Search Results (149)

The performance of reinforced concrete (RC) frame structures will gradually decrease over time, posing a threat to the safety of buildings. Although the performance of some buildings may still meet the safety requirements, they cannot meet new usage requirements. Therefore, this paper proposes a new-type joint to promote the development of research on the reinforcement and renovation of RC frame structures in response to this situation. The RC beams and columns of the joints are connected by embedded horizontal steel plate (a single plate with dimension of 150 mm × 200 mm × 5 mm), and the beams and columns are individually wrapped in steel. Through conducting low cyclic loading tests, this paper analyzes the influence of carrying out wrapped steel treatment and the thickness of wrapped steel of the beam and connector on mechanical performance indicators such as hysteresis curve, skeleton curve, stiffness, ductility, and energy dissipation. The experimental results indicate that the reinforcement using steel plate can significantly improve the dynamic performance of the joint. The effect of changing the thickness of the connector on the dynamic performance of the specimen is not significant, while increasing the thickness of wrapped steel of beam can effectively improve the overall strength of joint. The research results of this paper will help promote the application of reinforcement and renovation technology for existing buildings, and improve the quality of human living. Full article

The seismic risk assessment of large building stocks is crucial for informed asset management in earthquake-prone regions, providing decision-support for retrofit intervention planning. Many existing methodologies focus on a single structural typology or asset class (e.g., ordinary buildings or industrial facilities), thus limiting their applicability to mixed portfolios. This study proposes a comprehensive and adaptable methodology for the seismic assessment of diverse building stocks—a cross-typology approach encompassing masonry, reinforced concrete (r.c.), precast r.c., and steel structures. The approach integrates deficiency-based qualitative evaluations with simplified mechanical models tailored for each building class. Where validated methodologies were unavailable, new assessment tools were developed. The proposed framework was applied to an industrial-oriented building stock comprising 79 structural units at regional scale, demonstrating its capability to identify priority structures for retrofitting interventions. By overcoming the constraints of typology- or asset-specific approaches, this methodology enables a more comprehensive and scalable assessment. This ultimately contributes to effective risk mitigation planning and seismic resilience enhancing. Full article

Rapid visual screening has been used worldwide as the first approach to evaluate the seismic vulnerability of civil structures in a specific area, in order to prioritize buildings based on the need for upgrading or retrofitting. In this work, a novel mobile application tool for the rapid visual screening of reinforced concrete buildings is presented and discussed. The herein suggested “SeismicV” tool performs a pre-seismic visual screening based on the Japanese guidelines for the seismic evaluation of existing RC buildings. A preliminary seismic vulnerability assessment of a complex modern building situated in the capital of Brazil, Brasilia, was carried out using this mobile app. The data were collected from in situ and based on some data from plants and documents. The SeismicV tool consists of an effective, user-friendly, and straightforward mobile application. Since the methodology is based on a performance score that is compared to the seismic demand, this application design allows for the knowledge of intermediate indices at each step of the evaluation, including dominant variables such as structural irregularity, building age, ground index, and usage index. Although the application was conceived and applied to heritage buildings in the early stages, it can be employed for other complex structures. The findings highlight that utilizing SeismicV to assess the seismic vulnerability of complex buildings through the rapid visual screening method offers significant benefits, including faster evaluations, increased accuracy, and improved accessibility for field assessments. Full article

The progressive collapse performance of reinforced concrete (RC) building structures has been extensively investigated using the alternate load path method. However, most studies have focused on newly designed structures, with limited attention given to existing buildings. Since progressive collapse can occur at any point during a structure’s service life and at various locations within the structural system, this study examines the progressive collapse behavior of deteriorated RC frames subjected to simulated reinforcement corrosion. This paper presents an investigation into the system-level progressive collapse responses of deteriorated RC frames, which extends the current state of the art in this field. The influence of different material deteriorations, different corrosion locations, different column removal scenarios, and dynamic effects on structural response is explored. According to the results obtained in this research, a significant reduction in progressive collapse resistance can be resulted in with increasing corrosion levels. Notably, only reinforcement corrosion in the beams located directly above the removed column (i.e., within the directly affected part) for the investigated RC frame had a substantial impact on structural performance. In contrast, corrosion in other regions and concrete deterioration exhibited minimal influence in this work. An increased number of corroded floors further reduced collapse resistance. Dynamic progressive collapse resistance was found to be considerably lower than its static counterpart and decreased at a slightly faster rate as corrosion progressed. Additionally, the energy-based method was shown to provide a reasonable approximation of the maximum dynamic responses at different corrosion levels, offering a computationally efficient alternative to full dynamic analysis. Full article

