Search

Several species of migratory swifts breed in the Western Palearctic, but they differ in reproductive traits and nonbreeding areas explored in Africa. We examined survival and recapture probabilities of two species of swifts by capture–mark–recapture data collected in northern Italy (Pallid Swift Apus pallidus in Carmagnola, Turin, and Common Swift Apus apus in Guiglia, Modena) in the breeding season (May–July). Apparent survival rates were relatively high (>71%), comparable to other studies of European swifts, but showed marked annual variations. We used geolocators to establish the exact wintering areas of birds breeding in our study colonies. Common Swifts explored the Sahel zone during migration and spent the winter in SE Africa, while the Pallid Swifts remained in the Sahel zone for a longer time, shifting locations southeast down to Cameroun and Nigeria later in winter. These movements followed the seasonal rains from north to south (October to December). In both species, we found large yearly differences in survival probabilities related to different climatic indices. In the Pallid Swift, wintering in Western Africa, the Sahel rainfall index best explained survival, with driest seasons associated with reduced survival. In the Common Swift, wintering in SE Africa, the El Niño–Southern Oscillation (ENSO) cycle performed significantly better than Sahel rainfall or North Atlantic Oscillation (NAO). Extreme events and precipitation anomalies in Eastern Africa during La Niña events resulted in reduced survival probabilities in Common Swifts. Our study shows that the two species of swifts have similar average annual survival, but their survival varies between years and is strongly affected by different climatic drivers associated with their respective wintering areas. This finding could suggest important ecological diversification that should be taken into account when comparing survival and area use of similar species that migrate between temperate breeding areas and tropical wintering areas., We examined survival and recapture probabilities of two species of swifts by capture–mark–recapture data collected in northern Italy in the breeding season, and we used geolocators to establish the exact wintering areas of birds breeding in our study colonies. Survival rates were relatively high (>71%) and showed marked annual variations related to different climatic indices. In the Pallid Swift, the Sahel rainfall index best explained survival, with driest seasons associated with reduced survival, while in the Common Swift the El Niño–Southern Oscillation (ENSO) cycle was associated with survival.

The main consequence of Alkali-Silica Reaction is the formation of cracks due to expansion, which can lead to a reduction in resistance capacity of the section of the structural element. The addition of steel fibers (micro fibers and Macro fibers) in the concrete, leads to considerable changes in the material properties in terms of its mechanical and durability performance, even under operating loads. This involves reducing or eliminating the formation of cracks, thus limiting the penetration of corrosive agents. In order to understand the behavior of steel fibers on concrete subjected to ASR due to the presence of highly reactive coarse aggregate (Sudbury aggregate), a 4-month accelerated laboratory testing campaign was conducted with four mix designs (plain concrete, 0.5% Macro fiber, 1.0% Macro fiber, 1.0% Hybrid: 0.5% Macro and 0.5% micro fiber). To speed up the ASR reaction process the samples were exposed to 50 °C temperature and 100% R.H. in a moisture chamber for the entire maturation period. Prisms, cubes, cylinders and beams were cast and tested for: longitudinal expansion, dynamic elastic modulus, damage rating index, compressive strength, static modulus of elasticity and flexural tensile strength. The main result was that the 1.0% Macro mix design is the one that most mitigates the formation of cracks.

This paper concerns an investigation on six large-scale Steel Fiber Reinforced Concrete (SFRC) beams tested in pure torsion. All beams had longitudinal rebars to facilitate the well-known space truss resisting mechanism. However, in order to promote economic use of the material, the transverse reinforcement (i.e. stirrups/links) was varied in the six large scale beams. The latter contained either no stirrups, or the minimum amount of transverse reinforcement (according to Eurocode 2), or hooked-end steel fibers (25 or 50 kg/m3). Material characterization were also carried out to determine the performance parameters of SFRC. The results of this study show that SFRC with a post-cracking performance class greater than 2c (according to Model Code 2010) is able to completely substitute the minimum reinforcement required for resisting torsion. In fact, the addition of steel fibers contributes to significantly increase the maximum resisting torque and maximum twist when compared to the same specimen without fibers. Moreover, SFRC provides a rather high post-cracking stiffness and a steadier development of the cracking process as compared to classical RC elements. This phenomenon improves beam behavior at serviceability limit state. The experimental results are critically discussed and compared to available analytical models as well as with other tests available into the literature.

