Rehabilitation and strengthening of existing structures

Rehabilitation and strengthening of existing structures

1. REHABILITATION AND STRENGTHENING OF EXISTING STUCTURES

2. INTRODUCTION Repair: To bring back the position of the structure to its previous condition so it gives performance same as previously. It doesn’t cover the strength aspect of the structures. Some examples of repair……. Decoration of structure,Painting,WhiteWashing Checking the wiring of building Replastering of any wall if required Repairing of damaged flooring Repair of door and window Checking or repairing of pipe line connections, gas line connections and plumbing serveries.

3. INTRODUCTION Rehabilitation : Rehabilitation of a building means returning a building or a structure to a useful state by means of repair, modification , or giving strength to structure. It is related to the strength aspect of structures. To Bring back the position and condition of the structure by considering the strength aspect. Some of the examples of Rehabilitation … To fill the wide cracks using some suitable material Injecting epoxy like material in to cracks in walls , columns , beams, etc . Removal of damaged portion of masonry and reconstructing it using rich mortar mix.

4. INTRODUCTION Retrofitting: It is the modification of existing structures to make them more resistant to seismic activity, ground motion, or soil failure due to earthquakes.

5. INTRODUCTION When is Seismic Retrofitting Needed ? The two circumstances are:- Earthquake damaged buildings, and Earthquake-vulnerable buildings(with no exposure to severe earthquakes) Some examples of retrofitting ……… Increasing the lateral strength by reinforcement or by increasing wall areas or the numbers of walls and columns Giving unity to the structure by providing a proper connection between resisting elements. Avoiding the possibility of brittle modes of failure by proper reinforcement and connection of resisting members.

6. REPAIR METHODOLOGY Evaluation Relating observation to causes Selecting methods and materials Preparation of drawings and specifications Selection of a contractor Execution of the work Quality Control

7. MATERIALS FOR CRACK REPAIR The various materials used for repairs of cracks are: Cement Slurry Cement Mortar Epoxy resin

8. CRACK REPAIR TECHNIQUES Epoxy-injection Grouting Routing and Sealing Providing additional Reinforcement Prestressing steel Grouting

9. CRACK REPAIR TECHNIQUES Epoxy-injection Grouting Cracks as narrow as 0.002 in. (0.05 mm) can be bonded by the injection of epoxy. The technique generally consists of sealing the crack on exposed surfaces, and injecting the epoxy under pressure. Epoxy injection has been successfully used in the repair of cracks in : Buildings Bridges D ams and other types of concrete structures.

10. CRACK REPAIR TECHNIQUES The general procedure are given below : Clean the cracks: The first step is to clean the cracks that have been contaminated. Contaminants such as oil, grease, dirt, or fine particles of concrete prevent epoxy C ontamination should be removed by vacuuming or flushing with water or other specially effective cleaning solutions. Seal the surfaces: Surface cracks should be sealed to keep the epoxy from leaking out before it has gelled. A surface can be sealed by applying an epoxy, polyester, or other appropriate sealing material to the surface of the crack and allowing it to harden.

11. CRACK REPAIR TECHNIQUES Inject the epoxy: Hydraulic pumps may be used for injection. The pressure used for injection must be selected carefully. Increased pressure often does little to accelerate the rate of injection. If the crack is vertical or inclined, the injection process should begin by pumping epoxy into the entry port at the lowest elevation until the epoxy level reaches the entry port above. For horizontal cracks, the injection should proceed from one end of the crack to the other in the same manner. The crack is full if the pressure can be maintained. If the pressure can not be maintained, the epoxy is still flowing into unfilled portions or leaking out of the crack. Remove the surface seal: After the injected epoxy has cured, the surface seal should be removed by using hammer.

