Inevitably, natural disasters are the cause of the demise of close to fifty thousand people every year. 0.1% of the deceased, passed away because of such events. The world, its people, and its infrastructure endure extensive losses when encountering tsunamis, floods, earthquakes, and volcanic explosions.
Human technological prowess has not progressed to the point where natural events can be controlled. However, technology has come far enough to prevent and curb losses encountered when faced with such catastrophes.
Non-destructive techniques were formulated and advanced to ensure quality standards and assess the reliability of structures, components, machinery, and more. Further use of sensors, code, advanced materials, and techniques aided in active monitoring of components and machinery under operation, testing of subjects without their removal from the operating environment, testing subjects in uninhabitable and inaccessible environments, and detecting failure before it occurs.
Safety in Non-destructive testing has been a primary goal, and this testing process has ventured into the field of preventative engineering. Non-destructive testing is a pioneer in signifying advancement in technology, as its motive lies in using engineering, material, and analytical expertise in warding off or curtailing undesired effects and failure.
The concept of safety in non-destructive testing applies to unforeseen natural disasters wherein the behavior and structural integrity of large-scale and small-scale structures, expensive production and extraction units, oil rigs, vehicles, emergency shelters, etc. need to be thoroughly analyzed and experimented with to ensure minimum loss of human life, destruction of infrastructure and damage to the environment.
PREVENTATIVE AND SAFETY APPLICATIONS OF NDT
The outcomes of a structure, mechanism, or component in terms of their social and environmental impact are pre-determined in the design, manufacturing, and building stages. Extensive planning and testing are carried out during these preliminary stages in the life of any component, structure, or mechanism.
There are multiple phases to emergency management, which include the Prevention of disasters, prior preparation of measures taken in the event of a disaster, prompt response, safe recovery, and mitigation.
Natural disasters are extensive events that may cause extreme and often irreversible losses. These may include the following:
- Forest fires
Non-destructive testing comes under the Mitigation phase, wherein the damage to human life, loss of resources, and infrastructure collapse are curbed by reducing the effect of potential disasters. This
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requires an in-depth understanding of potential risks, tectonic events, and knowledge of the history of disasters in the zone the test subject is operational in, during the NDT safety testing procedures.
Certain pre-determined codes ensure conformity to structural and operational safety guidelines that are known to minimize losses; however, these mitigation methods are considered non-structural. Design and structural changes can be made using trial and error and simulating these disasters to have a thorough understanding of the behavior of the test subject under such catastrophic events.
The location of hazards is subject to the behavior of tectonic plates in a region, inconsistency and intensity of the weather, the presence of water bodies, and the terrain of the area. The presence of infrastructures, machinery, and vehicles can intensify the impact of natural disasters.
These disasters and their physical effects on structures and machinery can be analyzed by conducting seismic analysis and other simulation techniques on the test subject and then conducting non-destructive testing on the test subject to gather data on its structural and material behavior and failure under the impact of the induced loads and forces.
The analysis may lead to the detection of deformities induced by the following factors:
- Damages in the test subject after contact with excess water.
- Stress-induced due to sudden temperature fluctuations.
- Shrinkages due to drying of the test subject.
- Corrosion of metallic supports and reinforcements.
- Deterioration due to contact with chemicals.
- Weathering of the test subject.
- Miscalculations in the planning and design of the test subject.
- Impact of repairs and structural modifications on the safety of designs.
- Load effect on the test subject.
- Damages are caused due to environmental factors or peripheral components, structures, and machinery.
Safety in NDT techniques can ensure the usability of these mechanisms before the disaster may occur, during the event to assess what structures and machinery are safe to use and take shelter in, and after the event to analyze the methodology and design of reparative measures.
NDT TECHNIQUES THAT MAY BE USED TO CURB NATURAL DISASTERS
The prevention and control of natural disasters are carried out using Non-destructive techniques like visual testing, radiotracers, and radiography. Radiography and radiotracers can be used to carry out structural integrity analysis of buildings, test pipelines, and evaluate the integrity of water supply channels.
Radiotracers are materials that possess certain chemical, biological, radiographic, and physical tendencies that can help highlight the flows and functionality of the processes under study. The following methods are used to monitor the flow and analyze processes:
- Single photon emission computed tomography.
