scholarly journals Seismic Fragility Analysis of Base Isolated Structure Subjected to Near-fault Ground Motions

2021 ◽  
Author(s):  
Chengqing Liu ◽  
Dengjia Fang ◽  
Zhengxi Yan
Keyword(s):  
Horizontal Displacement ◽  
Element Model ◽  
Seismic Intensity ◽  
Fragility Curve ◽  
Near Fault ◽  
Damage Probability ◽  
Story Drift ◽  
Near Fault Earthquakes ◽  
Far Fault ◽  
Nonlinear Finite Element Model

In order to better evaluate the performance of the base isolated structure under the near-fault earthquakes, this paper takes into consideration an existing engineering case study in China as the prototype, and uses OpenSEES platform to establish the nonlinear finite element model of the base isolated structure. The nonlinear response of the isolated structure under the near-fault earthquake is analyzed. The incremental dynamic analysis (IDA) method is used to calculate the damage probability of the structure under the near-fault earthquake, and the fragility curve of the base isolated structure is established. The fragility equation is obtained by nonlinear regression, and the error of fragility equation is analyzed. The results show that the maximum value of the inter-story drift of the upper structure under the action of near-fault earthquake is significantly greater than that under the action of far-fault earthquake. With the increase of seismic intensity, the damage probability of base isolated structure increases nonlinearly, and the maximum response value of horizontal displacement of bearing and inter-story drift of superstructure increases generally. In addition, the exceeding probability of the fragility curve based on PSDA is greater than that based on EDP criterion. When the sample points of the two methods are the same, the exceeding probability points calculated based on PSDA can be regarded as accurate values. The fragility curve based on PSDA may overestimate the exceeding probability to some extent, and the overestimation may be enlarged with the increase of failure stage.

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.

Failure Mechanism of Reinforced Concrete Rib Arch Bridge under Near-Fault Earthquakes

2011 ◽  
Vol 90-93 ◽  
pp. 940-945
Author(s):  
Wen Jun Gao ◽  
Guang Wu Tang ◽  
Yi Da Kong
Keyword(s):  
Reinforced Concrete ◽  
Nonlinear Response ◽  
Plastic Hinge ◽  
Seismic Damage ◽  
Arch Bridge ◽  
2008 Wenchuan Earthquake ◽  
Near Fault ◽  
Pulse Type ◽  
Near Fault Earthquakes ◽  
Far Fault

A typical reinforced concrete rib arch bridge was chosen to investigate its nonlinear response to near-fault ground motions recorded in 2008 Wenchuan earthquake. Results showed that significant seismic damage may occur, maximum demands were higher for near-fault records having forward directive than far-fault motions, and the rotational capacity of rib plastic hinge is not enough for the large compression force of arch rib. While backward-directivity motions, typically do not exhibit pulse-type motions, only have medium seismic damage to the arch bridge.

scholarly journals Performance Evaluation of bi-directional Roller Bearings for Seismic Isolation of Buildings Under Near-fault Earthquakes

2021 ◽  
Author(s):  
Nelson Ortiz-Cano ◽  
Ricardo González-Olaya ◽  
Carlos Gaviria-Mendoza ◽  
Carlos Magluta ◽  
Ney Roitman
Keyword(s):  
Friction Force ◽  
Seismic Isolation ◽  
Sliding Friction ◽  
Roller Bearing ◽  
Experimental Tests ◽  
Element Model ◽  
Building Model ◽  
Near Fault ◽  
Frame Element ◽  
Near Fault Earthquakes

Abstract An advantage bidirectional sloped rolling type isolation device composed of multiple rollers in both orthogonal-in-plane directions is studied in this research. The analytical model of a single direction of roller bearing (RB) system is extended to a two-direction RB system. Also, a 3D linear-elastic frame element to build the finite element model is used to incorporate the response of the building model. Several experimental tests of a physical building model with and without an RB system are used to validate the numerical model. The model is used to assess the nonlinear response history analysis of a four-story multi-column building system with two different physical properties that represent buildings with low and high lateral stiffness when subjected to pairs of scaled near-fault earthquake records. The effect of the angle of inclination of bearing plates in the range of 1.0o to 4.0o and sliding friction force is also investigated in a parametric analysis to evaluate the performance of RB with supplementary damping mechanisms ranging from 0.0 to 0.5N/kg, i.e., friction force normalized with the structure mass. Results show that the proposed bi-directional RB system is suitable for reducing the seismic response of rigid and flexible multi-column structures. In particular, the RB system reduces structure acceleration responses by 5–85% in the flexible structure and 86–96% in the rigid structure. Furthermore, an angle of inclination of bearing plates greater than or equal to 3.0o is an advantage to ensure the self-centering capacity.

