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Utilization of standardized local and waste resources is of great importance to the economic development in the world. Besides, application of waste material results in more eco-friendly concrete at the same time. In this study, the effects of two different new fillers, named as sea sand powder (SS), as a local available material and olive waste bottom ash, (OW) as a waste material of different proportions incorporated with two different quantities of superplasticizer (SP), on physical and mechanical properties of SCC were aimed to be investigated and compared to those of limestone powder (LS) as a common filler. For these aimes rheology of fresh concrete, compressive and tensile strengths, initial defects, fracture energy and volume changes during hydration were measured. Results showed that there is no considerable difference in hardened properties of SCC by using SS instead of LS; however, differences in volumetric shrinkage and rheological properties, especially for bleeding and segregation, were more pronounced. On the other hand, OW mixes show different outcomes. OW gives more viscosity to SCC mixes and eliminates segregation and bleeding of the mixes containing this filler. Nevertheless, reduced compressive strength and fracture energy and increased volumetric shrinkage and porosity in these mixes were noticeable compared to LS mixes; however, when 5% OW was used, the results found to be more tolerable. Keywords: Self-consolidated concrete, Olive waste ash, Sea sand powder, Limestone powder, Compressive strengths, Fracture energy
In this thesis, the effects of High Density Polyethylene (HDPE) aggregates are studied on fresh and hardened properties of self-compacted concrete (SCC). Therefore, 5 different replacement levels of HDPE with coarse aggregate namely 0 %, 5 %, 10 %, 20 %, and 30 % by volume. In addition, superplasticizer (Glenium 27) and silica fume were added to SCC mixtures by 1.7 % and 10 % by weight of binder, respectively. Slump flow, L-box, and V-funnel tests were performed on the 5 different mixtures to study the workability of SCC. Compressive strength, splitting tensile strength, flexural strength and toughness tests were utilized to study the mechanical properties of the SCC mixtures, while plastic degradation at 100 and 200 °C temperatures, ultra-sonic pulse velocity, and surface cracks observations to determine the durability of the SCC mixtures. After these tests are performed, the results reveal that it is possible to produce self-compacted concrete using HDPE up to 30% replacement level. However, incorporation of HDPE in self-compacted concrete has negative effects on the properties of SCC, decrement in workability, compressive strength, splitting tensile strength, flexural strength, UPV, and it causes surface cracks. On the hand, adding HDPE in SCC has positive effects as well, since it increases the ductility of SCC, and reduces the self-weight of concrete which is promising to produce light-weight concrete. Keywords: high density polyethylene (HDPE), self-compacting concrete (SCC), silica fume, workability, mechanical properties, compressive strength, splitting tensile strength, ultrasonic pulse velocity (UPV), flexural strength, toughness.
Antakya city is in danger as a result of solid seismic actions happening in the territory, and diverse soil conditions that can create a variety of the ground motion amplification. In recent years, scientists and engineers have started to assess the existing structures and their behaviors in resistance to lateral loading, potential earthquake hazard, and vulnerability. Existing structures can be retrofitted to incorporate new improvements and techniques to oppose quake and seismic burdens, which was the most efficient approach to shield against the financial and social disaster influenced by serious seismic action in urban areas. This thesis presents a study on a five-storey reinforced concrete structure was built in 1988 and located in Antakya, Turkey. This work consists of three phases. The first stage, data collection which includes building plans, material properties, structural condition, and reinforcement details. Material properties are measured using non-destructive testing method called model calibration. The model calibration is obtained from building dominant periods and mode shapes of the existing building, which have been measured using forced vibration tests. In the second stage, the analytical modeling of the structure is made using SAP2000. After model calibration, the nonlinear static pushover analysis for the seismic performance evaluation based on the ATC-40 methods has been obtained. Finally, the existing building, which showed low performance according to code requirements, is strengthened by using two different types of external steel brace frames. They have been attached to Y-direction, which has poor performance for both sides until the second floor, and recommended that this strengthening technique is an appropriate method according to the performance and cost analysis. Keywords: Evaluation earthquake, Pushover analysis, Retrofitting, Forced vibration
Previously, various studies were performed to identify safety and environmentally friendly methods for disposing of plastics. Recently, various forms of plastics have been incorporated in concrete to prevent direct contact of plastics with the environment because concrete has a longer service life. In this thesis, the effects of coarse aggregate replacement of Polypropylene as a waste material on fresh and hardened properties of normal strength concrete (NSC) and high strength concrete (HSC) was investigated. To do so, different percentages of polypropylene were replaced by various volumes (0%, 10%, 20%, 30%, 40% and 50 %) of normal and high strength concretes, with the water to cement ratio of 0.58, 0.34 for normal and high strength concrete, respectively. In addition, Superplasticizer (Glenium 27) was added to the NSC and HSC mixed by 0.3% and 2% cement weight, respectively. Slump and VeBe time tests were done to analyse the physical properties of fresh concrete. Moreover, the influences of PP replacement in the hardened concrete were executed by performing splitting tensile strength (fs), compressive strength (fc) and flexural strength (ff) tests. Rapid chloride permeability (RCP), heat degradation at 200 °C, water absorption, and non-destructive tests such as Ultrasonic Pulse Velocity (Pundit) and Schmidt hammer (rebound) were also conducted. The results showed changes in mechanical properties of normal strength concrete and high strength concrete as the percentages of PP increases. The amount of fs, fc, and ff of normal and high strength concrete decreased with the increase in the amount of polypropylene at 28 days. Furthermore, high water absorption was observed with the increasing of PP. According to the results of the Pundit test the replacement of Polypropylene increased the quality of concrete up to 50% in comparison with the control samples. It is worth noting that negative effects in fc, fs, ultrasonic pulse velocity, and crack development were observed after 200 °C heat exposure. Keywords: Polypropylene (PP), Normal strength concrete, High strength concrete, workability, Mechanical properties, Non-destructive test, Water absorption, Permeability, Heat exposure
Attention to the mechanical properties of concrete for higher strength and ductility and also the increase in its durability has resulted in the innovation for several types of concrete. Ultra high performance concrete (UHPC) is one of the latest concrete with the unique properties such as high compressive strength, exhibiting tensile and flexural strength with increase in energy absorption (toughness), high durability, improved resistance against freezing- thawing and various chemical attacks. UHPC represents the highest development of high performance concrete in different curing conditions. One of the main disadvantages of UHPC is huge amounts of binder content used for producing UHPC. The purpose of this study was to improve the mechanical properties of UHPC relative to using local materials in two different phases: The purpose of phase one was to find the models of 7, 14 and 28-day compressive strength, 28-day splitting tensile strength, modulus of rupture, and flexural toughness of Ultra High Performance Concrete, as well as, study on the interaction and correlation of five variables including silica fume (SF), cement, steel fibers, superplasticizer (SP), and w/c ratio. The models are valid for mixes made with 1.0 part sand, 0.15-0.30 part silica fume amount, 0.70-1.30 part cement amount, 0.10- 0.20 part steel fiber, 0.04- 0.08 part superplasticizer (all values by sand weight) and 0.18- 0.32 water cementitious material ratio. In phase two, the effect of quartz powder (Qp), quartz sand (Qs), and different water curing temperatures on UHPC performance was investigated, the correlation between these variables and mechanical properties were found. The offered models are valid for the variables between: quartz powder 0 to 20% of cement substitution, quartz sand 0 to 50% of aggregate substitution, and water curing temperature 25 to 95 ºC. The experiments were designed by central composition with α=1 (face centered). The response surface methodology was analyzed between the variables and responses. The correlation of variables and mathematical models in terms of coded variables were established by ANOVA. Keywords: Ultra high performance concrete, strength, durability, silica fume, steel fiber, quality sand, modelling.
ABSTRACT: This study concentrates on evaluation and estimation of collapse of two 3-story and 9-story steel moment resisting frames designed by SAC/ FEMA for the place of Los Angeles California. “Collapse” in this research is defined as the loss of lateral load-resisting capacity of frame structural system by the application of ground motion and by considering P-Δ effects on the dummy column. Dummy column is connected to the steel moment-resisting frame in order to consider the effects of gravity loads of the real 3-D structure while 2-D frame is extracted from 3-D frame. Estimation of collapse performance requires the relation between a ground motion intensity measures (IM) and the probability of collapse defined as collapse fragility curve as well as the relation between the same ground motion IM and the seismic hazard for the building defined as seismic hazard curve. Among two methods of estimating the collapse fragility curve; IM-based and EDP-based, the first method is carried out in this research because of its better performance in collapse limit state according to the previous research. In this approach, collapse is associated with ground motion IM and it is obtained by using Incremental Dynamic Analysis. The collapse performance criteria that are obtained from this research are compared with the collapse performance criteria recommended by Haselton and SAC/FEMA guidlines. Keywords: Incremental dynamic analysis, Fragility curve, Mean annual frequency, Seismic Hazard Curve, Probabilistic. ……………………………………………………………………………………………………………………………………………………………………………………………………………………
Identifying roads’ hazardous locations and solving their problems are the key measures in traffic safety management. However, since the traditional hotspot identification (HSID) rests on the yearly-aggregated crashes, two problems appear: the locations that become unsafe at specific short periods may remain unidentified as they may not show noticeable crash counts, and the results of the problem diagnosis analysis on hotspots’ crashes potentially contain a great amount of uncertainty. Even though researchers have recently added the dimension of time and analyzed accidents spatio-temporally to obtain more insights, the mentioned problems have not been addressed fully. Hence, this study first suggests a new linear DBSCAN-based HSID method and demonstrates its acceptable performance by comparison with KDE+, the well-known clustering technique; second, employing the proposed technique, the study presents an algorithm for the spatial analysis of accidents through diverse time dimensions, which categorizes the risky locations based on their periodic reappearance. The tempocategorization purpose is to enhance diagnosing causative risks by understanding their arising periods. The algorithm is tested using Allegheny highways crash data from 2014 to 2019. Results illustrate the contribution of the suggested method to the problem diagnosis and for detecting hidden unsafe points. Keywords: traffic accidents, hotspot identification, DBSCAN clustering, spatiotemporal analysis, KDE+, safety problem diagnosis.
