forensic engineering

_ Rohit Madke(48)

“FORENSIC ENGINEERING OF CONCRETE STRUCTURES”

FORENSIC: •Forensic:•Scientific tests or techniques used in the investigation of crimes and evidence such as poison etc.•Forensic engineering:•Forensic engineering includes the investigation of the physical or technical causes of accidents and failures, quality analysis, failure analysis and root cause analysis.

Quality assurance: • Quality Assurance:

• It is defined by ISO 9000:2000&14000 as “providing confidence that requirements will be met”.• Quality assurance includes quality

control.

Quality assurance in construction activities guides the• Use of correct structural design,

specifications • Proper materials ensuring that the

quality of workmanship• Finally, maintaining the structure after

the construction is complete through periodic assessments for maintenance and repairs.

FEQA:

Now a days , combined FEQA program is developed to take Quality Assurance to another level.FEQA:Means : “Forensic Engineering / Quality Assurance”In this both the aspects are considered.

*Combining these FEQA program ;it not only examine procedures for providing top quality constructions & repairs ;

*But also also look at the cause of failure improve their operations and increase Service life.

Forensic Engineer:

• The forensic engineer is a specialist who applies the knowledge and skills of engineering.

Must possess:• PROFESSIONAL LICENCE• PROFESSIONAL CERTIFICATION• PROFESSIONAL AFFILIATIONS• FIELDS OF EXPERTISE:

eg:

accident/ investigation;

construction/reconstruction;

Safety Standards/Regulations;

Product Safety Evaluation;

Building Codes, etc.

INVESTIGATION:

This involves

*Quality inspections *collecting evidence *measurements

*developing models exemplar products

And

*performing experiments.

ANALYSIS:

analytical approach: When considering possible failures in a design – like safety, cost, performance, quality and reliability.

• also known as “cause-and-effect analysis”• Failure analysis in which an

undesired state of a system is analyzed.

*Failure mode effect analysis:(FMEA))

*Fault tree analysis (FTA) :

“FORENSIC ENGINEERING IN STRUCTURAL DESIGN AND CONSTRUCTION”

• In the pursuit of novelty(quality) and innovation(new techniques)

- even basic principles of sound structural design and good construction practice are often violated, leading to failures.

CAUSES OF FAILURES :

* Ignorance, carelessness, negligence

* Forgetfulness, errors, mistakes

* Reliance upon others without sufficient control

* Underestimation of influences

* Insufficient knowledge

* Objectively unknown situations (unimagined?)

* Others

• Type of errors in design/planning

• In damaged structures, the types of errors in design and planning are as follows:

• Conceptual errors

• Structural analysis

• Drawings and specifications

• Work planning and preparation

• Combinations

• Physical evidence

• Physical evidence includes, but is not limited to, the following:

• Condition of site

• Condition of work environment

• Condition of machinery and equipment

• Condition of materials

• Permits to Work, Safe Work Procedures

• Supervisors’ and signalmen’s forms

• Failure need not always mean that a structure collapses.

• It can make a structure deficient or

• dysfunctional in usage.

• It may even cause secondary adverse effects.

• (a) Safety failure-

Injury, death, or even risk to people.

• (b) Functional failure – Compromise of intended usage.

• (c) Ancillary failure –

Adverse affect on schedules, cost, or use.

Recommendations:

• Win or lose, and whether root causes for the accident can be found or not, the investigator

• should come up with improvements to the safety management system

TYPES OF FAILURES:

Forensic engineering of fire-damaged structures:

• Even after a severe fire, structures are often capable of being repaired rather than demolished.

The effect of fire on concrete structures:• For temperatures up to 300°C, the residual compressive strength of structural quality concrete is not significantly reduced • while for temperatures greater than 500°C the residual strength may be reduced to only a small fraction of its original value.• The effect of high temperature is more critical on prestressing steel than on reinforcing steel.• The assessment process determine the following:• · Depth of damage (spalling) or loss in strength of the concrete.• · Loss in strength of steel reinforcement or embedded structural steel elements.• · Damage or distress to the structure from movement, settlement or imposed loads.

View of the interior of fire-damaged reinforced concrete structure :

Methodologies of assessment:• The assessment can follow the two methodologies:

1.) Test the fire damaged concrete to directly assess the concrete quality. Typically

involving:

• · Visual inspection and hammer soundings.

• · Nondestructive testing.

• · Coring, sampling and subsequent laboratory testing.

2.) Estimate the fire severity so as to deduce temperature profiles and hence to calculate the

• residual strength of the concrete and the reinforcement. Typically involving:

• · Evaluation of fire severity – This can be performed based on debris examination or

• applying numerical evaluation methods, such as computational fluid dynamics.

• · Determination of temperature profiles

• This may be performed by applying numerical methods or simpler calculation techniques.

• · Assessment of residual strength of the concrete.

NON DESTRUCTIVE TESTING TECHNIQUES:

“We learn more from buildings that fall down than from buildings that stand up.”

As engineering professionals, or as individuals in every day life, it is important to learn from your mistakes and the mistakes of others, and to not repeat them.

REFERENCES:•Wikipedia• ASCE online journals.• Forensic Engineering investigations • Forensic materials• Concrete technology – M S Shetty.

THANK YOU.