scholarly journals An Experimental Study on Hybrid Noncompression CF Bracing and GF Sheet Wrapping Reinforcement Method to Restore Damaged RC Structures

2015 ◽  
Vol 2015 ◽  
pp. 1-13 ◽  
Author(s):  
Kang Seok Lee
Keyword(s):  
Seismic Retrofitting ◽  
Strengthening Effect ◽  
Reinforcement Scheme ◽  
Rc Structures ◽  
Rc Frames ◽  
Study Results ◽  
Lateral Strength ◽  
Strength And Stiffness ◽  
Cyclic Loading Tests ◽  
Bracing System

We describe a novel technique for restoration of reinforced concrete (RC) structures that have sustained damage during an earthquake. The reinforcement scheme described here is a hybrid seismic retrofitting technique that combines noncompression X-bracing using CF with externally bonded GF sheets to strengthen RC structures that have sustained damage following an earthquake. The GF sheet is used to improve the ductility of columns, and the noncompression CF X-bracing system, which consists of CF bracing and anchors to replace the conventional steel bracing and bolt connections, is used to increase the lateral strength of the framing system. We report seismic restoration capacity, which enables reuse of the damaged RC frames via the hybrid CF X-bracing and GF sheet wrapping system. Cyclic loading tests were carried out to investigate hysteresis of the lateral load-drift relations, as well as the ductility. The GF sheet significantly improved the ductility of columns, resulting in a change in failure mode. The strengthening effect of conventional CF sheets used in columns is not sufficient with respect to lateral strength and stiffness. However, this study results in a significant increase in the strength of the structure due to the use of CF X-bracing and inhibited buckling failure of the bracing. This result can be exploited to develop guidelines for the application of the reinforcement system to restore damaged RC structures.

scholarly journals Comparative Evaluation of Concentric Bracing Systems for Lateral Loads on Medium Rise Steel Building Structures

2020 ◽  
pp. 124-130
Author(s):  
Sisaynew Tesfaw Admassu
Keyword(s):  
Lateral Displacement ◽  
Level Structure ◽  
Lateral Load ◽  
Frame Structure ◽  
Lateral Stiffness ◽  
Building Structures ◽  
Steel Buildings ◽  
Lateral Strength ◽  
Strength And Stiffness ◽  
Bracing System

To resistance, the lateral load from wind or an earthquake is that the reason for the evolution of varied structural systems. Because, when a medium or any multi-level structure is exposed to horizontal or torsional deflections under the action of seismic burdens. Lateral stiffness is a major consideration in the design of the buildings. In addition to this, many existing steel buildings and reinforced concrete buildings for which the weak lateral stiffness is the main problem; should be retrofitted to conquer the insufficiencies to resist the lateral loading. Lateral load resisting systems are structural elements providing basic lateral strength and stiffness, without which the structure would be laterally unstable. The unstable nature of the structure is solved by the fitting arrangement of bracings systems. A bracing system is that forms an integral part of the frame. Thus, such a structure has to be analyzed before arriving at the best type or effective arrangement of bracing. Bracing is a highly effective strategy of resisting lateral forces in a frame structure. In this document, a ten-story building with incorporated bracing systems is analysed using ETABS 2016 analysis software as per Eurocode and Ethiopian Building Code Standards (EBCS). Then, the lateral displacement is evaluated under each of the bracing types.

Retrofitting Non-Ductile RC Frames for Seismic Resistance Using Post-Installed Shear Walls

2019 ◽  
Author(s):  
Chien-Kuo Chiu ◽  
Fu-Pei Hsiao ◽  
Wen-I Liao ◽  
Samuel Jonathan Quacoo ◽  
Chin-En Ho ◽  
...  
Keyword(s):  
Brittle Failure ◽  
Load Transfer ◽  
Shear Walls ◽  
Frame Structures ◽  
Seismic Capacity ◽  
Rc Structures ◽  
Structural Health ◽  
Rc Frames ◽  
Lateral Strength ◽  
Rc Frame Structures

