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Dynamic Response Prediction of a Cantilever Beam Under Different Boundary Constraints and Excitation Conditions Based on an Improved Physics‐Informed Neural Network
Zhang X., Zhu H., Xu W.
Q1
ABSTRACTThe cantilever beam structures, like wind turbine towers, space masts, solar wings, and high‐rise chimneys and buildings, are widely used engineering structures. It is crucial to fast and accurately predict their dynamic responses under complicated excitations. This paper establishes an improved physics‐informed neural network (PINN) called Fourier transformation‐PINN (FT‐PINN) for predicting the dynamic response of a cantilever beam subject to different boundary constraints and excitation conditions. The core idea of the FT‐PINN is to use the Latin hypercube sampling strategy for generating model training points and introduce multiple sets of control equations with different frequencies through Fourier expansion to achieve high solving accuracy and efficiency for partial differential equations. Two loss functions, including the mean square error and mean absolute error, are included in the FT‐PINN for comparison. Four test cases are designed to evaluate the performance of the FT‐PINN and classic PINN in solving dynamic equations of a cantilever beam structure with different boundary and excitation conditions. It is validated that the FT‐PINN model proposed in this paper has higher accuracy and efficiency than the classic PINN. This also provides a new approach for using PINN to handle local sharp gradients and complex high‐frequency problems in vibration equations.
Design Calculation of Deflection Curves of I‐Section Steel Beam With Longitudinally Profiled Flanges Under Concentrated Load
Yang D., Wang S., Xiuli D., Wang Z.
Q1
ABSTRACTWelded I‐beams with longitudinally profiled (LP) flanges (where LP steel plates are utilized as flanges) can be used to achieve structural optimization. However, its variable stiffness property poses a challenge for deformation design, which requires the formulation of computational equations. In this paper, the theoretical solution of the deflection curve under concentrated load at any position is derived using the unit load method and the mathematical integration method. The accuracy is verified by comparing with the finite element (FE) model. Further, a coefficient is introduced on the basis of the traditional flexural curve expression, and a simple design formula for the flexural curve is proposed by combining the location and coordinates of the load action, and the fitting coefficient is determined by fitting a nonlinear surface to a large number of theoretical results. The results show that the bending deformation MRE corrected by the bending deformation correction coefficient β is only −2.0%, which shows that the bending deformation correction coefficient has good accuracy and simplicity. The welded I‐beam with LP flanges elastic deformation design formulas established in this paper can be applied to the actual construction design of building and bridge structures, which will also promote the application of such advanced steel products.
Study on Mechanical Performance of Built‐In Octagonal Encase Steel Core Tube Fully Bolted Assembly CFSST Column Connection Joint
Zhang Y., Liu J., Zhang A., Li Y., Shen S.
Q1
ABSTRACTThis paper proposes a built‐in octagonal encase steel core tube fully bolted assembly CFSST column connection joint (OCFSST). The proposed static test study was carried out on this connection joint and the welded CFSST column connection joint (WCFSST), and the data were processed, analyzed, and compared in terms of hysteresis curves, skeleton curves, stiffness degradation, displacement ductility, bolt preload, strain changes, and the joint core area displacement angle. The average value of the horizontal bearing capacity of this joint is 5.60% higher than that of the welded CFSST column connection joint, which proves that this joint has better mechanical performance. The average difference of the hysteresis curves, skeleton curves, and stiffness degradation curves derived from finite element and test data is not more than 8.13%, which proves that the finite element simulation method is effective. In addition, octagonal encase steel core tube, self‐tapping bolts, and concrete have a good deformation co‐ordination property, which can ensure the safety and stability of the structure. The OCFSST meets the performance design goal of “strong joints, weak components” and can improve the site construction efficiency, which has a good prospect for application.
Studies on Wind‐Induced Fatigue Performance of Spacer Considering Galloping of Iced Conductors in Tall and Large‐Span Transmission Tower‐Line System
Rong K., Tian L., Wang X., Fan Y., Li N.
