Search Results (74)

Originally proposed by the authors, the spring pendulum pounding-tuned mass damper (SPPTMD)—a novel nonlinear damping system comprising a spring pendulum (SP) and motion limiter that dissipates energy through spring resonance amplification and controlled mass-limiter impacts—was theoretically validated for structural vibration control. To experimentally verify its efficacy, a two-story, lightly damped steel frame was subjected to sinusoidal excitation and historical earthquake excitations under both uncontrolled and SPPTMD-controlled conditions. The results demonstrated (1) significant vibration attenuation through SPPTMD implementation and (2) enhanced control effectiveness in soft soil environments compared to stiff soil conditions. Additionally, a numerical model of the SPPTMD–structure system was developed, with computational results showing excellent correlation to experimental data, thereby confirming modeling accuracy. Full article

Power transmission tower-line systems are exposed to various dynamic hazards, including wind and earthquakes, among others. Despite the multitude of dampers proposed to mitigate vibrations, the dual control effect on both seismic and wind-induced vibrations has rarely been addressed. This paper introduces a comprehensive methodology for evaluating the reliability of power transmission towers under a range of dynamic disasters, encompassing both earthquakes and wind loads. Subsequently, a lifelong reliability approach was employed to assess the efficacy of a pounding tuned mass damper (PTMD). The proposed algorithm leverages the incremental dynamic analysis (IDA) method to compute structural fragility with regard to each type of disaster and integrates these findings with hazard functions to determine the probability of overall failure. The results conclusively demonstrate that the PTMD substantially diminished the towers’ dynamic response to both earthquakes and wind loads, thereby enhancing their overall reliability. Specifically, the PTMD reduced the vibration reduction ratio by 10% to 30% under wind loads and by 20% to 80% under seismic actions, with more pronounced effects at higher wind speeds and peak ground accelerations (PGAs). Furthermore, the reliability index (β) of the transmission tower increased from 2.1849 to 2.4295 when the PTMD was implemented, highlighting its effectiveness in dual-hazard scenarios. This study underscores the potential for reliability to be considered as a key metric for optimizing damping devices in power transmission structures, particularly in the context of multi-hazard scenarios. Full article

Corrosion costs the Oil & Gas Industry billions of pounds annually, primarily due to environmental factors such as high salinity, temperature fluctuations, and humidity in marine environments. Mobile Offshore Drilling Units (MODUs), especially jack-up rigs, are particularly susceptible to these dangers. This paper examines the impact of cold stacking on aging jack-up rigs and highlights how the absence of an adequate corrosion control system can accelerate structural deterioration. Our findings show that repair costs following cold stacking can far exceed the costs associated with maintaining rigs in a warm-stacked state. Preload tanks are critical areas prone to degradation due to microbiologically influenced corrosion (MIC) and inadequate preservation practices. Furthermore, although high-strength steels are frequently utilized in the construction of jack-up rigs due to their durability, we illustrate that, in the absence of meticulously devised preventative measures, these steels are susceptible to considerable corrosion, resulting in substantial repair expenses and diminished operational lifespans. This study highlights the significance of proactive corrosion control measures in maintaining the long-term structural integrity and cost-effectiveness of offshore drilling units. Full article

The present paper deals with the asymmetric seismic interaction phenomenon between multistorey reinforced concrete buildings. The paper focuses on the so-called floor-to-column pounding and aims to identify the influence of two specific factors: the exact impact point location and the width of the pre-existing separation gap between the interacting structures. Furthermore, the estimation of the effective impact length, i.e., the part of the external columns directly suffering the hit within their clear height that experiences severe damage, is attempted. For this purpose, several interaction cases are analyzed by means of inelastic dynamic analysis, and representative response quantities are calculated. In addition, a well-documented analytical procedure is applied in order to determine the effective impact length. The whole investigation highlights the crucial role of the impact point location for the local response of the external columns. On the contrary, it demonstrates that the overall building behavior is not considerably affected. In addition, it reveals that the existence of inadequate seismic joints may be more unfavorable in comparison with the complete absence of separation between the interacting structures. Thus, the relevant code provisions imposing a minimum seismic joint width should be strictly abided by. Finally, the investigation confirms field observations and experimental results which indicate that the damage of external columns which undergo strong pounding forces is limited to a short area with length equal to about 1 m or less. Due attention should be given to this area during retrofitting of existing buildings. Full article

