Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Doctor of Philosophy

Program

Civil and Environmental Engineering

Supervisor

El Naggar, M. Hesham

Affiliation

Western University

Abstract

Reinforced concrete three-sided culverts (TSCs) are typically produced in large spans, up to 16.0 m, and low-rise profiles to handle heavy flows at sites with limited vertical clearance. Full-scale field studies and numerical analyses investigating TSCs do not exist to date. Accordingly, the current design practices specified in the Canadian Highway Bridge Design Code, CHBDC (CSA, 2014) and the American Association of State and Highway Transportation, AASHTO (AASHTO LRFD, 2014) do not distinguish between small-span box and large-span TSCs. A comprehensive study involving field monitoring and numerical analyses of TSCs is presented in this thesis. Three TSCs were instrumented to measure the soil-culvert interface pressures and the induced strains. The monitored TSCs covered intermediate to large spans, with spans of 7.3 m, 10.4 m, and 13.5 m. Each culvert had a unique geometry and installation method. Field data were collected for the three culverts during and after construction completion. These field measurements were analyzed, and then utilized to verify two-dimensional (2D) finite element (FE) models for the three culverts. The verified numerical models were employed to investigate the influence of many parameters on the applied earth pressures and the structural performance of TSCs at service and ultimate limit states (SLS and ULS). Moreover, three-dimensional (3D) FE models were developed to predict the ultimate capacity of the monitored TSCs precast units. In addition, parametric studies were conducted to investigate the influence of the precast unit width and sidewall height on its structural performance at ULS. The field measurements indicated that the CHBDC (CSA, 2014) overestimates the pressure along the top slab of TSCs for B1 installation. The results of the 2D models showed that the subsurface soil condition influenced the lateral earth pressure on the sidewall only. The sidewall and pedestal heights governed the deformation of the footing-culvert system. Equations have been proposed to estimate the applied earth pressures on large-span TSCs and limits to the midspan vertical deflection are proposed to satisfy the SLS requirements. Finally, the TSC precast units, without soil confinement, exhibited brittle failure.

Summary for Lay Audience

Culverts are a vital part of the urban infrastructure for all societies. They are structures buried in the ground to convey water, utilities, or pedestrian on top of new roads. In general, earth weights on buried structures, which are used for their design, are affected by a phenomenon called soil arching. Simply, rigid buried structures attract more earth loads compared to relatively flexible structures. The current design guidelines included in the different codes in North America are for rigid concrete box culverts. Recently, concrete culverts with three sides and no bottom slab, also known as three-sided culverts, are gaining popularity. They are much wider than box culverts and are considered more flexible. However, the codes in North America do not differentiate between them and the same design guidelines are used to design large three-sided culverts. Accordingly, sensors were installed on three of these structures before their construction to measure the actual earth loads acting on them. Afterwards, an engineering software was used to simulate the monitored culverts. The results from the software simulation were similar to the sensors data. Accordingly, many scenarios were simulated to understand the behavior of three-sided culverts and to quantify the acting earth loads on their body in different cases. A clear understanding of the performance of large three-sided culverts is presented based on the sensors readings and the covered scenarios using the engineering software. Moreover, specific design guidelines for three-sided culverts have been presented that would lead to more cost-effective, yet reliable design.

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