- Position emission tomography
- Computed radioactive particle tracking.
Radiotracers help detect and visualize process flow failures in mechanisms and pipeline units and help deter any potential failure that may cause large-scale material losses.
The radiographic testing method is considered a volumetric testing method, as it not only helps examine the surface of the test subject but the entire volume. This method ensures safety in NDT testing as it ascertains the reliability of the structure by assessing the defects and deformities present even on the interiors of the material under study.
The radiographic method aids in studying the internal integrity of a structure or test subject using X-rays or gamma rays on the test subject. Radiographic testing uses these radioactive waves to pass through an object under analysis and to record an image of the subject on film. Advanced modern technologies allow for a digital record of an image without the cumbersome process of developing and handling delicate radiographic film, which makes the process even more convenient.
The different methods of radiography include the following:
- Film radiography: This further includes X-ray testing, γ-ray testing, and accelerator testing.
- Paper radiography
- Radiography: This includes film radioscopy and screen radioscopy
- Computer Radiography Systems
- XD (X-ray diffraction)
- XDT (X-ray diffraction tomography)
- Neutron diffraction
Radiography can be used on practically any material, which allows for versatile usage. Modern radiography equipment is portable and user-friendly and provides a permanent record of data analyzed.
Thorough safety measures should be carried out as per industry standards due to the risks involved in the radiation used for these processes, however, if done correctly and with proper safety measures in place, these processes are extremely fruitful, accurate, and can provide a plethora of useful information.
SAFETY STANDARDS AND INDUSTRY CODES RELATED TO NATURAL DISASTERS
European Standards for Safety
- EN 1990 Eurocode: Basis of structural design
- EN 1991 Eurocode 1: Actions on structures
- EN 1992 Eurocode 2: Design of concrete structures
- EN 1993 Eurocode 3: Design of steel structures
- EN 1994 Eurocode 4: Design of composite and concrete structures
- EN 1995 Eurocode 5: Design of timber structures
- EN 1996 Eurocode 6: Design of Masonry structures
- EN 1997 Eurocode 7: Geotechnical design
- EN 1998 Eurocode 8: Design of structures for earthquake resistance and retrofitting of buildings- European Standard EN 1998-3
- EN 1999 Eurocode 9: Design of Aluminium structures
- UK Statutory Instruments-The Control of Major Accident Hazards Regulations 1999- No. 743
- Guide on methods for assessing the acceptability of flaws in metallic structures- BS7910: 2000
American Standards for Safety
- American Society of Civil Engineers- Minimum design loads and associated criteria for building and other structures- ASCE 7-16
- National Earthquake Hazard Reduction Program-Guidelines for the seismic rehabilitation of Buildings- NEHRP 97
- American Institute of Steel Construction- Specification for Steel Buildings- AISC 360
- Building Code Requirements and Specifications for Masonry Structures,
- Masonry Society, the American Concrete Institute, and the American Society of Civil Engineers- TMS 402/ACI 530/ASCE 5, TMS 602/ACI 530.1/ASCE 6
- North American Specification for the Design of Cold-Formed Steel
- American Iron and Steel Institute- Structural Members-AISI S100
- American Forest and Paper Association- National Design Specification
- American Concrete Institute- Building Code Requirements for Reinforced Concrete- ACI 318
Indian Standards for Safety
- Indian Standard Criteria for Earthquake Resistance Design of Structure Part- 1 General Provisions and Building, Bureau of Indian Standards, New Delhi, India -IS 1893:2002
- Indian Standard, Code of Practice for Design Loads (Other than Earthquake) for Buildings and Structures, For Dead Loads - IS: 875 (Part 1) –1987
- Indian Standard, Code of Practice for Design Loads (Other than Earthquake) for Buildings and Structures, For Imposed Loads- IS: 875 (Part 2) – 1987
- Indian Standard, Code of Practice for Design Loads (Other than Earthquake) for Buildings and Structures, For Wind Loads- IS: 875 (Part 3) – 1987
- Code of Practice for Plain and Reinforced Concrete, Bureau of Indian Standards, New Delhi, India- IS 456:2000
- Indian Standards-Code of Practice for Earthquake Design Resistant Design and Construction of Buildings- IS 4326
- Indian Standards-Improving Earthquake Resistance of Earthen Buildings- IS 13827
- Indian Standards- Improving Earthquake Design of Low-Strength Masonry Buildings- IS 13828
- Code of Practice for Ductile Detailing of Reinforced Concrete Structures Subjected to Seismic Forces- IS 13920
- Seismic Evaluation, Repair and Strengthening of Masonry Buildings – Guidelines- IS 13935
Canadian Standards for Safety
- Recommended Practice: Personnel Qualification and Certification in Non-destructive testing- SNT-TC-1A (2006)
- Non-destructive testing – Qualification and Certification of personnel- CAN/ CGSB-48.9712-2006 (ISO 9712:2005)
- Nuclear Substances and Radiation Devices Regulations (Nuclear Safety Control Act Canada)- SOR/2000-207
Australian Standards for Safety
- National Construction Code (NCC) - Structural design for earthquakes- AS 1170.4-2007
- Design and Installation-Suspended Ceilings –AS/NZS2785:2020.
