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Badri R.K.,Islamic Azad University at Tehran | Nekooei M.,Islamic Azad University at Tehran | Moghadam A.S.,Structural Engineering Research Center
Journal of Earthquake Engineering | Year: 2015

This study primarily investigates if the building asymmetry changes the variance of collapse capacity. The example models are five-story reinforced concrete buildings. The variance of collapse capacity is evaluated by first-order-second-moment method. There is a difference between the results of symmetric and asymmetric building models, independent of torsional behavior. The influence of record-to-record variability is more important than the effects of modeling uncertainty on the variance of collapse capacity. Plastic rotation capacity is the most important contributor to the variance of collapse capacity of high ductile buildings independent of the asymmetry. © Taylor and Francis Group, LLC.


Parulekar Y.M.,Bhabha Atomic Research Center | Reddy G.R.,Bhabha Atomic Research Center | Vaze K.K.,Bhabha Atomic Research Center | Guha S.,Bhabha Atomic Research Center | And 3 more authors.
Structural Control and Health Monitoring | Year: 2012

SUMMARY Smart materials such as shape memory alloys (SMAs) are recently being used in earthquake engineering applications to control the response of structures. In this paper, a shape-memory alloy damper device made up of austenite wires (e.g. Nickel Titanium wires) is used as a passive energy absorber. NiTi wires are very attractive for passive vibration control as they have a pseudo-elastic property and can sustain large amounts (upto 10% strain) of inelastic deformation. Moreover, in contrast to regular metallic materials they can recover that deformation. The damper device is designed, fabricated and tested. Validity study is made using a thermo-mechanical model of SMA taking into account the residual martensite accumulation irreversibly due to cyclic forward/reverse martensitic transformation. Further an analytical study of a supporting steel structure of dump tanks with and without SMA dampers subjected to design wave earthquake loading is carried out. Performance of the structure with SMA dampers is compared with that of the same structure with yielding dampers. Copyright © 2010 John Wiley & Sons, Ltd.


Poursha M.,Sahand University of Technology | Khoshnoudian F.,Amirkabir University of Technology | Moghadam A.S.,Structural Engineering Research Center
Soil Dynamics and Earthquake Engineering | Year: 2014

This paper aims to extend the consecutive modal pushover (CMP) procedure for estimating the seismic demands of two-way unsymmetric-plan tall buildings subjected to bi-directional seismic ground motions taking the effects of higher modes and torsion into account. Multi-stage and single-stage pushover analyses are carried out in both X and Y directions. Inelastic seismic responses obtained by multi-stage and single-stage pushover analyses for X and Y directions are combined using the SRSS combination scheme. The final seismic responses are determined by enveloping the combined results of multi-stage and single-stage pushover analyses. To evaluate the accuracy of the proposed procedure, it is applied to two-way unsymmetric-plan tall buildings which include torsionally stiff and torsionally flexible systems. The results derived from the CMP procedure are compared with those from nonlinear response history analysis (NL-RHA), as a benchmark solution. Moreover, the advantages of the proposed procedure are demonstrated by comparing the results derived from the CMP to those from pushover analysis with uniform and fundamental effective mode distributions. The proposed procedure is able to accurately predict amplification or de-amplification of the seismic displacements at the flexible and stiff edges of the two-way unsymmetric-plan tall buildings by considering the effects of higher modes and torsion. The extended CMP procedure can accurately estimate the peak inelastic responses, such as displacements and storey drifts. The CMP procedure features a higher potential in estimating plastic hinge rotations at both flexible and stiff sides of unsymmetric-plan tall buildings under bi-directional seismic excitation when compared to the uniform and fundamental effective mode force distributions. © 2014 Elsevier Ltd.


