Nonlinear seismic response of Milad Tower using finite element model

Abstract

Milad Tower is a 436-m-tall telecommunications tower ranked as the fourth tallest structure of its kind in the world. The study of its seismic behaviour is of great importance as it is located in a highly seismic-prone region. Because of the existence of the world's largest revolving restaurant in the head structure, and also because of the highly sensitive communication devices such as TV and telecommunications antennas installed on the tower, nonlinear deformation under future earthquakes should be studied. In this paper, a detailed fi nite element model is developed and nonlinear dynamic analysis was carried out under the design earthquakes. The foundation, concrete shaft, head structure and 120-m antenna structure were modelled. Three components of the earthquakes are considered, and the selected earthquakes were normalized based on three design levels: design basis level, maximum design level and maximum credible level. The results of the analysis showed that all parts of the tower behave in the plastic zone except the elements of the head structure. It is also observed that in some cases, the earthquakes with lower peak accelerations and higher energy contents may have more severe effect on the tower than that with higher peak accelerations. triangular and inclined walls, respectively. Three-dimensional truss elements are used for modelling the post-tension tendons that are embedded in the exterior ring of the circular foundation. Reinforcements are accurately placed in the fi nite element model according to the structural drawings.Four-node shell elements are used from the height level of 0.0 m to the height level of 307 m, where the section of the shaft is changed to accommodate the antenna mast. Eight-node solid elements are used above the height level of 307 m for modelling the concrete shaft. The concrete shaft is modelled accurately with every structural part.All members of the head structure are modelled using a 3-D Bernoulli-Euler beam, in which the shear deformation is ignored. To consider the fl oor rigidity, all of the nodes are tied together in every storey to have equal movements (equal transition in the X and Y directions and equal rotation about the Z-axis.Four-node shell elements are used for modelling the antenna mast, and the stiffeners are modelled by 3-D Bernoulli-Euler beam elements. This part is also modelled completely. The fi nite element of the tower is shown in Figure 4. It should be mentioned that the fi nite element model consists of 13 284 elements and 17 920 nodes. MATERIAL MODELLINGThe materials used in the structure are mainly steel and concrete, and convenient models are used to defi ne the behaviour using the ABAQUS software (ABAQUS, 2006). Figure 3. The head structure of Milad Tower 882 M. YAHYAI, B. REZAYIBANA AND A. SAEDI DARYANThe isotropic trilinear steel model is used for high-strength steel, and the isotropic bilinear steel model is used for tendons and high-strength bars that do not have a plastic plateau (Table 1). ConcreteThe 28-day compressive strength of the con...

Dynamic analysis of the Milad Tower

“…The octagons are post tensioned in order to increase the bending capacity and stiffness of the structure to reduce the deflections. The foundation and lobby area consists of a circular foundation which is a transition structure (Yahyai et al 2009). The circular mat foundation is approximately 66 metres in diameter and sits directly beneath the transition structure.…”

Nonlinear time history analysis of China Pavilion for Expo 2010 Shanghai China

“…Yahyai et al . () used finite element model analysis to study the nonlinear seismic response of Milad Tower. The results of the analysis showed that all parts of the tower behave in the plastic zone except the elements of the head structure.…”

“…Krawinkler (2006) believes that earthquake engineering is relying more and more on nonlinear analysis as a tool for evaluating structural performance and nonlinear analysis will be a good trend. Yahyai et al (2009) used finite element model analysis to study the nonlinear seismic response of Milad Tower. The results of the analysis showed that all parts of the tower behave in the plastic zone except the elements of the head structure.…”

Nonlinear time history analysis of a super‐tall building with setbacks in elevation

“…However, when time and cost are considered, an alternative way is to perform nonlinear analysis using finite element method to get insights about the performance of complex buildings. Yahyai et al () used finite element model analysis to study the nonlinear seismic response of Milad Tower. Epackachi et al () conducted a seismic evaluation of a 56‐story residential reinforced concrete building based on nonlinear dynamic time history analysis of finite element model.…”