Load Performance Of Hybrid Concrete Structures With Glass Fibre Reinforced Polymer Tubes And Bars

Glass fiber reinforced polymer is one type of new composite materials with exceptional characteristics such as low cost,lightweight,high strength,excellent insulation performance,durability,corrosion resistance,easy processing,and the similar thermal expansion coefficient with typical concrete.It substitutes for steel under some circumstances and has the great application potential,especially in bridge,water conservation,electric power,offshore,underground,and many other structural engineering applications.The concept of hybrid concrete structures with glass fibre reinforced polymer(GFRP)tubes and bars proposed in this thesis is a novel type of concrete structure with new materials and configurations.Its basic form is to fill the GFRP framework,including external GFRP tube and internal GFRP reinforcing bars,with concrete to form a new composite structure.Some earlier studies have shown that concrete structures using GFRP pipes or GFRP ribs have significantly enhanced the load bearing capacity and stiffness in comparison with conventional concrete,but there are not enough studies for promoting practical engineering applications.Focusing on applications in electric power delivery,the GFRP tubes and bars were used in the concrete transmission tower structures,and the concept of hybrid concrete structures with GFRP tubes and GFRP bars(GTGRC)was put forward.This study focuses on the load-bearing performance of the hybrid GTGRC components subjected to axial compression,bending,and eccentric compression,among others,and the feasibility of connection between the hybrid member and other structural components was investigated.To enable such engineering applications,a comprehensive analysis of design process and criteria was performed along with experimental verification.The tests of GTGRC structural members under axial compression,bending,and eccentric compression were designed and completed.The test results of deformation,failure pattern,and load-bearing capacity of typical components were obtained.The influence of quantities of GFRP bars,thickness of GFRP tube wall,eccentricity,and other parameters on the load-bearing performance of GTGRC was obtained.A simple procedure for calculating the bending stiffness of GTGRC member was established with two flexural rigidity formulae from current design codes of composite structures.The functioning principle was obtained based on the observation of specimen failure patterns.And the ultimate load-bearing capacity formulae,as well as the interaction of ultimate bearing capacity of GTGRC,under axial compression,bending,and eccentric compression,were analyzed and obtained,respectively.The normalized axial force versus moment interaction diagram of GTGRC columns was established.The simplified design formula for GTGRC structures under eccentric load was found from the normalized interaction formula of GTGRC.The test of steel cross arms inserted into GTGRC columns was designed and performed,and the influence of sizes of GFRP tube cross-section and cross arm on the strength and rigidity of specimens was analyzed.The main controlling factors of specimen failure patterns were obtained.The strain or deformation of GFRP tube and the cross arm were analyzed under different loading conditions.Two methods for predicting the displacements of cross arms were discussed.The feasibility of connecting GFRP tube and cross arm joint was verified.The research work was carried out in combination with the design of the transmission tower of the GFRP reinforced concrete.The objective was to provide the formulae and parameters of the performance under the typical loading conditions in applications,and to conduct the laboratory verification of the actual structure in combination with the existing design specifications.In the research,special attention was paid to the load bearing performance and strength of nodes and joints,as well as the failure pattern in the structural applications to ensure the functions and safety.In summary,some design parameters and methods were presented as a complete procedure for the design of practical structures with GFRP concrete for many applications in the future.