Normal Traffic Load Research Articles

Using the load distribution between girders to monitor the condition of bridges

This study looks at the load distribution among beams in a 3-dimensional bridge Finite Element Model under normal traffic loading and the resulting effect of damage, modelled as a localised loss of elements in a beam. The load distribution is captured, both transversely across the girders and also longitudinally along the girders, and used to identify damage that is remote from the strain sensor location. When there is a loss of elements in a section of the bridge (e.g. due to a strike from a vehicle passing underneath), a portion of the load will redistribute along alternative load paths in the structure. This is most pronounced when the position of the loading and the location of the damage align but also happens when they do not. The study examines the effect of vehicles of different weight and axle configuration on the load distribution, and how grouping results by axle configuration can overcome this. A further novelty of this approach is that the strain response can be transformed into an influence line, which then allows data from large populations of general traffic to be used irrespective of axle configuration. The effect of various transverse positions of vehicles within the driving lane is overcome by combining data from large populations of vehicles. An advantage of this method is that the load distribution from a vehicle crossing is calculated as a ratio i.e. when the bridge is experiencing the same general environmental conditions, and thus reducing the difficulty in controlling the effects of varying environmental conditions when comparing results to a healthy baseline.

Deformation characteristics of red-mud embankment under monotonic and cyclic loads

The rapid growth in the production of the red mud has led to the shortage of land for stockpiling in recent years. Although red mud has been considered as the filling material for embankments, the deformation characteristics of a red-mud embankment under traffic loads has not yet been clarified. To promote its application in embankment construction, a series of centrifuge model tests of red-mud embankment under monotonic and cyclic loads were conducted. The deformation and failure processes of red-mud embankment under normal and overproof traffic loads were analyzed. The results show that the deformation characteristics of red-mud embankment varied significantly depending on the value of the external load. The deformation induced by monotonic load was greater than that induced by the cyclic load of the normal traffic load. The monotonic and cyclic loads of normal traffic load induced similar influential areas, and their deformation processes can be divided into rapid and slow growth parts. Shear failure occurred in the red-mud embankment under overproof traffic load. The same load increment induced more deformation of red-mud embankment after failure. Under reasonable dry density and water content, the deformation of red mud was acceptable, thus meeting the engineering requirements of embankment construction.

Erlang-U: Blocking Probability of UAV-Assisted Cellular Systems

In modern and future communication systems, we expect peaks of traffic that largely exceed the capacity of the system, since they are originally designed to support normal traffic loads. Such peaks can be caused by emergency events and cultural or sporting gatherings, among others. Indeed, implementing more channels than the ones required in normal traffic conditions would entail higher costs and energy consumption. As such, when a traffic peak arrives, the system performance is greatly affected. To this end, we propose the use of mobile channels that assist cellular systems to increase the capacity of the network for a certain period. In this paper, we derive the blocking probability of a UAV (Unmanned Aerial Vehicle)-assisted cellular system to temporarily increase the capacity of the communication network in case of a traffic overload. The analysis presented in this work allows a careful design of future communication systems requiring fewer channels, that can serve users in normal traffic load conditions while using UAVs to maintain an adequate blocking probability when the traffic load increases. To this end, we develop the ErlangU formula, similar to the ErlangB formula for a conventional voice service cellular system.

An experimental study on hybrid fibre reinforced engineered cementitious composite link slabs under static and fatigue loadings

This study conducted experimental investigations on the structural performances of link slabs which are constructed by using a newly developed hybrid-fibre reinforced engineered cementitious composite (hybrid-ECC). Both static and fatigue loadings were applied to validate the feasibility, provide a proof of concept study and demonstrate the benefits using hybrid-ECC for bridge link slabs application. Three identical quarter-scaled hybrid-ECC link slabs, simulating a link slab used for a typical 35-meter multi-span simply supported bridge, were fabricated. These slabs, denoted as LS-1, LS-2 and LS-3, were tested under designated static and fatigue loadings. Slab LS-1 was tested under static loading to obtain the flexural strength of the slab. Slabs LS-2 and LS-3 were tested under fatigue loadings to evaluate their fatigue performances under normal service loading and overload scenarios, respectively. Structural performances of these slabs in terms of deformation and crack width control capability, strain development on reinforcement bars and estimated service life were evaluated. It was observed that multiple microcracks were developed under both static and fatigue loadings. Slab LS-2 survived ten million cycles of service fatigue loading while LS-3 survived two million cycles of overload fatigue loading. For all the tests conducted under static and fatigue loadings, the maximum crack width observed on the three link slab samples was all controlled within the allowable limit of 0.2 mm until failure occurred. Based on the test results, it was estimated that if only the effects due to normal traffic loading and temperature variation were considered, the hybrid-ECC link slab could achieve a service life of more than 40 years. Therefore, the experimental study reconfirmed that the hybrid-ECC showed a high potential to improve the fatigue performance and extend the service life of link slab in bridge construction.

