Steel Timber Research Articles

Instrumentation for Determination of Guardrail-Soil Interaction

A series of steel posts (W150 X 12.6) and timber posts (15.2 X 20.3 cm) were instrumented with soil pressure transducers to assess the soil-post load response to a 1,388-kg bogie striking the post at 33 km/hr. Soil pressure measurements demonstrated the dramatic effects of soil shear strength and modulus on the responses of both timber and wood posts. The differences in the failure mechanisms between stiff and soft cohesive soils and noncohesive soils are demonstrated by both stress distributions and total stresses measured by the pressure transducers. The measurement system has potential applications for measurement of loads during impact testing of guardrail systems and as a tool for developing more appropriate models of soil behavior during impact loading.

Instrumentation for Determination of Guardrail-Soil Interaction

A series of steel posts (W150 × 12.6) and timber posts (15.2 × 20.3 cm) were instrumented with soil pressure transducers to assess the soil-post load response to a 1,388-kg bogie striking the post at 33 km/hr. Soil pressure measurements demonstrated the dramatic effects of soil shear strength and modulus on the responses of both timber and wood posts. The differences in the failure mechanisms between stiff and soft cohesive soils and noncohesive soils are demonstrated by both stress distributions and total stresses measured by the pressure transducers. The measurement system has potential applications for measurement of loads during impact testing of guardrail systems and as a tool for developing more appropriate models of soil behavior during impact loading.

Geotechnical performance of a tunnel in till

Two parallel tunnels were built in 1976 as part of the first phase of the Edmonton Rapid Transit System. The tunnels, approximately 250 m long, 6 m in diameter, and having centres 11 m apart have been driven in downtown Edmonton with an average of 7.5 m overburden above the crown. The tunnels were located entirely within a dense, jointed till sequence of Wisconsin age.The tunnels were advanced using a mole followed by two systems of soil support. The temporary supporting system consisted of steel ribs and timber lagging while the permanent lining was cast-in-place reinforced concrete. To reduce drag friction, the cutting profile of the mole is about 20 mm larger than the diameter of the shield. The steel ribs are expanded into place by hydraulic jacks.Two finite element analyses were performed. One predicted surface settlements and the other predicted lining stresses. The settlements predicted for a single tunnel agreed closely with observed values but the observed amount was considerably more than predicted for both tunnels. The reasons for this are suggested as being due to a cross tunnel connecting the two main tunnels and to a decrease in stiffness of the soil mass brought about by the moling of the first tunnel.in situ assessment of stresses in the ribs was not successful due largely to the fact that the ribs were not expanded entirely against the soil. Thus comparisons with predicted values could not be made and values of the earth pressure at rest could not be established. However, rib deformations were essentially complete within a few days thus confirming the essentially time-independent character of the deformational behavior of the till.

Conceptual Substructural Systems for Short-Span Bridges

Systems approach for abutments of short-span bridges is presented. Ten different systems have been analyzed in detail with a view toward ease of erection, economy, maintenance, longevity, efficiency, versatility, etc. Reinforced earth, gabions, segmental plank, cellular box, steel bent, driven steel pile bent, concrete bent, stub system, concrete and timber cribbing are reasonable suggestions for short-span bridge abutments. Depending upon the merits and demerits gabions, concrete bent, cellular box, segmental plank and timber cribbing appear to be best suited from the industrialized construction viewpoint.