The behaviour of puzzle-shaped composite dowels — Part I: Experimental study

• An extensive programme of tests on the innovative PZ composite dowel connection
• The mechanism of failure of steel dowels has been identified.
• The size of the dowels has no effect on the bearing capacity of the connection.
• The bearing capacity of the steel dowels is a linear function of web thickness.
• The ductility is a linear function of the inverse of dowel size.

An innovative form of shear connection effected through puzzle-shaped (PZ) composite dowels is studied by means of full scale push-out tests (POST). 19 specimens were subjected to a programme of destructive tests focused on the load bearing capacity of the connection steel part, i.e. the steel dowels. The influence of web thickness, dowel size and steel grade were studied. The design and construction of the test specimens, test procedures, failure mechanisms and test results are presented in detail. On the basis of the test results, it is assumed that in the case of steel S460 and concrete C70/85, at a web thickness of 10 mm steel failure occurs, at 30 mm concrete failure occurs and at 20 mm mixed steel–concrete failure occurs. The steel dowel undergoing plastic deformations is a major factor initiating concrete failure. The tests have proven the thesis [7] that the size of the dowels has no influence on the load bearing capacity of the shear connection unit length. Furthermore, it was discovered that ductility is a linear function of the inverse of dowel size in the case when exhaustion of the load bearing capacity of the steel dowels determines the load bearing capacity of the connection. As the basis of this task, the experimental confirmation of this thesis was paramount. Analysis of the results for a single composite dowel and FEM simulations are presented in the adjoining paper — Part II: Theoretical investigations.