Search results for: reinforced concrete walls

Authors: Amer Ezoji, Mohammad Sedighi

Abstract:

In the article, the wire winding process for the reinforcement of a pressure vessel frame has been studied. Firstly, the importance of the wire winding method has been explained. The main step in the design process is the methodology axial force control and wire winding process. The hot isostatic press and wire winding process introduce. With use the equilibrium term in the pressure vessel and frame, stresses in the frame wires analyzed. A case study frame was studied to control axial force in the hot isostatic press. Frame and them wires simulated then friction effect and wires effect in elastic yoke in the simulation model considered. Then theoretical and simulate resulted compare and vessel pressure import to frame because we assurance wire wounded not received to yielding point.   

Keywords: Wire winding, Frame, stress, friction.

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Authors: R. Doubrava, R. Růžek

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Nonstandard tests are necessary for analyses and verification of new developed structural and technological solutions with application of composite materials. One of the most critical primary structural parts of a typical aerospace structure is T-joint. This structural element is loaded mainly in shear, bending, peel and tension. The paper is focused on the shear loading simulations. The aim of the work is to obtain a representative uniform distribution of shear loads along T-joint during the mechanical testing. A new design of T-joint test procedure, numerical simulation and optimization of representative boundary conditions are presented. The different conditions and inaccuracies both in simulations and experiments are discussed. The influence of different parameters on stress and strain distributions is demonstrated on T-joint made of CFRP (carbon fibre reinforced plastic). A special test rig designed by VZLU (Aerospace Research and Test Establishment) for T-shear test procedure is presented.

Keywords: T-joint, shear, composite, mechanical testing, Finite Element analysis, methodology.

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Authors: M. A. Karim

Abstract:

In countries with hot climates, air-conditioning forms a large proportion of annual peak electrical demand, requiring expansion of power plants to meet the peak demand, which goes unused most of the time. Use of well-designed cool storage can offset the peak demand to a large extent. In this study, an air conditioning system with naturally stratified storage tank was designed, constructed and tested. A new type of diffuser was designed and used in this study. Factors that influence the performance of chilled water storage tanks were investigated. The results indicated that stratified storage tank consistently stratified well without any physical barrier. Investigation also showed that storage efficiency decreased with increasing flow rate due to increased mixing of warm and chilled water. Diffuser design and layout primarily affected the mixing near the inlet diffuser and the extent of this mixing had primary influence on the shape of the thermocline. The heat conduction through tank walls and through the thermocline caused widening of mixed volume. Thermal efficiency of stratified storage tanks was as high as 90 percent, which indicates that stratified tanks can effectively be used as a load management technique.

Keywords: Cool Thermal Storage, Diffuser, Natural Stratification, Efficiency Improvement, Load management.

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Authors: M. Ramachandra, G. Dilip Maruthi, R. Rashmi

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This paper aims to study the corrosion property of aluminum matrix nanocomposite of an aluminum alloy (Al-6061) reinforced with zirconium dioxide (ZrO₂) particles. The zirconium dioxide particles are synthesized by solution combustion method. The nanocomposite materials are prepared by mechanical stir casting method, varying the percentage of n-ZrO₂ (2.5%, 5% and 7.5% by weight). The corrosion behavior of base metal (Al-6061) and Al/ZrO₂ nanocomposite in seawater (3.5% NaCl solution) is measured using the potential control method. The corrosion rate is evaluated by Tafel extrapolation technique. The corrosion potential increases with the increase in wt.% of n-ZrO₂ in the nanocomposite which means the decrease in corrosion rate. It is found that on addition of n-ZrO2 particles to the aluminum matrix, the corrosion rate has decreased compared to the base metal.

Keywords: Al6061 alloy, corrosion, solution combustion, stir casting, Potentiostat, Zirconium Dioxide.

