Search results for: steel fibre reinforce concrete

Authors: Felix Eyben, Simon Schaffrath, Markus Feldmann

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A building should maximize the potential for use through its design. Therefore, flexible use is always important when designing a steel structure. To create flexibility, steel beams with web openings are increasingly used, because these offer the advantage that cables, pipes and other technical equipment can easily be routed through without detours, allowing for more space-saving and aesthetically pleasing construction. This can also significantly reduce the height of ceiling systems. Until now, beams with web openings were not explicitly considered in the European standard. However, this is to be done with the new EN 1993-1-13, in which design rules for different opening forms are defined. In order to further develop the design concepts, beams with web openings under bending are therefore to be investigated in terms of damage mechanics as part of a German national research project aiming to optimize the verifications for steel structures based on a wider database and a validated damage prediction. For this purpose, first, fundamental factors influencing the load-bearing behavior of girders with web openings under bending load were investigated numerically without taking material damage into account. Various parameter studies were carried out for this purpose. For example, the factors under study were the opening shape, size and position as well as structural aspects as the span length, arrangement of stiffeners and loading situation. The load-bearing behavior is evaluated using resulting load-deformation curves. These results are compared with the design rules and critically analyzed. Experimental tests are also planned based on these results. Moreover, the implementation of damage mechanics in the form of the modified Bai-Wierzbicki model was examined. After the experimental tests will have been carried out, the numerical models are validated and further influencing factors will be investigated on the basis of parametric studies.

Keywords: damage mechanics, finite element, steel structures, web openings

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Authors: A. Pesin, D. Pustovoytov, M. Sverdlik

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During production of rolled steel strips the quality of the surface of finished strips influences steel consumption considerably. The most critical areas for crack formation during rolling are lateral sides of slabs. Deformation behaviors of the slab edge in roughing rolling process were analyzed by the finite element method with Deform-3D. In this study our focus is the analysis of the influence of edger’s form on the possibility to decrease surface cracking during roughing hot rolling.

Keywords: roughing hot rolling, FEM, crack, bulging

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Authors: Laura Vitola, Diana Bajare, Genadijs Sahmenko, Girts Bumanis

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About 8 % of CO2 emission in the world is produced by concrete industry therefore replacement of cement in concrete composition by additives with pozzolanic activity would give a significant impact on the environment. Material which contains silica SiO2 or amorphous silica SiO2 together with aluminum dioxide Al2O3 is called pozzolana type additives in the concrete industry. Pozzolana additives are possible to obtain from recycling industry and different production by-products such as processed bulb boric silicate (DRL type) and lead (LB type) glass, coal combustion bottom ash, utilized brick pieces and biomass ash, thus solving utilization problem which is so important in the world, as well as practically using materials which previously were considered as unusable. In the literature, there is no summarized method which could be used for quick waste-product pozzolana activity evaluation without the performance of wide researches related to the production of innumerable concrete contents and samples in the literature. Besides it is important to understand which parameters should be predicted to characterize the efficiency of waste-products. Simple methods of pozzolana activity increase for different types of waste-products are also determined. The aim of this study is to evaluate effectiveness of the different types of waste materials and industrial by-products (coal combustion bottom ash, biomass ash, waste glass, waste kaolin and calcined illite clays), and determine which parameters have the greatest impact on pozzolanic activity. By using materials, which previously were considered as unusable and landfilled, in concrete industry basic utilization problems will be partially solved. The optimal methods for treatment of waste materials and industrial by–products were detected with the purpose to increase their pozzolanic activity and produce substitutes for cement in the concrete industry. Usage of mentioned pozzolanic allows us to replace of necessary cement amount till 20% without reducing the compressive strength of concrete.

Keywords: cement substitutes, micro and nano fillers, pozzolanic properties, specific surface area, particle size, waste products

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Authors: Gökhan Yüksel, Serdar Akça, İlker Kalkan

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The present study is an attempt to demonstrate the significant levels of contribution of the moment-resisting beam-column connections with side plates to the earthquake behavior of special steel moment frames. To this end, the moment-curvature relationships of a regular beam-column connection and its SidePlate counterpart were determined with the help of finite element analyses. The connection stiffness and deformability values from these finite element analyses were used in the linear time-history analyses of an example structural steel frame under three different seismic excitations. The top-story lateral drift, base shear, and overturning moment values in two orthogonal directions were obtained from these time-history analyses and compared to each other. The results revealed the improvements in the system response with the use of SidePlate connections. The paper ends with crucial recommendations for the plan and design of further studies on this very topic.

