Master of Science

Integrating trees into pasture may be an effective management tool to improve water, nutrient, and light allocation and increase total system productivity in Appalachia. We tested this hypothesis in a silvopasture near Blacksburg, VA. In 1995, black walnut and honey locust trees were planted within plots (r=3) of predominantly tall fescue pasture. Across a 12% slope, trees were planted to create treatments of low, medium, and high tree densities at shoulder, mid, and toe slope positions within plots of honey locust and black walnut. Sampling sites (n=54) under tree density and slope position combinations were harvested May to October at 35-d intervals in 2002 and 2003 for determination of yield and nutritive value characteristics. Soil surface temperature, forage canopy temperature, soil moisture, and photosynthetically active radiation were measured to determine forage responses to field treatments as functions of resource allocation. Tree density had the greatest effect on forage production and nutritive value. Across both years, yields were 16% greater (P=0.0006) at medium density (6130 kg/ha) compared to forage mass at low (5280 kg/ha)) and high density (4970 kg/ha, SE=130). Increasing tree density did not affect (P>0.2) ADF, CP, P, K, and Mg levels, but reduced (P<0.001) NDF and TNC, and increased (P<0.0001) ADL and Ca. Elevated soil surface and forage canopy temperatures limited forage production and nutritive value at low density, while low light levels were the limiting factor at high density. Moderating forage microclimate with appropriately spaced trees is an effective way to improve forage production in temperate pastures. / Master of Science

In this investigation, thirty-six shear walls measuring 8 feet (2.4 m) in width and possessing heights of 8, 9 and 10 feet (2.4, 2.7 and 3.0 m) were subjected to the reversed, cyclic loading schedule of the standard CUREE protocol in order to determine the performance capabilities of shear walls greater than 8 feet (2.4 m) in height sheathed with long panels. Of the thirty-six walls, a total of twelve walls measuring 9 and 10 feet (2.7 and 3.0 m) in height were sheathed with 4 x 8 feet (1.2 x 2.4 m) panels which required additional blocking members between the studs of the frame. Values obtained from the tests performed on these walls provided a direct comparison to those obtained from the walls of equal height, but sheathed with a long panel capable of spanning the entire height of the wall. The capabilities of long panels were investigated when used as the sheathing elements of shear walls with and without a mechanical hold-down device attached to the base of the end stud. An advantage of the long panel was investigated in which it was extended past the bottom plate and down onto the band joist to determine if significant resistance to the uplift present in walls without mechanical hold-down devices could be provided. Also, the effects of orienting the fibers of a 4 x 9 feet (1.2 x 2.7 m) panel in the alternate direction were examined. Average values of the parameters produced by walls sheathed with long panels either matched or exceeded those of its counterpart sheathed with 4 x 8 feet (1.2 x 2.4 m) panels in all configurations except the 10 feet (3.0 m) tall wall without hold-down devices. In fact, 4 x 9 feet (1.2 x 2.7 m) panels increased the performance of 9 feet (2.7 m) tall walls equipped with hold-down restraint significantly. Extending the long panels past the bottom plate and down onto the band joist improved the performance of both 8 and 9 feet (2.4 and 2.7 m) tall prescriptive shear walls significantly. Walls sheathed with panels made of fibers oriented in the alternate direction performed identically to those sheathed with panels of typical fiber orientation until the point of peak load. Once peak load was reached, walls sheathed with panels of alternate oriented fibers failed in a more sudden and brittle manner. / Master of Science

M.S.