In this study, the difference between the displacements of structures (relative displacement) is selected as the control parameter in pounding problems. During an earthquake, an increase in the amplitude of relative displacement between adjacent structures indicates a potential pounding condition. Within the scope of this study, the optimal distribution of linear viscous dampers between adjacent structures and the effect of soil on this distribution are investigated. The structure is intended to be modeled in two different ways through rigid and three sandy soil models (loose, medium-dense, and dense) at the foundation level. Different analyses are performed by changing the total damping coefficient considering the 1st and 2nd modes of the coupled models of adjacent structures. The study presents important findings on how to design dampers to prevent pounding problems in adjacent buildings, especially in seismically hazardous regions. Within this study, an adjacent building model 5-5 story is examined. The optimum damping coefficients are compared, and their effectiveness is demonstrated using the first periods of both adjacent building models. The proposed method in the study shows that it is possible to minimize the collisions of adjacent structures with the optimum placement of viscous dampers. The method shown is quite effective for the design of dampers that will be added to the structures later or at the initial stage. Full article

Seismic accelerations and interlayer displacements can be reduced by Laminated Rubber Bearings (LRBs) efficiently. Isolators would amplify the displacement of the superstructure by extending the natural period, thereby reducing acceleration and seismic damage. However, as a result, the risk of pounding with adjacent structures would be raised. This study investigated the seismic responses and overturning resistance capacity of base-isolated structures subjected to pounding against an adjacent structure. Parameter studies were conducted to evaluate the effects of gap size, pounding stiffness, and horizontal stiffness of the isolation layer. Results show that poundings are characterized by intense, short forces causing acceleration spikes, amplifying the overturning coefficient and risk. The overturning risk initially decreases then increases with gap size under pulse-like earthquakes, while wider gaps mitigate effects during non-pulse events. Increased pounding stiffness intensifies poundings, heightening vulnerability. The structure’s overturning resistance initially improves with increased horizontal stiffness of the isolation layer but declines excessively with further stiffness increase. Full article

This study investigates the seismic response of two 20-story adjacent reinforced concrete structures with differing lateral load-bearing systems, emphasizing the influence of soil–structure interaction. In total, 72 numerical models explored the combined effects of 9 earthquake motions, 4 soil types, and 2 structural designs. Analytical fragility curves revealed superior seismic resilience for the structure with shear walls compared to the bare frame structure. Shear walls increased the capacity to withstand earthquakes by up to 56% for each damage level. Soil behavior analysis investigated the effect of soil properties. Softer soil exhibited larger deformations and settlements compared to stiffer soil, highlighting soil ductility’s role in the system’s response. The study further assessed potential pounding between structures. The connection between structural stiffness and soil deformability significantly affected pounding risk. The provided gap (350 mm) proved insufficient to prevent pounding under various earthquake scenarios and soil types, leading to damage to RC components. These findings emphasize the crucial need to consider both structural systems and soil properties in seismic assessments. Full article

The substantial influences of masonry infills used as partition walls on the seismic behavior of multistory reinforced concrete (RC) structures have long been recognized. Thereupon, in this study, considering open-ground floors due to a lack of infills (pilotis configuration), the structural pounding phenomenon between adjoining RC buildings with unequal story levels and unequal total heights is investigated. Emphasis is placed on the impact of the external columns of the higher structure, which suffer from the slabs of adjoining shorter buildings. The developing maximum shear forces of the columns due to the impact are discussed and compared with the available shear strength. Furthermore, it is stressed that the structures are partially in contact, as is the case in most real adjacent structures; therefore, the torsional vibrations brought about due to the pounding phenomenon are examined by performing 3D nonlinear dynamic analyses (asymmetric pounding). In this study, an eight-story RC frame structure that is considered to be fully infilled or has an open-ground floor interacts with shorter buildings with n_s stories, where n_s = 6, 3, and 1. Two natural seismic excitations are used, with each one applied twice—once in the positive direction and once in the negative direction—to investigate the influence of seismic directionality on the asymmetric pounding effect. Finally, from the results of this study, it is concluded that the open-ground story significantly increases the shear capacity demands of the columns that suffer the impact and the inelastic rotation demands of the structure, whereas these demands further increase as the stories of the adjoining shorter building increase. Full article

