Optimisation of reinforcement bar couplers.

Sheffield based company Ancon Clark manufactures, amongst other products, a family of reinforcement bar connectors for the construction industry. These are mechanical devices used for end-on joining of two bars. Reinforcement bars are cast into concrete structures. Presently Ancon have approximately a 1% share of the world market for this product although 90% of their connector products are exported to the European market. High initial cost of the product means that market expansion is limited and an imminent all encompassing European Standard exceeds the current product performance capability.The aim of this project was to redesign and develop this family of reinforcement bar connectors to produce a fully tested range to suit bar sizes from 8 to 50mm in diameter. The initial objectives were to reduce the product cost by 20% and increase product load carrying performance by 27%.The Ancon connectors consist of a length of steel tube into which the ends of the two pieces of reinforcement bar (to be joined) are inserted. The bar ends are held in the tube by a series of aligned lock-shear bolts which are tightened and penetrate the bar whilst forcing it against two serrated 'grips'. Ancon also manufacture a number of connector variants such as connectors for two bars of differing diameter and connectors for situations where a structure will be completed/continued at a later date to the first section.Two basic product development methods were considered, computer modelling and physical testing. Due to the complex nature of the product operating mechanisms computer modeling was seen as more costly and time consuming than testing of such an inexpensive product if the total number of tests was reasonable.On this basis a physical testing approach was taken. One mid-size connector in the standard family range was developed through selective alteration of components,through engineering analysis, and extensive physical testing to meet the performance and cost saving objectives.The knowledge gained during development of this one size was extrapolated to the rest of the standard range. Seven out of ten of the connector range met the objective performance criteria with an average product cost saving of 23%. The other three (largest) couplers were shown to be beyond the product configuration in terms of both performance and economics.The seven sizes redeveloped are the only sizes used in Europe so the bulk of the Ancon connector production is now less expensive and able to meet any impending European legislation.