Search

Bolted steel to laminated composite bio-based material connections are commonly used in truss systems. The aim of this study is to provide a more rational understanding of their tensile axial behavior. The aim of this paper is twofold: first, it investigates and compares the monotonic tensile axial behavior of bolted steel to laminated timber and bamboo connections with slotted-in steel plates. The test matrix comprised a total of 8 different connection configurations obtained by changing parameters relevant to the connection behavior (Laminated Veneer Lumber (LVL) and Glued Laminated Bamboo (glubam), 2 bolt diameters, and 1 or 2 bolts). Three test repetitions for each connection configuration were performed to investigate the repeatability and assess variability. Tests were performed by also employing Digital Image Correlation (DIC) apparatus to monitor the deformation process and measure relative displacements of bolts. Moreover, the physical and mechanical properties of the materials adopted are investigated. Second, based on the experimental findings, a new monotonic load vs displacement phenomenological prediction model characterized by four stages is proposed which is capable of defining more rationally the observed tensile monotonic behavior and differentiating between brittle and ductile failures. An extensive discussion of the calibration and physical meaning of the proposed model by using the experimental test results as benchmark is provided.

This paper presents a pilot study on the characterization of the high-strain rate compressive behavior of a novel concrete with two different substituted recycled plastic aggregates. A reference mix with an average compressive strength of about 55MPa is considered. Recycled PolyEthylene Terephthalate (PET) powder and recycled mixed plastic (composed of PolyPropylene (PP) and PolyEthylene (PE)) granules were adopted to substitute fine and coarse aggregates. Two different substitution strategies are employed. In the first one, the PET powder is used to substitute the fine sand by volume. In the second one, the PET powder is used to substitute the fine sand while the recycled mixed plastic granules are used to substitute the coarse sand and fine coarse aggregates by volume (50% for PET powder and 50% for recycled mixed plastic granules). Four total replacement levels (5%, 10%, 20%, and 30%) by volume were considered. The fresh concrete properties (slump and density) and quasi-static compressive behavior, are investigated. The micro-scale characterization of the material using SEM scans provided a complete understanding of the observed macro-scale behavior. Tests were performed using conventional quasi-static loading with a compressive testing machine and high-strain rate tests with a Φ80-mm Split-Hopkinson Pressure Bar (SHPB) for strain rates up to 200s−1. The dynamic tests revealed the marked strain rate dependency, although specimens with large plastic volume substitution were more sensitive to the strain rate effect. A probabilistic data-driven model for the Dynamic Increase Factor (D I F) is also proposed based on the test data. Ultimately, this study indicates that the proposed material has a good high-strain rate compressive behavior and can be a promising material to be employed for protective techniques against impact and blast loads.

This paper proposes a framework for rapid seismic risk assessment of bridges using aerial photogrammetric surveys conducted by Unmanned Aerial Vehicles (UAVs). First, the data acquisition process for the photogrammetric 3D reconstruction of an asset and the subsequent procedure for computer-vision-based automatic extraction of visible geometric features are presented. Then, the extracted features are combined in the structural models to perform a seismic risk assessment in terms of capacity-to-demand ratios. Uncertainties are related to the material and geometric hidden variables. Monte Carlo simulation is performed, assuming uniform (uninformed) distributions for the input variables affected by epistemic uncertainty. The ranges of such distributions are estimated based on engineering judgment and knowledge of construction practices. The analysis provides an estimate of the epistemic uncertainties of the capacity-to-demand ratios, with limited available information obtained from UAV aerial photogrammetry. The feasibility and applicability of the proposed framework are demonstrated through a case study of a simply supported bridge in the Italian highway network. The 3D reconstruction process is validated by comparing the aerial survey with a laser scanner survey. The seismic risk of the selected bridge is assessed using the geometric information obtained from the UAV aerial photogrammetric survey. Finally, the paper discusses the applicability of the proposed methodology for bridge management purposes in an automated framework and at network scale.

