final chapter 5 live cases

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Chapter 5 live cases

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CHAPTER 5

LIVE CASES


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In this chapter we will present few live cases of damaged concrete structures

which require a serial of repair and strengthening procedures these structures

includes residential building, hotels and bridges and it have different levels of

damages varies between major and minor damages.

Figure5- 1 Building that need's repair

5.1. Repair of residential building

5.1.1. Structure

Three storing residential building located in New Cairo district, the building is still

under-construction, it is still in the skeleton form.

5.1.2. Material used

The material used are; cement of high compressive strength (higher than the one

previously used in construction) and reinforcing steel bars.


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5.1.3. Project scope

In this building damages are detected after the removal of the wooden forms the

damage was presented as (figure2, 3, and 4)

5.1.3.1Causes of repair

Figure5- 2longitudinal crack Figure5-3spalling of concrete coversAnd appearof RFT

Figure5- 4 longitudinal crack due to construction and structural defects


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Figure5- 5 Figure5- 6Buckling of column due to high

compressive forces

5.1.4.Repair procedures

Splitting cracks due to buckling of column

5.1.4.1.Repair of column by using (concrete jacket)

1. The slab is lifted up by wooden sections to remove the load from column

Figure5- 7 First step lifting up the slab with wood to be able to remove concrete cover


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2. Cover is removed and steel bars have been inserted into old slab by epoxy to

welded thenew additional RFT to it (fig5-7)

Figure5- 8 Bonded steel bars

3. Creating voids in the slab to insert new RFT of the column into the slab to

increase the bond between the columns and to make the process of purring

concrete into shutter easier.

Figure5- 9 Breaking the slab to insert new RFT into it


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4. After cleaning the surface insert new additional RFT and additional

stirrups that preferred to be box stirrup to increase the bond then make

the new shutter of the column from one or more sides according to

repair design then pure the new concrete into column jacket.

Figure5- 10 Concrete jacket from one or more sides

Figure5- 11 Increase in the section dimensions of column after repair


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5.1.4.2. Strengthening of the first slab using section enlargement

Some elements were not in need to repair such as first floor it has small deflection

thats not critical; we insert new top RFT then cover it with a layer of concrete.

Figure5- 12 slab of first floor before and after adding additional top RFT

5.1.4.3. Reconstruction of the second and third floor slabs

1. Lift up the repaired slab by wooden sections to avoid slab collapse.

Figure5- 13 Slab lifted by wooden sections


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2. Remove base concrete and prepare the connection between slabs and columns

Figure5- 14Removing old concrete

3. Make sure of Cleaning RFT from old concrete and ducts of electric wires.

Figure5- 15 Clean the main RFT of embedded beam from concrete


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4. Build up the new shutter of the slab in the same level of floor then insert electric

ducts

Figure5- 16 Wooden forms from in and out sides

5. Pour concrete into shutter then remove wooden forms after harden of reinforced

concrete.

Figure5- 18 Curing surface of new concrete slab


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5.2. Repair of Hotel Concrete Balcony Columns

Concrete can crack and experience vertical stress under the most unexpected

circumstances affecting the structural building integrity and requiring immediaterepair. When these situations occur in buildings used by the public, such as

restaurants and hotels, repairs must be aesthetically pleasing and not raise public

concern related to the buildings safety. In this case, concrete columns were pulling

away from the balconies.

5.2.1. Structure

Grande Shores Ocean Resort, Myrtle Beach, South Carolina this is a 7-story resorthotel on the Atlantic beachfront. It is constructed using standard concrete skeleton

method.

5.2.2. Material Used

Pre-cured Pre-preg w/peel-ply column wrap vacuum laminated; Designed by

layout of job scope; Laminated with (#4020) Epoxy.

5.2.3. Project Scope

Concrete columns faade were pulling away from the balconies. Challenge was to

strap and reinforce columns, yet make reinforcement aesthetically pleasing.

Figure5 - 19 Repair of hotel column


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5.2.4. SolutionPre-preg column wraps allowed for fast installation, completing project with

minimal disruption and prior to hotels busy season. With this method they werestill able to function with only a small area of rooms closed off to public

Original design was to install 200 lb steel plates that would have added significant

weight, would not have been aesthetically pleasing and would have closed a large

area of the hotel losing them revenue.

Figure 5- 20 side view of concrete balcony columns

Figure5- 21 Elevation of concrete balcony columns


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5.3.Highway-Bridge, Support Column RepairConcrete bridge columns are an integral part of the integrity of highway bridges

that may be damaged by various physical forces including earthquakes and vehicleaccidents. Vertical effects on these bridge columns lead to significant variations in

axial force demand which can result in fluctuations in moment demands at the face

of the bent cap, amplification of moment demands at the girder mid-span, and

changes to moment and shear capacity of the column.

In this case, concrete columns were deemed to be fatigued due to deterioration of

steel reinforcement.

5.3.1. Material UsedFortec 600 gsm unidirectional carbon fiber fabric w/ #4550 Epoxy Saturant and

(#590) Epoxy paste.

5.3.2. Project Scope

Concrete Columns were deemed to be fatigued due to deterioration of steel

reinforcement. Repair was to wrap columns using 600 gsm carbon fiber wrap

utilizing onsite impregnator of epoxy saturate.

Figure5- 22 Wrapping column with FRP sheets

5.3.3. Conclusion

Wrapping column with Fortec carbon fiber fabric allowed for minimal road closure

as would have been needed with old method of teardown and replacement of

column. The #4550 epoxy allowed contractor to cure out in field under difficult

weather conditions. With highs in the 60's and lows dipping into the 40's a night

curing was a challenge.

final chapter 5 live cases

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