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Authors: K. J. Kachiashvili

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The Comparison analysis of the Wald-s and Bayestype sequential methods for testing hypotheses is offered. The merits of the new sequential test are: universality which consists in optimality (with given criteria) and uniformity of decision-making regions for any number of hypotheses; simplicity, convenience and uniformity of the algorithms of their realization; reliability of the obtained results and an opportunity of providing the errors probabilities of desirable values. There are given the Computation results of concrete examples which confirm the above-stated characteristics of the new method and characterize the considered methods in regard to each other.

Keywords: Errors of types I and II, likelihood ratio, the Bayes Type Sequential test, the Wald's sequential test, averaged number of observations.

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Authors: Abass Braimah, Maha Hussein Abdallah

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The global ascendancy of terrorist attacks on building infrastructure with economic and heritage significance has increased awareness of the possibility of terrorism in Canada. Many structures in Canada that are at risk of terrorist attacks include government buildings, built many years ago of historic stone masonry construction. Although many researchers are investigating ways to retrofit masonry stone buildings to mitigate the effect of blast loadings, lack of knowledge on the dynamic behavior of historic stone masonry structures under blast loads makes it difficult to ascertain the effectiveness of the retrofitting techniques. This paper presents a review of open-source literature for the experimental and numerical stone masonry structures under blast loads. This review yielded very little information of the response of the historic stone masonry structures under blast loads. Thus, a comprehensive study is needed to understand the blast load effects on historic stone masonry buildings. The out-of-plane response of historic masonry structures to blast loads is investigated by using single-degree-of-freedom analysis. This approach presents equations that can be used effectively in the analysis of historic masonry walls to out-of-plane blast loading.

Keywords: Blast loads, historical buildings, masonry structure, single-degree-of-freedom analysis.

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Authors: Soon-ok Myong, B.G. Nurzhanov

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This paper applies an anthropological approach to illuminate the dynamic cultural geography of Kazakhstani Korean ethnicity focusing on its turning point, the historic “Seoul Olympic Games in 1988." The Korean ethnic group was easily considered as a harmonious and homogeneous community by outsiders, but there existed deep-seated conflicts and hostilities within the ethnic group. The majority-s oppositional dichotomy of superiority and inferiority toward the minority was continuously reorganized and reinforced by difference in experience, memory and sentiment. However, such a chronic exclusive boundary was collapsed following the patriotism ignited by the Olympics held in their mother country. This paper explores the fluidity of subject by formation of the boundary in which constructed cultural differences are continuously essentialized and reproduced, and by dissolution of cultural barrier in certain contexts.

Keywords: Former Soviet Korean's Russianization, inferior/superior dichotomy, Seoul Olympic Games, subject's fluidity.

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Authors: S. K. Khosrowshahi, E. Güler

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This study investigates the reinforcement function of geosynthetics on the shear strength and strain profile of sand. Conducting a series of simple shear tests, the shearing behavior of the samples under static and cyclic loads was evaluated. Three different types of geosynthetics including geotextile and geonets were used as the reinforcement materials. An image processing analysis based on the optical flow method was performed to measure the lateral displacements and estimate the shear strains. It is shown that besides improving the shear strength, the geosynthetic reinforcement leads a remarkable reduction on the shear strains. The improved layer reduces the required thickness of the soil layer to resist against shear stresses. Consequently, the geosynthetic reinforcement can be considered as a proper approach for the sustainable designs, especially in the projects with huge amount of geotechnical applications like subgrade of the pavements, roadways, and railways.

Keywords: Image processing, soil reinforcement, geosynthetics, simple shear test, shear strain profile.

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Authors: H. Meddah, M. Berediaf-Bourahla, B. El-Djouzi, N. Bourahla

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Shear walls made of cold formed steel are used as lateral force resisting components in residential and low-rise commercial and industrial constructions. The seismic design analysis of such structures is often complex due to the slenderness of members and their instability prevalence. In this context, a simplified modeling technique across the panel is proposed by using the finite element method. The approach is based on idealizing the whole panel by a nonlinear shear link element which reflects its shear behavior connected to rigid body elements which transmit the forces to the end elements (studs) that resist the tension and the compression. The numerical model of the shear wall panel was subjected to cyclic loads in order to evaluate the seismic performance of the structure in terms of lateral displacement and energy dissipation capacity. In order to validate this model, the numerical results were compared with those from literature tests. This modeling technique is particularly useful for the design of cold formed steel structures where the shear forces in each panel and the axial forces in the studs can be obtained using spectrum analysis.

