Nonstructural Components Research Articles

Optimal design of self-centering bi-rocking braced frames using metaheuristic algorithms

Residual drift of structural systems after seismic events can make buildings uninhabitable and may cause their collapse in aftershocks, as seen in the 2023 Turkey-Syria earthquake. Self-centering rocking-core systems can eliminate plastic deformation of structures after earthquakes. In the current study, a bi-rocking steel-braced frame was designed using the modified modal superposition (MMS) method. The optimal location of the secondary joint was found to minimize the base shear, overturning moment, peak floor acceleration and inter-story drift. Damage to non-structural components has been considered. The models included 12-, 18- and 24- story frames that were subjected to far-field (FF), near-field-pulse (NP) and near-field-no-pulse (N) ground motion records. The seismic records were scaled to the maximum credible earthquake level. Nonlinear time-history analyses were performed using OpenSees open-source finite element software. Additionally, post-tensioned cables and energy dissipation fuses as variable parameters were optimized using particle swarm optimization. The performance of seven metaheuristic algorithms was compared and the results showed that placing the secondary joint at the mid-height of the structure reduced all seismic demand. The results also suggest that the story moment and FF records were most sensitive to the location of the secondary joint. It was observed that frames with lower stiffness and yield strength of the damper exhibited better seismic performance. Based on this, corrective percentages have been proposed for the design of the cable and dampers. A self-centering ratio of 1.07 was suggested at the mid-height and 1.19 for the base damper. The colliding bodies optimization algorithm performed best for time-history analysis-based optimization.

Probabilistic floor spectra for fully self-centering structures with flag-shaped hysteretic behavior

Self-centering structures are emerging structural systems developed for enhancing the seismic resilience of building structures by minimizing residual displacements. Various investigations were conducted to study the design methods and seismic performance of self-centering structural systems, but the research on nonstructural performance in self-centering structures is limited. This paper aims to develop the probabilistic floor spectra that can be used for designing the acceleration-sensitive nonstructural components in self-centering building structures under near-fault ground motions. To this end, comprehensive dynamic analyses were conducted to obtain the floor spectra. 320 near-fault ground motions were selected for considering the seismic excitation's uncertainty. The Anderson-Darling test was adopted to estimate the probabilistic distribution of the floor spectra. The test results indicate that the floor spectra follow the logarithmic normal distribution under earthquakes. The effects of the nonlinear properties of primary self-centering structures (including the initial period, hysteretic features, and structural damping) and the damping of the nonstructural components on the median and dispersion of floor spectra were discussed based on the parametric dynamic analysis results. The prediction model of the probability density function of the probabilistic floor spectra for self-centering structures was developed based on the artificial neural network algorithm. The software FloorSpectraNet was developed to facilitate practical applications.

Circular Economy: Upcycling Wood Byproducts from the Azores into Building Insulation Material

The promise of transforming wastes from the Azores into building materials is the focus of this research. The insulation properties of some of these materials can be advantageous to the building construction sector. These materials are upcycled into non-structural components of the building such as panels for ceilings and walls as a factor to control thermal comfort economically. In this paper, insulation panels using cryptomeria waste from the carpentry industry were developed and experimentally evaluated in terms of conductivity for further study of their thermal properties, as well as life cycle analysis. Sodium silicate was used as a primary binding material along with these treated materials. The different composite panels made from the waste and surplus materials are expected to be analysed in Test cells that are built in Azores using this together with other wastes available in the region. These panels will be tested for longer periods in these test cells subjected to the local climatic conditions. The results of thermal conductivity are promising for the two composites sampled.