Effect of rubber-sand particle size ratio on shear properties of rubber-sand mixtures under normal cyclic loading

The mechanical properties of rubber-sand mixtures are influenced by the ratio of rubber-sand particle sizes and the rubber content. Rubber-sand mixtures used as roadbed fillers are primarily subjected to normal cyclic traffic loading. Therefore, a series of direct shear tests on rubber-sand mixtures under normal cyclic loading were conducted using a large-scale direct shear apparatus. The effects of the rubber-sand particle size ratio, rubber content, initial stress, and amplitude of normal cyclic loading on the shear strength of rubber-sand mixtures were evaluated. Based on the indoor tests, discrete element models of rubber-sand mixtures with different particle size ratios were established to explore the meso-mechanical mechanism of the mixed soil during the direct shear process. The results indicate that rubber-sand mixtures with low rubber content and a particle size ratio >1 have a positive effect on the shear strength of the mixed soil. The impact of initial stress on the shear stress of the mixed soil is greater than that of the normal cyclic load amplitude. As the particle size ratio increases, the inter-particle contact force becomes larger, resulting in more noticeable group anisotropy. Additionally, the main direction of the normal contact force anisotropy in the mixture consistently aligns with the deflection direction of the force chain. Rubber particles in rubber-sand mixtures with a large particle size ratio actively participate in the contact force chain network system, facilitating load transfer and positively influencing shear strength.

Campus realities: Forecasting user bandwidth utilization using monte carlo simulation

Adequate network design, planning, and improvement are pertinent in a campus network as the use of smart devices is escalating. Underinvesting and overinvesting in campus network devices lead to low network performance and low resource utilization respectively. Due to this fact, it becomes very necessary to ascertain if the current network capacity satisfies the available bandwidth requirement. The bandwidth demand varies from different times and periods as the number of connected devices is on the increase. Thus, emphasizing the need for adequate bandwidth forecast. This paper presents a Monte Carlo simulation model that forecast user bandwidth utilization in a campus network. This helps in planning campus network design and upgrade to deliver available content in a period of high and normal traffic load.

Dynamic Tests in Bridge Health Monitoring

Abstract Dynamic tests are one of the most significant diagnostic procedures applied in Bridge Health Monitoring in many countries. The paper presents a proposal of unified classification of the bridge dynamic tests together with review of the testing methods, including tests under designed and controlled loads, arranged short-term tests under normal traffic loads as well as permanent dynamic monitoring by means of built-in gauges mounted on a structure. Classification of bridge dynamic tests is proposed taking into account various types of vibration excitation methods, measured parameters and possible applications of obtained results in the Bridge Health Monitoring. General rules and procedures of bridge dynamic tests are described and discussed.

Performance assessment of prestressed concrete bridge girders using fiber optic sensors and artificial neural networks

Structural health monitoring (SHM) activities are essential for achieving a realistic characterisation of bridge structural performance levels throughout the service life. These activities can help detect structural damage before the potential occurrence of component- or system-level structural failures. In addition to their application at discrete times, SHM systems can also be installed to provide long-term accurate and reliable data continuously throughout the entire service life of a bridge. Owing to their superior accuracy and long-term durability compared to traditional strain gages, fiber optic sensors are ideal in extracting accurate real-time strain and temperature data of bridge components. This paper presents a statistical damage detection and localisation approach to evaluate the performance of prestressed concrete bridge girders using fiber Bragg grating sensors. The presented approach employs Artificial Neural Networks to establish a relationship between the strain profiles recorded at different sensor locations across the investigated girder. The approach is capable of detecting and localising the presence of damage at the sensor location without requiring detailed loading information; accordingly, it can be suitable for long-term monitoring activities under normal traffic loads. Experimental laboratory data obtained from the structural testing of a large-scale prestressed concrete bridge girder is used to illustrate the approach.

