Tarihi tuğla duvarların tekstil donatılı harç (TRM) ile 
güçlendirilmesi
Retrofitting of historical brick masonry walls with 
textile reinforced mortar
Yazar: PELİN ELİF MEZREA
Danışman: PROF. DR. ALPER İLKİ ; YRD. DOÇ. DR. MECİT ÇELİK
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / İnşaat Mühendisliği Ana Bilim Dalı / Yapı Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2014
Konu: Deprem Mühendisliği = Earthquake Engineering ; İnşaat Mühendisliği = Civil Engineering
Dizin: Harman tuğlası = Moulded brick ; Sismik güçlendirme = Seismic strengthening ; İnşaat mühendisliği = Civil engineering

Özet:
Bu tez çalışması kapsamında, 1930'lu yıllarda inşa edilmiş tarihi fakat anıtsal olmayan bir binanın yıkımı sırasında toplanan hasarsız tuğlalar ile üretilmiş duvar numunelerinin güçlendirme öncesi ve sonrası kayma davranışı irdelenmiştir. Binanın taşıyıcı duvarlarının özgün mekanik özelliklerini temsil etmesine özen gösterilerek yeniden üretilmiş derz harcı ile toplam 14 adet duvar numunesi imal edilmiştir. Deney numuneleri yaklaşık boyutları 755x755x235 mm şeklindedir. İki adet numune referans davranışı incelemek için güçlendirme yapılmadan yalın halde, iki adet numune düşük dayanımlı harç ile sıvalı ve on adet numune farklı kombinasyonlar ile güçlendirilmiş şekilde diyagonal basınç yüklemesi altında denenmiştir. Tüm deneyler İstanbul Teknik Üniversitesi Yapı ve Deprem Laboratuvarı'nda gerçekleştirilmiş ve yükleme monotonik olarak yapılmıştır. 
Deneysel çalışmada incelenen parametreler; sıva harcının mekanik özellikleri, donatı olarak kullanılan tekstil malzemenin cinsi ve ankraj uygulamasıdır. Sıva harcının kayma davranışındaki etkisini belirlemek amacıyla, düşük dayanımlı ve orta dayanımlı olmak üzere iki çeşit sıva uygulanmıştır. Karbon veya bazalt lifli ızgara malzeme ile güçlendirilmiş numunelerin diyagonal basınç yükleri altında davranışı incelenerek lif cinsinin etkisi değerlendirilmiştir. Ayrıca dört adet numuneye süreksiz ankraj uygulaması yapılarak ankrajın kayma davranışındaki etkisi incelenmiştir.
Güçlendirme yapılan numunelerde tekstil malzemenin yüzeye yapıştırılmasında harç kullanılmıştır. Uygulamada alışılmış olan polimer malzeme yerine harcın kullanılmasının başlıca sebepleri; harcın yığma malzeme ile uyumlu çalışması, maliyetinin polimere kıyasla az olması ve yüzey ile etkin aderans sağlayacağı öngörüsüdür. 
Tüm numunelerin hasar gelişimi gözlenmiş ve göçme modu belirlenmiştir. Diyagonal basınç yüklemesi altında denenen numuneler; maksimum yük kapasitesi, kayma dayanımı, kayma şekildeğiştirmesi, kayma modülü ve tüketilen enerji başlıkları altında kıyaslanmıştır. 
Gerçekleşen deneyler sonucunda tüm numunelerin ortak göçme biçimini paylaştığı belirlenmiştir. Buna göre numuneler yatay derz düzlemi üzerinde kayarak göçmüştür. Herhangi bir güçlendirme ve sıva uygulanmayan referans numuneleri gevrek şekilde göçerken, yalnız sıvalı numunelerde referans numunelere göre daha sünek şekilde göçtüğü gözlenmiştir. Güçlendirme uygulanan numunelerin göçme modu ise hem referans hem de yalnız sıvalı numunelere kıyasla oldukça sünek biçimdedir. 
Kayma dayanımı ve yük taşıma kapasitesi açısından numuneler karşılaştırıldığında; sıvaya ait mekanik özelliklerin dayanım artışında belirleyici olduğu, tekstil malzemenin de bu artışı desteklediği görülmüştür. Ankraj uygulaması, kayma dayanımı açısından dikkat çekici bir artışa neden olmazken numunelerin deformasyon kapasitesini arttırdığı belirlenmiştir. Tekstil malzeme ile güçlendirme tüm numunelerde şekildeğiştirme yeteneğini belirgin biçimde iyileştirmiştir.
