structu system presentation

TALL STRUCTURESTALL STRUCTURES

STRUCTURAL SYSTEMSSTRUCTURAL SYSTEMS

-LATERAL LOAD -LATERAL LOAD RESISTANT SYSTEMSRESISTANT SYSTEMS

GROUP-3GROUP-3

PHASE-1PHASE-1

ROLL NO.:06MCL008ROLL NO.:06MCL008

Why is structural system Why is structural system study importantstudy important

The structural system is most important criterion The structural system is most important criterion for development tall building as it inter-for development tall building as it inter-

relates relates 1.1. Plan shapesPlan shapes2.2. Floor plateFloor plate

3.3. Floor heightFloor height4.4. Service core and Service core and

5.5. Vertical transportationVertical transportation

CRITERIA FOR SELECTION OF CRITERIA FOR SELECTION OF STRUCTURAL SYSTEM OF TALL STRUCTURAL SYSTEM OF TALL

BUILDINGSBUILDINGSApartment buildings are generally built-up of Reinforced Apartment buildings are generally built-up of Reinforced

concrete buildings with flat plate and core wallsconcrete buildings with flat plate and core wallsUp to 30 storey, concrete shear wall core with columns Up to 30 storey, concrete shear wall core with columns and flat plate slab floors are adequate to take care of and flat plate slab floors are adequate to take care of lateral loadlateral loadFor range of 30 to 60 storey, concrete shear wall core is For range of 30 to 60 storey, concrete shear wall core is inadequate, so usual practice is to provide outrigger inadequate, so usual practice is to provide outrigger beams or walls at service floors to connect core walls to beams or walls at service floors to connect core walls to exterior columnsexterior columnsFor more than 60 storey, bundled tube or tubular system For more than 60 storey, bundled tube or tubular system or other new approach by combinationsor other new approach by combinations

Structural system alternatives for Structural system alternatives for Tall structuresTall structures

Core walls i.e. cantilevered building systemCore walls i.e. cantilevered building systemCore walls with outriggerCore walls with outriggerTubular systemsTubular systems

Framed tubeFramed tube Deep spandrel tubeDeep spandrel tube Tube with parallel shear wallTube with parallel shear wall Tube in tubeTube in tube Bundled tubeBundled tube

Hybrid systemsHybrid systemsSpine wall systemSpine wall system

Core supported systemCore supported system

60 street bldg plan60 street bldg plan WTC planWTC plan

Frequent use of shear walls is in form of box shaped cores around stairs Frequent use of shear walls is in form of box shaped cores around stairs and elevatorsand elevatorsWalls around the core can be considered as a spatial system capable of Walls around the core can be considered as a spatial system capable of transmitting lateral loads in both directiontransmitting lateral loads in both directionCore has ability to resist all type of loadsCore has ability to resist all type of loadsShape of core to large extent is governed by elevator and stair requirementShape of core to large extent is governed by elevator and stair requirement

Core has the ability to Core has the ability to resist all types of loads; resist all types of loads; vetical loads, shear vetical loads, shear forces and bending forces and bending moments in two moments in two direction, as well as direction, as well as torsion especially when torsion especially when additonal stiffnes and additonal stiffnes and strength are provided strength are provided between flanges of open between flanges of open sectionssections

Single core serves to carry gravity and horizontal loadings.Single core serves to carry gravity and horizontal loadings.Slabs are supported at each levels from the coreSlabs are supported at each levels from the coreIn some cases, slabs are supported between the core and perimeter In some cases, slabs are supported between the core and perimeter columns, which terminate either on major cantilevers or as requiredcolumns, which terminate either on major cantilevers or as requiredMerits:Merits: Mainly architectural, in providing a column-free perimeter at Mainly architectural, in providing a column-free perimeter at the ground level and at other levelsthe ground level and at other levelsDemerits:Demerits: Resiting floor load by cantilevers-a highly inefficient Resiting floor load by cantilevers-a highly inefficient structural componentsstructural components Large quantity of steel at junction of cantilever slab and core due Large quantity of steel at junction of cantilever slab and core due to large negative momentto large negative moment Less efficient in resisting lateral forces compared to other systemLess efficient in resisting lateral forces compared to other system

