Search Results (707)

Nonlinear velocity dampers (NVDs) embedded in coupling beams may enhance the seismic performance of frame–core tube structures by dissipating energy and limiting structural damage. This study evaluates the seismic performance of a 20-story reinforced concrete (RC) frame–core tube building incorporating NVD-equipped coupling beams. Parametric studies are conducted at the frequent earthquake (FE) level, and nonlinear time-history analyses are performed at the design-basis earthquake (DBE) and rare earthquake (RE) levels. The results show that wall-pier flexure is the primary contributor to damper deformation, and mid-span placement is found to be relatively favorable. The optimal damping coefficient varies with the engineering demand parameters, whether base shear, drift, or additional damping, indicating that damping coefficient should be chosen based on a balanced consideration. For the N. Palm Springs ground-motion record considered in the damage assessment, the NVD-equipped models exhibit less flexural damage than the reference model for varying damping coefficients at both DBE and RE levels. These findings provide case-specific design guidance for applying NVD-equipped coupling beams in comparable RC frame–core tube buildings. Full article

The renovation of existing reinforced concrete (RC) buildings is essential to reduce the environmental impact of the existing building stock while improving its energy performance and resilience. However, existing renovation strategies are often addressed separately, making it difficult to compare their capabilities and limitations. This study presents a comprehensive review of renovation approaches for RC building envelopes, with particular emphasis on Southern European building stocks, where thermal and seismic deficiencies frequently coexist. The review examines three main renovation strategies: demolition and reconstruction, energy renovation, and combined seismic and energy renovation, and analyses representative systems identified through a structured literature review. A comparative analytical framework was developed based on four dimensions: functional integration, structural role, degree of prefabrication, and adaptability to existing building conditions. The analysis reveals a clear transition from conventional insulation-based interventions towards multifunctional and system-integrated envelope solutions. While prefabricated systems improve construction industrialization and production scalability, integrated seismic–energy solutions provide higher functional performance but require greater project-specific adaptation, reducing their large-scale applicability. The review also identifies the limited integration of spatial and architectural transformation within current renovation strategies. The proposed framework provides a structured basis for comparing existing solutions and identifies key challenges and future research directions for the development of more adaptive, industrialized, and integrated renovation systems. Full article

Roofing systems strongly influence the energy performance and environmental footprint of buildings, particularly in hot–arid climates such as Saudi Arabia, where cooling dominates electricity demand; however, the comparative lifecycle environmental performance of alternative roofing strategies remains underexplored in this specific climatic and market context. This study therefore aims to evaluate and compare the environmental performance of four sustainable roofing strategies against a conventional flat roof (FR) baseline in order to provide evidence-based guidance for climate-specific roofing selection in Saudi Arabia. This study conducts a comparative cradle-to-grave lifecycle assessment (LCA) of four sustainable roofing strategies considering the hot–arid climate of Saudi Arabia. Green roof (GR), cool roof (CR), solar photovoltaic roof (SPV), and roof canopy (RC) were assessed using the ReCiPe 2016 method in the SimaPro software. The environmental impacts of these strategies were assessed across product, construction, use, and end-of-life stages relative to conventional flat roofs (FRs). The results indicate that the production stage consistently contributes the highest environmental impacts, with increases ranging from 30 to 3000% for GR, CR, and RC and exceeding 10,000% for SPV. On the other hand, the use stage offers the greatest reductions ranging from 10 to 200%, particularly for SPV and CR, due to operational energy savings and electricity generation. Overall, CR demonstrates the most balanced environmental performance, combining high impact reductions with minimal trade-offs, while SPV provides significant climate and fossil resource benefits but increases mineral resource use. These findings highlight the importance of climate-specific and resource-conscious selection of roofing strategies in Saudi Arabia and provide a transferable comparative LCA framework that can inform sustainable roofing decisions in other hot–arid and hot–humid regions, in support of the Kingdom’s Vision 2030 objectives for sustainable urban development. Full article

