Adjacent Floors Research Articles

Predicting temporal evacuation travel time in staircases between adjacent floors of super high-rise buildings by artificial neural networks

Predicting temporal evacuation travel time in staircases between adjacent floors is crucial for dynamic evacuation guidance to improve vertical evacuation efficiency during emergencies in super high-rise buildings. However, the prediction methods used in previous studies mainly focus on the total evacuation time in buildings and cannot predict the temporal evacuation travel time in every single part of the total evacuation route. This study proposes a novel method to predict temporal evacuation travel time in staircases between adjacent floors of super high-rise buildings by using artificial neural networks. Firstly, evacuation simulation data of a 71-storey office building are analyzed for feature engineering and dataset building. Secondly, three types of artificial neural networks, including convolutional neural networks, RNN-based model (the traditional recurrent neural networks, long-short term memory networks, and bidirectional long-short term memory networks), and Attention-based model (Attention model and Transformer model) are extended to predict the temporal evacuation travel time in staircases between adjacent floors based on the simulation data. Finally, the prediction results by different artificial neural networks are compared. The results show that the artificial neural networks can provide accurate prediction values for the temporal evacuation travel time in staircases between adjacent floors of super high-rise buildings.

Noise control for curtain wall construction in residential buildings - a retrofit solution

In modern high-rise residential buildings, designers and architects utilize curtain wall construction either for the entire building or a portion of the building to achieve the desired visual impact in an urban setting. This poses significant challenges to satisfy the building code acoustical requirement (e,g., sound transmission class) between residential suites on adjacent floors. Apparent sound transmission class tests were completed after the curtain wall system was installed and concluded non-compliance with the Ontario Building Code acoustical requirement. A retrofit noise mitigation option was proposed and implemented. The ASTC field test was repeated and concluded compliance with the building code acoustical requirement.

Frequency response function-based closed-form expression for multi-damage quantification and its application on shear buildings

Vibration-based damage identification techniques have gained popularity immensely in the field of structural health monitoring (SHM). Frequency response function (FRF)-based damage quantification is mainly performed based on iterative model updating techniques. Most of these methods are time-consuming and erroneous in higher modes. Spectral element method (SEM) can overcome some of these limitations and can determine FRF expression directly for a broad class of civil structures. However, a closed-form expression for multiple damage severity is not proposed to date. In this study, an FRF-based formulation for quantifying damage has been proposed with the help of SEM in order to bypass the mode shape extraction for damage identification. To determine the effectiveness of the proposed formulation both numerical and experimental studies have been performed. A numerical simulation has been performed on a 14-storey shear building. Damage has been introduced by reducing the storey stiffness at intermediate and adjacent storeys. It has been perceived that damage severity at any storey can be estimated with only 3 sensors, one at the top storey and two others at the adjacent floors of the desired storey. To verify the effectiveness of the proposed expression, an experimental study has been carried out on a 9-storey miniature model. It has been observed that the first resonating peak amplitudes of the responses recorded simultaneously at desired locations of intact and damaged structures are sufficient to estimate the damage intensity. Thus, the proposed formulation is efficient as an output measurement-based approach. The novelty of this study lies in the proposed closed-form FRF-based multi-damage severity expression involving minimum number of sensors and without any information on the input excitation. The results obtained from both numerical and experimental study showcase the robustness, simplicity and applicability of the proposed formulation.

CNN‐based damage detection of buildings from wave propagation between two adjacent floors

AbstractStructural damages are expected to be detected from the changes in shear‐wave propagation in the vertical direction of the building. In the previous study, we constructed a convolutional neural network (CNN) model to recognize the changes in impulse responses at the inter‐floor with the virtual source at the top. However, it is difficult to tell the exact damaged stories, because it contains the information of all the stories between the virtual source and the receiver. In this study, to perform the story‐by‐story damage detection, wave propagation between two adjacent floors was proposed. The virtual source of the impulse response was changed from the top floor to the determined inter‐floor of the building. By recognizing the changes in the wavefield between the determined floor where the virtual source is located and its upper and lower adjacent floor, damages between two adjacent stories can be identified. The CNN model was used to automatically recognize the changes in the visualized impulse responses over time and validated using the data of a shake‐table test on a one‐third scaled 18‐story steel frame building.

