| In recent years,there is an increasing demand of super high-rise buildings with height over 300 meters in China.An extensive comparative analysis that is usually carried out in the conventional design process to determine the most effective structural system is proved to be time and manpower consuming.In this paper,based on conventional architectural assumptions,structural models were established using structural analysis software package ETABS and verifed by PKPM-satwe,a comprehensive and systematic comparative analysis was carried out from five design aspects,including: different overall aspect ratio,different inner core aspect ratio,structural systems(frame-core tube,braced-frame core tube,mega frame-core tube,Mega brace frame-core tube),different seismic intensity,and different wind loading.The conclusion can be made from this analysis are:(1)frame-core tube is the most effective system when the earthquake intensity does not exceed 7 degrees(0.1g)and the wind load is less than 0.5kN/m2 subjected the building meets stiffness to weight ratio requirement which can be achieved by an adequate inner core size and minimization of building self-weight.(2)when seismic intensity is 7 and a half degree(0.15g)and wind load does not exceed 0.9kN/m2,the braced frame-core tube or mega frame-core tube is the most effective system.(3)when seismic intensity is 8 degrees(0.2g)and the wind load does not exceed 0.9kN/m2,it has become necessary to use mega brace frame-core tube structure system combined with other strengthening measures.(4)In order to improve inter-storey drift and achieve minimum steel comsuption,the elememts can be used(structural efficiency ranked from high to low)are diagonal brace,outrigger truss and belt truss.(5)when seismic load governs to design,diagonal brace should be considered prior to outrigger truss as the later would induce abrupt change in structural stiffness.(6)Diagonal brace should be used combined with belt truss,while outrigger truss and belt truss are not closely related in the same system.Considering super-high-rise buildings are mainly distributed in the coastal city so a wind-govern building example was used to introduce design methodology and procedure which may be used as a future design guidance.In addition,inter-storey drift limit and structural stiffness requirements in different countries(or region)are studied and compared to determine a rational inter-storey drift limit under wind loading.Taking a building as a reference case,a simplified model is built and analysed to compare the design outcomes to Chinese standard and Hongkong standard.It can be concluded that structural stiffness requirement is different between two above standards due to different wind loading calulation and deformation control limits.Hongkong has experienced serveal strong typhoons and no severe damage was observed which has demonstrated that the code requirement does meet the actual need of structural stiffness.The stiffness requirement in standard can also be understood as the requirement of structural safety.The base shear force produced under the action of wind load in two above standards were compared.In terrain category A site,China National Standard has 30% more base shear demand than that from Hongkong Standard.In terrain category C site,China National Standard has the same base shear demand as Hongkong Standard.After considering the deformation control limits,this difference in category A site increases to 70%,and 40% different for category C site.In conclusion,China National Standard has stricter structural stiffness requirement comparing with Hongkong standards.Slightly reducing this requirement would potentially generate considerable economic benefits.This paper aims to provide reference for selection and design the structural system for 300-meter-tall buildings.From discussion on a rational inter-story drift limit to seek a reasonable balance between the structural safety and cost effiective design. |
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