Page 18 - Wire Rope News & Sling Technology
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continued from page 16
         note:  see  our article about the Akashi
         Kaikyo Bridge in the August 2014 issue
         of Wire Rope News.
           From an engineering viewpoint,
         there  is  a  better  ranking  method  if
         you realize the wire cables are always
         much longer than the main span.
         They must extend from one anchorage
         to the other. In 1883, when Rudolph
         Hering of the American Society of Civ-
         il Engineers emphasized the longer
         distance, he pointed out there were
         actually three spans of the Brooklyn
         Bridge. The four main cables, each of
         which is made up from 19 bundles of
         wire, extend 3455 feet between their
         anchorages! The 19 bundles, (which
         are  called  “strands”)  are  made  with
         wire looping back upon itself so that
         each is, in effect, only one long length
         of wire spliced end-to-end repeatedly.
         The 1864 Adams Plan                The Brooklyn Wire Mill on Imlay Street in the Red Hook neighborhood of Brooklyn as it looks today.
           Steel was relatively new as a struc-  The former Eagleton company name is still faintly visible on the building. All of the load-bearing
         tural metal in 1864  when  Julius Ad-  steel wire for the main cables was drawn and galvanized in this building. Photo by Maggie Blanck
         ams and Alfred Craven published their   from an entirely new and untried direc-  works the same with steel.
         plan to build a steel suspension bridge   tion. He visualized a concept of using   As of 1864, the foremost wire bridge
         across the East River from Brooklyn to   rolled steel ribbons to be joined end to   builder in the USA was John A Roe-
         Manhattan, two of the three largest cit-  end to stretch almost any length, and   bling. He was in the process of com-
         ies in the United States. The designer/  stacked carefully into a squared mass   pleting his Ohio River bridge between
         builder of the Brooklyn Bridge, Wash-  which could next be strapped outside to   Covington,  KY  and Cincinnati,  OH.
         ington Roebling, described it in 1896:  hold its shape. No one had ever created   He had been interested in the idea of
           “It was the dream of every engineer,   a steel ribbon suspension  bridge like   a bridge over the East River for many
         but  its  seeming  impracticability  made   his proposal, but Adams was a Brook-  years.  Kingsley  visualized  Roebling
         it appear an empty one. To Colonel Ju-  lyn resident. He had designed the city’s   as the right man to make plans.  By
         lius  W.  Adams  belongs  the  credit  for   sewer system. When his plan was pub-  enlisting  a  politician  named Murphy,
         first  showing  how  the  plan  might  be   lished it was noticed by William King-  he gained legislative approval for a
         consummated. Colonel Adams’ reputa-  sley, one of the leading construction   bridge based on Adams’ plan. He also
         tion was well-established  before that   contractors in Brooklyn.     convened a group of experts (including
         time and his ideas when first breached    Most of the longest-span suspension   Adams) who concurred Roebling was a
         received careful attention.”       bridges at that time were built with   better choice for the job. The selection
           The approach taken by Adams came   cables made of iron wire. Grooved rolls   of Roebling established the concept of a
                                            for producing long rods were an in-  wire-cable supported bridge closely re-
                                            novation of the prior century, but the   sembling his Ohio River crossing.
                                            starting point for any coil of wire was
                                            always the weight of a single rod rolled   The Wire Mill in Brooklyn
                                            in a rod mill. As of 1864, there was no   Brooklyn Bridge was built during
                                            way to make a 3500-foot length of iron   what we call the Victorian Era, named
                                            wire or steel wire in one piece because   for the  queen of  the UK  who  reigned
                                            there was no way to make a rod long   1837-1901.  During  that era,  female
                                            enough and heavy enough to be drawn   clothing fashions were dominated
                                            to that length.                    by  crinolines, better known as “hoop
                                              Another crucial  issue was the sea-  skirts.”  Steel  wire  was  being  used  in
                                            coast  environment.  Salt air  corrodes   short lengths for things like hoop skirts,
                                            iron very quickly. The East River is ac-  but  there  wasn’t  any  commercial  de-
                                            tually a tidal strait. Some engineers in   mand for long lengths of steel wire.
                                            Europe had adopted a practice of clean-  Although Roebling owned a factory at
                                            ing the surface of sheet iron before dip-  Trenton, NJ with a rolling mill and wire
         Brooklyn Bridge was built in the Victorian Era,
         named for the queen of the UK who reigned   ping it in  molten zinc  to protect it.  A   drawing  blocks  for  making  iron  wire,
         1837-1901. This portrait of Queen Victoria   French  chemist,  Stanislas  Sorel,  had   he wasn’t enthusiastic about steel wire.
         shows  her wearing crinolines, better  known   popularized the  name  “galvanizing”   He was influenced by the metallurgical
         as “hoop skirts”. She is seated at a spinning   for this technique. It was often called   opinions of his close friend Frederick
         wheel, a machine common in European and
         American homes. The similar appearance of   the sacrificial method because salt air   Overman.  Washington  Roebling  later
         the Roebling’s traveling wheel is the reason the   first attacks the zinc outer layer prefer-  said:  “…he paid but little attention to
         process became known as “spinning a cable”.  entially, thereby protecting the iron. It   continued on page 20

         18     Wire Rope News & Sling Technology   February 2017
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