Jan'20

The IUP Journal of Structural Engineering

Focus

parametric study of tall structures with diagrid structural system. In the diagrid structural system, the exterior is designed with diagonal members which resist the lateral forces with development of axial force action. Five buildings with storeys ranging from 12 to 60 floors with a typical plan layout were selected, provided with diagrid in the 4, 6 and 8 storeys and analyzed. Diagrid structural system differs from conventional braced systems. In such configurations, vertical columns in the outer periphery are eliminated. The gravity loads are shared by interior columns and diagrids almost equally. Further, most of the lateral loads are resisted by diagrids only. The case study buildings have been designed for gravity loads, earthquake and wind loads. It is assumed to be located in Zone V of India, which is considered to be a highly seismic zone. ETABS 2017 software has been used. The results indicate that earthquake forces are dominant up to 24 storeys and above that wind forces dominate. As the height of structure increases, the modal time period too increases, and it means that the building becomes more flexible. The shorter height buildings are stiffer and thus attracts more lateral forces and hence exhibit more base shear. The authors conclude that diagrid systems are a better solution for lateral load resistance. As the structures' height increases, the building becomes more flexible and resistance to wind forces decreases. The findings are not surprising. Hence, each tall structure must be designed with careful assessment for all forces, and for safety the resistance in the system must be provided accordingly to bear the effect of such forces.

The second paper, "Seismic Response of Shear Wall Buildings with Rigid and Flexible Foundations", by Shradha Patil and Kiran Koraddi, evaluates the behavior of buildings with shear wall and having rigid or flexible foundations. The shear walls are provided in the buildings to resist lateral forces. When a solid slab called raft or mat is designed below columns, it is a rigid foundation system and when isolated footings are designed below columns, then they are assumed as flexible. Generally, structures are considered to be fixed at base for analysis and design, but it is a well-known fact that the foundations and the soil supporting it also participate in shaking. Thus the effect of soil-structure interaction must be considered in the analysis. The inclusion of soil effect in analysis makes it more complicated. Here the building is assumed to be founded on soft soil. In the study, a 16-storey building is considered and analyzed, considering its fixed base and also including the soil foundation effect. For modeling of soil with springs, FEMA 356 guidelines are used. The building is analyzed using ETABS 2015 software. The results indicate that natural time period increases with inclusion of soil foundation in the analysis than with base fixed case. Similarly, base shear decreases when soil-structure interaction is considered in the analysis than in the case of base fixed. Storey drift values are higher in case of buildings with consideration of soil structure.

The third paper, "A Study on Electrically Conductive Concrete Made with Industrial Waste", by M Purushothaman, studies the behavior of concrete with addition of industrial waste. Genearlly, it is observed that normal concrete does not conduct electricity, but it may exhibit electrical conductivity when some conductive material is added to conventional concrete. Different types of industrial wastes like aluminum, steel, brass powder, blast furnace slag and cast iron are available. Similarly, fly ash in abundance is also readily available. The author has studied the workability of concrete with waste addition to find its suitability for further investigation. The results indicate that only bottom ash and copper slag are suitable material to make concrete by replacing fine aggregate. Two types of concrete mixes using bottom ash and copper slag were prepared with these chosen materials and tested. Experimental work was carried out in four stages. The first stage was preliminary testing to obtain specific gravity, etc., and the second stage dealt with mix proportioning by conducting several trials with chosen conductive materials. The third stage involved casting of specimens and testing as per Indian Standards. The fourth stage dealt with resistivity test and heating tests. The results indicate better compressive strength of concrete with use of copper slag than bottom ash. Water absorption in case of copper slag is less. The use of conductive material in concrete reduces the resistivity. It is observed that the copper slag concrete shows better resistivity than bottom ash concrete. The authors conclude that bottom ash in the conventional concrete improves conductivity and may be considered a good ingredient for making conductive concrete.

The last paper, "Shear Capacity of Headed Studs in Steel-Concrete Structures: Analytical Prediction via Soft Computing", by Miguel Abambrres and Jun He, evaluates analytically the shear capacity of shear connectors. Shear connectors are generally used on top of steel girders to transfer longitudinal forces coming through concrete deck in bridges. These connectors are used in building works too. Codes provide empirical equations to predict shear capacity of a shear connector and it is used in design. The authors have used Artificial Neural Network (ANN) technique to estimate the shear capacity of headed studs. The shear connector capacity is generally found by push out test. ANN-based solutions often outperform those provided by traditional approach. ANN requires various combinations of variables to arrive at convergence. Thus the study has reduced the computing time by cutting the number of variable combinations in ANN to be run on computer. The study outlines a way to use ANN for the problem of shear connector capacity determination. The proposed ANN-based analytical model yielded values close to the values found by other researchers.

