scholarly journals Energy Dissipation and Local, Story, and Global Ductility Reduction Factors in Steel Frames under Vibrations Produced by Earthquakes

2018 ◽  
Vol 2018 ◽  
pp. 1-19 ◽  
Author(s):  
Alfredo Reyes-Salazar ◽  
Edén Bojórquez ◽  
Juan Bojorquez ◽  
Federico Valenzuela-Beltran ◽  
Mario D. Llanes-Tizoc
Keyword(s):  
Energy Dissipation ◽  
Reduction Factor ◽  
Point Of View ◽  
Dissipated Energy ◽  
Steel Buildings ◽  
A Value ◽  
Local Point ◽  
Ductility Reduction Factor ◽  
Ductility Capacity ◽  
Reduction Factors

Ductility plays a central role in seismic analysis and design of steel buildings. A numerical investigation regarding the evaluation of energy dissipation, ductility, and ductility reduction factors for local, story, and global structural levels is conducted. Some steel buildings and strong motions, which were part of the SAC Steel Project, are used. Bending local ductility capacity (µLϕ) of beams can reach values of up to 20, as shown in experimental investigations. The values are larger for medium than for low-rise buildings, reflecting the effect of the structural complexity on µLϕ. Most of the dissipated energy occurs on beams; however, resultant stresses at columns are also significantly reduced by beam yielding. A value of 1/3 is proposed for the ratio of global to local ductility; thus, if local ductility capacity is stated as the basis for the design, global ductility capacity can be calculated by using this ratio. It is implicitly assumed in seismic codes that the magnitude of the global ductility reduction factor is about 4; according to the results found in this paper, it is not justified; a value of 3 is observed to be more reasonable. According to the well-known ratio of the ductility reduction factor to ductility, this ratio should be unity for the models under consideration; the results of this study indicate that, for global response parameters, a value of 3/4 is more appropriate and that, for local response parameters, values larger than 2 can be reached; the implication of this is that using simplified methods like the static equivalent lateral force may result in nonconservative designs from a global structural point of view, but in conservative designs from a local point of view. A value of 8 is proposed for the ratio of the global ductility reduction factor to the global normalized energy.

Ductility Reduction Factors for Steel Buildings Modeled as 2D and 3D Structures

2014 ◽  
Vol 595 ◽  
pp. 166-172
Author(s):  
Alfredo Reyes-Salazar ◽  
Eden Bojorquez ◽  
Achintya Haldar ◽  
Arturo Lopez-Barraza ◽  
J. Luz Rivera-Salas
Keyword(s):  
Lateral Force ◽  
Reduction Factor ◽  
Steel Buildings ◽  
Structural Representation ◽  
Global Response ◽  
A Value ◽  
Mdof Systems ◽  
Moment Resisting ◽  
2D And 3D ◽  
Reduction Factors

The global ductility parameter (μG), commonly used to represent the capacity of a structure to dissipate energy, and the associated ductility reduction factor (Rμ), are estimated for steel buildings with perimeter moment resisting frames (PMRF), which are modeled as 2D and 3D complex MDOF systems. Results indicate that the μG value of 4, commonly assumed for moment resisting steel frames, cannot be justified. A value of 3 is more reasonable. The values of μG and Rμ may be quite different for 2D and 3D structural representations or for local and global response parameters, showing the limitation of the commonly used Equivalent Lateral Force Procedure (ELFP). Thus, the ductility and ductility reduction factors obtained from simplified structural representation must be taken with caution.

scholarly journals Local, Story, and Global Ductility Evaluation for Complex 2D Steel Buildings: Pushover and Dynamic Analysis

2019 ◽  
Vol 9 (1) ◽  
pp. 200 ◽  
Author(s):  
Mario D. Llanes-Tizoc ◽  
Alfredo Reyes-Salazar ◽  
Eden Bojorquez ◽  
Juan Bojorquez ◽  
Arturo Lopez-Barraza ◽  
...  
Keyword(s):  
Dynamic Analysis ◽  
Pushover Analysis ◽  
Strong Motion ◽  
Steel Buildings ◽  
Structural Element ◽  
Mean Values ◽  
Weak Beam ◽  
A Value ◽  
Moment Resisting ◽  
Ductility Capacity

