COMPARATIVE DESIGN STUDY OF 85-STORY SUPER TALL BUILDING DUE TO WIND BETWEEN CODE-PRESCRIPTIVE APPROACH AND PERFORMANCE-BASED WIND DESIGN

• Main Author: Farrel Timothy, Estovio
• Format: Theses
• Language: Indonesia
• Subjects: Teknik sipil
• Online Access: https://digilib.itb.ac.id/gdl/view/75011
• Institution: Institut Teknologi Bandung

The cutback of land availability along with the annual exponential increase of population encourage land optimization with the construction of tall buildings. In planning a tall building, many aspects must be taken into account so that a tall building is suitable for use, both in terms of safety and comfort. Buildings in the modern era are getting taller, leaner, and more complex causing structures to be more sensitive to wind excitation than earthquakes because tall buildings generally have low natural frequencies and small damping ratios. In the design of structures against wind there are two ways that are often used, based on Code-Prescriptive as in SNI 1727: 2020, or based on Performance-Based Wind Design regulated in ASCE / SEI Prestandard for Performance Based Wind Design. In the design against wind for Code-Prescriptive using equivalent linear static simplification, i.e., equivaling the wind force along the height of the building as static force, ignoring the wind dynamic components and nonlinear capacity of the structure tends to lead to a conservative design. So, if a super-tall building is designed against wind with conventional methods, it will cause the excited wind force on the structure to be much greater than it should be and has implications for the design of the structure to be ineffective. While Performance-Based Wind Design applies wind force as a time history wind load charged on each floor with an angle of attack interval of every 10°, so that wind characteristics and structural response due to wind excitation can better represent the actual state. Performance-based approach can be an alternative approach to structural design due to wind so that structural performance is achieved more efficiently and optimally because it takes into account: the dynamic and inelastic components of wind. Although the codeprescriptive design uses a straightforward approach, the higher the building, especially for the super tall height, the more a Performance Based approach is needed. So that in this study a comparative design will be carried out between Code Prescriptive and Performance Based Wind Design on super tall structures in order to identify fundamental differences in it. In this study, a comparison of the design of an 85-story (301.5 m height) super tall building with a dual system will be carried out, this building is a modification of the Report for the Tall Buildings Initiative (PEER TBI). This building will be designed using Code-prescriptive approach (SNI 1727:2020) and Performance-based wind design (ASCE / SEI Prestandard for Performance Based Wind Design). The wind speed used in this study will refer to the recently developed Wind Map. In the design using PBWD, some information is needed such as wind time history obtained from field observations and wind tunnel test results that describe the forces that occur due to the interaction of wind and buildings. However, due to the limitations of this study, several approaches are made to both parameters. Wind time history will be created artificially using Inverse Fast Fourier Transform (IFFT) where information on wind speed, turbulence intensity and Power Spectral Density (PSD) is taken from SNI and ASCE provisions. Then the force that occurs because of the time history will be approximated using the Drag Coefficient for a similar cross section. Apart from that, this study will also focus on along-wind only, because it is more dominant. Although earthquakes are not a concern in this study, structures are also designed using a design-level earthquake load (? MCER) based on SNI 1726:2019. The parameters reviewed in this study are the comparison of reinforcement ratio, wind load (equivalent static wind load vs artificially generated time history), volume of the structure, as well as the resulting dynamic responses, which are produced in the structure if designed using Code-Prescriptive Wind Design and PerformanceBased Wind Design will be the main objectives in this study. This study shows the limitations of using Code-Prescriptive Wind Design. Based on the results, the average wind load comparison, PBWD is more efficient than code-prescriptive, but for maximum load PBWD is greater than codeprescriptive due to wind fluctuations. This study shows that at low altitudes, the effect of PBWD load fluctuations is more significant. There is a reduction in PBWD reinforcement for the Deformation-Controlled elements, while for the ForceControlled elements there is an additional reinforcement requirement. These results are different for beams, slabs, and shear walls. The overall reduction in reinforcement requirements using PBWD is relatively significant, especially on upper floors with a total reduction of around 10%.