EA-MAC: A QoS Aware Emergency Adaptive MAC Protocol for Intelligent Scheduling of Packets in Smart Emergency Monitoring Applications

The evolution of the wireless sensor network (WSN) in recent years has reached its greatest heights and applications are increasing day by day, one such application is Smart Emergency Monitoring Systems (SMESs) which is in vision of implementation in every urban and rural areas. The implementation of WSN architecture in the Smart Monitoring Systems needs an intelligent scheduling mechanism that efficiently handles the high traffic load as well as the emergency traffic load without sacrificing the energy efficiency of the network. However, the traditional scheduling algorithms such as First Come First Served (FCFS), Round Robin, and Shortest Job First (SJF) cannot meet the requirements of high traffic load in SMESs. To address these shortcomings, this paper presents Emergency Adaptive Medium Access Control protocol (EA-MAC), a fuzzy priority scheduling based Quality-of-service (QoS)-aware medium access control (MAC) protocol for hierarchical WSNs. EA-MAC protocol employs the most powerful fuzzy logics to schedule the sensor nodes with both normal and emergency traffic load without any data congestion, and packet loss and maintaining the better QoS which is considered to be more important in SMESs applications. Moreover, a novel rank-based clustering mechanism in EA-MAC protocol prolongs the network lifetime by minimizing the distance between the Cluster Head (CH) and the Base Station (BS). Both analytical and simulation models demonstrate the superiority of the EA-MAC protocol in terms of energy consumption, transmission delay and data throughput when compared with the existing Time Division Multiple Access (TDMA) based MAC protocols such as LEACH protocol and Cluster Head Election Mechanism-Based On Fuzzy Logic (CHEF) protocol.

Evaluation of Pavement Performance due to Overload Single-Trip Permit Truck Traffic in Wisconsin

This study investigated the impacts of overweight (OW) permit truck traffic on flexible pavement performance in Wisconsin using field investigation and analysis utilizing the AASHTOWare Pavement ME Design software. A database of overweight single-trip permit truck records was analysed to produce a network of Wisconsin corridors heavily travelled by OW trucks. Four Wisconsin highways were selected for investigation due to high levels of OW truck traffic. The research included field work (traffic counts and visual pavement surface distress surveys) and AASHTOWare Pavement ME Design. Comprehensive analyses were conducted to evaluate pavement performance due to normal traffic loads as well as normal traffic loads plus the OW truck traffic loads. The use of mechanistic-empirical (ME) pavement analyses provided a methodology for estimating the proportion of pavement deterioration attributable to OW truck traffic. OW axle load distributions were developed and integrated with baseline truck traffic levels to develop axle load spectra and other traffic input parameters for the ME pavement analysis. The predicted total pavement deterioration levels from the AASHTOWare Pavement ME Design software were generally consistent with the levels of deterioration observed. The proportion of pavement damage and deterioration attributable to OW truck traffic was predicted to constitute a relatively minor proportion of total deterioration, with most distress indices showing relative increases of approximately 0.5% to 4%, with a few outliers. However, due to the small proportion of OW vehicles relative to the overall traffic levels, the OW vehicles were generally predicted to cause up to ten times the per-truck damage as compared with a typical legal-weight truck, depending on the distress mode and the test site.

On the service behaviour of masonry viaducts

Railway viaducts are suffering damage short of collapse that is not predicted by current assessments, but which requires major interventions. This is a critical issue facing the UK rail network, where freight traffic is growing rapidly. This paper offers a new understanding of critical behaviour, which is not dominated by arching. Rather, the main section over each pier and extending well into the span either side behaves as a rigid block, rocking back and forth as loads pass. This behaviour explains spandrel cracks and horizontal cracks in spandrel walls and below parapets, which are both frequently seen in arch viaducts. With further research, including field measurement of behaviour under normal traffic loads, this understanding should lead to useful assessment guidelines and new methods of strengthening and repair.

Research and application of a black rapid repair concrete for municipal pavement rehabilitation around manholes

Cracks and potholes around manholes on carriageways have long been a problem for municipal asphalt concrete roads. The traditional repairing method not only requires a long period of traffic interruption, but also does not meet the requirements of durability and aesthetic appearance. A black rapid repair fibre concrete (BRRFC) was developed for asphalt concrete pavement rehabilitation around manholes, based on a series of optimisation and scaled tests. As a super high-early-strength concrete, BRRFC has capacity to carry normal traffic loads after pavement manholes repairs for 8h. Meanwhile, it offers other advantages such as uniform and stable black colour, good performance in dry-shrinkage and wear resistance, low-cost, and easy construction. Applications of BRRFC in numerous municipal maintenance works showed that rehabilitated manhole areas were still intact and no obvious colour difference between the new and old pavement concrete after several years of service, achieving significant social and economic benefits for sustainability.

