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This paper presents experimental results of combined cyclic load testing on a reinforced concrete (RC) column that was retrofitted with newly designed steel rods. The steel rods were installed around the column longitudinally and then anchored. The proposed steel rods utilize simple components and installation to enhance both the strength and ductility of RC columns. Cyclic lateral load tests were conducted on three specimens: one unreinforced specimen as reference, one specimen with the entire length of the column retrofitted, and one specimen with only the plastic hinge region of the column retrofitted. All specimens were tested under eccentric constant axial load and incrementally increasing lateral loading cycles with eccentricity. The implementation of steel rods resulted in significant improvement in ductility and an up to 60% increase in ultimate loading capacity. [ABSTRACT FROM AUTHOR]

The International Federation for Structural Concrete (fib) offers various publications and resources for those interested in concrete structures. One publication, fib Bulletin 111, focuses on modeling the performance of existing concrete structures, considering factors such as increased traffic loads and material deterioration. The fib Model Code (2020) provides comprehensive guidelines for planning, designing, and constructing concrete structures. The fib also recognizes and promotes innovative design and construction practices through awards and symposiums. The document also highlights the career and contributions of Peter Marti, a professor at ETH Zurich, who has made significant contributions to the field of structural engineering. Lastly, the document mentions upcoming congresses and symposia related to structural concrete. [Extracted from the article]

In this study, we utilized unmanned aerial vehicle (UAV) and high-precision 3D light detection and ranging (LiDAR) scanning to collect data before and after an earthquake-resistant behavior test on a reinforced concrete hybrid frame. We analyzed the deformation of the hybrid frame before and after the test and determined the specific deformation, scale, and change rule. The UAV image data was transformed into a 3D true-color model using the structure from motion (SfM) algorithm. Additionally, the 3D Delaunay surface reconstruction algorithm was used to create a 3D point cloud model and Rodriguez matrix, which are then used to align the two-phase model. Subsequently, a comparison was made in three dimensions between the distribution of the hybrid frame's photographic and 3D point cloud models before and after undergoing earthquake-resistant behavior tests. This method allows for a precise analysis of the local deformation degree of the hybrid frame structure compared with the sensors. While the sensors can only analyze internal structural changes, this method provides results for both local and surface deformation degrees, which are not available in the sensor data. The comprehensive experimental comparison results demonstrate that the reinforced concrete hybrid frame structure had a collective rightward displacement before and after the earthquake-resistant behavior test. Moreover, nodes and edges exhibited more significant deformation, and the test resulted in a more stable overall framework. [ABSTRACT FROM AUTHOR]

Regional seismic fragility assessment of bridge portfolios must address the embedded uncertainties and variations stemming from both the earthquake hazard and bridge attributes (e.g., geometry, material, design detail). To achieve bridge‐specific fragility assessment, multivariate probabilistic seismic demand models (PSDM) have recently been developed that use both the ground motion intensity measure and bridge parameters as inputs. However, explicitly utilizing bridge parameters as inputs requires numerous nonlinear response history analyses (NRHAs). In this situation, the associated computational cost increases exponentially for high‐fidelity bridge models with complex component connectivity and sophisticated material constitutive laws. Moreover, it remains unclear how many analyses are sufficient for the response data and the resulting demand model to cover the entire solution space without overfitting. To deal with these issues, this study integrates Gaussian process regression (GPR) and active learning (AL) into a multistep workflow to achieve efficient regional seismic fragility assessment of bridge portfolios. The GPR relaxes the probability distribution assumptions made in typical cloud analysis‐based PSDMs to enable heteroskedastic nonparametric seismic demand modeling. The AL leverages the varying standard deviation to select the least but most representative bridge‐model‐ground‐motion sample pairs to conduct NRHA with much‐improved efficiency. Both independent and correlated multi‐output GPRs are proposed to deal with bridge portfolios with seismic demand correlations among multiple components (column, bearing, shear key, abutment, unseating, and joint seal). Considering a single benchmark highway bridge class in California as the case study, the AL‐GPR framework and the associated component‐level fragility results are investigated in terms of their efficiency, accuracy, and robustness. The fragility results show that 70 AL‐selected samples would enable the GPR to derive bridge‐specific fragility models comparable to the ones using the multiple stripes analysis approach with 1950 ground motions considered for each individual bridge. The AL‐GPR model also successfully captures the physics of how bridge span length, deck area, column slenderness, and steel reinforcement ratio would change the damage state exceedance probabilities of different bridge components. The efficiency of AL stems from the fact that, with the multi‐output independent GPR, a stable and reliable fragility model can be achieved using 50 AL‐selected samples compared to at least 270 randomly chosen samples. The proposed methodology advances the state of the art in enabling more efficient and reliable regional seismic fragility assessment of multi‐component bridge portfolios. [ABSTRACT FROM AUTHOR]

Displacement response is critical data for post‐earthquake fast building assessment. However, directly measuring building displacement response remains a great challenge in practice. Therefore, it is practically common to estimate displacement response from acceleration response using double integration. Unfortunately, the low‐frequency component of displacement obtained by double integrating acceleration often contains noise that is indistinguishable from low‐frequency displacement components. Consequently, the maximum displacement estimated from acceleration is commonly underestimated in comparison to its true value due to the removal of the low‐frequency components. This can potentially lead to an underestimation of post‐earthquake building damage state, especially when a building undergoes significant nonlinear deformation. This study develops a framework to improve the accuracy of the maximum displacement obtained from floor acceleration data by fusing it with the low‐frequency displacement component estimated from an equivalent SDOF analysis for both reinforced concrete (RC) and steel structures. Procedures for constructing the equivalent SDOF model of a building and a procedure for extracting the low‐frequency component from the analysis displacement were developed. The proposed method was verified using a diverse range of case studies from numerical simulation and experimental studies under different seismic records for both RC and steel structures. The results showed that the proposed method was effective with a range of seismic characteristics and damage levels. A significant reduction in maximum displacement errors was observed for cases with significant nonlinear deformation, which may contribute to a more accurate post‐earthquake building assessment. [ABSTRACT FROM AUTHOR]

This article discusses a numerical study on predicting the bond-slip relationship of reinforced concrete using surface-based cohesive behavior. The study aims to develop a finite element modeling strategy to accurately predict the bond-slip behavior in reinforced concrete. The article provides a comprehensive review of previous research on bond-slip behavior and includes a table of maximum bond stress equations from different literature sources. The document discusses the testing procedure and finite element modeling strategy for studying the bond behavior between concrete and reinforcement in pullout tests. The document also explains the loading and boundary conditions applied in the finite element model and the interaction between reinforcement and concrete. The text discusses the different contact models available in ABAQUS for simulating contact between surfaces. It concludes by discussing the finite element mesh size and solution procedure used in the study. The text discusses the results of finite element analysis (FEM) conducted on reference specimens to predict their failure modes and bond stress-slip behavior. The analysis used different mesh sizes and analytical models to simulate the behavior of the specimens. The results showed that a finer mesh size of 10 mm provided more accurate predictions of failure patterns, while a mesh size of 10 mm or larger could be used to estimate specimen strength. The FEM developed using the analytical model by Strum and Visintin showed the most accurate prediction of maximum bond stress. The failure modes observed in the analysis included pullout failure, splitting followed by pullout failure, and splitting or splitting-pullout failure. The FEM models generally performed [Extracted from the article]

