1,720,987 research outputs found
Simplified pushover analysis for rapid assessment of shear‐type frames
Full text linkA simplified pushover method for rapidly assessing the seismic capacity of shear-type frames is presented. The frame global force-displacement capacity is described as a trilinear curve passing through three limit states (LS): Damage LS (DLS), Life safety LS (LLS), and Collapse LS (CLS). The global LSs are obtained consequently to the attainment of story-level, element-level, and section-level LSs. All LS capacities are described through closed-form equations. The validity of the proposed method is verified by applying it on several reinforced concrete (RC) frames with a varying number of stories. The results obtained with such an analytical procedure show a good match with those obtained from pushover based on finite element method (FEM) analysis models, in terms of both global force-displacement capacity curves and story displacements at various LSs. The proposed method has the potential to be conveniently applied in large-scale vulnerability/risk assessment studies, where the quality and quantity of the available data call for the use of simplified yet accurate models. More refined models would in fact require significantly heavier computational efforts, not justified by the quality of the results that are usually obtained. The simplicity of the proposed method in such a context is demonstrated through the development of the fragility curves of a five-story shear-type reinforced concrete frame, starting from a predefined set of mechanical and geometrical features characterizing a building typology
Lime-based mortar reinforced by randomly oriented short fibers for the retrofitting of the historical masonry structure
Full text linkRecent seismic events prompted research to develop innovative materials for strengthening and repair of both modern and historic masonry constructions (buildings, bridges, towers) and structural components (walls, arches and vaults, pillars, and columns). Strengthening solutions based on composite materials, such as the Fiber Reinforced Polymers (FRP) or the Fiber Reinforced Cementitious Matrix (FRCM), have been increasingly considered in the last two decades. Despite reinforcement made of short-fibers being a topic that has been studied for several years from different researchers, it is not yet fully considered for the restoration of the masonry construction. This work aims to experimentally investigate the enhancement of the mechanical properties of lime-based mortar reinforced by introducing short glass fibers in the mortar matrix with several contents and aspect ratios. Beams with dimensions of 160 mm × 40 mm × 40 mm with a central notch were tested in three-point bending configuration aiming to evaluate both the flexural strength and energy fracture of the composite material. Then, the end pieces of the broken beams were tested in Brazilian and compressive tests. All the tests were performed by a hydraulic displacement-controlled testing machine. Results highlight that the new composite material ensures excellent ductility capacity and it can be considered a promising alternative to the classic fiber-reinforcing systems
Effectiveness of Vibration-Based Techniques for Damage Localization and Lifetime Prediction in Structural Health Monitoring of Bridges: A Comprehensive Review
Full text linkBridges are essential to infrastructure and transportation networks, but face challenges from heavier traffic, higher speeds, and modifications like busway integration, leading to potential overloading and costly maintenance. Structural Health Monitoring (SHM) plays a crucial role in assessing bridge conditions and predicting failures to maintain structural integrity. Vibration-based condition monitoring employs non-destructive, in situ sensing and analysis of system dynamics across time, frequency, or modal domains. This method detects changes indicative of damage or deterioration, offering a proactive approach to maintenance in civil engineering. Such monitoring systems hold promise for optimizing the management and upkeep of modern infrastructure, potentially reducing operational costs. This paper aims to assist newcomers, practitioners, and researchers in navigating various methodologies for damage identification using sensor data from real structures. It offers a comprehensive review of prevalent anomaly detection approaches, spanning from traditional techniques to cutting-edge methods. Additionally, it addresses challenges inherent in Vibration-Based Damage (VBD) SHM applications, including establishing damage thresholds, corrosion detection, and sensor drift
Direct displacement-based design of dissipative bracings for seismic retrofit of reinforced concrete buildings
