Research For The Retrofit Scheme Of Xingtan Bridge

Xingtan Bridge locates at 1353+440 of NH 106 (National Highway) in Yangxin Country. It was originally designed as a reinforced concrete T-shaped beam bridgewith 6 spans of 16. 8m for each and 2 spans of 22. 2m for each. It was buiIt up and opened to traffic in 1972. As the reinforced concrete highway bridge built in 1960s ?70s in China, the load-bearing capacity of Xingtan Bridge is insufficient clue to the increasing traffic and the overloading of trailers and container vehicles.On the other hand,the bridge was wore out and damaged.So,a perfect retrofit scheme needs to be carried out in order to meet both safe and economical demands.After examining and assessing to the bridge in field, InspectIon Center of Water Transportation in llubet Province conducted carried out the following con elusions: scrious weathering and fractureon every pier surface; the concrete strength of T-boiims lower tlinn the originally design; and the originally designed load class of truck-13 and trailer-60 can't meet the present demand of truck-20 and trailcr-100 by secondary road.The research of the retrofit scheme includes the following two aspects:First 1y,what kinds of retrofit measures should be Used for the insufficient strength of the pier concrete? This is also the key problem discussed in this thesis. How to design and chocking the distributions of the stress between the now and old concretes,which possess different strength classes since the method of enlarging diameters of piers tends to be applied? This thesis suitably solve the problem of stress distributions between the concrete parts with different strength classes under tlie partially comprossion by regarding the do.design strength as t.he calculate strength in enlarging parts, and the tested strength as the calculate strength of the exlsting conerete.Secondly, the reinterced concroto T ?shaped benm shuld be strong thened.the T-shaped benm of the or glanl superst theture was implomentod neeording to the standnrd design issued by the Ministry of Communications in 1964. The main problem won1d be whether tenslle stregth conld sallsfy the demand of truck-20and trailer-100.After calculating internal forces.it is confirmed that the T-shaped beams with 16. 8m per span can meet the demand,while the ones with 22. 2m per span need to be replaced by prestressed concrete T-shaped beams to meet the demand. As to the problem of the insufficient concrete strength of slabs and wings,the method of enlarging the thick is employed to deal with.