Research on Engineering Structures and Materials

481-504

Authors: Ismail Luhar, Salmabanu Luhar

“More industrial developments equals more generation of wastes". Wastes of glasses are blameworthy for the grave issue of pollution of environments chiefly in virtue of their profound accessibility and inconsistency of this stream. With mounting environmental pressure to trim them down and to recycle them as much as possible, the concrete industry has lent a hand to incorporate them with the manufacturing of inorganic, user, and eco-benevolent innovative Geopolymer construction composites. The current review paper studies the most striking points in the context of the production of waste glass integrated Geopolymer paste stressing its valorization in lights of its properties. More often than not, the center of attention here is to embrace the "conversion of wastes into wealth" strategy. That is why, this article reviews with an objective of its confined literature to comprehend its characteristics viz., workability, compressive strength, thermal, microstructure, etc. As a final point, the paper pigeonholes research work challenges, endorsement of potential utilization for this promising brand-new, green valorized Geopolymeric building material in order to establish it as a cost-effective, sustainable, durable construction material as a "futures toolkit”.

523-538

Authors: Giovanni Falsone, Gabriele La Valle

In this work, the free vibration and the stability problems of functionally graded beams are analysed via the Timoshenko theory through the Navier procedure and via an appropriated finite element (FE) approach. In particular, it is shown how the definition of homogenized/generalized displacements allows to uncouple boundary conditions, obtaining a remarkable advantage in terms of computational effort. Moreover, a unified expression capable to express the buckling load for different constrain conditions is discovered. The latter may be considered the natural extension of the Euler’s one derived in the century XVIII. In order to verify the reliability of the proposed method, natural frequencies, buckling loads and static displacements of differently constrained beams are numerically evaluated.

551-577

Authors: Sahar Ismail, Wassim Raphael, Emmanuel Durand

Analysis of the structural failure of the Beirut port silos by the August 4, 2020 explosion is presented in this paper. The structural response of the silos due to the blast loading imposed by the explosion was assessed using 3D laser scan. Then, the silos were modeled using three-dimensional finite element models using Abaqus explicit. The silos’ damage and failure were investigated to estimate the blast magnitude and to check the silos structural response against the silos’ concrete strength and additional reinforcement and concrete coating added to the silos in 2000. In addition to the effects of reinforcing the ribs between the silos as well as the soil and foundation. Therefore, these parameters were tested after estimating the blast magnitude to check the structural status of the remaining part of the Beirut port silos (if they can be reusable), the role played by the foundation and soil and if the silos’ response would have changed if certain parameters were taken differently in the design. In this article, the damage and silos’ displacement obtained from the numerical models were compared to the results obtained by the 3D laser scan. The results of this investigated article show that a blast magnitude of 337.5 tons TNT (938 tons of Ammonium Nitrate) best captures the silos’ displacement and damage amount. The silos exhibit a tilt between 20 and 30 cm in the direction of the blast. The numerical results indicate that constructing the silos with higher compressive strength would not have affected the silos’ damage. Nevertheless, adding the extra concrete coating and reinforcement layer in 2000 to the outer silos decreased the amount of damage in the silos. Moreover, reinforcing the ribs between the silos would have decreased the silos displacement and damage amount. Finally, the soil and the foundation played a positive role in the explosion by absorbing part of the released energy while the silos, in the current state, cannot be reused.

595-615

Authors: Anjeza Gjini, Hektor Cullufi, Enio Deneko, Princ Xhika

On November 26, 2019, an earthquake with magnitude Mw = 6.4 occurred in the city of Durrës, with epicenter about 16 km southwest of Mamurras. This seismic event caused 51 loss of life, hundreds injured and hundreds of damaged buildings. One of the typified structures, identified by the authors with the most cases of damage or even collapse, is the structure Type no. 82/2 built in some areas of the city of Durrës, in the period 1983-1993. The purpose of this study is to analyze the behavior of this type of structure during seismic loading (for two cases, five and six storey, from the same typology), using the non-linear static procedure (Pushover). The obtained results are compared with the damages recorded in the field for these buildings, concluding with their main causes. According to this study it appears that the main cause of failures occurred in this type of building is the reduction of the reinforcement amount from the ground floor to the first floor by 35.5% and percentage of reinforcement required for the given section exceeds the requirements of design standards (Eurocode-2 and KTP-2-89) by around 30%. Also on these failures contribute the low strength of concrete used in construction of some of these buildings (the compressive strength results 50% less than required) and the use of smooth rebar.

