STR-997: INSTRUMENTATION AND LONG-TERM MONITORING OF AN INTEGRAL-ABUTMENT BRIDGE SUPERSTRUCTURE

Strain gauges were installed in the girders and deck of an integral abutment bridge to determine the behaviour of the superstructure to daily and seasonal thermal fluctuations. The two-span, 76 m-long bridge has no expansion joints; rather, the prestressed-concrete girders are cast directly into the abutments which are in turn supported by flexible pile foundations. Details of field instrumentation along with monitored data over a period of eight years are presented in this paper. Gauges measured the longitudinal strain in the girders and deck and were positioned at different elevations to provide a strain distribution across the superstructure depth. From the strain data, moments were computed at each of the installation locations. Data indicate that the superstructure responds to thermal fluctuations as expected with midspan moments smaller in magnitude when compared to the moments measured at the abutment and pier locations. Furthermore, data confirm that the level of sun exposure affects the thermally-induced moments measured in the girders

The Mechanics of Arching in Induced Trench Construction – A New Theoretical Formulation

Full-scale experimental case studies have shown that the induced trench construction method effectively reduces the vertical earth load that is exerted on culverts installed beneath high embankments. Induced trench culverts are traditionally designed on the basis of Marston’s theory; however, various theoretical shortcomings of this formulation have recently come to light. In this paper, a new induced trench theoretical formulation is presented. The proposed analytical model employs inclined shear planes within the embankment fill; such geometry is consistent with experimental findings reported in the literature, and leads to positive arching resulting from a reduction in vertical stress and an increase in horizontal stress (thus increasing the lateral earth pressure coefficient within the induced trench zone). A series of parametric studies are performed using finite element software. The proposed theoretical formulation is shown to be in good agreement with the numerical results, and correlations are developed to provide guidance in selecting the appropriate values of: 1) the induced trench lateral earth pressure coefficient, and 2) the height to the plane of equal settlement. Two instrumented full-scale induced trench case studies are discussed, and the proposed theoretical formulation is shown to produce results that are in good agreement with the experimental data.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Post construction performance of induced trench rigid culverts

Induced trench construction is commonly used to reduce earth pressures on rigid circular and box culverts. Most of the reported literature pertains to the performance of induced trench culverts during construction and shortly after construction. This paper addresses the post construction performance of induced trench culverts. First, results of field inspection reports are presented as an indirect assessment of performance of 90 induced trench culverts installed in New Brunswick which have been in service for up to 24 years. Second, earth pressure measurements are presented from three case studies where prototype installations were monitored over periods ranging from 4 to 9 years. The case studies presented include a single circular culvert, a cast-in-place double cell box culvert, and a twin circular culvert installation. The fill heights above the instrumented structures varied from 19 to 25 m. All the available data from both the field inspections and earth pressure measurements indicate that the culverts installed in induced trenches are performing in a satisfactory manner.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author