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Paper Information

Journal:   MODARES CIVIL ENGINEERING JOURNAL   APRIL 2017 , Volume 17 , Number 1 ; Page(s) 253 To 261.
 
Paper: 

EFFECT OF VERTICAL COMPONENT OF EARTHQUAKE ON SEISMIC DEMAND OF MEDIUM-RISE CONCRETE FRAMES

 
 
Author(s):  VAHDANI R., ANSARI M.*, ANSARI MASOUD
 
* FACULTY OF CIVIL ENG, BOZORGMEHR UNIVERSITY OF QAENAT
 
Abstract: 

According to the observations after the recent near-field earthquakes, structural damages are mostly attributed to the vertical component of the ground motion, i.e. concentration of the damages in column members leading to progressive structural collapse. This is whyinvestigation of ground motion’s vertical component effect has been widely regarded in recent studies. In seismic design, this component is considered less than other components of earthquake. However, in near fault earthquakes, large vertical acceleration components cause extensive damages compared to the ones with horizontal acceleration. Failure and damage in concrete columns is among the examples of the negative effects of vertical component. Vertical component of earthquake is considered in the design of specific members on the recommendation of seismic codes such as EC-8 and FEMA 356. The design is intended to use the scaled horizontal component, where this can result in incorrect answers due to lack of stimulation because of the specific characteristics of vertical component of earthquake and structural properties in the vertical direction. Also, the vertical component of earthquake is less studied in seismic risk analyses. In this study, the effects of vertical earthquake excitations on medium-rise concrete moment frames are investigated in two separate stages including near field and far field records.
In this research, various structural models, representative of real structures and designed in accordance to seismic codes and under actual gravitational loads have been subjected, simultaneously, to horizontal and vertical components of near- and far-field ground motion records at two stages. Nonlinear time history and progressive dynamic analyses have been performed in this regard. Furthermore, the effect of elevation orreduction of initial gravitational forces as well as columns’ initial axial forces have been investigated by applying differing gravitational loading coefficients. Structural response parameters including tensional and compressional axial loads of the columns as fluctuating forces, columns’ uplift forces at various plan positions and under various gravitational coefficients, the interactive axial-flexural forces of the columns at different gravitational coefficients, shear demand-to-capacity of columns, axial deformation of the columns in presence and absence of vertical component of the earthquake, have been comparatively investigated and the effect of vertical ground motion component has been assessed, separately, for far- and near-field acceleration records and for external and internal columns placed at different stories.
The obtained results reveal that tensional uplift forces are more critical in external columns than the internal ones. This is mainly true for lower stories, while at the upper stories the tensional forces experienced by internal columns are seen to be more critical. The existence of vertical component of earthquake leads the minimum compression forces to increase and change toward tension range. The amount of this reduction has been witnessed to reach to 84% in the more extreme case. It was also seen that for smaller gravitationalcoefficients, tensional axial forces are more frequently observed. The presence of earthquake’s vertical component has been shown to amplify the columns’ shear demand by the values reaching to 31% at the most extreme cases.

 
Keyword(s): VERTICAL COMPONENT OF EARTHQUAKE , AXIAL FORCE, SHEAR DEMAND VS CAPACITY, NEAR-FIELD EARTHQUAKE
 
 
References: 
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Click to Cite.
APA: Copy

VAHDANI, R., & ANSARI, M., & ANSARI, M. (2017). EFFECT OF VERTICAL COMPONENT OF EARTHQUAKE ON SEISMIC DEMAND OF MEDIUM-RISE CONCRETE FRAMES. MODARES CIVIL ENGINEERING JOURNAL, 17(1 ), 253-261. https://www.sid.ir/en/journal/ViewPaper.aspx?id=570307



Vancouver: Copy

VAHDANI R., ANSARI M., ANSARI MASOUD. EFFECT OF VERTICAL COMPONENT OF EARTHQUAKE ON SEISMIC DEMAND OF MEDIUM-RISE CONCRETE FRAMES. MODARES CIVIL ENGINEERING JOURNAL. 2017 [cited 2021May07];17(1 ):253-261. Available from: https://www.sid.ir/en/journal/ViewPaper.aspx?id=570307



IEEE: Copy

VAHDANI, R., ANSARI, M., ANSARI, M., 2017. EFFECT OF VERTICAL COMPONENT OF EARTHQUAKE ON SEISMIC DEMAND OF MEDIUM-RISE CONCRETE FRAMES. MODARES CIVIL ENGINEERING JOURNAL, [online] 17(1 ), pp.253-261. Available: https://www.sid.ir/en/journal/ViewPaper.aspx?id=570307.



 
 
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