scholarly journals Effects of Near Fault and Far Fault Ground Motions on Nonlinear Dynamic Response and Seismic Improvement of Bridges

2018 ◽  
Vol 4 (6) ◽  
pp. 1456 ◽  
Author(s):  
Mohammad Hajali ◽  
Abdolrahim Jalali ◽  
Ahmad Maleki
Keyword(s):  
Dynamic Response ◽  
Ground Motion ◽  
Nonlinear Dynamic ◽  
Nonlinear Dynamic Analysis ◽  
Time History ◽  
Relative Displacement ◽  
Near Fault ◽  
Acceleration Rate ◽  
Near Fault Earthquakes ◽  
Far Fault

In this study, the dynamic response of bridges to earthquakes near and far from the fault has been investigated. With respect to available data and showing the effects of key factors and variables, we have examined the bridge’s performance. Modeling a two-span concrete bridge in CSI Bridge software and ability of this bridge under strong ground motion to near and far from fault has been investigated. Nonlinear dynamic analysis of time history includes seven records of past earthquakes on models and it was observed that the amount of displacement in the near faults is much greater than the distances far from faults. Bridges designed by seismic separators provide an acceptable response to a far from fault. This means that in bridges using seismic separators, compared to bridges without seismic separators, Acceleration rate on deck, base shearing  and the relative displacement of the deck are decrease. This issue is not seen in the response of the bridges to the near faults. By investigating earthquakes near faults, it was observed that near-fault earthquakes exhibit more displacements than faults that are far from faults. These conditions can make seismic separators critical, so to prevent this conditions FDGM should be used to correct the response of these bridges. Based on these results, it can be said that the displacement near faults with forward directivity ground motion is greater than far from faults. So that by reducing the distance from the faults, the maximum value of the shearing and displacement of the deck will be greater.

scholarly journals Investigation on Seismic Behavior of Historical Tokatlı Bridge under Near-Fault Earthquakes

2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Memduh Karalar ◽  
Mustafa Yeşil
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Ground Motions ◽  
Element Model ◽  
Imperial Valley ◽  
Masonry Arch ◽  
Element Analysis ◽  
Near Fault ◽  
Earth Gravity ◽  
Near Fault Earthquakes

The main purpose of this study is to compare the static and dynamic behavior of a historical single-span masonry arch bridge under different near-fault earthquakes. The historical Tokatlı Bridge, built in Karabük, is chosen for this study. To investigate the behavior of near-fault earthquakes on the historical masonry bridge, first, a finite element model is built and analyzed under various near-fault earthquakes by using ANSYS and SAP2000. To build a finite element model, 162920 nodes and 47818 elements are used in ANSYS. First, finite element analysis results are compared to each other under Earth gravity. Then, ground motions near the fault are chosen to be used in this study. These earthquakes can be listed as follows: Cape Mend (1992), Kobe (1995), Superstition Hills (1987), Northridge (1994), Imperial Valley (1979), and Chi-Chi (1999). The behavior of the single-span historical bridge is obtained under these ground motions, and the results are compared with each other using contour diagrams using ANSYS. Furthermore, at the end of these analyses, it is observed that the tensile stresses have reached the permissible masonry tensile strength, especially on the upper side of the large belt, on the upper side of the belt, and on the side of the belt, and pose a risk for damage.

Effects of Fling Step and Forward Directivity on Seismic Response of Buildings

2006 ◽  
Vol 22 (2) ◽  
pp. 367-390 ◽  
Author(s):  
Erol Kalkan ◽  
Sashi K. Kunnath
Keyword(s):  
Seismic Response ◽  
Ground Motions ◽  
High Amplitude ◽  
Moment Frames ◽  
Steel Moment Frames ◽  
Damage Potential ◽  
Near Fault ◽  
Forward Directivity ◽  
Fling Step ◽  
Far Fault

This paper investigates the consequences of well-known characteristics of near-fault ground motions on the seismic response of steel moment frames. Additionally, idealized pulses are utilized in a separate study to gain further insight into the effects of high-amplitude pulses on structural demands. Simple input pulses were also synthesized to simulate artificial fling-step effects in ground motions originally having forward directivity. Findings from the study reveal that median maximum demands and the dispersion in the peak values were higher for near-fault records than far-fault motions. The arrival of the velocity pulse in a near-fault record causes the structure to dissipate considerable input energy in relatively few plastic cycles, whereas cumulative effects from increased cyclic demands are more pronounced in far-fault records. For pulse-type input, the maximum demand is a function of the ratio of the pulse period to the fundamental period of the structure. Records with fling effects were found to excite systems primarily in their fundamental mode while waveforms with forward directivity in the absence of fling caused higher modes to be activated. It is concluded that the acceleration and velocity spectra, when examined collectively, can be utilized to reasonably assess the damage potential of near-fault records.

