Düşeyde düzensiz taşıyıcı sistemli çok katlı betonarme bir binanın deprem davranışının incelenmesi

Abstract

Bu çalışmada, düşeyde düzensiz planda her iki aksa göre simetrik ortogonal çerçevelerden meydana gelen sekiz katlı bir binanın değişen konsol boylarına ve zemin şartlarına göre statik ve dinamik davranışları ele alınmıştır. İncelenen sistemin kurgusunda ve kesit boyutlarının belirlenmesinde deprem yönetmeliği dahilinde hareket edilmiştir. Bu bağlamda sistemimizin düşeyde düzensizliği; her iki yöndeki dış akslarda yeralan zemin kat kolon elemanları ile birinci kat kolon elemanları eksenlerinin çakışmamasından meydana gelmektedir. Birinci kat ve üzeindeki kat kolon elemanları süreklilik gösterecek şekildedirler. Birinci kat dış aks kolonları zemin kat kolonlarına kısa konsollar ile bağlanmış durumdadır. Sayısal çözümlerde; düşey yükler ile yatay zorlar etkisindeki sistemin davranışı, üç boyutlu doğrusal elastik çözümler ile ele alınmıştır. Sistemin yatay zorlarının değerleri Erzincan 1992 depremi ve Dinar 1995 depremi kayıtlan olup, analiz sonuçlan kritik sayılabilecek bazı kesitler için tablolar halinde düzenlenmiştir.

