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Znidaric, Ales
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Znidaric, Ales
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Znidaric, Ales
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- PublicationDynamic Load AllowanceChapter 4 provides a good explanation of the current state-of-the-art for the influence of dynamics on bridge traffic loading. It starts with an explanation of the concepts and a review of the various definitions used in the field, such as Dynamic Amplification factor and Impact Factor. It looks at how some of the main codes of practice in the world treat dynamics. A considerable portion of the chapter deals with the statistics of dynamic amplification. It is noted that the biggest dynamic amplifications tend to occur for light vehicle loading events. A statistical approach addresses this issue and provides a more appropriate allowance for dynamics which is called Assessment Dynamic Ratio. The influence of road surface roughness is considered and the implications of a local irregularity or pothole, as sometimes happens near the end joints. A number of field measurement campaigns of dynamic amplification are reported from various countries. These largely support the findings of the numerical studies.
53 - PublicationImpact factors on medium span bridges due to multiple vehicle presence(2002-06-20)
; ; ; The Dynamic Amplification Factor for Bridges is of major concern in both their design and assessment. Research to date has focused on the single truck event. However, in many bridges the critical loading case is that of multiple truck presence on the deck. To accurately determine the dynamic amplification factor it is necessary to examine the effects of multiple trucks traversing a bridge. Experiments in Slovenia were carried out to examine the dynamic amplification factor for single and two truck events. Numerical models were constructed and validated from these experiments. These models were then used to compare the dynamic amplification factors produced from both single and multiple trucks crossing the bridge at various speeds. Important conclusions are drawn for bridge design and assessment purposes.13 - PublicationRecommendations for Dynamic Allowance in Bridge AssessmentThis paper summarises the developments in the dynamic response of bridges to traffic loading based on a large amount of simulations and field tests carried out within the 6th EU framework ARCHES (2006-2009). When assessing the total traffic load effect on a bridge, there is a number of alternatives to characterise the associated dynamic component depending on the information available to the engineer. The simplest approach is to adopt the conservative values provided in bridge codes covering for many uncertainties. Nevertheless, if bridge drawings, bridge properties, updated weigh-in-motion data and road profile were known, then validated vehicle-bridge finite element interaction models can be used to reduce these uncertainties. Dynamic allowance can also be experimentally derived from measured total load effects using modern bridge weigh-in-motion technology. Guidelines are provided on how to obtain a site-specific value of dynamic allowance, both numerically and experimentally.
429 - PublicationEU FP6 - ARCHES Deliverable D10: Recommendations on dynamic amplification allowance(FEHRL, 2009-08-01)
; ; ; ; ; The ARCHES (Assessment and Rehabilitation of Central European Highway Structures) project (2006-09) involved partners from Belgium, Croatia, Czech Republic, Ireland, Italy, Poland, Slovenia, Spain, Switzerland and The Netherlands. The overall goal of the project is to reduce any gaps in the standard of highway infrastructure between Central and Eastern European Countries, particularly New Member States and the rest of the EU. Deliverable D10 is within WP2: optimise the use of existing infrastructure through better safety assessment and monitoring procedures which will avoid interventions, i.e., avoid unnecessary replacing or improving structures that are in fact perfectly safe. In particular, D10 provides a more realistic site-specific dynamic allowance for traffic loading than those genral values recommended in bridge codes.Correct evaluation of the behaviour of highway bridges under heavy traffic loading is extremely important both for the enhancement of design techniques, and also for the assessment of existing infrastructure. It is widely accepted that shortfalls exist in the determination of the traffic load which the bridge may be required to support during its expected lifetime due to inadequate consideration of amongst other factors, the dynamic interaction between the bridge structure and the heavy vehicles crossing it. Since it is the overall objective of this deliverable to combine lifetime static load effect values, with realistic dynamic amplification factors (to obtain an overall total lifetime load effect) there are two distinct parts:1) The calculation of bridge static load effect due to site-specific traffic flow, which is discussed in subtask 2.1.1 (Deliverable D08) along with the resultant assessment of bridge lifetime static load effect, and the selection of those loading events that are deemed critical (statically).Examples on how to determine these bridge traffic load models using Weigh-In-Motion (WIM) data and their configuration when using data from Central European countries are provided in subtask 2.1.1 on bridge traffic load monitoring. This subtask has also compared results between data from Western and Central European countries.2) Deliverable D10 focuses on the assessment of the levels of dynamic interaction occurring between a bridge and its associated vehicular traffic. This analysis incorporates a review of those recommendations given in current design/assessment codes for dynamic allowance.Then, the procedure to obtain a site-specific dynamic amplification factor using theoretical simulations and available experimental data is described. Some specific issues concerning the dynamic allowance associated to: (a) deteriorated bridges; (b) pre-existing bridge vibrations; (c) maximum total effects developing in sections different from midspan, (d) the existence of a bump prior to the bridge, or (e) critical loading cases such as cranes, are also discussed. Finally,general recommendations on dynamic allowance are provided.112 - PublicationBridgemon: Improved monitoring techniques for bridges(2014-08-29)
