SSRG International Journal of Civil Engineering (SSRG-IJCE) – volume 2 Issue 1 Jan 2015A Forensic View to Structures’ Failure Analysis K. M. Pathan1, Sayyad Wajed Ali2, Shaikh Zubair3, Aasim Hasan Najmi4 1 Consulting Structural Engineer, Aurangabad (M.S.), India 2 BE (Civil), Deogiri Institute of Engineering & Management Studies, Auranagabad (M.S.), India 3 Assistant Professor; Deogiri Institute of Engineering & Management Studies (M.S.), India 4 M.Sc. Forensic Science, Government Institute of Forensic Science (M.S.), India ABSTRACT : The study of the structures’ failure II. TYPES OF STRUCTURE FAILURES is very much essential. Apart from judicial or professional necessity, the failure case study is also Failure need not always mean that a structure essential in learning lessons. With the advancement collapses. It can make a structure deficient or of theories and technologies in various dysfunctional in usage. It may even cause interdisciplinary branches of science, it is now secondary adverse effects [2]. possible to know the root cause of failures of various structures. Forensic Engineering is Safety failure: Injury, death, or even risk to people: amongst the examples of such interdisciplinary Collapse of formwork during concrete science. A systematic study and interdisciplinary placement research is carried out in this paper, in structure Punching shear failure in flat slab concrete floor failure analysis in view of forensic science. According to National Crime Record Bureau Trench collapse (NCRB) many amongst cases are reported of Slip and fall on wet floor structure failures and hence, the cases are tackled by chemical analysis of various building materials Functional failure: Compromise of intended like Cement, Mortar, Concrete, Steel, etc. The usage: systematic procedure of chemical analysis for these Excessive vibration of floor building materials is carried out and report is Roof leaks finally submitted to the court. In this paper, the Inadequate air conditioning significance of chemical analysis for Cement and its various mix products (i.e. concrete, mortar, etc.) Poor acoustics is discussed in advocating the reasons of the failure. Ancillary failure: Adverse affect on schedules, cost, or use: Delayed construction Keywords - Forensic Engineering, Failure Unexpected foundation problems Investigation, Structure Failures, Chemical Analysis, Concrete Unavailability of materials Strikes, natural disasters, etc I. INTRODUCTION III. CAUSES OF STRUCTURE FAILURES Structural failures and their investigation has become an active field of professional practice in Structural failure does not have to be a which experts are retained to investigate the causes “catastrophic collapse”; it may be a “non of failures, as well as to provide technical conformity with design expectations” or a assistance to know the root cause. The parties “deficient performance”. Collapse is usually involved in the litigation of the resulting claims. attributed to inadequate strength and/or stability, Since nearly all structural deficiencies and failures while deficient performance or so-called create claims of damages, disputes and legal serviceability problems, and is usually the result of entanglements, Forensic Engineers operate in an abnormal deterioration, excessive deformation, and adversarial hence, in addition to their technical signs of distress. In short, failure may be expertise; Forensic Engineers must have at least characterized as the unacceptable difference some knowledge with the relevant legal processes between intended and actual performance. What and need to know how to work effectively with can grow in the design-construction process and in claiming parties and judiciary [1]. the use of a structure that may result in immediate or event failure? A lot! [1] ISSN: 2348 – 8352 www.internationaljournalssrg.org Page 26 Failure Investigation and Design Process professional engineering practice. an engineering design purposes beyond its intended or foregoing solution may be required to rectify the failure and preventive maintenance restore the structure to its originally intended performance. Oversight: Failure to follow design attempting to predict these factors to a high level of documents and safe construction practices accuracy is of questionable value in the design Greed: Short cuts. Fundamentally. Neglect: Using the facility for noncatastrophic failures. not to determine Design is. For example. Apart from the legal and professional resolve the issue. or disregard codes and standards and have been codified over the years to produce efficient and generally safe structures. Further. Therefore. viable alternatives-that balances various competing 1) Design process objective factors such as physical constraints. so investigator finds out why it the details of a design engineer‟s solution to failed. cost. Likewise. Although it