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Research Report 258 Detailed experimental investigation for foamed bitumen stabilisation

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

As the demand for a cost-effective and environmentally friendly pavement stabilisation method increases, so has foamed bitumen stabilisation for unbound granular pavement layers started to gain broad acceptance worldwide. The second phase of a study on foamed bitumen stabilisation is presented. It is a comprehensive experimental programme, carried out in 2003-2004, to investigate the properties and the expected performance of the foamed bitumen-stabilised mixes. The experimental work presented compares the foaming characteristics of nine bitumen types to provide a base for comparison between New Zealand sources and overseas sources. A new methodology to characterise the quality of foam is proposed. Temperature and moisture susceptibilities were studied and compared for different types and grades of bitumen. Volumetric properties, resilient modulus, indirect tensile strength, fracture energy, fatigue life and CBR values were investigated.

Research report 454 Concrete pile durability in South Island bridges

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

Alkali silica reaction (ASR) has, until recently, been considered to present a low risk to concrete in the South Island of New Zealand. The discovery in 2006 of evidence of ASR and delayed ettringite formation (DEF) associated with extensive deterioration of precast piles on two South Island structures prompted further investigation to identify the extent and severity of ASR and DEF in other South Island precast concrete bridge piles. The aim was to ensure affected structures could be managed effectively and thereby remain safe and serviceable, and to help identify effective means of minimising the risk of ASR/DEF in future structures. The work was carried out in New Zealand between 2008 and 2011.

Research Report 013 Evaluation sensitivity analysis

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

The guidelines for sensitivity analysis in project evaluation, as used in the Transit New Zealand Project Evaluation Manual (PEM), have been improved. This report provides an approach and methodology for sensitivity analysis that is of practical assistance in road project evaluation, and includes a revised version of Appendix A9, Sensitivity Analysis, for the PEM. Sensitivity analysis determines how sensitive a project analysis (eg its benefit:cost ratio) is to the effect of varying one input parameter at a time. Issues of uncertainty in relation to road project evaluations are discussed, sensitivity analysis and other methods for dealing with such uncertainties are described as are the current sensitivity analysis procedures applied by Transit New Zealand. Possible directions for development of improved procedures and the results of a consultation workshop are given, as well as recommendations for revising the procedures and for on-going developments for project evaluation.

Research Report 128 Application of Austroads Pavement design guide for Whanganui materials

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

The application of the Austroads Pavement design guide to Taranaki 'brown ash' has been investigated. The study was designed to determine if the subgrade strain and deflection criteria given in the guide was appropriate for use on volcanic soils. The research involved:

Task 1 – site selection and collection of data on the pavement history, present condition and traffic loadings. Task 2 – site testing to characterise the materials and pavement dimensions. Task 3 – comparison of the modulus values derived from the various site tests and analysis of the expected performance of the pavement using the measured parameters. This theoretical performance was then compared with the actual performance of the pavement.

Research Report 523 The effect of road roughness (and test speed) on GripTester measurements

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

This research investigated the effect of road roughness, macrotexture and testing speed on GripTester measurements. Field tests were conducted by the GripTester at various test speeds on sites with varying road roughness in South Auckland. The variables – road roughness, texture and test speeds – were measured and plotted against each other along with grip number (GN) as obtained from the GripTester. Tests with the DF Tester were also carried out at one site and directly correlated with GripTester results at various towing speeds. It was found the GN might not be dependent on test speeds while testing at speeds lower than 75km/h; however, an inverse relationship occurred at higher speeds, on a limited number of test sites. Road roughness was found to have no effect on GripTester measurements and texture appeared to be a minor factor.

Research Report 459 Extending pavement life: investigation of premature distress in unbound granular pavements

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

Premature distress in unbound basecourses has occurred regularly in New Zealand. In 2008, the New Zealand Transport Agency commissioned the assembly of an inventory of problem basecourses and subbases. Study of the inventory found that the long-term degree of saturation of basecourse was highly significant in the case histories of premature distress, ie the pavements failed through shear instability (shoving) in the basecourses. A common feature in basecourses with a high degree of saturation was gap grading in the sand fraction. Existing basecourse specifications limit gap grading through grading shape control requirements but the case histories demonstrate that tighter control is required. The basecourse inventory was used to establish regression equations for predicting the in situ long-term degree of saturation of a basecourse. This approach appears to be very promising. Timely decisions can now be made on acceptance or the need for corrective measures prior to sealing.

Research Report 129 Durability of concrete road bridges in New Zealand

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

Transit New Zealand regional offices and selected local authorities were asked for information from their records on age and proximity to the coast of their bridges. Together they maintain more than 10,500 bridges with concrete superstructures on New Zealand roads. They also completed a questionnaire to identify common durability problems on concrete bridges, and to identify ways that would enable the bridge asset to be more effectively managed. Responses showed that most concrete bridges are in acceptable condition. Deck joint deterioration is the most common maintenance problem, and affects bridges of all ages. Reinforcement corrosion is more common on older bridges and on those near the coast. Current standard concrete construction specifications ensure at least a 50-year service life if they are followed during design and construction. A national bridge management system would provide a cost-effective means of managing information on bridge condition, location and construction details.

Research Report 046 Maintaining the porous nature of friction course

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

Friction course surfacing has been used on New Zealand road pavements since the early 1970s. The porous nature of this surfacing gives advantages of high skid resistance when wet, low noise, and excellent spray suppression when compared to other surfacings. Although the surfacing will last in excess of eight years, the voids in the surfacing tend to clog within three years, so that its full benefits are not available for over half its life. A literature review was carried out in 1992 to identify techniques that could be used to maintain the porous nature of friction course for a longer period of its life than it currently gives. Factors that contribute to the loss of the porous nature have been identified and the entry of detritus is suggested as the primary mechanism affecting New Zealand mixes.

Research Report 525 Steel-concrete composite bridge design guide

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

This report provides guidance on the design of steel-concrete composite bridges, which consist of steel girders and reinforced concrete slabs on top. Two common forms are considered: multi-girder and ladder deck bridges. Guidance is given on the general considerations for the preliminary and detailed design process, in addition to guidance on the verification of structural adequacy in accordance with the NZ Transport Agency Bridge manual and relevant design and material standards. Additional guidance on cost effective design philosophy and durability design is also provided. The aim of the report is to provide guidance for both the novice and experienced bridge designer on the design of cost-effective steel-concrete composite bridges.

Research Report 081 Tourism benefits from sealing unsealed roads: perceptions of discomfort and risk

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

A research project was undertaken in 1994 to investigate motorists' perceptions of discomfort and risk factors associated with using unsealed roads in New Zealand. The investigations particularly addressed the extent to which these factors were not included in the evaluation procedures used in the Transit New Zealand 1991 Project Evaluation Manual. The project involved: a review of international literature on motorists' perceptions of the benefits of sealing unsealed roads; focus-group discussions with international tourists and domestic travellers to explore their perceptions of unsealed roads; roadside surveys on three unsealed roads, using a 'willingness to pay' approach to assess motorists' valuations of the benefits of sealing these routes; and a survey to assess motorists' valuations of the four characteristics of unsealed road surfaces, of roughness, grip, dust, loose stones.