This article reports the development of a novel embedded waveguide ultrasonic sensor for detecting the onset of damage in reinforced concrete structures. A sleeved waveguide is proposed to confine guided ultrasonic waves in one-dimension, with leakage to the surrounding media only through specially created openings, thus reducing attenuation losses and enhancing the capability to inspect large structures from a single transducer location. The test frequency and mode are identified through modelling, and the interaction of leaky guided ultrasonic waves with delamination within the concrete volume is studied. Numerical simulations validated by experiments are used to study the changes in wave features such as mode velocity, wavelength and wave reflection in the delamination region, helping to estimate its location. Further simulation studies are carried out to demonstrate the possibility of using multiple waveguide sensors and sleeve openings to provide a full view of the concrete volume. The results are encouraging for practical long-range and large-scale monitoring of concrete volumes using the proposed sleeved waveguide ultrasonic sensors. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive study focused on evaluating the strain generated within short concrete columns reinforced with glass-fiber-reinforced polymer (GFRP) bars and spirals under concentric compressive axial loads. This research was motivated by the lack of sufficient data in the literature regarding strain in such columns. Five full-scale RC columns were cast and tested, comprising four strengthened with GFRP reinforcement and one reference column reinforced with steel bars and spirals. This study thoroughly examined the influence of various test parameters, such as the reinforcement type, longitudinal reinforcement ratio, and spacing of spiral reinforcement, on the strain in concrete, GFRP bars, and spirals. The experimental results showed that GFRP–RC columns exhibited similar strain behavior to steel–RC columns up to 85% of their peak loads. The study also highlighted that the bearing capacity of the columns increased by up to 25% with optimized reinforcement ratios and spiral spacing, while the failure mode transitioned from a ductile to a more brittle nature as the reinforcement ratio increased. Additionally, it is preferable to limit the compressive strain in GFRP bars to less than 20% of their ultimate tensile strain and the strain in GFRP spirals to less than 12% of their ultimate strain to ensure the safe and reliable use of these materials in RC columns. This research also considers the prediction of the axial load capacities using established design standards permitting the use of FRP bars in compressive members, namely ACI 440.11-22, CSA-S806-12, and JSCE-97, and underscores their limitations in accurately predicting GFRP–RC columns' failure capacities. This study proposes an equation to enhance the prediction accuracy for GFRP–RC columns, considering the contributions of concrete, spiral confinement, and the axial stiffness of longitudinal GFRP bars. This equation addresses the shortcomings of existing design standards and provides a more accurate assessment of the axial load capacities for GFRP–RC columns. The proposed equation outperformed numerous other equations suggested by various researchers when employed to estimate the strength of 42 columns gathered from the literature. [ABSTRACT FROM AUTHOR]

This paper studies the impact of half-height infilled walls on the failure modes of frame columns through quasi-static tests of both frame models and half-height infilled wall frame models. Based on the experimental results, a seismic analysis model of reinforced concrete (RC) frame structures is established, and parametric studies are carried out to analyze the effects of masonry materials and masonry heights on the seismic performance of structures. The results show that the load-bearing capacity and stiffness of the structure are improved, while the ductility of the structure is reduced because of the existence of infilled walls. As the height of infilled walls increases, there is a notable decrease in the free height of frame columns. At a wall-to-column height ratio of 0.2, the masonry walls exert a negligible effect on the frame structure's seismic performance. In contrast, at a ratio of 0.6, there is a transition in column failure modes from bending to shearing. When evaluated at consistent masonry heights, aerated concrete block-infilled walls demonstrate the least impact on the seismic performance of RC frame structures. Thus, in the absence of additional structural enhancements, the use of aerated concrete blocks is recommended to mitigate the negative implications of infilled walls on the seismic integrity of RC frames. [ABSTRACT FROM AUTHOR]

This paper uses numerical simulation to investigate the behavior of fiber-reinforced concrete tested under combined shear and tension. The test setup was based on an inclined push-off test. The numerical simulation was carried out using an in-house finite element package that employs the multi-surface plasticity model for concrete material. Three fiber materials are being investigated: steel fiber, polypropylene fiber (PP), and polyvinyl alcohol fiber (PVA). The stress-strain model for each fiber material was obtained from the laboratory test. The accuracy of the finite element (FE) model was first validated with the available reinforced concrete specimen that was being tested under a push-off test. The numerical simulation found that the push-off model made with steelfiber reinforced concrete (SFRC) responds similarly to plain reinforced concrete (RC) but with a 72.48 % increase in load-carrying capacity. For the PVA-ECC FRC, the load-carrying capacity at the peak displacement of 5.20 mm increased to more than 113.78 %. On the other hand, using PP-FRC can only slightly increase the load-carrying capacity by 8.28 %. In addition, the PP-FRC has a much softer response during hardening due to lower elastic modulus than plain concrete. [ABSTRACT FROM AUTHOR]

The primary goal of in-situ load testing is to evaluate the safety and performance of a structural system under particular loading conditions. Advancements in building techniques, analytical tools, and monitoring instruments are prompting the evaluation of the appropriate loading value, loading process, and examination criteria. The procedure for testing reinforced concrete (RC) structures on-site, as outlined in the ACI Building Code, involves conducting a 24-h load test and applying specific evaluation criteria. This article detailed a retrofitting project for an RC slab-beams system by utilizing carbon fiber-reinforced polymer (CFRP) sheets to strengthen the structure following a fire incident. The RC structure showed indicators of deterioration, including deflections, concrete cracking, and concrete spalling in some zones. Whereas, a detailed presentation of the strengthening procedure as well as its evaluation, rationale for the loading procedure, instrumentation needs, assessment criteria, and outcomes of the field testing. The study concentrated on assessing the structure of the RC slab-beam system with widespread cracking in both the positive and negative moment areas. The finite element model was created and examined to help with the load test design, and it confirmed the field findings considerably. The proposed finite element (FE) model demonstrated a reduced estimation of net deflection value in comparison to the corresponding actual values. It maintained a highly acceptable mean value of 0.843 and a small deviation limit of 6.8%. [ABSTRACT FROM AUTHOR]

This research provides a study for an experimental program using sand‐perlite‐lightweight reinforced concrete (RC) beams strengthened and anchored with carbon fiber reinforced polymer (CFRP) materials. The main objective of this work is to showcase the efficiency of using U‐wrap anchors to secure the externally applied CFRP sheets on lightweight RC beams. A series of six full‐scale T‐beams with an increasing number of CFRP U‐wraps per shear span was prepared and tested. The use of U‐wrap anchorage enhanced the flexural performance of the sand‐lightweight concrete beams by progressively delaying the premature debonding of CFRP sheets as a direct function of the number of U‐wraps used per shear span. The beam flexural capacity gradually improved from 116 kN without the use of U‐wrap anchors to 182 kN when using six U‐wraps per shear span, which reflects a significant enhancement. Similarly, the ultimate deflection gradually improved from 56 mm for the beam without U‐wrap anchors to 94 mm when applying six U‐wraps per shear span. A design model established earlier, for normal weight concrete, has been successfully qualified to yield accurate findings against the experimental results. Also, the outcome of this study interestingly showed that the ultimate strength results of the anchored beams were close to their counterparts of normal weight concrete conducted on identical beams. This finding shows that U‐wrap anchors performed efficiently despite the lack of coarse aggregate interlock in the concrete mix. [ABSTRACT FROM AUTHOR]

