# Deep Embedment (DE) FRP Shear Strengthening of Concrete Bridge Slabs under Loads Close to Supports
## 1 Introduction  
Reinforced concrete slabs subjected to concentrated loads near linear supports are commonly found in practice, such as in bridge deck slabs [1]. The structural elements are characterized by high shear forces concentrated in the region between the concentrated loads and the linear support. Due to the increasing traffic loads and heavy truck loads close to supports, the existing bridge deck slabs could fail due to shear. Thus, more massive constructions or shear reinforcements are now required in bridge deck slabs [2]. This raises the question of whether there is a lack of safety for existing bridge deck slabs that were built mainly without shear reinforcement, or whether deck slabs under concentrated wheel loads exhibit reserves of shear capacity, which are neglected in current design codes [3].  
Shear strengthening techniques based on the use of fibre reinforced polymer (FRP) materials have been proposed and developed in the past thirty years [4; 5]. Externally bonded (EB) FRP is the most commonly used method for strengthening concrete structures using FRP material. To increase the shear behaviour of reinforced concrete structures, FRP sheets are generally applied on the side surface of concrete elements. Additionally, the near-surface-mounted (NSM) FRP rod method is another technique used to increase the shear resistance. In the NSM method, FRP rods are embedded grooves intentionally prepared on the concrete cover of the side faces of concrete structures. The efficiency of these strengthening schemes relies on the bond performance of concrete-adhesive-FRP interfaces. However, those two strengthening methods cannot be applied to increase the shear capacity of concrete deck slabs due to an inaccessible web of structures. Therefore, a new strengthening approachis adopted (see Figure 1): vertical holes are drilled into the deck slabs upwards from the soffit in the shear zones, high-viscosity epoxy resin is injected, and then FRP bars are embedded in place. This strengthening method is called deep embedment strengthening [6] or embedded through-section (ETS) strengthening [7]. Previous research [8; 9; 10] revealed that this strengthening technique provided higher strengthening efficiency compared to the EB and NSM strengthening methods. In addition, the shear capacity of strengthened concrete beams can be enhanced by this strengthening method [8; 9; 10].  
The aim of this paper is to study the structural behaviour of one-way reinforced concrete slabs in bridge deck structures strengthened with deep embedment FRP bars, see Figure 2. A series of experimental tests were carried out to investigate some structural variables on the behaviours of those slabs, which included deep embedment strengthening materials, spacing and diameter of deep embedment strengthening FRP bars, and the drilling of holes. After comparing the results of different test specimens, the influence of the deep embedment strengthening scheme on ultimate strength and failure mode was discussed and presented. An understanding of the effect of deep embedment shear strengthening method on the behaviour of concrete deck slabs can be extended. In addition, a nonlinear finite element analysis (NLFEA) model was developed simulate the behaviour of test slabs. The results from this NLFEA model showed good convergence ability and gave good agreement with test results in the validation analysis. Finally, a tow-way design approach for the prediction of ultimate capacity of concrete slabs strengthened with deep embedment FRP bars is proposed. The loading-carrying capacity predicted by this method showed good correlation with the test results.  
Figure 1: Deep embedment strengthening process: (**a**) Drill the hole; (**b**) Clean the hole; (**c**) Pour the epoxy resin into the slab; (**d**) Embed fibre reinforced polymer (FRP) rod into slab.