• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.839-844
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• 1998

The purpose of this study is to analyze the interface debonding failure on RC beams strengthened with carbon fiber sheet(CFS). The behavior of damaged RC beams strengthened with CFS is analytically investigated using both linear elastic fracture mechanics (LEFM) approach and the finite element method. This study includes the investigation of the separation mode by interface fracture of the strengthening materials due to the interfacial shear and normal stresses.

• Proceedings of the Korea Concrete Institute Conference
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• 1991.10a
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• pp.80-85
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• 1991

This experimental study was performed to derive the relationship between the measured values(corrosion potential) and the actual amount of corrosion products(reinforcing steel weight loss rate). Also the growth of crack due to the steel corrosion was oberved. First, the reinforcing steel of R/C specimen was corroded with chloride penetration and accelerated galvanostatic corrosion method. And then, the corrosion potential of reinforcing steel was measured with nondestructive tester.

• Structural Engineering and Mechanics
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• v.27 no.5
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• pp.589-607
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• 2007

Two series of tests were conducted to investigate the behavior of local thin jacketing for the retrofitting of reinforced concrete (RC) columns. In the first series, four full-scale RC columns with a height of 400 cm and a 30 cm square cross-section were tested under constant axial load and reversed cyclic lateral displacements. The heavily damaged columns were retrofitted with local thin jacketing. Self-compacting concrete (SCC) was used in the production of 7.5 cm thick, four-sided jacketing. The height of the jacketing was 100 cm for one specimen and 200 cm for all others. In the second series, the retrofitted columns were retested with the same axial load and displacement history. The effectiveness of local thin jacketing in the retrofitting of RC columns was examined with respect to lateral strength, stiffness, inelastic load-deformation behavior and energy dissipation.

• Structural Engineering and Mechanics
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• v.65 no.6
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• pp.751-760
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• 2018

Damages in concrete structures due to aging and other factors could be a serious and immense matter. Making the best selection of the most viable and practical repairing and strengthening techniques are relatively difficult tasks using traditional methods of structural analyses. This is due to the fact that the traditional methods used for assessing aging structure are not fully capable when considering the randomness in strength, loads and cost. This paper presents a reliability-based methodology for assessing reinforced concrete members. The methodology of this study is based on probabilistic analysis, using statistics of the random variables in the performance function equations. Principles of reliability updating are used in the assessment process, as new information is taken into account and combined with prior probabilistic models. The methodology can result in a reliability index ${\beta}$ that can be used to assess the structural component by comparing its value with a standard value. In addition, these methods result in partial safety factor values that can be used for the purpose of strengthening the R/C elements of the existing structure. Calculations and computations of the reliability indices and the partial safety factors values are conducted using the First-order Reliability Method and Monte Carlo simulation.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.165-168
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• 2008

This paper presents the design, fabrication and performance of a reinforced concrete beam strengthened by GFRP box plate and its possibility for structural rehabilitations. The load capacity, ductility and failure mode of reinforced concrete structures strengthened by FRP box plate were investigated and compared with traditional FRP plate strengthening method. This is intended to assess the feasibility of using FRP box plate for repair and strengthening of damaged RC beams. A series of four-point bending tests were conducted on RC beams with or without strengthening FRP systems the influence of concrete cover thickness on the performance of overall stiffness of the structure. The parameters obtained by the experimental studies were the stiffness, strength, crack width and pattern, failure mode, respectively. The test yielded complete load-deflection curves from which the increase in load capacity and the failure mode was evaluated.

• Structural Engineering and Mechanics
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• v.71 no.3
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• pp.211-221
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• 2019

To study the eccentric compression behavior of ultra-high performance fiber reinforced concrete (UHPFRC) columns, six UHPFRC columns and one high-strength concrete (HSC) column were tested. Variation parameters include load eccentricity, volume of steel fibers and stirrup ratio. The crack pattern, failure mode, bearing capacity, and deformation of the specimens were studied. The results showed that the UHPFRC columns had different failure modes. The large eccentric compression failure mode was the longitudinal tensile reinforcements yielded and many horizontal cracks appeared in the tension zone. The small eccentric compression failure mode was the longitudinal compressive reinforcements yielded and vertical cracks appeared in the compressive zone. Because of the bridging effect of steel fibers, the number of cracks significantly increased, and the width of cracks decreased. The load-deflection curves of the UHPFRC columns showed gradually descending without sudden dropping, indicating that the specimens had better deformation. The finite element (FE) analysis was performed to stimulate the damage process of the specimens with monotonic loading. The concrete damaged plasticity (CDP) model was adopted to characterize the behaviour of UHPFRC. The contribution of the UHPFRC tensile strength was considered in the bearing capacity, and the theoretical calculation formulas were derived. The theoretical calculation results were consistent with the test results. This research can provide the experimental and theoretical basis for UHPFRC columns in engineering applications.

