Effect of Cut-Out Openings in RC Walls : A Parametric Study with the Finite Element Program ATENA

It is common that buildings are renovated and their functional use is changed which leads tonew layouts of floor plans and that new installations are necessary to be made. These changesentails that load bearing walls are removed and new door, window and shaft openings needs tobe made in already existing load bearing walls. Reinforced concrete walls are nowadayscommon as structural members in buildings. Therefore, it is necessary to have knowledge ofhow cut-out openings affect their structural behavior. This is nowadays almost unexplored andthe international codes, for example Eurocode 2 (2008), treat openings in walls indirectly,through the column theory. Further research is necessary in this subject to gain knowledge onhow cracks, failure mode and the ultimate load are affected by a cut-out opening, reinforcementratio and placement and the eccentricity of the load.A parametric study was performed with the finite element method (FEM) program ATENA(Version 5.3.2) (2015). A benchmark process was performed against experimental tests,reported by Popescu et al. (2015b), on three different walls: one solid wall, one wall with largedoor opening (A0/A=50%) and one wall with small door opening (A0/A=25%). The materialparameters were benchmarked according to laboratory tests. The investigated walls in FEA andin the experimental tests were two-way walls with a centric reinforcement mesh.The parametric study included seven different wall types, one solid wall and six walls withopenings with A0/A between 25-75%. Each wall was investigated to four load eccentricities,e=0 mm, e= 10 mm, e=15 mm, e=30 mm. The influence of the reinforcement was investigatedby an analysis of an unreinforced wall and a wall with a centric placed reinforcement mesh.The influence of placement of the reinforcement was investigated by an analysis of a wall witha centric reinforcement mesh and a wall with two reinforcement meshes, one at each face ofthe wall. In both cases the reinforcement ratio was kept constant. The effect of the reinforcementratio was also investigated by increase the reinforcement ratio of a centrically placedreinforcement mesh by 4 times.The parametric study showed that the investigated door opening sizes gave a reduction of theultimate load with up to 74% compared to the solid wall. It was noted that the opening sizeaffects the crack pattern of the wall but the influence of the door opening size decreases withan increased eccentricity. The parametric study also showed that the investigated loadeccentricities gave a reduction of the ultimate load with up to 82% compared to when the loadact centrically on the wall. The influence of eccentricity decrease with increased door openingsize. It was also proved that reinforcement always increases the ultimate load. Anotherconclusion was that an increased reinforcement ratio by 4 times increases the ultimate load upto 11.2%. A placement of the reinforcement mesh in two layers, one at each face of the wall,instead of one centric increases the ultimate load up to 10.2%.Ultimate loads calculated in the finite element analysis (FEA) were compared to Eurocode 2(2008) and a design equation according to Doh and Fragomeni (2006). The most accurate wasDoh and Fragomeni (2006) compared to the FEA. But both Eurocode 2 (2008) and Doh andFragomeni (2006) showed ultimate loads with large deviations for some wall types. This masterthesis showed that an improved design method for reinforced concrete walls with cut-outopenings is needed.Validerat; 20160313 (global_studentproject_submitter