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Dr. Yousse Hammida

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Diagrid Structural Systemانواع جمل الخاليا الشبكية

من البروفيالت االنبوبية والبواري دنية ومقاطع الستيل والجاهزةباالضافة الى شبكيات المع -

والمقاطع الخرسانية المسلحة الى مسبقة الصنع كذلك يوجد الشبكات

وكذلك جملة الشبكيات الخشبية -

طابق 011حتى رتفاعات العاليةلكن تبقى الجمل والمقاطع المعدنية تناسب األبنية واال -

طابق 01ليس اكثر من على عكس الشبكات والمقاطع البيتنونية المسلحة -

الى زيادة كلفة الشدة الخرسانية والمقاطع الثقيلة

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SUMMARY

Diagrid has good appearance and it is easily recognized. The configuration and

efficiency of a diagrid system reduce the number of structural element required on

the façade of the buildings, therefore less obstruction to the outside view.

The structural efficiency of diagrid system also helps in avoiding interior and corner

columns, therefore allowing significant flexibility with the floor plan. Perimeter

“diagrid” system saves approximately 20 percent of the structural steel weight

when compared to a conventional moment-frame structure

The diagonal members in diagrid structural systems can carry gravity loads as well

as lateral forces due to their triangulated configuration. Diagrid structures are more

effective in minimizing shear deformation because they carry lateral shear by axial

action of diagonal members. Diagrid structures generally do not need high shear rigidity

cores because lateral shear can be carried by the diagonal members located on the

periphery

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Diagrid structural systems

are emerging as structurally efficient as well as architecturally significant

assemblies for tall buildings.

. The evolution of tall building structural systems based on new structural

concepts with newly adopted high strength materials and construction methods

have been towards “stiffness” and “lightness”. Structural systems are become

“lighter” and “stiffer”.

It is common knowledge that rather than directly standing the forces,

it is better to reduce them and dissipate the magnitude of vibrations.

Structure design of high rise buildings is governed by lateral loads due to

wind or earthquake.

Lateral load resistance of structure is provided by interior structural system

or exterior structural system.

The selected structural system should be such that it should be effectively

utilized for structural requirements.

Recently diagrid structural system is adopted in tall buildings due to its

structural efficiency and flexibility in architectural planning.

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Diagrid الشبكية الهيكليةالجمل م انظ ذات ةيرامعملا عوامللاكما هو تأثير الكفاءة الهيكلية ودعم روطتلاوفي الظهور آخذ .للمباني الشاهقةاألهمية وذات االرتفاع الشاهق القامة ةطويللألبنية الشبكية م الهيكليةانظتطور وقد . للشبكيات اس المفاهيم الهيكلية الجديدةعلى أس كما في ناطحات السحاب الوزن خفة"و " صالبة" منمواد عالية القوة المعتمدة حديثا وأساليب البناء امتالك مع

."صالبة"و وزنا وتركيبا "أخف"وأصبحت النظم الهيكلية ." وتقليل وتبديدفمن األفضل الحد منها تأثي القوى قفومن المعروف أنه بدال من مباشرة و

.حجم االهتزازات .األحمال الجانبية الناجمة عن الرياح والزالزل تصميم هيكل المباني العالية الى تأثير ويخضع - والقوى الجانبية للهيكل من قبل جملة لاحممقاومة األويتم توفير حيث من اطارات مقاومة للعزوم الى جمل مختلطة ثنائية داخليانشائي هيكلي نظام

والجدران القصيىمن االطارات المقاومة لألحمال Diagridوجملة االطارات الشبكية النظام الهيكلي الخارجي وفق أو -

ح والزالزلاحالثقالة والجانبية من الري من النوع الذي ينبغي أن تستخدم بشكل فعال مختارلاجب أن يكون النظام الهيكلي ي ةيلاعلا ةينبألا يف ةيرامعملاو لتلبية االحتياجات الهيكلية

