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اف كربونیةوالی األعمدة صمیم تقویةت

ھوFiber Reinforcement Polymer (FRP) البولیمر ألیاف استعمال ان األعضاء الخرسانیة التأھیل وإعادة الخارجیة التقویة مجال في األمثل الحل

المتضررة عالي تحمل وذات الكیمیائیة، للعوامل مقاومة مواد من ألیاف مصنوعة ھي -

من الناتج والتآكل للصدأ ومقاومة قلیل، حراري تمدد معامل ولھا لالجھادات الكربونیة باستعمال األلیاف خصوصا عالیة معامل مرونة وذات التعریة عوامل في PGFRP مسبقة الجھد الزجاجیة واأللیافGFRPالزجاجیة األلیاف

خارجیا األعضاء الخرسانیة تقویة

:)االیبوكسي (الرابطة المادة مواد بوجود إال یتم ال البولیمر بألیاف الخرسانیة لألعضاء الخارجي تغلیف عملیة

بأحكام الخرسانة سطح على البولیمر ألیاف التصاق على المواد ھذه تعمل رابطة،

تكون بلصق شرائح االلیاف الكربونیة على السطح طریقة التنفیذ بشكل عام -

إزالة طبقات التشطیب القدیمة و ازالة اى :الخرسانى مباشرة وذلك عن طریق

طبقات ضعیفة او مفككة من سطح الخرسانة حتى الوصول الى سطح خرسانى

قوي، و ذلك عن طریق الصواریخ او السفح بالرمال كما یجب التأكد من ان

2نیوتن/مم 1.5مقاومة االلتصاق للسطح الخرسانى ال تقل عن (من نسیج االلیاف الكربونیة یمكن استخدام اكثر من طبقة من الیاف الكربون -

عادةً) قد تصل الى سبعة طبقات فى بعض األحیان و تستخدم طرق معینة للتنفیذ الة العامةال تختلف كثیراً عن الح

ساعة على تثبیت شرائح 24یمكن البدء فى تنفیذ طبقات التشطیب بعد مرور - ".الیاف الكربون

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الكربون الیاف استخدام ممیزات

.خفیفة الوزن -١

.ال تصدأ -2

یتم تغطیتھا بطبقات التشطیب فال تترك أثراً -٥.

:الكربون الیاف عیوب

یجب وضعھا فى األماكن المعرضة للشد والقص .1

لذلك یراعى تكسیر سوك الكمرات و األعمدة و جعلھا –مادة قصفة جداً 2

.قوسیةحتى ال تتكسر األلیاف

یوجد دھانات معینة و أسالیب حمایة یمكن -لیس لھا اى مقاومة للحریق 3

.تطبیقھا لزیادة مقاومتھا للحریق

تستخدم ھذه المادة في التقویة للتعویض عن فوالذ التسلیح وللمقارنة فالمعروف -

بینما في األلیاف الكربونیة kg/cm2 4000أن اجھاد الخضوع في الفوالذ ھو

وانما تختلف عنھ بأنھ الیوجد kg/cm2 28000وسطیاً

فیھا عتبة سیالن

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enforcement, as reinforced polymer, FRP fiberThe use of

for concrete structures has been growing rapidly in

recent years.

This paper summarizes the current state of knowledge of

these materials and highlights the various FRP

strengthening techniques that have been used for

concrete and masonry structures.

Material characteristics of FRP and fundamental design

considerations are discussed.

Selection of the appropriate materials and their

corresponding advantages and disadvantages are

highlighted.

Design philosophies for concrete members reinforced

and/or strengthened with FRP are enumerated.

Fundamental flexure, shear and bond be heavier of

concrete members reinforced and/or strengthened with

FRP according to the current ACI design guidelines are

examined.