Enhancing the Quality of Service for Real Time Traffic over Optical Burst Switching (OBS) Networks with Ensuring the Fairness for Other Traffics.

Optical burst switching (OBS) networks have been attracting much consideration as a promising approach to build the next generation optical Internet. A solution for enhancing the Quality of Service (QoS) for high priority real time traffic over OBS with the fairness among the traffic types is absent in current OBS’ QoS schemes. In this paper we present a novel Real Time Quality of Service with Fairness Ratio (RT-QoSFR) scheme that can adapt the burst assembly parameters according to the traffic QoS needs in order to enhance the real time traffic QoS requirements and to ensure the fairness for other traffic. The results show that RT-QoSFR scheme is able to fulfill the real time traffic requirements (end to end delay, and loss rate) ensuring the fairness for other traffics under various conditions such as the type of real time traffic and traffic load. RT-QoSFR can guarantee that the delay of the real time traffic packets does not exceed the maximum packets transfer delay value. Furthermore, it can reduce the real time traffic packets loss, at the same time guarantee the fairness for non real time traffic packets by determining the ratio of real time traffic inside the burst to be 50–60%, 30–40%, and 10–20% for high, normal, and low traffic loads respectively.

Performance Analysis of Multi-Path TCP Network

MPTCP is proposed by IETF working group, it allows a single TCP stream to be split across multiple paths. It has obvious benefits in performance and reliability. MPTCP has implemented in Linux-based distributions that can be compiled and installed to be used for both real and experimental scenarios. In this article, we provide performance analyses for MPTCP with a laptop connected to WiFi access point and 3G cellular network at the same time. We prove experimentally that MPTCP outperforms regular TCP for WiFi or 3G interfaces. We also compare four types of congestion control algorithms for MPTCP that are also implemented in the Linux Kernel. Results show that Alias Linked Increase Congestion Control algorithm outperforms the others in the normal traffic load while Balanced Linked Adaptation algorithm outperforms the rest when the paths are shared with heavy traffic, which is not supported by MPTCP.

Using satellites to monitor Severn Bridge structure, UK

The Severn Bridge is a large UK suspension bridge. In 2010, a series of field surveys was commissioned to monitor the magnitude and frequencies of the bridge’s movements, through attaching nine dual-frequency survey grade global navigation satellite system receivers on the bridge and two reference satellite receivers adjacent to the structure. The satellite antenna locations and configuration allow the movements of the north cable to be analysed at four locations, as well as the differential movements of the two suspension cables to each other. In addition, this configuration allows the movements of the tops of the towers to be compared to the cables’ movements, as well as with each other. All in all, this allowed the relative movements of the various locations on the bridge’s suspension cables and tower tops to be compared to each other, at a rate of up to 20 Hz. Overall, some 3 days of raw code and carrier phase satellite data were gathered. During these sessions, normal traffic loading was experienced. This paper describes the survey, presents a selection of the key results and draws conclusions about the effective use of satellite positioning systems to enhance structural health monitoring.

Improving the Optical Burst Switching Networks Quality of Service by Ensuring the Fairness among the Network Traffic Types

The Optical burst switching (OBS) networks have been attracting much consideration as a promising approach to build the next generation optical Internet. Aggregating the burst in the OBS networks from the high priority traffic will increase the average of the loss of its packets. However, the ratio of the high priority traffic (e.g. real-time traffic) in the burst is a very important factor for reducing the data loss, and ensuring the fairness between network traffic types. This paper introduces a statistical study based on the significant difference between the traffics to find the fairness ratio for the high priority traffic packets against the low priority traffic packets inside the data burst with various network traffic loads. The results show an improvement in the OBS quality of service (QoS) performance and the high priority traffic packets fairness ratio inside the data burst is 50 to 60%, 30 to 40%, and 10 to 20% for high, normal, and low traffic loads, respectively.