A numerical investigation regarding ductility evaluation of steel buildings with moment resisting steel frames is conducted. Bending (µLϕ) and tension (µLδ) local ductilities as well as story (µS) and global ductilities are studied. Global ductility is calculated as the mean values of story ductilities (µGS) and as the ratio of the maximum inelastic to yielding top displacements (µGt). The ductility capacity is associated to drifts of about 5%. Ductility values significantly may vary with the strong motion, ductility definition, structural element, story number, type of analysis, and model. µLϕ is much larger for beams than for columns. Even though the demands of µLδ are considered an important issue they are less relevant than µLϕ. µS is much smaller than µLϕ for beams. µGS for dynamic analysis give reasonable values, but µGt does not. µLϕ, µS and µGS obtained from pushover are larger than those obtained from dynamic analysis and unlike the case of dynamic analysis, µLϕ tend to increase with the story number showing an opposite trend. Considering that: µGt for dynamic analysis results in unreasonable values, pushover analysis does not consider energy dissipation, the strong column–weak beam (SCWB) concept was followed in the model designs, and µLδ is not relevant in framed steel buildings, the ratio (RLG) of global to local ductility capacity is calculated as the ratio of µGS to µLϕ of beams, for dynamic analysis. A value of 1/3 is proposed. Thus, if bending local ductility capacity is stated as the basis for the design, the global ductility capacity can be easily estimated.

scholarly journals Shear Resistance Assessment of the Y-Type Perfobond Rib Shear Connector under Repeated Loadings

2021 ◽  
Vol 11 (16) ◽  
pp. 7667
Author(s):  
Sang-Hyo Kim ◽  
Oneil Han ◽  
Suro Yoon ◽  
Tuguldur Boldoo
Keyword(s):  
Shear Strength ◽  
Energy Dissipation ◽  
Composite Structures ◽  
Reduction Factor ◽  
Dissipated Energy ◽  
Ultimate Shear Strength ◽  
Residual Shear Strength ◽  
Shear Connectors ◽  
Repeated Load ◽  
Repeated Loads

The steel–concrete composite structures consist of two different material parts, which are connected with reliable shear connectors to enable the combined action of the steel and concrete members. The shear connectors may experience either one-directional repeated cyclic loadings or fully reversed cyclic loadings depending on the structural functions and acting loadings. It is essential for structural engineers to estimate the residual shear strength of the shear connectors after action of repeated loads. The characteristics of deteriorating shear capacities of Y-type perfobond rib shear connectors under repeated loads were investigated to estimate the energy dissipating capacity as well as the residual shear strength after repeated loads. To perform the repeated load experiments four different intensities of repeated loads were selected based on the monotonic push-out tests which were performed with 15 specimens with five different design variables. The selected load levels range from 35% to 65% of the representative ultimate shear strength under the monotonic load. In total, 12 specimens were tested under five different repeated load types which were applied to observe the energy dissipating characteristics under various load intensities. It was found that the dissipated energy per cycle becomes stable and converges with the increasing number of cycles. A design formula to estimate the residual shear strength after the repeated loads was proposed, which is based on the residual shear strength factor and the nominal ultimate shear strength of the fresh Y-type perfobond rib shear connectors. The design residual shear strength was computed from the number of repeated loads and the energy dissipation amount per cycle. The reduction factor for the design residual shear strength was also proposed considering the target reliability level. The various reduction factors for the design residual shear strength were derived based on the probabilistic characteristics of the residual shear strength as well as the energy dissipation due to repeated loads.

scholarly journals Seismic Ductility Reduction of Flexural-type Structures with Vertical Irregularities

2016 ◽  
Vol 10 (1) ◽  
pp. 1-11
Author(s):  
Weifeng Zhao ◽  
Xiaoquan Hu ◽  
Zhilin Long
Keyword(s):  
Ground Motions ◽  
Reduction Factor ◽  
Earthquake Excitation ◽  
Regular Structures ◽  
Irregular Structures ◽  
Ductility Reduction Factor ◽  
Reduction Factors

Seismic ductility reduction factors for flexural-type structures with vertical irregularities subjected to pulse-like and non-pulse-like ground motions are investigated in this paper. By establishing various multi-node flexural cantilever-column models, the ductility reduction factor of vertically irregular structures is studied by modifying the ductility reduction factor of irregular structures. The effects of various factors such as ductility level, irregular ratio and pulse-like earthquake excitation on modification coefficient are also explored. The analysis results reveal that: 1) the modification coefficient decreases with smaller irregularity ratio; 2) ductility reduction factors for vertically irregular structures are significantly smaller than those of regular structures; 3) ductility level exerts a certain influence on ductility reduction factor without an obvious trend; and 4) the modification coefficient under pulse-like excitation is smaller than those from non-pulse-like motions and the influence of pulse-like earthquake is coupled with irregularity ratio. This paper concludes with the statistical outcomes based on average of results and recommends modified factors for practice uses.