Q1
ABSTRACTTo investigate the influence of galloping on the fatigue performance of spacers in iced transmission lines, this study developed a coupled finite element model of a transmission tower‐quad‐bundled conductor‐spacer, along with a wind field model for quad‐bundled iced transmission lines, and the corresponding galloping loads are generated. A fatigue analysis method for spacers is proposed, and its fatigue performance and life under galloping conditions are assessed. Moreover, the influence of iced thickness and shape on spacer fatigue performance are analyzed. Results show that spacers connected to interphase spacers are most prone to fatigue damage during galloping. For crescent‐shaped iced, the highest fatigue damage occurs at a 10 mm iced thickness, 90° wind attack angle, and 10 m/s wind speed, with an average fatigue life of about 20 days. Dangerous spacers are located at the middle phase conductor for crescent, fan, and D‐shaped iced, with the most unfavorable wind attack angles being 90°, 0°, and 60°, and fatigue life of 13.35, 21.66, and 74.73 days, respectively. Spacer's fatigue damage increases with iced thickness, peaking at 10 mm. Crescent‐shaped iced causes the highest fatigue damage within the 30°–120° wind attack angle range, followed by fan‐shaped and D‐shaped iced. At 0° and 150°, fatigue damage values are similar for all iced shapes, while fan‐shaped iced results in the highest damage at 180°.
In Situ Dynamic Characteristic Test and Seismic Performance Analysis of Hybrid Brick‐Concrete and Timber Structure of Historic and Cultural Architectures
Wu C., Xue J., Bai F., Song D., Wang Z.
Q1
ABSTRACTIn order to study the dynamic characteristics and seismic performance of the hybrid brick‐concrete and timber (HBCT) structure, an in situ dynamic characteristic test was carried out, and peak picking method was used to calculate natural frequencies, damping ratios, and vibration modes. Considering semi‐rigid mechanical characteristics, a finite element model of the hybrid structure was established, and the calculation results agreed well with the test results. Kobe, El Centro and an artificial ground motion were input for displacement and acceleration response analysis. A set of fifteen ground motion records were selected, and incremental dynamic analysis and seismic fragility analysis were conducted. Results show that the first and second natural frequencies of the HBCT structure are 4.327 and 4.375 Hz, and the vibration modes are translation in the east–west direction and in the north–south direction, respectively. Taking the Kobe ground motion as an example, the maximum displacement of the pillar top of the second‐floor timber structure is 6.12 times that of the pillar top of the first‐floor brick‐concrete structure. The peak inter‐structural layer drift of 1/155 is less than the standard limit. Dynamic coefficients of the overall structure are less than 1, which indicates that the HBCT structure exhibits good shock absorption performance. The performance at different seismic intensities is in accordance with the “Three‐level and Two‐stage Seismic Fortification Goals,” which means no damage under minor earthquake, repairable damage under moderate earthquake, and no collapse under large earthquake.
Identification of Full‐Field Wind Loads on Buildings Using Displacement Measurements and Smoothing Kalman Filter Under Unknown Input Without Direct Feedthrough
Yin C., Yang X., Liu L., Yang S., Lei Y.
Q1
ABSTRACTCurrent wind load identification methods are mainly based on structural acceleration responses, which require the installation of many accelerometers on structures, to identify fluctuating wind loads that are assumed as independent white noise processes. With the development of machine vision, structural displacement responses under wind loads can be noncontact observed. In this paper, an identification method is proposed for full‐field wind loads including both the fluctuating and mean wind components on buildings using only structural displacement observations. Wind loads are treated as unknown forces on buildings without the assumptions of independent white noise processes of fluctuating wind loads in current identification methods. To reduce the number of independent unknown wind loads to be identified, the spatial correlations of wind loads are first analyzed. Then, as displacement observation equation does not contain the unknown forces, the smoothing Kalman filter under unknown input without direct feedback (Smoothing KF‐UI‐WDF) algorithm is used for wind load identification. To validate the effectiveness of the proposed method, both stationary and nonstationary wind loads on a 20‐floor shearing building are identified, and the identification results are validated in both time and frequency domains.
Experimental and Numerical Analysis of Plate–Fiber‐Reinforced Composite Double Coupling Beams
Tian J., Jiao S., Yu Q., Liu Y., Shi Q., Wang M., Zhao Y.
