English abstract
In this research, the behavior of a 14-story reinforced concrete building with 35m length, 15m width and 49.5 m height was analyzed using ETABs commercial software with 3D finite element non-linear analysis. The building was made of three-by-seven bays of 5m grid-to-grid spans each. Three column's sections, 500x500, 550x550 and 600x600mm, were examined. Seven models for each section were developed with different shear wall shapes and locations. Three Euro-code (EN 1990:2002 +A1:2005) load combinations were adopted in the analysis namely: (1) 1.35 DL + 1.5 LL, (2) 1.35 DL + 1.5 LL +0.9 WL and (3) 1.35 DL + 1.05 LL + 1.5 WL. Each model comprised 32 columns. Results from all of the 32 columns of each model were analyzed. The building was designed for general office use. A system made of 200mm thick flat slab with 400x700mm spandrel beams were used. A 300 mm thick masonry wall on the spandrel beams was considered in the analysis. A 100mm thick, 2m wide and 2m long drop panel was adopted. The thickness of the reinforced concrete shear wall was maintained as 200 mm. The concrete characteristic compressive strength, the steel characteristic tensile/compressive strength,
of safety for concrete, the factor of safety for steel were maintained as 40N/mm2, 460N/mm2, 1.5 and 1.15 respectively. The live was 3kN/m2 and the dead load of the floor and ceiling finishes was 2.5kN/m2. The dead load of the masonry walls was 4.275kN/m2. The basic wind speed was 3lm/sec. The seven models were: (1) Model 1: No shear wall, (2) Model 2: 5x5m central core shear walls, (3) Model 3: 5x3m leeward square shear walls, Model 4: 5x5m windward square shear walls, Model 5: 3x3m centra square core shear walls, Model 6: 2 L-shaped shear walls at diagonal axis corners, and Model 7: 4 straight line shear walls in the short direction. A systematic test procedure was followed for testing all of the models and the design results from the 32 columns of each model were studied in terms of required longitudinal reinforcement and lateral displacement. The method of elimination among all models was used to select the best two models based on total columns required reinforcement. The selection of the best column from the two best ones was based on the total required reinforcement, total required concrete and lateral displacement. The (Eurocode 2. 2004) recommendation on IS
the maximum area of reinforcement is 4% Ac (mm2) and the minimum is 1% Ac (mm2). It was found that the model with shear walls built in the external periphery in the short direction of building (model 7) gave the best results in terms of the amount of required reinforcement and lateral displacement. The second-best model was the one with shear walls built as L-shape in the opposite corners (model 6). The 600x600mm section was found to be oversized and required only the minimum reinforcement. When the cost of steel is critical, section 550x550mm would be more attractive than 500x500mm. The opposite would be case when the cost of concrete and the rent of space are more critical. In all cases, model 7 was the best followed by model 6. Model 1 of section 500x500mm failed in load combination 2 and 3. Model 1 of section 550x550mm failed load combination 3. Model 3 of section 500x500mm failed load combination 3. All successful models required reinforcement within the code limits (Eurocode 2,2004).
