Skip to main content

tv   Government Access Programming  SFGTV  December 17, 2018 10:00pm-11:01pm PST

10:00 pm
detail with an instrument using a scanning elect ron microscope to allow us to identify the mode of fracture and confirm the origin and also to identify that these preexisting defects formed at high temperatures, so the defects that we observed formed during the thermal cutting process of the access hole as well as subsequent to that was when the butt wells were made between the plates, they induced some residual stresses that were able to cause these larger defected to form, again, as elevated temperature, and that's basically what the next couple of slides show. this is a shot that shows that the fracture surface itself is covered with a large amount of oxide, and we know from the tenacity of this oxide and its appearance that it formed at elevated temperatures, which can only occur during the
10:01 pm
thermal cutting of the access hole or the butt welding of the plates together. this is what the cross section looks like through the access radius, and this is the actual fracture right over here on the top left. and then, along this radius there, through this side, it's martinsite. it's a normal development, and when you cut thick plates like this, because it's so brittle, you get these small little microcracks that build in. it exists in other industrial structures. other circumstances around them can cause into larger cracks, and then subsequent brittle cracks that we have in this instance. and here is a higher magnification shots, showing what they see cracks look like. and we found these cracks in all of the sections that we looked at that were removed from the girders.
10:02 pm
one of the other tests that we performed is something called surface hardness, where we look at how hard that thunderstormally cthermally cu surface is. it did have reduced hardness, which means they're very brittle and they're prone to form these very brittle microcracks. we also conducted something called a microhardness survey which is conducted as you go from the surface back into the material thickness, and this data, again, shows that at that surface, we have very high hardness, very brittle zone present, which enabled these fine cracks to form. we also conducted regular hardness surveys tlouded welded component itself. this is a view showing a cut. this is the stiffener that's present at this location. this is the flange plates here,
10:03 pm
and this is the weld that joins them. the survey showed the plate and the welds to be suspected, so there was nothing deficient in the welding itself and nothing deficient in the steel plates that were used for this -- for the buildup of these plate girders. we also performed an extensive amount of mechanical testing. the two primary were sharpie toughness impact tests and that's a test that resists the strength of the steel plates. and this diagram shows where the toughness specimens were removed from as well as the tensile specimens were removed
10:04 pm
from. we performed the same kind of tests on the first street girders, and this is just a layout of what those looks like. this looks like complicated data, but basically what it shows -- this is the temperature along the x axis, and this is the toughness level along the vertical axis, and what we found and what we typically find for these levels at the toughness surfaces of the plate are very good, and as you go to the t., it drops down. this is characteristic and typical of heavier plates like this, but it's a contributing factor to the fracture because it's in the same location where the defects were. so the defects were sitting in material that had very low toughness. i did want to point out again that the plate itself did meet the requirements for what is specified for this type of
10:05 pm
construction. we ran tensile tests and it met the requirements for what the project were, and that's shown in this table here. one of the things that we're doing as part of the analysis and we haven't completed this as yet, we're doing some stress analysis that's going to allow us to identify what the stresses were due to the loading process as well as the loading that was applied as the structure went into service. the next slide just shows some of the modelling that we're working on right now, the method that's used to determine stresses that we're applying here is called finite stress analysis where we break it up into small pieces and you do the mathematics on those small pieces. we've developed some very preliminary results at this point, and we're looking
10:06 pm
primarily at what the stress right side in the area where the fractures initialled, and this is a look into the access hole, and this is a path of the stresses. here's a typical distribution of what the stresses are. at the hole itself which is right here, the higher the stress corresponds to the red color, the lower stresses are in, you know, green and blue. so in this area where the radius is, the stresses are very high. when you go out from there, the stresses are where they should be that you'd expect from a normal girder. not that you'd expect high stresses in an access girder. these with what you'd expect when you invest geometry into a structure. this slide is kind of -- is a summary of the findings that we have to date.