Keywords: Cold-formed steel, cyclic loading, modeling technique, nonlinear analysis, shear wall panel.

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Authors: N. B. Fedosenko, A.A Iatcenko, S.A. Levanov

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The paper shows some ability to manage two-phase flows arising from the use of unsteady effects. In one case, we consider the condition of fragmentation of the interface between the two components leads to the intensification of mixing. The problem is solved when the temporal and linear scale are small for the appearance of the developed mixing layer. Showing that exist such conditions for unsteady flow velocity at the surface of the channel, which will lead to the creation and fragmentation of vortices at Re numbers of order unity. Also showing that the Re is not a criterion of similarity for this type of flows, but we can introduce a criterion that depends on both the Re, and the frequency splitting of the vortices. It turned out that feature of this situation is that streamlines behave stable, and if we analyze the behavior of the interface between the components it satisfies all the properties of unstable flows. The other problem we consider the behavior of solid impurities in the extensive system of channels. Simulated unsteady periodic flow modeled breaths. Consider the behavior of the particles along the trajectories. It is shown that, depending on the mass and diameter of the particles, they can be collected in a caustic on the channel walls, stop in a certain place or fly back. Of interest is the distribution of particle velocity in frequency. It turned out that by choosing a behavior of the velocity field of the carrier gas can affect the trajectory of individual particles including force them to fly back.

Keywords: Two-phase, mixing, separating, flow control

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Authors: Hans H. Diel

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A computer model of Quantum Theory (QT) has been developed by the author. Major goal of the computer model was support and demonstration of an as large as possible scope of QT. This includes simulations for the major QT (Gedanken-) experiments such as, for example, the famous double-slit experiment. Besides the anticipated difficulties with (1) transforming exacting mathematics into a computer program, two further types of problems showed up, namely (2) areas where QT provides a complete mathematical formalism, but when it comes to concrete applications the equations are not solvable at all, or only with extremely high effort; (3) QT rules which are formulated in natural language and which do not seem to be translatable to precise mathematical expressions, nor to a computer program. The paper lists problems in all three categories and describes also the possible solutions or circumventions developed for the computer model.

Keywords: Computability, Foundation of Quantum Mechanics, Measurement Process, Modeling.

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Authors: Samira Jebahi, Hassane Oudadesse, Eric Wers, Jiheun Elleuch, Hafedh Elfekih, Hassib Keskes, Xuan Vuong Bui, Abdelfatteh Elfeki

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Chitosan (CH) material reinforced by bioactive glass (46S6) was fabricated. 46S6 containing 17% wt% CH was studied in vitro and in vivo. Physicochemical techniques, such as Fourier transform infrared spectroscopy (FT-IR), coupled plasma optical emission spectrometry (ICP-OES) analysis were used. The behavior of 46S6CH17 was studied by measuring the in situ pH in a SBF solution. The 46S6CH17 was implanted in the rat femoral condyl. In vitro 46S6CH17 gave an FTIR - spectrum in which three absorption bands with the maxima at 565, 603 and 1039cm-1 after 3 days of soaking in physiological solution. They are assigned to stretching vibrations of PO4^3- group in phosphate crystalline. Moreover, the pH measurement was decreased in the SBF solution. The stability of the calcium phosphate precipitation depended on the pH value. In vivo, a rise in the Ca and phosphate P ions concentrations in the implanted microenvironment was determined.

Keywords: Bioglass, Chitosan, pH measurement, Hydroxyapatite Carbonateted Layer.

