Span Configuration Research Articles

Superstructure bridge selection based on Life-Cycle cost analysis for short and medium span bridges

Bridge life cycle cost analysis (BLCCA) is a method that evaluates the total cost of a structure. Historically, deterministic approaches of the method have been used for the cost-effective selection of maintenance/preventive alternatives for different projects. However, decision makers are inherently risk averse and deterministic approaches are not strong enough to do a comprehensive informed based selection. Therefore, implementation of stochastic methods could be beneficial for decision makers and structural engineers in the superstructure selection process. Based upon common practice in Indiana, three different span length ranges were selected and eight different superstructure types both in steel and concrete were evaluated. Substructures were neglected in the analysis. The analysis was conducted for span configurations that included simple spans, two and three span continuous girders, for each span range. Cost-effective life-cycle profiles for each superstructure type were used based on Indiana Department of Transportation experience. Both deterministic and stochastic analyses were performed. In general, the inclusion of long term-costs using BLCCA reduces the differences in cost-effectiveness between alternatives for the same span length. Galvanized steel options were found to be cost-effective for different span lengths, especially for shorter spans, while prestressed bulb tees were generally the best option for longer spans.

Rail Structure Interaction Analysis for Providing CWR on Un-Ballasted Multi-Span Open Web Steel Girder Bridge

Rail structure interaction (RSI) requires thorough study to understand the force transfer mechanism between the track and bridge components due to train vertical live loads, braking/traction loads and thermal loads accordingly. RSI analysis gives us an outline of the axial stress in rail, support reactions transferred to the bridge components and the relative displacement caused between the track and bridge. This paper investigates rail structure interaction analysis of unballasted multi-span steel through girder railway bridge carrying dedicated freight corridor (DFC) of 32.5t axle load. For this purpose, RSI analysis is performed as per the guidelines given in UIC774-3R [7] Code of Practice (International Union of Railways) for two different multi-span bridge with a span configuration of 7x63m and 6x48m respectively and the axial stress in rail, relative displacement between rail and bridge and support reactions transferred to the bridge components are calculated based on the span and stiffnesses of the bridges. From the analysis results, it shall be concluded whether to explore the possibility of providing a provision of continuous welded rail (CWR) on the bridge or to adopt switch expansion joints (SEJ) or other expansion devices accordingly.

Modeling and Simulation of Multi Adapted Routing Based on Queuing Theory for Energy Consumption in Wireless Network

The appropriate organization of waiting lines, sometimes known as queues, is the subject of queuing theory. In the field of queuing theory, the act of constructing a model for the purpose of predicting queue lengths and the amount of time spent waiting. Because the findings are often employed while making grouping choices about the nodes required to deliver a service in a network, the queuing theory included a scheduling for energy consumption as an important consideration. In this sense, the analysis of the causes causing system state to vitality exists on the system is related with the queuing system. A Grouping Based Multi-Routing Adapted (GBMRA) creation protocol with the goal of reducing the amount of energy used by individual nodes when they are in the presence of a network. For the purpose of analyzing the network’s energy usage based on queuing theory, we are implementing GBMRA. In wireless networks, one of the most effective ways to save energy is to cluster many nodes together into larger groups. The multi-event sources that were taken into consideration during the construction of the gathering techniques. This article demonstrates the model, which is to choose assets with higher levels of performance and vitality to display in the structure. The GBMRA algorithm, which is responsible for increasing system execution and reduction, caused the show on the system to be delayed. The network is simulated by utilizing use of the network testing system known as NS2. In this article, we have established a model of a social affair-based system by making use of the M/G/1 lined model, and we assess the execution of the proposed contrivance seeing execution characteristics such as the usual amount of vitality used and the mean latency. The settled span configuration set a similar hub degree, and it planned calculations of the wireless network based on theory to simply send messages in the particular four ways of neighbouring hubs. This was done with the intention of reducing the amount of energy that was spent on the parade of the wireless network.

