Jan'21

The IUP Journal of Structural Engineering

Focus

For the beam, it was found that the compressive, bending and shear strengths of cold formed section are higher than tubular steel section. It was further observed that the strength comparison for section under compression, bending and shear as per American standard is lesser than those calculated using British standards. It is felt that the Effective Width Method (EWM) is more cumbersome than Direct Strength Method (DSM) in design of portal frame which is under investigation. The authors have prepared ready-to-use table of load bearing capacities for different cold formed studs under compression, bending and shear. It is stated that such tables could be used by practicing engineers using EWM for strength calculations.

The second paper, "Soil-Structure Interaction of RC Building with Homogeneous and Non-Homogeneous Soil Condition: A Comparative Study" by Pavan Kumar C S and C M Ravi Kumar, investigates the effect of Soil Structure Interaction (SSI) of RC building. The authors have considered homogeneous and non-homogeneous types of soil under the structure foundation system. It should be realized that SSI effect may be small on dynamic response of many structures, but it may be quite significant in some cases. To consider soil effects, two methods are common, viz., direct and substructure approaches. In direct approach, soil and structure are included in the same dynamic model and analyzed as a complete system. But in substructure approach, the SSI is divided into distinct systems and they are combined to formulate the complete solution. In this study, ten-storey RC building is considered to be located in different seismic zones for analysis with fixed base and also having homogeneous and non-homogeneous soil underneath. When the building is considered fixed, the response is studied and lateral displacements along longitudinal and transverse direction of the building in two seismic zones of the country are calculated. Further, storey drift and base shear in fixed base condition are determined. For consideration of homogeneous soil condition, same material properties of soil are assigned for building response calculation. For non-homogeneous soil conditions, different soil properties at various depths of foundation are determined and used in the response analysis. It is found that seismic response of multi-storey building increases for flexible base condition than a fixed base condition. Thus, consideration of SSI effect becomes important. This study also indicates that structure response is more when non-homogeneous soil conditions are used. Though consideration of non-homogeneous soil condition in the analysis makes it more complex, with finite element analysis software, these complexities can be handled easily and analysis can be performed with reasonable accuracy.

The last paper, "Passive Seismic Protection of Shear Building Using Shape Memory Alloy-Based Tension Sling Damper" by Sujata H Mehta and Sharadkumar Purohit, studies the provision of tension damper to control seismic response of structure. For controlling the excessive response of structures during excitation, base isolation technique and some damping devices are frequently used. But provision of base isolation increases the natural period of the structure and reduces its acceleration response and works quite effectively for stiff structures. For other types of structures, primary damping mechanism is activated through passive energy dissipation mechanism. Shape Memory Alloys (SMA) are a new class of materials with unique characteristics and are being tried as damping devices. Improved damping characteristics and added stiffness offered by SMA when stretched due to input motion make it a candidate for developing passive, semi-active and hybrid control device for controlling structural response. Memory alloy tension sling damper using Tanaka model with isothermal conditions is studied. Equivalent linear model for damper is developed using Voigt model for linear dynamic theory for viscoelastic material with memory effect. The authors have used plane frame model with fixed base and also used one- and two-shaped memory alloy tension sling dampers. The ten-storey building considered is excited using strong motion data of El Centro 1940 earthquake with levels 50%, 100% and 150%. It is also excited using pulse type Kobe earthquake with level of 50%. For different models, seismic parameters like peak displacement, inter storey drift, acceleration and peak damper force are evaluated. It is found that building with two-shaped memory alloy tension sling damper very effectively controls seismic response for all types of seismic excitations and shows better performance compared to one-tension sling damper.

- Satyendra P Gupta
Consulting Editor

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Strength of Cold Formed Steel Sections: A Comparative Study Using Different International Standards
50
Soil-Structure Interaction of RC Building with Homogeneous and Non-Homogeneous Soil Condition: A Comparative Study
50
Passive Seismic Protection of Shear Building Using Shape Memory Alloy-Based Tension Sling Damper
50
     
Contents : (Jan 2021)

Strength of Cold Formed Steel Sections: A Comparative Study Using Different International Standards
M Jain, N Binnani and R K Khare

Cold Formed Steel (CFS) members are generally thin-gauged bent steel sheets or rolled into different shapes at ambient temperature which can carry significant load. They are used as the main component for construction of light gauge steel frame structures. However, being a thin-walled member, they often show many instability phenomena such as local buckling, distortional buckling and global buckling. Effective Width Method (EWM) and Direct Strength Method (DSM) are used to calculate the strength of CFS members. American standards (AISI S100) recommend both methods, whereas British Standard (BS 5950-5) uses EWM for design. DSM requires computational tools such as CUFSM (Constrained and Unconstrained Finite Strip Method), which is an open source software to determine the strength and buckling behavior of member. In this paper, a simple portal frame is designed using Tubular hot rolled steel section and CSF sections, and required quantity of steel has been compared. Also, design strengths of different cold formed Steel Stud Manufacture Association (SSMA) studs under compression (braced column), bending (laterally stable beam), and shear have been compared as per provisions mentioned in American (AISI S100) and British (BS 5950-5) standards. The results of the strength comparison can be further used as reference material by engineers.


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Soil-Structure Interaction of RC Building with Homogeneous and Non-Homogeneous Soil Condition: A Comparative Study
Pavan Kumar C S and C M Ravi Kumar

Design of a pile foundation involves solving the complex problem of transferring loads from the structure through the piles to the underlying soil. It involves the analysis of a structure-pile system, the analysis of a soil-pile system and the interaction of the two systems, which is highly nonlinear. Close cooperation between the structural engineers and geotechnical engineers is essential to the development of an effective design. Many factors must be considered when selecting an appropriate foundation for a hydraulic structure. Information is presented to identify the feasible foundation alternatives for a more detailed study. This coordination extends through plans and specifications, preconstruction meetings and construction. Some of the critical aspects of the design process require coordination. In this paper, a comparative study is made on the sesmic behavior of Soil-Structure Interaction (SSI) of RC building with homogeneous and non-homogeneous soil conditions.


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Article Price : ₹ 50

Passive Seismic Protection of Shear Building Using Shape Memory Alloy-Based Tension Sling Damper
Sujata H Mehta and Sharadkumar Purohit

Passive control force is obtained from Shape Memory Alloy-based Tension Sling Damper (SMA-TSD) fitted to a seismically excited 10 storeyed shear building. One-dimensional Tanaka model is considered to represent the hysteresis behavior of SMA-TSD. This exhibits a nonlinear relationship between damper force and input states; hence, its implementation with linear system is a nontrivial task. In the paper, SMA-TSD is represented by Voigt model comprising equivalent stiffness and damping components derived by mapping it with flag-shaped hysteresis loop defined by Tanaka model. The results for controlled response of the buildings are obtained in terms of peak response quantities, i.e., interstorey drift, displacement and acceleration. One SMA-TSD fitted at ground storey of the building yields moderate control (~29%) in peak response quantities. However, peak response quantities reduce substantially (~53%) for different levels of El Centro seismic excitations and moderately (~19%) for 50% Kobe seismic excitation when two SMA-TSDs are used in the building. The efficacy of SMA-TSD implemented in the study is a function of design parameters, diameter of SMA wire and length of SMA wire, and can be optimized.

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Article Price : ₹ 50

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