scholarly journals Improved parallel magnetic resonance imaging reconstruction with multiple variable density sampling

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Jinhua Sheng ◽  
Yuchen Shi ◽  
Qiao Zhang
Keyword(s):  
Magnetic Resonance Imaging ◽  
Variable Density ◽  
Reduction Factor ◽  
Resonance Imaging ◽  
Parallel Magnetic Resonance Imaging ◽  
Multiple Variable ◽  
Space Data ◽  
Sampling Pattern ◽  
Undersampled Data ◽  
Reduction Factors

AbstractGeneralized auto-calibrating partially parallel acquisitions (GRAPPA) and other parallel Magnetic Resonance Imaging (pMRI) methods restore the unacquired data in k-space by linearly calculating the undersampled data around the missing points. In order to obtain the weight of the linear calculation, a small number of auto-calibration signal (ACS) lines need to be sampled at the center of the k-space. Therefore, the sampling pattern used in this type of method is to full sample data in the middle area and undersample in the outer k-space with nominal reduction factors. In this paper, we propose a novel reconstruction method with a multiple variable density sampling (MVDS) that is different from traditional sampling patterns. Our method can significantly improve the image quality using multiple reduction factors with fewer ACS lines. Specifically, the traditional sampling pattern only uses a single reduction factor to uniformly undersample data in the region outside the ACS, but we use multiple reduction factors. When sampling the k-space data, we keep the ACS lines unchanged, use a smaller reduction factor for undersampling data near the ACS lines and a larger reduction factor for the outermost part of k-space. The error is lower after reconstruction of this region by undersampled data with a smaller reduction factor. The experimental results show that with the same amount of data sampled, using NL-GRAPPA to reconstruct the k-space data sampled by our method can result in lower noise and fewer artifacts than traditional methods. In particular, our method is extremely effective when the number of ACS lines is small.

The Control of the Eye's Intrinsic Muscles: A Multivariable Optimum Performance Control System

1968 ◽  
Vol 1 (8) ◽  
pp. T.129-T.132 ◽  
Author(s):  
F. M. Toates
Keyword(s):  
Control System ◽  
Control Systems ◽  
Pupil Diameter ◽  
Control Model ◽  
Point Of View ◽  
Theoretical Point ◽  
Pupil Control ◽  
Performance Control ◽  
A Value ◽  
Intrinsic Muscles

The reciprocal interaction between the accommodation and pupil control systems of the human eye is examined from a theoretical point of view. The system, which is responsible for maintaining pupil diameter at a value which is a compromise between conflicting requirements, is represented by a control model, and is considered in terms of the concept of a performance index.

scholarly journals Mitigating the seismic pounding of multi-story buildings in series using linear and nonlinear fluid viscous dampers

2021 ◽  
Vol 21 (4) ◽  
Author(s):  
Hytham Elwardany ◽  
Robert Jankowski ◽  
Ayman Seleemah
Keyword(s):  
Substantial Improvement ◽  
Point Of View ◽  
Steel Buildings ◽  
Viscous Dampers ◽  
Element Analysis ◽  
Fluid Viscous Dampers ◽  
Adjacent Buildings ◽  
In Series ◽  
Linear And Nonlinear ◽  
Nonlinear Fluid

AbstractSeismic-induced pounding between adjacent buildings may have serious consequences, ranging from minor damage up to total collapse. Therefore, researchers try to mitigate the pounding problem using different methods, such as coupling the adjacent buildings with stiff beams, connecting them using viscoelastic links, and installing damping devices in each building individually. In the current paper, the effect of using linear and nonlinear fluid viscous dampers to mitigate the mutual pounding between a series of structures is investigated. Nonlinear finite-element analysis of a series of adjacent steel buildings equipped with damping devices was conducted. Contact surfaces with both contactor and target were used to model the mutual pounding. The results indicate that the use of linear or nonlinear dampers leads to the significant reduction in the response of adjacent buildings in series. Moreover, the substantial improvement of the performance of buildings has been observed for almost all stories. From the design point of view, it is concluded that dampers implemented in adjacent buildings should be designed to resist maximum force of 6.20 or 1.90 times the design independent force in the case of using linear or nonlinear fluid viscous dampers, respectively. Also, designers should pay attention to the design of the structural elements surrounding dampers, because considerable forces due to pounding may occur in the dampers at the maximum displaced position of the structure.