Fire obviously causes negative effects on reinforced concrete (RC) structures. Assessment of these postfire structures is ultimately important to provide information for making decisions on demolishing or retrofitting. For retrofitting purpose, non-destructive assessment, which does not cause additional damage to structures, is preferable compared with destructive assessment. In this direction, non-destructive assessment of postfire RC frames was performed in this study. To achieve this aim, experiments were performed on eleven full-scale RC frames, included one, five, and other five frames exposed to 0 (control), 45 min, and 75 min of fire, respectively. These two fires had similar maximum temperature, but the 45-min fire had higher increasing rate of temperature (IRT). After fire exposure, methods of Schmidt rebounding, ultrasonic, and vibration tests were used to perform non-destructive assessment by comparing the results of postfire frames against the control frame. The results showed that the explosive spalling of concrete mainly occurred between 5 and 12th min and then proportionally decreased with the increase of fire duration. The IRT outstandingly affected the explosive damage of RC frames. The higher IRT resulted in higher cracking and explosive spalling of concrete; IRT is thus an important parameter to represent the severity of fire. The experimental non-destructive data was analysed and compared to provide some information on the assessment of postfire RC frames, which can be useful for decision making. [ABSTRACT FROM AUTHOR]

Reservoir computers (RCs) are powerful machine learning architectures for time series prediction. Recently, next generation reservoir computers (NGRCs) have been introduced, offering distinct advantages over RCs, such as reduced computational expense and lower training data requirements. However, NGRCs have their own practical difficulties, including sensitivity to sampling time and type of nonlinearities in the data. Here, we introduce a hybrid RC-NGRC approach for time series forecasting of dynamical systems. We show that our hybrid approach can produce accurate short-term predictions and capture the long-term statistics of chaotic dynamical systems in situations where the RC and NGRC components alone are insufficient, e.g., due to constraints from limited computational resources, sub-optimal hyperparameters, sparsely sampled training data, etc. Under these conditions, we show for multiple model chaotic systems that the hybrid RC-NGRC method with a small reservoir can achieve prediction performance approaching that of a traditional RC with a much larger reservoir, illustrating that the hybrid approach can offer significant gains in computational efficiency over traditional RCs while simultaneously addressing some of the limitations of NGRCs. Our results suggest that the hybrid RC-NGRC approach may be particularly beneficial in cases when computational efficiency is a high priority and an NGRC alone is not adequate. [ABSTRACT FROM AUTHOR]

Underground mine structures like mine seals or built-in-place (BIP) refuge alternatives (RA) are exposed to specific loadings like explosions because of overlying and underlying strata conditions. Previous studies worked on the vertical loading response of structures like abutments from panel extraction but not the explosion resistance upon being subjected to these vertical strata loads. In this study, two steel-reinforced concrete wall designs as seal and RA applications are simulated to examine the performance and failure analysis under abutment-loading conditions during an explosion for a coal mine model using dynamic analysis by a distinct element code (3DEC). The available abutment monitoring data by longwall stoppings was used to estimate the abutment-loading conditions. The model setup was calibrated through two validation stages: (1) the concrete wall simulation with the explosion test of steel-reinforced concrete mine seal conducted by previous researchers; and (2) the stress change at the strata by the tailgate convergence-abutment-load multiplier curve. The calibrated models are subjected to various dynamic loadings to simulate explosions. The findings demonstrate that, in addition to magnitude, the pressure versus time mode of loading significantly influences the wall response. Instantaneous loading criteria can provide more cautious measurements to assess how well such walls operate in similar situations. Except for a few cases, the deformations after a single explosion are more pronounced for the effects of subsequent second and third explosions. As a result, the changes in deformation during subsequent explosions are relatively minor compared with the initial permanent deflections. [ABSTRACT FROM AUTHOR]

This paper introduces a novel type of connection that integrates unbonded prestressed strands (UPS) and mortise-tenon in an assembly frame structure (UPS-MTF). First, the damage process and failure modes of the joints under reciprocating horizontal loads were systematically analyzed using refined numerical models. The recommended values of the design parameters of the joints were derived from the parametric analysis results. Refined numerical modeling results reveal the diagonal compression strut mechanism within the core region of the joint. The diagonal compression struts model assists in establishing the theoretical calculation formula for the skeleton curve of shear stress–strain in the core region. Second, a genetic algorithm (GA) parameter was identified for the restoring force model of the core region to determine the parameters of the hysteresis rules. Finally, a macro-simplified analytical model of the joint was created based on the restoring force model of the core region, and parameter analysis was conducted to verify the applicability of this macro-simplified analytical model. The research results prove that the damaged form of the joint proposed in this paper originates from the shear and relative slip damage between the components in the core region. The axial compression ratio significantly affects the hysteretic performance of the joints, and the upper and lower limit values were identified for the axial compression ratio of the joints. The area and initial effective stress of the UPS exert a minimal effect on the hysteretic performance of the joint. Based on the method proposed in this paper for determining the restoring force model in the core region of the joints, the hysteresis curves obtained from the macro-simplified analytical model closely match the refined numerical analysis model results. This correspondence verifies the applicability of the macro-simplified analytical model. [ABSTRACT FROM AUTHOR]

Aftershocks typically occur multiple times following major earthquakes, potentially inflicting enhanced damage. It is crucial to quantify the impact of aftershocks on the seismic performance of low-ductility reinforced concrete (RC) frames with different mainshock-induced damage states. For this purpose, this study investigated the aftershock fragility of low-ductility RC frames with different damage states induced by mainshocks via the case study of a six-story RC frame without a seismic design. The models of the low-ductility RC frames with different damage states were established via OpenSees software 2.5.0. Incremental dynamic analysis (IDA) was carried out to establish damage states induced by a mainshock. Then sixty-five real aftershocks were inputted to analyze the structures with different main-induced damage states. Aftershock fragility curves of low-ductility RC frame structures with different damage states were obtained. The results show that the exceedance probability of the low-ductility RC frame with mainshock-induced damage is higher than that of the intact low-ductility structure, corresponding to each limit state. The severity of the mainshock-induced damage directly amplifies the demand for a low-ductility RC frame in the subsequent aftershocks. As the mainshock-induced damage increases, the exceedance probability of the low-ductility RC frame undergoing more severe damage under aftershocks significantly increases. [ABSTRACT FROM AUTHOR]

