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Dr youssef Hammida

Transfer Slabs Beams Design

Tall Building

جوائز التحویلصمیم بالطات وت

األبنیة البرجیة

Construction of Transfer

Plate

from

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Transfer slab

(Transfer slab) في التصمیم الحصیرة لبشھا تشبھبالطھ ھي البالطھ التحویلیھ واستثماریة ف معماریھواعالھا مختلفھ عن االعمده اسفلھا وذلك لظر والجدران عمدهاال حیث

ھى و اوتاد خوازیق كأنھا لبشھ مسلحھ مرتكزه على العالیة و تصمم البرجیة للمشاریع االعمده أسفل البالطھ التحویلیھ حاالت التحمیل لالعمده أعلى البالطھ التحویلیھ من ریاح وزالزل واالحمال الحیھ والمیتھ والتى یتم الحصول

بالطبع المبنى الذى یحتوى على بالطھ تحویلیھ البد من عمل تحلیل دینامیكى قاط عدم االنتظام في البالطة التحویلیةوتكبیر قوى الزالزل واألفقیة لتواجد ن

خصوصا عندما تكون على ارتفاعات عالیة حیث ان وزن ھذه البالطة (السماكة تصل في بعض االحیان الى 3-5 متر ) وللتقلیل من سماكة البالطة التحویلیة یلجأ الىPosttension Transfer It is the Slab / Beam from which picked up columns may be started where there are no columns underneath.

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So, it is a kindl of frame in which upper storey columns are directly supported over these slab and hence are critical and important structural members.

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Axial forces in the perimeter columns with (a) a full size transfer (24.1 ft depth), and (b) a beam with a depth 1/10 of the full size beam (2.41 ft depth)

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Chapter 12 of ASCE 7 classifies a number of horizontal structural irregularities, such as reentrant corners, diaphragm

discontinuities, and torsional irregularities

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NSW Why Dee - Slab Transfer PT

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Construction Stages Analysis

In any Structural Analysis it is assumed that the entire loading is applied on the complete structure instantaneously. However, building structures are constructed and loaded gradually, sever floor at the time. Typically, in a building structure the construction loading is about 80% to 90% of the service loading. The loading of the 1st stage is supported only by the structure which is constructed up to that moment. The additional loading from the 2nd stage is supported by the structure which is constructed up to that moment (stage 1 and 2). The 2nd stage is constructed on already realized deflections from the 1st stage. This will influence the distribution of the internal forces in all structural elements, especially the reaction of the transfer floor. In the Constriction Stages Analysis the structure and the loading is applied gradually, as it is constructed. For instance, at the end of the first stage all the deflections due to the self weight are released, and the upper levels will be constructed on already realized deflections.

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R/C BUILDING software can perform this type of analysis in stages. The deflections and the internal forces are incrementally accumulated as the structure is constructed. This will provide the most accurate estimate of the reactions on the transfer slabs

- یجب األخذ بعین االعتبار مراحل تنفیذ الطوابق العلویة وتأثیر االنتقال على الطوابق السفلیىة بعد فك الشدة للطوابق السفلیة حیث یتم التنفیذ على مراحل ولیس دفعة واحدة ویجب ادخال تأثیر االنتقال وعلى فترات محددة كما قي الصورة

Soil-Structure Interaction

Normally, when a 3D model of a building is created, we need to constrain the vertical movement at all footings. In R/C BUILDING software we can assign the "Footing" property to some walls and columns. Usually, we need to assign the "Footing" property to all columns and walls at the lowest level. This approach is suitable for very stiff foundation soils, such as rock or compacted sands and gravel. But, when the soils is "softer", we need to consider the influence of the footing settlements on the internal forces on all structural elements.

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For example, if a building structure consists of a raft and a transfer slabs, supporting several floors of masonry (see figure below). R/C BUILDING software will consider the contribution of all structural elements in evaluation of the settlements, not just the raft slab. If only the rafts slab is considered, it might results in over-design of the raft itself, by the effect of the settlement will be ignored on all other structural elements, which might cause development of some cracks in the upper levels

- ھبوطات التربة في حال تواجدھا ولكامل المنشأ تأثیر یجب أخذ

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- This elevation of the lower part of the Brunswick structure shows the transfer of loads from closely spaced columns above to widely spaced columns below through a transfer wall beam

Figure 2: Column layout at 4th floor transfer slab showing garage columns below (red) and tower columns above (blue)

IncImage used with permission of WJE Associates

The design of Dolphin Tower includes a 3 story above ground parking garage with 12 additional residential stories rising from the middle. The building was designed and constructed entirely of cast in place reinforced concrete. Due to the difference in space requirements from the parking structure on level 3 to the

-residential units on level 4 the columns were designed to be disjoined as shown in figure 2 and therefore required the use of a

transfer slab in order to direct load forces from above down tothe foundation.