The estimation of the maximum displacements of RC beams subjected to impact loads is of pivotal importance to define demand models to be employed in structural design. The dynamic behavior is quite complex and the maximum displacements can be obtained through experimental tests or high-fidelity FEM models, while simplified analytical models accounting for few degrees of freedom have generally low accuracy. In this context, this paper presents a study on the training and interpretation of a machine-learning model that strategically combines several algorithms for the said purpose. To train the model, a comprehensive database of 342 samples of rectangular simply supported beams under rigid impact loads is adopted. Seven ML regression algorithms are adopted in this study to develop a predictive model: (1) Support Vector Regression (SV R), (2) Gaussian Process Regression (GPR), (3) Random Forest Regressor (RFR), (4) XGBoost, (5) CatBoost, (6) LightGBM, and (7) Artificial Neural Networks (ANN). Finally, a stacking model combining SV R, GPR, RFR, XGBoost, CatBoost and ANN is built to improve accuracy, wherein 75% and 25% of the data are used for training and validation, respectively, in combination with the 5 cross-validation technique. This effort resulted in approximately 90% validation accuracy exceeding current mechanics-based/semi-empirical models. Finally, the SHapley Additive exPlanations (SHAP) algorithm is used to estimate the relative importance of the input features; the most influential factors are impact velocity and impactor mass which are representing the initial kinetic energy. Moreover, a full parametric analysis of the proposed model is provided and the influence of each input is discussed. The model is finally applied to perform a structural check for three damage levels. The proposed model can be used in practical applications where a reliable estimation of the maximum displacements of RC beams under impact loading is required.

The use of composite beams made with traditional concrete and bio-based materials (such as timber and bamboo) is a valuable solution to reduce the environmental impact of the building sector. Timber-Concrete Composite (TCC) beams have been used for decades in structural applications such as new buildings, refurbishment of old timber structures, and bridges. Recently, different researchers suggested composite beams based on engineered bamboo, commonly named Bamboo-Concrete Composite (BCC) beams. This study presents a systematic comparison of structural performances and connection behavior of TCC and BCC beams under short-term static load. TCCs beams are compared to BCC ones using similar shear connectors. The most important aspects of the two composite systems are compared: mechanical behavior of connectors and structural behaviors of full-scale composite beams (e.g., failure modes, connection stiffness, connection shear strength, ultimate load-carrying capacity, maximum deflection and composite efficiency). This comprehensive review indicates that BCC beams have similar or even better structural performances compared with TCC.

This paper presents a study on Singular Value Decomposition (SVD) of pressure coefficients hyperbolic parabolic roofs. The main goal of this study is to obtain pressure coefficient maps taking into account spatial non-uniform distribution and time-depending fluctuations of the pressure field. To this aim, pressure fields are described through pressure modes estimated by using the SVD technique. Wind tunnel experimental results on eight different geometries of buildings with hyperbolic paraboloid roofs are used to derive these pressure modes. The truncated SVD approach was applied to select a sufficient number of pressure modes necessary to reconstruct the measured signal given an acceptable difference. The truncated pressure modes are fitted through a polynomial surface to obtain a parametric form expressed as a function of the hyperbolic paraboloid roof geometry. The superpositions of pressure (envelopes) for all eight geometry were provided and used to modify mean pressure coefficients, to define design load combinations. Both symmetrical and asymmetrical pressure coefficient modes are used to estimate the wind action and to calculate the vertical displacements of a cable net by FEM analyses. Results clearly indicate that these load combinations allow for capturing large downward and upward displacements not properly predicted using mean experimental pressure coefficients.

This article presents a comprehensive and critical review of the structural performances of reinforced recycled aggregate concrete beams and columns based on experimental results reported in the literature. Extensive data sets collected from the literature are categorized to investigate the effects on the local and global structural behavior. First, the flexural and shear response of reinforced recycled aggregate concrete beams is discussed. The structural performances are reviewed focusing on the main geometric and material variables such as the recycled concrete aggregate replacement ratio, the longitudinal reinforcement ratio, the transverse reinforcement ratio, and the shear span-to-depth ratio. Then, the behavior of reinforced recycled aggregate concrete columns under concentric and eccentric compressive loads and the seismic performance under low cyclic loading are discussed. The similarities and the differences between reinforced recycled aggregate concrete and reinforced natural aggregate concrete beams and columns are highlighted. The need for further research is pointed out at the end of the article. The results reported in this review clearly indicate that reinforced recycled aggregate concrete beams and columns with various recycled concrete aggregate replacement ratios have comparable or slightly lower structural performances to the reinforced natural aggregate concrete ones indicating the feasibility of recycled concrete aggregate for structural applications.