Impacts of grade configuration on Brazilian student outcomes

Abstract In this paper we evaluate the impact of grade span configuration on student outcomes. We build a model which shows that the more homogeneous the cohort of students the higher the share of them which achieves the minimum level of academic performance required in an exam. We then test this theoretical finding by comparing performances of 5th-grade students of elementary schools (1st to 5th grade) and those of elementary-middle schools (1st to 9th grade) in Brazil. PSM and PSM with Diff-in-Diff methodologies are used to control possible biases. We find that elementary schools present better results in Portuguese language and mathematics standardized score tests, higher passing rates and lower dropout rates than elementary-middle schools, which corroborates the theoretical results. The robustness of estimates is checked through several tests and alternative specifications. Finally, we found evidence that the main mechanisms behind our results are related to alternative pedagogical practices and school management policies.

Influence of bone defect position and span in 3-point bending tests: experimental and finite element analysis.

Three-point bending test is the most common mechanical test used for quantifying the biomechanical quality of bone tissue and bone healing in small animals. However, there is a lack of standardization for evaluation of bone repair by cortical perforation. The aim of this study was to determine the influence of bone defect position in the proximal metaphysis of rat tibias during load application and different span configuration on the three-point bending test outcomes. Cortical defects with 1.6 mm diameter were created at a standardized location on the medial surface of 60 tibias of male Wistar rats. The animals were euthanized 7 days after surgery. Five specimens were used to create 3D models for finite element analysis using high-resolution micro-CT images. Two spans (6 and 10mm) and three positions of the bone defect in relation to the load application (upward, frontal and downward) were evaluated experimentally (n = 10) and in finite element analysis (n = 5). Maximum load (N) and stiffness (N/mm) were statistically analyzed with 2-way ANOVA and Tukey test (α = 0.05). The results demonstrated that span and orientation of the bone defect significantly influenced the fracture pattern, stress distribution and force versus displacement relation. Therefore, reliable outcome can be achieved creating the bone defect at 8 mm from the extremity of the proximal epiphysis; placing a 10 mm distance span and downward facing defect position to allow a better distribution of stress and more fracture patterns that reached the bone defect target area with less intra-group variability.

Impact of Amplification and Regeneration Schemes on the Blocking Performance and Energy Consumption of Wide-Area Elastic Optical Networks

This paper studies the physical layer’s impact on the blocking probability and energy consumption of wide-area dynamic elastic optical networks (EONs). For this purpose, we consider five network configurations, each named with a network configuration identifier (NCI) from 1 to 5, for which the Routing, Modulation Level, and Spectrum Assignment (RMLSA) problem is solved. NCI 1–4 are transparent configurations based on all-EDFA, hybrid Raman/EDFA amplifiers (with different Raman gain ratio $\Gamma _{R}$ ), all-DFRA, and alternating span configuration (EDFA and DFRA). NCI 5 is a translucent configuration based on all-EDFA and 3R regenerators. We model the physical layer for every network configuration to determine the maximum achievable reach of optical signals. Employing simulation, we calculate the blocking probability and the energy consumption of the different network configurations. In terms of blocking, our results show that NCI 2 and 3 offer the lowest blocking probability, with at least 1 and 3 orders of magnitude of difference with respect to NCI 1 and 5 at high and low traffic loads, respectively. In terms of energy consumption, the best performing alternatives are the ones with the worst blocking (NCI 1), while NCI 3 exhibits the highest energy consumption with NCI $2\,\,\Gamma _{R}=0.75$ following closely. This situation highlights a clear trade-off between blocking performance and energy cost that must be considered when designing a dynamic EON. Thus, we identify NCI 2 using $\Gamma _{R}=0.25$ as a promising alternative to reduce the blocking probability significantly in wide-area dynamic EONs without a prohibitive increase in energy consumption.