How can we as design professionals contribute to increase the use of less carbon-intensive materials to build our growing cities? Cities are experiencing a resurgence in population growth and therefore the building industry ought to attend this demand with sustainable solutions. One way of responding to the growing urban population and increase demand for housing as well as to make efficient use of our limited resources is to increase the density in our cities. Since steel and concrete have high material strengths, we currently use either steel, concrete or composites of them to build skyscrapers. Unfortunately, both of these materials have a large carbon footprint. The design community has the challenge to achieve net-zero emissions buildings by the year 2030, and the efforts now should be focused on using less carbon intensive materials, such as timber. While cultures around the world have built with wood for centuries, recent technological innovations, such as Cross Laminated Timber (CLT), is allowing for new applications of wood as the main structural material and the potential to use it for large-scale projects. However, as expected with a new building material some constrains have still to be overcome. For my thesis, I desired to explore this issue through the design of a tall building using mass timber as its main structural material. Engineered timber is here, the future is bright! / Master of Architecture / Urban population is growing faster than ever before and at the same time, we have started to suffer the scarcity of resources. One way of responding to the growing urban population as well as to make efficient use of our limited resources is to increase the density in our cities. We currently use either steel, concrete or composites of them to build skyscrapers. Unfortunately, both of these materials have a large carbon footprint. While cultures around the world have built with wood for centuries, recent advances in wood-based building materials and construction techniques have made it possible to use wood even in large-scale projects. However, as expected with a new building material some constrains have still to be overcome. For my thesis, I desired to explore these issues through the design of a tall building using timber as its main structural material.

Infection of tall fescue (<i>Festuca arundinacea</> Schreb.) with the endophyte fungus (<i>Acremonium coenophialum</i>, Morgan-Jones and Gam) has been associated with toxicity symptoms observed in cattle. The overall objective was to investigate the influence of endophyte infection on growth and chemical composition of tall fescue and the toxicity of endophyte-infected (EI) tall fescue to cattle. In a greenhouse study with pairs of genetically identical EI and non-infected (NI) ‘Kenhy’ tall fescue clones, concentration of N, Ca, Mg, Al, B, Mn and Zn was higher and K and S was lower in NI, compared to EI tall fescue. Insect resistance was higher in EI, compared to NI. Yield and chemical composition of high and low EI tall fescue were measured at four growth stages (stockpiled, prebloom, bloom and regrowth after harvest at bloom), two sites (Glade Spring and Blackstone) and three rates of N fertilization (0, 40 and 80 kg/ha) in a field study. Tall fescue grown at Glade Spring was higher in N, Mg, Al, Cu, Fe and Mn, compared to Blackstone. Nitrogen fertilization increased N, Mg, Ca, B, Cu, Na, Zn and decreased NDF, ADF, cellulose, P and S concentration in tall fescue. Neutral detergent fiber, ADF, cellulose, lignin, Fe and Na were higher in low, compared to high EI tall fescue. Concentrations of Cu, Na and Zn in stockpiled and Ca, Cu, Na and Zn in bloom-cut tall fescue hay were below dietary requirements for 227-kg steers. A disc meter was also evaluated for use in predicting yield of tall fescue. The meter is useful for non-destructive estimation of yield. Three feeding studies were conducted with steers (6/treatment/year). Diets were orchardgrass/alfalfa hay, spring-cut EI tall fescue hay, spring-cut EI tall fescue silage and fall-cut EI tall fescue silage. Serum prolactin and cholesterol were depressed in steers fed fescue hay and silages, compared to steers fed orchardgrass/alfalfa hay. Differences in mineral composition of hay and silage were reflected in serum minerals in steers. Ergopeptine alkaloids in EI tall fescue may have contributed to the depression of serum prolactin. The spring-cut silage contained the highest concentration of ergopeptine alkaloids, compared to other diets. Steers fed the spring-cut tall fescue silage had the lowest basal and thyrotropin-releasing hormone stimulated prolactin compared to steers fed the other diets. / Ph. D.

Current planning and scheduling techniques ignore the requirements of activities for work area or space. Any task or activity requires a specific work space for its execution. This demand is based on the space requirements of each resource allocated to the activity. When such required demand becomes unavailable, the activity or task can not be executed or, in some cases, is performed with a lower productivity rate. This is because performance and maneuvering of either crew or equipment may become difficult and sometimes not possible. This research provides a structured methodology to deal with the problem of limited work space availability. The research’s domain focuses on multi-story building construction with particular focus on the repetitive portion of the facility (i.e. typical floors). The research studies the issues of work space as a new decision factor for schedule generation in this type of construction. A scheduling model is developed to define and incorporate work space availability in the scheduling process. The model includes a method to quantify work space parameters (space demand and space availability) for any activity. The model also presents a procedure to compare space demand to availability and provide scheduling decisions to Sequence each activity based on these two parameters. The model allows for availability limits to be placed on resources required for the work by implementing limited resource scheduling techniques in the scheduling procedures. Horizontal and vertical logic constraints associated with repetitive work are also incorporated in the scheduling process of the model. Work continuity issues and varying productivity rates are used as scheduling decision options. The model adopts a procedure to schedule non-continuous activities using variable length segments along the typical floors. In addition, the model allows for adjusting the initial defined resource demand pools for different activities to account for any modifications that may occur to the activity duration during scheduling. Loss of productivity as a result of the combined effect of travel time and learning curve phenomena is also incorporated in the generation of the schedule by the model. The model is taken to a prototype proof of concept by developing SCaRC (Space Constrained and Resource Constrained) scheduling system. The system is implemented using a knowledge-based approach. / Ph. D.

