Papers by Pier Giorgio Malerba
ABSTRACT The time dependent behaviour of two elementary structures, one made of a concrete cantil... more ABSTRACT The time dependent behaviour of two elementary structures, one made of a concrete cantilever beam, suspended at the tip by a pretensioned stay, and the other made of a concrete cantilever beam, post-tensioned through a horizontal cable, has been studied. After a short recall, which would outline how a suitable stay pretensioning or a suitable cable post tensioning, may balance the deflections due to selfweight only under elastic hypotheses, the effects of creep on the tip vertical displacement and on the tension in stay ...
The object of the paper is the study of the representativity of the grillage models with which di... more The object of the paper is the study of the representativity of the grillage models with which different types of bridge decks are schematized. First, the theoretical principles on which this kind of modelling is based are recalled; the equivalent condition between bi-dimensional continuous elements and corresponding grillage models are imposed through the use of a kinematics and an energetic criterion. Secondly, the same technique is generalized to three-dimensional structures and specialized to the case of cellular decks. For this kind of deck, structural behaviours usually neglected by the current technical approaches, like shear lag, distortion and warping, are considered. The paper presents some methods introducing these effects in a grillage analysis; these methods provide a series of criteria with which it's possible to define the rigidities of the equivalent model. These criteria are applied and compared with finite element solutions. Finally, a series of applications are executed in order to verify the efficiency and the accuracy of this kind of approach.
Studi E Ricerche Politecnico Di Milano Scuola Di Specializzazione in Costruzioni in Cemento Armato, 1995
Résumé/Abstract A Finite Element study of RC structures can be arranged at different levels of an... more Résumé/Abstract A Finite Element study of RC structures can be arranged at different levels of analysis. The most refined theories adopt constitutive laws which, by means of the methods of the science of the materials, model at a microscopic level the mechanical, rheological and thermodynamical properties of the concrete. The most diffused formulations, on the other hand, work together with constitutive laws deduced from basic mechanical tests performed on plain materials (concrete and steel) and on systems reproducing the ...
Studi E Ricerche Politecnico Di Milano Scuola Di Specializzazione in Costruzioni in Cemento Armato, 1996
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Studi E Ricerche Politecnico Di Milano Scuola Di Specializzazione in Costruzioni in Cemento Armato, 1994
Résumé/Abstract The analysis of the aerodynamic behaviour of suspended and cable stayed bridges i... more Résumé/Abstract The analysis of the aerodynamic behaviour of suspended and cable stayed bridges involves complex studies and wide tunnel investigations. This induces the designer to carry out the first estimates of the mechanical response to the wind action through reduced models having only few degrees of freedom. The fundamental historical studies and a wide literature on this matter, as well a series of a posteriori verifications, improved the simplified models and gave them a confidence degree sufficient to guide the ...
Studi E Ricerche Politecnico Di Milano Scuola Di Specializzazione in Costruzioni in Cemento Armato, 1997
Résumé/Abstract In previous works an optimization process of Strut-and-Tie modeling of RC structu... more Résumé/Abstract In previous works an optimization process of Strut-and-Tie modeling of RC structural elements was presented. Those optimization criteria are now briefly recalled and applied to the design of a deep beam shaped panel. As known, an element of this kind can be considered as a representative of many diffusive problems. The panel is then studied up to its collapse through a non linear FE analysis, based on the constitutive laws of the Modified Compression Field Theory. The comparative study confirms the results reported ...
Structural Engineering International, 2011
ABSTRACT In this paper, two recently completed bridges at the Malpensa Airport have been presente... more ABSTRACT In this paper, two recently completed bridges at the Malpensa Airport have been presented. The bridges overpass the railway (which runs in a cutting, at a lower level) linking the Malpensa Airport to the city of Milan, Italy; and are part of a U-shaped path called the H (Hotel) Ring which connects the southern ends of the two existing taxiways. Such a crossing had to: (a) intersect the railway track twice with a skew angle of about 45°; (b) carry the maximum aeronautical loads, corresponding to the gears of an Airbus 380 aircraft and; (c) host a 60 m wide taxiway strip, plus a lateral safety lane and a service road, for a total width of 105 m. This paper briefly describes how the above requirements were dealt with while designing two integral bridges.
