outrigger belt trusses design - الجائز الشبكي المركزي والحزام...

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D r Youssef Hammida

Analysis of outrigger & Belts

Trusses in Tall Buildings

والحزام الشبكي المركزي ائزالج متصمی

مع جدران الكورالمحیطي

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انواع االطارات الشیكیة المركزیة في الكور

المحیطيوالحزام الشبكی

ا

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السفليالحزام الشبكي المحیطي

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تصمیم ناطحات السحاب طحات السحاب یعتمد كلیا على احمال القوى الجانبیةان تصمیم نا

كلما زاد االرتقاع والنحافة البرجیة زاد من الریاح والزالزل

التحدي لمھندسي التصمیم

دراسة األبنیة العالیة والنحیفة یتطلب تأمین بعض العوامل

الضروریة في األمان

strength لمقطع وتسلیح العناصرالمقاومة -1

)(drift الصالبة واالنتقال -2

الحركة واالھتزاز من تأثیر الریاح -3

ویكون تصمیم االعناصر محكوك باالنتقال المسموحdrift)(

The design of skyscrapers is usually governed by the lateral loads imposed on the structure. As buildings have gotten taller and narrower, the structural engineer has been increasingly challenged to meet the imposed drift requirements The design of tall and slender structures is

controlled by three governing factors, strength (material capacity), stiffness (drift) and serviceability (motion perception and accelerations), produced by the action of lateral loading, such as wind.

The overall geometry of a building often dictates which factor governs the overall design.

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As a building becomes taller and more slender,

drift considerations become more significant.

Proportioning member efficiency based on maximum lateral displacement supersedes design based on

allowable stress criteria

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مقاومة ریاح+ زالزل –تصالب قطري قضبان فوالذیة

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الكور ومحیطي تربیط مائل قطريجائزشبكي مركزي في

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ان عمل الجوائز الشبكیة یتبع ااماكن تواجدھا وتوزیعھا

بالنسیة للكور وارتفاع البناء وعدد الطوابق واألعمدة

المحیطیة ونوع المواد المستعملة من الخرسانة المسلحة اة فوالذ ستیل

جائز شبكي مركزي مستمر مسنود على الكور aالشكل --

غیر مستمر مسند من طرف واحد bالشكل -

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على المحیط اطارات مقاومة للعزوم والداخل تصالب مائل قطري بین األعمدة

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جائز شبكي محیطي عند الطابق األخیر على المحیط ومركزي في الكور

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في حال تواجد اطار شبكي اعلى الكور او في الوسط عن عمل الكور مثل كابولي فیصیح الكور مسنودعلى الجائز عوضا حیث ینقص عزم الوثاقة وكذلك بنقص تسلیح الكور وانتقالھ الكبیردرفت

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انواع الجمل المقاومة للریاح والزالزل في األبنیة اعالیة

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اطار شبكي مركزي مع كور جدار خرساني مسلج واطار حزام محیطي

یكون ارتفاع الجائز الشبكي بین طابق واحد الى طابقین ماعادة ھرباءجیث یتوفر ھذا الفراغ في طوابق الخدمات وغرف المصاعد والك

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عمل مع األعمدة كوحدة منكاملةاالجوائز تزید من صالبة الكور وت حیث ھذه في مقاومة عزم االنعطاف وقوى القص واالنقالب التي تحولھا األعمدة

قوى شادة ضاغطة في مقطع العامود المحیطیة الى وھكذا یقل مقطع وتسلیح الكور الكثبف باالضافة الى نقص نسیة التسلیح في اطراف الكور ووسطھ

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The Efficient Use of Outrigger & Belt Truss in Tall

Buildings

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نالحظ من الشكل كیف الجوائز الشیكیة اصبحت تعمل كمساند سبرینغ

تمنع الكور من الدوران و تقلل االنتقال الدرفت حیث تشارك األعمدة

الطرفیة وتحویل عزوم العاملة على الكور الى قوى شادة ضاغطة

یتم تسلیج األعمدة بموجبھا

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اطار شبكي حزام محیطي ینقل الحموالت الشاقولیة واالفقیة الى ااألعمدة الطرفیة

transfer Beamكما في حال كمرات التحویل

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بریسنك + كور معدني وسطي ومحیطة مسنودة على الكور اطارات شبكیة مركزیة اطار معدني محیطي مقاوم للعزوم كمرات + اعمدة مدات معدنیة + دیك معدني + بالطة خرسانبة

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نقاط تثبیت الجوائز الشبكیة في جدران الكور

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All multi-story buildings require at least one core to accommodate elevators, stairs, mechanical shafts, and other common services. Because views are a significant part of the

intrinsic value in tall buildings, it is most common for their core or cores to be centrally located within the floor plan to place occupants along exterior walls.

