Proceedings of Italian Concrete Conference 2022

The recycling of concrete construction and demolition wastes to obtain coarse recycled aggregates for structural concrete production represents an interesting strategy to develop circular economy in the construction sector. It reduces landfill waste and raw material exploitation. In this applied research, the recycled aggregate, obtained from construction and demolition waste, was used in partial replacement of coarse natural aggregate for casting a set of real scale foundation plinths. These structures have been tested under lateral forces applied on the top of precast reinforced concrete columns connected to the plinths. The mechanism and force characterizing the collapse have been determined showing how concrete structures with recycled aggregates have similar performances to the ordinary ones.

Prevention and safety of protection systems against debris falling from ceilings are gathering increasing interest in the engineering community. The design of an adequate protection system can prevent severe damage and human losses. In this paper, the use of welded steel wire meshes as system against debris falling from ceiling, in retrofitting and repairing interventions, is investigated. The behaviour of galvanized steel wire meshes as system against debris falling is experimentally and analytically analysed in the case of diaphragms realised with concrete joists and interposed bricks, which represent a typical solution for existing reinforced concrete or masonry buildings, for both public and residential use. Firstly, the main outcomes of an experimental test carried out at the University of Parma are described. Secondly, a simplified analytical method is presented to evaluate the resistance of such a ceiling protection system subjected to uniformly distributed load. Finally, the suitability of the analytical method for design and verification purposes is demonstrated.

The construction sector has a great impact on the environment. The growing attention to more sustainable alternatives to traditional construction materials is stimulating the development of novel eco-friendly composites. This work presents the first investigations on novel concretes realized with earth and carbon fillers. In particular, electrical and mechanical tests have been carried out in order to evaluate the conductive and smart sensing properties of the novel composites. Cube samples doped with different amounts of carbon microfibers have been tested under compression, with the final aim of investigating the characteristics of the materials and identifying the most performant mixes. The tests demonstrated the good electrical and electromechanical properties of these new eco-earth concretes which appear promising to fabricate embedded sensors or structural smart elements in sustainable structures.

The use of different types of recycled materials in the building sector became of central importance in recent years as one of the main goals worldwide is to reduce the depletion of natural resources and favour the exploitation of already existing materials in a more sustainable manner. The aim of this paper is to present a recycled material deriving from the milling of asphalt pavement (Recycled Asphalt Pavement, RAP) and its possible uses as aggregate in mortars. More specifically, a preliminary review on the influence of RAP on the mechanical characteristics of mortars, such as grading, compressive strength, flexural strength, splitting tensile strength and durability, is presented in relation to the various percentages of substitution of natural aggregates with this recycled material. Lastly, an overview on the codes and standards regulating the use of recycled materials in mortars is given, together with the respective imposed restrictions.

Nonlinear response time-history analyses are used in well-known seismic performance assessment methods such as Incremental Dynamic Analysis, Multi-Stripes Analysis and Cloud Method to describe the relationship between chosen Damage Measure versus Intensity Measure. Numerous researches have presented simplified procedures or nonlinear static procedures to develop fragility over the last two decades. In NSPs, pushover analysis is used to assess the system capacity, and response spectra quantify the seismic demand. In addition to the known ones, Incremental Modal Pushover Analysis (IMPA) is a novel nonlinear static procedure that has been proposed in recent years and is used in this study to advance an IM-based fragility estimation. The accuracy and effectiveness of various vulnerability assessment methods are investigated by comparing fragility curves obtained from MPA-based Cloud Analysis, IMPA, Cloud Analysis to IDA fragility curves. The results from two relatively small bins of record motions differing by ranges of Joyner-Boore Distance and are scattered across a range of Magnitude are presented.

Several solutions are currently under investigation with the aim to reduce environmental impact of concrete production processes. These solutions often consist of partially/totally replacing ordinary “natural” constituents with recycled ones, in view of the twofold objective of both reducing the raw materials demand and the amount of waste to be disposed in landfills. This paper summarizes the results of an industrial R&D project aimed at evaluating the feasibility of recycling dismissed concrete poles for the production of new precast centrifuged reinforced concrete elements made of Recycled Concrete Aggregates. The results show that it is possible to obtain recycled concrete poles with mechanical performances compatible to the ordinary ones, provided that an adequate processing procedure are adopted for transforming concrete debris in recycled aggregates and a specific design method is required for the structural concrete mixture composition. Finally, a specific Life-Cycle Analysis with the aim to quantify the environmental impacts of the proposed recycling procedure.

Geopolymer cement is made up of waste materials, an efficient alternative to ordinary cement in order to reduce the emission of carbon dioxide. The use of geopolymer recycled aggregate concrete (GRAC) in structural elements has been an object of recent several experimental research in which the behaviour of either the material or structural element was investigated. A review paper will be done critically to compile the present research on the use of GRAC in construction. It will cover the effect of different materials composition in GRAC and the factors affecting its strength focusing on recycled aggregate’s replacement ratio. The problems related to the strength of GRAC structural members, their tensile and flexural behaviour will also be addressed. It will also help in finding the future prospects of the use of GRAC in construction.

