Structural design and analysis of vertical double-layer space structures in super-tall buildings
Hendry Yahya Sutjiadi *,†and Andrew W.Charleson
School of Architecture,Victoria University of Wellington,New Zealand
SUMMARY
This paper investigates the potential of double-layer space structures to be applied vertically as a new structural system in super-tall buildings.The investigation using ca studies covers four stages:structural designs of 100-storey buildings in order to obtain internal force distributions and determine appropriate structural member sizes,analys of the impacts of wind and ismic loads on the structures,nsitivity of structural weight ratios and lateral de flection constraints to changing structural geometry,and comparison of the lateral de flected shapes and structural weights per unit area with tho of other current tall structural systems.The results show that changing the angles of diagonal members to make them span two storeys rather than one storey reduces structural weight and has little impact on lateral de flection.Compared with other current tall structures,vertical double-layer space structures are relatively ef ficient structurally.The study concludes that double-layer space structures can be applied vertically as a structural system of super-tall buildings.Copyright ©2012John 绝望主妇大结局
Wiley &Sons,Ltd.
Received 27January 2012;Revid 4July 2012;Accepted 29September 2012
KEY WORDS :structural design;space structures;tall buildings;structural systems;steel structures;vertical structures
1.INTRODUCTION
romingoDouble-layer space structures,also known as space frames,have developed from the triangle concept as the most rigid geometry (Ambro,1994).The applications of this concept are commonly found in truss as two-dimensional structures and in space structures as three-dimensional structures.Stevens (1975)categorizes space structures into single-layer and double-layer space structures.The three-dimensional action of single-layer space structures relies on their curved geometries,whereas the connection of the dual layers of space structures by diagonal members also create two-way action.Double-layer space structures have been commonly ud for long-span horizontal structures such as domes,roofs and canopies becau of their structural advantages.In the structures,gravity loads travel in two directions in the plan through all members to columns and then the foundations.This makes double-layer space structures more effective compared with planar
truss,which distribute loads in one way only (Chilton,2000)(Figure 1).英翻中在线翻译
As three-dimensional structures,double-layer space structures also have the potential for vertical applications in super-tall buildings.Structural systems of tall and super-tall buildings have developed from two-dimensional to three-dimensional structures to ef ficiently resist lateral loads.Fazlur Khan argued that a structure can be designed to be more ef ficient as a three-dimensional unit (Ali,2001).Rigid frames for example,which are normally analyd as two-dimensional structures,are not ef ficient for taller buildings.Three-dimensional structures,such as framed-tubes,bundled-tubes and braced-tubes,have been ud in veral super-tall buildings,such as World Trade Center in New York,John Hancock Center and Willis Tower,both in Chicago.
*Correspondence to:Hendry Yahya Sutjiadi,School of Architecture,Victoria University of Wellington,New Zealand.†E-mail:
THE STRUCTURAL DESIGN OF TALL AND SPECIAL BUILDINGS Struct.Design Tall Spec.Build.23,512–525(2014)Published online 7November 2012in Wiley Online Library (/journal/tal).DOI:10.1002/tal.1057
Structural engineers have yet to u double-layer space structures for tall and super-tall buildings.Ho
wever,some building designers have considered their potential for high-ri structural systems.For example,in 1956Kahn and Tyng propod a project for a 184.8-m-high building using space structures (Ayad,1997).The tower,named the City Tower,was a triangulated precast and pre-stresd concrete frame.This project was not executed for structural and economic reasons (Komendant,1975).In 1971,Swenson propod a 150-storey building using a large-scale super-frame or double-layer space structure as the structural system (Swenson,1971).Unfortunately,this project also has yet to be realized.
We report on an investigation of the potential application of double-layer space structures in super-tall buildings.This application leads to veral issues including structural,systems integration and construction aspects.Initial rearch was conducted using a structural design of a 100-storey double-layer space structure building that has 48m Â48m footprint (Sutjiadi and Charleson,2010).On the basis of the results,we explored how to integrate the structure with architectural and rvices systems (Sutjiadi and Charleson,2011a)and the construction aspects of vertical double-layer space structures (Sutjiadi and Charleson,2011b,2011c).
This paper reports on structural issues of the application of double-layer space structures in super-tall buildings,such as appropriate member sizes,the impact of wind and ismic loads to the structur
es and their structural ef ficiency when compared with other current structural systems that were not covered in the initial rearch.
braceTo address the issues,we conducted rearch in veral stages.The first stage compris of a ca study of two 100-storey buildings using double-layer space structures.The aim is to analy force dis-tribution in the structure and determine appropriate structural member sizes.The cond stage investi-gates and compares the impacts of wind and ismic loads on the structures.The next stage evaluates the nsitivity of changing structural geometry on structural weight and lateral de flection.The last stage compares double-layer space structures with other current tall structural systems by considering lateral-de flected shapes and structural weights per unit area.The main purpo of this rearch is to investigate vertical double-layer space structures in super-tall buildings from a structural perspective.
