• Structural Engineering and Mechanics
• /
• v.73 no.4
• /
• pp.381-395
• /
• 2020

Study on the inelastic response of bare and masonry infilled Reinforced Concrete (RC) frames repaired using Carbon Fibre Reinforced Polymers (CFRP) and Glass Fiber Reinforced Polymers (GFRP) subjected to quasi- static loading is presented in the work. The hysteresis behaviour, stiffness retention, energy dissipation and damage index are the parameters employed to analyze the efficacy of FRP strengthening of bare and brick in-filled RC frames. It is observed that there is a significant improvement in load carrying capacity of brick infilled frame over bare RC frame. Also FRP strengthened brick infilled frame performs much better than FRP repaired bare frame under quasi static loading. Repair and retrofitting of brick infilled RC frame shows an improved load carrying and damage tolerance capacity than control frame.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.05a
• /
• pp.259-262
• /
• 2005

Numerous studies showed that safety and serviceability of many concrete infrastructures and buildings built in 1970's have capacity less than their design capacities and thereby require immediate retrofitting. Currently, these aged concrete structure are being repaired using many repair and strengthening methods developed in the past. Therefore, in this study, a repairing and strengthening method for retrofitting high strength concrete columns that can effectively improve the performance of high strength concrete columns is developed. The square high strength concrete column's cross-sectional shape is modified to octagonal shape by attaching precast members on the surface of the column. Then, the octagonal column surface is wrapped using Carbon Fiber Sheets (CFS). The method allowed the maximum usage of confinement effect of externally wrapped CFS, which resulted in improved strength and ductility of repaired high strength concrete columns.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.40 no.2
• /
• pp.82-90
• /
• 2024

It often happens that a removable partial denture needs to be repaired due to tissue changes in the remaining alveolar ridge, fracture of the denture, or fracture of the abutment tooth. There are several advantages to retrofitting a customized surveyed crown under the existing RPD. Retrofitting a crown to the RPD decreases the economic burden to the patient and avoids the need for several appointments to fabricate a new RPD. It is difficult for artificial teeth used to repair dentures due to fractured natural teeth to have a shape similar to that of natural teeth, and to repair aesthetic artificial teeth, it is necessary to manufacture customized artificial teeth similar to the shape of each patient's teeth. Recently, CAD/CAM technology has been used to fabricate customized prosthetics on existing RPD to achieve high retention and fitness accuracy, and by manufacturing customized artificial teeth, more aesthetic and harmonious artificial tooth repair is possible. This is a case in which a denture was repaired using a digital method to fabricate a customized prosthesis on an existing partial denture and customized artificial teeth that mirrored the adjacent dentition, saving time and cost, simplifying the process, and achieving aesthetically and functionally satisfactory results.

• Journal of the Korean Geophysical Society
• /
• v.9 no.4
• /
• pp.301-310
• /
• 2006

In this short paper, an elasto-plastic repair and retrofit element is developed for the investigation of the seismic performance of damaged reinforced concrete members. The developed element is capable of reflecting the increased characteristics due to both repair and retrofitting for degraded strength and stiffness of the members. The element having both birth and death time can freely be activated within the user-defined time intervals during static and dynamic time-history analysis. Comparative studies are conducted for reinforced concrete members being repaired and retrofitted. Analytical predictions including the developed element display reasonable correlation with experimental results. In short, it is concluded that the developed element is capable of providing salient features for the healthy assessment of seismic performance of RC members being repaired and retrofitted.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.4A
• /
• pp.611-622
• /
• 2008

Nonlinear analyses have been carried out for both bridge piers and a bridge structure being repaired using a repair element in order to assess the post-repair seismic response of such structures. For this purpose, a simplified CFRP stress-strain model has been proposed. The analytical predictions incorporating the current developments correlate reasonably well with experimental results in terms of strength and stiffness. In addition, nonlinear dynamaic analyses have also been conducted for a bridge structure in terms of the created multiple earthquake sets to evaluate the effect of pier repair on the response of a whole bridge structure. In these analyses, potential plastic hinge zones of piers are virtually repaired by CFRP and steel jacketing. Comparative results prove the virtual necessity of performing nonlinear post-repair analyses under multiple earthquakes, particularly when the post-repair response features are required. In all, the present approaches are expected to provide salient information regarding a healthy seismic repair intervention of a damaged strcuture.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.05a
• /
• pp.198-201
• /
• 2006