Keywords: seismic detailing, special moment frame, steel structures, beam-column connection, earthquake-resistant design

Procedia PDF Downloads 83

Authors: Keyvan Ramin

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The geometric nonlinearity of Off-Diagonal Bracing System (ODBS) could be a complementary system to covering and extending the nonlinearity of reinforced concrete material. Finite element modeling is performed for flexural frame, x-braced frame and the ODBS braced frame system at the initial phase. Then the different models are investigated along various analyses. According to the experimental results of flexural and x-braced frame, the verification is done. Analytical assessments are performed in according to three-dimensional finite element modeling. Non-linear static analysis is considered to obtain performance level and seismic behavior, and then the response modification factors calculated from each model’s pushover curve. In the next phase, the evaluation of cracks observed in the finite element models, especially for RC members of all three systems is performed. The finite element assessment is performed on engendered cracks in ODBS braced frame for various time steps. The nonlinear dynamic time history analysis accomplished in different stories models for three records of Elcentro, Naghan, and Tabas earthquake accelerograms. Dynamic analysis is performed after scaling accelerogram on each type of flexural frame, x-braced frame and ODBS braced frame one by one. The base-point on RC frame is considered to investigate proportional displacement under each record. Hysteresis curves are assessed along continuing this study. The equivalent viscous damping for ODBS system is estimated in according to references. Results in each section show the ODBS system has an acceptable seismic behavior and their conclusions have been converged when the ODBS system is utilized in reinforced concrete frame.

Keywords: FEM, seismic behaviour, pushover analysis, geometric nonlinearity, time history analysis, equivalent viscous damping, passive control, crack investigation, hysteresis curve

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Authors: Ming-Hsiang Shih, Wen-Pei Sung, Shih-Heng Tung

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The purposes of hydraulic gate are to maintain the functions of storing and draining water. It bears long-term hydraulic pressure and earthquake force and is very important for reservoir and waterpower plant. The high tensile strength of steel plate is used as constructional material of hydraulic gate. The cracks and rusts, induced by the defects of material, bad construction and seismic excitation and under water respectively, thus, the mechanics phenomena of gate with crack are probing into the cause of stress concentration, induced high crack increase rate, affect the safety and usage of hydroelectric power plant. Stress distribution analysis is a very important and essential surveying technique to analyze bi-material and singular point problems. The finite difference infinitely small element method has been demonstrated, suitable for analyzing the buckling phenomena of welding seam and steel plate with crack. Especially, this method can easily analyze the singularity of kink crack. Nevertheless, the construction form and deformation shape of some gates are three-dimensional system. Therefore, the three-dimensional Digital Image Correlation (DIC) has been developed and applied to analyze the strain variation of steel plate with crack at weld joint. The proposed Digital image correlation (DIC) technique is an only non-contact method for measuring the variation of test object. According to rapid development of digital camera, the cost of this digital image correlation technique has been reduced. Otherwise, this DIC method provides with the advantages of widely practical application of indoor test and field test without the restriction on the size of test object. Thus, the research purpose of this research is to develop and apply this technique to monitor mechanics crack variations of weld steel hydraulic gate and its conformation under action of loading. The imagines can be picked from real time monitoring process to analyze the strain change of each loading stage. The proposed 3-Dimensional digital image correlation method, developed in the study, is applied to analyze the post-buckling phenomenon and buckling tendency of welded steel plate with crack. Then, the stress intensity of 3-dimensional analysis of different materials and enhanced materials in steel plate has been analyzed in this paper. The test results show that this proposed three-dimensional DIC method can precisely detect the crack variation of welded steel plate under different loading stages. Especially, this proposed DIC method can detect and identify the crack position and the other flaws of the welded steel plate that the traditional test methods hardly detect these kind phenomena. Therefore, this proposed three-dimensional DIC method can apply to observe the mechanics phenomena of composite materials subjected to loading and operating.

Keywords: welded steel plate, crack variation, three-dimensional digital image correlation (DIC), crack stel plate

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Authors: Hyunseo Choi, Jaewan Hong, Seil Lee, Yang Mo Koo

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Non-oriented (NO) electrical steel is one of the most important soft magnetic materials for rotating machines. Si has usually been added to electrical steels to reduce eddy current loss by increasing the electrical resistivity. Si content more than 3.5 wt% causes cracks during cold rolling due to increase of brittleness. Al also increases the electrical resistivity of the materials as much as Si. In addition, cold workability of Fe-Al is better than Fe-Si, so that Al can be added up to 6.0 wt%. However, the effect of Al contents on magnetic properties of electrical steels has not been studied in detail. Magnetic domains of {100} grains in electrical steels, ranging from 1.85 to 6.54 wt% Al, were observed by magneto-optic Kerr microscopy. Furthermore, the correlation of magnetic domains with magnetic properties was investigated. As Al contents increased, the magnetic domain size of {100} grains decreased due to lowered domain wall energy. Reorganization of magnetic domain structure became more complex as domain size decreased. Therefore, the addition of Al to electrical steel caused hysteresis loss to increase. Anomalous loss decreased and saturated after 4.68% Al.