Loading protocols for quasi-static cyclic testing of flexure dominated reinforced concrete circular bridge columns under crustal, subcrustal, and subduction earthquakes

Experimental procedures involving quasi-static cyclic tests have been the most prevalent for seismic performance assessments of structural and non-structural components and systems. However, there is a lack of consensus among experimentalists and researchers on a standard loading protocol. This study aims to propose a set of standard loading protocols representative of the seismic demands imposed on typical flexure dominated reinforced concrete bridge columns under uniaxial bending. Variable parameters: axial-load ratio, aspect ratio, longitudinal and spiral reinforcement ratios, concrete compressive strength, and steel yield strength were initially screened for significance in terms of their influence on the number of inelastic cycles and cumulative displacement ductility - two key reference parameters for the development of loading protocols. The number of inelastic cycles cumulative displacement ductility were then determined for reinforced concrete bridge columns having unique combinations of upper and lower levels of the significant parameters under different earthquake types (crustal, subcrustal, subduction) and displacement ductility demand levels (2, 4, 8). These target ductility demands intend to capture a wide range of structural responses including minimal and collapse damage states. Statistical analyses revealed that for the considered bridge columns, it is feasible to develop one representative loading protocol for each earthquake type and target displacement ductility demand level. Hence, nine loading protocols were proposed and then compared against equivalent loading protocols found in standards and literature. Standard protocols were found to impose unrealistic damage on bridge columns subjected to crustal and subcrustal earthquake hazards leading to inaccurate assessments. The proposed loading protocols for subduction earthquakes had a comparable number of inelastic cycles to those found in the literature for the same earthquake hazard and are representative of the seismic demands imposed on bridge columns.

Seismic loss assessment of code-compliant moment-resisting RC buildings located on different soil conditions of Mexico City

This research aims to estimate the expected economic losses associated with the repair cost of a set of code-compliant moment-resisting reinforced concrete buildings located on different soil conditions in Mexico City. The loss assessment methodology is based on the second generation of the Performance-Based Earthquake Engineering (PBEE) framework, which quantifies the seismic performance of buildings in terms of metrics such as economic losses, downtime, and casualties, which are more meaningful to owners and stakeholders for the decision-making process. The methodology uses a probabilistic approach that takes into account uncertainties in seismic intensity, structural response, component damage, and consequence prediction. The seismic response of structures was calculated in terms of inter-story drifts and floor accelerations to assess the damage to their structural and non-structural components. In addition, taking into account the seismic hazard of the site, the expected annual losses (EAL) are calculated to provide insight into the seismic performance evaluation of structures with different characteristics in terms of the financial impact in seismic-prone regions like Mexico City.

Graphite Nanoplatelets Nanostructured Films as Multifunctional Protective Layer in Kevlar/Nomex Sandwich Composites

In the aerospace sector, structural and non-structural composite components are usually subjected to a wide range of environmental conditions. Among all, moisture can seriously damage these materials’ performance, reducing their mechanical, thermal, electrical, and physical properties as well as their service time. Lightweight protective barrier coatings capable of reducing the diffusion of gases and/or liquids in a material can improve the material’s resistance in humid environments. In this work, nanolamellar nanocomposites characterized by a high in-plane orientation of nanoplatelets have been employed as protective coatings for Kevlar sandwich panels, reproducing the construction of a nacelle engine. The effectiveness of the protection against water uptake of nanocomposites reinforced with graphite nanoplatelets (GNPs) at high filler contents (70, 80 and 90 wt%) has been investigated using moisture uptake and Ground-Air-Ground (GAG) tests in an environmental chamber. GNP coatings effectively work as barrier by generating highly tortuous paths for molecule diffusion. Results showed a dependence of the absorption on the coating composition and inner structure. Films @70 wt% GNPs showed the best protection against moisture uptake by delaying the phenomenon and reducing the absorption by −80% after 3 days and −35% after 41 days.

Quantifying fire resilience of buildings considering the impact of water damage accompanied by fire extinguishment

