Solutions for the Built World: Case Studies in Building Structures Investigations

Solutions for the Built World: Case Studies in Building Structures Investigations

This presentation is made each year to the Penn State AE 537 Class during the first week of September.  Paul J. Parfitt, S.E., P.E., Senior Associate, WJE is the visiting practitioner who provids the talk.   Mr. Parfitt discusses various categories of investigations that are customized and carried out appropriate to the type of problem to be solved or the need of the client.  Categories of investigations discussed included investigation for repair (PT inspections / repair), immediate response (failures / disasters /snow collapse) and the specialized investigation and testing techniques related to historic preservation and restoration.  Sample case studies of all these categories are discussed including the various tools and skills necessary for the particular situation ranging from industrial rope access to the use of specialized non-destructive field testing to the role of the testing laboratory.  Mr. Parfitt also comments on the background and knowledge learned in AE at Penn State relative to the skills that will help students entering the forensic or building technology / waterproofing sectors of the industry.

For those interested in Post-Tensioning another presentation by Mr. Parfitt titled “SPECIALIZED POST-TENSIONING ASSESSMENT AND REPAIR OF BRIDGES” can be found here and the full article associated with this presentation is available in Canvas.

An excellent follow up article that compliments this presentation was written by Robert T. Ratay, PhD, P.E. and published in Structure magazine titled Professional Practice of Forensic Structural Engineering.  Students are encouraged to review this article in conjunction with the content of the seminar by Mr. Parfitt for inclusion in the online discussion that follows.

 

 

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38 Responses to “Solutions for the Built World: Case Studies in Building Structures Investigations”

  1. Steven B
    September 12, 2018 at 8:49 pm #

    I would like to piggy back off some of the points that the class has raise about the presentation by Mr. Parfitt. As a practicing Structural Engineer, it can be very easy for you or your firm to be type cast. What I mean by this is that you may become known for your designs of a specific type of structure or even a specific type of construction. This is not necessarily a bad thing, unless your wish to come into work every day with a new challenge. A different type of project on your desk every few months. The presentation made it clear that as a Forensic Engineer, every day has the possibility to put you in a situation completely different from the situation you were in yesterday.
    The second point I wanted to comment on is the opportunities of a forensic Engineer. ASCE once again has given the nations infrastructure a ‘D+’ grade https://www.infrastructurereportcard.org/ . Yes, some of the aging infrastructure will be replace, but with tightening budgets there will be more opportunities for engineers that are experienced in retrofitting.

  2. Clayton T
    September 11, 2018 at 7:37 pm #

    The recent guest lecture presented by Mr. Paul Parfitt of WJE provided some valuable insights into the causes and effects that surround building failures of all types. I think one of the most interesting aspects of WJE and the work they are involved with is the scope of the projects and which components of a building are to be considered within a “failure”. From structural collapse to historic building inspection, each system or material for that matter that does not act as intended will be considered a failure. Historic buildings in particular as Mr. Parfitt discussed typically containing stone ornamentation as an architectural component are common areas of failures exposed to the elements or just years of use, which may cause a great amount of damage or very little to the surrounding area and public but in my mind would be very much overlooked with an extreme case of failure, i.e. falling into a crowd.

    Another area that sparked my interest was the fabric tensioned roof exposed to an excessive snow load ultimately resulting in collapse. While this system as a whole is very different and would require a type of specialty engineer for design, I am more interested in the way the failure was assessed through the construction documents. Without a typical construction method, the given design had to be examined and calculations made to assess that areas that failed. Specifically, the connections details of the fabric to the reinforced concrete wall . Also, this failure emphasized the importance of communication between the design engineer, general contractor and the owner as the design engineer specified the snow/ice limit that the assembly could withstand before the need for removal. However, this design limit was not coordinated, if the design note was even notice, no removal procedure was discussed with the process obviously to be unique undertaking avoiding creating additional loading on the assembly while working around the unique architecture for access. Hindsight is 20/20 but with such specific loading criteria, maintenance and upkeep coordination is crucial.