This paper investigates for the first time the high-strain rate splitting tension behavior of Fiber-Reinforced Rubberized Concrete (FRRC). Splitting tension tests were performed on Phi 100-mm specimens. Quasi-static tests were carried out using conventional quasi-static loading with a compressive testing machine and dynamic high-strain rate tests with a Phi 80-mm Split Hopkinson Pressure Bar (SHPB) for strain rates up to 10 s(-1). The experimental program comprises the characterization of Plain Concrete (PC), Fiber Reinforced Concrete (FRC), Rubberized Concrete (RuC), and FRRC with a full test matrix (a total of 240 specimens) covering fiber contents up to 1.5% and rubber volume substitution ratios up to 30%. A high-speed camera was used to capture the cracking development processes together with Digital Image Correlation (DIC). The addition of fibers enhances the deformation capacity with a marked increase in the tensile strength both for quasi-static and dynamic conditions while the substitution with rubber aggregates significantly reduces the tensile strength with a similar enhancement of the deformation capacity. For FRRC, a combination of the two effects was observed. FRC, RuC, and FRRC are characterized by marked strain rate dependency within the considered test range. Furthermore, data-driven models for compression and tension strength reduction factor (SRF(c )and SRFt) and tension Dynamic Increase Factor (DIF) are proposed for different types of FRRC. Finally, a discussion on the image-based damage development processes is provided based on the high-speed camera videos. This study indicates that FRRC has an excellent high-strain rate tension behavior reducing and controlling the crack propagation.

In this study, we are proposing a novel concrete-based material for jacketing bridge piers against vehicular impacts. The goal is to have a material with large dissipative capabilities (i.e., high ductility), moderate strength (because not carrying dead or live loads) and low environmental impacts. A candidate material with such characteristics is steel fiber-reinforced rubber concrete. The following mixes were investigated: (1) normal concrete with a mean compressive strength of around 70MPa; (2) concrete with fine rubber content of 30%; (3) concrete with steel fiber content of 1.5%; (4) concrete with rubber content of 30% and steel fiber content of 1.5%. First, the compressive quasi-static performances are investigated by universal testing machine tests. Then, the dynamic compressive behavior under high strain rate is investigated by Split Hopkinson Pressure Bar tests with a diameter of 80mm with variable gun pressure in the range of 0.3 to 0.6MPa. The preliminary results indicate that this new material can provide enhanced dissipation performances and can be potentially suitable for full-scale application of jacketing of bridge piers against vehicular impacts.

The effectiveness of CFRP-retrofit of circular reinforced concrete (RC) columns under vehicular lateral impact is experimentally investigated. Eight 1/3 scale RC columns with two different configurations of FRP-wrapping (0 layer and 2 layers) were tested, with cantilever and propped cantilever conditions, under two different impact velocities. The impact load was applied at the typical vehicular impact location. Transient dynamic responses, damage evolution and post-impact damage are investigated by comparing the results obtained with different configurations and loading conditions. It is shown that the dynamic response and post-damage of RC columns are significantly affected by the CFRP-retrofit configurations, the impact velocity, and the boundary conditions. CFRP-wrapping can effectively reduce the vulnerability under lateral impact loading, converting the failure mode from shear- to flexural-dominated. Generally, brittle shear failure mode was observed for plain columns. Larger damage was obtained by increasing the impact velocity. Moreover, the influence of boundary conditions on the dynamic behavior of RC columns has been studied. The results indicate that the propped cantilever RC column experienced much more considerable damage than the cantilever one.

In this study, we propose a digital twin pilot study for bridge monitoring and maintenance. In particular, an infrastructure management framework using UAV and surveillance cameras, and accelerometers-based digital twins is proposed to perform long-term and non-interruptive monitoring. Real-world monitoring data are obtained through an experimental test performed on the Juanhu bridge (Haning, Zhejiang, China). Traffic flow and accelerometer data of the tested bridge were measured. The digital twin model of the bridge is created as a real-time Finite Element model in OpenSees. The FE model geometry is produced using a 3D photogrammetric reconstruction, and its dynamic properties are updated based on Bayesian modal identification. The traffic flow information on the bridge is processed through computer vision techniques using the video footage from the UAV and surveillance cameras. The object detection algorithm YOLO and tracking algorithm DeepSORT are used to derive the time-space diagrams. These elements operate in tandem with the accelerometer data and the digital twin FE model to acquire a preliminary vehicle loading estimation. The results are presented in this study and showcase the feasibility of the proposed digital twin framework for bridge monitoring and maintenance.