ABSTRACT The paper concerns the analysis of reinforced concrete sections of arbitrary shape under... more ABSTRACT The paper concerns the analysis of reinforced concrete sections of arbitrary shape under axial load and biaxial bending moments. Equilibrium and compatibility equations are recalled and put in an effective and general matrix form. The kernel of the problem is the integration of the terms of the stiffness matrix of the section. The integration is carried out by subdividing the section into parametrics subdomains and by using Gauss integration rules. In particular it is shown how, through a double transformation, a more refined discretization of circular and hollow circular sections is possible. Many comparative examples are presented and, in particular, it is also shown how the widely used fiber method is a particular case of the present more general approach. In the end, a rational way to determine the frontier of the interaction domain and characteristic applications are shown. The sectional discretization proposed is also of great relevance as an intermediate tool for integrating the element stiffness matrix in a general finite element code for the analysis of R.C. framed structures.
Studi E Ricerche Politecnico Di Milano Scuola Di Specializzazione in Costruzioni in Cemento Armato, 1996
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Bridge scour is the removal of sediment (sand and rocks) around bridge abutments and piers due to... more Bridge scour is the removal of sediment (sand and rocks) around bridge abutments and piers due to the different river flow over the year. Approximately the 60% of collapses occurring to the of bridges is directly or indirectly associated to scour; this phenomenon is very important in the bridges safety assessment. The depth of scour depends on many factors: type and amount of bed/embanked material transported by the river flow, nature and occurrence of flood, accumulations of debris, constriction or realignment of flow due to the presence of the bridge, geometry and orientation of piers, etc. Under a design point of view, the depth of scour can be evaluated through theoretical models involving hydraulic parameters. However, many of these parameters (flow characteristics, sediments, structural and geotechnical factors, etc.) are affected by uncertainty; in the safety assessment of bridges, a deterministic approach to the problem cannot be adopted.
ABSTRACT In recent years, cable-strut assemblies attract a lot of attention from engineers, due t... more ABSTRACT In recent years, cable-strut assemblies attract a lot of attention from engineers, due to their versatile shapes, their lightweight and architectural impact. Cable-strut structures have become popular as roofs for arenas, stadiums and sport centers. Yet their working principle is not so easy to understand since they can carry loads thanks to prestress, so that their behavior under loads must be studied taking into account, at least, the geometrical non-linearity. For these reasons, design experience and intuition may not be enough when engineers work with cable systems. In this article, the matrix theory of a generic three-dimensional pin-jointed structure is first referred. Then, by using modeFRONTIER, a general method able to provide a design solution, which is not only technologically sound, but optimal with respect to the design requirements, is applied to the design of a Geiger Dome. Introduction A structure, with a new particular shape cannot be considered as an innovation just because it is very complex. An innovation is a new system working with new mechanical principles, for a better use of materials, lightness etc. Cable-strut assemblies are not an innovation because they are truss systems that are well-known for centuries. However, their last development -the tensegrity systems – can be seen as a real innovation
Computer Assisted Mechanics and Engineering Sciences, 1999
Streszczenie angielskie: A general solution of the diffusion problems which concern the RC struct... more Streszczenie angielskie: A general solution of the diffusion problems which concern the RC structures, may be deduced by the limit analysis, by means of truss schemes suitable to model the load transfer mechanism. In particular such schemes allows us to share the carrying functions between concrete and steel reinforcement. Latest developments call this kind a solution Strut-and-Tie (S&T) modellization. In this paper a procedure for the automatic search for optimal S&T models in RC elements proposed. A highly indeterminate ...
In recent years, the need for the modernization of industry and the infrastructural system has pr... more In recent years, the need for the modernization of industry and the infrastructural system has propelled the growth of the Italian construction industry. In this paper, some basic data will be provided about the production and consumption of raw materials connected with the building industry, and the different sectors in which the country is now engaged will be presented. In
Structural Engineering International, 2011
ABSTRACT In this paper, two recently completed bridges at the Malpensa Airport have been presente... more ABSTRACT In this paper, two recently completed bridges at the Malpensa Airport have been presented. The bridges overpass the railway (which runs in a cutting, at a lower level) linking the Malpensa Airport to the city of Milan, Italy; and are part of a U-shaped path called the H (Hotel) Ring which connects the southern ends of the two existing taxiways. Such a crossing had to: (a) intersect the railway track twice with a skew angle of about 45°; (b) carry the maximum aeronautical loads, corresponding to the gears of an Airbus 380 aircraft and; (c) host a 60 m wide taxiway strip, plus a lateral safety lane and a service road, for a total width of 105 m. This paper briefly describes how the above requirements were dealt with while designing two integral bridges.
