Farhang Farrokhi - Assistant Professor, Civil Engineering Department, University of Zanjan , Zanjan, Iran
mehdi shahidi - Student, Civil Engineering Department, University of Zanjan , Zanjan, Iran

This study presents strut-and-tie models (STM) explaining the development of bond strength along bonded length together with anchorage by head bearing of headed bars. The anchorage at a head requires construction of a biaxial compressed nodal zone and bond resistance needs to use the concept of a smeared node. This model consists of a strut with the nodal zone at head for head bearing and fan-shaped stress field for bond stresses along the development length. This modeling clarifies interaction between head bearing and bond resistances where a bond transfers along the development length of headed bars is necessary for a smooth force flow. The experimental results For series of headed bars with relatively small area of plate heads are interpreted 1 by this proposed model

headed bar, strut-and-tie model (STM), bar anchorage, bar development, failure Mechanism, bond strength