Nowadays, bamboo as a readily available, inexpensive, renewable raw material is increasingly used in construction in several countries around the world. In this context, the use of bamboo culm for structural applications is one of the key concepts increasingly grown over the past few decades. This is motivated by the fact that regardless of being a rough-and-ready (low-tech) material, round bamboo culms are found to be easy to implement and capable of yielding architectural and structurally high-performing light-weight constructions and building designs. In this study, we aim to review design approaches for round bamboo structures, to provide a recent state-of-the-art of the relevant scientific and technical literature.

The disposal of waste rubber products is a significant issue globally and it poses a serious threat to the environment creating long-term ecological problems. The possible use of rubber aggregates in concrete is a valid alternative to obtain a green construction material. This paper develops probabilistic models for the concrete Strength Reduction Factor (SRF) and Elastic modulus Reduction Factor (ERF) accounting for the amount of rubber aggregates as well as several variables defining the mix design. Three different rubber aggregate types are considered, namely fine and coarse replaced individually and fine and coarse replaced simultaneously. A total of 644 sets of concrete compressive strength and elastic modulus tests are collected from the literature for the model calibration. The paper presents a discussion about the formulation of the models, variance stabilizing transformations, model calibration, and model selection. Once formulated, we calibrate the probabilistic models using data from experimental tests. The unknown model parameters are estimated using a Bayesian approach implemented using A Markov Chain Monte Carlo (MCMC) simulation method. The proposed probabilistic models are used to evaluate the reliability of rubberized concrete structures. As an illustration, the proposed probabilistic models are used to estimate the reliability of an example column made of rubberized concrete under compressive axial force and of an example one-way slab made of rubberized concrete under distributed load.

The development of smart Internet-of-Things (IoT) solutions requires sensor nodes to be placed at different locations of monitored structures. Wireless solutions are quite attractive because of their simplicity although requiring for local energy supply. In this context, this study investigates the influences of the predefined angle of attack on the piezoelectric energy harvesting based on transverse galloping of different bluff bodies. The investigation is based on a lumped electro-aero-mechanical model with linear electrical and mechanical properties and nonlinear aerodynamic forces evaluated using the quasi-steady theory. The performances of energy harvesters with six different bluff bodies are analyzed at various predefined angles of attack: four rectangular cross-sections with different width-to-height ratios (i.e., b/d), one trapezium section, and one equal angle section. The main purpose is to understand the sensitivity of various bluff body-based energy harvesters on the predefined angle of attack, and further suggest a bluff body-based energy harvester that is robust to the predefined angle of attack. The results show that the response is quite dependent on the characteristic of the electro-mechanical system and the bluff body cross-section and angle of attack. In all cases, the load resistance should be tuned to maximize energy production. The largest vibration amplitude (i.e., largest power output) is predicted for the rectangular bluff body with b/d = 1.0 at a 0° angle of attack. However, its performances are quite dependent on the angle of attack, resulting in a zero-power output for an angle of attack exceeding 4°. A rectangular bluff body with b/d within 1.62 to 2.5 exhibits a reduced energy production compared with b/d = 1.0 at a 0° angle of attack but better robustness varying the angle of attack. Finally, the trapezium and the angle bluff bodies are not suitable for energy harvesting due to their very high onset velocities within the considered range of angles of attack.

The application of bamboo in construction is briefly introduced in this chapter. The basic mechanical properties of bamboo under different loading directions are given. The compression and tensile stress–strain models in the bamboo fiber direction are reported. In terms of round bamboo, engineered bamboo, and hybrid bamboo structures, bamboo structures are introduced with various construction examples. The carbon emission of bamboo construction was also discussed, compared with other mainstream construction forms. These research results and construction practices validate that bamboo is a promising natural source that can be used as a sustainable construction material.

In 2019, the International Bamboo and Rattan Organisation (INBAR) launched the International Bamboo Construction Competition 2019 (IBCC 2019). IBCC 2019 is an international contest aimed at university students of architecture, civil engineering, landscape, and other construction-related courses. The objective of the competition is to invite students to explore the potential construction applications for both bamboo poles and engineered bamboo products. IBCC 2019 was sponsored by several important companies working in the development of innovative bamboo products for the construction and design industries. The competition was organized on three different stages: pre-selection and qualification; selection of the three projects to be realized; and realization and award of the best project. This chapter opens with a discussion on the nature of the competition and then summarizes the key steps of the IBCC 2019 from the ideation to the award ceremony. The key design goals are widely discussed together with a deep analysis of the potentiality of bamboo for the construction industry.