تقویة األعمدة باستعمال البولیمیرات المسلحة باأللیاف الكربونیة :

تعتمد تقویة األعمدة الخرسانیة سواء المستطیلة أو الدائریة باستعمال طوق من زیادة المقاومة التي تنتج في باأللیاف الكربونیة وذلك الصفائح البولمیریة المسلحة

الخرسانة نتیجة الحصر من ھذا الطوق. تصبح الخرسانة المطوقة عاملة تحت ضغط ثنائي المحور حصر باالتجاه األفقي من الصفائح البولیمیریة. ویؤدي ذلك الى

باالتجاه الشاقولي. العامودزیادة مقاومة

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-This study investigates the behavior and failure modes of fiber

reinforced polymer (FRP) confined concrete wrapped with

ferent FRP schemes, including fully wrapped, partially dif

wrapped, and non wrapped concrete cylinders. By -uniformly

using the same amount of FRP, this study proposes a new

wrapping scheme that provides a higher compressive strength

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concrete, in comparison with confined-and strain for FRP

conventional fully wrapping schemes. A total of 33 specimens

were cast and tested, with three of these specimens acting as

reference specimens and the remaining

specimens wrapped with different types of FRP (CFRP and

GFRP) by different wrapping schemes.

For specimens that belong to the descending branch type,

ad a lower compressive wrapped specimens h-the partially

strength but a higher axial strain as compared to the

wrapped specimens. In addition, the -corresponding fully

wrapped specimens achieved both a higher -no uniformly

compressive strength and axial strain in comparison with

apped specimens. wr-the fully

wrapping scheme changes the -Furthermore, the partially

failure modes of the specimens and the angle of the failure

surface.

A new equation that can be used to predict the axial strain

of concrete cylinders wrapped partially with FRP is

proposed

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Design of FRP Axial Strengthening of RCC Columns -ACI 440.2R-08 Home/ How To Guide / Design of FRP Axial Strengthening of RCC Columns -ACI 440.2R-08

FRP axial strengthening systems are used to improve or enhance the capacity of reinforced concrete columns. It can be used for both circular and rectangular shaped columns but it is more effective in the former shape.

In this article the design of FRP axial strengthening system for columns is discussed.

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Fig.1: Applying Continuous FRP Systems for Axial Strengthening of RCC Columns Advantages of FRP Axial Strengthening Systems for Columns

Increases the ultimate load carrying capacity of reinforced concrete member

Improves shear capacity of reinforced concrete element

Reinforcement bar lap splice capacity of the member is improved due to FRP axial strengthening system application

The ductility of reinforced concrete column is improved considerably.

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Design of Axial FRP Strengthening Systems for Columns FRP axial strengthening is usually conducted by providing fiber reinforced polymer (FRP) around reinforced concrete columns. This strengthening technique is specifically influential when the column is circular.

However, if the reinforced concrete column is rectangular and the ratio of depth to width of column is larger than 2 or the smallest side of the column is greater than 900mm, then ACI 440.2R-08 is not applied for this strengthening method.

Figure-2 illustrates the confined area in different shapes of concrete columns.

Fig.2: Confined Area in Circular, Square and Rectangular Concrete Columns

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The ineffectiveness of rectangular or square column confinement might be attributed to the non-uniform stress distribution and stress concentration at the corner of the section. This may lead to premature failure of strengthened element.

It is essential to wrap reinforced concrete column completely with FRPs in order confine and improve the element effectively. Unlike the flexural and shear strengthening of reinforced concrete beams, the FRPs which surround the column activated only if the member is enlarged laterally and exert stresses on the FRPs. This means that, beam strengthening is an active system whereas column strengthening is a passive system.

The FRP system which wrapped around the column creates circumferentially uniform confine pressure that acts against the radial compression enlargement. Figure-3 illustrates how FRP systems create a pressure against the compression expansion of the concrete column.

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Fig.3: Forces Acted in a Confined Concrete Column

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Fig.4: Reinforced Concrete Column Confined with Continuous FRPs Strengthening of RCC Column Under Pure Compression The compression strength of reinforced concrete column can be increased through confinement of the column. The confinement is achieved by directing FRP systems around the column transverse to longitudinal direction of the column. It should be said that, any FRP system that applied to in other directions should be ignored.

