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.

scholarly journals Prediction of the Fundamental Period of Infilled RC Frame Structures Using Artificial Neural Networks

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Panagiotis G. Asteris ◽  
Athanasios K. Tsaris ◽  
Liborio Cavaleri ◽  
Constantinos C. Repapis ◽  
Angeliki Papalou ◽  
...  
Keyword(s):  
Neural Networks ◽  
Artificial Neural Networks ◽  
Fundamental Period ◽  
Critical Parameters ◽  
Frame Structures ◽  
Rc Frame ◽  
Infill Walls ◽  
Rc Structures ◽  
Artificial Neural ◽  
Rc Frame Structures

The fundamental period is one of the most critical parameters for the seismic design of structures. There are several literature approaches for its estimation which often conflict with each other, making their use questionable. Furthermore, the majority of these approaches do not take into account the presence of infill walls into the structure despite the fact that infill walls increase the stiffness and mass of structure leading to significant changes in the fundamental period. In the present paper, artificial neural networks (ANNs) are used to predict the fundamental period of infilled reinforced concrete (RC) structures. For the training and the validation of the ANN, a large data set is used based on a detailed investigation of the parameters that affect the fundamental period of RC structures. The comparison of the predicted values with analytical ones indicates the potential of using ANNs for the prediction of the fundamental period of infilled RC frame structures taking into account the crucial parameters that influence its value.

Effects of Modeling Staircases on Seismic Responses of Concrete Frames

2017 ◽  
Vol 23 ◽  
pp. 72-87 ◽  
Author(s):  
Majid Ghaderi Garakani ◽  
Saeed Mahjoubi ◽  
Shervin Maleki
Keyword(s):  
Frame Structures ◽  
Second Step ◽  
Seismic Loads ◽  
Rc Frame ◽  
Concrete Frames ◽  
Strong Earthquakes ◽  
Shell Elements ◽  
Rc Frames ◽  
Rc Frame Structures ◽  
Bracing System

Staircases in reinforced concrete (RC) frame structures have suffered severe damages in past earthquakes, despite being regarded as the main means of egress during emergencies. To make sure that staircases perform as safe passages in strong earthquakes, the performance of RC stair structures should be scrutinized under major earthquakes. In this research at first, staircases were simulated as shell elements in RC frames and analyzed under gravity loads in order to find the maximum forces and moments. In the second step, the influence of staircases on the structural behavior of RC frame structures under seismic loads was studied. The results showed that stairs act as a K-type bracing system. Furthermore, a parametric study was carried out and relations for calculating force and moment in stairs slabs that had been determined under gravity loads, were modified. In addition, affected areas of structure interacting with the stairs in an earthquake were distinguished.

scholarly journals Experimental and Analytical Study on Seismic Behavior of Strengthened Existing Single Frame Structures with Exterior Cantilevers

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Bo Hu ◽  
Xinyu Wei ◽  
Henglin Lv ◽  
Tribikram Kundu ◽  
Ning Li
Keyword(s):  
Shear Walls ◽  
Shear Wall ◽  
Hysteretic Behavior ◽  
Frame Structures ◽  
Structural Redundancy ◽  
Skeleton Curve ◽  
Rc Frames ◽  
Weak Beam ◽  
Single Frame ◽  
Strength And Stiffness

Three single reinforcement concrete (RC) frames, including 1 reference specimen and 2 specimens strengthened with shear walls, were fabricated and subjected to low cyclic loadings, in order to evaluate seismic performances of strengthened single frame structures with exterior cantilevers. Through comparison and analysis of failure mode, hysteretic behavior, skeleton curve, energy dissipation, strength, and stiffness degradation of the tested frames, the validity of the shear wall-based reinforcement method for single frames was verified. Test results indicate that the stiffness and load-bearing capacities of strengthened frames increased considerably in comparison with the reference frame. A “strong column-weak beam” failure pattern was observed on the cantilever side, and the failure of the shear wall was always prior to the column, which can increase the structural redundancy and improve the failure mechanism and seismic performance of an existing single frame.

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.

Structural Health Monitoring for Local Damages of RC Walls Using Piezoceramic-Based Sensors Under Seismic Loading

2017 ◽  
Author(s):  
Wen-I Liao ◽  
Wen-Yu Jean
Keyword(s):  
Structural Health Monitoring ◽  
Earthquake Engineering ◽  
Health Monitoring ◽  
Shear Walls ◽  
Seismic Loading ◽  
The Other ◽  
Loading Test ◽  
Rc Structures ◽  
Engineering Research ◽  
Structural Health

Structural health monitoring of reinforced concrete (RC) structures under seismic loads have recently attracted dramatic attention in the earthquake engineering research community. In this study, reversed cyclic loading test of structural health monitoring of RC shear walls using piezoceramic (PZT)-based sensors are presented. The piezoceramic-based sensors called “smart aggregate (SA)”, was pre-embedded before casting of concrete and adopted for the structural health monitoring of the RC shear wall under seismic loading. Two RC walls were adopted in this test, one is the wall having damages in the boundary columns and foundation of the specimen, and the other is the wall having damages in the upper part of the wall panel. During the test, SAs embedded in the foundation were used as actuators to generate propagating waves, and the other selected SAs were used to detect the waves. By analyzing the wave response, the existence and locations of cracks and damages can be detected and the severity can be estimated. The experimental results demonstrate the sensitiveness and the effectiveness of the piezoceramic-based approach in the structural health monitoring and the identification of damage locations of shear governed concrete structures under seismic loading.