635-646

Authors: Akshansh Mishra, Devarrishi Dixit, Raheem Al-Sabur

A wide range of opportunities in the field of automotive and structural applications are being offered by Magnesium matrix composites because of their enhanced mechanical properties. Magnesium alloys based on Metal Matrix Composites (MMCs) are the best candidates for lightweight structural applications due to their improved creep properties. In the present study, three specimens of specially reinforced magnesium composites were manufactured by using the squeeze casting process. Specimen 1 has a composition of 7 % aluminum alloy in addition to 1% zinc and the composition of reinforcement is Titanium Carbide 0.3 % in addition to 1.5% Carbon nanotubes. Specimen 2 has a composition of 12 % aluminum alloy in addition to 1 % zinc and the composition of reinforcement is 2% B4C in addition to 2 % Carbon nanotubes. Specimen 3 has a composition of 14 % aluminum alloy in addition to 1 % zinc and the composition of reinforcement is 2 % B4C in addition to 2 % Carbon nanotubes. The mechanical properties analysis showed that specimen 2 has a higher hardness value in comparison to other manufactured specimens and it was also observed that specimen 2 possesses a higher tensile strength value in comparison to the other two specimens. Microstructure analysis shows that there was a uniform distribution of the reinforcements in the matrix. So it can be inferred that this uniform distribution causes higher hardness and higher tensile strength in the manufactured specimens.

661-675

Authors: Selale Elcin Sungur, Umit Turgay Arpacioglu, Mustafa Ozgunler

In this study, London The Shard skyscraper structure was examined under the concepts of sustainability and wind engineering dynamics. The aerodynamic examination of the building in accordance with the wind dynamics principles and the relevant CFD simulations as proof, created. In the simulations carried out in the Matlab CFD environment, the Navier Stokes equation principles with k-omega turbulance model were followed. The skyscraper model 1-1 was created in its original form and simulated under real wind data at its location in London. In the results obtained after the simulations, the velocity increased by V-3V in the first 600-800 meters distance range, in the x direction of the model, created a vortex around the structure. While the speed-vortex effects mechanisms were examined on the model by V-3V, the pressure load P within the first 25 meters in the z direction (structure height) of the model was reached to 5P, up to the limit of 280-300 meters. When it is reached to 300 meters height, a 5-fold increase in pressure was detected. In the x-direction, pressure change of the model tested. The variation of the pressure load at the rate of P - 2P was determined in the first 800-1000 meters of the model in the x-direction, and the pressure exerts a double effect in the first 800-1000 meters of the model. In addition to the norms and regulations of supertall design principles, all risk scenarios of wind, under the effect of velocity and pressure need to be simulated before safe construction.

331-346

Authors: Atike Ince Yardimci, Ahmet Sabri Ogutlu, Deniz Ogutlu

In this study, the influence of the oxidizers on the synthesis of carbon nanotubes by C2H4 decomposition over Fe catalyst has been investigated. CO2, O2, and H2O have been used as oxidizers, and to control catalyst particle formation and their sizes in the pretreatment stage. The same oxidizers have also been used in the growth stage to maintain the catalyst particle size, remove amorphous carbon formation to keep catalyst particle active. The results of scanning electron microscopy indicated that the average diameters of nanotubes decreased from 13.4±1.2 nm to 6.2±0.5 nm and extremely dense nanotubes were obtained when we added a small amount of CO2. Adding O2 extremely decreased the areal carbon nanotube density while widens the diameter distribution. H2O addition resulted in larger average diameters and made the growth strongly pretreatment dependent. Within the parameters tried for catalyst pretreatment and CNT growth processes, CO2 seemed the best choice for a weak oxidizing assistant. The strong dependency of the average diameter on pretreatment conditions indicated that pretreatment is a very important step in deciding the final diameters and their distribution.