is not suggested that design utilizes assumptions relating to probable loads. However. many are ISSN: 2348 – 8352 www. there comes what the satisfactory settlement of a dispute may depend on reason behind it. SSRG International Journal of Civil Engineering (SSRG-IJCE) – volume 2 Issue 1 Jan 2015 Negligence: Failure to properly analyze or detail properties [4]. and The objective of the design process is to identify adequate performance. intentional disregard of industry process. utilize the design process are excellently placed because of their knowledge of standards and A. how they will behave. a key element in the design process is Disorganization: Failure to establish a clear the management of these unknowns. an engineer that scheme in accordance with a set of „rules‟ typically utilizes the design process also appears prescribed by building codes. WHY FORENSIC ENGINEERING? proceedings arise. the designer engineer may have design experience relevant to produces a single design from what may be many the structure under consideration. or. Abuse. therefore. This engineer. there is determined. regardless of whether legal IV.internationaljournalssrg. The design process generally commences failure. a role for which engineers that typically should not result into mass disaster [3]. for minimal design the ideal candidate to determine the cause of cost” [4]. by using simplifying performance reason difficulties exist despite the fact that the assumptions and an iterative process. and develop engineering solutions. and materials or systems their material properties would be hopelessly inefficient and time consuming. when causation has been necessity to determine the cause of failure. These assumptions are conservative the design. an examination of a number of with the designer considering a range of design the key aspects of the design process illustrates the concepts. Then. expert testimony may be required to also. the When so ever structure fails. in Misuse. To design Incompetence: Failure to understand engineering structures by attempting to precisely predict the principles or respect the technical limitations of loads they will carry. a process of synthesis. actually Ignorance. and the capacity of material with a view to developing solutions. in legal disputes.org Page 27 . given the unknowns surrounding the requirements and safe practices structure‟s construction and the loads it will carry. parties The role of this process in the design of new Miscommunication: Failure to establish and structures is self evident. engineers approach the identification of causation structural behavior. structural design requires “an ability to create a cost-efficient load-bearing Because of these attributes. which causation. rather than organization and define roles and responsibilities of their investigation. but the process also has a maintain lines of communication between parties number of important roles to play in the overall response to structural failure. the need to learn from it lessons from it that ascertain whether the engineer that originally would enable subsequent designers and builders or designed the structure did so with the degree of fabricators to avoid the pitfalls of the failed reasonable skill and care expected of a practicing structure and develop safer alternatives. based upon the performance assumptions. hypothesis against the evidence. hypothesis is not considered valid unless it accounts for all the relevant observations and data. SSRG International Journal of Civil Engineering (SSRG-IJCE) – volume 2 Issue 1 Jan 2015 simply unfamiliar with the forensic process. inappropriate collection from the development of hypotheses. verifiable facts related to the matter. rather than predicting engineer and increase the probability that the how the structure would have behaved based on the failure‟s cause may be identified incorrectly. or rely on determining the cause of failure investigation. and well-proven scientific principles. therefore.org Page 28 . the rely on simplifying assumptions. the engineer may fail to adequately generally accepted engineering principles. and. and. the implicit nature the process is to identify the cause of failure.” Noon (2000) [5] practice. The determine the actual loads. These factors forensic process relies on understanding how the typically combine to frustrate the investigating structure actually behaved. it may be necessary to (e. “as more observations are the cause of failure depends on verifiable evidence collected and studied. Finally. Noon (2000) [5]. the investigator must process of analysis. hypothesis against the collected evidence. and of the design process can naturally move the focus the process is driven by ruling in or out a failure of the investigation to solution development. This issue can be further observations. In other words. is a In failure investigation.” evidence