The primary factor that affects the functionality of buildings due to fire is the deterioration caused by heating from hot flames and smoke. The application of water, whether by occupants, firefighters or sprinkler systems, takes an important role in reducing the intensity of the fire. However, it can lead to the impairment of non-structural components, equipment systems and stored items inside the building rendering them unusable and disrupting the building's functionality for an extended period. Past studies on fire resilience have mainly focused on assessing burn losses in buildings, neglecting the consideration of water losses. This study introduces a new approach that enables a reasonable evaluation of fire resilience of buildings by accounting for the water loss accompanied by fire extinguishment. The new approach is based on the physical prediction of water spread inside the building, which involves calculation of the changes in water levels in each room over time due to transfers between rooms through openings, staircases and gaps, and absorption by room boundary members. The estimated area of water damage is then correlated statistically with the time required for functional recovery, which allows for the assessment of fire resilience. To illustrate the proposed method, we conducted a case study on a four-story office building. When the fire originated on the fourth floor, water applied to the building spread through the corridors and staircases, with the extent of water damage decreasing on the lower floors. Additionally, we employed a Monte Carlo simulation with randomly assigned fire origins to quantitatively evaluate the impact of sprinkler systems on fire resilience. Comparing burn and water losses, we found that burn losses generally exceeded water losses in many cases. However, under specific fire and water application conditions, opposite results were observed, underscoring the importance of assessing both burn and water losses simultaneously for a comprehensive evaluation of fire resilience.

Development of a Simulation Model for Digital Twin of an Oscillating Water Column Wave Power Generator Structure with Ocean Environmental Effect

This research article focuses on developing a baseline digital twin model for a wave power generator structure located in Yongsu-ri, Jeju-do, South Korea. First, this study performs a cause analysis on the discrepancy of the dynamic properties from the real structure and an existing simulation model and finds the necessity of modeling the non-structural masses and the environmental factors. The large amounts of the ballast are modeled in the finite element model to enhance the accuracy of the digital twin. Considering the influence of environmental factors such as tide level and wave direction, the added mass effect of structural members, one of the hydrodynamic effects, depending on the change of the ocean environments is calculated based on the rule of Det Norske Veritas and applied. The results indicate that non-structural mass components significantly impact the dynamic characteristics of the structure. Additionally, environmental factors have a greater effect on the dynamic behavior of the box-type structure compared to lightweight offshore structures.

Equipment response spectra for wind turbines considering the baseline control system

As more and more wind turbines are installed in areas with high seismic intensity, various published works have studied the seismic performance of wind turbines. However, these studies usually focus on the wind turbine, and less attention is paid to the electrical equipment mounted on the wind turbine. Electrical equipment is a non-structural component on wind turbine, which is prone to failure and damage, resulting in the loss of function of the wind turbine. Therefore, it is necessary to study the seismic performance of the electrical equipment installed on the wind turbine. This study focuses on evaluating and quantifying the dependence of equipment spectrum accelerations on the location of the electrical equipment in the structure, the damping ratio of the equipment, and the baseline control system. The baseline control system is used to control the output power by adjusting the rotor speed and the blade pitch angle, which affects the equipment spectrum of the wind turbines. There is a stronger relationship between the equipment response spectrum and the peak floor acceleration. Therefore, the equipment spectral amplification function is calculated as the ratio of the equipment spectral acceleration to the peak floor acceleration for different height. The equipment spectra amplification function is proposed and validated to estimate peak acceleration demands on the design of electrical equipment placed on wind turbines. The results indicate that current seismic code provisions will not always provide an adequate characterization of equipment accelerations. And the effect of wind turbine baseline control and equipment damping is more pronounced in the range of the structural tuning period than in the non-tuning range.

Facade isolation in seismic design of tall buildings

Vulnerability of non-structural components in buildings subjected to earthquake incidents has caused human and financial losses in recent years. A part of such losses is related to the facade of buildings. In typical structures, facade assembly is directly connected to the structural system and is subjected to large lateral deformation during seismic actions. To reduce the level of earthquake-induced damage to the facade and the main structural system, the method of Facade Isolation (FI) is introduced. In this approach, facade frame is isolated from the main structural system using high damping flexible isolators. Numerical studies on the role of FI in a typical 15-story building with different facade configurations have been carried out in this work. According to the results of this study during seismic actions lateral drift response of facade frame in the isolated building is reduced to about 1/3 of that in the non-isolated one. This has happened while lateral force and drift ratio for the main structural system has also been reduced. In this approach facade frame serves as an integrated part of the structural system; to not only improve seismic performances of the building but to diminish the possibility of breakage and falloff for cladding materials during seismic actions.