    • mkev
      September 11, 2018 at 9:16 pm #

      Good point about the snow removal but that is exactly the process in place at a number of tension structures and in particular many of the older air supported structures. You may be interested in this post on the Metrodome which collapsed many times before it was demolished. https://buildingfailures.com/2010/12/12/metrodome-roof-fails-once-again/ The Syracuse University Carrier Dome is one of the last large remaining air supported arenas. They use a combination of fire hoses and hot water along with raising the inside temperature to prevent snow build up.

  3. Katie W.
    September 11, 2018 at 2:27 am #

    After listening to Mr. Paul Parfitt’s presentation both in class and in the informational session, I gained a greater understanding of the full scope of what a forensics engineer is and what they do. A lot of what he mentioned was surveying not just collapses and failures, but also possible sites for future failures and repairs. It makes sense that the people who are investigating the causes of failures are also the ones looking for signs of imminent collapse. There also seems to be a larger crossover between civil engineers and architectural engineers in the forensics industry. Though he said a lot of architectural engineers work on building enclosures and technology, he
    also mentioned working on bridges several times as well as any other structure that holds load. I assume most of the skills learned are transferable, especially basic structural analysis and design. However, are there any areas that, as architectural engineers students, we don’t learn as much about but might need to know if we were to go into the forensics industry?
    I also didn’t realize that span of time that can sometimes pass before the company is called out to the failure. Often, I assume, this is because the owners did not suspect there was any reason to investigate the failure. A lot of evidence could be lost within a few days or weeks, especially if they have already begun clearing the site. Some evidence, if not properly preserved could rust over or melt away. Time seems key in any investigation involving forensics. Trying to reconstruct a failure from images seems a much more difficult process. I wonder if there were any cases where the cause of collapse was indeterminable due to insufficient evidence, and in that case, who is liable.

    • Paul P.
      September 12, 2018 at 8:02 am #

      Katie, all excellent points. A lot of the skills can be transferable and there are other non-engineering related items that you’ll transfer such as technical writing that we utilize a lot in our field. While I feel from personal experience that the PSU AE program is one of the best for preparing new engineers for a job in the forensic world, there are things that just aren’t readily taught. Mostly pertaining to the building sciences. There are a handful of courses at universities around the country that touch base on it but to my knowledge none of them support degrees in these specific fields, unlike in Canada and Europe where they have building science fields at universities. These types of skills are mostly learned on the job at most forensic firms. At WJE we have experts in just about every field imaginable though so it’s not difficult to find someone to provide insight to a topic you may not have a lot of knowledge about. Most of our engineers gain that knowledge through experience in the field.

      To your second point, time can be a very big factor in some disaster/collapse response cases. Delays in being mobilized to a site can happen for multiple reasons but I have yet to see a job where the reason for collapse could not be determined due to insufficient evidence. Whether the cause can be proved in court due to the available evidence is a different topic.

    • Jackson H
      September 12, 2018 at 10:12 pm #

      I think that the the transfer in skills from Architectural Engineering vs. Civil Engineering when evaluating failed or failing infrastructure is worth looking in to. I am curious to see if there are any advantages or disadvantages that either major initially has over the other when applied to the forensics industry. If an Architectural Engineer wants to start a career of evaluating infrastructure projects, are there any specific technical skills that need to be acquired first other than the basic practical knowledge that comes with working in the field? All questions that beg further research. The WJE lecture answered many questions that I had or didn’t even know I had about forensic engineering, but it has also prompted me to look into the finer details of what is actually required to be a forensic engineer.

      Even though I am not particularly fond of heights, I am immeasurably envious of Mr. Parfitt’s task to scale these incredible buildings as a part of the difficult access team. There is something to be said for loving what you do and it seems like forensics can be the perfect fit for someone who likes to get out, or in this case….up.