Application of Data-Driven Building Information Modeling in the Visual Simulation of Disease Transmission and Route with Pipeline System

Currently, preventing epidemics is an extremely critical global topic. Using present data to quickly conduct virus simulations is a difficult but interesting problem, especially when real situations are difficult to experimentally demonstrate. In the past, most studies have used package software for disease transmission simulation, but this approach is limited by availability and software cost. Therefore, we propose a visual simulation of disease transmission using building information modeling data and a 3D model using Unity. The results show that the proposed method can effectively predict the probability and route of disease transmission; it also verifies that the vertical pipeline on the floor plane is conducive to the spread of the virus (90%), and disease transmission on the plane gradually expands outward from the starting room and has a higher probability of spreading (80%) from the opposite room. In addition, a vertical pipeline was simulated using a toilet exhaust air ventilation pipeline, from which it can be observed that the adjacent floors have a higher diffusion probability (70%). It has also been confirmed that distance is the primary factor affecting disease transmission. This framework may provide designers and managers further protection against the spread of future epidemics.

Učinak tla na kapacitet viskoznih prigušivača između susjednih zgrada

This study investigated the seismic pounding of two adjacent buildings considering soil–structure interaction (SSI). A comprehensive parametric study of buildings with different heights was performed to reveal the pounding-involved behaviour considering the soil effect. Wavelet transform has been conducted to gain insight into the differences in the frequency contents of the impact forces between fixed- and flexible-base adjacent structures. Linear viscous dampers (LVDs) between adjacent floors were used as pounding protection measures. The required supplemental damping ratio of the LVDs was determined through optimisation analysis under different soil types to verify the effect of the SSI on structural damping. Comparative results with and without SSI showed that incorporating the SSI worsens the pounding-involved responses during earthquakes.

Pyroclastic deposits of Ubehebe Crater, Death Valley, California, USA: Ballistics, pyroclastic surges, and dry granular flows

Abstract We describe and interpret deposits associated with the final Ubehebe Crater-forming, phreatomagmatic explosive phase of the multivent, monogenetic Ubehebe volcanic center. Ubehebe volcano is located in Death Valley, California, USA. Pyroclastic deposits occur in four main facies: (1) lapilli- and blockdominated beds, (2) thinly bedded lapilli tuff, (3) laminated and cross-laminated ash, and (4) massive lapilli ash/tuff. Lapilli- and block-dominated beds are found mostly within several hundred meters of the crater and transition outward into discontinuous lenses of lapilli and blocks; they are interpreted to have been deposited by ballistic processes associated with crater-forming explosions. Thinly bedded lapilli tuff is found mainly within several hundred meters, and laminated and cross-laminated ash extends at least 9 km from the crater center. Dune forms are common within ~2 km of the crater center, while finer-grained, distal deposits tend to exhibit planar lamination. These two facies (thinly bedded lapilli tuff and laminated and cross-laminated ash) are interpreted to record multiple pyroclastic surges (dilute pyroclastic currents). Repeated couplets of coarse layers overlain by finer-grained, laminated horizons suggest that many or most of the surges were transient, likely recording individual explosions, and they traveled over complex topography in some areas. These two factors complicate the application of classical sediment-transport theory to quantify surge properties. However, dune-form data provide possible constraints on the relationships between suspended load sedimentation and bed-load transport that are consistent using two independent approaches. Massive lapilli ash/tuff beds occur in drainages below steep slopes and can extend up to ~1 km onto adjacent valley floors beneath large catchments. Although they are massive in texture, their grain-size characteristics are shared with laminated and cross-laminated ash facies, with which they are locally interbedded. These are interpreted to record concentrated granular flows sourced by remobilized pyroclastic surge deposits, either during surge transport or shortly after, while the surge deposits retained their elevated initial pore-gas pressures. Although similar surge-derived concentrated flows have been described elsewhere (e.g., Mount St. Helens, Washington, USA, and Soufriére Hills, Montserrat, West Indies), to our knowledge Ubehebe is the first case where such processes have been identified at a maar volcano. These concentrated flows followed paths that were independent of the pyroclastic surges and represent a potential hazard at similar maar volcanoes in areas with complex terrain.

