Technical papers

TP1 - An Overview of the Thaumasite form of sulfate attack

Noting that concretes made with Portland cements are vulnerable to attack by sulfates, usually originating in the ground this paper examines the minerals formed by this attack (ettringite and gypsum). It also examines the formation of thaumasite (recognised as a separate form of sulfate attack), which has the potential to affect a wide variety of structures. It gives case studies and reference to design guidance.

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TP2 - Towards the Design of Soil Loading for Integral Bridges

Experiments are described and results are presented to indicate that the peak stresses bear a close correlation to the magnitude of the thermal length changes of the bridge deck through the rotation of the abutments which are caused. The mechanics of the backfill soil during the cyclic straining process are explained. Shortcomings in our current knowledge for providing a comprehensive design method are highlighted.

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TP3 - Guide to Compressive Membrane Action

The enhancement in slab strength, due to arching or Compressive Membrane Action (CMA), has been incorporated into some design standards; BD81/01, 'Use of Compressive Membrane Action in Bridge Deck Slabs'. This paper comments on these design codes, reviews the research undertaken and outlines in detail the method by which the capacity of a laterally restrained slab can be calculated.

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TP4 - Flush Bond Tests

Previous research has provided a formula for the calculation of bond strength when reinforcement is delaminated to the safe level of half barrel. Where delamination is not quite as deep a more accurate calculation of bond strength could be obtained by interpolating between bond for half barrel exposure and bond for flush exposure. This paper describes bond tests in a beam situation to determine bond strength with the concrete cast flush with the top of the main bars. The tests comprised of two series, each of four beams.

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TP5 - The Effect of Shear Enhancement on the Resistance of an Infill Deck

The term infill deck is used to describe a form of construction consisting of precast, prestressed-concrete inverted T-beams, or similar, placed side by side, with "infil!" concrete cast between and over them to form a solid slab. The Highways Agency carried out research on the shear capacity of infill decks in two specific regions - where the structure was flexurally cracked and flexurally uncracked. This paper reports on an extended range of tests to cover the short shear-span region where shear enhancement might be present.

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TP6 - Guidance on Joining Concrete Bridges

The paper reviewed current knowledge on the construction of joints between existing and new construction, reports on the views of members of the CBDG on anticipated problems with jointing techniques adopted in practice, and provides a report on joining existing construction to new, setting out the constraints, the significant factors for consideration and a description of current methods for construction joints.

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TP7 - Testing of High Strength Concrete Beams with Limestone Aggregates

This report summarizes the research work undertaken to assess the shear resistance of reinforced concrete made with limestone aggregate. Six beams without shear reinforcement were tested to failure under continuous deflection control and all of the beams failed in shear, as designed. It recommends further research work is carried out for the shear strength of beams with and without shear reinforcement and with a range of aggregate types, sources and concrete strength, and proposes that a limit is placed on the design shear strength of reinforced concrete beams.

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TP8 - Implementation of European Concrete and Aggregate Standards and
their influence on the use of Recycled Aggregates in Concrete for Bridges

This paper reports on recent changes in British and European Standards and Specifications that influence the use of recycled aggregates in concrete. On 1 December 2003 the European and its complementary British Standards for concrete, EN 206-1 and BS 8500 Parts 1 and 2, were fully implemented. These standards set out various requirements for aggregates used as a component in concrete and these are summarized in this paper.

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TP9 - Fast Construction - Segmental and Launched Bridges

This paper considers a number of developments in precast segmental and incrementally launched bridge construction methods and highlights particular developments in both methods, by looking at bridges recently constructed in the UK, Ireland, Malaysia, Singapore and Hong Kong. The paper also describes the successful design and construction of externally post-tensioned concrete box structures. The importance of taking into account temporary loading conditions in both the construction stage and the service life has been highlighted.

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TP10 - Long Term Monitoring of Stresses behind Three Integral Bridge Abutments

This report focuses on comparing the measured seasonal trends of stress change with the historic data. The distributions of stress with depth acting on the abutment are compared with the design values evaluated using BA42. Included in the design advice are recommendations for revisions to BA 42 which are appropriate for integral bridges constructed from concrete.

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TP11 - A Case Study of Cathodic Protection using Sacrificial Anodes

This describes the installation of the sacrificial anode cathodic protection (SACP) systems. The results from the monitoring are presented showing how the system has performed over the first year after installation. Fosroc Ltd (Fosroc) supplied the sacrificial anodes installed monitoring system. This report has been prepared jointly by Fosroc and RMBC.

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