The Experts below are selected from a list of 41136 Experts worldwide ranked by ideXlab platform

Fabio De Angelis - One of the best experts on this subject based on the ideXlab platform.

  • nonlinear dynamic analysis for multi storey rc structures with hybrid Base isolation systems in presence of bi directional ground motions
    Composite Structures, 2016
    Co-Authors: Donato Cancellara, Fabio De Angelis
    Abstract:

    Abstract Multi-storey reinforced concrete (RC) structures may experience a weak structural behavior when subject to seismic and dynamic actions. In such cases the Base isolation techniques are innovative strategies to protect the structures from seismic and dynamic loadings. In the present work three different hybrid Base isolation systems are analyzed in order to protect reinforced concrete structures with regards to bi-directional ground motions. The three considered hybrid Base isolation systems are the Elastomeric Spring Dampers operated in parallel with Friction Sliders, the Lead Rubber Bearings operated in parallel with Friction Sliders and the High Damping Rubber Bearings also operated in parallel with Friction Sliders. The analyzed Base isolation systems have been designed in compliance to the European seismic codes EC2 and EC8. The Base isolation devices are realized by elastomeric materials and steel-teflon bearings. The highly nonlinear behavior of the composite sliding isolation systems is investigated. A detailed analysis is reported of the hysteretic cycles of the friction slider bearings and the hysteretic cycles of the composite rubber bearing isolators. Bi-directional ground motions corresponding to recorded accelerograms have been considered as seismic actions. A spectrum compatibility analysis has been performed for the chosen recorded sets of accelerograms. A comparative analysis is illustrated for the three Base isolated composite structures by reporting the time history of the Base acceleration, the time history of the Base Shear, the time history of the Base displacements and of the inter-storey drifts and the peak values of the Base Shear. The seismic and dynamic response of the considered Base isolated structure is illustrated and a comparative analysis is finally presented between the Base isolated structure with the three considered Base isolation systems and the fixed Base structure.

Douglas P Taylor - One of the best experts on this subject based on the ideXlab platform.

  • simulated bilinear elastic behavior in a sdof elastic structure using negative stiffness device experimental and analytical study
    Journal of Structural Engineering-asce, 2014
    Co-Authors: D T R Pasala, M. C. Constantinou, Satish Nagarajaiah, A A Sarlis, A M Reinhorn, Douglas P Taylor
    Abstract:

    AbstractThe acceleration and Base Shear of structures during strong ground motion can be attenuated by achieving bilinear-elastic behavior without any permanent displacement—also referred to as “apparent weakening.” The negative stiffness device (NSD), used in this study, exhibits nonlinear-elastic negative stiffness behavior; by adding NSD to the elastic structure, the resulting structure-device assembly behaves like a bilinear-elastic structure. Peak acceleration and Base Shear experienced by the structures can be reduced by adding the negative stiffness device, and the additional deformations caused by the reduced stiffness can be contained by adding a viscous damper. This paper presents the experimental study on a three-story fixed-Base structure (3SFS), acting as a single-degree-of-freedom (SDOF) system (because of bracing in the top two stories), that demonstrates the concept of apparent weakening in elastic structural systems. Two NSDs and a viscous damper are installed in the first story of 3SFS. ...

  • negative stiffness device for seismic response control of multi story buildings
    Scopus, 2012
    Co-Authors: D T R Pasala, M. C. Constantinou, Satish Nagarajaiah, A A Sarlis, A M Reinhorn, Douglas P Taylor
    Abstract:

    Weakening and damping of structures has proven to be an effective method for mitigating the structure's response. This approach has drawn further attention after the invention of negative stiffness device (NSD), developed by the authors. Preliminary analytical and experimental studies reported on the NSD have revealed that by adding the NSD to a single story structure the Base Shear demands and peak acceleration of the main structure are reduced significantly and the inter-story deformations are contained by adding a passive damper. In this paper an analytical study is carried on an inelastic multistoried Shear building to demonstrate the effectiveness of placing NSDs and dampers at multiple locations along the height of the building. It has been shown that by placing a NSD in a particular story the superstructure above that story can be isolated. It has also been shown through simulation studies that the NSD will limit the amount of energy transmitted to the superstructure from the ground excitation. Essentially, NSD acts as a vibration isolator. Large Base deformations is one major limitation in Base-isolating the structural systems but using NSDs this can be overcome as the isolation is achieved over the height of the building and not confined to the Base. It has been shown through the simulation studies that by placing NSDs in all the lower story's the acceleration of the superstructure and Base Shear can be reduced significantly without affecting the drifts. Simulation results of a nine-storied 1:3 scale inelastic Shear building subjected to periodic ground motion and Kobe fault normal ground motion

Donato Cancellara - One of the best experts on this subject based on the ideXlab platform.