The growth of urbanization in the last decades has already created a considerable number of Construction and Demolition Waste (CDW) materials. Concrete, bricks, glass, and tiles are widely used in residential construction accounting for a large proportion of CDW. The use of CDW as aggregates in the new concrete mixture has been recognized as an attractive approach to conserve natural resources and reduce the environmental influence of the construction industry. Nowadays the application of crushed bricks as coarse aggregate has recently been a reasonable target of research. However, construction structure and material can be subjected to vehicular impacts (e.g., cars, trucks, trains, boats, aircraft, etc.) and to other complex fast varying dynamic loads during their service life. Given that response of different aggregate concrete can be quite different due to its sensitivity to strain rate effects, the high-strain rate compressive behavior of recycled bricks aggregate concrete (RBC) is with little attention yet, the availability of this data is crucial for the definition of the constitutive laws accounting for the strain rate effects and allows for the evaluation of the structural response under fast varying loads such as impacts and blasts. The dynamic compressive behavior of RBC under high strain rate is investigated by large diameter Split-Hopkinson Pressure Bar (SHPB, diameter is 155 mm) in this study. Specimens are prepared by four different substitution levels respectively, from 0% (natural plain concrete) to 100% (all coarse aggregate is substituted by crushed bricks). A total of 36 specimens (with a diameter of 150mm, and a height of 75mm) are tested under three different air pressure corresponding to three strain rates. Tests can reach a maximum strain rate of 100s−1. The stress-strain relationships and the dynamic increase factor (DIF) for RBC under different strain rates are obtained and discussed. The results show that RBC is quite strain-rate sensitive constructional material.

The performance of GFRP (Glass Fiber polymer) bar RC (Reinforced Concrete) circular columns subjected to lateral impact was experimentally investigated. Sixteen GFRP bar RC column specimens representing offshore bridges were constructed and tested. Laboratory tests were performed considering two types of loading conditions (static monotonic and lateral impact) and two different boundary conditions (cantilever and propped cantilever). For the static tests, the displacement and loading performances were estimated by applying lateral monotonic static load through a hydraulic actuator. For the dynamic impact tests, a steel-made truck with a rigid nose was used to simulate the typical vehicle or vessel collision scenarios. The dynamic lateral impact and displacement responses were detailed evaluated under three different impact velocities (2.25, 3.00, and 4.50 m/s). Moreover, a semi-empirical model based on experimental results was proposed for a performance displacement-based structural assessment and maximum displacement prediction. It is found that GFRP bar RC columns have similar performance compared to traditional steel RC columns under lateral impact loads given the same static capacity.

Reinforced concrete (RC) bridge piers of highway viaducts are exposed to the vehicular impact hazard with impact location usually close to the ground (i.e., bottom of the pier), thus resulting in dominant shear damage. Different simplified approaches for the assessment of RC bridge pier performance under impact loads are generally based on equivalent static models. One crucial element for these approaches is the determination of the static shear performances and residual axial capacity. Because of limited experimental results available under these conditions, six half-scale rectangular RC columns with different volumetric reinforcement ratios and axial compressive loads were tested under near-ground lateral loads with monotonic static conditions. Test results indicate a clear major diagonal crack at the bottom of RC columns with an inclination angle of approximately 30° below the point of application of the lateral load, and it eventually slips along the crack surface under axial loads followed by failure (i.e., loss of residual axial capacity). The increase in the volumetric reinforcement ratio significantly improves the shear deformation capacity and shear crack resistance with a slight increase in the shear capacity. The increase in the axial load can also slightly increase the shear capacity of the columns but is accompanied by a reduction in shear deformation capacity. Additionally, prediction performances of three commonly used shear capacity models for the case of RC columns under near-ground lateral loads are investigated. Finally, based on the test results, an existing residual axial capacity model is modified to improve its prediction performance.