In order to evaluate the seismic performance of reinforced concrete bridge piers, an inelastic time-dependent element is proposed. The proposed element enables increased characteristics due to structural intervention (i.e., repair and retrofitting) to be accurately reflected to the degraded strength and stiffness of the members. Comparative studies are conducted for reinforced concrete bridge columns being repaired and retrofitted and show good correlation between analytical prediction and experimental results. In addition, a nonlinear time-history analysis of a reinforced concrete bridge under multiple earthquakes confirms the applicability and effectiveness of the present development.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.3 no.3
• /
• pp.203-211
• /
• 1999

This study is to examine the feasibility of carbon fiber sheet(CFS), a kind of fiber reinforced plastic(FRP), for a repair and reinforcement of R/C beams. The flexural strength of R/C beams, that were preloaded and then the cracks were repaired, maintains that of the uncracked R/C beams. The flexural strength of R/C beams increases with the reinforcement of CFS. In order to practically apply the repair and reinforcement method, further research is needed for the distribution, amount, and bond of CFS. In this study, an experiment was conducted for R/C beams reinforced with CFS, for various wrapping method and amounts of CFS. Experimental results showed the wrapping method increasing the bond area and amount of CFS layer caused the increase in the strength of the beams. It is found that the strength of CFS should be used as 70% of the maximum strength in retrofitting reinforced concrete beams in evaluating flexural capacity on the basis of ultimate strength design method.

• Steel and Composite Structures
• /
• v.45 no.1
• /
• pp.83-100
• /
• 2022

Timber is one of the few natural, renewable building materials and glulam is a type of engineering wood product. In the present work, timber-based braces are applied for retrofitting midrise Special Moment Resisting Frame (SMRF) using two types of timber base braces (Timber base glulam, and hybrid Timber-Steel-BRB) as alternatives for retrofitting by traditional steel bracings. The improving effects of adding the bracings to the SMRF on seismic characteristics of the frame are evaluated using load-bearing capacity, energy dissipation, and story drifts of the frame. For evaluating the retrofitting effects on the seismic performance of SMRF, a five-story SMRF is considered unretofitted and retrofitted with steel-hollow structural section (HSS) brace, Glued Laminated Timber (Glulam) brace, and hybrid Timber-Steel BRB. Using OpenSees structural analyzer, the performance are investigated under pushover, cyclic, and incremental loading. Results showed that steel-HSS, timber base Glulam, and hybrid timber-steel BRB braces have more significant roles in energy dissipation, increasing stiffness, changing capacity curves, reducing inter-story drifts, and reducing the weight of the frames, compared by steel bracing. Results showed that Hybrid BRB counteract the negative post-yield stiffness, so their use is more beneficial on buildings where P-Delta effects are more critical. It is found that the repair costs of the buildings with hybrid BRB will be less due to lower residual drifts. As a result, timber steel-BRB has the best energy dissipation and seismic performance due to symmetrical and stable hysteresis curves of buckling restrained braces that can experience the same capacities in tension and compression.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.14 no.6
• /
• pp.153-161
• /
• 2010

Numerous past studies have shown that safety and serviceability of many concrete infrastructures and buildings built in 1970's have far less strength capacities than their original intended design capacities, thereby requiring repair and strengthening. Currently, aged concrete structures are being repaired using various methods developed in the past. Unfortunately, these methods do not consider the specific conditions that these members are under, but they merely attach repairing materials on the external surface for random strength improvements. Therefore, in order to improve repair and strengthening methods by considering composite behavior between repairing material and structural member, enhanced construction methodologies are needed. Also, the enhanced repairing and strengthening methods must be able to be implemented on structural members constructed using high performance concrete to meet the present construction demand of building mammoth structures. Therefore, in this study, a repairing and strengthening method for retrofitting high strength concrete (HSC) columns that can effectively improve column performance is developed. A square HSC column's cross-sectional shape is converted to an octagonal shape by attaching precast members on the surface of the column. Then, the octagonal column surface is surface wrapped using Carbon Fiber Sheets (CFS). The method allows maximum usage of confinement effect from externally jacketing CFS to improve strength and ductility of repaired HSC columns. The research results are discussed in detail.

• Proceedings of the Computational Structural Engineering Institute Conference
• /
• 2008.04a
• /
• pp.50-55
• /
• 2008

In order to investigate and estimate the cause of fatigue crack occurred to curved girder bridge that is used during 20 years, in this study, filed tests to obtain the characteristic of stress hysteresis were performed under the real traffic flows. From these test results, we analyzed the cause of fatigue crack for various fatigue crack patterns. Also, the characteristic of structural behavior for the curved girder bridge were examined from the FE analysis. In addition, to retrofit various fatigue cracks occurred in the bridge, FE analyses considering the characteristics of crack patterns were performed and retrofitting methods were suggested.