Papers by Keyword: Strengthening

Abstract: This article mainly aims at the frame structure seismic identification and reinforcement, and example analyzed a middle school building structure of the framework aseismatic appraisal and reinforcement.

Abstract: The experimental study was carried out on the cyclic loading behaviors of impaired reinforced concrete beams strengthening with prestressed CFRP sheets. Eight beams in four groups with or without strengthening with prestressed CFRP sheets were tested, in which one or two layers of prestressed CFRP sheet were bonded on the bottom surface of the beams. Based on the analyses of test results, the flexural stiffness and ultimate resistance under cyclic load were effectively enhanced for the strengthened beams with the increasing layers of CFRP sheet, but the ductility of their mid-span deflection was reduced.

Abstract: Two large impaired reinforced concrete beams with pre-loading cracks were strengthened by the externally bonded steel frame composed with bottom steel plate and side hoop steel belts. The cyclic loading behaviors of these beams were tested to verify the effectiveness of this strengthening method specified in current Chinese design code. Based on the analyses of test results, the steel plate worked well with bonded concrete under normal service load, the hoop steel belts were necessary to prevent the peeling of bottom steel plate. The strengthened beams were effectively enhanced in flexural stiffness and ultimate resistance, and no new cracks appeared under the normal service load.

Abstract: Some calculated methods of shear capacity of RC beams strengthened with NSM(near-surface mounted) CFRP(Carbon fiber reinforce polymer) rods are reviewed based on the experimental data on shear capacity of RC beams strengthened with NSM CFRP rods. Therefore, according to the destruction forms of steel reinforced concrete beam strengthened with NSM CFRP rods, the formula for calculating the shear capacity of the beam is given. The formula is expressed clearly, simple and easy to use.

Abstract: Most of the short span suspension bridges with steel truss girders early constructed will approach their design service life. Correctly evaluating the actual service performance is the basic basis of repairing, strengthening and technical reconstruction. First, load-bearing capacity evaluation based on static load test was briefly introduced. Then, combined with Chengnan bridge, the main existing damages and their causations of the bridge were summarized and analyzed. Based on the field detection datum and original design load grade, the finite element mode with some damages was established. Then, by analyzing the calculation results, the scheme of static load test was confirmed. Through comparing the static load test results with the results of upgraded finite element, the actual conditions of the existing bridge structure were evaluated. In order to resume its load-bearing capacity, some of measurements and suggestions of strengthening were proposed.

Abstract: In order to study the influence of beam-reduction and rib-addition strengthening method on the natural vibration properties of hollow slab bridges, based on bridge natural vibration frequency and the vibration mode in the first three orders as main comparison parameters, according to the comparison between the theoretical values as well as experimental values of the natural vibration properties before and after strengthening, the practical effect of this strengthening method is studied. The test data show that the beam-reduction and rib-addition strengthening method results in an obvious enhancement of the natural vibration frequency of simply supported hollow slab bridges, which proves that the strengthening method has remarkable improvement effect on the rigidity of bridges. It can be seen from the comparison of the changes of the vibration mode in the first three orders before and after strengthening that the transverse connection of bridge is strengthened and the integrity is prominently enhanced after strengthening. The study result is that the beam-reduction and rib-addition strengthening method can greatly enhance the structural behavior of hollow slab bridges.

Abstract: A hysteretic model of conventional steel braces consisting of 18 parameters is proposed. This model is able to simulate the hysteretic behavior of conventional steel braces accurately. The collapse-prevention strengthening effect with steel braces for a typical reinforced concrete (RC) frame that was close to the epicenter and collapsed during the Great Wenchuan Earthquake is discussed via push-over analysis and collapse fragility analysis based on incremental dynamic analysis. The result could be referred to for the seismic collapse prevention design of RC frames.

Abstract: Mechanical grinding method was employed in this study to disperse CaCO3 whiskers in cement matrix. Mechanical properties of the ground whisker reinforced cement were measured. It is shown that the mechanical grinding method was advantageous to the dispersion and mechanical properties of composites. But the grinding process must be proper to assure a certain length and integrality of the whiskers. Crack deflection and whisker pullout mechanisms could account for the strengthening and toughening effects caused by whiskers.

Abstract: The strength and stiffness characteristics are important parameters in the design of metal structure of gantry crane. In this paper, the modeling of a gantry crane before and after reconstruction was performed by using Finite Element Method, and the strength and static stiffness of the gantry crane were analyzed. The results show that the insufficient stiffness of the reconstructed gantry crane in the shaking direction causes its laterodeviation. A strengthened method was determined after comparison of four reinforcement measures. The present results can provide an importantly theoretical basis for the reconstruction or strengthening of gantry cranes.

Abstract: This paper presents the results of the experimental investigation on the shearing performance of beams strengthened with steel wire-polymer mortar. The numerical results by finite element method are compared with experimental results. A total of three rectangular doubly RC beams were constructed, strengthened and tested to failure. A new convenient method to measure elongation of steel wire was proposed. Two models, named separated model and composite model respectively in software ANSYS, are used to analyze the beams. In separated model, strains of longitudinal steel bars and stirrups are in good agreement with the test results, and strains of longitudinal steel bars by composite model are also in good agreement with the test results, while stirrups strains are not, but both of steel wire deformations obtained by ANSYS analysis models are slightly different with tests results. Strengthened beams increased ultimate capacity, delayed the crack occurs and crack development. More closer and disorder cracks distribute in the strengthened beams than the unstrengthened beam. Cracks in beams by ANSYS analysis models, comparing with test results, are not very obvious.