The advent of performance-based codes in the United States underscores the need for a thorough, systematic approach to the documentation and accomplishment of a performance-based design. This project has three objectives: economic analysis of performance-based codes from a social view point, documentation of a performance-based design, and an example application of the ICC Performance-Based Code to high-rise office building. Economic issues explored include the externalities, insurance, and liabilities associated with performance-based codes. Documentation of a performance-based design includes delineation of the scope and goals with agreement between the designer, architect, building owner, and authority having jurisdiction, examination of the relevant code statutes, development of appropriate fire scenarios which meet the requirements of the performance matrices, thorough documentation of all design tool and calculation assumptions and limitations, and a clear demonstration of satisfactory accomplishment of stated goals and objectives. Finally, performance-based design alternatives to a prescriptively-designed 40 story office building were developed. There were three major design alternatives. The first design feature was the evacuation of occupants using elevators. The second alternative was the use of the assured fire safety system, which combined emerging technologies in fire detection, alarm, and suppression. The final design alternative was the routing of the domestic water supply through the sprinkler riser in order increase the reliability of the sprinkler system and save design, material, and installation costs associated with the domestic water supply risers. Finally, this project analyzed the specific life-cycle economic impact of the design alternatives when compared to the prescriptive design.

Treatment of endophyte-infected tall fescue [Lolium arundinaceum (Schreb.) Darbysh] with the broad leaf herbicide Chaparral® can mitigate fescue toxicosis and enhance forage quality by suppressing seedhead emergence. Applying the herbicide to fescue pastures also reduces forage mass and promotes severe spot grazing when pastures are continuously grazed. A grazing experiment was conducted with steers (2013) and heifers (2014) to evaluate animal and plant responses in fescue-bluegrass (Poa pratensis L.) mixtures treated with Chaparral to determine the effects of grazing management on pasture carrying capacity, nutritive values, botanical composition, and animal performance. Continuous and rotational (i.e., four subdivisions to provide a 7-d grazing period and a 21-d rest period) grazing treatments were assigned to six, 3.0-ha fescue-bluegrass pastures in a randomized complete block design with three replications. Each pasture had six tester animals, and stocking rates were varied using put-and-take animals. Pastures were grazed from 16 April to 8 July 2013 (Year 1) and 20 May to 12 Aug (Year 2) and cattle were blocked by body weight for allotment to pastures. Pasture carrying capacities were greater (P = 0.07) for rotational compared to continuous pastures across both years. Calves on rotationally grazed pastures had greater average daily gain (P = 0.03) and gain per acre (P = 0.05) than those on the continuous treatment across both years. Canopies of continuously grazed pastures contained less (P = 0.01) tall fescue than those in rotationally grazed pastures. Herbage in pre-grazed paddocks had less NDF and ADF than post-grazed paddocks and continuously grazed pastures in 2013 (P < 0.10), but did not differ in 2014 (P > 0.10). In vitro digestible dry matter was greater (P = 0.07) in pre-graze rotational pastures in 2013 compared with continuous and post-graze rotational, and IVDDM did not differ (P < 0.01) between pre-graze rotational and continuous in 2014, but was greater than post-graze rotational. Crude protein was lower (P = 0.06) in both years in post-graze rotational pasture than in continuous or pre-graze rotational pasture, which did not differ. In 2013, there was no difference (P = 0.60) in root WSC among treatments; however, in 2014, WSC levels were greater (P = 0.01) in rotationally grazed pastures compared with continuously grazed pastures. This grazing experiment indicated that rotational grazing of Chaparral treated fescue-bluegrass mixtures can improve both animal performance and the sustainability of pasture productivity.

