scholarly journals Optimal FRP Jacket Placement in RC Frame Structures Towards a Resilient Seismic Design

2019 ◽  
Vol 11 (24) ◽  
pp. 6985 ◽  
Author(s):  
G. Mahdavi ◽  
K. Nasrollahzadeh ◽  
M. A. Hariri-Ardebili
Keyword(s):  
Heuristic Algorithms ◽  
Plastic Hinge ◽  
Optimization Procedure ◽  
Frame Structure ◽  
Frame Structures ◽  
Rc Frame ◽  
Rotation Capacity ◽  
Rc Frame Structure ◽  
Story Drift ◽  
Rc Frame Structures

This paper proposes an optimal plan for seismically retrofitting reinforced concrete (RC) frame structures. In this method, the columns are wrapped by fiber-reinforced polymer (FRP) layers along their plastic hinges. This technique enhances their ductility and increases the resiliency of the structure. Two meta-heuristic algorithms (i.e., genetic algorithm and particle swarm optimization) are adopted for this purpose. The number of FRP layers is assumed to be the design variable. The objective of the optimization procedure was to provide a uniform usage of plastic hinge rotation capacity for all the columns, while minimizing the consumption of the FRP materials. Toward this aim, a single objective function containing penalty terms is introduced. The seismic performance of the case study RC frame was assessed by means of nonlinear pushover analyses, and the capacity of the plastic hinge rotation for FRP-confined columns was evaluated at the life safety performance level. The proposed framework was then applied to a non-ductile low-rise RC frame structure. The optimal retrofit scheme for the frame was determined, and the capacity curve, inter-story drift ratios, and fragility functions were computed and compared with alternative retrofit schemes. The proposed algorithm offers a unique technique for the design of more resilient structures.

Seismic Damage Analyses of Staircases in RC Frame Structures

2012 ◽  
Vol 446-449 ◽  
pp. 2326-2330 ◽  
Author(s):  
Huan Jun Jiang ◽  
Hai Yan Gao ◽  
Bin Wang
Keyword(s):  
Internal Force ◽  
Frame Structure ◽  
Frame Structures ◽  
Rc Frame ◽  
Structural Members ◽  
First Line ◽  
Strong Earthquakes ◽  
Rc Frame Structure ◽  
Rc Frame Structures ◽  
Recent Earthquakes

Staircases in Reinforced Concrete (RC) frame structures suffered severe damages in recent earthquakes although they are regarded as critically important passages during emergencies. Staircases act as the first line of defense in earthquakes, and therefore they first yield and fail. Then they lose the action of safe passages so that the anticipated seismic performance objectives cannot be satisfied. To make sure that staircases work as safe passages in strong earthquakes, the current Chinese code for seismic design of buildings claims special requirements on the design of staircases. At first, the influence of staircases on the structural behavior of a typical RC frame structure is studied by the comparison of internal force in the structural members considering and neglecting the effect of staircases under frequent earthquakes. Besides, the effect of staircases on the yielding and failing mechanism of the frame structure is investigated through static elasto-plastic analyses. From this study the reason of the damages suffered by cast-in-site staircases in RC frame structures under earthquakes can be understood.

Analysis on the Effect of Filler Wall to the Dynamic Characteristics and Storey Displacement of RC Frame Structure

2011 ◽  
Vol 255-260 ◽  
pp. 644-648
Author(s):  
Yan Xia Ye ◽  
Hua Huang ◽  
Dong Wei Li
Keyword(s):  
Dynamic Characteristics ◽  
Seismic Waves ◽  
Great Influence ◽  
Reduction Factor ◽  
Frame Structure ◽  
Vibration Modes ◽  
Rc Frame ◽  
Soft Storey ◽  
Rc Frame Structure ◽  
Rc Frame Structures

Comparative analyses of twenty-eight finite element structures with filler walls were established to study dynamic characteristics of RC frame structures under seismic waves. The results of these analyses show that filler walls have little influence on vibration modes of the structure. But as a result of soft storey in the bottom of building caused by reduction of the filler walls, vibration modes have a great influence. As the stiffness of filler wall decrease, the stiffness of soft storey decrease shapely, vibration mode curve becomes much smoother. Considering the filler wall has influence on the vibration periods of framework, the reduction factor of 0.7 should be taken. The influence of filler wall to the value of lateral drift and storey displacement angle of frame can not be ignored. The main effect factors to the dynamic characteristics of framework are included quantity, location, material of the fill wall and the selection of seismic waves.

