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Effect of damping and yielding on the seismic response of 3D steel buildings with PMRF.

Reyes-Salazar A, Haldar A, Rodelo-López RE, Bojórquez E - ScientificWorldJournal (2014)

Bottom Line: 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.Much more research is needed to reach more general conclusions.

View Article: PubMed Central - PubMed

Affiliation: Facultad de Ingeniería, Universidad Autónoma de Sinaloa, Ciudad Universitaria, 80040 Culiacán, SIN, Mexico.

ABSTRACT
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.

Show MeSH
Global damping reduction factors for shear, SAC Models, and N-S direction.
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Related In: Results  -  Collection


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fig4: Global damping reduction factors for shear, SAC Models, and N-S direction.

Mentions: The symbol RζG,SAC is specifically used to represent the damping reduction factors for global response parameters of the SAC Models. For a given model, earthquake, direction and interstory, the damping reduction factors for shears or displacements are estimated and averaged over all the plane frames that conform the 3D structure for the interstory under consideration. Results for interstory shears are presented in Figure 4 for Models SC1 and SC2 and the N-S direction. In this figure, the word “ST” stands for the story level. It can be observed that the RζG,SAC values significantly vary from one earthquake to another, even though the earthquakes were normalized with respect to Sa(T1). It reflects the effect of the earthquake frequency contents and the contribution of several modes on the structural responses. Values closer to 0.4 are observed in many cases for the 0–2 damping range indicating that increasing damping from 0 to 2% can reduce the response in almost 60%. It is also noted that the reduction in the response is, in general, larger for the 0–2 than for the 2–5 range which in turn is larger than that of the 5–10 range, confirming the well-known results observed in typical SDOF systems: damping is more effective in reducing the response in low ranges. Results also indicate that the reduction in the response is larger for the upper interstory. Plots for RζG,SAC for the E-W direction were also developed but are not shown. The major conclusion made before applies to this case. The only additional observation that can be made is that, for both horizontal directions, the variation of RζG,SAC from one story to another generally decreases as damping increases. The effect of damping on the reduction of the average interstory displacements is also estimated; considering two models, two directions, and three cases of damping increments, as for the case of average interstory shears, 12 figures were developed, but they are not shown. A high correlation is observed between the plots of interstory shears and displacements. Thus, the major conclusions made before are valid for the displacement reduction.


Effect of damping and yielding on the seismic response of 3D steel buildings with PMRF.

Reyes-Salazar A, Haldar A, Rodelo-López RE, Bojórquez E - ScientificWorldJournal (2014)

Global damping reduction factors for shear, SAC Models, and N-S direction.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4109077&req=5

fig4: Global damping reduction factors for shear, SAC Models, and N-S direction.
Mentions: The symbol RζG,SAC is specifically used to represent the damping reduction factors for global response parameters of the SAC Models. For a given model, earthquake, direction and interstory, the damping reduction factors for shears or displacements are estimated and averaged over all the plane frames that conform the 3D structure for the interstory under consideration. Results for interstory shears are presented in Figure 4 for Models SC1 and SC2 and the N-S direction. In this figure, the word “ST” stands for the story level. It can be observed that the RζG,SAC values significantly vary from one earthquake to another, even though the earthquakes were normalized with respect to Sa(T1). It reflects the effect of the earthquake frequency contents and the contribution of several modes on the structural responses. Values closer to 0.4 are observed in many cases for the 0–2 damping range indicating that increasing damping from 0 to 2% can reduce the response in almost 60%. It is also noted that the reduction in the response is, in general, larger for the 0–2 than for the 2–5 range which in turn is larger than that of the 5–10 range, confirming the well-known results observed in typical SDOF systems: damping is more effective in reducing the response in low ranges. Results also indicate that the reduction in the response is larger for the upper interstory. Plots for RζG,SAC for the E-W direction were also developed but are not shown. The major conclusion made before applies to this case. The only additional observation that can be made is that, for both horizontal directions, the variation of RζG,SAC from one story to another generally decreases as damping increases. The effect of damping on the reduction of the average interstory displacements is also estimated; considering two models, two directions, and three cases of damping increments, as for the case of average interstory shears, 12 figures were developed, but they are not shown. A high correlation is observed between the plots of interstory shears and displacements. Thus, the major conclusions made before are valid for the displacement reduction.

Bottom Line: 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.Much more research is needed to reach more general conclusions.

View Article: PubMed Central - PubMed

Affiliation: Facultad de Ingeniería, Universidad Autónoma de Sinaloa, Ciudad Universitaria, 80040 Culiacán, SIN, Mexico.

ABSTRACT
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.

Show MeSH