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Amazing Old Trestle (a Haupt Bridge)
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<p>[quote user="VGN Jess"]</p> <p>Yep; that's the Appomattox River near Farmville, VA. Not very wide (40-50) yards and not very deep (3-5 ft) in normal flow situations. Where I live (Colonial Heights, VA) the Appomattox becomes over 200 yards wide and 20 feet deep until it's confluence with the James River at Hopewell, VA. The bridge needed to be so high, not because of the river, per se, but because of the deep valley the river carved out hundreds of thousands of years ago.</p> <div style="clear:both;"></div> <p>[/quote]</p> <p class="MsoNormal"><span style="font-family: verdana,geneva;"><span style="font-size: small;">So that little bridge in the lower right corner of the photo must be the wagon road and bridge over the river that was attempted to be burned during the civil war, but proved to be too wet and green to burn.</span></span></p> <p class="MsoNormal"><span style="font-size: small;"><span style="font-family: verdana,geneva;"><span style="font-size: small;"> Referencing this photo again:</span></span></span></p> <p class="MsoNormal"><span style="font-size: small;"><span style="font-family: verdana,geneva;"><span style="font-size: small;"><a href="http://upload.wikimedia.org/wikipedia/commons/b/b4/High_Bridge_Farmville_Virginia.jpg">http://upload.wikimedia.org/wikipedia/commons/b/b4/High_Bridge_Farmville_Virginia.jpg</a></span></span></span></p> <p class="MsoNormal"><span style="font-size: small;"><span style="font-family: verdana,geneva;"><span style="font-size: small;">This bridge known as the “High Bridge” on the South Side Railroad is covered in Civil War Railroads by George Abdill.<span style="mso-spacerun: yes;"> </span>The bridge was fired by the Confederates on 4/7/1865 as they evacuated Petersburg.<span style="mso-spacerun: yes;"> </span>Four of the box trusses burned before the pursuing Federal forces extinguished the fire.<span style="mso-spacerun: yes;"> </span>The fill-in spindly trestlework is temporary replacement for the four trusses that were destroyed by the fire.<span style="mso-spacerun: yes;"> </span>A close-up photo in the book shows the piers to be made of brick, not of stone as mentioned one of the other links to the top post photo.<span style="mso-spacerun: yes;"> </span>The poles of the trestle rest on horizontal members sitting on the surface of the ground rather than being driven in like piling.<span style="mso-spacerun: yes;"> </span></span></span></span></p> <p class="MsoNormal"><span style="font-size: small;"><span style="font-family: verdana,geneva;"><span style="font-size: small;"> <o:p></o:p></span></span></span></p> <p class="MsoNormal"><span style="font-size: small;"><span style="font-family: verdana,geneva;"><span style="font-size: small;">The author shows another bridge with just one of those timber box trusses with the bow or arch timber feature.<span style="mso-spacerun: yes;"> </span>He says that is a special truss designed by the military for quick implementation, as railroad bridges were being continuously destroyed and rebuilt during the Civil war.<span style="mso-spacerun: yes;"> </span>He says the timbers in this type of truss were all alike and interchangeable, and could be reversed end for end and still fit together.<span style="mso-spacerun: yes;"> </span>They could build a bridge in one-third the time with this truss design.<span style="mso-spacerun: yes;"> </span>They could also run on either the top or on the bottom deck.<span style="mso-spacerun: yes;"> </span>That is very interesting insight into the reasoning behind the trusses used on the High Bridge.<span style="mso-spacerun: yes;"> </span>Apparently the expediency of this special truss was attractive for the application of 25 of them to the High Bridge.<span style="mso-spacerun: yes;"> </span></span></span></span></p> <p class="MsoNormal"><span style="font-size: small;"><span style="font-family: verdana,geneva;"><span style="font-size: small;"> <o:p></o:p></span></span></span></p> <p class="MsoNormal"><span style="font-family: verdana,geneva;"><span style="font-size: small;">In an above post, I wondered what purpose was served by the bowed timber arch feature of these box trusses.<span style="mso-spacerun: yes;"> </span>Without that feature, this type of timber truss requires iron rods in tension between the top and bottom chords.<span style="mso-spacerun: yes;"> </span>I don’t know if this military truss was built completely without iron hardware, but I suspect that it did not use iron tension rods.<span style="mso-spacerun: yes;"> </span>So the arch is the element that creates the triangulation needed to support the span.<span style="mso-spacerun: yes;"> </span>The rest of the timber box holds the arch in position and compliments the structure.</span></span></p> <p class="MsoNormal"><span style="font-size: small;"><span style="font-family: verdana,geneva;"><span style="font-size: small;"> <o:p></o:p></span></span></span></p> <p><span style="font-size: 12pt; mso-fareast-font-family: 'Times New Roman'; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;"><span style="font-family: verdana,geneva;"><span style="font-size: small;">So this is a highly specialized railroad bridge truss that would be interesting to research further.<span style="mso-spacerun: yes;"> </span>The citation in the book does not provide a name for this type of truss.<span style="mso-spacerun: yes;"> </span>This special truss meant that erecting bridge structures could be prosecuted so rapidly that bridge foeman, E. C. Smeed expressed his humorous opinion that he could assemble such a bridge about as fast as a dog could trot.<span style="mso-spacerun: yes;"> </span></span></span></span></p>
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