Prasad Rao N.,Structural Engineering Research Center | Samuel Knight G.M.,Anna University | Mohan S.J.,Structural Engineering Research Center | Lakshmanan N.,Structural Engineering Research Center
Engineering Structures | Year: 2012

The towers are vital components of the transmission lines and hence, accurate prediction of their failure is very important for the reliability and safety of the transmission system. When failure occurs, direct and indirect losses are high, leaving aside other costs associated with power disruption and litigation. Different types of premature failures observed during full scale testing of transmission line towers at Tower Testing and Research Station, Structural Engineering Research Centre, Chennai are presented. Failures that have been observed during testing are studied and the reasons discussed in detail. The effect of non-triangulated hip bracing pattern and isolated hip bracings connected to elevation redundant in 'K' and 'X' braced panels on tower behaviour are studied. The tower members are modeled as beam column and plate elements. Different types of failures are modeled using finite element software and the analytical and the test results are compared with various codal provisions. The general purpose finite element analysis program NE-NASTRAN is used to model the elasto-plastic behaviour of towers. Importance of redundant member design and connection details in over all performance of the tower is discussed. © 2011 Elsevier Ltd.


Prabakar J.,Structural Engineering Research Center | Manoharan P.D.,Anna University | Chellappan A.,Structural Engineering Research Center
Construction and Building Materials | Year: 2010

Concrete durability mainly depends on the diffusion characteristics of concrete. Chloride ion diffusion is one of the main parameters affecting the durability of Reinforced Concrete Structures. The chloride ion penetration is determined under accelerated diffusion test condition with 12 V (Norwegian method). Depending upon the concrete quality, the diffusion test duration will vary. Generally, high grade concrete will have longer test duration as compared to lower grade concrete. In this paper, OPC concrete of M30, M40, M50, M60 and M75 grades were studied for diffusion properties under different voltages 12, 20, 30, 40, 50 and 60 V. A comparative study was made with standard Rapid Chloride Permeability Test with respective voltages. It has been observed that chloride profile and diffusion coefficient were high in low grade OPC concrete and low for high grade concrete. Minimum test duration was observed at higher voltages. With the increased voltage, the chloride profile and diffusion coefficient were found to be high. © 2009 Elsevier Ltd. All rights reserved.


A cooling system is an integrated part of a power plant with steam cycles. Ambient winds can significantly alter the flow field around a natural draft cooling tower which reduces the plant's efficiency. On the other hand, a wind load is extremely important in structural design of natural drought cooling towers (CT). In this paper, a method which utilizes a variable height for towers is introduced to reduce the structural design wind loads. This method reduces the height of the CT under high speed crosswinds. In order to examine the validity of the proposed method, a real scale CT is selected as a case study and the structural design wind loads as well as the thermal performance of the selected CT are analyzed for both the whole and reduced height towers. The structural design wind loads are calculated based on German guidelines, and the CT thermal performance is evaluated by Computational Fluid Dynamic (CFD) model. The numerical results confirm the validity of the proposed method in which the structural design wind loads are properly reduced without considerable reduction in the thermal performance of the CT. This method can be used for effective natural drought cooling towers design. © 2013 Elsevier Ltd.


Guru Jawahar J.,Jawaharlal Nehru Technological University Anantapur | Sashidhar C.,Jawaharlal Nehru Technological University Anantapur | Ramana Reddy I.V.,Sri Venkateswara University | Annie Peter J.,Structural Engineering Research Center
Materials and Design | Year: 2013

This investigation is mainly focused on finding the unit weight, compressive strength, modulus of elasticity (MOE) and splitting tensile strength (STS) of SCC mixes with different coarse aggregate blending (60:40 and 40:60) (20. mm and 10. mm) and coarse aggregate content (28% and 32%) and these properties were compared to a conventional concrete (CC). All SCC mixes had 35% replacement of cement with class F fly ash. The coarse aggregate blending did not affect the compressive strength of SCC mixes, but it affected the unit weight, MOE and STS of SCC mixes. A new parameter called coarse aggregate points (CAPs) has been introduced to study the effect of coarse aggregate blending in a particular coarse aggregate content on mechanical properties of SCC mixes. It is observed that for the given strength, SCC mixes with the same CAP value have shown similar mechanical properties. The measured MOE of all mixes were compared with ACI 363R and AASHTO LRFD/ACI 318 predicted equations. The measured STS of all mixes were compared with ACI 363R and CEB-FIP predicted equations. © 2012 Elsevier Ltd.