12. CRACK REPAIR TECHNIQUES

13. REPAIR BY ROUTING AND SEALING

14. REPAIR BY ROUTING AND SEALING

15. REPAIR BY ROUTING AND SEALING

16. REPAIR BY ROUTING AND SEALING

17. REPAIR BY PROVIDING EXTRA REINFORCEMENT

18. REPAIR BY PROVIDING EXTRA REINFORCEMENT

19. REPAIR BY PRESTRESSING STEEL

20. REPAIR BY PRESTRESSING STEEL

21. GROUTING Grouting is a process of injecting mixture of cement, sand water at high pressure in the cracks, joints, voids etc. Purpose of grouting: To strengthen the porous Concrete To prevent the seepage in dam and water retaining structures To fill the cracks in concrete structure

22. GROUTING Procedure for grouting: Drilling of Grouting holes For drilling grouting holes, equipment's like jack hammer, diamond drill, shot drill etc are used. The choice of type of drilling equipment depends upon the type of stone, size of hole and depth of hole. Arrangement of grout pipes Grout pipes or packer of 4 to 5 cm dia and 45 to 90 cm length are inserted in the grout holes. The space surrounding the pipe is filled with cement mortar. The top end of the pipe is connected to the pump. Cleaning of cracks Before injecting grout mixture in the cracks, it is necessary to clean the cracks. Inserting grout in holes Normally grout is inserted in the holes at a pressure 0.65kg/cm2 per m depth hole.

23. GROUTING Types of grouting: 1. Consolidation Grouting: This type of grouting is used for shallow depth grouting holes. Normally pressure below 3 kg/cm2 is known as low pressure grouting. 2. Stage grouting: When thick layers are to be grouted the total thickness of layer is divided into stages of 1m each and grouting of each layer is carried out one by one. Grouting of upper layer is started only after the grout in the lower layer had properly set. 3. Curtain Grouting: This type of grouting is done to prevent the seepage of water below foundation of dam.

24. Types of GROUTING

25. Portland cement GROUTING This type of grouting is particularly used in dams and thick walls. This method is effective in preventing water leakage. First of all clean the cracks by air jetting or water jetting. Flushing the crack to clean it. Installing grout at suitable interval and seal the crack . Then grout the whole area. Grout mixtures may contain cement and water or cement plus sand and water,depending upon the width of crack Water reducers or admixtures may be used to improve the properties of the grout. For large volumes , a pump is used and for small volumes ,a manual injection gun may be used for injection of grouting. After the crack is filled, the pressure should be maintained to ensure proper penetration of grout.

26. Portland cement GROUTING

27. Chemical grouting

28. Chemical grouting

29. Epoxy grouting

30. UNDERPINNING DEF: In construction, underpinning is the process of strengthening and stabilizing the foundation of an existing building or other structure. Reasons for Underpinning • The original foundation is simply not strong or stable enough. • The usage of the structure has changed. • The properties of the soil supporting the foundation may have changed (possibly through subsidence) or were mischaracterized during design.

31. Process Of Underpinning Underpinning is accomplished by extending the foundation in depth or in breadth so it either rests on a more supportive soil stratum or distributes its load across a greater area. All of these processes are generally expensive and elaborate.

32. Types of Underpinning • Mass Concrete Underpinning • Mini-piled underpinning

33. Mass Concrete Underpinning • Also known as 'traditional underpinning, 'This underpinning method strengthens an existing structure's foundation by digging boxes by hand underneath and sequentially pouring concrete in a strategic order. The final result is basically a foundation built underneath the existing foundation. This underpinning method is generally applied when the existing foundation is at a shallow depth, however, the method still works very well even at fifty feet deep. The method has not changed since its inception with its use of utilitarian tools such as shovels and post hole diggers. Heavy machinery is not called for in this method due to the tight nature of the boxes being dug .

34. Mini-piled underpinning Mini-piles have the greatest value where ground conditions are very variable,where access is restrictive. Mini-piled underpinning is generally used when the loads from the foundations need to be transferred to stable soils at considerable depths - usually in excess of 5.0 meters.

35. CAUSES OF damage OF MASONRY BUILDINGS Heavy Weight and very stiff buildings, attracting large seismic forces. Very low tensile strength particularly with poor mortars Low shear strength Brittle behavior in tension as well as in compression Weak connection between wall and wall Weak connection between roof and wall Stress connection at corners of doors and windows Overall unsymmetry in plan and elevation of buildings

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