  4. Jackson H
    September 11, 2018 at 12:52 am #

    The lecture given by Paul Parfitt from WJE helped me reaffirm my preference for forensic engineering over design. Seeing examples and hearing an industry professional explain the responsibilities and opportunities that a forensic engineer has as a part of their career seems infinitely more fulfilling to me. In general, when I think of building forensics and work relating to building failures I think of engineers sifting through the rubble of a collapsed building looking for the proverbial “smoking gun”, or more often “guns” as we have come to realize. However, from Mr. Parfitt’s lecture, I have been introduced to new fields of structural engineering that include preventative maintenance and other specialized structural rehabilitation.
    As pointed out in both the lecture and the “PT Bridge Repair” article, these areas use innovative and interesting technology such as LiDAR and other 3D imaging technique to record and analyze structures and facades. Forensic engineering can provide the opportunity to use emerging technologies to put together the best possible assessment of aging or failed structures. With the condition of our aging infrastructure, it is clear that there is, and will be, a demand for structural engineers to assess and recommend rehabilitation for the foreseeable future.
    The case study that I found most interesting was the collapse of the fabric roof. There was a clear procedure for ruling out possible causes and the cause of the collapse was distinct. This procedural analysis follows the load path from the initial application of the snow load all the way to the foundation system. I always wondered how forensic engineers know where to start, and this case study was a good example of a common methodology.
    To summarize, the lecture and article opened my eyes to how vast and varied the opportunities in structural engineering are that don’t revolve around design. As a 5th year student who is not particularly interested in doing design work as a career, it was extremely beneficial to hear about the experiences of an industry professional in a field that I am considering starting my career in.

    • Abby S
      September 12, 2018 at 11:39 pm #

      Jackson,

      I think it’s great that you know you prefer forensic engineering to design. I have gone back and forth when trying to decide if I would prefer a career in design or forensics. I see pros and cons for both, and unfortunately it seems like it is difficult to work in both areas at the same time.

      I saw that you mentioned how you wondered where forensic engineers know where to start, and I have wondered the same thing myself. I think there are obvious places to start, like with the basic loads for example; however, I think a lot of that extra knowledge and intuition comes over time after gaining a lot of experience in the field. I have spoken to a few forensic engineers who say that it is beneficial to get a strong background in design in order to have a better understanding of the structure and how it works. Then, as Mr. Parfitt said, you can “ask the structure” to find out what went wrong. I’m curious as to whether it would be better to have the design background or start gaining experience in the forensics field as soon as possible. I would be interested to hear other opinions on this topic, as well, and what the transition to a career in forensic engineering is like after graduating or after getting a background in design.

  5. Josiah M
    September 11, 2018 at 12:21 am #

    After attending both of Mr. Parfitt’s lectures and reading the additional article provided. It becomes abundantly clear that the field of forensic engineering is not limited to investigating catastrophic failures and collapses. It also applies to preventing and recognizing possible failures.

    What I gained from Mr. Parfitt’s lectures was that inspection comprises a good portion of the forensic engineering field. These inspections are essential when it come to preventing failures. One example of these inspections is facade inspections. The facade is an important part of the building that protects the inner workings of the building from the elements. Therefore it is essential to ensure that it is doing its job properly. Furthermore, it is important that the facade isn’t decaying in a way that could cause injuries, as facade elements have become detached and fallen from buildings in the past. Mr. Parfitt even mentioned that, during an inspection, a piece of the facade had become detached with the slightest touch. Otherwise, that piece may have been detached by another force and fallen to the ground, possibly injuring someone.

    Inspection is also mentioned in the article “Specialized PostTensioning Assessment and Repair of Bridges”, where multiple inspection procedures regarding grouted tendons is discussed. In the past, “specialized inspection protocols have been at the discretion of individual engineers/contractors” that lead to arbitrary results. Eventually the FHWA published an article titled “Guidelines for Sampling, Assessing, and Restoring Defective Grout in Prestressed Concrete Bridge Post-Tensioned Duct”, in which there is guidance for grout sampling, testing, analysis, and the interpretation of the results. Even though the FHWA document lays out procedures there is still a bit , the owner may want to use specific method or the structure may cater to a specific method. From there, it’s left to the engineer, along with the owner, to judge what method will be best and if additional inspection or monitoring should be done.

    What I learned from Mr. Parfitt is that forensic engineering doesn’t always have to be in reaction to a failure. Forensic engineering can be preventative in nature to ensure that failures won’t happen, or at the very least, will happen less often.

    • Smithr
      September 12, 2018 at 8:20 pm #

      Josiah, you reinforced to me an important but not as flashy side of Building Forensics – Inspections. Preventative measures may just be as important as our investigations post failure. We often overlook the importance of inspections because, on a good project, the inspection reports are relatively clean and folks start to ignore the inspection reports. However, this provides us a “check” against ourselves. Too often do I find that once you have gained the trust of another individual, you tend to look past double checking or inspecting their work. This is what scares me as a construction manager. Even though a worker may produce quality work, it is the unforeseen conditions that he does not notice that can be the problem children.

