# Fatigue Testing of Shear Reinforcement in Prestressed Concrete T-Beams of Bridges
## 2 Experimental Investigations
### Test Setup and Test Procedure
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Beam No.**} & **Age** & \(f_{\text{cm,cyl}}\) & \(f_{\text{cm,sp}}\) & \(\text{E}_{\text{c}}\) **Modulus** & \(V_{\text{max}}\) & \(V_{\text{min}}\) & **Cycles**\(N_{\text{i}}\) & \(\Sigma\) **N\({}_{\text{i}}\)** \\ \cline{2-10}  & **(day)** & **(N/mm2)** & **(N/mm2)** & **(N/mm2)** & **(kN)** & **(kN)** & **(\(10^{3}\))** & **(\(10^{4}\))** \\ \hline T-22-1a & 26 (S) & 42.9 & 3 & 25,900 & 217 & - & 0.001 & 0.001 & initial crack \\  & - & - & - & - & 238.7 & 98.8 & 7,396 & 7,396 & stopped \\  & 62 (E) & 44.6 & 3.6 & 25,900 & 617 & - & 0.001 & 7,396 & residual \\ \hline T-22-2a & 42 (S) & 41.3 & 2.9 & 25,600 & 192.2 & - & 0.001 & 0.001 & initial crack \\  & - & - & - & - & 238.7 & 63.7 & 1,496 & 1,496 & cyclic fail. \\ T-22-2b & 69 (E) & 41 & 3.1 & 25,100 & 238.7 & 63.7 & 1,697 & 3,193 & cyclic fail. \\ \hline T-33-1a & 65 (S) & 46.6 & 3.6 & 28,500 & 197.5 & - & 0.001 & 0.001 & initial crack \\  & - & - & - & - & 238.9 & 55.1 & 4,300 & 4,300 & no failure \\  & 111 (E) & 47.5 & 3.3 & - & 282.2 & 98.4 & 2,075 & 6,375 & cyclic fail. \\ \hline T-33-2a & 53 (S) & 45.2 & 3.7 & 26,700 & 202.2 & - & 0.001 & 0.001 & initial crack \\  & - & - & - & - & 282.1 & 53.3 & 1,071 & 1,071 & cyclic fail. \\ T-33-2b & 67 (E) & 45 & 3.5 & 26,800 & 282.1 & 53.3 & 301 & 1,372 & cyclic fail. \\ \hline T-33-3a & 27 (S) & 43.8 & 3.2 & 26,300 & 232.2 & - & 0.001 & 0.001 & initial crack \\  & - & - & - & - & 355.7 & 171.9 & 1,291 & 1,291 & no failure \\ T-33-3b & 47 (E) & 45.8 & 3.4 & 26,800 & 355.7 & 171.9 & 618 & 1,909 & cyclic fail. \\ \hline T-33-4a & 14 (S) & 43.9 & 3.1 & 27,600 & 217.2 & - & 0.001 & 0.001 & initial crack \\  & 31 (E) & 44.3 & 3.4 & 27,600 & 327.2 & 98.4 & 1,863 & 1,863 & cyclic fail. \\ \hline T-67-1a & 18 (S) & 45.5 & 3.6 & 26,800 & 252.2 & - & 0.001 & 0.001 & initial crack \\  & 68 (E) & - & 3 & - & 378.2 & 73.7 & 3,112 & 3,112 & cyclic fail. \\ \hline T-67-2a & 50 (S) & 41.9 & 3.7 & 26,200 & 252.2 & - & 0.001 & 0.001 & initial crack \\  & 77 (E) & - & - & - & 429.7 & 124.7 & 2,032 & 2,032 & cyclic fail. \\ \hline T-67-3a & 14 (S) & 39.8 & 3.3 & 25,600 & 227.7 & - & 0.001 & 0.001 & initial crack \\  & 34 (E) & 42.7 & 3.7 & 26,500 & 429.7 & 49.6 & 1,191 & 1,191 & cyclic fail. \\ \hline T-67-4a & 19 (S) & 32.4 & 2.8 & 22,100 & 267.2 & - & 0.001 & 0.001 & initial crack \\  & 29 (E) & 35.2 & - & 23,200 & 482.2 & 102.1 & 0,747 & 0,747 & cyclic fail. \\ \hline \hline \end{tabular} \(f_{\text{cm,cyl}}\) = Mean value of concrete cylinder compressive strength; \(f_{\text{cm,cyl}}\) = Mean splitting tensile strength of concrete; \(V_{\text{max}}\) = upper cyclic shear force; \(V_{\text{min}}\) = lower cyclic shear force; cycles \(N_{\text{i}}\) = number of load cycles of this test phase; \(\Sigma\) \(N_{\text{i}}\) = Sum of load cycles up to this phase; (S) = test start; (E) = test end; initial crack = initial shear cracks due to static preloading; no failure = no shear failure of beam; stopped = stop of cyclic load; cyclic fail = cyclic shear failure; residual = residual static shear strength.  
\end{table} 
Table 2: Concrete strength (mean values), load combinations, load cycles, and failure types. consisting of stirrups and concrete struts. Afterwards, the planned cyclic loading with upper shear force \(V_{\text{max}}\) and lower shear force \(V_{\text{min}}\) (Table 2) was applied until a cyclic shear failure in one shear span occurred or the cyclic loading was stopped after a large number of cycles. Depending on the load amplitude (\(V_{\text{max}}\)-\(V_{\text{min}}\)) and the deformation caused by crack growth and thereof induced reduction in stiffness, the beams were tested at a frequency between 0.5 Hz and 3.0 Hz. All tests were performed force controlled. This guaranteed that the planned cyclic loads, according to Table 2 were applied, even if the stiffness of the beam decreased. The first part of cyclic testing was four-point bending, which is indicated by \"a\" in the beam numbering (Table 2).