April'21

The IUP Journal of Structural Engineering

Focus

This issue consists of four papers. The first paper, "Wind-Induced Ovalling Effect on Cylindrical Wall of Ground Elevated Empty Reinforced Concrete Silo", by Amiya K Samanta, studies the effect of wind on concrete silo. The author has used analytical approach to study the effect of wind on ground elevated reinforced concrete silo. Ground elevated reinforced concrete silo is used in coal and cement industries, power plants and similar setups. In this study, using static approach of analysis, only ground elevated type silo with different height-to-diameter ratios is considered. With different height and diameter ratios, several models of silo have been considered. The study, first, focuses on the silo wall under wind excited deformation. Then, a numerical approach has been used. The entire silo structure columns, ring beam, conical hopper and roof slab have been modeled with Abaqus in three dimensions. The structure is assumed to be fixed at the top of raft for analysis. The results obtained indicate that finite element analysis values for hoop stresses are significantly lower than the values obtained in analytical results. The analytical study provides values only for hoop stress, whereas finite element analysis provides not only hoop stress but also longitudinal and vertical stress which could be significant in design. It is found that the values of hoop stress and vertical stress are of significant concern in designing and detailing such structures. The study concludes that cylindrical walls of silo structures are prone to ovalization when subjected to wind effects.

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The second paper, "Optimization of Steel Trusses Using Genetic Algorithm", by Kiran R Naik and Kiran Koraddi, studies steel truss optimization. Optimization is increasingly being used in construction industry to save material uses. Weight optimization is one of the structural engineering problems to minimize use of components in construction. With this, saving is achieved in the cost of the project. Three types of structural optimization are generally used in steel construction, viz., weight, size and shape. The objective is to understand various types of optimization methods developed and to understand the processes and its applications in structural engineering problems. The study chooses three demonstrative examples and applies genetic algorithm to solve the problem. The analyzed results using MATLAB are compared with STAAD Pro software. The results show that both MATLAB and STAAD Pro results vary slightly because of rounding off the values. But the difference between the two is not very large. The two-bar truss example shows a saving in weight by 34.72% as compared to manual design. The three-bar truss example shows a saving in weight by 22.58%. The ten-bar truss example shows a weight optimization of 33.85%. These reductions in weight are quite significant as compared to manual conventional design of truss elements.

The third paper, "Experimental Investigation of Concrete Filled Steel Tube (CFST) Columns", by Malatesh Ganiger, Pavan V Gudi and Sachin R Kulkarni, investigates the behavior of concrete filled steel tube. In high-rise construction, Concrete Filled Steel Tube (CFST) columns are being extensively used. The main objective of this study is to understand the behavior of such columns filled with M40 concrete with w/c ratio kept at 0.45 and having different slenderness ratio. The concrete used has been prepared as per IS:10262-2019 and cured for 28 days before testing. Ultimate axial load carrying capacity and failure mechanism is observed. Load deflection curve is also plotted. The authors conclude that the load carrying capacity of specimens used gradually decreased with increase in slenderness ratios. This is natural. The modes of failure for some specimens were crushing of concrete without yielding, whereas some other specimens showed yielding with optimum behavior at failure stage. The specimens whose slenderness ratios were high failed by buckling. A few test specimens possessed sufficient amount of strength and rigidity. The load deflection curve plotted showed a good energy dissipation capacity of the specimens.

The last paper, "Strength Properties of Concrete by Partial Replacement of Cement with Egg Shell Powder and Fly Ash: An Experimental Study", by M Vijaya Sekhar Reddy and K Chandrasekhar Reddy, studies the strength of concrete by partially replacing cement with egg shell powder and fly ash. Numerous publications are available on replacement of cement with fly ash, but replacing it with egg shell powder seems to be a new addition in this area. Egg shell is a calcium-rich substance which has a chemical composition nearly same as that of lime stone. Lime stone has been successfully used as partial substitute for cement. For making concrete in the study, ordinary portland cement, crushed granite rock, well-graded river sand, fly ash and crushed egg shell powder were used. The quantity of cement used was reduced with the use of egg shell powder and fly ash. Broken egg shells were cleaned, crushed, air-dried and sieved to obtain its powder for use. The egg shell powder varied from 0% to 15% in steps and fly ash varied from 0% to 30% in preparation of concrete. VaraplastSP123 superplasticizer was also used. Concrete mix design of M30 grade was prepared as per IS: 10262-2009. Cubes of various concrete mixes were cast to test compressive strength and cylinders were used for tensile strength. The study shows that with 15% replacement of cement by egg shell powder, the compressive strengths obtained for seven days and twenty eight days test were 29.67 Mpa and 39.75 Mpa, respectively. For same duration test, the maximum split tensile strengths were 2.72 MPa and 4.10 MPa. The other trial mixes did not reach the desired target strength because of slow pozzolanic reaction of fly ash.