CONCRETE CORE WITH OUTRIGGERSCONCRETE CORE WITH OUTRIGGERS

Concept taken from the tall and slender mast of the Concept taken from the tall and slender mast of the ships with spreaders i.e. horizontal member tied with ships with spreaders i.e. horizontal member tied with mast and vertical end stays, helps in resisting wind mast and vertical end stays, helps in resisting wind force efficientlyforce efficientlyIn high rise buildings, concrete In high rise buildings, concrete core relates to tall mast of ship outriggers core relates to tall mast of ship outriggers relates to spreaders exterior column relates to spreaders exterior column related to end staysrelated to end staysThese outriggers serve to reduce the overturning These outriggers serve to reduce the overturning moment in the core that would otherwise act as a pure moment in the core that would otherwise act as a pure cantilever, and to transfer the reduced moment to cantilever, and to transfer the reduced moment to columns outside the core by way of a tension-columns outside the core by way of a tension-compression couple, which takes advantage of compression couple, which takes advantage of increased moment arm between these columns. increased moment arm between these columns.

Many high rise bldg consists of central elevated Many high rise bldg consists of central elevated core and exterior support columns which results in core and exterior support columns which results in greater functional efficiency and it also disconnects greater functional efficiency and it also disconnects both systems which leads to less efficiency to resist both systems which leads to less efficiency to resist lateral loads and overturning force because of lateral loads and overturning force because of sum of independent resistances of individual sum of independent resistances of individual elementselements

The incorporation of outrigger in this systems The incorporation of outrigger in this systems couples these two components and enhances the couples these two components and enhances the systems ability to resist the overturning forces.systems ability to resist the overturning forces.

A core system alone can also generate excessive A core system alone can also generate excessive uplift forces in the core structure along with high uplift forces in the core structure along with high overturning forces in the building’s foundation overturning forces in the building’s foundation systemsystem

In foundation system, these uplift forces can In foundation system, these uplift forces can lead to the need for:lead to the need for:

1. 1. The addition of expensive and labour-intensive rock The addition of expensive and labour-intensive rock anchors to an otherwise simple foundation alternativeanchors to an otherwise simple foundation alternative

2. Greatly enlarged mat dimensions and dimensions 2. Greatly enlarged mat dimensions and dimensions and depth solely to resist overturning forces.and depth solely to resist overturning forces.

3. Time consuming and costly rock sockets for caisson 3. Time consuming and costly rock sockets for caisson systems along with the need to develop reinforcement systems along with the need to develop reinforcement throughout caisson depththroughout caisson depth

4. Extensive and intensive field-work connections at 4. Extensive and intensive field-work connections at the interface between core and foundationthe interface between core and foundation

Outrigger Benefits:Outrigger Benefits:1. Core overturning moments and their associated 1. Core overturning moments and their associated induced deformation can be reducedinduced deformation can be reduced2. Significant reduction and possibly the complete 2. Significant reduction and possibly the complete elimination of uplift and net tension forces throughout elimination of uplift and net tension forces throughout the columns and the foundation systemthe columns and the foundation system3. The exterior column spacing is not driven by 3. The exterior column spacing is not driven by structural considerations and can easily mesh with structural considerations and can easily mesh with aesthetic and functional considerationsaesthetic and functional considerations4. Exterior framing can consist of “Simple” beam and 4. Exterior framing can consist of “Simple” beam and column framing without the need for rigid-frame-type column framing without the need for rigid-frame-type connections, resulting in economiesconnections, resulting in economies5. Outrigger systems can efficently incorporate almost 5. Outrigger systems can efficently incorporate almost every gravity column into the lateral load resisting every gravity column into the lateral load resisting system, leading to economiessystem, leading to economies