scholarly journals Reconstruction of the 3D pressure field and energy dissipation of a Taylor droplet from a $$\upmu$$PIV measurement

2021 ◽  
Vol 62 (4) ◽  
Author(s):  
Ulrich Mießner ◽  
Thorben Helmers ◽  
Ralph Lindken ◽  
Jerry Westerweel
Keyword(s):  
Energy Dissipation ◽  
Pressure Gradient ◽  
Pressure Field ◽  
Estimation Method ◽  
Dissipated Energy ◽  
Spatial Integration ◽  
Mean Flow ◽  
Bypass Flow ◽  
Taylor Flow ◽  
Piv Measurement

Abstract In this study, we reconstruct the 3D pressure field and derive the 3D contributions of the energy dissipation from a 3D3C velocity field measurement of Taylor droplets moving in a horizontal microchannel ($$\rm Ca_c=0.0050$$ Ca c = 0.0050 , $$\rm Re_c=0.0519$$ Re c = 0.0519 , $$\rm Bo=0.0043$$ Bo = 0.0043 , $$\lambda =\tfrac{\eta _{d}}{\eta _{c}}=2.625$$ λ = η d η c = 2.625 ). We divide the pressure field in a wall-proximate part and a core-flow to describe the phenomenology. At the wall, the pressure decreases expectedly in downstream direction. In contrast, we find a reversed pressure gradient in the core of the flow that drives the bypass flow of continuous phase through the corners (gutters) and causes the Taylor droplet’s relative velocity between the faster droplet flow and the slower mean flow. Based on the pressure field, we quantify the driving pressure gradient of the bypass flow and verify a simple estimation method: the geometry of the gutter entrances delivers a Laplace pressure difference. As a direct measure for the viscous dissipation, we calculate the 3D distribution of work done on the flow elements, that is necessary to maintain the stationarity of the Taylor flow. The spatial integration of this distribution provides the overall dissipated energy and allows to identify and quantify different contributions from the individual fluid phases, from the wall-proximate layer and from the flow redirection due to presence of the droplet interface. For the first time, we provide deep insight into the 3D pressure field and the distribution of the energy dissipation in the Taylor flow based on experimentally acquired 3D3C velocity data. We provide the 3D pressure field of and the 3D distribution of work as supplementary material to enable a benchmark for CFD and numerical simulations. Graphical abstract

scholarly journals Dynamic Integrated Model for Assessing Fisheries: Discard Bans as an Implicit Value-Added Tax

2021 ◽  
Author(s):  
Jose Maria Da Rocha ◽  
Javier García-Cutrín ◽  
Maria-Jose Gutiérrez ◽  
Raul Prellezo ◽  
Eduardo Sanchez
Keyword(s):  
Value Added ◽  
Point Of View ◽  
Value Added Tax ◽  
Biological Variables ◽  
A Value ◽  
Long Run ◽  
The Social ◽  
Negative Effect ◽  
Short Run ◽  
The Impact

AbstractIntegrated economic models have become popular for assessing climate change. In this paper we show how these methods can be used to assess the impact of a discard ban in a fishery. We state that a discard ban can be understood as a confiscatory tax equivalent to a value-added tax. Under this framework, we show that a discard ban improves the sustainability of the fishery in the short run and increases economic welfare in the long run. In particular, we show that consumption, capital and wages show an initial decrease just after the implementation of the discard ban then recover after some periods to reach their steady-sate values, which are 16–20% higher than the initial values, depending on the valuation of the landed discards. The discard ban also improves biological variables, increasing landings by 14% and reducing discards by 29% on the initial figures. These patterns highlight the two channels through which discard bans affect a fishery: the tax channel, which shows that the confiscation of landed discards reduces the incentive to invest in the fishery; and the productivity channel, which increases the abundance of the stock. Thus, during the first few years after the implementation of a discard ban, the negative effect from the tax channel dominates the positive effect from the productivity channel, because the stock needs time to recover. Once stock abundance improves, the productivity channel dominates the tax channel and the economic variables rise above their initial levels. Our results also show that a landed discards valorisation policy is optimal from the social welfare point of view provided that incentives to increase discards are not created.

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