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Building Structural Health report and Estimation
Structural Audit is an important tool for knowing the real status of the old bldgs. The Audit should highlight & investigate all the risk areas, critical areas and whether the bldg. needs immediate attention. It should also cover the structural analysis of the existing frame and pinpoint the weak structural areas for static, wind & earthquake loads. If the bldg. has changed the user, from residential to commercial or industrial, this should bring out the impact of such a change.
This CSR document gives step by step guidelines for carrying out Structural Audit of old buildings. We have also provided a detailed format to collect data from the field. The details regarding the various non-destructive tests and other tests to be carried out are also given. Includes photographs of structural defects & rectification procedure.
The Purpose of Structural Audit is :
● To save LIFE & PROPERTY.
● To know the health of your building. and to project the expected future life.
● Highlight the critical areas that need to be attended with immediate effect.
● To proactively assist the residents and the society to understand the seriousness of the problems and the urgency required to attend the same.
● To comply with Municipal or any other statutory requirements.
If we are serious about the Structural Audit, how do we carry it out? What do we tell to our Structural Engineers? What are our expectations?
STEP 1 :
It is imperative that we must have Architectural and Structural plans of the bldgs. it will be helpful if we have detailed structural calculations including assumptions for the structural design. The assumptions can also include the allowable live loads; Whether the bldg. is designed for residential, commercial, light industry or heavy industry and whether any future provision for adding new floors is considered? What type of Earthquake loads are considered? Which I.S. Code requirements have been met?
STEP 2 :
If the Architectural plans and Structural plans are not available, the same can be prepared by any Engineer by measuring the size of the bldg. & locating the position of the columns, beams and size of all such structural elements.
STEP 3 :
Inspection of the Bldg. - A detailed inspection of the bldg. can reveal the following :
1. Any settlements in the foundations.
2. Visual cracks in columns, beams and slabs
3. Concrete disintegration and exposed steel reinforcements – photographs can be helpful.
4. Slight tapping with hammer can reveal deterioration in concrete.
5. Extent of corrosion in reinforcement.
6. Status of Balconies – sagging, deflection, cracks?
7. Status of Architectural features viz. chhajjas, fins, canopies etc.
8. Cracks in walls indicating swelling in R.C.C. members or distress or deflection or corrosion.
9. Leakages from terrace & Toilet blocks.
10. Leakages & dampness in walls resulting into cracks and corrosion.
11. Changes carried out affecting structure. Toilet blocks - Added or changes made? Change of user – from Residential to Commercial to Industrial? Change of Partition Walls?
12. Status of lift and lift machine room – Type of Maintenance Contract, renewal of license.
13. Status of electrical wiring from meter room to all the flats. Substation status. Any explosion in the meter room, substation?
14. Status of overhead & underground water tanks - capacity. Leakages, cracks & frequency of cleaning, status of pumps.
15. Plinth protection in the compound including status of drainage, water pipes & pumps. How much the Ground was flooded during recent monsoons?
16. External paint – When last painted and type of paint.
17. Status of repairs & last repaired.
18. Last Structural Audit prepared?
STEP 4 :
Tests Recommended :
It is important that various tests are carried out in the old bldgs. This will give an idea about the extent of corrosion, distress and loss of strength in concrete & steel.
Tests may include:
1. Concrete Core Cutting & Compression testing for columns, beams and slabs for Strength Assessment of concrete.
2. Half Cell Potential test for determining the probability of corrosion in the embedded steel.
3. Carbonation test for carbonation depth measurement for Steel.
4. Ultrasonic Pulse Velocity Test (UPV) for Strength Assessment of concrete.
5. Integrity tests for pile foundations.
STEP 5 :
Highlight the critical areas and how to go for repairs. For e.g.
1. No. of columns requiring immediate attention including treating rusted steel, adding new steel, jacketing of columns etc. – Repairing foundations, repairing balconies, chhajjas.
2. Attending of beams and slabs wherever required.
3. Attending water proofing of terrace, toilet blocks.
4. Attending cracks in external walls and providing good quality of paint.
5. The critical areas highlighted need to be attended immediately.
STEP 6 :
Earthquake Criteria :
Mumbai is located in Earthquake Zone III as per Indian Standard Codes. The Earthquake Code IS 1893-2002 provides rigorous analysis and designs of Bldg. structures so that it can withstand the Earthquake forces. It may be possible to retrofit the old buildings, so that they do not collapse during Earthquake; but may develop some cracks and allow enough time for people to escape. Thus saving precious lives.
STEP 7 :
Compliance of Audit requirements as per Municipal Corporation bye laws for Society.
Audit is a good thing, but in itself Audit is not sufficient. It is important that the findings and/or recommendations of audits are implemented satisfactorily, within a stipulated time limit and are certified by Structural Engineers; Otherwise the Audit findings will remain on paper. Is it a costly process? Of course, this is going to be costly; but human lives are important and they need to be saved at any cost.
if your bldg. is more than 15 years old, it is important that rigorous audit is carried out every five years. After 30 years, every 3 years structural audit should take place. This will be a continuous process as it is difficult to guarantee future life of old bldgs. However, regular Audits and implementing audit findings will avoid sudden collapse of bldgs. and save thousands of life. This process will also increase the future life of bldgs.
STEP 8 :
Estimate for maintenance or repair of building
1. Considering the extend of maintenance or repair needed for the society, a brief Bill of Quantities is drawn for estimation purpose. This should fare idea for the budgetory purpose.