Show TRAFFIC WEAR ON BRIDGES now mow instrument measures measure with eclen I 1 title tine precision the effect of I 1 every shock prepared by th un J states department 0 of A A new instrument delind del ed iod by the bureau of public roads of tile the united department or of agriculture measures with scientific precision tile the effect of every aery shock and blow delivered by moving vehicles in cr crossing a bridge attached to tiny any part of the bridge this eniti athes ft a gerord of the effect of the moving lond the th amount of nt stretching or shortening of the part its BB pt result of the chocks Is 1 rep rement ed d hy by n R fine black line on the photo km X ph no blow or shock hoek crin he b delivered ra quickly that ha in will not reco record rd its ita effect it has never neter before been pos possible able to raen gure the effect of such blows have long heen been I 1 able to ro the effect of standing londs very terr exactly lint be cArvie of their inability to measure the effect 0 of delivered blows or impacts they betris never neter heen been able to proportion he ahm barlous parts of a with absolute abo lute insurance amii ans rance urance it hai heen been necessary essary to make a liberal allowance for this unknown quantity nun tUy in bonte the allowance allo has not heen been sufficient and the bridges have collapsed under movina loada many bridles still in arp probably pro bubly too weak to withstand safely tile the sharp blow blot 0 ot swiftly Il moving loving i chicles vehicles though they will safely carry tho the antna vehicles at rest reft or moving at slow speed tho far nIllar warning at the portals of a bridge limit on oil this bridge eight nilles miles per hour means that the alie lealan of tho the bridge to which alch it la Is attached Is not strong enough to allow for impact in the light of the recent ex experiments its with motor truck in ili which it was shown that a swiftly il loving motor Co concheta cochet Con creta cret structure built to withstand swiftly moving heavily loaded Motor truck trucks truck track mry may strike a aln blow equivalent to seven times its actual weight it I 1 t 1 IS rather the depart department nien t rond experts say that failures have hae been so few it is believed this new measuring instrument ment will anon in do away with uncertainty the knowledge pained by its use will enable the engineer to design bridgen hr halilah lilaH which are sure to hold up under frat fant moving vehlen lel anil to britie such auch bridges without endue waste of material anti and maney |