In this study, wavelet-based damage-sensitive features are employed to derive the seismic fragility functions/curves for reinforced concrete moment-resisting frames. Two different wavelet transform functions, namely, Bior3.3 and Morlet mother wavelet families, were applied to absolute acceleration time histories of building frames to extract the wavelet-based and refined wavelet-based damage-sensitive features (i.e., DSF and rDSF). The accuracy of seismic assessments and certainty in predicting structural behavior strongly depend on the specific optimal intensity measures selected, reliability of wavelet-based damage-sensitive features, and some such intensity measures as PGA, PGV, PGD, Sa, and Sdi as the conventionally utilized measures to detect the damage state of a structure. These measures were examined against their statistical properties of efficiency, practicality, proficiency, coefficient of determination, and sufficiency to select the appropriate optimal intensity measures, which were then used to drive the fragility curves disclosing the failure or other damage states of interest. For the purposes of this study, three different concrete moment-resisting frames with four-, eight-, and twelve-story building frames were adopted for implementing the proposed approach. The findings demonstrate that the wavelet-based damage-sensitive features (DSFs/rDSF) simultaneously satisfy all the statistical properties cited above. This is evidenced by the low variance and dispersions observed in the frame damage state predictions by the fragility functions derived from the wavelet-based DSF when compared with those derived from the classical fragility analyses such as spectral acceleration at the first mode period of the structure. A final aspect of the study concerns the superior performance and efficiency of the fragility curves derived by the Bior3.3 wavelet-based DSF over those derived from Morlet wavelet-based DSF. [ABSTRACT FROM AUTHOR]

The steel reinforcement within concrete beams is vulnerable to corrosion.In order to explore the flexural load-carrying capacity of beams under varying corrosion rates, a theoretical calculation and prediction model was proposed in this study. The study involved accelerated corrosion testing of three beams, with an additional beam serving as a control. A four-point bending test was conducted on all beams in accordance with predetermined corrosion rates. Strain gauges were positioned at the midspan to monitor strain data, and dial gauges were employed to measure deflection deformation at vulnerable sections. Experimental investigation was employed to ascertain the parameters that influence the deformation of a beam due to corrosion rate variations during loading, and the predictive model for the bending bearing capacity in relation to corrosion level was established. Results demonstrate the correlation between the elevated corrosion rate and the gradual increase in the average and maximal crack widths on the beam surfaces. The increase rate of maximal crack width exceeds the average, although both display a similar linear growth trend. The impact of corrosion on the initiation of crack and propagation in the test beams increase with high corrosion levels. Conversely, the effect of corrosion is limited when the corrosion rate remained below 15%. Nevertheless, once the corrosion rate exceeds 25%, a more pronounced effect becomes evident. Furthermore, the corrosion of steel reinforcement has a considerable effect on the yield and ultimate load-carrying capacity of the test beams. Upon reaching a corrosion rate of 25%, the flexural capacity of the corroded beams is found to be 54% of the uncorroded beams. This result indicates that as corrosion increases, the flexural capacity decreases linearly. This study offers a reference for accelerating the corrosion testing of reinforced concrete beams and predicting the bending bearing capacity of the corresponding corrosion level. [ABSTRACT FROM AUTHOR]

Calculating impact forces in asymmetrical lateral structures has been a complex challenge that spans decades in engineering. Traditional models often fall short due to the inherent complexity of asymmetrical members and the need for significant computational resources or a vast pool of training data. This paper develops an approximate formula for accurately calculating the impact force of asymmetrical lateral-impact members under lateral impact. Existing methods for assessing impact forces have been limited in their application due to the inherent complexity of asymmetrical members and the significant computational resources or extensive training data they often require. Our approach employs the residuals margin method, and Laplace transforms to derive an efficient and accurate formula for impact force calculation. The paper rigorously validates this Formula through experimental testing, demonstrating high precision with an error margin of less than 5%. Further validation against diverse impact data from multiple studies on different materials and loadings under static and dynamic conditions confirmed the Formula's consistency. Despite simplifying assumptions, this research contributes a novel and computationally efficient approach for calculating impact forces. The formula offers engineers a practical tool while advancing a fundamental understanding of asymmetric impact dynamics. Rigid experimentation verified its significant accuracy, establishing the formula as a valuable structural impact analysis and design resource. This research presents an analytical formula for calculating impact forces on structures like buildings, bridges, and vehicles experiencing asymmetrical lateral impacts. Such impacts commonly occur due to falling debris, vehicle collisions, seismic pounding, and derailed train strikes. However, existing design formulas often oversimplify impact mechanics or require complex simulations. The proposed method provides engineers with a simple spreadsheet-compatible equation relating impact force directly to tangible mechanical quantities like momentum. This enables rapid impact load assessments essential for performance-based design against accidental hazards. The formula was validated through laboratory impact tests on reinforced concrete slabs, demonstrating precision within 5% of measured forces. Additional validations against published experimental and simulation data on different construction materials confirmed accuracy. The proposed formula equips structural engineers and safety analysts with a practical impact analysis tool by offering a computationally efficient approach with proven reliability. It facilitates assessing design performance for asymmetrical impact load scenarios, helping improve resilience for critical facilities subjected to hazardous lateral impacts. [ABSTRACT FROM AUTHOR]

Reinforced concrete frame-wall (RC frame-Wall) structures are generally solved in a global manner by modeling the entire structure by assembling the RC frame and wall stiffness matrices into a global matrix. The bar-wall element interface is modeled at the mean line of the beam-column element, according to RPA 99, which limits the interaction to the axial and transverse components of the forces (mechanical and kinematic) thus neglecting the effects of section rotations. In order to take into account, the rotational components of the mechanical behavior of the beams (section rotation and bending moment), the interaction between the RC frame and the wall must take place at the real interface of the two substructures, i.e. at the extreme fiber of the bar elements (beams and columns). The transmission of force from the wall to the RC frame is done by transforming the tangent stresses of the wall into moment in the beam. [ABSTRACT FROM AUTHOR]

Processing ground motion signals at early stages can be advantageous for issuing public warnings, deploying first-responder teams, and other time-sensitive measures. Multiple Deep Learning (DL) models are presented herein, which can predict triaxial ground motion accelerations upon processing the first-arriving 0.5 s of recorded acceleration measurements. Principal Component Analysis (PCA) and the K-means clustering algorithm were utilized to cluster 17,602 accelerograms into 3 clusters using their metadata. The accelerograms were divided into 1 million input–output pairs for training, 100,000 for validation, and 420,000 for testing. Several non-overlapping forecast horizons were explored (1, 10, 50, 100, and 200 points). Various architectures of Artificial Neural Networks (ANNs) were trained and tested, such as Convolutional Neural Networks (CNN), Recurrent Neural Networks (RNN), Long Short-Term Memory (LSTM) networks, and CNN-LSTMs. The utilized training methodology applied different aspects of supervised and unsupervised learning. The LSTM model demonstrated superior performance in terms of short-term prediction. A prediction horizon of 10 timesteps in the future with a Root Mean Squared Error (RMSE) value of 8.43 × 10−6 g was achieved. In other words, the LSTM model exhibited a performance improvement of 95% compared to the baseline benchmark, i.e., ANN. It is worth noting that all the considered models exhibited acceptable real-time performance (0.01 s) when running in testing mode. The CNN model demonstrated the fastest computational performance among all models. It predicts ground accelerations under 0.5 ms on an Intel Core i9-10900X CPU (10 cores). The models allow for the implementation of real-time structural control responses via intelligent seismic protection systems (e.g., magneto-rheological (MR) dampers). [ABSTRACT FROM AUTHOR]