2.CASE STUDY OF 100-STOREY BUILDINGS
As a ca study,we conducted design and analysis of two 100-storey buildings with typical floor plan dimensions of 48m Â48m and 60m Â60m.The double-layer space structures carry a combination of lateral and gravity loads.We designed vertical double-layer space structures positioned on the buildi
ng perimeters in order to maximize their capacity to resist lateral loads (Figure 2).The buildings also have horizontal double-layer space structures vertically subdividing the building into four ctions (Figure 3).The horizontal double-layer space structures transfer gravity loads from suspended columns underneath them to the perimeter vertical double-layer space structures.The aim is to optimize the capacity of vertical double-layer space structures to resist the combination of gravity and lateral loads.The horizontal double-layer space structures are two floors deep.Floor-to-floor height is 4m.In the 48m Â48m building,the structural module is 8m and the distance between internal and external layers of the vertical
space Figure 1.De flection of planar truss and a space structure under concentrated loads (Chilton,2000,p.13).STRUCTURAL DESIGN AND ANALYSIS OF VERTICAL DOUBLE-LAYER SPACE STRUCTURES 513
structure is 4m on all sides.The 60m Â60m building has a 10-m module and a 5-m cavity within the vertical double-layer space structure.
We ud ASCE7-05,Minimum Design Loads for Buildings and Other Structures (ASCE,2005),to determine building loads and load combinations consisting of dead and live gravity loads and wind lateral loads.The buildings ’location is assumed to be in Los Angeles with a wind speed of 85mph.The exposure type is B for a location in an urban area.The importance factor is 1.15bad
dream
on Figure 2.Position of a vertical perimeter double-layer space
structure.
Figure 3.Structural model.
514H.Y.SUTJIADI AND A.W.CHARLESON
occupancy category III and the topographical factor is1for aflat area.We do not include ismic load at this stage but discuss it in a later ction.
The material for the double-layer space structures is steel ASTM500with50ksi or345MPa yield strength.We ud AISC360-05,Specification for Structural Steel Buildings(AISC,2005),for the steel design.For structural member profiles and sizes,we input a variety of rectangular hollow ctions into the structural analysis program,ETABS(ETABS version9,2005).The structure has all joints pinned except the connection between adjacent gravity beams which were designed as continuous beams to minimize vertical deflections.Becau of an expectation of minimum construction tolerances and a high accuracy of construction,geometrical irregularities were neglected.Thefloor slab system comprid a conventional gravity system comprising of steel I-beams and concrete over corrugated steel decks.We specified H/500as the lateral deflection limit.Although lateral deflection limits of tall buildings vary between H/200and H/800(Khan,1970),the limit H/400–H/500is generally sufficient to
minimize damage to cladding and non-structural internal walls in tall buildings(Taranath,2005).ETABS then analyd and designed the structures iteratively to optimize all the structural members.
3.INTERNAL FORCES AND STRUCTURAL MEMBER SIZES
3.1.Internal force distribution
The results from the design by ETABS show the behaviour of double-layer space structures in resisting lateral and gravity loads:
1.Wind force distribution
-Wind forces within the structure travel as compression and tension forces mainly through the vertical and diagonal members of the double-layer space structures to the foundation.
-Wind loads acting on the structures cau overturning moments.External vertical members of the double-layer space structure make a large contribution in resisting them in compression and tension.
-The double-layer space structures act as two different systems:vertical cantilevered beams and momonicol
ment resisting frames(Figure4(a)).If acting upon a vertically cantilevered beam,the overturning moment generates compression and tension at the two ends of the vertical structure that are perpen-
dicular to the wind load.Frame action occurs from the interaction of the horizontal and
vertical
Figure4.(a)Beam and moment frame action and(b)axial forces in the vertical members under wind
load only.
STRUCTURAL DESIGN AND ANALYSIS OF VERTICAL DOUBLE-LAYER SPACE STRUCTURES515
double-layer space structures.The frame resists some wind load in bending causing compression and tension at the external and internal vertical layers.The accumulation of compression at the external vertical layer on the leeward side caus larger compression on the bottom floors.On the other hand,tension from frame action reduces the compression at the internal vertical layer on the leeward side.As a result,the external vertical members sustain larger axial forces on the lower floors,but the axial forces in the internal vertical members decrea on the lower floors (Figure 4(b)).
-On the ground floor,axial wind forces travel uniformly to the external columns that are perpendicular to the wind direction (Figure 5).The internal columns take a small proportion of the axial forces.Axial loads at the outer internal columns are larger than tho at the middle internal columns becau of the shear lag effect.
-Diagonal members in the two sides of the structure parallel to the wind direction resist shear forces caud by wind load.Section A –A (Figure 6)shows the axial forces in the diagonal members along the sides parallel to the wind direction.Compression and tension increa from the top to the bottom members.Section B –B shows the difference between forces in the diagonal members in the side perpendicular to the wind direction (left side of the structure)and parallel to the wind direction (right side of the structure).
2.Gravity force distribution
-Gravity loads travel from steel floor beams through the suspended gravity columns to the horizon-tal double-layer space structures and then down through the perimeter structures to the foundations (Figure 7).The horizontal double-layer space structures act as deep beams/slabs,where their diagonal members resist shear force from the gravity
loads.
its ok
the way you look tonightFigure 5.(a)Wind force distribution in tension (light colour)and compression (dark colour)in the
ground floor columns and (b)wind force distribution in the ground floor internal
白打columns.
Figure 6.(a)Two sides of the perimeter structure parallel to the wind load resist shear forces caud by
the wind load and (b)axial forces under wind load in the diagonal members.
516H.Y.SUTJIADI AND A.W.CHARLESON
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