Investigation of Shear Lag Phenomenon in High-Rise Reinforced Concrete Structures with Tube-in-Tube System under the Effect of Wind Load
Subject Areas : Analysis of Structure and Earthquake
Kourosh Mehdizadeh
1
*
,
Seyede Vahide Hashemi
2
,
Abbasali Sadeghi
3
1 - Department of Civil Engineering, Engineering Faculty, Garmsar Branch, Islamic Azad University, Garmsar, Iran
2 - Department of Civil Engineering, Engineering Faculty, Sistan and Baluchestan University, zahedan, Iran
3 - Islamic azad university< Mashhad branch, Mashhad, Iran.
Keywords: Shear Lag, High-Rise Reinforced Concrete Structure, Tube-in-Tube System, Column Cut, Bundled Columns,
Abstract :
The tube-in-tube system is one of the most practical structural forms in high-rise buildings. One of the most important disadvantages of this system is the shear lag phenomenon, which increases the axial force in the side columns and decreases the axial force of the middle columns of the flange of structure. Therefore, in this study, the shear lag is investigated in high-rise reinforced concrete structures with tube-in-tube system with and without columns cut according to the height and plan under the effect of wind load. Thus, two high-rise concrete buildings, 40 and 60-story are modeled in ETABS 2017 software three dimensionally in three states. 40-story and 60-story prototypes are considered with and without columns cut in stories 11, 21 and 31, and then in stories 16, 31, and 46, respectively. Models were analyzed by wind force in order to calculate and compare the shear lag phenomenon. The results show that shear lag index has been changed from positive to negative phase at the height of building from the bottom to top and the axial force of the middle columns is higher than the corner columns in top stories. For example, the shear lag indices average is 1.2 and 0.61 in the 5th and 35th floors of 40-story building without column cut, respectively. Then the above values are 0.52 and 1.14 in the 5th and 55th floors, respectively for 60-story building without column cut. Also, the results indicate that the performance of structures has been improved at height by bundling of the columns in structures.
_||_