Japanese Standards for Safety
- Ministry of Land, Infrastructure and Transport (1980)-Technical Standard for Calculation of Seismic Story Shear Distribution Factor along the Height of a Building Structure- Notification No.1793-1980.
- Japan Road Association. Specifications for Highway Bridges, PART 5 Seismic Design. 2002-03
- Ministry of Land, Infrastructure and Transport (2000)-Technical Standard for Structural Calculation of Response and Limit Strength of Buildings- Notification No.1457-2000.
- Recommendation for the Design of Base Isolated Buildings, Architectural Institute of Japan- AIJ (1989)
- Seismic Loading — Strong Motion Prediction and Building Response, Architectural Institute of Japan, Tokyo- AIJ (1992)
- Seismic Evaluation and Retrofit of Concrete Buildings, Report No. SSC 96-01, Applied Technology Council- ATC-40 (1996)
- The Ports & Harbours Association of Japan. Technical Standards and Commentaries for Port and Harbour Facilities in Japan. 2007-07, vol. 1, 2.
- Shuto Chokka Jishin Taisaku Senmon Chosakai- Cabinet Office, Government of Japan, Central Disaster Management Council -2004-11. vol. 12, no. 2-2.
- Japan Building Disaster Prevention Association-Kizon RC Zou Entotsu no Taikyu- Taishin Shindan Shishin. 1981
- Japan Gas Association-Seizou Setsubi Tou Taishin Sekkei Shishin Kaiteiban. 2001-08.
- Japan Building Disaster Prevention Association- Kizon Tekkin Concrete Zou Kenchikubutsu no Taishin Shindan Kijun · Dou Kaisetsu-2001
Japanese structural codes have been modified and updated after multiple earthquakes that devastated the country. Two major building codes exist, which include the Kyu-tailspin, which refers to the building codes applicable for buildings constructed up to 1981. Shin-taishin were the updated building codes applicable to structures that were built post-1981.
The presence of such structural codes and industrial standards, along with structural analysis methods like taishin shindan for conducting seismic diagnosis has advanced Japan’s preventative engineering to great extents. These codes have not only managed to save human and animal life during such disasters but prevented major loss of resources for even large-scale seismic activity (earthquakes of a magnitude of 5-7 Richter’s)
Mankind has learned immensely from the horrors of the past. There is a dire need to understand and learn further from these negative experiences we have survived as a species, and to ensure that we use our intelligence and resources in minimizing the effect of such uncontrollable events.
The Japanese government incurred major losses because of the series of earthquakes they experienced, however, they funded and focused on research on Non-destructive testing and the use of nuclear methods of non-destructive testing and analysis.
Non-destructive testing is being researched and adopted by various such countries around the globe that aim to mitigate the risks and devastation that such catastrophic events cause. Non-destructive testing is the most appropriate analysis method available because of its versatility and accessibility as well as prompt results and accuracy.
Financial and time restrictions hinder research and understanding of the behavior of a material under extreme environmental conditions, hence non-destructive testing has proven to not only be the best available methodology for manufacturers, construction industries, and governments but has also aided scientists and researchers in furthering their studies and understanding of materials, systems, and structures under varied conditions.
Adoption of non-destructive methodology in organizations will not only help the organizations in their operation and cut losses incurred due to defects and deformities, but it will also encourage research and development in the scientific field due to an increase in demand.