    • Clayton T
      September 13, 2018 at 7:53 am #

      While guest lecturer Paul Parfitt did provide clarity on the realistic scope of structural forensics, I wonder abut the percent of buildings that could benefit from forensic inspections but the owners simply lack the knowledge of such. Without previous experience with building failures especially on smaller endeavors, owners may not know to continue professional monitoring performance. As we’ve seen from previous failures ranging from major collapse to enclosure performance issues, lack of communication is a prominent trend. How do we bridge this gap in communication industry wide no matter the scale of the project?

  6. SamZ
    September 10, 2018 at 6:54 pm #

    The guest presentation from Paul Parfitt was a beneficial lecture as it provided a great overview into what exactly forensic engineering is. Most of our education within AE so far had been tailored toward new design, while this is beneficial to form a base knowledge, it did not bring much up about other avenues structural engineering could go. I found that forensic engineering can be engaging and utilize broader and more conceptual principles of structural engineering.It also offers a lot of potential to bring about new and challenging engineering problems that require creative thinking to reach a viable solution. Also the quantity, variety, and the quick turn over of projects for WJE engineers makes it seem like few days at work are the same keeping the work fresh and engaging.

    Some the projects that interest me the most were the structural rehabilitation of old and historic structures. I appreciated how the process for the Old Main repairs consisted of reviewing historic photos and drawings to get a sense of what the original designers had intended. I also think it would be very interesting to become familiar with the historic methods of construction and design that are common to older building but no longer in the repertoire of most designs and craftsmen, such as the case with the leaded glass at Hotel Monaco.

    • mkev
      September 10, 2018 at 11:08 pm #

      Sam
      Those old materials, such as the leaded glass can also be a forensic tool. I once investigated a fire where another engineer claimed the fire was so hot it destroyed the steel framing. We pointed out that if that was the case, the leaded glass window just next to the beam should have had the lead melt out at a temperature much lower than what would have been necessary to severely damage the steel.

  7. Jordan O
    September 10, 2018 at 6:45 pm #

    The WJE guest lecture presented by Mr. Paul Parfitt provided us with some great information both about the company itself and the field of forensic engineering. WJE employees are fortunate enough to be exposed to a wide variety of work in the design, testing, and forensics sides of the industry. It is definitely beneficial to have all of those areas of expertise under one roof because they are able to learn from each other and promote growth and innovation to make great buildings.

    I think a big part of forensic engineering that goes overlooked, which we have talked about in class but was definitely highlighted in this lecture, is the large amount of rescue, recovery, and general ensuring of safety that goes on at the site. It is often assumed that forensic engineers are responsible solely for figuring out what happened and assessing blame. Making the site safe while maintaining high levels of organization with all of the materials being moved is a significant part of the work done on many projects. This is especially true in the very unfortunate event that people are stuck in the building that failed. The quick reactions of first responders to save lives while also attempting to keep everything organized for the rest of the forensic engineering process is a tedious but very necessary task to ensure that as many lives as possible are saved, and the forensic process is able to move forward without complications.

    Another important point brought up was the importance of great communication and clarity with everyone else involved in the project. In the warehouse roof collapse, small avoidable errors were some of the root causes of the eventual failure. One of the causes of failure was that they re-roofed too many times, which was discovered after pulling roof samples to calculate the weight. If the owner had checked with the design professionals before hiring the work to be done, it could have been communicated that there was a certain limit to allowable re-roofing material weight that the structure was already nearing the threshold of. They also made the mistake of jacking up the roof to insert mini columns that were bolted into the original columns. One of the main areas of failure was at this column to column connection when the roof was overloaded and this seems like another issue that could have been prevented with better communication.

    • mkev
      September 10, 2018 at 9:37 pm #

      Jordan,
      You may also recall that one of the factors for the collapse of the Peppermill parking deck in State College was repaving of the parking surface without removing the old layers. Asphalt weighs a whole lot more than roofing but it still didn’t click when they did it.