The present work reports the results of two quasi-static reverse cyclic tests performed on an unreinforced hollow clay block masonry building before and after repairing with a single 30-mm ...

Thin layers of mortar reinforced with steel fibers can be applied on one or both sides of bearing walls as an effective seismic strengthening of existing masonry buildings. To assess the effectiveness of this technique, an experimental study on masonry sub-assemblages was carried out at the University of Brescia. This paper summarizes and discusses the main results of the investigation, which included mechanical characterization tests on masonry and its components as well as on the Steel Fiber Reinforced Mortar (SFRM) used to retrofit the masonry samples. Uniaxial and diagonal compression tests were carried out on both unstrengthened wallets and masonry samples retrofitted with 25 mm thick SFRM coating. Both single-sided and double-sided retrofitting configurations for application on wall surfaces were considered. The results highlighted the ability of the technique to improve the compressive and the shear behavior of masonry, even in case of single-sided strengthening. Moreover, no premature debonding of coating was observed. Lastly, the manuscript presents the results of a numerical investigation that was performed both to simulate the diagonal compression tests described in the first part of the paper and to predict the response of panels with different strengthening configurations.

Spectacular long-distance migration has evolved repeatedly in animals enabling exploration of resources separated in time and space. In birds, these patterns are largely driven by seasonality, cost of migration, and asymmetries in competition leading most often to leapfrog migration, where northern breeding populations winter furthest to the south. Here, we show that the highly aerial common swiftApus apus, spending the nonbreeding period on the wing, instead exhibits a rarely found chain migration pattern, where the most southern breeding populations in Europe migrate to wintering areas furthest to the south in Africa, whereas the northern populations winter to the north. The swifts concentrated in three major areas in sub-Saharan Africa during the nonbreeding period, with substantial overlap of nearby breeding populations. We found that the southern breeding swifts were larger, raised more young, and arrived to the wintering areas with higher seasonal variation in greenness (Normalized Difference Vegetation Index) earlier than the northern breeding swifts. This unusual chain migration pattern in common swifts is largely driven by differential annual timing and we suggest it evolves by prior occupancy and dominance by size in the breeding quarters and by prior occupancy combined with diffuse competition in the winter.

It is well known that the inclusion of steel fibres into a concrete matrix has the potential to improve both the serviceability and strength characteristics of reinforced concrete. As a result of decades of academic interest into the material, design provisions for flexural strength, shear strength and short-term serviceability have been incorporated into international codes of practice. However, available design guidelines typically contain little or no guidance for engineers to confidently predict the long-term behaviour of structures manufactured with steel fibre reinforced concrete (SFRC). This limits the full utilization of the material in design practice. This paper presents a simplified model, suitable for design, that can reliably predict the effects of creep and shrinkage in SFRC members containing conventional reinforcement which are subjected to a sustained in-service flexural load. Predictions of the proposed model are compared to available data in the literature and are shown to correlate well.

Fibre reinforced concrete (FRC) increases shear capacity mainly by providing post-cracking residual strengths and by improving the aggregate interlock mechanism on the two crack faces. Hence, direct shear tests can be adopted to study the shear transfer mechanisms across a crack. Several researches studied the behaviour of steel fibre reinforced concrete by means of shear tests initially developed for plain concrete (PC). Due to an increased heterogeneity of material (caused by a random fibre distribution) and the need to carry out the test up to a higher crack width (Mode I) and slip (Mode II), tests on FRC are more difficult as compared to PC and the issue related to the rotation of the cracking plane is more likely to develop. In addition, other fibre types or materials different than ordinary concrete have not been studied in depth so far. In this context, the present study firstly evaluates the influence of rigid (steel) and non-rigid (polypropylene) fibres on the direct shear behaviour of ordinary concrete (considering a broad range of FRC toughness). To do this, the modified JSCE SF6 test was improved by avoiding friction and by providing a steel system to control rotations. Secondly, the direct shear behaviour of alkali activated concrete (AAC) reinforced by steel fibres was compared against ordinary FRC in order to underline possible differences. Experimental results showed that, under direct shear tests, the fibre influence on the shear stresses transferred across a crack is only related to FRC toughness and not to fibre type (rigid or non-rigid). AAC also showed to have a shear behaviour comparable to ordinary concrete.