Guru Jawahar J.,Jawaharlal Nehru Technological University Anantapur | Sashidhar C.,Jawaharlal Nehru Technological University Anantapur | Ramana Reddy I.V.,Sri Venkateswara University | Annie Peter J.,Structural Engineering Research Center
Materials and Design | Year: 2013

This investigation is mainly focused on the development of cost-effective normal strength M 25 grade of self compacting concrete (SCC) for the use of normal building constructions. Keeping in view of the normal strength, cost, quality and durability of SCC and greenhouse gas emissions, a combination type of SCC was developed with 35% replacement of cement with class F fly ash. This study recommended a SCC mix with moderate fines to obtain a cost-effective normal strength SCC for the normal building constructions. Studies also revealed that further reduction in fines content in SCC with the same replacement level of fly ash decreased the SCC strength and its performance. Cost analysis has been done between M 25 grade of SCC and conventional concrete (CC). Results shown that the SCC material cost is slightly higher than that of CC of the same strength class, but the savings in labour cost and construction time and quality of SCC would offset the SCC material cost and reduce the total life cycle cost of SCC. © 2013 Elsevier Ltd.


Guru Jawahar J.,Jawaharlal Nehru Technological University Anantapur | Sashidhar C.,Jawaharlal Nehru Technological University Anantapur | Ramana Reddy I.V.,Sri Venkateswara University | Annie Peter J.,Structural Engineering Research Center
Materials and Design | Year: 2013

This investigation is mainly focused on the effect of class F fly ash on the micro and macrolevel properties of self compacting concrete (SCC) after 28, 56 and 112. days of curing. The microlevel properties studied were the microcrack widths between aggregate and paste and atomic Calcium-Silica (Ca/Si) ratio. The macrolevel properties studied were compressive strength, modulus of elasticity and splitting tensile strength. A conventional concrete (CC) having an equivalent 28-day SCC compressive strength has also been examined at different ages. Scanning electron microscope (SEM) analysis was carried to examine the width of microcracks and energy dispersive X-ray analysis (EDAX) was carried out to determine the chemical elements of both SCC and CC. Studies revealed that pozzolanic action of class F fly ash improved the microlevel properties of SCC with age by reducing the microcracking width and Ca/Si ratio and thus enhanced the macrolevel properties. © 2012 Elsevier Ltd.


Vijaya Lakshmi C.S.,Indian Institute of Technology Kharagpur | Srinivasan P.,Structural Engineering Research Center | Murthy S.G.N.,Structural Engineering Research Center | Trivedi D.,Indian Institute of Technology Kharagpur | Nair R.R.,Indian Institute of Technology Kharagpur
Journal of Earth System Science | Year: 2010

Extreme wave events of 1000 and 1500 years (radiocarbon ages) have been recently reported in Mahabalipuram region, southeast coast of India. Subsequently, we carried out extensive sedimentological analysis in regions covering a total lateral coverage of 12 km with a new archeological site as the central portion of the study area. Twelve trenches in shore normal profiles exhibit landward thinning sequences as well as upward fining sequences confirming with the global signatures of extreme wave events. The sediment size ranges from fine-to-medium and moderately well sorted-to-well sorted, and exhibit positive skewness with platykurtic-to-leptokurtic nature. We now propose the abrupt winnowing or back and forth motion including unidirectional transport of these deposited sediments, which results in positive skewness. Textural analyses derived from scanning electron microscope studies (SEM) demonstrate the alteration produced, in the ilmenite mineral with vivid presence of pits and crescents with deformation observed on the surface due to extreme wave activities. This is further confirmed with the predominance of high-density mineral such as magnetite (5.2) and other heavy minerals in these deposits inferred the high-intensity of the reworking process of the beach shelf sediments. © Indian Academy of Sciences.

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