    • Josiah M
      September 13, 2018 at 12:57 am #

      Jordan,

      The oversight of the issues that come along with re-roofing a structure is one that I think happens far too often. In my experience in residential construction, I’ve seen quite a few roofs that have been re-roofed without stripping away the previous layers. Some going as far as having three layers of shingles. Not only does this add load that wasn’t anticipated, it could also hide decay that may be occurring on the structure beneath the shingles. Decay that would have otherwise been seen if proper maintenance was done. Water damage is some of the most common damage that I’ve seen upon stripping roofs under there conditions.

    • Katie W.
      September 13, 2018 at 8:32 am #

      Jordan,
      I definitely agree with your points on communication both onsite after a failure and during construction and design. So many simple mistakes might have been avoided if they had checked with an structural engineer or contractor. This seems especially evident in light of the most recent Quiz readings, where communication between the contractor and designers was key for many of the cases. I was surprised by the number of warning signs disregarded during construction that could have alerted them to a problem. However, there was one instance where after concerning cracks and deflections, the structural engineer was asked to verify the buildings stability and maintained that the building was structurally sound. Even though communication can help in many situations, there are still some where it fails.

  8. Abby S
    September 10, 2018 at 5:56 pm #

    The lecture given by Paul Parfitt, along with his PT Bridge Repair Article, made me realize how significantly forensic analysis techniques can vary in scale and complexity. When I hear the term forensic engineering, I initially think of the on-site investigations and subsequent load analysis that often take place when a failure occurs; however, Mr. Parfitt mentioned several different techniques that WJE uses for investigation and analysis.

    It was very interesting to learn about the many unique hands-on inspections that WJE has performed, such as at the Washington Monument and Hotel Monaco. I was surprised to hear that these types of investigations are often done as a precaution rather than after a failure since it must be an expensive, although worthwhile, process. Last summer, a large piece of the granite façade fell off the Frick Building in Pittsburgh, so unfortunately it does not seem like these types of investigations are done often enough. While computer analysis tools are very useful, sometimes it is necessary to perform visual and hands-on inspections in unique and difficult to reach places.

    Some of the other techniques that Mr. Parfitt discussed include nonlinear iterative testing for the tensioned fabric roof, nondestructive testing for the grain silo, and numerous other methods used at the WJE technical center. His PT Bridge Repair Article also discusses inspection methods such as drilling hole openings, using a borescope, using infrared thermography, conducting vibration analysis, or mechanical sounding. I interned at PennDOT in the bridge inspection unit and spent a lot of time using a hammer to sound concrete, which was a simple yet tedious process, so it is interesting to learn about all of the highly complex techniques that can be used. The appropriate testing method certainly varies based on the situation, but it seems like it would be difficult for an owner to decide on the best method since some are more costly or time consuming but also may be more accurate and detailed.

    • mkev
      September 10, 2018 at 9:34 pm #

      Interestingly enough, relative to the Frick Building, The Burg has a facade ordinance. http://www.facadeordinance.com/assets/images/pages/pdfs/pittsburgh-facade-ordinance-property-maintenance-code-1004-01-1004-02.pdf
      See WJE site: http://www.facadeordinance.com/

    • mkev
      September 10, 2018 at 9:46 pm #

      PS: Speaking of Grant Street in Pittsburgh, someone, who may or may not be your instructor, investigated and helped with emergency repairs on the historic balcony of this grant street building: http://www.post-gazette.com/local/city/2016/05/14/Grant-Street-side-of-City-County-Building-getting-a-face-lift/stories/201605140086 #oldstuffwantstofalloff

    • Sierra S
      September 11, 2018 at 5:11 pm #

      Abby,

      When it comes to forensic engineering I had the same initial thoughts. I thought of larger failures that were pursued by detailed analysis. This past summer, even though I wasn’t in the forensic engineering division of the company, I saw a lot of building failures. However, these failures were in regards to the building not performing as design. The failures ranged from water infiltration, air infiltration and thermal bridges. In these cases the problem could not be solved through software. Drawings could be used as reference but the main source of information came from testing and observing the built conditions.

      I performed many water tests this summer but one that stood out to me was when we couldn’t reproduce the leak. Methods, such as driven rain from a spray rack and flooding was used. In theory, these tests should have reproduced a majority of natural conditions during storms and therefore produce similar leaks to those reported. However, sometimes the entry points aren’t clear. These failures provide just as much mystery, initially, as some of the building collapse.

