William D. Lawson

Acclimating International Graduate Students to Professional Engineering Ethics

This article describes the education portion of an ongoing grant-sponsored education and research project designed to help graduate students in all engineering disciplines learn about the basic ethical principles, rules, and obligations associated with engineering practice in the United States. While the curriculum developed for this project is used for both domestic and international students, the educational materials were designed to be sensitive to the specific needs of international graduate students. In recent years, engineering programs in the United States have sought to develop a larger role for professional ethics education in the curriculum. Accreditation requirements, as well as pressures from the private sector, have helped facilitate this shift in focus. Almost half of all engineering graduate students in the U.S. are international students. Further, research indicates that the majority of these students will remain in the U.S. to work post-graduation. It is therefore in the interest of the profession that these students, coming from diverse backgrounds, receive some formal exposure to the professional and ethical expectations and norms of the engineering profession in the United States to help ensure that they have the knowledge and skills—non-technical as well as technical—required in today’s engineering profession. In becoming acculturated to professional norms in a host country, international students face challenges that domestic students do not encounter; such as cultural competency, language proficiency, and acculturation stress. Mitigating these challenges must be a consideration in the development of any effective education materials. The present article discusses the project rationale and describes the development of on-line instructional materials aimed at helping international engineering graduate students acclimate to professional engineering ethics standards in the United States. Finally, a brief data summary of students’ perceptions of the usefulness of the content and instructional interface is provided to demonstrate the initial effectiveness of the materials and to present a case for project sustainability.

Chip Seal Maintenance: Solutions for Bleeding and Flushed Pavement Surfaces

This study summarizes the research directed at identifying maintenance solutions for bleeding and flushed pavements surfaced with a chip seal. Factors that contribute to bleeding and flushed chip seals pertain to aggregates, binders, traffic, environment, and construction. No better advice exists for dealing with bleeding and flushed chip seals than to avoid the problem from the outset by employing a preventive maintenance perspective. Bleeding is an immediate maintenance problem that must be addressed; corrective maintenance, or in some cases emergency maintenance, would be done. Basic approaches to treat bleeding include bridging over the live asphalt by applying aggregate of various types and gradations, cooling off the pavement surface by applying water with or without additives, and removing the bleeding asphalt and rebuilding the pavement seal. Flushing, in contrast to bleeding, is typically not a maintenance problem that must be addressed immediately. Basic approaches to treat flushed chip seals are to retexture the existing surface or to add a new textured surface over the flushed pavement. Three promising areas for further research and implementation relative to bleeding and flushing solutions include the uses of lime water, ultrahigh pressure water cutting, and the racked-in seal at intersections.

Evaluation of Production Models for Load Rating Reinforced Concrete Box Culverts

Analyses of two production-oriented culvert load-rating demand models were performed using live-load test data from three instrumented RC box culverts under four cover soil depths. The demand models were a two-dimensional (2D) structural-frame model and a 2D soil-structure interaction model. As expected, increased sophistication in the soil-structure model compared with the structural-frame model resulted in higher precision and accuracy for predicted moments. The impact of modeling accuracy for sections in a culvert where the demand moments approach zero was deemed practically insignificant. When evaluating model accuracy, it is of first importance that the models predict meaningful load magnitudes. Variations in predicted moment accuracy and precision were not uniform but were a function of the location of the critical section in the culvert structure. Improvements in modeling prediction associated with increased modeling sophistication were seen only when the structural-frame model was very imprecise.

Influence of Cover Soil Depth on the Load Rating of Reinforced Concrete Box Culverts

This paper describes the influence of cover soil depth on the load rating of the designs of multibarrel, cast-in-place (CIP) reinforced concrete (RC) box culverts and highlights implications for the load rating and design of culvert structures. The basics of culvert load rating are discussed and are followed by a history of culvert design policy and the challenges created by the use of culvert standard designs. A population of Texas Department of Transportation CIP RC standard culvert designs developed between 1930 and 1980 was load rated by using AASHTO policy guidance and a two-dimensional model of direct stiffness structural demand for a full range of cover soil depths. This analysis resulted in a set of 1,081 relationships of load rating versus cover soil depth. Three typical relationships of rating versus depth are illustrated and described in detail. The distribution of characteristic relationships of rating versus depth on the basis of culvert geometry, design cover soil depth, and design era is explored. Cover soil depth is shown to be a critical parameter that must be explicitly considered for the intelligent load rating and design of RC box culverts.

Pullout Resistance Factors for Steel MSE Reinforcements Embedded in Gravelly Backfill

Abstract This paper presents results from a laboratory program of 287 pullout tests of galvanized steel reinforcements used in the construction of mechanically stabilized earth (MSE) walls. Results focus on the evaluation of pullout resistance factors for ribbed steel strip and welded steel grid reinforcement embedded in gravelly backfill. This project used Texas Tech University’s large-scale MSE test box with dimensions of 3.6 × 3.6 × 1.2 m and an applied overburden capacity equivalent to 12 m of soil fill. The research design evaluated pullout resistance factors for both ribbed strip and welded grid reinforcements for a variety of independent variables, including overburden pressure, reinforcement length, grid bar size, and grid geometry including both transverse and longitudinal bar spacing. Appropriate statistical analyses were used to interpret the data within the context of published design guidance for inextensible MSE reinforcements. The results show that pullout resistance factors for both ribb...