To enhance the seismic performance of existing reinforced concrete (RC) buildings during retrofitting, the study introduces a new type of joint connected by a T-shaped steel plate. Compared with previous similar strengthening methods, this novel structure incorporating a post-installed beam not only effectively improves the mechanical properties of RC columns, but the connectors also further enhance the integrity of the post-installed beam. Low-cycle reversed loading tests on one cast-in-place specimen (RC) and three T-shaped steel plate connection specimens (TRC1–TRC3) were conducted to evaluate failure modes, hysteresis and skeleton curves, and energy dissipation. Results show that the novel joint failure concentrates at beam-end–column steel jacket weld seams and column-side steel plate cracking, while the core-zone concrete remains intact. Compared with RC, the novel joints TRC1–TRC3 exhibit bearing capacity variations of −1.03%~+15.80% and significantly enhanced energy dissipation. The thickness of the beam’s wrapped steel improves the carrying capacity and energy dissipation, whereas the T-shaped connector thickness has limited influence on bearing capacity. ABAQUS parametric analysis indicates that bolt quantity, concrete strength, and connector thickness have limited influence and serve as secondary design factors. These findings provide a theoretical basis for retrofitting existing buildings. Full article

Simulation-dependent energy analysis has long dominated building retrofit research, yet this paradigm presents substantial barriers for non-expert building owners who lack technical software proficiency and detailed building documentation-a challenge compounded by the “curse of dimensionality” when multivariate analysis requires thousands of samples beyond available empirical records. Leveraging retrofit data accumulated through Korea’s Green Remodeling programs since 2017, this study proposes a Copula-Genetic Algorithm (Copula-GA) integrated framework that enables rational retrofit decision-making with minimal user inputs (construction year, floor area, structural type). From 178 documented retrofit cases, Gaussian copula-based multivariate sampling generated 10,000 synthetic records while preserving inter-variable dependency structures. Building physics constraints addressing vintage-thermal performance and capacity-efficiency relationships filtered implausible combinations, yielding 9898 valid cases with correlation matrix fidelity confirmed by a Frobenius norm deviation of 0.043. Evolutionary clustering employing a composite fitness function of Silhouette coefficient (0.68) and Davies-Bouldin Index (0.52) identified K = 16 as the optimal partition, categorizing outcomes into four reference model archetypes: Lightweight Structure (Type A, 27.0% reduction, 15.7-year payback), Masonry Structure (Type B, 29.0%, 14.8 years), RC Structure (Type C, 30.7%, 13.4 years), and Mixed Structure (Type D, 30.9%, 13.1 years). The proposed Copula-GA framework bridges the gap between advanced energy optimization methodologies and practical accessibility for non-expert building owners. By transforming limited empirical samples into reliable reference models, this research supports building-sector decarbonization. Using three minimal inputs, a building can be matched to one of the 16 standard models to obtain its expected saving rate, payback period, and recommended measures without detailed simulation. Full article

Building supervisory control requires accurate, prior-consistent, and computationally tractable thermal models. This study proposes a physics-guided neural ordinary differential equation (PG-NODE) framework for thermal prediction and model predictive control (MPC). It combines a resistance–capacitance (RC)-inspired reference, a neural residual, RC-prior directional regularization, and validation-based checkpoint selection; the selected predictor remains fixed during MPC operation. Using 30 min EnergyPlus data from five zones, the framework was evaluated through held-out prediction, Gaussian noise and control-input-mismatch tests, ablation, and surrogate-based closed-loop experiments. Long short-term memory achieved the lowest prediction root mean square error (RMSE), whereas PG-NODE achieved the lowest RMSE among the evaluated neural ODE models and the lowest directional inconsistency rate among learned nonlinear models. In five-seed × five-window BACK SPACE experiments using independently trained, fixed PG-NODE surrogate environments rather than direct EnergyPlus interaction, fixed-block analysis supported lower reference-tracking RMSE for PG-NODE-MPC than for rule-based control and lower tariff-weighted normalized control effort than for the extended Kalman filter-based RC-MPC benchmark. This benchmark achieved the lowest descriptive mean reference-tracking RMSE and total objective. Mean PG-NODE-MPC optimization time was 0.86 s. Results suggest the potential for low-frequency building management system supervisory decision support, subject to physical command mapping and staged field validation. Full article

