Design and evaluation of the shear strength of deep beams by strut and tie model (STM)



Strut and Tie Model (STM) has been widely applied for the design of non flexural and deep members in reinforced concrete structures in the last few decades. Experimental research on STM is underway to further rationalize the method for the analysis and design of disturbed regions in reinforced concrete structures.  In this research six deep beams with a shear span to depth ratio (a/d) of 0.64, 0.76 and 0.94 have been designed against the external assumed loads. The beams were later tested under monotonic two point loads and the actual shear strength of the deep beams was determined at the failure loads of the beams. The load carrying capacity of the deep beams was also calculated on the basis of the actual strengths of the compression struts and nodes with the help of guidelines given by ACI-318-06, for the use of STM. The observed failure loads were compared with the load carrying capacity of beams worked out from the strengths of the struts. The failure loads were also compared with the provisions of EC-02. It has been observed that both STM based on ACI 318-06 and EC-02 have given a reasonable prediction of the shear strength of deep beams.