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Figure 4: Cross section at column showing shear plane failure

extending beyond top reinforcing

nother major concern with the transfer slab was punching shear due to the garage columns below. Punching shear is due to localized forces on slabs at supporting columns which attempt to punch a hole upwards through the slab. Due to the close offset nature of several of the garage columns and tower columns at the fourth floor transfer slab, these localized forces became great enough to cause concern. Typically reinforcing is used in these circumstances in order to resist the stresses caused by punching shear and in fact was used for the transfer slab at the top of the columns.

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عند التقاء االعمدة punching shear تركیب ھوكات لمقاومة قوة االختراق مع البالطات

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Transfer Truss over 28m Support 57 floors

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Construction of Transfer Plate from various case studies Transfer plate is a structure sometimes finds inhigh-rise

buildings in Hong Kong. Building design often involves a podium structure that houses other functional spaces such as a shopping mall or a large lift lobby which require an unobstructed spatial layout in order to give a more impressive view. While for the upper structure, it is often used as office or residential units using moreeconomical shorter span design, or sometimes even with the putting in of very congested core

the following methods or provisions are often employed. 1. A very heavy duty falsework system is erected as support and work platform to carry out the works (including formwork erection, steel fixing, concreting and sometimes tensioning works). 2. The placing of concrete to be done in several layers in order to reduce the total loading of the falsework. The hardened concrete on the bottom layer can take up loading very quickly. 3. The use of tensioning technique in the transfer plate to lower the thickness and thus the weight of the structure. 4. Or, the combination of method 2 and 3.

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تصمیم بالطة التحویل یشبھ تصمیم لبشة حصیرة عامة -

اوتاد وتحقق شرط الصالبة والثقب-مسنودة على خوازیق واعتبار حموالت الطوابق العلویة موزعة بانتظام ویمكن اجراء

الحساب یدویا او على الحاسب كما في تصمیم اللبشة تفریبا

ویجب تحقیق االشتراطات التالیة: - 1 - قص الثقب أعمدة علویة وسفلیة سماكة البالطة تحقیق وضع تسلیح خاص للثقب اسفل األعمدة و جائز التحویلمع بالطة ا 2 – تسلیح علوي حراري اتجاھین على كامل بالطة التحویل 3 – تحقیق االنتقال طویل األمد المسوح وفق الكود تحقیق ھبوطات وتقاصر األعمدة خالل مراحل التنفیذ – 4

Construction Sages Analysis

تحقیق تأثیر ھبوط وتفاعل التربة مع الھیكل – 5

Soil-Structure Interaction

6 – تواجد حالة عدم انتظام وتغیر العامل )R( اعلى واسفل بالطة التحویل وتأمین مسارات وممررات

Path collector للفوى األفقیة 7- یفضل للعنلصر الموقوفة والغیر مستمرة عند بال طة التحویل

ان تكون عادیة وال تشارك في مقاومة الزالزل واستنادھا مع عزم الفتل تأثیر مفصل ولیس وثاقة لتجنببالطة او جائز التحویل

تورشین

وجوائز التحویلالخالصة والتوصیات في تصمیم بالطات

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1- chick punching shear high and bilow slab from columns loads

2- add spcial bent pars bilow coulmns throw slab

3- add tempreture steel – MIN reinforecment

4 – chick fore- a transition long-term permissible according to the code

5 – design for Construction Stages Analysis

6 – There is case of irregularity and change factor (R) Top and bottom of transfer slab and ensuring paths and passages Horizontal force Path collector

7 - preferred for items Discontinued non-continuous with transfer Slab Be normal does not participate in earthquake resistance and they are connected with Slab is Bin not fixed To aviod the impact of torque twist Torshin.

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Dr Youssef Hammida

Thank - YOU