Expansion joints render bridge structures highly vulnerable to damage during strong ground motions. Failures of expansion joints triggered by earthquakes not only jeopardize the post-earthquake serviceability of the bridge but also have a significant impact on the bridgeâs overall seismic performance. Despite extensive investigations and efforts to integrate these measures into design specifications aimed at mitigating the consequences of relative movements between adjacent bridge spans, major earthquakes have still revealed instances of damage related to expansion joints. On 6 February 2023, strong earthquake sequences occurred in KahramanmaraÅ, Turkey, with magnitudes of M7.7 and M7.6. The fault lines and epicenters of these shallow earthquakes were near the city and town centers and caused severe structural damage to buildings and infrastructures. There are approximately 1000 railway and highway bridges in the earthquake-affected region. Although both highway and railway bridges have generally performed well, some bridges experienced structural damage during the KahramanmaraÅ earthquakes. A large number of damage on the bridges is due to pounding and opening relative movements in expansion joints. This paper presents a comprehensive seismic evaluation of expansion joint failure mechanisms on bridges without viscous dampers during the 2023 KahramanmaraÅ earthquake sequences and an in-depth investigation into the seismic performance of bridge expansion joints equipped with viscous dampers and shock transmission unit devices are implemented utilizing the strong ground motion data collected throughout the earthquake sequences. It can be stated that the near-fault induced significant directivity and fling effects, resulting in notable velocity pulses and permanent tectonic deformations, and that these effects contributed to the failures of expansion joints, viscous damper devices, pot bearings, and shear keys. Full article

Almost every year, earthquakes threaten many lives, so not only do developing countries suffer negative effects from earthquakes on their economies but also developed ones that lose significant economic resources, suffer massive fatalities, and have to suspend businesses and occupancy. Existing buildings in earthquake-prone areas need structural safety assessments or seismic vulnerability assessments. It is crucial to assess earthquake damage before an earthquake to prevent further losses, and to assess building damage after an earthquake to aid emergency responders. Many models do not take into account the surveyor’s subjectivity, which causes observational vagueness and uncertainty. Additionally, a lack of experience or knowledge, engineering errors, and inconspicuous parameters could affect the assessment. Thus, a consensus-based Likert–LMBP (the Levenberg–Marquardt backpropagation algorithm) model was developed to rapidly assess the seismic performance of buildings based on post-earthquake visual images in the devastating Kahramanmaraş earthquake, which occurred on 6 February 2023 and had magnitudes of 7.7 and 7.6 and severely affected 11 districts in Türkiye. Vulnerability variables for buildings are assessed using linguistic variables on a five-point Likert scale based on expert consensus values derived from post-earthquake visual images. The building vulnerability parameters required for the proposed model are determined as the top hill–slope effect, weak story effect, soft story effect, short column effect, plan irregularity, pounding effect, heavy overhang effect, number of stories, construction year, structural system state, and apparent building quality. Structural analyses categorized buildings as no damage, slight damage, moderate damage, or severe damage/collapse. Training the model resulted in quite good performance (mse = 7.26306 × 10⁻⁵). Based on the statistical analysis of the entire data set, the mean and the standard deviation of the errors were 0.00068 and 0.00852, respectively. Full article