10:07 pm
essentially, they state that we identifies very shallow cracks because of the cutting process. we know that those formed as -- at elevates temperature, and then once it went into service, the stressed due to normal service were enough to pop those oxidized defects into the main structure that went across the entire girder. and at this stage, we are just about complete with all the metallurgical analysis. we're just about to develop a root cause. and with that, i thank you for
10:08 pm
your time, and if you have any questions, i'll do the best i can to answer them. >> questions from board members? yes, director reiskin? >> so to put it simply -- and i appreciate you taking what is very flex information and putting it in -- complex information and put transgender in fairly lay terms. my understanding is it was the fabrication of the access holes that was the root cause and other issues such as the welding maybe exacerbated the situation? >> well, we haven't arrived at a root cause yet. a significant contributing factor is the presence of these flaws that developed during the fabrication process. we haven't concluded what the driving force -- if it was sufficient to push everything through at this stage, but it's certainly a contributing factor. but i wouldn't assign a root cause. we can't do that until we've conducted an analysis. >> and how would the access
10:09 pm
holes have been fabricated? >> the way they're put into plates like this is that they're thermally cut. they're oxy acetylene cut. when it does that, it's brittle, and it's a very thin player. then after the plates were joined and they were butt welded, the residual stress caused the cracks to pop into those larger, about 1.5 inches long, three-eights of an inch deep cut that you saw there that was very prominent.
10:10 pm
and then, the question becomes whether those -- where does all those stresses come from, are the stresses high in the hole due to a number of different reasons, which we haven't finished evaluating yet. >> and the shape of the access hole looks like it was not round, it was rectangular with round corners? >> yes. essentially it was round with radii as you make the transition from one edge to another edge. >> would it typically be that shape as opposed to a circle that maybe more -- >> there's a number of different shapes that you can have when you cut into plates like this. there's a number of different geometries that are permitted. and then, you have size restrictions and there are requirements for different sizes, which we have not finance issued evaluating at this point. >> and then just as -- last question -- part -- as part of that thermal cutting process, is there any kind of finishing
10:11 pm
process that's a best practice or a normal practice to prevent -- >> depending upon the plate thickness, there are procedures where you're supposed to come in and grind off that surface to a bright metal finish and then perform magnetic particle testing on the ground surface to see if there are any microcracks left, and that's generally done in plates that are greater than 2 inches thick. these plates are 4 inches thick. >> did our specifications required that? >> it's required by the construction code. >> it's required by code? >> by code. >> maybe this isn't a question for you. was that done? >> my understanding is the construction complied with the code, but director reiskin, there's still a lot of questions, and one robert is done with his final analysis, we'll be able to answer
10:12 pm
questions with more detail. >> and what -- when do we expect that work to be done? >> we're targeting next board meeting. i'm putting robert on the spot, but yeah, our thought is to share more details with you at the board meeting. this is just a snapshot, and as robert said, we still have to do the final element analysis to really determine the root cause, so right now, we're just presenting data to you. >> okay. >> yes? >> so i appreciate you slain explainislain -- explaining this in terms that i understand. you've been doing this a long time. you've seen similar failures i assume around the world, and i understand you're still looking for root cause, but in your professional experience, would a failure of this type suggest other places we should look in the design or fabrication of the structure? >> yes. the answer to your question is yes, and we are looking at that now with thornton thomasetti, the engineer of record. we're reviewing all of the shop drawings, we're looking at the
10:13 pm
material specifications to identify what other regions in the structure are potentially susceptible. one of the things that we're doing right now in regard to the safety of the structure is we have technicians looking at right now for example the bolts and connections at the ends of the girders to make sure that they are intact and didn't sustain any damage due to the release of the energy during the girder fractures themselves, so there are a lot of tests being done right now to answer your question. >> so your firm is testing, and those results of other areas will wind their way into a final report? >> yes. we're working with thornton thomasetti on that. >> thank you. >> if i can clarify something. these reports are being turned over to the peer review panel, and the peer review panel will provide us with their input, and we will follow that recommendation.
10:14 pm
>> yes. >> thank you, commissioner gee. thank you for the report and the update. in your report, there have been a number of lab tests performed on different samples. can you just tell us or share with the group, you know, how long these samples or the analysis takes? because we've been trained by network t.v. that you can get a d.n.a. analysis in two minutes. >> i'll be safe. i don't think you can get d.n.a. analysis that quickly, either. i know i've done the d.n.a. thing with ia with ancestry, a takes six weeks. we have several hundred of these sharpie specimens, and each bar is ten by ten millimeters, and you have to put a precise notch in it, and the testing takes -- the reason we're doing this many specimens so we have a thorough statistical understanding of this. it takes weeks.