Keywords: electrical steel, magnetic domain structure, Al addition, core loss, rearrangement of domains

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Authors: E. Faizan, Wahab Abdul Ghafar, Tao Zhong

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Steel plate shear walls (SPSWs) are a robust lateral load resistance structure because of their high flexibility and efficient energy dissipation when subjected to seismic loads. This research investigates the seismic performance of an innovative infill web strip (IWS-SPSW) and a typical unstiffened steel plate shear wall (USPSW). As a result, two 1:3 scale specimens of an IWS-SPSW and USPSW with a single story and a single bay were built and subjected to a cyclic lateral loading methodology. In the prototype, the beam-to-column connections were accomplished with the assistance of semi-rigid end-plate connectors. IWS-SPSW demonstrated exceptional ductility and shear load-bearing capacity during the testing process, with no cracks or other damage occurring. In addition, the IWS-SPSW could effectively dissipate energy without causing a significant amount of beam-column connection distortion. The shear load-bearing capacity of the USPSW was exceptional. However, it exhibited low ductility, severe infill plate corner ripping, and huge infill web plate cracks. The FE models were created and then confirmed using the experimental data. It has been demonstrated that the infill web strips of an SPSW system can affect the system's high performance and total energy dissipation. In addition, a parametric analysis was carried out to evaluate the material qualities of the IWS, which can considerably improve the system's seismic performances. These properties include the steel's strength as well as its thickness.

Keywords: steel shear walls, seismic performance, failure mode, hysteresis response, nonlinear finite element analysis, parametric study

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Authors: U.N. Emiri, E. Moroyei

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Mycoflora associated with the seed rot disease of Mucuna sloanei and their effects on nutrient and phytochemical composition of the seeds were investigated. The fungal pathogens implicated in the seed rot disease were Rhizopus stolonifer, Aspergillus flavus, Aspergillus niger, and Fusarium oxysporum. The fungal isolates were aseptically inoculated into healthy M. Sloanei seeds and incubated for 7 days at room temperature of 25 ± 30c. The results of the proximate and mineral analysis in mg/100g of fungal infected and non-infected (control) seeds that were carried out revealed that there was an increase in Moisture and Carbohydrate content of the fungal infected seeds relative to the non-infected seeds (control). However, there was a decrease in Ash, Fibre, Lipid, and Protein content of the fungal infected seeds relative to the non-infected (control). It was observed that moisture had increased from 10.50 ± 0.16 in the non-infected seeds to 17.60 ± 0.20 in the infected samples and Carbohydrate content had also increased from 49.6 ± 0.25 in the non-infected to 52.50 ± 0.29 in the infected seeds. The following parameters decreased in the infected than in the non-infected seeds. They include Ash 2.60 ± 0.12, Crude fibre 1.9 ± 0.08, Lipid 6.50 ± 0.16, and Protein content 18.50 ± 0.06. Similarly, Calcium 2.50 ± 0.12, Phosphorus 1.80 + 0.12 and Potassium 1.80 + 0.09 increased in the infected than in the non-infected seed, while iron 0.20 ± 0.05, Sodium 0.02 ± 0.01 and Magnesium 0.06 ± 0.02 decreased in the infected seeds. All phytochemical contents analyzed increased in the infected seeds viz Tannim 0.50 ± 0.12, Oxalate 1.60 ± 0.05, Hydrogen cyanide 1.82 ± 0.06, and Saponin 2.50+0.28. However, the nutrient compositions and Phytochemical between the infected and non-infected seeds are not significantly different (p > 0.05).

Keywords: Mycoflora, mucuna sloanei, seeds, phytochemical, nutrient composition

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Authors: Shrikant Charhate, Gayatri Deshpande

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Permeable pavements have significant benefits like managing runoff, infiltration, and carrying traffic over conventional pavements in terms of sustainability and environmental impact. Some of the countries are using this technique, especially at locations where durability and other parameters are of importance in nature; however, sparse work has been done on this concept. In India, this is yet to be adopted. In this work, the progress in the characterization and development of Permeable Articulated Concrete Blocks (PACB) pavement design is described and discussed with reference to Indian conditions. The experimentation and in-depth analysis was carried out considering conditions like soil erosion, water logging, and dust which are significant challenges caused due to impermeability of pavement. Concrete blocks with size 16.5’’x 6.5’’x 7’’ consisting of arch shape (4’’) at beneath and ½” PVC holes for articulation were casted. These blocks were tested for flexural strength. The articulation process was done with nylon ropes forming series of concrete block system. The total spacing between the blocks was kept about 8 to 10% of total area. The hydraulic testing was carried out by placing the articulated blocks with the combination of layers of soil, geotextile, clean angular aggregate. This was done to see the percentage of seepage through the entire system. The experimental results showed that with the shape of concrete block the flexural strength achieved was beyond the permissible limit. Such blocks with the combination could be very useful innovation in Indian conditions and useful at various locations compared to the traditional blocks as an alternative for long term sustainability.