- Satyendra P Gupta
Consulting Editor

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Article   Price (₹) Buy
Wind-Induced Ovalling Effect on Cylindrical Wall of Ground Elevated Empty Reinforced Concrete Silo
50
Optimization of Steel Trusses Using Genetic Algorithm
50
Experimental Investigation of Concrete Filled Steel Tube (CFST) Columns
50
Strength Properties of Concrete by Partial Replacement of Cement with Egg Shell Powder and Fly Ash: An Experimental Study
50
     
Contents : (April 2021)

Wind-Induced Ovalling Effect on Cylindrical Wall of Ground Elevated Empty Reinforced Concrete Silo
Amiya K Samanta

Wind-induced ovalling effect on the cylindrical wall of single flexible empty steel silo has been studied by various investigators in the past. The paper presents the same effect on cylindrical wall of ground elevated rigid (reinforced concrete) silo using a very simplified analytical approach, which may easily be accessed by practicing engineers for the purpose of design. An approximate analysis of circular cross-section of silo is performed to evaluate the effect of ovalling, but the same is much on conservative end, and also it cannot provide the effect to be taken into consideration for the entire height of the silo. To make the design procedure simple and cost-effective, a few case studies have been performed using the actual wind load distribution and numerical/finite element model in Abaqus. The results obtained from the three-dimensional finite element model of the silo show that the values of deformation and stresses obtained are much on lower end compared to the results of approximate analysis in bending of silo wall, whereas it also evaluates longitudinal stress which is equally significant. The paper also proposes graphs/charts to derive a modification factor over the values obtained by analytical/approximate method so that the designers and practicing professionals may take appropriate measures in the process of designing and detailing of the silo wall without going for detailed investigation of the model under consideration.


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Article Price : ₹ 50

Optimization of Steel Trusses Using Genetic Algorithm
Kiran R Naik and Kiran Koraddi

The use of optimization process is a much-needed step in the field of construction today. But optimization is not being used very efficiently in structural engineering. Weight optimization is one of the structural optimization processes which optimizes the weight of the material used in the construction. The process provides an optimum area of cross-section for the steel sections. By optimizing the weight, the material cost has been reduced. It helps in improving the economic sustainability. The paper presents a study of optimization of trusses using genetic algorithm. The trusses considered for optimization are a two-bar truss, a three-bar truss and a ten-bar truss. The software used for this process is MATLAB2013a. The results are cross-checked using STAAD.Pro and manual calculations.


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Experimental Investigation of Concrete Filled Steel Tube (CFST) Columns
Malatesh Ganiger, Pavan V Gudi and Sachin R Kulkarni

Concrete Filled Steel Tube (CFST) is a composite material which is currently used in high-rise buildings due to excellent seismic-resistant structural properties. CFST columns combine the best characteristics of both steel and concrete material, since they have high strength, ductility and high stiffness. The paper investigates the effect of slenderness ratio on behavior of CFST columns under axial compression for mix design of M40 grade concrete with w/c 0.45 as per IS: 10262 (2019) for 28 days curing period. Nine specimens with heights ranging from 350 mm to 750 mm with intervals of 50 mm were tested under axial compression. The slenderness ratio (L/D) is varied from 3 to 7. The effect of slenderness ratio on ultimate load carrying capacity is studied. It is observed that an increase in slenderness ratio gradually decreased the ultimate load carrying capacity of CFST. The large slenderness ratio specimens resulted in failure by buckling. The shorter columns are failed by crushing of the concrete. The effect of failure mechanism is also studied. It is noticed that as load approached the ultimate load the strains gradually increased. A relation between load and deflection is plotted. The effect of varying slenderness ratios on axially loaded CFST columns depends upon the geometric and material properties under short-term and long-term loadings.

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Strength Properties of Concrete by Partial Replacement of Cement with Egg Shell Powder and Fly Ash: An Experimental Study
M Vijaya Sekhar Reddy and K Chandrasekhar Reddy

The carbon dioxide produced by cement industries causes environmental pollution and global warming. In 1000 Kg of cement manufacturing processes, approximately 900 Kg of CO2 is emitted. In order to reduce the impact of cement production on atmosphere, waste bi-products are used as admixture. In India, every year 75 million tons of fly ash, which are rich in silica, are disposed to landfill as waste. Also, Egg Shell Powders (ESP), which are rich in calcium, are thrown away as waste. In the paper, these two wastes are used as a partial replacement of cement, and various properties like workability, compressive strength, split tensile strength and flexural strength are studied. ESP was varied up to 15.0% (0%, 2.5%, 5%, 7.5%, 10%, 12.5% and 15%) and fly ash was added to cement from 0% to 30% (0%, 5%, 10%, 15%, 20%, 25% and 30%). The results further showed that addition of fly ash along with ESP is beneficial for improved performance of concretes.

© 2021 IUP. All Rights Reserved.

Article Price : ₹ 50