Miguel A. Pando

Characterization and Demonstration of Reuse Applications of Sewage Sludge Ash

In this paper sewage sludge ash (SSA) refers to ash material product of incineration of municipal and industrial sewage water. SSA from a waste water treatment plant in Eastern United States was characterized in order to investigate and demonstrate potential reuse applications for the ashes produced by this plant. To date most research on reuse applications for ash materials has focused largely on coal-sourced ashes such as fly ash or bottom ash. In contrast very little research has been reported on SSA, which typically will have important differences with coal-based ashes in terms of physical and chemical composition and cementitious properties. This paper presents the results of an elemental and morphological characterization as well as a demonstration of clay brick admixture and soil stabilization admixture reuses applications.

Load Transfer Mechanisms of Tip Post-Grouted Drilled Shafts in Sand

Post-Grouted Drilled Shafts (PGDS) are a deep foundation system in which grout is injected at high pressure through the tip after the drilled shaft has been installed. Available field load tests show significant load and stiffness improvements of PGDS due to tip pressure grouting. The improved ultimate load capacity and stiffness of PGDS compared to conventional drilled shafts are believed to be related to the pre-stressing effect which the tip post grouting has on the shaft side friction due to the generated upward movement. It also is related to the grout bulb formed at the PGDS tip. This grout bulb pre-compresses the soil beneath the tip as well as any disturbed material generated during construction, and results in an enlarged tip area. This paper investigates the contribution of these factors through a series of T-Z analyses applied to a well-documented, full-scale load testing case history.

Using Information Technology to Incorporate Natural Hazards and Mitigation Strategies in the Civil Engineering Curriculum

AbstractNatural and environmental hazards include earthquakes, tsunamis, volcanoes, hurricanes, floods, landslides, and droughts, among several others. These hazards present high risk to human lives and infrastructure. This is particularly true when such systems affect populated areas, devastating homes, highways, buildings, and social structure. A key aspect of natural hazard mitigation is the implementation of adequate strategies for data collection, processing, and sharing. This implementation can be prior to a natural disaster event for purposes of risk assessments and planning or postevent for disaster relief efforts and to document and learn from these case histories. In this paper, the authors present their experience in developing and implementing a course on natural hazards, which also focused on the benefits of using information technology (IT)-based solutions for natural hazard risk management. In the United States, most civil engineering (CE) curricula offer elective courses focusing primarily...

Finite Element Analyses of Offshore Monopile Deflection Accumulation under Harmonic Loading

A wide variety of ocean energy converters (OEC) are being considered worldwide, including tidal, wave, and current ocean energy. Regardless of the type of ocean energy device a major technical and cost challenge for these systems is their foundation systems. The specific focus of this paper is for ocean stream energy converters supported on monopile foundations. One of the key design considerations for these OEC devices is related to the long-term performance of the foundation system, which can be subjected to more than 107 cycles of low-magnitude lateral loading during its design life. This very high number of lateral load cycles can result in a gradual long-term accumulation of pile head deformations and rotations. In some cases these pile head deformations can exceed the OEC serviceability limits. Analyses of laterally loaded piles, based on conventional p-y methodologies, typically cannot predict these accumulations of deformations and rotations. This manuscript presents results of 3D dynamic finite element analyses for this soil-structure interaction (SSI) problem. Results from these analyses reveal that this gradual accumulation of pile head deformation could be an important design consideration for certain monopile conditions. These numerical results correspond well with published experimental data. Finite element analysis (FEA) parametric studies, which investigate the influence of different pile installation variables, are presented to shed light on possible design options that mitigate or minimize the accumulation of pile head deformations.

Stress redistributions in unit cells of fibre-reinforced polymer composites with interface degradation

Experimental evidence indicates that the main damage mechanisms found in fibre-reinforced composites under static loading or environmental action are matrix damage, fibre damage and interface damage, leading to various forms of strong inhomogeneities at the micromechanical level. The main objective of this paper is to identify the stress redistributions that take place at the unit cell level, in which damage has already occurred due to an independent process. A deterministic approach is carried out to illustrate the main features of the transverse behaviour of a unidirectional fibre-reinforced composite under static loading. Damage is modelled by means of interface defects, in which the number and size of defects are considered as parameters of the damaged configuration and also by changes in material properties. The two-dimensional problem is solved using a general purpose finite-element code. The results show the extent of damage propagation to be expected in several configurations with inhomogeneities.

Tire Derived Aggregates As a Sustainable Recycled Material for Retaining Wall Backfills

Tire derived aggregates (TDA) offer potential environmental, technical, and economical benefits for retaining wall applications. For example, when compared to natural soils, TDA materials offer the advantage of reduced lateral pressures and settlement due to smaller unit weight, and potentially higher drainage capacity. This paper presents a technical and economical assessment of TDA materials for retaining wall backfills. The technical assessment includes results on model retaining wall tests and also from centrifuge tests to assess the lateral pressures generated by TDA materials. The lateral pressures are compared to tests using conventional mineral soil backfills. The test results show TDA backfills generate lower lateral pressures for at- rest conditions and for active conditions. The lower lateral pressures, coupled with lower unit weights translate into substantially lower retaining wall costs due to savings from smaller wall and footing dimensions, and less steel reinforcement quantities associated with the lower loading demand.

