Numerically integrated modified virtual crack closure integral technique for 2-D crack problems

Palani, G.S.,Dattaguru, B.,Iyer, Nagesh R. Techno-Press 2004 Structural Engineering and Mechanics, An Int'l Jou Vol.18 No.6

Modified virtual crack closure integral (MVCCI) technique has become very popular for computation of strain energy release rate (SERR) and stress intensity factor (SIF) for 2-D crack problems. The objective of this paper is to propose a numerical integration procedure for MVCCI so as to generalize the technique and make its application much wider. This new procedure called as numerically integrated MVCCI (NI-MVCCI) will remove the dependence of MVCCI equations on the type of finite element employed in the basic stress analysis. Numerical studies on fracture analysis of 2-D crack (mode I and II) problems have been conducted by employing 4-noded, 8-noded (regular & quarter-point), 9-noded and 12-noded finite elements. For non-singular (regular) elements at crack tip, NI-MVCCI technique generates the same results as MVCCI, but the advantage for higher order regular and singular elements is that complex equations for MVCCI need not be derived. Gauss numerical integration rule to be employed for 8-noded singular (quarter-point) element for accurate computation of SERR and SIF has been recommended based on the numerical studies.

Flexural Behaviour of Steel-Foam Concrete Composite Light-Weight Panels

Prabha, P.,Palani G. S.,Lakshmanan N.,Senthil R. 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.9

The present study explores the applicability of composite panel made of thin profiled steel sheets of thickness 0.8 mm as the outer skins with an infill Light-weight Foam Concrete (LFC) core of density 1200 kg/m3 for use as floor/roof panel in buildings by conducting experimental studies. This study was carried out in continuation with the previous studies reported by Prabha et al. (2013) on composite wall panels. Through-through mild steel connectors were used for the load transfer between sheet and concrete. Two types of concrete core, namely (a) Normal Foam Concrete (NFC) and (b) Fibre Reinforced Foam Concrete (FRFC) were investigated. The polypropylene fibres were used for improving the tensile strength of LFC. The composite panels exhibit gradual load-deflection response and ductile failure mode at higher deflections under four point bending test. The ultimate load of FRFC specimen is found to be 6% stronger than NFC panels, which implies that the use of polypropylene fibers marginally improved the flexural strength. The panels possess sufficient flexural capacity for spans upto 5 m and high ductility factor of 10 to be used as floor/ roof panels in residential buildings. Numerical parametric studies indicate that the configuration 24 nos. of studs used in the experiment is found to be optimal and the flexural capacity increases proportionally for the higher thickness of steel sheet. Simplified equation is proposed for the evaluation of flexural strength of the panel.

Numerically intergrated modified virtual crack closure integral technique for 2-D crack problems

B. Dattaguru,G. S. Palani,Nagesh R. Iyer 국제구조공학회 2004 Structural Engineering and Mechanics, An Int'l Jou Vol.18 No.6

Effects on corrosion resistance of rebar subjected to deep cryogenic treatment

Srinivasagam Ramesh,B. Bhuvaneswari,G. S. Palani,D. MOHAN LAL,Nagesh R. Iyer 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.1

An attempt has been made to evaluate the effect of deep cryogenic treatment on the corrosion resistance of rebar. Corrosion behavior of samples subjected to deep cryogenic treatment and samples tempered after deep cryogenic treatment was studied by linear polarization method. The Vickers hardness and ultimate tensile strength of the samples were also measured. The possible mechanism for increase in corrosion resistance has been explained based on Scanning electron micrographs (SEM) and X-Ray diffraction (XRD) study. The morphology of the corroded surfaces of the samples was studied using Atomic force microscopy (AFM). It was found that there is 69 % improvement in corrosion resistance because of deep cryogenic treatment, further it was seen that the increase in corrosion resistance was due to the contribution of increased pearlite phase. Deep cryogenic treatment had no adverse effect on ultimate tensile strength and hardness, which are crucial properties to be considered for rebar.

Remaining life prediction of concrete structural components accounting for tension softening and size effects under fatigue loading

Murthy, A. Rama Chandra,Palani, G.S.,Iyer, Nagesh R. Techno-Press 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.32 No.3

This paper presents analytical methodologies for remaining life prediction of plain concrete structural components considering tension softening and size effects. Non-linear fracture mechanics principles (NLFM) have been used for crack growth analysis and remaining life prediction. Various tension softening models such as linear, bi-linear, tri-linear, exponential and power curve have been presented with appropriate expressions. Size effect has been accounted for by modifying the Paris law, leading to a size adjusted Paris law, which gives crack length increment per cycle as a power function of the amplitude of a size adjusted stress intensity factor (SIF). Details of tension softening effects and size effect in the computation of SIF and remaining life prediction have been presented. Numerical studies have been conducted on three point bending concrete beams under constant amplitude loading. The predicted remaining life values with the combination of tension softening & size effects are in close agreement with the corresponding experimental values available in the literature for all the tension softening models.