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Authors: Ammar Alsabery, Habibis Saleh, Norazam Arbin, Ishak Hashim

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Unsteady natural convection and heat transfer in a square cavity partially filled with porous media using a thermal non-equilibrium model is studied in this paper. The left vertical wall is maintained at a constant hot temperature Th and the right vertical wall is maintained at a constant cold temperature Tc, while the horizontal walls are adiabatic. The governing equations are obtained by applying the Darcy model and Boussinesq approximation. COMSOL’s finite element method is used to solve the non-dimensional governing equations together with specified boundary conditions. The governing parameters of this study are the Rayleigh number (Ra = 10^5, and Ra = 10^6 ), Darcy namber (Da = 10^−2, and Da = 10^−3), the modified thermal conductivity ratio (10^−1 ≤ γ ≤ 10^4), the inter-phase heat transfer coefficien (10^−1 ≤ H ≤ 10^3) and the time dependent (0.001 ≤ τ ≤ 0.2). The results presented for values of the governing parameters in terms of streamlines in both fluid/porous-layer, isotherms of fluid in fluid/porous-layer, isotherms of solid in porous layer, and average Nusselt number.

Keywords: Unsteady natural convection, Thermal non-equilibrium model, Darcy model.

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Authors: A. Al-Mosawe, R. Al-Mahaidi

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Carbon fiber reinforced polymersarewidely used to strengthen steel structural elements. These structural elements are normally subjected to static, dynamic and fatigue loadings during their life-time. CFRP laminate is commonly used to strengthen these structures under the subjected loads. A number of studies have focused on the characteristics of CFRP sheets bonded to steel members under static, dynamic and fatigue loadings. However, there is a gap in understanding the bonding behavior between CFRP laminates and steel members under impact loading. This paper shows the effect of high load rates on this bond. CFRP laminate CFK 150/2000 was used to strengthen steel joints using Araldite 420 epoxy. The results show that applying a high load rate significantly affects the bond strength but has little influence on the effective bond length.

Keywords: Adhesively-bonded joints, Bond strength, CFRP laminate, Impact tensile loading.

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Authors: Belkacem Selma, Boumediene Selma, Samira Chouraqui, Hanifi Missoum, Tourkia Guerzou

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Natural disasters have occurred and will continue to cause human and material damage. Therefore, the idea of "preventing" natural disasters will never be possible. However, their prediction is possible with the advancement of technology. Even if natural disasters are effectively inevitable, their consequences may be partly controlled. The rapid growth and progress of artificial intelligence (AI) had a major impact on the prediction of natural disasters and risk assessment which are necessary for effective disaster reduction. Earthquake prediction to prevent the loss of human lives and even property damage is an important factor; that, is why it is crucial to develop techniques for predicting this natural disaster. This study aims to analyze the ability of artificial neural networks (ANNs) to predict earthquakes that occur in a given area. The used data describe the problem of high energy (higher than 104 J) seismic bumps forecasting in a coal mine using two long walls as an example. For this purpose, seismic bumps data obtained from mines have been analyzed. The results obtained show that the ANN is able to predict earthquake parameters with  high accuracy; the classification accuracy through neural networks is more than 94%, and the models developed are efficient and robust and depend only weakly on the initial database.

Keywords: Earthquake prediction, artificial intelligence, AI, Artificial Neural Network, ANN, seismic bumps.

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Authors: S. Boughanem, D. A. Jesson, M. J. Mulheron, P.A. Smith C. Eddie, S. Psomas, M. Rimes

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Cements, which are intrinsically brittle materials, can exhibit a degree of pseudo-ductility when reinforced with a sufficient volume fraction of a fibrous phase. This class of materials, called Engineered Cement Composites (ECC) has the potential to be used in future tunneling applications where a level of pseudo-ductility is required to avoid brittle failures. However uncertainties remain regarding mechanical performance. Previous work has focused on comparatively thin specimens; however for future civil engineering applications, it is imperative that the behavior in tension of thicker specimens is understood. In the present work, specimens containing cement powder and admixtures have been manufactured following two different processes and tested in tension. Multiple matrix cracking has been observed during tensile testing, leading to a “strain-hardening" behavior, confirming the possible suitability of ECC material when used as thick sections (greater than 50mm) in tunneling applications.

Keywords: Cement composite, polymeric fibers, pseudoductility, test-geometry.

