Research on Engineering Structures and Materials

1-11

Authors: Hayri Baytan Ozmen

Earthquakes are natural events that turns into disasters in our country due to faults made in construction of structures. In order to prevent this, we need to determine solutions and act accordingly. The author wrote this paper to humbly share his knowledge and ideas on the subject with the public and his colleagues and encourage more discussions on the subjects. The mentioned points include views on the common public earthquake debates, main reason of damages being inadequacies in having healthy civil engineering services, the importance of informing and taking into consideration of the feelings of the suffered people, shortages of official damage assessment procedures, the necessity for unique building identifier and a fixed financial aid policy, suggestions on the civil engineering education, and how essential the proficient engineering concept is for robust construction of the structures.

35-49

Authors: Samson Olalekan Odeyemi, Omolola Titilayo Odeyemi, Adewale George Adeniyi, Zainab Tolu Giwa, Ademola Kamorudeen Salami, Adeyemi Adesina

Steel reinforcement corrosion emanating from ingress of chloride into concrete is the key reason for weakening of concrete structures globally. Infiltration of chloride into concrete happens by absorption and diffusion. On the other hand, reinforced concrete containing supplementary materials is more susceptible to corrosion exposure due to its high permeability. In this paper, two concentrations of sodium chloride (NaCl) were applied on concrete containing palm kernel shell as full replacement to granite. Concrete cube specimens of Grade 20 were cast into 150 mm by 150 mm by 150 mm moulds, and their workability were determined by compacting factor and slump tests. The hardened specimens were soaked in sodium chloride (NaCl) solution of 3% and 6% concentration. Spray, Absorption and Compressive strength tests were conducted at 7, 14, 21 and 28 days. Equations were generated by means of the data gotten from the laboratory tests to forecast the chloride penetration depth into the palm kernel shell concrete under the conditions considered in this work. The models generated revealed that absorption affected chloride ingress into the concrete significantly at 6% NaCl concentration. The models also reveal that the cover to reinforcements in Palm Kernel Shell Concrete subjected to chloride attack should be more than what is presently endorsed for reinforced concrete structures.

65-86

Authors: Ercan Işık, İbrahim Baran Karaşin

Structural dimensions and number of floors are some of the factors affecting the building behaviour under the earthquake effects. In this study, the structural footprint and the number of floors were selected as a variable. For this purpose, a steel structure model with fixed dimensions and properties of load-bearing system elements was selected. The structural footprint was selected as the first variable and then five different structure models were created. The structural footprint was changed by setting each axial clearance in both directions. Each axial clearance was increased by 0.5m in each structure model. Three different number of floors as to be 5, 6 and 7 floors were selected as the second variable. Eigenvalue and pushover analyses were performed for each model and each number of floors. As a result of the analyses, the target displacement values for period, frequency, cumulative participation mass ratio, base shear force, settlement, stiffness and degree of damage were acquired separately. As the structural footprint and number of the floors increase, while the period, settlement and the target displacement values increased, on the contrary, there was a decrease in participation mass ratio, base shear forces and stiffness values. In the study, cost comparisons of building construction were also made considering the change in the total structural area and the number of floors. The criterion of safety and economy was ignored due to increase both in the number of floors and the footprint. This study emphasizes the importance of avoiding the unnecessary structural dimensions via optimum design principles. As structural footprint area and number of floors increase, period values increase, stiffness and seismic capacity values decrease. As the number of floors and footprint area increases, the total building area increases, so the approximate building cost has also increased.

97-120

Authors: Tanay Karademir

One of the most important properties of a fabric (geotextile) and also one of the focus areas of the current research study is its tensile strength, and thus, mechanical properties (modulus, resilience, strength, toughness). To this end, the mechanical properties of the geotextiles must properly be evaluated at the “macro-scale” as well as at the “micro-scale” as they are fibrous synthetic materials including polymeric fibers as well as significant volume of void space. As being a polymer, the mechanical behavior of the geotextile micro-fibers is highly dependent on the ambient conditions including particularly the temperature. In light of this, the tensile behavior of geotextile single micro-fibers was characterized by performing micro-mechanical tensile tests at “micro-scale” level at different cold temperature conditions using Dynamic Thermo-Mechanical Analyzer (DMA) to measure the developed “micro-scale” tensile stress – strain behavior of geotextile micro-fibers. The results examined from the influence of micro-mechanical properties of polymeric fibers on the observed temperature dependent stress-strain curve were used to determine the modulus of elasticity (E), modulus of resilience (UR), ultimate tensile strength (τmax), amount of plastic strain (εp), toughness (UT), rupture strength (τR) for the polypropylene (PP) micro-fiber of needle-punched nonwoven (NPNW) geotextile and the variation in those important mechanical properties with a change in ambient temperature conditions. The experimental results show that the mechanical properties of the PP fibers do not remain constant within the common range of cold temperatures (-10 °C – 21 °C) found in typical civil engineering applications such that the temperature change was found to be an important factor affecting the PP fiber micro-mechanical properties such as modulus, strength, toughness and plastic elongation. Therefore, the test results provide an index of behavior at “micro-scale” level for the polymeric geotextile single fibers at cold temperature conditions.

135-156

Authors: Güliz Akyüz, Aykut Elmas, Müberra Andaç, Ömer Andaç

Metal Organic Frameworks (MOFs) have found wide applications as a drug carrier in nanotherapeutics because of adjustable pore-sizes, controllable structural properties, large surface area and high pore volume. In this work, nanosized Mg@BTC is synthesized by electrochemical method and used as a new drug carrier for ibuprofen. The ibuprofen (IB) is loaded to the Mg@BTC 1:1 ratio with the amount of %99.8. The release of ibuprofen from nanocarrier has been observed experimentally for long term. After 100.5 hours, the release ratio yields 36 %. The ibuprofen has been tested at 40 ± 0.5 °C. System showed a rapid release after 100 hours, the release ratio yields 72.29 %. The release profile of IB loaded Mg@BTC is tested by using model depended mathematical models to get observation and prediction of the release. Zero Order Model, First Order Model, Higuchi Model, Peppas Model and Hixon Model functions are fitted to the release profiles. Watson’s U Squared Method is used to test the fit strength of the models. Observation from the release profiles, it is seemed Peppas Model yields the best results. Also, thermodynamic analysis has been studied.