Maurizio Orlando

Wind-induced interference effects on two adjacent cooling towers

This paper presents the results of experimental tests carried out in the boundary layer wind tunnel (BLWT) on a rigid model of two adjacent cooling towers. Pressures measured on the two towers were compared with those registered on an isolated tower. The variation of the flow-induced forces produced on each tower by the other one is referred to as interference. Using the registered pressures, numerical linear analyses were performed to calculate the structural responses of the isolated and grouped towers. The results obtained agree with those of other researchers and demonstrate the reliability of the procedure adopted to estimate wind-induced stresses on rigid structures in close proximity.

Displacement capacity of masonry piers: parametric numerical analyses versus international building codes

The nonlinear behaviour of masonry piers loaded in their plane is investigated by parametric numerical simulations. Each pier has a cantilever scheme, is loaded by a constant axial load and is subjected to an increasing horizontal displacement at the top. The macro-modelling approach is used to perform numerical analyses, adopting two different constitutive laws: a total strain crack model and a plastic model. The numerical model is calibrated on a block-masonry type for which experimental tests are available in literature. Parametric numerical simulations are performed by varying the aspect-ratio and the compression level, in order to assess the influence of such parameters on both shear strength and displacement capacity. By comparing numerical results with formulas of international codes, a good agreement for the shear strength is obtained, while significant differences are observed for the displacement capacity, which is influenced by both parameters. The authors propose a simple empirical formula for the displacement capacity, obtained by fitting the numerical results. The expression can be useful in the practical design for considering the influence of aspect-ratio and compression level, currently neglected by building codes.

Unreinforced masonry walls with irregular opening layouts: reliability of equivalent-frame modelling for seismic vulnerability assessment

Equivalent-frame modelling for the estimate of in-plane seismic vulnerability of masonry wall is endorsed by international codes. However, in presence of irregular layouts of openings, the definition of equivalent-frame becomes non-unique and may lead to epistemic modelling errors. The aim of this paper is to develop a simplified tool to estimate such errors as functions of the level or geometric irregularity. Four types of irregularity are considered and quantified by geometric indexes. Nonlinear static analyses are carried out through an equivalent-frame model and a nonlinear finite-element model. It is assumed that both models are exact for perfectly-regular walls, while in presence of irregularities only the continuum approach is able to correctly predict the vulnerability, so that the difference between the two results can be taken as a measure of the error of the equivalent frame. A regular wall is taken as case study and both numerical models are calibrated on experimental data. The four typologies of irregularity are introduced separately, each in steps of increasing magnitude. The results show that the equivalent frame approach is usually not safety-preserving and may be affected by a significant error. A tentative global measure of irregularity, weighting the average effects of each irregularity type, is proposed. The resulting simplified relationship between irregularity level and expected error can be used to define a confidence factor on the modelling, which penalizes the application of the equivalent frame in case of irregular walls. Eventually, an applicability limit of the equivalent-frame model might be set.

Experimental investigation on static and cyclic behaviour of flanged unions for precast reinforced concrete columns

Dry connections are widely used in precast structures for their reduced dimensions and faster installation than wet cast-in situ joints. Above all, column-to-footing and column-to-column dry joints represent a very effective alternative to conventional monolithic solutions for columns higher than three storeys, whose transportation and installation turn out to be too much complicated or unfeasible. A wide and safe use of dry joints in precast columns asks for an in-depth analysis of their behaviour, as both their density and technology affect the overall performance of precast structures, especially under seismic loading. The paper shows results of an experimental campaign performed on full-scale specimens to investigate the behaviour of dry connections for precast columns, under both static and cyclic loading. Tests were performed on two types of joints: in the first type the flexural continuity is achieved by welding column’s longitudinal bars to its steel base plate, while in the second type column’s longitudinal bars are overlapped with sufficient length to rebar dowels welded to the steel column base plate. Experimental results show a good performance of investigated joints, in terms of both overstrength and stiffness. Moreover, the ductility and energy dissipation properties of the column’s region adjacent to the joint were evaluated.

Seismic response of masonry-infilled steel frames via multi-scale finite-element analyses

Effects of masonry infills on the seismic vulnerability of steel frames is studied through multi-scale numerical modelling. First, a micro-modelling approach is utilized to define a homogenized masonry material, calibrated on experimental tests, which is used for modelling the nonlinear response of a one-story, single span, masonry-infilled portal under horizontal loads. Based on results of the micro-model, the constitutive behavior of a diagonal strut macro-element equivalent to the infill panel is calibrated. Then, the diagonal strut is used to model infill panels in the macro-scale analysis of a multi-span multi-story infilled moment-resisting (MR) steel frame. The seismic vulnerability of the MR frame is evaluated through a nonlinear static procedure. Numerical analyses highlight that infills may radically modify the seismic response and the failure mechanism of the frame, hence the importance of the infill correct modelling.

Flexural Capacity of Steel Rack Connections Via The Component Method

Received: October 01, 2017 Revised: November 01, 2017 Accepted: December 01, 2017 Abstract: Background: In pallet rack structures, cold-formed steel (CFS) beams and columns are connected through dry joints, so beams can be easily disconnected according to changes of the rack geometric layout. Due to the great variety of connector types and member geometries, recent design codes recommend experimental tests on rack connections to assess their mechanical features. Nevertheless, tests only allow for the overall response of a joint to be evaluated, without providing information about the contribution of each component of the joint to its stiffness and strength.

An innovative cladding panel connection for RC precast buildings

Recent Italian earthquakes highlighted some critical issues of mechanical devices usually utilized to fasten reinforced concrete cladding panels to precast structures. These devices were often designed to uncouple the displacements of cladding panels and the frame structure. Unfortunately, during the last earthquakes, the cladding-to-structure connections did not perform as expected, and in most cases, they failed causing the overturning of cladding panels. The paper presents results of a wide experimental campaign on both commercial and innovative mechanical cladding-to-structure connections, both for vertical and horizontal panels. Tests were performed in the Structures and Materials Testing Laboratory of the Department of Civil and Environmental Engineering of Florence, where a specific and original setup was designed to perform dynamic cyclic tests, under different load conditions. Commercial connections showed a hysteretic behaviour until the collapse, due to the flexural failure of the strap or to the failure of the anchor channel fixed to beams or columns and the expulsion of the hammer-head screws. Proposed innovative connections, especially those used for vertical panels, proved to be able to uncouple in-plane horizontal displacements of panels and the structure, as expected in their design. Moreover, no significant damage was detected in these connections during tests, as friction forces were very low.