Reduced Equivalent Static Wind Loads for Tall Buildings with Tuned Liquid Dampers

This paper proposes an equivalent static wind load calculation method based on response-related scale for the wind load calculation of large-span roof structures. The effectiveness of this method is verified by wind tunnel tests and finite element analysis of the roof of the east entrance of Hangzhou Convention and Exhibition Center. The research results show that the equivalent static wind load method based on response-related scale has high accuracy in reflecting the overall response characteristics of the structure, and its error in calculating the node displacement response is the smallest, only 4.6%, which is better than the traditional single-objective equivalent method and least squares method.

Probabilistic serviceability-performance assessment of tall mass-timber buildings subjected to stochastic wind loads: Part I - structural design and wind tunnel testing

A novel probabilistic approach is presented for estimating the equivalent static wind loads that produce a static response of the structure, which is equivalent in a probabilistic sense, to the extreme dynamic responses due to the unsteady pressure random field induced by the wind. This approach has especially been developed for complex structures (such as stadium roofs) for which the unsteady pressure field is measured in a boundary layer wind tunnel with a turbulent incident flow. The proposed method deals with the non-Gaussian nature of the unsteady pressure random field and presents a model that yields a good representation of both the quasi-static part and the dynamical part of the structural responses. The proposed approach is experimentally validated with a relatively simple application and is then applied to a stadium roof structure for which experimental measurements of unsteady pressures have been performed in boundary layer wind tunnel.

A conventional tuned liquid damper (TLD) generates a relatively small control force associated with low density of sloshing water. To overcome this main drawback, proposed in this study is a new TLD system composed of water and fine particles in a rectangular tank of sloping bottom. The effectiveness of the proposed mass-variable TLD system was demonstrated with shake table tests. In comparison with a conventional TLD, the mass-variable TLD can more effectively reduce structural responses particularly under large external excitations. The mass-variable TLD can also be effective in the earlier stage of an earthquake event due to the increasing mass nature as the excitation increases. This attribute makes the new TLD particularly attractive under impulsive loads such as near-field ground motions.

Investigation on wind-induced aero-elastic effects of tall buildings by wind tunnel test using a bi-axial forced vibration device

Gust response envelope approach to the equivalent static wind load for large-span grandstand roofs

Wind-induced response behavior of long-span roof structures is very complicated, showing significant contributions of multiple vibration modes. The largest load effects in a huge number of members should be considered for the sake of the equivalent static wind loads (ESWLs). Studies on essential matters and necessary conditions of the universal ESWLs are discussed. An efficient method for universal ESWLs on long-span roof structures is proposed. The generalized resuming forces including both the external wind loads and inertial forces are defined. Then, the universal ESWLs are given by a combination of eigenmodes calculated by proper orthogonal decomposition (POD) analysis. Firstly, the least squares method is applied to a matrix of eigenmodes by using the influence function. Then, the universal ESWLs distribution is obtained which reproduces the largest load effects simultaneously. Secondly, by choosing the eigenmodes of generalized resuming forces as the basic loading distribution vectors, this method becomes efficient. Meanwhile, by using the constraint equations, the universal ESWLs becomes reasonable. Finally, reproduced largest load effects by load-response-correlation (LRC) ESWLs and universal ESWLs are compared with the actual largest load effects obtained by the time domain response analysis for a long-span roof structure. The results demonstrate the feasibility and usefulness of the proposed universal ESWLs method.

Most international codes and standards provide guidelines and procedures for assessing the along-wind effects on tall structures. Despite their common use of the “gust loading factor” (GLF) approach, sizeable scatter exists among the wind effects predicted by the various codes and standards under similar flow conditions. This paper presents a comprehensive assessment of the source of this scatter through a comparison of the along-wind loads and their effects on tall buildings recommended by major international codes and standards. ASCE 7-98 (United States), AS1170.2-89 (Australia), NBC-1995 (Canada), RLB-AIJ-1993 (Japan), and Eurocode-1993 (Europe) are examined in this study. The comparisons consider the definition of wind characteristics, mean wind loads, GLF, equivalent static wind loads, and attendant wind load effects. It is noted that the scatter in the predicted wind loads and their effects arises primarily from the variations in the definition of wind field characteristics in the respective codes and standards. A detailed example is presented to illustrate the overall comparison and to highlight the main findings of this paper.

