Eric J Ancich

Abstract: Environmental noise complaints from homeowners near bridges with modular bridge expansion joints (MBEJs) led to an engineering investigation into the noise production mechanism. The investigation identified modal vibration frequencies in the MBEJ coupling with acoustic resonances in the chamber cast into the bridge abutment below the MBEJ. This initial acoustic investigation was soon overtaken by observations of fatigue induced cracking in structural beams transverse to the direction of traffic. These beams are, in the English-speaking world, universally referred to as center beams. However, in Europe the term lamellae is equally common. A literature search revealed little to describe the structural dynamics behavior of MBEJs but showed that there was an accepted belief dating from around 1973 that the loading was dynamic. In spite of this knowledge many bridge design codes used throughout the world specify a static or quasi-static load case with no mention of the dynamic behavior. This paper identifies the natural modes and operational response modes of vibration of the MBEJ installed into Sydney�s Anzac Bridge. In addition, the paper will introduce the dynamic range factor (DRF) and report a DRF of 4.6 obtained after extensive static and dynamic strain gage measurements. The studies indicated that the Anzac Bridge MBEJ was very lightly damped (<2% of critical) and a reduction in the measured DRF through the introduction of additional damping was an option.

Abstract: Modular bridge expansion joints are widely used throughout the world for the provision of controlled pavement continuity during seismic, thermal expansion, contraction and long-term creep and shrinkage movements of bridge superstructures. It was known that an environmental noise nuisance occurred as motor vehicle wheels passed over the joint but the mechanism for the generation of the noise nuisance was not previously known. Noise abatement options were investigated before settling on a Helmholtz Absorber installation. The benefit is most obvious in the frequency range of 50 to 200 Hz. The noise reduction provided by the Helmholtz Absorber installation is of the order of 10 dBA

Abstract: This paper deals with some recent developments in the design and performance of roadside barriers that are applied as a means of controlling road traffic noise.It is a review paper that is based on the outcomes of literature and information searches undertaken for and on behalf of the Roads and Traffic Authority of NSW. Some interesting, ongoing developments in the design and performance of traffic noise barriers have been identified. In particular, three types of innovative barrier designs were identified that appear to offer the potential for increased attenuation without the need for substantial increases in barrier height. Each of these development s is considered in some detail in the paper and recommendations are made of the possibility of pursuing them further.

Abstract: This paper deals with some recent developments in the design and performance of roadside barriers that are applied as a means of controlling road traffic noise.It is a review paper that is based on the outcomes of literature and information searches undertaken for and on behalf of the Roads and Traffic Authority of NSW. Some interesting, ongoing developments in the design and performance of traffic noise barriers have been identified. In particular, three types of innovative barrier designs were identified that appear to offer the potential for increased attenuation without the need for substantial increases in barrier height. Each of these development s is considered in some detail in the paper and recommendations are made of the possibility of pursuing them further.

Abstract: This paper deals with some recent developments in the design and performance of roadside barriers that are applied as a means of controlling road traffic noise.It is a review paper that is based on the outcomes of literature and information searches undertaken for and on behalf of the Roads and Traffic Authority of NSW. Some interesting, ongoing developments in the design and performance of traffic noise barriers have been identified. In particular, three types of innovative barrier designs were identified that appear to offer the potential for increased attenuation without the need for substantial increases in barrier height. Each of these development s is considered in some detail in the paper and recommendations are made of the possibility of pursuing them further.

Abstract: The complaints by residents concerning quarry blasting usually specify structural movement or vibration. At times these complaints become vociferous leading to the formation of Residents Action Groups and objections to Planning Approval for quarry operation or expansion. A case study approach will be used to show that, where a residence is more than 500 metres from the quarry, air blast overpressure rather than ground vibration is the stimulus for residents' complaints. Typical blasting overpressures are related to structural displacement and some aspects of housing design which accentuate overpressure response are discussed. Operational overpressure damage level criteria are offered together with suitable methods of measurement and control.

