Non-linear analysis of composite steel-concrete beams with incomplete interaction

Miran Saje,Igor Planinc,Bojan Cˇ as,Sebastjan Bratina 국제구조공학회 2004 Steel and Composite Structures, An International J Vol.4 No.6

The flexibility of the connection between steel and concrete largely influences the global behaviour of the composite beam. Therefore the way the connection is modelled is the key issue in its structural analysis. Here we present a new strain-based finite element formulation in which we consider nonlinear material and contact models. The computational efficiency and accuracy of the formulation is proved with the comparison of our numerical results with the experimental results of Abdel Aziz (1986) obtained in a full-scale laboratory test. The shear connectors are assumed to follow a non-linear load−slip relationship proposed by Ollgaard et al. (1971). We introduce the notion of the generalized slip, which offers a better physical interpretation of the behaviour of the contact and gives an additional material slip parameter. An excellent agreement of experimental and numerical results is obtained, using only a few finite elements. This demonstrates that the present numerical approach is appropriate for the evaluation of behaviour of planar composite beams and perfect for practical calculations.

On the local stability condition in the planar beam finite element

Planinc, Igor,Saje, Miran,Cas, Bojan Techno-Press 2001 Structural Engineering and Mechanics, An Int'l Jou Vol.12 No.5

In standard finite element algorithms, the local stability conditions are not accounted for in the formulation of the tangent stiffness matrix. As a result, the loss of the local stability is not adequately related to the onset of the global instability. The phenomenon typically arises with material-type localizations, such as shear bands and plastic hinges. This paper addresses the problem in the context of the planar, finite-strain, rate-independent, materially non-linear beam theory, although the proposed technology is in principle not limited to beam structures. A weak formulation of Reissner's finite-strain beam theory is first presented, where the pseudocurvature of the deformed axis is the only unknown function. We further derive the local stability conditions for the large deformation case, and suggest various possible combinations of the interpolation and numerical integration schemes that trigger the simultaneous loss of the local and global instabilities of a statically determined beam. For practical applications, we advice on a procedure that uses a special numerical integration rule, where interpolation nodes and integration points are equal in number, but not in locations, except for the point of the local instability, where the interpolation node and the integration point coalesce. Provided that the point of instability is an end-point of the beam-a condition often met in engineering practice-the procedure simplifies substantially; one of such algorithms uses the combination of the Lagrangian interpolation and Lobatto's integration. The present paper uses the Galerkin finite element discretization, but a conceptually similar technology could be extended to other discretization methods.

Exact buckling load of a restrained RC column

Krauberger, Nana,Saje, Miran,Planinc, Igor,Bratina, Sebastjan Techno-Press 2007 Structural Engineering and Mechanics, An Int'l Jou Vol.27 No.3

Theoretical foundation for the buckling load determination in reinforced concrete columns is described and analytical solutions for buckling loads of the Euler-type straight reinforced concrete columns given. The buckling analysis of the limited set of restrained reinforced concrete columns is also included, and some conclusions regarding effects of material non-linearity and restrain stiffnesses on the buckling loads and the buckling lengths are presented. It is shown that the material non-linearity has a substantial effect on the buckling load of the restrained reinforced concrete columns. By contrast, the steel/concrete area ratio and the layout of reinforcing bars are less important. The influence on the effective buckling length is small.

An analytical model of layered continuous beams with partial interaction

Schnabl, Simon,Planinc, Igor,Saje, Miran,Cas, Bojan,Turk, Goran Techno-Press 2006 Structural Engineering and Mechanics, An Int'l Jou Vol.22 No.3

Starting with the geometrically non-linear formulation and the subsequent linearization, this paper presents a consistent formulation of the exact mechanical analysis of geometrically and materially linear three-layer continuous planar beams. Each layer of the beam is described by the geometrically linear beam theory. Constitutive laws of layer materials and relationships between interlayer slips and shear stresses at the interface are assumed to be linear elastic. The formulation is first applied in the analysis of a three-layer simply supported beam. The results are compared to those of Goodman and Popov (1968) and to those obtained from the formulation of the European code for timber structures, Eurocode 5 (1993). Comparisons show that the present and the Goodman and Popov (1968) results agree completely, while the Eurocode 5 (1993) results differ to a certain degree. Next, the analytical solution is used in formulating a general procedure for the analysis of layered continuous beams. The applications show the qualitative and quantitative effects of the layer and the interlayer slip stiffnesses on internal forces, stresses and deflections of composite continuous beams.

Analytical solution of two-layer beam including interlayer slip and uplift

Kroflic, Ales,Planinc, Igor,Saje, Miran,Cas, Bojan Techno-Press 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.34 No.6

A mathematical model and its analytic solution for the analysis of stress-strain state of a linear elastic two-layer beam is presented. The model considers both slip and uplift at the interface. The solution is employed in assessing the effects of transverse and shear contact stiffnesses and the thickness of the interface layer on behaviour of nailed, two-layer timber beams. The analysis shows that the transverse contact stiffness and the thickness of the interface layer have only a minor influence on the stress-strain state in the beam and can safely be neglected in a serviceability limit state design.