Direct floor response spectra for nonlinear nonstructural components

Direct floor response spectra for nonlinear nonstructural components

Comparison on seismic resilience of hybrid, isolation, and damping control reinforced concrete frame-shear wall buildings

To investigate the effectiveness of different vibration control methods in realizing seismic resilience of reinforced concrete (RC) frame-shear wall structures, four cases with different control methods were designed, including the damping control building using energy dissipation cladding panels (EDCPs) (RCFSW7-D), isolated building (RCFSW7-I), isolated building with enhanced stiffness of superstructure (RCFSW7.5-I), and hybrid control building using both EDCPs and isolation (RCFSW7-H). The critical seismic responses and resilient performance of four cases were analyzed based on the Chinese code. Maximum inter-story drift ratios (MIDRs) of RCFSW7-I, RCFSW7.5-I, and RCFSW7-H under maximum considered earthquake were 36%, 51%, and 72% lower than that of RCFSW7-D, respectively. Although the stiffness of superstructure of RCFSW7.5-I and RCFSW7-H were approximately identical, the MIDR of RCFSW7-H was 44% smaller than that of RCFSW7.5-I. Meanwhile, the maximum absolute floor accelerations (MAFAs) of three isolated structure under MCE were approximately 70% lower than that of RCFSW7-D. The seismic resilience level of RCFSW7-D was Level 1, which is dominated by the damage of structural components (SCs) controlled by MIDR and acceleration-sensitive non-structural components (ASNSCs) controlled by MAFA. The seismic resilience levels of RCFSW7-I and RCFSW7.5-I successfully increased to Level 2, leading by the effectively control of MAFA and damage of ASNSCs. However, the MIDR was not sufficiently controlled even the stiffness of superstructure was increased. In contrast, hybrid control building significantly reduced both the MIDR and MAFA through the currently utilization of seismic isolation and EDCPs, especially the MIDR and damage of SCs, leading to a seismic resilience level of Level 3.

Precipitation pattern changed the content of non-structural carbohydrates components in different organs of Artemisia ordosica

BackgroundNon-structural carbohydrates (NSC) play a significant role in plant growth and defense and are an important component of carbon cycling in desert ecosystems. However, regarding global change scenarios, it remains unclear how NSCs in desert plants respond to changing precipitation patterns. [Methods] Three precipitation levels (natural precipitation, a 30% reduction in precipitation, and a 30% increase in precipitation) and two precipitation intervals levels (5 and 15 d) were simulated to study NSC (soluble sugar and starch) responses in the dominant shrub Artemisia ordosica.ResultsPrecipitation level and interval interact to affect the NSC (both soluble sugar and starch components) content of A. ordosica. The effect of precipitation on NSC content and its components depended on extended precipitation interval. With lower precipitation and extended interval, soluble sugar content in roots increased and starch content decreased, indicating that A. ordosica adapts to external environmental changes by hydrolyzing root starch into soluble sugars. At 5 d interval, lower precipitation increased the NSC content of stems and especially roots.ConclusionsA. ordosica follows the “preferential allocation principle” to preferentially transport NSC to growing organs, which is an adaptive strategy to maintain a healthy physiological metabolism under drought conditions. The findings help understand the adaptation and survival mechanisms of desert vegetation under the changing precipitation patterns and are important in exploring the impact of carbon cycling in desert systems under global environmental change.

Seismic acceleration demands in tall CLT buildings, predictive models and intensity measures

An accurate prediction of floor accelerations is crucial for estimating damage to contents and non-structural components in a building. Oversimplifying the nature of acceleration demands might result in biased estimates of building damage and consequently bias in the calculation of economic losses. However, given the relative novelty of multi-storey tall timber buildings, dedicated studies and models of their seismic acceleration demands are lacking. The need for these is stressed further when we recognise that the behaviour of walled timber structures is decidedly different from that of other conventional structural types. In this study, we apply modern data-driven approaches to evaluate efficient intensity measures (IMs) and develop regression models for predicting the peak floor acceleration (PFA) of multi-storey cross-laminated timber (CLT) buildings. Twenty-four IMs are evaluated and their prediction performance is compared. The sensitivity of acceleration demands to different IMs over a wide range of CLT buildings is investigated. We perform a systematic feature selection process using three different data-driven techniques. The selected features are then used to develop nine regression models to estimate PFA. Various modelling techniques, consisting of conventional (Linear and Polynomial regressions) as well as machine learning algorithms (Decision trees, Random forest, K-nearest neighbour, and Support vector regression) are used. The dataset used to train the models is obtained from numerical results of 69 CLT building models with variations in building height, panel fragmentation levels, and q-factors (ductility levels) subjected to a large set of strong earthquakes. After assessing the accuracy of our model predictions, their PFA estimates obtained are compared against previous research and design codes. Finally, simplified expressions for estimating peak floor accelerations in CLT structures are provided for practical purposes.