Deviation of the flexural reinforcement spacing from code specifications appears to underly the cause of the loss of bond (LoB) between concrete and steel that preceded the unexpected collapse of the top-floor balcony of a building under service load conditions on 15 October 2021 in Athens. Although rare, LoB has also been identified as the cause of collapse of buildings under similar conditions in the UK and Canada. However, the codes of practice for reinforced concrete (RC) design neither make reference to the effect of LoB on structural behaviour, nor include LoB in the parameters that the formulae currently used for assessing load-carrying capacity are dependent on. In view of this, a description of the effect of LoB on the function of RC beams is provided in this paper and this description is used as the basis for the derivation of a formula linking LoB with load-carrying capacity. The validity of the proposed formula is verified using published experimental information on the subject. The proposed formula is used for the structural assessment of the collapsed balcony, taking into account the design details, physical state and loading conditions of structural members similar to the one that collapsed. [ABSTRACT FROM AUTHOR]

One of the effective methods of non-destructive testing of structures is active vibration diagnostics. This approach consists of the local dynamic impact of the actuator on the structure and the registration of the vibration response. Testing of massive reinforced concrete structures is carried out with the use of actuators, which are able to create sufficiently high-impact loads. The actuators, which are based on piezoelectric elements, cannot provide a sufficient level of force and the areas where it is possible to register the vibrations excited by such actuators are quite small. In this paper, we propose a variant of a piezoactuator with attached mass, which ensures an increase in the level of dynamic impact on the structure. The effectiveness of this version is verified by numerical modeling of the dynamic interaction of the actuator with a concrete slab. The simulation was carried out within the framework of the theory of elasticity and coupled electroelasticity. An algorithm for selecting the value of the attached mass is described. It is shown that when vibrations are excited in a massive concrete slab, an actuator with an attached mass of 1.3 kg provides a 10,000-fold increase in the force compared to an actuator without attached mass. In the pulse mode, a 100-fold increase in force is achieved. [ABSTRACT FROM AUTHOR]

The dual‐function retrofitting system that uses the carbon‐fabric reinforced cementitious matrix (C‐FRCM) as both the anode of impressed current cathodic protection (ICCP) system and the structural strengthening (SS) material, that is, an ICCP‐SS system, is investigated. The experimental program mainly focused on the shear behavior of C‐FRCM strengthened reinforced concrete (RC) continuous beam under the dual‐function retrofitting system. The influence of anode polarization on the shear strengthening of RC continuous beams is analyzed. Shear tests were conducted on a total of 14 corroded RC continuous beams to investigate the influence of key parameters, including anode polarization degree of prefabricated C‐FRCM plate, layer of carbon fiber mesh and side‐wrapping. The failure modes, shear capacities, and load‐deflection curves of the shear‐strengthened RC continuous beams are reported. Based on the test results, the applicability of relevant design codes was evaluated and found to provide rather conservative predictions for the shear capacity of the examined C‐FRCM strengthened RC continuous beams. [ABSTRACT FROM AUTHOR]

This study introduces an enhanced octree-based framework for integrated geotechnical analysis, combining geological, microseismic, and Mobile Laser Scanning (MLS)-based change detection data. Our approach leverages efficient statistical inference-based change detection techniques and additional octree data structures, enabling voxel-level data integration and association, semantic clustering, and comprehensive geotechnical analysis. We detail the implementation of our method, demonstrating capabilities such as integrating geological fault data, seismic energy exposure modeling, and combination of Random Sample Consensus (RANSAC) classification with Density-Based Spatial Clustering of Applications with Noise (DBSCAN). We conduct a suite of statistical analyses to investigate multi-dimensional trends and correlations among MLS-measured changes, distances to geological faults, and seismic energy exposure. We found that binary change classification and change magnitude negatively correlate with three investigated fault-distance metrics. Multivariant analysis reveals that increased seismic energy exposure and decreased fault distance positively correlates with MLS-based change classification and magnitudes. Our findings imply that proximity to geological faults and seismic energy exposure can be statistically linked to increases in geotechnically relevant deformations. This study is the first to demonstrate that octree-based MLS data processing can reveal multi-dimensional trends in underground mine datasets, thereby enhancing understanding of complex geomechanical behaviors crucial for mining productivity and safety. Highlights: Introduced octree-based framework for integrated geotechnical analysis. Combined geological, microseismic, and MLS data at voxel level. Utilized statistical inference for change detection in framework. Found correlations between MLS changes, fault proximity, and seismic energy. [ABSTRACT FROM AUTHOR]

The shear behaviour of fibre-reinforced polymer reinforced concrete (FRP-RC) beams without web reinforcement suffers from low strength, low stiffness, more brittleness and wide and quick propagated cracks. Fortunately, the addition of various types of fibres could improve most of these weaknesses. On the other hand, the shear strength prediction of FRP-RC beams with various types of fibres is one of the most complex cases in structural engineering applications. Developing generalised, precise and consistent prediction models are necessary and very limited. This paper investigates the impacts of various types of fibres on shear strength and presents proposing four new prediction models, utilising artificial neural networks and empirical nonlinear regression analysis, and modifying the combination of available models based on a collected database of 49 shear test results of FRP-RC members with various types of fibres. The comparison of the developed models with the available equations from the literature indicates that the developed models yielded excellent performance, great efficiency and a high level of accuracy over all other existing models. Additionally, the parametric study confirmed that all the developed models have great abilities to accurately predict the actual response of each parameter, in spite of its complexity, on the shear strength of FRP-reinforced fibrous concrete beams without stirrups. [ABSTRACT FROM AUTHOR]

This document is a compilation of research articles on the topics of microbial self-healing concrete and corrosion monitoring in concrete structures. The articles discuss the use of bacteria and other microorganisms to repair cracks and prevent corrosion in concrete. They explore different methods and materials to enhance the self-healing and corrosion resistance properties of concrete. The articles also discuss non-destructive evaluation techniques for monitoring corrosion in concrete structures. Overall, the research provides valuable insights into the development and application of self-healing concrete and corrosion prevention methods. Additionally, the document includes references to articles on various aspects of reinforced concrete structures, such as effective stiffness ratios, flexural stiffness of beams, aging concrete dams, and the mechanical behavior of corroded steel in lightweight concrete. These articles can be useful for researchers and engineers studying these topics. [Extracted from the article]

Exterior beam-column joints are the most vulnerable part of substandard reinforced concrete (RC) buildings and are often the first to be damaged during earthquakes. This article presents an experimental and numerical investigation into the behaviour of exterior RC beam-column joints repaired and strengthened using Post-Tensioned Metal Straps (PTMS) for active confinement. The study focused on full-scale beam-column joints with an inadequate core zone detailing, thus emulating the deficiencies found in existing substandard RC buildings. Initially, four "bare" joints were subjected to cyclic tests to induce substantial damage within the core zone. Subsequently, the damaged core of the joints was repaired and recast with new concrete, and PTMS were applied to strengthen the joints, followed by another round of cyclic testing. The experimental findings were compared with predictions generated through established models from existing literature. The results revealed that ASCE/SEI 41–17 guidelines accurately predict the shear capacity of the bare joints. It is shown that recasting the core with new concrete significantly increased the joint's shear capacity by up to 42% compared their bare counterparts. The use of PTMS strengthening further enhanced the capacity by up to 25%. A "scissors model" was employed for numerical simulations of both bare and PTMS-strengthened joints using DRAIN-2DX, which proved effective at predicting their nonlinear load-displacement envelope response. This article contributes towards the development of new cost-effective post-earthquake strengthening techniques for beam-column joints, with the potential to reduce the vulnerability of substandard RC buildings in developing countries. [ABSTRACT FROM AUTHOR]