The high mechanical performances showed by geopolymer concrete led several researchers to investigate about possibilities of using this material in reinforced structural elements. Since geopolymer binder has a different microstructure from ordinary Portland Cement (OPC) it is necessary to investigate on its bonding behavior with steel bar that as well-known influences the service and ultimate conditions. For this reason, in the last decades both direct pull-out and beam-end tests were carried out with this material. Generally, it has been observed that geopolymer concrete (GPC) has higher bond strength than OPC due to the higher compression strength and the dense and compact microstructure of GPC. This means that the existing design equation for bond strength prediction of ordinary concrete can be conservatively used also for GPC. In this paper the mechanical properties of GPC will be analyzed and the bond-slip behavior of GPC and both CFRP and GFRP bars has been studied. The experimental data are analyzed and discussed in terms of bond stress transfer mechanisms and mode of failure.

The need for more environmentally and economically sustainable structures pushes towards ahead the formulation of new advanced cementitious materials which, on the one hand, can reduce the carbon footprint in the production phase, and, on the other hand, can significantly improve the structural durability, thus resulting into a longer service life. In this context, the ReSHEALience project has been launched in 2018 within the Programme Horizon 2020. The project aims at developing a new approach for the design of structures exposed to extremely aggressive environments, based on durability and life cycle analysis. The starting point is represented by a novel concept of Ultra-High Performance Fibre-Reinforced Cementitious Composites (UHPFRCCs), which has been called Ultra-High Durability Concretes (UHDC), characterized by multiple cracking behavior and enhanced self-healing. In a design perspective, this makes it necessary to develop an effective approach for identifying the main parameters describing the overall behavior in tension. In the paper an overall description of the concepts and of the structure behind ReSHEALience project is provided. The core is represented by Sustainability of structures and infrastructures, intended as optimization of materials performance and extension of the service life.

Among the new technologies driving the fourth industrial revolution in the construction industry, 3D Concrete Printing (3DCP) is playing a key role. The typical process is made through robotic arms or gantries equipped with nozzles, similarly to contour crafting in other industries. Despite 3DCP is appealing when applied to complex architectural shapes, the structural behaviour and geometrical size are limitations difficult to overcome. Upscaling the extrusion process to full sections, introducing a new concept of ultrafast adaptable slip-forming, is the access key to different sectors of the construction industry, as infrastructures. This paper will present the Extruded Tunnel Lining Regeneration (ETLR) technology developed by HINFRA with the scope to automatically regenerate the lining of existing damaged tunnels. “Tailored” features and issues of the aforesaid technology will be discussed in this paper, together with a design validation related to a Fibre Reinforced Concrete (FRC) tunnel lining.

Existing reinforced concrete buildings subjected to medium intensity earthquake loads often exhibit significant damage to structural and non-structural components that may compromise the structural safety and the building repairability. This damage is commonly concentrated on infills and partitions leading to relevant economic losses. This makes the research on the lateral response of infills and on the role of infill-to-frame connection of paramount importance to reliably assess the seismic performance of existing buildings. This paper discusses the results of an experimental program on full-scale multi-storey infilled RC frames tested under pseudo-dynamic loads. Emphasis is given to the variability of the results with the different infill-to-frame connection realized with classic mortar applied on four sides or with a gap below the beam. The lateral response and the observed damage at increasing earthquake intensities are discussed and compared.

The fight against climate changes has encouraged the development of most research on new binders, with the aim of progressively reducing the use of Ordinary Portland Cement, with its huge carbon footprint. Within this context, geopolymer-like binders can represent an eco-friendly alternative, also for the production of mortars for masonry buildings. In this work, a “one-pot” all in powder formulation was developed to the purpose, and special attention was given to explore the influence of different additives on mortar workability and mechanical properties. Different types of adhesives (like rice starch or maize starch, and alginate) were considered, which were separately applied at first, and finally mixed together with water retention additives and super-plasticizers. The obtained results highlighted the achievement of an adequate workability and adhesion to the support, at the cost of reduced mechanical performances.

In the last decades, there has been an increment in the use of Fabric-Reinforced Cementitious Matric (FRCM) composites, in both the restoring and the upgrading of the load carrying capacity of existing structural elements. At the beginning, FRCMs were mainly applied on masonry buildings, while the recent literature documents growing interventions on Reinforced Concrete members. In the present work, the results of a series of bending tests on RC shallow beams, alternatively strengthened or retrofitted with the application of FRCM composites at the intrados, are reported. The effect of predamage conditions is also discussed. At the end, the estimation of the mechanical response by means of a simplified plane-sectional approach and a proposal for the evaluation of the crack spacing are reported in case of the FRCM-strengthened RC beam.

