Connections and joints between precast concrete units

The aim of the research project was, firstly, to analyse and develop the connections and joints of the present column-beam structures used in the Frame BES system and, secondly, to seek for new solutions to connections and joints. The first part, dealing with the connections of the Frame BES system, is intended to serve as a basis for drawing up detailed recommendations and instructions. In the second pare, an attempt is made to find and create new types of joints and connections which would stimulate industry to further efforts in product development work. The column to base connections in a socket and by bolts as well as the beam to column connections have been dealt with in detail. The calculation method of the socket joint has been made more precise. The effect of the shrinkage taking place in grout on the performance of the bole connection of the column has been examined. It could be established that the good quality of concrete and proper grouting are the most important factors ascertaining the ability of connections and joints to function. As a bearing between the column and the beam neoprene rubber is nearly always used. In the research, different design methods presented in the literature are compared and, in conclusion, a simple design method for a neoprene bearing suited to the Frame BBS system is proposed. The floor beams nearly always rest on a corbel projecting from the column. Moreover, the corbels are often made low, as they are often buried into the beam. The performance of the low corbel has been analysed on the basis of the two-dimensional yield criterion of concrete. The failure capacity of low corbels can also be considerable if they are provided with heavy reinforcement. The accuracy of the design method developed on the basis of analysis and the area within which it is valid has been studied by comparing calculated capacities with test results presented in the literature. In order to succeed in developing the new solutions to joints and connections the requirements set on connections are presumed to be known and analysed. Account shall then be taken of all requirements, including technical, economical and aesthetic aspects, that appear during different work stages and in use; the most important requirements for connections are also given. The bolt connection, toothed plate connectors, dowelled connectors and glued joints are introduce as new solutions to joints and connections without grouting. In many cases prestressing of the bolts improves the performance of joints. By such means the joint can be made to act as a friction joint, partly or completely. The joints between facade elements are subjected to stresses of different kind. There is a great need to develop the durability of the elements and their outward appearance. Several solutions to joints presented in the literature are compiled to the research report, and the solutions best suited to Finnish prefabrication techniques are described. The durability of horizontal joints is essentially improved, if the joint is made to incline outwards at the external concrete layer. Fading of the joints, which greatly contributes to the appearance of buildings, has been dealt with, particularly when considering the needs of complimentary construction taking place in the housing area with buildings finished by rendering.