  • nonlinear dynamic analysis for multi storey rc structures with hybrid Base isolation systems in presence of bi directional ground motions
    Composite Structures, 2016
    Co-Authors: Donato Cancellara, Fabio De Angelis
    Abstract:

    Abstract Multi-storey reinforced concrete (RC) structures may experience a weak structural behavior when subject to seismic and dynamic actions. In such cases the Base isolation techniques are innovative strategies to protect the structures from seismic and dynamic loadings. In the present work three different hybrid Base isolation systems are analyzed in order to protect reinforced concrete structures with regards to bi-directional ground motions. The three considered hybrid Base isolation systems are the Elastomeric Spring Dampers operated in parallel with Friction Sliders, the Lead Rubber Bearings operated in parallel with Friction Sliders and the High Damping Rubber Bearings also operated in parallel with Friction Sliders. The analyzed Base isolation systems have been designed in compliance to the European seismic codes EC2 and EC8. The Base isolation devices are realized by elastomeric materials and steel-teflon bearings. The highly nonlinear behavior of the composite sliding isolation systems is investigated. A detailed analysis is reported of the hysteretic cycles of the friction slider bearings and the hysteretic cycles of the composite rubber bearing isolators. Bi-directional ground motions corresponding to recorded accelerograms have been considered as seismic actions. A spectrum compatibility analysis has been performed for the chosen recorded sets of accelerograms. A comparative analysis is illustrated for the three Base isolated composite structures by reporting the time history of the Base acceleration, the time history of the Base Shear, the time history of the Base displacements and of the inter-storey drifts and the peak values of the Base Shear. The seismic and dynamic response of the considered Base isolated structure is illustrated and a comparative analysis is finally presented between the Base isolated structure with the three considered Base isolation systems and the fixed Base structure.

S Pampanin - One of the best experts on this subject based on the ideXlab platform.

  • analytical seismic assessment of rc dual wall frame systems using slama proposal and validation
    Engineering Structures, 2019
    Co-Authors: Roberto Gentile, S Pampanin, Domenico Raffaele
    Abstract:

    Abstract A paramount step in seismic assessment of existing structures is the determination of the structural capacity. It is widely recognised that non-linear numerical approaches are arguably the most reliable tool to achieve this goal. However, reliable yet simple analytical procedures are needed to identify potential structural weaknesses and their influence on the overall capacity, to cross-check and/or interpret numerical analyses. This paper presents a novel analytical -or “by-hand”- procedure to calculate the non-linear capacity curve of RC dual wall/frame systems within the framework of the Simple Lateral Mechanism Analysis (SLaMA). The mechanical interaction among frame(s) and wall(s) is explicitly considered to calculate their Base Shear and overturning moment contributions. The procedure is outlined and applied to 28 case studies with different geometry, wall(s) position, wall-to-frame strength ratio and plastic mechanism. The results are compared to refined numerical pushover analyses, showing a maximum 5% error both in terms of ultimate Base Shear and displacement for the majority of the case studies.

  • non linear analysis of rc masonry infilled frames using the slama method part 1 mechanical interpretation of the infill frame interaction and formulation of the procedure
    Bulletin of Earthquake Engineering, 2019
    Co-Authors: Roberto Gentile, S Pampanin, Domenico Raffaele, Giuseppina Uva
    Abstract:

