In the present study, a novel parametric family of fuzzy implications is introduced and its properties are examined. The parametric family of implications is produced only via a fuzzy negation. This in turn enables the effortless production of a wide range of implications from which to select the one that best fits a given problem, for example in fuzzy inference systems or fuzzy neural networks. The fuzzy negations that have been selected as a basis for the proposed methodology are strong, i.e., involutions, thus leading, in general, to the generated fuzzy implications possessing many desirable additional properties. We have examined which of these properties hold for the implications produced by our algorithm and under which conditions. Finally, it is demonstrated that the family of implications generated via the proposed methodology generalizes other well-established implications, including the Łukasiewicz implication.

One of the most critical components of reinforced concrete structures are beam–column joint systems, which greatly affect the overall behavior of a structure during a major seismic event. According to modern design codes, if the system fails, it should fail due to the flexural yielding of the beam and not due to the shear failure of the joint. Thus, a reliable tool is required for the prediction of the failure mode of the joints in a preexisting population of structures. In the present paper, a novel methodology for the derivation of analytical equations for this task is presented. The formulation is based on SHapley Additive exPlanations values, which are commonly employed as an explainability tool in machine learning. Instead, in the present paper, they were also utilized as a transformed target variable to which the analytical curves were fitted, which approximated the predictions of an underlying machine learning model. A dataset comprising 478 experimental results was utilized and the eXtreme Gradient Boosting algorithm was initially fitted. This achieved an overall accuracy of ≈84%. The derived analytical equations achieved an accuracy of ≈78%. The corresponding metrics of precision, recall, and the F1-score ranged from ≈76% to ≈80% and were close across the two modes, indicating an unbiased model.

Seismic vulnerability assessment is one of the most impactful engineering challenges faced by modern societies. Thus, authorities require a reliable tool that has the potential to rank given structures according to their seismic vulnerability. Various countries and organizations over the past decades have developed Rapid Visual Screening (RVS) tools aiming to efficiently estimate vulnerability indices. In general, RVS tools employ a set of structural features and their associated weights to obtain a vulnerability index, which can be used for ranking. In this paper, Machine Learning (ML) models are implemented within this framework. The proposed formulation is used to train binary classifiers in conjunction with ad hoc rules, employing the features of various Codes (e.g., the Federal Emergency Management Agency, New Zealand, and Canada). The efficiency of this modeling effort is evaluated for each Code separately and it is clearly demonstrated that ML-based models are capable of outperforming currently established engineering practices. Furthermore, in the spirit of the aforementioned Codes, a linearization of the fully trained ML model is proposed. ML feature attribution techniques, namely SHapley Additive exPlanations (SHAP) are employed to introduce weights similar to engineering practices. The promising results motivate the potential applicability of this methodology towards the recalibration of the RVS procedures for various types of cases.

One of the most critical aspects in the seismic behavior or reinforced concrete (RC) structures pertains to beam–column joints. Modern seismic design codes dictate that, if failure is to occur, then this should be the ductile yielding of the beam and not brittle shear failure of the joint, which can lead to sudden collapse and loss of human lives. To this end, it is imperative to be able to predict the failure mode of RC joints for a large number of structures in a building stock. In this research effort, various ensemble machine learning algorithms were employed to develop novel, robust classification models. A dataset comprising 486 measurements from real experiments was utilized. The performance of the employed classifiers was assessed using Precision, Recall, F1-Score, and overall Accuracy indices. N-fold cross-validation was employed to enhance generalization. Moreover, the obtained models were compared to the available engineering ones currently adopted by many international organizations and researchers. The novel ensemble models introduced in this research were proven to perform much better by improving the obtained accuracy by 12–18%. The obtained metrics also presented small variability among the examined failure modes, indicating unbiased models. Overall, the results indicate that the proposed methodologies can be confidently employed for the prediction of the failure mode of RC joints.

