Actual Traffic Load Research Articles

Evaluation of Structural Behavior of Precast Prestressed Concrete Pavement with Finite Element Analysis

A full-scale precast prestressed concrete pavement (PPCP) system was constructed and evaluated under actual traffic load conditions to develop the design guideline under Florida conditions. This test section showed good load transfer efficiency and riding quality. However, information was lacking about its structural response and potential performance. A three-dimensional finite element model was developed for stress analysis of PPCP under critical loading conditions. The developed three-dimensional model was calibrated by using deflection data obtained with a falling weight deflectometer. The model was used to perform a parametric analysis to determine the effects of critical loading location, concrete modulus, coefficient of thermal expansion of concrete, loss of prestress force, and subgrade stiffness under typical Florida conditions. Results of the parametric study indicate that the maximum stresses in the concrete increased significantly as the concrete modulus and coefficient thermal expansion increased. Because of the increase in flexural strength associated with the increase in elastic modulus of the concrete, an increase in elastic modulus of the concrete results in a decrease in the computed stress-to-strength ratio under critical load–temperature conditions. The PPCP system that was evaluated appeared to have a good predicted pavement performance with a computed stress-to-strength ratio of less than 0.5, with up to an additional loss of 20% of prestress force in the longitudinal and transverse directions. Variations in the base and subbase properties were found to have a minimal effect on the maximum induced stresses in concrete. This finding indicates that the PPCP system is appropriate for a wide variety of subbase and subgrade conditions.

Congestion Aware Multipath Routing: Performance Improvements in Core Networks

In this paper the improved Congestion Aware Multipath Routing algorithm is analysed in terms of Core network throughput and longer paths contribution. The algorithm discovers unused network resources and dynamically adapts to the actual traffic load and available resources displacement. Several simulation scenarios have been benchmarked in order to verify algorithm in typical Internet Service Provider cases. Simulation scenarios in this paper are focused on verifying functionality in dense core networks. For this purpose, tests were performed on TeraStream based network – the Deutsche Telekom Group design concept. Simulation results have proven better performance and resource utilization of the proposed algorithm than traditional Bellman-Ford based algorithms and equal cost multipath approaches.

A Self-Tuning Receiver-Initiated MAC Protocol for Wireless Sensor Networks

Receiver-initiated medium access control protocols for wireless sensor networks are theoretically able to adapt to changing network conditions in a distributed manner. However, existing algorithms rely on fixed beacon rates at each receiver. We present a new received initiated MAC protocol that adapts the beacon rate at each receiver to its actual traffic load. Our proposal uses a computationally inexpensive formula for calculating the optimum beacon rate that minimizes network energy consumption and, so, it can be easily adopted by receivers. Simulation results show that our proposal reduces collisions and diminishes delivery time maintaining a low duty cycle.

Congestion Aware Multipath Routing: Aggregation Network Applicability and IPv6 Implementation

Currently, the service provider network capacity utilization is low due to the shortest multipath based routing protocols Opens Shortest Path First (OSPF) and Intermediate System-to-Intermediate System (ISIS). Due to inefficient routing approach, certain paths can be overloaded and link capacity is required while alternative paths are unused. The overall network has to be dimensioned with higher link bandwidth requirements introducing additional line, linecard, routing engine and overall solution cos. This paper provides improved Congestion Aware Multipath Routing (CAMRv2) algorithm overview. The new network routing algorithm allows higher throughput, network load-balancing and stability to ensure lower congestion and data drop on critical links. The algorithm discovers unused network resources and dynamically adapts to the actual traffic load and displacement. The focus in this paper is on new parameters for path computation performance improvement. Additionally, detailed IPv6 source routing CAMRv2 implementation for parallel coexistence with present networks is presented. Finally, the new routing algorithm is simulated in several scenarios over aggregation network. The result of simulations have proved better performance and resource utilization of the proposed algorithm in sparse aggregation network in terms of load-balancing between uplinks to the core network

Recent developments in bridge weigh in motion (B-WIM)