Abstract: This paper describes the use of Acoustic Emission (AE) technology to establish the structural health and integrity of each centre beam in the single support bar design of the Modular Bridge Expansion Joint (MBEJ) at Mooney Mooney Creek Bridge and Karuah Bridge. The methodology and procedures used are fully described and this application to MBEJs is believed to be original. The report also details how the results from the AE survey have been successfully implemented by the RTA into pro-active inspection and maintenance as part of a condition based maintenance strategy that will reduce the through life cost of MBEJ ownership whilst also improving road user safety. This paper also introduces two new phenomena observed during the AE survey of the MBEJs namely the premature excitation of the piezo-electric sensors used by the AE monitoring system and the modal energy waves travelling and reverberating along the length of the centre beams of the single support bar MBEJs.

Abstract: Great advances have been made in modular expansion joint technology since this most versatile type of joint was invented forty years ago, and the use of such joints, especially on very large bridges, has increased steadily. As a consequence, national standards have been written and continually developed to keep up with this technology, in order to ensure that the great potential of this type of joint is fully realised. Key contributions towards the development of these standards have been made by the engineering communities of Australia, America and Europe in particular, governing the design, manufacture and testing of the joints. Commentary on these contributions is presented, with reference in particular to the testing requirements of various national standards.

Abstract: Alkali aggregate reaction, or AAR, is one of the major causes of degradation in older concrete structures. AAR occurs when the hydroxide ions that exist in the cement react with aggregate, often with water acting as a catalyst to speed up this reaction [1]. AAR causes degradation in its parent concrete structure by causing concrete expansion, which in turn creates cracks that expand over time. In order to arrest the rate of expansion caused by the AAR reactions, a �jacketing� system was developed and/or installed in a number of bridges. These were also designed to limit the exposure of micro cracks to further water ingress. The effect of these jacketing elements were analysed to assess their potential effectiveness using numerical (finite element) methods. Installation of such jacketing elements have had an unintended adverse consequence to the piles by changing the scouring pattern near the base of the piles as the cross sectional area was changed and increased in size. Riverbed scouring has been known to be one of the most common mechanisms to cause bridge failures in the past, and to better understand possible changes to scouring patterns due to jacketing numerical (computational fluid dynamics) analyses were carried out.

Abstract: Fatigue cracking was observed in a three cell, three span, continuously curved steel trough girder bridge in far western NSW. The bridge over the Darling River at Wilcannia had been in service for about 11 years and the fatigue cracks were all associated with asymmetric internal stiffeners. The bridge was investigated using a structural dynamics based approach and the results showed that the premature fatigue failure was due to the design of the asymmetric internal stiffeners that were not continuous over the full perimeter. As the stiffeners form a partial height U-frame, this allowed the webs, above the stiffeners, and the deck to rack under load. A calibrated FEA model of the bridge was used to investigate a range of solution options including continuing the stiffeners over the full perimeter and the complete removal of the stiffeners. As the confined space inside the box girders was not conducive to welding or cutting, a unique and innovative solution using external rib stiffeners was devised, modelled and adopted.

Abstract: It is known that 75% of the total Australian road freight task passes through NSW and the Pacific Highway is a major recipient of this freight. There are numerous crossings of major rivers between Newcastle and the Queensland border and until the late 1960�s, steel bridges were preferred as lift spans could be easily incorporated in the design. Over the past 10-15 years, heavy vehicle numbers using the Pacific Highway have increased dramatically, with a stepwise increase in 2001 and exponential growth of about 2% per year otherwise. This growth has been matched by a parallel exponential growth in loads and an even faster growth in axle group repetitions due to the greater utilisation of B-doubles and tri-axle semi-trailers. Three bridges along the Pacific Highway were investigated using a structural dynamics based approach. The investigation revealed numerous compression/tension stress reversals for each heavy vehicle transit. Whilst the dynamic amplification factor (DAF) for a single controlled heavy vehicle transit was comparable with current Codes, the load effect for fatigue from uncontrolled heavy vehicle traffic significantly exceeds the value which would be predicted using the test vehicle factored for dynamic effects and multiple presence.