- Satyendra P Gupta
Consulting Editor

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Article   Price (₹) Buy
A Parametric Study of Tall Structures with Diagrid
50
Seismic Response of Shear Wall Buildings with Rigid and Flexible Foundations
50
A Study on Electrically Conductive Concrete Made with Industrial Waste
50
Shear Capacity of Headed Studs in Steel-Concrete Structures: Analytical Prediction via Soft Computing
50
     
Contents : (Jan 2020)

A Parametric Study of Tall Structures with Diagrid
Ajaykumar G Shah and Vishal B Patel

The paper makes an attempt to parametric study the tall structures with diagrid structural system. Diagrid is an exterior structural system which resists the lateral forces by axial actions of diagonals provided in periphery. The main objective is to determine the optimum module size of diagrid. The study considers five steel buildings having typical plan area, and loadings of 12, 24, 36, 48 and 60 storeys were analyzed for the 4, 6 and 8 storey diagrid module size. The analysis was carried out in ETABS 2017 software. Various parameters like fundamental time period, maximum storey displacement, maximum storey drift, maximum base shear were considered.


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Article Price : ₹ 50

Seismic Response of Shear Wall Buildings with Rigid and Flexible Foundations
Shradha Patil and Kiran Koraddi

The significance of incorporating Soil Structure Interaction (SSI) effect in the analysis and design of RC framed structure is increasingly recognized but still has not penetrated to the large level owing to various complexities involved. It is a well-established fact that the SSI effect considerably influences the design of high-rise storey buildings subjected to lateral seismic loads. The shear walls are often provided in such structure to increase the lateral stability to resist seismic lateral loads. The paper presents a linear soil structure analysis of a G + 15 storey RC shear wall building frame resting on isolated footing and raft foundations and supported by deformable soil. The modeling and analysis is carried out using ETABS 2015 software under gravity loads and seismic loads. The interaction work analysis is carried out with and without shear wall to study the effect of inclusion of shear wall on the forces in the footing due to settlement of soil mass. Both the frame and soil mass are considered to behave in a linear elastic manner. It is observed that the SSI effect significantly alters the time period, base shear, stiffness, storey drift and storey forces of the building due to soil settlement. The non-interaction analysis of space frame shear wall suggests that the presence of shear wall significantly reduces time period and displacement of the building but the interaction effect causes restoration of time period and displacement to a great extent.


© 2020 IUP. All Rights Reserved.

Article Price : ₹ 50

A Study on Electrically Conductive Concrete Made with Industrial Waste
M Purushothaman

Generally, conventional concrete does not conduct electricity but conducts when some conductive components are added to the conventional concrete. This concrete is called Electrically Conductive Concrete (ECC). The paper studies the suitability of industrial waste materials for making ECC. Different industrial wastes such as lathe turns of aluminum and steel, powder of brass and cast iron, copper slag and lignite bottom ash were used as conductive materials. It was observed that industrial wastes such as bottom ash and copper slag were suitable materials for making concrete by replacing fine aggregate. From the number of trials, the optimum quantity of industrial waste to replace the conventional fine aggregate river sand was found. Then two different ECC mixes, Mix with Bottom Ash (MBA) and Mix with Copper Slag (MCS), were prepared based on volume basis. The strength, electrical resistivity and thermal properties of both the ECC specimens were studied.

© 2020 IUP. All Rights Reserved.

Article Price : ₹ 50

Shear Capacity of Headed Studs in Steel-Concrete Structures: Analytical Prediction via Soft Computing
Miguel Abambres and Jun He

Headed studs are commonly used as shear connectors to transfer longitudinal shear force at the interface between steel and concrete in composite structures (e.g., bridge decks). Code-based equations for predicting the shear capacity of headed studs are summarized. The paper proposes an Artificial Neural Network (ANN)-based analytical model to estimate the shear capacity of headed steel studs. 234 push-out test results from the previous published research were collected into a database in order to feed the simulated ANNs. Three parameters were identified as input variables for the prediction of the headed stud shear force at failure, namely, the steel stud tensile strength, diameter and the concrete (cylinder) compressive strength. The proposed ANN-based analytical model yielded maximum and mean relative errors of 3.3% and 0.6%, respectively, for all the collected data. Moreover, it is illustrated that the neural network approach clearly outperformed the existing code-based equations, which yielded mean errors greater than 13%.

© 2020 IUP. All Rights Reserved.

Article Price : ₹ 50

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