Arch bridges – unlocking their potential

Arch bridges are strong, durable, aesthetically pleasing and require little maintenance but very few have been built since the early 1900s. However, this trend has changed as more than 60 FlexiArch bridges have been installed since the system was launched in 2007. The FlexiArch uses precast concrete voussoirs, requires neither corrodible reinforcement, nor centring, can be installed in hours and is contractor friendly. Details of this innovative method of construction and installation of arch bridges are given and the enormous potential of the system for multi-span viaducts is also highlighted. </jats:p

Influence of chloride ions on progress of carbonation in concretes

Our infrastructure and environment face unprecedented challenges in addressing a low carbon future with limited natural resources, expanding population, increased pollution and climatic uncertainties. Adaptation and innovations must therefore play a vital role in addressing the anticipated wide ranging complex scenarios ahead. The environment in which construction materials will need to function will become far more complex and aggressive and hence a fundamental revaluation of the most appropriate materials for future infrastructure and environment will be required in order to tackle those challenges. This paper focuses on a class of construction materials, both old and new, based on magnesia (MgO). They include a wide range of materials from those that contain MgO as a small additive to those which solely consist of MgO. They include concrete with MgO as an expansive additive, pervious concrete, alkali-activated cements, magnesium phosphate cements, carbonated products, stabilising additives for ground improvement, self-healing additives, carbon capture and storage materials and binders for waste 105 and contaminated land remediation. Those materials and products offer a range of technical and sustainability benefits for a range of structural, geotechnical and environmental applications. The paper highlights the applications and benefits that would be achieved with magnesia-bearing construction materials

Monitoring the hygrothermal and ventilation performance of retrofitted clay brick solid wall houses with internal insulation: Two UK case studies

This work assesses the hygrothermal and ventilation performance of two ‘hard-to-treat’ historic, clay brick, solid wall houses that are internally insulated. Retrofit A is a two bedroom bungalow with the addition of internal plasterboard and air cavity and Retrofit B is a 5 bedroom house with sheep wool, phenolic and plasterboard insulation. To evaluate the long term performance of the retrofit measures, the testing is carried out 7 and 8 years respectively after completion. The first part of the work investigates whole building hygrothermal performance, ventilation and internal conditions. It was found that both retrofits are operating below specification in regards to their ventilation performance. An in-situ performance based specification for mechanical ventilation via CO2 monitoring is proposed. The second part focuses on the hygrothermal behaviour of the clay brick wall assembly. Both presented high relative humidity within critical layers of the wall make up. In Retrofit A the wall thermal transmittance was found to be much higher than designed due to inappropriate construction detailing while Retrofit B showed excellent thermal performance and minimal effects of thermal bridging

Performance-based Testing Methodology for Concrete Durability

This report presents an overview of performance based testing methodology for concrete durability and work currently underway jointly at Queens University Belfast and Heriot Watt University, Edinburgh, to undertake this research under a EPSRC funded project (EP/G02152X/1). EN206-1 superseded BS 5328 on 1st December 2003 and allows designers and producers to use a wide range of cements and aggregate types for a variety of exposure conditions. In this new standard, the durability of concrete is specified in terms of the constituent materials of concrete, properties of fresh and hardened concrete, limitations for concrete composition, specification of concrete, delivery of fresh concrete, production control procedures, conformity criteria and evaluation of conformity and verification of these properties. Within this, six basic forms of exposure is also specified, namely XO (no risk of corrosion), XC (Corrosion induced by carbonation), XF (Freeze / thaw attack), XS (Corrosion induced by chlorides from seawater), XD (Corrosion induced by chlorides other than from seawater) and XA (Chemical attack). According to EN206-1, the performance method adopted should be based on satisfactory experience with local practices in local environments from data obtained from an established performance test method for the relevant mechanism, or using appropriate proven predictive models. Therefore, the methods that may be used include those methods based on:- · long-term experience of local materials and practices and on detailed knowledge of the local environment. · approved and proven tests that are representative of actual conditions and have approved performance criteria. · analytical models that have been calibrated against test data representative of actual conditions in practice. The concrete composition and the constituent materials should be closely defined to enable the level of performance to be maintained. In order to determine the best methods for assessing concrete durability for performance, it is important to review those methods which have been developed and used in Queens University Belfast and Heriot Watt University to test for permeability, diffusion and absorption as well as electrical methods used to assess if the performance criteria have been achieved in structures using non-destructive testing methods. Prior to specifying durability performance testing methods, a review of previous projects where limits on permeability, diffusion, electrical resistivity etc, are presented along with the various durability tests used to assess these limits. The examples given are from a number of projects in the UK, Ireland and Europe of varying complexity and size. Due to the relatively small number of such examples in the UK and Ireland, the need for the research presented here is further justified. The proposed experimental work for the EPSRC project is presented which includes a breakdown of the concrete samples, tests and details of a new marine exposure site on the Northwest coast of Ireland. Based on the findings of this experimental work and the numerical calibration using the ClinConc model, development of a methodology for testing the concrete durability to assess the performance limits set will be determined. Through this work, the performance methods adopted will satisfy the EN206-1 guidelines above

Emergency rehabilitation of Brownsbarn bridge

This paper outlines the repair methodology of Brownsbarn Bridge situated over the N7 near Dublin. The repair strategy was formulated following impact damage to the soffit from a low- loader carrying an excavator passing underneath the bridge. Significant damage was observed to one of the beams. The repairs were carried out as emergency works over a bank holiday weekend in Ireland successfully. The rehabilitation methodology is based on preloading the bridge before repair followed by a removal of load to ensure the reestablishment of some of the lost prestress. This paper outlines the various stages of rehabilitation and establishes the timelines of significant events along with practical discussions on the execution of the rehabilitation methodology. The bridge was continuously monitored throughout the refurbishment process. This case study is expected to be of topical interest to researchers, practicing engineers, bridge owners and end-users alike