This study aimed to develop an approach to accurately predict the wind models and wind effects of large wind turbines. The wind-induced vibration characteristics of a 5 MW tower-blade coupled wind turbine system have been investigated in this paper. First, the blade-tower integration model was established, which included blades, nacelle, tower and the base of the wind turbine system. The harmonic superposition method and modified blade element momentum theory were then applied to simulate the fluctuating wind field for the rotor blades and tower. Finally, wind-induced responses and equivalent static wind loads (ESWL) of the system were studied based on the modified consistent coupling method, which took into account coupling effects of resonant modes, cross terms of resonant and background responses. Furthermore, useful suggestions were proposed to instruct the wind resistance design of large wind turbines. Based on obtained results, it is shown from the obtained results that wind-induced responses and ESWL were characterized with complicated modal responses, multi-mode coupling effects, and multiple equivalent objectives. Compared with the background component, the resonant component made more contribution to wind-induced responses and equivalent static wind loads at the middle-upper part of the tower and blades, and cross terms between background and resonant components affected the total fluctuation responses, while the background responses were similar with the resonant responses at the bottom of tower.

Using several formulas of across-wind aerodynamic forces and aerodynamic damping of rectangular super-high-rise buildings with side ratios smaller than 2 proposed previously by the authors, across-wind equivalent static loads and responses of super-high-rise buildings are evaluated through a proper combination of resonant and background components. The resonant component is computed according to the power spectral density of the base moment and the aerodynamic damping. The background component, whose vertical distribution is derived from background moment responses at different heights and then expressed as a cubic equation of the relative height, is computed using the base moment coefficients. Furthermore, comparisons are made for the equivalent static wind loads and responses of a hypothetical typical building between the present method and the AIJ (1996) method, which indicate the applicability of the present method. Finally, the effects of background component and aerodynamic damping on the equivalent wind loads and responses are also discussed.

With the development of construction technology and material, more and more super high-rise buildings will be constructed in the future. In a specific metropolitan area, super high-rise building with various cross-section and high side ratio have to been designed and constructed due to the size limitation of construction site. This kind of building is also very prone to wind excitations. In this research, wind tunnel tests for a practical case of this kind of building with surrounding buildings were carried out in atmospheric boundary wind tunnel. Equivalent static wind loads (ESWLs), wind-induced responses and wind load distribution on the building were analyzed. In particular, the base overturning moment along the axis with weak lateral stiffness were investigated for bearing capacity limit state design of the building. The results demonstrate that the maximum value of wind-induced base overturning moments and acceleration responses appears at 60° or 330° wind directions instead of the orthogonal wind direction, and the aerodynamic interference of surrounding buildings affects the wind pressure distribution on facades of the building. These results and conclusion may be helpful to wind-resistant design of super high-rise buildings with high side ratio.

SummaryHigh‐frequency force balance test is a major technical means to evaluate the wind effect of super high‐rise buildings. Most super high‐rise buildings have the characteristic that the first two‐order modal frequencies are close, and thus, considerable modal coupling effects (MCEs) may occur under wind load. For a balance model system (BMS), MCEs increase the difficulty of correcting aerodynamic distortion signals. For the wind‐induced vibration analysis of a structural system (PSS), the calculation results of the wind‐induced response and the equivalent static wind load (ESWL) may be significantly affected without considering MCE. Based on the above‐mentioned signal distortion of BMS and the modal coupling problem of PSS, this study proposes a wind‐induced vibration calculation method for the two coupled systems (BMS and PSS). The method uses the second‐order blind identification technique based on complex modal theory and the Bayesian spectral density method considering full aerodynamic characteristics to achieve effective correction of the distortion signal in BMS. In addition, it deduces the calculation method of the wind‐induced response and ESWL considering the three‐dimensional coupled vibration of a super high‐rise building. The wind effect calculation results of a 528‐m super high‐rise building confirm the necessity and effectiveness of the proposed method.

Tuned liquid dampers with a Keulegan–Carpenter number-dependent screen drag coefficient

Wind resistant size optimization of geometrically nonlinear lattice structures using a modified optimality criterion method

The aim of the present study is determinate if the steel space grid envelope structures, for tall buildings (framed tube), are more optimal and efficient if their design is based on the isostatic lines of their equivalents structural elements according to their solicitations. In this study, 600 models of tall buildings, for different triangled facades and geometric slenderness, are analyzed. The methodology employed consisted of detecting the wind loads that affects tall buildings applying the Equivalent Static Wind Loads (ESWL) in relation to the wind speed and turbulence result of the roughness terrain and the topographic. However, it was also needed to establish the frequencies and modes of vibration of each structure as well as defining the coefficients of pressure, force and moments produced by the wind. The results conclude that space grids are more efficient if they do adopt the trajectory of the main and dominant load, in this case the wind.