Natalino Gattesco

Experimental Response of Brick-Masonry Spandrels under In-Plane Cyclic Loading

AbstractThis paper investigates the behavior of spandrels in perforated walls of existing unreinforced masonry buildings. The main results of experimental tests carried out on full-scale brick-masonry coupling beams under in-plane cyclic loading are presented and critically discussed. The effectiveness of different strengthening techniques has been examined by testing damaged spandrels reinforced using steel ties or angles. The resistant mechanisms, the degradation of strength and stiffness, and the hysteretic energy dissipation capacity of the tested coupling beams have been analyzed. The experimental shear resistance of the unstrengthened and strengthened spandrels have been then compared against analytical predictions obtained by using expressions provided by current codes of practice. Finally, these analytical formulations calibrated against the experimental results have been employed to study the effects of the main spandrel geometrical characteristics. The results achieved provide relevant informati...

Moment Redistribution in Continuous Steel-Concrete Composite Beams with Compact Cross Section

The paper investigates the design of continuous steel-concrete composite beams with compact cross section using the elastic analysis with limited redistribution. The permissible moment redistribution which satisfies the requirements of the ultimate limit state collapse and serviceability limit state crack width in the concrete slab was computed. An advanced finite element program accounting for all mechanical nonlinearities and time-dependent phenomena creep and shrinkage of concrete was used. An extensive parametric analysis aimed to determine the influence of several geometrical parameters on the permissible moment redistribution was carried out on propped cantilevers and fixed-end beams. The analyzed parameters include the shape of the steel profile, the ratio between the depths of concrete slab and steel beam, the steel to concrete area ratio, and the reinforcement percentage of the concrete slab. The analysis was limited to compact steel sections AISC 360-05 or class 1 steel sections Eurocode 3 and low ductility reinforcing steel elongation at maximum load ru=2.5%. The moment redistribution domain which satisfies the rotation compatibility in the critical sections, due to the attainment of the rupture of the reinforcement or the local buckling of the steel profile, and the control of cracking 0.3 mm in service was evaluated and compared with the limits recommended by current codes of practice. A proposal for the allowable moment redistri- bution domain according to the limits of the study was given. DOI: 10.1061/ASCEST.1943-541X.0000098 CE Database subject headings: Composite beams; Concrete; Steel; Continuous beams; Bending; Nonlinear analysis; Finite element method; Moment distribution; Cross sections. Author keywords: Composite beams; Concrete; Steel; Continuous beams; Bending moments; Nonlinear analysis; Finite-element method.

Experimental Behavior of Masonry Vaults Strengthened with Thin Extradoxal or Intradoxal Layer of Fiber Reinforced Lime Mortar

The results of a first experimental research program on masonry vaults strengthened by means of GFRP meshes embedded in a thin layer of lime mortar, are herein presented. The tests were designed to reproduce the pattern of a transversal horizontal load proportional to the vault self-weight. The typical simplified loading patterns generally used for the experimental tests concern concentrated vertical loads at the crown section or at 1/4 of the span, but some numerical investigations evidenced that these configurations are not able to reproduce the actual behavior and the effectiveness of the reinforcement. So a specific rig was designed to apply the horizontal load pattern.Solid brick masonry barrel vaults were considered (thickness 120 mm, arch span 4000 mm, arch rise/radius = 0.75). Three quasi-static cyclic tests were performed: the first concerned an unreinforced vault, the second a vault reinforced at the extrados through the application of a mortar coating reinforced with a GFRP mesh and the third reinforced at the intrados surface with the same technique. The experimental results demonstrated the technique effectiveness and the important increment of ductility of the vaults.

Pushdown Tests on Masonry Infilled Frames for Assessment of Building Robustness

AbstractThe research presented in this paper addresses the influence of nonstructural masonry infill on the resistance of multistory buildings to progressive collapse under sudden column loss scena...

Seismic enhancement of masonry buildings strengthened through GFRP reinforced mortar coating

The reduction of seismic vulnerability of existing masonry buildings through the application on the walls of a mortar coating reinforced with a GFRP (glass fiber reinforced polymer) mesh is studied and discussed. Numerous experimental tests, carried out by the authors, demonstrate the effectiveness of this technique for enhancing the mechanical response of the walls, both subjected to in-plane and out-of-plane actions. In the study, the capacity curves of an existing unreinforced masonry building are compared with those of the same building strengthened with the GFRP reinforced mortar coating technique. An almost regular two storey building is considered in the numerical study and it is analyzed by adopting the method of the equivalent frame. Two different types of masonry are considered in the study: solid bricks and rubble stones. Static nonlinear analyses are carried out and the nonlinearity of the material of the wall elements (piers and spandrels) is considered through the introduction of plastic hinges in the plane of the masonry wall. The results evidence a significant increase in terms of shear resistance, displacement capacity and total strain energy. The collapse due to bending of piers in most cases of strengthened buildings occurred before than the ultimate shear drift was obtained.

