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Research Report 547 Fatigue design criteria for road bridges in New Zealand

Published: | Category: Activity management , Research programme , Research & reports | Audience: General

Road bridges are subjected to millions of cycles of heavy vehicle loading over their design lives, and the introduction of higher vehicle mass limits on New Zealand roads will significantly increase the rates of fatigue damage in bridge superstructures. The NZ Transport Agency's Bridge manual has relied on British and Australian standards for fatigue design criteria, and the aim of this project was to provide the basis for amended fatigue loadings based on New Zealand heavy vehicle characteristics, with allowances for forecast long-term growth in volumes and vehicle masses. The base fatigue loading was derived from analyses of effects on bridge spans of heavy vehicles recorded at weigh-in-motion sites between 2007 and 2011. The base fatigue loading was then adjusted for increases in legal vehicle masses permitted under a 2010 Land Transport Rule amendment (introducing HPMV – high productivity motor vehicles).

Research Report 617 Transition from visual condition rating of cracking, shoving and ravelling to automatic data collection

Published: | Category: Activity management , Research & reports | Audiences: General, Road traffic engineers & consultants

Robust condition data feeding into asset management processes is a key step towards having confidence in long-term strategies for renewals and replacements. The manual condition rating system was originally developed as an input into the treatment selection algorithm; however, in later years the data has been used for pavement deterioration modelling and trend monitoring, which are outside the intended scope of the rating system. It was therefore not unexpected that both field inspectors and researchers highlighted shortcomings in the quality and repeatability of manually recorded data. Automated scanning technologies promise to overcome many of the issues associated with manual condition data collection. However, before a wide-spread adoption of the scanning technology is possible, research had to prove the accuracy of the measurements and determine the impact of new data items in the asset management processes.

Research Report 638 Network and asset management: benefits of real-time data

Published: | Category: Activity management , Research programme , Research & reports

Data is essential for understanding the demands placed on road assets and transport networks. There is an opportunity through advances in real-time technologies to improve the delivery of network management and asset management activities. This requires an understanding of both the real-time technologies that are available, and the real-time information needs of network managers and asset managers. This research investigated the applications of real-time technologies and data in asset and network management. This included identifying a range of opportunities for expanding the use of real-time technology, for example by making better use of existing datasets and improving the detection of incidents and defects. A range of challenges were also identified, including the difficulties of working with ‘big’ real-time datasets, the risk of reliance on technology and the need for specialist expertise to develop real-time applications.

Research Report 633 Analysis and interpretation of New Zealand long-term pavement performance data

Published: | Category: Activity management , Research programme , Research & reports | Audience: General

A comprehensive statistical analysis and review of the dataset was undertaken on the March 2015 LTPP database, including application of transformations on the skewed raw data. Following a detailed analysis, it was found that the numerical data available to undertake a statistical analysis to identify factors that need to be present for accelerated condition trending was not sufficiently robust. It is not possible to find useful or significant correlations with this data set as it stands

A manual investigation by a person with extensive experience in road engineering and maintenance was undertaken. This investigated engineering explanations for the sites highlighted by the statistical analysis, which involved interpreting site photographs, notes and construction records. This review was unable to identify any reliable data to show pavements displaying cracking are at a higher risk of failure.

Research Report 634 Effect of road seal type on resistance to traffic stresses

Published: | Category: Activity management , Research programme , Research & reports | Audience: General

This report details research carried out from 2016 to 2017 as the preparatory stage of a larger programme to understand how chipseals may be improved to withstand increases in horizontal shear forces imposed by traffic loadings. The research aimed to develop an understanding of mechanisms and factors that lead to chip loss resulting from surface shear stresses, and to develop a methodology for testing seal performance under realistic but controlled laboratory conditions. The report commences with a literature review to collate and examine existing data and experience on seal selection and chip loss processes from New Zealand and overseas. Physical mechanisms, site and vehicle factors that contribute to seal damage are also investigated. Finally, an experimental test method and plan is developed to quantitatively compare and evaluate the effect of seal and binder type on overall seal performance in the laboratory, but under realistic loading and temperature conditions.

