1,720,973 research outputs found
Strength verification of circular crown arch-shaped fillet welds under static loads
No full textDue to the lack of literature studies on the use of analytical methods to determine the stress distribution in curved fillet welds, this study proposes an analytical procedure to determine the stresses in curved fillet welds subjected to an eccentric force coplanar with one of the fillet sides. The procedure is based on the theory of infinitely rigid bodies and the principle of superposition of effects, valid for steel in the elastic range. The procedure is then used to determine the strength of a fillet weld with circular crown arch shape, under different inclination and locations of the external force. Two scenarios are examined: one accounting for the eccentricity of the applied force relative to the centroid of the flipped throat surface, and one without it. Based on the results, the most unfavorable directions of the external force are identified. These findings are then used to determine the optimal location of fillet welds with circular or elliptical crown arch shapes, considering variations in force inclination, force location, and fillet configuration. It is also found that, when the force is applied at the centroid of the flipped throat surface, the magnitude of force resisted by the fillet is independent of its inclination only if the fillet is subtended by a central angle greater than or equal to 180°. Conversely, the fillet cross-section(s) experiencing the most critical stress state is(are) the end section(s) of the fillet. Moreover, a comparison with an established method demonstrates that the proposed approach yields accurate and reliable results. The findings of this study provide valuable insights into the design and strength verification of curved welded joints, aiding engineers in optimizing their design
Sur deux nouveaux Scolytides du genre Xyleborus nuisibles aux rameaux du Caféier à Madagascar [Col.]
No full textFrappa G. Sur deux nouveaux Scolytides du genre Xyleborus nuisibles aux rameaux du Caféier à Madagascar [Col.]. In: Bulletin de la Société entomologique de France, volume 38 (12),1933. pp. 178-181
Stability Assessment of the Brick Masonry Veneer Walls of an Existing Reinforced Concrete Building
No full textThis paper presents a stability assessment of the masonry veneer walls of a recent building, which displayed visible damage in its masonry cladding system. The investigation campaign, conducted on-site, provided valuable data about the structural performance of the veneer walls. The assessment of out-of-plane stability was carried out analytically, in accordance with the Italian Building Code and the recommendations of UNI EN 1996-1-1:2022, which guide the design and analysis of masonry structures. The effects of thermal variations on the veneer walls stability are also assessed. From the results of the investigations and subsequent analyses, the paper identifies the primary causes of the observed damages. To address these issues and ensure compliance with the safety requirements prescribed by the Code, a series of safety interventions are proposed
Seismic retrofitting of a reinforced concrete building with strongly different stiffness in the main directions
No full textThe displacement capacity of the existing reinforced concrete building under study does not satisfy the seismic Italian Code requirements. The modal analysis highlights that the structure has strongly different stiffnesses along its main directions and, in the stiffer one, translation is coupled with torsion. To improve the seismic behavior of the building, it is proposed to install an external steel frame with stiff braces along the side of the structure which is the most deformable due to torsional effect. Conversely, in the orthogonal direction, where the ductility demand is much higher, external steel frames with dissipative braces are used. The effectiveness of the proposed solution is checked by push-over analysis
Tensile Tests for the Improvement of Adhesion between Rubber and Steel Layers in Elastomeric Isolators
Full text linkSteel reinforced elastomeric isolators are currently the most used bearings for seismic
isolation purposes. The steel reinforcements are cut to the desired shape, sandblasted, cleaned with
acid, and coated with bonding compound during the manufacturing process. Then the elastomer
and steel layers are stacked in a mold and subjected to vulcanization so that they are glued together
and constitute a single body. Good adhesion between the layers is very important for the correct
functioning of the device. Adhesion conditions become critical when the isolators are subjected to
tensile stresses, which arise under direct tensile actions or large shear strains. To analyze the
influence of changes in the manufacturing process on the isolator adhesive behavior, the authors
performed tensile tests on square‐shaped small‐scale specimens rather than expensive shear tests
on full‐scale isolators. Hence, the adhesion behavior between elastomer and steel layers was
investigated through the tensile tests discussed herein. Among the influencing parameters that were
considered, it was found that an increase in vulcanization time does not improve the adhesion, but
it may actually worsen the capacity of the isolator in terms of strength. Moreover, it was found that
using elastomer without an oily component improves the adhesion between the layers and increases
the isolator’s dissipative capacity
Failure analysis of three rigid block assemblies – A real collapse resulting in death
Full text linkThe failure analysis of three rigid block assemblies is often necessary to assess the stability of
architectural and historical assets.
An analytical method for the assessment of the overturning stability of assemblies composed by
three rigid blocks fitted atop one on another is proposed. The method takes account of several
load configurations and all possible collapse mechanisms involving the overturning of one, two or
three blocks.
In the category of historical assets fall many holy water stoups with pillar, often realized as
three rigid block assemblies. A great number of holy water stoups disarticulations occurred in
Italy in the last decades, leading, in some cases, to children death.
A 7 years old girl died due to the disarticulation of an historical holy water stoup in the Santa
Chiara Church, in Udine, Italy, caused by the force applied by the girl on the basin.
The stoup is realized as a three rigid block assembly with connections of the type mortise and
tenon both between the basement and the shaft and between the shaft and the basin. In the
connections the presence of mortar is detected. In order to evaluate the ability of the mortar to
stabilize the connections between the three rigid blocks, the mineralogical and petrographic
analyses of a mortar sample are performed. Moreover, a loading test is carried out in laboratory to
obtain an experimental value of the holy water stoup failure load. This value is determined by
applying a vertical force to the outer circumference of the basin.
