Planda düzensiz binaların deprem etkisi altında doğrusal davranışları
Linear behaviours of irregular buildings in plan under earthquake excitation
Yazar: SERKAN COŞKUN
Danışman: DOÇ. DR. KADİR GÜLER
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / İnşaat Mühendisliği Ana Bilim Dalı
Derece: Yüksek Lisans, 1997
Konu: İnşaat Mühendisliği = Civil Engineering
Dizin: Deprem = Earthquake ; Düzensiz yapılar = Irregular structures ; Eurocode 8 = Eurocode 8 ; Yönetmelikler = Regulations

Özet:
Yüksek lisans tezi olarak sunulan bu çalışmanın birinci bölümü planda düzensiz binalar hakkında bilgi vermektedir. 1996 Depreme Dayanıklı Yapı Yönetmeliği' ne ve Eurocode 8 'e göre planda düzensizlik durumları şekillerle gösterilmiş ve alınacak önlemler belirtilmiştir.Ayrıca Eurocode 8 'de bulunan dinamik analiz yöntemleri hakkında bilgi verilmiştir. Yapıların deprem yükü etkisindeki davranışı ve Türk Depreme Dayanıklı Yapı Şartnameleri incelenmiştir. İkinci bölümde planda düzensiz yapıların deprem etkisindeki davranışları incelenmiştir. Düzenli yapılar hakkında bilgi verilmiş L, T, H, + veya bunların kombinasyonlarım içeren yapılar ve plan çevresi boyunca rijitlik ve dayanımda değişiklikler gösteren sistemler ve taşıyıcı eleman eksenleri paralel olmayan sistemler incelenmiştir. i" Üçüncü bölümde, L - planlı bir bina 4 katlı çubuk sistem, plak sistem olarak depremli ve depremsiz haller için ayn ayn S.A.R90 bilgisayar programında analiz edilmiş ve 4 katlı durum için Erzincan Depremi spektral ivme-zaman kayıtlarının kullanıldığı dinamik yöntem kullanılmıştır. Aynı bina 8 katlı ve 16 katlı çubuk sistem olarak ayrıca analiz edilmiştir. + şekilli planlı ayn bir bina 4 katlı, 8 katlı ve 16 katlı olarak S.AP.90 bilgisayar programında analiz edilmiş ve 16 katlı durum Erzincan Depremi için dinamik hesap yapılarak ayrıca incelenmiştir.

Abstract:
In the fast part of the study, information about regularity in plan is given. In Eurocode 8, abuilding is called regular in plan if it is approximately symmetrical in plan with respect to two orthogonal directions, in what concerns the lateral stiffness and the mass distribution.. The plan configuration is compact, i.e. it does not present divided shapes as e.g. +, I, X etc. The total dimension of re-entrant corners or recesses in one direction does not exceed 25 % of the overall external plan dimension of the building in the corresponding direction. ^ The in-plane stifrhess of the floors is large enough in comparison with the lateral stiffness of the vertical structural elements, so that a rigit floor diaphragm behaviour may be assumed. Under the seismic force distribution applied with 5 % accidental eccentricity at any storey maximum displacement in the direction of the seismic forces does not exceed the avarage storey displacement more than 20 %. XI3gî&*s&:^sr The reentrant comer is the common characteristic of overall building configurations that, in plan, assume the shape of an L, T, H, +, or a combination of these shapes. There are two related problems created by these shapes. The first is that they tend to produce variations of rigidity, and hence differential motions, between different parts of the building, resulting in a local stress concentration at the "notch" of the reentrant corner. In Figure 1, if the ground motion occurs with a north-south emphasis at the L-shaped building shown, the wing oriented north-south will, purely for geometrical reasons, tend to be suffer man the wing oriented east-west. The north- south wing, if it were a separate building, would tend to deflect less than the east-west wing, but the two wings are tied together and attempt to move differentially at their notch, pulling and pushing each other. Figure 1 The L-shaped building and separeted buildings The second problem is torsion. This is because the center of mass and the center of rigidity in this form can not geometrically coinside for all possible earthquake directions. -xnThere are two basic alternative solutions to this problem : to separate the.- v building structurally into simple shapes,. or to tie the building together strongly at the *-? lines of stress concentration and locate resistant elements to reduce torsion. Wide variations in strength and stiffness around a building perimeter that provides seismic resistance is an another problem. The centers of mass and resistance will not coincide, and torsional forces will tend to cause the building to rotate around the center of resistance as seen in Figure 2.. CENTER OF RESISTANCE CENTER 0? x.-o. A Figure 2 Torsional response The fir--* arroach is to design a frame structure with aproximately equal strength and stiffne entire perimeter. The opaque portions of the perimeter can be constructec ructural cladding that will not affect the seismic performance of the frame. A sc-. _ aproach is to increase the stiffness of me open facades by adding shear walls at or near the open face. A third solution is to use a very strong moment-resisting - or braced frame at the open front, which approaches the solid walls in stiffness. This is, however, a good solution for wood frame structures as a long steel frame can never approach a long concrete wall in stiffness. Finally, the possibilty of torsion may be XIII*, accepted and the structure designed to resist it. This solution will only apply to small v structures with stiff diaphragm s, which can act as a unity as seen in Figure 3. LIGHT WEIGHT FRAME STIFF WALLS AT OPEN FACE STIFF DIAPHRAGM. SMALL STRUCTCBE V. ?.,',>>'?>,',? &HZ STEEL MB FRAME Figure 3 Solutions to open front design The vertical load-resisting elements are not paralel to or symmetric about the major orthogonal axes of lateral-force-resisting system. This condition results in a high probâbilty of torsional forces under ground motion, because the centers of mass and resistance can not coincide for all directions of ground motion. Moreover, the narrower portions of the building will tend to be more flexible than the wider ones. which will increase the tendency to torsion as seen in Figure 4. XIVFigure 4 Wedge-shaped plan : invitation to torsion Particular care must be exercised to reduce the effects of torsion. In general, opaque walls should be designed as frames clad in lightweight materials, to reduce the stiffness discrepancy between these walls and the rest of the structure. In the third part of the study, L-shaped and +-shaped two buildings which are irregular in plan are computed by S.A.P.90 program. The earthquake behaviour of four. storey, eight-storey and sixteen -storey buildings are investigated when lateral force is given to master joints. Systems with or without slabs are computed.Also dynamic analysis is computed by using Erzincan spectral acceleration -period input.We see that the best way to examine a structrure at earthquke excitation is by using dynamic analysis. It is more clear in the behaviour of eight-storey and sixteen storey buildings. Stress concentration at the notch of the reentrant corners is seen. XV