Seismic evaluation of a composite high-rise building based on nonlinear dynamic time history analysis

The majority of the population has intensified to major cities by the impact of globalization, causes the need for high-rise buildings. High buildings which have been designed with conventional design procedures, have faced huge structural damages in consequence of middle and high level of earthquakes in past 50 years. Due to damages caused, great number of life, economical and social losses show the necessity of designation of earthquake impacts close to reality. In earthquake regions, development of deformation based design procedures have been commenced as an alternative method of strength based design. The main philosophy of performance based design is, identification of displacement, deformation and damage levels of structural members that faced to earthquake forces during the design process. Especially contribution of reports such as ATC, FEMA that are published results of studies which have performed in USA in last 20 years, performance based design have became more popular than strength based design. Displacement based design procedure is used for current global design method for high-rise buildings in seismic regions. In scope of this study that is completed as a master of science thesis, 47 story composite high-rise building's, which consist of frames and special concentric braces preliminary design has been completed. Also seismic evaluation of a structure has been made with nonlinear dynamic time history analysis. In numerical examination, structural system that have material and geometrical nonlinearity, is analysed with finite element software named Etabs with scaled ground accelerations according to Istanbul High-rise Building Earthquake Code MCE level (D3) earthquake acceleration spectra. AISC 360-10 design code is followed for the gravity load design of the structure with load and resistance factor design. For ductile members, especially special concentric braces are designed according to AISC 341-10 and AISC 360-10. Nonlinear material properties and idealized force deformation relationship of the members are formed by following ASCE 41-13 and ATC-72 documents. In order to determination of the lateral loads of the structure, local wind and earthquake codes of Istanbul are used. Istanbul High-Rise Buildings Wind and Earthquake codes are not official codes however they both are recommended to be followed for the buildings higher than 60 meters located in Istanbul thats why; in this study these reports are based on determination of lateral effects. Connection of special concentric braces and frames are performed according to capacity principles also design steps are explained with construction rules and limitations. This study consist of 6 parts. In first part, definition of performance based design concept and necessity of seismic evaluation are explained. Moreover, earthquake effects and damage levels caused to create displacement based design method are mentioned. General scope of this study is also summarized in this part. Second part begins with development process of multi story structures. From past to present, design of high buildings are investigated, and evolution of structural systems which allow structural engineers to be able to design higher structures, are indicated as well. Additionally, distribution of high-rise buildings according to regions and materials used is mentioned in this chapter. Third section of the study includes, high-rise building design parameters with taking into consideration of other disciplines as a design team. Also properties of structural systems and application cases for the building types, are explained in detail. While classification of structural systems, significant points are discussed for arrangement of structural system of given building. In fourth chapter, necessity of performance based design and historical development of methods are explained. This part includes design process of seismic design codes until today for the buildings constructed in seismic regions. Moreover, related parts of Turkish Seismic Code 2007 are investigated while missing topics and concepts are mentioned. Fifth part of the study starts with, explanation of details for high-rise building that is considered in numerical examination, structural system properties and design assumptions are also mentioned. Afterwards, required expressions are given for creating design acceleration spectra for different intensity of earthquakes using with Istanbul High-Rise Buildings Seismic Code. One of the most important section as selection and scaling of ground motions takes place in fifth part as well. Important issues about selecting ground motions and limitations offered by seismic codes are investigated. While methods for scaling ground motions are explained in details, comparison has been made for parameters and results for mentioned scaling methods. In order to investigate dynamic wind effects for a high-rise building, Istanbul High-Rise Wind Provision is followed. Although Turkish Wind Code is on regulation, it has not been updated for a long time and doesn't include dynamic effects of the wind pressure therefore; that code is not considered in this study. Determination of wind loads, required expressions are explained in order to create wind speed profile of the structure. After calculation of wind loads, design phases of structural members are mentioned. First of all, concrete filled tube design according to AISC 360-10 provision is explained in detail with supplied expressions for each step, then major points for taken into consideration during the design are suggested. Limit states for creating capacity curves of concrete filled tubes are also defined in this chapter, these states are supported with expressions. Take advantage of capacity curves, moment axial force design curve including buckling is given as well. Composite beam calculation phases with plastic stress distribution is explained in detail. The part, which composite beam design limitations and rules are identified according to AISC provisions, also includes calculation of shear studs needed for composite action on beam. After columns and beams, calculation and sizing of special concentric braces are mentioned with specifying tension and compression strength of the brace member in ultimate limit states. As a part of numerical examination, connection checks for special concentric braces and frames are investigated with supported equations and geometric limitations. Capacity limit states are applied for identifying maximum effects that connection might encounter, by considering different loading cases. Calculation of typical beam-column connection where brace is also joined, is likewise shown in fifth chapter with taking into consideration of plastic hinge occurrence in brace section. Finally, important issues are discussed for creating nonlinear analysis model. Additionally, nonlinear material properties and damping values are explained, moreover monotonic and cyclic behavior of force-deformation relationship of steel members are indicated. Before concluding this part, reasons of degredations for force deformation relationships in steel elements are discussed and definitions of nonlinear time history analysis application are explained briefly. Section six includes, results of numerical examination of the study and suggestions for further development studies respectively. Calculation tables, charts, figures of numerical analysis model, spreadsheets of structural member design, scaled ground motions and performance assessment results are given in appendix section.