Study On The Mechanical Performance And Design Method Of CFRP Parallel-rod Cables And Anchorages

The Carbon Fiber Reinforced Polymer (CFRP) cable is a new type of structuralmaterial manufactured by pultrusion process. The light-weight, high-strength andnon-corrosive properties make it more suitable for large-span bridge structures orprestressed structures compared to conventional steel cables. Using CFRP cables instructures can reduce the dead weight, lower the loss of prestress, prolong the fatiguelife and improve the long-term behaviors. Based on the sub-topic of China863Project‘Study and application of the structural carbon fiber reinforced polymer cable andanchorage’, the key issues including the shot and long term properties of CFRP cablesand the mechanical performance of CFRP cable anchorages are discussed andinvestigated. All the research works and conclusions are as follows.(1) The ultimate tensile capacity， failure probability and safety number ofmultiple parallel CFRP rods are analyzed and the calculating mechanism is obtainedbased on the conception of reliability. Several reduction factors are introduced tocalculate the loading capacity of parallel rods. Monte Carlo method is used to calculatethe reduction factors. In addition to the reduction factor in standard tension state, theeffect of installation and slippage of the anchorage, the tension-bending state and thelength of the parallel rods on the reduction factors is studied, which could be used forthe design of the CFRP cable. A series of tensile strength test values of single domesticCFRP rod are organized and the reduction factors of multiple parallel rods arecalculated. The strength design values of the parallel rods are then gained.(2) The creep behavior of the CFRP rod is investigated through experiments withindifferent stress levels and temperatures. The experimental results indicate that the creepvalue increases as the temperature rises but has no significant relationship with thestress level. In addition, the slippage of the rod in the bonding anchor increases as thestress level rises. The micro structure of the CFRP rod after the creep experiment is thenobserved by scanning electron microscope (SEM).(3) The shear stress distribution at the CFRP-adhesive interface of a single rod anda multi-rod straight-pipe bonding anchorage is derived by elasticity theory. Thecalculation method of the stress distribution in an elastic state is proposed and confirmed to be right by the comparison between theoretical and finite element analysisresults of six anchorage models. The mechanical performance of the inner-cone bondinganchor for multi-rods which is usually used in project is evaluated by finite elementanalysis. The influence of the design parameters including coefficients of friction, innerinclined angle, elastic modulus of the adhesive and anchorage length on the stiffnessand stress distribution of the anchorage is investigated. The results could be used toguide the preliminary design of CFRP rod bonding anchors.(4) The tensile tests of both bonding anchors and barrel-wedge type anchors forsingle CFRP rod are conducted, and three kinds of failure modes are summarized asexplosive failure, section fracture and slippage. The failure mechanism is discussedrespectively. Based on the single rod anchor tests, an inner-cone bonding anchor forseven CFRP rods and a bond-wedge combined type of anchor for nineteen CFRP rodsare designed and experimented, and the results indicate that the anchorage efficiencymainly depends on the uniformity of the tensile stress in CFRP rods.In summary, this thesis has made some progress on the anchorage, bearingcapacity design and long-term behavior of domestic CFRP cables. The research resultscould provide a theoretical and data support for the engineering application.