Keywords: connections, geotextile, permeable ACB, pavements, stone base

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Authors: Devina Jain

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The choice between single-use drinking glasses and reusable glasses is of major concern to our lifestyles, and hence, the environment. This study is aimed at comparing three systems - a disposable paper cup, a disposable cup and a reusable stainless steel cup or glass - with respect to their effect on the environment to find out which one is more advantageous for reducing the impact on the environment. Life Cycle Assessment was conducted using modeling software, Umberto NXT Universal (Version 7.1). For the purpose of this study, the cradle to grave approach was considered. Results showed that cleaning is of a very strong influence on the environmental burden by these drinking systems, with a contribution of up to 90 to 100%. Thus, the burden is determined by the way in which the utensils are washed, and how much water is consumed. It maybe seems like a small, insignificant daily practice. In the short term, it would seem that paper and plastic cups are a better idea, since they are easy to acquire and do not need to be stored, but in the long run, we can say that steel cups will have less of an environmental impact. However, if the frequency of use and the number of glasses employed per use are of significance to decide the appropriateness of the usage, it is better to use disposable cups and glasses.

Keywords: disposable glass, life cycle assessment, paper, plastic, reusable glass, stainless steel

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Authors: Hemanth K. Balaga, Prakash Nanthagopalan

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Every year a huge amount of paper gets discarded of which only a minute fraction is being recycled and the rest gets dumped as landfills. Paper fibres can be recycled only a limited number of times before they become too short or weak to make high quality recycled paper. This eventually adds to the already big figures of waste paper that is being generated and not recycled. It would be advantageous if this prodigious amount of waste can be utilized as a low-cost sustainable construction material and make it as a value added product. The generic term for the material under investigation is paper-concrete. This is a fibrous mix made of Portland cement, water and pulped paper and/or other aggregates. The advantages of this material include light weight, good heat and sound insulation capability and resistance to flame. The disadvantages include low strength compared to conventional concrete and its hydrophilic nature. The properties vary with the variation of cement and paper content in the mix. In the present study, Portland Pozzolona Cement and news print paper were used for the preparation of paper concrete cubes. Initially, investigations were performed to determine the minimum soaking period required for the softening of the paper fibres. Further different methodologies were explored for proper blending of the pulp with cement paste. The properties of paper concrete vary with the variation of cement to paper to water ratio. The study mainly addresses the parameters of strength and weight loss of the concrete cubes with age and the time that is required for the dry paper fibres to become soft enough in water to bond with the cement. The variation of compressive strength with cement content, water content, and time was studied. The water loss of the cubes with time and the minimum time required for the softening of paper fibres were investigated .Results indicate that the material loses 25-50 percent of the initial weight at the end of 28 days, and a maximum 28 day compressive strength (cubes) of 5.4 Mpa was obtained.

Keywords: soaking time, difference water, minimum water content, maximum water content

Procedia PDF Downloads 237

Authors: D. Cardone

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Past earthquakes have shown that seismic events may incur large economic losses in buildings. FEMA P-58 provides engineers a practical tool for the performance seismic assessment of buildings. In this study, FEMA P-58 is applied to two typical Italian pre-1970 reinforced concrete frame buildings, characterized by plain rebars as steel reinforcement and masonry infills and partitions. Given that suitable tools for these buildings are missing in FEMA P- 58, specific fragility curves and loss functions are first developed. Next, building performance is evaluated following a time-based assessment approach. Finally, expected annual losses for the selected buildings are derived and compared with past applications to old RC frame buildings representative of the US building stock. 

Keywords: FEMA P-58, RC frame buildings, plain rebars, Masonry infills, fragility functions, loss functions, expected annual loss

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Authors: Do-Kyu Hwang, Ho-Young Kim, Ho-Hyeoung Choi, Gi-Beom Park, Jae-Hoon Lee

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Currently there are many use of threaded reinforcing bars in construction fields because those do not need additional screw processing when connecting reinforcing bar by threaded coupler. In this study, reinforced concrete bridge piers using threaded rebar coupler system at the plastic hinge area were tested to evaluate seismic performance. The test results showed that threads of the threaded rebar coupler system could be loosened while under tension-compression cyclic loading because tolerance and rib face angle of a threaded rebar coupler system are greater than that of a conventional ribbed rebar coupler system. As a result, cracks were concentrated just outside of the mechanical coupler and stiffness of reinforced concrete bridge pier decreased. Therefore, it is recommended that connection ratio of mechanical couplers in one section shall be below 50% in order that cracks are not concentrated just outside of the mechanical coupler. Also, reduced stiffness of the specimen should be considered when using the threaded rebar coupler system.

Keywords: reinforced concrete column, seismic performance, threaded rebar coupler, threaded reinforcing bar

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Authors: Bijit Kalita, R. Jayaganthan

