Gadar Big Four

Gadar Big Four gada ce mai tsawon ƙafa shida wadda ta ratsa Kogin Ohio, wadda ta haɗa Louisville, Kentucky, da Jeffersonville, Indiana . An kammala ta a shekarar 1895 kuma aka sake gina ta a shekarar 1929. An cire ta daga aikin layin dogo a shekarar 1968, kuma an fara cire hanyoyin da suka shafi zirga-zirgar jiragen ƙasa zuwa manyan hanyoyin a tsakanin 1974 zuwa 1975, wanda hakan ya ba wa Babban Gadar Lakabi da "Gadar da Ba Ta Zuwa Ko'ina". An mayar da ita ga amfani da keke da masu tafiya a ƙasa a shekarar 2013. Tsawonta ya kai  ; dukkan gadar ta kai  . Sunanta ya samo asali ne daga tsohon layin dogo na Cleveland, Cincinnati, Chicago da St. Louis, wanda aka yi wa lakabi da "Babban Layin Dogo na Huɗu".

 Bayani 
Babban Gadar Hudu gada ce mai tsawon ƙafa shida, wadda jimillarta ta kai  tsayi,  tare da fadin  . Tsawon arewa shine wani shinge mai sassa takwas, mai siffar Parker mai tsawon  tsayi, kuma an yi su da rivets, Pennsylvania mai bangarori 16 ta cikin trusses. Ra'ayoyin kudu guda biyu an yi su da rivets, Parker mai bangarori 10 ta cikin trusses. 

Da farko yana ɗauke da layin dogo ɗaya tilo . A yau, hanyar shiga Babban Gadar Huɗu ta takaita ne ga masu tafiya a ƙasa da kuma masu keke.

 Gadar asali 

 Tsare-tsare da gini 
An fara ƙirƙirar gadar Big Four a Jeffersonville a shekarar 1885 ta hanyar wasu abubuwan da suka shafi birni. An kafa Kamfanin Gadar Louisville da Jeffersonville a shekarar 1887 don gina gadar Big Four, bayan wani hayar da jihar Indiana ta yi; Kentucky ita ma ta yi hayar kamfanin a shekarar 1888. Masana'antar jiragen ruwa na kogi, babban abin da ya shafi tattalin arziki a Jeffersonville, ta nemi a gina gadar daga magudanar ruwa ta Ohio, amma Rundunar Injiniyoyi ta Amurka ta amince da wurin ginin, ko da bayan zanga-zangar da aka yi. 

An fara ginin ne a ranar 10 ga Oktoba, 1888. Gadar Big Four ita ce kawai gadar Louisville da ke da manyan haɗurra a lokacin gininta; mutane 37 sun mutu a lokacin gininta. 14 na farko sun mutu a ranar 9 ga Janairu, 1890, da ƙarfe 5:40 na yamma yayin da suke aiki a kan gidauniyar Pier Number 5 lokacin da wani kauye da ake tsammanin zai hana ruwan kogin ambaliya, ya nutsar da ma'aikatan. Wasu maza shida sun mutu bayan 'yan watanni a ranar 14 ga Mayu, 1890, da ƙarfe 5:10 na yamma lokacin da wani katako ya karye yayin da yake aiki a kan wani kauye daban, Kauyen Pier Number 4. 

Babbar Babbar Babba tana da daya daga cikin manyan bala'o'in gada a Amurka, wanda ya faru a ranar 15 ga Disamba, 1893, a karfe 10:20 na safe lokacin da iska mai karfi ta rushe wani gini, wanda ya haifar da lalacewar goyon bayan truss kuma truss - tare da ma'aikata arba'in da daya a ciki - ya fada cikin Kogin Ohio. Ashirin daga cikin ma'aikatan sun tsira, amma 21 sun mutu. Hadarin kusan ya kashe rayuka da yawa, yayin da jirgin ruwa da ke tsallaka Kogin Ohio kawai ya rasa ta hanyar bugawa. Sa'o'i bayan haka, wani sashi kusa da lalacewar ya fada cikin kogi, amma ba a shagaltar da shi a lokacin ba, ba tare da haifar da rauni ba. A sakamakon haka, an karfafa aikin ƙarya don hana ci gaba da faruwa, da kuma hana iskõki masu ƙarfi daga haifar da irin wannan lalacewa ta hanyar amfani da ƙarfafawa na musamman a kan ƙasan ƙasa na truss. Har ila yau, an tilasta sabuwar doka: "ba za a taɓa amincewa da haɗin gwiwa ba fiye da yadda ya kamata don sanya wanda aka ɗora a wurin".

 Manazarta