Structure and Infrastructure Engineering, 2014
ABSTRACT In this study, two bridges recently completed at the Malpensa Airport are presented. The... more ABSTRACT In this study, two bridges recently completed at the Malpensa Airport are presented. The bridges overpass the trench where the railway track from Malpensa Airport runs to the city of Milan. They are part of a U-shaped path, called the hotel (H) ring, which connects the southern ends of the two existing taxiways. Such a crossing had to: (a) intersect the railway track twice with a high skew angle, (b) carry the maximum aeronautical loads, corresponding to the gears of an AIRBUS 380 aircraft and (c) host a 60-m wide taxiway strip, plus a lateral safety lane and a service road, for a total width of 96 m. For a bridge operating in such an environment, it was imperative to reduce inspections and maintenance activities to a minimum. Therefore, the designers excluded any detail arrangements or auxiliary devices having life-cycle performances much shorter than that of the main structure. In particular, expansion joints and movable or deformable bearing supports were excluded. Such constraints led to design two structures having the peculiar features that characterise them as integral bridges. This paper will firstly recall the aeronautical and railway specifications and the other operating constraints that characterised the design. In the second part, the criteria followed in designing the foundations, the abutments and the deck are presented. The structural analyses were set out in accordance to the sequence of the construction stages. For the bridge in its service configuration, self-weight and permanent loads give rise to a set of internal forces typical of a portal frame, while the localised loads, due to the aircraft gears, induce bubble deformed shapes characterised by particular transversal load distribution mechanisms. Details of completions and finishing works are finally given.
The fuzzy optimum design of concrete structures under static loads as regards both serviceability... more The fuzzy optimum design of concrete structures under static loads as regards both serviceability and ultimate limit conditions is presented. The procedure is oriented to the optimal design of R.C. frames but it is also suitable for other kind of structures. Design variables include either the shape and the dimensions of the concrete cross-sections, or the amount and location of the reinforcement. These quantities are assumed as deterministic. However, additional fuzzy variables are considered to take the uncertainties involved in the basic properties of the materials into account. The objective of the design process is to minimize the structural cost of the system according to side and behavioral constraints. An optimal solution is achieved for several levels of uncertainties by using genetic algorithms. The structural analyses needed for the solution process are performed by means of a composite finite beam element able to take mechanical and geometrical nonlinearities into account. An application to the optimization of a R.C. frame shows the effectiveness of the procedure.
The behavior of pre-stressed and of cable stayed concrete bridges may be strongly affected by the... more The behavior of pre-stressed and of cable stayed concrete bridges may be strongly affected by the time dependent response due to the creep and shrinkage of concrete. The assessment of safety and serviceability performance of these structures during their whole service life requires a reliable estimation of the influence of these phenomena.
Studi E Ricerche Politecnico Di Milano Scuola Di Specializzazione in Costruzioni in Cemento Armato, 1995
Résumé/Abstract The structural analysis of Reinforced and Prestressed Concrete Frames continues t... more Résumé/Abstract The structural analysis of Reinforced and Prestressed Concrete Frames continues to be of interest for scientists, consultants and design engineers. The purpose of this paper is to propose a solution of wide generality, based on a direct formulation of the stiffness matrix of a RC beam element, which is able to deal with the material and geometric nonlinear behaviour of Reinforced and Prestressed Concrete Frames. The nonlinearity is treated through an iterative secant approach and solutions both for applied loads and ...
IABSE Congress Report, 2008
ABSTRACT Summary Some aspects of the life-cycle performances of the bridge deck of the cable-stay... more ABSTRACT Summary Some aspects of the life-cycle performances of the bridge deck of the cable-stayed bridges at Malpensa airport in Italy are investigated, in both deterministic and probabilistic terms, by taking the beneficial effects of repair interventions into account. The results show that the repair interventions allow to decrease the rate of deterioration and the dispersion of the involved uncertainty.
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Papers by Pier Giorgio Malerba