PSI - Issue 64

Abbas S.A. Al-Hedad et al. / Procedia Structural Integrity 64 (2024) 1386–1393 Abbas S. A. Al-Hedad and Muhammad N. S. Hadi/ Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction Concrete structures used in transportation engineering such as concrete pavements, airport runways, and deck slabs of bridges are more likely to suffer from the initiation and propagation of cracks. The reason is that these kinds of concrete structures have a thin depth compared with their other dimensions. The propagation of cracks follows the short path, which is the depth of the concrete pavement. This results in a gradual decline of the flexural strength of concrete pavements. Experimental studies have recently been conducted with various types of geogrids such as uniaxial, biaxial and triaxial geogrids as the main structural reinforcement or confinement material (Wang et al., 2016, Siva Chidambaram and Agarwal, 2015 and Shobana and Yalamesh 2015). The experimental studies illustrated that the ductility of the concrete elements reinforced with the geogrids could be increased. In addition, Tang et al. (2008) illustrated that the geogrids could provide more control against the reflective cracking of concrete reinforced with geogrids by absorbing the concentrated stresses at the crack tips of the concrete. They also reported that the geogrids could delay the propagation of cracks. Al-Hedad and Hadi (2017) and Al-Hedad and Hadi (2018) illustrated that the flexural load capacity of the concrete slab reinforced with geogrids could be improved. It was also demonstrated that the geogrid could extend the path of cracks along the depth of the concrete slab before the failure takes place. Geogrids were used in this study as the main reinforcement material of the concrete beam specimens. The concrete beam specimens were tested under static and cyclic loads. The effect of geogrids on the flexural strength, fatigue life, fracture energy and maximum cyclic loads of the concrete beam specimens with the existence of crack were investigated in this study. Such a study is important as it provides an alternative reinforcement that does not corrode thus leading to prolonging the life of structural members. 2. Experimental Work 2.1. Geogrids Triaxial geogrid was used in this study as the main reinforcement material. The geogrid was manufactured from polypropylene composite materials (Maccaderri Australia Put Ltd, 2015). The properties of the geogrid samples were measured in the study. As shown in Fig. 1, the geogrid had triangular openings with a side length of 45 mm measured from the center to center of nodes. The ribs of the geogrid had an average cross sectional area of 2.325 mm 2 . The average thickness and the average diameter of the nodes were 3.5 mm and 10.0 mm, respectively. Five triaxial geogrid samples were prepared and tested in this study to determine the tensile properties of the geogrid according to the requirements of BS EN IS 10319 (2015). The average width of the geogrid samples was 200 mm, as listed in Table 1. The average nominal gauge length of the geogrid samples, which was measured between the ends of steel clamps (Fig. 1), was 109 mm. The geogrid samples were tested at a strain rate of 20% per minute until the rupture of the geogrid samples.

Table 1. Properties of geogrid (average of five geogrid samples). Property

Test results

Width (mm)

200 109 0.04

Nominal gauge length (mm)

Elongation at 1% tensile strength per unit width (%)

True gauge length (mm)

109.05

Tensile strength per unit width (kN/m)

18.5 12.1

Tensile strain at the tensile strength per unit width (%) Secant stiffness at 5% of tensile strength (kN/m/strain %)

2.4