361-373

Authors: Lütfiye Altay, Mehmet Sarikanat, Merve Sağlam, Tuğçe Uysalman, Yoldaş Seki

Polypropylene is one of the commodity thermoplastics that is widely used in many different applications such as automotive, building, electric-electronics, textile, and packaging industries due to its properties and favorable cost-benefit ratio. The incorporation of mineral fillers such as mica, talc, wollastonite, and calcium carbonate into thermoplastics is a common practice in the plastics industry in order to reduce the production costs of molded products and enhance processibility, mechanical, and thermal properties. Mineral filled polypropylene composites provides high mechanical stiffness, thermal stability, and good dimensional stability over a wide temperature range. The filler weight ratio, type, size, and dimension have significant effect on mechanical, thermal, physical, and rheological properties of composites. Four different mineral fillers (talc, mica, calcite, and feldspar) at weight fractions of 40% were compounded with polypropylene by using a twin-screw extruder. Test specimens were obtained by injection molding process. The effect of various filler types on rheological and mechanical properties of polypropylene was investigated in this study. It was found that talc and mica loadings at 40 wt. % into polypropylene increased the flexural strength of polypropylene. The rheological properties of samples were more affected by the talc than calcium carbonate.

393-411

Authors: Hikmat Daou, Wassim Raphael

Concrete is the most widely used material in the construction industry due to its strength, workability and durability. But under a sustained load, concrete is prone to creep causing excessive long-term deflection of structural members, cracks in tensile members, redistribution of stresses over time in composite structures, and loss of prestressing force in prestressed concrete elements. Therefore, structural engineers must accurately predict the concrete creep over the long-term. The concrete creep coefficient is an important entry in many calculations and analyses of reinforced concrete structures. Currently, many models such as the Eurocode 2 model have predicted the concrete creep coefficient. Based on a large database for creep tests, this study aims to improve the prediction of the Eurocode 2 creep coefficient model at long-term by implementing correction coefficients into the model. Since Bayesian-type inferences are suitable tools for revising and updating design codes, the correction coefficients are calculated based on Bayesian linear regression. Statistical indicators demonstrate the accuracy and effectiveness of the proposed improvement and modification.

431-444

Authors: Ali Bozer

Tuned Liquid Dampers (TLD) consist of a container that is generally partially filled with water. When the sloshing frequency of the water mass is tuned to the fundamental mode of the primary structure a significant amount of sloshing and wave breaking can be achieved which are the primary sources of energy dissipation. Although TLDs are easy to install, operate and maintain; it is generally challenging to model the nonlinear nature of sloshing water. Equivalent mechanical models provide a simplified solution in which sloshing liquid mass, liquid damping, and sloshing frequency are represented by an equivalent mass, damper, spring system. Equivalent mechanical model derivations are generally based on linear sloshing of water mass, which is possible when the water depth/tank length ratio is high and excitation amplitude is low. In this study, a well-known and widely accepted Housner equivalent mechanical model is used to model water sloshing. The water depth/tank length ratio is kept low to enhance the energy dissipation of TLD. The main objective of this study is to experimentally investigate the effectiveness of TLD and check the accuracy of Housner equivalent mechanical model under seismic excitations and low water depth/tank length ratio. Water depth is optimized by the Artificial Bee Colony algorithm which is a population-based optimization algorithm. Frequency sweep analysis and seismic excitations are employed to investigate TLD performance. It is shown that even TLD behavior is modeled by a simplified linear equivalent mechanical model, it is still effective in reducing structural response under large amplitude seismic excitations and low water level/tank length ratios. This is due to more energy dissipation with an increased amount of sloshing and wave breaking.

465-480

Authors: Cameron R. Rusnak, Craig C. Menzemer

Hand-holes are used in welded aluminum light poles which provide access to electrical wiring for both maintenance and installation. Light poles are usually slender and subjected to cyclic loading due to the response from wind. In the field, localized fatigue cracking around hand-holes has been observed but few studies have focused on the resistance of welded aluminum hand-holes. In this study, three-point bending fatigue tests were conducted on full-scale light poles samples. Specimens were constructed with a “flush” hand-hole utilizing reinforcement placed on the inside of the tube, with the handhole located 18 in from the base. Five of these poles, each containing two separate details were tested. Among the ten details that were tested, eight failed as a result of fatigue cracking and the resulting data is compared to current design S-N curves of the Aluminum Design Manual (ADM). A finite element model was created to help understand the local stresses around the hand-hole. this study, the estimation of shear force for blind shear ram type blowout preventer was investigated by using Finite Element Method (FEM). So, the effect of the blowout preventer working condition on shear force requirement for shear operation could be accurately approximated by simulating the entire process, and ram geometry could be optimized to reduce force and energy used to shear the tube by plastic deformation.

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.

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.