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Authors: M. S. Meon, M. N. Rao, K-U. Schröder

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Mechanical fasteners especially bolting is commonly used in joining carbon-fiber reinforced polymer (CFRP) composite structures due to their good joinability and easy for maintenance characteristics. Since this approach involves with notching, a proper progressive damage model (PDM) need to be implemented and verified to capture existence of damages in the structure. A three dimensional (3D) failure criteria of Puck is established to predict the ultimate bearing failure of such joint. The failure criteria incorporated with degradation scheme are coded based on user subroutine executed in Abaqus. Single lap joint (SLJ) of composite bolted joint is used as target configuration. The results revealed that the PDM adopted here could sufficiently predict the behaviour of composite bolted joint up to ultimate bearing failure. In addition, mesh refinement near holes increased the accuracy of predicted strength as well as computational effort.

Keywords: Bearing strength, bolted joint, degradation scheme, progressive damage model.

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Authors: R. Abbasnia, F. Mohajeri Nav, S. Zahedifar, A. Tajik

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Recent years, adaptive pushover methods have been developed for seismic analysis of structures. Herein, the accuracy of the displacement-based adaptive pushover (DAP) method, which is introduced by Antoniou and Pinho [2004], is evaluated for Irregular buildings. The results are compared to the force-based procedure. Both concrete and steel frame structures, asymmetric in plan and elevation are analyzed and also torsional effects are taking into the account. These analyses are performed using both near fault and far fault records. In order to verify the results, the Incremental Dynamic Analysis (IDA) is performed.

Keywords: Pushover Analysis, DAP, IDA, Torsion.

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Authors: N. AlShaya, R. Alhomidan, S. Alromizan, W. Labib

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Plant-based natural fibers are used more increasingly in construction materials. It is done to reduce the pressure on the built environment, which has been increased dramatically due to the increases world population and their needs. Plant-based natural fibers are abundant in many countries. Despite the low-cost of such environmental friendly renewable material, it has the ability to enhance the mechanical properties of construction materials. This paper presents an extensive discussion on the use of plant-based natural fibers as reinforcement for cement-based composites, with a particular emphasis upon fiber types; fiber characteristics, and fiber-cement composites performance. It also covers a thorough overview on the main factors, affecting the properties of plant-based natural fiber cement composite in it fresh and hardened state. The feasibility of using plant-based natural fibers in producing various construction materials; such as, mud bricks and blocks is investigated. In addition, other applications of using such fibers as internal curing agents as well as durability enhancer are also discussed. Finally, recommendation for possible future work in this area is presented.

Keywords: Cement composites, plant fibers, strength, mechanical properties.

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Authors: Amin Almasi

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Composite laminates are relatively weak in out of plane loading, inter-laminar stress, stress concentration near the edge and stress singularities. This paper develops a new analytical formulation for laminated composite rotating disc fabricated from symmetric sequential quasi isotropic layers to predict three dimensional stress and deformation. This analysis is necessary to evaluate mechanical integrity of fiber reinforced multi-layer laminates used for high speed rotating applications such as high speed impellers. Three dimensional governing equations are written for rotating composite disc. Explicit solution is obtained with "Frobenius" expansion series. Based on analytical results, there are two separate zones of three dimensional stress fields in centre and edge of rotating disc. For thin discs, out of plane deformations and stresses are small in comparison with plane ones. For relatively thick discs deformation and stress fields are three dimensional.

Keywords: Composite Disc, Rotating Machine.

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Authors: Magdi M. E. Zumrawi, Faiza O. A. Khalill

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Steel slag is a by-product of the steel industry and can be used potentially as aggregate in the asphalt mixture. This study evaluates the use of Steel Slag Aggregates (SSA) as a substitute for natural aggregates in the production of hot mix asphalt (HMA) for road construction. Based on intensive laboratory testing program, the characteristic properties of SSA were assessed to determine its suitability to be used in HMA. Four different percentages (0, 50, 75, and 100%) of SSA were used, and the proposed mix designs for HMA were conducted in accordance with Marshall mix design. The experiment results revealed that the addition of SSA has a significant improvement on the properties of HMA. An increase in density and stability and a reduction in flow and air voids values were clearly observed in specimens prepared with 100% SSA. It is concluded that the steel slag can be considered reasonable alternative source of aggregate for concrete asphalt mixture production.

