Three-Dimensional FE Modelling of Simply-Supported and Continuous Composite Steel-Concrete Beams

AbstractComposite steel-concrete beams represent an economic form of construction used in both building and bridge applications. The composite action is usually provided by the presence of shear connectors welded to the top of the steel joist and embedded in the concrete slab. The flexural response is strongly dependent on the rigidity provided by these connectors. Initial studies in this area highlighted that their deformability needs to be evaluated and included in the modeling for an accurate structural representation. For this purpose, different types of push-out tests have been proposed to date to describe the load-slip relationships of shear connectors. These relationships are usually used in numerical simulations when modeling experimental tests or performing parametric studies. In this context, the finite element model proposed in this paper intends to provide a representation of the composite behaviour of floor beams without the need to rely on constitutive relationships obtained from push-out tests. The model is validated against experimental results available in the open literature carried out using simply-supported and continuous static configurations and based on composite beams with solid and composite slabs

Considerations on the slip demand of shear connectors in composite steel-concrete beams with solid slabs

The objective of this study is to provide insight into the expected slip demand in composite steel-concrete beams through numerical simulations. A wide parametric analysis is carried out evaluating the partial interaction performance of simply-supported beams designed considering a variety of floors, i.e. span length, slab thickness, shear connection strength, dead load to live load ratio and slab concrete strength. For each of these beams, the slip demand required to achieve the expected design capacity is evaluated. In this process, key parameters influencing the slip requirements are identified. These also include the construction sequence (propped or unpropped) and the shear connection distribution (uniform or non-uniform with different layouts)

Hydrologic vulnerability to climate change of the Mandrone glacier (Adamello-Presanella group, Italian Alps)

In order to assess the annual mass balance of the Mandrone glacier in the Central Alps an energy-balance model was applied, supported by snowpack, meteorological and glaciological observations, together with satellite measurements of snow covered areas and albedo. The Physically based Distributed Snow Land and Ice Model (PDSLIM), a distributed multi-layer model for temperate glaciers, which was previously tested on both basin and point scales, was applied. Verification was performed with a network of ablation stakes over two summer periods. Satellite images processed within the Global Land Ice Measurements from Space (GLIMS) project were used to estimate the ice albedo and to verify the position of the simulated transient snowline on specific dates. The energy balance was estimated for the Mandrone and Presena glaciers in the Central Italian Alps. Their modeled balances (−1439 and −1503 mm w.e. year−1, respectively), estimated over a 15 year period, are in good agreement with those obtained with the glaciological method for the Caresèr glacier, a WGMS (World Glacier Monitoring Service) reference located in the nearby Ortles-Cevedale group. Projections according to the regional climate model COSMO-CLM (standing for COnsortium for Small-scale MOdeling model in CLimate Mode) indicate that the Mandrone glacier might not survive the current century and might be halved in size by 2050

Potential climate change effects on the meteorological forcing and the design efficiency of urban drainage systems

Urban drainage systems design and management are strictly connected to meteorological forcing. For design purposes synthetic forms (e.g. depth duration frequency curves) are usually adopted to represent the meteorological solicitation, while a stochastic representation could be more promptly used to investigate the effects of potential climate change both on the design and on the efficiency of urban drainage devices. A simplified semi-probabilistic approach, relying on simple models of the stochastic rainfall process and of the rainfall-runoff (hydrological) transformation, is expected to be a sound tool. Since the rainfall process is described through the definition of three random variables and their probability distribution, the main advantage is the possibility of changing one, two or more characteristics of the rainfall model at a time. The effect of the change can then be easily evaluated through the application of the hydrological model. The semi-probabilistic approach is applied to study some aspects of the drainage system design for locations in the Italian territory. Potential effects of climate change on fictitious urban basins are evaluated through a rainfall stochastic model calibrated on the basis of long series observations recorded at site. Precipitation climate change scenarios were defined on the basis of both international climate studies report and local meteorological observation analysis. The effects on the urban drainage system are evaluated with respect to specific urban drainage devices and the efficiency of the design procedure in the hypothesis of climate change is finally discussed

Non-linear analysis of two-layer timber beams considering interlayer slip and uplift

A new mathematical model and its finite element formulation for the non-linear analysis of mechanical behaviour of a two-layer timber planar beam is presented. A modified principle of virtual work is employed in formulating the finite element method. The basic unknowns are strains. The following assumptions are adopted in the mathematical model: materials are taken to be non-linear and can differ from layer to layer; interacting shear and normal contact tractions between layers are derived from the non-linear shear contact traction-slip and the non-linear normal contact traction-uplift characteristics of the connectors; the geometrically linear and materially non-linear Bernoulli's beam theory is assumed for each layer. The formulation is found to be accurate, reliable and computationally effective. The suitability of the theory is validated by the comparison of the numerical solution and the experimental results of full-scale laboratory tests on a simply supported beam. An excellent agreement between measured and calculated results is observed for all load levels. The further objective of the paper is the analysis of the effect of different normal contact traction-uplift constitutive relationships on the kinematic and static quantities in a statically determined and undetermined structure. While the shear contact traction-slip constitutive relationship dictates the deformability of the composite beam and has a substantial influence on most of the static and kinematic quantities of the composite beam, a variable normal contact traction-uplift constitutive relationship is in most cases negligible