Under the impetus of achieving global sustainable development goals, the civil construction industry is accelerating its transition towards high-quality, green, and low-carbon practices. Prefabricated, modular building technology has become a key tool due to its advantages in energy conservation, emission reduction, and shortened construction periods. However, existing research on the seismic performance of prefabricated, modular, reinforced concrete column–beam (RCS) composite structures often focuses on the construction form of beam–column joints, paying less attention to the impact of floor slabs on the seismic performance of joints during earthquakes. This may make joints a weak link in structural systems’ seismic performance. To address this issue, this paper designs a prefabricated, modular RCS composite joint considering the effect of floor slabs and uses the finite element software ABAQUS 2023 to perform a quasi-static analysis of the joint. The reliability of the method is verified through comparisons with the experimental data. This study examines various aspects, including the joint design and the material’s constitutive relationship settings, focusing on the influence of parameters, such as the axial compression ratio and floor slab concrete strength, on the joint seismic performance. It concludes that the seismic performance of the prefabricated, modular RCS composite joints considering the effect of floor slabs is significantly improved. Considering the composite effect of the slabs, the yield loads in the positive and negative directions for node FJD-0 increased by 78.9% and 70.0%, respectively, compared to that of the slab-free node RCSJ3. The ultimate bearing capacities improved by 13.2% and 9.98%, respectively, and the energy dissipation capacity increased by 23%. Additionally, the variation in the axial load ratio has multiple effects on the seismic performance of the joints. Increasing the slab thickness significantly enhances the seismic performance of the joints under positive loading. The bolt pre-tensioning force has a crucial impact on improving the bearing capacity and overall stiffness of the joints. The reinforcement ratio of the slabs has a notable effect on the seismic performance of the joints under negative loading, while the concrete strength of the slabs has a relatively minor impact on the seismic performance of the joints. Therefore, the reasonable design of these parameters can optimize the seismic performance of joints, providing a theoretical basis and recommendations for engineering application and optimization. Full article

Corrosion significantly contributes to the deterioration of reinforced concrete (RC) structures. This work investigates its impact on the seismic behaviour of RC buildings. A simplified numerical simulation strategy was developed and validated, analysing two columns with corrosion rates of 0% and 20%, based on existing experimental research found in the literature. Subsequently, five distinct scenarios were developed, incorporating various corrosion rates of 0%, 10%, and 20%, applied to a structure designed in accordance with the Eurocode 8. Nonlinear pushover analyses were conducted to derive capacity curves and bilinear curves, focusing on key parameters such as maximum strength and corresponding drift, initial stiffness, secant stiffness, yield force and drift. Displacement and drift profiles per floor were analysed at the significant damage performance point (SD). The results indicate a clear negative impact of corrosion on structural performance, evidenced by reduced capacity to withstand deformations and lateral forces, alongside an increased likelihood of damage to non-structural elements. Full article

In seismic risk analyses, collapse assessment is of critical importance, as it leads to most injuries and fatalities, as well as significant economic losses. In this paper, the seismic collapse response of some 3D prototypes representative of the 1970s Italian reinforced concrete building stock has been analyzed. The considered prototypes have been selected based on two of the most important typological parameters, namely the number of storeys (three types: 2-, 4-, and 6-storey) and the design level (two types: gravity load design, representative of pre-code types, and earthquake-resistant design with low lateral load intensities without anti-seismic details, representative of low-code types). Incremental non-linear dynamic analyses have been performed along the two in-plane directions using a set of 20 real signals scaled up to collapse. The inter-storey drift ratio values at collapse have been analyzed to estimate the mean and dispersion values of the best-fitting distribution functions. These results can be used as capacity thresholds for assessing seismic performance in numerical analyses. Fragility curves have also been derived using different intensity measures to estimate the exceedance probability of collapse, accounting for their inherent efficiency, to be used in seismic risk analyses. Results have been compared to provide valuable insights into the influence of the considered typological parameters on collapse. Full article