Steel Reinforced Polymer (SRP) systems represent an appealing solution for the external strengthening and repairing of existing reinforced concrete structures. However, similarly to what known for composite materials employing other fibers, such as carbon or glass ones, to assure an adequate bond between the reinforcement and the concrete substrate is fundamental for the success of many strengthening applications. In this paper, an analytical procedure recently published by the authors is applied for an indirect identification of the concrete-SRP interface law by varying some parameters, such as the compressive strength and the surface finish of the concrete. To this purpose, results from a wide experimental campaign performed by the authors have been considered. The bond-slip laws found case by case, implemented in the analytical procedure, allow for accurately fitting the experimental load-slip curves obtained from the performed direct shear tests.

The design of massive structures such as the shallow foundations of wind turbines is not a trivial task also in light of the fact that this structural typology is not specifically covered in technical Standards. The structural modelling of onshore wind turbine shallow foundations deals with combined complex phenomena, such as material nonlinearities, soil-structure interaction and local stress concentration in both reinforced concrete foundation and soil. The design practice basically adopts two methods: (i) an elastic approach where wind tower foundations are usually designed by modelling the foundation as a slab with variable thickness using shell finite elements and by introducing very simplified assumptions for the soil behaviour (i.e. Winkler model), and (ii) an approach where wind tower foundations are designed by using limit analysis. The paper aims to highlight the limits and the safety margins of the current design practice by comparing the aforementioned methods (i) and (ii) with nonlinear numerical simulations fully accounting for soil-structure interaction based on three-dimensional elements for both concrete foundation and soil, contact surfaces for their interface, and beam elements for reinforcing bars.

With a production of more than 30 billion tons each year, concrete is the building material most widely used in the world, which means a high environmental impact, especially in terms of carbon dioxide emissions and consumption of raw materials. Moreover, some of the industrial wastes are unavoidable, hence there is an increasing interest in finding new solutions for their recycling. To this end, this work aims at the development of innovative concretes able to meet the new trends related to sustainability, from a circular economy perspective. In particular, two different kinds of waste are investigated to be inserted in the concrete mix: plastic, which derives from industrial processing waste but is mixed in composition, so making it difficult to reuse or recycle, as well as biochar, which is the solid carbonaceous by-product resulting from wood-waste pyro-gasification. The developed concretes are characterized in terms of physical-mechanical performance, in order to assess the feasibility of using these industrial wastes as secondary raw materials for the building industry.

The present study relates to comparison between different approaches for definition of global safety factors for non-linear analysis of slender RC members with reference to new or existing structures. Firstly, a benchmark set of 40 experimental results on reinforced concrete columns is presented. After the description of the main features of the benchmark test sets the related non-linear numerical models have been realized using fiber-modelling as solution strategy. Then, appropriate assumptions concerning aleatoric and epistemic uncertainties have been performed with the aim to run probabilistic analysis of global resistance for each one of the 40 columns. The results of the probabilistic analysis are useful to define global safety factors in line to the global resistance method. Finally, the comparison between different approaches to derive global safety factors is presented and discussed.

Following a brief description of the context and of the project as a whole, the report presents the solution adopted for the excavation of the Cut&Cover Tunnel planned at the beginning of the 2nd lot, before the excavation of the mining method tunnel. The Cut&Cover Tunnel, 136 m long, will house the main axis, characterized by a platform with a total width of 8.5 m (two lanes of 3.5 m plus two docks of 0.75 m) and two ramps, one for the entrance and one for the exit, with lane widths of 5.2 m and 5.5 m respectively. The geometric complexity and the resulting size of the work, as well as the boundary conditions typical of a highly anthropized environment, led to a top-down excavation method, up to a depth of approximately 20 m, with large diameter (1.2 m) perimetral piles, 1.5 m spacing and intermediate 1,0 m piles, the casting of the roof slab in cast in situ reinforced concrete and temporary tie rods during the lowering phases of the excavation, before the construction of the inner shell in cast in situ reinforced concrete.

Reinforced concrete Gerber half-joints are characterized by D-Regions in which the de Saint Venant theory is not valid. Therefore, in the capacity assessment of existing Gerber half-joints, the correct assumptions about the stress fields and the strut-and-tie models play a crucial role. Digital Image Correlation (DIC) is an optical technique for the determination of displacements and strains of specimens subjected to mechanical actions. In this work, the DIC technique is applied within an experimental campaign aimed at identifying the nonlinear behavior of Gerber half-joints according to different construction details. The results obtained using the DIC technique allow to identify the shape of the compression fields (struts) and to predict the development of the crack patterns. Therefore, the outcomes are compared with the expected shapes of the strut-and-tie models and interpreted to analyze the different failure mechanisms oh the half-joints.

The inherent aging of existing bridges together with adverse surrounding environmental conditions that have accelerated material degradation phenomena emphasize the need of a comprehensive quality control and management system of the Italian roadway bridge stock. In this context, this paper presents a procedure oriented to a comprehensive quality control and structural safety assessment of prestressed concrete (PC) girder decks in existing bridges. The proposed procedure combines experimental material characterization, field tests in serviceability conditions (static load tests and free vibration tests) and numerical simulation through a finite element model of the PC girder deck (linear and nonlinear analysis at ultimate limit states). The procedure, which is here illustrated in the context of a case study represented by the Zappulla viaduct (Sicily, Italy) built in the first 1970s, accounts for both serviceability and ultimate loading conditions, thus representing a reliable tool for the quality control of existing bridge structures.