High-sensitive flexural sensors for health monitoring of composite materials using embedded carbon nanotube (CNT) buckypaper

The health monitoring for the service status of the composite materials is particularly crucial, calling for highly sensitive piezoresistive strain sensors. This paper outlined the working mechanisms of CNT buckypaper sensor during loading and releasing processes by analyzing the electrical conduction mechanism of the adjacent CNT and developing the macroscopical and mesoscopic models of CNT electrical networks inside of the bukypaper. The CNT-based nanocomposite specimens underwent monotonic and cyclic flexural loading in low strain range to examine the dynamic stability and durability of the in-situ nano sensor. The different support span configurations were also employed and operated to obtain the recommended application scenarios. The long-term response behavior of the nano sensor was also concluded as three typical phases. The desirable agreement was demonstrated by comparing the responses of ΔR/R0 signals and phenomena of the breakage and propagation of micro cracks and the rearrangement and reconnection of CNT conductive networks within the Scanning electron microscope (SEM) images of the buckypaper. The proposed flexural nano sensor is suitable for potential health monitoring application of composite materials.

Flexural and shear characteristics of bio-based sandwich beams made of hollow and foam-filled paper honeycomb cores and flax fiber composite skins

Abstract In this paper, bio-based sandwich panels made of fiber-reinforced polymer (FRP) skins and two types of paper honeycomb core (namely, hollow and foam-filled) with three different thicknesses (namely, 6 mm, 12 mm, and 25 mm) were studied. Flax FRP composites made of a unidirectional plant-based flax fabric and bio-based epoxy resin (30% bio content) were used for the skins. The panels were cut into a total of 36 sandwich beam specimens with the width of 50 mm and tested under four-point bending with two span configurations to characterize the flexural and shear stiffness of the panels. The specimens with foam-filled paper honeycomb cores showed a higher load capacity than those with hollow honeycomb, however their stiffnesses were not fundamentally different. Major non-linearity was observed in the load-deflection and load-strain behavior of the specimens. An analytical model was successfully developed based on the non-linearity of the skins in tension/compression and the core in shear to predict the non-linear behavior of the specimens. A parametric study was performed on different geometrical parameters and it was shown that contribution and bending and shear changes and it can be engineered to achieve desirable strength and stiffness. Overall, the bio-based sandwich panels can be used for interior walls, doors, and furniture in building application with much less impact on the environment in comparison with their synthetic counterparts.

PEMFC Flow‐field Design, Channel/land Width Ratio Optimization

AbstractThe impact of different land width and channel span configurations was evaluated on a 260 cm2 active area short stack. Polarization curves were compared at 65 °C cell output, max 7 °C cell delta T, 50% RH humidified air, ambient pressure at cell outlet, air pressure drop below 4 kPa at 1 A cm−2.Adequate opening ratio, about 50% or more is widely recognized as an optimal value to minimize contact resistance and diffusion losses at high current density. However, this work tends to show that performance optimization is linked to the total channel edge length per centimeter squared, ponderated by the opening ratio value. Total channel edge length is simply the sum of the edge length values on the flow‐field in contact with the membrane electrode assembly (MEA). Edges actually concentrate all the conditions for the reaction to occur: presence of gas phase and easy electron transport thanks to plate bulk conductivity. This could explain contrasted results existing in literature. Based on this work, a new cell design was developed allowing to reach 1 W cm−2 (extrapolated) with less than 20 kPa pressure drop (i.e., unchanged operating conditions except that pressure drop reached 10 kPa due to shallower channels compared to base case).

Steel Bridge Load Rating Impacts Owing to Autonomous Truck Platoons

Autonomous truck platoons are two or more trucks driving together as a single unit through the use of vehicle-to-vehicle communication technology. These platoons can automatically accelerate or brake together, allowing them to travel at closer distances. With the world moving towards a more environment-friendly approach to everyday decisions, it is not a surprise that the concept of truck platooning is gaining momentum, as it reduces CO2 emissions by lowering fuel consumption. However, studies need to be performed to confirm that existing bridges will be able to adequately support truck platoons. The scope of this research is to study the effects of truck platooning on steel girder bridges in the United States (US). A multi-dimensional parametric study was conducted, which evaluated a variety of bridge span configurations and span lengths. Load ratings (using three different methodologies) were calculated for each of these structures for a range of truck platoons (both the number of trucks within a platoon and spacing between trucks). For comparison, the American Association of State Highway Transportation Officials (AASHTO) design and legal load ratings were also calculated for each bridge and were used to quantify the adequacy of current bridges to carry truck platoons. The study was able to identify the potentially inadequate existing bridges based on the original design methodology, configuration, and span length. This information is intended to be valuable to bridge owners as an initial screening process along corridors that will be subjected to regular truck platoon traffic.