No full textA non-iterative direct displacement-based method is proposed for the design of dissipative bracings for seismic retrofit of gravity-load-designed (GLD) reinforced concrete (RC) frames. The design methodology aims at limiting the interstorey drifts of the GLD frame to prevent damage in the existing columns, by appropriately designing both stiffness and damping of the bracings. The method is based on a simplified yet accurate representation of the braced frame, through a socalled stick model, whose elements stiffness and damping are obtained by equivalent linearization of each braced storey. This allows performing a simplified modal analysis and obtaining an optimal design of the bracing system at each storey, both in terms of stiffness and damping. The design method efficiency has been validated by assessing the obtained performance of three GLD RC frames retrofitted with bracing systems and by comparing the outcomes with two other design methods available in the literature
Integrated solution-base isolation and repositioning-for the seismic rehabilitation of a preserved strategic building
Full text linkThis paper deals with the design of the seismic rehabilitation of a case-study building located in Florence, Italy. The particular reinforced concrete building hosts an important operational center of the main company that manages the Italian highway network. It is composed of the juxtaposition of three reinforced concrete edifices standing out from a common basement. The design of the interventions for the seismic rehabilitation of this case study posed different challenges, some even in contrast with each other. The main design challenge was to reach the seismic retrofitting, due to the strategic role of the activities hosted herein, safeguarding as much as possible the peculiarity of the architectural elements. Moreover, the design was made harder by the presence of existing thermal joints between adjacent edifices which were inadequate to prevent the latter from pounding upon each other during an earthquake. This outcome yielded the need to intervene by enlarging the gap between the adjacent buildings. This latter intervention was in stark contrast with the explicit request of the client to bring the least possible disturbance to the strategic activities carried out within it; in fact, the joints are crossed by optical fibers and other technological systems which can be damaged easily. The need to fulfill all these design constraints brought the development of an original design strategy based on the employment of base-isolation in a rather unusual configuration. The details of the design procedure, along with the innovative aspects and the designed devices, are presented. With the objective to refine the adopted strategy in view of its possible repeatability by colleague engineers, the paper also presents a fair discussion of every aspect with regards to both the design and the realization phases. Possible ideas for new research and developments are also highlighted
Thermo-mechanical characterization and hysteretic behavior identification of innovative plastic joint for masonry infills in reinforced concrete buildings
No full textModern approaches in buildings design strive to fulfill multiple performance requirements simultaneously. Accordingly, as far as buildings in earthquake-prone areas are concerned, damage limitation under seismic loads must be ensured while paying attention on the issues related to the environmental sustainability of the construction, ranging from its ecological footprint to the thermal efficiency. Masonry infills in framed reinforced concrete buildings are especially important in this context. In fact, they are vulnerable to earthquakes and greatly impact on the environmental sustainability of the building because they employ a significant amount of construction materials and influence its energy consumption throughout the lifetime. In light of this, the main novelty of the present work is concerned with a new deformable joint for masonry infills in framed reinforced concrete buildings. A detailed description of such innovative system for masonry infills is provided, together with numerical and experimental investigations about its mechanical and thermal behavior. The proposed joint is made of recycled plastic material, namely Regenerated Polypropylene Homopolymer.
Geometry and manufacturing process of the proposed joint are initially described. Then, stress–strain relationships for the plastic material are obtained from uniaxial tensile tests at different temperatures. An assembly of fired hollow clay bricks and plastic joints is also tested under in-plane cyclic load, and a phenomenological model is thus proposed to simulate the experimental hysteretic behavior. Finally, experimental tests and finite element-based numerical simulations are performed to investigate the thermal performance of masonry infills with plastic joints
Solidarizzazione di Muri Ortogonali tramite Barrette di AFRP: Modelli Analitici di Capacità e Riscontri Sperimentali
No full textLe costruzioni esistenti in muratura presentano talvolta strutture con muri ortogonali fra loro adiacenti ma non ammorsati convenientemente.