Nonlinear Analysis of a RC Frame Structure with Semi-Interlayers Damaged during Wenchuan Earthquake

2010 ◽  
Vol 156-157 ◽  
pp. 467-472
Author(s):  
Peng Tao Yu ◽  
Jing Jiang Sun
Keyword(s):  
Nonlinear Analysis ◽  
Wenchuan Earthquake ◽  
Time History ◽  
Large Earthquake ◽  
Frame Structure ◽  
Nonlinear Time History Analysis ◽  
Frame Structures ◽  
Rc Frame ◽  
Rc Frame Structures ◽  
Nonlinear Time History

Under the excitation of large earthquake, structures enter into high nonlinear stage. Currently, Opensees, Perform-3d and Canny are used as the most popular nonlinear analysis procedures. The fiber model will be introduced firstly and the nonlinear analysis models in Canny are explained in detail. Then Canny2007 is used to conduct nonlinear time history analysis on a heavily damaged frame structure with interlayer in Dujiangyan during Wenchuan Earthquake. Analysis shows that the maximum inter-story drift appears between the interlayer and its upper layer, and the heavy damage agrees well with the results of damage investigation. By comparing the damage extent of frame structures with or without interlayer, it reveals that the seismic performance of RC frame structures without interlayer is obviously better than that of ones with interlayer.

Inter-Story Capacity Spectrum for the Performance Based Seismic Design of Vertically Irregular RC Frame Structures II: Examples

2012 ◽  
Vol 517 ◽  
pp. 749-754
Author(s):  
Jin Jie Men ◽  
Qing Xuan Shi ◽  
Qi Zhou
Keyword(s):  
Time History ◽  
Earthquake Hazard ◽  
Frame Structure ◽  
Rc Frame ◽  
Direct Displacement Based Design ◽  
Capacity Spectrum ◽  
Story Drift ◽  
Performance Based Seismic Design ◽  
Hazard Level ◽  
Rc Frame Structures

The procedure to establish the inter-story capacity spectrum method is explained detailedly in partⅠ. In this part examples are presented to demonstrate the applicability and utility of the proposed method. It is shown that the vertically irregular RC frame structure can be directly designed with the methodology proposed in this work. It is also concluded that the new method can control the inter-story drift, the order and position of hinges of vertically irregular structures under different earthquake hazard level. Comparing to time history analysis method, it leans to cautious and is superior to direct displacement-based design (DDBD).

Analysis for Collapse Process of Multi-Layer RC Frame Structures under Earthquakes

2014 ◽  
Vol 1065-1069 ◽  
pp. 1402-1407 ◽  
Author(s):  
Jia Ming Gao ◽  
Chang Quan Zhou ◽  
Bo Long Liu ◽  
Bo Quan Liu
Keyword(s):  
Time History ◽  
Frame Structure ◽  
Great Earthquake ◽  
Rc Frame ◽  
Structural Collapse ◽  
Constant Stiffness ◽  
Finite Element Software ◽  
Rc Frame Structure ◽  
Object Of Study ◽  
Rc Frame Structures

Multi-storey RC-frame structure occupies a large proportion of the building structure in our country, the collapse of multi-storey frame structure in great earthquake is very serious, and it has become a major threat to people's life and property security, so research of the rule about structural collapse and define the critical state of structural collapse accurately is necessary. This paper focuses on the rule of structural collapse, takes constant stiffness multi-layer RC-frame structure as the object of study, with height, span and number of floors as the variables, uses nonlinear finite element software ANSYS/LS-DYNA, bases on elastic-plastic time history analysis, studies the rule of plastic deformation’s development of constant stiffness multi-layer RC-frame structure, and the relationship between story-drift and structural collapse.

scholarly journals Seismic Performance Assessments of RC Frame Structures Strengthened by External Precast Wall Panel

