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 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.

scholarly journals Effect of Damping and Yielding on the Seismic Response of 3D Steel Buildings with PMRF

2014 ◽  
Vol 2014 ◽  
pp. 1-21 ◽  
Author(s):  
Alfredo Reyes-Salazar ◽  
Achintya Haldar ◽  
Ramon Eduardo Rodelo-López ◽  
Eden Bojórquez
Keyword(s):  
Seismic Response ◽  
Three Dimensional ◽  
Lateral Force ◽  
Viscous Damping ◽  
Steel Buildings ◽  
Local Response ◽  
Equivalent Viscous Damping ◽  
Response Parameter ◽  
Mdof Systems ◽  
Crude Approximation

The effect of viscous damping and yielding, on the reduction of the seismic responses of steel buildings modeled as three-dimensional (3D) complex multidegree of freedom (MDOF) systems, is studied. The reduction produced by damping may be larger or smaller than that of yielding. This reduction can significantly vary from one structural idealization to another and is smaller for global than for local response parameters, which in turn depends on the particular local response parameter. The uncertainty in the estimation is significantly larger for local response parameter and decreases as damping increases. The results show the limitations of the commonly used static equivalent lateral force procedure where local and global response parameters are reduced in the same proportion. It is concluded that estimating the effect of damping and yielding on the seismic response of steel buildings by using simplified models may be a very crude approximation. Moreover, the effect of yielding should be explicitly calculated by using complex 3D MDOF models instead of estimating it in terms of equivalent viscous damping. The findings of this paper are for the particular models used in the study. Much more research is needed to reach more general conclusions.

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 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.

Influence of High Mode Effects on Ductility Reduction Factors for MDOF Shear-Type Structures

2014 ◽  
Vol 578-579 ◽  
pp. 412-416
Author(s):  
Hui Ying Wang
Keyword(s):  
Time History ◽  
Degree Of Freedom ◽  
High Mode ◽  
Lumped Mass ◽  
Ductility Demand ◽  
Mdof Systems ◽  
Mode Effect ◽  
Modification Factor ◽  
Shear Type ◽  
Reduction Factors

The influences of high mode effect on ductility reduction factors for multi-degree-of-freedom (MDOF) systems are studied by modifying ductility reduction factors for equivalent single-degree-of-freedom (SDOF) systems. Based on MDOF lumped-mass shear-type models, nonlinear dynamic time history analysis are performed to investigate the influence of ductility demand increase owing to high mode effect on ductility reduction factors. An empirical estimating model of MDOF modification factor is proposed. The results demonstrate that ductility reduction factors for MDOF systems are clearly smaller than those for SDOF systems. The modification factor is mainly affected by the fundamental period and ductility.

An Adaptive Loading Test on Collapse Mechanism Formation of Multi-Story Steel Frames Subjected to Uncertain Lateral Load Pattern

2007 ◽  
Vol 345-346 ◽  
pp. 1169-1172
Author(s):  
Kenichi Ohi ◽  
Jae Hyouk Choi
Keyword(s):  
Limit State ◽  
Lateral Force ◽  
Collapse Mechanism ◽  
Loading Test ◽  
Design Point ◽  
Steel Moment Resisting Frames ◽  
Random Combination ◽  
Moment Resisting ◽  
Earthquake Load ◽  
Load Pattern

An adaptive loading system is developed to examine a design point of multi-story steel test frames subjected to uncertain load pattern. Lateral loads are given as a random combination of basic load patterns, and the system drives a test frame to the most likely failure situation. Two-story steel moment resisting frames are tested considering a failure mechanism formation of plastic collapse as a tentative limit state. A random 2-dof lateral force is given by a random combination of two basic load patterns, which are arranged to represent elastic earthquake load effects. Hybrid design point search or adaptive loading tests on the 2-story frame are performed, and the detected likely failure mechanisms are compared with the results of pseudo-dynamic response tests to deterministic excitations.

scholarly journals Seismic Reduction Factor Evaluation and its Components for Steel Buildings Undergoing Nonlinear Deformations

2019 ◽  
Vol 116 (11) ◽  
pp. 1850
Author(s):  
Alfredo Reyes-Salazar ◽  
Eden Bojórquez ◽  
Juan Bojórquez ◽  
Federico Valenzuela-Beltran ◽  
J. Ramon Gaxiola-Camacho ◽  
...  
Keyword(s):  
Reduction Factor ◽  
Steel Buildings ◽  
Factor Evaluation ◽  
Nonlinear Deformations

scholarly journals Assessment of seismic responses toward multi-story buildings of steel special moment resisting frame by considering the setback irregularities

2021 ◽  
Vol 331 ◽  
pp. 05007
Author(s):  
Ridho Aidil Fitrah ◽  
Masrilayanti Masrilayanti ◽  
Gita Zakiah Putri ◽  
Zev Al Jauhari
Keyword(s):  
Response Spectrum ◽  
Nonlinear Static Analysis ◽  
Steel Buildings ◽  
Seismic Responses ◽  
Base Shear ◽  
Moment Frame ◽  
Moment Resisting ◽  
Drift Limit ◽  
Special Moment Resisting Frame ◽  
Special Moment Frame

Setback irregularities are considered where discontinuity between adjacent stories is excessive. This irregularity caused the probability of high damage at structures subjected to strong earthquake motion. For this purpose, this study was conducted by modeling the steel special moment frame (SMF) structures using a finite element calculation program with nonlinear static analysis compared to Padang city’s response spectrum. The buildings are also modeled with two types of setbacks: single and multiple setbacks. The results of this paper are discussed including the explanation of many parameters that relate to elastic and inelastic seismic responses of steel special moment frame (SMF). Based on the results, the setback irregularities, both single and multiple setbacks, the inelastic seismic responses are adequately sufficient to SNI 1726 2019 regarding drift limit. The other seismic responses are also discussed in terms of fundamental periods, inter-story drifts, story stiffness, and base shear. Referred to Indonesian Seismic Provision, SNI 1726 2019, it is found that single setback building has more adequate than multiple setbacks in terms of seismic responses. Then, the seismic assessments between these setbacks are explained to address the recommendations about future prevention toward damages and failures in steel buildings.

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