Introduction

 

Physical non-linear (PNL) calculation represents very powerful tools for analysing any kind of structure in civil engineering build-up not only from reinforced concrete but also from the other materials. Generally, there could be significant differences of results towards to linear analysis, especially in case of hyper-static structures. In case of linear analysis, just E-modulus of material is taken into account for preparation of stiffness matrix. There is no stress distribution based on increasing of strain in component. On the other side the non-linear calculation provides stress distribution and increasing of bearing capacity after reaching of the ultimate strain until the collapse mechanism based on different values of stress and strain dependent on predefined nonlinear stress-strain relationship in material diagram.

Physical non-linear calculation combined with geometrical allows to analysis of second order effects with axial load by general method , where equilibrium and resistance shall be verified in the deformed state, deformations shall be calculated taking into account relevant effects of cracking, non-linear material properties and creep, see clause 5.8.6 in EN 1992-1-1.

 

Procedure for calculation

• User switches on functionality material nonlinearity for reinforced or steel fibre reinforced concrete in Project data , see "Project setting"
• User defines nonlinear material of the concrete, steel fibre concrete and reinforcement, see "Material"
• User defines nonlinear combination, where is possibility to defined local and global imperfection for each nonlinear combination
• User defines real (user) reinforcement for analysis, see "Reinforcement"
• User calculate nonlinear analysis , see "Nonlinear analysis"
• User evaluates the results after nonlinear analysis, see "Nonlinear analysis - Results"

Limitation

Although various types of non-linearity may be combined in the same project, it is not possible to cumulate several types of non-linearity on the same 1D or 2D member. The material nonlinearity (PNL calculation)is not possible to combine with:

• 2D press-only behaviour: the press-only behaviour will be ignored and the 2D member will behave as elasto-plastic (material non-linearity is taken into account)
• membrane behaviour: the membrane behaviour will be ignored and the 2D member as elasto-plastic (material non-linearity is taken into account)
• orthotropy behaviour: the orthotropy behaviour will be ignored and the 2D member will behave as elasto-plastic (material non-linearity is taken into account)
• beam local nonlinearity behaviour: the beam local nonlinearity will be ignored and the 1D member will behave as elasto-plastic (material non-linearity is taken into account)