Wenjuan Lou

INTEGRATED STRUCTURAL OPTIMIZATION AND VIBRATION CONTROL FOR IMPROVING WIND-INDUCED DYNAMIC PERFORMANCE OF TALL BUILDINGS

Structural optimization and vibration control have long been recognized as effective approaches to obtain the optimal structural design and to mitigate excessive responses of tall building structures. However, the combined effects of both techniques in the structural design of wind-sensitive tall buildings with excessive responses have not been revealed. Therefore, this paper develops an integrated design technique making use of both the advantages of structural optimization and vibration control with an empirical cost model of the control devices. While the structural optimization is based on a very efficient optimality criteria (OC) method, a smart tuned mass damper (STMD) is used for the structural control purposes. Utilizing data obtained from synchronous pressure measurements in the wind tunnel, a 60-story building of mixed steel and concrete construction with three-dimensional (3D) mode shapes was employed as an illustrative example to demonstrate the effectiveness of the proposed optimal performance-based design framework integrating with structural vibration control.

Experimental and computational simulation for wind effects on the Zhoushan transmission towers

Long-span transmission tower and conductor line systems become important infrastructures in modern societies. The analysis of wind-induced dynamic responses of transmission towers is an essential task in the design of spatial lattice tower structures. Wind effects on the worlds tallest transmission tower are presented in this paper. The tower with a total height of 370 metres, part of the Zhoushan long-span transmission project, enables high voltage conductor lines to span as long as 2750 metres over the typhoon-prone sea strait. A multi-DOF aeroelastic model test with and without conductor lines was carried out to investigate the dynamic performances of Zhoushan tower during typhoon events. Using the response measurement results in the wind tunnel, the inertial force based gust loading factors (GLFs) are applied to represent dynamic wind load effects on the tower for structural design purposes. Time domain computational simulation approach is also employed to predict dynamic responses of the transmission tower and the displacement based gust response factors (GRFs). The fair comparison of GLFs or GRFs are made between the results of the experimental approach and the computational simulation approach, which is an effective alternative way for quickly assessing dynamic wind load effects on high-rise and complex tower structures.

Hermite Extreme Value Estimation of Non-Gaussian Wind Load Process on a Long-Span Roof Structure

AbstractThis paper presents a combined study of wind tunnel experiment and numerical simulation of the wind-induced pressures on the long-span roof of the Hangzhou East Railway Station Building. Wind tunnel tests were performed on a 1∶250-scale rigid model of the station building. Based on the measured pressure data, the third and fourth statistical moments of the pressure processes were evaluated to quantify the non-Gaussian nature of the wind-induced pressures on the station roof. Using the recently reported Hermite moment model, an analytical form of the non-Gaussian peak factor was proposed for a given hardening load process and was verified using numerical integration. The currently available simulation algorithm was revised to generate sample functions of skewed hardening load processes. The simulated pressure data samples provide a basis for the direct statistical analysis of extreme peaks. The peak factors for non-Gaussian wind load effects were estimated by employing various state-of-the-art meth...

Time-domain dynamic drift optimisation of tall buildings subject to stochastic wind excitation

Wind-resistant design of tall buildings has been traditionally treated using the equivalent static load approach. In order to account for the uncertainties in random wind excitation, it is necessary to develop a comprehensive and reliable dynamic optimisation technique in the time domain. The optimal lateral stiffness design problem of wind-excited tall buildings consists of (1) identifying the critical dynamic drift response in the time domain and (2) searching for the optimal distribution of element stiffness of the building subject to multiple drift design constraints. The critical time-history drift constraints of a wind-excited building are first treated by the worst-case formulation and then explicitly expressed in terms of element sizing variables using the principle of virtual work. The extreme value distribution and the Gaussian assumption are employed to formulate and simplify the probabilistic drift constraints, which are explicitly considered in the dynamic optimisation problem. The system reliability associated with the inter-story drift is estimated approximately by the bound approach to ensure that the most cost-efficient solution also attains an acceptable reliability level. A full-scale 45-story building example under wind tunnel derived time history wind loading is presented to illustrate the effectiveness and practicality of the reliability-based dynamic optimisation technique.

Estimation Method of Loss Coefficient for Wind-Induced Internal Pressure Fluctuations

AbstractAs the importance of wind-induced internal pressure for building safety has continually been highlighted, increasing attentions have been paid to numerical methods for estimating fluctuating internal pressures, leading to the emergence of numerous second order nonlinear governing equations with two ill-defined parameters, namely inertial coefficient (CI) and loss coefficient (CL). Because resonance frequency and damping ratio of fluctuating internal pressures are susceptible to the values of inertial and loss coefficients, respectively, a correct understanding, and reasonable estimates, of these two parameters are required before using the governing equations to predict internal pressure responses. Compared with the inertial coefficient, which can be easily obtained from the Helmholtz frequency, a wider range of values of loss coefficient is in use, therefore this study focuses on the more uncertain parameter CL and presents an alternative method to identify loss coefficients of measured internal ...

Two-Parameter Bifurcation and Stability Analysis for Nonlinear Galloping of Iced Transmission Lines

AbstractThis paper presents an analytical approach in the study of bifurcation and stability behavior for nonlinear galloping of iced transmission lines. Equations of motion are established to describe three-dimensional galloping behavior observed on iced transmission lines. Stability analysis of iced conductor galloping is carried out. The center manifold theory, together with the normal form theory, is used to derive the governing bifurcation equations. A new formula is also proposed to calculate the maximum dynamic tension of iced conductors. The technique developed in this paper is implemented using a symbolic analysis module for practical usage. A real transmission line with a span of 244 m, which was damaged by the galloping accidents, is presented to demonstrate the effectiveness and accuracy of the developed two-parameter bifurcation analysis technique for nonlinear galloping of iced conductors. The galloping amplitudes in three orthogonal directions are analytically obtained for a broad range of ...

Full-scale measurement and analysis of K11 building in Hong Kong during typhoon

The full-scale measurement of typhoon effects on K11 building in Hong Kong was studied.This paper presented the acceleration data of the building under Typhoon Kammuri in 2008.The acceleration data were analyzed in terms of the third and fourth moments,The occupant comfort of the building under wind-induced vibration was evaluated.The vibration frequencies of the building were identified by spectral analysis technique,and were compared with the finite element method results and empirical results.Both the traditional peak factor method and the improved Gumbel method were applied to estimating the peak factor of wind-induced acceleration response.The peak factor results show good agreement with the other two methods.The values in GB50009-2001 are low.

The effects of wind-induced dynamic response by added air mass for membrane structures

Publisher Summary This chapter presents theoretical formulae of the added air mass for the membrane structures that are applied to analyze the wind-induced dynamic response of large-span flexible roof. The thin airfoil aerodynamic theory is applied to calculate added air mass of membrane structures. The vortex sheet of thin airfoil theory fitted to membrane structures in unsteady flows is established. The vortex filaments are used to calculate added mass action on membrane structures. These theoretical results are obtained by some techniques, such as coordinate mapping and mathematical denotation integral, and the formulae of added air mass for the membrane structures are convenient to study the flexible roofs including long-span structures. Finally, the inertia loads induced by the added air mass are used to analyze the dynamic response of the membrane structures in time domain, and some important results of wind-induced vibration of the membrane structures are obtained. The chapter finally discusses the results obtained on the application of FEM and time domain analysis to study vortex-induced vibration of the membrane structures.