Outrigger Drawbacks:Outrigger Drawbacks:

The most significant drawback with use of outrigger The most significant drawback with use of outrigger systems is their potential interference with occupiable systems is their potential interference with occupiable and rentable spaceand rentable space

The obstacles can be minimized by following The obstacles can be minimized by following approachesapproaches

Locating outriggers in mechanical and interstitial levelsLocating outriggers in mechanical and interstitial levels

Skewing and offsetting outriggers in order to mesh Skewing and offsetting outriggers in order to mesh with the functional layout of the floor spacewith the functional layout of the floor space

Incorporating multilevel single diagonal outriggers to Incorporating multilevel single diagonal outriggers to minimize the member’s interference on any single minimize the member’s interference on any single levellevel

JIN MAO BUILDING, JIN MAO BUILDING, SHANGHAISHANGHAIThe tower is built The tower is built around an octagon-around an octagon-shaped concrete shaped concrete shear wall core shear wall core surrounded by 8 surrounded by 8 exterior composite exterior composite super columns and super columns and 8 exterior steel 8 exterior steel columns. Three columns. Three sets of a two-story sets of a two-story high outrigger high outrigger trusses connect the trusses connect the columns to the core columns to the core at six of the floors at six of the floors to provide to provide additional support.additional support.

PETRONAS TOWER, MALAYSIAPETRONAS TOWER, MALAYSIA

CITY SPIRE,NEWYORKCITY SPIRE,NEWYORKArchitect: Murphy JahnArchitect: Murphy Jahn

Year of completion:1987Year of completion:1987

Ht from street to roof: 248mHt from street to roof: 248m

Number of stories: 75Number of stories: 75

Number of levels below GL:2Number of levels below GL:2

Building use:office & residentialBuilding use:office & residential

Frame material: concreteFrame material: concrete

Earthquake loading:not applicableEarthquake loading:not applicable

Basic wind speed:47m/sBasic wind speed:47m/s

Fund time period:5.5 Hori & 2 torsFund time period:5.5 Hori & 2 tors

Type of systemType of system: Shear wall with : Shear wall with outriggers at transfer level and outriggers at transfer level and interior diagonals in office interior diagonals in office levellevel

Core:Core: concrete walls of varying concrete walls of varying thickness thickness

Conc grade: 56MPaConc grade: 56MPa

Most slender structure at time Most slender structure at time of constof const

The modelling of city spire was The modelling of city spire was complex because the structure is complex because the structure is subdivided into nine major subdivided into nine major structural subsystemsstructural subsystemsThe main structural system is a The main structural system is a shear-wall-open-core system, shear-wall-open-core system, which traverses the center 24.4m which traverses the center 24.4m wide octagon in each directionwide octagon in each directionStaggered rectangular concrete Staggered rectangular concrete panels were used to form space panels were used to form space diagonal in the lower office levels. diagonal in the lower office levels. These panels were used to These panels were used to provede continuity between the provede continuity between the 1.7x2.1m jumbo columns1.7x2.1m jumbo columnsThe east and west octagon The east and west octagon columns were similarly connected columns were similarly connected by stagered concrete panelsby stagered concrete panelsThe apartments above 26 floors The apartments above 26 floors required too many coupling required too many coupling beams to connect many parts of beams to connect many parts of shear walls as above this 26shear walls as above this 26thth floor floor large open span, free of support large open span, free of support was maintained between the was maintained between the esterior and the central elevator esterior and the central elevator core to accommodate flexible core to accommodate flexible duplex and penthouseduplex and penthouse

SHEAR LAG EFFECTSHEAR LAG EFFECT

The Bernoulli-Euler The Bernoulli-Euler assumption that, plane section assumption that, plane section before bending remains plane before bending remains plane after bending is often used for after bending is often used for analysis of beam structureanalysis of beam structure

According to this assumption, According to this assumption, the longitudinal stresses in the longitudinal stresses in web and flanges should be web and flanges should be linearly and uniformly linearly and uniformly distributed.distributed.