Keywords: Aggregate, asphalt mixture, stability, steel slag.

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Authors: Jiuyang Lin, Wenyuan Ye, Arcadio Sotto, Bart Van der Bruggen

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Application of nanoparticles as additives in membrane synthesis for improving the resistance of membranes against fouling has triggered recent interest in new membrane types. However, most nanoparticle-enhanced membranes suffer from the tradeoff between permeability and selectivity. In this study, nano-WS2 was explored as the additive in membrane synthesis by non-solvent induced phase separation. Blended PES-WS2 flat-sheet membranes with the incorporation of ultra-low concentrations of nanoparticles (from 0.025 to 0.25%, WS2/PES ratio) were manufactured and investigated in terms of permeability, fouling resistance and solute rejection. Remarkably, a significant enhancement in the permeability was observed as a result of the incorporation of ultra-low fractions of nano-WS2 to the membrane structure. Optimal permeability values were obtained for modified membranes with 0.10% nanoparticle/polymer concentration ratios. Furthermore, fouling resistance and solute rejection were significantly improved by the incorporation of nanoparticles into the membrane matrix. Specifically, fouling resistance of modified membrane can increase by around 50%.

Keywords: Nano-WS2, Nanoparticle enhanced hybrid membrane, Ultralow concentration, Antifouling.

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Authors: M. Aboudalle, Le Btth, M. Sari, F. Meftah

Abstract:

In parallel with the appearance of new materials, brick masonry had and still has an essential part of the construction market today, with new technical challenges in designing bricks to meet additional requirements. Being used in structural applications, predicting the performance of clay brick masonry allows a significant cost reduction, in terms of practical experimentation. The behavior of masonry walls depends on the behavior of their elementary components, such as bricks, joints, and coatings. Therefore, it is necessary to consider it at different scales (from the scale of the intrinsic material to the real scale of the wall) and then to develop appropriate models, using numerical simulations. The work presented in this paper focuses on the mechanical characterization of the terracotta material at ambient temperature. As a result, the static Young’s modulus obtained from the flexural test shows different values in comparison with the compression test, as well as with the dynamic Young’s modulus obtained from the Impulse excitation of vibration test. Moreover, the Young's modulus varies according to the direction in which samples are extracted, where the values in the extrusion direction diverge from the ones in the orthogonal directions. Based on these results, hollow bricks can be considered as transversely isotropic bimodulus material.

Keywords: Bimodulus material, hollow clay brick, impulse excitation of vibration, transversely isotropic material, Young’s modulus.

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Authors: Salma Saleh Alrdahe, Mahmood Ameen Abdulla, Shaharudin Abul Razak, Farkaad Abdul Kadir, Pouya Hassandarvish

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Swietenia mahagoni have been used in traditional medicine for treatment of different diseases. Present study was performed to evaluate anti-ulcerogenic activity of ethanol seed extract against ethanol induced gastric mucosal injury in rats. Six groups of rats were orally pre-treated respectively with carboxymethyl cellulose, omeprazole 20 mg/kg, 50, 100, 200 and 400 mg/kg plant extract one hour before oral administration of absolute ethanol to generate gastric mucosal injury. After additional hour, rats were sacrificed and ulcer areas of gastric walls were determined. Grossly, carboxymethyl cellulose group exhibited severe mucosal injury, whereas pre-treatment with plant extract exhibited significant protection of gastric mucosa. Histology, carboxymethyl cellulose group exhibited severe damage of gastric mucosa; edema and leucocytes infiltration of sub mucosa compared to plant extract which showed gastric protection. Acute toxicity study did not manifest any toxicological signs in rats. Conclusions, results suggest that S. mahagoni promotes ulcer protection as ascertained grossly and histologically.

