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Understanding fundamental track behaviors under dynamic load conditions is important to optimize design practices and achieve high-quality track performance. The American Railway Engineering and Maintenance-of-Way Association provides recommended practices to estimate trackbed pressures, which are primarily based on the Talbot equations. The Talbot methodology for computing crosstie-ballast (CT-B) interfacial pressures may "not" be valid for modern railroad design due to several factors, including the sensitivity of pressure measuring equipment, the presence of uneven support conditions, and the implementation of jointed rails in testing different wheel loadings, which contributed to overestimation of pressure readings as a result of impact loading. However, modern railroad infrastructure has been designed with a smooth track layout and well-supported rails as well as incorporating rolling stock equipped with smooth wheels, particularly in high-speed train operations. This study proposes a new approach to estimate the pressures at the CT-B interface, which was developed using measured in-track CT-B interfacial pressures taken from an active mainline. The data from the in-track measurements were filtered by using a signal processing tool and analyzed to develop basic equations to predict interfacial pressures as a function of basic train characteristics, including train speed, wheel loads, and wheel spacing, assuming no impact loading from wheel defects. To validate the efficacy of the square wave theory, the predicted pressures were compared with the data obtained from in-track tests. Further, a method to estimate dynamic pressures of a moving train at the CT-B interface was developed using square wave theory. By representing the vehicles of a train as a periodic square waveform, the dynamic CT-B interfacial pressures can be predicted for an unlimited number of locomotives and cars for smooth track geometry, smooth wheels, limited rail surface roughness, and well-supported track. [ABSTRACT FROM AUTHOR]

Excessive crosstie wear and abrasion and ballast wear and fouling are fundamental problems contributing to inadequate railroad track performance. This adversely affects the attainment and long-term maintenance of desired track geometric requirements. The magnitudes and distribution of the stresses at the crosstie-ballast (CT-B) interface must be known to determine the stress distribution on and within the ballast. However, the track design recommendations to determine these pressures, which are largely based on a methodology from the 1980s, are currently valid for modern-day railroad applications for multiple reasons discussed in this study. This study analyzed CT-B interfacial pressure data measured on an active freight mainline in Mascot, Tennessee. Dynamic contact pressures at the CT-B interface were measured using hydraulic earth pressure cells for various wheel loads and train speeds. The test train was a Federal Railroad Administration (FRA) test train consisting of a diesel electric locomotive, a test car that had different wheel loads based on the deployable axle load, and an inspection car. Although the maximum train speed was limited to 64 km=h, this research found that speed variation has a minimal effect on the CT-B interfacial pressures. From the measured data, a Gaussian stress distribution equation is proposed to determine longitudinal pressure distribution transmitted to the CT-B interface for static conditions. In addition, the stress distribution along the length of a crosstie was investigated via laboratory experimentation using a half-length crosstie. As a result of the experimentation, a dimensionless trilinear approximation was developed to estimate the stress distribution along the length of the crosstie. In general, this research recommends that the longitudinal and lateral stress distributions be considered together to design a better railroad track. [ABSTRACT FROM AUTHOR]

Cross-laminated timber (CLT) panels are an innovative wooden product that has gained popularity in recent years because it has a high strength-to-weight ratio, improves construction efficiency, and it is a natural and renewable material. Therefore, the recently released 2021 International Building Code (IBC) include guidelines for CLT panels for the construction of buildings of up to 18 stories. The construction applications of CLT panels as well as the research initiatives have largely centered on softwood tree species such as laminates, and the application of hardwood species has yet to be investigated. This paper documents the structural behavior of several hardwood species abundant in the Appalachian region and demonstrates the promising feasibility of using these species in the construction industry with CLT panels considering the architectural and structural behavior and economic aspects. The hardwood tree species selected are abundant in the Appalachian region and this paper highlights their potential as a construction material and provides an insight for future development. Three hardwood species including red maple, sweetgum, and sycamore are considered for this study, and three- and five-ply panels are fabricated to evaluate their behavior. The samples are tested in three directions for compression to understand the orthotropic behavior. Considering the softwood species including southern yellow pine and Douglas fir as a baseline for comparison, a total of 120 samples are tested and evaluated based on ASTM standards. The results show an average higher compressive strength from sweetgum panels followed by red maple, sycamore, Douglas fir, and southern yellow pine in the main directions used for structural walls. The findings imply a potential market for the underutilized hardwood species in Appalachia, which may lead to future economic development in the region. [ABSTRACT FROM AUTHOR]