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Additive manufacturing (AM) is a novel manufacturing method which provides more freedom in design, manufacturing near-net-shaped parts as per demand, lower cost of production, and expedition in delivery time to market. Among various metals, AM techniques, Laser Powder Bed Fusion (L-PBF) is the most prominent one that provides higher accuracy and powder proficiency in comparison to other methods. Particularly, 17-4 PH alloy is martensitic precipitation hardened (PH) stainless steel characterized by resistance to corrosion up to 300°C and tailorable strengthening by copper precipitates. Additively manufactured 17-4 PH stainless steel exhibited a dendritic/cellular solidification microstructure in the as-built condition. It is widely used as a structural material in marine environments, power plants, aerospace, and chemical industries. The excellent weldability of 17-4 PH stainless steel and its ability to be heat treated to improve mechanical properties make it a good material choice for L-PBF. In this study, the microstructures of martensitic stainless steels in the as-built state, as well as the effects of process parameters, building atmosphere, and heat treatments on the microstructures, are reviewed. Mechanical properties of fabricated parts are studied through micro-hardness and tensile tests. Tensile tests are carried out under different strain rates at room temperature. In addition, the effect of process parameters and heat treatment conditions on mechanical properties is critically reviewed. These studies revealed the performance of L-PBF fabricated 17–4 PH stainless-steel parts under cyclic loading, and the results indicated that fatigue properties were more sensitive to the defects generated by L-PBF (e.g., porosity, microcracks), leading to the low fracture strains and stresses under cyclic loading. Rapid melting, solidification, and re-melting of powders during the process and different combinations of processing parameters result in a complex thermal history and heterogeneous microstructure and are necessary to better control the microstructures and properties of L-PBF PH stainless steels through high-efficiency and low-cost heat treatments.

Keywords: 17–4 PH stainless steel, laser powder bed fusion, selective laser melting, microstructure, additive manufacturing

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Authors: Shijie Liu, Jehnming Lin

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This study mainly discussed the mechanical properties of selective laser sintered 304L stainless steel powder specimen. According to a single layer specimen sintering, the microstructure and porosity were observed to find out the proper sintering parameters. A multi-layer sintering experiment was conducted. Based on the microstructure and the integration between layers, the suitable parameters were found out. Finally, the sintered specimens were examined by metallographical inspection, hardness test, tensile test, and surface morphology measurement. The structure of the molten powder coated with unmelted powder was found in metallographic test. The hardness of the sintered stainless steel powder is greater than the raw material. The tensile strength is less than the raw material, and it is corresponding to different scanning paths. The specimen will have different patterns of cracking. It was found that the helical scanning path specimen will have a warpage deformation at the edge of the specimen. The S-scan path specimen surface is relatively flat.

Keywords: laser sintering, sintering path, microstructure, mechanical properties

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Authors: Chong Wang, Alexandre Urbano Hoffmann

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Interaction between a crack and a trapezoidal aggregate in a single edge notched concrete beam is simulated using boundary element method with an automatic crack extension program. The stress intensity factors of the growing crack are obtained from the J-integral. Three crack extension paths: deflecting around the particulate, growing along the interface and penetrating into the particulate are achieved in terms of the mismatch state of mechanical characteristics of matrix and the particulate. The toughening is also given by the ratio of stress intensity factors. The results reveal that as stress shielding occurs, toughening is obtained when the crack is approaching to a stiff and strong aggregate weakly bonded to a relatively soft matrix. The present work intends to help for the design of aggregate reinforced concretes.

Keywords: aggregate concrete, boundary element method, two-phase composite, crack extension path, crack/particulate interaction

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Authors: Mohammed A. Sakr, Tarek M. Khalifa, Walid N. Mansour

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External bonding of fiber reinforced polymer (FRP) plates to reinforced concrete (RC) beams is an effective technique for flexural strengthening. This paper presents an analytical parametric study on the behavior of RC continuous beams flexurally strengthened with externally bonded FRP plates on the upper and lower fibers, conducted using simple uniaxial nonlinear finite element model (UNFEM). UNFEM is able to estimate the load-carrying capacity, different failure modes and the interfacial stresses of RC continuous beams flexurally strengthened with externally bonded FRP plates on the upper and lower fibers. The study investigated the effect of five key parameters on the behavior and moment redistribution of FRP-reinforced continuous beams. The investigated parameters were the length of the FRP plate, the width and the thickness of the FRP plate, the ratio between the area of the FRP plate to the concrete area, the cohesive shear strength of the adhesive layer, and the concrete compressive strength. The investigation resulted in a number of important conclusions reflecting the effects of the studied parameters on the behavior of RC continuous beams flexurally strengthened with externally bonded FRP plates.

Keywords: continuous beams, parametric study, finite element, fiber reinforced polymer

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Authors: Yeo Kyeong Lee, Hae Won Min, Ji Yeon Kang, Hee Sun Kim, Yeong Soo Shin