An experimental study including reverse quasi-static cyclic tests on solid and hollow Unreinforced Masonry walls strengthened with thin steel fiber-reinforced mortar (SFRM) coating is herein presen...

A significant number of Infilled Reinforce Concrete (RC) frame structures constructed worldwide are not designed to withstand seismic actions. An important contribution to the lateral resistance of the bare frame is usually provided by weak masonry infills, whose interaction with the frame has been frequently neglected by designers. In case low-rise buildings placed in low seismicity areas are considered, the moderate inelastic demand resulting from the seismic excitation allows implementing retrofitting techniques aiming at improving the structure resistance rather than its ability to dissipate energy by inelastic mechanisms. This paper studies a retrofitting approach aiming at exploiting the frame-to-infill interaction by using a thin layer of mortar coating connected to the outer surfaces of the perimeter walls of the RC buildings. The coating is applied on the existent plaster and is reinforced with an Alkali-Resistant glass fiber mesh properly anchored to the infill. A series of reverse cyclic tests on three hollow clay brick masonry infills, including a not strengthened wall as well as a strengthened and a repaired specimen, was carried out. A special RC frame provided with steel hinges at the columns edges was built to simulate flexural mechanisms generally occurring in weakly reinforced frames. Results proved the ability of the adopted technique to significantly improve both lateral stiffness and resistance of infills. However, the observed behavior suggested future improvements that may lead to a further increment of the infill capacity.

It is well-known that concrete is the most widely utilised construction material in the world [...]

Different tests are proposed by international standards for the evaluation of the mechanical properties of fiber reinforced concrete (FRC); among them, either beams or round determinate panels are generally used. However, different tests are accepted by design codes if reliable correlation factors between standard parameters are provided (fib Model Code 2010). Within this context, a broad experimental program on both beams and round determinate panels was carried out in order to provide a critical discussion on material characterization and to evaluate possible correlation factors. Beam tests according to European (EN 14651), American (ASTM 1609), and Japanese (JCI-SF4) standard, as well as small round panels and large round panels (according to ASTM 1550) were studied within an experimental program comprising 189 beams and 90 round panels. Unlike previous researches, mainly focused on steel fibers, two types of macro-synthetic fibers were considered. Based on these experimental results, a comparison between test methods is presented, along with correlation approaches are proposed and critically discussed.

Der Einsatz von Makrofasern aus Stahl gewinnt seit der bauaufsichtlichen Einfuhrung der Richtlinie „Stahlfaserbeton” des Deutschen Ausschusses fur Stahlbeton (DAfStb) auch in tragenden Betonkonstruktionen zunehmend an Bedeutung. Insbesondere beim Nachweis ausreichender Querkrafttragfahigkeit erweist sich die Fasertragwirkung als gunstig, da eine Querkraftbewehrung auch bei Balken rechnerisch vollstandig durch Fasern gebildet sein kann – Bugel also entfallen. Haupteinflussparameter ist die Nachrisszugfestigkeit, die aufgrund vielfaltiger interagierender Einflussparameter hohen Streuungen unterliegt und nach Ansatzen der DAfStb-Richtlinie bzw. den Modellen des Model Codes 2010 deutlich unterschiedlich einfliest. Der Beitrag vergleicht die Prognosegenauigkeiten rechnerischer Querkrafttragfahigkeiten, indem rechnerische Bruchlasten experimentellen Daten von Schubversuchen aus der Literatur gegenubergestellt werden. Die aufgebaute Schubdatenbank umfasst dabei uber 250 Versuche mit praxistypischen Konfigurationen, d. h., dass Querschnittsgeometrie, Langs- und Bugelbewehrungsgehalt, Nachrisszugfestigkeit des Stahlfaserbetons sowie Betondruckfestigkeit variable Parameter sind.