A three-story school supported by shallow foundations was affected by an adjacent 12.2-m-deep excavation in soft clay in which the excavation support system was a 0.9-m-wide secant pile wall braced by both cross-lot struts and tiebacks. The school is a reinforced concrete frame structure with exterior reinforced concrete foundation walls. This paper summarizes the conditions at the site and presents correlations among construction activities, measured deformations and distortions, and attendant damage in the school. The lateral ground movements associated with the excavation were monitored with four inclinometers placed around the school. The building movements were monitored with optical survey points established on interior columns, exterior walls and on the roof, and with tiltmeters installed on the exterior foundation walls. The damage to the school mainly consisted of 300 to 500-mm-long hairline cracks in nonload bearing walls. Only a few cracks had widths greater than 6 mm. The school deformed such that the portion closest to the excavation sagged and the remainder hogged. Damage was first observed in the area of sagging when angular distortions reached 1/940 and the excavation was approximately 5.5-m deep. Angular distortions as large as 1/300 were observed at the end of the project. The data suggest that angular distortions had to be less than 1/1000 to preclude any damage to the school. DOI: 10.1061/(ASCE)0887-3828(2002)16:1(10) CE Database keywords: Soft clay; Excavation; Shallow foundations; Distortion; Foundation settlement.

A major concern for urban construction projects involving deep excavations is the impact of excavation-related ground movements on adjacent buildings and utilities. Consequently, stiff excavation support systems are required to execute the work. The conventional approach for designing an excavation support system is to use a limit equilibrium approach to determine the required capacity and stiffness of the excavation support system. Although this approach may provide an adequate factor of safety against structural failure, it may yield excessive system deformations and subsequent ground movements, causing nearby structures to possibly sustain damage. Thus, it is critical that design methods for excavation support systems consider the potential of induced damage in adjacent infrastructure. Current methods that consider potential damage to adjacent structures in the excavation support system design compare predicted damage to acceptable damage at the end of the support system design process. These design methodologies involve iterations of the support system characteristics until the required stiffness of the system complies with the acceptable level of damage. Any variation in the ground or adjacent structure characteristics from a previous definition may cause a complete redefinition of the support system characteristics. This paper presents a new design methodology that directly designs an excavation support system by first considering an acceptable level of damage in the surrounding facilities and estimating the corresponding ground deformations. The wall and support elements of the support system are then designed such that the system yields the limiting ground deformations. The resulting excavation support system limits damage to adjacent structures below an acceptable level and automatically satisfies the structural stability requirements. More significantly, the design of the excavation support system does not require an iterative process. [ABSTRACT FROM AUTHOR]

Many constitutive models have been developed to describe hydromechanical characteristics of unsaturated soils. However, most models lack the capability to adequately simulate the change of the yield stress with suction, the deformation of a soil over the drying process, and the soil volume change as soil transitions from a saturated state to an unsaturated state. The Sheng, Fredlund, and Gens (SFG) model was developed to address these issues. This model has been shown to perform better than most models in the literature in modeling the yield surface, as well as the consolidation and shear behavior of the unsaturated soils. However, two deficiencies are associated with the SFG model. The SFG model utilizes a constant small-strain shear modulus to estimate the elastic shear strain, although the small-strain shear modulus changes with hydrological variations in the environment. In addition, the hysteresis function used to govern the water content-volume change relationship under loading conditions requires at least one set of unsaturated constant suction consolidation data. These data must be obtained via performing very advanced and time-consuming tests. In this current study, the original SFG model was modified such that a unique hydrologic behavioral model was developed to predict the small-strain shear modulus of the unsaturated soils. In addition, the hysteresis equation was modified based on a redefined water content-volume change function. The proposed modified-SFG model was found to perform very well in simulating the hydromechanical behavior of various unsaturated soils over several loading and suction conditions. [ABSTRACT FROM AUTHOR]