Keywords: Cytoprotection, Gastric ulcer, Histology, Swieteniamahagoni seed.

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Authors: Kerim Emre Öksüz, Mehmet Çevik, A. Enbiya Bozdağ, Ali Özer, Mehmet Simsir

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Metal matrix composites (MMCs) have gained a considerable interest in the last three decades. Conventional powder metallurgy production route often involves the addition of reinforcing phases into the metal matrix directly, which leads to poor wetting behavior between ceramic phase and metal matrix and the segregation of reinforcements. The commonly used elements for ceramic phase formation in iron based MMCs are Ti, Nb, Mo, W, V and C, B. The aim of the present paper is to investigate the effect of sintering temperature and V-B addition on densification, phase development, microstructure, and hardness of Fe–V-B composites (Fe-(5-10) wt. %B – 25 wt. %V alloys) prepared by powder metallurgy process. Metal powder mixes were pressed uniaxial and sintered at different temperatures (ranging from 1300 to 1400ºC) for 1h. The microstructure of the (V, B) Fe composites was studied with the help of high magnification optical microscope and XRD. Experimental results show that (V, B) Fe composites can be produced by conventional powder metallurgy route.

Keywords: Hardness, Metal matrix composite (MMC), Microstructure, Powder Metallurgy.

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Authors: Milorad Pavlovic, Anna Manzato, Antonella Cecchi

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Cultural heritage conservation is a challenge for contemporary society. In recent decades, significant resources have been allocated for the conservation and restoration of architectural heritage. Historical buildings were restored, protected and reinforced with the intent to limit the risks of degradation or loss, due to phenomena of structural damage and to external factors such as differential settlements, earthquake effects, etc. The wide diffusion of historic masonry constructions in Italy, Europe and the Mediterranean area requires reliable tools for the evaluation of their structural safety. In this paper is presented a free modal analysis performed on a minor historical architecture located in the village of Bagno Grande, near the city of L’Aquila in Italy. The location is characterized by a complex urban context, seriously damaged by the earthquake of 2009. The aim of this work is to check the structural behavior of a masonry building characterized by several boundary conditions imposed by adjacent buildings and infrastructural facilities.

Keywords: FEM, masonry, minor historical architecture, modal analysis.

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Authors: T. Thompson, E. F. Zegeye

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Bacterial Cellulose (BC) is a structural organic compound produced in the anaerobic process. This material can be a useful eco-friendly substitute for commercial textiles that are used in industries today. BC is easily and sustainably produced and has the capabilities to be used as a replacement in textiles. However, BC is extremely fragile when it completely dries. This research was conducted to improve the mechanical properties of the BC by reinforcing with an organic polymer and exfoliated graphite (EG). The BC films were grown over a period of weeks in a green tea and kombucha solution at 30 °C, then cleaned and added to an enhancing solution. The enhancing solutions were a mixture of 2.5 wt% polymer and 2.5 wt% latex solution, a 5 wt% polymer solution, a 0.20 wt% graphite solution and were each allowed to sit in a furnace for 48 h at 50 °C. Tensile test samples were prepared and tested until fracture at a strain rate of 8 mm/min. From the research with the addition of a 5 wt% polymer solution, the flexibility of the BC has significantly improved with the maximum strain significantly larger than that of the base sample. The addition of EG has also increased the modulus of elasticity of the BC by about 25%.

Keywords: Bacterial cellulose, exfoliated graphite, kombucha scoby, tensile test.

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Authors: Balwinder Singh

Abstract:

The present research is a paper on the characterization of aluminum alloy-6063 hybrid metal matrix composites using three different reinforcement materials (SiC, red mud, and fly ash) through stir casting method. The red mud was used in solid form, and particle size range varies between 103-150 µm. During this investigation, fly ash is received from Guru Nanak Dev Thermal Plant (GNDTP), Bathinda. The study has been done by using Taguchi’s L9 orthogonal array by taking fraction wt.% (SiC 5%, 7.5%, and 10% and Red Mud and Fly Ash 2%, 4%, and 6%) as input parameters with their respective levels. The study of the mechanical properties (tensile strength, impact strength, and microhardness) has been done by using Analysis of Variance (ANOVA) with the help of MINITAB 17 software. It is revealed that silicon carbide is the most significant parameter followed by red mud and fly ash affecting the mechanical properties, respectively. The fractured surface morphology of the composites using Field Emission Scanning Electron Microscope (FESEM) shows that there is a good mixing of reinforcement particles in the matrix. Energy-dispersive X-ray spectroscopy (EDS) was performed to know the presence of the phases of the reinforced material.

