Experimental Study On The Flexural Behavior Of RC Beams Strengthened With Stranded Wire Mesh And Polymer Mortar

The strengthening technique using stranded-wire mesh and polymer mortar hasthe advantages of thin added layer and ease installation, and possesses a wideapplication prospect in the strengthening of existing structures. Aiming at solving theproblems existing in the application, the following studies were carried out in thisdissertation:(1) Study on the practical and control method of applying prestress to thestranded wire;(2) The strain measurement method of the stranded wire was putforward;(3) The experimental study on the flexural behavior of RC beamsstrengthened with stranded wire mesh and polymer mortar;(4) According to the testresults and theoretical model, propose the formula of the flexural bearing capacity.Aim at preventing the failure of end anchorage on the existing method, a newanchorage method was put forward. Based on this anchorage method, a practical andcontrol method of applying prestress to the stranded wire was proposed. The law ofprestress loss at the construction stage and the effective prestress coefficient had beendiscussed. Test results showed that the stranded wire experienced prestress loss in theconstruction stage, and the prestress loss mainly occurred in first12hours. Theeffective prestress coefficient can be determined by the prestress value after12hours.The tightening torque T and the force Q were in the linear relationship based on thetest.An experimental study was conducted to investigate the flexural behavior of6RC beams strengthened with stranded wire mesh and polymer mortar and1controlbeam. The main parameters included the number of steel strand, the types of polymermortar and prestress level of the stranded wire. Test results showed that:(1) Theultimate failure mode of the specimen with the high rope rate was influenced by thebond strength between the mortar layer and the beam. The strength demand of the endanchorage increased after the failure of the bond occurred. The greater the amount ofthe stranded wire, the higher possibility of the failure of end anchorage.(2) Thestranded wire mesh and polymer mortar can improve the stiffness of the strengthenedbeam, slow down the growth of the reinforcement stress, delay the formation and propagation of the crack and reduce the crack spacing and width.(3) The strandedwire mesh and polymer mortar can effectively improve the ultimate load of beams,when the ratio of the stranded wire was0.028%,0.046%and0.065%, the increase inthe load was10.0%,37.5%, and56.3%, respectively.(4) The moment-deflectioncurve increased as a straight line before the cracking of the strengthened beam. Aftercracking, the slope of the curve decreased significantly. With the yielding of thereinforcement, the curve was close to a horizontal line. When the stranded wireruptured, the bearing capacity of the beams dropped suddenly and then stayed stable,while the deflection grew rapidly.(5) The prestressing stranded wire can effectivelyimprove the cracking moment and yield moment of the beams by40.0%and34.8%,while the specimen without prestressing increased by20.0%and19.7%. Theprestressing of the stranded wire had no obvious influence on flexural strength of thestrengthened beams (6) The mortar for strengthening had little impact on the aboveresults. With the same rope ratio, the beam using one-component polymer mortar hadan ultimate load only5%less than the beam using two-component mortar.A model to predict the flexural strength of the strengthened beams was proposedbased on the experimental study. The calculation results and test results were in goodagreement. The obtained overall results can provide a reference for the furtherresearch and the practical engineering application.Using the finite element software ABAQUS, the three-dimensional nonlinearfinite element model was established. The calculation results were compared with thetest results, and a good agreement was obtained.