The Kahramanmaraş (Türkiye) earthquake on 6 February 2023, one of the largest earthquakes of the century, caused the collapse or severe damage of thousands of structures. This catastrophic disaster resulted in over 53,000 fatalities and rendered many structures unusable. This study addresses the observed damage in reinforced concrete (RC) structures, which constituted the majority of the existing urban building stock. In this study, firstly, information about the destructive Kahramanmaraş earthquakes was given. The predicted PGAs in the last two earthquake hazard maps used in Türkiye were compared with the measured PGAs from actual earthquakes to determine whether the earthquake hazard is adequately represented for eleven affected provinces in the earthquake region. The damages in RC structures were evaluated within the scope of civil and earthquake engineering. Structural analyses for the model created to represent mid-rise RC buildings in the region were carried out separately for each province using predicted and measured PGAs. Additionally, target displacements that were used in performance-based earthquake engineering for damage prediction, were examined comparatively for all provinces. While the predicted earthquake hazard and targeted displacements were exceeded in some provinces, there was no exceedance in the other provinces. The realistic representation of earthquake hazards will allow the predicted displacements for various performance levels of structures to be determined in a much more realistic way. Consequently, the performance levels predicted for the structures will be assessed with greater accuracy. The study highlights the importance of accurately presenting earthquake hazards to predict building performance effectively. Full article

In recent years, innovative Non-Destructive Testing (NDT) techniques, applicable for the assessment of existing civil structures, have become available for in situ analysis on Reinforced Concrete (RC) and masonry structures, but they are still not established for regular inspections, especially after seismic events. The damage assessment of RC buildings after seismic events is a very relevant issue in Italy, where most of the structures built in the last 50 years are RC structures. Furthermore, there is also a growing interest in being able to monitor structural health aspects by storing them on the building’s digital twin. For these reasons, it is necessary to develop an affordable and ready-to-use NDT procedure that provides more accurate indications on the real state of damage of reinforced concrete buildings after seismic events and to integrate these data into an interoperable digital twin for automated, optimized building performance monitoring, management, and preventive maintenance. To this end, a case study was conducted on a building in the Marche region in Italy, damaged by the 2016 earthquake. Non-destructive tests were performed and inserted into the LIS platform for the creation of a digital twin of the building. This platform seamlessly manages, visualizes, and analyzes the collected data and integrates various sensor nodes deployed throughout the building. The paper also presents a methodology to simplify the work of the test operator and make the entire process of knowledge of the building faster and more sustainable through a QR-code interface. Full article

Establishing dependable and resilient methodologies for identifying damage that may compromise the integrity of reinforced concrete (RC) infrastructures is imperative for preventing potential catastrophic failures. Continuous evaluation and Structural Health Monitoring (SHM) can play a key role in extending the lifespan of new or existing buildings. At the same time, early crack detection in critical members prevents bearing capacity loss and potential failures, enhancing safety and reliability. Furthermore, implementing discrete fibers in concrete has significantly improved the ductility and durability of Fiber-Reinforced Concrete (FRC). The present study employs a hierarchical clustering analysis (HCA) to identify damage in FRC by analyzing the raw Electromechanical Impedance (EMI) signature of piezoelectric lead zirconate titanate (PZT) transducers. The experimental program consisted of three FRC standard cylinders subjected to repeated loading. The loading procedure consists of 6 incremental steps carefully selected to gradually deteriorate FRC’s structural integrity. Additionally, three PZT patches were adhered across the height of its specimen using epoxy resin, and their EMI response was captured between each loading step. Subsequently, the HCA was conducted for each PZT transducer individually. The experimental investigation demonstrates the efficacy of HCA in detecting load-induced damage in FRC through the variations in the EMI signatures of externally bonded PZT sensors. Full article

The European building stock is aging and needs renovation. Holistic renovation approaches, including Vertical Forest (VF) systems, are emerging as sustainable alternatives to demolition and reconstruction. This paper reviews and defines missing reliable damage and hazard intensity measures for the holistic renovation of existing reinforced concrete (RC) buildings with VF systems. Based on an extensive literature review and preliminary studies, including empirical multiparametric system evaluation assessments, Monte Carlo simulations, and System-Theoretic Process Analysis (STPA), combined structural, non-structural, vegetation, and human comfort components are examined. Key damage indicators are identified, including interstory drift ratio, residual deformation, concrete and reinforcement strains/stresses, and energy dissipation, and their applicability to VF-integrated structures are evaluated. Green modifications are found to have higher risk profiles than traditional RC buildings (mean scores from Monte Carlo method: 9.72/15–11.41/15 vs. 9.47/15), with moisture management and structural integrity as critical concerns. The paper advances the understanding of hazard intensity measures for seismic, wind, and rainfall impacts. The importance of AI-driven vegetation monitoring systems with 80–99% detection accuracy is highlighted. It is concluded that successful VF renovation requires specialized design codes, integrated monitoring systems, standardized maintenance protocols, and enhanced control systems to ensure structural stability, environmental efficiency, and occupant safety. Full article

