Research on Engineering Structures and Materials

173-182

Authors: Seda Yeşilmen

Engineered Cementitious composites (ECC) became widely popular in the last decade due to their superior mechanical and durability properties. Strength prediction of ECC remains an important subject since the variation of strength with age is more emphasized in these composites. In this study, mix design components and corresponding strengths of various ECC designs are obtained from the literature and ANN models were developed to predict compressive and flexural strength of ECCs. Error margins of both models were on the lower side of the reported error values in the available literature while using data with the highest variability and noise. As a result, both models claim considerable applicability in all ECC mixture types.

199-209

Authors: Rasheed Abdulwahab, Samson Olalekan Odeyemi, Habeeb Temitope Alao, Toyyib Adeyinka Salaudeen

Cement industry being source of emission of carbon dioxide (CO2) causing global warming; it is necessary to source for alternative binder in concrete. The problem of longer age strength attainment by pozzolanic blended concrete calls for introduction of treated pozzolans. This paper investigates the influence of co-addition Metakaolin (MK) and Treated Rice Husk Ash (TRHA) in the production of concrete. The kaolin was calcined at a temperature of 650C for 2 hours and thereafter, characterized. Furthermore, the rice husk (RH) was roasted to temperature of 700C and thereafter, treated with H2SO4. MK was replaced in varying percentages of 0%, 5%, and 10%. Thereafter, TRHA was added by weight of the cement in varying percentages of 1%, 2%, and 3% to the optimum MK replacement (5%). From the results, it was found that concrete with 5% MK and 2% TRHA had enhanced compressive strength as against the control. Hence, it can be inferred that 5% MK and 2% TRHA concrete could be used in the construction industry. The increase in the strength properties of the concrete could be as a result of additional binding tendency exhibited by MK and TRHA.

225-244

Authors: P N Ojha, Abhishek Singh, Brijesh Singh, Vikas Patel

In view of reducing the cost of concrete and to meet the demand of conventional raw materials used in concrete, various industrial and solid wastes are being studied for their utilization in concrete without affecting its fresh, hardened and durability properties. Ferrochrome slag is waste material obtained from manufacturing of high carbon ferrochromium alloy. Depending upon cooling process, two types of ferrochrome slag are produced i.e. air cooled by letting molten slag cooled down under normal temperature and water cooled ferrochrome slag by quenching molten slag. Presence of chromium in Cr+3 and Cr+6 state in ferrochrome slag is an area of concern towards its feasibility to be used as a constituent material in concrete. In this study, physical and chemical properties of both types of slags were evaluated to check the feasibility of replacing natural fine aggregates with water cooled ferrochrome slag and natural coarse aggregates with air cooled ferrochrome slag. In concrete mix designs, natural aggregates were replaced with ferrochrome slag at replacement levels of 30%, 60% and 100%. Mixes were prepared at two w/c ratios and were evaluated for different fresh, hardened and durability properties of concrete. It was concluded that 60% replacement of natural coarse aggregate with air cooled ferrochrome slag and 60% replacement of natural fine aggregate with water cooled ferrochrome slag in concrete is feasible.

259-272

Authors: Irmak Karaduman Er

In this work, the effects of Cd doping on the gas sensing properties of ZnO thin films were synthesized by SILAR method and studied gas sensing characteristics against NO, CO, ammonia, methanol and acetone, systematically. Whereas the operating temperature of NO gas was found 90 C, CO and acetone were 150 C and 170 C. The response was not observed in methanol and ammonia gases. Especially, it was observed that the response continued to increase as the temperature increased for methanol gas. In addition, the 5% Cd doped ZnO sensor exhibits the excellent selectivity for NO compared to other test gases as ∼12% at 0.01 ppm. NO gas sensing reactions are accelerated with Cd doping because Cd doping was created increasing oxygen vacancies surface chemisorbed oxygen species, and defects in the lattice.

281-295

Authors: Kadir Akcan, Eren Billur, H. İbrahim Saraç

As advanced high strength steels (AHSS) find more use in automotive industry to meet crashworthiness and light weighting targets, concurrently. AHSS typically have higher strength, but lower formability; often limiting a part’s dimensions and geometric complexity. Several studies have clearly shown that, in sheet metal forming, significant portion of the work done to overcome friction and to plastically deform a sheet is converted into heat. In this study, a thermomechanical finite element model has been developed to calculate the temperature rise in forming DP800 (AHSS). The model was validated with experiments from literature. A multi-cycle model is developed to find out possible problems due to tool heating. The process and material are selected to speed up the heating. Under different realistic press conditions, failures are observed after 20 to 80 hits.

315-330

Authors: Neritan Shkodrani, Huseyin Bilgin, Marjo Hysenlliu

On November 26,2019, an earthquake of magnitude 6.4 hit Durres city, Albania. After the earthquake, the inspection carried out by the authors in the region has provided relevant findings regarding the methods of construction, quality of the materials and the performance of structures. The dominant building types in the Albanian building stock comprise unreinforced masonry (URM) structures with load-bearing masonry walls. These units suffered the worst damage. Dynamic response of masonry is highly nonlinear, and generally shows high vulnerability to seismic loading. Moreover, many buildings of these type have undergone structural interventions like adding floors, or wall openings, especially in the first floors of the buildings, which are parallel to the main roads, because of great demand for shops and stores. This paper aims at making seismic performance assessment of the intervened buildings based on macro-element modeling approach. Due to its efficiency, this approach is becoming popular among the practitioners and field experts in this area and allows simulating the non-linear behavior of masonry buildings. This method is applied to two old masonry buildings from the Albanian construction practice that are representatives of mid-size residential buildings with and without interventions. It must be said that in Albania, masonry buildings have been built using templates all over the country, so both models with and without intervention are common. Capacity curves of the investigated buildings are derived to assess the most probable seismic response of the investigated housing construction in the region as well as to evaluate the seismic performance of the tested structures.