The need for enhancing the sustainability of civil constructions has originated an increasing interest in the use of engineered bamboo-based products within the building sector. Nonetheless, while the static response of bamboo-made structures has been largely investigated, experimental and numerical researches concerning the response under dynamic loads are limited. Therefore, the present work deals with the assessment of the seismic behavior of modern bamboo lightweight shear walls, with focus on the energy dissipation ensured by sheathing-to-framing connections. Initially, a short discussion about architectural, sustainability and manufacturing issues related to the use of bamboo in modern civil constructions is provided. Then, the experimental cyclic response of fasteners employed within glued laminated bamboo (glubam) shear walls is simulated by using a suitable phenomenological model whose parameters are identified through a soft computing-based numerical technique. A parametric finite element model developed within OpenSees is thus employed to assess the global seismic response of the wall. A comparison between the response of glubam- and timber-based shear walls is finally provided. This highlights that the main parameter dictating their global behavior is the local non-linear behavior of the single fastener when the cross-section size of the framing elements allows the full exploitation of its capacity and plastic deformation. The numerical simulations well agree with the main evidence carried out from the available experimental data. Particularly, it is found that glubam lightweight shear walls usually exhibit larger capacity and reduced ductility with respect to equivalent timber walls.

Recycled concrete aggregates (RCAs) generated from waste concrete have been recognized as a potential alternative to natural aggregates (NAs) for utilization in structural concrete to reduce the environmental impact and achieve the sustainability of resources in engineering constructions. However, it is well known that the overall performances, such as strength, ductility, energy dissipation, durability, etc., of recycled aggregate concrete (RAC) are slightly lower than those of conventional concrete made by NAs. An innovative structural component, namely RAC-filled steel tube (RACFST), was proposed to improve the deficient properties of RAC by using a steel tube to confine concrete. However, literature at large lacks methods to predict the structural performance of RACFST under seismic-induced actions. To address the scarcity of technical information on modelling the seismic performance of circular RACFST, in this study, a fiber-based FEM model is first proposed and then validated using the available experimental data on the hysteresis loops of these columns. The so-validated numerical model is then used to conduct a complete parametric study to investigate the influence of the key parameters governing the mechanical properties of the RAC and of the steel tube on the hysteretic characteristics of circular RACFST columns. Additionally, the compiled database is used to conduct a grey correlation analysis that aims to establish quantifiable evidence of the parametric sensitivity of the seismic performance of circular RACFST columns. The evaluation results show that the use of the additional water method absorption of RCAs in manufacturing RAC reduces the lateral load capacity of the columns, whereas the opposite occurs when this method is not employed. It is also demonstrated that RCA percentage has a less remarkable effect on the seismic performance of CFST manufactured using RCAs, although this effect should be considered in the seismic assessment.

The bridge over the Basento river in Potenza, Italy, designed by Sergio Musmeci, is supported by a continuous double-curvature RC shell optimized to reduce bending forces. This 300 m long bridge can be considered as a unique representative example of pioneering research on the design and construction of optimized structures. First, the design process employed for determining the form of the shell and the relevant constructive issues are described. A refined 3D geometric model of the shell is then obtained through an aerial survey carried out by a commercial UAV and a photogrammetric image-based reconstruction. A recent formulation of the Force Density Method allowing for non-isotropic stress state is exploited to numerically derive the form of the supporting shell; it is validated versus the surveyed geometry of the shell by employing a nonlinear optimization procedure in order to identify forces and stresses to be used as input parameters. Finally, the derived form of the shell is tested by a Finite Element analysis to verify its funicular efficiency, i.e., whether it is capable to withstand design loads by pure membrane actions.

The behavior of a material under high-strain rate compression can be different from quasi-static one and can be determined by using the so-called Split-Hopkinson Pressure Bar (SHPB). The aim of this study is to investigate the high-strain rate compressive behavior of Carbon Fiber Reinforced Polymer (CFRP) confined concrete in comparison with unconfined concrete. A total of 112 specimens with a diameter of 150 mm were tested under quasi-static (with a length to diameter ratio of 0.5 and 2) and under high-strain rate axial compression (with a length to diameter ratio of 0.5 ) using a universal testing machine and a SHPB with a large diameter of 155 mm , respectively. The specimens were characterized by two different strength classes, namely C30 and C60, and by a different number of CFRP layers ranging from 0 (plain cylinder) to 3. Tests were executed up to a strain rate of 100 s - 1 . The measurements were validated by checking the consistency of the large diameter SHPB and by comparing the results of plain concrete with the data available in the literature. The results indicate that the strength of CFRP confined concrete is not significantly sensitive to strain rate effects.

