HOW DID THE TITANIC SINK? part 1

By Dan Deitz, Executive Editor of MEMAGAZINE
This article is based on a paper, "Titanic, The Anatomy of a Disaster, A Report from the Marine Forensic Panel,"presented at the 1997 annual meeting of the Society of Naval Architects and Marine Engineers, that documents the work of William H. Garzke, Jr. and David Wood, Gibbs & Cox, Inc.; David K. Brown, RCNC; Paul K. Matthias, Polaris Imaging; Dr. Roy Cullimore, University of Regina; David Livingstone, Harland & Wolff; Prof. H.P. Leighly, Jr., University of Missouri-Rolla; Dr. Timothy Foecke, National Institute of Standards and Technology; and Arthur Sandiford, Consultant. Eyewitness accounts are from various sources, including the official transcripts of the 1912 U.S. Senate investigation.

When our boat had rowed about half a mile from the vessel, the Titanic—which was illuminated from stem to stern—was perfectly stationary, like some fantastic piece of stage scenery,"recalled Pierre Marechal, a French aviator and a surviving first-class passenger of the ill-fated liner. "Presently, the gigantic ship began to sink by the bows ... suddenly the lights went out, and an immense clamor filled the air. Little by little, the Titanic settled down ... and sank without noise ... In the final spasm the stern of the leviathan stood in the air and then the vessel finally disappeared."
British and U.S. investigations of the Titanic tragedy have resulted in greater lifeboat capacity, improved subdivision of ships, and the creation of an ice patrol.
Elmer Z. Taylor, who watched from Lifeboat No. 5, close enough to the Titanic to observe its final demise, would later write, "The cracking sound, quite audible a quarter of a mile away, was due, in my opinion, to tearing of the ship's plates apart, or that part of the hull below the expansion joints, thus breaking the back at a point almost midway the length of the ship."
"At that time the band was playing a ragtime tune, "remembered Harold Sydney Bride, the surviving wireless operator of the Titanic. "I saw a collapsible boat on deck ... I went to help when a big wave swept it off, carrying me with it. The boat was overturned and I was beneath it, but I managed to get clear. I swam with all my might and I suppose I was 150 feet away when the Titanic, with her aft quarter sticking straight up, began to settle."
"The orchestra belonging to the first cabin assembled on deck as the liner was going down and played 'Nearer My God to Thee.' By that time,"as Miss C. Bounnell, first-class survivor, relived the night, "most of the lifeboats were some distance away and only a faint sound of the strains of the hymn could be heard. As we pulled away from the ship, we noticed that she was hog-backed, showing she was already breaking in two."
Four survivors with firsthand knowledge, remembering probably the most important—certainly the most traumatic—event in their lives, disagreed on one major point, and it has remained a mystery for more than 80 years: Did the Titanicbreak apart at the surface or sink intact?
Although all the officers testified that the ship sank intact, some survivors and crew testified to a hull failure at the surface. Even during the American and British inquiries into the disaster, few questions focused on the structural aspects of the ship. Despite survivors' testimonies, it was concluded that the ship sank intact.


Evidence from the DepthsThe mystery arose again when the wreck of the Titanic was discovered in 1985 and the hull was found in two pieces. Many theories were developed as to how the ship broke apart during the sinking process, and research was begun to determine how this could have happened. The speculation intensified further when the wreck site was revisited in 1986 and a third 17.4-meter section from the midship region of the ship was found.
To help solve this mystery, the Discovery Channel, in developing its award-winning "Titanic: Anatomy of a Disaster"television documentary, approached Gibbs & Cox, Inc., one of the oldest naval architecture and marine engineering firms in the world. Gibbs & Cox agreed to perform a stress analysis to help determine the possibility of hull fracture at the surface.
With funding provided jointly by the Discovery Channel and the Society of Naval Architects and Marine Engineers, Gibbs & Cox conducted a basic study of the breakup of RMSTitanic using linear finite-element-analysis (FEA) software. This study was done in conjunction with materials testing of the Titanic steel by the University of Missouri-Rolla, with advice from Prof. H.P. Leighly Jr., Dr. Timothy Foecke, and Dr. Harold Reemsnyder of the Bethlehem Steel Corp.'s Homer Research Laboratory in Bethlehem, Pa.
Important to the analysis effort was accurate weight and buoyancy data for the ship at the time it struck the iceberg, and then later while it was sinking. These data were provided via a recent study of the ship's breakup undertaken for another technical paper, "The Titanic and Lusitania, A Final Forensic Analysis,"published in a 1996 issue of Marine Technology. The study provided the loading information needed to take "snapshots"of the ship's state of stress during the sinking process. Tests conducted on the steel recovered from the wreck site were performed at the University of Missouri and the National Institute of Standards and Technology in Gaithersburg, Md. The results from these metallurgical tests of Titanic steel and rivets were also input as data for the finite element analysis.
Gibbs & Cox engineers selected MSC/NASTRAN, from the MacNeal-Schwendler Corp. in Los Angeles, to perform the analysis. FEMAP engineering-analysis modeling and visualization software from Enterprise Software Products in Exton, Pa., was used to perform the pre- and postprocessing of the analyses. Gibbs & Cox had been using MSC/NASTRAN for approximately five years. According to David Wood, the firm's structures department manager, MSC worked closely with his team during the development of MSC/NASTRAN Version 70 to provide the special program solutions needed for use in their industry.
Engineers analyzed the stresses in the Titanic as the flooding progressed within the bow region, using modern FEA techniques that simply were not available until the 1960s, and certainly were not known to the structural designers of the ship in the first decades of the century. In the 1960s, engineers started to analyze the stresses in ship hulls using finite-element modeling (FEM). As a pioneer of FEA technology, MSC has been in the forefront of dramatically improving this technique to take advantage of advances in computer technology.
A full-ship model was graphically constructed, employing a modern approach similar to that used for U.S. Navy destroyers and cruisers today. Loadings for the model were developed based on one flooding scenario from the paper, "The Sinking of the Titanic,"by Chris Hackett and John C. Bedford.
The corresponding weight and buoyancy curves, developed by Arthur Sandiford and William H. Garzke, Jr., were used to model the critical flooding conditions believed to represent the hull loading just prior to hull fracture. Since the flooding process took place over several hours, a quasi-static analysis was considered appropriate. The initial modeling effort focused on the determination of the location and magnitude of high-stress regions that developed in the hull while she remained on the surface.
Engineers determined that stress levels in the midsection of the ship were at least up to the yield strength of the steel just prior to sinking. When considered alone, stresses at these levels do not indisputably imply catastrophic failure. Additional analyses, focusing on probable locations of initial hull fracture, are required to indicate that the ship sustained possible catastrophic failure at the surface and began to break apart.
Significant stresses were developed in the vicinity of the two expansion joints, and in the inner bottom of the ship between the forward end of Boiler Room No. 1 and the aft end of the Reciprocating Engine Room. Structural discontinuities, such as expansion joints, result in stress-concentration development. Typically, stress concentration levels are three to four times that of free-field stresses. While these structural discontinuities have not yet been thoroughly investigated, it is believed that stresses developed at these locations were significantly higher than the material yield stress.

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