286 / 2023-01-19 18:00:20

Structural behavior of ECC link slabs strengthened with GFRP reinforcement

Link slabs; Engineered cementitious composites; Glass fibre reinforced polymer; Structural behavior; Nonlinear finite element; Sensitivity analysis

A majority of high-way bridges are composed of multiple-span steel or prestressed concrete girder simply supported at piers. those expansion joints are designed to protect the substructure from exposure to corroding substances by provided watertight seal between the adjacent bridge decks over piers and abutments. However, it is well reported that the mechanical joints are expensive to install and maintain. Deterioration of traditional mechanical expansion joints significantly affects the durability of bridge structures (Fig. 1).



A possible approach to solve the durability problem and reduce the high cost of maintenance in expansion joints is the elimination of mechanical deck joints in multi-span bridges. One type of jointless bridge design proposed by a number of researchers is the application of link slab elements within bridge decks (Fig. 2). Engineered cementitious composites (ECC) have been proposed as an expansion joint material that can eliminate the joints in bridge decks. The ECC link slab concept was developed based on the high ductility and tight crack-width in ECC materials for structural application. ECC link slab was designed to resist an expected moment due to end rotations of the adjacent decks. As a result of the moment demand and restrictions on the working stress of the reinforcement, which was limited to 40% of the yield strength, the link slab was heavily reinforced and consequently did not behave as a joint. Due to this high reinforcement percentage generally used, the resulting large bending stiffness of the link slab and consequently the negative moment generated in the joint are undesirable effects and deserve additional consideration.



Glass fiber reinforced polymer (GFRP) has been utilized in the ECC link slabs for joint-less bridge due to the light weight, high tensile strength, non-corrosive and nonmagnetic properties. According to correct researches, GFRP bars reinforced ECC link slab has greater deformation capacity and smaller stiffness. In this paper, six full-scale ECC link slabs (Fig. 3) reinforced with GFRP bars were cast and tested under monotonic cyclic loading (Fig. 4). The parameters included reinforcement diameter and ECC fiber volume.



The proposed link slabs demonstrated sufficient flexibility to meet the current design protocols (Fig. 5). The diameter of GFRP bar has a significant influence on the deformation stiffness of the link slab. It is due to the link slab are mainly subjected to tensile deformation. The volume of ECC fibers has limited effect on the deformation stiffness at the initial stage of deformation. The link slab has small crack width, which can meet the limitation of the crack width of 0.1mm (Fig. 6). Simultaneously, it is beneficial to improve the deformability of link slab.



The sensitivity analysis of parameters based on linear finite element models were constructed (Fig. 7). ECC fiber volume, depth-span ratio and reinforcement ratio of such link slabs should not exceed 2.4%, 8% and 1.2%. Link slab debonding length should be larger than 4% of span length of bridge to obtain low bending stiffness. This research may further lead to the diversified and integrated application of GFRP reinforced ECC link slab for jointless bridge.