الشاهقة بسبب الكفاءة ةينبألافي diagrid م الهيكليتم اعتماد النظا اثيدحو مؤخرا .في التخطيط المعماري روطتلا ةبكاومو المرونةب ناج ىلا الهيكلية نم ةيلاعلا ةيسدنهلا اهلاكشأب ةلئاملا عالضالاو ةيحنملاو ةجومتملا حوطسلاو ةيغارفلا تايكبشلا هذه - تارالودلل رده تسيلو ةينيزت ةيرامعم تاحولو فرت طقف يه تسيل ةيلاعلا ينابملا تاهجاو يف ةيرامعم ةوزنوا نزاوتو تابثل يئاشنالا سدنهملا اهجاتحي يذلا ةيئاشنالا ةلمجلا بلص نم يه لب لاخادلا يف تاراطالاو ةىيصقلا ناردجلاو روكلا جاتحن امك أشنملا ةمواقم ةيئاشنا لمجك جراخلا يف ةجومتملاو ةلئاملا تاراطالاو تايكبشلا هذه جاتحن - ةيئاشنا ةيرامعم تاهجاوك لزالزلاو حايرلل ةيجراخلا ةدمعألل bracing يرطقلا بلاصتلا ميدقلا ماظنلا معتسا نع ينغتو يرامعم لامج ىندأب يحوي الو كلاملا يضري ال انايحا يذلاو

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Diagrid Structural System

Def In general, structural systems are groups of interacting components that function

as one, to safely transmit gravitational and lateral loads to the ground. A Diagrid is a form of

such system. However, compared to conventional framing systems, Diagrids transfer loads

more efficiently as it combine gravitational and lateral resisting systems into one, through the

use of repetitive triangular framing. Such framing is used because of the efficient shape of a

triangle, which does not deform easily as each member is braced by the other two.

Because of this feature, Diagrids can span greater lengths and do not require interior columns, thus

increasing useable space in a building. In addition, the ability of a Diagrid system to dissipate

loads quicker with lesser building materials, allow design of more complex yet lighter structures,

making it an efficient system to use in sky scrapers and high rise buildings.

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Typical Diagrid Connection

Nodes

o Joints that connects all the members

o Typically formed by bolting or welding the ends of the members to a gusset plate

Diagonal Members

o Members that transfer both lateral and gravity loads through axial action

Horizontal Members

o Members that transfer gravitational loads to diagonal members through shear

action Members that transfer lateral loads to diagonal members through axial action

Load Distribution

The load distribution in a Diagid is similar to that of a truss, where loads applied at the

nodes are transferred by each each member through axial forces. However, unlike trusses

where one basic assumption is that all loads are applied at nodes (thus eliminating shear

forces), analysis of Diagrid systems include non-nodal loads, which induce shear forces.

The following figure shows the load path in a Diagrid system under a gravity point

load. As evident from the figure, the nodal load is transmitted by the diagonal members,

quickly dissipating the load.

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Load Path in a Diagrid Under a Gravity Point Load

Similar to this load distribution is that of a lateral point load applied at a node. The

diagonal members serves as a brace frame, which transmits the lateral loads axially to the

ground. The following figure shows this load path.

Load Path in a Diagrid Where

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Lateral Loads are Applied at the Nodes

However, for the transmission of distributed loads or loads that are not applied at the

nodes, horizontal members transfer loads to diagonal members through shear forces. The

following figure shows how the loads are transmitted to the ground. The green lines show

the transfer of loads by shear action, while the red lines show transfer through axial action.

Load Path in a Diagrid System Under

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Distributed Gravity Loads

The load paths shown verifies the ability of a Diagrid system to provide both lateral

and gravity support in one system. The diagonals, as stated earlier, provides a quicker way

of transferring loads to the ground through axial forces, while horizontal may transfer forces

axially or by shear, depending on the type of loading applied.

Compared to conventional framing, Diagrid systems have a wider spread of loads,

and lesser contact with ground (as it has lesser members), which may affect the selection of

its foundation system. Depending on the foundation system chosen, Diagrids may require

lesser support. For instance, for a deep foundation, Diagrids may require less piles, since

there is less members and concentrated loads.

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Cybertecture Egg, Mumbai, India Capital Gate, Abu Dhabi, United Arab Emirates Al Faisaliah Tower 2, R

iyadh , Saudia Arabia

How diagrid system adopt in high-rise building?

Background of "diagrid" structure

The early era, tall building relied on portal frame and fix joint to resist lateral and wind load. Latter the structure build higher, more load and forces have to consider in the

structure. Additional bracing in the form of diagonal placed in between the structure to take the lateral load. Portal frames are insufficient in the lateral forces for the tall

building. Diagonal bracing make the structure resist wind forces instead creating stronger frame connection

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How diagrid works?

Original diagonal bracing member laid over exterior structure as supplementary support.

However, the current diagrid system that used in exterior structures is primary mean of

support. Diagrid tower is model as vertical cantilever. The size of diagonal grid is defined

by the diving tower height into series of modules.