Fiber Reinforced Concrete (FRC) has shown significant promise in enhancing the safety and reliability of civil infrastructures. Structural Health Monitoring (SHM) has recently become essential due to the increasing demand for the safety and sustainability of civil infrastructures. Thus, SHM provides critical benefits for future research to develop more advanced monitoring systems that effectively detect and diagnose the damage in FRC structures. This study investigates the potential of an Electro-Mechanical Impedance (EMI) based SHM system for detecting cracks in FRC prisms subjected to four-point repeated loading. For the needs of this research, an experimental investigation of three FRC specimens with the dimensions 150 × 150 × 450 (mm) were subjected to three different loading levels where no visual cracks formed on their surface. Next, prisms were subjected to reloading until they depleted their load-carrying capacity, resulting in pure bending fracture at the mid-span. A network of nine cement paste coated Piezoelectric lead Zirconate Titanate (PZT) transducers have been epoxy bonded to the surface of the FRC prisms, and their frequency signal measurements were utilized for quantitative damage assessment. The observed changes in the frequency response of each PZT sensor are evaluated as solid indications of potential damage presence, and the increasing trend connotes the severity of the damage. The well-known conventional static metric of the Root Mean Square Deviation (RMSD) was successfully used to quantify and evaluate the cracking in FRC specimens while improving the efficiency and accuracy of damage detection. Similarly, the dynamic metric of a new statistical index called “moving Root Mean Square Deviation” (mRMSD) was satisfactorily used and compared to achieve and enhance accuracy in the damage evaluation process.

The study is part of an experimental program on full-scale Un-Reinforced Masonry (URM) wall panels strengthened with Textile reinforced mortars (TRM). Eight brick walls (two with and five without central opening), were tested under the diagonal tension (shear) test method in order to investigate the strengthening system effectiveness on the in-plane behaviour of the walls. All the URM panels consist of the innovative components, named ???Orthoblock K300 bricks??? with vertical holes and a thin layer mortar. Both of them have great capacity and easy application and can be constructed much more rapidly than the traditional bricks and mortars, increasing productivity, as well as the compressive strength of the masonry walls. Several parameters pertaining to the in-plane shear behaviour of the retrofitted panels were investigated, including shear capacity, failure modes, the number of layers of the external TRM jacket, and the existence of the central opening of the wall. For both the control and retrofitted panels, the experimental shear capacity and failure mode were compared with the predictions of existing prediction models (ACI 2013, TA 2000, Triantafillou 1998, Triantafillou 2016, CNR 2018, CNR 2013, Eurocode 6, Eurocode 8, Thomoglou et al. 2020). The experimental work allowed an evaluation of the shear performance in the case of the bidirectional textile (TRM) system applied on the URM walls. The results have shown that some analytical models present a better accuracy in predicting the shear resistance of all the strengthened masonry walls with TRM systems which can be used in design guidelines for reliable predictions.

Lately, there is an increasing demand for resilient infrastructure assets. To support the documentation of resilience, Structural Health Monitoring (SHM) data is a necessity, as well as traffic loads. Those diagnosis and function data can be the basis for the prognosis of future prediction for the performance of the assets. Towards this direction, this paper develops a new methodology that uses real monitoring data and Artificial Intelligence (AI) algorithms to quantify the resilience based on future traffic load predictions of functionality. It includes the case study of the “Hollandse Brug” bridge in the Netherlands considering strains and traffic load predictions and other external. Resilience is derived as a function of both functional and structural parameters throughout the lifecycle. The quantification is supported by sustainability indices and key performance indicators representing the traffic flow, the structural integrity and the sustainability level of the asset.

This study is part of an experimental program on full-scale strengthened Un-Reinforced Ma-sonry (URM) walls with Textile reinforced mortars (TRM). Four solid brick walls (one con-trol and three strengthened specimens with central opening), were tested under the diagonal tension (shear) test method in order to investigate the effectiveness of the strengthening sys-tem on the in-plane behavior of the walls. All the URM panels consist of solid bricks and a high strength binder mortar. Both of them have increased mechanical properties leading to improved shear behavior of the masonry walls. Several parameters pertaining to the in-plane shear behavior of the retrofitted panels were investigated, including shear capacity, failure modes, the number of layers of the external TRM jacket and the existence of the central opening of the wall. The experimental work allowed an evaluation of the shear behavior in the case of the bidirectional textile (TRM) system applied on URM walls. The experimental re-sults of URM and retrofitted walls with different layers are compared with each other. The purpose is to investigate in depth and to draw conclusions about the in-plane shear behavior.