However, this assumption is However, this assumption is approximate and applicable approximate and applicable strictly when there is no shear strictly when there is no shear force or structure having force or structure having infinite shear stiffnessinfinite shear stiffness Axial stress distribution with no shear lagAxial stress distribution with no shear lag

In actuality, when structure is In actuality, when structure is subjected to shear forces, a shear subjected to shear forces, a shear flow would be developed between flow would be developed between web and flange panels, and owing web and flange panels, and owing to shear deformation of panels the to shear deformation of panels the longitudinal dispacements in the longitudinal dispacements in the parts of web and flanges remote parts of web and flanges remote from the web-flange junctions would from the web-flange junctions would lag behind those at junctionslag behind those at junctions

As a result, longitudinal stresses in As a result, longitudinal stresses in web and flanges would become web and flanges would become distributeddistributed

Such shear lag phenomenon Such shear lag phenomenon reduces the effectiveness of web reduces the effectiveness of web and flanges and increase the and flanges and increase the longitudinal stresses at web-flange longitudinal stresses at web-flange junctions and lateral deflection of junctions and lateral deflection of structurestructure

Axial stress distribution with Axial stress distribution with effect of shear lageffect of shear lag

Axial stress Axial stress distribution with or distribution with or without shear lag without shear lag effecteffect

Framed Tube StructuresFramed Tube Structures

A framed tube structure is a new addition to A framed tube structure is a new addition to the structural systems. Khan is generally the structural systems. Khan is generally credited with its invention in the 1960s.credited with its invention in the 1960s.

"a three dimensional space structure "a three dimensional space structure composed of three, four, or possibly more composed of three, four, or possibly more frames, braced frames, or shear walls, joined frames, braced frames, or shear walls, joined at or near their edges to form a vertical tube-at or near their edges to form a vertical tube-like structural system capable of resisting like structural system capable of resisting lateral forces in any direction by cantilevering lateral forces in any direction by cantilevering from the foundation."from the foundation."

Dr.Fazlur Rehman KhanDr.Fazlur Rehman Khan

Framed Tube StructuresFramed Tube StructuresThe framed-tube structure has its columns The framed-tube structure has its columns closely spaced around the perimeter of the closely spaced around the perimeter of the building, rather than scattered throughout building, rather than scattered throughout the footprint, while stiff spandrel beams the footprint, while stiff spandrel beams connect these columns at every floor level. connect these columns at every floor level. This structural system was first This structural system was first implemented in 1964 in the construction of implemented in 1964 in the construction of the DeWitt-Chestnut Apartments in the DeWitt-Chestnut Apartments in Chicago, a 43-story reinforced concrete Chicago, a 43-story reinforced concrete tower designed by Dr.Fazlur Rehman tower designed by Dr.Fazlur Rehman Khan and his colleagues at Skidmore, Khan and his colleagues at Skidmore, Owings & Merrill (SOM). Because of its Owings & Merrill (SOM). Because of its great relative strength and stiffness, the great relative strength and stiffness, the tubular form immediately became a tubular form immediately became a standard in high-rise design. standard in high-rise design.

The revolutionary framed-The revolutionary framed-tube structural system was tube structural system was first seen in the construction first seen in the construction of the DeWitt-Chestnut of the DeWitt-Chestnut Apartments in Chicago.Apartments in Chicago.

In 1998 the city of Chicago named the intersection In 1998 the city of Chicago named the intersection of Jackson and Franklin Streets (located at the of Jackson and Franklin Streets (located at the foot of the Sears Tower) “Fazlur R. Khan Way.”foot of the Sears Tower) “Fazlur R. Khan Way.”