A central core also locates the center of lateral stiffness close to the center of lateral wind load

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and center of mass for lateral seismic loads, minimizing torsional forces.

In high-seismic regions many tall buildings have a dual system, sometimes called “core and frame” or “tube in tube,” with a perimeter moment frame providing significant torsional stiffness but a smaller contribution to overturning stiffness.

When direct or conventional outrigger walls or trusses are not acceptable for the building due to space limitations or a column layout which is not aligned with the core walls, an indirect, “virtual”outrigger or belt truss system may be used.

في األبنیة البرجیة ال بد من تواجد كور خرسانة مسلحة او معدني سنیل الكتلة والصالبة وتقلیل مركزیة تمركز محوري تقربیا متطابق مع مركز

الفتل البد من تواجد اطارات محیطیة مقاومة للعزوم خرسانیة ام معدنیة ستیل صندوقي فیمكن استعمال اطار شبكي محیطي عندما ال یتواجد كور نظامي

virtual”outrigger or belt truss

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ى الكور واألعمدة الخارجیةاطار الشبكي الداخلي مسنود علال مسنود على االطار الشبكي الداخلي المحیطي الشبكياالطار

او األعمدة المحیطیة

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The outrigger and belt truss system is one of the lateral loads resisting system in which the external columns are tied to the central core wall with very stiff outriggers and belt truss at one or more levels.

The belt truss tied the peripheral column of building while the outriggers engage them with main or central shear wall

The belt truss tied the peripheral column of building while the outriggers engage them with main or central shear wall The aim of this method is to reduce obstructed space

compared to the conventional method. The floor space is usually free of columns and is between the core and the external columns, thus increasing the functional efficiency of the building.

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Exterior columns restrained the core wall from free rotation through outrigger arms.

Outrigger and belt trusses, connect planar vertical trusses and exterior frame columns.

Outrigger system can lead to very efficient use of structural materials by mobilizing the axial strength and stiffness of

exterior columns.

المركزیة والمحیطیة الغایة منھا مقاومة القوىاالطارات الشبكیة األفقیة من الریاح والزالزل

عمدة الخارجیةحیث االطارات الشبكیة تربط عنصر الكور مع األ لتعمل كوحدة واحدة وزراع مزدوجة طویلة یحول عزم انقالب الكور

الى فوة شادة ضاغطة في األعمدة عوضا عن اطراف الكور داخلیة والحصول على مساحات فراغ واسعة وعادة ال توجد اعمدة

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Types Of Outrigger Truss System

On the basis of connectivity of core to exterior columns, this system may be divided as in two types:

Conventional Outrigger Concept Virtual Outrigger Concept

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نقاط نثبیت الجائز الشبكي المركزي مھ الكور

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Tall building with conventional outriggers,

In the conventional outrigger concept, the outrigger trusses or girders are connected directly to shear walls or braced frames at the core and to columns located outboard of the core.

Typically, (but not necessarily), the columns are at the outer edges of the building

Virtual Outrigger Concept In the “virtual” outrigger, the same transfer of

overturning from the core to elements outboard of the core is achieved, but without a direct connection between the outrigger trusses and the core.

The basic idea behind the virtual outrigger concept is to use floor diaphragms, which are typically very stiff and strong in their own plane Belt Trusses As Virtual Outriggers

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Frames, Vertical Trusses, Belt and Outrigger

Trusses The exterior fascia shear frames and the vertical trusses

in the core can be tied together by a system of outrigger and

belt trusses which are provided at plant room levels, where the

trusses will not interfere with the interior space planning. Figure 4 shows the arrangement of trusses. The primary

result of the outrigger trusses is the development of axial

forces in the exterior columns due to wind action. The use of belt trusses on the facades, at the same level

and perpendicular to the outrigger trusses, further enhances

participation of exterior frames in the cantilever behaviour. The belt trusses transform the two-dimensional frame system

into a three-dimensional

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Outrigger trusses

run parallel to the direction of lateral force. Belt trusses run perpendicular to the direction of the lateral force, along the perimeter of the building. This behavior significantly improves the lateral stiffness

under wind forces. The use of belt trusses on the facades, at the same level and perpendicular to the outrigger trusses, further enhances participation of exterior frames in the cantilever behavior.

. The belt trusses transform the two-dimensional frame system into a three-dimensional frame system which resists wind action.

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The building sway under wind is significantly reduced by the introduction of these trusses.

A review of the deflection curve indicates two stiffening effects: one related to the participation of the external columns in a total-building-width cantilever mode; the other related to the stiffening of the facade frame by the belt trusses.

Improvements in overall stiffness of up to 25% can result as compared to the Shear Truss and Frame System without

such outrigger-belt trusses.