; ; ; Many bridges in the world’s transport infrastructure are old and have deteriorated over time. The solution to this problem is to either repair or replace a bridge or to establish its safety and maintain it in service. It is generally very costly to repair or replace a bridge. With reduced maintenance budgets there is an increasing interest in maintaining these old bridges in service by using probabilistic methods to prove that they are safe. Bridge safety is assessed based on (i) the loading which it will experience in service and (ii) the resistance of the structure. Improved knowledge of loading and resistance allows a more accurate assessment of whether a bridge is safe to remain in service without the requirement for expensive repair or replacement strategies. BridgeMon is an EU-FP7 funded project which aims to improve current monitoring techniques for road and rail bridges. This will be done by developing improved methods of evaluating traffic loading on bridges and carrying out Structural Health Monitoring (SHM) to identify damage and assess their remaining resistance. Bridge Weigh-in-Motion (B-WIM) refers to the technique of using the measured response of a bridge to calculate the vehicle loads crossing it and is a useful tool in monitoring traffic loading on bridges. BridgeMon will improve the accuracy of current B-WIM technologies and develop the first B-WIM system for railways. It is also developing the concept of virtual monitoring, whereby sensors are used to calculate vehicle weights which are then used to calculate stress histories throughout the bridge. Results of testing of a rail B-WIM system on a bridge in Poland are presented. Results show that the system is capable of accurately calculating train weights.173 - PublicationRecommendations on dynamic amplification allowanceThe ARCHES (Assessment and Rehabilitation of Central European Highway Structures) project (2006-09) involved partners from Belgium, Croatia, Czech Republic, Ireland, Italy, Poland, Slovenia, Spain, Switzerland and The Netherlands. The overall goal of the project is to reduce any gaps in the standard of highway infrastructure between Central and Eastern European Countries, particularly New Member States and the rest of the EU. Deliverable D10 is within WP2: optimise the use of existing infrastructure through better safety assessment and monitoring procedures which will avoid interventions, i.e., avoid unnecessary replacing or improving structures that are in fact perfectly safe. In particular, D10 provides a more realistic site-specific dynamic allowance for traffic loading than those genral values recommended in bridge codes.Correct evaluation of the behaviour of highway bridges under heavy traffic loading is extremely important both for the enhancement of design techniques, and also for the assessment of existing infrastructure. It is widely accepted that shortfalls exist in the determination of the traffic load which the bridge may be required to support during its expected lifetime due to inadequate consideration of amongst other factors, the dynamic interaction between the bridge structure and the heavy vehicles crossing it. Since it is the overall objective of this deliverable to combine lifetime static load effect values, with realistic dynamic amplification factors (to obtain an overall total lifetime load effect) there are two distinct parts:1) The calculation of bridge static load effect due to site-specific traffic flow, which is discussed in subtask 2.1.1 (Deliverable D08) along with the resultant assessment of bridge lifetime static load effect, and the selection of those loading events that are deemed critical (statically).Examples on how to determine these bridge traffic load models using Weigh-In-Motion (WIM) data and their configuration when using data from Central European countries are provided in subtask 2.1.1 on bridge traffic load monitoring. This subtask has also compared results between data from Western and Central European countries.2) Deliverable D10 focuses on the assessment of the levels of dynamic interaction occurring between a bridge and its associated vehicular traffic. This analysis incorporates a review of those recommendations given in current design/assessment codes for dynamic allowance.Then, the procedure to obtain a site-specific dynamic amplification factor using theoretical simulations and available experimental data is described. Some specific issues concerning the dynamic allowance associated to: (a) deteriorated bridges; (b) pre-existing bridge vibrations; (c) maximum total effects developing in sections different from midspan, (d) the existence of a bump prior to the bridge, or (e) critical loading cases such as cranes, are also discussed. Finally,general recommendations on dynamic allowance are provided.