In areas of medium and high seismic hazard, reinforced concrete frame structures in seismic events often are damaged at the joints (beam-column connections) and then need to be repaired for further use of the structure. In the following, a new strengthening procedure and experimental investigations will be presented. Test specimens with previously generated moderate pre-damage are repaired with high-strength repair mortar and Carbon Fiber filament bundles (C-FRP) at the beam-column connection. The test results of a test specimen on a scale of 1:1 in the undamaged state (JA1V) as well as in the pre-damaged rehabilitated state (JA1FXb) are evaluated and compared. To simulate the earthquake effects, the undamaged test specimen is first cyclically loaded on the test bench. Subsequently, the same test specimen pre-damaged by the first test is strengthened with C-FRP in the node and beam area and again exposed to identical cyclic loads on the test bench. The essential measurement results of both tests are recorded and compared with each other with regard to load-bearing capacity, stiffness, absorbed energy (ability to dissipate energy). Furthermore, the applied rehabilitation technique is presented in detail. On the basis of the investigations carried out, it is shown that rapid and efficient rehabilitation of joints by high-strength cement without high-pressure injection is possible.

Unreinforced masonry (URM) walls present low shear strength and are prone to brittle failure when subjected to inplane seismic overloads. This paper discusses the shear strengthening of URM walls with Textile Reinforced Mortar (TRM) jackets. The available literature is thoroughly reviewed and an extended database is developed including available brick, concrete and stone URM walls retrofitted and subjected to shear tests to assess their strength. Further, the experimental results of the database are compared against the available shear strength design models from ACI 549.4R-13, CNR DT 215 2018, CNR DT 200 R1/2013, Eurocode 6 and Eurocode 8 guidelines as well as Triantafillou and Antonopoulos 2000, Triantafillou 1998, Triantafillou 2016. The performance of the available models is investigated and the prediction average absolute error (AAE) is as high as 40%. A new model is proposed that takes into account the additional contribution of the reinforcing mortar layer of the TRM jacket that is usually neglected. Further, the approach identifies the plethora of different block materials, joint mortars and TRM mortars and grids and introduces rational calibration of their variable contributions on the shear strength. The proposed model provides more accurate shear strength predictions than the existing models for all different types of the URM substrates, with a low AAE equal to 22.95%.

In Gebieten mittlerer und hoher seismischer Gefährdung werden in Stahlbetonskelettkonstruktionen bei Erdbebenereignissen häufig die Rahmenknoten (Anschluss Stütze/Riegel) beschädigt und müssen anschließend für eine weitere Nutzung der Konstruktion instand gesetzt werden.

In many cases, existing reinforced concrete (RC) columns have been designed according to old seismic recommendations and present inefficient seismic behavior. Moreover, they usually have prior damages due to moderate earthquake excitations. Therefore, it is necessary these columns to be retrofitted. Many researches concern the seismic strengthening of RC columns with fiber reinforced polymers (FRP) and models have been proposed for calculating shear strength (VR) and ultimate chord rotation capacities (θu). This paper focuses on columns with lap-spliced bars, with or without previous damages, externally confined with FRPs. The accuracy of KANEPE and EC8.3 equations for estimating VR and θu is investigated as well as reasonable modifications are proposed to improve the accuracy of predictions.

This paper presents the experimental results of the structural behavior of four reinforced concrete beams with corroded steel reinforcement at service loads. One beam was non-corroded, one beam was corroded under an accelerated electrochemical technique to a small corrosion level (for one corrosion cycle), while two beams were corroded under the same conditions of an accelerated electrochemical technique and then subjected to vertical service loads that corresponded to 60% and 75% of the yield load of the non-corroded beam respectively for three corrosion cycles (with maximum mass loss around 25% for the first and 31% for the latter). Longitudinal cracks due to corrosion and flexural cracks due to loading were thoroughly recorded at the end of each cycle. The beam under the 75% service load had higher deflection increase for heavier corrosion. After the three successive serviceability load tests, the cracked concrete cover was removed and the steel rebars were treated. The cement-based repair mortar and two NSM FRP laminates were applied to both beams and were tested to failure. Despite the heavy corrosion, the patch repair and NSM strengthening enhanced the load-bearing capacity of the beams when compared with the non-corroded beam. All 10 tests are thoroughly discussed.