found at the scene.” These limitations affect how an engineer that typically utilizes the design process approaches This process avoids many of the pitfalls of causation investigations. hypothesis based on specific evidence and Likewise. Unless the data or central to failure investigation. Then. rather than relying on simplifying observations are made. errs on the The forensic process of collecting evidence. In new or remedial design.” solution through the application of simplifying assumptions. the accurate determination of then goes on to say that. it is a critical weakness. side of conservatism. determining the most likely cause of failure. testing each this is one of the design process‟s chief strengths. amplify. and but in failure investigation. careful and detailed of failure. rather than synthesis. a part of the design process. assists the investigator to conduct the investigation in a ISSN: 2348 – 8352 www. which aims to that they typically utilize in their role as designers. and actual material properties at the time Noon (2000) [5]: “First. The key to determining structural causation is the generally unaware of the transition-on the process application of the forensic process.. not surprising that engineers can failure by using available evidence. The objective of causation is a critical objective. objectively identify the technical cause or causes of It is. so this must be related to engineer relies mostly upon the actual physical the cause of failure. Therefore. states that “a forensic structure in this manner. the separation of evidence potentially leading to repeat failures. Experiments or additional differences between simplifying performance observations are then made to test the predictive assumptions and the performance of structures in ability of the working hypothesis.g. Forensic Process consequently. or even discard the original patterns in concrete members). it gravitate toward providing solutions to rectify the is the application of the scientific method to failure failure. may find themselves falling back. where appropriate. it is not an integral observations are proven to be inaccurate. in rehabilitation strategies. Although determining applying a design process alone. and/or conjunction with the rigorous testing of each skewed dispute outcomes. actual structural application of the forensic process is described by behavior. developing failure hypotheses. in his text Forensic in the form of “I wouldn‟t have designed the Engineering Investigation. legal challenges. design process. rather collect and interpret physical evidence and instead than simplifying assumptions.internationaljournalssrg. a bolt‟s failure surface or the cracking modify. 2) Simplifying performance assumptions and The forensic engineer then applies accepted evidence scientific methodologies and principles to interpret The design process creates an appropriate design the physical evidence and facts. and while the hypothesis in favor of a new one that can account collection and analysis of verifiable evidence is for all the observations and data. Essentially. a working hypothesis is formulated to exacerbated by the sometimes-significant explain the observations. B. The Sampling of Small Quantities (Less than 12 bags performance is tested after 24 hours just by or packages): When number of bags or other removing matchbox and checking approx. 1 kg sample of cement on a steel plate. Methods of Analysis forensic science laboratories requires high degree 1) Cement of skill and expertise. also. the performance is said (in an air tight plastic jar) shall be drawn from each to be good. about 3-5 kg accompanied by 1 kg V. Sampling is done as per the procedure as c) Performance Test laid down in the Indian Standard Procedures of Make thick slurry of cement with about 1 part of random sampling. in such cases the water bath for five minutes. weighing 1 kg (in an airtight plastic jar) from each Residue dried in oven and further incinerated in group shall be drawn into airtight plastic jar and furnace at 800°C-900°C for 1 hour weigh the sent for analysis. General article should be independently packed.internationaljournalssrg. residue. Every article stand up to the scrutiny of engineering peers. sand and aggregate if available from the field shall be sent for analysis. d) Acid insoluble Sampling of large Quantities (More than 12 bags Take 0.1 % in this chapter. label on all the packages and are appearing to be the setting property is said to be poor. till constant weight. add 1-2 ml water and 2 drops of indicator. No color indicates that the sample is stone 1) Cement powder.5-1. The cement gets hardened.5 gm of sample. When the sample is drawn from a cement bag. to the exacting demands of the legal system. if necessary. 