Direct Displacement Based Design of Regular Steel Moment Resisting Frames

AbstractDisplacement Based Design method represents a new approach to performance-based design. This research tries to assess the Direct Displacement Based Design (DDBD) method for regular steel moment resisting frames and develop a reliable design method for them so that they withstand various seismic levels within certain performance levels. For this purpose, regular steel frames with 4, 8, 12, 16 stories are designed based on DDBD approach utilizing displacement spectrum of the Iranian Code of Practice for Seismic Resistant Design of Buildings (Standard No. 2800). In order to evaluate seismic response of the designed structures, a series of non-linear time-history analyses have been performed under different records compatible with Standard No. 2800. All the non-linear analyses were carried out using the fiber-element models developed in Seismostruct computer program. According to the results, inter-story drift profile of the structure which is corresponding to its damage was less than the allowable value in most cases. Also, Maximum displacement profile of the structure along its height is completely matched with the primary assumed design profile. The structures have mostly experienced similar residual drift values under different records. In summary, the method performed quite satisfactorily in terms of story maximum displacements, maximum interstory drifts and story ductility demands, even for tall models

Chattering-free sliding mode control with a fuzzy model for structural applications

This paper proposes a chattering-free sliding mode control (CFSMC) method for seismically excited structures. The method is based on a fuzzy logic (FL) model applied to smooth the control force and eliminate chattering, where the switching part of the control law is replaced by an FL output. The CFSMC is robust and keeps the advantages of the conventional sliding mode control (SMC), whilst removing the chattering and avoiding the time-consuming process of generating fuzzy rule basis. The proposed method is tested on an 8-story shear frame equipped with an active tendon system. Results indicate that the new method not only can effectively enhance the seismic performance of the structural system compared to the SMC, but also ensure system stability and high accuracy with less computational cost. The CFSMC also requires less amount of energy from the active tendon system to produce the desired structural dynamic response.ARC DE150101703 and ARC LP14010059

Heterogeneous integration of contact-printed semiconductor nanowires for high-performance devices on large areas

In this work, we have developed a contact-printing system to efficiently transfer the bottom-up and top-down semiconductor nanowires (NWs), preserving their as-grown features with a good control over their electronic properties. In the close-loop configuration, the printing system is controlled with parameters such as contact pressure and sliding speed/stroke. Combined with the dry pre-treatment of the receiver substrate, the system prints electronic layers with high NW density (7 NWs/μm for bottom-up ZnO and 3 NWs/μm for top-down Si NWs), NW transfer yield and reproducibility. We observed compactly packed (~115 nm average diameters of NWs, with NW-to-NW spacing ~165 nm) and well-aligned NWs (90% with respect to the printing direction). We have theoretically and experimentally analysed the role of contact force on NW print dynamics to investigate the heterogeneous integration of ZnO and Si NWs over pre-selected areas. Moreover, the contact-printing system was used to fabricate ZnO and Si NW-based ultraviolet (UV) photodetectors (PDs) with Wheatstone bridge (WB) configuration on rigid and flexible substrates. The UV PDs based on the printed ensemble of NWs demonstrate high efficiency, a high photocurrent to dark current ratio (>104) and reduced thermal variations as a result of inherent self-compensation of WB arrangement. Due to statistically lesser dimensional variations in the ensemble of NWs, the UV PDs made from them have exhibited uniform response

Study of nonlinear vibration of Euler-Bernoulli beams by using analytical approximate techniques

In this paper, nonlinear responses of a clamped-clamped buckled beam are investigated. Two efficient and easy mathematical techniques called He's Variational Approach and Laplace Iteration Method are used to solve the governing differential equation of motion. To assess the accuracy of solutions, we compare the results with the Runge-Kutta 4th order. The results show that both methods can be easily extended to other nonlinear oscillations and it can be predicted that both methods can be found widely applicable in engineering and physics