Burulma düzensizliği olan yapılarda sismik izolasyon kullanımının deprem yükleri altındaki davranışa olan etkisi
The effect of using seismic isolation to behavior of structures with torsional irregularity under earthquake loads
Yazar: TAHA TOPRAK
Danışman: PROF. DR. ÜNAL ALDEMİR
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / İnşaat Mühendisliği Ana Bilim Dalı / Yapı Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2012
Konu: Deprem Mühendisliği = Earthquake Engineering ; İnşaat Mühendisliği = Civil Engineering
Dizin: Deprem mühendisliği = Earthquake engineering ; Sismik taban yalıtımı = Seismic base isolation

Özet:
Çağımızın en büyük doğal felaketlerinden olan depremler zeminin alt katmanlarındaoluşan şekil değiştirme enerjisinin temel aracılığıyla yapıya aktarılması sonucu ağırmaddi hasarlara ve toplu can kayıplarına neden olmaktadır. Doğadan gelen buözelliğe ilave olarak mimari gereksinimler ve istekler eklendiğinde felaketkaçınılmaz bir son olmaktadır. Tamamen estetiğe hitap etme arayışına yönelik olarakinşaat mühendisliği gerekliliklerinden uzak bir dizayn felsefesi ile tasarlananyapılarda yönetmeliklerde düzensizlik olarak belirtilen esasen yapının deprem etkisialtındaki davranışının olması gerekenin haricinde olması durumu ortaya çıkmaktadır.Bu düzensizlikler arasında en yaygın olanları burulma düzensizliği ve daha çokyumuşak kat düzensizliği olarak bilinen komşu katlar arası rijitlik düzensizliğidir.Aynı zamanda olmuş depremlerdeki yapı hasarlarına ve oluş sebeplerinebakıldığında yapı davranışına kötü yönde etki eden ilk iki düzensizlik türü bunlardır.Bu sebeple bu çalışma kapsamında bu iki düzensizlik türü içerisinde de en sıkkarşılaşılan tip olan burulma düzensizliği ve yatay yükler altındaki davranışında budüzensizliği bulunduran yapıların sismik izolasyon yöntemi ile davranışbozukluğunun giderilmesi amaçlanmıştır. Bu amaçla öncelikle üst yapı sünekliğininetkisinin de göz önüne alınabilmesi için üç, beş ve on katlı modeller oluşturulmuşdaha sonrasında ise bu modellerin her birinde geçerli olmak üzere burulmanınolmadığı, %5 olduğu, %10 olduğu ve son olarak da %20 olduğu alt modellertüretilmiştir. Böylelikle oluşturulan tüm modellere zaman tanım alanında analizlerdekullanılmak üzere El Centro, Northridge ve Kocaeli depremlerinin ivme kayıtdataları yüklenmiş ve SAP2000 (CSI,2011) genel amaçlı sonlu elemanlar paketprogramında analizler tamamlanmıştır. Çalışma kapsamında ülkemizde yürürlükteolan Deprem Bölgelerinde Yapılacak Binalar Hakkında Yönetmelik (2007)kullanılarak sismik izolasyonlu yapıların analizi gerçekleştirilemediğinden UniformBuilding Code (1997) Amerikan şartnamesinden yararlanılmıştır. Sismik izolasyonyönteminin kullanılmasıyla amaçlanan avantajlar, süneklik düzeyi yüksek yapılarüretme felsefesi üzerine kurulu geleneksel depreme dayanıklı yapı tasarımıanlayışıyla tasarlanan binaların tersine toplu kütleli hareket yapan yapılar oluşturaraküst yapının rijit davranış sergilemesi fakat bunun yanı sıra göreli katdeplasmanlarının ve kat ivmelerinin sınırlandırılarak istenilen seviyelere çekilmesiolarak sıralanabilir. Bu amaçları tam manası ile inceleyebilmiş olmak için yükseksönümlü kauçuk mesnet ve kurşun çekirdeki kauçuk mesnet olmak üzere iki türizolatör modellenmiştir.