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Fire incidents have been steadily increased over the last year according to national emergency management agency of South Korea. Even though most of the fire incidents with property damage have been occurred in building, rehabilitation has not been properly done with consideration of structure safety. Therefore, this study aims at evaluating rehabilitation effects on fire damaged normal strength concrete beams through experiments and finite element analyses. For the experiments, reinforced concrete beams were fabricated having designed concrete strength of 21 MPa. Two different cover thicknesses were used as 40 mm and 50 mm. After cured, the fabricated beams were heated for 1hour or 2hours according to ISO-834 standard time-temperature curve. Rehabilitation was done by removing the damaged part of cover thickness and filling polymeric mortar into the removed part. Both fire damaged beams and rehabilitated beams were tested with four point loading system to observe structural behaviors and the rehabilitation effect. To verify the experiment, finite element (FE) models for structural analysis were generated using commercial software ABAQUS 6.10-3. For the rehabilitated beam models, integrated temperature-structural analyses were performed in advance to obtain geometries of the fire damaged beams. In addition to the fire damaged beam models, rehabilitated part was added with material properties of polymeric mortar. Three dimensional continuum brick elements were used for both temperature and structural analyses. The same loading and boundary conditions as experiments were implemented to the rehabilitated beam models and non-linear geometrical analyses were performed. Test results showed that maximum loads of the rehabilitated beams were 8~10% higher than those of the non-rehabilitated beams and even 1~6 % higher than those of the non-fire damaged beam. Stiffness of the rehabilitated beams were also larger than that of non-rehabilitated beams but smaller than that of the non-fire damaged beams. In addition, predicted structural behaviors from the analyses also showed good rehabilitation effect and the predicted load-deflection curves were similar to the experimental results. From this study, both experiments and analytical results demonstrated good rehabilitation effect on the fire damaged normal strength concrete beams. For the further, the proposed analytical method can be used to predict structural behaviors of rehabilitated and fire damaged concrete beams accurately without suffering from time and cost consuming experimental process.

Keywords: fire, normal strength concrete, rehabilitation, reinforced concrete beam

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Authors: Inas Kamel, Noor Z. Habib

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Utilizing construction and demolition wastes in hotmix asphalt (HMA) pavement construction can reduce the adverse environmental effect of its inadequate disposal and reduce the pressure of extracting and processing mineral aggregates (MA). This study aims to examine the viability of replacing MA by recycled construction and demolition waste aggregates (RCDWA) in the wearing course of asphaltic concrete (AC) pavements without compromising its loadbearing capacity. The Marshall Method was used to evaluate the performance of AC wearing course specimens by replacing MA by 10%, 20% and 30% RCDWA. Grade 60/70 bitumen was used in the range 3.0-5.5%, with 05% increments, to generate the optimum bitumen content (OBC). From the volumetric analysis and test property curves, the mixture containing 20% RCDWA was chosen as the preferred mix at 5.1% OBC. It possessed a 10% increase in Marshall Stability compared to the reference specimen, containing 100% MA, and a 6% increase in Marshall flow.

Keywords: aggregate, asphaltic concrete, Marshall method, optimum bitumen content, recycled construction and demolition waste

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Authors: Ali Kezmane, Said Boukais, Mohand Hamizi

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This paper presents an analytical study on the behavior of reinforced concrete walls with rectangular cross section. Several experiments on such walls have been selected to be studied. Database from various experiments were collected and nominal shear wall strengths have been calculated using formulas, such as those of the ACI (American), NZS (New Zealand), Mexican (NTCC), and Wood and Barda equations. Subsequently, nominal shear wall strengths from the formulas were compared with the ultimate shear wall strengths from the database. These formulas vary substantially in functional form and do not account for all variables that affect the response of walls. There is substantial scatter in the predicted values of ultimate shear strength. Two new semi empirical equations are developed using data from tests of 57 walls for transitions walls and 27 for slender walls with the objective of improving the prediction of peak strength of walls with the most possible accurate.

Keywords: shear strength, reinforced concrete walls, rectangular walls, shear walls, models

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Authors: Mannal Tariq

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Construction industry is making progress at a high pace. The trend of the world is getting more biased towards the high rise buildings. Deep beams are one of the most common elements in modern construction having small span to depth ratio. Deep beams are mostly used as transfer girders. This experimental study consists of 16 reinforced concrete (RC) deep beams. These beams were divided into two groups; A and B. Groups A and B consist of eight beams each, having 381 mm (15 in) and 457 mm (18 in) depth respectively. Each group was further subdivided into four sub groups each consisting of two identical beams. Each subgroup was comprised of solid/control beam (without opening), opening above neutral axis (NA), at NA and below NA. Except for control beams, all beams with openings were strengthened with carbon fibre reinforced polymer (CFRP) vertical strips. These eight groups differ from each other based on depth and location of openings. For testing sake, all beams have been loaded with two symmetrical point loads. All beams have been designed based on strut and tie model concept. The outcome of experimental investigation elaborates the difference in the shear behaviour of deep beams based on depth and location of circular openings variation. 457 mm (18 in) deep beam with openings above NA show the highest strength and 381 mm (15 in) deep beam with openings below NA show the least strength. CFRP sheets played a vital role in increasing the shear capacity of beams.

Keywords: CFRP, deep beams, openings in deep beams, strut and tie modal, shear behaviour

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Authors: Dimitrios Karanatsis

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Non-crimp fabrics (NCFs) allow for high mechanical performance of a manufacture composite component by maintaining the fibre reinforcements parallel to each other. The handling of NCFs is enabled by the stitching of the tows. Although the stitching material has negligible influence to the performance of the manufactured part, it can affect the ability of the structural fabric to shear and drape over the part’s geometry. High resistance to shearing is attributed to the high tensile strain of the stitching yarn and can cause defects in the fabric. In the current study, a correlation based on the stitch tension and shear behaviour is examined. The purpose of the research is to investigate the upper and lower limits of non-crimp fabrics manufacture and how these affect the shear behaviour of the fabrics. Experimental observations show that shear behaviour of the fabrics is significantly affected by the stitch tension, and there is a linear effect to the degree of shear they experience. It was found that the lowest possible stitch tension on the manufacturing line settings produces an NCF that exhibits very low tensile strain on it’s yarns and that has shear properties similar to a woven fabric. Moreover, the highest allowable stitch tension results in reduced formability of the fabric, as the stitch thread rearranges the fibre filaments where these become packed in a tight formation with constricted movement.