In this study, the static and dynamic behaviors of a building of eight stories having symmetry to the both axis in the plan and vertical irregularity, consisting orthogonal frames are investigated. The vertical irregularity of this system comes from not coinciding the ground floor column components which appears on outer axis of both sides with first floor column axis. The first floor and the other floor columns show continuity. The first floor outer columns attach to the ground floor outer axis columns with corbels. The analyzing of this structural system which mentioned above, first of all, it is approached to the study in terms of strong design to the earthquake. In such a design, the resisting of the earthquake forces safely is the one element of the basic elements. The most important thing to ensure safety is the design of the structural system that is to built in a safely way. In such an earthquake resistant design, the most desired features for a structural system are the simplicity, symmetry, continuity, regular structural system, foundations adequate system and no abrupt change of rigidity and no abrupt mass differences of a building. Observation showed that the more simple designed buildings are the more resistant against to earthquake. The simple and regular building are easy to construct and cause less fault in the construction. Both estimating earthquake behavior of such building and creating an analyses accordingly are easier. To design a model for and consider the torsional effects of complicated and irregular buildings more complicated. What is wiser is not to allow any torsional effect. xu For the similar reason, structures are desired to have a symmetry in two directions in the plan. So, the behavioral way in the analysis and the actual behavioral way approximates to each other. Buildings in the shape of H, L, T and Y in plan have been damaged considerably due to the earthquakes. For this reason, only symmetry is not sufficient every time, but also a building must have simplicity at the same time. What else, component elements must be arranged in a way not to cause torsional effects. Buildings have parts like wing at the practice usually. That is a dangerous condition, there are important internal effects in region mat the main part combine with the other parts and this condition is not wanted. So that, big building masses should cut in to pieces and than put in order. It is important to arrange elements in both in plan and vertical section in a regular and continuous way in the structural system. Such arrangement will not allow tension accumulation. All columns and shear walls must have continuity from foundation to the top of the building and have no eccentricity. Reinforcement in sections must be ensured to have continuity so that cross-section effects coining of the elements occur as desired. While continuity and strength capacity beyond elastic behavior of elements are increased, elimination of dynamic energy is also increased. For this cases opposed to that, joining case in short time may occur. In addition to continuity, rigidity of some elements must not change abruptly. An important point to be avoided is the lower rigidity in ground floor comparing to upper floors. External effects of earthquake can be reduced by deterring adequate rigidity of the component elements and adjusting vibration period to a certain level. The point to be paid attention is that the dominant period of ground and vibration period of building must occur at levels distant to each other. xm Increase rigidity of a building, displacement in a building can be reduced. So, damage can be reduced to minimum structural and non-structural element of the structural system. Ductility of structural system elements in addition to required resistance becomes important about buildings only which under dynamic loads. [ 1 ] The important points specified above have been underlined trough explanations and several figures in the present study. On the other hand, built area intensifying in the districts with high density of population. In this context, value of plots increase and becomes an important factor in the building costs. And finally, architectural design is enforced to use plot in maximum level. So, due to new approaches of architectural design occur irregularity and some cases undesirable for engineering. Discontinuity in vertical and horizontal, instantaneous rigidity changes and mass differences of structural system are to be avoided. Buildings with such features are deemed to be irregular buildings. Since earthquake behavior of such building are not known exactly, earthquake analyses of such buildings is problematic. Using methods use for regular buildings in the irregular buildings are debatable. By means of the design of the consoles, net area is increased in the upper floors. Nevertheless, this is also problematic, since columns in the external axis, especially corner columns remain in the net volume of the upper floor and reduces using of such place and they are undesirable regarding aesthetics and architecture. As a solution to the problem, columns in the external axis are transferred to console edges. As a result of such approach, an irregular building undesirable for structural system take place. Analysis and calculation of building forming at the end are problematic for technical personnel. av The building subjected to the study is a building whose structural system is composed of column and beam elements and having irregular frames vertically. In the design here, a building with an irregular structural system in vertical is created by attaching the first floor external columns to the ground floor external axis columns with corbels. Floor mold plans and a vertical section plan are specified in the section two. No sufficient study has been found shed a light on the foregoing matters. Many studies are mentioned in the text. In the second part the thesis, problem is defined and numerical results are obtained by conducting analysis' s. In the structural arrangement subject to problem, consoles created by moving external axis 1.25m from ground floor ceiling mould, columns in the external axis of floors upper of the ground floors are also pushed in the same proportion and fixed on the edge of the corbels. What else, as a second approach, system with 1.50m console length are arranged. In the system, the high of storey is 3m, frame beams are 0.25/0.60m and external axis beams dimensions are 0.25/0.40m. The section dimension of corbel beams which coincide with the column are 0.50/1.60m, and the end part of it are 0.50/0.50m. Thickness of slabs are 0.12m high. The dimension of columns are defined in the given plans. The problems is to determine the behavior of the structure with the mentioned geometrical features and symmetrical in both axes in the plan under the vertical and horizontal loads. For static case, presence of the service load on beams are accepted, and inadequent loading cases are ignored for the sake of simplicity respectively, and critical cross- section effects are arranged in the tables for beams and corbels between A and C as well as 5 and 7 axis. XV First of all, static results under vertical loads are obtained as to the way they are built- in the fixed base. Such result are arranged in the corresponding tables. Important values are obtained in the corbel beams end in the beams next to the corbel. Torsional moments at the levels we must consider when the making reinforcement are obtained in the corner corbels. Regarding equivalent static analyze, natural vibration period of the building is obtained from free vibration analyze. Base shear forces have been calculated in accordance with the earthquake code. The base shear forces have been calculated by distributing such side pull obtained. Tables have been provided in respect to critical section effects. As to dynamic analysises, masses are assumed to accumulate in the nodal points. In the dynamic case, first of all, free vibration periods of the buildings are analyzed, taken 10 modes into consideration. Such analysis has been conducted by taking into consideration the cases when columns built-in on the fixed base and when the foundation rigidity is given as a parameter respectively. Results have been shown in the tables. Regarding built-in fixed base case, the first 7 modes in the free vibration of the building occur in the way of bending and distortion and the 8., 9., 10., modes in the way of vertical vibrations. Period values of the vertical vibration are less than vibration period values of bending and distortion. In the forced dynamic case, values of spectrum curves in Erzincan 1992 and Dinar 1995 earthquakes have been used as an external effects. In such performance, North- South component of earthquake records effected the building in the direction x, East- West component in the direction y, and vertical component in the direction of z. In the analyzes, earthquake component combinations suggested by Eurocode-8 have been performed. XVI In the end of the section, analyzes result have been appraised, and for both earthquakes, acceleration diagram and base shear force diagram have been specified. In the section 3, rigidity values of foundation have been added to the analysises as a parameter. For such case, for the sake of simplicity, 3mX 3m foundations under all the columns have been assumed. Through elastic foundation, free vibration period values shoved increment according to the built-in fixed case. In the cases where softness of the soil increase, free vibration periods of building have been seen to increase too. Base shear forces decrease according to the built-in fixed case. An appraisal about the result of analyzes have been made in the end of the section. In the section 6, general information about short corbels have been given. Behavior of the short corbels are different from the available beam approvals. Knowledge obtained from the experimental studies has been given here. In the reinforcement, an arrangement has been set up according to cracking. The balance of the internal forces of the section can be estimated according to cracking, and reinforcement has been conducted. So, corbel load is balanced with tractive power and concrete comparison bar with horizontal reinforcement. In the last section of part, points to be paid attention in reinforcement have been deal with. [ 2,3 ] In the seventh section of the study, numerical dimensions are given for three types structural element. At the first of others, reinforcement for the corner column and external axial columns of the ground floor have been given. Calculation values have been determined in accordance with suggestion of the earthquake code. Section calculations for each column have been specified. Secondly, corbel section calculation which may be deemed to be the most important component of the study has been performed. Calculation values are obtained xvu in a similar way columns. Section calculation has been performed in accordance with French code. Thirdly, internal beams next to the corbels have been used. Considerable internal effects occurs in the sections where they joint to corbels. Calculation values have been determined in such section values in a similar way with others. In the last section of the study, important points obtained in the study have been emphasized. Results have been obtained under certain criteria and assumption. The present study can bee deemed to be a step to shed light on the existing problem, and the result rules will appear more definitely when many similar study is conducted.