Abstract: Most experimental studies concerning the stress-strain behavior of concrete columns confined with carbon fiber-reinforced polymer (CFRP) focused on plain concrete columns with small section. In this study, 34 concrete columns with large-scale circular and square cross section confined with CFRP were tested under axial compression to investigate the influence of sectional dimensions, internal steel reinforcement and thickness of CFRP jackets on the stress-strain behaviors. Test results indicated that the confinement of CFRP resulted in significant increase in axial stress and strain for circular RC columns, while remarkable enhancement in axial strain but slightly in axial stress for square RC columns. The stress-strain responses of CFRP-confined square RC columns were significantly influenced by sectional dimensions and internal transverse reinforcement. The typical confinement ratio, which is obtained from studies on CFRP-confined unreinforced concrete columns with small cross sections, was not applicable for the case of large-scale square RC columns.
Abstract: Differential settlement of the new foundation was produced after the building monolithic moving was finished. The internal forces of the top building were changed due to the existence of the differential settlement and the original differential settlement, which affected structural safety. A three-dimensional finite element model was established based on the ANSYS program to attain the foundation settlement law of a fifteen-story moving building. Through calculation and comparation of the settlement values and differential settlement between slab foundation and pile foundation, the pile foundation was finally selected as the construction scheme. Simultaneously, numerical analysis of foundation differential settlement during the moving process was performed. The monitoring results were showen to be in reasonable agreement with the numerical analysis results.
Abstract: Friction loss is an important component of the calculation of prestressing loss for external prestress strengthening technology. Unfortunately, the test data of relevant curvature friction and wobble coefficients is scarce, especially for beams strengthened by external prestressing Carbon Fiber-Reinforced Polymer (CFRP) tendons. Through the experiment of 12 concrete beams strengthened by external prestressing CFRP tendons, this study attempts to discuss the friction loss algorithm and the reasonable value of friction coefficient. The test results demonstrated that traditional friction loss algorithm for prestressed steel tendons is also suit to external prestressing CFRP tendons, but the value of curvature and wobble coefficients should be determined by different types of CFRP tendons and saddle design. What is more, aiming at the domestic production of CFRP tendons and the adopted special saddle design in this paper, the curvature friction coefficient is 0.263 and the wobble coefficient is 0.0067 at the deviator. Results of the research provide a reference for external prestress strengthening design with CFRP tendons.
Abstract: The method of strengthening the existing reinforced concrete suspension bridges by changing suspension system into cable – stayed- suspension system is presented in this paper. Based on a typical bridge, the analysis of the static behavior of the bridge before and after the strengthening is preformed. The results show that the bending moment of the girder is reduced obviously and the capacity of carrying load is greatly improved. The original cable system is fully utilized and can meet force requirement. It has certain theory significance and practical engineering value to the similar bridge’s strengthening.
Abstract: The static load test is done on 5 concrete beams. One beam is loaded to the destruction as a contrast specimen, and the other 4 are loaded to the predetermined damage load (80kN), then unloaded to the different load level separately, keeping the load invariable, and tested the improvement in flexing resistance after structural strengthening by CFRP.The research indicates: The ultimate capabilities of the reinforced concrete beam specimens reinforced by carbon fiber sheets can increase 20.93%~39.80% compared with the specimen without CFRP.
Abstract: Every earthquake always cause serious destruction of engineering structure , and bring about disastrous heavy losses to society economy. In view of confusion phase of reinforcement philosophy and method in existing engineering structure now, the paper analyses wreck of existing engineering structure as a result of the earthquake, put forward “Degree of Monolithic Secure” thought and probe into its application in aseismic strengthening of existing engineering structure. The “Degree of Monolithic Secure” means using the human being’s thinking and judgment, deciding the fundamental question, conception, and principle of engineering structural reinforcement in macrocosm, on the basis of its essence characteristic and purpose request. The Strengthening philosophy emphasize fundamental of three-dimension conception, spatial function, receiving the strength rationally, coordinating the deformation. It expound basic conception of self-organize theory, whole pre-stressing Strengthening technology directed by Degree of Monolithic Secure.
Abstract: This paper introduces a new box girder widening method- Steel cantilever widening concrete box girder method without piers (SCWCGM for short). Without additional piers, SCWCGM can still meet the need of widening range, which is an effective widening method for urban bridges. In this paper, the widening conception and the structure style of SCWCGM is detailed. In order to study the mechanical properties of this method, the full-scale model test was conducted. The results show that, the SCWCGM is reasonable and feasible.
Abstract: To investigate failure mechanism and toughening features of fiber reinforced concrete (FRC) with different reinforced fibers, meso-level numerical simulations have been conducted on FRCs incorporated with steel, glass and polypropylene fibers, respectively (which were named as SFRC, PPRC and GRC). The complete failure process of crack initiation, coalescence and development, interaction and final break have been simulated. By analyzing the failure patterns of specimens, also the spatial and temporal distribution of acoustic emission and loading - step curves, it can be concluded that both peak strength and toughness of SFRC and GRC can be greatly improved. However, for PRC, the improvement of peak strength is little while its toughness can be enhanced significantly.
Abstract: The building structure reinforcement simulation system is very necessary for the rapid development of the building reinforcement industry, in this paper, the feasibility of the simulation on concrete structure bonding with steel plate was analyzed, and the influence of deformation and stress of concrete beam was studied by the thickness of steel plate and bonding layer. The research results show that the cracking load of the original concrete beam model is 8.712 KN, the limit load is 8.92 KN, and the midpoint displacement is 0.4443 mm; when the thickness of steel plate is 4 mm, the limit load is 11.579 KN, comparing it to the 8.92 KN of the original concrete beam model, the bearing capacity can be improved to 32.91%; The maximum adhesion stress at the end of the bonding layer increases first and then decreases as the thickness of the bonding layer increases, the ratio between the maximum adhesion stress and the minimum adhesion stress increases first and then decreases as the thickness of the bonding layer increases.
Abstract: The paper proposed a new reinforcement technique-planting steel technique. By numerical simulation analysis of planting steel, the load – slip curve, the load – stress curve and others were obtained. Meanwhile, ultimate bearing capacity of angle was calculated, and the ultimate bearing capacities with the same model at different anchorage depths were compared. With the anchorage depth increased, the ultimate bearing capacity increased too. But while the anchorage depth increased to a certain value, the ultimate bearing capacity no longer increased. All these provided a theoretical basis for the engineering application of planting steel technique.