Experimental Study On Bond-Anchorage Properties Between BFRP Bar And Concrete

Basalt fiber reinforced polymer (BFRP) bar is considered as a new material applied in concrete structure that can solve structural corrosion instead of bar due to its high tensile strength, good corrosion resistant performance, approximate thermal expansion coefficient to concrete and light weight. The key index of whether BFRP can take place of bar is the bond property between BFRP bar and concreteIn addition, in the cold regions of north China, most bridge constructions are affected by low temperature. Existing experimental researches mostly take single factor analysis method with little temperature factors analysis confined to the work efficiency and workload. Taking the above factors into account, this paper design16groups altogether96bonding specimen with different parameters to conduct pull-out test with the purpose of studying bond-anchorage properties using orthogonal experimental design. The main contents are as following:Firstly, on equal terms, in order to arrange the factors and levels to be studied as much as possible, bond-anchorage properties design principle was taken to consider the effect of four factors such as temperature, bar diameter, bond length, and concrete strength on bond-anchorage properties between BFRP bar and concrete under factor level changes and then to design pull-out test program.Secondly, three kinds of failure mode were gained which is respectively pull-out failure, splitting failure and broken bar failure. The failure mode of BFRP bar is rib wear failure model whose wear degree of specimen is more seriously than splitting failure ones. Through analysis of bond-slip curve, loading process of BFRP bar is generally classified into four stages which are micro-slippage segment, slippage segment, descending segment and residual segment.Thirdly, making use of range analysis and variance analysis in orthogonal test, trial value and their mean value were calculated under various factors and levels taking bonding strength as trial value. The calculation results were classified in the light of factors. The change rule of bond property under this factor could be observed qualitatively according to the average change of experiment value under certain factor and various levels.Fourthly, mathematical model was analyzed using grey system theory. Data series of grey correlation analysis was established which were selected from existing test data. Through the calculation of correlation coefficient and degree of association, bond property degree of various factors was analyzed using the method of quantitative analysis.Lastly, improvement was made on the basis of existing bond-slip constitutive model and theoretical model which was suitable to BFRP bar and concrete bond-slip constitutive relation was founded. The model and test results are in good agreement. which can well reflect the loading process between BFRP bar and concrete as well as provide a reference for the design and construction of BFRP bar and concrete.