1,721,007 research outputs found
The Role of Infill Walls in the Dynamic Behavior and Seismic Upgrade of a Reinforced Concrete Framed Building
No full textMasonry infill walls are commonly used in the frames of reinforced concrete (RC) buildings around the world. The seismic performance of these buildings is strongly affected by the presence of the infill walls and partitions, as shown by the post-earthquake damage in many cases. The effect of these components is particularly important for RC frame constructions underdesigned for seismic actions that usually are characterized by deformable frames magnifying the contribution of the infill walls to the seismic response. Also the flexibility of the floors could be influenced by the collaboration of the infill walls to the transversal stiffness of the building. The paper addresses the seismic assessment of a typical infilled RC frame building designed only for gravity loads in the 1960s in the Southern of Italy that currently is a high-seismic zone. The structural identification of the building based on ambient vibration test has been already done pointing out the significant role of infill walls and partitions through the updating of the numerical model. Based on the results of the calibrated model, the effect of the floor flexibility on the dynamic behavior of the structure is discussed, and the seismic capacity at life safety limit state (LSLS) is assessed by means of the linear dynamic analyses. The effects of the infill walls on the seismic performance of the building are discussed in detail considering a strengthening solution that involves the infill panels as masonry walls cut from the RC columns to avoid the local interaction but strengthened by composite grids in mortar matrix (FRCM)
Model assessment of a bridge by load and dynamic tests
No full textThe assessment and monitoring of structures through in situ tests, especially dynamic tests, is becoming a common procedure due to the evolution of the instruments and numerical processing of data. However, the use of the data based on the supervised approach, which requires engineering knowledge of the structure is needed before assessing the numerical model that will be the “digital twin” model of the construction for future analysis, monitoring and upgrading of the structure. This process is very complex and requires strong competence in the field of structural engineering, but it allows a real reference for the periodic check of the structure health with a method to also define a solution for its maintenance and upgrade. In this paper, a case study of a PC bridge designed by Riccardo Morandi in 1952–1955 is proposed to apply the process of updating a numerical model by static and dynamic in situ tests. The process based on the two different types of tests was separately conducted to evaluate the efficiency and the difference in the results. The main results of the two types of tests overlap for most features, but specific evidenced aspects that are observed have to be considered
The structural identification of the infill walls contribution in the dynamic response of framed buildings
No full textReinforced concrete (RC) frame buildings containing unreinforced masonry infill walls are commonly used in structural systems around the world. The performance of this type of building can be significantly affected by the presence of infill walls according to their type and distribution in the plane and along the height as revealed by earthquakes. This paper presents data collection, system identification, and finite element modeling of an existing RC framed building designed for gravity loads and containing unreinforced masonry infill walls. Based on a previously carried out ambient vibration test, a three-dimensional finite element model, comprising infill walls and partitions, was successfully updated on the basis of the global modes identified by the in situ test, pointing out the important role of the nonstructural components for this type of building. The influence of the infill walls and partitions on the vibration period was examined, introducing a comparison with simple formulations for the period calculation suggested by codes or available in the literature. The updated model has been further used to assess an approach for an approximate estimation of the story and global stiffness of the building considering the effect of the secondary elements. The dynamic test with the model updating results an efficient procedure for a complete identification of the elastic behavior of the structure
In-plane deformability of RC floors: assessment of the main parameters and influence on dynamic behaviour
No full textIn-plane floor deformability is an important issue for the correct assessment of the behaviour of Reinforced Concrete (RC) structures subjected to seismic loads. Several studies have demonstrated that in-plane floor deformability is often not negligible in structures with RC walls as vertical resistant elements, since it mainly depends on the relative stiffness of floor and vertical elements. In this paper, approximately 700 simple buildings constructed with RC walls were simulated in finite element models considering both two-dimensional and one-dimensional modelling strategies. First, the reliability of the simplified modelling strategy was evaluated. Then, the simplified model was used to assess the effects of building shape and number of walls on the in-plane floor deformability. The differences between the behaviour of the buildings under the assumption of deformable and rigid floors were examined in terms of both floor displacements, based on static analyses, and the main vibration periods of the building, based on linear dynamic analyses. Finally, based on the collected numerical results, reliable regression curves for both the maximum displacements and the periods evaluated under the assumption of deformable and rigid floors were obtained as function of a parameter significant of floor and walls stiffness. The curves may provide a tool for evaluating the error related to an incorrect assumption about the in-plane floor deformability
