Search results for "concrete"
showing 10 items of 262 documents
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…
Fractional model of concrete hereditary viscoelastic behaviour
2016
The evaluation of creep effects in concrete structures is addressed in the literature using different predictive models, supplied by specific codes, and applying the concepts of linear viscoelastic theory with ageing. The expressions used in the literature are mainly based on exponential laws, which are introduced in the integral expression of the Boltzmann principle; this approach leads to the need of finding approximated numerical solutions of the viscoelastic response. In this study, the hereditary fractional viscoelastic model is applied to concrete elements, underlining the convenience of using creep or relaxation functions expressed by power laws. The full reciprocal character of cree…
Structural assessment of a reinforced concrete water tower
2019
The paper presents a structural appraisal of a reinforced concrete water tower at the Public Abattoir in Malta. The water tower was constructed in the first half of the 20th century and consists in a reinforced concrete thin shell structure supported on twelve columns. Detailed drawings and a refined 3D model were prepared based on detailed site measurements of the structure. The concrete was assessed through non-destructive tests and with reference to extracted concrete core samples from different parts of the structure and extracted steel reinforcement samples. Detailed deterioration mapping was conducted for the entire structure. This data was used to model the structure and analyse it t…
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…
Towards Concrete Syntax Based Find for Graphical Domain Specific Languages
2019
One of the main reasons why Model-Driven Engineering (MDE) technologies including Domain-specific modelling languages (DSML) have not reached the expected acceptance in the industry is a poor tool support. One of the features with a limited support even in commercial modelling tools is search (find). Typically, MDE tools support only a simple keyword-based textual search functionality. The same is true for the tools built using Domain-specific language (DSL) tool definition frameworks. It is proposed to provide the concrete syntax-based find functionality as a service of a DSL tool definition framework. The find diagrams are defined in a concrete syntax of a DSL. A definition of a DSL is us…
Experimental Survey on Dry Asphalt Rubber Concrete for Sub-ballast Layers
2012
The railway traffic through a town or near built-up areas causes heavy effects such as noise and vibration on surroundings. In order to minimize the level of these impacts the railway companies with researchers and practitioners seek suitable solutions especially in the field of the rail-track because the main source of the ground borne vibrations and noise is the bad wheel-track contact. In particular, a big effort is addressed to new materials with high mechanical and environmental performance that can be utilized within the sub-ballast layer. This paper presents the results of an experimental survey on the potential application of Dry Asphalt Rubber Concrete (DARC) in sub-ballast layers …