Experimental Investigation And Analysis Of Adhesive-Bonded Interfacial Mechanical Property Of Pultruded GFRP Bridge Deck

In recent years, the rapid development of GFRP bridge deck in bridge engineering for owing many virtue such as lightweight, high strength and higher corrosion resistance. The bonding interface between GFRP profiles plays an important role in GFRP bridge deck structure, which determines the integrity of GFRP bridge deck and bears the deformation causing by temperature changing. Interface debonding is one of the major failure modes for GFRP bridge deck structures. Once it happens, it may lead to stiffness degradation and decrease the capacity of whole structure. In this paper, the inter- facial failure modes, failure mechanism, and fracture behavior of adhesively-bonded GFRP components were investigated with the support of National Science Foundation in China(50878048,50978055) and the subtopic of 973 Project (2012CB026200). The structure responses of GFRP bridge deck especial for the effect of interface were studied suffering vehicle loads and the action of temperature. The main works of this paper are summarized as follows:1. The construction of the adhesively-bonded GFRP components, the load-transferring mechanism as well as the failure modes were introduced. The plastic-elastic stress analysis of single lap joint was conducted base on Hart-Smith formula. The carrying capacity expression was got by the adhesive layer maximal shearing strain criterion. The effect of bonding parameters on elastic peak stress and bearing capacity was discussed. An experimental study of adhesively-bonded pultruded GFRP joints was designed to investigate actual failure modes and various bonding behaviors. The bond strength criterion was proposed under complex stress state.2. By modeling an interface cracked adhesively-bonded GFRP double cantilever beam(DCB) as two elastic foundation and Timoshenko’s subbeams, and considering the displacement and angle of crack tip, the flexibility and the energy release rate was calculated. Taking adhesive layer as Good-man’s elastic layer, the deflection of the Four-point bending end-notched flexure GFRP-GFRP beam specimen(4ENF) and Four-point bending mixed-mode bending specimen(4MMB) was obtained. The expression of energy release rate was got based on crack compliance method. The fracture toughness values of GFRP-GFRP bonded interface and the fracture criterion of bonded interface were determined under mode Ⅰ,Ⅱ and mixed loading experiments. Appling crack propagation criterion, the numerical simulation of crack propagation was realized. Upon the comparison with the experimental result, the calculated load-displacement curve shows good agreement. This dedicated that the proposed fracture criterion in this paper is feasible.3. By static test of GFRP bridge deck, the bonding interface was earlier than other failure mode. From the analysis of stress field about interface edge, the singularity of adhesive interface edge and the method for decreasing stress singularity were found. Micromechanics model of GFRP bridge deck combined with adhesive layer was presented according to Chamis method to predict the mechanical response of pultruded GFRP deck. The finite element model was validated by load test result of GFRP deck, and the result demonstrated that there is high shear stress in adhesive-bonded joint between GFRP components. The maximum interface failure index is 0.66, but the maximum Tsai-Wu failure index is 0.42, which implies that the interface debonding is earlier than material failure. The buckling checking of GFRP bridge deck is carried out to design superior GFRP bridge deck. The effect of geometrical parameters on the interface failure coefficient and plate buckling was discussed.4. Equivalent mechanical parameters of GFRP Bridge are calculated using elastic equivalent analysis. Using orthorhombic anisotropic thin plate’s theory on Kirchhoff’s hypothesis, the governing equation of flexure plane was conducted under temperature effect. The deflection, corner and internal force were solved by employing navier’s method. By analyzing thermal effect on GFRP bridge deck, the temperature is bad for GFRP bridge deck structure strength. The stress within GFRP bridge deck and interfacial stress caused by uniform variation in temperatures is greater than by positive temperature gradients. The action of temperature should be considered in GFRP bridge deck design.5. A three-dimensional finite element model of GFRP Bridge deck containing interfacial crack was developed. Then, the virtual crack closure technique (VCCT) is put forward to calculate the energy release rate G of adhesive-bonded joint crack between GFRP compoment. Based on the change of G along with the change in the loading position of the axle-load, the worst loading location of the axle-load on the cracking adhesive-bonded joint of the GFRP bridge deck was established. The crack energy release rate between GFRP compoment adhesive-bonded joint was analyzed combined with crack propagation criterion. By adopting Paris’ formula, the the fatigue life of the adhesive-bonded joint is forecasted. The crack’s detrimental effect on critical buckling stresses, stiffness and strength of GFRP bridge deck is discussed. The result indicates that the quality of interfacial adhesion is important to improve the service life.