Keywords: Reinforcement, silicon carbide, fly ash, red mud.

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Authors: R. Gary Black, Abolhassan Astaneh-Asl

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The International Building Code (IBC) and the  California Building Code (CBC) both recognize four basic types of  steel seismic resistant frames; moment frames, concentrically braced  frames, shear walls and eccentrically braced frames. Based on  specified geometries and detailing, the seismic performance of these  steel frames is well understood. In 2011, the authors designed an  innovative steel braced frame system with tapering members in the  general shape of a branching tree as a seismic retrofit solution to an  existing four story “lift-slab” building. Located in the seismically  active San Francisco Bay Area of California, a frame of this  configuration, not covered by the governing codes, would typically  require model or full scale testing to obtain jurisdiction approval.  This paper describes how the theories, protocols, and code  requirements of eccentrically braced frames (EBFs) were employed  to satisfy the 2009 International Building Code (IBC) and the 2010  California Building Code (CBC) for seismically resistant steel frames  and permit construction of these nonconforming geometries.

 

Keywords: Eccentrically Braced Frame, Lift Slab Construction, Seismic Retrofit, Shear Link, Steel Design.

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Authors: A. D'Alessandro, F. Ubertini, A. L. Materazzi

Abstract:

In the field of civil engineering, Structural Health Monitoring is a topic of growing interest. Effective monitoring instruments permit the control of the working conditions of structures and infrastructures, through the identification of behavioral anomalies due to incipient damages, especially in areas of high environmental hazards as earthquakes. While traditional sensors can be applied only in a limited number of points, providing a partial information for a structural diagnosis, novel transducers may allow a diffuse sensing. Thanks to the new tools and materials provided by nanotechnology, new types of multifunctional sensors are developing in the scientific panorama. In particular, cement-matrix composite materials capable of diagnosing their own state of strain and tension, could be originated by the addition of specific conductive nanofillers. Because of the nature of the material they are made of, these new cementitious nano-modified transducers can be inserted within the concrete elements, transforming the same structures in sets of widespread sensors. This paper is aimed at presenting the results of a research about a new self-sensing nanocomposite and about the implementation of smart sensors for Structural Health Monitoring. The developed nanocomposite has been obtained by inserting multi walled carbon nanotubes within a cementitious matrix. The insertion of such conductive carbon nanofillers provides the base material with piezoresistive characteristics and peculiar sensitivity to mechanical modifications. The self-sensing ability is achieved by correlating the variation of the external stress or strain with the variation of some electrical properties, such as the electrical resistance or conductivity. Through the measurement of such electrical characteristics, the performance and the working conditions of an element or a structure can be monitored. Among conductive carbon nanofillers, carbon nanotubes seem to be particularly promising for the realization of self-sensing cement-matrix materials. Some issues related to the nanofiller dispersion or to the influence of the nano-inclusions amount in the cement matrix need to be carefully investigated: the strain sensitivity of the resulting sensors is influenced by such factors. This work analyzes the dispersion of the carbon nanofillers, the physical properties of the fresh dough, the electrical properties of the hardened composites and the sensing properties of the realized sensors. The experimental campaign focuses specifically on their dynamic characterization and their applicability to the monitoring of full-scale elements. The results of the electromechanical tests with both slow varying and dynamic loads show that the developed nanocomposite sensors can be effectively used for the health monitoring of structures.

Keywords: Carbon nanotubes, self-sensing nanocomposites, smart cement-matrix sensors, structural health monitoring.

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