Earthquake behavior investigation of industrial structures with tensegrity systems

Cost of steel structures is a function of steel weight. Two main costs are important for steel structures. One of them is manufacturing costs and the other is installation costs. An important consideration in installation costs is the crane. Due to the large and heavy assemblies, the cost of the crane is high. Crane costs may have a major affect on the total cost. Different steel systems are proposed for different structural systems by engineers to reduce the cost of structures. For example, truss systems and space trusses are more economical comparing to frame systems for longer spanned structures. Mass is a primary concern in calculating earthquake loads. The mass of the structure comprises the system self weight and a certain percentage of live loads. Live loads are standard for structures and it can't be reduced. Earthquake loads can be reduced when self weight of structures are minimized. Earthquake loads are directly proportional to the mass value. When mass value is expanded, that means earthquake loads are expanded for structure. Increased earthquake loads requires larger column and beam section profiles. Larger profiles causes heavier steel and that affects the cost of the structure directly. In steel structures, lower mass for lateral forces is more effective comparing to vertical forces on the system. Lateral forces creates relative displacements between storeys. According to steel structure codes, relative displacements must stay within a specified limit. The steel codes restrict relative displacements. In keeping lateral displacement in limits, designers add steel diagonals or masonry walls to the structures. "I" steel profiles' load carrying capacity is negligible at the weak direction, so at the weak direction, profiles should be supported. Steel systems are not stable at the weak direction. The solution is to support the systems. Generally, steel diagonal and masonry walls are preferred in such solutions. Steel diagonal frames are one of the most common systems for industrial structures. Steel diagonals are preferred since the same materials are used for consistency in the structures. Generally, steel diagonals are used for irregular structures and axises which includes windows, doors and holes. Masonry wall systems are preferred to protect the structures from differences in internal and external temperatures and other effects. The area between the external axises columns are walled, so this results improved lateral stiffeners than steel diagonal systems. Tensegrity systems are the cables which are under tension. Tensegrity is composed of the words tension and integrity. Tensegrity structures are balanced systems under compression and tension forces. Tensegrity systems should be geometrically uniform systems. Tensegrity structures should be a particular shape of form. There are several kinds of formfinding ways for tensegrity structures. In this study, an industrial steel stucture is modelled for investigation of earthquake implementation of tensegrity systems. The industrial steel structure is modelled by finite element method program. For analysis of systems, SAP2000 software program is used. SAP2000 software is common universally and is used to back up theoritical calculations. For lateral stiffeners, the industrial steel structure is modelled in four different types. All models are designed with the same standards, using the same material, columns, beams and brace profiles. Loads are the same for each model and without the lateral frame, all cases are the same. In the first model, Model 1 is without any lateral stiffeners. Model 2 is with steel diagonal. Model 3 uses masonry and Model 4 uses cable systems. Model 4 is changed for different cable cases. Model 4.1 and 4.2 have different cable diameters than Model 4. Model 4.3 and 4.4 have the same cable diameters as Model 4, but pretension forces are different. Model 4.5 and 4.6 have the same cable diameters as Model 4, but the number of diagonal cables are increased. The aim of this study focuses on cable systems. Four different systems are analyzed and the results are compared and discussed. Cable systems are compared with the steel diagonal, masonry system and bare model. Model 4 is compared with Models 1, 2 and 3. Model 4 is compared with Models 4.1, 4.2, 4.3, 4.4, 4.5 and 4.6. The results of comparisons are illustrated with graphs. There are six chapters in this thesis. The first chapter includes the introduction, explanation of thesis, thesis aim and scope. In this chapter, thesis is summarized. The second chapter includes literature review summaries and information about topic. In this chapter previous studies are considered. Calculation steps, load combinations and new analyses for tensegrity systems are discussed at this chapter. In the third chapter, aim focuses on the tensegrity systems. Tensegrity structures, principles, applications, analysis methods and previous studies are given. Tensegrity backgrounds and history are explained. The fourth chapter is about the case study and model analysis. It provides analysis information, structure of models' properties, material properties, profile sections, masonry wall calculation and earthquake statistics are given in this chapter. All models analyzed with two different cases. The first analysis is pushover analysis and second is time history analysis. For pushover analysis, 1000 N load assigned beam-column connection joint at all axises, system displacement and base shear force is controlled step by step. For time history analysis, twenty different eathquakes are selected from the PEER database. PGA value is the most important criteria for selecting earthquakes. Generally, large scale PGA earthquakes are preferred. Seismic response modification factor R is 1. Models are analysed using an elastic analysis case. The fifth chapter provides results of analysis. Two types of analysis results charts, using pushover analysis and time history, are shown in this chapter. For pushover analysis charts, vertical line shows base shear force value. Horizontal line shows displacement of point, which is the top of the structure. Model charts, base shear force – displacement values are shown. Charts include base shear force – displacement comparison between models. Model 4 is compared with Model 1, 2 and 3. Model 4 and Model 1 are shown in the same chart. Model 4 and Model 2 are shown in the same chart. Model 4 and Model 3 are shown in the same chart. Model 4 is compared with Model 4.1, 4.2, 4.3, 4.4, 4.5 and 4.6. Model 4 and Model 4.1 are shown in the same chart. Model 4 and Model 4.2 are shown in the same chart. Model 4 and Model 4.3 are shown in the same chart. Model 4 and Model 4.4 are shown in the same chart. Model 4 and Model 4.5 are shown in the same chart. Model 4 and Model 4.6 are shown in the same chart. Model 4, Model 4.1, Model 4.2, Model 4.3, Model 4.4, Model 4.5 and Model 4.6 are shown in the same chart. Time history analysis results, charts show base shear force – displacement for each earthquake data. Each of twenty earthquake names are shown as a list. Model 4 is compared with Model 1, 2 and 3. Model 4 and Model 1 are shown in the same chart. Model 4 and Model 2 are shown in the same chart. Model 4 and Model 3 are shown in the same chart. Model 4 is compared with Model 4.1, 4.2, 4.3, 4.4, 4.5 and 4.6. Model 4 and Model 4.1 are shown in the same chart. Model 4 and Model 4.2 are shown in the same chart. Model 4 and Model 4.3 are shown in the same chart. Model 4 and Model 4.4 are shown in the same chart. Model 4 and Model 4.5 are shown in the same chart. Model 4 and Model 4.6 are shown in the same chart. In the final chapter, analysis results are discussed and investigated. Analysis comments and suggestions are given. Results of charts are discussed. Pushover analysis charts for each model and comparison chart models are discussed and explained. Time history analysis charts of each model and comparison charts models are discussed and explained. In conclusion, behavior of diagonal cables are explained. Effects of cable diameter, pretension and multiple cable are compared. Cable systems analysis is explained.