Non-linear fire-resistance analysis of reinforced concrete beams

Bratina, Sebastjan,Planinc, Igor,Saje, Miran,Turk, Goran Techno-Press 2003 Structural Engineering and Mechanics, An Int'l Jou Vol.16 No.6

The non-linear structural analysis of reinforced concrete beams in fire consists of three separate steps: (i) The estimation of the rise of surrounding air temperature due to fire; (ii) the determination of the distribution of the temperature within the beam during fire; (iii) the evaluation of the mechanical response due to simultaneous time-dependent thermal and mechanical loads. Steps (ii) and (iii) are dealt with in the present paper. We present a two-step computational procedure where a 2D transient thermal analysis over the cross-sections of beams are made first, followed by mechanical analysis of the structure. Fundamental to the accuracy of the mechanical analysis is a new planar beam finite element. The effects of plasticity in concrete, and plasticity and viscous creep in steel are taken into consideration. The properties of concrete and steel along with the values of their thermal and mechanical parameters are taken according to the European standard ENV 1992-1-2 (1995). The comparison of our numerical and full-scale experimental results shows that the proposed mechanical and 2D thermal computational procedure is capable to describe the actual response of reinforced concrete beam structures to fire.

Analytical solution of two-layer beam including interlayer slip and uplift

Ales Kroflic,Igor Planinc,Miran Saje,Bojan Cas 국제구조공학회 2010 Structural Engineering and Mechanics, An Int'l Jou Vol.34 No.6

A mathematical model and its analytic solution for the analysis of stress-strain state of a linear elastic two-layer beam is presented. The model considers both slip and uplift at the interface. The solution is employed in assessing the effects of transverse and shear contact stiffnesses and the thickness of the interface layer on behaviour of nailed, two-layer timber beams. The analysis shows that the transverse contact stiffness and the thickness of the interface layer have only a minor influence on the stress-strain state in the beam and can safely be neglected in a serviceability limit state design.

Carbon stock in influenced forest of Srinagar hydroelectric project, Uttarakhand, India

Munesh Kumar,Mehraj A. Sheikh,Sajed Saleem 한국산림과학회 2014 Forest Science And Technology Vol.10 No.3

In the Uttarakhand Himalaya, hydroelectric projects are the major source of power generation and subsequently the sourceof income. The dam constructions in the hills of the Uttarakhand are diminishing large areas of forest cover. The presentstudy was focused on the estimation of tree and soil carbon stocks in the influenced forest (close to the submergence forest)that is likely to be affected by the Alaknand hydroelectric river project, Srinagar in Uttarakhand, soon after its completion. For the study, five different forest sites, i.e., site-I, site-II, site-III, site-IV and site-IV, were selected from an area ofapproximately 12 km from the main reservoir area along the Alaknanda against the river flow. Among the forest sites,above- and belowground carbon density of forests was highest in site-II because of the highest number of tree species. Thelowest number of tree species was in site-I, which was close to the dam construction area, and therefore had the highestpercentage forest cover destruction compared to other sites. Soil organic carbon density was reported highest in site-IV andlowest in site-I. But the total carbon density of forest sites was reported highest (293.51 t ha1) in site-II and lowest(109.82 t ha1) in site-I. Thus, site-II was reported most productive in terms of carbon sequestration.

An analytical model of layered continuous beams with partial interaction

Simon Schnabl,Igor Planinc,Miran Saje,Bojan Cas,Goran Turk 국제구조공학회 2006 Structural Engineering and Mechanics, An Int'l Jou Vol.22 No.3

Association of Chicken Growth Hormones and Insulin-like Growth Factor Gene Polymorphisms with Growth Performance and Carcass Traits in Thai Broilers

Nguyen, Thi Lan Anh,Kunhareang, Sajee,Duangjinda, Monchai Asian Australasian Association of Animal Productio 2015 Animal Bioscience Vol.28 No.12

Molecular marker selection has been an acceptable tool in the acceleration of the genetic response of desired traits to improve production performance in chickens. The crossbreds from commercial parent stock (PS) broilers with four Thai synthetic breeds; Kaen Thong (KT), Khai Mook Esarn (KM), Soi Nin (SN), and Soi Pet (SP) were used to study the association among chicken growth hormones (cGH) and the insulin-like growth factor (IGF-I) genes for growth and carcass traits; for the purpose of developing a suitable terminal breeding program for Thai broilers. A total of 408 chickens of four Thai broiler lines were genotyped, using polymerase chain reaction-restriction fragment length polymorphism methods. The cGH gene was significantly associated with body weight at hatching; at 4, 6, 8, 10 weeks of age and with average daily gain (ADG); during 2 to 4, 4 to 6, 0 to 6, 0 to 8, and 0 to 10 weeks of age in $PS{\times}KM$ chickens. For $PS{\times}KT$ populations, cGH gene showed significant association with body weight at hatching, and ADG; during 8 to 10 weeks of age. The single nucleotide polymorphism variant confirmed that allele G has positive effects for body weight and ADG. Within carcass traits, cGH revealed a tentative association within the dressing percentage. For the IGF-I gene polymorphism, there were significant associations with body weight at hatching; at 2, 4, and 6 weeks of age and ADG; during 0 to 2, 4 to 6, and 0 to 6 weeks of age; in all of four Thai broiler populations. There were tentative associations of the IGF-I gene within the percentages of breast muscles and wings. Thus, cGH gene may be used as a candidate gene, to improve growth traits of Thai broilers.