1,720,988 research outputs found
Least-thickness symmetric circular masonry arch of maximum horizontal thrust
Full text linkThis analytical note shall provide a contribution to the understanding of general principles in the Mechanics of (symmetric circular) masonry arches. Within a mainstream of previous research work by the authors (and competent framing in the dedicated literature), devoted to investigate the classical structural optimization problem leading to the least-thickness condition under self-weight (“Couplet-Heyman problem”), and the relevant characteristics of the purely rotational five-hinge collapse mode, new and complementary information is here analytically derived. Peculiar extremal conditions are explicitly inspected, as those leading
to the maximum intrinsic non-dimensional horizontal thrust and to the foremost wide angular inner-hinge position from the crown, both occurring for specific instances of over-complete (horseshoe) arches. The whole is obtained, and confronted, for three typical solution cases, i.e., Heyman, “CCR” andMilankovitch instances, all together, by full closed-form explicit representations, and elucidated by relevant illustrations
Finite-Friction Effects in Self-standing Symmetric Circular Masonry Arches
No full textThis note concerns a general issue, in the mechanics of masonry arches, with reference to symmetric circular geometries, with variable opening, and possible stereotomy with radial joints (to be potentially formed, at failure, within the ideal continuous arch), in a least-thickness condition, under self-weight, namely the role that a finite inherent friction, among the theoretical joints, may play in ruling out the selfstanding conditions and the mechanical features at incipient collapse, setting a change from purely-rotational modes to mechanisms that may include sliding. The issue is systematically investigated, by a full analytical derivation, and validated through an original Complementarity Problem/Mathematical Programming formulation, and numerical implementation, reconstructing the complete underlying map of thicknessto-radius ratio versus friction coefficient of all arch states, and corresponding collapse mechanisms. This investigation shall clear the issue, of the theoretical influence of finite friction, in the above-stated setting, and contribute to provide a full understanding of basic aspects in the methodological description, and physical interpretation, of the mechanics
of masonry arches, with implications that may come up to appear also in practical terms, once dealing with this traditional and remarkable structures, in real cases, possibly endowed of historical character and architectural value, to be preserved and renewed
Evolutive and Kinematic Limit Analysis Algorithms for Large-Scale 3D Truss-Frame Structures: Comparison Application to Historic Iron Bridge Arch
No full textTwo new computational algorithms for the Limit Analysis (LA) of large-scale 3D truss-frame structures recently proposed by the authors are reconsidered and adapted for a comparison prediction of the elastoplastic response of a strategic beautiful historic infrastructure, namely the Paderno d'Adda bridge (or San Michele bridge), a riveted wrought iron railway viaduct that was built in northern Italy in 1889. The first LA algorithm traces a fully exact evolutive piece-wise linear elastoplastic response of the structure, up to plastic collapse, by reconstructing the true sequence of activation of made-Available plastic joints (as a generalization of plastic hinges), in the true spirit of LA. The second LA algorithm develops an independent kinematic iterative approach apt to directly determine the plastic collapse state, in terms of collapse load multiplier and plastic mechanism, based on the upper-bound theorem of LA. Specifically, the marvelous doubly built-in parabolic arch of the bridge is analyzed, under a static loading configuration at try-out stage, and its elastoplastic response is investigated, in terms of evolutive load-displacement curve, collapse load multiplier and plastic collapse mechanism. The two LA algorithms are found to much effectively run and perform, despite the rather large size of the computational model, with a number of dofs in the order of four thousands, by achieving good corresponding matches in terms of the estimate of the load-bearing capacity and of the collapse characteristics of the arch substructure, showing this to constitute a well-set structural element. Moreover, the direct kinematic method displays a rather dramatic performance, in truly precipitating from above onto the collapse load multiplier and rapidly adjusting to the collapse mode, in very few iterations, by a considerable saving of computational time, with respect to the complete evolutive elastoplastic analysis. This shall open up the way for further adoption of such advanced LA tools, with LA regaining a new momentum within the modern optimization analysis of structural design and form-finding problems