Numerical Evaluation of Mechanical Parameters Role in GFRP Strengthened Cobblestone Masonry Walls

The use of a GFRP (Glass Fiber Reinforced Polymers) mesh, embedded as a reinforcement in a mortar coating on both wall sides, proved to be effective and reliable in increasing the masonry wall resistance and the plastic deformation capacity.In this study, a NL finite element model, developed to predict the in-plane behaviour of masonry walls strengthened by means of this technique, is refined and used in an extensive parametric study. Numerical results were compared with diagonal compression test data on URM and RM cobblestone masonry samples, showing good agreement. The masonry panel and the mortar coating were modelled as isotropic homogeneous materials with a smeared crack approach, whereas the GFRP reinforcement was modelled as a mesh of truss elements. Properties assigned to materials were derived from experimental tests.The parametric study performed before on some involved mechanical properties, considering a standard range of variation, is now extended to other parameters. Moreover, the combined variation of different properties is considered. The actual contribute of each component (masonry, GFRP mesh, mortar) on some macroscopic parameters (strength and ductility of the specimen) is evaluated.The parametric analysis highlights the important role of the GFRP mesh not only on the peak load increment but also on the post-peak behavior and, in particularly, on the ductility increment of the reinforced masonry panel. These results can address the optimization of the intervention technique and the deliverable of operative guidelines for practitioners.

Comparison of In-Plane Mechanical Performances of Masonry Walls Strengthened with Different Mortar Coatings Reinforced with Glass or Carbon Fiber Composite Meshes

The results of some diagonal compression tests performed on solid brick masonry samples (1160x1160x250 mm3) to evaluate and compare the effectiveness of different shear reinforcement techniques for existing masonry based of the application, on both sides of the wall, of a mortar coating layer reinforced with fiber composite meshes are presented and discussed in the paper. In particular, 30 mm and 10 mm thick mortar coatings, made of three different mortar types and reinforced by means of both glass and carbon-fibers composite meshes were considered. Significant resistance increases (about 110%) were attained in respect to plain masonry; moreover, it emerged that the meshes are able to prevent the masonry brittle collapse, absorbing tensile stresses in the cracked areas. By maintaining constant the coating thickness, better mortar characteristics determined an increase of the resistance increment ratio but a more rapid decrease of resistance after peak. Similar performances were attained by samples characterized by approximately constant values of shear stiffness and diagonal compression resistance. The differences attributable to the different type of meshes resulted minimal, due to the similar reinforcement percentage.

Pushover analysis based on equivalent diagonal springs for the assessment of the seismic safety of post-and-beam timber buildings braced with nailed shear walls

A method for a simplified modeling of post-and-beam timber buildings braced with nailed shear walls, useful for seismic design purposes, is presented and discussed in the paper. This strategy is based on the schematization of the vertical diaphragms through equivalent diagonal springs with elastic-plastic behavior and allows the assessment of the resisting ground acceleration by performing nonlinear static analysis; the Capacity Spectrum method based on equivalent viscous damping was applied. This nonlinear procedure constitutes a reliable and simple alternative to the linear static analysis using the behavior factor q. The procedures to determine the characteristics of the equivalent elements (stiffness and load-carrying capacity) are based on analytical evaluations, starting from the actual characteristic of shear walls. A comparison between the results of numerical simulation based of more refined and complex models, previously presented by the authors, and this time-reducing, simplified analysis proved the good reliability of the method.

Masonry Vaults Subjected To Horizontal Loads: Experimental and Numerical Investigations to Evaluate the Effectiveness of A GFRM Reinforcement

The paper investigates the effectiveness of a modern reinforcement technique based on a Glass Fiber-Reinforced Mortar (GFRM) for the enhancement of the performances of existing masonry vaults subjected to horizontal seismic actions. In fact, the authors recently evidenced, through numerical simulations, that the typical simplified loading patterns generally adopted in the literature for the experimental tests, based on concentrated vertical loads at 1/4 of the span, are not reliable for such a purpose, due to an unrealistic stress distribution. Thus, experimental quasi-static cyclic tests on full-scale masonry vaults based on a specific setup, designed to apply a horizontal load pattern proportional to the mass, were performed. Three samples were tested: an unreinforced vault, a vault reinforced at the extrados and a vault reinforced at the intrados. The experimental results demonstrated the technique effectiveness in both strength and ductility. Moreover, numerical simulations were performed by adopting a simplified FE, smear-crack model, evidencing the good reliability of the prediction by comparison with the experimental results.

Structural Performance of Old Composite Floors Made up of Wrought Iron Joists and Masonry Vaults

In this paper the behaviour of old floors made up of wrought iron beams supporting shallow masonry vaults is analysed. The performance of this structural system, which was extensively used in Europe in the XIX century, has been only marginally investigated thus far. Very few studies on masonry-iron composite floors are available in the literature, where the role played by the physical interaction between the vaults and the metallic profiles has yet to be fully understood. When assessing historical buildings with floors characterised by the analysed floor system, a realistic estimate of this interaction may be critical to avoid unnecessary and costly strengthening works. The floor structure with composite wrought iron beams and solid brick vaults of the “Military Hospital” in Trieste built in 1840 by the Hapsburg Military Administration have been investigated performing physical experiments and numerical simulations. Experimental tests were carried on the floor and used to calibrate finite element numerical descriptions. These have been adopted in numerical simulations to investigate the response of the analysed floor system up to collapse considering different geometrical characteristics for the floor. The numerical results shed some light on the actual interaction between the different components of the composite floor which significantly influences the floor stiffness and load bearing capacity.