Mechanical Behavior Of BFRP Shell-Concrete Composite Bridge Deck Under Long-term Loads

To solve the problem of the poor durability and the fatigue failure under the long-term traffic load for the traditional concrete bridge decks,a high performance prestressed BFRP shell-concrete composite bridge deck was developed by our research group.The BFRP shell with good corrosion resistance and high tensile strength was located in the tension zone,and the concrete with better compression performance was in the compression area,taking advantages of BFRP and concrete material properties.In addition,considering the low elastic modulus of FRP profiles and the deflection requirement under the construction load,the prestress was used to get the pre-arched of BFRP shell.At the same time,corrugated tooth and sticky sand were applied by BFRP shell surface to enhance the BFRP shell and concrete bonding performance.Static tests showed that the composite bridge deck had good resistance to deformation and superior combination properties,and the prestressing force was maintained well under static load.Based on the study of static performance,the fatigue damage propagation and key control factors of composite bridge deck under long-term load,the fatigue life prediction model were further studied.Then the data supports were provided for achieving high performance and long life of bridge decks.In this paper,the following aspects were studied:Static and fatigue behavior of bonded interface between BFRP shell and concrete were studied.By simulating the interfacial treatment of the bridge deck,three kinds of interface treatment methods were investigated(non-stick sand,sticky sand by a layer of glue,sticky sand by two layers of glue).The results showed that the interface treatment of sticking sand by a layer of glue had better bond performance.The bond slip constitutive relation of the three interface treatments was proposed.The performance degradation under fatigue was studied for the interface treatment of sticking sand by two layers of glue,which showed that the interface had good fatigue performance.The fatigue S-N curve of the interface was given by data fitting.Fatigue behavior of BFRP shell-concrete composite bridge decks were studied.The fatigue tests of 5 composite bridge decks under varying load level were carried out.The fatigue failure modes,stress and strain of shell,stress and strain of prestressed slab,interface shape and stiffness of composite bridge deck were monitored and analyzed.The results showed that the fatigue failure of the composite bridge deck was concrete crushing in the compression zone and part of BFRP shell tearing;the composite bridge deck maintained a plane-section assumption under fatigue,and the neutralization axis moved down slightly with the loading of the fatigue cycle;BFRP shell and prestressed slabs had a very good fatigue performance without occuring significant fatigue damage;the fatigue performance of interface was superior;after fatigue,the composite bridge decks had a good residual strength.At the same time,the fatigue S-N curve of the composite bridge deck was given by data fitting,which can predict the fatigue life under different loads.Fatigue behavior of BFRP shell-concrete composite bridge deck was studied by Finite element analysis.The interface bond slip was considered in the ANSYS finite element modeling,so that the ultimate bearing capacity and load displacement curve were consistent with the test under static loading.By considering the S-N curve of BFRP shell,the concrete and the interface,the fatigue life of the composite bridge deck was simulated and the key control factors of the composite decks were obtained,which were consistent with experimental results.The finite element fatigue life prediction model established in this paper can be used to optimize the design of composite bridge decks.