Numunelerin kayma modülü elastik bölgede tanımlandığından ve tekstil malzeme henüz maksimum yüke ulaşmadan önce etkisini göstermediğinden, tekstil malzeme ile güçlendirme rijitliğe etkisi belirgin değildir.
Tüm deneysel sonuçlar değerlendirildiğinde, tekstil donatılı harç ile güçlendirilen ve diyagonal basınç yüklemesi altında denenen numunelerin gerek kayma dayanımı gerekse deformasyon kapasitesi dikkat çekici biçimde artmış ve kayma davranışı oldukça iyileşmiştir.

Abstract:
Masonry structures do not require qualified workmanship; encourage using local resources and enable significant durability. Because of many advantages, masonry structures have been universally preferred. In general, primary load-bearing element of masonry structures are brick masonry walls. Despite that, horizontal loads are often ignored in design step of these walls. Material deterioration over time and remarkable earthquakes lead structural system to deficiency in terms of strength and ductility.
Turkey has important cultural heritage since many empires like Roman, Byzantine and Ottoman remained thousands of monumental structures. Intervention procedures enable to protect this heritage, avoid possible loss and hand over the future. 
The type and mechanical characteristic of material used in masonry buildings and quality of workmanship cause great variety in structural behavior. There are inadequate researches in comparison to numerous existing masonry structures in Turkey. One of targets of this experimental study is to provide reference for historical masonry data especially which were built in the 1900s. 
Strengthening application aims to improve strength and deformability characteristics of several elements or the whole structural system. Traditional strengthening techniques such as jacketing with shotcrete and prestressing with steel ties have certain disadvantages. They are time-consuming and not economical, create additional weight and restrict application areas. Therefore, new intervention procedures would be necessary. 
The usage of textiles as a strengthening material for concrete and masonry structures based on the studies in 1980s. Experimental outcomes indicate that masonry walls strengthened with fiber reinforced polymer results in significant enhancement in terms of shear strength and deformability. On the other hand, the organic binder forms undesired effects: not efficient at low temperatures and on wet surfaces, lack of vapour permeability, high cost and health problems. Application of inorganic binder instead of organic one enables to avoid aforementioned disadvantages.
Not only improvement of structural properties but also preservation of genuine architectural properties should be offered by an optimum strengthening technique. Rehabilitation with textile-reinforced mortar satisfies all these features. Besides, it is easy to apply and removable. This study primarily intends to research experimentally the efficiency of retrofitting historical brick walls with textile reinforced mortar and compare the shear behavior of walls before and after strengthening procedure. 
In order to achieve this target, a total of fourteen wall specimens are constructed with solid clay bricks. Bricks were obtained from a historical, but not monumental building which is constructed 85 years ago. A reproduced mortar that represents original mortar characteristics is used for joints. Test parameters are type of plaster, type of textile (basalt and carbon) and application of anchorage. 
This study consists of four main parts. In the first part, mechanical and physical tests were carried out to identify material characterization. Flexural and compression tests were performed on undamaged bricks which were collected from the historical building and reproduced mortar. The average flexural strength of the solid bricks was 1.7 MPa and obtained by six bricks. Standard deviation and coefficient of variation was 0.7 MPa and 0.42 respectively. The average compressive strength of fourteen half bricks found 9.0 MPa. Standard deviation and coefficient of variation was 2.3 MPa and 0.26, respectively. Both mechanical and physical test results indicate that bricks has relatively great coefficient of variation since they were produced regardless of a certain standard. Mortar is compatible with masonry and provides efficient adherence. Moreover, it is economical and reversible. So, unlike the literature, mortar was preferred to use as bonding material instead of polymers. The local mortar used for joints was reproduced to represent existing mortar characteristics whose design mixture comprises cement, lime, sand and water. Two different mortar types were used for each specimen as adhesive to plaster and bond fiber grids on the surface: the local mortar with sub-standard characteristics and a mortar that has relatively better mechanical characteristics, Tyfo C-matrix Type F. The average flexural and compression strengths of local mortar used for joints 90 days are calculated as 0.56 and 1.56 MPa, respectively. Compression tests were carried out on half specimens which were collected from bending tests. Water ratio in plaster was increased to achieve enough workability for both plastering surface and bonding the fiber efficiently. The average flexural and compressive strengths at 90 days were 0.41and 1.09MPa, respectively for local mortar which was applied as plaster. The average flexural and compression strengths at 90 days were 4.77 and 10.37 MPa, respectively for Tyfo C-matrix Type F. This part also contains features of textile materials.