In caso di necessità di adeguamento sismico, può risultare utile accoppiare tali muri per aumentarne la rigidezza e la resistenza rispetto alle azioni orizzontali. Infatti, qualora il semplice consolidamento della muratura nel piano non sia sufficiente, l’accoppiamento dei muri può evitare di dover ricorrere all’inserimento di nuovi elementi strutturali. Un ulteriore vantaggio è poi rappresentato dall’incremento di stabilità dei singoli muri alle azioni trasversali.
In passato, interventi di questo tipo sono stati realizzati mediante l’impiego di iniezioni di malte cementizie o resine, armate con barre metalliche, che attraversano un muro trasversalmente e penetrano in profondità ancorandosi longitudinalmente nel secondo. Peraltro, tali interventi disturbano notevolmente la struttura muraria intima, arrivando anche a disgregarla localmente nella fase della perforazione, pur legandola di nuovo con la malta.
Si è quindi studiato e sperimentato un metodo di ammorsatura non distruttivo per il collegamento di due muri a T, operato con barrette sottili ( 5 ÷ 10 mm) di polimero rinforzato con fibra aramidica, che: a) attraversano in fori il muro “di ala”, secondo una inclinazione di ± 45°, b) si ancorano sulla faccia esterna di questo e lungo le superfici laterali del muro “di anima” mediante sfioccamento delle fibre e loro incollaggio sulla superficie muraria.
Il metodo, se dall’analisi strutturale risulta sufficiente il sistema dei muri collegati, permette di sfruttare i muri esistenti, senza aggiungerne di altri con le rispettive fondazioni.
Il programma delle prove comprende 3 muri già testati e altri 3 in fase di validazione sperimentale.
I campioni sono pannelli di muro alti circa 2 m, con due ali alle testate, realizzati in muratura a una testa. Essi sono stati sottoposti a prove quasi-statiche, con un carico verticale fisso e carico laterale alternato con cicli di ampiezza crescente.
Le prove condotte sul primo gruppo di campioni dimostrano l’efficacia della soluzione proposta, mentre i modelli analitici sviluppati in questa fase forniscono una buona stima degli incrementi di capacità flessionale
Incremental seismic retrofitting of infill walls using plastic joints and fiber-reinforced mortars: LCA, analytical modeling and size effect assessment
No full textIn high-seismicity areas, the behavior of non-structural components like double-layer infill walls is critical to building safety and post-earthquake functionality. This study introduces an incremental seismic retrofitting strategy that combines plastic dissipative joints and fiber-reinforced mortars (FRMs) to restore and enhance wall performance after significant in-plane (IP) and out-of-plane (OoP) damage. Plastic joints preserve panel integrity through controlled sliding and crack mitigation, while FRMs recover safety levels without requiring the removal of damaged infill. The incremental approach consists of a sequential intervention strategy carried out in distinct stages: i) plastic joints for damage prevention under moderate-to-high seismic events, and ii) FRMs for post-event reinforcement when damage exceeds the effectiveness of joints. This approach allows performance-based upgrades with reduced demolition, cost, and environmental impact. Experimental results are supported by analytical models and a Life Cycle Assessment (LCA) is proposed to evaluate the effectiveness of the Incremental Retrofitting Technique (IRT). Experimental results highlighted an out-of-plane size effect, with the flexural strength of fiber-reinforced mortar layers decreasing markedly when applied to full-scale masonry elements compared to standard laboratory prisms. To account for this behavior, an empirical bivariate fitting was performed, introducing two dimensionless parameters to represent the effect of structural scale and partial section utilization. The fitting expression enables a rational estimate of the nominal flexural strength in full-scale structures. Key findings indicate a full recovery of IP strength (C/NC = 1.13), a 50 % improvement in OoP capacity, and significant environmental and economic benefits of IRT over reconstruction, with savings up to 61 % in LCA indicators. The proposed size-effect model accurately predicts flexural behavior, with a deviation of only 4 % from experimental results
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