This document is a summary of a special issue of the journal Fire Technology, titled "Structures in Fire 2022." The issue focuses on the research area of structures in fire, which is important for the safety and resilience of engineering infrastructures and urban environments. The special issue includes 24 papers that were selected from the 12th International Conference on Structures in Fire (SiF2022). The papers cover a range of topics, including the performance of structural members in fires, fire safety of timber members, system-level structural response to fire, and the incorporation of sprinkler systems in structural fire evaluation. The research presented in this special issue contributes to enhancing our knowledge of structures in fire. [Extracted from the article]

Based on experiments and micro-modelling analyses, the interaction between the RC frame and the infill wall with/without openings under lateral loads was investigated. According to the load transmission mechanism and the stress states around the openings, a macro-model with multiple blocks around the opening was proposed. In a comparison with the experimental data, the proposed macro-model was proven to adequately simulate the different failure modes and hysteretic behaviours of masonry infilled RC frames with openings. By using the opening rate and opening position as variables, 52 macro-modelling analyses of masonry infilled RC frames with different window and door openings were carried out. The results showed that the presence of masonry infill walls greatly increased the initial stiffness and ultimate load bearing capacities of single-story, single-bay RC frame structures. A larger opening rate resulted in lower initial stiffness and ultimate load-carrying capacity values, which decreased more as the opening locations deviated further from the centre to the sides. [ABSTRACT FROM AUTHOR]

This paper consists of the results of experimental and analytical studies carried out to determine the moment redistribution in reinforced concrete (RC) continuous beams realistically, which are frequently used structural forms in buildings. It was determined that the parameter affecting the moment redistribution the most was the reinforcement ratio, so six RC continuous beams were produced with different reinforcement ratios. In this study, the tensile reinforcement ratio (ρ), the compressive reinforcement ratio (ρ'), and the balanced reinforcement ratio (ρb) in the intermediate support sections are considered as the main variables, and the effects of two parameters on the moment redistribution capacities of the beams are investigated. While one of them is (ρ'/ρ), the other one is (ρ/ρb). Considering the experimental results obtained, a simple formulation has been proposed by taking into account the neutral axis depth factor (c/d), which is the parameter frequently used in the determination of moment redistribution in the literature and in the design code provisions. Moreover, a database was created by considering the experimental results of 80 beams collected from the literature and it was aimed to determine the effectiveness of this proposed formulation compared to the equations in the literature and in the design code provisions. According to the results, it was determined that the proposed formulation gave better statistical outcomes than the others. It is thought that the design codes statistically give more negative results than the results of this study, as they generally prefer to be on the safe side deliberately. In addition to moment redistribution, the general behaviors of RC continuous beams under concentrated loads, such as load-displacement relationships, ductility, energy dissipation, and moment-curvature relationships have also been investigated in detail. [ABSTRACT FROM AUTHOR]

Determination and validation of material parameters for the non‐linear modelling of concrete This article shows that the load‐bearing behavior of concrete and reinforced concrete beams can be successfully simulated using the material models included by default in the widely used ANSYS Mechanical software. The necessary material parameters are determined using laboratory tests. These are tests on concrete cylinders to determine the compressive and tensile strength as well as the modulus of elasticity. The fracture energy is determined on notched beams. This test is then simulated using the Drucker‐Prager model in combination with Rankine yield surfaces and exponential softening. The calculated load‐deformation behavior matches the test curves well when using the experimentally determined material parameters. A comparative calculation with normatively proposed parameters overestimates the fracture energy and thus the load‐bearing capacity of the test specimens. The numerical model is then validated using reinforced concrete beam tests. The model with the experimentally determined material parameters can reproduce the load‐bearing behavior of the test specimens well, but it also becomes clear that appropriate modeling of the bond behavior is important. In this case, the load‐bearing behavior of the beams with spring elements between concrete and reinforcement nodes is best described. Furthermore, it is shown that the use of reduced or fully integrated elements can have a major influence on the simulated softening behavior of concrete. [ABSTRACT FROM AUTHOR]

The presence of the air–water interface (or free‐surface) creates two major problems in marine seismic data for conventional seismic processing and imaging: free‐surface multiples and ghost reflections. The attenuation of free‐surface multiples remains one of the most challenging noise attenuation problems in seismic data processing. Current solutions suffer from the removal of the primary events along with the multiple events especially when the primary and multiple events overlap (e.g., adaptive subtraction). The effective attenuation of ghost reflections (or deghosting) requires acquisition‐ and/or processing‐related solutions which generally address the source‐side and receiver‐side ghosts separately. Additionally, an essential requirement for a successful implementation of free‐surface multiple attenuation and seismic dehosting is the requirement of dense seismic data acquisition parameters which is not realistic for two‐dimensional and/or three‐dimensional marine cases. We present a convolutional neural network approach for free‐surface multiple attenuation and seismic deghosting. Unlike the existing solutions, our approach operates on a single trace at a time, and neither relies on the dense acquisition parameters nor requires a subtraction process to eliminate free‐surface multiples, and it removes both the source ghost and receiver ghost simultaneously. We train a network using subsets of the Marmousi and Pluto velocity models and make predictions using subsets of the Sigsbee velocity model. We show that the convolutional neural network predictions give a correlation coefficient of 0.97 on average with the numerically modeled data for the synthetic examples. We illustrate the efficacy of our convolutional neural network–based technique using the Mobil AVO Viking Graben field data set. The application of our algorithm demonstrates that our convolutional neural network–based approach removes different orders of free‐surface multiples (e.g., first and second orders) and recovers the low‐frequency content of the seismic data (which is essential for, for instance, full‐waveform inversion applications and broadband processing) by successfully removing the ghost reflections while preserving and increasing the continuity of the primary reflection. [ABSTRACT FROM AUTHOR]

Underwater bottom-sitting shell structures face threats from underwater explosion shock waves. To investigate the damage characteristics and dynamic response of bottom-sitting shell structures under underwater explosion shock waves, three-dimensional numerical models of semi-spherical and semi-cylindrical bottom-sitting reinforced concrete (RC) shells under underwater shock waves were established based on the Arbitrary Lagrangian–Eulerian (ALE) algorithm using LS-DYNA software. The influences of the shock wave transmission medium, explosive equivalent, explosive distance, hydrostatic pressure, and reinforcement on the damage characteristics and dynamic response of semi-spherical and semi-cylindrical bottom-sitting RC shell structures were studied. The results indicated that the damage and center vertical deformation of RC shells under underwater shock waves are significantly greater than those under air shock waves. With an increase in explosive equivalent or decrease in explosive distance, the damage and center vertical deformation of RC shells are increased. The damage to the inner surface of RC shells is more severe than the outer surface. The damage and center vertical deformation of RC shells can be reduced by bottom reinforcement and an increase in the diameter of the steel bar. The 'hoop effect' caused by hydrostatic pressure restrains the horizontal convex deformation and slightly decreases the macroscopic damage and vertical center deformation of the semi-spherical RC shell with an increase in hydrostatic pressure within the range of 0–2.0092 MPa. The hydrostatic pressure restrains the horizontal convex deformation of the semi-cylindrical RC shell. However, inward concave deformation of the shell center is increased by hydrostatic pressure, inducing an increase in the damage to and center vertical deformation of the semi-cylindrical RC shell. These findings may offer a reference for the construction and design of protective measures for underwater bottom-sitting shell structures. [ABSTRACT FROM AUTHOR]

