Product development of standardized reinforcing units: Part 1: Principles of product development and prefabricated reinforcing systems

The aim of this research at VTT has been to develop the reinforcing products for beams, columns, slabs and footings that are suitable for industrial prefabrication. The research is concerned with a study of the reinforcement systems based on the reinforcing strips and wire fabrics formed by joining the bars with longitudinal wires together. In the research, a new reinforcement system has been developed. The system is suitable for prefabrication purposes and is based on reinforcing strips joined by welding the deformed bars together with the principles for the appropriate product selection. The reinforcement system includes the following: 1. The tensile reinforcing unit of a beam (reinforcing strip) 2. The shear reinforcing unit of a beam, in which it is included - reinforcing unit for anchorage of tensile reinforcement - the shear reinforcing unit of a span(3 alternatives) - the diagonal reinforcing unit of a span 3. The reinforcing unit of a column (reinforcing strip) 4. The reinforcing strip of a slab 5. The reinforcing strip of a wail 6. The reinforcing strip of a footing In using these prefabricated reinforcing units the reinforcement of a structure is composed of some of these reinforcing units. This way it is possible to succeed in accomplishing the flexible use of reinforcing units in combination and good flexibility of dimensions. In designing and fabricating the reinforcement of the structures use can be made of reinforcing units with few exceptions in accordance with the present authorised specifications. This new reinforcement system makes possible the fabrication, of all reinforcing units as stocked items, what provides completely new fabrication and application possibilities for the prefabricated reinforcing unit. The share of work on site is essentially reduced compares with in-situ reinforcement work and the same applies to the use of present-day prefabricated reinforcing units. On the basis at the information gathered from the literature and during two months' visit to the Federal Republic of Germany by Pekka Nykyri, research officer of the Concrete and Silicate laboratory at VTT, the principles of a reinforcement system based on the use of wire fabric and a proposal for a cage reinforcement system suitable for various structural members in our country have been presented. Wire fabric reinforcements can be used as an alternative to bar strip reinforcements wherever applicable. In the research report, general features of the use of prefabricated reinforcing units and the state of development in this respect in different countries are considered. In particular possibilities of improving anchorages of tensile and shear reinforcing units of the beams and their splicing are discuessed. The proposed reinforcement systems still need further development and performance studies, as well as detailed product development and guidance on dimensioning.