The use of waste and byproducts as recycled and manufactured aggregates in concrete affects significantly mechanical behavior, with different impacts depending on the peculiarity of each recycled component. Thus, realizing concrete mixtures with alternative aggregate types might influence different concrete properties at the same time, i.e., specific weight, compressive and tensile strength, elastic properties, which impact on masses and stiffnesses that characterize the structural response of reinforced concrete (RC) structures. Further on, the intrinsic heterogeneity of recycled materials might result in a different response of structural elements, too. Among all the byproducts that may be used, in this chapter, the effects of adopting electric arc furnace slag (EAFS) as aggregate in structural concrete are illustrated, showing some successful real-scale applications. Additionally, a case study is presented, to comparatively compute the structural reliability of a code-conforming reinforced concrete (RC) framed structure realized with EAF and reference concrete, made with natural material only.

This study experimentally investigates the effects of the unbonded post-tensioning on the response of reinforced concrete (RC) beams under impact loads. A total of fifteen specimens were cast and tested. All specimens had identical longitudinal reinforcement, but varying shear rein forrement ratios designed to be both flexural-and shear-deficient in static conditions according to the ACI code. In particular; thirteen unbonded post-tensioned (PT) beams were tested under drop weight impact applied at the midspan in simply supported conditions and compared with conventional type RC beams. The main variables investigated include increasing levels of PT force and the application of two different impact energies per each specimen type, shear- or flexural-deficient. The experimental results showed that the levels of PT force and shear reinforcements of the specimens played an important role in their overall behavior: With respect to beneficial design recommendations, relationships between the impact resistance and the static capacity are provided; a general increase in strength of around three times that of the static capacity is observed when impacted. Additionally, relationships between the ratio of the impact energy to static capacity are developed with regard to the maximum and residual member displacements.

The high-strain rate compressive behavior of concrete made with different levels of substitution and types of coarse aggregate is addressed in the present work. The compressive behavior was investigated by performing standard quasi-static tests and Split-Hopkinson Pressure Bar tests with a large bar diameter of 155 mm . Two different types of concrete with different substituted coarse aggregates are studied, namely Recycled Aggregate Concrete (RAC) and Recycled clay Bricks Concrete (RBC). Specimens were divided into 9 groups with different levels of substitution and types of coarse aggregate ranging from 0 % (Natural Aggregate Concrete, NAC) up to 100 % (full substitution with recycled crushed concrete or clay bricks). Tests were executed up to a strain rate of around 100 s - 1 . Data-driven predictive equations were proposed for the compressive strength Dynamic Increase Factor (DIF). Results indicate that RAC and RBC are more strain-rate sensitive than NAC. In particular, DIF markedly depends on the level of substitution in RAC, while this dependency is less marked for RBC.

The compressive mechanical properties of concrete-based materials are strongly affected by the presence of additions in the mix and load application velocity. Fiber-Reinforced Rubberized Concrete (FRRC) was recently proposed in the literature as a concrete-based material with the aim of obtaining a ductile material with reduced environmental burden and characterized by excellent energy absorption performances during impact loading. FRRC joins and balances the advantages and drawbacks of Fiber Reinforce Concrete (FRC) and Rubberized Concrete (RuC). However, its behavior has rarely been investigated under dynamic loadings, although gaining sufficient knowledge on their high strain rate behavior is crucial for their full-scale application. This study aims to investigate the high-strain rate compressive behavior of FRRC with fine rubber aggregates and micro-straight steel fibers. Tests were performed using conventional quasi-static loading with a compressive testing machine and high-strain rate tests with a Φ80-mm Split Hopkinson Pressure Bar (SHPB) for strain rates up to 200s−1. The experimental program comprises the characterization of Plain Concrete (PC), FRC, RuC, and FRRC with a full test matrix (a total of 192 specimens) covering fiber contents up to 1.5% and rubber volume substitution ratios up to 30%. The micro-scale characterization of the material using SEM scans provided a complete understanding of the observed macro-scale behavior. A high-speed camera was used to capture the cracking development processes. The measurements both for quasi-static and dynamic tests indicate that the addition of fibers improves the ductility or toughness with a slight increase in the compressive strength and the substitution with rubber aggregates significantly reduces the compressive strength with improved ductility or toughness. The combination of fiber and rubber (FRRC) leads to a combination of the previously described single marginal effects. The dynamic tests reveal the marked strain rate dependency, although specimens with large rubber volume substitution were more sensitive to the strain rate effect within the considered test range. Based on the test data, data-driven models for strength reduction factor (SRF) and dynamic increase factor (DIF) are proposed for different types of FRRC. The image-based waveform discussion provides evidence of the “double-peak” phenomenon highlighting the different features of the observed signals and damage evolution. Ultimately, this study indicates that FRRC has an excellent high-strain rate compressive behavior and can be a promising material to be employed to protect structures against impact and blast loads.