Field lysimeters for the study of fate and transport of explosive chemicals in soils under variable environmental conditions

Landmines and other buried explosive devices pose in an immense threat in many places of the world, requiring large efforts on detection and neutralization of these objects. Many of the available detection techniques require the presence of chemicals near the soil-atmospheric surface. The presence of explosive related chemicals (ERCs) near this surface and their relation to the location of landmines, however, depends on the source characteristics and on fate and transport processes that affect their movement in soils. Fate and transport processes of ERC is soils may be interrelated with each other and are influenced by chemical characteristics and interrelated soil and environmental factors. Accurate detection of ERCs near the soil surface must, therefore, take into the variability of ERC concentration distributions near the soil surface as affected by fate and transport processes controlled interrelated environmental factors. To effectively predict the concentration distributions of ERCs in soils and near soil surfaces, it is necessary to have good understanding of parameters values that control these processes. To address this need, field lysimeters have been designed and developed at the University of Puerto Rico, Mayaguez .This paper presents the design of two field lysimeter used to study the fate and transport behavior of ERC in the field subjected to varying uncontrolled subtropical environmental conditions in two different soils. Both lysimeters incorporate pressure and concentration sampling ports, thermocouples, and a drainage system. Hydrus-2D was used to simulate soil moisture and drainage in the lysimeter for average environmental conditions in the study for the two soils used. The field lysimeters allow collection and monitoring of spatial and temporal ERC concentrations under variable, uncontrolled environmental conditions.

Pre-college interactions, early expectations, and perceived barriers of first year Black and Latino engineering students

One of the most significant challenges facing engineering education in the United States is the persistent problem of inclusion and retention of underrepresented racial and ethnic groups. As part of a larger, federally funded project on student-faculty interaction in engineering, a case study was conducted to describe engineering-related interactions prior to college, perceived barriers during engineering studies, and early expectations of interactions with faculty among first year Black and Latino engineering students at a large university in the Southeastern United States. Descriptive data were gathered through focus groups and questionnaires. Findings indicated that recommendations from pre-college educators, mostly middle and high school math and science teachers, were important for deciding to study engineering in college. Students had expectations of minimal contact with engineering faculty based on early interactions, but expressed the desire to seek relationships with professors who would be able to connect them with engineering-related opportunities and resources. The most likely perceived barriers to studying engineering were financial problems and difficulties in science and engineering coursework. These findings are particularly useful to engineering education professionals involved with first year orientation experiences, and they further current understanding about pre-college and early experiences that are linked to engineering enrollment.

Integration of Centrifuge Testing in Undergraduate Geotechnical Engineering Education at Remote Campuses.

We report the results of a pilot study aimed at developing, implementing, and assessing an educational module that integrates remote major research instrumentation into undergraduate classes. Specifically, this study employs Internet Web-based technologies to allow for real-time video monitoring and execution of cutting-edge experiments. The students’ activities within the module are centred on building a model of a shallow foundation on a sand deposit utilising a centrifuge facility and using this model for: (1) visual observation of the response of soil-foundation systems, (2) learning the use of instrumentation, (3) interpretation of acquired data, and (4) comparing experimental results to theoretical predictions. Testing a soil-foundation system helped the students identify the lab experiments needed to analyse and design the system. A survey was used to gauge students’ perceptions of learning as a result of introducing the module, which were found to be positive.

Preliminary Methodology for the Integration of Lean Construction, BIM and Virtual Reality in the Planning Phase of Structural Intervention in Heritage Structures

The main purpose of this article is to describe a proposed methodology to integrate modern construction management tools and procedures such as Lean Construction (LC), Building Information Modeling (BIM), and Virtual Reality (VR) in the planning phase of structural intervention of heritage structures. The proposed methodology that integrates these techniques is referred to as Lean Project Delivery System (LPDS). This paper explains the main principles, tools, techniques, practices and technologies, like VR, laser scanner, and photogrammetry that integrated result in synergy with the design, and planning components of the selection of the structural retrofitting alternatives. The proposed method associates the workflow design, workflow execution, LPDS elements and Management of Heritage Structures (MHS) requirements. The proposed LPDS methodology is applied to the St. Jerome Hall, a sector of the Church of the Nativity, located in Bethlehem, Palestine where the selection of the most feasible structural consolidation technique was required to retrofit this area due to some archaeological excavations. The conclusions drawn from the application of the proposed methodology to this case history may have some biases due to unique constraints in this project related to regional and project specific considerations. However, the paper hopes to contribute by providing an integrated framework for modeling and planning that can improve the state of practice in this area of knowledge.