Q1
ABSTRACTCoupling beams characterized by a small span‐to‐depth ratio are particularly susceptible to brittle shear failures during seismic activities. To improve their seismic performance and alter their modes of failure, four distinct types of coupling beams were conceptualized, designed, and fabricated. The low‐cyclic reversed loading tests of the reinforced concrete (RC) single coupling beam, the RC double coupling beam, the plate‐reinforced composite (PRC) double coupling beam, and the plate–fiber‐reinforced composite (PFRC) double coupling beam were completed. The test results indicate that the double coupling beam demonstrates commendable ductility and a notable capacity for energy dissipation. It is beneficial for dissipating a significant amount of seismic energy and delaying damage to the wall limb. Adding steel plates to the double coupling beams can enhance their shear bearing capacity and prevent brittle shear failure. Substituting the matrix material with fiber‐reinforced concrete (FRC) significantly enhances the interaction between the concrete and the steel plates, leading to improved seismic performance of the coupling beams. Compared to RC double coupling beams, PFRC double coupling beams reach peak bearing capacity more quickly and exhibit an approximately 56.27% increase in bearing capacity. The axial forces exerted on the embedded steel plates within the PFRC double coupling beam are higher than those observed in the PRC double coupling beam. The use of fiber can improve the failure mode of the PRC double coupling beam. Finally, based on the experiments, a parametric analysis of the PFRC double coupling beams was conducted using ABAQUS software.
Seismic Behavior of Buckling‐Restrained Steel Plate Shear Walls With Various Interconnection Ratios
Zhao C., Yu J., Zhong W., Feng X., Zhang P.
Q1
ABSTRACTTo minimize the panel forces applied on the frame columns and to safeguard the high seismic performance of the inner steel plates, the concept of buckling‐restrained steel plate shear walls (BRSPSWs) with partial plate‐frame connections was proposed. However, further investigation is needed to promote the application of this structure to supertall and tall structures, particularly regarding the influence of interconnection ratio on the performance of BRSPSW with various partial connection forms. In this study, finite element (FE) models of BRSPSW with groove and four‐corner connections were established, and the influences of span‐to‐height ratio, height‐to‐thickness ratio, and interconnection ratio on the seismic performance were parametrically analyzed. Subsequently, calculation methods for the shear bearing capacity of partially connected BRSPSWs under different interconnection ratios were proposed, and 51 FE models were used to verify the accuracy of the calculation methods. The changes in span‐to‐height ratio and height‐to‐thickness ratio on the seismic performance indexes for two partial connection BRSPSWs with the increase of connection ratios were summarized. Recommendations for the interconnection ratios of BRSPSWs with groove and four‐corner connections were provided. Additionally, the calculation formulas for the shear bearing capacity of partially connected BRSPSWs can provide accurate predictions.
Theoretical Model and Shaking Table Experiment of Eddy Current–Enhanced Friction Pendulum Tuned Mass Damper
Du J., Du J., Bao C., Cao J., Yu Z., Ma X., Lu J.
Q1
ABSTRACTTraditional pendulum tuned mass dampers (PTMDs) necessitate substantial vertical space, and conventional friction pendulum systems (FPS‐TMDs) struggle to balance low activation thresholds with adequate damping levels due to their reliance on friction forces. This study presents an innovative eddy current–enhanced friction pendulum tuned mass damper (ECEFP‐TMD), which capitalizes on eddy current damping to lower the activation threshold effectively. Simultaneously, incidental friction damping provides a complementary dual–damping scheme. We developed a robust theoretical model, underpinned by shaking table experiments, to demonstrate the ECEFP‐TMD's superior vibration mitigation. Findings reveal that eddy current damping not only diminishes the activation threshold but also streamlines the adjustment of damping levels. The integrated dual–damping mechanism substantially augments energy dissipation, thus reducing the acceleration response of structures subjected to seismic activity. Particularly, for FPS‐TMDs with minimal friction coefficients, the inclusion of eddy current damping substantially elevates seismic resilience, mitigating stick–slip behavior typically induced by excessive friction damping.