Fiber-reinforced polymer (FRP) confined concrete columns under axial compression reveal significantly enhanced axial strength and ductility compared to unconfined columns. Adequate FRP confinement provide hardening stress – strain behavior up to failure especially in columns of circular section. However, it is difficult to model and predict accurately the maximum stress and ultimate strain of the noncircular confined concrete columns in the presence of internal steel reinforcement, which is the real case for the majority of existing structures. Numerous experimental investigations have been carried out for axially loaded circular section concrete columns with or without internal steel reinforcement confined with FRP materials and other techniques. Also, a lot of predictive expressions of peak axial strength and strain and ultimate stress and strain, suitable for similar concrete sections, have been proposed. On the other hand, fewer studies concern reinforced concrete columns of square and rectangular section. The presented investigation gathers all the newest available test results on square and rectangular reinforced or plain concrete columns confined with composite reinforcements and assesses the performance of significant predictive expressions published in literature. The developed database includes these columns confined with FRP materials and other techniques and assesses the performance of 24 existing models proposed for the peak and ultimate conditions.

Unreinforced masonry (URM) structures have high seismic vulnerability mainly due to the low shear strength of walls, which are prone to brittle failure when subjected to in-plane loads. The strengthening of these existing structures with fabric reinforced cementitious mortar (FRCM or TRM) or FRP jacket has attracted considerable research interest as alternative to traditional strengthening methods. This paper presents the analyses of unreinforced masonry strengthened with external composite reinforcement subjected to diagonal compression, using 3dimensional finite elements. A micro non-linear model, with general purpose finite element code ANSYS, is used to reproduce the experimental results of masonry wall shear tests. The advanced FE modeling includes bricks units, mortar of URM and composite materials as well as their interfaces and interactions. The three dimensional eight-node solid isotropic element Solid186 is utilized to model nonlinear behavior of the brittle materials. In order to simulate the FRP, shell element Shell181 is used and is able to transfer forces at panel and strengthening material interfaces. Micro-modeling approaches require more computational effort, but may provide more detailed results, taking into account the local behavior of the unreinforced masonry wall and are able to predict the different failure mechanisms. Several experimental results have been gathered to validate the reliability of the proposed finite element model. The paper compares the experimental results of the shear stress and strain at ultimate with the analytical ones as well as the predictions of shear stress of existing design equations.

The use of crossed inclined bars as shear reinforcement in external beam-column connections subjected to cyclic loading is experimentally investigated. The presented experimental work consists of full-scale specimens with different reinforcement arrangement in the joint area as follows: (a) A control specimen without shear reinforcement in the joint area, (b) a specimen with only one stirrup in the joint area, (c) a specimen with inclined bars that form two pairs of Xtype reinforcement. The effectiveness of this X-type, non-conventional reinforcement on the overall seismic performance of the tested joints is examined. Comparisons between the test results of the examined specimens indicated that the cyclic behavior of the joint with X-bars was drastically improved in comparison with the one of the control specimen in terms of load carrying capacity and hysteretic energy dissipation. Further, load capacity and hysteretic energy dissipation values of the joint with the X-reinforcement were alike with the corresponding values of the specimen with one stirrup and two vertical side bars in the joint area.