The development of nanocomposite photocatalysts with high photocatalytic activity, cost-effectiveness, a simple preparation process, and scalability for practical applications is of great interest. In this study, nanocomposites of TiO₂ Degussa P25 nanoparticles/activated carbon (TiO₂/AC) were prepared at various mass ratios of (4:1), (3:2), (2:3), and (1:4) by a facile process involving manual mechanical pounding, ultrasonic-assisted mixing in an ethanol solution, paper filtration, and mild thermal annealing. The characterization methods included XRD, SEM-EDS, Raman, FTIR, XPS, and UV-Vis spectroscopies. The effects of TiO₂/AC mass ratios on the structural, morphological, and photocatalytic properties were systematically studied in comparison with bare TiO₂ and bare AC. TiO₂ nanoparticles exhibited dominant anatase and minor rutile phases and a crystallite size of approximately 21 nm, while AC had XRD peaks of graphite and carbon and a crystallite size of 49 nm. The composites exhibited tight decoration of TiO₂ nanoparticles on micron-/submicron AC particles, and uniform TiO₂/AC composites were obtained, as evidenced by the uniform distribution of Ti, O, and C in an EDS mapping. Moreover, Raman spectra show the typical vibration modes of anatase TiO₂ (e.g., E_1g⁽¹⁾, B_1g⁽¹⁾, E_g⁽³⁾) and carbon materials with D and G bands. The TiO₂/AC with (4:1), (3:2), and (2:3) possessed higher reaction rate constants (k) in photocatalytic degradation of methylene blue (MB) than that of either TiO₂ or AC. Among the investigated materials, TiO₂/AC = 4:1 achieved the highest photocatalytic activity with a high k of 55.2 × 10⁻³ min⁻¹ and an MB removal efficiency of 96.6% after 30 min of treatment under UV-Vis irradiation (120 mW/cm²). The enhanced photocatalytic activity for TiO₂/AC is due to the synergistic effect of the high adsorption capability of AC and the high photocatalytic activity of TiO₂. Furthermore, TiO₂/AC promotes the separation of photoexcited electron/hole (e⁻/h⁺) pairs to reduce their recombination rate and thus enhance photocatalytic activity. The optimal TiO₂/AC composite with a mass ratio of 4/1 is suggested for treating industrial or household wastewater with organic pollutants. Full article

The 6th February 2023 Pazarcık and Elbistan earthquakes (M_w = 7.7 and M_w = 7.6) caused great destruction in many cities and were the disaster of the century for Türkiye. The greatest destruction was caused in the provinces of Hatay, Kahramanmaraş, and Adıyaman during these earthquakes, which were independent of each other and occurred on the same day. Information about earthquakes and strong ground motion records is given within the scope of this study. Reinforced concrete (RC) structures which constitute a large part of the urban building stock in the earthquake region were exposed to structural damage at different levels. The structural damage in the RC structures in the city center, Gölbaşı, and Kahta districts of the province of Adıyaman was evaluated within the scope of earthquake and civil engineering after field investigations. Insufficient RC, low-strength concrete reinforcement problems, RC frame failure, heavy overhang, short columns, soft story, and pounding effect are the main causes of the earthquake damage. The presence of these factors that reduce the earthquake resistance of RC structures increased the damage level. In addition, the fact that the earthquakes occurred nine hours apart and the continuation of aftershocks during that period negatively affected the damage levels. It has been observed that structures that receive the necessary engineering services during the construction and project phases ensure the safety of life and property, even if the structure is slightly damaged. In this study, we also tried to reveal whether the target displacements were satisfactorily represented by numerical analysis for a sample RC structure. Full article

Structures in proximity subjected to a substantial lateral load (e.g., wind and earthquakes) can lead to a significant hazard known as structural pounding. If not properly mitigated, such impacts can lead to local and global damage (i.e., structural failure). Mitigation approaches can include providing a suitable separation gap distance between structures, installing adequate shock absorbers, or designing the structure for the additional pounding impact loads. Wind-induced pounding of structures can be of higher risk to buildings due to large deflections developed during wind events. The current study develops various mathematical formulas to determine the suitable separation distance between structures in proximity to avoid pounding. The developed procedure relies first on wind-load evaluations using Large Eddy Simulation (LES) models. Then, the extracted wind loads from the LES are applied to finite element method models to determine the building deflections. Various building heights, wind velocities, and flexibility levels are examined to prepare a training database for developing the mathematical formulas. A genetic algorithm is utilised to correlate the required separation gap distance to the varying parameters of the tall buildings. It was found that more complex formulas can achieve better mapping to the training database. Full article