Reference Structural Investigation on a 19th-Century Arch Iron Bridge Loyal to Design-Stage Conditions
No full textThis work gathers the outcomes of a comprehensive case study concerning a reference structural investigation on the bridge at Paderno d’Adda, a monumental arch iron viaduct completed in 1889, situated in Lombardy (northern Italy), still keeping today a crucial position within the local railway and road transportation networks. The bridge is part of precious architectural heritage, together with a few rather similar bridges in Europe, which may be in the predicate to become part of the UNESCO list. A comprehensive structural analysis loyal to design-stage conditions was developed. After the constitution of a detailed linear elastic numerical model of the structure, various static analyses were first performed; comparisons with available recorded data at the try-out stage proved the model’s consistency. Then, further insight into the linear range, concerning the modal dynamic behaviour, was investigated, with a reasonable matching with available experimental modal characteristics. Finally, a complete non-linear inelastic analysis was developed, up to detect plastic-collapse features, to assess the safety margin at increasing live loads. This case study shall contribute in setting up a reference scene about the present bridge structural capacity, within the current debate on the destinies of the structure and the screening of possible intervention scenarios
A novel formula for resistance reduction in perforated steel plate shear walls
No full textRecently, many researches have been devoted to predicting Perforated Steel Plate Shear Wall (P-SPSW) behaviour, from which some have been able to propose resistance reduction formulas. Nevertheless, new findings have witnessed some nonconformance between the actual response of P-SPSWs and the values predicted by available closed form solutions. In this study, the possible sources of such nonconformances have been investigated and a novel formula for resistance reduction in P-SPSWs has been proposed. To this end, 28 SPSWs having 3~6 stories with aspect ratios ranging from 0.8 to 2.0, have been carefully designed according to the AISC requirements for thin infill panels. Afterwards, the SPSWs were simulated using practical infill panels and by adopting a rectangular perforation layout, the optimum perforation sizes were explored in such a way that the P-SPSW would exhibit a lateral sway similar to the original SPSW. Finally, all design parameters for SPSWs and P-SPSWs were collected in a database and used to propose some improved linear, bilinear and logarithmic formulas. A survey done on the proposed formula revealed an average absolute error less than 4% in estimating the perforation diameters, which is relatively small compared to the error margin of other formulas and, as a result, the formula in question is concluded to be a reliable tool for design purposes. Finally, the proposed formula for diagonal perforation has been successfully verified for estimating the strength reduction in an available experimentally studied single-story P-SPSW
On optimum perforation layout in low-rise steel plate shear walls.
No full textThe design and performance of Steel Plate Shear Walls (SPSW) strongly depends on infill panels. Any unnecessary increase in the thickness of infill panels, which is a common occurrence in low-rise buildings, results in extremely large boundary elements and a noneconomic design. Among the several remedies that have been proposed and discussed by researchers, infill panel perforation has become more popular in SPSW design and construction. As a designer, one should primarily choose a desirable perforation layout, then adopt an approximate stiffness reduction formula and try to replace the infeasible design infill panel with a perforated one which possesses a minimum practical thickness and provides a similar lateral stiffness and strength. In this paper for a 4-story SPSW, primarily designed with practically infeasible thin infill panels, the optimum perforation diameters corresponding to diverse diagonal and rectangular perforation layouts are explored and the results have been compared to those provided by the available stiffness reduction formulas. The optimization outcomes reveal that the uniformly spaced rectangular perforation layouts are more efficient in the sense of SPSW stiffness reduction. Also, the efficiency of stiffness reduction formulas for rectangular perforation layouts have been assessed and the reliable methods introduced. Finally, on the basis of the resulted optimum sets, some formula improvements and design recommendations are concluded which would be useful and beneficial for practicing engineers
Effective Limit Analysis Computational Approaches for the Structural Characterization of Nervi’s Palazzetto dello Sport
