Analysis of finite elements: failure by pandeo of walls of mampostería

The experimental proof to be modelada consists in wall of mampostería subjected to eccentric compressesion in the plane and articulated by both extremes. For this, have to represent the rótulas real. And, as some walls reinforce with textile embebidos in mortars (TRM), also modelamos this superficial reinforcement.

The model bases in a hypothesis of flat deformation. Each row of mampostería (including a row of bricks and the corresponding half board of mortar in each side) is modelada homogéneamente like a part that is in contact with the ones of around. The rótulas real have simplified with two triangles, one in each extreme of the wall, and like the analysis of the same remain to the margin of the investigation, the geometry of the rótulas real is not necessary.

By each row, associate a rectangular part to one of the free edges of the parts that represent the mampostería. This is thought to represent the layer of reinforcement TRM.

The way of failure would have to be associated to the geometrical unsteadiness (pandeo), by what the most important properties of the materials are those related with the deformation of the wall (module of elasticity) and the resistance to flexión of the boards, which determines the opening between the rows facilitating that it produce the pandeo. The resistance to the compressesion is not the most significant property of this analysis.

By these reasons, decides modelar the mampostería and the layer of reinforcement TRM like materials isotrópicos homogéneos. modela With plasticidad perfect the behaviour to compressesion further of the resistance to compressesion. It can that this was not the most realistic behaviour but is simple and represents the majority of the cases in which the maximum tension is far of the resistance to compressesion.

modela The contact between the rows of mampostería and between the layers of TRM with a criterion of zone cohesiva (CZM) to represent the behaviour to the traction of these two compound materials, that fracturan when reaching the resistance to traction. This resistance and the power of fracture of the first way are the parameters used to define the contacts.

The wall is connected with the bodies that represented the two rótulas of his extremes (triangles) with fixed contacts. The inferior triangle has prevented the movements of traslación of the free vertex and only can turn modelando the rótula inferior. Of the same way, the upper triangle has prevented the horizontal movement in the free vertex, but the vertical movement is imposed by a rampa (100 steps), being the condition of load.

The mallado of the wall and of the TRM is homogéneo and structured by means of elements of four sides. They use automatic options of mallado, but fixes the size (after a study of convergence) in a maximum value of 10 mm for the mallado of mampostería and of 3 mm for the one of TRM.

The two main characteristics of the model are the possibility to develop big deformations and an analysis step by step through 100 steps, during which the load applies gradually.

The simulation calculates always some steps further of the maximum capacity of load of the wall, by what can determine the way of collapse without having to go in in an explicit analysis.

Realises the simulation of different walls and compare with the results of experimental proofs. All the simulations give like result a collapse by pandeo because of the conditions of outline and to the way in which it defines the model. It checks that it exists a clear dependency of the eccentricity of the load and of the esbeltez of the wall. The effects of the real geometrical imperfections represented in detail because it used the real geometry of each wall tested.

Once validated, the model allowed the extension of the rank of the study: analyse walls with elder esbeltez or different eccentricities of load to the ones of the experimental proofs, with distinct systems of reinforcement TRM, with different conditions of outline and with different types of mampostería.

Define in detail the behaviour to traction in mampostería and TRM is essential to realise the simulation of the structural answer of the walls of mampostería (reinforced or no) properly subject to geometrical conditions, conditions of outline or conditions of load that do the pandeo the main cause of collapse.

The model of zone cohesiva (CZM) applied in the contacts that represent the boards of horizontal mortar of the real wall, is the best solution for the micromodelado in the surroundings of Ansys.

The results obtained represented faithfully the experimental proofs. The analysis of finite elements realised allowed to expand the rank of the study to obtain additional practical information on the application of systems of reinforcement TRM or of behaviour of structures more complex, more resembled the real applications of the mampostería.