scholarly journals Fragility Analysis of RC Frame Structures Subjected to Obliquely Incident Seismic Waves

2021 ◽  
Vol 13 (3) ◽  
pp. 1108
Author(s):  
Bo Huang ◽  
Jiachen Guo ◽  
Kailong Liao ◽  
Yu Zhao
Keyword(s):  
Structural Damage ◽  
Seismic Waves ◽  
Incident Angle ◽  
Structural Characteristics ◽  
Frame Structure ◽  
Fragility Analysis ◽  
Exceedance Probability ◽  
Rc Frame ◽  
Foundation Soil ◽  
Obliquely Incident

Obliquely incident seismic waves have been habitually overlooked in fragility analysis. In this paper, a new approach to solving the equivalent loads on the infinite element boundary due to obliquely incident seismic waves is proposed. Based on the site conditions and structural characteristics in the Jiaxing area, the seismic response of a multi-story reinforced concrete (RC) frame structure has been fully investigated through the finite element method. Under obliquely incident SV waves (shear wave in the vertical x-z plane), the distribution of internal forces on the structure in the case of homogeneous foundation soil is significantly asymmetrical. Among the 3 obliquely incident angles investigated in this paper, the maximum inter-story displacement is smallest when the incident angle is 20° and largest when the angle equals 30°. For the structural fragility, the exceedance probability at each structural damage level is smallest when the incident reflection angle is 20° and largest when the angle equals 30°. When the structure is located in the silty valley, the influence of oblique incidence is attenuated and there is no obvious stress asymmetry on the structure due to the refraction of seismic waves on the interface.

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 Analysis and the Study of Reinforcement Measures for RC Frame Structure Building in Civil Engineering

2012 ◽  
Vol 568 ◽  
pp. 85-88
Author(s):  
Ming Gao
Keyword(s):  
Structural Damage ◽  
Civil Engineering ◽  
Seismic Damage ◽  
Frame Structure ◽  
Bottom Plate ◽  
Rc Frame ◽  
Structure Building ◽  
Damage Degree ◽  
Rc Frame Structure ◽  
Reinforcement Measures

In 5·12 Wenchuan earthquake, most of the buildings were damaged at different degrees in Mianyang. To analysis seismic damage of RC frame structure building, and investigate its reinforcement situation，the results show that: For destruction of frame column or bottom frame structure column, enlarge section method is used mostly for reinforcement in civil engineering；To serious damage of affiliated structure such as filler wall and Parapet, most of them will be demolished and built again, and add constructional column; To the situation of concrete bottom plate with crack, paste carbon fiber sheet or bottom plant steel was used depending on the structural damage degree, and jet concrete for strengthening.

scholarly journals Dynamic Damage Mechanism and Seismic Fragility Analysis of an Aqueduct Structure

2021 ◽  
Vol 11 (24) ◽  
pp. 11709
Author(s):  
Xinyong Xu ◽  
Xuhui Liu ◽  
Li Jiang ◽  
Mohd Yawar Ali Khan
Keyword(s):  
Ground Motion ◽  
Structural Damage ◽  
Large Scale ◽  
Seismic Analysis ◽  
Fragility Curves ◽  
Limit State ◽  
Fragility Analysis ◽  
Seismic Fragility ◽  
Exceedance Probability ◽  
Computation Efficiency

The Concrete Damaged Plasticity (CDP) constitutive is introduced to study the dynamic failure mechanism and the law of damage development to the aqueduct structure during the seismic duration using a large-scale aqueduct structure from the South-to-North Water Division Project (SNWDP) as a research object. Incremental dynamic analysis (IDA) and multiple stripe analysis (MSA) seismic fragility methods are introduced. The spectral acceleration is used as the scale of ground motion record intensity measure (IM), and the aqueduct pier top offset ratio quantifies the limit of structural damage measure (DM). The aqueduct structure’s seismic fragility evaluation curves are constructed with indicators of different seismic intensity measures to depict the damage characteristics of aqueduct structures under different seismic intensities through probability. The results show that penetrating damage is most likely to occur on both sides of the pier cap and around the pier shaft in the event of a rare earthquake, followed by the top of the aqueduct body, which requires the greatest care during an earthquake. The results of two fragility analysis methodologies reveal that the fragility curves are very similar. The aqueduct structure’s first limit state level (LS1) is quite steep and near the vertical line, indicating that maintaining the excellent condition without damage in the seismic analysis will be challenging. Except for individual results, the overall fragility results are in good agreement, and the curve change rule is the same. The exceedance probability in the case of any ground motion record IM may be estimated using only two factors when using the MSA approach, and the computation efficiency is higher. The study of seismic fragility analysis methods in this paper can provide a reference for the seismic safety evaluation of aqueducts and similar structures.

