L. Sebastian Bryson

Research Database of Water Distribution System Models

AbstractSince the 1960s, researchers have continued to develop new methodologies and algorithms in support of the planning, design, and management of water distribution systems. While initial research focused on modeling the hydraulics of such systems, the 1980s gave rise to additional research focus on water quality issues. More recent research has expanded into issues of system reliability and resilience, energy management, and sensor and chlorine booster station placement. In most cases, researchers have relied on either hypothetical water distribution systems or a handful of actual systems for use as benchmark test systems. Some of the more widely used actual systems include the New York tunnel system and the Hanoi water distribution system. This paper describes the development of a database of several water distribution systems synthesized from a statewide database of systems originally developed by the Kentucky Infrastructure Authority. The developed models include both small and medium networks, as...

Method for Estimating System Stiffness for Excavation Support Walls

AbstractExcessive excavation-induced movements are major concerns for most underground construction projects in urban areas. These movements can lead to significant damage in adjacent structures. When average to good workmanship is employed during the installation process of the excavation support systems, the consequent ground movements are most influenced by the support system stiffness. Therefore, choosing the most appropriate stiffness for an excavation support system is crucial to minimizing excavation-related damage to adjacent buildings and utilities. This paper presents a semiempirical design methodology that facilitates the selecting of the excavation support system stiffness in such a way that limits excavation-related ground movement. As part of the proposed design methodology, a new parameter was developed called the relative stiffness ratio. This new parameter relates the strength and stiffness of the soil with the stiffness of the excavation support system and was developed from a comprehens...

FULLY AUTONOMOUS ROBOT FOR PAVING OPERATIONS

Efficiency is low in conventional concrete construction. This fact, combined with high accident rates at construction sites, low product quality, and insufficient controls of the project schedules have led researchers to develop autonomous robots to perform specific tasks. Such robots are highly advantageous for a multi-task operation such as concrete paving. Concrete pavement construction is ideally suited for robotics in that the complete construction process is made up of many single-tasks that can be automated and integrated into a single machine. Although the state-of-the-art paving process includes a high level of automation, the process is still labor intensive and the final quality of the pavement section is a function of the skill of the paving crew. Introducing autonomous robotics into paving operations provides a means to consistently produce high-quality products, faster and safer than conventional concrete paving techniques. Ohio University is developing a 1:20 scale prototype of a fully autonomous robot for concrete paving called RoboPaver. The purpose of the prototype is to serve as a proof-of-concept concrete pavement construction robot. The full-scale version of the RoboPaver will occupy about the same volume as a typical commercially-available slipform paver, but will combine all the operations of a conventional paving system into one robot. The RoboPaver prototype will also implement an intelligent concrete construction system that will allow real-time remote monitoring and control of the paving operations, based on sensors and other machine performance data. The tangible benefits of using RoboPaver for pavement construction will include lower labor costs, lower equipment maintenance costs, less construction downtime, and lower demobilization and cleanup costs. Other potential RoboPaver benefits include increased construction site safety and higher quality of the finished pavement section, both of which can be directly related to a reduction of overall project costs.

Water Quality Sensor Placement Guidance using TEVA-SPOT

Contamination warning systems involve a network of sensors that can assess the water quality in a water distribution system and alert an operator of a potential contamination event. Utilities developing these water quality monitoring systems are faced with the decision of what locations are best suited for deployment of these sensors to maximize their ability to detect contamination events. TEVA-SPOT is sensor placement software tool that uses an optimization algorithm to evaluate the hydraulic model of a system and recommend optimal locations for water quality sensor deployment. This paper presents a study in which several systems were investigated using the TEVA-SPOT software. A database of distribution system models of small utilities was first created to support this research. Models were then used in the TEVA-SPOT software and input data such as contamination scenario, number of sensors to be deployed, and sensor design objective were then assigned. The locations recommended by the software as optimal sensor locations were evaluated and investigated for patterns as compared to other systems. Each sensor placement recommendation was analyzed to determine the proximity of the sensor locations relative to one another and evaluated in terms of the need for additional sensors. Results of the sensor placement evaluation were grouped by system configuration, and trends were examined based on loop, grid, or branch configuration. The results of this study indicated that 50 to 75 percent of sensor designs had the two sensor locations placed close together for the loop and grid systems, respectively. However, no sensor designs had two sensor locations placed close together in the branch systems. These same trends were reflected in the need for additional sensors.