Keywords: carbon fibres, composite manufacture, shear testing, textiles

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Authors: Majid Saaly, Shahriar Tavousi Tafreshi, Mehdi Nazari Afshar

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Most reinforced concrete structures are designed only under heavy loads have large transverse reinforcement spacing values, and therefore suffer severe failure after intense ground movements. The main goal of this paper is to compare the shear- and axial failure of concrete bending frames available in Tehran using incremental dynamic analysis under near- and far-field records. For this purpose, IDA analyses of 5, 10, and 15-story concrete structures were done under seven far-fault records and five near-faults records. The results show that in two-dimensional models of short-rise, mid-rise and high-rise reinforced concrete frames located on Type-3 soil, increasing the distance of the transverse reinforcement can increase the maximum inter-story drift ratio values up to 37%. According to the existing results on 5, 10, and 15-story reinforced concrete models located on Type-3 soil, records with characteristics such as fling-step and directivity create maximum drift values between floors more than far-fault earthquakes. The results indicated that in the case of seismic excitation modes under earthquake encompassing directivity or fling-step, the probability values of failure and failure possibility increasing rate values are much smaller than the corresponding values of far-fault earthquakes. However, in near-fault frame records, the probability of exceedance occurs at lower seismic intensities compared to far-fault records.

Keywords: IDA, failure curve, directivity, maximum floor drift, fling step, evaluating probable bending of frames, near-field and far-field earthquake records

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Authors: Ahsan R. Khokhar, Fizza Hassan

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Alkali-Silica Reaction (ASR) has been recognized as a potential cause of concrete degradation in the world since the 1940s. In Pakistan, mega hydropower structures like dams, weirs constructed from aggregates extracted from a local riverbed exhibited different levels of alkali-silica reactivity over an extended service period. The concrete expansion potential due to such aggregates has been categorized as slow-reactive. Apart from hydropower structures, ASR existence has been identified in the concrete structural elements of a Textile Mill building which used aggregates extracted from the nearby riverbed. The original structure of the Textile Mill was erected in the 80s with the addition of a textile ‘sizing and wrapping’ hall constructed in the 90s. In the years to follow, intensive spalling was observed in the structural members of the subject hall; enough to threat to the overall stability of the building. Limitations such as incomplete building data posed hurdles during the detailed structural investigation. The paper lists observations made while assessing the extent of damage and its effect on the building hall structure. Core testing and Petrographic tests were carried out as per the ASTM standards for strength degradation analysis followed by the identifying its root cause. Results confirmed significant structural strength reduction because of ASR which necessitated the formulation of an immediate re-strengthening solution. The paper also discusses the possible tracks of rehabilitative measures which are being adapted to stabilize the structure and seize further concrete expansion.

Keywords: Alkali-Silica Reaction (ASR), concrete strength degradation, damage assessment, damage evaluation

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Authors: Jagannath Prasad Tegar, Zeeshan Ahmad

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The Ordinary Portland Cement (OPC) is a major constituent of concrete, which is being used extensively since last half century. The production of cement is impacting not only environment alone, but depleting natural materials. During the past 3 decades, the scholars have carried out studies and researches to explore the supplementary cementatious materials such as Ground granulated Blast furnace slag (GGBFS), silica fumes (SF), metakaolin or fly ash (FA). This has contributed towards improved cementatious materials which are being used in construction, but not the way it is supposed to be. The alkali activated slag concrete is another innovation which has constituents of cementatious materials like Ground Granuled Blast Furnace Slag (GGBFS), Fly Ash (FA), Silica Fumes (SF) or Metakaolin. Alkaline activators like Sodium Silicate (Na₂SiO₃) and Sodium Hydroxide (NaOH) is utilized. In view of evaluating properties of alkali activated slag concrete blended with polypropylene shredding and accelerator, research study is being carried out. This research study is proposed to evaluate the effect of polypropylene shredding and accelerating admixture on mechanical properties of alkali-activated slag concrete. The mechanical properties include the compressive strength, splitting tensile strength and workability. The outcomes of this research are matched with the hypothesis and it is found that 27% of cement can be replaced with the ground granulated blast furnace slag (GGBFS) and for split tensile strength 20% replacement is achieved. Overall it is found that 20% of cement can be replaced with ground granulated blast furnace slag. The tests conducted in the laboratory for evaluating properties such as compressive strength test, split tensile strength test, and slump cone test. On the aspect of cost, it is substantially benefitted.

