ABSTRACT
Traffic simulation can generate vehicle load sequences with variable and complex traffic conditions, which is critical for the extrema prediction of bridge loading response. Recent advances indicate the influences of weight and configuration on the microscopic behavior of vehicles are essential to capture the bridge extreme loading responses (O’Brien et al. 2012). Hence, precise modeling of vehicle behavior such as lane-changing, queuing and lateral position is needed. While, as for bridge with super spans, the influence surfaces of structural effects are complex and present long loading length (Zhou et al. 2014). If the precise simulation is implemented in the whole regions, massive computation and low efficiency are produced.
This paper aims to simplify the traffic simulation for bridge with long loading length. Two aspects of influence line and sensitiveness to vehicle loading types are analyzed. A case bridge with arrangement of 270 + 5 X 428 + 270 m is utilized, and the structural effects of girder bending moment in the center of middle span (BM1) and bending moment in the bottom of middle pylon (BM2) are compared and investigated. Three vehicle loading types of axle weight loading, gross vehicle weight loading and equivalent uniformly distributed weight from general and congested conditions are applied in the influence lines, responses are analyzed and compared.
The metrics of influence lines for BM1 and BM2 indicate there are some regions where negligible influence values are presented, which are identified as nonsignificant regions. Further, a limited region where significant influence values and areas included is recognized as sensitive region, and other regions are treated as considerable ones. Therefore, a precise simulation of vehicle sequence and weight is needed in sensitive region, and simplified simulation can be conducted in nonsignificant and considerable regions.
The statistical parameters and tail tendency of BM1 and BM2 give a same result between general and congested conditions. structural effect (BM1) that has sharp influence lines are really sensitive to the vehicle loading types, a precise modelling of axle weight is important. While, structural effect that has smooth influence lines (BM2) are not sensitive to the loading types. Further, simulation of traffic in smooth influence line can be simplified as well. Tail tendencies of the upper responses from various loading types in congested condition. https://s3-euw1-ap-pe-df-pch-content-public-p.s3.eu-west-1.amazonaws.com/9781315207681/cd556cd4-4dcf-4efe-8e29-56fc67b8bfbd/content/fig27_1.tif"/>
An outlook into the simplified simulation of traffic is that the uniformly distributed weight can be further processed as a fuzzy distributed line load with varied values, and the varied values can be produced as the function of time-dependent traffic volume, density and vehicle composition etc.. Therefore the simulation of traffic can be efficiently and precise enough made in these regions.
