Practical application of ndt method.pptx

Ndt

1. Topic “Practical application of NDT method ” Subject Name: Non Destructive Testing of materials Subject Code: SE-204 DEPARTMENT OF CIVIL ENGINEERING UNIVERSITY INSTITUTE OF TECHNOLOGY – RGPV BHOPAL GUIDED BY Krishnakant Ahirwar Enrollment No: 0101CE23ME04 course : M.E ( Structural engineering ) Semester: 2 nd Prof . SALEEM AKHTAR PRESENTED BY

2. Introduction : Practical Applications of NDT in Structural Engineering Non-destructive testing (NDT) plays a vital role in ensuring the safety and integrity of structures throughout their lifecycle. Unlike destructive testing methods that damage the material, NDT allows engineers to assess a structure's health without compromising its functionality. Here's how NDT methods are utilized in practical structural engineering:

3. 1. Inspection of Existing Structures: Identifying Defects:  NDT helps detect cracks, voids, delaminations , and other hidden flaws in concrete, steel, and wood elements. This information is crucial for evaluating the structural capacity and planning necessary repairs. Assessing Concrete Quality:  Techniques like ultrasonic testing measure the speed of sound waves traveling through concrete. This can indicate variations in density, strength, and potential cracking. Weld Inspection:  In steel structures, ultrasonic testing and radiographic testing are used to identify cracks, porosity, and other imperfections in welds, ensuring their integrity.

4. 2. Quality Control During Construction: Verifying Rebar Placement:  NDT methods like electromagnetic testing can locate and verify the placement of reinforcing steel bars within concrete elements, crucial for ensuring the designed structural strength . Weld Quality Assurance:  During construction, real-time NDT methods like radiographic testing can be used to inspect welds for defects, allowing for immediate corrective actions if needed.

5. 3. Condition Monitoring and Maintenance: Bridge Inspection:  NDT is essential for routine bridge inspections. Techniques like visual testing, eddy current testing, and ground penetrating radar (GPR) can identify corrosion, delamination in concrete decks, and defects in cables or support structures . Building Assessments:  Prior to renovations or after extreme weather events, NDT helps assess the health of building components. This can involve detecting water damage in concrete or identifying hidden structural weaknesses.

6. 4. Structural Details In order to assess the load bearing capacity of the structural system, engineers must obtain accurate information about the size and configuration of existing elements. Some of these important details are listed below : Cross-Sectional Dimensions Rebar Size Rebar Spacing and Pattern Concrete Cover Thickness Concrete Element Thickness with one side access only Location of pre-stressing/post-tensioning tendons in Concrete Girders and slabs. Visual inspection and tape measurement can help determine the overall cross sectional dimensions of accessible structural components. However, it does not provide information about sub-surface components.

7. 5. Structural Integrity Surface and Sub-surface defects can affect structural integrity. It is important to obtain information about potential issues in the structural components. Below is a list of important defects that can affect structural performance. Concrete Cracks Voids and Cavities in Concrete Delamination in Concrete Slabs, Bridge Decks, etc. Bond issues (Old and New Concrete) Poor quality materials (Honeycombing) Deteriorated concrete (Alkali-Silica Reactions, Weathered Concrete, etc.) Non-destructive test methods for structural condition assessment can be used to evaluate the structural integrity and locate potential defects in structures. Ultrasonic testing of concrete provides a cost-effective approach to evaluating concrete material, and crack depth in concrete structures. 

8. 6. Corrosion of Steel Rebar Corrosion is commonly observed in existing reinforced concrete structures. When performing structural condition assessments, engineers need to find proper answer to the following three questions: What is the current state of structure? What is the rate of corrosion? (kinetics of corrosion) What is the remaining capacity and service life? Non-destructive testing has long been used in the corrosion inspection and monitoring of reinforced concrete structures. (NDT Methods of Corrosion Inspection) Researchers have developed various tools and methods for evaluating corrosion activity in reinforced concrete structure. Half-Cell Corrosion Potential mapping is a quick non-destructive method for evaluating the likelihood of corrosion in concrete structures. It can be used to assess the probability of having active corrosion. The simplicity of the test makes it popular for inspection of large areas, such as parking garage slabs, and bridge decks. The test can also be used to verify the quality of a repaired concrete structure.

9. 7. Durability of Concrete Surface Electrical Resistivity is a useful non-destructive test for evaluating the durability performance of concrete.  The test provides information on the conductivity of concrete materials and help evaluate the resistance of concrete against aggressive agents, such as chloride ion.  The information obtained from these tests can be used to determine the remaining service life of the structure.

10. Benefits of NDT in Structural Engineering: Cost-effective :  NDT eliminates the need for destructive testing, saving time and money. Minimally Invasive:  NDT methods typically require minimal preparation and cause no damage to the structure. Improved Safety:  Early detection of flaws allows for timely repairs, preventing potential structural failures. Informed Decision Making:  NDT provides valuable data to engineers for making informed decisions regarding repairs, renovations, or load capacity limitations.

11. Common NDT Methods in Structural Engineering: Ultrasonic Testing (UT):  Uses sound waves to detect internal flaws. Radiographic Testing (RT):  Uses X-rays or gamma rays to create images of internal structures. Eddy Current Testing (ECT):  Uses electromagnetic fields to detect surface and near-surface cracks. Ground Penetrating Radar (GPR):  Uses electromagnetic waves to map features beneath the surface. Visual Testing (VT):  The most basic but crucial method for identifying surface defects.

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