Keywords: ordinary Portland cement, activated slag concrete, ground granule blast furnace slag, fly ash, silica fumes

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Authors: Gamal Alamri, Tariq Iqbal

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This paper presents an optimum designs and thermal analysis of concrete house in the hot climate of Libya. For this goal we have used BEopt software (building energy optimization) that provides capabilities for estimating residential building design and thermal analysis. The most area of the house that is exposed to the sunlight’s is the roof leading to heat gain. Therefore, house cooling consumes high energy. The cooling energy consumption is three times the heating energy consumption. In order to maintain comfortable indoor conditions in a low-energy house, the entire building envelope needs to be perfectly insulated and prevented from air leakages. Insulated roof is selected to reduce cooling demand, and the paper presents details and BEopt simulation results. Designed house needs 12.02mmbtus/year. Furthermore, the modeling indicates that the designed house is close to achieving the Passive standard.

Keywords: concrete house design, thermal analysis, hot climate, BEopt software

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Authors: Nasim Fallahi, Erasmo Carrera, Alfonso Pagani

Abstract:

Variable angle tow describes the fibres which are curvilinearly steered in a composite lamina. Significantly, stiffness tailoring freedom of VAT composite laminate can be enlarged and enabled. Composite structures with curvilinear fibres have been shown to improve the buckling load carrying capability in contrast with the straight laminate composites. However, the optimal design and analysis of VAT are faced with high computational efforts due to the increasing number of variables. In this article, an efficient optimum solution has been used in combination with 1D Carrera’s Unified Formulation (CUF) to investigate the optimum fibre orientation angles for buckling analysis. The particular emphasis is on the LE-based CUF models, which provide a Lagrange Expansions to address a layerwise description of the problem unknowns. The first critical buckling load has been considered under simply supported boundary conditions. Special attention is lead to the sensitivity of buckling load corresponding to the fibre orientation angle in comparison with the results which obtain through the Genetic Algorithm (GA) optimization frame and then Artificial Neural Network (ANN) is applied to investigate the accuracy of the optimized model. As a result, numerical CUF approach with an optimal solution demonstrates the robustness and computational efficiency of proposed optimum methodology.

Keywords: beam structures, layerwise, optimization, variable stiffness

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Authors: B. S. Abdelwahed, B. B. Belkassem

Abstract:

Beam-column joints are a critical part in reinforced concrete RC frames designed for inelastic response to several external loads. Investigating the behaviour of the exterior RC beam-column joints has attracted many researchers in the past decades due to its critical influence on the overall behaviour of RC moment-resisting frames subjected to lateral loads. One of the most critical zones in moment-resistant frames is the knee joints because of restraints associated with providing limited anchorage length to the beam and column longitudinal reinforcement in it and consequentially causes a lot of damage in such building frames. Previous numerical simulations focussed mainly on the exterior and interior joints, for knee joint further work is still needed to investigate its behaviour and discuss its affecting parameters. Structural response for an RC knee beam-column joint is performed in this study using LS-DYNA. Three-dimensional finite element (FE) models of an RC knee beam-column joint are described and verified with experimental results available in literature; this is followed by a parametric study to investigate the influence of the concrete compressive strength, the presence of lateral beams and increasing beam reinforcement ratio. It is shown that the concrete compressive strength has a significant effect on shear capacity, load-deflection characteristics and failure modes of an RC knee beam-column joints but to a certain limit, the presence of lateral beams increased the joint confinement and reduced the rate of concrete degradation in the joint after reaching ultimate joint capacity, added to that an increase in the maximum load resistance. Increasing beam reinforcement ratio is found to improve the flexural resistance of the anchored beam bars and increase the joint maximum load resistance.

Keywords: beam reinforcement ratio, joint confinement, numerical simulation, reinforced concrete beam-column joints, structural performance

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Authors: S. Bouhouche, R. Drai, J. Bast

Abstract:

This paper is concerned with a method for uncertainty evaluation of steel sample content using X-Ray Fluorescence method. The considered method of analysis is a comparative technique based on the X-Ray Fluorescence; the calibration step assumes the adequate chemical composition of metallic analyzed sample. It is proposed in this work a new combined approach using the Kalman Filter and Markov Chain Monte Carlo (MCMC) for uncertainty estimation of steel content analysis. The Kalman filter algorithm is extended to the model identification of the chemical analysis process using the main factors affecting the analysis results; in this case, the estimated states are reduced to the model parameters. The MCMC is a stochastic method that computes the statistical properties of the considered states such as the probability distribution function (PDF) according to the initial state and the target distribution using Monte Carlo simulation algorithm. Conventional approach is based on the linear correlation, the uncertainty budget is established for steel Mn(wt%), Cr(wt%), Ni(wt%) and Mo(wt%) content respectively. A comparative study between the conventional procedure and the proposed method is given. This kind of approaches is applied for constructing an accurate computing procedure of uncertainty measurement.

Keywords: Kalman filter, Markov chain Monte Carlo, x-ray fluorescence calibration and testing, steel content measurement, uncertainty measurement

Procedia PDF Downloads 266