Abstract:
Since Turkey is placed on an active earthquake belt, each passing day an earthquakeincident can be seen in the news. In addition to this natural status, people who haveaesthetical concerns build constructions without applying civil engineering rules andneeds turn this natural disaster out to be an artificial disaster. Structural irregularitieswhich appear due to architectural concerns cause more destructive impact on thebuilding and extra losses.There are two main types of these irregularities which are torsion irregularities andsoft storey irregularities. Torsion irregularities appear when mass center and stiffnesscenter of the structure does not overlap. As an example of this condition would becantilevers which are built on the top floors.There are two main reasons for soft storey irregularities. First one is the lack of wallson the ground floor. Since ground floor is generally used as an office, walls whichare put on upper floors cannot be seen on the ground floor. Secondly, for the samereason, ground floors are higher than other upper ones.Principally, it is very easy to prevent from these irregularities yet practically ways toprevent are not implemented. Thus, this research is made for answering suchquestions as ?Is it possible to prevent from negative impacts of torsion irregularitiesby seismic isolation method even though the torsion irregularity appeared due todesign mistakes of architectural concerns and irregularity is not corrected?? and ?If itis possible, what are the limits for seismic isolation method to be effective??Parameters such as numbers of storey of the structure, rate of torsion irregularity,isolator type and type of earthquake exposed are taken into account in this research.First, a prototype is programmed on STA4CAD in order to control sufficiency oftransporter system features of the chosen models. After the transporter systemsections are identified certainly by this program the same parameter models ischanged one by one and created on SAP2000 program. On this program, dead loadsof transporter system elements are accepted as zero and only one lumped mass isidentified for each storey. These identified lumped masses are directly accepted asthe numbers given by STA4CAD program. Models are divided into 3 groups whichare 3, 5 and 10 storey structures according to their storey numbers. Then every modelis divided into 4 groups according to their irregularity amount which are nontorsion(%0 torsion), %5 torsion, %10 torsion and %20 torsion conditions. Models aredivided into two groups according to their support types. These are base fixed systemand seismic isolation system. Then isolated models are divided into two groupsaccording to used isolator types. These are high damped rubber bearing used seismicisolation system and lead rubber bearing used seismic isolation system.After models are created and divided in such way, linear time history analysis is usedas analysis method and 3 different earthquake acceleration records are loaded in bothtwo directions. These are El Centro earthquake, Northridge earthquake and Kocaeliearthquake acceleration records.Performance criterias which are used to interpret the results within the research (orstudy) are: comparing top floor relative storey drifts of structures, comparing topfloor absolute acceleration numbers, comparing the maximum moment numbers andmaximum shear force which appears in the direction of earthquake load, comparingthe maximum moment numbers and maximum shear force which appears verticallyto the direction of earthquake load as torsion irregularity amount increased.Within the thesis, first step was the detailed literature scanning about irregularitytypes, theory of seismic isolation and isolator types. Then, analysis method andregulation which is used with the data related to this method and how unknownswhich are necessary to use this regulation are they chosen was explained.Afterwards, information about how models are created was given under the title ofmathematical model.Calculations of every model which is created under this title for both two isolatortypes was done by using an Excel table. In order to make every step clear and easilyunderstandable, example calculation procedures of both high dumped natural rubberbearing and lead rubber bearing were explained. Rest of the isolator calculations wasgiven as a table under the title of Appendix A. After the procedure of modeling thesuperstructure and isolation system was described, models were created on SAP2000general purpose finite element package program in 3D and models under the statedearthquake data loadings were analyzed in 3D.To create performance criterias for each model, primarily relative displacementnumbers were determined by subtracting top and bottom point displacement numbersfor upper storeys of a structure on a column which is chosen a SAP2000 program.Absolute acceleration numbers were drawn for only top point. Since an earthquake isa reversible loading, added numbers on the chart are the maximum in terms ofabsolute value for maximum shear force and moment numbers. When these numbersare chosen, maximum shear force and moment numbers were used not only for upperstoreys but also for every storey on the same column along the structure.Furthermore, in order to see how seismic isolation method prevents torsionalirregularity from having a bad impact on the behavior, which is the main subject ofthe thesis, chosen maximum shear force and moment numbers vertical to loadingdirection during the earthquake data loading were shown in a chart.When torsion irregularity rate is %0, charts showing maximum element forces whichis vertical to loading direction was not created. All different charts which are createdfor each different earthquake data loading is given under the title of Appendix B.In this way, the appendixes are arranged in two different tittles. This arrangement isgiven due to the number of pages for all the tables and figures exceeds 4 pages. Forthe reason of tables and figures could not to be put over four pages, this procedure isused. Subsequently all of this tables are collected under a title and they are explainedand interpreted.For all analyzes Specification for Structures to be Built in Disaster Areas (2007)which is valid in our country and shortly known as the Turkish Earthquake Code wasused for the structural load bearing system, for substructure (seismic isolation system) Uniform Building Code (1997) which is valid in the United States ofAmerica was used.By the data obtained from the study, the comparison of base fixed structural systemsand seismic isolated structural systems, the comparison of the structure isolated withhigh damping natural rubber bearing and natural rubber bearing with lead core, thecomparison of systems with non-torsional irregularity, five percent torsionalirregularity, ten percent torsional irregularity and twenty percent torsionalirregularity, and finally the comparison of the usage of seismic isolation for low-risebuildings and multi-storey buildings were made.Therefore all the comparisons for all irregularity ratios can be given as follows;comparison of fixed base structures to base isolated structures, comparison of highdamping rubber isolators to lead core rubber isolators, comparison of low risebuildings to high rise buildings.As results of comparisons the reached conclusions regardless of the number of storeyand the ratio of torsional irregularity on seismic isolated structures, top floor relativestorey drifts of structures, top floor absolute acceleration values, the maximum shearforce values and the maximum moment values in the top floor columns which is inline with the direction of earthquake loading, the maximum shear force values andthe maximum moment values in the top floor columns which is in vertical line withthe direction of earthquake loading had decreased by large amounts and thecomparison results are given in tables and figures are evaluated and summarized in?Conclusions?.It is concluded from the numerical results that the results achieved are expected andpromises the significant potential of base isolators in earthquake resistant design.