Probabilistic assessment of live load effects on continuous span bridges with regular and irregular configurations and its design implications

Studies on live load effects reported in recent literature are based on simple span bridges or on a limited number of continuous span bridges and regular configurations. In this study, an extensive probabilistic assessment of live load effects on continuous bridges is carried out for regular and irregular span configurations using weigh-in-motion data. Single vehicle passage is considered, and live load effects are compared with those from a live load model developed for simple spans from the same database. Truck models from Canada are also used for comparison purposes. Discussion of the fitting of extreme distribution is included, and an optimization scheme for the fitting is proposed. The most important finding of the study is that the use of live load models developed from simple spans or a limited number of continuous spans may not be suitable for designing continuous bridges, especially those with irregular configurations and short spans.

Optimal mechanical sag estimator for leveled span overhead transmission line conductor

Mechanical sag of the overhead transmission line (OTL) is a critical parameter for power system operation. However, remote locations of the conductor limit observability of sag. To monitor sag, distributed (DMS) or point measurement systems (PMS) are used. But, due to the limitation of DMS to use ruling span method, PMS is preferred. PMS requires sensors on every tower; as a result, sensor and data transmission requirements are high. This paper attempts to reduce the sensor requirement and estimate the sag in leveled span. To reduce the number of sensors and identify their location a linear integer programming based optimal sensor placement approach is proposed while keeping the redundancy intact. Using this, a reduced order, least-square based state estimator is proposed to estimate the sag in leveled span configuration. The estimator uses the conductor temperature and tension at one end of the span as input. Though, designed assuming ideal leveled span configuration, it is found to work for actual operating conditions. The performance of the proposed estimator is validated on the sag and tension data obtained with simulations on PLS-CADD™. Moreover, to eliminate the bad data, sensitivity based bad data elimination approach is presented. It allows replacement of bad data with almost exact values. The results show the robustness of the proposed approach.

Optimal Hyperelliptic Cambered Span Configurations for Minimum Drag

The current study considers an analysis of hyperelliptic cambered span wing configurations, optimized for minimum drag. This study encompasses a multidimensional design optimization approach wherein the wing geometries are optimized with respect to both span load and spanwise camber to achieve minimum aerodynamic drag. A discrete vortex element method was coupled with a constrained gradient-based optimization routine to achieve these drag-optimal design configurations. Optimum drag configurations were obtained at a fixed design lift coefficient as well as a fixed bending moment constraint. Navier–Stokes simulations were also performed, which revealed an gain of 29.01 and 25.35% at design conditions, relative to an elliptically loaded planar wing for the upward and downward cant configurations, respectively. Different wake trace characteristics for the two hyperelliptic cambered span configurations were observed along with surface flow features indicating different wake vortex and boundary-layer transition behaviors for the two hyperelliptic cambered span configurations.

Wind tunnel quantification of dynamic stall on an S817 airfoil and its control using synthetic jet actuators

AbstractWind tunnel experiments were performed to quantify the aerodynamic characteristics of the S817 airfoil in dynamic stall conditions, and the subsequent application of active flow control to modify the manner by which dynamic stall incepts. Both quasi‐2D and cantilevered finite span configurations were tested. Surface pressure, six‐component force‐torque sensor, and stereoscopic particle image velocimetry (SPIV) were used to quantify the baseline flow and the benefits of actuating synthetic jets (installed at x/c = 0.35, angled 45° into the flow, and at a momentum coefficient Cμ = 0.012). The airfoil was pitched at reduced frequencies of kf = 0.025 and 0.05 and at shallow and deep stall. Vortex induced lift from dynamic stall was observed and was eliminated by the use of synthetic jets for nearly all conditions; pitching moment deviation was also observed to be significant, and was eliminated at shallow stall and significantly reduced during deep dynamic stall when the synthetic jets were actuated. Moreover, the activation of synthetic jets resulted in significant reduction in the hysteresis (area within the pitching up and pitching down load history) of the lift and pitching moment through all experimental conditions, as much as 41% and 85%, respectively. SPIV flow fields in shallow dynamic stall demonstrated that actuation of synthetic jets confined the separated region to the trailing edge, in both the instantaneous and time averaged sense. To further reduce the lift and pitching moment hysteresis at high angles of attack, a pulse modulation technique was used and showed a marked increase in synthetic jet performance compared with the continuously actuated case and achieved this result with approximately 65% less power consumption.

