A Roadmap for Participatory Chestnut Breeding for Nut Production in the Eastern United States

Chestnut cultivation for nut production is increasing in the eastern half of the United States. Chinese chestnuts (Castanea mollissima Blume), or Chinese hybrids with European (C. sativa Mill.) and Japanese chestnuts (C. crenata Sieb. & Zucc.), are cultivated due to their high kernel quality, climatic adaptation, and disease resistance. Several hundred thousand pounds of high-quality fresh nuts are taken to market every fall, and several hundred additional orchards are entering bearing years. Grower-led on-farm improvement has largely facilitated this growth. A lack of significant investments in chestnut breeding in the region, paired with issues of graft incompatibility, has led many growers to cultivate seedlings of cultivars rather than grafted cultivars. After decades of evaluation, selection, and sharing of plant materials, growers have reached a threshold of improvement where commercial seedling orchards can be reliably established by planting offspring from elite selected parents. Growers recognize that if cooperation persists and university expertise and resources are enlisted, improvement can continue and accelerate. To this end, the University of Missouri Center for Agroforestry (UMCA) and chestnut growers throughout the eastern United States are partnering to formalize a participatory breeding program – the Chestnut Improvement Network. This partnership entails the UMCA providing an organizational structure and leadership to coordinate on-farm improvement, implement strategic crossing schemes, and integrate genetic tools. Chestnut growers offer structural capacity by cultivating seedling production orchards that provide financial support for the grower but also house segregating populations with improved individuals, in situ repositories, and selection trials, creating great value for the industry.

Drop of Pressure Behavior of Open-Cell Aluminum Foams at High Pressure Flow

Open-cell aluminum foams were produced by the replication technique in three different pore sizes, ranging from 0.71 to 4.75 mm. The manufactured specimens were physically characterized, determining their porosity, relative density, pores per inch and interconnection windows density. A new experimental design is proposed in order to assess the drop of pressure behavior resulting from the injection of gasoline additive at increasing high pressure intervals, ranging from 200 to 25,000 psi, reproducing the tests at room temperature and 200 °C. The regime governing the flow through the investigated samples was determined as a function of flowrate and the foams physical properties. The structural capacity of open-cell Al foams to conduct highly pressurized flow was evaluated by means of compression tests. It was found that at room temperature, the drop of pressure behavior is strongly associated to physical parameters, whilst at 200 °C, dimensional and geometrical properties are negligible. In addition, in this investigation, it is presumed that the studied foams have the structural capacity to conduct fluids at critical conditions of pressure and temperature.

Full-Scale Experimental Evaluation of the Flood Resiliency of Thin Concrete Overlay on Asphalt Pavements

The capacity to resist flooding is one of the critical challenges of pavement resiliency in locations subject to inundation. Flooding increases moisture contents, which weakens most pavement materials. Although the effect of moisture on the mechanical properties of most pavement materials is reversible, the structural damage caused by trafficking applied on the weakened pavement structure is not. The critical time for structural damage is typically after the flood and before “life-line” pavements have dried back when trucks are bringing in relief supplies and hauling out demolition. This fact, together with the increased occurrence of extreme weather events and sea level rise resulting from climate change, emphasizes the need to better understand the impacts of flooding on identified life-line pavements. This paper evaluates the flooding resiliency of thin concrete overlay on asphalt (COA) pavements by studying the effects that water saturation produces on the pavement structure. The research is based on the structural response and distresses measured in five thin COA sections that were instrumented with sensors and tested with a heavy vehicle simulator (HVS) under flooded conditions. The research shows that the flooding did not produce a noticeable change in the structural capacity of the COA, based on the structural response measured under the loading of the HVS wheel and the falling weight deflectometer, but did result in some structural damage to the asphalt base in some of the sections.