      Similar to your observation on the Frick Building in Pittsburgh, many inspection don’t take place until an issue arises and this was no different with my work that I conducted this summer.

    • Eric I
      September 11, 2018 at 5:58 pm #

      Abby,

      I think that you brought up a very interesting point in saying that a lot of these forensic investigations take place as a precautionary measure. I know that when I hear forensics, my mind automatically jumps to “what happened?” rather than “what could happen?” I imagine that these kind of preemptive investigations are expensive and may be a tough sale to an owner who is rolling the dice, but as we push towards new methods and materials, the rate of failures is sure to increase due to limited knowledge/experience with them. Also, now that we are in an age where information and news spread so quickly, building failures are heard about more frequently as well rather than requiring a lot of research. I wonder now that as code officials start to hear more about failures, if they will require more strict rules on building “check-ups.” Solving a problem before it is a problem sounds like a no brainer to us, but it may have to become a law for others to feel the same way.

      You also brought up a great point with how many techniques are available. From the ultra-high tech to the simplistic, there are so many methods around and being able to select the right one while considering budget/accuracy is vitally important. Also, for as involved as these computer programs have become, sometimes there is no substitute for actually visiting the site.

      Great post!

    • Jordan O
      September 13, 2018 at 2:58 am #

      Abby,

      The mention of sounding of concrete got me thinking about my past internship. New York City has a law in place called Local Law 11. This makes it mandatory for buildings taller than 6 stories to have periodic inspections of the facade. If any deficiencies are found, depending on their severity and risk to public safety, they must be remediated within a certain period of time otherwise the owner will incur fines from the Department of Buildings. I’m sure this has become common place in most major cities, but what interests me is why 6 stories? Would a piece of terra cotta from only 3 or 4 stories not cause serious bodily harm? It might be because deficiencies less than 6 stories off the ground are more easily observable from the street and can be taken care of once noticed, but if no one is looking someone could still easily get injured. I’m curious to know why they chose 6 stories and I also wonder if other cities have similar entry requirements for mandatory periodic facade inspections. Public safety must be the number 1 priority so it would make sense that any building with material at risk of cracking or spalling should be inspected regularly regardless of its height.

  9. Smithr
    September 10, 2018 at 3:26 pm #

    The case study about the warehouse roof collapse really reinforced one of the main topics that has been mentioned in this class quite often. It is the idea that the majority of the building collapse/failures are a combination of conditions that lead to a failure. The difference in this case is that the trigger mechanism was was, for the most part, known prior to investigation. The roof of this structure collapsed mainly due to the mistake of a forklift operator. However, there were a handful of other factors involved such as the sagging rodded connections and the use of docks plank. It was a nice refresher on one of the more important themes of this class.

    • mkev
      September 10, 2018 at 9:16 pm #

      Glad to see all of you are actually listening when I say stuff! Seriously though, I have investigated several warehouses for various problems and multiple times I have found holes in pipe columns that were caused by being “speared” by the end of a fork from a lift. The buildings did not collapse which reinforces that in many cases, there are likely to be other contributing factors beyond what may seem obvious.

  10. rgstanza
    September 10, 2018 at 2:16 pm #

    As many others have pointed out, Mr. Parfitt opened our eyes to a whole new realm of possibilities for structural engineers that does not involve design from the ground-up. However, even though his work is focused on forensics, the failures he presented are great to see for a design engineer because it shows better than anything else what the building codes are trying to prevent.

    For instance, the tensioned fabric roof collapse was a failure mode of anchor rods which could have been prevented if the engineer knew with proficiency exactly what he was trying to design for. Having spent part of the summer determining limit states for anchor rods, I am familiar with the multitude of checks that need to be completed for this type of connection. There are lots of parameters and multipliers and sometimes it is easy to get tripped up in the numbers and forget what you’re really looking to accomplish. Knowing which limit state controls and understanding how to tweak and manipulate your design to satisfy the conditions is absolutely imperative.