Abstract 5381: Understanding the genesis and oncogenic consequences of tandem duplicator phenotypes in human cancers

Abstract Genome-scale instability configurations in cancer genomes are commonly found across different types of cancers. We and others have described an enrichment of head-to-tail somatic segmental tandem duplications (TDs) in primarily breast and ovarian cancers, a configuration known as the Tandem Duplicator Phenotype (TDP). Here, we perform a meta-analysis of 2,717 human cancer genomes, representing 30 different tumor types and refine the TDP classification based on the identification of highly specific and recurrent TD span profiles. Overall, we identify the TDP as a highly recurrent chromosomal instability configuration, occurring in 14% of the cancer genomes examined. The TDP is remarkably prevalent in triple negative breast cancer (50%), ovarian cancer (55%), and uterine cancers (45%), but is infrequent in most other cancer types. In TDP tumors, TD span sizes can be classified into three major discrete intervals with modal values of 10 Kb, 230 Kb, and 1.7 Mb. TDPs with a dominant TD modal span size of 10 Kb are strongly associated with conjoint TP53 mutations and BRCA1 deficiency across different tumor types. TDPs with larger span sizes (230 Kb and 1.7 Mb) are associated with CCNE1 pathway activation and CRKRS/CDK12 gene disruptions. We proved the driver role of the conjoint abrogation of the BRCA1 and TP53 genes for the induction of TDP cancers with the 10 Kb predominant span peak by generating mammary cancers with a Tandem Duplicator Phenotype of the ~10 Kb TD span configuration type in genetically modified mouse models harboring deleterious mutations in only these same two genes. Lastly, we describe how heterogeneous combinations of tumor suppressors and chromatin topologically associating domains are disrupted, and oncogene and tissue-specific super enhancers are duplicated as a consequence of TD formation in TDP tumors. In summary, our work unifies a number of observations around a specific cancer genomic signature, shows how a number of genetic drivers converge on creating the tandem duplicator phenotype, and how the downstream consequences of the TDs generate oncogenic diversity that allows for further formation of genetic subgroups. The implications of TDP-based stratification for therapy response are currently under investigation. Citation Format: Francesca Menghi, Floris Barthel, Vinod Yadav, Ming Tang, Bo Ji, Gregory Carter, Jos Jonkers, Roel Verhaak, Ralph Scully, Ed Liu. Understanding the genesis and oncogenic consequences of tandem duplicator phenotypes in human cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5381.

Optimal morphing – augmented dynamic soaring maneuvers for unmanned air vehicle capable of span and sweep morphologies

This paper investigates autonomous dynamic soaring maneuvers for a small Unmanned Aerial Vehicle (sUAV) having the capability to morph. Dynamic soaring for UAVs have mostly been confined in literature to fixed configurations. In order to analyze the extent to which dynamic soaring is influenced by different morphologies, an innovative concept of integrating dynamic soaring with morphing capabilities is introduced. Moreover, optimal soaring trajectories are generated for two basic wing morphologies: variable sweep and variable span. Three-dimensional point-mass UAV equations of motion and nonlinear wind gradient profile are used to model the flight dynamics. Parametric characterization of the key performance parameters is performed to determine the optimal platform configuration during various phases of the maneuver. Results presented in this paper indicate 15% lesser required wind shear by the proposed span morphology and 14% lesser required wind shear by the proposed sweep morphology, in comparison to their respective fixed wing counterparts. This shows that the morphing UAV can perform dynamic soaring in an environment, where fixed configuration UAVs might not, because of lesser available wind shears. Apart from this, span morphology reduced drag by 15%, lift requirement by 11% and angle of attack requirement by 20%, whereas increased the maximum velocity by 6.2%, normalized energies by 9% and improved loitering parameters (approximately 10%), in comparison to fixed span configurations. Similarly, sweep morphology guaranteed 20% drag reduction, 16% lesser angle of attack requirement and improved loitering performance over the fixed sweep configurations. The results achieved from this study strongly support the idea of integrating dynamic soaring with morphing capabilities and its potential benefits.

