Türkiye'deki tarihi kemerli yığma demiryolu köprülerinin deprem davranışının incelenmesi
Seismic behaviour evaluation of masonry arch railway bridges in Turkey
Yazar: FATİH GÖKHAN GÜRÜN
Danışman: DOÇ. DR. KASIM ARMAĞAN KORKMAZ
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / İnşaat Mühendisliği Ana Bilim Dalı / Yapı Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2016
Konu: İnşaat Mühendisliği = Civil Engineering

Özet:
Tasarlandıkları ve inşaa edildikleri dönemler düşünüldüğünde, kültürel mirasımız olan yapıların korunması giderek önem arzeden boyutlara ulaşmıştır. Bu yapıların büyük çoğunluğu taş veya tuğladan yapılmış yığma yapılardır. Sadece malzeme özellikleri düşünüldüğünde, günümüzdeki sabit malzeme modellerinden ne kadar farklı olduğunu gözler önüne sermektedir. Kullanılan taşın ve tuğlanın türüne göre değişen dayanımlar ve elastisite modülleri sebebiyle yapılar üzerinde detaylı araştırmalar yapılması gerekmektedir. Bu yapıların deprem davranışlarının bilinmemesi, yapıların deprem kuvvetleri altında nasıl tepkiler vereceğinin bilinmemesine sebep olmaktadır. Bu amaç doğrultusunda, çalışma kapsamında dört adet tarihi kemerli yığma demiryolu köprüsünün deprem davranışı incelenmiştir. Yapıların modellenmesinde makro model yöntemi esas alınarak, solid sekiz noktalı elemanlar kullanılmıştır. Malzeme özellikleri köprülerin boyutlarına benzer özelliklerdeki köprülerde yapılmış çalışmalardan ve çalışma kapsamındaki köprüler üzerinde daha önce yapılmış olan çalışmalardan alınmıştır. Köprülerin genel deprem davranışına ulaşılmak istendiği için yapılar, üç farklı zemin grubunda görülmüş yer hareketinin hızlarıyla uyumlu olacak şekilde seçilen deprem ivme kayıtları altında analiz edilmiştir. Dört köprüden ikisinin modelleri oluşturulurken; arazi koşulları ve mesnetlenme etkilerinden ötürü değişen dinamik özelliklerinin arazideki ölçümleri bu çalışma kapsamında yapılmadığı için, göz önüne alınmamıştır. Başköy ve Hacıkırı köprülerinde ise, literatürde mevcut çalışmalarda arazi ölçümlerinin yapıldığı ve yapıların hakim modlarının bulunduğu yayınlardan faydalanılarak, bu köprülerde periyot değerleri çakışacak şekilde modelleme yapılmıştır. Analizlerde dinamik yaklaşımlar yapılmış ve köprü üzerinde tren kütlesi de var olacak şekilde çalışma yürütülmüştür. Analizler incelendiğinde, ayak yüksekliği, elastisite modülü ve köprü kütlesinin yatay harekete önemli ölçüde etkilediği görülmüştür. Herhangi bir fiziksel özelliğin sonuçları etkilemediği görülmüştür. Yapıdaki stress dağılımına bakıldığında ise köprü kemer bölgesi ve yan duvarlarının en çok zorlandığı alanlar oduğu ve bu alanlarda daha detaylı çalışmalarla, deprem sonrası ve öncesinde gözlemeler yapılması gerektiği görülmüştür.

