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doi: 10.1002/tal.1443pmid: N/A
Based on translation models, both Gaussian and non‐Gaussian wind fields are generated using the harmony superposition method for examining the reliability of a typical wind turbine at operational and parked conditions. Using the blade aerodynamic model and multibody dynamics, wind turbine responses are calculated and then probability characteristics are analyzed in details. The short‐term extreme response distribution is estimated by the average conditional exceedance rate method at each mean wind speed bin, and the long‐term extreme response distribution is then determined by further integrating the short‐term extreme response distribution conditional on wind speed with the distribution of mean wind speed. Additionally, crack initiation life and crack propagation life are evaluated using the linear cumulative damage theory and linear crack propagation theory, respectively. The results indicate that non‐Gaussian characteristics of wind inflows have a noticeably greater influence on both extreme response and fatigue damage, and the Gaussian assumption cannot suit wind turbine in complex terrain.
Havaei, GholamReza; Moayyedi, Seyyed Amirhossein
doi: 10.1002/tal.1418pmid: N/A
In this study, performances of 2 types of bridges, with and without seismic isolation, are addressed in 2 damage analysis scenarios, where, in the first, the side column and, in the second, the middle column are removed from the bridge piers. The performance was assessed using nonlinear dynamic analysis, and the time history and maximum structural responses were evaluated. Initially, sliding‐rubber isolators were designed according to AASHTO guide specifications, and then the bridges were modeled in OpenSees software package. Additionally, the coefficient of friction for the isolator was considered as a variable due to sudden removal of the columns and the consequent changes in the sliding velocity and axial forces. The results indicate that use of seismic isolation systems caused an increase in all maximum structural responses except that of the base shear. Considering the frictional performance of the isolators, slides in the deck are not caused by yielding of seismic isolators, and the reason for permanent displacements of the deck may be attributed to bridge instabilities in the first scenario. However, decrease in the horizontal stiffness results in increased maximum permanent displacement. In the first scenario, uplift of the deck occurred in the case of isolated bridge.
Shu, Zhan; He, Minjuan; Li, Zheng
doi: 10.1002/tal.1440pmid: N/A
As one key to the implementation of the performance‐based design methodologies for wood structures, the performance objectives and their corresponding limit state criteria are usually correlated with the peak (maximum) interstory drift demands. This paper evaluates the inelastic drift demands including the peak drift and the residual drift for the prototype timber portal frame structural elements. Analytical 2D‐framed model representative of the study‐case were subjected to a suite of 50 pulse‐type earthquake ground motions. In addition, an accumulated damage index is added to the inputs of the nonlinear analyses to account for the damage caused by the previous ground excitations. Larger accumulated damages lead to larger inelastic drifts. Strong correlation is revealed among the drift demands, the peak ground accelerations, and the variables characterizing the nonlinear system behavior. Finally, estimation formulas for the peak and residual drift demands are proposed and validated with the simulated results from nonlinear time‐history analyses. Based on the presented formulas, the resilience ratio and the effective elastic drift are further derived to comprehend the nonlinear behavior of such timber made structures.
Macêdo Wahrhaftig, Alexandre; Silva, Marcelo Araujo
doi: 10.1002/tal.1442pmid: N/A
Wind is the main horizontal force acting on tall buildings. This force is proportional to the drag coefficient. The drag coefficient is an important factor in their structural design. Designers have historically relied upon experimental wind tunnel results to estimate the drag coefficient. However, this process is both expensive and time consuming. In this study, we alternatively computed the drag coefficient (apart from the pressure, force, and bending moment) using computational fluid dynamics for a typical 93‐m‐high residential building. The simulation considers the actual building geometry, as well as the neighborhood roughness effects. We compared these results with the conventional estimates contained in the Brazilian code NBR‐6123/1988 and Eurocode EC1. The results indicated that the pressures obtained herein near the top of the building were lower compared to those obtained using conventional estimation methods given in codes. Comparatively, the obtained bending moment relative to the base of the building was higher, indicating the existence of significant drag forces not considered in codes. In fluid dynamics simulations, the drag coefficient is determined for each terrain condition. Computational fluid dynamics can effectively simulate the drag force and resultant forces in the direction of the flow, as well as the vortices that result during coating detachment and other types of damage.
Abdollahzadeh, G.R.; Yapang‐Gharavi, S.; Hoseinali‐Beygi, M.
doi: 10.1002/tal.1420pmid: N/A
The behavior of beam‐to‐column connections is significantly complicated because it depends on the material, nonlinear relationship between different members, and contact of connecting elements. Their hysteretic response exhibits highly inelastic characteristics and continuous variation in stiffness, strength, and ductility. Therefore, accurate hysteretic models of bolted connections are essential to accurate seismic assessment and design. Composed (Hybrid) modeling approach is presented to represent the complex hysteretic behavior of I beam‐to‐concrete‐filled‐tube (CFT) column bolted connection. For the purpose in this study, experimental evaluation of I beam‐to‐CFT column connection with bolted end‐plate under cyclic loading is done. It must be mentioned to make the connection easily applicable practically and also prepare the column flanges continuity, a connection with the bolts penetrated into the CFT column are used since using the stiffeners in hollow sections is not easily applicable. In the composed mechanical–informational modeling framework, the conventional mechanical model is complemented by information‐based model components. Finally, moment–rotation curves of composed model have been compared with experimental results. Comparison showed that the composed model has a good agreement with experimental results. A newly designed specimen for validation purpose of the composed modeling was made and experimented. Composed model was well applied to predict the behavior of new connections. The presented results show that the composed model has a good ability to predict of hysteretic behavior.
Zhang, Xiao‐nan; Shan, Ren‐liang; Lu, Man
doi: 10.1002/tal.1439pmid: N/A
The tilting of buildings not only leads to inconvenience but also causes serious building collapses with heavy casualties and serious social impacts. However, rectification and reinforcement construction method started late in China. Now, this construction pattern mainly depends on sophisticated design techniques, without systematic techniques to reference. Based on the in‐depth analysis on tilt reason of a brick‐wooden building in Yunnan Province in China and combined with jacking rectification method, the impact pile project, artificial inserting shield engineering for steel box girder project, unbonded prestressed engineering project and concrete filled steel tube reinforcement example. Analyzing the multipoint synchronous lifting process by 3‐dimensional numerical simulation in ANSYS finite software. The actual monitoring results showed that the maximum inclination rate was reduced to less than 2.95‰ in the end, and the architectural distortion was stabilized in the process of rectification and reinforcement, which guarantees building safety and efficiency in the process of rectification.
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