Bridge weigh in motion (B-WIM) uses accurate sensing systems to transform an existing bridge into a mechanism to determine actual traffic loading. This information on traffic loading can enable efficient and economical management of transport networks and is becoming a valuable tool for bridge safety assessment. B-WIM can provide site-specific traffic loading on deteriorating bridges, which can be used to determine if the reduced capacity is still sufficient to allow the structure to remain operational and minimise unnecessary replacement or rehabilitation costs and prevent disruption to traffic. There have been numerous reports on the accuracy classifications of existing B-WIM installations and some common issues have emerged. This paper details some of the recent developments in B-WIM which were aimed at overcoming these issues. A new system has been developed at Queens University Belfast using fibre optic sensors to provide accurate axle detection and improved accuracy overall. The results presented in this paper show that the fibre optic system provided much more accurate results than conventional WIM systems, as the FOS provide clearer signals at high scanning rates which require less filtering and less post-processing. A major disadvantage of existing B-WIM systems is the inability to deal with more than one vehicle on the bridge at the same time; sensor strips have been proposed to overcome this issue. A bridge can be considered safe if the probability that load exceeds resistance is acceptably low, hence B-WIM information from advanced sensors can provide confidence in our ageing structures.

Deflection monitoring and assessment for a suspension bridge using a connected pipe system: a case study in China

Summary This paper discusses the application of a connected pipe system (CPS) to a suspension bridge in China for the purpose of vertical deflection monitoring and assessment. The CPS mainly consists of three main parts: the pressure transmitters to detect the height change of liquid, the pipes to connect the reference point and measurement points, and the liquid to fill the connected pipes. Multiple pressure transmitters, taken as the measurement point, were mounted inside of the girder. A reference transmitter was mounted inside of a tower, taken as a fixed point. To verify the performance and reliability of the CPS, a controlled load test after the completion of the bridge construction and an uncontrolled load test under the actual traffic loading were carried out. The results showed that the CPS exhibited excellent capability in real-time measurement of vertical deflection of the suspension bridge. With the long-term deflection data monitored by the CPS, the extreme deflections with respect to vehicle loads were predicted by extreme value analysis. The generalized extreme value distribution was adopted to establish the probability models of the daily maximum and minimum deflection sequences, and then the extreme deflections within the design reference period of 100 years were determined based on the probability models. Comparison of the extreme deflections and the deflection thresholds was carried out. The deflection monitoring and assessment method proposed in this paper have shown high potential of applicability in the practice of health monitoring for long-span bridges. Copyright © 2015 John Wiley & Sons, Ltd.

4.75 mm SMA Performance and Cost-Effectiveness for Asphalt Thin Overlays

This paper presents the design of stone matrix asphalt (SMA) with 4.75-mm nominal maximum aggregate size (NMAS) and alternative surfacing cross-section for an asphalt wearing course that may improve pavement performances while controlling costs by using locally available aggregates. The 4.75 -mm NMAS dense-graded mix was previously used in several states to reduce layer thickness and cost. Because of its poor friction and limited performance, however, it was generally used as levelling binder and placed on low-volume roads. The 4.75-mm SMA is proposed for thinner asphalt overlays in this study to improve its performance as well as surface texture. The ultimate goal of this study is to develop the 4.75-mm SMA and evaluate its performance and engineering benefits as a wearing course under laboratory and field conditions. Test pavement sections were constructed in Northern Illinois and on-site performance tests were conducted to evaluate its performance under actual traffic loading. The engineering cost-benefit analysis with respect to performances from both laboratory and field studies suggests the proper application of 4.75-mm SMA as an efficient and cost-effective wearing course for asphalt thin overlays.

Prediction of Rigid Pavement Responses under Axle Loads Using Artificial Neural Network

The analysis of stresses, strains and deflections in rigid pavement is an important step in the mechanistic pavement design of new pavements and rehabilitation design of existing pavements. However rigid pavements are complex structures to analyze utilizing closed form solutions. In order to simulate actual traffic loading cases and realistic pavement structures a finite element analysis is needed. However, in order to perform finite element analysis for different axle load configurations to analyze pavement damage using traffic spectra, it will require a great amount of time for each design option. In addition, using finite element analysis will require special expertise and software which might not be available in many highway departments of transportation. In this research, the outputs of finite element analysis for multiple axle load configurations, rigid pavement structures and material properties were used to train an artificial neural network to predict stresses and deflections in rigid pavement with great accuracy. The fully trained artificial network can be used to predict principal and normal stresses and deflections with reasonable accuracy with a mean squared error of 0.002. The artificial neural network can be used in any mechanistic empirical pavement design procedure to replace chart solutions or lengthy finite element analysis.

