Influence Of Revision Of The Load And Load Combination On The Design Of Standard Span Highway Concrete Bridge

Aiming at the problems,experiences and techniques in the process of bridge construction in recent years,the Ministry of Transport released a series of specifications in 2015 to solve the adaptability problem of the old specifications in the new period.As a guidance document of bridge design,the revision of General Code for Design of Highway Bridges and Culverts(the JTG D60-2015)and Code for Design of Highway Reinforce Concrete and Pre-stressed Concrete Bridges and Culvers(JTG D62-2015)has a great influence on the design and construction of small and medium-span bridges which are widely used in our country.By calculating and analyzing the commonly used standard span simply supported slab bridges and simply supported T beams selected from the Standard Drawings which was published by the Ministry of Transport,this paper compared and studied the revision part between the new and old codes,and assessed the applicability of Standard Drawings under the new specification.The main contents are as follows:(1)By studying and and analysing the new and old codes,this paper summarized the revision of the new specification at the aspects of materials use,load effects and its combinations,stress crack resistance,crack width,and deformation etc.What's more,the differences of vehicle load standard and correlation coefficient between the two codes are emphasized.(2)The load effects,bearing capacity,stresses and deflection of the sample bridges were obtained by calculating the strength limit states and service limit states under the short-term stage or sustainability of operation.Then this paper made a comparative analysis based on the above data under the new and old codes.And the results showed that the new specification significantly increase the design internal force value of the small and medium-span simply supported beam bridges,especially,the maximum growth rate of design value of mid-span moment almost reach 30%.At the same time,the new specification improves the control of the crack width,crack resistance and simplifies the deflection calculation of the reinforced concrete slab bridge by the revision of the formula and load effect.(3)Based on the above calculation results,the applicability of the Standard Drawings under the new specification is checked.The results show that the Standard Drawings does not meet the bearing capacity requirements for reinforced concrete slab bridges.For prestressed concrete beams bridges,Standard Drawings can continue to apply,but the safety reserves have been reduced.The study can provide theoretical basis for bridge designers to refer to Standard Drawings design and provide a reference for whether the original bridge can continue to serve under the new standard.