269 - PublicationComparison of Two Independently Developed Bridge Weigh-In-Motion SystemsThis paper describes an experiment in which 2 independently developed bridge weigh-in-motion (WIM) systems are tested and compared, both for accuracy and durability. The systems, an Irish prototype still under development and a commercially available American system, were tested on a bridge in Slovenia. 11 statically pre-weighted trucks were each driven over the bridge several times at a range of typical highway speeds. Accuracies for axle and gross vehicle weights are presented within the framework of the draft European WIM specification, and the bias which can be introduced by the selection of a calibration truck is demonstrated. Performance factors relating to durability are also discussed with particular emphasis on axle detectors
857 - PublicationA Combined Structural Health Monitoring and Weigh-in-Motion System for Railway Bridges(2015-07-30)
; ; ; Many bridges in the world’s transport infrastructure are old and have deteriorated over time. The solution to this problem is to either repair or replace a bridge or to establish its safety and maintain it in service. It is generally very costly to repair or replace a bridge. With reduced maintenance budgets there is an increasing interest in maintaining these old bridges in service for longer by using probabilistic methods to prove that they are safe. Bridge safety is assessed based on (i) the loading which it will experience in service and (ii) the resistance of the structure. Improved knowledge of loading and resistance allows a more accurate assessment of whether a bridge is safe to remain in service without the requirement for expensive repair or replacement strategies. A system that combines Structural Health Monitoring (SHM) with Bridge Weigh-in-Motion (B-WIM) can provide bridge owners with information about the true safety of a bridge structure. The B-WIM part of this system is a method of collecting traffic load data using measurements taken from the bridge as vehicles cross it (WAVE, 2001) (WAVE, 2001) (WAVE, 2001) (WAVE, 2001). Hence the traffic data is current and specific to the bridge in question. The SHM part of this system continuously monitors the bridge for new damage and assesses its remaining resistance.160 - PublicationA Review of Road Structure Data in Six European CountriesThe European Union has expanded significantly in recent years. Sustainable trade within the Union leading to economic growth to the benefit of the 'old' and 'new' member states is thus extremely important. The road infrastructure is strategic and vital to such development since an uneven transport infrastructure, in terms of capacity and condition, has the potential to reinforce uneven development trends and hinder economic convergence of old and new member states. Significantly, in the decades since their design and construction, loading conditions have significantly changed for many major highway infrastructure elements/networks due primarily to increased freight volumes and vehicle sizes. This coupled with the gradual deterioration of a significant number of highway structures, due to their age, and the absence of a pan-European assessment framework can be expected to affect the smooth functioning of the infrastructure in its as-built condition, through increased periods of reduced flow due to planned and unplanned interventions for repair/rehabilitation. This paper reports the findings of a survey regarding the current status of the highway infrastructure elements in six countries within the European Union as reported by the owners/operators. The countries surveyed include a cross section of ‘existing’ older countries and ‘new’ accession countries. The current situations for bridges, culverts, tunnels and retaining walls are reported along with their potential replacement costs. The findings act as a departure point for further studies in support of a Centralized and/or Synchronised EU approach to Infrastructure Maintenance Management. Information in the form presented in this paper is central to any future decision making frameworks in terms of trade route choice and operations, monetary investment, optimized maintenance, management and rehabilitation of the built infrastructure and the economic integration of the newly joined member states.
667 - PublicationExperimental determination of dynamic allowance for traffic loading in bridges(Transportation Research Board, 2010)
; ; ; Bridge codes adopt values for dynamic allowance in traffic load models that are necessarily conservative to cover for an entire range of bridges with different mechanical characteristics, boundary conditions, and the large number of uncertainties associated to the vehicle-bridge interaction problem. A further level of conservatism occurs due to the independent manner in which the governing static load and the corresponding allowance for dynamics are specified. In particular, certain bridges are not susceptible to high levels of vehicle-bridge interaction when loaded by a critically heavy vehicle or a critical combination of vehicles. Recent advances in Bridge Weigh-In-Motion technology allow not only to collect information on the weights, spacings and speeds of the traffic loads traversing a bridge, but also to separate the maximum static strain from the total measured strain using a filtering procedure. In this paper, maximum static and total load effects are collected and analysed for three different sites as part of the European project ARCHES (6th RTD framework programme). Bridge measurements are used to discuss the dynamics of the most frequent truck classes and the entire traffic sample. The measurements reveal a decrease in percentage increment in dynamics and a reduction on the variability of the dynamic increment as the static load effect increases. This phenomenon can be of particular relevance in the assessment of the dynamics of extreme loading cases.243