The spirit of the ecological transition applied to seismically deficient structures should inspire the development of simple methods capable of identify the “optimal” retrofitting solution (with reference to some predefined criteria). In order to support the intervention choice, an “objective” approach could be implemented making use of recently-invented Artificial Intelligence (AI) procedures. Specifically, the application of Genetic Algorithms (GAs) is usually thought as a suitable way in civil engineering optimization problems. In the present paper, a parametric study on a RC structure based on a GA procedure is reported. Consequently, the design of retrofit interventions results to be based on one objective criterion related to their cost-effectiveness, rather than on the highly subjective “engineering judgement”. Moreover, the adoption of GAs enables to set more than one optimization criteria, in order to achieve not only strictly economic objectives, but also relevant targets intended to make seismic retroftting or upgrading interventions more sustainable.

In recent decades, many concrete bridges, built in the 60s and 70s of the 20th Century with a Gerber-girder scheme, show severe damage of the saddles due to concrete degradation and reinforcement corrosion. On the basis of the recent Ministerial Guidelines for the assessment of existing bridges, it is necessary to evaluate the state of the Gerber saddles in a large number of bridges on both main and secondary roads. To do this, it is necessary to apply flexible assessment procedures that can be adapted to several situations and that allow a speedy assessment of the intervention priorities. The methodologies of intervention represent the crucial point for a rapid rehabilitation of these infrastructures. In this paper, on the basis of some case-studies, assessment and strengthening methodologies are proposed that can be applied to different real cases, in consideration of the budget available, with the aim of drafting an operative list of priorities and improving as many bridges as possible, currently in service.

During last decades, prestressed reinforced concrete (PC) was widely used in the construction of bridge decks. Recent assessments of existing bridges demonstrated how degradation phenomena and construction defects can significantly reduce performance levels of PC elements. In the case of post-tensioned tendons, insufficient grouting of ducts is one of the most common types of defects in existing girders. This paper presents preliminary results of an experimental testing program on 1/5 scale PC bridge girders. The specimens were casted in different configurations including local voids and lacking grout within ducts, while varying the prestress level in the tendons. Experimental outcomes provide useful information for load-bearing capacity assessment of PC girders with defective grout.

Half joints are very common construction details, often used for precast beams connections or bridge deck supports, since they allow the creation of an effective joint without increasing the height of the nodal region. If not adequately designed, dapped-end beams can show premature shear failure, due to the abrupt variation in the cross-section dimension. Given the very low shear span, preventing the application of the Bernoulli’s beam theory, strut and tie models need to be taken into account. In this context, experimental tests provide a powerful instrument to detect the stress flows and define the associated capacity models. The presented work supplies a wide literature review of experimental tests and numerical formulations, aiming to characterize the shear behavior of dapped-end beams. It can be a useful tool for design and assessment procedures of such beams.

The renovation of existing buildings to improve the safety and resilience of our building stock is now recognized as a priority, and many retrofit techniques have been recently proposed, especially carried out from the outside to avoid inhabitants’ relocation. The ability of the existing floors to act as seismic diaphragms is however rarely addressed, if not in terms of diaphragm flexibility. Analyzing data from numerical and experimental studies carried out on a real beam and block floor system, some considerations about the role of existing diaphragms on the structural response of RC buildings are made with particular emphasis on in-plane capacity, deformability, and collapse mechanisms. Practical implications for the design of seismic retrofit interventions are defined.

In the high seismic hazard region of Kashmire, close to the Himalayan mountains, an important cable stayed railway bridge, with a main span of 290 m crossing the Anji valley 190 m above the river bed, is under construction. Due to the particular orography of the valley, the bridge shall have an asymmetric structural scheme, with a 200 m high single tower and 20 m diameter well foundation. The main features of the already completed tower will be illustrated more specifically with reference to heavily stressed post-tensioned transition pieces..

The structural safety assessment of existing infrastructures is a central issue in civil engineering, especially after recent disasters that have hit different Italian bridges. Several data collected showed how existing Italian bridges are mainly composed by simply supported, beam-type, prestressed concrete decks. In this work, the response of a scaled prestressed concrete bridge girder was investigated through experimental test, different types of numerical models and analytical methods. Nonlinear models were developed according to the finite element method and the applied element method. The two numerical approaches were considered: the Finite Element Method and the Applied Element Method, computing the accuracy and the computational efficiency of each one. The results of the analytical prediction and the numerical simulations are then compared with the experimental test outcomes, showing good agreement on both local and global response parameters.

