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Rockfall hazards are present throughout the state of Ohio. The Ohio Department of Transportation (DOT) employs Test Level 3 standard concrete barriers along the edges of roadways to contain rockfalls in high-risk areas. The performance of these barriers under impact from rocks on the ditch side and their effectiveness for rockfall catchment are relatively unknown. Full-scale impact tests were performed on concrete barriers to simulate the effects of impacts from rocks of various sizes and shapes. Numerous impacts were made at different sections and levels of the barriers to test their structural integrity and energy absorption capacity. The results from this study revealed that 32-in.-high precast concrete barriers with current Ohio DOT details had an impact energy absorption capacity of up to 24 kJ under a single impact. The corresponding energy absorption capacity of 42-in.-high cast-in-place concrete barriers was about 56 kJ under a single impact. Moreover, these barriers experienced severe cracking and spalling of concrete under impact loading. Several design modifications were studied in this test program. These modifications included reducing the spacing of rebars and rebar sizes, using welded wire fabric, and using different types of fibers in the concrete. The tests conducted on the modified concrete barriers showed an impact energy increase of more than 100% with the modifications suggested in this study. Barriers made from the modified designs also experienced significantly reduced extent and severity of cracking and a reduction in spalling and splashing of concrete under impact loading.

This paper presents a performance-based, probabilistic framework for design of a drilled shaft under axial and lateral loading that can consider spatial variability of soil properties at a project site. The performance criteria of a drilled shaft are stated in relation to the limiting tolerable deformations for strength limit and service limit, respectively. The computational algorithm for calculating the deformation of a drilled shaft is based on the commonly adopted load transfer method and the p-y method. “Geotechnical failure” is defined as an event in which the specified performance criteria are not met. Three failure modes are considered: axial movement, lateral deflection, and angular distortion. The spatial variability of soil properties is considered by using random field modeling techniques in which correlation length is introduced to account for site variability in addition to mean and variance. The method of fitting a sample autocorrelation function to a prescribed correlation function by using the method of ordinary least squares is introduced for determining site-specific correlation length for soil parameters. Geostatistical principles known as kriging are employed to estimate unknown parameters at unsampled locations from neighboring sampled locations. A numerical example is given to illustrate the application of the proposed methodologies. The example demonstrates that correlation length is an important statistical descriptor for characterizing site variability. Performance-based design provides unified consideration for both strength limit and service limit. Finally, the overall probability of failure for a drilled shaft when all three failure modes are considered is greater than the failure probability for any individual failure mode.

The use of drilled shafts to stabilize an unstable slope has gained popularity in highway applications, mainly because it is a structural fix that does not require additional right-of-way. An analysis method for determining the factor of safety of a drilled shaft or slope system and for determining the earth thrust on the drilled shafts for structural design is introduced. The concept of the analysis is cast in the limiting equilibrium approach via the method of slices, while incorporating the drilled shaft–induced arching effects as the soil mass moved downslope and around the drilled shafts. The mathematical equations based on the limiting equilibrium calculation, together with the load transfer factor for accounting for the drilled shaft–induced arching effects, are presented. The three-dimensional finite element model parametric study using ABAQUS program was used to derive the semiempirical equations for quantifying the arching effect. A UASLOPE computer program was written to incorporate these algorithms for applications to real cases. A case study of a fully instrumented and monitored slope stabilization project, ATH-124, in Ohio, is presented. The analysis of the slope at the project site using finite element modeling and the computer code UASLOPE is presented, together with field-monitored data. On the basis of field monitoring data and the comparison between the finite element analysis results with the computer code UASLOPE results, the suggested analysis and design approach appears to be reasonable.

A field live load test and a finite element method (FEM) analysis performed on an existing 60° skew, three-span continuous steel girder bridge are presented. The live load testing program with nonstandard truck load was carried out to allow for assessing the adequacy of existing structures and pier support to carry an HS25 standard load. In particular, it was of interest to evaluate the effect of bridge skew on the distribution of reaction forces at interior piers. The measured bridge response under the live load was used to develop and calibrate a FEM model by using the ANSYS computer program. The calibrated FEM model was then used to predict bridge response under an HS25 load. For all load cases investigated, the FEM results showed that distribution of vertical reaction forces on the interior piers was nonuniform. The analysis results indicated that higher reaction forces were experienced by piers on the side of the bridge closer to the obtuse corner than on the side near the acute corner. The importance of using actual field measured test data to develop and calibrate a realistic FEM model is demonstrated.

The performance of permeable base materials used by the Ohio Department of Transportation (ODOT) was evaluated with a calibrated finite element modeling technique. Two bound permeable base materials (asphalt-treated base and cement-treated base) and four unbound base course materials (typical ODOT 304, 307-IA, 307-NJ, and 307-CE) were built on two monitoring sites on I-90 in Ashtabula County, Ohio. Moisture content measurements were made with time domain reflectometry. Movement of water through the six pavement sections at the project site was modeled by the finite element method. The two-dimensional finite element software (Seep/W) capable of simulating unsaturated water flow in layered systems was used. Precipitation recorded from an automated weather station at the monitoring site was used as an input in the model. Numerical simulation results showed that the finite element method can be used to simulate water flow through pavement layers. Accurate modeling of the boundary and initial conditions is important for results in accurate simulation of the measured field moisture regimes. The concept of time to drain outlined by AASHTO was used to evaluate the drainage efficiency of different permeable base materials. In general, both bound and unbound base materials specified in ODOT materials specifications meet drainage efficiency requirements. However, the ODOT 304 fill material, if it contains 13% of fines or more, cannot provide efficient drainage according to the time-to-drain criteria.