Stone columns (SC) have become a widely-utilized technique of enhancing the bearing capacity of soft soils. Although the SCs in single-layered soil have been studied extensively, SCs constructed in a ground consisting of varying soil layers are not fully understood. In this study, to investigate the behavior of single and group of SCs in different soil layering systems, small scale laboratory tests were conducted on non-encased (NEC) and encased (EC) floating and end bearing SCs installed in single-layered and layered soil consisting of loose sand overlying the soft soil. Different area replacement ratios (ARRs), which is the SC area to unit cell area ratio, 1.56% and 6.25% and the length to diameter ratios (L/D) of 5, 7.5, 10 and 15 were selected to evaluate the effect of these factors on the vertical stress-settlement behavior, bearing improvement ratio, subgrade modulus and bulging failure of NEC and EC-SCs in single-layered and layered soils. Test results indicated that bearing capacity of single-layered and layered soils was improved in all cases of single SC applications. In both soil layering systems, the single NEC floating SC (FSC) with smaller area replacement ratio (1.56%) and L/D of 10 gave much better results than all other NEC-SCs applications. The inclusion of geotextile encasement resulted in further improvement of both soil layering systems. The single encased FSC with smaller ARR (1.56%) had superior improvement among all single SC applications. However, in both soil layering systems, in case of single EC end bearing SC (EBSC) with higher ARR of 6.25% and L/D of 7.5, reduction in bearing capacity and subgrade modulus were obtained. For single SC applications, in single-layered soft soil, with smaller ARR of 1.56%, the inclusion of geotextile encasement resulted in a reduction in bulging diameter and increased the bulging depth of FSC which resulted in an increase in SC bearing capacity. While for single SC applications, in singlelayered soft soil, in case of encased floating and end bearing SCs with higher ARR of 6.25 % there was no bulging confronted. The bearing capacity and subgrade modulus of non-encased central column among group of SCs in both soil layering systems, were higher than the other SCs in the group. In addition to these, the bearing capacity and subgrade modulus of soils were significantly improved with reducing the spacing to diameter ratio of SCs. Moreover, the geotextile encasement provided an additional improvement to the SCs. In single-layered soil, non-encased floating central SC with spacing to diameter ratio of 2.5, bulging failure occurred and with decreasing the spacing to diameter ratio to 1.5, the bulging in the central SC was reduced. Whereas, with the geotextile encased floating group of SCs in single-layered soil, with smaller spacing to diameter ratio of 1.5, no bulging failure happened.
Load and Resistance Factor Design (LRFD), is a widely used procedure in the design of reinforced concrete, wood and steel structures. It is a reliability-based procedure for design, which gives a framework that is consistent with civil engineering design codes, in accordance with reliability theories. In this study, Advance First Order Second Moment (AFOSM) approach is used as the reliability approach in carrying out the analysis. Uncertainties related to material properties (i.e. compressive strength of concrete, yield and ultimate strength of reinforcing steel bars.), dimensions of reinforced concrete structural members (beams and columns) and the effect of load variables (i.e. Dead and Live load), are considered. Under the framework of AFOSM the failure mode in different reinforced concrete structural members were analyzed, which focused mainly on flexure failure, shear failure and the combined action of flexure and axial load failure. Reliability indexes are calculated according to the flexure and shear failure modes in beams and columns, in addition to failure due to the combine action of flexure and axial load on columns. Target reliability indexes are selected for different load combinations from values reported by other researchers from different countries, which are used as the safety level to evaluate the computed reliability indexes. New load and resistance factors are selected for different failure modes in different structural members, considering the design practice in North Cyprus and specifications given in the Turkish codes (e.g. TS500). Keywords: Model Uncertainty, Reliability, LRFD, Reliability Index, Safety Level