The Italian government has recently instated guidelines on risk classification, management, safety assessment and monitoring of existing bridges. Such guidelines can also be used as a rapid prioritisation method that, based on the limited information available about assets in the inventory, allows the identification of bridges requiring special attention in the form of inspection, detailed analysis, monitoring and possible retrofitting. However, these guidelines are based on qualitative indicators that can produce overly conservative results. In this paper, the recent Italian guidelines are explored and a quantitative partial modification is proposed, based on average annual loss prioritization results from detailed risk assessment. The proposed modification is evaluated on a case study of 617 reinforced concrete bridges, using seismic hazard to demonstrate its potential large-scale implementation. The results show a notable improvement in the identification of high-risk assets in the portfolio, encouraging the adoption of similar strategies to other hazards and bridge typologies, with a view to multi-hazard and data-driven quantitative prioritization schemes for the Italian territory.

This paper intends to discuss the design aspects of the foundations of bridge piers with long piles, with particular reference to the case of the railway bridge over the Volta River in Ghana, designed for both conditions and finally built with four/six long raked piles for the four piers in water. Due to the significant length of the foundation piles, raked piles are more effective and efficient than vertical piles to take the high seismic and train horizontal loads and to satisfy the requirements of the bridge-track interaction analysis. The design with vertical piles requires a significant increase of foundation quantities. The lateral load test between piers with raked piles is a very effective method to check the compressive/tensile piles’ capacity and the actual foundation horizontal displacement and stiffness, in order to confirm the bridge-track interaction analysis.

Existing national road and highway bridges require periodical inspections and, in some cases, urgent structural measures. The Italian Guidelines for risk classification and management, safety assessment and monitoring of existing bridges (LG20) outline a procedure for estimating approximately the risk associated to bridges, by defining for each of them an Attention Class, on the basis of hazard, vulnerability and exposure parameters. For each Attention Class, consequential actions in terms of surveys/monitoring/verifications are required, in order to prevent inadequate levels of damage. A set of 4 existing RC bridges are considered herein as case study. The static scheme is simply supported beam. Initially, the Attention Classes are obtained. Then, the preliminary safety evaluation is provided. Based on the outcomes, a priority classification of the bridges to be further investigated is estimated. Potentials and criticisms of the LG20 are also discussed in the work.

A possible methodology for streamlining the structural safety verifications, needed for authorizing the transit of exceptional transportation vehicles (ETV) on road bridges, is discussed. ETVs, and mainly those classified as such due to total weight, entail a legal obligation of supporting the granting or not of transit permits, by structural calculations that verify adequate load-bearing capacity of the highway bridges the ETV will go over. This method treats vehicle weight and number of axles of a generic fictitious ETV as parameters and is based on progressively increasing the value of both. Cross-sectional forces on bridges due to thusly defined ETVs are expediently obtained using influence lines, then inserted in code-mandated load combinations and compared to structural capacity that is calculated using material properties considered in the original design, deduced from in-situ testing data, or evaluated from simulated design based on the practice at time of construction. Although virtually applicable to any structural typology, a case-study application to an existing underpass with prestressed concrete deck is considered here.

In recent years it has become clear that many western countries infrastructures require scrupulous and continuous monitoring. The main purpose of Structural Health Monitoring (SHM) is the evaluation of the safety of existing structures and the guide for maintenance interventions, where necessary. One of the techniques used in structural monitoring is the measurement of angles using clinometers Nevertheless, many issues on the reliability and the correct use of measures done with clinometers have to be addressed to achieve a trustworthy SHM. In this paper the most relevant issues related to the f.e.m. modelling of a prestressed concrete bridge deck related to the use of clinometers for SHM are presented. The study presents a test-case deck that has been under continuous monitoring for many months. A brief explanation of the data-cleaning process and the interpretation of the clinometers outputs is also given, stressing out the limitations of the technology and possible outcomes.

Past and recent seismic events have highlighted undesirable brittle failure in RC frame structures, indicating that a substantial damage may result from beam-column joints in non-seismically designed buildings. This paper presents a numerical investigation on exterior RC joints under seismic loading based on a macro-modelling approach, which employs the “scissors model” to schematize the shear behavior of the joint and the bond-slip of the longitudinal steel rebars at the beam-joint interface. A set of literature experimental tests have been used to develop a model for the estimate of the maximum shear strength and a new multi-linear shear stress-strain law of the joint element. Cyclic analyses have been also performed by implementing the “pinching4” material parameters available in OpenSees, governing the hysteresis rules and pinching effect.

Reinforced concrete (RC) discontinuity regions (D-regions), such as dapped ends and corbels, can represent highly vulnerable zones in existing RC structures, since they are characterized by brittle failure mechanisms. In common design practice, the ultimate strength of D-regions is assessed through Strut and Tie models (STM). The present work shows that, if on the one hand, the resistant lattice trusses suggested by construction standards like Eurocode 2 are on the safe side in the design phase, on the other hand, they can provide non-conservative results in the assessment of the ultimate strength of existing D-regions, as they cannot be appropriate to reproduce the actual distribution of steel reinforcement. Within this work, some indications are provided to identify the resistant mechanisms of D-regions in existing RC members together with some preliminary indications how to increase their ultimate strength and ductility.