Framed Tube StructuresFramed Tube Structures

Mode of Behaviour of frame tube systemMode of Behaviour of frame tube systemAlthough, the structure has a tube-like form, its behavior Although, the structure has a tube-like form, its behavior is much more complex than that of a plain unperforated is much more complex than that of a plain unperforated tube, and the stiffness may be considerably lesstube, and the stiffness may be considerably lessWhen subjected to bending under the action of lateral When subjected to bending under the action of lateral forces, the primary mode of action is that of a forces, the primary mode of action is that of a conventional vertical cantilevered tube, in which the conventional vertical cantilevered tube, in which the columns on opposite sides of the neutral axis are columns on opposite sides of the neutral axis are subjected to tensile and compressive forcessubjected to tensile and compressive forcesIn addition, the frames parallel to the direction of lateral In addition, the frames parallel to the direction of lateral load are subjected to in-plane bending and shearing load are subjected to in-plane bending and shearing action assocaited with an independent rigid frameaction assocaited with an independent rigid frameThe primary action is complicated by the fact that the The primary action is complicated by the fact that the flexibility of the spandrel beams produces a shear lag flexibility of the spandrel beams produces a shear lag that increses the stresses in the corner columns and that increses the stresses in the corner columns and reduces those in the inner columnsreduces those in the inner columns

Framed Tube StructuresFramed Tube Structuresplan & modelled 3-D viewplan & modelled 3-D view

DIAGONAL TRUSS DIAGONAL TRUSS TUBE SYSTEMTUBE SYSTEM

100 storey JOHN 100 storey JOHN HANCOCK CENTRE HANCOCK CENTRE IN CHICAGOIN CHICAGO

THE BUILDING WAS THE BUILDING WAS COMPLETED IN COMPLETED IN 19701970

Trussed tube structuresTrussed tube structures

The inherent weakness of the framed tube lies in The inherent weakness of the framed tube lies in the flexibility of it spandrel beams. Its rigidity is the flexibility of it spandrel beams. Its rigidity is greatly improved by adding diagonal members.greatly improved by adding diagonal members.

The shear is now primarily absorbed by The shear is now primarily absorbed by diagonals, and not spandrels.diagonals, and not spandrels.

The diagonals carry the lateral forces directly in The diagonals carry the lateral forces directly in predominantly axial action.predominantly axial action.

Shear lag effect is comparatively reduced Shear lag effect is comparatively reduced compared to frame tubecompared to frame tube

Tube in TubeTube in Tube

The stiffness of a hollow tube system is very The stiffness of a hollow tube system is very much improved by using the core not only for much improved by using the core not only for gravity loads but to resist lateral loads alsogravity loads but to resist lateral loads alsoThe exterior columns and beams are spaced so The exterior columns and beams are spaced so closely that the façade has the appearance of a closely that the façade has the appearance of a wall with perforated window openings.wall with perforated window openings.The floor structure ties the exterior and interior The floor structure ties the exterior and interior tubes together, and they respond as a unit to tubes together, and they respond as a unit to lateral forceslateral forcesThe entire building acts as a hollow tibe The entire building acts as a hollow tibe cantilevering out of the groundcantilevering out of the ground

Tube with parallel shear wallsTube with parallel shear walls

The exterior tubular wall can be stiffened by The exterior tubular wall can be stiffened by incorporating interior shear walls into the plan.incorporating interior shear walls into the plan.

One can visualize the exterior tube walls as the One can visualize the exterior tube walls as the flanges of a huge built-up beam system in which flanges of a huge built-up beam system in which the shear walls represent the webs.the shear walls represent the webs.