scholarly journals Study on the Effect of Extra Pole Support on Seismic Resistance for Low-Rise RC Structures

2019 ◽  
Vol 2019 ◽  
pp. 1-15 ◽  
Author(s):  
Pengjie Lu ◽  
Guoxin Wang
Keyword(s):  
Rural Areas ◽  
Structural Damage ◽  
Frame Structure ◽  
Seismic Resistance ◽  
Rc Frame ◽  
Rc Structures ◽  
Frame Building ◽  
Rc Frame Structure ◽  
Rc Frame Building ◽  
Almost All

There is a common way to enhance the collapse safety of residential houses using extra tilted poles supporting poor structures from the outside before and/or after earthquakes in seismic regions, especially in rural areas. But, almost all of these supporting measures are still weak and lack of scientific design and evaluation. This study takes a poorly designed two-bay and three-story RC frame building as an object to explore the effect of this kind of support measures on structural seismic resistance by comparing with a standard-designed RC frame structure model as a contrastive case. The results obtained by performance-based methods indicate that extra poles can improve the seismic collapse safety and reduce structural seismic damage of the poorly designed structure (PDS) effectively. The median collapse capacity parameter θ increases from 1.31 g to the range of 1.92∼2.39 g, and SaT1;10% (spectral acceleration at the first-mode period which causes 10% probability of structural collapse) also increases from 0.57 g to the range of 0.75∼1.08 g. Study of dynamic structural damage shows a great damage reduction of PDS under seismic loads, especially SaT1 = 0.2 g. This study proves that this simple measure can improve the seismic resistance of PDS into an acceptable level by taking our suggested practical and efficient supporting schemes.

scholarly journals Evaluation of the Seismic Retrofitting of Mainshock-Damaged Reinforced Concrete Frame Structure Using Steel Braces with Soft Steel Dampers

2021 ◽  
Vol 11 (2) ◽  
pp. 841
Author(s):  
Fujian Yang ◽  
Guoxin Wang ◽  
Mingxin Li
Keyword(s):  
Reinforced Concrete ◽  
Structural Damage ◽  
Time History ◽  
Evaluation Framework ◽  
Seismic Retrofitting ◽  
Frame Structure ◽  
Rc Frame ◽  
Severe Damage ◽  
Rc Frames ◽  
Better Than

Most reinforced concrete (RC) frames would exhibit different degrees of damage after mainshock excitations, and these mainshock-damaged RC (MD-RC) frames are highly vulnerable to severe damage or even complete collapse under aftershock excitations. In the present study, the effectiveness of utilizing soft steel damper (SSD) as a passive energy dissipation device for seismic retrofitting of MD-RC frame under aftershock actions was investigated. A common three-story RC frame in the rural area was employed and a numerical evaluation framework of retrofitting analysis of the MD-RC frame was also proposed. Based on proposed evaluation framework, nonlinear dynamic time history analysis of the MD-RC frame with and without retrofitting schemes was conducted to evaluate the retrofit effect of the retrofitting schemes on the MD-RC frame. The results revealed that the retrofitting schemes could effectively improve the natural vibration characteristics of the MD-RC frame, especially the first-order natural frequency with a maximum increase of nearly four times. The retrofit effect of the MD-RC frame under pulse-like aftershocks is better than non-pulse-like aftershocks and the retrofit effect of minor damage MD-RC frame is slightly better than that of severe damage. In addition, only retrofitting the bottom story of MD-RC frame might cause aggravate structural damage.

Optimal Sensor Placement Algorithm for Structural Damage Identification

2020 ◽  
Vol 14 (1) ◽  
pp. 69-81
Author(s):  
C.H. Li ◽  
Q.W. Yang
Keyword(s):  
Structural Damage ◽  
Damage Identification ◽  
Sensor Placement ◽  
Optimization Procedure ◽  
Frame Structure ◽  
Truss Structures ◽  
Optimal Sensor Placement ◽  
Structural Damage Identification ◽  
Placement Algorithm ◽  
Sensor Locations

Background: Structural damage identification is a very important subject in the field of civil, mechanical and aerospace engineering according to recent patents. Optimal sensor placement is one of the key problems to be solved in structural damage identification. Methods: This paper presents a simple and convenient algorithm for optimizing sensor locations for structural damage identification. Unlike other algorithms found in the published papers, the optimization procedure of sensor placement is divided into two stages. The first stage is to determine the key parts in the whole structure by their contribution to the global flexibility perturbation. The second stage is to place sensors on the nodes associated with those key parts for monitoring possible damage more efficiently. With the sensor locations determined by the proposed optimization process, structural damage can be readily identified by using the incomplete modes yielded from these optimized sensor measurements. In addition, an Improved Ridge Estimate (IRE) technique is proposed in this study to effectively resist the data errors due to modal truncation and measurement noise. Two truss structures and a frame structure are used as examples to demonstrate the feasibility and efficiency of the presented algorithm. Results: From the numerical results, structural damages can be successfully detected by the proposed method using the partial modes yielded by the optimal measurement with 5% noise level. Conclusion: It has been shown that the proposed method is simple to implement and effective for structural damage identification.