Due to the complicated three-dimensional behaviors and testing limitations of reinforced concrete (RC) members in torsion, torsional mechanism exploration and torsional performance prediction have always been difficult. In the present paper, several machine learning models were applied to predict the torsional capacity of RC members. Experimental results of a total of 287 torsional specimens were collected through an overall literature review. Algorithms of extreme gradient boosting machine (XGBM), random forest regression, back propagation artificial neural network and support vector machine, were trained and tested by 10-fold cross-validation method. Predictive performances of proposed machine learning models were evaluated and compared, both with each other and with the calculated results of existing design codes, i.e., GB 50010, ACI 318-19, and Eurocode 2. The results demonstrated that better predictive performance was achieved by machine learning models, whereas GB 50010 slightly overestimated the torsional capacity, and ACI 318-19 and Eurocode 2 underestimated it, especially in the case of ACI 318-19. The XGBM model gave the most favorable predictions with R2 = 0.999, RMSE = 1.386, MAE = 0.86, and λ ¯ = 0.976 . Moreover, strength of concrete was the most sensitive input parameters affecting the reliability of the predictive model, followed by transverse-to-longitudinal reinforcement ratio and total reinforcement ratio. [ABSTRACT FROM AUTHOR]

The objective of this paper is to present the methodology used to validate the threshold levels of durability indicators from data acquired from existing reinforced concrete structures that may present corrosion problems resulting from carbonation or chloride ingress. This study was conducted in the framework of the French National Project PERFDUB in close collaboration with the MODEVIE ANR project. Durability tests form the basis of a performance‐based approach for the durability of concrete structures, and in order to set the threshold level for each of these durability indicators, it is important to take into account the experience feedback that can be obtained from the actual behavior of existing structures. This paper presents the investigations carried out on eight reinforced concrete structures, all of them having an age well in excess of 50 years, and the main data gathered on some relevant durability and lifetime indicators. Based on all these data, predictive models of carbonation and chloride penetration are applied in order to validate the threshold levels to be adopted for the durability indicators, and several other conclusions are drawn. [ABSTRACT FROM AUTHOR]

Bond at the rebar-concrete interface plays a critical role in the structural performance of reinforced concrete (RC) structures. This bond behavior is typically described by a bond stress-slip relationship, where there are two critical quantities: bond strength ̶ the maximum shear stress that bond can withstand, and peak slip ̶ the slippage at the interface when the bond strength is reached. It is understood that the bond deteriorates when corrosion is present and behaves differently under two distinct bond failure modes (i.e. splitting and pull-out). Thus, this study aims to develop probabilistic prediction models for bond strength and peak slip under the two bond failure modes considering corrosion. In particular, multivariate nonlinear regression with all-possible subset model selection and symbolic multi-gene regression are adopted for the model development. The results show that the developed models outperform other existing models, and also provide satisfactory flexural behavior predictions when they are applied to RC beams. [ABSTRACT FROM AUTHOR]

Inelastic displacement demand is an important part of the performance-based design and it should be estimated realistically to determine a reliable seismic performance of a structure. In this context, the coefficient method is an easy and practical method for this estimation. The coefficient method is a method that is used to estimate inelastic displacement demand by the multiplication of the elastic displacement demand and inelastic displacement ratio. Thus, it is clear that a reliable estimation of inelastic displacement demand depends on a reliable inelastic displacement ratio. After a reliable estimation of the inelastic displacement ratio, it is essential to propose an equation for the usage of engineering practice. Although nonlinear regression analysis is preferred in the literature as a classical method to estimate an equation, the Artificial Neural Network method is a new and modern way that can be used in the estimation of inelastic displacement ratio. In this study, Artificial Neural Network models have been proposed by using data of inelastic displacement ratios of Single Degree of Freedom systems with stiffness and strength degrading peak-oriented hysteretic model and collapse potential by performing nonlinear time history analyses. Firstly, a large number of trials have been conducted to obtain an optimum Artificial Neural Network model. The results of Artificial Neural Network models have been compared to the results of equation estimated by using nonlinear regression analysis and given in the previous studies. According to the results, Artificial Neural Network models give closer values to the inelastic displacement ratios of time history analysis than nonlinear regression analysis. Especially, the Bayesian Regularization Backpropagation model of the Artificial Neural Network method with two hidden layers achieved the best performance among the other Artificial Neural Network models. It can be said that Artificial Neural Network methods can be used to estimate inelastic displacement ratio since it yields better accuracy than previous techniques for different parameters. [ABSTRACT FROM AUTHOR]

Shake-table tests of a full-scale 3-story reinforced concrete frame building were performed at the E-Defense facility (Miki City, Japan) as part of the Tokyo Metropolitan Resilience Project. Building data were collected before and after each shake-table experiment, using light detection and ranging (lidar) scanning technology. Three-dimensional point clouds were generated and processed to investigate the damage features that can be extracted, which are important for postdisaster structural assessment purposes. To this end, this paper discusses aspects pertaining to lidar data processing and registration, calculation of residual displacements and interstory drifts, and concrete cracking and spalling identification and measurement. Most notably, this paper deals with very large data sets, processed to extract structural response information at both global and local scales. Limited multiscale work has been done in the past, and the different sets of challenges that arise have typically been addressed separately. Evidently, this gap needs to be filled before lidar can be effectively used in the field for structural assessment applications. A series of examples in which lidar data are processed and analyzed to assess specific structural components is illustrated, showing that point cloud data can indeed be processed to obtain measurements of global residual drifts or of the extent of visible damage (e.g., crack width and spalling). Although preliminary in nature, the results presented in this paper indicate that collecting postdisaster data using terrestrial lidar scanners has the potential to contribute improving how buildings are assessed in the aftermath of seismic events. [ABSTRACT FROM AUTHOR]

Potentials of direct material testing on existing structures – Strength reserves of a prestressed concrete viaduct Recurring questions regarding the selection of appropriate populations in the context of material testing for reinforced and prestressed concrete bridge, as well as the strength reserves of existing concrete, were investigated through a special case study of a prestressed concrete viaduct with in‐section construction on formwork carriage. In this scope, 141 drill cores were taken from Unterrieden Viaduct, which is to be dismantled, and tested for either compressive strength, splitting tensile strength or Young's modulus. The data sets were statistically analyzed. The results impressively demonstrate the potential of the direct determination of material parameters on existing structures. In particular, the anticipated compressive strength values were surpassed by 40 %, and the characteristic values from material testing even exceed the assumptions based on as built documents by over 100 %. Furthermore, an investigation of potential populations on the superstructure is carried out in order to develop recommendations for future sampling. For this purpose, the sample taken is divided into different potential populations and statistically analyzed. The result shows a very uniform structure with a dispersion well below the normative assumptions. This hardly provides any arguments for subdividing the superstructure into different populations. [ABSTRACT FROM AUTHOR]