Fig shows respectively two approaches, Fig shows respectively two approaches, 1. wide spacing of façade columns requiring shear wall for every 1. wide spacing of façade columns requiring shear wall for every

columncolumn2. Close spacing of façade columns, requiring only two shear 2. Close spacing of façade columns, requiring only two shear

wallswalls

Bundled tubesBundled tubes

Looking up at the Looking up at the Sears Tower, the Sears Tower, the worlds tallest worlds tallest building for over building for over twenty years. The twenty years. The design for this design for this 1454-foot tall 1454-foot tall tower introduced tower introduced the bundled tube the bundled tube structural system, structural system, as well as a new as well as a new vocabulary in vocabulary in architectural form.architectural form.

The bundled tube The bundled tube system can be system can be visualized as an visualized as an assemblage of assemblage of individual of individual individual of individual tubes resulting in a tubes resulting in a multiple-cell tube.multiple-cell tube.

The increase in the The increase in the stiffness is apparentstiffness is apparent

The system allows for The system allows for the greatest height the greatest height and most floor areaand most floor area

•The structure is formed from 9 bundled square tubes, each 75 feet wide with no columns between the core and perimeter. Two of the tubes are 50 floors high, two are 66 floors, three are 90, and two are 108.

Hybrid StructuresHybrid Structures

Structures are often built in which the Structures are often built in which the lateral resistance is provided by a mixture lateral resistance is provided by a mixture of structures. The most common are of structures. The most common are moment resisting frames combined either moment resisting frames combined either with structural walls or diagonal bracing.with structural walls or diagonal bracing.

Both externally and Both externally and internally the new Toyota internally the new Toyota building is visually excitingbuilding is visually exciting

OTHER PLAN WITH CORE OR OTHER PLAN WITH CORE OR TUBE SYSTEMSTUBE SYSTEMS

SOME STRUCTURAL SYSTEMS USED IN ASIA PACIFIC REGIONAL SOME STRUCTURAL SYSTEMS USED IN ASIA PACIFIC REGIONAL BUILDINGSBUILDINGS

STRUCTURAL SYSTEM OF BURJ DUBAISTRUCTURAL SYSTEM OF BURJ DUBAI

Designer purposely shaped Designer purposely shaped the plan of Y-shaped to the plan of Y-shaped to reduce the wind forces on reduce the wind forces on towertowerThe structural system could The structural system could be described as buttressed be described as buttressed core. Each wing with its own core. Each wing with its own high performance concrete high performance concrete core and perimeter column, core and perimeter column, buttresses the other via six buttresses the other via six –sided central core–sided central coreThis results in tower which This results in tower which is extremely torsionally rigidis extremely torsionally rigid

SPINE WALL SYSTEMSSPINE WALL SYSTEMS

Walls are placed along the corridors as a Walls are placed along the corridors as a spine running through the length of floors.spine running through the length of floors.

Triangular core wall along stair and Triangular core wall along stair and elevators in the core of the building takes elevators in the core of the building takes care for improving the torsional resistance care for improving the torsional resistance of tower.of tower.

ConclusionConclusion

Structural systems that are suitable for Structural systems that are suitable for different ranges of number of storiesdifferent ranges of number of stories

THE TWO COMMONLY USED THE TWO COMMONLY USED STRUCTURAL SYSTEMS FOR TALL STRUCTURAL SYSTEMS FOR TALL BUILDINGS AREBUILDINGS ARE

1.1. CEN TRAL CORE AND OUTRIGGER CEN TRAL CORE AND OUTRIGGER SYSTEMSYSTEM

2.2. REINFORCED CONCRETE TUBE-IN-REINFORCED CONCRETE TUBE-IN-TUBE SYSTEM WITH OR WITHOUT TUBE SYSTEM WITH OR WITHOUT OUTRIGGERSOUTRIGGERS

REFERENCESREFERENCES

Steel,concrete design of tall buildings Steel,concrete design of tall buildings --By: B.S.Taranath --By: B.S.Taranath

Tall structures --By Smith & CoulTall structures --By Smith & Coul

ACI Manual for tall building designACI Manual for tall building design

Proceeding for Structural system Proceeding for Structural system

Highrise Building –W SchuellerHighrise Building –W Schueller

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