ABSTRACT: Earthquake design philosophy based on capacity, directs the following two unpleasant states: 1. The situation that continues to increase the elastic strength and stiffness; in fact this is not economical and also cause higher floor accelerations. 2. The situation that limits the elastic strength and increasing ductility by detailing; indeed this approach is the acceptance of non-repairable structural damages. Base isolation is a different approach than the mentioned ones. It is based on the concept, which reducing the seismic demands rather than increasing the earthquake resistance capacity of the structure. On the other hand, application of base isolators to the structure reduce elastic base shear by shifting period of the structure and provide better performing structure that will remain essentially elastic during large earthquakes. However, in this thesis, general information about seismic isolated structures such as type of isolators, world-wide applications, practical applications, properties, code requirements and different processes required for designing various seismic isolators are discussed. Then, 3 different buildings (3, 6 and 9 story) which were isolated by 3 various isolators (Lead Rubber Bearing, High Damping Rubber Bearing and Friction Pendulum System) were analyzed by applying dynamic response spectrum analysis, as a linear elastic analysis method, to evaluate the optimum one according to the seismic demands. Transmitted acceleration, maximum structural displacement and seismic coefficient for each building were shown in the different graphs. Furthermore, the 3 story optimum isolated building was compared with its conventional fixed base one in performance and material. Based on obtained results, it could be inferred that Lead Rubber Bearings represent minimum transmitted acceleration and seismic coefficient among other types. Low effective stiffness and high damping which is represented by Lead Rubber Bearings are the most important factors for this minimization. Structural displacement is minimized by Friction Pendulum Systems due to the high friction of coefficient which they produce. In addition, in rubber bearings transmitted acceleration and structural displacement is affected by damping of isolation system. Furthermore, in the comparison process of base isolated building with its conventional fixed base one , it is concluded that application of the base isolators to the structure increase cost of the building around 5.8 % of total cost. Keywords: Base isolation, Isolator, Cost, Earthquake, Strengthening. …………………………………………………………………………………………………………………………………………………………………………………………………………………… ÖZ: Sismik Taban Yalitimli Binalarda Temel Prensip ve Uygulamalar. Kapasiteye dayanan deprem tasarim felsefesi bizi asagidaki iki kötü seçime yönlendirmektedir: 1. Elastik dayanimi sürekli olarak artirmak; Bu yaklasim ekonomik degildir ve yüksek kat ivmelerine sebep olmaktadir. 2. Elastik dayanimi sinirlandirmak ve detaylandirarak düktiliteyi artirmak; Bu yaklasim ise ileride binada tamir edilemeyecek yapisal hasarlarin kabülü sayilir.Sismik taban izolasyonu yukarida belirtilenlerden farkli bir yaklasimdir. Yapinin deprem direnç kapasitesini artirmak yerine sismik talepleri azaltmaya yönelik bir yaklasimi temel alir. Diger taraftan, yapiya taban yalitiminin uygulanmasi yapinin periyodunu kaydirarak elastik taban kesme kuvvetini azaltir. Bununla beraber büyük depremlerde esasen elastik davranisi koruyan daha iyi bir yapi performansi saglanmis olur. Bu tez çalismada izolasyon sistemleri, dünyadaki uygulamalari, pratik applikasyonu, özellikleri, yönetmelik esaslari ve degisik izolatörlerin tasarimi gibi konularda detayli bilgi verilmistir. Daha sonra ise degisik kat yüksekliklerine sahip (3, 6 ve 9), 3 ayri binaya 3 farki tip taban izolatörü (kursun çekirdek mesnet sistemi, yüksek sönümlü dogal kauçuk mesnet sistemi ve sürtünmeli sarkaç sistemi) uygulanarak response spektrum analizi yapilmistir. Farkli grafiklerde maksimum kat ivmeleri, maksimum deplasman ve taban kesme katsayilari karsilastirilmistir. Son olarak 3 katli ankastre ve izolatörlü yapilar performans ve malzemeye dayali olarak karsilastirilmistir. Elde edilen sonuçlardan yola çikarak kursun çekirdek mesnet sistemi digerleri arasinda minimum ivme ve sismik katsayiyi vermistir. Yüksek viskoz sönüm ve düsük rijitlik özellikleri bunu saglayan en önemli faktörlerdir. Yapisal deplasman sürtünmeli sarkaç sisteminde yüksek sürtünme katsayisina bagli olarak minimize edilmistir. Buna ilaveten, kauçuk mesnet sistemlerinde ivme ve yapisal deplasmanin izolasyon sisteminin viskoz sönümden etkilendigi söylenebilir. Sonuç olarak ankastre ve izolatörlü yapilar arasinda yapilan karsilastirmaya dayali olarak temel izolatörlü yapilarin toplam maliyeti 5.8% artirdigi gözlenmistir. Anahtar Kelimeler: Taban izolasyonu, Izolator, Maliyet, Deprem, Güçlendirme.