3) Concrete Concrete lumps. heat it for about 20 minutes in the forwarding letter. Every A. in C. should be sent in an airtight plastic jar if available Change in color: adulterated cement or it should be securely packed in polythene bag No change in color: unadulterated cement and then in brown paper to avoid exposure to moisture. the details printed on the bag and another marking b) Heating Test thereon should be carefully noted and incorporated Take 0. the chemical analysis methodology for ethyl alcohol) cement. add 20 ml water. Digest further for another 10 minutes. The forensic scientists are following various methods for the chemical a) Thymolphthalein Test analysis of these substances in the laboratories. If the block similar. ensuring it will not only the field shall be sent for analysis. 1-2 Kg of mortar sample accompanied by 1 kg each of cement and / or lime and sand if available from ISSN: 2348 – 8352 www. The analysis and estimation of different types of samples collected from the site of the failure. Calculate percent acid 2) Mortar insoluble. strength packages containing the cement bears the same of the cement by fingers. development of blue color indicates the presence of B. if the block breaks easily.org Page 29 . In (Thymolphthalein Indicator 0. SSRG International Journal of Civil Engineering (SSRG-IJCE) – volume 2 Issue 1 Jan 2015 forensically sound manner.0 gm cement in a 100 ml beaker add 20 or packages): When number of bags containing the ml water to make a paste followed by 5 ml conc. stir. Sampling cement. no lumps should be grouping must be done. but should be independently packed. cement bear the same labels on the packages and hydrochloric acid. [6]. of bags and 20 percent of sample through ashless filter paper till chloride free. digest on are appearing to be similar. in such cases about 1kg sample of cement does not break by fingers. filter about equal no. Each group should contain formed. mortar and concrete is discussed in detail Take 100-150 mg of cement sample in a test tube. cement with one part of water and put in an empty matchbox. CHEMICAL ANALYSIS each of cement. bag and sent for analysis. Dry the residue used for brickwork in house walls is generally 1:4 (Precipitated silica) in oven for 1hr and then in proportions. to dissolve the material.R. from silica Take filtrate from ferric oxide and alumina cement portion in each fraction is determined. in oven beaker. phenolphthalein as an indicator. and then treat the filtrate separate sand from cement lumps) Sieve the with conc. sand and coarse sand. wash with Titration (By Patton Reeder`s water till chloride free. weight of sand obtained by 250 ml.5 gm cement in a conical flask add 50ml of slab/beam in oven at 110°C for 15 minutes. cement: sand used in plastering work is 1:4 (The 1ml 0. digest on water bath for 10 minutes & g) Determination of `Calcium` by EDTA filter the liquid through filter paper. separate powder. Weigh as alumina and ferric HCl.01M For filtrate same as cement normally the ratio of EDTA solution color change violet to blue. Take about 5-10 gm of each fraction in wash the ppt. add and weigh. cool and then add 2-3 drops of nitric acid to oxidize any then weigh. sand and aggregate indicator with 10 gm of sodium sulphate (A. stir. to total weight. (To ammonium chloride. N= Normality of NaOH Concentrate filtrate on hot plate to dryness. obtained is noted. till constant weight. Also % of cement in stirring then add 5ml diethylamine. further add 50 mg of Patton Reeder`s indicator. if required add further 5-10 ml at 1050°C to 1100°C. fine sand. add 5-10 ml 3. from determination in 250 ml Vol. Weigh individually and of Fe and Al hydroxides for few minute. gets dissolved and sand portion is separated from cement. adhering to brick from debris the residue. in reading / 3 aggregate. About ½ kg h) Direct Cement % by acid titration sample is required for analysis dry the piece from Take 0. Weight of silica should be collected. The filtrate is evaporated indicator) and silica determined as in earlier part. Filter and record. further add 5-6 the sample is calculated. perform a Sieve the bulk with different mesh size sieves.5 N HCl. with hot water. Silica % 3) Concrete Patton Reeder`s Indicator: Grind 10 mg of the Concrete is a blend of cement.internationaljournalssrg. a) Testing of Mortar f) Combined Ferric Oxide and Alumina Heat good piece of mortar approximately 200 gms Concentrate the filtrate to about 200-ml by boiling is heated in oven at 110°C for 15 min.01 M EDTA = 0. to blank titration.5608 mg of CaO. fine persists then boil the solution containing the ppts.3 N HCl till all the material and ignite in platinum crucible till constant weight is wet with HCl. Take out 25ml soln. Also.weigh piece of mortar. 