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. 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 its

microcracks. >> when it cools, it forms a structure that can be very brittle. and it cracks very easily. but it's a very thin layer. >> reporter: robert vekio is the president of lpi which conducted the tests. it was either stress from the construction or the use of the building that caused these microcracks. that then contributed to the two larger cracks, which forced the closure of the transbay transit center. heard corporation was responsible for fabricating the beams that cracked. the president underlined that these findings are prelimy.ar you say it could be a design issue or a fabrication issue, and you have presentations that only look at the fabrication and materials, i feel like i'm underrepresented right now. >> reporter: a final report on the root cause of the cracks is expected by next month. in the meantime, a fix to the problem was presented today. it's expected to be approved by the peer review panel of engineers within the next few weeks. >> put a plate underneath the crack flange and one plate on top of the cracked flange and tie them up with bolts. >> reporter: as for w

microcracks. >> when it cools, the molten surface layer of the steel cools very rapidly and forms a structure which can be very brittle and because it's so brittle, it cracks very easily, but it's a very thin layer. >> robert is the president of lpi, an independent company out of new york which conducted the tests. it was either the stress from the construction or the use of the building that caused these microcracks. that then contributed to the two larger cracks which forced the closure of the transbay transit center. the corporation was responsible for fabricating the beams that cracked. its president today underlined the findings are preliminary. >> i think when you say hey, it could be a design issue, it could be a fabrication issue, then you have presentations that really only look at the fabrication and materials, i feel like i'm underrepresented right now. and i think we have more things to talk about. >> members of the transbay joint powers authority were told a final report on the root cause of the cracks is expected by next month. in the meantime, a fix to the problem was presented today. it's expected to b