10:15 pm
>> yes. >> i also want to express my appreciation for your work, your expert on the grounds and clear explanation -- expertise, and clear explanation. what would the stress analysis help us to understand and how would this intersect with any design review that perhaps your firm is not under taking but that someone else on the team is doing? >> right. so the purpose of the stress analysis is that there's a couple of things that we're doing with that. one is to identify what the driving force was, what the influence of residual stresses are, what the influence of the shape and size of the access hole has on the stresses locally that initiated the fracture. the other stress is in terms of the safety and integrity of the rest of the structure, we're performing analysises that will allow us to analyze the
10:16 pm
subseptiblity of the structure in other locations and that goes to your question of integrity in other parts of the structure. >> great. and i don't know if there's another part of the intention, director zabaneh about the peer review. >> robert mentioned other presenters. the next presenter will be the designer and the peer review. but for the directors, we provided this report -- limited report to the peer review. the peer review's also being provided information on the basis of design and the design criteria, so they're also reviewing that, as well. >> any other questions? thank you. >> at this time, i want to invite mr. bruce gibbons with thornton thomasetti to speak to their working with the data and looking at the possible repair me havologies, as well.
10:17 pm
as to the review of the design, some of that's going to be informed by this data gathering for our peer reviews, and thornton thomasetti, just to lend a little more clarity to that. so with that, mr. gibbons. >> thank you, robert. good morning. i'll summarize work that's been undertaken to understand whether any other elements of the building might have been affected by the fracture. so as robert vecchio said, specimens were removed from the girder, so that means about the central 20 inches of the bottom flange was removed and also
10:18 pm
6 inches of the vertical stiffener in the middle. so the intent -- for your -- to get a -- an idea of the scale of this, this repair is localized to this region. it's understood that the cause was localized to the hangar, and the holes around the hangar, so what this repair will do is bypass that region and reinstate the bottom flange so it has the same capacity that was originally designed. there have been calculations that have been reviewed and submitted to the p.r.p. to show that the actual strength in the net girder met the code requirements, so the intent is really to look at the capacity of the existing flange and replace it in kind.
10:19 pm
the first thing to do is there's still some residual welds. that's the gray element, that's the hangar plate which connects to the hangar beneath. those welds will be ground off, everything tidied up, and part testing of the surface just to make sure everything is clean. this is an exploded view of the components of the repair. so -- and this has been discussed also with the fabricators so that everybody i think is in agreement that this is the right fix for an in s u situ installation. it shows two plates that are designed to have the full capacity of the flange. they will be placed on the flange and then drilled through in situ to ensure that there's close alignments for the bolts.
10:20 pm
the bolts themselves are friction bolts. they will deliver the pull capacity of the plates into the flange, and the central stiffener, there are two plates shown just above in the center -- i think i can put with the mouse -- in the center here, which will be installed to bear down on the stop of the new cover plates to reinstate that central stiffener. so that is the -- that's the installed final repair. it has been submitted to p.r.p. for their review. i know that that's happening now, and we welcome their comments on this. the load shedding or -- really, what we've looked at in addition to understand whether
10:21 pm
there could have been any impact from the fracture is to understand whether any load may have redistributioned at the point in which the girder cracked. so first, we looked at the girder itself, and we found that actually the girder, even with the reduced section, had sufficient capacity to carrie the forces around it at the time of the fracture and thereafter. this is partly because it did not experience the full design loads, the live loads on the girder are much less than what would have been anticipated. also, there are load factors in the code. if we look at it -- and we take the load factors out, we can take a look at what the real stresses are at the time of fracture in the girder. also, the midspan bending moments in the girder are somewhat less than designed for because the roof slabs -- the slab are actually very thick, so the slab has capacity to
10:22 pm
distribute load more uniformly on the girder than more centrally than the initial design would have suggested, so the big bending were also less than anticipated. so the consequence of this is that even without the bottom flange, there was sufficient capacity in the bottom of the web of the member to transfer the forces through. the other thing that's relevant is the actual stiffness of the girder was reduced by this crack. but it wasn't significantly reduced, which means there wasn't a lot of deflection when it transferred. so in terms of looking after cracking where the load may have gone, the load will follow the path of stiffness. so as the girder deflects, the load will be transferred to