Diagrid “tube” does not have the sufficient strength to achieve stability in the structure.

Ring beam connection to the floor edge can tied diagrid with the floor and the core.

Normally multiple floors interesting with each long diagonal of the grid, these intersections

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will occur at the nodes as well as the several instances along the diagonal. When the

diagonal bracing extends over several stories, each floor’s edge beam can frame into the

diagonal members providing connection the core to support the floor edge beam.

“diagrid is a series of triangle that combine gravity and

lateral support into one, making the building to be stiff,

efficient, and lighter than a traditional high rise”

These diagonals were affected by the width and height ratio.

The base of the building have to designed to resist moment while the top have to resist the

shear force. As a result, the foundation of a diagrid system is more concentrate on a point

to reach stability yet the bundle tube system are relying of greater surface area.

What make Diagrid Structure works ?

- Diagrid structure required overall building plan dimension to counteracting the overturning

moment and provide rigidity though axial action in the diagonal members rather bending

moment in beams and column.

- Diagrid system maximum shear rigidity once the module reach equal 35° . However, the

maximum engagement of the diagonal member for bending stiffness corresponds to value

90 °. Vertical columns can be eliminated but the diagrid system relies on the optical angle

and module dimension.

- The diagonal members in diagrid carry shear and moment. The optical angle of the

diagrid will dependent on the building height and module. The expected optimal angle for

diagonal members for diagrid structure will fall in the rage of 60° to 70°.

Who mentioned that, “ a pure steel diagrid tower doesnot require a core for lateral

resistance

Diagrid nodes

The relatively new and the joints off diagrid are more complicated than conventional frame

structure.

The fabrication of the connection and joint are much complex than conventional rectilinear

structure. So shop fabrication before send to site work is needed.

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There are two school interpreting the need of node

(1) pin node

Not rigid pin connection can be used in the symmetrical structure since the structure have

balance load.

(2) Rigid Node

the needs of rigid nodes to assist the structure to support during the construction process.

Diagrams show the function responding to the load: Under vertical load (left) and under

horizontal load (right)

Diagrid Joint

Welding joint for the Swiss Re Tower interior

There are two type of cladding system which affected by the diagrid type;

(i) diagrid structure sit external and the envelope or curtain wall will clad on floor structure,

(ii) diagrid structure sit internal and the envelope have to clad on the diagrid.

This tend to change the typical rectilinear curtain wll system into triangulate shapes.

(Boaske, 2013)

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There are two main joint for the diagrid structure: welding or bolting.

This have to rely on the what appearance require for the design. for example when the

structure to be expose, welding cans provides better aesthetic value. In the contrast,

if the structure will be expose to external and cannot be visible, bolt and nut will be the

better choice.

A welding connection is needed if the diagrid structures decided to architectural exposed it

but required more skillful workers . Somehow, if the structure are to be clad or concealed

like Hearts Tower, the diagrid can choose to bolted on site for speed erection.

Diagrid Load

Vertical - Lateral - Shear through triangulation

Compared with conventional framed tubular structures without diagonals, diagrid structures

are much more effective in minimizing shear deformation because they carry shear by axial

action of the diagonal members, while conventional framed tubular structures carry shear

by the bending of the vertical columns.” (MOON, Connor, & Fernandez, 2007). Below are

the force study diagram from the seminar lesson of EngineerBlog:

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Vertical Load

The gravity and vertical load from the building will distribute toward the apex of the

diagonal structure. Somehow, it will affected by the height and angle of the diagonal. The

vertical forces will be divide/disperse into the other diagonal member. Compression and

tension result in the diagonal will transfer into the bottom section.

Lateral Load

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the lateral load happened toward the "flange" of the structure receiving directional wind

load. this will result the lateral load into two part; windward and leeward. As a

consequence, these diagonal members receiving two different direction of force load. It will

respond relatively. The structure able to resist both force and achieve equilibrium.

Shear Load

the shear load happened when the structure receive a moment. This forces react toward

the angle of the apex. Comparing to the conventional frame structure, triangular properties

allow the force to be distribute and achieve a balance. In other hand, it also means that the

more diagonal structure able to transfer the shear load, it cans ensure the structure

standing even though received certain impact that may cause structure failure.