Cross-story installation of viscous dampers in timber frame houses for earthquake damage reduction

Timber frame structures are commonly used in housing construction that use squared-off timber beams, columns, and walls as lateral load-bearing members. A small-size viscous damper can be applied to timber frame houses to reduce damage caused by major earthquakes. Dampers are normally installed inter-story (between adjacent floors) to absorb vibration energy and reduce seismic response. Another method is the cross-story installation wherein a damper is installed between the rooftop and base of the structure across intermediate floors. This study investigated the effectiveness of cross-story installation of a viscous damper by conducting eigenvalue analyses of 2DOF models and earthquake response analyses of a two-story timber frame house subjected to the 2016 Kumamoto earthquake and other major earthquakes. We compared the damping factors and response reduction effects of the cross-story installation with those of conventional inter-story installations. The results showed that the cross-story installation of dampers was more effective than the inter-story installation in terms of reducing story drift. Furthermore, the cross-story installation reduced the number of dampers required for preventing severe damage by half. Finally, the cross-story installation allowed the viscous damper in the first story to absorb vibration energy nearly twice as much as that of the inter-story installation. Therefore, while the cross-story damper is typically installed on an outer frame fixed to the house, our results conclude that it can be applied to an existing house as a seismic retrofitting measure.

Shaking table test and seismic behavior of Ningbo Hengda Tower

SummaryA super tall building named Ningbo Hengda Tower is located in Ningbo City, China. It has 91 stories with a total height of 450 m. The structure system of the building consists of three parts, that is, the reinforced concrete core, the outer frame system, and the outrigger trusses connecting the core wall and outer frame. The unique outer frame system is spindle shaped with oblique columns. The outrigger trusses are located at three different levels above the ground, thus strengthening the building and creating irregularities in the stiffness of the structure along the building height. Great challenges are existed in seismic design and analysis of the building. Shaking table test was carried out for a 1/40 scaled model of the building under a series of different base excitations with increasing amplitudes. The dynamic properties, seismic responses, and failure mechanism of the structure are investigated. Test results show that the structure behaved well under designed level earthquakes. The weak points of the structure are identified based on visible damage of the tested model, and some suggestions are made for the improvement of the seismic behavior of the building. It is suggested that measures be taken to improve the ductility of the building from floor 71 to floor 79 and the adjacent floors.

ECC: Passenger Counting in the Elevator Using Commodity WiFi

Elevators have become a kind of indispensable facility for everyday life, which bring people both convenience and safety hazards. Specifically in the household environment, an elevator’s lifespan is expected to be more than 20 years. An appropriate and regularly maintained counterweight is conducive to extending elevator life. This paper proposes a passenger counting approach in the elevator for regular counterweight adjustment based on commodity WiFi called ECC. Since the running time of the elevator between two adjacent floors is short, the major challenge of ECC is how to count passengers from the limited captured data. This paper first theoretically analyzes the relationship between the number of passengers and the variation of channel state information (CSI). Then ECC constructs a multi-dimensional feature by extracting the average of amplitude (AOA), time-varying spectrum (TVS), and percentage of non-zero elements (PEM) features from the limited data. Finally, the random forest (RF) classifier is used for passenger counting and the local optimization problem is solved by expanding the feature dataset through data segmentation. ECC is implemented by using off-the-shelf IEEE 802.11n devices, and its performance is evaluated via extensive experiments in typical real-world scenes. The estimated precision of ECC can reach more than 95%, and more than 97% of estimation errors are less than 2 persons, which demonstrates the superior effectiveness and generalizability of ECC.