The experimental results on the effectiveness of patch repair and FRP bonded laminates to retrofit reinforced concrete beams with corrosion damage are discussed in this paper. The uncovering of the damaged concrete cover provides a more accurate assessment of the corrosion degree, as the actual mass loss of reinforcement can be better calibrated. The mass loss of the tensile reinforcement varied at approximately 7.5%–24%. The necessity of the removal of the cracked concrete substrate, treatment of corroded reinforcement and repair by patching with a polymer modified mortar is highlighted. Two different strengthening techniques are implemented, of externally bonded EBR or NSM Carbon FRP laminates, having equivalent axial rigidity. CFRP wraps were also applied for shear strengthening to replace corroded stirrups. The load-deflection curves showed that the effect of corrosion on load bearing capacity and bond between the concrete and steel was detrimental for high mass losses. A satisfactory force transfer through the old and patch repaired concrete and through repair mortar and CFRP reinforcement interface was noted. The shear strengthening not only prevented the debonding of the EB laminate at the end but also improved the bond performance between the laminate and concrete, especially for the high corroded beam.

Corrosion of steel reinforcement is one of the major causes that limit durability and serviceability performance of reinforced concrete (RC) structures. This paper reviews thoroughly available experiments and analytical approaches in the relevant international literature and introduces a calculation model for assessing steel bar mass loss and contributes to further utilization of common in-situ inspections from a structural point of view. The model is based on the width of longitudinal crack of concrete cover, as a function of cover depth, bar diameter and mechanical properties of concrete. The model includes the well-known relationships for the steel mass loss during the first phase of rust formulation, filling the porous zone as well as during the phase that the radial pressure exceeds the concrete strength and causes cover cracking. The assumption followed herein for the flexibility of cracked concrete allows for the estimation of steel bar corrosion rate even beyond concrete cover cracking, by visual mapping of the width of longitudinal cracks. Then, the corresponding flexural capacity of the beams at yield and at maximum may be assessed. The predictions of the model are validated against 51 non-strengthened corroded beams and 24 strengthened corroded beams with Fiber Reinforced Polymer (FRP) materials published in the international literature.

The present study deals with the validation of a numerical model that can approximate the flexural behavior of corroded reinforced concrete beams patch repaired and strengthened with carbon fiber reinforced polymer (CFRP).Six reinforced concrete beams were corroded under an accelerated corrosion technique to low and medium corrosion levels respectively.Two beams were used as control, while the remaining four were patch repaired and strengthened with externally bonded reinforcement (EBR) and near surface mounted reinforcement (NSM) with equivalent axial rigidity.After repairing the concrete substrate and subsequent bonding of the CFRP reinforcement, the beams were tested to failure under fourpoint loading.The developed 3D finite element models take into account the different mechanical properties and detailing of corroded bars and of the mortar patch as well as of the existing concretemortar patch interface and of the NSM or EBR FRPmortar patch interface.The FE analyses may reproduce the observed modes of failure including crushing of the concrete after steel yielding and debonding of CFRP.The analytical load-deflection curves compare well with the experimental flexural behavior of the corroded RC beams patch repaired and strengthened with EBR and NSM CFRP laminates.

This paper presents the experimental and analytical behavior of four reinforced concrete beams with corroded steel reinforcements with low mass loss (around 7.5%), yet in need of removal of cracked concrete cover, treatment of steel bars, application of cement-based repair patch and of externally bonded EBR or NSM FRP laminates. It comes out the assessment of residual flexural capacity of the as built corroded beams and the suitable strengthening measures depend largely on the concrete cover crack pattern and width, as accelerated corrosion-related cracks were measured just wider than 0.3 mm (failing to fulfill serviceability limit state requirements marginally). This study also demonstrates that assessment of contribution of corroded steel and treatment in the above cases requires partial uncovering in order to apply inhibitors and better calibrate the actual mass loss with corresponding cover concrete damage. All the above may be fulfilled at the characteristic limit state of initiation of concrete cover separation. The observed failure modes, the recorded force deflection curves and strains on steel and FRP laminates, validate for the strengthened corroded beams the full force transfer through old concrete patch interface and through patch and FRP laminate interface, as predicted in the case of non patched beams. The beam strengthened with two NSM FRP strips of equivalent axial rigidity with EBR FRP laminate presented 18.2% higher load and 41.6% higher deflection than the latter. The P-d behavior of all beams was modeled with advanced 3D Finite Elements (FE) that enabled further analytical investigation of the observed modes of failures and patch repair effects. (C) 2016 Elsevier Ltd. All rights reserved.