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Diagrid Structural Systemانواع جمل الخاليا الشبكية

من البروفيالت االنبوبية والبواري دنية ومقاطع الستيل والجاهزةباالضافة الى شبكيات المع -

والمقاطع الخرسانية المسلحة الى مسبقة الصنع كذلك يوجد الشبكات

وكذلك جملة الشبكيات الخشبية -

طابق 011حتى رتفاعات العاليةلكن تبقى الجمل والمقاطع المعدنية تناسب األبنية واال -

طابق 01ليس اكثر من على عكس الشبكات والمقاطع البيتنونية المسلحة -

الى زيادة كلفة الشدة الخرسانية والمقاطع الثقيلة

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Diagrid Structural System

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Figure 5. Aldar HQ in Abu Dhabi is the only circular diagrid tower. The diagrid has been constructed

from standard structural steel(wide flange or universal column sections) and a spray fire protection used.

Capital Gate in Abu Dhabi also uses triangulated glazing but makes a more unobtrusive gesture

on the façade regarding the location of the diagrid situated behind the glass. The very small 2

storey module size for Capital Gate, to support the 18 decree lean, has resulted in one of the smallest modules to date.

The member sizes are large and to translate this to the façade would have been

quite overbearing. Instead a slight color change at the grid is used to acknowledge the pattern.

These sorts of twisted forms tend to subdue the reading of the module through to the façade.

EXTERIOR DIAGRIDS

The majority of structural diagrids have been placed on the interior of the envelope. This is especiallycritical in cold climates where thermal expansion is significant and thermal bridges must be avoided. In highly corrosive environments exterior diagrids can also

require ongoing maintenance due to oxidation and weathering of the finish. However diagrids have been used outside of the envelope in several instances to satisfy different programmatic requirements. This is more frequent in hot or temperate climates where

thermal issues are less.

Perhaps the most notable exterior diagrid structure to date is for One Shelley Street in Sydney, Australia.

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The temperate climate has permitted the diagrid to exist outside of the curtain wall façade, effectively maximizing the internal leasable area. Although the designers were originally planning to construct the members from architecturally exposed steel, it was decided for economic reasons to instead use conventional universal column sections and clad these. As corrosion resistance is a great concern in Australia, this was likely a prudent decision.

The triangulation of the diagrid is completed by the floor edge beams on the interior.

This is always structurally necessary for stability, but normally this functionality is not separated by the placement of the curtain wall.

Exterior diagrids are also being used in double façade construction as a lightweight but stable means to support the outer layer of glazing. Although not structural in terms of the

support of the building, they do take advantage of the structural attributes of diagrid design

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the difference between conventional exterior-braced frame structures and current

diagrid structures is that, for diagrid structures, almost all the conventional vertical

columns are eliminated. This is possible because the diagonal members in diagrid

structural systems can carry gravity loads as well as lateral forces owing to their

triangulated configuration, whereas the diagonals in conventional braced frame structures

carry only lateral loads.

Compared with conventional framed tubular structures without diagonals, diagrid

structures are much more effective in minimizing shear deformation because they carry

shear by axial action of the diagonal members,

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while conventional framed tubular structures carry shear by the bending of the vertical

columns. Diagrid structures do not need high shear rigidity cores because shear can be

carried by the diagrids located on the perimeter Diagrid has good appearance and it is

easily recognized.

The configuration and efficiency of a diagrid system reduce the number of structural

element required on the façade of the buildings, therefore less obstruction to the

outside view. The structural efficiency of diagrid system also helps in avoiding interior

and corner columns, therefore allowing significant flexibility with the floor plan.

Perimeter “diagrid” system saves approximately 20 percent structural steel

weight when compared to a conventional moment-frame structure.

. IBM Building, Pittsburgh DIAGRID STRUCTURAL SYSTEMS

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Diagrid Structural Systems

Diagrid Structural System‎ > ‎Numeric Parameters

Diagrid systems are generally used for high rise towers,

oughly 20 - 100 stories tall, depending on location and

materials used. And the angle of the diagrid is most

effective between 53 and 76 degrees (See figure Below).

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Forces and Deflections/Member Sizing at members at associated floor heights of 60 story building.

Above are the calculated member sizes based on floor height and stresses affected on those

members. Obviously, the higher the member, the lower load associated with that specific member,

and therefore a smaller member is required. Notice that for a 60 story building, the Bending stress

exceeds the shear stress in a member around the 18th story mark, which means that would be the

primary force to pay attention to at the lower levels.