Shaking table testing of the reinforced concrete staggered slab-column structure

In order to study the seismic performance of the reinforced concrete staggered slab-column structure, one 1/7 scaled test specimen was fabricated and tested. The acceleration response, displacement distribution, dynamic characteristics, torsion responses, failure mechanism, shear force, and strain of test specimen were measured and evaluated. Test results indicated that the natural frequency and acceleration magnification factor of the test specimen gradually reduced, while the floor shear force and torsion response gradually increased. Meanwhile, the maximum inter-story drift angle of test specimen in the elastic and elastic-plastic stage was 1/196 and 1/78, respectively, indicating that the lateral stiffness of staggered slab-column structure was relatively small. The inter-story angles of the second and fifth floors were larger than adjacent floors. It was suggested that the stiffness of the test specimen was inhomogeneously distributed due to staggered slabs and a lack of frame beams. The damage of columns between staggered slabs was obviously larger than other columns. The plastic hinges were successively observed at slab-column junctions on the first and second floor and bottom of columns. Finally, the plastic hinges at slab-column junctions lost their capacity, followed by plastic hinges at the bottom of columns, and the test specimen collapsed. The failure process of the staggered slab-column structure exhibited undesirable brittle failure mode. Based on the experimental results, several design suggestions were proposed to improve the overall seismic behavior of the staggered slab-column structure. Such comprehensive research helps enhance understanding of this newly developed type of structure.

Optimal design and performance assessment of multiple tuned mass damper inerters to mitigate seismic pounding of adjacent buildings

This work investigates the efficiency of tuned inerter dampers (TIDs) in controlling seismic response of two adjacent buildings and the pounding distance between them. Pervious research on this subject has shown that installing TIDs in every floor of one of the buildings and coupling each floor of the two buildings with additional inerters (CS1) provides the best control performance. Some potential drawbacks of this solution are the large number of control devices used and practical difficulties associated with sharing inerters between adjacent buildings. To overcome these drawbacks, we propose a new configuration of TMDIs, called here as CS2. The proposed configuration makes use of much fewer control devices than CS1 and does not require coupling between the two buildings. Contrary to the findings of the published literature, we show that uncoupled control systems can be configured and tuned to be more effective than coupled systems. This superior performance of the proposed system is primarily due to the different arrangement of inerter devices in CS2 compared to that in CS1. In CS2, the inerters are connected to TMD masses rather than to the adjacent floors as is done in CS1. Performance assessment of the proposed solution and its comparison with CS1 is carried out through two numerical examples and several ground motions covering a large range of amplitude and frequency content. In the first numerical example, the adjacent buildings are of different heights but similar fundamental periods of vibration. In the second one, the buildings are of the same height but different fundamental periods of vibrations. These two examples cover cases of adjacent buildings facing lower and higher risk of pounding, respectively. The proposed solution is found to be effective and better than existing TID configuration in both the numerical examples studied here.

Investigation of Seismic Performance of Reinforced Concrete Buildings Having Stiffness Irregularity between Adjacent Floors

Türk Bina Deprem Yönetmeliği-2018’de (TBDY-2018) tanımlanan ve düşey doğrultuda düzensizlik durumlarından biri olan komşu katlar arası rijitlik düzensizliği (yumuşak kat), özellikle zemin katları ticari amaçlar nedeniyle üst katlardan farklı tasarlanan mevcut betonarme binalarda yaygın olarak görülmektedir. Yumuşak kat düzensizliğinin bulunduğu katta yer alan kolonlarda, deprem etkisi altında oluşan yerdeğiştirmeler sonucunda kırılmalar gerçekleşmektedir. Bu çalışma kapsamında, yumuşak kat düzensizliğine sahip mevcut 3, 5 ve 7 katlı mevcut betonarme binaların taşıyıcı sistem güvenlikleri TBDY-2018’e göre incelenmiştir. Mevcut binalarda, kat planı, kesit ve malzeme özellikleri aynı olarak alınmıştır. Doğrusal olmayan yöntemlerinden sabit tek modlu itme yöntemi, binaların deprem performanslarını belirlemek için kullanılmıştır. Bilgisayar analizleri SAP2000 yapısal analiz programı ile gerçekleştirilmiştir. Farklı zemin sınıflarında bulunan binaların taşıyıcı sistem elemanlarında oluşacak hasar durumlarını belirlemek için, analizler iki farklı zemin sınıfı için yapılmıştır. Mevcut betonarme binaların performans düzeyleri, farklı kat adetleri ve zemin sınıflarına göre karşılaştırmalı olarak sunulmuş ve önerilerde bulunulmuştur.