10:23 pm
adjacent members and those will be other girders themselves and also the slabs. the beam connections, they're bolted -- suppliplice connecti and also the butt stake slab is up to 14 inches thick, so it's actually a very thick element within the structure. so what we did was we bounded the structure. and the conclusions for this, as i said, the girders were actually pretty stiff. the cracks we're estimating about three-quarters of an
10:24 pm
inch. the code allows for life load deflection of 360, so this was much less than what the girder was designed to deflect under full loads. the fact that the deflection is low is reinforced by the observations. there's been no noted damage to finishes within the facility, and also, when we installed the shoring, and we jacked the shoring up, measurements were made of the amount that it was jacked, and it was actually a pretty small amount, so we think this was pretty consistent of what we've seen in the field. from this, we've -- the amount of load that was sheared after cracking we think was somewhere in the neighborhood of 5 to 10%, so it's not a huge load. the other thing is the hangar load's reduced slightly after cracking. and therefore, it reduced the
10:25 pm
demand on the hangar. the consequence of this is the adjacent beams and columns are not always stressed. so we've done stress checks now, looking at this incremental load from the redistribution. we've checked the adjacent members and found that there's no other stressing of those members, and again, those calculations have been submitted to the p.r.p. for their review. so whilst there's no indication of any damage as mr. vecchio said, we're testing the bolting and bolt testing. we want to make sure that there's no physical stress to those elements. so thank you for your time, and i invite my questions. >> questions from board members? no questions?
10:26 pm
yes. >> so it looks like the cracks that had started at the access holes in the original design, when you showed the repair, it didn't look like it had the same access holes, so are they not shown or are they not necessary -- >> the repair is to actually take a continuance plate and bolt it on so there is no welding in this fix. it's essentially a bolted connection and it bypasses that area. >> okay. and so what was the purpose of the access holes to begin with if we don't need them. >> because the original design is a welded girder. so now, given what we have, we feel a bolted connection is simpler. >> so let me try that another way. the access hole was to get the welding equipment in to do the welding of the original buildup? >> correct. >> okay. >> just one clarification. when -- i think you said that
10:27 pm
the building wasn't at the full load it was designed for, but there were buses running and creating vibrations, there were people on the rooftop park, so you're saying that because there weren't as many buses at the weight that it was designed for. >> the roof -- if everyboload d get if you packed as many people as you could get in an elevator. the actual bus deck was designed for 250 pound per square inch of life load. so we assumed in the calculations, i assumed 20 pounds per inch of life load. >> did you do sensitivity analysis on that or is that just an -- >> that's an assumption, but i think it's very valid.
10:28 pm
i think everybody who's looked at the centering service will realize they're really low. >> valid as conservative? >> conservative, yes. >> including with -- sorry. to just follow up, including rain and anything else that could happen, that's anticipated? skbl yes. you know, we did check the roof park loading. we actually looked at the -- the soil as it was delivered was delivered -- they were -- the actual density of the soil is in the delivery sheets, and the density of the soil is quoted as fully saturated, so that's been accounted for in the calculations. >> bruce, let me qualify. when you designed the bus deck,
10:29 pm
did you design it for buses or did you design it for direct loading? >> well, at the time we designed it, the bus deck wasn't deck. it was designed for caltrancaltrans caltrans p-15 loading. the actual design loading on the bus deck was very high and much higher than would be seen by buses. >> can you elaborate on what's a p-50 loading. >> i can't remember. >> how many axles? >> overside load. >> question. is there anything -- since the report we just heard from l.p.i. was preliminary, is there anything that we should sort of wait for as far as the concluesiveness of your recommendation on the fix or
10:30 pm
was this just a preliminary fix concept? >> i don't believe so because -- was of the fact that this -- because of the fact that this bypasses the area. i think everybody knows the area where the failure occurred, and it completely goes around that area. so no, i don't believe so. i don't know what the scheduling is. i suspect that by the time all these models are revealed in the timeline that mr. vecchio revealed, that will probably be before this fix is installed. regardless, i think, and i think most people who have been looking at this agree that this is a pretty fault-free approach not to have to worry about any further revelations from the finite elements analysis. >> director chang, i think that the peer review panel is next.
