Advanced Materials Research Vols. 163-167

Abstract: In modern municipal construction and earthquake engineering, semi-cylindrical gap and shallow-buried cavity structure are used widely. In this paper, the solution of displacement field for elastic semi-space with multiple semi-cylindrical gaps and a shallow-buried cavity while bearing anti-plane harmonic line source force at any point is studied. In the complex plane, considering the symmetry of SH-wave scattering , the displacement field aroused by the anti-plane harmonic line source force and the scattering displacement field impacted by multiple semi-cylindrical gaps and a cylindrical cavity comprised of Fourier-Bessel series with undetermined coefficients which satisfies the stress-free condition on the ground surface are constructed. Through applying the method of multi-polar coordinate system, the equations with unknown coefficients can be obtained by using the stress-free condition of the gaps and the cylindrical cavity in the radial direction. According to orthogonality condition for trigonometric function, these equations can be reduced to a series of algebraic equations. Then the value of the unknown coefficients can be obtained by solving these algebraic equations. The total wave displacement field is the superposition of the displacement field aroused by the anti-plane harmonic line source force and the scattering displacement field. By using the expressions, an example is provided to show the effect of the change of relative location of semi-cylindrical gaps , the cylindrical cavity and the location of the line source force. Based on this solution, the problem of interaction of multiple semi-cylindrical gaps , a cylindrical cavity and a linear crack in semi-space can be investigated further.

Abstract: Large-span cantilevered roofs are wind sensitive structures, this paper presents the finding of large eddy simulation(LES) of turbulent wind field around large-span cantilevered roofs with grandstand in atmosphere boundary layer. For a typical horizontal cantilevered roof, the wind pressure is researched in fluid mechanic view, the large scales of wind motion are computed explicitly while the small scales are modeled by LES, the contours of wind pressure and velocity are present to reveal the coherent structures. Some general issues related to LES in wind engineering are discussed also.

Abstract: As an important seismic analysis method, Pushover is widely used in high-rise buildings, while there is still lack of investigation on applicability of Pushover analysis on diagonal grid structural system. Two structures with height 144 and 288 meters are respectively built, and then Pushover analysis and Incremental dynamic analysis are conducted. Results calculated by two different methods are compared, including top displacement vs. base shear curve, inter-story drift vs. inter-story shear curve, distribution of inter-story drift angle along the building height and plastic developing sequence of structural weak positions. Meanwhile, influence of three lateral load patterns (uniform pattern，inverted triangle pattern and SRSS pattern) on the results is investigated. Analysis results demonstrate that Pushover analysis can in some extent reflect seismic performance of structures and SRSS load pattern can better capture global and local information of structures compared with other two patterns.

Abstract: With vibration amplitude increasing, the super high-rise building appears obvious pseudo-beat vibration under the combination of vortex-induced force and nonlinear damping force. Therefore, based on Scanlan nonlinear empirical model the first-order nonlinear pseudo-beat vibration responses of the super high-rise building are deduced with KBM method. And then the aerodynamic parameters and vortex-induced force can be identified with least square method. By using the aeroelastic model wind tunnel test of a certain super high-rise building, the wind-induced displacement vibration responses are gathered. By the least square method, each aerodynamic parameter is identified. It shows by analysis that the pseudo-beat vibration force is mainly offered by linear and nonlinear damping forces but secondary offered by linear stiffness force and periodic excitation force. The pseudo-beat vibration force calculated by KBM approximation has the predominant frequency like that of beat vibration response as well as high-order harmonic wave.

Abstract: The traditional analysis method about dynamic characteristics with frame structures was building story models instead of structures. In this paper, the series-parallel-connection models with considering joint rotation on frame structures subjected to vertical vibration were presented, and the result what’s computed between the two models was compared, a notion called “natural frequency zone” was advanced. At last, some conclusions on the frame structures subjected to vertical vibration were obtained.

Abstract: Energy-based modal pushover analysis method has been proved to be an appropriate approach to perform seismic analysis for structures whose high mode effect is not negligible. It directly establishes the capacity spectrum based on energy increments, which corrects the deficiency of conventional modal pushover method that the capacity curve would not be unique or even be retorted while the base shear-top displacement curve is established with respect to different reference nodes of the structure. In this paper, a continuous rigid frame bridge with tall piers in seismic zone is analyzed with EMPA method. The results showed that EMPA is more adaptable than conventional methods, and the seismic performance of the bridge can satisfy the demand of the design code.

Abstract: This paper presents the results of full-scale numerical wind tunnel tests of wind pressure on structure roofs with suspension solar panels. Solar roof project is popularized in this century. Solar panels are suspended above the structure roof. So the wind load effect on the structure roof is varied. The wind tunnel experiments are often expensive. A 3D model is introduced and solved using ADINA. The wind pressure distribution coefficients are calculated.

Abstract: In this paper, a system identification approach is proposed for high-rise building under unknown seismic excitation with limited output measurements. A high-rise building is decomposed into small size substructures based on its finite element formulation. Interaction effect between adjacent substructures is considered as ‘equivalent known inputs’ to each substructure. Unknown seismic excitation is considered as ‘equivalent unknown inputs’ at the first floor. By sequentially utilizing the extended Kalman estimator for the extended state vectors and the least squares estimation for the ‘equivalent unknown inputs’, structural parameters above the first story of a shear building can be identified. Then, with the analysis of the measured absolute acceleration responses in frequency domain and the peak-picking method for the estimation of the first natural frequency of the building, structural parameters of the first story can be identified from the frequency equation. Finally, the unknown seismic excitation can be identified via the numerical solution of a first-order differential equation. It is shown by a numerical example that the proposed method can identify high-rise building parameters and the seismic excitation with good accuracy.

Abstract: The main seismic objective in China is defined as “no failure under minor earthquake, repairable damage under moderate earthquake and no collapse under major earthquake”. Both strength and deformation are important to evaluate the seismic performance. For masonry building, only the shear strength check under minor earthquake is stipulated in the current Chinese seismic design code. Due to the poor ductility of masonry building, the seismic design analysis method may not guarantee the collapse-resistant capacity under major earthquake. For the achievement of the seismic objective, the demand of ductility is discussed. A typical severely damaged masonry building by the 5.12 Wenchuan Earthquake of 2008 is presented for the analysis of the through X-shape crack on the load-bearing wall. In order to enhance the collapse-resistant capacity, the authors suggest more shear strength margin to take the influence of structural ductility into consideration. The feasible way can be easily realized as a target to raise the limitation for the shear strength check parameter under minor earthquake and to keep uniform seismic capacity in two directions. The investigated building is also illustrated here as an example to process the shear strength check for better seismic performance by the authors’ suggestion.

Abstract: This study proposed a wavelet method for estimating seismic energy in single-degree-of-freedom (SDOF) structure. With the recent development of wavelet-based procedures for structure seismic response, which the displacement and velocity of linear SDOF structure can be expressed with wavelet transform of acceleration process, it is easy to estimate seismic energy in SDOF linear structure, and strain, kinetic, damping energy and energy input based on wavelets introduced in a range of time and frequency assigned to the wavelet coefficient, Expressions have been derived for (i) the equation of motion. (ii)the wavelet coefficients of the response processes. By using these principles, a linear SDOF structure which subjected to 1988 LanCang-GenMa earthquake ground motions is analyzed, time-histories of strain, kinetic, damping energy and energy input for various ranges of frequencies are identified.