    Seeing the failed connection due to concrete breakout paints a very clear picture that sometimes it doesn’t matter if you change one parameter if it’s not contributing to the critical failure mode. You can give your connection more embedment depth, but really what you need is more edge distance or vice versa. This breakout failure allowed me to visually construct a better image of what the big picture is for these limit states imposed by the code.

  11. Ryan L
    September 10, 2018 at 1:56 pm #

    Throughout the case studies that we have reviewed, non-destructive testing has shown to be a method / skill set that is imperative to analyzing partial failures, systems designed in similar manners where complete failure has occurred, and/or work on protected historical buildings.

    It has been shown that determining the cause of failures goes well beyond a fixed process / numbers crunching approach, as Mr. Parfitt and others in this thread have noted… ” (What is the building saying to you)”. Experience and a thorough approach make forensic engineering more of an art form than, perhaps, designing to a set of mostly uninhibited requirements.

    I think this is shown very well through analysis of systems you may not be able to see. Mr. Parfitt’s and Mr. Green’s Post Tensioning Assessment and Repair of Bridges highlights multiple minimal or non-destructive techniques where the data collection and analysis are not cut and dry. Most interestingly, to me, is the future of short and long term monitoring of PT elements leading to real-time data collection and analysis. As noted in the article, there are challenges to using these methods on existing structures. However, I wonder how much advancement there will be in monitoring structural elements in the near future. MEP system monitoring has advanced quickly over the past decade due to technological advances…. Are building envelope and other structural systems far behind?

    • Paul P.
      September 12, 2018 at 4:25 pm #

      Ryan, we do in fact do a lot of building monitoring in structural as well as envelope work. Structural health monitoring is something that a lot of DOT’s are looking into for some of their more critical bridges where they will monitor strain, corrosion, deflections etc to determine how a bridge is behaving and we are constantly installing monitoring devices inside wall assemblies to monitor what the temp, humidity, corrosion potential etc. is in order to assess if a building envelop is performing adequately. Most times however these are done only after someone suspects there is a problem. Unlike MEP systems where you can monitor mostly through software in the unit, setting up these systems on brand new assemblies that are expected to function properly is not economical from a preventive measure most times and is mostly used to study and resolve existing issues.

      • Ryan L
        September 14, 2018 at 1:26 pm #

        Paul,

        Do you see monitoring systems, at initial construction/for PM purposes, becoming more economical in the near future?

  12. Steven B
    September 9, 2018 at 2:33 pm #

    Slide number 7 of Mr. Paul Parfitt presentation peaked my interest. In particular, as a company, WJE only spends about 8 percent of there time on structural analysis and even less on document review. In the article by Robert T Ratary, he states that a “Failure may be characterized as the unacceptable difference between intended and actual performance”. So that means that in order to know if something is truly failing you have to know what it was designed for. What were its intended limits. At first glance it would seem that more time would be spent on reviewing design/construction/maintenance documents and then performing their own calculations to confirm the limits of the design. But rather, the majority of the time is spent “asking the structure” as Mr. Parfitt referred to it as in his presentation. This leads you to think that if field inspection is done correctly, then the forensics engineer is able to narrow their focus to specific sections of the structure. Then less time is spent over old files and calculations as the time is devoted to documents related to that section only. The only calculation performed are for that section of interest.

    • mkev
      September 9, 2018 at 5:30 pm #

      Steven,
      I think what Mr. Parfitt was referring to was the percentage of work for his company. I think your point is why is more time not spent during the original design phase (which is not necessarily by WJE or the other forensic firms who get involved after the fact) in peer review or checking? If so, why do you think that is the case?

      • Steven B
        September 9, 2018 at 9:12 pm #

        Dr. Parfitt,
        The bidding process rewards firms that can provide the service on time and usually with the lowest budget. In an attempt to have the winning bid, the peer review process is likely the first thing to be cut as the original firm believes that they will perform the design correctly and therefore the review process is a luxury they can live without. This view has to be corrected across the construction industry.

        • Ryan L
          September 11, 2018 at 6:09 pm #

          I think that the technological push (BIM etc.), observed benefits of integrated design and integrated project delivery contracting starting to gain a bit more traction, all could have positive impacts on the issues Steven B. raises.

          A lot of public sector contracts are dictated by acquisition regulations. For instance the Federal Acquisition Regulations has a limit of 6% of construction cost for design (subject approval from higher ups).