10:31 pm
he can shed some light -- because we would not move forward until we get their concurrence on the design fix. as bruce mentioned, the preliminary design is being submitted for their review. >> okay. so we'll hear from the peer review panel. thank you very much. >> thank you. >> okay. now that we've heard from our experts, we did want our m.t.c. peer review panel to weigh in on the data received, and for this segment of the presentation, andy fromier from the m.t.c. will present. >> good morning, chair nuru and members of the board. my name is andrew fromier. i'm the deputy director of operations at the m.t.c. commission. on november 15, m.t.c. was asked by the mayors of oakland and san francisco to find the cause of the cracked beams and to make repairs.
10:32 pm
i'm happy to say by october 12 we had accepted the assignment and assembled a peer review planl that included a panel of experts. at that time, m.t.c. committed to an expeditious but thorough review of the failure and proposed fix. we provided an update to the mayor's on november 9 that outlined our approach for conducting the review. we also indicated that we got good -- we have gotten good support from the transbay terminal staff as well as their consultants and contractors and that continues to be the case. they've been very receptive to input by the peer review panel. so what i'd like to do is introduce dr. michael engelhart, who is the chair of our committee. he's a professional engineer, a professor at the department of civil, architectural and environmental engineering at
10:33 pm
the university of texas at austin. he is also the director of the ferguson structural engineering laboratory. he's got a broad array of background in this type of w k work. he is also to be commended on keeping the panel focused on what they're doing. they're spread across the united states, and they have committed to many meetings, both in terms of getting educated on the scope of the work as well as the structure and its cause. so michael is going to talk to you more directly about the makeup of the panel, how we've decided to attack the review and then, the status of that review. dr. engelhart? >> okay. >> if you could -- please. >> good morning. as just mentioned, my name is
10:34 pm
mike engelhart. i'm a professor at the university of texas austin. been there about 30 years, and i have the pleasure of serving as the chair of the peer review panel. just have a few slides to let you know who we are and what we're doing. the makeup of the panel is on the slide. i'm chair. we have several members, including tom sable who's a practicing structural engineer in los angeles, bob shaw, who is a specialist in steel fabrication and welding. and then, when we started this process, m.t.c. let me know that if we needed additional targeted technical expertise as we go through this investigation, that they can bring on additional experts, so we brought on one additional expert. at this point, it's dr. bill moore who's with the edison welding institute in columbus,
10:35 pm
ohio. we brought him onto review what l.p.i. is doing in their stage of the work. we have a fairly broad range of expertise, as andy mentioned. we do have experts on fracture investigations and then more broadly, structural engineering, structural design, and with brian cozy, kind of the bridge expertise. we think we have a pretty good panel that's qualified to look at what's going on. and then, again, as additional issues come up, we'll ask m.t.c., you know, to bring on additional experts. we're probably going to bring on one additional expert very soon to participate in the stage of the study looking at other areas at the transit center where there may be similar conditions prone to brittle fracture where we have the conditions that were similar to what occurred on fremont street to see if there's anything like that anywhere else on the transit here.