A proposal to control the structural pounding hazard imposed on multistory reinforced concrete (RC) structures is presented. The main goal is to guarantee the seismic performance of a structure with an acceptable (predefined) risk-targeted parameter without the need to eliminate structural pounding collisions. The key target parameters of this study are the annual probability of exceeding an engineering demand parameter (EDP) capacity level and the separation distance d_g between adjacent structures. In this direction, a method that ensures the performance level of critical EDPs due to structural pounding conditions is proposed. The new method involves two decision frameworks that define (a) the optimal separation gap distance $\left({\mathrm{d}}_{\mathrm{g},\mathrm{m}\mathrm{i}\mathrm{n}}^{{\mathrm{P}}_{\mathrm{t}}}\right)$ at a targeted value of pounding risk (probability per year) P_t (Decision A) and (b) the minimum acceptable structural pounding risk ${\mathrm{P}}_{\mathrm{m}\mathrm{i}\mathrm{n}}^{{\mathrm{d}}_{\mathrm{g},\mathrm{t}}}$ at a targeted value of separation gap distance d_g,t (Decision B). The demand parameters that are incorporated in the proposed method are the peak relative displacement δ_max at the top level of colliding without considering pounding conditions and any other critical EDP due to the structural pounding effect. The overall method is based on two distinct acceptable performance objectives, the POs-δ_max and the POs-EDP, defined as a function of P vs. d_g. For this purpose, a seismic hazard curve compatible with Eurocode’s 8 hazard zone is adopted, and the corresponding demand hazard curves of δ_max and EDP are developed. The proposed method is implemented to study the floor-to-floor structural pounding hazard of an eight-story RC frame taking into account different risk-targeted scenarios. The results show that the seismic risk (probability per year) of exceeding the EDP’s capacity level is significantly increased due to structural pounding in comparison to the case of no pounding. Calibration of the structural pounding risk can be obtained by adjusting the separation gap distance d_g between the adjacent structures based on the acceptable POs. The POs-δ_max is not always an accurate criterion for verifying the capacity level of the critical EDP. Finally, with the proposed method, a variety of POs-EDPs can be used to control the structural pounding risk in terms of ${\mathrm{d}}_{\mathrm{g},\mathrm{m}\mathrm{i}\mathrm{n}}^{{\mathrm{P}}_{\mathrm{t}}}$ and/or ${\mathrm{P}}_{\mathrm{m}\mathrm{i}\mathrm{n}}^{{\mathrm{d}}_{\mathrm{g},\mathrm{t}}}$. Full article

Replacing eggs without influencing pound cakes’ texture, appearance, and taste is challenging. Ovalbumin, the major protein in egg white, contributes to the structures of cakes by providing SH Groups that form a firm gel during baking. However, there is a shift in the consumers’ behaviour regarding health, well-being, animal welfare standards, and environmental concerns. To meet upcoming trends and consumer needs, 102 egg replacement products were launched globally to the best of the authors’ knowledge, with 20 of them advertised as suitable for baking applications. Ten locally available commercial egg replacers with a range of protein contents were chosen and applied in a pound cake model system to evaluate their functionality by evaluating cake and cake batter quality. Three different categories of egg replacements were chosen: replacers containing no protein (R1–R3), a low amount of protein (1–10 g/100 g; R4–R5), and a high amount of protein (>10 g/100 g; R6–R10). Those were compared to three control cakes containing powdered whole egg, fresh egg, and liquid whole egg. All the analysed egg replacers significantly differed from the control cakes, including low-protein egg replacement R4. Despite R4 achieving the highest specific volume (1.63 ± 0.07 mL/g) and comparable texture values, none of the examined egg replacers compared favourably with the egg control cakes regarding appearance, physical and textural properties, and nutritional value. Full article