Abstract Reinforced Concrete (RC) frame structures that were designed and built according to older standards can be damaged during destructive earthquakes as a result of insufficient lateral strength and/or deformation capacity. Such structures must be retrofitted to satisfy the current requirements and to survive future earthquakes. Owing to its high lateral strength and stiffness capacity of an RC wall, the post-installation of an RC wall in a non-ductile frame for retrofit is a widely used retrofitting technique. However, for frame structures with low-strength concrete, the typically used connected construction method on the interface between existing and new concrete may be not able to provide effective force transfer, and may cause unexpected brittle failure in the retrofitted structure. Such unexpected brittle failure may reduce the seismic capacity of the structure and threaten its safety. Therefore, in this experimental investigation, two retrofitting methods that use a post-installed RC wall are proposed to improve the load transfer mechanism on the interface. The first involves a wall with diagonal rebar and boundary spirals, and the second involves a wall with an additional inner frame. A typical traditional retrofitting specimen was constructed and tested for comparison. Reversed cyclic loading is used to test the seismic capacity of the specimens. Finally, post-embedded piezoceramic-based sensors were used to monitor the structural health and detect damage in one of specimens during the test. The experimental results demonstrate the effectiveness of the piezoceramic-based approach to structural health monitoring and the ability of the method to detect damage in shear governed RC structures under seismic loading.

Restoring Force Model of Joints of RC Frame Retrofitted by FRP

2012 ◽  
Vol 256-259 ◽  
pp. 693-696
Author(s):  
Peng Li ◽  
Ya Ping Peng ◽  
Er Lei Yao
Keyword(s):  
Seismic Performance ◽  
Seismic Retrofitting ◽  
Frame Structure ◽  
Force Model ◽  
Strengthening Effect ◽  
Rc Frame ◽  
Restoring Force ◽  
Rc Frames ◽  
Restoring Force Model ◽  
Hysteretic Performance

In order to evaluate the seismic performance of reinforced concrete (RC) frames retrofitted by FRP, the experiment of RC frames retrofitted at joints by FRP was carried out. The enhancement in seismic performance of the retrofitted frames is evaluated in hysteretic performance, bearing capacity, stiffness degradation and energy dissipation. And the strengthening effect of the frame retrofitted by CFRP and C/GFRP was compared in the experiment. The restoring force model of RC frame joints retrofitted with FRP was proposed and ranges of the characteristic parameters were determined. The equation of restoring force model for joints strengthened by C/GFRP was suggested. The result show that seismic performance of RC frame retrofitted by FRP based on joints can be improved remarkably. The restoring force model which proposed can be used in seismic elasto-plastic analysis of RC frame structure retrofitted by FRP and practical engineering seismic retrofitting design by FRP.

An Experimental Study on Reinforced Concrete Infilled Frames with Openings

2013 ◽  
Vol 747 ◽  
pp. 429-432 ◽  
Author(s):  
Fatih Suleyman Balik ◽  
Hasan Husnu Korkmaz ◽  
Mehmet Kamanli ◽  
Fatih Bahadir ◽  
Serra Zerrin Korkmaz ◽  
...  
Keyword(s):  
Reinforced Concrete ◽  
Experimental Studies ◽  
Rc Buildings ◽  
Concrete Frames ◽  
Rc Frames ◽  
Lateral Strength ◽  
Structural Failures ◽  
Strength And Stiffness ◽  
Recent Earthquakes ◽  
Infilled Rc Frames

In the last decade, seven major earthquakes caused significant casualties and extensive structural failures. Thousands of RC buildings were severely damaged or collapsed in Turkey due to various deficiencies. This has initiated experimental studies on strengthening methods and intensive researches regarding the rehabilitation of reinforced concrete structures by introducing reinforced concrete infill walls were carried out. Strengthening of reinforced concrete frames by cast-in-place reinforced concrete infills is commonly used in practice. Many structures were also repaired using this technique after the recent earthquakes. In this experimental research, six, one-bay/two-story, 1/3-scaled non-ductile, undamaged reinforced concrete (RC) frames were constructed and tested to investigate the behavior of frames strengthened by introducing infills with or without openings. The test specimens were subjected to reversed cyclic quasi-static lateral loading. The specimens were constructed with the most commonly observed deficiencies in residential RC buildings in Turkey. The first specimen was the reference bare specimen and contained no strengthening. The other specimens were infilled with RC panels with openings having different ratios and configurations. Strength, stiffness and storey drifts of the test specimens were measured and compared. Test results indicated that infilled RC frames displayed significantly higher lateral strength and stiffness than the non-ductile bare frame considerably.