Finding the Key: Designing Timber Connections for CLT Panels

<p>In a climate where standard methods of construction are being challenged, developments in engineered timbers are allowing mass timber construction to be explored as a sustainable alternative to traditional building methods. Cross- laminated timber (CLT) is at the forefront of this evolution and, with the advancement in computational design and digital fabrication tools, there lies an opportunity to redefine standard construction. This project explores how digital modelling and advance digital fabrication can be combined to generate a connection system for CLT panels. The advantages of CLT and mass timber construction are numerous and range from environmental and aesthetic benefits to site safety and cost reduction benefits. There are, however, issues that remain surrounding the connections between CLT panels. Steurer (2006, p.136) stated that, “Progress in engineered timber construction is directly related to developments in connector technology.” This thesis creates connections inspired by traditional Japanese joinery that have been adapted to be used for the panel construction of CLT structures. Using CLT offcuts as a primary connection material, the system not only reduces waste but also mitigates thermal bridging and lowers the number of connection points whilst increasing the ease of building and fabrication. The connections are first considered at a detail scale. They use the literature review and case studies as a base for design before being tested using digitally fabricated prototypes. These prototypes are evaluated against a framework created in line with the aforementioned criteria. Within this framework, the connections are analysed against existing connection systems as well as previous designs to establish a successful system. The connections are then evaluated within the context of a building scale and considers large-scale fabrication and on- site assembly whilst continuing to focus on the reduction of waste. This research found that the simplicity of the connections is key to a successful system as this allows for faster and cheaper fabrication and installation. However, there is still further research needed surrounding large-scale fabrication and the structural capacity of timber connection systems.</p>

Finding the Key: Designing Timber Connections for CLT Panels

<p>In a climate where standard methods of construction are being challenged, developments in engineered timbers are allowing mass timber construction to be explored as a sustainable alternative to traditional building methods. Cross- laminated timber (CLT) is at the forefront of this evolution and, with the advancement in computational design and digital fabrication tools, there lies an opportunity to redefine standard construction. This project explores how digital modelling and advance digital fabrication can be combined to generate a connection system for CLT panels. The advantages of CLT and mass timber construction are numerous and range from environmental and aesthetic benefits to site safety and cost reduction benefits. There are, however, issues that remain surrounding the connections between CLT panels. Steurer (2006, p.136) stated that, “Progress in engineered timber construction is directly related to developments in connector technology.” This thesis creates connections inspired by traditional Japanese joinery that have been adapted to be used for the panel construction of CLT structures. Using CLT offcuts as a primary connection material, the system not only reduces waste but also mitigates thermal bridging and lowers the number of connection points whilst increasing the ease of building and fabrication. The connections are first considered at a detail scale. They use the literature review and case studies as a base for design before being tested using digitally fabricated prototypes. These prototypes are evaluated against a framework created in line with the aforementioned criteria. Within this framework, the connections are analysed against existing connection systems as well as previous designs to establish a successful system. The connections are then evaluated within the context of a building scale and considers large-scale fabrication and on- site assembly whilst continuing to focus on the reduction of waste. This research found that the simplicity of the connections is key to a successful system as this allows for faster and cheaper fabrication and installation. However, there is still further research needed surrounding large-scale fabrication and the structural capacity of timber connection systems.</p>

Structural Performance Assessment of Airfield Concrete Pavements Based on Field and Laboratory Data

Maintenance interventions and rehabilitation actions in airfield pavements are time-consuming and adversely affect pavements’ serviceability (i.e., airport closures), with a profound impact on the airport economics. Once a pavement is constructed, a robust asset management prerequisites systematic and accurate knowledge of pavement condition throughout its service life. Evaluating a pavement’s structural capacity in the field involves the integration of multiple Non-Destructive Testing (NDT) systems, with the Falling Weight Deflectometer (FWD) being the most indicative NDT system for pavement evaluation. The purpose of the present study is to develop a methodology for the assessment of airfield concrete pavements. A new and non-trafficked Jointed Plain Concrete Pavement (JPCP), facing early-life cracks shortly after a runway’s expansion activities, was utilized for the investigation. Multiple types of data collected in the field, including deflections, load transfer efficiency at joints and cracks, concrete thickness through coring as well as data retrieved in the laboratory (concrete’s flexural strength), helped to define the pavement’s performance and assess its damage potential. Overall, the integration of such data can provide the related airport authorities the necessary information in order to make a rational asset management and enhance the efficiency of airfield infrastructures. The methodology is applicable for both new and in-service pavements.