Locking-free two-layer Timoshenko beam element with interlayer slip

A new locking-free strain-based finite element formulation for the numerical treatment of linear static analysis of two-layer planar composite beams with interlayer slip is proposed. In this formulation, the modified principle of virtual work is introduced as a basis for the finite element discretization. The linear kinematic equations are included into the principle by the procedure, similar to that of Lagrangian multipliers. A strain field vector remains the only unknown function to be interpolated in the finite element implementation of the principle. In contrast with some of the displacement-based and mixed finite element formulations of the composite beams with interlayer slip, the present formulation is completely locking-free. Hence, there are no shear and slip locking, poor convergence and stress oscillations in these finite elements. The generalization of the composite beam theory with the consideration of the Timoshenko beam theory for the individual component of a composite beam represents a substantial contribution in the field of analysis of non-slender composite beams with an interlayer slip. An extension of the present formulation to the non-linear material problems is straightforward. As only a few finite elements are needed to describe a composite beam with great precision, the new finite element formulations is perfectly suited for practical calculations. (c) 2007 Elsevier B.V. All rights reserved

Failure Probability Analysis of Levees Affected by Mammal Bioerosion

Mammal bioerosion is an emergent threat to the functionality of levees. In the present paper, the problem of assessing the failure probability of levees affected by mammal bioerosion is addressed. A fully bivariate description of peak flow discharge and flood duration is combined with a deterministic unsteady seepage flow model to obtain a suitable model of variably disturbed levee response to the observed natural variability of floods. Monte Carlo analysis is also implemented to evaluate the epistemic uncertainty connected to the description of the river system. The obtained model is tested with respect to a real-world levee located along the Secchia River in northern Italy, which underwent a disastrous failure caused by mammal bioerosion in 2014. The convex linear combination of two Archimedean copulas is found to fit the empirical dependence structure between peak flow discharge and flood duration. The reliability of the unsteady seepage flow model is tested against detailed numerical simulations of the seepage occurring through the levee body. A limit state function is obtained by comparing the maximum extent of the seepage front to the distance between the den end and the riverside levee slope, and the corresponding levee safety and failure regions are delimited. Results obtained from the developed model reveal a significant impact of mammal dens located near the levee crest in terms of failure probability and related return period. This impact is consistent with failures observed in the study area

Exact slip-buckling analysis of two-layer composite columns

A mathematical model for slip-buckling has been proposed and its analytical solution has been found for the analysis of layered and geometrically perfect composite columns with inter-layer slip between the layers. The analytical study has been carried out to evaluate exact critical forces and to compare them to those in the literature. Particular emphasis has been placed on the influence of interface compliance on decreasing the bifurcation loads. For this purpose, a preliminary parametric study has been performed by which the influence of various material and geometric parameters on buckling forces have been investigated. (C) 2009 Elsevier Ltd. All rights reserved

Profiles and species of Mn, Fe and trace metals in soils near a ferromanganese plant in Bagnolo Mella (Brescia, IT)

For the last forty-five years (from 1974 to present) ferroalloy production in Bagnolo Mella, Northern Italy, has generated particulate emissions enriched in potentially toxic metals and metalloids including arsenic (As), lead (Pb) and manganese (Mn). Of these, Mn is unique in that it has a significant background concentration and is seldom studied as a contaminant but is potentially a significant toxin derived from dusts regionally. Here we examine the distribution, redistribution, speciation and bioavailability of the Mn-contaminated top soils affected by atmospheric emissions adjacent to the ferroalloy plant. Four sites, variably located in the study area in terms of both distance and direction from the plant, were considered as representative of increasing levels of industrial influence. Soil profiles showed that metal concentrations (measured by X-ray fluorescence) varied considerably by location, i.e. higher in the sites closer to the plant and also at the surface level, although distributed throughout the top 15 cm, suggesting appreciable redistribution possibly due to soil mixing or infiltration. Most metal concentrations were correlated, except Mn which was independent and more variable across the sites than the other elements. Sequential chemical extractions indicated that Pb was primarily associated with Mn oxides, while As was most significantly associated with iron oxides. When Mn concentration significantly exceeded background levels, it was present in phases that were resistant to acid dissolution, very different from typical uncontaminated soils. X-ray Absorption Near Edge Spectroscopy (XANES) analyses suggested this recalcitrant Mn phase is likely a Mn-bearing spinel such as magnetite, that can be particularly toxic if ingested or inhaled. These first results highlight the legacy of ferroalloy production on surrounding soils, as well as the importance of Mn speciation for soil apportionment evaluation and human exposure estimation