The small-strain shear modulus of soils is a key parameter in the design of geotechnical systems and analysis of the soil–structure response to earth and earth-supported infrastructure. However, the small-strain shear modulus is not unique to a specific soil type. The small-strain shear modulus is a complex function of the state conditions (e.g., void ratio, suction) and stress states (e.g., in situ stresses, preconsolidation stresses). For unsaturated soils, the variations of the state conditions at a given stress state are captured by the soil–water characteristic curve (SWCC). This paper presents a general method to predict the small-strain shear modulus of unsaturated soils based on an inverse relationship between the small-strain shear modulus and the SWCC. Both vary with matric suction, but the two do not exactly mirror each other. Thus, the original SWCC was modified to improve the alignment with the small-strain shear modulus. In addition, a change in the void ratio induced by changing the net normal stress led to a change in the SWCC. Therefore, the modified SWCC was further adjusted for net normal stresses different from the original net normal stress. Finally, a small-strain shear modulus prediction equation was developed in accordance with the modified SWCC. The proposed equation consisted of several fitting parameters that were estimated from the modified SWCC. The developed prediction models were shown to be applicable to the numerous case studies for various net normal stresses and over a large range of matric suctions. [ABSTRACT FROM AUTHOR]

The 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 based on soil type that describes the small-strain shear modulus in terms of the stress state variables. [ABSTRACT FROM AUTHOR]

Since 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 well a range of system characteristics (i.e., system configuration-grid, looped, and branched systems-and system components-number of tanks, pump stations, and supply sources). The development of the database is described, as well as how to gain access to the developed models. All models have been developed to support use by water distribution system modeling software. [ABSTRACT FROM AUTHOR]

Excessive 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 comprehensive parametric analysis that incorporated a fully three-dimensional finite-element analysis of a generalized excavation that realistically modeled the excavation geometry, excavation support system configuration, and excavation activities. The performance of the proposed methodology was evaluated using several excavation case histories reported worldwide. The results of the evaluation show that the new relative stiffness ratio performed well in predicting the support system bending stiffness and the actual excavation-induced lateral deformations of the case history support systems. [ABSTRACT FROM AUTHOR]

A major concern for projects involving deep excavations in urban areas is the response of adjacent buildings and utilities to excavation-related ground movements. Unfortunately, a purely theoretical approach to estimating building response to excavation-related deformations is not possible due to the variability of the many factors that contribute to the response. Consequently, building response must be estimated and evaluated primarily based on empirical observations and various structural approximations. The goal of estimating and evaluating building response is to provide limiting criteria that will safeguard the structure against unacceptable damage. Thus, estimating the extent of the building response and consequently the severity of excavation-related building damage is critical to establishing rational limiting criteria for excavation support system designs. The most common measure of damage severity is the onset and growth of cracks in interior walls of adjacent structures. Although several procedures have been suggested for estimating excavation-related crack growth, all of the procedures have a common aspect in that they require the input of a critical strain, or the strain at the onset of cracking, as a critical input parameter. This paper presents the results of three-dimensional finite-element analyses of a building adjacent to an excavation. The analyses were used to evaluate the magnitude of strain that developed in the interior walls in response to the excavation-related ground movements. This paper describes the procedures used to model and analyze the building. The paper also presents computed building responses at dates corresponding to observations of cracking and presents discussions of strain levels in infill panel walls where cracking was observed and in panels where cracking was not observed. The analyses showed that the initial cracking observed in selected infill wall panels could not have occurred solely in response to excavation-related deformations. Consequently, it was found that the wall panels cracked as a result of a combination of strains induced in the structure from self-weight settlement and excavation-induced displacements at the supports. These analyses allowed the writers to suggest critical strain criteria. [ABSTRACT FROM AUTHOR]