The recent fib Model Code for Concrete Structures 2010 (MC2010) recognizes fiber reinforced concrete (FRC) as a new structural material, favoring its usage in innovative structural applications. FRC is considered primarily a material with a non-negligible residual strength after cracking. According to MC2010, FRC can be adopted as the only reinforcement in structures provided that both strength and ductility requirements are fulfilled. This paper presents a discussion on the MC2010 requirements for FRC structures applied to both experimental and numerically simulated structural elements, proposing a refined set of equations to check FRC structures (not containing any classical reinforcement) against both service and ultimate limit states.

An increase of infrastructures needing repair and rehabilitation has led to a growing use of bonded overlays to members such as slabs, columns, bridge decks, bridge piers, etc. These overlays are nowadays made of High Performance Concrete (HPC) able to significantly increase the structural performance with a smaller thickness. However, HPC is generally characterized by a higher percentage of cement paste that increases shrinkage phenomena. Therefore, despite the many advantages, the performance of overlays is usually affected by debonding (from the original surface) and/or early age cracking. In this context, results from an investigation to assess edge curling, debonding and cracking in concrete slab elements reinforced with different overlay materials are presented herein. Unlike in previous studies, actual strain measurements, carried out on the bonded overlay, were used to evaluate the shrinkage behavior. Results highlight the effect of both the rate and magnitude of shrinkage on overlay performance. The use of a shrinkage reducing admixture (SRA) was also shown to be beneficial. Furthermore, through both experimental and numerical analysis, the use of randomly distributed fibers was shown to be effective in improving overlay performance, by reducing the width of the shrinkage induced cracks.

Elevated concrete slabs are typically used as columns/piles supported floors in multi-story buildings or industrial facilities. The need to reduce construction time and costs has favoured the use of ever more advanced materials, like Steel Fiber Reinforced Concrete, as an alternative to conventional reinforced concrete. Many research studies and on-site applications have proven that steel fibers can be successfully used to totally substitute the main flexural reinforcement generally placed in conventional reinforced concrete slabs. However, in order to ensure the required minimum structural performance both at ultimate and serviceability loading conditions, the total removal of rebars requires the use of very high steel fiber contents (>70 kg/m3). However, the use of a proper combination of fibers and conventional rebars, generally known as Hybrid Reinforced Concrete (HRC), may represent a feasible solution to get the required structural performance by minimizing, at the same time, the total amount of reinforcement (fibers+rebars).

Although concrete performance has increased significantly over the last 20 years, the durability of concrete structures still remains a major concern. In fact, while concrete permeability has been remarkably reduced, aggressive agents can still penetrate concrete structures through cracks, which are generally present due to shrinkage or tensile stresses. A possible solution for crack control in structural members reinforced with conventional steel rebars is represented by fibre-reinforced concrete. In fact, fibre reinforcement improves the tension stiffening in the concrete portions between cracks and allows tensile stresses to be transmitted between the crack faces; both aspects reduce the crack distance and, as a consequence, the crack width. Within this framework, the aim of this paper is to shed new light on the crack control exhibited by steel-fibre-reinforced concrete (SFRC), having high post-cracking residual strength, in combination with steel rebars. In this regard, 32 tension ties under direct tension were tested. Special attention was devoted to the influence of the SFRC post-cracking performance on crack formation and development. The results confirmed a reduction in mean crack spacing compared with reinforced concrete members. However, beyond a nominal residual strength of around 5 MPa, no considerable reduction of the mean crack spacing was found.