This study presents an overview of the design of reinforced concrete (RC) structures (moment frames, shear walls and large panels) for Romania and the impact on seismic exposure and vulnerability within the context of the recent European Seismic Risk Model 2020 (ESRM20). The overview is focused on the design of structural elements for bending moment and shear force, as well as on the constructive and detailing requirements imposed by various codes. The design of RC structures in Romania over the past century involved the use of material- and element-oriented design codes, besides the seismic design code. In addition, economic constraints regarding the material (steel) consumption influenced considerably the design process. The observations made from various literature sources regarding the design and construction practice in Romania are used for a better understanding and evaluation of the seismic exposure and vulnerability. In addition, the key observations regarding the seismic behaviour of each particular structural type are also presented. [ABSTRACT FROM AUTHOR]

The bond strength between reinforcing steel bars and cement concrete plays significant role in the structural performance for civil infrastructure. This work presents the bond performance of steel and concrete as interfacial shear strength, with the inclusion of effects of specimen diameter on embedment length, different aggregate grading and corrosion. The experimental procedure for proposed study includes a series of pullout tests on reinforced concrete cylindrical specimens with embedded steel bar. Cylindrical concrete specimens with varying specimen diameters with respect to different embedment lengths, changing the aggregate grading pattern, i.e., well and gap graded were casted and said effects on bond strength were evaluated through a pullout test. The corrosion effect is also studied through an accelerated corrosion process. The test results revealed that the diameter of the specimen and the embedment length substantially impact the bond strength between reinforcing bars and concrete. Due to the increasing surface area and mechanical interaction between the bar and the surrounding concrete, the bond strength increased as the diameter decreased. The bond performance of well-graded aggregates was effective compared to gap-graded aggregates. Moreover, the study found that as the number of corrosion days increased, the bond strength of corroded reinforcing bars considerably decreased. The results contribute essential insights to the field of reinforced concrete structures and can aid engineers and researchers in designing durable and reliable infrastructure systems. [ABSTRACT FROM AUTHOR]

Many researchers have investigated the solutions for the problem of solid waste in different ways. An example of that is reusing polyethylene terephthalate (PET) as reinforcement to concrete. Strapping plastic belts used to tie clay bricks while transportation in trucks are one of the common waste of construction that could be beneficial in enhancement of concrete flexural behaviour due to its high tensile strength. This paper is a trial to investigate the effect of utilizing waste strapping plastic belts on the flexural behavior of concrete. Concrete prisms (100*100*500mm) were reinforced with plastic belts as the main reinforcement for flexural strength. Five amounts of reinforcement were added to the concrete section in the tension zone (81, 67.5, 54, 40.5, 27 sqr mm). The reinforcement was included in concrete sections internally or externally using suitable glue. The behavior of the reinforced prisms was compared to plane concrete prisms (containing no reinforcement). Tests results showed an enhancement in flexural strength of concrete section while reinforcement ratio is increased externally. The addition of 81 mm² of plastic straps externally, increased the flexural strength by 21% compared to sections with 27 mm² reinforcement. The enhancement in flexural strength as internal reinforcement is added was limited. According to the flexural test of reinforced concrete prizms. Adding 81 mm² of plastic straps internally, reduced the flexural strength by 18% compared to sections with 54 mm² reinforcement due to the splitting of the cover as the area of the reinforcement increases. Increasing the number of belts in the section results in a sever reduction in the spacing between each two belts, leading to increase concrete cover tendency to split. For that, increasing the amount of plastic diversely affects connectivity for the internally reinforced sections. [ABSTRACT FROM AUTHOR]

The present article is an effort to quantify the flexural strength of corroded reinforced concrete (RC) beams. Eight RC beams with dimensions of 150 × 200 × 2200 mm were tested in four-point bending, including six beams corroded in a chloride environment with average corrosion of longitudinal reinforcement in the range of 5% to 15%. The remaining two beams were used as control beams. The ultimate strength, failure mode and particularly the relationship between crack width and corrosion level are analyzed and discussed. A two-dimensional non-linear finite element model has been presented to simulate the steel bar corrosion considering the deterioration of concrete strength and steel-concrete bond stress. The generalised regression neural network (GRNN)-based model for the ultimate flexural strength of corroded RC beams has been established based on 123 experimental data collected from previous studies. The experimental results were used to separately validate the non-linear finite element model and novel GRNN model. Experimental results indicate that if the overall corrosion rate is used, the corrosion crack width can be a function of the percentage of section loss. The GRNN model provides superior predictive results compared to previous empirical methods with the highest correlation coefficient (r), and the smallest normalised root mean square error. [ABSTRACT FROM AUTHOR]

This paper aims to summarize the findings of a comprehensive study on the correlation of displacement and deformation demands estimated using various code-compliant nonlinear modeling approaches commonly used in real-life performance-based seismic design and assessment applications, with experimental results obtained from the full-scale shake table tests on the 10-story reinforced concrete building performed at the E-defense testing facility in 2015. Nonlinear response history analysis results obtained using ASCE-41 and Turkish Building Earthquake Code model configurations with the lumped plasticity modeling approach adopted for beams and columns, as well as an additional configuration adopting the distributed plasticity approach, were compared with test measurements. Analysis sets were also conducted to evaluate the sensitivity of the analytical predictions to specific modeling assumptions that incorporate varying degrees of uncertainty, including consideration of beam effective flange widths, modeling of the floor slabs, adopting a tensile strength for concrete, selecting alternative effective shear moduli for structural walls, consideration of the vertical component of the ground motion, and selection of the damping ratio. Analysis results were compared with experimental measurements in terms of various global displacement and local deformation demands on the structure, including story displacement time-histories, peak interstory drift ratios, flexural and shear deformations on structural walls, and flexural deformations on beams and columns. The relative effectiveness of different methodologies and assumptions in replicating the experimentally-measured deformation demands on the test building are discussed in detail. Limitations of the adopted modeling approaches in simulating salient experimentally-observed response characteristics of the building are also identified. [ABSTRACT FROM AUTHOR]

Reinforcement corrosion is the main cause of performance deterioration of reinforced concrete (RC) structures. Limited research has been performed to investigate the life-cycle cost (LCC) of coastal bridge piers with nonuniform corrosion using different materials. In this study, a reliability-based design optimization (RBDO) procedure is improved for the design of coastal bridge piers using six groups of commonly used materials, i.e., normal performance concrete (NPC) with black steel (BS) rebar, high strength steel (HSS) rebar, epoxy coated (EC) rebar, and stainless steel (SS) rebar (named NPC-BS, NPC-HSS, NPC-EC, and NPC-SS, respectively), NPC with BS with silane soakage on the pier surface (named NPC-Silane), and high-performance concrete (HPC) with BS rebar (named HPC-BS). First, the RBDO procedure is improved for the design optimization of coastal bridge piers, and a bridge is selected to illustrate the procedure. Then, reliability analysis of the pier designed with each group of materials is carried out to obtain the time-dependent reliability in terms of the ultimate and serviceability performances. Next, the repair time of the pier is predicted based on the time-dependent reliability indices. Finally, the time-dependent LCCs for the pier are obtained for the selection of the optimal design. [ABSTRACT FROM AUTHOR]