Seismic design of long-period reinforced concrete tall buildings is drift-dominated, and yet closed-form tuned mass damper (TMD) calibration lacks a rank-oriented robustness framework and a deterministic treatment of inelastic period drift. First, a two-layer closed-form calibration procedure is verified on 30-, 48- and 60-storey RC towers with periods of 3.80 to 8.45 s on a rock-like Istanbul site under eleven spectrum-matched records. The first layer, a Robust Tuning Index built on four design requirements, weighs nominal suppression against detuning robustness through a closed-form dominance condition and a unique crossover at the ±13% band. The second layer, a period-elongation-aware anchor, sets the calibration period to the mean of the elastic and DD-2 secant first-mode periods, capping the worst-case offset at ±9.0% to ±12.1% against +19.7% to +27.6% under elastic anchoring. Response-history analyses give mean peak roof-drift reductions of 2.8% to 4.6% with statistically inseparable formulation means at exact tuning, while the Sadek calibration cuts dispersion by more than a third and stroke by roughly a third, carries 2.3 to 2.5 times less frequency-response loss at the anchor offsets, and ranks first in 122 of 144 envelope scenarios. The framework replaces numerical retuning with a transparent closed-form route within the linear verification tier. Full article

Reinforced concrete (RC) slabs in buildings and protective structures are vulnerable to repeated low-velocity impacts caused by falling objects, vehicle collisions, industrial accidents, and successive debris strikes. Such repeated impacts can result in cumulative damage, progressive stiffness degradation, and eventual structural failure. Although externally bonded carbon fiber-reinforced polymer (CFRP) sheets have been widely adopted to improve the impact resistance of RC members, their effectiveness under repeated impact loading is often limited by premature debonding, while the contribution of mechanical anchorage systems to mitigating debonding and improving structural performance remains insufficiently understood. Accordingly, this study experimentally and numerically investigates the repeated low-velocity impact behavior of RC two-way slabs strengthened with externally bonded CFRP sheets incorporating boundary and distributed mechanical anchorage configurations. Four slab groups were investigated: unstrengthened control slabs (SL1), CFRP-strengthened slabs (SL2), CFRP-strengthened slabs with boundary anchors only (SL3), and CFRP-strengthened slabs with distributed anchors across the entire slab area (SL4). Repeated impact tests were conducted using a 92 kg drop weight released from progressively increasing heights until failure. The outcomes showed that strengthening of RC slab with CFRP sheets significantly improved the impact resistance at a 1.50 m drop height by reducing the residual displacement, crater diameter, and indentation depth by up to 67%, 55%, and 70%, respectively, compared with the control slabs. The incorporation of mechanical anchors further delayed premature CFRP debonding, maintained the CFRP–concrete bond, and enhanced the structural response, achieving maximum reductions of 77%, 63%, and 85%, respectively. Furthermore, the anchored slabs withstood repeated impacts from a 2.50 m drop height, whereas both the control and unanchored CFRP-strengthened slabs failed at a 2 m drop height. The developed finite element model accurately captured the structural response, CFRP debonding, anchorage failure, and damage evolution of the RC slabs, with good agreement between the numerical predictions and the experimental observations in terms of failure patterns, damage characteristics, and residual displacements. The proposed strengthening strategy and validated numerical model provide a reliable framework for assessing the effectiveness of different mechanical anchorage configurations and predicting the progressive failure behavior of CFRP-strengthened RC slabs subjected to repeated low-velocity impacts. Full article