Abstract: It is known that 75% of the total Australian road freight task passes through NSW and the Pacific Highway is a major recipient of this freight. There are numerous crossings of major rivers between Newcastle and the Queensland border and until the late 1960�s, steel bridges were preferred as lift spans could be easily incorporated in the design. Over the past 10-15 years, heavy vehicle numbers using the Pacific Highway have increased dramatically, with a stepwise increase in 2001 and exponential growth of about 2% per year otherwise. This growth has been matched by a parallel exponential growth in loads and an even faster growth in axle group repetitions due to the greater utilisation of B-doubles and tri-axle semi-trailers. Three bridges along the Pacific Highway exhibiting fatigue cracking were investigated using a structural dynamics based approach. The investigations revealed numerous compression/tension stress reversals for each heavy vehicle transit. Whilst the dynamic amplification factor (DAF) for a single controlled heavy vehicle transit was comparable with current Codes, the load effect for fatigue from uncontrolled heavy vehicle traffic significantly exceeds the value that would be predicted using the test vehicle factored for dynamic effects and multiple presence. A cost effective fatigue life extension modification was proposed and tested on one of the bridges in this study. This �compliant fastener� modification in concept reduces the out of plane bending resistance at the stringer-to-cross girder connection, and hence reduces the stress range experienced by the fasteners and cope. In the bridge that was experiencing multiple fatigue and fastener failures every month, no further failures have been recorded in the three years subsequent to installation of the modification.

Abstract: Although it is not unusual for modular bridge expansion joints (MBEJ�s) to be designed using the Finite Element Method, it appears that designers have been more concerned with quasi-static modelling rather than the development of a fully dynamic model that reproduces all of the characteristics of an operational MBEJ. The paper reports the calibration of a finite element model of both single support bar and multiple support bar design MBEJ�s using experimental modal analysis and strain gauge data. Once calibrated, the models accurately reproduce the empirical vibrational modes and dynamic strains of the operational joints. Modelled results display acceptable variation with the measured data. As motor vehicle excitation is transient, a unique procedure was developed that utilised measured strain data to simulate the force-time history of a vehicle pass-by. This is described as a �virtual dynamic truck pass-by� and its application to the models permitted the accurate reproduction of all the dynamic characteristics including the dynamic amplification factor. The experimental modal analysis results of the single support bar MBEJ strongly suggested that in some regions, the dynamic response was linear and in other regions, non-linear. A moderately successful attempt was made to reproduce this effect by introducing non-linear stiffness into the model by way of the elastomeric bearings.

Abstract: In an almost universal approach to the design of the modular bridge expansion joint (MBEJ), the various national bridge design codes do not envisage that the embedded joint may be lightly damped and could vibrate as a result of traffic excitation. These codes consider only an amplification of the static load to cover sub-optimal installation impact, poor road approach, and the dynamic component of load. The codes do not consider the possibility of free vibration after the passage of a vehicle axle. Codes also ignore the possibilities of vibration transmission and response reinforcement through either following axles or loading of subsequent components by a single axle. Dynamic strain gauge measurements were made on a 9-seal MBEJ installed in Sydney�s Anzac Bridge using a 42t GVM test vehicle. At some speeds it was found that each vehicle passage produced around 30 vibration cycles where the peak-to-peak strain equalled or exceeded the quasi-static strain of 100 µe and that the dynamic strain maxima were 4-5 times greater than the quasi-static strain. A series of trials were conducted using a range of prototype support bar bearings and compression springs before a design was selected for installation. Post-installation measurements confirmed stress reductions such that the fatigue damage that would have occurred in any pre-modification year would now take well over 50 years to occur.

