[1] “Longitudinal Thermal Behaviour of a Concrete Box Girder Bridge in Italy”, Structural Engineering International, N°4, 1996.
(in collaborazione con: N.Hariga, G.Nati, M.Orlandini)

  • Abstract: This paper deals with the thermal behaviour of the Casilina prestressed box girder bridge over the Fiano Romano-San Cesareo motorway , Italy.
    During three years of field monitoring, temperature measurements were taken, transmitted and stored by means of computer-aided facilities.
    A theoretical modeling, executed by a F.E.M. transient thermal analysis, proved to be satisfactorily close to the experimental values and allowed the calibration of an empirical algorithm by means of which effective mean temperature and effective linear vertical and horizontal gradients could be deduced from the set of field temperatures at each measurement instant.

[2] “Discontinuous Deformation of Tensile Steel Bars: Experimental Results”, A.S.C.E., Journal of Engineering Mechanics, Vol.125, N°11, pgg. 1243-1250, Nov.1999.
(in collaborazione con G.Royer)

  • Abstract: Marked differences have been observed between the global and the local responses of tensile steel bars – the first traditionally defined by considering average strains (displacement of the bar’s ends divided by its undistorted length), and the second obtained by local strain measures through high performance resistance strain gauges. This distinction highlights the peculiarities of various qualities of steel normally employed as reinforcement in concrete. In particular, the phenomenon of serrated deformation at yielding (the Portevin-Le Chatelier effect) and the peculiarities of this metastable state, when unloading sequences are performed, will be discussed. It will be shown how the presence of ribs can influence the local behaviour and how this is reflected in the gross response. In the analysis, the importance of strain hardening in improving the ductility performance of steel bars is observed.

[3] “A Mechanical Model for the Elastic-Plastic Behavior of Metallic Bars”, International Journal of Solids and Structures, Vol.37, pgg. 3901-3918, Apr. 2000.
(in collaborazione con G.Royer)

  • Abstract: A simple mechanical model, which consists of a particular assemblage of elementary units composed of elastic springs and frictional sliding blocks, appears suitable for describing the various aspects of the elastic-plastic behaviour of steel bars in standard tensile tests: oscillations in the average stress-strain curve, the distinction between local and global responses, instability due to the transition from an upper to a lower yield point, the spread of plastic deformation, strain-hardening behaviour, elastic unloading and the influence of loading-device stiffness.

[4] “Statistical Analysis of Thermal Actions on a Concrete Segmental Box-Girder Bridge”, Structural Engineering International, N° 2, pgg. 111-116, 2000
(in collaborazione con R.Barsotti).

  • Abstract: The paper presents a method for statistical treatment of thermal actions measured on concrete bridges during long-time monitoring campaigns. The method is based on recognising that thermal actions are not entirely random, but contain deterministic components due to the Earth’s rotation and revolution.
    Greater precision and reliability could be attained in calculating frequent, quasi-permanent and fifty-years time period thermal actions for structural design by applying separate statistical analyses to these random and deterministic parts.
    The procedure is then applied to checking the validity of the empirical relationships set forth in Eurocode 1, Parts 2-5, between a bridge’s effective mean temperature and shade air temperatures.

[5] “Transient Temperature Fields and Thermal Actions in the Leaning Tower of Pisa”, Bautechnik, Heft 5, Mai 2001.
(in collaborazione con E.Ulivieri).

  • Abstract: Based on the analytical description of the daily variations of the main meteorological agents all over an idealised, mean meteorological year and taking also into account shadowing effects, a complete yearly transient study of the thermal response of the Tower of Pisa is performed.
    The model describes the hourly evolution of the temperature fields in the basement, in the shaft and in the columns of the monument at any day of the idealised year.
    The theoretical knowledge of the punctual time and space variation of the temperature fields over the cross sections of the Tower allows the calculation of synthesis quantities like the Effective Mean Temperature and the Effective Global Linear Gradient which constitute the bases to predict thermal movements and eigenstresses.

[6] “Statistical Analysis of Temperature Measurements in the Leaning Tower of Pisa in Comparison with Theoretical Predictions”, Bautechnik, Heft 10, Oktober 2002.
( in collaborazione con P.Formichi).

  • Abstract: The wide amount of temperature measurements collected in the shaft of the Leaning Tower of Pisa during four years monitoring is here analysed by means of statistical methods and compared with the theoretical values calculated with a F.E.M. analysis in a precedent work, where the transient boundary conditions reproduce the hourly variations of the main meteorological agents all over an idealised, mean meteorological year.