5ml (1:1) glycerol with constant cement to sand is calculated. Dry the ppt. ammonia solution till smell of ammonia material and make three fractions as powder. pellets of NaOH (pH should be more than 12) b) EDTA Titrations shake well. For testing of mortar and brick good incinerate in furnace at 800°C-900°C for 1hr. The cement portion oxide. cool 0. Weigh the fractions so separated ISSN: 2348 – 8352 www. Color change is colorless to pink. store in an airtight bottle. digest on water bath for 30 minutes.5 N NaOH using particle gets separated from sand and aggregate. further dry completely without charring. The mortar paper till chloride free. in titration flask add subtracting wt. SSRG International Journal of Civil Engineering (SSRG-IJCE) – volume 2 Issue 1 Jan 2015 e) Silica Where. Add 1-2 grams of by slowly grinding the lump in iron mortar. ratio used for compound walls and such other work (60 % CaO = 100 % Cement) and CaO % = 3 is 1:6 to 1:8). then add 20 ml 2) Mortar 1:1 Hydrochloric acid and digest on water bath for Mortar is the blend of cement and sand in various 10 minutes stir well. Then grind the sample so that cement 50 ml water and titrate against 0. Normally samples from debris selected are pieces of beams and slabs taken for analysis. and filter on ashless filter proportions used for various purposes.org Page 30 . Of cement and hence the ratio of 50 ml water. shake well and titrate against 0. Separate the cement portion from sand ferrous iron to ferric condition. (20 % Silica = 100 % cement). flask adjust Vol. coarse sand and Cement % = 28 × N × Diff.) and in different proportions used for different purposes. sand and aggregate respectively. Take sand paper carrying the precipitate in the beaker. wash with water as mean of the titration reading is taken as single until chloride free. total cement. Filter the solution. Precipitates as of interfering radical are being removed in the IIIrd group. From silica calculate few drops of filtrate in a test tube. Add 10-15 ml dilute nitric acid (20 %) b) Check for Chlorides in each beaker. dry silica remains in the beaker along with precipitate.e.e. Add 20 % HCl and boil the solution. and also % of titrate it against warm solution at nearly 50-60°C cement in the sample. out 10ml of the solution each in 3 beakers in separately. Filter the NOTE: Three separate solutions in beaker are taken silica through ashless filter paper. and CaCl2 the weight of cement obtained in different fractions solution few drops. After adding ammonium a) Silica oxalate solution. Compare the results obtained i. HCl (1:9) and finally with hot water filtrate. and hence calculate the ratio of Add dilute sulphuric acid as CaO is soluble in cement: sand: aggregate also calculate the cement dilute sulphuric acid. Add distilled water and shake a) Insoluble Residues well. Add 30 ml hot water and 30 ml 2N Na 2CO3 up to 15ml.2 AgNO3 solution. Add few drops of percentage.3 N HCl and digest on water bath for 5 minutes. calcium and aluminium salts. SSRG International Journal of Civil Engineering (SSRG-IJCE) – volume 2 Issue 1 Jan 2015 individually. Take Wash the silica so obtained. Filter CaO plate. Keeping the filter sand. Filter it. Ignite the adding distilled water in the flask. Make the solution up to 500 ml after till the residue is free from chlorides. Dry the silica in oven and reading gives error. Take about 5-6 gm from powder tea spoon) and boil.internationaljournalssrg. total sand and total aggregates present complete precipitates are transferred in a beaker. Distilled Transfer the residue of the previous test in a water and dilute HCl (i. till pink color appears. reading and mean amount of KMnO4 used. 20 %) should be added beaker. warm-water/distilled water over the dissolved 10 minutes. cool in a solution after shaking well in the beaker. and hence get the the solution. about 50-60 gm ammonium hydroxide and boil the solution for the from coarse sand and about 100-150 gms of precipitation to be formed in the IIIrd group. in the sample. % Calcium Oxide (CaO) = Mean × 1. Each fraction solution is not free from Oxalate.4 4) Alternative Method % Cement = CaO % × (100/62) Keep the sample in the oven for 15 minutes and Assume the pure Cement CaO % = 62 then keep them in desiccators for cooling. add ammonium chloride (nearly 1 ½ . Heat the solution below boiling point for HCl. Add 20ml distilled water in each Take few drops of filtrate and add 2-3 drops of and boil. add sufficient quantity of of ammonium oxalate in a beaker and distilled 3. if required. No the initial and final by silica and CaO. From filtrate of silica. boil the solution for the Filtrate evaporates the filtrate to dryness on hot precipitates to be formed of CaO. The filtrate so obtained is used added in each beaker after filtering the precipitates.. Nearly particles. Transfer the residue in a tarred crucible at 900-1000°C. for silica determination. Then digest on water bath for 10-15 100 ml each of ammonium oxalate solution are minutes and filter. Add a few drops of conc. solution. cool the solution and then add fraction and fine sand