Electromagnetic effects of lightning currents during a direct hit to tall communication towers, other instrumented towers and chimneys can be hazardous to associated cables, as well as, electrical and electronics systems. The standard practice in telecommunication and other related fields is to bond the cable sheath to the tower and ground connection is made before it enters the base station. However, in some specific cases when power, signal and data logging cables are to be supported on the same tower, isolation of power cables is demanded. In a totally different situation, attempts are also made to have a dedicated isolated down conductor. A critical review of the situation demanded a more quantitative answer to the following questions: (i) whether it is possible to electrically isolate a dedicated down conductor, (ii) is it possible to electrically isolate the cables and their terminal equipment both mounted on towers serving as down conductor and if so, what will be the nature of current induced in the cables and (iii) as per the standard practice, if the cable sheaths are connected to the tower/structure, what will be the nature of the current shared by them. Addressing these important issues formed the scope of the present work. For the tall structures considered in this work, for the critical time periods, wave nature of the current dominates. This called for electromagnetic modeling covering Transverse Magnetic (TM) mode of the wave propagation. Owing to the complex geometrical features involved with the problem, both experiments on electromagnetically scaled laboratory models, as well as, theoretical simulation is attempted. An electromagnetically scaled laboratory model is employed for the time domain experimental investigation. This approach, which has been validated earlier, is further scrutinized to ensure its adequacy. In order to achieve generality and noting the fact that the associated parameters are rather difficult to be varied in the experimentation, theoretical investigation is also employed. For this, both NEC-2, as well as, an in-house thin wire time domain code developed for this work is employed. NEC-2 could handle multi-wire multi-radius junctions, while in-house time domain code could handle proximity and non-cylindrical shapes encountered with tower lattice elements. The investigation of induction to isolated cables on simple down conductors and towers is considered first. The induced current is shown to be bipolar oscillatory with the period of oscillation governed by the length of the cable. It is shown that the level of induction for good earth termination is below 5 – 10 % while that with moderate inductance in the earth termination can enhance the induction to higher levels. The level of induction is shown to be not critically dependent on the length of the cable, gap between cable and down conductor/tower. When multiple cables are mounted, they seem to influence each other and individually carry currents of lower amplitude. Also, the effect of shape and proximity of the tower lattice elements on induction is investigated. If the cable is housed inside a metallic tray, the amplitude of induced current is shown to be quite small. Subsequently, the evaluation of electrical stress between the isolated down conductor on tower and simplified representation of the structure is considered. A suitable definition of the electric stress for the wave regime is evolved and then it is shown that, at present, the voltage difference defined by the path integral of electric field across shortest path between the two entities is the best indicator for the stress. The electrical stress in the case of isolated down conductor on tower, as well as, down conductor with isolated cable is shown to reach very dangerous levels. On the other hand, the stress on the isolated cables on towers also serving as down conductors is shown to be relatively moderate. Interestingly, it is shown that the electrical stress and the voltage difference is dependent on the gap and for the critical time period, can be much lower than that calculated as a product of equivalent tower surge impedance and the stroke current, even before the arrival of ground end reflections. Finally, the current shared by cables connected to the down conductor is investigated. For the case of simple cylindrical down conductor with cable connected to it at the top, it is shown that the amount of current shared by the cable is not dependent on its length and the relative radii (cross section) have only a weak influence. For the case with down conductor formed by L and + angles, it is shown that the placement of cable at their interior corner can reduce the initial current shared by the cable. In order to model best possible situation with towers, experiments are conducted with cable inside an aluminum pipe. Even in this case, cable current builds up with successive reflections to become comparable with the current through the pipe itself. Subsequent investigation with 1:40 and 1:20 tower models lead to several interesting observations. Cables running along leg/face of the tower whether placed inside or outside the tower, always shares good amount of current. Further, frequent bonding of the sheath to the tower increases the current shared by the cable. Cable when housed in a metallic tray shares less than 50% of the current shared without the tray. Even though a complete quantification is not to be achieved in this work, it has made a good beginning with some significant contribution towards lightning protection issues pertaining to tall towers and structures.