10:36 pm
so we're bringing in a specialist and looking at shop drawings and -- to help with that process and to review what's being done by the tjpa team. so that's who we are. so in terms of our marching orders that we have received from m.t.c. and that we're trying to live up to is to first do an independent review. there's very good people working on the tjpa side, very competent people, but it is our job to do an independent review, and we are doing that. and second, to be expeditious. we understand that this is an yurgent situation, and so all f us on the peer review panel are committed to making this a priority. sleepless nights and long weekends and things, but we understand it's an urgent situation, so we're trying to
10:37 pm
be thorough. and to be careful because we understand when this is all said and done, people have to have confidence in this transit center, so we're trying to be very thorough in what we're looking at. we've kept very busy since we were put together on october 12, so constant meetings on-line, conference calls, trips to the transit center, trips to robert's laboratory in new york. meetings with the various consultants, so it's been a very, very active, ongoing process and continues to be so. and mentioned we've gotten very good cooperation with tjpa and the whole list of consultants have been very responsive and provided the information we needed. they're listening to us and so forth. and m.t.c.'s provided us great logistical support to make sure we can get our work done. in terms of the scope of our review in terms of how it's presented to us and how we're
10:38 pm
proceeding, it's listed in these five items. one is to review the temporary shoring system on fremont street and first street. the second was to review the sampling and testing being done -- that has been done by l.p.i., the removal of the material from the girders, the testing plan and so forth. the third thing is to, when it is completed, review the cause -- the root cause of failure as determined by l.p.i. and the rest of the tjpa consultants. our fourth item is to look at the condition of the structure that is -- may have been impacted by the fractured girders. as bruce gibbons just mentioned, there was redistribution of load, so try to make sure that nothing else was damaged in consequence with those fractures, and then, to also look at the repair solution that is being proposed for the fremont street girders. and then, ultimately whatever's
10:39 pm
being proposed for first street, and we haven't seen that yet. in terms of where we're at, essentially, the first two items are essentially done. wi we've completed shoring review and has concurrence with what's been done. this has been done before material samples were done, where it's removed, what will be removed and what tests will be conducted at l.p.i. the third item, looking at the cause of failure, that's ongoing, so we're reviewing the work of l.p.i. i have to say so far we have general concurrence with the investigations that robert vecchio mentioned today. other impacted locations, that's ongoing, so this is
10:40 pm
again, looking at where similar conditions may exist in the transit center that may be -- where there may be the possibility of another fracture, thick materials, intersecting wells, and that's where we're going to bring in a consultant who has a great deal of expertise in that area to review what's being done by the tjpa team. and then finally, the repair approach. what bruce gibbons has presented with the bolted plates, we received kind of the official report from them on tuesday, a couple of days ago, but they've presented preliminary versions to us, and we're in concurrence with that. it's a very reasonable approach, and we're still reviewing the details. we'll get them -- our report on that soon, in the next few days is our target. so that's basically where we stand and what we're doing, and i'd be glad to answer any questions. >> questions from board members?
10:41 pm
yes, director reiskin? >> so first, i want to thank you for kind of getting this up and going quickly and for the short nights and long weekends. i think the three ad jekttives that you used, access, -- ad k adjectives that you used, access, thorough, and slide are what we want. i think what our concern or desire was that this review would look at all structural elements because we only learned of this incidentally because somebody was doing some work and had the good sense to flag something that wouldn't have otherwise been seen or known. so i think what this board is seeking and ultimately the public will be seeking is really a clean bill of health for the entire structure.
10:42 pm
so i don't know if i misread or misinterpreted what you were saying, but i think what we're really seeking is a review of the entire structure. >> right. and so what we're working on is beyond sort of -- we've taken a liberal interpretation of our mission here to be broughter than what is -- broader than what's actually written. so we identified four additional areas that we think should be studied that go beyond just the immediate area of concern. so one of those we've already talked about is just to look at any other locations in the transit center locations where it may be prone to brittle sections. there's a lot of heavy steel in this project, so that will be the entire transit center in
10:43 pm
terms of heavy steel. the second place is the girders that go down to the bus deck level and support them. we feel that they're quite critical members, so we want to have a very close look at their integrity. the third item that we identified and bruce gibbons already talked to it, and it's more along the lines of our scope to say when those girders tracked, did it release a scope, and the fourth issue we looked at was just the issue of fatigue since there are buses rolling in and out of the center. so we have broadened our scope to try to just say as good engineers what we think should be looked at and have passed those recommendations on. >> okay. great. thank you. >> thank you so much for your