A new power profiling method and power scaling mechanism for energy-aware NetFPGA gigabit router

Today the ICT industry accounts for 2–4% of the worldwide carbon emissions that are estimated to double in a business-as-usual scenario by 2020. A remarkable part of the large energy volume consumed in the Internet today is due to the over-provisioning of network resources such as routers, switches and links to meet the stringent requirements on reliability. Therefore, performance and energy issues are important factors in designing gigabit routers for future networks. However, the design and prototyping of energy-efficient routers is challenging because of multiple reasons, such as the lack of power measurements from live networks and a good understanding of how the energy consumption varies under different traffic loads and switch/router configuration settings. Moreover, the exact energy saving level gained by adopting different energy-efficient techniques in different hardware prototypes is often poorly known. In this article, we first propose a measurement framework that is able to quantify and profile the detailed energy consumption of sub-components in the NetFPGA OpenFlow switch. We then propose a new power-scaling algorithm that can adapt the operational clock frequencies as well as the corresponding energy consumption of the FPGA core and the Ethernet ports to the actual traffic load. We propose a new energy profiling method, which allows studying the detailed power performance of network devices. Results show that our energy efficient solution obtains higher level of energy efficiency compared to some existing approaches as the upper and lower bounds of power consumption of the NetFPGA Openflow switch are proved to be 30% lower than ones of the commercial HP Enterprise switch. Moreover, the new switch architecture can save up to 97% of dynamic power consumption of the FPGA chip at lowest frequency mode.

Experimental Analysis of Stiffness of the Riveted Steel Railway Bridge Deck Members’ Joints

Abstract The paper deals with the real behaviour of the riveted steel railway bridge deck members’ connections with respect to their bending stiffness. Attention is paid to the stringer-to-cross beam connection as well as the cross beam-to-main girder connection. The stiffness of the two connections is investigated on the basis of evaluation of the experimentally determined stress response of the observed structural members to the actual traffic load on an existing railway bridge.

Traffic load models for Latvian road bridges with span length up to 30 meters

Bridges are structures that propose the service life up to hundred years. However, the actual traffic load models significantly differ from the characteristic load models used in the design. The analysis of former design codes of bridges used in the last century in Latvia showed the considerable increase in values of characteristic traffic loads. The traffic loads proposed in Eurocode 1: Actions on Structures – Part 2: Traffic Loads on Bridges considerably increase the actual traffic loads passing Latvian bridges. Therefore, the use of the actual traffic load models for assessment of the load carrying capacity of the older bridges will extend the service life and save financial funds for the maintenance of the bridges. Earlier, the obtaining of the correct traffic data was complicated. Today after implementation of the Weight-in-Motion system, it is possible to collect vehicle information without interrupting traffic flow. This includes data of the number of axles, vehicle wheelbase, speed and axle loads that describes the actual loading cases on the roads and bridges. The analysis of the recorded data of Weight-in-Motion the system enabled to obtain the load distribution diagrams, to determine the position of the heaviest axel, traffic speed and intensity values. The obtained results of statistical analysis of actual traffic loads allowed developing the integrated traffic load models for bridges, based on actual traffic load in Latvia. Obtained integrated traffic load models for bridges in Latvia is used for evaluation of the value of the adjustment factor α of the load model LM1 proposed in Eurocode 1: Actions on Structures – Part 2: Traffic Loads on Bridges.

