Civil Engineering / İnşaat Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/13
Browse
5 results
Search Results
Now showing 1 - 5 of 5
Article Citation - WoS: 16Citation - Scopus: 24Developing Polymer Composite-Based Leaf Spring Systems for Automotive Industry(Walter de Gruyter GmbH, 2018) Öztoprak, Nahit; Güneş, Mehmet Deniz; Tanoğlu, Metin; Aktaş, Engin; Eğilmez, Oğuz Özgür; Şenocak, Çiler; Kulaç, GedizComposite-based mono-leaf spring systems were designed and manufactured to replace existing mono-leaf metal leaf spring in a light commercial vehicle. In this study, experimentally obtained mechanical properties of different fiber-reinforced polymer materials are presented first, followed by the description of the finite element analytical model created in Abaqus 6.12-1 (Dassault Systemes Simulia Corp., RI, US) using the obtained properties. The results from the finite element analysis are presented next and compared with actual size experimental tests conducted on manufactured prototypes. The results demonstrated that the reinforcement type and orientation dramatically influenced the spring rate. The prototypes showed significant weight reduction of about 80% with improved mechanical properties. The hybrid composite systems can be utilized for composite-based leaf springs with considerable mechanical performance.Article Citation - WoS: 55Citation - Scopus: 64High-Early Ductile Cementitious Composites With Characteristics of Low Early-Age Shrinkage for Repair of Infrastructures(Springer Verlag, 2015) Şahmaran, Mustafa; Al-Emam, Muhannad; Yıldırım, Gürkan; Şimşek, Yunus Emre; Erdem, Tahir Kemal; Lachemi, MohamedReduced performance in concrete infrastructures is mainly caused by the formation of cracks, which may arise due to deteriorating mechanisms during service life. In most cases, reduced performance calls for urgent repairs to the degraded section. Therefore, it is highly desirable to develop dimensionally stable, ductile repair materials that can attain adequately high strength in a limited amount of time, compensate for significant deformation due to mechanical and environmental loadings, and prevent early-age shrinkage cracks. In this paper, the performance of such a material (high-early-strength engineered cementitious composites, HES-ECC, with very low early-age shrinkage capacity) was investigated by studying mechanical properties and dimensional stability. Composites were produced with different water to cementitious materials and slag to Portland cement ratios. In order to enhance composite properties in terms of ductility and early-age shrinkage characteristics, saturated lightweight aggregates replaced sand in the mixtures. The experimental results show that the majority of HES-ECC mixtures developed in this study attained compressive strength values of more than 20.0 MPa and minimum flexural strength of 6.0 MPa within 6 h. Moreover, the HES-ECC mixtures exhibited strain-hardening behavior with strain capacities comparable to normal strength ECC, as well as substantially reduced autogenous shrinkage strain, both of which are unlikely to trigger the formation of cracks in tension at early ages. The integration of these conflicting parameters suggests that HES-ECC can easily meet the need for fast and durable repairs.Article Citation - WoS: 62Citation - Scopus: 75Specimen Size Effect on the Residual Properties of Engineered Cementitious Composites Subjected To High Temperatures(Elsevier Ltd., 2014) Erdem, Tahir KemalIn this study, size effect on the residual properties of Engineered Cementitious Composites (ECC) was investigated on the specimens exposed to high temperatures up to 800 C. Cylindrical specimens having different sizes were produced with a standard ECC mixture. Changes in pore structure, residual compressive strength and stress-strain curves due to high temperatures were determined after air cooling. Experimental results indicate that despite the increase of specimen size, no explosive spalling occurred in any of the specimens during the high temperature exposure. Increasing the specimen size and exposure temperature decreased the compressive strength and stiffness. Percent reduction in compressive strength and stiffness due to high temperature was similar for all specimen sizes.Article Citation - WoS: 77Citation - Scopus: 93Improving the Workability and Rheological Properties of Engineered Cementitious Composites Using Factorial Experimental Design(Elsevier Ltd., 2013) Şahmaran, Mustafa; Bilici, Zafer; Özbay, Erdoğan; Erdem, Tahir Kemal; Yücel, Hasan Erhan; Lachemi, MohamedIn the development of Engineered Cementitious Composites (ECC), micromechanics-based design theory is adopted to properly select the matrix constituents, fiber, and fiber-matrix interface properties to exhibit strain hardening and multiple cracking behaviors. Despite the micromechanics design constraints, practical applications show that the workability and rheological properties of matrix can affect the fiber dispersion uniformity, which have also direct concerns on composite mechanical properties. For this reason, in this research, parameters of micromechanics-based optimized ECC mixture design, which most possibly affecting the workability and rheological properties, are investigated. An experimental program that contains 36 different ECC mixtures was undertaken to quantitatively evaluate the combined effects of the following factors on workability and rheological properties: water-binder (w/b), sand-binder (s/b), superplasticizer-binder (SP/b) ratios and maximum aggregate size (Dmax). A mini-slump cone, a Marsh cone and a rotational viscometer were used to evaluate the workability and rheological properties of ECC mixtures. Compressive strength and four point bending tests were used for mechanical characteristics of ECC mixtures at 28 days. The effects of studied parameters (w/b, s/b, SP/b and Dmax) were characterized and analyzed using regression models, which can identify the primary factors and their interactions on the measured properties. Statistically significant regression models were developed for all tested parameters as function of w/b, s/b, SP/b and Dmax. To find out the best possible ECC mixture under the range of parameters investigated for the desired workability and mechanical characteristics, a multi-objective optimization problem was defined and solved based on the developed regression models. Test results indicate that w/b, s/b and SP/b parameters affect the rheological and workability properties. On the other hand, for the range of studied aggregate sizes, Dmax is found to be statistically insignificant on the rheological and workability properties of ECC.Article Citation - WoS: 75Citation - Scopus: 87Use of Spent Foundry Sand and Fly Ash for the Development of Green Self-Consolidating Concrete(Springer Verlag, 2011) Şahmaran, Mustafa; Lachemi, Mohamed; Erdem, Tahir Kemal; Yücel, Hasan ErhanIn the United States alone, the foundry industry discards up to 10 million tons of sand each year, offering up a plentiful potential resource to replace sand in concrete products. However, because the use of spent foundry sand (SFS) is currently very limited in the concrete industry, this study investigates whether SFS can successfully be used as a sand replacement material in cost-effective, green, self-consolidating concrete (SCC). In the study, SCC mixtures were developed to be even more inexpensive and environmentally friendly by incorporating Portland cement with fly ash (FA). Tests done on SCC mixtures to determine fresh properties (slump flow diameter, slump flow time, V-funnel flow time, yield stress, and relative viscosity), compressive strength, drying shrinkage and transport properties (rapid chloride permeability and volume of permeable pores) show that replacing up to 100% of sand with SFS and up to 70% Portland cement with FA enables the manufacture of green, lower cost SCC mixtures with proper fresh, mechanical and durability properties. The beneficial effects of FA compensate for some possible detrimental effects of SFS.