ABSTRACT
This chapter describes strut and tie modelling (STM) of reinforced concrete (RC). STM provides safe estimates of strength irrespective of cracking. The problems of Finite Element Analysis modelling of concrete were illustrated by the Sleipner-A oil rig, which sank whilst being lowered into a Norwegian fiord. The STM method is used for modelling areas of stress concentration within structures. These are termed ‘D-regions’, with D for discontinuity. Areas where conventional beam theory proves accurate are termed ‘B-regions’, where B stands for beam. The D-regions are generally assumed to be square in proportion, that is, equal in length to the member depth. The D-regions result from either geometric discontinuities or from concentrated loading. Compression struts are classified into two main types: prismatic and bottle shaped. The important difference between these is that stress is spreading in bottle-shaped struts, whereas it is uniform for prismatic ones.