10:44 pm
work and that of the panel, professor. is there anyone taking a look at the design of the terminal in terms of just independently looking at the design of the terminal and is that part of your scope or perhaps is that a question for your executive director? >> yep. >> well, two things. we had a peer review panel during the process that looked at the design, and m.t.a. has been presented with the design and looked at the design. >> we're not doing an independent review of the entire design from a to z. we are looking at various specific aspects of the design, and if we see any reason to be concerned that there might be a broader review required, we would certainly say so, but we have not seen that. >> okay. >> so yeah, we don't plan to look from the foundation all the way up to the roof on the design. and from what we've seen, we
10:45 pm
don't see that as being necessary. >> okay. >> director chang, what we can do at the next board meeting, we can bring in the peer review for the design, and have them tell you about how they reviewed the design if you wish. >> colleagues, wish. >> thank you. chairman? >> well, thank you, and i hope i'm not shooting the messenger. i want to clarify on that previous point that i'm asking for somebody to look at everything are, electrical, plumbing, fire, life, safety. as i can emergency, someone has to do something when it rains heavily on the report. if it's not your assignment, perhaps you could recommend who and what should be looked at. my concern, i'm fascinated at what caused the forensic analysis of the fracture, but it seems like this access hole was a commonly accepted practice, but i'm sure that
10:46 pm
somebody was supposed to come along and check the access holes and the welding was properly treated. did it in fact happen, are there records and what else were they supposed to look at, and did that happen? >> our panel is not looking at who's responsible or what was missed or whatever. we're just reviewing, do we understand the technical cause of the failure, what caused those fractures to occur. in terms of why did it happen, you know, why did these conditions occur, that obviously shouldn't. this is not something you expect happen. i don't know if you view that as the responsibility of our panel. >> so i would just like to register my request that that also happened. basically, we're talking about the quality assurance. >> director hursh, may i elaborate on this because we've
10:47 pm
kind of wandered outside a little bit, but i do want to underscore. as i mentioned, we're trying to do a meticulous review and be informed by data. but if i can speak as to the general health and state of the building beyond this spot, beyond structure, the framework that i mentioned last month that we're striving to do is develop criteria that will give us guidance on where to work, what's important, what's not, and that's what this group is starting to develop as it relatives to the structure. the remaining of the building validation plan would include reafirm the structural integrity of the building, which is what we're speaking of. we would be reevaluating the fire and life safety systems, most of which are operational and fine. you know, there are life systems that inform us as to
10:48 pm
their state of -- live systems that inform us as to their state of performance. other systems, we had to peel them away to deal with the immediate area, but at the end of the day, the fire department, fire marshal and our inspectors will go throughout and ensure that the fire and life safety systems are operating and functioning as designed. and beyond fire and life safety systems, somewhat less critical but if you recall, the building has a building management control system throughout, so if there's something going awry in that area through beyond the conditioning, the building will inform us of what may be awry. but then again, we will be, you know, looking at all those systems to ensure that we have a good start point for operations and opening. so the broader question is
10:49 pm
being addressed in the appropriate sequence and format. so i just wanted to underscore that to narrow down your concerns a bit. >> thank you. >> yes. vice chair chu? >> yes. thank you for the update. these are great reports today. mark, i'm just curious, could you share with the board and the public your concerns about how if we just focus on safety, the repair, and opening the transit center what the approval process will look like. you know, who approved, who decides -- will the board decide based on -- what goes first, second, third, and who approves? >> first, we will receive the approval from the peer review panel that will let us know -- approve the fix, provide us with recommendations to what to look for, and provide any other
10:50 pm
approvals that we need. then, we'll undertake that work, and then, we'll present -- and then, ron talked about reverifying the fire-life safety system with the fire department. and then, we'll bring to the board that -- in plenty of time when we accomplished, how we accomplished it, and explain to the board why we're confident that this has all been accomplished and that the building is sound and safe for the public to inhabit it, and then, the board will wish to take any actions they want. >> and it we take it to another -- maybe a little lower detail. so we've heard this state of the forensics. it's fairly on its way, but not complete. we've heard our engineer of record say here's our proposed solution and then, the design and calcs have been submitted to peer review. who decides that that's the right fix, and who approves the fix at that level?