Interconversion between viscoelastic functions using the Tikhonov regularisation method and its comparison with approximate techniques

Asphalt concrete behaves as a viscoelastic material under normal traffic loading and field conditions. The stress–strain behaviour depends on the rate of loading as well as the actual pavement temperature. In order to model the viscoelastic behaviour of the asphalt materials, viscoelastic functions need to be determined. In this study, a uniaxial static creep test was carried out for AC 20 and AC 14 asphalt mixtures. Several asphalt specimens were tested at different temperatures subjected to various deviator stresses in order to verify the proposed approach. Prony series for the creep compliance were determined for raw and smoothed data. Various optimisation techniques were utilised to ensure a monotonic increase in the Prony coefficient. A number of approximate interconversion techniques were evaluated in determining relaxation modulus resulted from the creep compliance interconversion. It was clear that Prony series constants affect the interconverted relaxation modulus. It was also obvious that using the discretisation of the slope of n value (slope of log creep compliance with log t) over the time domain instead of using one single constant value of the slope provides a better solution of the interconverted relaxation modulus. Finally, the exact interconversion method was applied to check the accuracy of approximate techniques. Tikhonov regularisation with the L-curve method was considered to solve the convolution integral. The exact solution was recommended as a result of investigating the extracted data. The approximate solution showed around 7.0% error comparing different approaches.

Fatigue life evaluation through field measurements and laboratory tests

The maintenance cost of old bridges is rapidly increasing, since many of them are reaching their design life. Hence requirements for remaining life evaluation of existing bridges are overwhelmingly increasing for bridge authorities all over the world. Fatigue phenomenon seems to be a great concern in this regard whereas no theoretical methods can evaluate the remaining life of existing bridges accurately. This paper presents the procedures used for assessment of remaining fatigue life of an aging orthotropic steel deck bridge in Tehran including strain field measurements carried out on critical fatigue details as well as laboratory tests on limited samples, taken from similar details of an identical disassembled bridge. Field measurements have been carried out under normal traffic loading during an 8-day period of time. Laboratory tests are made on samples taken from the most critical fatigue details on a region of high stress fluctuation (mid span) and the same details at a stagnant region (supports location) and compared. Similar results were obtained from both approaches showing the investigated bridges will not experience fatigue failure under the current traffic regime.

An Inter-Domain Path Computation Scheme Adaptive to Traffic Load in Domains

The establishment of inter-domain traffic engineered paths is a requisite to accomplishing an end-to-end bandwidth guarantee and end-to-end resource optimization. Though the inter-domain paths must be reliable, it is difficult to compute suitable backup inter-domain paths in advance when the traffic engineering information is not disclosed outside of each domain. This means that the inter-domain path computation must satisfy the severe requirement of path establishment delay, since all inter-domain paths traversing the links in failure need to be computed after the failure occurs. Though several inter-domain path computation schemes have been proposed, their relative characteristics remain unknown. First, this paper classifies the conventional inter-domain path computation schemes into two types, i.e. end-to-end and per-domain schemes, and compares their performances under various traffic loads. Based on results of the comparisons, this paper proposes an adaptive inter-domain path computation scheme that can satisfy the severe requirement of the path establishment delay. In this scheme, the domain sequence from the source node to the destination node is divided into multiple sub-domain sequences according to the traffic load in each domain. The end-to-end path computation scheme is applied to the sub-domain sequences under heavy traffic loads, while the per-domain path computation scheme is applied to those under normal traffic loads. The simulation results show that the proposed scheme can adaptively satisfy the requirement for the path establishment delay while it maintains the optimality of path computation, even if the traffic load applied to each domain changes.

Evaluation of Surface-Related Pavement Damage due to Tire Braking

ABSTRACT The response of flexible pavement at near-surface is significantly affected by interfacial tire-pavement contact stresses. In addition to highly non-uniform vertical stresses and surface tangential shear stresses at tire-pavement interface, tire braking at an intersection causes additional significant longitudinal contact stresses on the pavement surface. In this paper, the flexible pavement responses to three-dimensional (3-D) tire-pavement contact stresses at various tire rolling conditions were determined using a developed 3-D finite element model. The hot-mix asphalt (HMA) layer was characterized as a viscoelastic material, and the transient dynamic tire loading was simulated using a continuous moving load and implicit dynamic analysis. The analysis matrix includes two typical flexible pavement structures (76 mm and 152 mm HMA thicknesses) and three tire rolling conditions (free rolling at high speed, free rolling at low speed, and braking). The study concluded that the low-speed vehicle loading and tire braking aggravates the pavement deterioration at an intersection in terms of rutting or shoving in the HMA and surface cracking at the pavement surface. During tire braking, the damage ratios for pavement surface cracking may be as high as 8 to 32 depending on HMA thickness, compared to the normal traffic loading conditions. The tire braking increases the HMA rutting or shoving potential by 2.0 to 2.6 times due to the increased shear strains in two directions. Hence, pavements for intersections should be specified, designed, and constructed differently than regular asphalt pavements to withstand the more severe loading conditions.