# Fatigue Assessment of Prestressed Concrete Slab-Between-Girder Bridges
## 2 Materials and Methods
### Description of Experiments  
We built two 1:2 scale models of an existing bridge in the laboratory, which we tested monotonically, as well as under cycles of loading. Full descriptions of the first series of static tests [5; 13], first series of fatigue tests [33; 34; 35], and second series of fatigue tests [36; 37] can be found elsewhere. The description in this paper was limited to the information necessary to interpret the test results for application in assessment of the case study bridge. The first 1:2 scale model (6.4 m \(\times\) 12 m, see Figure 3) used four prestressed concrete T-girders with a center-to-center spacing of 1.8 m, length \(l\) = 10.95 m, and height \(h\) = 1.3 m; two post-tensioned crossbeams (\(b\) = 350 mm, \(h\) = 810 mm), and three transversely post-tensioned decks with \(h\) = 100 mm and \(b\) = 1050 mm between the girders. The choice of the size of the scale model and number of girders was determined as a function of the available test floor space in the laboratory. The post-tensioning of the deck was applied through prestressing bars placed in 30 ducts with a 40 mm diameter, and spaced 400 mm apart. To increase the number of experiments that could be carried out on this scale model, the middle deck was removed after testing and a new deck was cast. Therein, one segment of the new deck contained ducts of diameter 30 mm that were spaced 300 mm apart to study the influence of the duct spacing. Figure 2: Live load model 1 from NEN-EN 1991-2:2003 [1]: (**a**) elevation; (**b**) top view. Edited from Reference [12], and reprinted with permission. The second 1:2 scale model (4.6 m \(\times\) 12 m, see Figure 4) used three prestressed concrete bulb T-girders and two post-tensioned decks. The dimensions of the girders, crossbeams, and decks were similar to the dimensions for the first 1:2 scale model, with the exception of the shape of the girders (T-girders in the first scale model and bulb T-girders in the second scale model). For the second scale model, the top flange of the girders was cast in the laboratory, monolithically with the deck. The advantage of this approach was that the weight of the girders was reduced, which facilitated transportation and handling. Standard cube specimens were used to determine the concrete compressive strength for the concrete of the different casts. The results for the 28 days strength were as follows: \(f_{cm,cube}\) = 75 MPa for the original slab in setup \(1,f_{cm,cube}\) = 68 MPa for the newly cast slab in setup \(1,f_{cm,cube}\) = 81 MPa for the first cast of setup 2, and \(f_{cm,cube}\) = 79 MPa for the second cast of setup 2. Mild steel reinforcement is used for the longitudinal and transverse reinforcement in the deck slabs. In setup 1, the longitudinal reinforcement was \(\varphi\) = 6 mm at 200 mm o.c. top and bottom, and the  
Figure 4: Overview of the second 1:2 scale setup: (a) top view; (b) cross-section view. Figure adapted from Reference [37]. Reprinted with permission. This figure was originally published in Vol. 116 of the ACI Structural Journal. Figure 3: Dimensions of first 1:2 scale model: (a) top view; (b) cross-section view. Figure adapted from Reference [34]. Reprinted with permission. This figure was originally published in Vol. 116 of the ACI Structural Journal. transverse reinforcement was \(\varphi\) = 6 mm at 250 mm o.c. top and bottom. In setup 2, the longitudinal reinforcement was \(\varphi\) = 8 mm at 200 mm o.c. top and bottom, and the transverse reinforcement was \(\varphi\) = 8 mm at 240 mm o.c. top and bottom. The clear cover to the reinforcement was 7 mm. The mild steel reinforcement in the setups was B500B steel, except for the bars of a 6 mm diameter, for which B500A steel was used. Stress-strain curves of the mild steel for all the bar diameter were measured in the laboratory, see References [33; 36]. The prestressing steel in the girders were Y1860S tendons, and the prestressing steel in the crossbeams and slabs were Y1100H prestressing bars with a diameter of 15 mm.