scholarly journals Optimization and Effectiveness of The Placement of Energy Dissipators In Rc Frame Structures 

2021 ◽  
Author(s):  
David Jesus Dominguez
Keyword(s):  
Time History ◽  
Frame Structures ◽  
Existing Buildings ◽  
Capacity Curves ◽  
Rc Frames ◽  
Dynamic Analyses ◽  
Energy Dissipators ◽  
Lower Height ◽  
Rc Frame Structures ◽  
San Andres

Abstract This document explores and analyzes the optimization of the use and placement of energy dissipators in the bays of frame structures located in seismic zones. This study may be applied to new and existing buildings. In order to do this, three RC frames of 5, 10 and 15 stories are analyzed and compared, using four brace arrangements (Chevron braces San Andrés cross and diagonal braces (two cases)). The behavior of these frames is analyzed in terms of modal parameters, capacity curves (Push-over) and dynamic analyses (Time-History). For the study, the Lorca record of mean magnitude was used, also in this case, hysteretic dissipators have been used as they are cheap and easy to install solutions. The efficiency of the energy dissipators is improved as the frames increase in height. In the lower height frames, the use of braced solutions without any device improves the structural behavior. The ductility of all frames increases with the placement of dissipators.

scholarly journals Seismic performance of brick masonry infilled frame structures with bed joint reinforcements

2020 ◽  
Vol 156 ◽  
pp. 03004
Author(s):  
Maidiawati ◽  
Jafril Tanjung ◽  
Yulia Hayati ◽  
Agus ◽  
Satria Rangga
Keyword(s):  
Seismic Performance ◽  
Frame Structure ◽  
Frame Structures ◽  
Rc Frame ◽  
Infilled Frame ◽  
Rc Frames ◽  
Lateral Strength ◽  
Plane Direction ◽  
Infilled Rc Frames ◽  
Reversed Cyclic

This paper presents the evaluation of the seismic performance of brick infilled RC frame structures with bed joint reinforcements based on reversed cyclic lateral load tests. Three specimens of the structural model of 1/4 scale-down single-story single-bay brick infilled RC frame was prepared, which were brick infilled RC frames with and without bed joint reinforcements. Two specimens of brick infills with bed joint reinforcements were different in the spacing of bed joint rebars. The specimens were tested by applying a reversed cyclic lateral loading in-plane direction. During the tests, the crack propagation was observed at the peak and residual drifts of each loading cycle to recognize the failure mechanisms of the specimens. As the results, although the use of the bed joint reinforcements ineffective to increase the lateral strength of the overall infilled frame structure. The rebars in mortar bed joints role to sustain the lateral strength in plastic deformation, and provide the whole structure with high ductility. It seemed that the rebars in mortar bed joints confined the brick infills. Therefore, the infilled RC frames can survive in large deformation without failure of the infills in out of the plane direction.

Cumulative damage effects of mainshock-aftershock sequences on RC-frame structures

2019 ◽  
Vol 32 (3-4) ◽  
pp. 157-169
Author(s):  
Lingxin Zhang ◽  
◽  
Baijie Zhu ◽  
Yunqin Xue ◽  
Jialu Ma ◽  
...  
Keyword(s):  
Cumulative Damage ◽  
Frame Structures ◽  
Rc Frame ◽  
Aftershock Sequences ◽  
Rc Frame Structures

scholarly journals Seismic Response of RC Frames with a Soft First Story Retrofitted with Hysteretic Dampers under Near-Fault Earthquakes

2021 ◽  
Vol 11 (3) ◽  
pp. 1290
Author(s):  
Santiago Mota-Páez ◽  
David Escolano-Margarit ◽  
Amadeo Benavent-Climent
Keyword(s):  
Cost Effective ◽  
Far Field ◽  
Soft Story ◽  
Near Fault ◽  
Rc Frames ◽  
Story Drift ◽  
Number Of Cycles ◽  
Rc Frame Structures ◽  
Near Fault Earthquakes ◽  
Hysteretic Dampers

Reinforced concrete (RC) frame structures with open first stories and masonry infill walls at the upper stories are very common in seismic areas. Under strong earthquakes, most of the energy dissipation demand imposed by the earthquake concentrates in the first story, and this eventually leads the building to collapse. A very efficient and cost-effective solution for the seismic upgrading of this type of structure consists of installing hysteretic dampers in the first story. This paper investigates the response of RC soft-story frames retrofitted with hysteretic dampers subjected to near-fault ground motions in terms of maximum displacements and lateral seismic forces and compares them with those obtained by far-field earthquakes. It is found that for similar levels of total seismic input energy, the maximum displacements in the first story caused by near-fault earthquakes are about 1.3 times larger than those under far-field earthquakes, while the maximum inter-story drift in the upper stories and the distribution and values of the lateral forces are scarcely affected. It is concluded that the maximum displacements can be easily predicted from the energy balance of the structure by using appropriate values for the parameter that reflects the influence of the impulsivity of the ground motion: the so-called equivalent number of cycles.

Sign in / Sign up

Export Citation Format

Share Document