2020 ◽  
Vol 10 (5) ◽  
pp. 1749
Author(s):  
Seung-Ho Choi ◽  
Jin-Ha Hwang ◽  
Sun-Jin Han ◽  
Hyo-Eun Joo ◽  
Hyun-Do Yun ◽  
...  
Keyword(s):  
Energy Dissipation ◽  
Seismic Performance ◽  
Precast Concrete ◽  
Frame Structure ◽  
Frame Structures ◽  
Rc Frame ◽  
Analysis Model ◽  
Energy Dissipation Capacity ◽  
Precast Walls ◽  
Rc Frame Structures

In recent years, a variety of strengthening methods have been developed to improve the seismic performance of reinforced concrete (RC) frame structures with non-seismic details. In this regard, this study proposes a new type of seismic strengthening method that compresses prefabricated precast concrete (PC) walls from the outside of a building. In order to verify the proposed method, a RC frame structure strengthened with precast walls was fabricated, and cyclic loading tests were performed. The results showed that specimens strengthened using the proposed method exhibited further improvements in strength, stiffness and energy dissipation capacity, compared to RC frame structures with non-seismic details. In addition, a nonlinear analysis method, capable of considering the flexural compression and shear behaviors of the walls, was suggested to analytically evaluate the structural behavior of the frame structures strengthened by the proposed method. Using this, an analysis model for frame structures strengthened with precast walls was proposed. Through the proposed model, the analysis and test results were compared in relation to stiffness, strength, and energy dissipation capacity. Then, the failure mode of the column was evaluated based on the pushover analysis. In addition, this study proposed a simplified analysis model that considered the placement of longitudinal reinforcements in shear walls.

Mechanism of Frictional Mortar-Less Panel and its Application in Reinforcement Concrete Frame

2014 ◽  
Vol 894 ◽  
pp. 82-86
Author(s):  
Xiao Hong Zhou
Keyword(s):  
Finite Element ◽  
Seismic Behavior ◽  
Horizontal Displacement ◽  
Frame Structure ◽  
Rc Frame ◽  
Base Shear ◽  
Concrete Frame ◽  
Rc Frame Structure ◽  
Story Drift ◽  
Considerable Benefit

In order to improve the seismic behavior of the reinforcement concrete frame, a frictional mortar-less panel (FMP) was researched. In this masonry, the bricks are built without mortar and the lateral capability is supported by the friction between bricks. FMP has less rigid in-plane contribution, and contribute mostly to the energy dissipation of structure. To investigate the seismic behavior of FMP, a simple finite element modeling method has been proposed and verified with ANSYS. After that, the FMP was infilled in a typical reinforcement concrete frame structure and a Taft wave has been applied to research on its seismic behavior. The horizontal displacement, story drift, acceleration and base shear/axial force of RC frame has been achieved, results showed the FMP has considerable benefit to the seismic behavior of RC frame structure and worth to be promoted.

scholarly journals Dynamic analysis of multilayer-reinforced concrete frame structures based on NewMark-β method

2021 ◽  
Vol 60 (1) ◽  
pp. 567-577
Author(s):  
Yizhe Liu ◽  
Bofang Zhang ◽  
Ting Wang ◽  
Tian Su ◽  
Hanyang Chen
Keyword(s):  
Reinforced Concrete ◽  
Seismic Analysis ◽  
Frame Structure ◽  
Frame Structures ◽  
Stiffness Coefficient ◽  
Rc Frame ◽  
Rc Frame Structure ◽  
Rc Structure ◽  
Reduction Coefficient ◽  
The Impact

Abstract The analysis method of the simplified structure formation model provides the basis for the analysis of the reinforced concrete (RC) structure under earthquake and dynamic load, which has important significance for seismic analysis of RC structure. In this paper, the three-layer RC frame structure is simulated and analyzed by MATLAB based on the NewMark-β method, considering the influence of time-varying simple harmonic loads and seismic waves on acceleration, displacement, and velocity of RC structure. The vibration response of the RC structure is analyzed by introducing the stiffness reduction coefficient. The results show that NewMark-β method provides a new idea for the seismic response of RC frame structures, making the seismic analysis of frame structures more practical; the variation range of its elastic modulus is obtained through the analysis of the constitutive model of RC, which provides the basis for the value of the stiffness coefficient; the application of the top load and the bottom load has different structural responses to the RC frame structure, and the impact of the load on the structure is more adverse when the load acts on the bottom; with the change of time, the binding stiffness coefficient will also change, and the stability of the structure will decrease greatly; the function relationship between the acceleration of the third floor and the reduction coefficient of rigidity is obtained by taking different values of the reduction coefficient of rigidity.

