Investigation Of The Behaviour Of Fibre Reinforced Polymer(FRP) Reinforced Engineered Cementious Composites(ECC) Link Slab In Bridge Deck Structures

With the development of the national economy in China,the traffic loads has been increased rapidly.Many medium and small spanning simply supported bridges were distributed widely in China,which is an important component in the high-way system.However,it is evident that the deterioration of expansion joint components in those bridge structures in the long-term service,such as rubber aging and steel corrosion,has been one of the major factors in the deterioration of the bridge structures,decreased structural durability and transportation comfort.According to the need of bridge expansion joint device,a novel high toughness link slab for jointless bridges was proposed by using the Engineered Cementitious Composites(ECC)reinforced with fibers.ECC material is a type of fiber reinforced cementitious material based on micromechanics design,which has many crack propagation characteristic and macroscopic deformation resilience.This material can satisfy the requirement high deformation capacity and strength.The toughness and durability of ECC is significantly high.Due to the high deformation capacity and low elastic modulus,ECC can be an ideal material applied in the bridge expansion joints,which can ensure enough linking slab deformation capacity,durability and resistance to permeability,small influence on main body deformation of bridge structure.Based on the study of mixing proportions of ECC,a suitable proportion of ECC material for link slab application was proposed in this study.Thereafter,a series study of the proposed ECC material was conducted:(i)mechanical behavour;(ii)shrinkage behaviour under temperature effect;(iii)Bonding behaviour in the interaction between ECC and concrete;(iv)the structural behaviour of FRP reinforced ECC flexural components.Based on those investigation results,the properties of the proposed ECC was determined.In the experimental test of ECC link slabs in bridge structures,the structural behaviour of those link slabs were investigated and discussed.Some test data were studied significantly,which included strain of reinforcement,strain of FRP,strain of ECC and the global deformation behaviour.Finally,a series of design method of this link slab was proposed to calculate the deformation and strain values of reinforcement and study the influence of reinforcing material and reinforcement percentage.The research works in this thesis can be summarised as below:(1)The study of mixing proportion of ECC materials is carried out by the experimental test.Based on the test results,a suitable mixing proportion for link slabs in expansion joints of bridge deck slabs was proposed.Thereafter,a series of parametric study of materials was coducted:(i)binder material;(ii)sand-to-binder ratio;(iii)superplasticer.The test results was used to evaluate the influce of those variables on material properties,such as workability,strength,tensile strain,flexural behaviour.(2)According to the ECC tensile stress-strain curve and thin plate bending load-displacement curve of the ECC test specimens with target mix proportion,the five stages of analysis methed was proposed with the initial crack and strengthening after fraction.Based on the test results,the shrikage behaviour of ECC materials was investigated by the designed test apparatus,including steel ring test and shrikage test coupling with temperature effect.Subsequently,the influence of temperature and humity on the shrikage behaviour was disucssed and presented.Additionaly,bond strength and shear strength test were performed to verify the interface properties of ECC and concrete.The bending tests of FRP reinforced ECC beams were carried outr to study the flexural behaviour with varying reinforcing material and cover thickness.(3)According to the design principle of deformation capacity of jointless simply supported bridges,a FRP reinforced ECC slab was used as joint link slab in bridge deck structures.Therefore,the deformation stiffness of link slab can be reduced.The structural behaviour of the bridge deck structures cannot be affected by the link slab significantly.To study the structural behaviour of ECC link slab,a group of three test specimens were conducted in this thesis,including ECC link slab,ECC link slab reinforced with FRP grid and ECC link slab reinforced with FRP bars.A series of monotonic repeated loading was applied for all the test specimens.To study the flexural behaviour of link slabs under repeated loading,some test data,including strain values of link slab,strain values of FRP and steel reinforcement and deformation,was used to validate and investigate the influence of stress distribution and influence of reinforcement materials.In addition,the deformation behaviour of link slabs were studied to evaluate the effect of reinforcing materials on this structural performance.(4)The existing design method for ductile link slabs was adopted to calculate the strength and deformation capacity of the proposed link slab in this study based on the investigation of this design principle.In this analytical study,the influence of reinforcement percentage and reinforcing materials on the structural behaviour of link slab was investigated majorly.Compared to the analytical results of steel reinforced link slabs,FRP reinforced ECC slab has better deformation capacity,lower reinforcement percentage and higher durability.