Overall stability design of T-shaped irregular concrete-filled steel tubular columns under axial compression

This paper presents investigations into the overall stability design of irregularly-shaped concrete-filled steel tubular columns with T-shape (T-ICFSTCs). The T-ICFSTC consists of I-steel, U-steel, and infilled concrete, forming a multi-cell steel tubular column. They are applied in the T-shaped sectional corner of the intersection between two walls in the residential buildings structures. The overall instability of the slender T-ICFSTCs may still be a significant concern in their strength design when they are placed in a higher spacing between two adjacent floors. This paper mainly focuses on establishing a design method for predicting the overall stability capacity of T-ICFSTCs subjected to axial load. Firstly, experimental investigations of an end-hinged T-ICFSTC and an end-fixed T-ICFSTC under axial load were carried out for checking its overall stability bearing capacity. Subsequently, the refined finite element (FE) model of the T-ICFSTCs is established and validated by the experimental results. In addition, the elastic buckling behavior of T-ICFSTC is studied by employing finite element (FE) eigenvalue buckling analysis, and the corresponding normalized slenderness ratio is obtained in the form of the Euler formula. Finally, based on the FE model validated experimentally, the parametric analyses of T-ICFSTCs are performed to investigate their overall stability capacities through changing the effects of steel ratio, sectional size, and material strength combination between concrete and steel. With these FE parametric analytic results, the overall stability coefficient φ, as well as φ-λ curves of T-ICFSTCs, are then obtained. These curves form the overall stability design formula of T-ICFSTCs loaded axially and apply in a common range of the percentage of load-carrying capacity shared by concrete. This design formula provides fundamentals to further develop a comprehensive design method of the T-ICFSTCs subjected to combined axial loads and moments.

Numerical Block-Based Simulation of Rocking Structures Using a Novel Universal Viscous Damping Model

Unreinforced masonry structures, particularly façade walls, are seismically vulnerable due to their weak connections with adjacent walls, floors, and/or roofs. During an earthquake, such walls formulate local mechanisms prone to out-of-plane collapse. This behavior has been largely investigated using classical rocking theory, which assumes the structure responds as a rigid body undergoing rocking motion, with energy dissipation at impact. Due to the complexity of the problem, however, e.g., number of degrees of freedom or boundary conditions, numerical block-based modeling is gaining momentum. However, numerical models lack a consistent and reliable treatment of the energy loss at impact. This paper bridges the gap between the well-established energy loss of classical rocking theory and the treatment of damping in numerical modeling. Specifically, it proposes an equivalent viscous damping model through novel ready-to-use predictive equations that capture the dissipative phenomena during both one-sided and two-sided planar rocking motion. The results reveal a satisfactory performance of the proposed model through comparisons with experimental results from literature and highlight its universality and robustness through applications of the model in fundamentally different block-based numerical modeling software.

Joint strengthening by external bars on RC beam-column joints

Column strengthening is a very common practice for improving the seismic performance of reinforced concrete frame structures or repairing damage after a seismic event. Several methods are employed for column strengthening, which can improve column strength by preventing its shear, bending or compression failure. However, not all methods allow column strengthening connections between adjacent floors, thus the beam-column joint strength could be limited by the column-joint interface capacity. This work aimed to analyse two joint strengthening designs, for which an experimental campaign of eight full-scale beam-column joints strengthened with steel caging, and subjected to cyclic and gravity loads, was carried out. As access to joint panels is very complex in existing structures, joint strengthening consists of external solutions: vertical or diagonal bars and capitals connecting columns. The results showed that these techniques significantly increased beam-column joint strength and highlighted that failure can be undesirably transferred to the joint. Vertical bars prevented the bending failure of the column-joint interface, but failure occurred at the joint in this study. Diagonal bars can also prevent joint failure.

Seismic Risks Mitigation of Façadism Constructions with Supplemental Energy Dissipation