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Three-Dimensional Model

A three-dimensional typical floor structural model will be used for the study.

The model is a60-storey reinforced concrete consisting frame atthe periphery and core wall in the center.

The building is viewed as an assemble of vertical frames interconnected at each storey level by diaphragm floor slab while the secondary beam was considered as point load on main beam. The static and dynamic computer analysis was carried out using ETABS program [9].

الجوائز الشبكیة الفراغیة بوكس یكون ارتفاعھا على كامل ارتفاع الطابق وبشكل

او بشكل قطري متصالب یصل بین عامودین مع عناصر تصالب قطریة وحاملة بالطة السقف العلوي والسفلي

مسنودة على كمرات معدنیة كیردر والسقف مدعم بمدادات معدنیة تعمل كدیافرام صلب في نقل القوى األفقي +بالطة خرسانة

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وى الشد والضط في العناصر القطریةق

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The stress diagram in Figure 1 illustrates the relative

efficiency of hinging the belt trusses to the perimeter columns rather than fixing them rigidly. If the trusses were to be continuously connected to the columns, the entire system would act as a unit, thus utilizing only a small percentage of the moment-resisting capacity of the core, whose walls are relatively close to the neutral axis of the building

Equation of Outrigger Structures

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This is indicated by the continuous distribution of stresses shown for the rigid frame in Figure 1.a. On the other hand, belted musses that are cantilevered from the core and hinged to the perimeter columns better develop the moment resisting capacity of the core while still engaging the exterior columns as in the rigid system (Figure 1.b).

In fact, since the hinged shear connections induce no bending moments into the columns, the axial capacity of the columns is increased relative to that for the case of fixed shear connections. The response of a core frame building with belt trusses to lateral loading is shown in Figure 2.

This Figure schematically shows the reduction of moment in the shear-core for a one-outrigger system (Figure 2.b) and a two-outrigger system (Figure 2. c) compared to that for a no-outrigger system (Figure 2. a).

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The outrigger braced structure in Figure 4 shows a shear wall with rigidly connected outriggers. At the outer ends they are connected to the foundation through the exterior columns.

When subjected to horizontal loading, the wall and outriggers will rotate causing compression in the downwind column and tension in the column on the upwind side. These axial forces will resist the rotation in the wall. A simplified method of analysis of this structure has been presented earlier (Stafford Smith and Coull, 1991; Stafford Smith and Salim, 1981).

It was assumed that the structure behaves linear elastically, columns onlycarry axial forces and that the sectional properties of wall and columns remain unchanged

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up the height of the structure

ي في اعلى الطوابقحساب االنتقال األعظم The maximum deflection at the top of the structure

consists of two terms: the free deflection of the wall subject to the full horizontal loading and a reduction term representing the decrease in lateral deflection due to the restraining moment formed by the axial forces in the columns.

w is a uniformly distributed lateral load, H is the total height of the structure, E is the modulus of elasticity, Iw is the second moment of

area of the wall and

حساب فاصلة تثبیت الشبكي مع الكور

x represents the distance measured from the top. The

restraining moment on the wall is

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Ac is the sectional area of the column, l` is the distance between the columns and

EIo is the bending stiffness of the outrigger. Introducing flexibility parameters for vertical and horizontal structure, respectively

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Offset and Alternative Offset Outrigger Concepts

the outriggers may be located elsewhere than in the planes of the core walls, while retaining all the advantages and mitigating some of the disadvantages of the conventional outrigger system. For the offset outrigger system to work, it is essential that the floor slabs be effectively rigid and strong enough in their planes to transfer the horizontal plane shears between the outrigger arm and the core

- یمكن للجائز الرئیسي الشبكي ان یكون بعید عن جدران الكور وبنفس الصالبة مع تأمین بالطة دیافرام صلب لنقل قوى القص

من الشبكي الى الكور

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القص من الجائز الشبكي الطرفي الى جدران الكورمیكانیزم عودة قوى

بعد انتقال بالطات الطوابق

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استعمال بالطة سقف وارضیة البدروم كجائز تحویلي لقوى القص

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l building with belt trusses Example

The method of analysis of the above mentioned system is

based up on the assumptions that the outriggers are rigidly attached to the core; The core is rigidly attached to the foundation;

The sectional properties of the core, beams and columns are uniform throughout the height;

Tensional effects are not considered; Material behavior is in linear elastic range;

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The Outrigger Beams are flexurally rigid and induce only axial forces in the columns;

The lateral resistance is provided only by the bending resistance of the core and the tie down action of the exterior columns connected to the outrigger;

The rotation of the core due to the shear deformation is negligible.