Numerical modelling of the behaviour of steel-confined rc columns
No full textThe use of steel plates externally glued to RC members is still an efficient solution due to relatively low costs, ductile stress-strain behaviour, simple and fast mounting with possible removing and reuse of the material. Many applications for flexural and shear strengthening can be realized but a typical intervention is the transversal confinement with angles and strips to increase the axial load capacity of columns. However, the design provisions for this application are still lack even if specific rules are necessary because the confinement effect can be strongly influenced by the amount and geometric configuration of the external steel. In this paper a detailed 3D FE model of RC columns confined with external steel plates is proposed. The model is firstly calibrated on available experimental results available in the scientific literature obtaining a good agreement of the loading capacity. The influence of the perfect bond between the steel angles and the RC column is evaluated too. Finally, the model is used for considering the variation of the steel configuration in terms of strips spacing and thickness of the steel elements
Evaluation of the plastic hinge length of steel-concrete composite beams under hogging moment
No full textLumped plasticity is one of the most commonly used approaches for the nonlinear analysis of framed structures, but its effectiveness depends on the reliability of the plastic rotational capacity. In the case of RC or steel structures, this approach is based on well-known and reliable formulations, but no specific rules have been established for steel-concrete composite structures. This paper reports the results of a detailed analysis of the nonlinear behaviour of the section and entire element of a composite beam with the goal of determining its flexural ductility. In particular, the composite beam was examined under a hogging moment that results in its worst performance due to the concrete experiencing tension and the steel compression. An FE model is used to study the element; it was considered all the features of the materials and the geometry of the section to develop a parametric analysis that enabled to study the effect of different parameters on the rotational capacities of the composite beams. This formulation considers the local phenomenon of profile buckling and the global dimensions of the composite section. Finally, the obtained results allowed to define an equivalent plastic hinge length that provides the available plastic rotation when multiplied by the plastic curvature of the cross-section
Dynamic Characterization of Glazed Partition Walls by Operational Modal Analysis Technique
No full textThe vulnerability assessment of glazing systems and partitions under dynamic loads is still an open topic, requiring huge efforts. Especially in terms of dynamic-related effects, the use of Finite Element (FE) software packages can represent an efficient tool for design but special care should be spent for the definition of key input parameters, such as for example the restraints features. Moreover, boundary conditions could also modify, during the lifetime of a given glazed partition, due to external factors or materials degradation, hence resulting in possible unsafe structural performances or premature damage. In this paper, the dynamic characterization of two types of glazed partition is presented based on Operational Modal Analysis (OMA) techniques and Finite Element (FE) numerical simulations. The dynamic in situ tests have been carried out in the framework of the PON research project CADS- “Creating a Safe Home Environment”. It is shown, in particular, how the actual restraint condition with respect to ideal boundaries can affect the vibration parameters (frequency, modal shape) of a given glazed partition
Seismic performance assessment of piping systems in bare and infilled RC buildings
No full textRecent studies evidenced that non-structural damage in buildings caused by earthquakes leads to high economic losses and can represent a threat for life safety. Particularly, piping network damage has been widely documented in post-earthquake inspections. In this study, a cascade analysis is conducted to evaluate the seismic demand on two types of piping networks installed in a reinforced concrete framed building. The cascade analysis is performed employing floor acceleration time-histories obtained through non-linear dynamic analyses of infilled and bare frames. The dynamic response of the piping networks is defined accounting for the non-linear behaviour of pipe joints and suspended piping restraint installations. The results show that the acceleration demand and the damage on the network significantly increase in infilled frames compared to bare frames. Additionally, a different seismic damage rate was observed comparing the two piping networks. The outcome of this study is used to provide design recommendations for suspended piping restraint installations, aimed at reducing the seismic vulnerability of the piping networks
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