Research on the Seismic Performance of Concrete Compressed‐Flexural Members After Cumulative Damage From 100 Years of Design Usage
Liu H., Liu M., Yang X., Wang L., Liu J.
Q1
ABSTRACTThis study investigates the long‐term effects of cumulative damage on concrete members over a century, emphasizing its critical inclusion in design protocols. Employing both static and dynamic experimental approaches, the research first examines the fundamental mechanical properties of damaged concrete at the material level. Earthquake intensity data from Northeast China are then analyzed to establish the frequency of predominant intensities over a 100‐year timeframe. Subsequently, four frame columns are exposed to cumulative pseudodynamic seismic damage, followed by pseudostatic testing to assess their seismic resistance. The results demonstrate that repeated sub‐cracking‐stress damage increases concrete's uniaxial compressive strength while reducing its ultimate deformation capacity. For elements with a low axial load ratio, minor seismic damage minimally impacts ultimate deformation but enhances ultimate bearing capacity, with the steel reinforcement reaching yield at an earlier stage. In contrast, for elements with a high axial load ratio, minor seismic damage has negligible effects on both ultimate deformation and bearing capacity, though it still accelerates the onset of yield in the steel reinforcement.
Axial Compression Performance of Square Steel Tube Steel Fiber Concrete Columns
Jia S., Xu X., Yang A., Hao W.
Q1
ABSTRACTThis study investigates the influence of microsteel fibers on the axial compressive properties of concrete‐filled square steel tubes (CFSSTs). Axial compression experiments and finite element analysis (FEA) were conducted on 10 specimens with varying steel fiber volume contents, steel tube wall thicknesses, and slenderness ratios to examine the failure modes, load–displacement curves, and ultimate bearing capacities of steel fiber‐reinforced concrete‐filled square steel tubes (SCFSSTs). Parameters such as force, ductility, energy dissipation capacity, and Poisson's ratio were assessed. The experimental results indicated that the addition of microsteel fibers can delay damage to the core concrete and buckling of the steel tubes. Specifically, increasing the volume content of steel fibers from 0% to 1.2% enhanced the ductility coefficient by 70%. Concurrently, both the energy dissipation and bearing capacities were improved as the steel fibers enhanced the postpeak performance of the CFSST. FEA was performed using the ABAQUS software to establish a steel fiber model. The FEA results were found to be consistent with the experimentally obtained load–displacement curves, and a parameter analysis was performed for further study. Finally, the applicability and accuracy of the four current international codes for calculating the ultimate bearing capacity of SCFSST were evaluated.
Structural Stressing State Characteristics for Unbonded Prestressed Concrete Continuous Slabs Under Different Fire Conditions
Yang C., Dong Y., Qi J., Duan J., Zhang D.
Q1
ABSTRACTThis paper reveals the general working law of unbonded prestressed concrete (UPC) continuous slabs under different fire conditions by applying the structural stressing state theory. Firstly, the experimental deflection data are transformed into generalized work of force (GWF) values to represent the structural stressing state and the corresponding characteristic parameters. Then, the Mann–Kendall criterion is adopted to detect the mutation points where the characteristic parameter curves show a trend change with increasing temperature. Accordingly, it is verified that the evolutions of stressing state modes also present the corresponding mutation characteristics. The stressing state mutations reveal the linear‐elastic branch (LEB) points, elastoplastic branch (EPB) points, and failure starting (FS) points of the continuous slab's working process, complying with the natural law from quantitative change to qualitative change of a system. Finally, the formula is fitted to calculate the failure loads with a verification, and the existing failure loads were redefined to provide a new and valuable reference for analyzing the working behavior of UPC continuous slabs in fire.
Shaking Table Tests of Underground Substation Considering Soil–Structure–Equipment Interaction
Zhihao W., Jing L., Guanglin P., Wei Z., Longfei J., Peng L., Bo W., Yongkang K., Fan Z., Peng X.