This paper discusses objectives, methodologies and results from a campaign of non-destructive investigations on a cable-stayed bridge in Lisbon (Portugal). Among the investigations held, the campaign encompassed dynamic testing of the stay cables in order to identify their natural vibration frequencies and to estimate their tension force. A frequency-domain output-only approach was carried out to identify the natural frequencies of the cables. Subsequently, the cable tension force was estimated on the basis of the flat taut string model. In an advantageous and cost-effective way, vibration tests were carried out without the interruption of the vehicular traffic. Results of the testing campaign were finally incorporated in the bridge condition assessment and used to provide both short- and long-term maintenance prescriptions.

This work deals with the static safety check of a real case study concerning a viaduct with simply supported prestressed concrete beams and reinforced concrete piles, recurrent in Italy in the 1960s–70s. A review of the typical design methods used in the past for bridges is provided, starting from the load case definitions and their possible combinations to the verification criteria. Moreover, the typical assumptions made in the original design procedure are shown, also considering the simplified models used. These original results are compared to the ones obtained from the application of the actual design method proposed in the national technical codes and the FEM modelling of the bridge. The whole static safety check process of the viaduct is also illustrated, starting from the structural survey plan and dynamic identification of the viaduct up to the development of the bridge structural elements checks, highlighting the most important aspects in the assessment of the typical viaduct examined.

During the last years, the use of performance-based approach according to the Fire Safety Engineering (FSE) is becoming ever more widespread. This approach is particularly used for the definition of the potential fires and of the structural fire behaviour of buildings with intended use of car parks. However, if the park is used for motor scooters, the international scientific framework offers very few information about its fire safety, both for fluid dynamic and thermomechanical aspects.In this work, several fire scenarios correlated to the two different park intended uses were investigated, starting from experimental Heat Release Rate curves. These curves were used for CFD analyses to define the time-temperature distributions during selected fire scenarios. Several thermomechanical analyses of a reinforced concrete structure were performed using both natural and nominal fire curves. A benchmark between the different cases were performed, underlining the importance of the FSE to reduce the structural fire demand.

Many of the existing reinforced and prestressed concrete infrastructures, such as bridges, subways or overpasses have reached or will reach, in this decade, half a century of existence, making it timely to assess their structural safety accounting for their state. It is desirable that the assessment of existing structures is carried out following a design philosophy by Levels-of-Approximation (LoA) as described in Model Code 2010. This design philosophy consists in starting with a lower LoA corresponding to simple and fast calculations with some safety margin (corresponding to an approach typically used in the design of new structures), refining in the following stages (higher LoAs) only the calculations associated with the governing structural verifications. This work aims at addressing the fundamental aspects of this methodology, based on the experience in Switzerland in the last three decades, discussing briefly the calculation methods that can be applied in higher LoA and that allow considering some reserves of structural resistances typically neglected for design of new structures.

The gerber half-joints assessment is today a topical problem since these are widespread in the italian infrastructure heritage. These elements, classified as “critical” by the recent italian guidelines (LG20), are often affected by chloride corrosion phenomena due to their positioning under the deck joint. The research program, aimed at evaluating the non-linear behaviour of gerber half-joints, includes the cast of sixteen specimens, which were designed and tested until failure according to different design models, reinforcement amount, and increasing corrosion levels of the reinforcement. This paper presents the first results of two un-corroded and two corroded specimens. The experimental outcomes show that both design details and reinforcement corrosion could compromise the strength and ductility requirements of the saddles. Furthermore, the authors believe that the results can represent a strong scientific reference for the analytical and numerical structural assessment of existing corroded gerber half-joints.

Based on different theories (plasticity theory, modified compression field theory and compression chord capacity theory), this paper investigates the effects of corrosion of the transverse reinforcement on the shear strength of reinforced concrete beams. The effects of corrosion of the transverse reinforcement are firstly described and, then, adequately introduced in the formulations of the plasticity and modified compression field theories. The considered formulations are applied to a set of RC beams tested in laboratory by other researchers and a comparison is first drawn between the shear strength values resulting from the considered models and the shear strength resulting from the laboratory tests. Then, the effects of corrosion on the mechanical parameters involved in the ultimate response of the examined reinforced concrete beams are investigated.

The corrosion of steel reinforcement in reinforced concrete beams is cause of several structural-damage effects. When corrosion distresses stirrups, the shear response is drastically affected. The corrosion of stirrups produces rust all around causing reduction of cross-section steel rebar and spalling of concrete cover. This study presents a theoretical model to reproduce the shear response of reinforced concrete slender beams with corroded stirrups. The formulation extends an established procedure, based on the Modified Compression Field Theory, and, introducing the structural effects of stirrups corrosion, provides the entire load-displacement curve. Information about crack condition and compression field inclination at each stage of loading are also obtained. Firstly, the proposed model is assessed against a database of sixty-two specimens collected in the literature; then, it is used for a parametric analysis to highlight the role of the parameters involved.

