Parametric Investigation of Factors Influencing the Dynamic Response of Buried Reinforced Concrete Culverts

Abstract

In the current practice of bridge engineering, structures are designed and evaluated using static loads. In order to account for the dynamic nature of the true loading condition, static vehicle loads are increased by a dynamic amplification factor (DAF). The DAF has been widely studied for conventional bridges and has been found to be a function of vehicle forcing frequency and the fundamental frequency of the bridge. As a simplification, many design codes determine the DAF factor based on common bridge characteristics, namely the span length. The AASHTO LRFD Bridge Design Specifications simply use a single, conservative value for conventional bridge types. In the case of buried bridge structures, the dynamic behavior is complicated by the soil layer present between the asphalt and structure. In order to accurately determine the response of buried box culverts in a dynamic loading scenario, the interaction between the asphalt, soil, and structure must be taken into account. Through a parametric finite element analysis, four aspects of the asphalt-soil-structure system are examined in order to determine the factors which most influence its dynamic response. Parameters under scrutiny are depth of fill, fill stiffness, culvert span length, and culvert flexural rigidity. This research shows that fill depth and slab thickness are most influential in determining the dynamic amplification factor. However, span length and soil stiffness do have some effect.

Assessment of Dynamic Load Allowance for Buried Culverts

“…Noting the discrepancies between observations made during field tests of culverts and the values of DAF from AASHTO, Wells (2016) concluded that AASHTO recommended values of DAF are too conservative. In addition, by performing a parametric study, Wells et al (2016) showed that parameters other than the fill depth affect DAF significantly. In a pioneering study, Turneaure et al (1911) reported the DAF's strong dependency on the span length of culverts.…”

“…The behavior of culverts under dynamic loading conditions has not been extensively explored. Recently, however, the topic of dynamic behavior of culverts seems to have gained interest (e.g., Chen and Harik 2012;Beben 2013;Wells 2016;Wells et al 2016). Among these studies, the experimental investigation performed by Beben (2013) found out that the value of DAF for culverts increases with increasing span length and decreasing fill depth.…”

“…Performing a two dimensional (2-D) finite element analysis, Chen and Harik (2012) showed that DAF values for culverts increase with increasing vehicle speed and decrease with increasing surface roughness. Recently (Wells 2016;Wells et al 2016), by performing 2-D FEM analysis and in situ testing, determined that the AASHTO recommended DAF values are too conservative. The latter two studies recommended that the calculation of DAF should account for span length, slab thickness, asphalt rigidity, and Young's modulus of the soil in addition to the AASHTO specified fill depth.…”