10:51 pm
>> yeah, yeah, absolutely. yeah -- no, we're -- the peer review. we're deferring to the peer review to approve the proposed fix by the designer. once that's done, then, the fix will be implemented by the contractor. that's -- the peer review will also inform us on what areas of the building we need to look at and what should we do if we -- what do we look for, and what potential remedies we need to do. >> the gee are wiengineering -, the peer review says the design will be completed. is that also being submitted for a permit? >> yeah. we'll be working with d.b.i. as well on whatever permits we need and whatever approvals we need. >> and once the permit's issued and d.b.i.'s approved, then, the subsequent repairs are -- >> yes, but i'm hoping that
10:52 pm
things are done in parallels, as well. >> thank you. >> so as we submit the final report for fix to the peer review, we'll be getting approved by d.b.i., as well. >> do we have an estimated timeline for that whole process? >> once we get the approval from the peer review of the fix, we will be in discussions with the contractor. we are in discussions with the contractor on lead time to procure the material and installation. so i'm sorry i don't have a definite date for you, but i'm really hoping at the next board meeting, we can clarify you some clarity as to the interim steps. maybe not when we open the transit officer, but when this particular fix -- the girder fix will be done and other efforts we need to reopen the building. because whatever other investigation we need to do will inform us on when we can open. >> and i just wanted to underscore the importance in terms of permitting and all, we
10:53 pm
also have i.s.i. and our special inspectors on board. so it's not d.b.i. alone. as you know, the tjpa is the authority having jurisdiction, so it's a collection of internal engineers, i.s.i., as well as d.b.i. participating and advancing review and approval each step of the way. if i could backtrack a little bit, i failed to address director hursh's question had everything been looked at appropriately before, and the answer's yes. you may recall there was a very rugged q.a. -- q.c.-q.a. program in place. if you look back at the board meeting of november 2015 that kind of spoke to all the steps
10:54 pm
that were implemented, and turner and pete and our other consultants are reviewing the records as to what transpired in each of these steps to see if there's any red flags coming out of that. short -- we have been doing the q.a.-q.c. program, and we will continue along that route. >> i guess i would ask outside of the girders, and in all your discussions, are there any other items that you believe that we should be looking at at this time that you know of? >> not at this time. again, there's some discussions about what criteria to follow. as i think mentions earlier, there may be areas susceptible to similar loading and conditions, but the check list hasn't been fully developed, but i would imagine it would include areas that have plates
10:55 pm
that are over 2 inches, maybe a concentration of welds, areas that have access holes or weld termination holes. so we're going back and forth on how long is that check list, and what is critical to be an indicator of concern to go back and look rather than go back and look at anything and everything just in the sake of retracing steps that were already traced two or three times already. >> any other board member questions in. >> one last thing. it seemed like there was some indication the peer review could use just in terms of the scope and the presser. i'm hoping that executive director zabaneh, you can take that feedback and do what needs to be done with respect to the m.t.c. peer review scope to
10:56 pm
make sure they have the right direction and resources. >> we're fully engaged with m.t.c., and we'll continue to look at that, but really, we're deferring to the peer review panel to let us know. they're the structural engineers, they're the experts, to let us know what to look at in the building. >> thank you very much. >> okay. thank you. >> that completes our agenda item, i believe. >> clerk: you did have two members of the public that wanted to comment on this item. we had robert hazelton and rafael zabelli. >> hi. i'm robert hazelton. i'm president of the herrick corporation, and we fabricated the girders. thank you for giving me an opportunity to speak today. i don't have a lot of comments
10:57 pm
related to the report. [please stand by]
10:58 pm
are not shown in the design drawings. they were added later on, on approval and subsequent r.f.i. and the peer review, when looking at the design drawings, they would haven't seen the access holes that we're looking at right now. thank you for letting me speak. >> hello, i'm rafael sabelli with walter p. moore. thank you for hearing my comments. i'd like to speak to two things. first of all, i'd like to clarify the scope of what was presented today and then suggest some questions for you to ask the peer review panel and other experts. first of all, the presentation today spoke about a root cause assessment. really it was the first step of a root cause assessment.
10:59 pm
this was just proximate cause, the mechanism of how the crack formed and propulgated. the root cause assessment has to include investigational loading, fatigue, design and specification issues. a root cause assessment often results in a change in practice. i will point out that the fabrication methods used have been used can on previous projects and will continue to be used on future projects. the design detail is not one that is used from previous projects and probably will not be repeated on future projects. some suggested questions include, with respect to the sharpie v-notch toughness, which is very important in the propulgation mechanism, is it low compared to the details.
11:00 pm
the mechanism presented focused on so-called pop-ins that were evident in two of the fractures, but not evident in the third. and that needs to be explored a little bit further. what explains the crack that happened in the third fracture. the micro cracks and hardness that were reported were similar in the whole region and on the cut surface, the outer surface of the flange. so there is -- those things alone do not explain the initiation of the crack and it is that in combination with the stresses in the detail that needs to be investigated. and finally i appointment out that 1st street is currently short and there is discussion of a retrofit for 1st street. so, if the mechanisms that were discussed with respect to the cracks at freemont street, those conditions are not

8 Views

info Stream Only

Uploaded by TV Archive on