Strength Assessment of Structural Elements

Reinforced concrete structures, built in the last century, are reaching end of their life span and need strength assessment for their continuous safe use. Strength assessment is also required with increase in loads due to change in use or increasing weight of applied loading. Quite often people use finite element programs based on linear elastic theory to assess the carrying capacity of structural elements. However, the real behaviour of reinforced concrete structures in the vicinity of failure is plastic. In this paper, assessment methods based on nonlinear finite element (NLFE) method (using DIANA) and yield line theory (following the hodograph approach) are explained. In addition, new yield line mechanisms for flat slabs supported on non-rectangular column grid are introduced and compared with experimental observations and NLFE predictions. Based on comparison between the predictions by NLFE and Yield line theory conclusions are made.