Accurate measurements of gross vehicle weight through bridge weigh-in-motion: a case study

In a bridge design code, the design live loads should be based on actual traffic loads. In the past, the information about the actual truck loads on highway bridges was obtained from truck surveys, in which the trucks are stopped for measurement and weighed on ‘static’ weighing scales. During the past few decades, however, the information about truck loads is collected either by pavement weigh-in-motion or bridge weigh-in-motion (BWIM) systems. This paper provides details of three BWIM methods, which were calibrated with extensive testing on a slab-on-girder bridge in Winnipeg, Canada. The first two methods are based on the assumption that truck loads could be represented by an equivalent uniformly distributed load. The first method uses the asymmetry in the shape of the bending moment diagram to calculate the gross vehicle weight (GVW), while the second method compares the girder response at two instrumented transverse sections. The third method calculates GVW using strain signal area as proposed by Ojio and Yamada in 2002. The results show that the first method was inconsistent in its accuracy; the second method’s accuracy reduced with the length of the vehicle. The third method proved consistent and accurate to within 5 % for the test trucks provided that the vehicle speeds could be estimated accurately. Accurate calculations of the truck speeds were achieved by using the time delay in the peak responses of the straps that confine the externally restrained deck slab of the bridge.

A pattern matching approach to speed forecasting of traffic networks

Unlike other existing traffic data collection techniques, probe vehicles, or floating cars traveling on a road network, have appeared as a complementary solution for increasing coverage areas without requiring expensive infrastructure investments. When organized in a fleet with communication capabilities and exchange of information with a central data system, they give rise to a Floating-Car Data (FCD) system. The purpose of this paper is to present a model for short-term traffic speed forecasting based on an operating FCD system, developed and operated in Italy, delivering real-time traffic speed information throughout the Italian motorway network and along some important arterial streets located in major Italian metropolitan areas. Specifically, a database covering the whole period ranging from April 2008 to October 2011 is available for Rome Ring Road, a toll-free motorway that encircles Rome (Italy), and the developed case study pertains to a portion of its available speed data. A Pattern Matching method of prediction will be detailed, which reports interesting properties in terms of forecast accuracy; the method tries to identify, in the past data history, patterns neighboring (in a proper sense) the current one, which describes the actual traffic load, and produces forecasts supposing that the current situation will evolve in a similar way.

Effects of Principal Stress Rotation on the Cumulative Deformation of Normally Consolidated Soft Clay under Subway Traffic Loading

The authors investigated the effects of principal stress rotation (PSR) on the traffic load–induced settlement of subways in soft subsoil. Here, a series of hollow cylinder tests on normally consolidated, medium-plasticity soft clay with and without principal stress rotation were performed along with finite-element modeling and simulation. The results show significant increases in both excess pore-water pressure and cumulative deformation of the normally consolidated soft clay when PSR is present and simulated, and the effects become more pronounced as the maximum effective principal stress ratio or load frequency increases. Under the actual traffic load–induced stress in subsoil below the subway tunnel, the presence of PSR increases the cumulative deformation of soft clay by 9–23% compared with that without PSR. As an approximation, the cumulative deformation of soft clay with the effect of PSR can be estimated by multiplying the deformation derived from the repeated triaxial testing without PSR with the ratio of axial strain between the two tests.

Dynamic power management in energy-aware computer networks and data intensive computing systems

Energy awareness is an important aspect of modern network and computing system design and management, especially in the case of internet-scale networks and data intensive large scale distributed computing systems. The main challenge is to design and develop novel technologies, architectures and methods that allow us to reduce energy consumption in such infrastructures, which is also the main reason for reducing the total cost of running a network. Energy-aware network components as well as new control and optimization strategies may save the energy utilized by the whole system through adaptation of network capacity and resources to the actual traffic load and demands, while ensuring end-to-end quality of service. In this paper, we have designed and developed a two-level control framework for reducing power consumption in computer networks. The implementation of this framework provides the local control mechanisms that are implemented at the network device level and network-wide control strategies implemented at the central control level. We also developed network-wide optimization algorithms for calculating the power setting of energy consuming network components and energy-aware routing for the recommended network configuration. The utility and efficiency of our framework have been verified by simulation and by laboratory tests. The test cases were carried out on a number of synthetic as well as on real network topologies, giving encouraging results. Thus, we come up with well justified recommendations for energy-aware computer network design, to conclude the paper.