    The simple lateral mechanism analysis (SLaMA) is an analytical method to assess the force–displacement capacity curve of Reinforced Concrete (RC) structures composed of frames, cantilever walls or dual wall/frame systems. The current version of the method was proposed in the 2017 New Zealand guidelines for the seismic assessment (NZSEE in New Zealand Society for Earthquake Engineering, the seismic assessment of existing buildings—technical guidelines for engineering assessments, Wellington, 2017). Regarding frame structures, the possible influence of infill walls is currently considered locally with checks on the RC members. However, it is universally known that infills have a major effect on the global capacity curve of the frame. In this paper, a comprehensive SLaMA method for infilled frames is proposed, which allows considering the influence of the infills on the global force–displacement curve without any numerical algorithm. The extended SLaMA method is herein formalised and it is validated in a companion paper (part 2) through an extensive parametric analysis. The extended SLaMA is Based on the possibility to separately calculate the Base Shear contributions of the frame and the infills, in turn Based on global equilibrium considerations. Such considerations also allow defining a novel procedure to post-process the results of pushover or time-history analyses where infills are modelled as diagonal struts, or to interpret experimental tests. This allows, within a single numerical analysis, to decouple the frame and infills contributions to the Base-Shear capacity. The decoupling procedure is herein demonstrated for an ideal two-storey, one-bay masonry-infilled frame with different infills configurations.

  • reshaping structural hysteresis response with semi active viscous damping
    Bulletin of Earthquake Engineering, 2017
    Co-Authors: Nikoo K Hazaveh, J G Chase, G W Rodgers, S Pampanin
    Abstract:

    Semi-active control devices offer significant promise for their ability to add supplemental damping and reduce seismic structural responses in an easily controllable manner, and can be used to modify or reshape overall structural hysteretic response. This study uses a spectral analysis of semi-active viscous dampers to compare the impact of three methods of re-shaping structural hysteretic dynamics that resist: motion in all 4 quadrants (1–4), motion away from equilibrium (1–3) and motion towards equilibrium (2–4). Performance is assessed by evaluating reduction factors (RFs) from an uncontrolled structure for maximum displacement (Sd) total Base-Shear (Fb), and maximum acceleration (Sa) which assess performance in mitigating response damage, a risk of foundation damage and contents damage respectively. Spectra are created using 20 design level earthquakes from the medium suite of the SAC project with equal probability of occurrence and structural periods of T = 0.1–0.5 s. The RF spectra results are presented as median (50th) and 5th, 25th, 75th, and 95th percentile RF to define the distribution and change in risk across the 20 events. Statistical summaries of the results indicate that a 2–4 control method reduces the median value of Sd, Fb and Sa by approximately 10–40%, over all periods up to 5.0 s. These results are consistent over the 5–95th percentile range of all responses for a given period. The other control laws (1–3, 1–4) reduce Sd as much or more, but at a cost of increased Base-Shear (Fb) in comparison to the uncontrolled state. Overall, the reduction in terms of both displacement and Base-Shear demand is only available with the semi-active 2–4 control method. Finally, analytical expressions for the median displacement reduction factor are presented and compared to current Eurocode standards for comparison. These results indicate the robustness of simple semi-active viscous dampers could be better managed to mitigate response to the structure, foundation and risk.

Gregory A Macrae - One of the best experts on this subject based on the ideXlab platform.

  • spectral analysis for a semi active passive net zero Base Shear design concept
    Earthquake Engineering & Structural Dynamics, 2012
    Co-Authors: Geoffrey W Rodgers, J G Chase, T Roland, Gregory A Macrae
    Abstract:

    SUMMARY Passive high force-to-volume (HF2V) dampers offer significant displacement reduction and energy dissipation, but cannot customise overall response. Semi-active resettable devices offer adaptive, custom hysteresis loops that reduce displacement and Base Shear, but have limited dissipation. This paper presents a new, combined concept to maximise displacement reduction without increasing Base Shear – a net-zero Base-Shear concept. HF2V devices, up to a maximum of 10% structural weight, are combined with fixed stiffness resettable devices. Spectral analyses are run for the three SAC ground motion suites that iteratively size the HF2V device at each structural period to achieve maximum displacement reductions without increasing median Base Shear. HF2V velocity dependence and the need to scale HF2V capacity to spectral velocity are examined in terms of their impact on the results of these analyses. The net-zero approach reduces Base Shear by up to 50% and displacements by 30–70% over all ground motions, exceeding reductions obtained by either device separately by 30–50% (relative). The net-zero condition is not reached within the device limits defined, except at relatively long periods (>3.5 s) because of a virtuous circle of reduced displacement from the resettable and HF2V devices outweighing the increased Base Shear from the HF2V devices alone. These results are independent of HF2V device scaling, design and velocity dependence. The overall net-zero concept offers a significant advantage in a combination that cannot be achieved by passive or semi-active solutions alone. Copyright © 2011 John Wiley & Sons, Ltd.