In the following study, the mechanical properties of steel and macro-PP fibre reinforced concretes based on an alkali-activated slag (AAS), an alkali-activated fly ash (AAFA) and an Ordinary Portland Cement (OPC) were studied. The influence of different fibre materials (macro-PP fibres and steel fibres mix) and contents (0, 0.3 and 0.6 vol%) on the compressive, splitting tensile and flexural tensile strength was investigated at an age of 28 days. The obtained load-deformation curves and the characteristic post crack behaviour (according to EN 14651) were interpreted by additional analyses of the bond behaviour via micro X-ray computer tomography (μXCT) and scanning electron microscopy (SEM).

After more than fifty years from the opening of the largely discussed “Autostrada del Sole” Highway in 1964, the infrastructure system in Italy appears marked by the passing of time, similarly to what observed in several other countries worldwide. The great heterogeneity of the Italian landscape has determined a great variety of construction types, such as large span concrete bridges over the northern rivers and large arch concrete bridges over the valleys of the central region. Increment of vehicle traffic and new seismic regulations are setting new requirements to adapt the existing infrastructure, which should be otherwise replaced. Moreover, reinforced concrete (RC) aging and deterioration have led to structural and material degradation, including severe cracking and corrosion. Specialized materials such as High Performance Concrete (HPC) could represent a viable convenient solution for repairing, strengthening and retrofitting of RC structures as both structural capacity and durability can be refurbished. However, alongside high mechanical performance, HPC is characterized by a high cracking sensitivity at very early age, due to its high stiffness and shrinkage. Restrained shrinkage cracking, particularly significant in repaired structures where the existing concrete generates a considerable restraint against the free movement of the repair material, may represent a limit to the effective application of these materials. For this reason, shrinkage compatibility of HPC with the existing concrete substrate needs to be experimentally and numerically assessed. A study is herein presented where, based on experimental tests, different numerical models are developed and compared to assess and eventually minimize the risk of shrinkage cracking in bridge piers strengthened with HPC.

This paper reports the experimental results of 11 full scale thin plates (dim. 4200 × 2500 × 80 mm3): 8 slabs containing three types of fiber reinforcement (2 types of high strength fibers, one added in two different contents) were tested first. Then, one slab cast with traditional reinforced concrete was tested and used as a reference slab. Finally, two slabs were produced with a typical rectangular opening, which determines a disturbed stress region: the first one was cast in classical reinforced concrete (RC) whereas the second by suitably combining fibers and rebars under a hybrid reinforced concrete (HRC) perspective. Results show that these slender plates, undergoing light loads, might be an effective structural application in which fibers could represent the unique flexural reinforcement. In presence of disturbed regions due to openings, frequent in practice, a suitably combination of rebars and fibers is proposed and discussed. Emphasis on cracking phenomena and energy absorption capacity is provided. A comparison with the requirements of the fib Model Code 2010 for members containing only fibers is subsequently discussed.

Many existing Reinforced Concrete (RC) buildings infilled with masonry panels are vulnerable to seismic actions due to lack of proper seismic detailing. For buildings located in low-moderate seismicity regions, a possible retrofitting option could be a reinforced mortar coating applied on the building facades in order to significantly increase its seismic resistance. The present paper studies thin glass fiber mesh reinforced mortar overlays for strengthening RC weak frames infilled with hollow brick masonry. Attention is devoted to the steel dowel connection between the masonry panel and the RC frame to reduce shear sliding. An experimental evaluation of the effectiveness of this enhanced technique is presented and compared against previous results in which shear sliding significantly limited the structural response. In addition, a finite element model has been developed and calibrated to properly simulate the response of the test specimens.

The load-deformation response of Fiber Reinforced Concrete (FRC) elements subjected to pure shear is still matter of strong debate within the scientific community. In this paper, the tests on six fiber reinforced concrete panels under pure shear are presented and discussed. The tests were conducted under displacement control and a peculiar loading frame was designed to ensure that a pure shear state of stress was established. Steel fibers were added in relatively low amounts (20 and 50 kg/m3), and two steel reinforcements (0.21% and 0.74%) were selected, aiming at simulating lightly reinforced elements. A critical discussion on the influence of fibers on both global and local behavior (tension stiffening, cracking formation and propagation, post-cracking stiffness and residual strength) is presented. Finally, a novel crack spacing formulation, extended to FRC, is proposed and compared against available experimental data.