The paper investigates the cyclic behaviour of a column-to-foundation joint for precast concrete structures. The connection investigated in the experimental campaign is realized using corrugated steel ducts in which column protruding longitudinal rebars are an-chored by grouted high performance mortar. The research program includes six full-scale RC columns having a square section, tested under an increasing cyclic lateral load and a constant axial load, with the aim to investigate the influence of the connection typology (cast-in-place or grouted connection), of different bar anchorage lengths and of different rebars diameters. Results are analysed in terms of hysteretic behaviour, energy dissipation, ductility values and plastic hinge location, and show a comparable structural behaviour between specimens with the precast joint and reference cast-in-place ones.

In Europe, the vast majority of RC structures is characterized by a lack in both material quality and structural detailing, which significantly influences their seismic behaviour. Furthermore, a huge number of them may be affected by severe material degradation phenomena, since classical procedures adopted in concrete structures design have often failed to achieve sufficiently durable performances. Nowadays, code provisions towards durability rely on some “deemed-to-satisfy” rules concerning the values of concrete cover and of concrete strength to be adopted. The present paper reports a parametric study on the time-dependent variation of structural seismic reliability due to carbonation-induced corrosion. To this aim, a simple and explicit procedure has been applied. Such procedure involves a mechanically-consistent implementation of carbonation-induced effects and requires the use of nonlinear static (Pushover) analyses, although it is possible to extend its use to different degradation phenomena and to the use of nonlinear dynamic analyses.

Prestressed concrete elements are nowadays used in several applications very different from the standard concrete structures built in the past. In such cases, post-tensioning systems are by far the best choice, considering their great flexibility. To achieve the most effective results for post-tensioning applications, a dedicated careful design is always required, even more when special boundary conditions are given to the project, such as construction of a post-tensioned structure in arctic climates. This case is nowadays more and more common, due to research in new energy sources like the use of liquefied natural gas.In these conditions, special winterization measures for the post-tensioning system have to be designed, in order to manage properly extreme low temperature conditions. Among post tensioning activities, ones of the most important requiring special winterization measures are the grouting operation, i.e. how to fill tendons’ ducts, and the pouring of special post-tensioning anchorages. In all these cases, heating of ducts and anchorages is required to guarantee proper grout curing.The aim of this article is to provide a review of the possible winterization systems used in post-tensioning works, highlighting pros and cons for each one of them. Then, several applications used in job sites are presented.

Global warming derives from the emission of large quantities of greenhouse gases (ghg) into the atmosphere and cement production is one of the main processes responsible for environmental pollution. The production of eco-sustainable concretes with recycled aggregates can contribute to emissions reduction, but the development of new binders able to replace, at least in part, cement would be even more important. This paper presents some results on innovative concretes investigated in marewind project, an ambitious eu project that aims the development of a more durable concrete materials to achieve a sustainable foundation structure (lighter and enhanced durability) for an offshore wind turbine compared to the traditional solution. The results of the tests carried out on two different mixtures of eco-sustainable concretes, Alkali Activated Concrete (AAC) and Ultra High-Performance Concrete (UHPC), will allow to identify the best performing formulations in terms of mechanical and durability behaviour of the concretes in relevant environment.

The actual level of deterioration, especially connected to corrosion, is a critical information to be included in the whole assessment process for existing RC structures, to allow for a reliable assessment of the structure as-is condition, an effective choice of the renovation strategy, and the prediction of the structural performances along the renovated life cycle. The DEMSA protocol, enabling the detection, evaluation, and modelling of corrosion effects on RC structures was recently proposed by the authors. The whole procedure guiding the engineer from the on-site inspection to structural evaluation is briefly described herein, and focus is made on the description of the new tools conceived to define such a simplified procedure available for the professional practice. In this paper, the validation of the procedure is presented, through the application of the protocol to some reference case-studies.

Clear knowledge of the seismic vulnerability of corroded reinforced concrete structures is very important. Reinforced concrete has been used from over a century and properties of materials have changed and evolved, so the evaluation of the seismic behaviour of existing structures (corroded or not) should consider such progress of used materials. The aim of the present research is to investigate about the seismic capacity of a simple corroded reinforced concrete structure, considering three different building periods (evaluated by considering properties of materials related to different periods), two different corrosion levels of the structure (evaluated by considering bar reduction and concrete cover cracking/delamination). Push-over analyses were performed in order to understand the influence of materials in terms of seismic capacity of structures and how much corrosion phenomenon contributes to this reduction. Results show that material properties have a limited influence on seismic behaviour, but older ones allow for a faster and earlier corrosion process leading to faster and earlier reduction of structural capacity.

Fibre optical sensors technology is widely employed for structural health monitoring of civil engineering structures, mainly existing structures, to guarantee a proper structural safety level. This research proposes an industrial solution which leads to the production of self-monitoring prestressed, precast RC beams through optical fibre technology, for quality prebuilt beam control and to monitor structures when the implementation in the construction site is done. As a first step, steel strands have been instrumented with Fiber Bragg Grating sensors. It was feasible through the embedding of FBGs into fibreglass manufactured saddles for easy positioning and the fixing of optical sensors on rebars during the pre-cast production site of beams. The following step consists of performing executing tensile tests for comparing and validating FBG monitoring results to traditional measurement systems (extensometers) and Digital Image Correlation measurement system (DIC). Throughout this article, the manufacturing saddles process and preliminary thermal tests are presented to display the first monitoring parameters’ results.

