PSI - Issue 84

Alessandro Lipari et al. / Procedia Structural Integrity 84 (2026) 1087–1094

1088

About half of the existing reinforced concrete solid slab bridges in the Netherlands are skewed (Lu et al., 2022). When the slab is skewed, the assessment is further complicated as questions arise on how the skew angle influences the capacity – particularly the shear capacity – and on how the acting shear stress should be determined. It is known that the largest acting shear stress will occur in the obtuse corner of the slab with large stress concentrations (Cope, 1985). When studying skewed slabs, either the skew angle (0° for a straight slab) or the crossing angle (90° for a straight slab) can be used for referring to the slab skewness. Before the work presented here, the only experimental campaign in the literature was carried out by Cope (1985), who tested nine models with skew angles of 30°, 45° and 60° under the loading configuration used at the time in the British Standard. The models failed in shear, except for the most skewed model, which failed in punching shear. Lipari (2020) found that the experimental shear resistances were much larger than the resistances predicted with the 2004 version of Eurocode 2 (European Committee for Standardization, 2004). To advance the understanding of the behavior of reinforced concrete solid slab bridges, this paper addresses the effect of the skew angle on the shear capacity of slabs without shear reinforcement. A series of experiments is presented, along with the analytically determined shear capacities and the acting shear forces derived using linear finite element analyses. The experiments are carried out on 1:2 scale members, subjected to a single concentrated load, and they all result in a shear failure. 2. Experimental campaign The tested specimens were designed to represent existing reinforced concrete solid slab bridges from the Netherlands. The skew angles were selected based on the inventory of skewed slab bridges in the Netherlands and the reinforcement layout was selected by analyzing the bridge reinforcement layouts (Lu et al., 2022). The specimens are named according to the crossing angle, as per the Dutch convention. All slabs have a width of 2 m and a thickness of 300 mm, with a span length of 3.6 m. To keep this span length, the total length of the slab varies between 4.3 m for the 75° crossing angle specimen and 5.9 m for the 45° specimen. The reinforcement consists of ribbed B500B steel bars of 10 mm and 20 mm diameter. The measured average yield strength of the reinforcing steel, f ym , is 477 MPa. The “O” specimens have an orthogonal reinforcement layout, with longitudinal bars parallel to the free edge, and the “N” specimens a non-orthogonal reinforcement layout with the transverse bars parallel to the supported edge. The concrete cover is 25 mm, resulting in an effective depth to the longitudinal reinforcement, d x , of 265 mm. The concrete is of class C35/45 with a characteristic value of the cube compressive strength of 45 MPa. The maximum aggregate size, D max , is 32 mm. To test the slabs, a support consisting of one HEA 700 steel beam on box girders was used, with a welded cylinder on top to create a roller support, as well as a loading plate of 200 mm × 200 mm to apply the concentrated load. By adjusting a screw at the support, one support has the conditions of a roller and the other of a pin. The height under the specimen is 1.9 m, allowing for space to set up a Digital Image Correlation (DIC) system. A 3D DIC system is used on the top and bottom of the slab, to monitor changes in the thickness of the slab, which is considered an indication of internal crack opening. In addition, Linear Variable Displacement Transducers (LVDTs) are used to measure horizontal deformations, and laser distance sensors to measure deflections. In the experiments, the load is applied in proximity of the obtuse corner to study the effect of the stress concentrations on the shear capacity. The load is placed at 435 mm in the width direction from the free edge, and at a / d x = 3, with a being the shear span from the center of the load to the center of the support. The total experimental campaign consists of 15 experiments on 5 specimens. In this work, four representative experiments are studied to focus on the effect of the skew angle and the reinforcement layout. Table 1 gives an overview of the analyzed experiments, giving experiment number, skew angle, age of the specimen at testing, average measured cube compressive strength tested at the age of testing, f cm,cube , longitudinal and transverse reinforcement ratios, ρ l and ρ t , and failure load, P max . For S75N1Auc the average splitting tensile strength is also determined at the age of testing. All experiments result in a shear failure. Fig. 1 illustrates the cracking pattern at failure of the S60 specimens.