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The nominal capacity of short, non-prestressed, normal weight reinforced concrete column with tie and spiral reinforcement can be calculated by the following two equations which is provided by ACI 318-11:

For tie:

For spiral

The confined compressive strength is estimated using formula provided by ACI 440.2R-08:

If is larger than zero but smaller than , the following formula is applied:

When is larger than but smaller than , then the following expression is used:

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Where: : Strength reduction factor which 0.75 for spiral

and 0.65 for tie

fc‘: Concrete strength Ag: Gross concrete area Ast: Longitudinal reinforcement area fy: yield strength of longitudinal reinforcement fc: confined compressive strength Ec: Concrete modulus of elasticity : Concrete strain

: Ultimate axial compressive strain of confined concrete and it can be computed by applying equation 10 and its value should not exceed 0.01.

E2 and are slope of linear portion of stress

strain model for FRP confined concrete and transition strain in stress strain curve of FRP confined concrete respectively and both may be estimated by the following equations:

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The maximum confined concrete compressive strength (fcc‘) in equation-5 is calculated as follows:

Where:

: Strength reduction factor taken as 0.95

ka: Efficiency factor for FRP reinforcement in

determination of maximum confined compressive strength and it depend on geometry of cross section as shown in figure 2. It can be taken as 1 for circular cross section as per the ACI 440.2R-08 recommendation.

fl: Maximum confined pressure because of FRP

system and it is computed as:

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Where:

Ef: Modulus of elasticity of FRP reinforcement n: Number of plies of FRP reinforcement

tf: Nominal thickness of one ply of FRP

reinforcement D: diameter of circular cross section compression member

: Effective strain level in FRP reinforcement achieved at failure and can be evaluated using the following expression:

Where:

: is the FRP strain efficiency factor takes FRP system premature failure into consideration and it is usually taken as 0.58

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: design rupture strain of FRP reinforcement

The maximum axial compressive strain of confined concrete can be calculated by the following equations:

Where:

: Maximum strain of unconfined concrete

kb: Efficiency factor for FRP reinforcement and it

can be considered as 1 for circular cross section based on recommendations of ACI 440.2R-08

fl / fc‘: Confinement ratio and a minimum of 0.08

should be considered as per ACI 440.2R-08 recommendation. If non-circular cross section is strengthened, the equivalent diameter should be used in equation 8 as illustrated in Figure-5:

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Fig.5: Equivalent Circular Cross Section

And both efficiency factor (ka) in equation-7 and (kb)

are based on the cross-sectional area of effectively confined concrete (Ae) and (h?b) ratio as can be observed from the following equations:

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Where:

rc: Radius of the corner of the section as it can be

seen from figure 5 pg: Longitudinal steel reinforcement ratio Column Subjected to Combined Axial Compression and Bending Reinforced concrete column that is subjected to both axial compression and bending can be strengthened by axial FRP strengthening systems. If the eccentricity is smaller than 0.1h then equation-1 and equation-2 can be employed to anticipate the confinement effect on the strength improvement.

However, when the eccentricity surpasses 0.1h then the two previous equations is employed to

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estimate the concrete material properties of the cross-section element under compression. This will be used to construct interaction (P-M) diagram, Figure-6, for the concrete element that has been confined by FRP systems.

Moreover, there are several restrictions which should be considered when the member is subjected to axial compression and bending.

The first condition which should be considered is that, FRP effective strain must be greater than 0.004.

Moreover, if maximum applied bending moment and axial force located below the line that connect the balanced point in the interaction diagram for unconfined member and the origin, then strength improvement should not be considered.

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Fig.6: Interaction Diagram

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CFRP patterns used to strengthen axially loaded RC walls with openings

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Methods of FRP strengthening for RC columns: a – wrapping of

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Exposing Rusted Rebar First we removed all loose concrete at the surrounding area of each crack or spall. We then sandblasted to remove all rust and debris from the exposed reinforcing steel.

The sandblasting sprayed a good amount of debris in the air, and to protect the surrounding vehicles we had to be very creative with our containment during this process.

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