Steel seven-wire strands are highly vulnerable to corrosion phenomena, which can strongly reduce their strength and ductility capacities. In the present work, the key parameters governing the mechanical response of corroded wires and strands are identified. They include parameters related to both the geometrical configuration of the corrosion (in terms of reduction of cross-sectional area and longitudinal extension) and to the material constitutive model (strength, hardening and ductility). In this respect, both elastic-perfectly plastic and bilinear with hardening models are considered for the steel material. A simplified mechanical model describing the tensile force-displacement behavior of corroded wires and strands is proposed. The corroded strand is modelled as a parallel system of corroded wires. Parametric simulations have been then carried out in order to highlight the effects of the identified parameters, in terms of force-displacement relationship. The objective of this work is to provide an estimation of the corroded strand maximum force under tensile load, which is of great interest from both design and safety assessment points of view.

Nowadays, calcium chloride is commonly used as de-icer on roads and infrastructures to remove ice and snow, ensuring the safety of vehicles and pedestrian. The deterioration of Portland-based reinforced concretes exposed to CaCl2 is well known while no data are available for alternative and innovatie binding materials. This paper focuses on the resistance to chemical attach of mortars manufactured with different low-carbon binders such as alkali activated slag cements and calcium sulphoaluminate (CSA) cement-based blends in presence of calcium chloride-based de-icing salts in cold weathers. Results indicated that alkali activated slag-based mortars are quasi-immune to CaCl2 attack due to their mineralogical composition. On the contrary, calcium sulphoaluminate-based blends show strong deterioration, especially when CSA cement is used with gypsum and Portland cement. In this case, the total loss of binding capacity can be detected both in cold (4 ℃) and hot (38 ℃) climates.

Replacing natural aggregate with recycled materials can decrease the environmental impact of concrete by reducing not only the use of natural resources, but also the disposal of waste materials. Recycled asphalt pavement (RAP) is a granular material obtained from the maintenance of road pavements whose size and distribution make it suitable as aggregate for concrete. This note presents the results of an experimental research aimed at characterising properties of concretes made with RAP as replacement of natural aggregate (in fractions ranging from 0 to 100%), considering the effect of compositional parameters such as the cement type (a limestone portland cement, CEM II A-LL 42.5R, and a pozzolanic cement, CEM IV/A (P-V) 42.5N-SR) and the water/cement ratio (0.45 and 0.65). Besides basic characterisation at fresh and hardened state, also durability properties were measured, such as resistance to carbonation, sorptivity, water absorption and electrical resistivity.

The research features a series of tests on two types of Ultra-High Performance Concrete (UHPC, 150 and 180 N/mm2) with polypropylene (PP) fibres (0.27% of volume) and variable content of steel (S) fibres (0% to 1.92%), aimed at investigating the residual mechanical properties of the material after high temperature exposure. The results are compared to available research on small UHPC specimens exposed to high temperatures, with PP fibres from 0.03% to 2%, and S fibres from 0 to 3% of volume. The results demonstrate that UHPCs need hybrid fibre reinforcement (PP + S) to withstand high temperatures, and that the residual strength increases after 200 ℃ exposure, at all steel fibre dosages; this is in line with literature. Available research also shows that strength loss is possible in hot conditions, as found in the present research, while PP fibres alone do not always prevent the occurrence of spalling in small UHPC samples.

Smart carbon-based cementitious composites possess multifunctional properties, adding novel capabilities to mechanical ones. Of great interest in civil engineering are self-sensing materials, which permit to carry out a continuous, diffuse and simple monitoring on structures and infrastructures. In the field of infrastructures, weigh-in motion, traffic and health monitoring are especially worthy of investigation, because they permit to control the safety of critical structures, such as bridges, and to identify states of damage or loss of structural integrity. The authors present the characterization and investigation of smart cementitious composites for road pavements doped with carbon microfibers and graphite, with self-monitoring capabilities. The optimal material was developed by carrying out laboratory tests on small-scale samples with different amounts of hybrid fillers, and the sensing properties were proved through fields tests. The results demonstrated the valuable capabilities of the developed cementitious pavement in weigh-in-motion and traffic monitoring of vehicles.

This article is aimed to the study of the influence of water/binder ratio, set retarding admixture dosage and curing condition on the properties of low environmental impact expansive concretes manufactured with calcium sulphoaluminate cement (CSA), gypsum, lime and supplementary cementitious materials instead of Portland cement (OPC). Experimental results indicated that tartaric acid-based set-retarding admixture influences the behaviour of concrete both in fresh and hardened state. In addition, according to Abram's model, results evidenced the water/binder ratio as a key factor in strength gain. Moreover, tartaric acid allows the production of shrinkage-compensating Portland-free concretes recommended for slabs on ground. Finally, by replacing OPC with CSA-based binders, it is possible to obtain, both for CO2-emissions and energy consumption, a reduction up to 60% at equal strength class respect to an OPC-based concrete.