Dynamic and Probabilistic Seismic Performance Assessment of Precast Prestressed Rcfs Incorporating Slab Influence Through Three-Dimensional Spatial Model

The dynamic and probabilistic seismic performances of precast prestressed RCFs are assessed in this paper, and the slab influence in the overall structural behavior is considered during the process. The threedimensional spatial model is established to provide the numerical basis, and the slab is modelled through L-/T-section beam-slab fiber-sections considering the effective width and centroid positions. The adopted model is verified with the experimental data, and the slab influence in hysteresis curves is investigated by parametric study. Then, two groups of precast prestressed RCFs are well designed to evaluate the slab influence in dynamic responses through seismic excitations, and the modal analysis, roof displacement analysis, maximum and residual drift ratio analysis are conducted for discussion. Moreover, the incremental dynamic analysis and fragility analysis are also conducted to investigate the probabilistic performance of precast prestressed RCFs with or without slabs. In general, different demand parameters may result in the variability of analyzing results, and ignoring the slab influence may underestimate the structural capacity under the frequent earthquakes (i.e., elastic stage) and overestimate the structural capacity under the rare earthquakes (i.e., plastic stage). In a sense, the research proves the significance of slabs in the seismic performance of dry-connected precast prestressed RCFs, and meanwhile provides the reference for the further explorations of slab factors in precast concrete structures.

Fuzzy Analytical Hierarchy Processes for Damage State Assessment of Arch Masonry Bridge

The present work proposes a fuzzy analytical hierarchy approach for decision making in the maintenance programming of masonry arch bridges. As a practical case, we propose to classify the degradation state of the Mohammadia masonry bridge. A large number of criteria and sub-criteria are combined to classify this type of bridges through visual inspections. The main criteria (level 1) considered in this work are the history of the bridge, the environmental conditions, the structural capacity and the professional involvement of the bridge. In addition, these criteria are subdivided into several sub-criteria (level 2) which are, in turn, subdivided into sub-criteria (level 3). Considering these criteria and sub-criteria, weights Wiare calculated by fuzzy geometric mean method of Buckley. Subsequently, expert scores were assigned to calculate the overall score CS reflecting the degradation of the considered infrastructure. Thereafter, the masonry arch bridges are classified respecting the French IQOA scoring system using the overall scores value CS. The proposed classification method gave similar results provided by an expert’s study realized previously as part of a national patrimony preservation policy. The obtained results are in good agreement, which makes this method an effective scientific tool for decision-making in view of prioritization of the maintenance after systematic inspection of masonry bridges such as the bridge studied in this work. Doi: 10.28991/cej-2021-03091770 Full Text: PDF

STRUCTURAL CAPACITY OF NSM STEEL BARS STRENGTHENED DEEP BEAMS UNDER COMBINED LOADS OF REPEATED AND ELEVATED TEMPERATURE

The current experimental investigation is devoted to study the structural capacity of near-surface mounted steel bars strengthened deep beams. Six reinforced SCC deep beam specimens with a dimension of 1400mm x175mm x350mm were tested under Combined Loads of Repeated and Elevated Temperature. The adopted variable includes the type of loading, degree of elevated temperature, and presence or absence of the strengthening by NSM-steel bars. The experimental results show that the ultimate load of B2-R-T20 decreased by about 33% when the applied load changed from monotonic to repeated; also, when the degree of burning increased to (200oC) and (350oC), the ultimate load decreased by 44% and 65% , respectively. The presence of the strengthened NSM-steel bars leads to increase the lateral strength of the tested beams and arrested the diagonal cracks to be widening as a result, the ultimate load capacity increases by (193%-197%) for the samples exposed to elevated temperature, in comparison with reference beams. The adopted strengthened technique proved to be adequate to restore and increase the shear capacity of the tested beams.