          Again, front loading cost/effort will help I think, but you will still have the communication issues from planning, design, construction/operations and the push for on-time/under budget. individual accountability is still paramount, as I don’t believe 100% oversight will ever be achievable or cost effective.

  13. Sierra S
    September 9, 2018 at 10:41 am #

    The guest speaker, Paul Parfitt, provided valuable insight into what WJE does daily. He proved that our major can lead to more opportunities than just structural design. In their forensic engineering division a large chunk of their time is spent on site collecting evidence or examining existing conditions. Due to the special nature of this work Mr. Parfitt emphasized the appropriate steps that had to be taken during this investigation. First, since the failure of a structure is life threatening the number one priority is ensuring the safety of the site and helping anyone in need of assistance. Second, the site needs to be preserved. That means all fractured surfaces need to be sealed and failure documented. Finally, the engineers can catalog and analyze the structure.

    The failure that caught my attention was the Grain Silo. This was unique situation because no significant event occurred that could have triggered the failure of this structure. Over time that acidity in the silo’s contents eroded the welds which led to the structure splitting open.The metal of the silo, though, was not affected by the contents. Over the summer I was working in the BT field and the importance of material compatibility came up often. This often referred to the compatibility of two waterproofing membranes lapping into one another or the interaction of two different metals. While the silo’s weld were compatible with its casing it must of been unknown or overlooked the reaction it would have with its contents. In the end, this was a learning lesson and changed the materials for silo’s constructed down the line.

    Like everything else, determining the cause of failure takes experience. No two failures are the same but using prior experience to piece information together is crucial in forensic engineering. In the case study I mentioned above, Mr. Parfitt said it wasn’t like anything he had seen before but due to prior knowledge and examination of the structure the forensic engineers were able to determine the cause of failure.

    • mkev
      September 9, 2018 at 5:27 pm #

      Nice observation from your summer experience, Sierra. We also have the issue of incompatible metals coming into contact with each other, sometimes as flashing or various system termination.

      Does anyone know what that is called and can give an example?

      • Ryan L
        September 10, 2018 at 1:30 pm #

        I think you are referring to putting dissimilar metals in contact with each other and causing galvanic corrosion. The first thing that comes to mind is the lower unit of boat motor or outdrive…. Installing a stainless prop on aluminum cased outdrive. Or just installing a sacrificial anode on the lower unit to protect the unit acting as the cathode.

  14. Eric I
    September 8, 2018 at 5:23 pm #

    The guest lecture given by Mr. Paul Parfitt gave a great deal of insight into the field of forensic engineering. Outside of this class, most of our education so far has focused on new deign and analysis so it was great to learn more about how our degree can take us down multiple different paths.

    Throughout all of the different case studies presented, the most interesting piece of advice I heard was to listen to what the structure is telling you. Running numbers and looking at photographs/reports is great but sometimes there is no substitute for spending a few days in the field. Mr. Parfitt had multiple instances where the solution to his problem wasn’t necessarily obvious but through careful analysis of the site, he and his team were able to identify the problem. From my own experience, sorting through evidence and documenting everything you see can become mundane but the last piece of the puzzle is always somewhere within reach.

    The most interesting case study to me was the tensioned fabric roof collapse. I enjoyed this one in particular because when he explained the investigation process, I noticed that the steps ultimately followed the load path. First, WJE analyzed the snowload on the structure to determine if the conditions were “an act of God” or if the weight was under design values. The loads were well under design values which meant something else failed. The next step was to see if there was a tear in the fabric covering the roof. After that was ruled out, they worked their way all the way down to the connections. In the end, this was what failed and it was due to low concrete breakout strength.

    I found this to be a valuable lesson because I learned that simply following the load path can be a great way to eliminate variables and solve the problem. In practicing this methodology, one can find the break in the chain and determine the failure point in a more logical way. I think this is a great thought process to establish a starting point for investigations of any kind.

    • mkev
      September 9, 2018 at 9:33 am #

      Great point about the load path Eric. You may recall how easy it was to analyze the forces in the load path for the Kansas City Hyatt Regency collapse. Perhaps a good pointer is to double check the load path as a part of the final check before a project goes out.

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