Improved Load Rating of Reinforced-Concrete Box Culverts Using Depth-Calibrated Live-Load Attenuation

AbstractThis paper describes depth-calibrated live-load attenuation for the load rating of reinforced-concrete box culverts using production-simplified models. In-plane depth calibration is accomplished using a production-simplified, two-dimensional, linear-elastic, finite-element, soil-structure interaction model with results compared with those from the recommended direct-stiffness, structural-frame model. Out-of-plane live-load attenuation considers each potential critical section depth rather than the cover soil depth only. The effectiveness of depth calibration is assessed by comparing predicted live-load moments obtained from the models versus measured live-load moments obtained from full-scale culvert load tests. A load rating case study illustrates the potential for improved alignment between load rating and observed performance. Findings show that depth calibration improves current load rating practice by increasing the accuracy and precision of live-load demand predictions, particularly in culve...

Pullout Resistance Factors for Steel Reinforcements Used in TxDOT MSE Walls

This paper presents results from an extensive laboratory program of pullout testing of steel reinforcements used for Mechanically Stabilized Earth (MSE) walls constructed in Texas. Results focus on evaluation of pullout resistance factors for sandy backfill and MSE reinforcement combinations used by the Texas Department of Transportation (TxDOT). A unique aspect of this study is that this project uses Texas Tech Universitys large-scale MSE Test Box, one of the largest such devices in the world, with dimensions of 3.7m x by 3.7m x 1.2m (12ft x 12ft x 4ft) and an applied overburden capacity of 12.2m (40ft) of backfill. This test box facilitates pullout testing at a scale not unlike typical field construction. Results consist of pullout resistance factors for both ribbed strip and welded grid reinforcements for a variety of test variables including overburden pressure, reinforcement length, level of compaction, grid wire size, and grid geometry. We evaluate the data within the context of published AASHTO design guidance for inextensible MSE reinforcements.

Pullout Resistance Factors for Inextensible Mechanically Stabilized Earth Reinforcements in Sandy Backfill

This paper presents results from a laboratory program of 402 pullout tests of inextensible reinforcements used for walls of mechanically stabilized earth (MSE). Results focus on the evaluation of pullout resistance factors for ribbed-steel strip and welded-steel grid reinforcements embedded in sandy backfill that marginally met AASHTO requirements for select granular fill. This project used Texas Tech Universitys large-scale MSE test box with dimensions of 12 3 12 3 4 ft and an applied overburden capacity of 40 ft of backfill. This test box facilitated pullout testing at a scale not unlike typical field construction. The research design evaluated pullout resistance factors for both ribbed-strip and welded-grid reinforcements for a variety of independent variables, including overburden pressure, reinforcement length, level of compaction, grid wire size, and grid geometry, such as transverse and longitudinal wire spacing. Appropriate statistical analyses were used to interpret the data within the context of published AASHTO design guidance for inextensible MSE reinforcements. The results show that pullout behaviors of both ribbed strips and welded grids in properly compacted sandy backfill are conservative compared with the default pullout resistance factors provided by AASHTO. The data also suggest that the current AASHTO equations for pullout resistance factors for grid reinforcement do not accurately capture the influence of transverse and longitudinal bar spacings.

Instrumentation and Monitoring of an MSE/Soil Nail Hybrid Retaining Wall

MSE/soil nail hybrid earth retaining walls provide a more economical design for applications in cut/fill situations than the traditionally used full height MSE and drilled shaft retaining walls. MSE/soil nail hybrid earth retaining walls use a soil nailed wall in the cut section and an MSE wall in the fill section. In spite of the significant cost savings they offer, hybrid walls have not seen widespread use primarily because of lack of understanding on wall design and performance. This paper describes an instrumentation and monitoring effort that was undertaken with the objective of improving our understanding of hybrid wall design and performance. In this project, two separate panels of a hybrid wall constructed in San Antonio, Texas were selected for instrumentation and monitoring. The first wall panel consisted of a 4.0m soil nail wall and a 5.4m MSE wall while the second wall panel consisted of 5.0m soil nail wall and a 4.4m MSE Wall. The instrumentation scheme for the wall included vibrating wire strain gages, vertical inclinometers, horizontal inclinometers, and tiltmeters. The data collected from these two instrumented wall sections provide valuable insight to the mechanisms controlling the performance of MSE/Soil Nail Hybrid Wall systems.

Efficacy and Performance in Professional Development Higher Education-Sponsored ITV Instruction

THIS STUDY compares the efficacy of interactive video (ITV) delivered instruction to traditional course instruction in three distinct learning environments: traditional face-to-face format, ITV host (instructor present), and ITV distant (instructor not physically present) sites. Data were obtained from a half-day professional development course offered to maintenance personnel in a state transportation agency. Results indicate that although content retention (surface learning) did not differ across groups, student perceptions of ability efficacy, instructional efficacy, and interaction efficacy did differ. Authors discuss the implications and application to academic instruction, including practical recommendations for enhancing efficacy and consideration for transfer (deeper) learning.