We report a CMOS-compatible ferroelectric memristor based on a TiN/AlScN/n⁺ Si metal ferroelectric semiconductor (MFS) structure, fabricated entirely via low-temperature sputtering processes. The ultrathin AlScN film exhibits robust ferroelectricity with a high remanent polarization (2P_r ≈ 80.91 μC/cm²) and excellent endurance over 10⁵ cycles, while maintaining uniform switching across cells. Notably, the use of a heavily doped silicon bottom electrode enables full compatibility with conventional back-end-of-line (BEOL) CMOS processes and facilitates integration with silicon-based circuits. Beyond stable memory performance, the device demonstrates volatile short-term memory (STM) behavior originating from depolarization field-induced polarization relaxation, which is essential for neuromorphic dynamics. Leveraging this STM feature, the device was implemented as a physical reservoir in a reservoir computing (RC) framework, achieving 97.64% classification accuracy on the MNIST dataset using temporally coded inputs. These results highlight the potential of AlScN-based ferroelectric memristors as dynamic CMOS-compatible building blocks for in-memory and neuromorphic computing. Full article

The twin earthquakes (Mw = 7.7 and Mw = 7.6) that struck Kahramanmaraş on 6 February 2023 caused severe damage to reinforced concrete (RC) buildings in southeastern Türkiye. Field observations showed that concrete quality and transverse reinforcement details have a major influence on the shear resistance of RC columns and beams. These factors also affect the fracture behaviour and structural integrity of the elements. The surveys revealed several common deficiencies. These included excessive transverse reinforcement spacing, insufficient bar diameters, inadequate hook details, low-quality materials, and poor workmanship. The lack of seismic design principles or their improper implementation further increased the level of damage observed in the buildings. In this study, reinforcement-induced failure in columns and beams was evaluated in detail and observationally in the context of seismic and structural engineering. The main novelty of this work is the direct integration of these in situ post-earthquake field assessments with comprehensive 3D non-linear static simulations of 20 distinct structural models. Variations in parameters such as tie spacing, rebar diameter, bend angle of hooks, and structural material strength were numerically investigated through these models. It was determined that mechanisms close to fracture occurred, especially in columns, owing to deficient concrete compressive strength and transverse reinforcement deficiencies. Findings show that an upgrade in column shear capacity of up to 10% is achievable by reducing the spacing from 300 mm to 200 mm, whereas the implementation of a 135° hook anchorage substantially restrains the buckling of longitudinal reinforcement. As a key practical contribution, this study also proposes a specific FRP retrofitting design that successfully restores the lost shear capacity in all deficient columns. This blended field-and-computational strategy offers actionable, data-backed guidance for engineering design, the optimization of building regulations, and the identification of rehabilitation priorities in highly active seismic zones. Full article

Interest in applying hybrid retrofitting approaches to existing buildings is steadily increasing. In this study, an attempt was made to seismically retrofit an RC (reinforced concrete) building using CFRP (carbon fiber-reinforced polymer) and dampers. For this purpose, nonlinear time history analysis was performed. The placement of dampers in the RC frame required the use of panels. Panels do not interact with columns; however, the interaction between the panels and the beams was considered. First, the behavior of a single-story RC frame with panels was numerically analyzed using Abaqus 2017. Then, a typical old RC building was modeled in SAP2000 v26 under three configurations: its existing condition with hollow brick infill walls, a CFRP-retrofitted condition, and a condition retrofitted with a hybrid CFRP–damper system, in which lightweight concrete panels replaced the hollow brick infill walls. When the results were compared, the hybrid retrofitting approach with CFRP and Idrizi dampers reduced story displacement by 41.13–42.70% in the X direction and by 32.74–46.89% in the Y direction, on average. Base shear forces were reduced by approximately 31–33% in the X direction and 6–9% in the Y direction. Improvements were also observed in beam plastic hinge conditions. Thus, the hybrid approach was found effective for seismic retrofitting. Full article

