Built in the late 1950s, the Cypress Street Viaduct, a stretch of Interstate 880, was a double-deck freeway section made of nonductile reinforced concrete[60] that was constructed above and astride Cypress Street in Oakland. Roughly half of the land the Cypress Viaduct was built on was filled marshland, and half was somewhat more stable alluvium.[61] Because of new highway structure design guidelines—the requirement of ductile construction elements—instituted following the 1971 San Fernando earthquake, a limited degree of earthquake reinforcement was retrofitted to the Cypress Viaduct in 1977. The added elements were longitudinal restraints at transverse expansion joints in the box girder spans, but no studies were made of possible failure modes specific to the Cypress Viaduct.
fra74 wrote: 2) Il terremoto negli Stati Uniti di cui parla con crollo di ponti e viadotti è sicuramente quello di Loma Prieta del 1989. Peccato
Wiki EN Northridge earthquake wrote:The earthquake also gained worldwide attention because of damage to the vast freeway network, which serves millions of commuters every day. The most notable of this damage was to the Santa Monica Freeway, Interstate 10, known as the busiest freeway in the United States, congesting nearby surface roads for three months while the freeway was repaired. Farther north, the Newhall Pass interchange of Interstate 5 (the Golden State Freeway) and State Route 14 (the Antelope Valley Freeway) collapsed as it had 23 years earlier in the 1971 Sylmar earthquake even though it had been rebuilt with minor improvements to the structural components.
Wiki IT terremoto di kobe wrote:La dimensione dei danni fu assai più grande di quella del terremoto di Northridge, che era avvenuto esattamente un anno prima. La differenza della dimensione dei danni fu in parte dovuta al tipo di sottosuolo sul quale era costruita la città di Kobe e sulla tipologia delle costruzioni (molte case di antica costruzione non dotate di strutture in calcestruzzo vennero rase al suolo). Inoltre l'intensità del sisma fu molto più elevata (~7.3 contro ~6.6 a Northridge). La popolazione coinvolta nei due terremoti (Kobe e San Fernando Valley di Los Angeles) fu invece circa la stessa intorno a 2 milioni di abitanti.
fra74 wrote:nel caso di Kobe è ben risaputo che l'autostrada crollata fu costruita secondo standard edilizi assolutamente inadatti, tanto che furono cambiati più volte fino all'inizio degli anni '80 ma i nuovi standard si applicavano solo alle nuove strutture, quindi il ragionamento dell'autore si basa su una ipotesi non vera
Poi lasciamo stare come liquida i problemi di sicurezza nelle gallerie...
Great Hanshin earthquake wrote:The damage to highways and subways was the most graphic image of the earthquake, and images of the collapsed elevated Hanshin Expressway made front pages of newspapers worldwide. Most people in Japan believed those structures to be relatively safe from earthquake damage because of the steel-reinforced concrete design. Although the initial belief was construction had been negligent, it was later shown that most of the collapsed structures were constructed properly according to the building codes in force in the 1960s. However, the steel-reinforcement specifications in the 1960s regulations had already been discovered to be inadequate and revised several times, the latest revision being in 1981, which proved effective but only applied to new structures.
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