Remaining life prediction of concrete structural components accounting for tension softening and size effects under fatigue loading

A. Rama Chandra Murthy,G.S. Palani,Nagesh R. Iyer 국제구조공학회 2009 Structural Engineering and Mechanics, An Int'l Jou Vol.32 No.3

This paper presents analytical methodologies for remaining life prediction of plain concrete structural components considering tension softening and size effects. Non-linear fracture mechanics principles (NLFM) have been used for crack growth analysis and remaining life prediction. Various tension softening models such as linear, bi-linear, tri-linear, exponential and power curve have been presented with appropriate expressions. Size effect has been accounted for by modifying the Paris law, leading to a size adjusted Paris law, which gives crack length increment per cycle as a power function of the amplitude of a size adjusted stress intensity factor (SIF). Details of tension softening effects and size effect in the computation of SIF and remaining life prediction have been presented. Numerical studies have been conducted on three point bending concrete beams under constant amplitude loading. The predicted remaining life values with the combination of tension softening & size effects are in close agreement with the corresponding experimental values available in the literature for all the tension softening models.

Replaceable Fuses in Earthquake Resistant Steel Structures: A Review

M. Saravanan,Rupen Goswami,G. S. Palani 한국강구조학회 2018 International Journal of Steel Structures Vol.18 No.3

In earthquake-prone regions, steel structures are considered to be one of the best choices due to inherent material properties in terms of homogeneity and ductility. In the conventional seismic design of steel structures, prevalent specifi cations recommend that the column and joints should be strong enough such that the inelastic action or damage occurs in the beams in lateral load resisting frames. By following these design provisions, structural collapse can be prevented in the event of severe earthquakes to ensure occupant safety. However, repair and rehabilitation of damaged primary members is a challenging task and also time-consuming process, resulting in severe inconvenience to the occupants. To simplify the repair works in earthquake resistant steel structures after the event of severe earthquakes, recent research work is concentrated on designing structures to have localized inelastic damages at intended locations, which will dissipate the seismic energy and can be easily replaced after the event of a strong earthquake, so that normal life of the occupants can be restored immediately with lesser cost of repair. This paper presents a critical review of the state-of-the-art related to steel lateral load resisting systems comprising of replaceable fuses that help in the easy repair of steel structures following strong earthquakes.

On the Tensile Capacity of Single-bolted Connections between GFRP Angles and Gusset Plates-Testing and Modelling

M. D. Raghunathan,R. Senthil,G.S. Palani 대한토목학회 2017 KSCE JOURNAL OF CIVIL ENGINEERING Vol.21 No.6

The polymer composite known as Glass Fibre Reinforced Polymer (GFRP) has several advantages over conventional materials. It has been slowly incorporated into civil infrastructures. Because of lack of knowledge about the behaviour and design criteria of structural connections, the wide-spread application of GFRP in this field has been rather limited. In this study, analytical and experimental behaviour of GFRP structural angle members with gusset plate connections for net-tension strength, with an emphasis on transmission line tower connections, were investigated. Thirty-five single-lap, single-bolted connections were tested. The widths of the gusset plate and edge distance were varied. A tensile load was applied on the joint and then failure modes and the corresponding loads were observed. The effect of the plate width and edge distance on the connection efficiency was also studied. Based on the studies, the optimum plate width and edge distance were determined as three and five times diameter of the bolt, respectively. A semi-empirical analytical stress concentration model proposed by Hart-Smith (1978), is adopted to determine the cross-correlation coefficient ‘C’ which is linearly correlated to the stress concentration factors of composite and elastic isotropic materials. Using regression analysis, the coefficient ‘C’ was obtained, and an ultimate net-tension strength design formula is proposed.

Fracture analysis and remaining life prediction of aluminium alloy 2014a plate panels with concentric stiffeners under fatigue loading

A. Ramachandra Murthy,Rakhi Sara Mathew,G.S. Palani,Smitha Gopinath,Nagesh R. Iyer 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.53 No.4

Fracture analysis and remaining life prediction has been carried out for aluminium alloy (Al2014A) plate panels with concentric stiffener by varying sizes and positions under fatigue loading. Tensioncoupon tests and compact tension tests on 2014A have been carried out to evaluate mechanical propertiesand crack growth constants. Domain integral technique has been used to compute the Stress intensity factor(SIF) for various cases. Generalized empirical expressions for SIF have been derived for various positions ofstiffener and size. From the study, it can be concluded that the remaining life for stiffened panel for particularsize and position can be estimated by knowing the remaining life of corresponding unstiffened panel.

Fracture analysis and remaining life prediction of aluminium alloy 2014A plate panels with concentric stiffeners under fatigue loading

Murthy, A. Ramachandra,Mathew, Rakhi Sara,Palani, G.S.,Gopinath, Smitha,Iyer, Nagesh R. Techno-Press 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.53 No.4

Fracture analysis and remaining life prediction has been carried out for aluminium alloy (Al 2014A) plate panels with concentric stiffener by varying sizes and positions under fatigue loading. Tension coupon tests and compact tension tests on 2014A have been carried out to evaluate mechanical properties and crack growth constants. Domain integral technique has been used to compute the Stress intensity factor (SIF) for various cases. Generalized empirical expressions for SIF have been derived for various positions of stiffener and size. From the study, it can be concluded that the remaining life for stiffened panel for particular size and position can be estimated by knowing the remaining life of corresponding unstiffened panel.