This study explores the use of buckling-restrained aluminum shear-yielding panels (BRASYPs) as energy-dissipation devices. These are integrated into exoskeletons designed for sustainable interventions. A retrofit strategy was defined for a school building employing exoskeletons integrating BRASYPs. A displacement-based retrofit strategy was applied and validated through nonlinear time-history analyses. Results confirm the effectiveness of the intervention: the peak inter-story drift ratio remains below the collapse-prevention limit, and devices dissipate energy according to design. Full article

This paper presents a displacement-based design method for aluminum shear panels used in the seismic retrofit of RC buildings. The approach follows performance-based principles, directly controlling structural displacements while ensuring stable hysteretic behavior and concentrating damage in replaceable panels. The procedure links displacement demand to panel properties and geometry, enabling efficient design. A case study shows significant reductions in inter-story drift and residual deformations, improving seismic performance. The results demonstrate that aluminum shear panels are an effective and sustainable retrofit solution, offering reliable energy dissipation, easy replacement, and minimal impact on existing structures. Full article

Numerous existing RC frame buildings in China suffer from seismic deficiencies. This paper proposes a novel Π-shaped connector connection joint for the rapid strengthening of existing beam–column joints: steel plates are wrapped around existing columns, and Π-shaped connectors are welded to link new beam reinforcement. Quasi-static cyclic loading tests were conducted on one RC reference specimen and three strengthened specimens. The strengthened joints showed varying performance—two specimens (JGJ1 and JGJ2) exhibited peak loads below the RC reference, while the best specimen (JGJ3) achieved 9.8% enhancement in peak load and a nearly threefold increase in cumulative energy dissipation. The failure mode transitioned from brittle concrete crushing in the RC specimen to weld cracking and bolt fracture in the strengthened joints, thereby preserving the integrity of the core concrete. Finite element models were established using ABAQUS and validated against the test data. A parametric study investigated the effects of bolt quantity, beam and column dimensions, concrete strength, and steel plate thickness. The FE results indicate that increasing beam height from 400 mm to 450 mm yields the most significant improvement, with peak load increasing by up to 15.59% relative to the base parametric model. Favorable seismic performance was achieved with column concrete grade C50, beam concrete grade C40, steel plate thickness of 6 mm, eight bolts, and connector thickness of 6 mm. The proposed connection provides a potential strengthening alternative for existing RC frame structures. Full article

Staggered-floor steel-reinforced concrete beam–column joints are extensively applied in turbine buildings of nuclear power plants to meet the requirements of spatial layout and pipeline arrangement. Such joints feature distinct geometric discontinuity and suffer additional torsion effects as well as asymmetric stress distribution when the middle column is lost, which greatly impairs the structural progressive collapse resistance. In this study, three 1/5-scale joint specimens, consisting of two staggered-floor steel-reinforced concrete joints and one reinforced concrete joint, were tested under vertical monotonic static loading. The failure pattern, deformation property, torsional performance, strain development and load-bearing mechanism were comprehensively analyzed. Finite element models considering the coupling effect of torsion, bending and shear were established and validated via ABAQUS. The test results show that the peak load-bearing capacities of the SRC-1, SRC-2, and RC specimens were 148.2 kN, 149.7 kN, and 69.3 kN, respectively. Compared with the RC specimen, the peak load-bearing capacity of the SRC specimens more than doubled, indicating that the embedded H-section steel can significantly improve the load-bearing capacity of staggered beam–column joints. However, when the staggered height distance was increased from 140 mm to 280 mm, the ultimate collapse displacement of the specimens decreased from 340 mm to 310 mm, indicating a reduction in deformation capacity. The finite element model reasonably reproduced the specimens’ primary load–displacement response and damage characteristics, with a peak load error of 8.93% for SRC-1. Finally, corresponding design recommendations are put forward for staggered-floor steel-reinforced concrete joints in nuclear power plant structures. Full article