Abstract: The Roads and Traffic Authority NSW (RTA) has formulated a specification for the design, fabrication and installation of modular bridge expansion joints (MBEJs). The RTA specification encourages dynamic analysis and testing of MBEJs by otherwise prescribing higher dynamic amplification factors (DAFs) if design is based only on static analysis. The specifications also prescribe, in detail, the checking of fatigue stress ranges in connections, which are often more critical than in the main members. In this paper, salient features of this specification are compared with those of AASHTO LRFD and German and Austrian specifications, which were submitted during the design tender of one MBEJ. Analysis of the MBEJ in accordance with the four specifications showed that the RTA specifications were the most demanding and the AASHTO LRFD specifications were the least conservative. One of the installed MBEJs was then tested by running a truck over it at different speeds. The results showed that the higher DAFs prescribed by the RTA specification were justified. Where support bars rest on elastomeric bearings, it is critical to model the stiffnesses of the spring supports correctly as this significantly affects the bending moments in the centre beams

Abstract: Recent experimental modal analysis (EMA) work by an Australian State Government Road Agency [Roads and Traffic Authority of NSW (RTA)] has enabled the development of calibrated FEA modular bridge expansion joint (MBEJ) models. Previously a relatively unexplored topic, this combination of FEA/EMA transient analyses helps reveal the underlying dynamic structure applicable to general classes of MBEJs. Such dynamic characteristics as fundamental mode shapes, energy storage, damping effects, resonance, dynamic amplification factors, and dynamic stiffness in elastomeric support elements can be parametrically studied for design guidance. Many questions, such as why large joints have higher failure rates, how the dynamic amplification factor is affected by box spacing and bearing stiffness, what causes joint resonance, how it is prevented, what is the tire impact factor due to increased momentum, why joints do not move significantly in a horizontal sense when impacted, etc., can be derived and answered. The paper summarizes recent advances in the area of modular bridge expansion joint dynamics, focusing on FEA and EMA analyses. The experimental and theoretical confirmation of the single support bar phenomenon of coupled center beam resonance is also discussed

Abstract: Modular bridge expansion joints (MBEJ�s) are considered to be the most modern design of waterproof bridge expansion joint currently available; nevertheless, there have been endemic occurrences of structural fatigue failures of MBEJ�s throughout the world. Whilst there was an accepted belief amongst academic researchers from around 1973 that a significant part of the load history of the MBEJ was dynamic, international bridge design codes continued to base the design requirements around quasi-static principles without fully embracing the highly dynamic response of the MBEJ to transient traffic loading until 2004. Similarly, it would appear that almost all MBEJ designers use a static or quasi-static design with little consideration of the dynamic behavior, either in the analysis or the detailing. Work done in the RTA over the past six years work has identified a major defect in the quasi-static load case assumption used universally in bridge design codes. The defect has now been recognized in Australian Standard AS5100:20041 and the RTA has recently produced a specification (RTA QA Specification B316)2 for modular expansion joints, which includes a number of design requirements based on dynamic analysis for these joints. Subsequent to the installation of MBEJ�s designed in accordance with this specification in bridges on the Karuah Bypass, the RTA conducted an experimental study of the dynamic response of the joint to the passage of a truck at different speeds. The results showed that the dynamic amplification factor (DAF) specified in RTA B316 was in good agreement with measured values. The RTA also made a comparative study of the design of the MBEJ in accordance with design codes of different countries that had tendered for the design. Calculations showed that there are quite significant differences in the results obtained in accordance with different codes, based on the DAF and other requirements prescribed by these specifications. Most international codes also leave a number of factors un-specified; hence, tendered designs cannot be evaluated on a uniform basis. RTA B316 has incorporated several design requirements to eliminate this lacuna