• Structural Engineering and Mechanics
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• v.19 no.6
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• pp.653-677
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• 2005

Concrete filled steel tubular columns (CFT) are widely used in civil engineering works, especially in large scale of works because of high strength, deformation, toughness and so on. On the other hand, as a kind of strengthening measure for seriously damaged reinforced concrete piers of viaduct in Hansin-Awaji earthquake of Japan in 1995, reinforced concrete piers were wrapped with steel plate. Then, a new kind of structure appeared, that is, reinforced concrete filled steel tubular column (RCFT). In this paper, compression test and bending-shearing test on RCFT are carried out. The main parameters of experiments are (1) strength of concrete, (2) steel tube with or without rib, (3) width-thickness ratio and (4) arrangement of reinforcing bars. According to the experimental results, the effect of parameters on mechanical characteristics of RCFT is analyzed clearly. At the same time, strength evaluation formula for RCFT column is proposed and tested by experimental results and existed recommendations (AIJ 1997). The strength calculated by the proposal formula is in good agreement with test result. As a result, the proposed evaluation formula can evaluate the strength of RCFT column properly.

• Structural Engineering and Mechanics
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• v.81 no.1
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• pp.69-79
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• 2022

The dynamic responses of a pier-pile-soil system subjected to a barge/flotilla collision are analyzed. A coupled high-speed train and bridge system with a damaged pier after barge/flotilla collision is established by taking the additional unevenness of the track induced by the damaged pier as the self-excitation of the system. The whole process of a CRH2 high-speed train running on the 6×32 m simply-supported PC (prestressed concrete) box-girder bridge with a damaged pier is simulated as a case study. The results show that the lateral displacements and accelerations of the bridge with a damaged pier are much greater than the ones before the collision. The running safety indices of the train increase with the train speed as well as with the number of barges in the flotilla. In flotilla collision, the lateral wheel/rail forces of the train exceed the allowable values at a certain speed, which influences the running safety of the trains.

• Computers and Concrete
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• v.32 no.6
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• pp.625-637
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• 2023

The application of ML approaches in determining the resisting capacity of fire damaged RC columns is introduced in this paper, on the basis of analysis data driven ML modeling. Considering the characteristics of the structural behavior of fire damaged RC columns, the representative five approaches of Kernel SVM, ANN, RF, XGB and LGBM are adopted and applied. Additional partial monotonic constraints are adopted in modelling, to ensure the monotone decrease of resisting capacity in RC column with fire exposure time. Furthermore, additional suggestions are also added to mitigate the heterogeneous composition of the training data. Since the use of ML approaches will significantly reduce the computation time in determining the resisting capacity of fire damaged RC columns, which requires many complex solution procedures from the heat transfer analysis to the rigorous nonlinear analyses and their repetition with time, the introduced ML approach can more effectively be used in large complex structures with many RC members. Because of the very small amount of experimental data, the training data are analytically determined from a heat transfer analysis and a subsequent nonlinear finite element (FE) analysis, and their accuracy was previously verified through a correlation study between the numerical results and experimental data. The results obtained from the application of ML approaches show that the resisting capacity of fire damaged RC columns can effectively be predicted by ML approaches.

• Structural Monitoring and Maintenance
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• v.10 no.4
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• pp.283-297
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• 2023

This research aims to simulate and investigate the efficiency of strengthening damaged concrete columns using concrete jacketing.The numerical program included unjacketed reference column made of ordinary RC concrete had a cross-sectional dimension of (100×100) mm and 560 mm long reinforced concrete. These cores were damaged by loading them with approximately 60% of their actual ultimate load capacities as a service load. Then, column specimens were strengthened by applying two types of self-compacting concrete SCC jacketing, which were 25 and 30 mm thick, on all four sides. Exposed to external loads at different directions vertically and horizontally simulate to the seismic load. The 3D Finite Element (FE) simulation is used to predict of three structural criteria that were selected and evaluated (deflection, stress, cracks). The results show that the failure of the strengthening columns is interesting and corresponds to the characteristics of the cracks formed in the concrete section,which was documented numerically using 3D Finite Element (FE). A significant improvement of deflection has been noted at the values at the top SECTION of columns compared to the reference sample reaching an average of up to 36.6% when using a 25 mm thick SCC-3500 jacket.