Q1
ABSTRACTTo investigate the seismic dynamic response characteristics of underground substations, considering the interaction among soil, structure, and equipment, a model soil field shaking table test with a similarity ratio of 1:25 was conducted. Detailed analysis was conducted on the acceleration amplification factors, Fourier amplitude spectra, and displacements of soil, structure, and equipment during the experimental process. The experimental study revealed the following findings: It was concluded that the seismic excitation had a significant impact on the acceleration response of equipment near the edges of the structure, demonstrating an amplification effect. Both the acceleration amplification factors of the station structure and the site generally decreased with increasing input seismic intensity. As the seismic intensity increased, this decreasing trend gradually weakened. Additionally, the peak values of acceleration Fourier spectra often decrease with increasing burial depth. The examination of the postearthquake model system revealed the presence of surface cracks in the soil, which exhibited varying degrees of severity. These cracks were observed both parallel and perpendicular to the direction of excitation, with a significant concentration of soil fissures occurring directly above the structural elements.
Research on Integrated Technology of Overall Aerial Building Formwork Equipment and Concrete Placing‐Boom
Tingchen F., Jian G., Desheng Y., Fengyu, Yimin Z.
Q1
ABSTRACTThe overall aerial building formwork is an independently invented support equipment in China, specifically designed for the construction of concrete structures in super high‐rise buildings over 200 m. The integration of a concrete placing‐boom and integrated aerial building formwork equipment plays a crucial role in this new type integrated system. This article provides a comprehensive summary and analysis of the integrated connection structure between the existing concrete placing‐boom and the overall aerial building formwork equipment. It also presents an innovative design for a lightweight unit‐type formwork concrete placing‐boom integrated platform, along with detailed explanations of its structure design and construction process. Furthermore, calculations and analyses were conducted to determine maximum stress and deformation under various conditions such as climbing, steel bar binding and formwork synchronization operation and concrete pouring by using MIDAS finite element software. The results demonstrate that the maximum stress and deformation meet the control requirements effectively. This article invents a novel overall aerial building formwork equipment integrated with a concrete placing‐boom, compared to the existing integrated platform, the lightweight unit‐type formwork concrete placing‐boom integrated platform offers advantages including flexible assembly, strong structural applicability, excellent safety performance, high construction efficiency, superior load‐bearing capacity as well as overall performance enhancement. These features make it more suitable for meeting the specific construction needs of super high‐rise buildings over 200 m, and provided a new equipment for the construction of super‐high‐rise reinforced concrete core.
Seismic Performance of Shaped Steel Reinforced High‐Strength Concrete Walls: Cyclic Loading Test and Analytical Modeling
Zhang Q., Ma L., Zhao B., Ding K., Ni X.
Q1
ABSTRACTThe thickness of the bottom shear walls in tall and super‐tall structures is often designed too large to meet the limit requirements of axial compression ratios, which increases the weight and cost of the structure. To address this issue, high‐strength concrete (HSC) and shaped steel are combined to form composite shear wall members. This paper focuses on seismic performance and analytical hysteresis model of steel reinforced HSC shear walls (SRHCW) under high axial compressive load. Firstly, the reversed cyclic test was conducted to investigate the influence of concrete strength and the steel ratio on the seismic performance of SRHCWs by comparing the failure mechanism, hysteretic curves, stiffness degradation, ductility, energy dissipation, and steel bar strain variation of each specimen. Then, a hysteresis model for SRHCWs was established, and the model can be used for the nonlinear analysis and seismic performance evaluation of SRHCWs. Finally, the accuracy of the proposed hysteresis model was evaluated by the experimental data. The experimental results show that under high axial compression ratio, the interstory drift ratio capacity of SRHCWs can reach 3.03% showing excellent deformation performance. The wall specimens built with different strength concrete and shaped steel ratios exhibited similar strength, deformation, and initial stiffness, indicating that the steel ratio of the wall can be effectively reduced by upgrading the concrete strength of the wall specimens while ensuring its seismic performance. The analytical model can well predict the hysteresis force–deformation curves of SRHCWs under high axial load ratios.
Stability Study of Single‐Layer Spherical Shell Roof Under Nonuniformly Distributed Snow Load
Jianshuo W., Tinghao M., Zhihua C., Haonan G., Xiaoyu G., Hao W.