A Novel Technique of Seismic Strengthening of Nonductile RC Frame using Steel Caging and Aluminum Shear Yielding Damper

2009 ◽  
Vol 25 (2) ◽  
pp. 415-437 ◽  
Author(s):  
Dipti R. Sahoo ◽  
Durgesh C. Rai
Keyword(s):  
Energy Dissipation ◽  
Lateral Load ◽  
Rc Frame ◽  
Test Protocol ◽  
Shear Yielding ◽  
Reduction In Force ◽  
Rc Frames ◽  
Lateral Strength ◽  
Lateral Displacements ◽  
Strength And Stiffness

A novel strengthening scheme for seismically-weak RC frames is proposed which utilizes external steel caging to improve flexural/shear strength of columns and aluminum shear-yielding damper ( Al-SYD) to further enhance lateral strength, stiffness and overall energy dissipation capacity of the frame. This paper describes the effectiveness of this scheme as evidenced in an experimental study on a reduced scale (1:2.5) single-story, single-bay, gravity-only designed reinforced concrete (RC) frame. The strengthened frame was simultaneously subjected to gravity loads and reversed cyclic lateral displacements as per ACI-374 loading protocol. An innovative connection scheme was designed to transfer a portion of frame lateral load to the energy dissipation device ( Al-SYD). Besides the significant increase in lateral strength and stiffness of the strengthened frame, RC frame members did not suffer any major damage during the entire test protocol. This indicates significant reduction in force demand on existing RC members because of enhanced energy dissipation through hysteretic shear yielding of aluminum panels. Moreover, the simple connection scheme proposed in this study proved very efficient in transferring the frame lateral load to strengthening elements.

scholarly journals Seismic Strengthening Effects of Full-Size Reinforced Concrete Frame Retrofitted with Novel Concrete-Filled Tube Modular Frame by Pseudo-Dynamic Testing

2021 ◽  
Vol 11 (11) ◽  
pp. 4898
Author(s):  
Jin-Seon Kim ◽  
Ju-Seong Jung ◽  
Dong-Keun Jung ◽  
Eui-Yong Kim ◽  
Kang-Seok Lee
Keyword(s):  
Dynamic Analysis ◽  
Shear Failure ◽  
Dynamic Testing ◽  
Seismic Intensity ◽  
Seismic Retrofitting ◽  
Restoring Force ◽  
Rc Structures ◽  
Linear Dynamic ◽  
Non Linear ◽  
Force Characteristics

The present study proposes a new seismic retrofitting method using a concrete-filled tube modular frame (CFT-MF) system, a novel technique to overcome and improve the limitations of existing seismic strengthening methods. This CFT-MF seismic retrofitting method makes the most of the advantages of both concrete and steel pipes, thereby significantly improving constructability and increasing integration between the existing structure and the reinforcement joints. This method falls into the category of typical seismic retrofitting methods that focus on increasing strength, in which the required amount of seismic reinforcement can be easily estimated. Therefore, the method provides an easy solution to improving the strength of existing reinforced concrete (RC) structures with non-seismic details that are prone to shear failure. In the present study, a full-size two-story test frame modeled from existing domestic RC structures with non-seismic details was subjected to pseudo-dynamic testing. As a result, the effect of the CFT-MF system, when applied to existing RC structures, was examined and verified, especially as to its seismic retrofitting performance, i.e., restoring force characteristics, stiffness reinforcement, and seismic response control. In addition, based on the pseudo-dynamic testing results, a restoring force characteristics model was proposed to implement non-linear dynamic analysis of a structure retrofitted with the CFT-MF system (i.e., the test frame). Finally, based on the proposed restoring force characteristics, non-linear dynamic analysis was conducted, and the results were compared with those obtained by the pseudo-dynamic tests. The results showed that the RC frame (building) with no retrofitting measures applied underwent shear failure at a seismic intensity of 200 cm/s2, the threshold applied in seismic design in Korea. In contrast, in the frame (building) retrofitted with the CFT-MF system, only minor earthquake damage was observed, and even when the maximum seismic intensity (300 cm/s2) that may occur in Korean was applied, small-scale damage was observed. These results confirmed the validity of the seismic retrofitting method based on the CFT-MF system developed in the present study. The non-linear dynamic analysis and the pseudo-dynamic test showed similar results, with an average deviation of 10% or less in seismic response load and displacement.

scholarly journals Multiobjective optimal design of reinforced concrete frames using two metaheuristic algorithms

2021 ◽  
Vol 9 (4B) ◽  
Author(s):  
Mehdi Babaei ◽  
◽  
Masoud Mollayi ◽  
Keyword(s):  
Reinforced Concrete ◽  
Optimal Design ◽  
Optimization Problem ◽  
Numerical Models ◽  
Steel Structures ◽  
Metaheuristic Algorithms ◽  
Rc Structures ◽  
Weighted Sum Method ◽  
Rc Frames ◽  
Single Objective

