unit flexural and shear specimens were named UF(Unit-Flexural) and US(Unit-Shear), and the flexural and shear specimens with cast-in-place concrete were named CF(Composite-Flexural) and CS(Composite-Shear), respectively. Since the JAS is manufactured through the pretension method, a transfer length zone exists, and the stress of the strands in this region is smaller than the effective prestress (\(f_{ce}\)). Therefore, for the US and CS specimens, shear tests were conducted in the transfer length zone and the strain plateau zone, respectively, as shown in Figure 3. To distinguish between the test specimens, 't' and 'f' were added to each of the specimen names. Here, the USf and CSf specimens were additionally strengthened with eight 19 mm diameter rebars on the tension side, in order to avoid flexural failure and to induce shear failure. The magnitude of the effective prestress (\(f_{se}\)) introduced in the specimen was 61% of the ultimate strength (\(f_{pu}\)) of the tendon. The concrete compressive strength (\(f_{c}\),\(\prime\)) of the PC unit specimens was 27.0 MPa, and the PC compressive strength in the composite specimens was 36.0 MPa. In addition, the compressive strengths of the cast-in-place concrete were 18.5 and 21.3 MPa, respectively. It is noted that the designed compressive strengths of PC and cast-in-place concrete were 40 and 30 MPa, respectively; however, the compressive strengths were found to be smaller than the designed compressive strengths because the outdoor air temperature was below zero degree Celsius during the fabrication of the specimens [15].  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  
* Tensile strength of the prestressing strands (\(f_{m}\)) was 1936 MPa. ** Yield strengths of the tensile reinforcement (\(f_{y}\)) and stirru (\(f_{xy}\)) were 503 and 406 MPa, respectively. ** Notations: \(h\): member height, \(d_{s}\): effective depth, \(A_{p}\): sectional area of strands, \(A_{s}\): sectional area of tensile reinforcement,\(f_{c}\): compressive strength of concrete.  
\end{table}
Table 1: Details of the test specimens.  
Figure 2: Cont.  
As shown in Figure 2, in the UF specimen, strain gauges were attached to the strands on the tension side and concrete at the extreme compression fiber, whereas they were attached to the strands on the tension side and compression reinforcement in the CF specimen. Strain distributions in cross-sections according to loads were then measured in detail. For shear specimens, the shear contributions of the stirrups were measured by attaching gauges to the lattice bars placed in the test region.