The second part explains the design criteria and steps for construction of wall specimens. All specimens were constructed on a wood palette which was smeared with grease oil. Each masonry wall was composed of eight brick rows bonded with seven bed mortar joints and several head mortar joints. Some of rows contain half bricks at two edges to provide checker brickwork. The nominal dimensions of each masonry wall were 755x755x 235 mm (length x height x thickness). The longest side of brick (235 mm) was positioned to compose thickness of wall for not to encounter out-of plane deformations and slenderness effect. The thicknesses of bed joints and head joints were 21 mm and 13 mm respectively. 
The third part contains strengthening procedure and test setup. Ten of specimens were retrofitted by applying one layer of open-grid fiber alternatives on each side of walls. The local mortar and Tyfo C-Matrix Type F were used to plaster and bond fibers on the surface. Two of specimens were control specimens, so open grid material or plaster was not applied. The installation phases of retrofitting procedure followed regular steps. The surfaces of each specimen were cleaned from the remaining particles and soaked with water adequately. Bonding matrix (the local mortar or Tyfo C-Matrix Type F) was applied on the wall surface with help of a trowel. Open-grid fiber layer (basalt or carbon) was embedded in whole surface of wall by hand and covered with plaster again. Open-grid layers were applied on both surfaces of walls aiming to avoid out-of plane effects. The ultimate mortar thickness including fiber layer was in a range of 15-25 mm and trowel used again to attain a smooth surface. Within an half hour the strengthening procedure was completed, the surfaces of each specimen were soaked with water to avoid cracks on mortar. The implementation of basalt anchors which were supplied by manufacturer began with marking point of anchor holes. Compression strut lied along a diagonal between two opposite corner of the specimen which were subjected to loading and tension strut was perpendicular to it. Tension strut was axis of symmetry for anchor holes. Anchor points were marked on wall surface in the way that the distance between two points which were on the same diagonal was 45-50 cm and equidistant from corners. The distance between two points which were different side of symmetric axis was 17.5-20 cm. Geometrical tolerances were used to position anchor points on bed joints. Then, 7.5 cm depth discontinuous anchor holes Ø18 mm were opened by a drill into both wall surfaces and cleaned with high air pressure. Following that, the surfaces were plastered with one of the bonding matrices and the holes were revealed. The next step was applying open-grid material on the wall surface. After the holes were soaked with mortar which had more plastic consistency than plaster, they were filled with plaster mortar. Basalt anchors were screwed with steel bar in the holes. All anchor holes were covered with 20 x 20 cm square fiber layer after basalt anchors were placed. The final step was plastering the surface with bonding matrix. Two opposite corners of each wall specimen were capped with rapid-hardening gypsum aiming uniform loading. The experimental program was carried out approximately five months after the implementation of basalt/carbon fiber reinforced mortar. Overall wall specimens were subjected in-plane diagonal compression loading. A hydraulic jack with the load capacity of 500 kN is used to apply load and a 1000 kN load cell is used to record the applied load. Two linear variable differential transducers (LVDTs), one of which is vertical and the other is horizontal, with 25 mm capacity is placed for each side aiming to record deformation. Additionally, four LVDTs with 1000 mm capacity are positioned at four corners of the specimen in order to measure vertical deformation taking place through the diagonal of the specimen. 
Fourth part aims to explain failure mode and numerical assessment for diagonal compression tests. The obtained experimental outcomes are examined based on the shear stress – average shear strain graphs. The graphs are obtained by four LVDTs which were placed in the middle of wall surface. In brief, quantitative results in terms of unreinforced strength, reinforced strength, shear deformation, shear modulus and energy dissipation were calculated for all specimens.  The failure begins with vertical cracks occurred on both surfaces of wall just before maximum load for all specimens. After that, the joint sliding failure forming through a horizontal plane is a common failure mode for both control and reinforced specimens. Control specimens failed in a brittle manner due to the vertical cracks occurring at both left and right corners of the wall surfaces and the specimen lost its load carrying capacity suddenly. The strengthened specimens failed in a ductile manner with respect to controlled specimens. It is considered that failure type of specimens does not allow fiber grids to be efficient due to the sub-standard characteristics of the local mortar, the joint sliding occurred before debonding force.
The results obtained by this experimental study show that strengthening of historical brick masonry walls with textile-reinforced mortar is an efficient application to improve earthquake performance of shear walls both in terms of strength and deformability.