Abstract:
Throughout the history, transportation and carriage were played significant role for ancient civilizations. They used some devices to cross some areas for transportation, such as; timber hitch or canoe for passing lake, river and sea, mounts and their own foots while crossing mountains or valleys. After the invention of engine which is working with steam, some technological devices were getting used instead of them. Trains, planes, ships and cars had been spread into the people' life in the world after this invetion. So that, these does not seem to getting out from their life, because they ease their life. From the transportation types, railways and highways are much used types of them. These carrying fields are built according to topography of the country. So that, there are built such engineering structures, when meeting with an obstacle like valley, river, lake, forrest and sea to decrease the time waste in the transportation. For the rives, culverts are built. Some ways that passing over or under the main road, Underpass or overpass are built. For sharp valleys, lakes and seas, bridges and viaducts are constructed. In Turkey, these kinds of Infrastructures are widely seen in the highways and railways while crossing these drawbacks. The most significant of them can be the masonry arch bridges, which are inherited from the past and also are getting thought as a historical artifacts nowadays. There are many bridges was descended from a number of nations such as, Romans, Byzantines, Seljuk and Ottomans. Most of their bridges are masonry arch and they used them for highway, railway and walk way to transport something. Highway is most used type of transportation system today, however in the Ottoman Emperor, there were too many railway lanes constructed and they had too many bridges on them. One of them is masonry arch railway bridges which have been used by TCDD from their built day to the present day. Technology had not been improved in the construction field at that age, and their design methodologies have not liked today's construction technics. Engineers had used some simple and ampricial formulas to determine the size of structural elements of Masonry Arch Bridges and there were not exact information about, earthquake loads to size column, arch, spandrel Wall etc. In literature review, a number of study is faced about this type of bridges. Two type of groups are exist in material modelling of structure. One of them is micro modelling which provide exact results. The compenents of masonry, which stone/brick and mortar, are define by each solid element. This is not only being complex, but also taking time. While observing a detailed effects of mortar and stone, this is very useful to see this materials' own characteristic behaviour under different loading conditions. Other one is macro modelling. The more simple solution is the better solution for a problem so stone/brick and mortar are defined as one material like composite materials. So that, the system is became more simple than micro modelled ones. In this thesis study, modelling of elements were proccessed with macro models. The behaviour of stone and mortar composition was taken in studied experiment in literature. On the other hand, macro modelling is chosen because, the number of analysis is too much, approximately 240 analysis, and SAP2000, used program, is allowed simple models for solid elements. The other categorization of literature view about stone arch bridges is structural analysis. It can be divided in two kinds of analysis genre. The first one is calculation of arch vertical load capacity. Beside this, experiments and studies also are conducted to find influencing factors of the capacity such as, spandrell walls' and cohesion value of fill's effect on the arch capacity. The second is about bridges' longitudinal displacement and sway mechanism demands. This calculations were done with some methods which were incremental push over analysis, non-linear time histroy and modal analysis according to a code. By this dynamic and static anaylsis, lateral displacement capacity of bridge and fragility curves are obtained and also time history analysis carried out to compare and discuss the results. There were several analysis programmes used and they had different numerical calculation types, so some analysis used non-linear material models and modeled with micro modelling way to demonstrate the critical sections of bridge and obtain an exact result about conduct. But in this thesis, material and analysis model were chosen simplest ones to reduce the analysis time. Due to this reason, models had just second order effects' for non-linear behaviour. The other options had not added this analysing proccess.
This thesis was conducted to comprehend the general behaviour of stone arch railway bridges under earthquake loads. For this purpose, 4 railway bridges, which have been still used, were chosen and applied time histroy analysis with 60 earthquake acceleration records, that selected for 3 different soil type (A, B, C), for each bridge. For these bridges, seems as historical artifacts, there weren't any conducted experiment to determine the material properties. So this properties are taken from literature review. Fisrt birdge is Cetinkaya-Divrigi having 6 arch, 10m arch span and 10m pier height. Second one is Fevzipasa-Diyarbakir having 3 arch, 15m arch span and 15m pier elevation. Third bridge is Başköy having 7 arch, 14.8m arch span and 40m elevation of maximum depth. The last one is called Hacıkırı located in Adana, having 3 main arch, 30m arch span and 65m pier height. These bridges were modelled with some assumptions from literature review's material and modal properties. Modal properties had had for two bridges which were Başköy and Hacıkırı bridges. These created bridge models are located on soil springs and these spring coefficient were iterated, so that, models' first modal shape and frequencies tried to match with the experimented first modal shape. The other bridges are simply supported. Before the analysis, some simplifications and dynamic properties determined. Damping ratio and the integration types were some of them. On the other hand, mass of bridge determined with some assumption. While the earthquake happens, the train must be exist on the bridge or not. So for obtaining the critical results, the train load, which is UIC LM-71 load modal impacted on the bridges. Lateral displacement results for each bridges' analysis were significantly different from unloaded condition. So, all acceleration records are implemented to bridges having additional train masses.
Examining the results showed that, elasticity modulus, elevation of pier and mass are directly proportioned to lateral displacement demand of the bridges. The much mass and higher elevation having bridges, the more oblique shift gaining at top of them. The other result from curves of lateral behaviour was that, B soil type records produce more base shear at the biggest piers. So the R2 values obtained higher than results of A and C soil type records. The last conclusion is the stress distribution. When the earthquake motion dominated through the longitudinal direction of bridges, the first and last arch were more strained than the others and displayed much stressed. And, at the most lateraly shifted time of the bridges, the middle arches exposed the double stress which is tension and compression at the key stone. So, the arch can collapse easily by these forces. Not only stress, occured on the arch, is more important, but also spandral walls can produce the critical collapse mode of the bridges such as fail and overturn of the them.