Q1
ABSTRACTAfter snowfall, the snow load distribution on building roofs is generally nonuniform, and most cases of large‐span structural collapse are related to nonuniform load. The existing regulations provide limited snow distribution coefficients for different roofs, and with the diversification of building forms, they can no longer meet the current calculation requirements for roof snow loads. This article conducts numerical simulations of wind‐induced snow drift on a spherical shell roof, which rise‐span ratio is 1/5. It is found that the friction velocity of the roof is distributed in a band shape and is higher in the windward direction, whereas the friction velocity on the leeward side is lower, which increases the possibility of snow accumulation. Based on this, a simplified snow load distribution model is proposed to improve the economic efficiency of the project. Based on the above research, the stability analysis of K6 single‐layer Kevitt mesh shell was carried out using ABAQUS finite element software. The results show that under uniformly distributed load conditions, the buckling modes of the structure are symmetrical, whereas under nonuniform snow load conditions, the first mode deforms more on the side with higher load, and the position of structural deformation is closer to the edge; when the snow cover range is the same, the larger the extreme snow load, the more unfavorable it is for structural stability; when the extreme snow load is the same, the smaller the snow coverage, the more unfavorable the initial defect is for structural stability.
Numerical Investigation and Cross‐Section Type Selection of Concrete‐Filled Double Steel Plate (CFDSP) Composite Shear Walls Under Cyclic Loading
Cobanoglu O., Ni X., Zhao B.
Q1
ABSTRACTConcrete‐filled double steel plate (CFDSP) composite shear walls have excellent seismic performance and are generally used as lateral resistance for high‐rise buildings. However, the numerical simulation of such walls is complicated because of the complex contact between the concrete, the external steel plate, and the shear studs. Eighteen CFDSP walls in the present literature were numerically simulated under cyclic and constant axial loading, and the accuracy was evaluated by comparing them with the experimental results. Then, the impact of cross‐section variations on the structural performance of CFDSP walls under the same steel content ratio was numerically investigated. Designed numerical walls were evaluated under the same loading conditions with four distinct cross‐sections for comparative analysis. Finally, parametric analysis was performed to observe the influence of aspect ratio, steel thickness, and stud spacing on the seismic performance of CFDSP walls. The analysis results show that the proposed numerical model can accurately recover the hysteretic curves of CFDSP walls regarding strength reduction, energy dissipation, and pinch behavior.
Effects of Attached Afterbody Shapes on Wind Forces on Rectangular Tall Buildings
Li M., Li Q., Li Y.
Q1
ABSTRACTThe knowledge of aerodynamic forces has important implications for the wind‐resistant design of tall buildings. At present, the aerodynamic characteristics of conventional rectangular‐shaped tall buildings have been extensively studied, while those of irregular‐shaped tall buildings have received relatively less attention. Therefore, in the current study, several tall building models are designed to investigate the aerodynamic characteristics of a rectangular tall building with and without attaching different shapes of afterbody. The influences of the afterbody shapes (i.e., semicircle, rectangle, and triangle attached to a rectangular tall building called the basic model in this paper), atmospheric boundary layer (ABL) flows, and models' aspect ratios on the aerodynamic forces are analyzed and discussed in detail based on wind tunnel test of pressure measurements on the models. It is shown that the attached afterbodies can significantly increase the local fluctuating lift coefficients and base fluctuating moment coefficients comparing to those of the basic model. Moreover, a larger aspect ratio causes the increase of local fluctuating lift coefficients and base fluctuating moment coefficients of the basic model attached with rectangular afterbody in suburban terrain. On the other hand, the above increases are strongly attenuated or even suppressed by the ABL flow over urban terrain. The results of this study are expected to provide useful information for the wind‐resistant design of irregular‐shaped tall buildings.
Analysis of the Seismic Vulnerability of a Masonry Pagoda Based on Increasing Dynamic Analysis
Lu J., Jia X., Li M., Wang Z., Tian J.
