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.

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.

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 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 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.

The Influence of Slab on Yield Mechanism of RC Frame Structure

2014 ◽  
Vol 578-579 ◽  
pp. 864-867
Author(s):  
Meng Zhou Lv ◽  
Tian Peng Pan ◽  
Xiao Bo Wu
Keyword(s):  
Seismic Design ◽  
Structure Design ◽  
Frame Structure ◽  
Rc Frame ◽  
Weak Beam ◽  
Rc Frame Structure ◽  
Rc Frame Structures ◽  
Rigid Component ◽  
Structural Engineers ◽  
Beam Form

"Strong column weak beam" form of frame structure is widely considered to be a reasonable framework structure yield mechanism in the seismic damage. The current structure design is mostly on the basis of that yield mechanism for structural seismic design. Generally the structural engineers ignore the bearing capacity contribution of frame beams that comes from the slab in the seismic design. The structure engineers considered the slab as a rigid component and simply calculate the slab stiffness by magnification factor method, which ignores the core of the problem. This paper analyzes mainly the influence of the destruction of slab form frame structure , studying further how slab affect the yield mechanism of frame structure, and explores the destruction form of difference between two models after analyzing two structure models by the method of Push – over. It shows that the existence of slab make the yield mechanism of RC frame structures different from the design.

Research on the Collapse Performance of RC Frame Structure

2014 ◽  
Vol 556-562 ◽  
pp. 712-715
Author(s):  
Jing Zhao ◽  
Jing Zhao ◽  
Xing Wang Liu
Keyword(s):  
Reinforced Concrete ◽  
Frame Structure ◽  
Rc Frame ◽  
Hydraulic Actuator ◽  
Reinforced Concrete Frame ◽  
Concrete Frame ◽  
Load Paths ◽  
Rc Frame Structure ◽  
Gravity Load ◽  
Middle Column

In collapse-resistant design of a structure under accidental local action, it is important to understand the failure mechanism and alternative load paths. In this paper, a pseudo-static experimental method is proposed. Based on which, the collapse of frame structure was simulated with testing a 1/3 scale; 4-bay and 3-story plane reinforced concrete frame. In the experience, the middle column of the bottom floor was replaced by mechanical jacks to simulate its failure, and the simulated superstructure’s gravity load acted on the column of the top floor by adopting a servo-hydraulic actuator with force –controlled mode.

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