scholarly journals Seismic Collapse Risk Assessment of Braced Frames under Near-Fault Earthquakes

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1271
Author(s):  
Jeet Kumar Sonwani ◽  
Gaofeng Jia ◽  
Hussam N. Mahmoud ◽  
Zhenqiang Wang
Keyword(s):  
Numerical Models ◽  
Distribution Functions ◽  
Model Parameters ◽  
Braced Frames ◽  
Concentrically Braced Frames ◽  
Large Variability ◽  
Near Fault ◽  
Seismic Collapse ◽  
Near Fault Earthquakes ◽  
Pulse Characteristics

Special concentrically braced frames (SCBFs) located in regions close to earthquake faults may be subjected to near-fault ground motions, often characterized by pulses with long periods. These near-fault pulses could impose additional seismic demands on structures and increase the risk for structural collapse. Currently, there is limited research on the seismic collapse risk of SCBFs under near-fault earthquakes. This paper uses a general simulation-based framework to assess the seismic collapse risk of SCBFs under near-fault earthquakes. To quantify the large variability and uncertainty associated with the seismic hazard, a stochastic ground motion (SGM) model is used where the near-fault pulse characteristics are explicitly incorporated. The uncertainties in the SGM model parameters (including the near-fault pulse characteristics) are addressed through appropriate selection of probability distribution functions. To accurately predict the occurrence of collapse, numerical models capable of capturing the nonlinear and collapse behavior are established and used. Efficient stochastic simulation approaches are proposed to estimate the seismic collapse risk with or without considering the near-fault pulse. As an illustration, the seismic collapse risks of two SCBFs are investigated and compared. Probabilistic sensitivity analysis is also carried out to investigate the importance of uncertain model parameters within the SGM towards the seismic collapse risk.

Rehabilitation of steel concentrically braced frames with rocking cores for improved performance under near-fault ground motions

2016 ◽  
Vol 20 (6) ◽  
pp. 940-952 ◽  
Author(s):  
Bing Qu ◽  
Francisco Sanchez-Zamora ◽  
Michael Pollino ◽  
Hetao Hou
Keyword(s):  
Ground Motions ◽  
Braced Frames ◽  
Concentrically Braced Frames ◽  
Braced Frame ◽  
Near Fault ◽  
Modal Properties ◽  
Concentrically Braced Frame ◽  
Core Technology ◽  
Concentrically Braced ◽  
Near Fault Earthquakes

This article focuses on evaluating the adequacy of a seismic rehabilitation technology which adds rocking cores to deficient steel concentrically braced frames in near-fault regions. Two demonstration buildings were rehabilitated with the technology. Seismic performance of the rehabilitated buildings was evaluated through numerical simulations. Analysis results suggest that the code-compliant concentrically braced frames may be vulnerable to collapse under the fault-normal components of the near-fault ground motions, approximately having a probability of exceedance of 10% in 50 years. It is found that the Rocking Core technology is effective in reducing the inter-story drift responses of the demonstration buildings under near-fault earthquakes. The rehabilitated systems can further benefit from the use of hysteretic energy dissipating links between the rocking cores and existing concentrically braced frames. This article also addresses the influence of the rocking cores on modal properties of the rehabilitated buildings. It is found that the rocking core with moderate stiffness does not significantly alter the modal properties of a rehabilitated concentrically braced frame.

Peak and residual responses of steel moment-resisting and braced frames under pulse-like near-fault earthquakes

2018 ◽  
Vol 177 ◽  
pp. 579-597 ◽  
Author(s):  
Cheng Fang ◽  
Qiuming Zhong ◽  
Wei Wang ◽  
Shuling Hu ◽  
Canxing Qiu
Keyword(s):  
Braced Frames ◽  
Near Fault ◽  
Moment Resisting ◽  
Near Fault Earthquakes

scholarly journals The Effect of Local Fuse on Behavior of Concentrically Braced Frame by a Numerical Study

2018 ◽  
Vol 4 (3) ◽  
pp. 655 ◽  
Author(s):  
Ali Kachooee ◽  
Mohammad Ali Kafi ◽  
Mohsen Gerami
Keyword(s):  
Seismic Response ◽  
Numerical Study ◽  
Numerical Models ◽  
Compressive Loading ◽  
Braced Frames ◽  
Concentrically Braced Frames ◽  
Reduced Cross Section ◽  
Braced Frame ◽  
Concentrically Braced Frame ◽  
Concentrically Braced

The concentrically braced frames (CBFs) are one of the most widely used lateral load-resisting systems. Seismic performance of these structures has a weakness that is due to the brace buckling at a lower loading than the ultimate compressive loading capacity. In this paper, attempt is made to enhance the seismic response of CBFs through utilizing a local fuse. For this purpose, first the formulation of fuse area and length are presented. Then based on this formulation, several numerical models have been built and analyzed to examine the effect of implementing this fuse on seismic response of CBFs. From the analyses results, it is found that if the reduced cross-section fuse (RCF) is properly designed and also the end of brace is fixed, the CBFs with equal energy dissipation capacity, that are equipped with this fuse exhibit a better ductility than the customary CBFs.

scholarly journals SEISMIC COLLAPSE ANALYSIS OF CONCENTRICALLY-BRACED FRAMES BY THE IDA METHOD

2017 ◽  
pp. 273-292 ◽  
Author(s):  
Y. B. Yang ◽  
◽  
Gang Li ◽  
Zhi-Qian Dong ◽  
Hong-Nan Li ◽  
...  
Keyword(s):  
Braced Frames ◽  
Concentrically Braced Frames ◽  
Concentrically Braced ◽  
Collapse Analysis ◽  
Seismic Collapse

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.

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.

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