Structures are designed to with stand safely a particular predetermined load during their life period. Generally reinforced concrete structures can suffer a varying degrees of damage due to several reasons including materials decoration construction technique adopted, poor workmanship, overloading, aggressive environments fatigue and corrosion of Steel reinforcement embedded in concrete.RCC buildings have been extensively constructed throughout the world since 1950. The deterioration of RCC is a natural phenomena and has started exhibiting in large numbers of concrete structures and a systematic approach is needed in dealing with such problems.
1. Objectives
to understand the terms used in repair and rehabilitation of structures.
2. Contents
Quality of concrete
Damages in RC structures
Deterioration of structures
Damages assessment of structures
Repair and rehabilitation
Repair management
Maintenance of structures
3. Quality of concrete
The performance of concrete structures depends not working on the improper use but also the quality of concrete. In most of the cases the root cause of concrete disintegration is the inherent porosity which in turn leads to absorption, diffusion and permeability of water. The quality of concrete depends on the following factors.
1. Water cement ratio
2. sand/stone ratio
3. Cover depth
4.Chloride content in constituency
5. Moisture content
6. Oxygen
7. PH value
8. Temperature
9. Permeability of concrete
10. Method and time of curing
11. Electrical resistivity of concrete
12. crack width
13. Type and size of reinforcement bars.
Concrete provides excellent protection to reinforcing Steel full stuff but large numbers of structures have been reported in which corrosion of reinforcement has caused damage to concrete structures within a few years. Repairing of corrosion damaged reinforced concrete elements is very difficult in practice. Reinforcement corrosion caused by carbonation is arrested great great extent through repairs executed in a sound Manna. But, the treatment of chloride include corrosion is very difficult and more often to the problem continues even after extensive repairs have been made carried out. In variably Riya curse in a short. Of time will stop when chlorides are present in concrete, it is very difficult to protect reinforcing Steel from chloride attack.
4. Damages in RC structures
Cracking
Leakage
Settlement
Over deflection
Wearing
Spalling
This integration
Disintegration
Delamination
Overloading
Aggressive environment
Materials used for construction
Fatigue and corrosion
5. Deterioration of structures
Major factors responsible for concrete detoriation permeability. Carbonation, chemical attack, alkali aggregate reaction and physical aggression like thermal shock and operation. The general deterioration of concrete structures is usually accompanied by cracking and spelling. Reinforcement corrosion plays the most vital role in the deterioration of the concrete structures. In spite of Advanced development in building construction, all the building detoriate from the time they are completed. the rate of deterioration depends upon a number of factors. Not all the factors are under the control of occupants. During the design and construction stages, the following factors are considered as essential parameters for durability of structures.
1. Right choice of material
2. Proper construction method
3. Adequate specification for construction and installation work
4. Effective supervision throughout the construction period and rectification of defects prior to final handover of the building.
5. Provision of adequate space for landscaping with proper design.
6. Damage assessment of structures.
To identify the suitable repair procedure, it is necessary to have a plan approach to investigate the condition of concrete and reinforcement. This will require trot technical inspection and an understanding of the behaviour of the structural component, which is being repaired. By the visual inspection, a detailed mapping of affected areas, documentation of time and location of symptoms, ill history and photographic evidence are prepared. A comprehensive inspection data helps in making an effective strategy for repair and Rehabilitation.
Early detection of structural damage is an important issue to minimise the cost of repair.
Non-destructive tests (NDT) can be effectively employed to evaluate the damages in structures and to choose a suitable method of repair techniques to extend their service life. Strength and life depends on the duration of structures and intern changes structural parameters leg stiffness of a member. The extent of damage can be effectively assessed using the stiffness degradation in the member. The level of damages in RC structures should be effectively assisted in order to ensure safety and serviceability conditions.
7. Repair and rehabilitation.
Repair and Rehabilitation mean restoring the damage structures to make them fit for serviceability condition. Rehabilitation of structural integrated RC structures is one of the major tasks for the construction Industries worldwide. Use of properly selected repair materials can solve the tough task. durable repair can be obtained only by matching the properties of the base concrete with those of the repair material intended to for use. This action of repair materials is based on their properties and some of them are listed below.
1. Dimensional stability.
2. Modulus of elasticity.
3. Permeability
4. Chemical resistant.
5. adhesion with parent concrete.
6. Coefficient of thermal expansion.
7. Easy to use.
Selecting a most appropriate material and repair methodology is very important to achieve durable, effective and economic repairs. Matching the response of the paid sections with the main structure is an important task. Compatibility of materials and matching specifications are essential in any repair job. Just as building durable construction requires understanding of structural engineering, material science, and environment/exposure conditions, repair jobs also require the same level of attention in These areas. The engineer in charge should be familiar with the repair methodology and repair materials. The engineer understanding search specialized you should have true knowledge of new materials, repair methodologies, its limitations and the fundamentals of structural engineering to and food safety and service ability of the building during repair and thereafter.
8. Repair management.
Repair job involves three distinct stages in different levels. In 1st Stage, documentation of damage, type of damages and it's extent forecasting the repairs structure and recommendations on repair methodology. II requires preparation of detailed drawings, sketches come excution guidelines on roads, materials and work specifications and tender document. That on stage is actual execution of repairs. For specialised job scam exposed in this repair field and resource in terms of tools and plants should be engaged. The engineer in charge should have a good understanding of procedures and give an attention supervision. To find out effectiveness of repairs various tests before and after repairs have been employed.
9. Maintenance of structures.
Building maintenance is work undertaken to keep, restore or improve every facility at every part of the building, its service include Horticulture operations to current acceptable standard and to sustain the utility and value of the facility. The objectives of maintenance include the following.
1. To preserve machinery, building and services, in good operation condition.
2. To restore it back to its original standards.
3. To improve the facilities depending upon the development that is taking place in the building engineering.
Maintenance AIMS at effective and economic means of giving the building and service fully utilizable. It involves a lot of skills as influenced by Occupancy underperformance level expected of a building. Programming of vox to be carried out to keep the building in a good condition cause for High Schools. Feedback on construction stages. Preventive maintenance is also carried out to avoid breakdown of machinery and accurance. In buildings and services. It should be carried out on the basis of regular inspection of buildings.
Comments
Post a Comment