[7] “The Calculation of Thermal Movements and Eigenstresses in the Leaning Tower of Pisa“, Bautechnik, Heft 1, Januar 2006.
(in collaborazione con E.Ulivieri)

  • Abstract: Starting from predicted yearly and daily distributions of the temperature fields induced by the climatic agents over the cross- sections of the Leaning Tower of Pisa, the correlated time histories of thermal movements and eigenstresse have been calculated by simply assimilating the monument to a prismatic, inhomogeneous elastic body. Comparisons performed between calculated and measured daily and seasonal thermal displacements evidenced a good prediction capability of the model and its attitude to be used as a interpretation tool to understand also thermal periodical movements in other tower-shaped buildings.

[8] “Analytical Remarks on the Anchorage of Elastic-plastically bonded Ductile Bars”, International Journal of Mechanical Sciences, Vol.49, N°5, May 2007 (www.sciencedirect.com).

  • Abstract: A simple analytical extension of Hermite-Bresson’s results to the domain of the irreversible relative displacements allows the description of the non-linear force-displacement response of a tensile bar embedded in a massive support by means of an elastic-plastic bonding agent.The analytical model evidences the influence of the main governing parameters on the attainment of two ideal anchorage conditions of plasticity initiation occurring in the bar simultaneously with that of the bond material (anchorage length LIP), or of plasticity initiation occurring in the bar just after the complete yielding of this one (anchorage length LCP).The ratio between the expressions of these two anchorage lengths reveals an interesting, compact mathematical form of eloquent mechanical meaning which allows the immediate determination of anchorage length LIP.

[9] “Rheological Modelling of Residual Stresses and Deformations of Plates during Non-uniform Cooling”, International Journal of Mechanical Sciences, Vol. 49, N°12,  pagg. 1366-1376,  2007.
(in collaborazione con G.Buratti)

  • Abstract: The time-space distribution of eigen-stresses and residual deformations of a plane plate which reaches its final solid state through a given transition process of non uniform cooling is here described by means of a simple visco-elastic rheological model.The aging processes of the elastic and viscous properties are supposed to be temperature dependant in order to directly control the influence of the thermal history on the final stress and deformation conditions of the solid.The model is able to reproduce qualitatively well the development of eigen-stresses in the spatially symmetrical cooling processes of tempering or toughening, as well as the formation of eigen-stresses and permanent bending in the spatially asymmetrical cooling processes of heat curving.

[10] “A Proposal to Roof the Courtyyards of an historical Building in Pisa with Glass Shells: Form Finding and Stability Problems”,  International Journal of Architectural Engineering, ASCE, (ISSN 1076-0431), Vol.15, n° 2, pp. 62-66, 2009.
(in collaborazione con G. Del Guerra)

[11] “Glass Tensegrity Trusses”, Structural Engineering International , 4/2010.
(in collaborazione con L.Lani)

  • Abstract:High transparency and modularity, retarded first cracking, non-brittle collapse and fail-safe design were the basic requirements that inspired and guided the development of a new kind of glass beams. The two basic conceptual design goals were to avoid any cracking at service and to get a ductile behaviour at failure. These objectives were reached by a preliminary subdivision of the beam into many small triangular laminated panes and by assembling them together by means of prestressed steel cables. Two prototypes have been constructed at the University of Pisa, tested in the elastic domain under dynamics loads and successively brought to collapse under quasi-static, increasing load cycles. In order to investigate the decay process of residual mechanical resources, the second prototype has been repaired twice by substituting just the damaged triangular panes and then tested again each time up to failure. Experimental results resulted in a good agreement with non-linear numerical simulations performed by appropriate finite element modelling

[12] “A Contribution to the Theoretical Prediction of Life-Time in Glass Structures”, Journal of
the International Association for Shell and Spatial Structures, Vol.52, N° 4, n° 170, pgg. 225-231,
December 2011.
(in collaborazione con Manuel Santarsiero)

  • Abstract:In order to assess the safety levels of glass structures a scattered and inhomogeneous variety of mostly complicated resistance criteria is presently available, very often requiring specially developed softwares. For this reason engineers who wants to assess with reliability the actual safety level of glass structures of relevant economical importance are still obliged to undertake expensive experimental tests.
    In the attempt to overcome this problem, it was formulated a new semi-probabilistic failure prediction method called “Design Crack Method” (DCM), which is a compromise between the necessity to accurately model the complex mechanical behaviour of glass at breakage and the need to reduce the analytic complexity of the calculations. On the basis of Linear Elastic Fracture Mechanics, such aim has been analytically reached in the present work by defining a new quantity called Design Crack, characterized by a mathematical expression that depends on the probability of failure and on the surface damaging level.
    The proposed method, which is in accordance with the basic principles of the Structural Eurocodes, allows to predict glass lifetime taking into due account the influence of parameters like the surface extension and the loading time-history of the structural element.
    A design safety assessing procedure of glass structures is also briefly explained and several experimental tests (four point bending test) on real glass elements are numerically simulated by the D.C.M. showing a good agreement with the measured values.