Reinforced concrete (RC) structures in coastal atmospheres commonly suffer the penetration of chloride ions, which can lead to the corrosion of reinforcements and, thus, a reduction in their structural performance under earthquakes. In recent years, time-dependent seismic fragility analysis has been widely used as an effective tool to represent the deterioration in the seismic performance of aging RC structures. However, few studies have considered the influences of varying chloride ion exposure environments due to the different distances of structures from a coastline. In light of this, this study performs a time-dependent seismic fragility analysis for aging RC frames, considering varying distances of the buildings from the coastline. To conduct this, a time-dependent reinforcement corrosion rate model that can consider the effect of the distance of a building from the coastline is established by combining a concrete surface chloride ion concentration model, an initial corrosion time model, and an electrochemical corrosion rate model. By integrating material deterioration models for reinforcements and concrete, the seismic fragility relationships for structures with different degrees of corrosion damage can be developed. A corrosion deterioration factor is then proposed to quantify the relationship between the seismic fragility function parameters and the corrosion rate. Subsequently, time-dependent fragility functions considering the effect of the distance from the coastline can be established. A nine-story RC frame designed according to the existing Chinese codes is used for illustration. The time-dependent seismic fragility relationship of the structure is developed considering different distances of buildings from the coastline. The results show that the effect of the distance of a building from the coastline varies under different categories of environment. The seismic fragility results for a structure under a III-a environment are more significantly influenced by the structural distance from the coastline compared to those for a structure under a II-a environment. Full article

Strengthening reinforced concrete (RC) buildings is a critical challenge in the construction industry, pushed by the necessity to address aging infrastructure, environmental degradation, and growing use requirements. Ultra-high-performance fiber-reinforced concrete (UHPFRC) is one of the advanced materials that present a viable solution owing to its exceptional durability and mechanical characteristics, which encompass higher compressive and tensile strengths, low permeability, and resilience against intense environmental as chloride ingress, cycles of freeze–thaw, and chemical assaults. This literature review comprehensively examines UHPFRC as a rehabilitation or strengthening mix material for the RC slabs and beams. Experimental key subjects include the influence of bonding techniques, strengthening configurations, steel fiber ratios, UHPFRC thickness, and reinforcing steel within the UHPFRC layer. In addition, the existing numerical and analytical approaches for forecasting the flexural or shear capability of reinforcing concrete structures retrofitted with UHPFRC were examined and critically assessed. Despite the improvements in the RC structures achieved through experiments utilizing UHPFRC as a reinforcement layer, this study highlights some deficiencies in the existing knowledge, such as the absence of effective ways to address debonding, insufficient research on cyclic loading, and the necessity for economical and sustainable strengthening techniques. This review establishes a basis for future research, intending to create an innovative UHPFRC-based strengthening system that mitigates current limits and improves the overall efficacy, performance, and durability of RC structures. Full article

Optimizing energy efficiency in existing buildings can yield substantial savings, though collecting the necessary data for energy modelling often poses challenges. This study developed a flexible, room-level framework for evaluating retrofit strategies using simplified energy models. The approach, based on the RC model, estimated parameters from readily available data such as solar radiation, indoor and outdoor temperatures, and heating system characteristics. The model was validated through case studies of an office and a daycare room in Denmark, guiding energy retrofit decisions. Results showed that adding roof insulation provided greater energy savings compared to wall insulation. A multi-objective optimization was employed to balance energy efficiency and thermal comfort, achieving a 6.58% reduction in energy demand during January while maintaining occupant comfort for 744 h. This framework not only facilitates building–energy retrofitting but also supports the development of digital twins and operational optimization, improving both energy performance and indoor environmental quality. Full article

The purpose of this study is mainly to investigate, through fragility curves, the effect of soil–structure interaction (when it is neglected during design) on damage probability. It also examines how realistic it is to conduct a performance estimation with rapid assessment methods without considering soil–structure interaction. Three RC frame buildings, with varying numbers of stories, were designed according to the Turkish Seismic Design Code, 2007. Incremental dynamic analyses of the considered structures, both with and without soil–structure interaction (SSI), were performed using 21 ground motion records to determine the damage limits. The cone model with springs was used to take soil–structure interaction into account. The discrete damage probabilities of each considered performance level were calculated, using statistical methods, in terms of elastic spectral acceleration, and continuous fragility curves were obtained. The results show that the effect of SSI on fragility was remarkable and that damage probability generally increases when soil–structure interaction is taken into consideration. The effect of site class becomes significant for life safety and collapse prevention performance levels. The increase in the probability of exceeding the collapse prevention performance level can reach up to 72% due to the existence of SSI. Thus, the results of damage estimation made without considering SSI can sometimes be significantly misleading. Full article