Genetic algorithm (GA) and differential evolution (DE) are metaheuristic algorithms that have shown a favorable performance in the optimization of complex problems. In recent years, only GA has been widely used for single-objective optimal design of reinforced concrete (RC) structures; however, it has been applied for multiobjective optimization of steel structures. In this article, the total structural cost and the roof displacement are considered as objective functions for the optimal design of the RC frames. Using the weighted sum method (WSM) approach, the two-objective optimization problem is converted to a single-objective optimization problem. The size of the beams and columns are considered as design variables, and the design requirements of the ACI-318 are employed as constraints. Five numerical models are studied to test the efficiency of the GA and DE algorithms. Pareto front curves are obtained for the building models using both algorithms. The detailed results show the accuracy and convergence speed of the algorithms.

scholarly journals Pounding Effects on the Earthquake Response of Adjacent Reinforced Concrete Structures Strengthened by Cable Elements

2014 ◽  
Vol 44 (2) ◽  
pp. 41-56 ◽  
Author(s):  
Angelos Liolios ◽  
Asterios Liolios ◽  
George Hatzigeorgiou ◽  
Stefan Radev
Keyword(s):  
Reinforced Concrete ◽  
Numerical Approach ◽  
Earthquake Response ◽  
Existing Buildings ◽  
The Finite Element Method ◽  
Time Step ◽  
Engineering Structures ◽  
Rc Structures ◽  
Incremental Approach ◽  
Rc Frames

Abstract A numerical approach for estimating the effects of pounding (seismic interaction) on the response of adjacent Civil Engineering structures is presented. Emphasis is given to reinforced concrete (RC) frames of existing buildings which are seismically strengthened by cable-elements. A double discretization, in space by the Finite Element Method and in time by a direct incremental approach is used. The unilateral behaviours of both, the cable-elements and the interfaces contact-constraints, are taken strictly into account and result to inequality constitutive conditions. So, in each time-step, a non-convex linear complementarity problem is solved. It is found that pounding and cable strengthening have significant effects on the earthquake response and, hence, on the seismic upgrading of existing adjacent RC structures.

scholarly journals Damage Source Identification of Reinforced Concrete Structure Using Acoustic Emission Technique

2013 ◽  
Vol 2013 ◽  
pp. 1-5
Author(s):  
Alireza Panjsetooni ◽  
Norazura Muhamad Bunnori ◽  
Amir Hossein Vakili
Keyword(s):  
Acoustic Emission ◽  
Reinforced Concrete ◽  
Nondestructive Evaluation ◽  
Analysis Method ◽  
Reinforced Concrete Structure ◽  
Acoustic Emission Technique ◽  
Rc Structures ◽  
Rc Frames ◽  
Damage Monitoring ◽  
Investigation Process

Acoustic emission (AE) technique is one of the nondestructive evaluation (NDE) techniques that have been considered as the prime candidate for structural health and damage monitoring in loaded structures. This technique was employed for investigation process of damage in reinforced concrete (RC) frame specimens. A number of reinforced concrete RC frames were tested under loading cycle and were simultaneously monitored using AE. The AE test data were analyzed using the AE source location analysis method. The results showed that AE technique is suitable to identify the sources location of damage in RC structures.

Unilateral Damage in Reinforced Concrete Frames

2015 ◽  
pp. 445-502
Keyword(s):  
Cyclic Loading ◽  
Damage Mechanics ◽  
Industrial Applications ◽  
Concrete Frames ◽  
Dual Systems ◽  
Rc Structures ◽  
Damage Models ◽  
Rc Frames ◽  
Earthquake Vulnerability ◽  
Inertia Forces

One of the main applications of the lumped damage mechanics or the damage mechanics of dual systems is the earthquake vulnerability assessment of structures. This means not only the consideration of the inertia forces but, mainly, the adequate description of crack propagation under general cyclic loading. Chapter 9 described the concept of unilateral damage (i.e. the appearance of distinct and independent sets of cracks after loading reversals). This phenomenon can also be observed in RC structures, and the models presented in Chapters 10 and 11 do not describe it; thus, they should be used only in the cases of mono sign loadings. The first goal of this chapter is the generalization of the damage models, including unilateral effects; the next one consists of the development of lumped damage models for tridimensional analysis of RC frames. Finally, some guidelines for the use of the damage models in industrial applications are presented.

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