Design of an office building with concrete filled composite columns according to turkish earthquake code for buildings 2018 and nonlinear analysis of the building

The building to be modeled is designed as a 6 storey office building with a total height of 19 m and dimensions of 24,00 m x 30,00 m with a total area of 720 m2. The columns of this structure, which are designed as a moment resisting frame system, are composite columns consisting of a concrete fillled steel pipe profile. Three different sizes of composite columns were used. Respectively, the dimensions of the composite columns are 400 mm × 10 mm, 400 mm × 12 mm and 400 mm × 15 mm. Also beams are IPE 360 and HEA 400. The dimensions of the elements were determined as a result of the analyzes. It was thought that this work took place in Maslak / Sarıyer / ISTANBUL. The earthquake calculations for this structure are done using both DBYBHY and TBDY 2018. Equivalent Seismic Load Method which is explained method of statement and limits of usage is used in the calculation of earthquake. It was considered that the building is at first earthquake zone and Z2 local ground class for the calculations according to DBYBHY. Moreover it was thought that the building is at Earthquake Ground Motion Level-2 and ZD local ground class for the calculations according to TBDY 2018. SPT / N values are taken into account when determining the local ground class. Various investigations have been made for this system type which is not preferred in our country and in the world. According to one of the research, when a structure which has all structural elements made of steel and a structure which has the columns are made of composite columns with steel beams are compared it is observed that the composite column structure shows better performance under the earthquake load and it was seen that it is more economical according to steel structure. In another study, it was observed that the structure which has composite columns and steel beams performed better when compared to a structure which has columns with reinforced concrete. Equivalent Seismic Load Method was also applied for both codes (DBYBHY & TBDY 2018) and the changes coming with TBDY 2018 were investigated by this study. Structural acceleration values in the earthquake calculation made with the new earthquake regulations are located at the site indicated in the regulation as "AFAD" in every region of Turkey depending on local earthquake and ground conditions. This makes a significant difference in terms of finding acceleration values with the previous regulation. In this context, the earthquake loads obtained by TBDY 2018 are obtained to be larger than the earthquake loads obtained by DBYBHY. xxviii Earthquake loads which is applied to structure found by using Equivalent Earthquake Load Method in accordance with TBDY 2018 code. Earthquake loads which are found by using DBYBHY code was not used for the sizing of the structure elements. Wind loads are determined in accordance with TS EN 1991-1-4 and snow loads are determined in accordance with TS EN 1991-1-3. Design calculations related to composite columns and beams were carried out in accordance with TBDY 2018 and New Steel Code. Internal forces were found by considering the conditions given by TBDY 2018 as binding to the load combinations given by New Steel Regulation. In the presence of internal forces, the D (Coefficient of Strength Excess) coefficient used in TBDY 2018 load combinations with earthquake effect and given in the relevant sections of the regulation for the presence of compressive strength in column members is used. When comparing the compressive strength obtained by using the D coefficient with the internal forces (shear, compressive and moment) obtained by not using the D coefficient, the internal forces were taken which caused the most unfavorable state. In addition, P-Δ effects are taken into consideration determining internal forces by using ETABS analysis programme. The expected behavior of the moment transferring frame systems is that the displacements occurring in the column members under the structural influent loads remain in the linear region while the beam members displace the boundaries in the nonlinear region as described in the relevant portions of this work. In this context, expected level of structure performance is determined as Controlled Damage Performance Level as given by TBDY 2018. The aim of the study was to determine the expected performance level by comparing the plastic deformation demands and the internal force capacities of a given earthquake. Non-linear calculation methods; static pushover analysis method with nonlinear calculation method in time domain which is dynamic push analysis method. Static pushover analysis is used for low-rise structures without torsional irregularities where high mode effects are not observed is suitable as specified in the relevant regulations. The static pushover analysis method was applied to the structure modeled within the scope of this study, taking into consideration the above mentioned factors. Static pushover analysis was performed using ETABS software. As a result of the analysis, two methods were used by the relevant analysis program in determining the structure performance. These methods are Capacity Spectrum Method and Coefficient Spectrum Method. The results obtained by both methods are given in the relevant sections of this work. The Capacity Spectrum Method is influenced by the floor mass and the lateral load (earthquake effect) depending on the floor height under the influence of the structure constant and moving loads. Base shear and peak displacements are found after the analysis. After each lateral loading, checked by programme whether the elements which have the plastic deformation or not and the peak displacement obtained against each base shear force is marked on the graphic. The curve of the capacity spectrum is drawn on spectral acceleration and spectral displacement graph generated by the earthquake effector. The earthquake-affected structure is intersected at a point on the graph. This point is called the performance point. For this point, the plastic hinge elements are determined by looking at the performance points of the elements. xxix In the coefficient spectrum method, there is no need to convert the capacity curve to spectral coordinates. In this method, the target location is used instead of the performance point. First of all, as mentioned in the related regulations, using related equations the displacements which will demand by structure is determined. Using the ETABS analysis program, the lateral loads are applied to structure until this displacement value is reached. As a result of these iterative loads, the base shear force for the initial displacement is obtained. According to these methods, the plastic deformations are determined during the earthquake and the plastic hinges are investigated for this deformations. As a result, it was observed that the plastic hinges were observed only on the beam members in accordance with the strong column weak beam principle, and no plastic hinges were observed on the column members. Thus, the Controlled Damage Performance Level, which was initially determined as the expected performance level from the structure, was achieved performing nonlinear analysis.