Lateral Displacement Capacity Research Articles

Effects of Seasonal Freezing on Bridge Column–Foundation–Soil Interaction and Their Implications

Several seismic regions around the world experience seasonal freezing that can drastically alter the soil-foundation-structure interaction and structural response under earthquake loads. This paper analytically investigates the effects of seasonal freezing on lateral load response of a bridge column supported by a cast-in-drilled-hole (CIDH) foundation shaft. Accounting for the temperature effects on materials, the analyses were conducted at ambient temperatures of 23° C, −1° C, −7° C, −10° C, and −20° C, and the results obtained at 23° C and −10° C were validated using experimental data. In comparison to the response at 23° C, the response of the column-shaft system in the range of −1° C to −20° C exhibited 40%–188% increase in the effective elastic stiffness, 17%–63% reduction in the lateral displacement capacity, 0.54–0.82 m upward shift in the maximum moment location, 25%–30% increase in the column shear demand, and 25%–80% increase in shear and 19%–68% reduction in the length of the plastic region in the CIDH shaft.

Experimental tests and numerical analysis of a real RC structure upgraded by means of C-FRP

The paper presents results of the analysis of the lateral-load response of an existing RC structure seismically upgraded by means of C-FRP. The structure was tested “as-is” under monotonic lateral loading conditions. It failed by a column-type collapse mechanism. The structure was repaired and upgraded by means of C-FRP. The structure has been tested again by a cyclic load test. Results demonstrate the successful implementation of C-FRP with a significant improvement of stiffness, strength and lateral displacement capacity of the upgraded structure. Finally a numerical study has been started with the aim to correctly capture the experimental results.

Analytical Prediction of Thermal Displacement Capacity of Integral Bridges Built on Sand

In this research, analytical equations are developed to calculate the lateral displacement capacity and maximum length limits of integral bridges built on sand based on the low-cycle fatigue performance of the piles under cyclic thermal variations and the ultimate strength of the abutment under positive thermal variations. To formulate the displacement capacity and maximum length limits of integral bridges based on the low cycle fatigue performance of steel H-piles under cyclic thermal variations, first, H-piles that can accommodate large plastic deformations are determined based on their local buckling instability. Then, a low cycle fatigue damage model is used as a tool to formulate the maximum cyclic curvatures and corresponding bending moments that such piles can sustain. Next, this information is employed in static pushover analyses of two integral bridges to study the effect of various geometric, structural and geotechnical parameters on their displacement capacity as determined by the low-cycle fatigue performance of steel H-piles under cyclic thermal variations. The findings from these static pushover analyses are then used to formulate the displacement capacity and maximum length limits of integral bridges as determined by the low-cycle fatigue performance of steel H-piles under cyclic thermal variations. The results from the same static pushover analyses are also used to formulate the displacement capacity and maximum length limits of integral bridges as determined by the ultimate strength of the abutments under positive thermal variations. It is observed that the stiffness of the deck, height of the abutment, properties and orientation of the piles as well as the density of the sand affect the displacement capacity of integral bridges. It is also found that the maximum length limit of integral bridges ranges between 65 and 310 m based on the properties of the bridge and climatic conditions.

Effect of cyclic thermal loading on the performance of steel H-piles in integral bridges with stub-abutments

In this paper, analytical equations are developed to estimate the lateral displacement capacity of steel-H piles in integral bridges with stub abutments subjected to cyclic thermal variations. First, steel H piles that are capable of sustaining large plastic deformations are identified based on their local buckling strength. The normalized moment–curvature relationships of these piles are then obtained for various axial load levels. Next, a low-cycle fatigue damage model is employed to determine the maximum cyclic curvatures that such piles can sustain. The obtained moment–curvature relationships and cyclic curvature limits are used in static pushover analyses of two steel H-piles driven in soil to obtain the maximum thermal-induced cyclic lateral displacements such piles can sustain. Using the pushover analyses results, the displacement capacity of steel H-piles are formulated as a function of pile’s properties, soil type and stiffness. Based on the obtained pile cyclic displacement capacities, the maximum length limits for integral bridges subjected to cyclic thermal variations are calculated. It is found that the maximum length limit for concrete integral bridges ranges between 150 and 265 m in cold climates and 180 and 320 m in moderate climates and that for steel integral bridges range between 80 and 145 m in cold climates and 125 and 220 m in moderate climates.