scholarly journals Influence of Elastomeric Bearings in Tension on the Seismic Performance of Base-Isolated r.c. Buildings

2020 ◽  
Vol 11 (1) ◽  
pp. 82
Author(s):  
Fabio Mazza ◽  
Mirko Mazza
Keyword(s):  
Base Isolation ◽  
Nonlinear Models ◽  
Vertical Component ◽  
Computer Code ◽  
Nonlinear Phenomena ◽  
Isolation System ◽  
Elastomeric Bearings ◽  
Near Fault ◽  
Base Isolation System ◽  
Near Fault Earthquakes

Elastomeric bearings are commonly used in base-isolation systems to protect the structures from earthquake damages. Their design is usually developed by using nonlinear models where only the effects of shear and compressive loads are considered, but uncertainties still remain about consequences of the tensile loads produced by severe earthquakes like the near-fault ones. The present work aims to highlight the relapses of tension on the response of bearings and superstructure. To this end, three-, seven- and ten-storey r.c. framed buildings are designed in line with the current Italian seismic code, with a base-isolation system constituted of High-Damping-Rubber Bearings (HDRBs) designed for three values of the ratio between the vertical and horizontal stiffnesses. Experimental and analytical results available in literature are used to propose a unified nonlinear model of the HDRBs, including cavitation and post-cavitation of the elastomer. Nonlinear incremental dynamic analyses of the test structures are carried out using a homemade computer code, where other models of HDRBs considering only some nonlinear phenomena are implemented. Near-fault earthquakes with comparable horizontal and vertical components, prevailing horizontal component and prevailing vertical component are considered as seismic input. Numerical results highlight that a precautionary estimation of response parameters of the HDRBs is attained referring to the proposed model, while its effects on the nonlinear response of the superstructure are less conservative.

Character Analysis of Balance and Imbalance of Varying Rigidity of Rigid Pile Composite Foundation under Seismic Load

2014 ◽  
Vol 1065-1069 ◽  
pp. 19-22
Author(s):  
Zhen Feng Wang ◽  
Ke Sheng Ma
Keyword(s):  
Finite Element ◽  
Bending Moment ◽  
Horizontal Displacement ◽  
Element Model ◽  
Composite Foundation ◽  
Seismic Load ◽  
Seismic Loads ◽  
Element Analysis ◽  
Rigid Pile ◽  
Rigid Pile Composite Foundation

Based on ABAQUS finite element analysis software simulation, the finite element model for dynamic analysis of rigid pile composite foundation and superstructure interaction system is established, which selects the two kinds of models, by simulating the soil dynamic constitutive model, selecting appropriate artificial boundary.The influence of rigid pile composite foundation on balance and imbalance of varying rigidity is analyzed under seismic loads. The result shows that the maximum bending moment and the horizontal displacement of the long pile is much greater than that of the short pile under seismic loads, the long pile of bending moment is larger in the position of stiffness change. By constrast, under the same economic condition, the aseismic performance of of rigid pile composite foundation on balance of varying rigidity is better than that of rigid pile composite foundation on imbalance of varying rigidity.

System Level Bench Test for Trailing Arm Strength Estimation

2006 ◽  
Author(s):  
Jaychandar Muthu ◽  
Kanak Soundrapandian ◽  
Jyoti Mukherjee
Keyword(s):  
Failure Mode ◽  
Real Life ◽  
Element Model ◽  
Suspension System ◽  
System Level ◽  
Bench Test ◽  
Component Level ◽  
Arm Strength ◽  
Bench Testing ◽  
Nonlinear Finite Element Model

For suspension components, bench testing for strength is mostly accomplished at component level. However, replicating loading and boundary conditions at the component level in order to simulate the suspension system environment may be difficult. Because of this, the component's bench test failure mode may not be similar to its real life failure mode in vehicle environment. A suspension system level bench test eliminates most of the discrepancies between simulated component level and real life vehicle level environments resulting in higher quality bench tests yielding realistic test results. Here, a suspension level bench test to estimate the strength of its trailing arm link is presented. A suspension system level nonlinear finite element model was built and analyzed using ABAQUS software. The strength loading was applied at the wheel end. The analysis results along with the hardware test correlations are presented. The reasons why a system level test is superior to a component level one are also highlighted.

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