Parametric analysis on punching shear resistance of reinforced concrete continuous slabs

Punching shear resistance formulations provided by codes are usually calibrated on test results of isolated specimens that typically simulate the slab zone within the points of contraflexure around the column (hogging area). However, the behaviour of actual continuous flat slabs can be different to that of isolated specimens owing to the beneficial contributions of moment redistributions and membrane actions that cannot take place in isolated specimens. This paper presents a parametric study carried out to highlight the influence of the main geometrical features and the reinforcement layout affecting the punching shear resistance of continuous slabs around internal columns

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Bearing Capacity Assessment of RC Flat Slab Frame Structures

After the Ronan Point partial collapse (1968), several design methods have been proposed in Technical Code and Guidelines to mitigate the progressive collapse phenomenon of reinforced concrete structures, such as Tying Force prescriptive rules and Alternative Load Path analysis. The latter is a direct method, where the capacity of the structure to sustain the applied loads after the loss of a loadbearing element is investigated. Two different approaches are used in this study to analyse the ultimate resisting mechanisms of reinforced concrete flat slab in case of a column loss scenario: 1) a simplified approach which consists of an analytical method developed in the framework of the strip method and that takes into the tensile membrane effect, 2) a detailed approach which consists of a finite element analysis using multi-layered shell elements where the nonlinear behaviour is evaluated using the PARC_CL 2.0 crack model, implemented in Abaqus Code as user subroutine. The aim of this paper is the progressive collapse assessment of a reinforced concrete flat slab frame structure by comparing the simplified and the detailed approaches with experimental data available in literature

Application of an analytical method for the design for robustness of RC flat slab buildings

Nowadays the structural engineering community needs reliable and design-oriented methods for the design of low and medium-rise reinforced concrete (RC) buildings with regard to progressive collapse. In this context, the current work aims to validate and apply a new analytical method suitable for the design for robustness of RC buildings characterised by the presence of flat slabs falling in low and medium consequence classes. The analytical method presented in this study is an extension of a method recently proposed by some of the authors for the analysis of two-way slabs in which flexural capacity and punching and post-punching failure criteria are added to reproduce the ultimate behaviour of flat slabs. In this paper, the design for robustness is applied together with the design for ultimate and serviceability limit states in the framework of the partial safety factor method of verification for RC flat slabs. The analytical method is applied as a direct method to evaluate the level of robustness of RC flat slabs to sustain a localised failure simulated by considering an internal column removal scenario. First, the method is validated by comparing the analytical results with both experimental data available in the literature and nonlinear finite element results obtained by adopting a multi-layered shell element approach and the PARC_CL 2.0 crack model. The comparison of the results demonstrates the reliability of the analytical approach in reproducing the ultimate load and ultimate chord rotation of flat slabs with a good approximation by considering the effect of tensile membrane action (TMA). Second, in strategies based on unidentified accidental actions, the analytical method is used to carry out a parametric analysis in the context of an internal column loss scenario. The parametric analysis allows the level of robustness to be evaluated by varying the main geometrical properties that affect the failure mode, resistance and ductility of RC flat slabs. Finally, the paper presents—for a given span and span-to-depth ratio—the required reinforcement ratios, design load in the accidental load combination and ultimate chord rotation in the form of design nomographs useful for engineering

PARAMETRIC ANALYSIS ON PUNCHING SHEAR RESISTANCE OF REINFORCED CONCRETE CONTINUOUS SLABS

Punching shear resistance formulations provided by codes are usually calibrated on tests results of isolated specimens that typically simulate the slab zone within the points of contraflexure around the column (hogging area). However, the behaviour of actual continuous flat slabs can be different than that of isolated specimens due to the beneficial contributions of moment redistributions and membrane actions that cannot take place in isolated specimens. This paper presents a parametric study carried out to highlight the influence of the main geometrical features and the reinforcement layout affecting the punching shear resistance of continuous slab

Probabilistic assessment of the moment-curvature response of PC beams subjected to corrosion

In recent literature, several approaches have been proposed for the sectional response of corroded reinforced concrete structures. However, the lack of knowledge on corroded prestressed concrete (PC) members is still present. The present work focuses on the probabilistic assessment of the sectional response of a PC member by considering the influence of chloride-induced corrosion. First, the probability distributions of the mechanical properties and the maximum pit depth are established. Second, the SCPS-model is then adopted to derive the residual stress-strain relations of corroded strands. Third, the effect of the random nature of the mechanical properties is investigated via Monte-Carlo simulations. Finally, the main outcomes enable to: (i) quantify the expected failure mode in a probabilistic way, and (ii) assess the influence of the selected random variables on the moment-curvature response

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