Urban renewal projects typically involve redevelopments of under-utilized old buildings and revitalizing precious land resources. Due to architectural and social-economic reasons, historical facades are sometimes retained, and new constructions are built behind them. This allows the historical facade, typically the street elevation, to remain while new real estate can be redeveloped. In the profession of architecture, this is called facadism. In many cases, these historical facades are constructed with unreinforced masonry (URM). When these facades are retained and the remaining of the building is demolished, they become free-standing walls. Temporary supports are required throughout construction works and the retained facades must be designed to prevent excessive movements, allowed for differential movements and to resist wind forces. These historical facades were made of brittle materials and were constructed many decades ago before modern design standards and materials are available. They possess very little ductility and become vulnerable when subjected to ground shaking. The present study suggests a structural system that attempts to mitigate seismic risk of facadism constructions effectively. The structural system divides the new construction, which can be a reinforced concrete structure or a steel frame structure, into two separate frames. A seismic gap is introduced between them and produces two systems of different vibrational characteristics. Supplemental energy dissipating devices such as viscous fluid or friction dampers are placed in-between adjacent floors. The proposed structural system utilizes the different vibrational responses of two frames to facilitate energy dissipation in dampers. In this article, governing equations are presented, followed by numerical simulations using historical earthquake acceleration histories. Results demonstrate that the suggested structural system is an effective methodology to suppress seismic responses of the facade and the new construction. It is concluded that damage on the retained facades can be prevented, and at the same time seismic responses to the newly constructed structure can be controlled.

Composite Multiscale Cross-Sample Entropy Analysis for Long-Term Structural Health Monitoring of Residential Buildings.

This study proposesd a novel, entropy-based structural health monitoring (SHM) system for measuring microvibration signals generated by actual buildings. A structural health diagnosis interface was established for demonstration purposes. To enhance the reliability and accuracy of entropy evaluation at various scales, composite multiscale cross-sample entropy (CMSCE) was adopted to increase the number of coarse-grained time series. The degree of similarity and asynchrony between ambient vibration signals measured on adjacent floors was used as an in-dicator for structural health assessment. A residential building that has been monitored since 1994 was selected for long-term monitoring. The accumulated database, including both the earthquake and ambient vibrations in each seismic event, provided the possibility to evaluate the practicability of the CMSCE-based method. Entropy curves obtained for each of the years, as well as the stable trend of the corresponding damage index (DI) graphs, demonstrated the relia-bility of the proposed SHM system. Moreover, two large earthquake events that occurred near the monitoring site were analyzed. The results revealed that the entropy values may have been slightly increased after the earthquakes. Positive DI values were obtained for higher floors, which could provide an early warning of structural instability. The proposed SHM system is highly stable and practical.

Application of double glazed façades with horizontal and vertical louvers to increase natural air flow in office buildings

The results of previous researches clearly indicate that the main concern in applying double skin façades (DSF) is overheating of the cavity and increasing the cooling energy consumption in warm seasons. The present study intends to consider the excessive heat trapped between two skins of double glazed façades in hot arid climates as a driving force to reinforce the natural airflow across the floors of an office building. To meet this purpose, numerical simulation of airflow and heat transfer inside the cavity of the double glazed façades and the adjacent floors, as well as the effect of different types of solar shading systems in horizontal and vertical modes on the airflow has been investigated using the CFD technique. The results show that the stack effect formed inside the cavity has enough power for air suction from the floors of the building and reinforcement of the natural airflow. The type of shading device has a significant effect on the airflow behavior and the heat transfer rate in the facade. In double skin facades with horizontal louvers, the buoyancy forces inside the cavity are stronger and the ventilation rate in the building floors is higher than the model with vertical louvers. On the other hand, due to the stronger convective flow in the cavity with horizontal louvers, the heat flux on the interior glass is higher than the cavity with vertical louvers and part of the heat inside the cavity is transmitted through the interior skin to the occupied spaces.

New approximate method to identify soft story caused by infill walls

When the stiffness of a story is much less than the story above it, a significant portion of lateral displacement of the building is concentrated in this story and soft story is formed. One of the main reasons of soft story in buildings is eliminating or reducing the infill walls in lower stories. This reason is more important than the others because structural engineers usually neglect infill walls in modeling the structure, and on the other hand, architects do not consider the seismic behavior of infill walls during architectural design. In this research, based on the provision of soft story in seismic codes, 2277 macro models with different arrangements of infill walls in the adjacent floors were analyzed. By combining the three linear regression equations derived from the results of analyses, an approximate method was proposed for identifying the soft story. In this method, there is no need to the structural specifications and only by geometric specifications of architectural drawings, the arrangement of infill walls in adjacent stories can be checked. So, it can be used from the final stages of basic architectural design both by architects and structural engineers. The evaluation of this method on the analyzed models showed that 93% of models with soft story were identifiable by this method and in 97% of models, the results were reliable, which indicated high performance of this method.