Then, in order to determine the holy water stoup failure load under an inclined force statically
applied at the top of the basin, the stoup overturning stability is theoretically analysed. The
analysis is performed considering all possible collapse mechanisms of the three rigid block assembly
and the variability of the force inclination with respect to the horizontal plane. The
performed analysis is suitable because it confirms that the disarticulation of the holy water stoup
can be caused by a force applied by the kid at the top of the basin.
The presented paper is the first one that analyses the overturning stability of three rigid block
assemblies under external forces which do not depend on the single blocks masses and with
variable direction
Effectiveness of Tuned Mass Damper in Reducing Damage Caused by Strong Earthquake in a Medium-Rise Building
Full text linkA case study where a tuned mass damper (TMD) was installed at the top of a five-story reinforced concrete (RC) building is presented. The aim of the study was to investigate the effectiveness of the TMD in changing the structural behavior of medium-rise existing buildings from dissipative to non-dissipative in order to eliminate reparation or demolition costs resulting from damages caused by strong earthquakes. The TMD mass is made by a RC slab lying on flat surface sliders. Horizontal stiffness and damping of the TMD are both provided by lead rubber isolators in the first proposed solution and by low-damping rubber isolators and viscous linear dampers, respectively, in the second. The improvement in the building’s structural behavior attained with the installation of the TMD was assessed by considering the flexural demand over capacity ratios of structural elements and the energy dissipated by the TMD. These results are compared with those of the same building retrofitted with a base isolation system. In both of the proposed solutions, TMD remarkably changed the modal behavior of the considered building, improved the flexural verifications, and dissipated most of the input seismic energy. It is therefore demonstrated that a TMD is a valid solution for the retrofit of medium-rise existing buildings
Destructive and non-destructive tests on columns and cube specimens made with the same concrete mix
Full text linkThis research work presents the results of an experimental campaign performed on column specimens to investigate the capacity of destructive coring test and non-destructive tests to predict the in-place concrete strength. The considered non-destructive tests are Surface Hardness (SH) and Ultrasonic Pulse Velocity (UPV) ones. Using these tests’ results also SonReb method is applied. The peculiarity of this research is that the results of all the performed test on the columns are compared to results obtained from cube specimens made with the same concrete of the columns. The non-destructive predictive methods are performed on both column and cube specimens during the curing of the concrete at different ages, while the destructive coring test on columns specimens at 28th day after casting. A discussion on the comparison between drilled cores’ strength, determined using provisions of different building codes, and cube specimens’ strength is provided. In particular, the code providing the safest concrete strength predictions is identified. Moreover, the influence of different core diameters on the evaluation of in-place concrete strength is analyzed. The variation of core specimens’ strength, depending on the position of test execution along the columns’ height, is also investigated. To assess the in-place concrete strength by non-destructive tests, correlation formulae are calibrated on the bases of cores strength determined according to ACI Code. The prediction ability of these formulae is assessed. Results obtained from SH and UPV tests at different concrete ages are compared to the cube specimen strength at the same ages, and the influence on the measured parameters of different moisture conditions during curing is analyzed. The minimum number of cores to adequately predict the in-place concrete strength by means of SH and UPV methods is also determined. Best predicting SonReb formulations are identified
Methods to Reproduce In-Plane Deformability of Orthotropic Floors in the Finite Element Models of Buildings
Full text linkIn the modelling of reinforced concrete (RC) buildings, the rigid diaphragm hypothesis to represent the in-plane behavior of floors was and still is very commonly adopted because of its simplicity and computational cheapness. However, since excessive floor in-plane deformability can cause a very different redistribution of lateral forces on vertical resisting elements, it may be necessary to consider floor deformability. This paper investigates the classical yet intriguing question of modeling orthotropic RC floor systems endowed with lightening elements by means of a uniform orthotropic slab in order to describe accurately the building response under seismic loads. The simplified method, commonly adopted by engineers and based on the equivalence between the transverse stiffness of the RC elements of the real floor and those of the orthotropic slab, is presented. A case study in which this simplified method is used is also provided. Then, an advanced finite element (FE)-based method to determine the elastic properties of the equivalent homogenized orthotropic slab is proposed. The novel aspect of this method is that it takes into account the interaction of shell elements with frame elements in the 3D FE model of the building. Based on the results obtained from the application of this method to a case study, a discussion on the adequacy of the simplified method is also provided
Structural Behaviour of Masonry Newly Concept Vault Through Tilting Table Testing on a Scaled Model
No full textMasonry vaults represent one of the most recurrent types of horizontal structural elements in architecture in European countries, even in areas characterized by a high level of seismicity. Therefore, the evaluation of their structural safety and their mechanical behaviour remains of primary importance. This paper proposes to apply already consolidated structural analysis methodologies on a contemporary vaulted space. The aim, therefore, is to investigate the dynamic behaviour of a newly concept vault generated starting from the “Flat vault of Abeille” patented in 1699. The reinterpretation of this vault and its use would allow both to enhance the existing Architectural Heritage and to characterize the realization of new buildings using traditional construction materials and techniques, without going against the canons and guidelines of architectural restoration. It follows that the identification of this “new type” of vault is essential to design it correctly and to optimize the geometry for structural purposes. The present paper describes the results of an experimental campaign about tilting table tests on a 1:8 small scaled vault and and the numerical simulation of the model through the Distinct Element Method (DEM). The physical model is coherent with the numerical one because it has been realized with 3D printed blocks assembled with dry joints. The seismic behaviour of the vault was experimentally studied through quasi-static tests by means of a tilting table to evaluate the collapse angle and the Horizontal load Multipliers for different in-plane angles in order to define a resistance domain of the vault
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