Applied Mechanics and Materials Vols. 256-259

Abstract: According to the recent earthquakes, the asymmetric buildings suffer from severe damages caused by increased torsional response. The new seismic codes try to take into account this effect and during the modeling it is difficult to assess all the parameters that have an influence on the behavior of this kind of structures. In this work, a study on the influence of the effects of torsion on the behavior of structure is done. The proposed structures consist of an irregular 3-storey reinforced concrete frame with infinitely rigid slabs. The uncertainties of input parameters, such as seismic Arias intensity, peak ground acceleration, predominant period and output ones such as, inter-story Drift, and dynamic eccentricity upon the torsion is investigated. Using a finite element code, dynamic linear and non linear time analysis and pushover analysis have been performed, based on 116 seismic records with a magnitude varying between 6.2 and 7.7.

Abstract: This study presents an innovative approach to enhance the seismic performance of precast structures. Friction devices were inserted at the beam-to-column connections with the aim of providing supplemental energy dissipation and structural drift control. A single-story industrial building and a multi-story frame were analyzed in this study to assess the effectiveness of the dissipative friction devices. A simplified model describing the hysteretic behaviour of the friction device was developed and parametric analyses were carried out in order to establish the optimum value of the plastic moment of the device for the different precast structures. The results of the numerical investigations showed that the installation of the friction devices caused a significant decrease of displacements at the top of the structures. The energy dissipation mostly concentrated in the devices and the plastic demand on structural members was considerably reduced, along with the potential for structural damage.

Abstract: This study investigates the influence of the in-plan structural layout on the seismic response of symmetric and asymmetric steel structures. A five-storey steel frame building was used as reference structure and two different structural systems were employed to represent torsional stiff and torsional flexible structures. Accurate numerical models of the different typologies of structures were developed and both nonlinear static and dynamic analyses under bi-directional ground motion were carried out. The influence of axial force-bending moment interaction in columns in the two main directions and second order effects were taken into account in the numerical analyses. The results of the numerical investigations on symmetric structures showed that the reduction of the number of moment resisting connections may lead to an increase of the structural damage. Asymmetric variants of the investigated structures were created by assuming different mass eccentricities in each of the two main directions and extensive parametric studies were performed. For the torsionally flexible building, the influence of ground motion intensity was very strong. A transition from torsionally flexible to torsionally stiff behaviour in the weaker direction of the initially torsionally flexible structure was observed for severe seismic actions. The change of the stiffness of the structure in one direction due to high levels of plastic deformations affected the structural response in the orthogonal direction. Torsional effects decreased in case of severe seismic excitations and high levels of plastic deformations. The reduction of torsional effects observed for low seismic actions on the stiff side of torsionally stiff buildings disappeared under strong seismic excitations.

Abstract: There are a large number of concrete dams worldwide. Some of the dams are in areas prone to seismicity and were built many years ago with minimal consideration to seismic loads. Dam safety during and after an earthquake, is the aim of the present study. The failure of a dam during an earthquake will be catastrophic in terms of human life and financial losses. In the present work, an analytical fragility analysis was performed in order to characterize the seismic vulnerability of concrete gravity dams by using a probabilistic method to model sources of uncertainty that could impact dam performance. The assessment of the seismic vulnerability of concrete gravity dams under near-fault ground motions was performed to assess their performance against seismic hazards. A case study was considered, it is about the dam of Oued el Fodda on the Oued Chelif River, West Algeria. This dam was designed in the early 1930s.

Abstract: In the present work we discuss on the seismic vulnerability of reinforced concrete existing buildings. In particular we consider a reinforced concrete building originally designed for only gravitational loads and located in a zone recently defined at seismic risk. According to the Italian seismic code NTC 2008 a displacement based approach is adopted and the N2-method is considered for the nonlinear seismic analysis. In the analysis all the masonry infill panels in effective interaction with the structural frame are considered for the nonlinear modeling of the structure. The influence of the effective masonry infills on the seismic response of the structure is analyzed and it is discussed how the effect of the masonry infills irregularly located within the building can give rise to a worsening of the seismic performance of the structure. It is shown that in the present case a not uniform positioning of the masonry infills within the building can give rise to a fragile structural behavior in the collapse mechanism. Furthermore a comparative analysis is performed by considering both the structure with the effective masonry infills and the bare structural frame. For these two structures a pushover analysis is performed, the relative capacity curves are derived and it is shown that fragile collapse mechanisms can occur depending on the irregular positioning of the effective masonry infills. Accordingly it is discussed how in the present case a decoupling of the effective masonry infills from the structural frame can give rise to a smoother response of the capacity curves. For the examined case of an obsolete building with irregular positioning of the masonry panels, the choice of decoupling the effective masonry panels from the structural frame may facilitate the retrofitting strategies for the achievement of the proper safety factors at the examined limit states.

Abstract: Based on the bilinear hysteretic model, the elastic-plastic time history analysis of single mass point for parallel base isolation system is carried out. The approximate treatment method of the inflexion point is introduced and the formula of each energy consumption for parallel base-isolated structure is given. Through an engineering example, the time history curve of each energy dissipation for parallel base-isolated system is drawn, and the isolation effect is given.

Abstract: The work presented a structural identification method based on recurrent neural network and auto-regressive and moving average model. The proposed approach involves two steps. The first step is to build a recurrent neural network to map the complex nonlinear relation between the excitations and responses of the structure-unknown system by on-line learning . The second step is to propose a procedure to determine the modal parameters of the structure from the trained neural networks. The dynamic characteristics of the structure are directly evaluated from the weighting matrices of the trained recurrent neural network. Furthermore, a illustrative example demonstrates the feasibility of using the proposed method to identify modal parameters of structure-unknown systems.

Abstract: Measurement and identification of the existing structure or residential flats have the structure of the safety assessment of the correct structure has important reference value, the detection and results of this paper, the measurement of the actual project , given the project overall lateral , for the structure post- processing programs and strengthening measures provide an important design basis .

Abstract: A 3-axis electronic compass is designed for small multi-rotors unmanned vehicle. The STM32F103 is used as E-compass’ CPU, and ADXL345 and MAG3110 is used as the acceleration and geomagnetic sensor. The E-compass’ software is programmed by using IAR EWARM. For outdoor applications, the ellipsoid assumption theory is simply proved and used for E-compass’ self-calibration. By using the zero-bias adjustment for pre-calibration and the fitellipsoid compensation for precise calibration, the E-compass’ precision is nearly 1 degree.

Abstract: Digital urban management system is an important part of digital city construction and urban components collecting system is base of digital urban management system. This paper proposes a scheme of urban collecting system mainly with collecting urban components information by car-borne road information system and supplementing with RTK survey.