SEISMIC RESPONSE OF POWER TRANSMISSION TOWER-LINE SYSTEM UNDER MULTI-COMPONENT MULTI-SUPPORT EXCITATIONS

2012 ◽  
Vol 06 (04) ◽  
pp. 1250025 ◽  
Author(s):  
TIAN LI ◽  
LI HONGNAN ◽  
LIU GUOHUAN
Keyword(s):  
Seismic Waves ◽  
Power Transmission ◽  
Incident Angle ◽  
Ground Motions ◽  
Three Dimensional ◽  
Transmission Tower ◽  
Line System ◽  
Time Stepping ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

The effect of multi-component multi-support excitations on the response of power transmission tower-line system is analyzed in this paper, using three-dimensional finite element time-stepping analysis of a transmission tower-line system based on an actual project. Multi-component multi-support earthquake input waves are generated based on the Code for Design of Seismic of Electrical Installations. Geometric non-linearity was considered in the analysis. An extensive parametric study was conducted to investigate the behavior of the transmission tower-line system under multi-component multi-support seismic excitations. The parameters include single-component multi-support ground motions, multi-component multi-support ground motions, the correlations among the three-component of multi-component multi-support ground motions, the spatial correlation of multi-component multi-support ground motions, the incident angle of multi-component multi-support seismic waves, the ratio of the peak values of the three-component of multi-component multi-support ground motions, and site condition with apparent wave velocity of multi-component multi-support ground motions.

Seismic microzoning in New Zealand

1971 ◽  
Vol 4 (1) ◽  
pp. 43-50
Author(s):  
W. R. Stephenson
Keyword(s):  
New Zealand ◽  
Structural Damage ◽  
Seismic Waves ◽  
Multiple Reflection ◽  
Ground Failure ◽  
Seismic Microzoning ◽  
Popular View ◽  
Wave Trains ◽  
Local Geology ◽  
Ground Damage

"Seismic Microzoning" means many different things to different people. There is always included the element of different damage in nearby areas, but how the differences arise, how we should study them, and how we should apply the results of our studies, are still uncertain. To some people, microzoning refers to structural damage due to ground failure; faulting, slumping and liquefaction all belong in this category. To others, microzoning is the effects of the focussing of seismic waves by boundaries, resulting in modified ground damage and building damage. A third very popular view of microzoning holds that it concerns multiple reflection of seismic waves in layers, with interference of the wave trains giving rise to maxima, where ground and structural damage will be accentuated. Microzoning can be defined as the division of land areas into small regions of differing local geology for which differences in earthquake attack on structures are specified. This paper is an attempt to set down aspects of microzoning in a logical manner, and to relate them. It also discusses activities here and overseas, and considers where microzoning and microzoning research in New Zealand should head.

Diffraction of elastic waves by a fluid-filled crack in a fluid-saturated poroelastic half-space

2021 ◽  
Author(s):  
Zhongxian Liu ◽  
Jiaqiao Liu ◽  
Sibo Meng ◽  
Xiaojian Sun
Keyword(s):  
Half Space ◽  
Seismic Waves ◽  
Incident Angle ◽  
Excitation Frequency ◽  
Vertical Displacement ◽  
Crack Model ◽  
P Waves ◽  
Amplification Effect ◽  
Resonance Frequencies ◽  
Angle Crack

Summary An indirect boundary element method (IBEM) is developed to model the two-dimensional (2D) diffraction of seismic waves by a fluid-filled crack in a fluid-saturated poroelastic half-space, using Green's functions computed considering the distributed loads, flow, and fluid characteristics. The influence of the fluid-filled crack on the diffraction characteristics is investigated by analyzing key parameters, such as the excitation frequency, incident angle, crack width and depth, and medium porosity. The results for the fluid-filled crack model are compared to those for the fluid-free crack model under the same conditions. The numerical results demonstrate that the fluid-filled crack has a significant amplification effect on the surface displacements, and that the effect of the depth of the fluid-filled crack is more complex compared to the influence of other parameters. The resonance diffraction generates an amplification effect in the case of normally incident P waves. Furthermore, the horizontal and vertical displacement amplitudes reach 4.2 and 14.1, respectively. In the corresponding case of the fluid-free crack, the vertical displacement amplitude is only equal to 4.1, indicating the amplification effect of the fluid in the crack. Conversely, for normally incident SV waves at certain resonance frequencies, the displacement amplitudes above a fluid-filled crack may be lower than the displacement amplitudes observed in the corresponding case of a fluid-free crack.

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