The effectiveness of Carbon Fiber Reinforced Polymer (CFRP) seismic-retrofit of circular Reinforced Concrete (RC) bridge piers under vehicular lateral impact loading is addressed in the present work performing experimental tests. Sixteen 1 / 3 scale RC bridge piers with circular cross-sections characterized by three different configurations of longitudinal and transverse reinforcements were tested with and without CFRP seismic-retrofit. In the first case, tested columns represent common shear-deficient RC bridge piers designed with obsolete design practice or for non-seismic areas. In the second case, CFRP wrapping is applied according to common seismic-retrofit practices to increase the shear capacity and ductility of columns. Experimental tests were carried out under static and lateral impact loading with propped cantilever conditions reproducing a typical short-span viaduct bridge pier configuration. In the static tests, the lateral load was applied monotonically through a hydraulic jacket under equivalent impact conditions. In impact tests, the lateral impact load was applied through a colliding truck equipped with a rigid hammer at the typical vehicular impact location adopting two different impact velocities (3 and 4.5 m / s ). A critical investigation of the transient dynamic characteristics, damage evolution, and post-impact damage is conducted by comparing the results obtained with and without CFRP seismic-retrofit, and under static and dynamic loading conditions. It is shown that CFRP seismic-retrofitting of circular RC bridge pier can also be effective in reducing the vulnerability under lateral impact loading. The CFRP-retrofit approach adopted in this study meets the requirement of multi-hazard prevention improving the robustness of the bridge. Finally, a semi-empirical equation for predicting the maximum displacement under impact loading is derived based on experimental results. The proposed equation adopts the results of a static test as a proxy for assessing the dynamic behavior allowing for the design of the required shear and flexural load-carrying capacity.

This paper proposes a Bayesian model updating approach applied to mechanical properties of recycled aggregate concrete (RAC) under uniaxial or triaxial compression. In particular, a probabilistic calibration method is proposed for evaluating the accuracy and applicability of available deterministic models for the mechanical performances of RAC based on the Bayesian theory and the Markov Chain Monte Carlo (MCMC) method. With the aid of the Bayesian parameter estimation technique, assessments of important parameters in the updating process are conducted using a variable selection approach. The selected existing deterministic models for the estimation of RAC mechanical performances are updated accordingly. To conduct the model updating, two large databases of the mechanical properties of RAC were obtained from the literature, including 749 compressive strengths, 476 elastic moduli, 145 flexural strengths, and 324 splitting tensile strengths. Finally, the accuracy and applicability of available deterministic models were calibrated and updated improving their prediction performances.

This paper reports the results of an extensive experimental investigation on the behavior of shear-deficient reinforced circular RC columns under lateral impact loading. First, it provides a brief literature review on studies of the dynamic response induced by vehicle collisions on RC columns highlighting the lack of experimental tests on vertical elements. In this context, a novel facility for testing of vertical elements under lateral impact loading was realized. Two different types of RC columns characterized by different hoop spacing were tested, representing a one-third scaled model of a reinforced circular bridge pier, designed with obsolete design practice with particular reference to non-seismic areas. A total of 10 specimens (5 for each type) were tested under a lateral rigid-hammer impact at different impact velocities (2.25, 3 and 4.5 m/s) and boundary conditions (cantilever and fixed-simply-supported). The impact load was applied at the typical vehicular impact location, i.e. near the base. A description of the impact and reaction forces, of the lateral displacements and accelerations, of the damage development and of the post-impact damage is given. The dynamic response and the observed damage are found to be significantly affected by the column type, the impact velocity and the boundary condition. A brittle shear-type damage was observed, characterized by one main diagonal crack originating from the base of the column to the impact point, revealing the high vulnerability of these structural elements.