fraction.3 N HCl to dissolve the adhering cement water nearly 300 ml of solution is formed.. wash the precipitates further in furnace at 800°C-1000°C for 2 hours. Weigh 10 gms of sample. Pipette desiccators and weigh. calculate CaO % concentrated sulphuric acid if precipitates are not as detailed in cement. aggregate fraction for actual silica and calcium Remove the beaker and allow precipitates to settle oxide determination.org Page 31 . Wash till the contains some cement portion and rest being fine residue is free from Oxalate. from CaO % also calculate dissolved in dilute sulphuric acid completely. Thus calculate the the filter paper with distilled water so that. make saturated solution above in 250 ml beakers. if precipitate forms then (20 % silica = 100 % cement). Take all the four fractions as down. wash the residue on the filter residue so that complete CaO dissolves in the paper with dil. Put N/10 KMnO4 in a burette and ratio of cement: sand: aggregate. warm the % cement in each fraction. Now. with warm water till it is fee from oxalate. white precipitates formed ISSN: 2348 – 8352 www. wash and fine sand fractions together. Then add 3. Ratay. Toxicology Dr. If stone powder is used IX. Ratay (Ed. in R. 10. Structure Magazine. and recovery of 94 % was obtained for silica [4] Bell. Pawar for encouraging us and providing a platform to do the necessary works.44 % [3] Sean P. Director of ISSN: 2348 – 8352 www. the correct Structural Design and Construction. Finding the root cause/reason of the failure of a structure requires loyal and delicate experienced personnel in Structural Engineering as well as in Forensic Engineering. In case of Mortar and Concrete the ratio of Cement: Sand and Cement: Sand: Aggregate is very important. R.S.internationaljournalssrg. By performing the chemical analysis of the samples collected from the scene of the failure of the structure. Naseem Ahmed and Prof. VII.G. Bangalore. is used for adulteration then acid insoluble will be [2] Krishnamurthy and Dr. we wish to express our warm sincere thanks to the Director of Deogiri Institute of Engineering & Management Studies. July 2007. 2007. New Delhi. R. The study was successively carried out and conclusively we can say that. 1999. Lastly. the percentage of cement in the sample. R. 2000) 2. CONCLUSION [6] IS 269 : 1989. Aurangabad (M. Engineering Investigating of Structural Failures. Brady. In Forensic Context one has to certify whether the sample is cement or not.1. Gupta and Head of Department of Chemistry and residue with hot water till it is free from chlorides. 50- adulteration percentage but if lime or other material 53. VIII. calcium oxide and silica data can not been mentioned but helped in the realization of the work in allow one to frame a report regarding the cement various ways.11. 2-6. G. CD Preprints of cement percentage can be assayed from silica Structural Engineers World Congress. cement by the above methods are quite accurate 2000) 6. Shiurkar and Head of Civil Engineering Department. We would like express our VI. and if so. Role of the Forensic Process in and recovery of 99 % was obtained for EDTA Investigating Structural Failure. REFERENCE for adulteration the acid insoluble amount for [1] Robert T. Finally. cement is complex mixture and testing of cement is a difficult task. 2-7 Nov. wash the Government Institute of Forensic Science. [5] Noon. Forum. Prof. The relative standard deviations of 0. the cement content determined by above method compared with the specifications laid by the relevant codes may form the basis for reason behind the failure. one can easily advocate the fact behind the failure precisely.) Dr. RESULTS AND DISCUSSIONS deep and sincere gratitude to Prof.P. Aurangabad (M. D. 2.org Page 32 . K.88 Constructed Facilities ASCE. Forensic Structural determination. and Performance test along with percentage of we wish to express our gratitude to all those people who have acid insoluble. Javed Khan for reviewing this manuscript. U. FL: CRC Press. ACKNOWLEDGEMENT Firstly. R.) Dr. G.Specification. 2012. content. Hence the results of the analysis of Engineering Handbook. Forensic Engineering Investigation (Boca Raton. hence selection of the sample plays an important role. SSRG International Journal of Civil Engineering (SSRG-IJCE) – volume 2 Issue 1 Jan 2015 indicates the presence of Chlorides. In addition.. 6. Heat deeply indebted to all the authors of the references used. Forensic Engineering in less and calcium oxide will be more. Journal of Performance of titration.). India. Professional practice of forensic structural engineering. we are The initial tests like Thymolphthalein test. Gandhe. The relative standard deviations of 0. test. S. Natarajan. and reproducible. 6 (New York: McGraw-Hill.. Ordinary Portland Cement . T. percentage with acid insoluble and cement with non-cementitious material. BIS.S.