Abstract: Environmental noise complaints from homeowners near bridges with modular expansion joints (MBEJ) led to an engineering investigation into the noise production mechanism. The investigation identified modal vibration frequencies in the MBEJ coupling with acoustic resonances in the chamber cast into the bridge abutment below the MBEJ. This initial acoustic investigation was soon overtaken by observations of fatigue induced cracking in structural beams transverse to the direction of traffic. These beams are, in the English-speaking world, universally referred to as centre beams. However, in Europe the use of lamella to describe these beams is equally common. A literature search revealed little to describe the structural dynamics behaviour of MBEJ�s but showed that there was an accepted belief amongst academic researchers dating from around 1973 that the loading was dynamic. In spite of this knowledge almost all designers use a static or quasi-static design with little consideration of the dynamic behaviour, either in the analysis or the detailing. Principally, this paper identifies the natural modes of vibration of the single support bar design MBEJ installed into Sydney�s Anzac Bridge and the welded multiple support bar design MBEJ installed into the southern abutment of the southbound carriageway of the bridge over the south channel of the Manning River (Taree By-pass). Secondly, the paper will report the dynamic amplification factors (DAF) obtained after extensive static and dynamic strain gauge measurements of both MBEJ�s

Abstract: Modular bridge expansion joints are widely used throughout the world for the provision of controlled thermal expansion and contraction in bridges. Modular Bridge Joint Systems (MBJS) are considered to be the most modern design of waterproof bridge expansion joint currently available. It was known that an environmental noise nuisance occurred as motor vehicle wheels passed over the joint but the mechanism for the generation of the noise nuisance was not previously known. Observation suggested that the noise generation mechanism involved possibly both parts of the bridge structure and the joint itself as it was unlikely that there was sufficient acoustic power in the simple tyre impact to explain the persistence of the noise in the surrounding environment. Engineering measurements were undertaken at Georges River (Tom Ugly�s) Bridge and the analysis of these measurements indicated that an environmental noise nuisance resulted from the interaction of vibration of the modular bridge expansion joint with acoustic resonances produced within the void space of the abutment below the joint. A number of engineering methods of noise abatement were considered or investigated before a Helmholtz Absorber installation was adopted. �Before� and �After� noise measurement results show a significant decrease of low frequency noise due to the Helmholtz Absorber installation. The benefit is most obvious in the frequency range of 50 to 200 Hz which encompasses all the natural vibration modes. The noise reduction provided by the Helmholtz Absorber installation is of the order of 10 dBA which is equivalent to a halving of the perceived loudness

Abstract: Modular bridge expansion joints (MBEJ) are widely used throughout the world for the provision of controlled pavement continuity during seismic, thermal expansion, contraction and long-term creep and shrinkage movements of bridge superstructures. Modular Bridge Joint Systems (MBJS) are considered to be the most modern design of waterproof bridge expansion joint currently available. It was generally known that an environmental noise nuisance occurred as motor vehicle wheels passed over the joint but the mechanism for the generation of the noise nuisance has only recently been described. Observation suggested that the noise generation mechanism involved possibly both parts of the bridge structure and the joint itself as it was unlikely that there was sufficient acoustic power in the simple tyre impact to explain the persistence of the noise in the surrounding environment. Engineering measurements were undertaken at Anzac and Georges River (Tom Ugly�s) Bridges and the analysis of these measurements indicated that an environmental noise nuisance resulted from modal vibration frequencies of the MBEJ coupling with acoustic resonances in the chamber cast into the bridge abutment below the MBEJ. This initial acoustic investigation was soon overtaken by observations of fatigue induced cracking in structural beams transverse to the direction of traffic. A literature search revealed little to describe the structural dynamics behavior of MBEJ�s but showed that there was an accepted belief amongst academic researchers dating from around 1973 that a significant part of the load history was dynamic. In spite of this knowledge it would appear that almost all designers use a static or quasi-static design with little consideration of the dynamic behavior, either in the analysis or the detailing. Principally, this paper identifies the role of vibration in the generation of environmental noise complaints and links this vibration to the now endemic occurrence of structural fatigue failures of MBEJ�s throughout the world.

Abstract: This thesis investigates the mechanism for noise generation and propagation through the use of structural dynamics to explain both the noise generation and the significant occurrence of fatigue failures world-wide. The successful fatigue proofing of an operational modular joint is reported together with the introduction of an elliptical loading model to more fully explain the observed fatigue failure modes in the multiple support bar design.