A research program was conducted to study the behavior of different drainable base and subbase materials used by the Ohio Department of Transportation (ODOT). Two construction sites were chosen from this program to be built with different base course materials. Site I (ATB-90–19.56) consisted of ODOT 306 cement-treated, ODOT 308 asphalt-treated, and ODOT 304 sections. Site II (ATB-90-0.00) consisted of 307-NJ, 307-IA, 307-CE, ODOT 306 cement-treated, ODOT 304, and ODOT 308 asphalt-treated sections. Time domain reflectometry (TDR) probes were installed in subgrade and unbound subbase layers to provide continuous monitoring of the moisture variation in the pavement system. The laboratory calibration for TDR probes resulted in the development of suitable calibration coefficients for the studied materials and more accurate conversion of TDR field measurements to the in situ water content. The monitored moisture content variation was used to determine the drainage efficiency of different drainable base materials used by ODOT. The treated base materials (cement and asphalt) exhibited better drainage performance than did the other unbound materials.

A field instrumentation and monitoring study on a 52-ft (15.8-m) high mechanically stabilized earth wall was undertaken. The field monitoring program was carried out on different sections along the wall, representing three different wall heights and two geometries. Monitoring results pertaining to reinforcement working forces, earth pressures at the base of the reinforced soils, and wall deformations are presented. The magnitudes and locations of maximum axial forces measured in the reinforcement are discussed and compared with the predictions by the method adopted by the Federal Highway Administration (FHWA) and the load and resistance factor design (LRFD) method. Comparisons between the field measurements and the design methods for the tallest section with straight backfill (simple geometry) indicated that the LRFD method predicted the reinforcement forces more closely than the FHWA-adopted method. However, both methods failed to predict the locations and magnitudes of the maximum axial forces that developed in the reinforcement at the wing-wall section (sections with three-dimensional sloping backfill). The geometry of the wall and backfill, the type of wall-facing panels, and the interpanel connections appear to influence the deformation and settlement response of the reinforced earth wall. From the measured reinforcement wall connection forces, it was determined that the connection forces depended on the depth of embedment and the shape of the line of limiting equilibrium. The vertical pressure measurements deviated from those predictions by the three methods: Meyerhof, trapezoidal, and uniform distribution. These discrepancies are attributed to the lack of knowledge of the influences of the wall-facing element and the frictional stresses that may have developed along the interface between the retained soil and the reinforced soil

The use of anchored geosynthetic systems (AGS) was proposed by Koerner et al. for the stabilization of slopes at or near their failure state. AGS provides in-situ stabilization of soil slopes by combining a surface-deployed geosynthetic with an anchoring system of driven reinforcing rods similar to soil nailing. Installation of the system involves tensioning a geosynthetic over a slope’s surface by driving anchors through the geosynthetic at a given spacing and distance. By tensioning the geosynthetic over the slope’s surface, a compressive load is applied to the slope. Benefits of AGS are described to include the following: ( a) increased soil strength due to soil compression, including increased compressive loading on potential failure surfaces; ( b) soil reinforcement through soil nailing; ( c) halt of soil creep; ( d) erosion control; and ( e) long-term soil consolidation. Following installation of the AGS and 1 year of monitoring, it was found that the anchored geosynthetic system provided only some of the reported benefits and in general did not function as an active stabilization system. This was in part because the system could not provide and maintain loading on the geosynthetic. The geosynthetic, however, did tension when slope movement occurred, preventing the slope from failing. Thus, the system functioned more as a passive restraint system and appeared to function well over the monitoring period.

Aging of asphalt has been an important subject area that has received extensive studies in recent years. Test results of short-term and long-term aging behavior of crumb rubber modifier (CRM) modified asphalt paving materials are presented. Eighteen combinations of CRM modified binders in terms of CRM size, CRM content, and base asphalt cement grade were studied by Brookfield viscometer test and dynamic shear rheometer test. The short-term aged binders were prepared using thin film oven test. Viscosity was measured at 350°F in the Brookfield thermosel after mixing at 375°F for 2 hr. The test results showed that the size and percentage of CRM affected the viscosity development in the modified binders: the smaller the CRM size and the higher the CRM content, the higher the viscosity measured after 2-hr reaction at 375°F. Short-term aging exerted more viscosity increase in the CRM modified binders than in the unmodified binders. Modified binders showed less weight loss than unmodified binders. The modified binders showed higher complex modulus G* than unmodified. Short-term aging increased G*, with modified binders exhibiting higher increase. The Marshall mix design yielded various CRM modified mixes. The result of indirect tensile strength tests showed that short-term and long-term aging increased the measured tensile strengths. The resilient modulus test results, in general, supported the general understanding that aging tended to increase resilient modulus.