No full textIn this work, two formulations, and computational implementations, of Limit Analysis (LA), for large-scale 3D truss-frame structures are employed to efficiently investigate the limit elastoplastic response of the fascinating and well-known Palazzetto dello Sport (1957), located in the Flaminio district of Rome (Italy), designed by Pier Luigi Nervi. To this end, a spatial FEM modeling was first generated, whereby the characteristic inclined trestles and supporting skeleton of the above concrete shell dome were modelled according to the corresponding geometric characteristics and mechanical properties acquired by inspecting original design drawings and relevant bibliographic sources. In performing the structural Limit Analysis, the first algorithm step-by-step traces a fully exact evolutive piece-wise linear elastoplastic response of the structure, up to plastic collapse, by reconstructing the sequence of activation
of localised plastic joints. The second algorithm, relying on a kinematic iterative direct approach, determines just the collapse mechanism and associated collapse load multiplier, but in a much shorter computational time, showing a rather impressive performance, in truly precipitating from above on the collapse load multiplier, by rapidly adjusting possible
mechanisms to the sought collapse mode, in very few iterations. The performed investigation reveals the ingenuity of Nervi’s work, not only with respect to ordinary structural bearing tasks, within the elastic range of regular-service structural response, but also to post-yield performance and ultimate limit load capacity, up to possible ductile failure
Procedures for characterization of compressive material parameters for GRE pipes, using flexural modulus test results and inverse analysis
No full textNowadays, the use of pipes manufactured with composite materials is preferred for transferring fluid by the oil and gas industries. For the correct design of such infrastructures, determining their material parameters makes recourse to specifically regulated experimental tests. The tensile properties of glass resin epoxy (GRE) pipes can be determined using conventional direct tensile and internal hydrostatic pressure tests. However, the conventional shear and compressive test methods for determining the compressive and shearing properties of a single GRE layer cannot be followed reliably due to uncertainties relevant to buckling, stress concentrations and material locality. In addition, the filament winding's direction, characterizing the orthotropic behaviour of such (GRE) composite material, can be chosen in order to optimize the mechanical behaviour of the pipe. Herein, an inverse analysis approach, previously applied successfully by authors to different mechanical contexts, is proposed to overcome the possible above-mentioned uncertainties relevant to the compressive and shearing properties of GRE material and to optimize the filament winding's direction. The load-displacement response of the flexural modulus test ASTM D 2412 is considered as a measurable quantity to be used in the inverse procedure. The efficiency of the proposed method, in the sense of accuracy and stability, is verified after creating some pseudo-experimental tests, whose numerical results have been statistically perturbed in order to simulate experimental data's noise. The proposed identification procedure would require a relatively high computing time, an uncommon knowledge in computational mechanics, and a sophisticated computing system. Therefore, in order to speed up the characterization procedure and remove any need of deep computational mechanics knowledge and advanced computing devices, an "Offline" analysis tool, based on proper orthogonal decomposition and radial basis functions which has previously been developed in different mechanical contexts, is here adapted to this specific mechanical problem by developing a (light) software, to be easily executed on a portable computer by any laboratory technician. As a consequence, in the authors' viewpoint, the proposed GRE pipe characterization for shear and compression should be considered in the quality control process of such industrial products
Consistent Complementarity Problem Formulation for the Mechanical Modellisation of Spatial Cable–Rib Structures
No full textThis paper outlines a general mechanical formulation to computationally handle cable–rib structures by a consistent Complementarity Problem modellisation, so far considering potential material non–linearity within the ribs, localised at plastic joints, as per a classical plastic hinge hypothesis in the Limit Analysis of frames. The formulation is also outlined in a prototype self–made implementation, allowing to achieve and display first consistent results on sample test structures, for necessary understanding and control. This shows that the present modellisation concept, and implementation, shall constitute a liable mechanical tool for promising utilisation and end use adoption in different related application scenarios
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