Machine vision‐based automated earthquake‐induced drift ratio quantification for reinforced concrete columns

SummaryThis paper presents a novel method for estimating the seismic peak interstory drift ratio (IDR) in reinforced concrete (RC) columns after an earthquake using surface crack image analysis. The quantitative representation of the complexity and irregularity of crack images in damaged RC columns is obtained through the consideration of the generalized fractal dimensions. The authors have compiled a comprehensive database consisting of 445 crack maps obtained from cyclic experiments conducted on 110 rectangular RC column specimens exhibiting double‐curvature deformation mode. This database is utilized by the authors to develop and validate the proposed procedure. The research database contains a wide range of structural and geometric features. Five closed‐form equations are developed with the objective of estimating the peak IDR experienced by the RC columns during a seismic event. The predictive equations are derived through the utilization of symbolic regression technique, with the input parameters varying according to the availability of columns characteristic parameters. Results reveal that generalized fractal dimensions, especially D−1, are strong vision‐based indicator of damage in RC columns having correlation coefficients with IDR ranging from 0.82 to 0.92 across the considered plans. The seismic peak IDR obtained through the empirical equations can serve as the input engineering demand parameter (EDP) in the seismic loss estimation frameworks. This allows for the determination of the probability of exceeding damage states for structural and nonstructural components of concrete buildings. Finally, the practical implementation of the methodology is examined by its application to an actual case of a damaged column during the Kermanshah earthquake of magnitude 7.3 that occurred in 2017.

Seismic resilience analysis of self-centering prestressed concrete frames with generalized flag-shaped hysteretic behavior

To increase the stiffness and energy dissipation of conventional self-centering concrete joints, this paper proposes a self-centering prestressed concrete frame with a generalized flag-shaped hysteretic behavior (GFS-SCPC). First, the working mechanism of the GFS-SCPC joint is clarified, and the key parameters affecting the generalized flag-shaped hysteresis are proposed: the second stiffness ksθ and the energy dissipation ratio βE. Subsequently, the three-dimensional self-centering prestressed concrete frame with flag-shaped hysteretic behavior (FS-SCPC) and GFS-SCPC frames are established, and the time history analysis and incremental dynamic analysis (IDA) method are carried out to compare their seismic performances. Finally, according to the FEMA P-58 specification, the resilience indexes of the frames with different hysteretic parameters are evaluated to clarify the influence of ksθ and βE. The results show that the energy dissipation capacity of the GFS-SCPC frame increases with larger second stiffness ksθ and the energy dissipation ratio βE. The increase of ksθ effectively controls the maximum drift angle and acceleration response of the GFS-SCPC frame, which would reduce the vulnerability of the structure. The main structure of the GFS-SCPC frame remains undamaged after the earthquake, and the loss mainly comes from the damage of the acceleration-sensitive non-structural components of the upper floors. The increase of ksθ can effectively reduce the damage degree of non-structural components and further reduce the resilience indexes, including casualties, repair time and repair cost, while the increase of βE alone does not significantly improve the resilience indexes. Therefore, the proposed GFS-SCPC frame with larger second stiffness has better seismic resilience performance.

Mixed reality drills of indoor earthquake safety considering seismic damage of nonstructural components

The damaged indoor nonstructural components in the earthquake often cause casualties. To improve the indoor earthquake safety capacity of occupants, a mixed reality (MR) drill method for indoor earthquake safety considering seismic damage of nonstructural components is proposed. First, an MR device, HoloLens, is used to capture indoor point clouds, and the indoor three-dimensional scene is reconstructed using point clouds. Subsequently, the seismic motion models of indoor components are established, so that the indoor nonstructural seismic damage scene is constructed using the physics engine and displayed using HoloLens. Finally, a guidance algorithm for a safe zone was designed for the drills. Taking a typical office as an example, an indoor earthquake safety drill was performed. The drill results show that the proposed MR method can increase the average efficiency of moving to a safe zone by 43.1%. Therefore, the outcome of this study can effectively improve the earthquake safety ability of occupants, thereby reducing casualties.