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The diagrid structural system

has been widely used for recent tall buildings due to the structural efficiency and aesthetic

potential provided by the unique geometric configuration of the system. This paper

presents a stiffness-based design methodology for determining preliminary member sizes

of steel diagrid structures for tall buildings.

The methodology is applied to diagrids of various heights and gridgeometries to determine

the optimal grid configuration of the diagrid structure within a certain height range.

Constructability is a serious issue in diagrid structures because the nodes of diagrids are

more complicated than those of conventional orthogonal structures.

Design methodology

A diagrid structure is modeled asa vertical cantilever beam on the ground, and subdivided

longitudinally into modules according to the repetitive diagrid pattern.

Each module is defined by a single level of diagrids that extend over multiple

stories. Figure 2 illustrates the case of a 6-story module. Depending upon the direction of

loading, the faces act as either web planes (i.e., planes parallel to wind) or flange planes

(i.e., planes perpendicular to wind). The diagonal members are assumed to be pin-ended,

and therefore resistthe transverse shear and moment through axial action only.

With this idealization, the design problem reduces to determining the cross-sectional area of

typical web and flange members for each module. Following the design methodology

developed by Moon et al. (2007), member sizes for the modules can be computed using

Equations (1) and (2) customized for each design case.

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Ad,w: Area of Each Diagonal on the Web

Ad,f: Area of Each Diagonal on the Flange

V: Shear Force

M: Moment

Ld: Length of Diagonal

Ed: Modulus of Elasticity of Steel

θ: Angle of Diagonal Member

γ: Transverse Shear Strain

χ: Curvature

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Nd,w: Number of Diagonals on Each Web Plane

Nd,f: Number of Diagonals on Each Flange Plane

δ: Contribution of Web Diagonals for Bending Rigidity

B: Building Width in the Direction of Applied Force

Optimal stiffness-based design corresponds to a state of uniform shear and bending deformation

under the design loading. Uniform deformation states are possible only for statically determinate

structures. Tall building structures can be modeled as verticalcantilever beams on the ground, and

uniform deformation can be achieved for these structures (Connor, 2003). Then, the deflection at

the top, , is given by

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Since, determination of a value for α, which is generally in the neighborhood of 500, is an

engineering decision, it remains to establish a value for ‘s.’ Then, the design of diagonals

in each module can be performed using Equations (1) and (2) customized for each design

case. The following section investigates the impacts of different ‘s’ value selections toward

the optimal stiffness-based design, which uses the least amount of material to meet the

design requirements. Further, diagrids of different height-to-width aspect ratios are

designed with various grid geometries to determine the optimum grid configuration of the

system depending on its aspect ratio.

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CONSTRUCTION OF STEEL DIAGRID STRUCTURES

Node construction for diagrid structures

the joints of diagrid structures

are more complicated and tend to be more expensive than those of conventional

orthogonal structures. In order to reduce jobsite work, prefabrication of nodal

elements is essential. Due to the triangular configuration of the diagrid structural

system, rigid connections are not necessary at the nodes, and pin connections

using bolts can be made more conveniently at the jobsite. Ifconsiderately

designed using appropriate prefabrication strategy, constructability will not be

such a limiting factor of the diagrid structures. Prefabrication of diagrid nodes for

conventional rectangular shape buildings can be done relatively easily and

economically because many nodes ofthe same configuration are required in this

case.

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Node detail for a freeform diagrid building

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Façade construction for diagrid structures

Different from conventional orthogonal structures, which are generally clad with

rectangular shape curtain wall units, diagrid structur esare clad with not only

rectangular but also triangular, diamond or parallelogram shape curtain wall units.

The Hearst Headquarters (Figure 1) uses rectangular shape curtain walls, while

the 30 St.

Mary Axe (Figure 8) uses diamond shape curtain walls.

Figure 9 shows a curtain wall unit of parallelogram shape composed of two

triangles to clad diagrid tall building structure.

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النتيجة والخالصة:

هي اكثر مقاومة وتوازن ةالشبكية القطري القول ان الجمل يمكن -

من جملة االطارات العادية

عزم االنقالب مناكثر تقاوم ذات االضالع المائلة الجملة الشبكية حيث -

(تورشن )وعزم الفتل

مج والمنحني والذي يزيد خاصية الجمال المتو من خالل شكلها

والردع االنشائي المعماري

وتحقيق التوازن االنشائي وسالمة البناء فهي تعمل لثبات

ذوق المعماريوال الجمال تحقيق خاصية الى ة باالضاف

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Dr. Youssef Hammida