The "Anatomy & Physiology" Of the Structural Fireground by ProQuest

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									  FIRE SERVICE LEADERSHIP                                                        >>>
 By MARK EMERY




    The “Anatomy & Physiology”
    Of the Structural Fireground
Part 5 – Tension & Compression




                                             I
                                                    believe there is no better way to understand the relationship between tension and
                                                    compression than to analyze how a suspension bridge works. Perhaps there is no bet-
                                                    ter suspension bridge to analyze than the Golden Gate Bridge in San Francisco, CA.

                                                  There are plenty of books and manuals that define tension and compression, but do firefight-
                                             ers truly understand the tension/compression relationship and why structural engineers choose
                                             either tension or compression to move stress from one structural component to the next? This
                                             article will describe how the Golden Gate Bridge uses tension and compression to transfer live
                                             and dead loads – cars, trucks, concrete, steel, rain, wind, people and concrete – to the bottom of
                                             San Francisco Bay as compression. We begin with some Golden Gate Bridge background, fol-
                                             lowed with a photographic tour that will describe how the bridge uses tension and compression
                                             to resist gravity.

                                             The Golden Gate Bridge
                                                  Engineered by Joseph B. Strauss, Golden Gate Bridge construction started in 1933 and was
                                             completed in 1937 at a cost of $27 million – five months late and $1.3 million under budget. (Strauss
MARK EMERY, EFO, is a shift battalion        said, “It took two decades and 200 million words to convince people that the bridge was feasible.”)
chief with the Woodinville, WA, Fire &       Eleven workers were killed during construction; at least 1,200 people have jumped from the bridge.
Life Safety District. He is a graduate of
the National Fire Academy’s Executive Fire   From abutment to abutment, the Golden Gate Bridge stretches 1.7 miles (8,981 feet). The total
Officer program and an NFA instructor spe-   length of the suspended span sections is 1.2 miles (6,450 feet). The middle span suspended between
cialist. Emery received a bachelor of arts   the towers stretches 4,200 feet. The length of one side span is 1,125 feet. The highest clearance above
degree from California State University at   the water is 220 feet. The height of the towers above the water is 746 feet. The height of the towers
Long Beach and is a partner with Fire Com-   above the roadway is 500 feet. The width of the bridge is 90 feet. The width of the roadway between
mand Seattle LLC in King County, WA. He
may be contacted at fci@usa.com or access    curbs is 62 feet. The sidewalk is 10 feet wide. Each leg of each tower base measures 33 by 54 feet.
his website www.competentcommand.com.             As of 1986, the total combined dead load of the Golden Gate (bridge, anchorages and ap-
                                             proaches) was 887,000 tons. The live-load capacity was calculated to be 4,000 pounds per lineal
88 Firehouse               ®
                                                                    www.Firehouse.com                                                November 2009
                                                                                 >>> FIRE SERVICE LEADERSHIP

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