Uniqueness of a Constitutive Shear Modulus Surface for Unsaturated Soils

AbstractThe measurement of shear modulus at small strains in unsaturated soil is critical to evaluating the deformation behavior of soils at working loads. However, little has been done to determine if the small-strain shear modulus surface is unique during variation in either net mean stress or matric suction. In this context, uniqueness is defined as similar samples subjected to different stress paths that converge to the same stress state. Research is presented herein in which a unique constitutive shear modulus surface was established by independently controlling mean net and matric suction stress in a modified resonant column apparatus. Uniqueness was also investigated using data extracted from literature studies. Uniqueness of the shear modulus surface was shown for single-direction stress and hydraulic paths, by the convergence of modulus and by the agreement between predicted and measured modulus. The presence of a unique shear modulus surface allows for the use of a constitutive relationship base...

Cable-Suspended Robotic Contour Crafting System

This paper introduces a new concept for a contour crafting construction system. Contour crafting is a relatively new layered fabrication technology that enables automated construction of whole structures. The system proposed here consists of a mobile contour crafting platform driven by a translational cable-suspended robot. The platform includes an extrusion system for laying beads of concrete as well as computer-controlled trowels for forming the beads as they are laid. This system is fully automated and can be used to construct concrete structures rapidly and economically. The novel attributes of this system enable significant improvements over other proposed contour crafting systems, including easier portability, lower cost, and the potential to build much larger structures. This paper presents the kinematics and statics of the proposed system, and uses the reachable workspace of the robot as well as the corresponding cable tensions to approximate the maximum size structure that can be built using this manipulator.Copyright

A simplified procedure for sensor placement guidance for small utilities

Water distribution systems are vulnerable to intentional, along with accidental, contamination. A network of water quality sensors can provide early detection of contamination, but these sensors must be placed in locations that maximise their ability to detect contaminates. Robust models and algorithms have been developed to aid in sensor placement, but many require calibrated hydraulic/water quality models. Many small utilities do not possess the financial resources or expertise to build calibrated models. Because of such limitations, a simple procedure is proposed to recommend optimal placement of a sensor without a model or complicated algorithm. The procedure uses simple information about the geometry of the system and does not require explicit information about flow dynamics. While the proposed method does not claim to be as reliable as currently available sensor placement software, it should accomplish the goal to provide an effective solution for small utilities with limited technical and financial resources.

Sensitivity Analysis of Selected Input Parameters for an Advanced Constitutive Model

Experimental results and simulated behavior of a medium plasticity clay were compared to investigate the performance of an advanced soil constitutive model. The soil model employed for this study was the 3-SKH model. The performance of this model was compared to the performance of two other critical state models; the Cam Clay (CC) and Modified Cam Clay (MCC) models. In addition, the influences of some of the input parameters on the performance of the 3-SKH model were investigated by performing sensitivity analyses. The comparisons demonstrated that the CC model was able to predict normally consolidated compressive behavior of the remolded medium plasticity clay. The compression behavior of overconsolidated clay was better captured by both the 3-SKH and CC models. For extension behavior of the normally consolidated samples, the MCC model performed better than the CC and 3-SKH models in predicting the stress path. The 3-SKH model was found to be very sensitive to varying the exponent in the hardening function. In particular, a difference between the evaluated values as small as 0.01 had a noticeable effect on the predicted stress–strain values for the overconsolidated compression and extension samples.

Direct Approach for Designing an Excavation Support System to Limit Ground Movements

Traditionally, excavation support systems are designed solely on the basis of satisfying limit equilibrium, using apparent earth pressure diagrams. Using this approach, the support system design becomes a function of the maximum anticipated earth pressure and is governed by overall structural stability as opposed to maximum allowable horizontal or vertical deformation. This approach produces a support system that is adequate with regards to preventing structural failure, but may result in excessive wall deformations and ground movements. This paper presents a design methodology that facilitates the sizing of all components of the excavation support system in such a way that limits the maximum lateral and vertical excavation-induced deformations. Based on the fundamental approach of the presented design methodology, structural and basal stability is

Physical Modeling of Supported Excavations

As a result of the complexities associated with analyzing and evaluating supported excavations, numerical modeling techniques are often employed. Often, there is a great deal of uncertainty associated with the validity of the assumptions and approaches made regarding numerical modeling. Physical models can be used to evaluate complex geotechnical systems whose performances are highly dependent on construction techniques, nonlinear soil-structure interactions, and variable geometries. Physical model tests can be used as alternatives to numerical models or as supplements. Data from physical model tests is often used to verify the validity of the various assumptions and approaches of the numerical models. The data can also be used to calibrate numerical models to the anticipated loading conditions. This paper presents an evaluation of several efforts that utilized physical modeling to investigate the behavior of excavation support systems and the associated ground deformations. Model test results are compared to the state-of-the-practice ground deformation prediction methodologies and to field observations. The information presented herein shows that scale model test data can be reliably extrapolated to equivalent prototype data. Thus, small scale laboratory tests at normal gravity, centrifuge tests, and small scale field tests can all used to evaluate excavation support system behavior and soil response associated with deep excavations. These findings are particularly important in that often full-scale field test cannot be performed.