External unbonded rebars represents a suitable strengthening technique for the retrofitting of existing Reinforced Concrete (RC) members. Advantages regard the ease of installation, a minimum invasiveness and possibility of future inspections. Structurally, increment of flexural stiffness and bearing capacity and enhancement of shear-flexure behavior can be achieved. The presence of both bonded and unbonded bars introduces a change in the way the shear actions are resisted. Unbonded rebars develop an arch action component, with no bond present and constant force in the rebars, in addition to the beam action component, normally developing in presence of bonded bars. The present paper reports the results of four point loading tests on full-scale beam, with the aim of studying the influence of different bond condition. Moreover, the Double Harping Point technique, using external rebars and vertical deviators, is presented, with attention to the definition of the vertical equivalent stiffness of the deviators.

The shear strength of elements reinforced by fibres is predicted by Codes using formulations generally developed from a limited set of test results. In fact, only few of available test results are combined with a material mechanical characterization, allowing to evaluate and compare the different performances of Fibre Reinforced Concretes (FRC). To address this problem, a material-performance-based shear database for FRC elements and their related reference samples in Reinforced Concrete (RC, with and without web reinforcement) is presented herein, merging the experiences carried out in the last decade at the University of Brescia and at the Universitat Politecnica de Valencia. The database is composed by 171 specimens: 93 in FRC and 78 in RC with or without web reinforcement. For FRC elements, the post-cracking resistance (fR,1 and fR,3) is also given according to EN 14651 standard. The evaluation of the shear database was also carried out, discussing the influence of the different factors affecting the shear strength both in FRC and RC samples. Finally, the two formulations suggested by Model Code 2010 for FRC elements are compared against the database results in order to shed new light on code requirements.

A constitutive model for simulating the compressive response of unreinforced brick masonry subjected to cyclic loading is presented and discussed. The developed formulations are consistent ...

Numerical analyses represent an important way to study the behaviour of both reinforced concrete and fibre reinforced concrete (FRC) structural elements under different loading conditions. Even though advanced computer codes able to model concrete fracture phenomena were developed in the past decades, numerical and analytical tools still require improvements and verifications against new experimental evidences, especially with respects to non-standard or quite critical structures. The present paper focuses on the numerical modelling of the shear behaviour of deep beams whether with fibres (FRC) or no shear reinforcement (PC), by means of a suitable implementation of the modified compression field theory (MCFT) and the disturbed stress field model (DSFM). After a numerical validation against some new available experimental results, specific numerical analyses were performed in order to study the size effect influence on the shear behaviour of FRC elements. These analyses were conducted considering a broad variety of beams, from 250 to 1500 mm high and with different amount of fibres. In the modelling, particular attention was devoted to the nonlinear behaviour of materials, especially with regard to the tension softening of FRC. The latter was modelled through inverse analysis on 3PBTs (EN14651) and by using the recently published Model Code 2010 linear model (MC2010). Refined nonlinear constitutive models and relationships for describing crack spacing and crack width, both in case of PC and FRC, were utilized as well. The numerical results show the reliability of the MCFT and DSFM in modelling both PC and FRC deep beams critical in shear. Moreover, the positive influence of fibres in reducing and significant altering the size effect trend is clearly confirmed by a broad parametric study herein reported.

Many experiments available in the literature show that fibres, when provided in sufficient amount to guarantee an adequate toughness to Fibre Reinforced Concrete (FRC), are significantly effective as shear reinforcement. However, most of the experiments relate to elements reinforced by steel fibres and very few present research on structures produced with other kinds of fibres, i.e. polypropylene (PP) fibres, which can present a series of advantages (durability and corrosion avoidance above all). Today PP fibres might be able to impart significant toughness and ductility to concrete. This paper reports the results of a recent experimental programme on reinforced concrete (without any shear reinforcement, PC) and Polypropylene Fibre Reinforced Concrete (PFRC) Wide-Shallow Beams (WSBs) subjected to shear, focusing on the role of the width-to-effective depth ratio (b/d) and on the beneficial influence of newly developed PP fibres. Fourteen WSBs with different widths and depths, fibre content and, also, minimum amount of classical shear reinforcement, were tested. Results show that PC WSBs having width-to-effective depth ratio from 2 to 3 reach a higher ultimate shear stress (compared to the corresponding not-wide PC beams), generally disregarded by most of standards. Moreover, the ability of PP fibres in promoting a substantially more stable shear behaviour was experimentally observed, as well as the possibility of using PP fibres as minimum shear reinforcement.