Q1
ABSTRACTFor the seismic vulnerability analysis method of masonry pagodas, the dynamic characteristic of the Bayun Pagoda in China was conducted by using environmental excitation technology. A numerical model of the masonry pagoda was established with the finite element software Abaqus. Ten seismic waves were selected as excitation signals to conduct incremental dynamic analysis (IDA) on the pagoda. The Sa(T1,5%) served as the seismic intensity indicator, whereas the damage factor (d) and relative stress () were employed as damage indicators for seismic vulnerability analysis of the pagoda. The failure probability of the structure reaching the limit state under different seismic intensities was determined. The results indicate that, comparing the IDA curves and seismic vulnerability curves under two different damage indicators, the Sa(T1,5%) range required for the IDA curves under the damage factor (d) is smaller than the relative stress (), with lower dispersion. Additionally, the failure probability of the pagoda reaching different limit states is higher under the damage factor (d). Considering the existing damage status of the masonry pagoda, the damage factor (d) is more reasonable as the damage indicator.
Simulation and Deformation Analysis of Construction Process of Large Eccentric Frame‐Core Tube Structure
Yin G., Zhang D., Ma X., Wang K., Wang X., Lin X.
Q1
ABSTRACTThe large eccentric frame‐core tube structure may generate nonnegligible horizontal deformation in the eccentric direction during the construction process, which should be given due attention. The construction process of a 388‐m‐high super high‐rise structure was simulated with the effects of concrete properties and construction processes. The reinforcement effect of steel bar in reinforced concrete shear wall and the hoop effect of steel tube in concrete filled steel tube (CFST) columns were considered by using the two‐cell simulation method, respectively. The accuracy of the finite element model was effectively verified based on the measured data under different construction process. The results show that the construction process has a large influence on both the vertical and horizontal deformation. The measures of construction leveling effectively reduce the vertical and horizontal deformation of super high‐rise structures, which is important for controlling the structural deformation. The proportion of creep‐shrinkage deformation in the total deformation is large. In this case, the proportion of creep‐shrinkage deformation in the shear wall is 45% to 50%, whereas it is about 30% in the frame columns. The eccentricity caused by floor slab gravity will be mitigated if the construction of the frame slab lags behind the construction of the steel frame, which is beneficial to the control of the horizontal structural deformation. After construction completion, the deformation caused by nonload factors is limited compared to the deformation caused by live loads.
Design Method of a Novel Interface Connection Device for Multiscale Test Model Considering Multiparametric Similarity of Internal Forces
Li G., Wang R., Dong Z., Yu D., Zhou C., Zhang H., Li J.
Q1
ABSTRACTThe multiscale model of building structures, as a balanced solution between accuracy and cost, has been widely used in the analysis of structural seismic performance. A reasonable interface connection method can accurately ensure load transfer and motion coordination between models of different scales. In this paper, a novel interface connection device and the corresponding design method for a multiscale test model of building structures were proposed, in which the upper structure with smaller sized components was replaced by a simplified story‐scale model, and the lower structure was adopted as a component‐scale model. The overall and local equations of motion for this multiscale model were established. For the interface connection between different scale models, a design method considering multiparametric similarity of shear force, axial force, and bending moment was proposed. In this method, the internal nodes at the interface of the component scale model were decomposed, and the coupling relationship of internal force between two adjacent nodes was established. The axial force of each node was decoupled into the interstory shear force and bending moment provided together. Additionally, the overturning moment is provided by adding the overlapping domain. According to the equilibrium relationships of the nodes at the interface, the corresponding transfer matrix was provided, and the design method of the interface connection device was proposed. The accuracy and feasibility of the method were validated by static and shaking table tests on a frame structure.
Quantitative Study of Thermal Response of Timber–Concrete Composite Structures Under Traveling Fire Using Energy Equivalence Method
Zhang Y., Li L., Zhang L., Zhang X., Ni W., Wang L.