Serviceability evaluation of highway tunnels based on data mining and machine learning: A case study of continental United States

The appraisal of a tunnel service condition usually takes into account the lining deformations and defects of the lining structure, with the assessment technique heavily rely on the expertise of the evaluation. In this study, based on the US National Tunnel Inventory (NTI) database, a TOPSIS-CRITIC evaluation system was established to comprehensively evaluate the service performance of tunnels during the operation period from three categories of structural, traffic & civil, and non-structural components, resulting in the Tunnel Service Performance Index (TSPI). Then, a K-means clustering method was used to unevenly divide the TSPI of tunnels into service levels I ∼ IV. After consulting with experts, 23 important features were selected from 88 basic characteristics of tunnels, and further refined this list to 19 key factors using Spearman correlation analysis. These features were grouped into five categories: traffic, geological, space & time, planning & construction, and operational. Due to the imbalance of categories, SMOTE oversampling method was employed for data augmentation. Further, a TPE Bayesian optimized LightGBM classifier was proposed to predict the service level of tunnels and compared with nine common machine learning models (LR, KNN, SVM, DT, RF, GBDT, XGB, ET and MLP). After comprehensive experiments and numerical testing, the TPE-LGBM classifier achieved the highest overall performance among the ten models. Lastly, the SHapley Additive exPlanations (SHAP) interpretability model in conjunction with GIS spatial geographic information was employed to conduct an in-depth analysis of how full life cycle features impact tunnel service performance during operation.

Bioengineered Hybrid Rep 2/6 Gene Improves Encapsulation of a Single-Stranded Expression Cassette into AAV6 Vectors.

The production of clinical-grade recombinant adeno-associated viral (AAV) vectors for gene therapy trials remains a major hurdle in the further advancement of the gene therapy field. During the past decades, AAV research has been predominantly focused on the development of new capsid modifications, vector-associated immunogenicity, and the scale-up vector production. However, limited studies have examined the possibility to manipulate non-structural components of AAV such as the Rep genes. Historically, naturally isolated, or recombinant library-derived AAV capsids have been produced using the AAV serotype 2 Rep gene to package ITR2-flanked vector genomes. In the current study, we mutated four variable amino acids in the conservative part of the binding domain in AAV serotype 6 Rep to generate a Rep2/6 hybrid gene. This newly generated Rep2/6 hybrid had improved packaging ability over wild-type Rep6. AAV vectors produced with Rep2/6 exhibited similar in vivo activity as standard AAV6 vectors. Furthermore, we show that this Rep2/6 hybrid also improves full/empty capsid ratios, suggesting that Rep bioengineering can be used to improve the ratio of fully encapsulated AAV vectors during upstream manufacturing processes.

Assessing the feasibility of achieving functional recovery goals through seismic retrofit of existing reinforced concrete buildings

Damage from past earthquakes has significantly hampered post-earthquake building function, threatening community resilience, and motivating consideration of functional recovery in building design and assessment. This study examines whether it is feasible to achieve functional recovery in retrofit of existing reinforced concrete buildings, focusing on seven buildings retrofit with various motivations and strategies. The seismic response of these buildings was nonlinearly simulated, and functional recovery was probabilistically assessed. The results show that retrofits targeting life safety may or may not achieve functional recovery goals. Achieving functional recovery depends especially on the reduction of drift demands and collapse probability. However, the acceleration increase associated with many retrofits can increase function loss due to the criticality of acceleration-sensitive nonstructural components if such components are not retrofitted. We also examine other performance metrics, that is, economic losses and immediate occupancy limits of ASCE/SEI 41, showing that these provide imprecise, and in the case of the immediate occupancy conservative, proxies for functional recovery.