Differences in Academic Achievement by Grade Span Configuration: A Multiyear Texas Investigation

Differences in Academic Achievement by Grade Span Configuration: A Multiyear Texas Investigation

An investigation of AASHTO’s requirements for providing continuity in simple span bridges made continuous

AASHTO’s requirements for providing continuity in simple span bridges made continuous are investigated by performing a parametric study which consists of 140 time dependent analyses for various precast concrete beam shapes. The beam shapes considered include three precast concrete bulb tees (PCBT), two AASHTO type beams, and two Florida I-beams (FIB). Various beam spacing and span configurations are considered. A sectional analysis approach that employs the age adjusted effective modulus method for capturing creep effects is presented for calculating restraint moments. AASHTO models for creep and shrinkage are used to conduct the parametric study. For each case considered a minimum girder age for when continuity can be established is recommended such that the total restraint moment at the intermediate support is equal to or smaller than zero. The recommended minimum girder ages at continuity vary from 55 to 90 days for PCBTs, 55–70 days for AASHTO type beams, and 55–80 days for FIBs. The influence of fci′, choice of creep and shrinkage model, and choice of analysis method on the magnitude of restraint moments is investigated. The specification of a higher fci′ is an effective technique to reduce the minimum required girder age at continuity. The magnitude of restraint moments appears to be highly sensitive to the selected creep and shrinkage model. The proposed analysis method addresses the shortcomings of other closed form formulations and results in restraint moments that are more sensitive to the girder age at continuity.

New insights on span selection for Chinese solar greenhouses using CFD analyses

Chinese solar greenhouses (CSG), with thin plastic films on the south roof for transmitting the sun’s rays during the daytime and a heavy cover at night over the south roof with large thermal masses in the wall, north roof and soil to retain heat, can be used to produce vegetables and flowers year round without auxiliary heating during the winter. CSG spans can be increased to increase the production area; however, although the effect of increasing the span on the inside climate has been investigated experimentally, there is still no good guidance on selecting a suitable span configuration for growers. This investigation analyzed three groups of span configurations with spans of 10m, 12m and 14m. The first set of designs had all the other dimensions varied in proportion to the span width. The second set had the same dimensions for the north roof and north wall with the other dimensions varied to fit the longer spans. The third set had the same south roof with a longer north roof to fit the longer span. The analyses were based on a 12m span CSG simulation model validated in a former study with the thermal environments predicted using computational fluid dynamics (CFD) analyses. The results show that, for the CSG with all the dimensions varied in the same proportion, the inside air temperature is highest with the 14m span and lowest with the 10m span. For CSG with the same north roof and north wall dimensions, the air temperature is the highest with the 12m span and lowest with the 14 m span. For the configurations using the same south roof size, the 10m span with the taller north wall has similar air temperatures as the 12m span, with temperatures inside both spans being higher than the other 10m span with the shorter north wall height. Analyses of the solar heat gains, heat losses and temperature distributions for each group give good guidance for span selections for the growers.

Which Middle School Model Works Best? Evidence From the Early Childhood Longitudinal Study

There are few areas of school organization that reflect more dissatisfaction than how to structure the education of adolescents in the middle grades. This study uses multilevel models on nationally representative data provided by the Early Childhood Longitudinal Study to investigate the relationship between schools’ middle-level grade span and students’ math achievement. Classroom quality was considered as an explanation for any relationships between grade span and achievement. Also examined was whether gender and family structure moderated this relationship. Results indicate that there is no generalizable relationship between grade span configuration and math achievement, but that measures of classroom quality predicted math achievement. The results should give reflective pause to reformers considering whole-scale changes to the ways in which grade spans are organized and sharpen the policy focus on classroom quality.