Pushover analysis of reinforced concrete framed structures: comparison between response obtained using beam or multi-layered shell elements

In the context of the seismic vulnerability assessment of existing reinforced concrete buildings, the load-carrying capacity of structures is strongly affected by steel and concrete mechanical properties and construction details. In this work, the institute “A. De Gasperi – R. Battaglia”, located in Norcia, is chosen as case study. Two different modelling strategies have been adopted by using beam elements or multi-layered shell elements for the structural schematization. The non-linear behavior and the ductile or brittle failure mode of shell elements are evaluated using PARC_CL 2.0 crack model, implemented as user subroutine in Abaqus Code. The non-linear ductile behavior of beam elements is evaluated using, at each integration point, the moment/curvature and the axial force/strain relationships which are uncoupled. Brittle failure mode in columns, beams and beam-to-column joints are calculated using post-processing procedures based on analytical formulations provided by Italian NCT 2018 and Eurocode 8 Standard Code. The main scope of this paper is thus the evaluation of the structural response of the case study by using nonlinear finite element analyses, highlighting the benefits of using beam or shell element modelin

Treatment outcome of posterior composite indirect restorations: A retrospective 20-year analysis of 525 cases with a mean follow-up of 87 months

The purpose of this study was to evaluate the survival of 525 composite indirect restorations in premolars and molars after a follow-up of 20 years. For each patient, the following variables were recorded and analyzed: age, sex, smoking status, presence of plaque according to O'Leary index, and presence of bruxism. For each restoration, the following variables were collected: restoration class, tooth type (premolar or molar), and restoration material. Mean 20-year survival rate of composite restorations was 57%, ranging from 44% to 75%. The Kaplan- Meier method demonstrated a probability of survival at 10 years of 80% and 90%. Surviving restorations kept their clinical characteristics extremely well, as assessed on the basis of the United States Public Health Service criteria. The results of this study demonstrate the efficacy of indirect composite restorations, confirming their reliability as a posterior prosthetic clinical option

Dependency of punching shear resistance and membrane action on boundary conditions of reinforced concrete continuous slabs

The design of reinforced concrete flat slabs can be governed at failure by punching shear close to concentrated loads or columns. Geometrical features, reinforcement layouts and in-plane forces provided by external vertical elements, such as shear walls, can affect the membrane action and, consequently, the punching shear resistance. This paper presents a study on reinforced concrete continuous flat slab whose lateral expansion is restrained by the presence of vertical elements considering also shrinkage effects

Verification of deflections and cracking of RC flat slabs with numerical and analytical approaches

The Serviceability Limit States (SLS) of reinforced concrete structures, where cracking and deflection limits are verified in the design process, are directly related to time-dependent properties of concrete. In this study, the effects of creep and shrinkage of concrete, implemented in a Finite Element Model for Non-Linear Analysis, are in-deeply investigated for reinforced concrete flat slabs at SLS and used as basis for the development of an analytical framework. In particular, the paper focuses on: (i) the description of the FE model, (ii) the comparison between the numerical and experimental results of some reinforced concrete (RC) flat slab tests from literature characterized by different mechanical properties, span-to-depth ratios, boundary conditions and loading histories and (iii) the development of an analytical framework for the evaluation of long term-term deflections and crack openings in hogging regions of flat slabs near columns. Based on the findings, useful insights for the evaluation of the long term-term deflections and crack opening in the context of Serviceability Limit States are provided for practical purposes

Role of structural details in progressive collapse of precast RC structures

Nowadays, the structural robustness is one of the most important challenges in structural engineering. During last years, several studies have been carried out to develop design strategies for mitigation of progressive col lapse risk through the achievement of sufficient robustness levels. However, most of the research has focused on cast in-situ concrete, with minor attention to precast structures. Therefore, a considerable effort to improve the knowledge about this issue is required. In this paper, different connection types and diaphragm configurations are analyzed to better understand their contribution when removing load-bearing elements (e.g. columns) in the alternate load path method. Special emphasis is given on structural detailing for distributed tie

Nonlinear Dynamic Response of a Precast Concrete Building to Sudden Column Removal

: Robustness of reinforced concrete (RC) structures is an ongoing challenging research topic in the engineering community. During an extreme event, the loss of vertical load-bearing elements can activate large-deformation resisting mechanisms such as membrane and catenary actions in beams and floor slabs of cast-in-situ RC buildings to resist gravity loads. However, few studies have been conducted for precast concrete (PC) buildings, especially focused on the capacity of such structures to withstand column loss scenarios, which mainly relies on connection strength. Additional resistance resource and alternate load paths could be reached via tying systems. In this paper, the progressive collapse resistance of a PC frame building is analyzed by means of nonlinear dynamic finite element analyses focusing on the fundamental roles played by beam-to-column connection strength and tying reinforcement. A simplified modelling approach is illustrated in order to investigate the response of such a structural typology to a number of sudden column-removal scenarios. The relative simplicity of the modelling technique is considered useful for engineering practice, providing new input for further research in this field