Research Report 635 Pavement maintenance patch trials

Published: | Category: Activity management , Research programme , Research & reports | Audience: General

There is anecdotal evidence that pavement maintenance patches fail within a few years and research was undertaken to develop a framework for predicting the life of patches to enable asset managers to choose the right treatment to give the life required with the lowest whole-of-life costs. A total of 12 maintenance patches were constructed consisting of cement stabilisation (two cement contents 1. 5 percent and 3 percent); mill and asphaltic concrete inlay; and full depth granular reconstruction replicated on three different state highways. These maintenance patches were treated as full pavement renewals in terms of testing and investigation prior to their construction. This information allowed basic pavement characteristics, such as the impact of traffic; pavement depth (adequate, inadequate or very inadequate); aggregate quality (good, average or poor); and pavement deflection (high, medium or low), to be determined prior to patching.

Research Report 628 Standardisation of laboratory compaction energies

Published: | Category: Activity management , Research programme , Research & reports | Audience: General

This research reviewed the New Zealand vibrating hammer laboratory compaction test and energy standardisation thereof. The area of laboratory aggregate compaction was found to have significant problems with variability of results and reduced correlations with field compaction results, which suggests there are problems with standardisation of the compaction energies used. A list of components of the New Zealand vibrating hammer test as it is actually performed in laboratories throughout New Zealand is provided, with each component introducing a larger or smaller amount of variability into the results. Methods of rectifying each component are identified to improve the standardisation of compaction energy and recommendations are made into how an alternative test method might be developed, tested and compared to the existing methods. Keywords: compaction, compaction effort, compaction energy, granular materials, laboratory compaction, maximum dry density (MDD), optimal moisture content, vibrating hammer, vibrating table

Research Report 626 The long-term acoustic performance of New Zealand standard porous asphalt

Published: | Category: Activity management , Research programme , Research & reports | Audiences: General, Road traffic engineers & consultants, Roading contractors

Research was commissioned to investigate the long-term acoustic performance of New Zealand standard porous asphalt made to TNZ P/11 Specification for open graded porous asphalt (OGPA). The research findings should be considered applicable only to New Zealand OGPA laid in high-speed environments (speed limits of 80 to 100 km/h). A method for acoustic measurement was selected, developed and applied using drafts of ISO 11819-2 for guidance. Measurements were made of a set of OGPA sections of different ages from four regions of New Zealand. The oldest OGPA sections were around 8 to 10 years old, which matches current expectations of OGPA ‘life’. The measurements show OGPA acoustic performance deteriorating at a steady but slow rate over time, yielding about 2 dB(A) deterioration of acoustic performance over 8 to 10 years.

Research Report 622 Best practice guide for pavement stabilisation

Published: | Category: Activity management , Research programme , Research & reports

New Zealand pavement engineers, in collaboration with colleagues in South Africa and Australia, are recognised internationally as leaders in the use of stabilisation in highway, road, airport, port and industrial hardstand pavement applications. Stabilisation is used to rectify a deficiency in a soil, aggregate or surfacing material. Stabilised materials contribute to the strength and performance of pavements at all levels: subgrade; subbase; base and surfacing. Applied research into and development of leading edge testing and design knowledge, coupled with significant improvements in the capacity and effectiveness of stabilisation construction plant and work site processes now offer the wider transport industry in New Zealand relatively safe, efficient and sustainable pavement construction, rehabilitation and maintenance options incorporating stabilisation.

Research Report 618 Trialling best value delineation treatments for rural roads

Published: | Category: Activity management , Research programme , Research & reports | Audiences: General, Roading contractors

Providing a safe, comfortable, cost-effective visual environment to help drivers navigate rural roads requires a better understanding of the strengths and limitations of different delineation devices, materials and treatment configurations. An international literature review examined different options to test on low-volume rural New Zealand road settings, and an expert panel prioritised four of these options to be trialled.  

Four on-road trials were run to examine delineation configurations and materials that could provide better value for rural roads. The key aspects to deciding treatments were to do with targeted delineation (to assist drivers in intuitively signalling more difficult parts of the road network), consolidation (where one configuration with a new product might replace two traditional products), and better delineation in rain, which is arguably a common poor visibility environment (where crashes are over represented).