Claudio Amadio

Effective width evaluation for steel–concrete composite beams

In this paper the problems connected to the effective width evaluation for serviceability and ultimate analysis of steel–concrete composite beams are analyzed. By a parametric study carried out through the Abaqus code it is pointed out how the actual codes do not provide, in general appropriate results, for elastic and ultimate limit state checks. The most important parameters that influence the effective width are analyzed. Some preliminary criteria for an adequate design are presented.

Buckling of Laminated Glass Elements in Compression

Monolithic and laminated glass beams or panes are frequently adopted as structural elements in modern and innovative architectural applications. Several aspects related to the load-carrying behavior of these new construction elements are very complex to evaluate. For example, the degradation of mechanical properties of the interlayer, the amplitude of the imperfections affecting the beams, or the presence of added external loads represent only some aspects that contribute to the complexity of evaluating the buckling response of these innovative structural components, characterized by high slenderness ratios and brittle behavior in tension. For these reasons, the buckling of laminated glass beams in compression is investigated in this paper by using a simple analytical model developed on the basis of Newmark’s theory of composite beams with deformable connections. Buckling curves are presented to illustrate how a combination of simultaneous weathering variations, initial imperfections, or particular load c...

Experimental study and numerical investigation of Blockhaus shear walls subjected to in-plane seismic loads

AbstractBlockhaus systems represent a traditional construction technology in which structural resistance is obtained by direct contact between multiple timber surfaces obtained through carvings, notches, and ancient joints. Native of forested areas, this technology is currently used for the construction of log buildings also in earthquake-prone areas. Their seismic structural behavior hence represents an interesting and not well known research topic. In the paper, experimental results obtained by cyclic and monotonic tests recently performed on Blockhaus shear walls with three different types of joints are presented and discussed. At the same time, sophisticated finite-element numerical models able to take into account the complex structural behavior of log-walls subjected to in-plane seismic forces are described. Performed numerical simulations highlighted that in general multiple factors affect the global structural response of Blockhaus shear walls, including the presence of imperfections (small gaps) ...

A novel hybrid system with RC-encased steel joists

ABSTRACT The paper presents the main results of an experimental and numerical study on a novel structural frame system, which employs RC encased steel joist beams and columns. An accurate 3D numerical model has been used to represent the resistance mechanisms in beams and beam-to-column connections. Experimental and numerical outcomes have been employed to develop suitable analytical models to be used in practical design. In particular, the beam flexural response has been investigated, providing a simple relationship for the flexural rigidity at different load levels. Capacity models have been then proposed for the bending and shear resistance of partially and fully-encased beams, and for exterior beam-to-column joints.

Application of Damage Mechanics Concepts to the Boundary Element Method

The boundary element method is applied to damage problems by introducing convenient inelastic strains which account for strength and/or stiffness decrease. Thus, a damage parameter is not considered explicitly and the material stiffness matrix is maintained constant throughout the domain during the whole load history. As a consequence, the material remains homogeneous and a traditional boundary element approach can be followed, as well as for any other quasi-static inelastic problem (e.g., for elastic-plastic structural analysis). The main features of the technique proposed in the paper are pointed out and numerical examples are given.

Passive Control Systems for the Blast Enhancement of Glazing Curtain Walls Under Explosive Loads

Glass curtain walls are used in modern buildings as envelopes for wide surfaces due to a multitude of aspects. In glass curtain walls, tensile brittle panels are connected through mechanical or adhesive joints with steel frameworks or aluminum bracing systems, and due to the interaction of several structural components, the behaviour of the so assembled system is complex to predict, especially under exceptional loading conditions such as explosive events. In the paper, glazing curtain walls are investigated by means of Finite-Element (FE) numerical simulations, under the effect of air blast pressures of variable intensity. Their typical dynamic behaviour and criticalities under high-strain impact loads are first analyzed. By means of extended nonlinear dynamic FE parametric studies, innovative devices are applied to traditional curtain walls, at their support points, in order to improve their expected dynamic response. Two possible solutions, namely consisting of viscoelastic (VE) or elasto-plastic (PL) dampers, are proposed as passive control systems for the mitigation of maximum effects in the façade components deriving from the incoming blast pressures. As shown, although characterized by specific intrinsic mechanical behaviours, either VE or PL dampers can offer beneficial structural effects. In the first case, major advantages for the façade components derive from the additional flexibility and damping capacities of VE devices. In the latter case, PL dampers introduce additional plastic energy dissipation in the traditional curtain wall assembly, hence allowing preventing severe damage in the glazing components. It is thus expected that the current outcomes could represent a valid background for further experimental validation as well as detailed assessment and optimization of the proposed design concept.

Application of a Translational Tuned Mass Damper Designed by Means of Genetic Algorithms on a Multistory Cross-Laminated Timber Building

AbstractThis paper presents a numerical study conducted on a seven-story timber building made of cross-laminated (X-lam) panels, equipped with a linear translational tuned mass damper (TMD). The TMD is placed on the top of the building as a technique for reducing the notoriously high drifts and seismic accelerations of these types of structures. TMD parameters (mass, stiffness, and damping) were designed using a genetic algorithm (GA) technique by optimizing the structural response under seven recorded earthquake ground motions compatible, on average, with a predefined elastic spectrum. Time-history dynamic analyses were carried out on a simplified two-degree-of-freedom system equivalent to the multistory building, while a detailed model of the entire building using two-dimensional elastic shell elements and elastic springs for modeling connections was used as a verification of the evaluated solution. Several comparisons between the response of the structure with and without TMD subjected to medium- and h...

A seismological and engineering perspective on the 2016 Central Italy earthquakes

The strong earthquake (M 6.0-6.2) that hit the central Apennines on August 24, 2016, occurred in one of the most seismically active areas in Italy. Field surveys indicated severe damage in the epicentral area where, in addition to the loss of human life, widespread destruction of cultural heritage and of critical buildings occurred. Using the neo-deterministic seismic hazard assessment (NDSHA), we apply the maximum deterministic seismic input (MDSI) procedure at two of the most relevant sites in the epicentral area, comparing the results with the current Italian building code. After performing an expeditious engineering analysis, we interpret as a possible cause of the reported damages the high seismic vulnerability of the built environment, combined with the source and site effects characterising the seismic input. Therefore, it is important to design and retrofit with appropriate spectral acceleration levels compatible with the possible future scenarios, like the ones provided by MDSI.

Dynamic response of cable-supported façades subjected to high-level air blast loads: numerical simulations and mitigation techniques

A glazing facade subjected to blast loads has a structural behaviour that strongly differs fromthe typical response of a glazing system subjected to ordinary loads. Consequently, sophisticatedmodelling techniques are required to identify correctly its criticalities. The paper investigates the behaviour of a cable-supported facade subjected to high-level blast loading. Nonlinear dynamic analyses are performed in ABAQUS/Explicit using a sophisticated FE-model (M01), calibrated to dynamic experimental and numerical results. The structural effects of the total design blast impulse, as well as only its positive phase, are analyzed. At the same time, the possible cracking of glass panels is taken into account, since this phenomenon could modify the response of the entire facade. Finally, deep investigations are dedicated to the bearing cables, since subjecting them to elevated axial forces and their collapse could compromise the integrity of the cladding wall. Based on results of previous studies, frictional devices differently applied at their ends are presented to improve the response of the facade under the impact of a high-level explosion. Structural effects of various solutions are highlighted through dynamic simulations. Single vertical devices, if appropriately calibrated, allow reducing significantly the axial forces in cables, and lightly the tensile stresses in glass panes.

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...