scholarly journals Refined Seismic Design Method for RC Frame Structures to Increase the Collapse Resistant Capacity

2020 ◽  
Vol 10 (22) ◽  
pp. 8230
Author(s):  
Mengmeng Gao ◽  
Shuang Li
Keyword(s):  
Seismic Design ◽  
Design Method ◽  
Frame Structure ◽  
Elastic Response ◽  
Frame Structures ◽  
Rc Frame ◽  
Structural Collapse ◽  
Damage State ◽  
Rc Frame Structures ◽  
Seismic Design Method

In current structural design codes, elastic vibration modes are used for seismic design. However, when a structure is subjected to strong earthquakes and inelastic response or even when collapse damage is observed, the damage state is always unevenly distributed along the height of the structure. Such a phenomenon implies the materials of stories with elastic response and slight damage are not fully utilized. In this paper, a new practical and effective method, which improves collapse resistant capacity by making full use of materials, is proposed for reinforcement concrete (RC) frame structures at a structural collapse state. In this method, incremental dynamic analysis (IDA) is used to evaluate the structural collapse capacity. Tangent_ratio (TR) is formulated based on the IDA curves, and the longitudinal reinforcement of columns is modified based on the TR to achieve uniform distribution of damage along the height of building. Fewer variables are optimized and constraints of the provisions in current codes are considered, which makes the proposed procedure more computationally efficient and practical. The proposed method is employed on a 5-story RC frame structure to illustrate its feasibility and practicality. Comparison work indicates that the refined seismic design method can significantly increase the collapse resistant capacity and decrease the maximum inter-story drift ratio response under strong ground motion in a few iterative steps without a cost increase.

scholarly journals Assessing Seismic Collapse Safety and Retrofitting Low-Ductility RC Frame Structures on the Basis of the Acceptable Collapse Safety Margin in China

2020 ◽  
Vol 10 (4) ◽  
pp. 1238
Author(s):  
Lina Xian ◽  
Haiqing Liu ◽  
Zhongwei Zhao ◽  
Ni Zhang
Keyword(s):  
Cross Sections ◽  
Safety Margin ◽  
Frame Structure ◽  
Rc Frame ◽  
Collapse Probability ◽  
Rc Frame Structure ◽  
Collapse Resistance ◽  
Seismic Collapse ◽  
Before And After ◽  
Rc Frame Structures

The relationship between the average annual collapse probability and collapse safety margin of structures is identified to evaluate structural collapse performance quantitatively. A method is then proposed to determine the acceptable collapse margin ratio (CMR) with a certain annual collapse probability. Two methods, namely adopting steel braces and enlarging column cross sections, are used to retrofit a four-story, low-ductility reinforced concrete (RC) frame structure. On the basis of the acceptable CMR, the seismic collapse resistance of the structure is assessed before and after strengthening. Furthermore, a four-story RC frame structure, which is designed in conformity to the minimum design criteria of the building code, is constructed. The incremental dynamic analysis method is used in consideration of collapse uncertainties. Results show that when the acceptable annual collapse probability is equal to 1.24 × 10−4, which is calculated using the collapse probability at maximum considered earthquake (5%, as proposed in CECS 392), the collapse safety margin of the four structures does not satisfy the seismic collapse resistance requirements with large collapse uncertainty. The structures that are retrofitted and designed in conformity to the code can satisfy the collapse safety margin requirements when the acceptable annual collapse probability is increased to 2 × 10−4. The comparison of the two retrofitting schemes used to improve the seismic collapse resistance of the structure indicates that the steel brace-retrofitting method is better than increasing the column section. This work is an important reference for the reinforcement of the seismic resistance of structures and for corresponding research on collapse resistance.

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