DeSimone Consulting Engineers is one of only ten New York based structural engineering companies that have been at the World Trade Center site since the events of September 11, 2001. Originally on a volunteer basis, DCE is now contracted by the Department of Design and Construction of New York to serve as one of the assessment and safety teams that have been working ‘round-the-clock’ shifts since the tragedy.
DCE has been involved in many areas of the rescue and removal effort. The early weeks were spent assisting FEMA and FDNY in their search and rescue operations. We reviewed building plans to locate stairwells and other exit points where the FDNY should concentrate their effort. In order to access the stair towers, routing was assessed taking into account falling debris and collapse potential. We worked with the FDNY to secure portions of the towers that were precariously canted against and on top of surrounding intact structures. In addition, damaged scaffolding and shattered windows were assessed as to their potential dangers to the workers. Finally, DCE had several teams of people performing Rapid Assessments of the perimeter structures (per ATC-20 guidelines) to determine the extent of structural damage.
Once the search and rescue operation shifted to search and recovery, DCE continued working at the site to provide engineering and safety assistance to the construction companies mired in the debris removal operations. Throughout the site many large tower pieces were interlaced making removal difficult. DCE worked with the construction companies to find safe sequences to remove the debris that would not cause further collapse or shifting of the rubble. Member weights were determined to define cut lengths that could be achieved by adjacent cranes with large outstretched boom spans. The sequence and removal of the 14-story corner of Tower 2 known as the “fence” was a particularly long and painstaking process due to the inherent potential instabilities of the section.
Once some of the major interior pieces were removed, DCE worked to find ways of bringing the cranes and equipment into the central regions of the site. We evaluated the existing structures for safe areas to drive trucks and cranes. As the removal started to drop below grade level, we were involved in the safety issues concerning the slurry wall for the below grade complex. Many of the below grade floor slabs that braced the wall were not intact. Therefore, many tiebacks had to be installed through the slurry wall before it was safe to proceed.
At the end of the twelve-hour shift our team must file a report with
DDC and then brief the command post and the next engineering group on the
activities that transpired earlier. DCE is continuing to provide
engineering service into the New Year and hopes to be part of the rebuilding
Photos by A. Christopher Cerino – PSUAE ‘95 and DCE