Search results for "Reinforced Concrete"
showing 10 items of 92 documents
Nonlinear Analysis of Beams Reinforced in Shear with Stirrups and Steel Fibers
2012
The modified compression field theory (MCFT) and the disturbed stress field model (DSFM) are often used to predict the nonlinear behavior of reinforced concrete structures. This study presents several extensions of the MCFT and DSFM to the case of high-strength steel fiber-reinforced concrete beams subjected to transverse loads. Experimental four-point bending tests were conducted on 12 concrete beams with a different percentage of fibers and/or stirrups. To validate the updates introduced in the analytical models, numerical analysis was performed using nonlinear finite element software. Modeling of the post-peak softening branch of the tensile and compressive constitutive curves of fibrous…
Experimental Tests and FEM Model for SFRC Beams under Flexural and Shear Loads
2008
The complete load-vs-displacement curves obtained by four-point-bending tests on Steel Fiber Reinforced Concrete (SFRC) beams are predicted by using a nonlinear finite element code based on the Modified Compression Field Theory (MCFT) and the Disturbed Stress Field Model (DSFM) suitably adapted for SFRC elements. The effect of fibers on the shear-flexure response is taken into account, mainly incorporating tensile stress-strain analytical relationship for SFRC. The numerical results show the effectiveness of the model for prediction of the behavior of the tested specimens reinforced with light amount of stirrups or with fibers only. © 2008 American Institute of Physics.
Shakedown optimum design of reinforced concrete framed structures
1994
Structures subjected to variable repeated loads can undergo the shakedown or adaptation phenomenon,-which prevents them from collapse but may cause lack of serviceability, for the plastic deformations developed, although finite, as shakedown occurrence postulates, may exceed some maximum values imposed by external ductility criteria. This paper is devoted to the optimal design of reinforced concrete structures, subjected to variable and repeated loads. For such structures the knowledge of the actual values taken by the plastic deformations, at shakedown occurrence, is a crucial issue. An approximate assessment of such plastic deformations is needed, which is herein provided in the shape of …
A study of spalling behaviour of PAN fibre-reinforced concrete by thermal analysis
1993
Comparisons are made between polypropylene (PP) fibres and polyacrylonitrile (PAN) fibres in order to relate the thermal properties of fibres with the respective fibre mortar behaviour under thermal exposure. Thermogravimetry (TG), differential scanning calorimetry (DSC) and thermochromatography (ThGC) are utilized. When a cementitious fibre mortar is being heated, several physical phenomena occur in the temperature range between 100°C and 200°C. There is a significant difference in the thermal behaviour between PP and PAN fibres. PP fibres melt at 160–170°C. The non‐melting behaviour of PAN fibre together with its rapid exothermic degradation reactions at around 300°C may add risk to the s…
Performance of a historical cantilever reinforced concrete bridge with half-joint degradation
2022
The lack of maintenance of roadway concrete bridges built from the Second World War until the 70 s of the 20th century has led in recent years to an ever-increasing request for safety assessments. When bridge performance in terms of Serviceability Limit State (SLS) and Ultimate Limit State (ULS) has to be evaluated, in-situ visual inspections and load tests for safety and maintenance assessment have to be coupled with structural analysis. In order to identify a sound bridge structural model and to assess the actual conservation state, more refined models than those usually considered for section and reinforcement design should be used to reproduce the results of load tests and perform globa…
Parameters affecting the fundamental period of infilled RC frame structures
2015
Despite the fact that the fundamental period appears to be one of the most critical parameters for the seismic design of structures according to the modal superposition method, the so far available in the literature proposals for its estimation are often conflicting with each other making their use uncertain. Furthermore, the majority of these proposals do not take into account the presence of infills walls into the structure despite the fact that infill walls increase the stiffness and mass of structure leading to significant changes in the fundamental period numerical value. Toward this end, this paper presents a detailed and in-depth analytical investigation on the parameters that affect…
BIAXIAL CURVATURE AND DUCTILITY CAPACITY OF RC COLUMN BASE CROSS SECTIONS
2014
The deformation performance of the base cross sections of reinforced concrete buildings is fundamental when large seismic events occur allowing the structure to have large excursions in nonlinear field and guaranteeing an overall ductile behaviour. It is well known that the axial force acting on columns significantly reduces the curvature capacity of the sections and for this reason the technical codes give design criteria stating a limitation in order to preserve the displacement capacity. It is also recognized that when biaxial bending occur the cross section undergo a loss in strength capacity. Starting the study of from Bresler (1960), which provided suitable expression to predict 3D li…
Applicazione delle Linee guida italiane alle valutazioni di sicurezza strutturale del ponte Corleone sulla tangenziale di Palermo
2022
The "nominal life" of a large part of existing reinforced and prestressed concrete bridges, in Italy, is expiring, often in the absence of ordinary or extraordinary maintenance. Consequently, the Italian infrastructural network is in a critical phase, followed by the alarmed awareness of the public opinion, especially after the collapse of the Polcevera viaduct. Specific guidelines on risk classifi-cation, management, safety assessment, monitoring of existing bridges have been issued by the Superior Council of Public Works in 2020, to address the emergency. Between ‘50s and ‘70s of the last century, important examples of reinforced and prestressed concrete bridges were built in Italy by the…
Stress-strain models for normal and high strength confined concrete: Test and comparison of literature models reliability in reproducing experimental…
2017
SUMMARY: The adoption of proper constitutive laws for confined concrete is basic for seismic assessment of new and existing reinforced concrete civil structures. The deformation capacity of reinforced concrete (RC) columns subjected to axially centred and eccentric loads depends on the effectiveness confinement action. A proper assignment of the stressstrainlaws for concrete allows obtaining an adequate definition of the ductility of the crosssections and correctly identifying mechanical nonlinearities in computational models.Several studies concerning the behaviour of confined concrete have been carried out, highlighting the role of different geometrical and mechanical parameters to the ov…
Nonlinear Response of RC Structures: Statistical Effects of Artificial Ground Motions
2020
The selection of seismic inputs for nonlinear dynamic analysis is widely debated, mainly focusing on the advantages and disadvantages provided by the choice of natural, simulated or artificial records. However, most of the available technical codes do not provide always the same suggestions and well-defined procedures for the generation of artificial ground motions. Considering that the strategy of the generation of accelerograms makes some doubts raise about the possible effect on the structural response, the work aims to investigate on the differences of the structural behavior by using accelerograms nominally equivalent but different in terms of stationarity. This paper presents a compar…