Study On The Effect Of Bridge Jack-Up Construction On Driving Comfort

Jacking construction is the bridge reconstruction method which has been widely used in recent years. This technology realizes the functions such as connecting with the new roads and increasing the clearance under the bridge by way of elevating the elevation of each section of the bridge without destroying the structure of the main bridge. It gains more and more attention because of its good economic performance, short construction period and the characteristics of energy saving and environmental protection. The road vertical alignment after construction is optimized mainly on adjusting the constant load value such as the thickness of the deck pavement. However, the scope of the surplus space on the adjustment of the bridge deck load is limited. So in many cases, it is difficult to get a kind of smooth road vertical alignment. To deal with this problem, we commonly use the method of directly connecting the two adjacent cross structures, which creates a certain slope of the break point. While the vehicle driving across the break point, it vibrates because of the irregularity of the road, which may cause the passengers in the car feeling uncomfortable and even affect traffic safety. The dynamic load generated by the vibration of vehicle may also aggravate the pavement damage near the break point. In order to control the effect of the road break point on passengers and road, this paper made analysis and research on the break point under different condictions from the perspective of driving comfort and safety and the vehicle's dynamic load on road, so that get the standard slope control of break points' differences on different road grades.Through summering and analyzing, this paper firstly chose the weighted acceleration RMS value as the index to reflect human body vibration comfort and chose the 1/2 vehicle model to establish the motion equations on body and the vehicle. And then it was calculated based on Laplace Transform, and compiled into MATLAB calculation program. This calculation program was used to analyze the impacts of vehicle's parameters, driving speed, passenger position and road alignment elements on human driving comfort.Secondly, the minimum load of vehicle tires on the road was chosen as the evaluating indicator on driving safety. On the other hand, the maximum load and dynamic load coefficient were chosen as analysis index on the load of the driving vehicle. Based on the above results of vehicle vibration calculations, the load equations of the vehicle to the road were established and compiled into calculation program on Matlab. This program was used to analyse the effects of vehicle's parameters, driving speed and road alignment elements on the load of the vehicle.Finally, this paper calculated the control standards of the break points' slopes on different grades of roads from the aspects of driving comfort and safety as well as road load. The results were used to ayalyse the break point in practical construction so as to guarantee the specific requirements.