Q1
ABSTRACTThe time equivalent method can be used to quantify the fire intensity of a traveling fire into the time of action of the standard fire, which in turn can be used to assess the extent of damage to a structure under a traveling fire. However, an effective time equivalence method for timber structures has not been developed yet. Therefore, this paper proposed an energy‐based time equivalent method, referred to as the “energy equivalence method (EEM)”, for evaluating the fire resistance of timber structures under traveling fire, and validates its effectiveness through a series of fire tests. The results demonstrate that the EEM effectively quantifies the fire intensity endured by glulam under traveling fire as the equivalent exposure time under the standard fire. Furthermore, the EEM was utilized to investigate the damage behavior of a single‐layer Timber‐Concrete Composite (TCC) frame under traveling fire. The results reveal variations in the fire intensity experienced by the structure at different locations under the same traveling fire scenario, with the most severe damage occurring at a position 40% relative to the ignition end. The fire scale determines the non‐uniformity of the fire intensity and the extent of structural damage, as smaller‐scale fires (fire sizes between 10% and 40%) not only result in significant variations in damage levels at different locations but also have a more adverse impact on the structure. In fire safety design, the selection of standard and traveling fire design methods should be based on the fire scale.
Progressive collapse resistance of prestressed concrete frame structures with infill walls considering instantaneous column failure
Qu T., Zeng B., Zhou Z., Huang L., Chang D.
Q1
AbstractPrestressed concrete frames with infill walls (IW‐PC frames) are commonly used in civil engineering as a structural element. The possibility of structures undergoing progressive collapse is a cause for concern due to its severe consequences. This has become a significant topic in the academic community in recent years. However, research on the resistance of IW‐PC frame structures to progressive collapse is still insufficient. Therefore, this paper investigated the dynamic effects of progressive collapse on the IW‐PC frame, reinforced concrete frame with infill walls (IW‐RC), prestressed concrete frame (PC), and common reinforced concrete frame (RC). The study was conducted using the finite element software OpenSees. The study revealed that the vertical displacement during stabilization of the IW‐PC frame increased by 92.5% and 71.7% compared to the IW‐RC frame and decreased by 93.9% and 92.6% compared to the PC frame for middle column and side column failure, respectively. Additionally, the IW‐PC frame exhibited the highest dynamic load carrying capacity, which was 7.67 and 7.56 times higher than that of the RC frame, respectively. The mechanical properties of the frame were altered by the coupling effect of prestressed tendons and infill walls, making the IW‐PC frame more monolithic.
Investigation on the Seismic Damage and Identification of Lateral Stiffness for Ancient Timber Structures
Liu K., Xue J., Bai F., Ma L., Song D., Xue H.
Q1
ABSTRACTThis paper investigates the seismic damage and identification of lateral stiffness for ancient timber structures. Based on the shaking table test of a palace‐style timber structure, the lateral displacement responses, interstory equivalent lateral stiffness (IELS), and sensitivity of lateral displacement to degradation of IELS were analyzed to investigate the degradation and identification of IELS. The state and observation equations of a simplified mechanical model of the timber frame considering the friction slipping of the column base were predicted. Considering the noise disturbance in the test, the IELS of the model was identified by the partial least squares–singular value decomposition (PLS‐SVD) and extended Kalman filter (EKF) method. Results shown that the ratio of the IELS of the column frame layer to Ru‐Fu layer decreased as the seismic damage increased, and the peak lateral displacement was more sensitive to the damage of the column frame layer than the Ru‐Fu layer. Under nondamage conditions, the identification error of the IELS was about 10%, while the error ranged from 15% to 20% under damage conditions. Through the identification of the equivalent lateral stiffness of the Xi'an bell tower, it was validated that the hybrid method is effective in monitoring the IELS of ancient timber structures.
Analysis of wind vibration characteristics of a slab‐type high‐rise residential building
Xia Y., Shen Y., Yuan J., Chen S.
Q1
AbstractA slab‐type high‐rise residential building with a depth‐to‐width ratio exceeding 6 was studied. Multi‐point surface pressure measurements and high‐frequency force balance (HFFB) wind tunnel tests were conducted to investigate the wind‐induced dynamic characteristics of the building. The dynamic responses, especially accelerations closely related to serviceability performance, were determined and examined in both time and frequency domains. The spectral properties of the time‐history acceleration responses were compared with frequency‐domain results. Analyses showed acceleration responses were amplified when along‐wind or across‐wind directions aligned with the shorter building axis. The slab‐type cross‐section reduced vortex shedding in the across‐wind direction. As a result, peak accelerations were often dominated by along‐wind excitations. Torsional accelerations approached those induced by along‐wind winds, likely due to both fundamental and higher modes.