Tiered Adaptive Large-Scale Storage System with High Performance

There are various calculations, transmission, and storage devices in terms of performance or reliability characteristics in great physical differences exist of large-scale cluster storage systems. Meanwhile, the actual traffic load data access for storage devices is also not uniform in space and time and there is a big difference. It is unrealistic and unwise if all the data stored on the high-performance devices. In order to resolve this problem effectively, we propose large-scale adaptive tiered storage system architecture in which structure can carry out effective monitoring access to the load and adapting allocation of storage resources based on the application environment. This can fulfill the full potential to the advantages of high-performance storage nodes to improve the performance of large-scale clustered storage systems.

Experimental investigation and monitoring of a polypropylene-based fiber reinforced concrete road pavement

In this work, basic guidelines are provided for the design of a polypropylene-based fiber reinforced concrete (PFRC) road pavement, as applied in an actual testing section resting inside a tunnel of the “Quadrilatero Marche-Umbria” road empowerment project, Italy. Results of a six-month monitoring carried out on actual traffic loads are also presented, as a feedback to the designing stage. Monitoring encompasses direct measurement of the strain level inside the cast as well as acoustic measurement. It is shown that the fiber reinforced concrete technology provides an efficient, safe as well as cost-effective design solution for roadways, especially inside tunnels.

Design and testing of corrosion damaged prestressed concrete joists: the Pescara Benchmark

An experimental campaign named the Pescara benchmark and devoted to study the dynamic behaviour of corroded p.c. joists has been conducted. The steel corrosion reduces the area of the reinforcement and causes cracking of concrete so that r/c members are subjected to loss of strength and stiffness. It is of interest to evaluate the corrosion level at which the damage can be detected through signal processing procedures and how close such level is to the r/c member safety limits. Joists of current industrial production having different steel to concrete ratios are tested in different laboratory conditions. Dynamic tests involve either free vibrations and forced vibrations due to a moving mass simulating actual traffic loads in railway bridges. The paper discusses the rationale of the tests including the set up of the artificial corrosion, the static characterization of the joist and the dynamic tests in the different stages of corrosion experienced.

Plastic load bearing capacity of multispan composite highway bridges with longitudinally stiffened webs

The introduction of the Eurocodes makes plastic design criteria available also for composite bridges, leading to more economical solutions compared with previous elastic design rules. Particularly for refurbishment old bridges with higher actual traffic loads, up to date outside the scope of the Eurocodes, strengthening should therefore be avoidable or at least be necessary only to a minor extent. For bridges with smaller spans and compact cross sections, the plastic load bearing capacity is clearly justified. In this work, however, the focus is placed on long span continuous composite bridges with deep, longitudinally stiffened girders, susceptible to local buckling. In a first step, the elastic - plastic cross section capacity of the main girder in bending is studied as an isolated case, based on high preloads acting on the steel girder only, due to the common assembling procedure without scaffolding. In a second step, the effects on the whole structure are studied, because utilising the plastic section capacity at midspan leads to a redistribution of internal forces to the supports. Based on the comprehensive study of an old, actual strengthened composite bridge, some limitations for plastic design are identified. Moreover, fully plastic design will sometimes need additional global analysis. Practical recommendations are given for design purposes.

Validation of Backcalculated Modulus Values from Falling Weight Deflectometer through Instrumentation on I-35 in Oklahoma

Several state departments of transportation evaluate the modulus of pavement layers from nondestructive deflection tests such as the falling weight deflectometer (FWD). Although the FWD is a widely used nondestructive testing device, it still does not fully represent the loading conditions generated by moving vehicular traffic. Therefore, the modulus values backcalculated from FWD data may be different from those values backcalculated from vehicular traffic loading data. A comparison is presented of modulus values backcalculated from FWD and strain gauge measurements collected on a 1,000-ft-long instrumented section of I-35 in central Oklahoma. The FWD data were captured at different temperatures with different loading configurations. Meanwhile, longitudinal and transverse strain data were captured from May 30, 2008, through October 28, 2009, over a wide range of middepth pavement temperatures (40°F to 110°F) under actual vehicular traffic loading. The influence of different backcalculated modulus values is demonstrated through the prediction of remaining life in terms of number of equivalent single-axle loads of the existing pavement. Also presented is a description of the testing program, data collection efforts, and subsequent analysis for the I-35 instrumented section. Overall, modulus values backcalculated from the FWD and from longitudinal strain gauges showed close agreement at temperatures above 50°F.