The following load combinations are used to determine the maximum lateral deflection in the structure. i) DL+LL ii) DL+LL±WL(x or y) iii) DL+LL±EL(x or y) iv) DL±WL(x or y) v) DL±EL(x or y)

The structure with above mentioned specifications and assumptions is analyzed using the program ETABS and bending moments, shear forces, lateral deflections are calculated for both Wind & Earthquake loading.

Since the wind load cases are governing, the graph and tables are represents the same.

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Moments

Another very important factor that is monitored is the moments along the height of the concrete core. The moments that were monitored as shown in figure 5.3 and are 1. The moments below the first outrigger (cap truss). 2. The moments above the second outrigger. 3. The moment below the second outrigger. 4 . The core base moment

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جزء من الشبكي داخل الكور –طرق تثبیت الجائز الشبكي في جدران الكور

تثبیت صفحیة معدنیة قوالذیة ملحمومحة مع قضیان الكور

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Middle outrigger girder connection to embed plate.

وصل ال صغائح بقضبان فوالذیة طرفي الكور

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تمریر الجائز الشبكي ضمن جدران الكور انشاء مركب

تثبیت الجوائز العادیة الشكیة اعمدة خارجیة

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عقدة تالقي شبكي مع العامود -

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استناد الجائز الشبكي على جدران الكور واألعمدة المحیطیة

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العامود القوي والجائز الضعیف وتشكل المفصل اللدن في الكمرة

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اشكال عقد تثبیت العناصر الشیكیة على جدران الكور

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صفائح معدنیىة ملحمومة الى تسلیح الكور األفقیة لوصل العتاصر الشبكیة مع جدران الكور

Embedded anchors for the connection between steel beam and concrete wall

The embedded anchors for the connection between steel beam and concrete wall could adopt different types according to the magnitude of load applied on the beam, see Table 3.3. The experiments show that type 1, the headed stud anchor would lead to the cracking of the concrete wall and slippage of the studs under the cyclic reversed loading, see Figure 3.3.

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Type 2, stud-steel bar anchor and type 3, sandwich-like steel bar anchor, as well as type 4, the embedded steel shape, their failures mainly depended on the upper or lower embedded steel bars or steel plates. While type 4 its anchorage capacity, energy dissipation and ductility are better than the others, it is suggested using to the major bearing member in high seismic fortification areas

اتصال الجائز الشبكي مع العامود الطرفي

تصدع نقطة االستناد من جدار الكور

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following conclusions are made from the present study 1. The use of outrigger and belt truss system in high-rise buildings

increase the stiffness and makes the structural form efficient under lateral load.

2. The maximum drift at the top of structure when only core is employed is around 50.63 mm and this is reduced by suitably selecting the lateral system.

The placing of outrigger at top storey as a cap truss is 48.20

mm and 47.63 mm with and without belt truss respectively. Hence there are not much reductions in drift with belt truss.

3. Using second outrigger with cap truss gives the reduction of 18.55% and 23.01% with and without belt truss.

The optimum location of second outrigger is middle height of the building. 4. It can be conclude that the optimum location of the outrigger is between 0.5 times its height.

CONCLUSIONS

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اعتبارات یجب تداركھا مع التصمیم تطبیق ما جاء في الكود اطارات خاصة مقاومة للعزوم -

وتشكل المفصل اللدن والعامود القوي والجائز الضعیف اعمدة محیطة والمحیطي الطابق اللین والضعیف وخاصة في طابق الجائز الشبكي المركزي - البالطة ودیافرام صلب مع ممرات ونقل القوى األفقیة وخاصة في طابق التحویل - تحلیل دراسة تقاصر الألعمدة وتأثیر حمولة محوریة ضاغطة -

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تفاصیل اتصال عناصر الشبكي مع جدران الكور الخرساني

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متر2اول جائز شبكي محیطي مع عامود مفرغ قطر

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تسلیح الكور ووصل العناصر الشبكیة

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مرورتسلیح الوصل والمقاطع الفوالذیة خالل جدران الكور

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وصل العناصر المعدنیة ومرورھا خالل الكور

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م2یل قطر=المركزیة والمحیطیة تقریمیكا عامود انشاء مركب مع الجوائز

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ربط الجائز المركزي مع جدرام الكور الخرساني

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لحام بسامیر القص مع قضبان تسلیح الدك

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الكور الى قضبان تسلیح البالطة الدك مثبتة في صل نشاریك قضبانو

وصل الجائز المركزي الشبكي المسنوج بین الكور وعامود میكا المحیطي

sequenceمع اعتبار التقاص ربین العامود وجدران الكور

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سویة مناسیب األعمدة نتیجة التقاصر من االنضغاطت

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عامود مركب عنلصر معدنیة فوالذیة مغموسة ضمن خرسانة مسلحة

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Dr Youssef Hammida