A numerical non-linear procedure able to represent the behavior of cracked steel fiber reinforced concrete (SFRC) is herein presented and verified. The involved post-cracking mechanisms, particularly tension softening and tension stiffening, have been investigated and properly taken into account. Different tension softening relationships have been implemented and discussed, one based on a micro-mechanical approach, another obtained from inverse analysis and finally the Model Code 2010 (MC2010) law. These models have been adopted in conjunction with a smeared crack approach to perform FE simulations of R/FRC ties characterized by different cross-sections and fiber volume fractions. Numerical results have been validated against a comprehensive experimental program on R/FRC (characterized by a tension softening behavior) and RC ties recently carried out at the University of Brescia. Comparisons between experimental and numerical results indicate that smeared models can be adopted also for the analysis of this structural typology, subjected to a uniaxial state of stress, as a valuable alternative to discrete approaches.

The interface between new concrete (overlay) and old concrete (substrate) plays an important role in the overall success of any repair. A good bond ensures long-term durability and monolithic action (i.e. the overlay contributes to both the stiffness and load-carrying capacity). Research has shown that the substrate roughness, which is highly dependent on the surface preparation method, has an influence on the interface bond strength, though there is no consensus on the extent of this effect. Thus, through a new bond test, an experimental study was conducted to evaluate the effect of substrate roughness on bond strength, also considering the effect of overlay strength. In addition, the possible consequence of roughness on interface ductility was evaluated. The results indicate an increase in bond strength with an increase in surface roughness, although the resulting increase in ductility with surface roughness was more pronounced. The strength of the overlay was also found to be an important parameter for smooth substrates or substrates with low roughness.

Self-compacting fibre reinforced concrete (SCFRC) is a useful material in precast industry, leading to a significant reduction in construction time and costs, and possibly even labour shortages. The addition of fibres enhances the behaviour of structures at both serviceability limit state (durability, cracking, deformation) and ultimate limit state (bearing capacity and ductility), allowing in many cases to replace, totally or partially, the web reinforcement. In this context, the present paper focuses on the use of macro-synthetic fibres as shear reinforcement in self-compacting concrete prestressed double tees. Experimental results of full-scale tests on six prestressed double tees made in self-compacting concrete and self-compacting polypropylene fibre reinforced concrete are presented. Firstly, shear tests were conducted in areas where the prestressing is uniformly distributed, in order to evaluate the possibility of replacing the minimum amount of shear reinforcement by macro-synthetic fibres only. Secondly, several tests were also carried out at the end zones, which are more critical in shear since the beneficial effects of prestressing is not totally active. Experimental results show that macro-synthetic fibres can be used as shear reinforcement both in the zone with uniform prestressing (minimum shear reinforcement) and in the end zones (shear reinforcement required by equilibrium). Finally, the experimental results obtained were compared against the predictions of three international codes: Eurocode 2, ACI318-11 and Model Code 2010.

The characterization of the tensile behavior of cementitious materials has been a long-standing researchtopic and a general consensus on how to accomplish this task has not yet been reached. Many standardized tests are available but each with different test set-up and prescriptions on the definition ofmeasured and derived parameters, including toughness, elastic properties and strength. This paperdiscusses a number of test procedures for selected material properties including tension and flexure. Acomparative experimental study was carried out using two distinct fiber reinforced cementitious composites with strain hardening and strain softening behavior. Digital Image Correlation was utilized in the experimental program to detect and quantify the formation of cracks. Results show that the different test methodologies valuate specific aspects of material performance. The outcome of these evaluation procedures is compared and critically analyzed.