New method for modal identification of super high‐rise building structures using discretized synchrosqueezed wavelet and Hilbert transforms

Measured signals obtained by sensors during dynamic events such as earthquake, wind, and wave contain nonlinear, nonstationary, and noisy properties. In this paper, a new approach is presented for modal parameter identification of structures particularly suitable for very large real‐life structures such as super high‐rise building structures based on the integration of discretized synchrosqueezed wavelet transform, the Hilbert transform, and the linear least‐square fit. Its effectiveness is demonstrated first by application to a two‐dimensional frames from the literature, and then to the 123‐story Lotte World Tower (LWT) under construction in Seoul, Korea. The LWT measurements are very low‐amplitude ambient vibrations. Extracting the natural frequencies and damping ratios from such low‐amplitude signals are known to be very challenging. Further, the new methodology was compared with the empirical mode decomposition. It is demonstrated that the new method is capable of extracting both natural frequencies and damping rations from low‐amplitude signals effectively and with a higher accuracy compared with the empirical mode decomposition approach. The results of this research indicate a super high‐rise building like LWT has a damping ratio in the range 0.7–3.4%. The new method is quite promising for practical implementations of health monitoring of large real‐life structures.     

Diagrid: An innovative,sustainable, and efficient structural system

In recent years, diagrid structures have received increasing attention among both designers and researchers of tall buildings for creating one‐of‐a‐kind signature structures. This paper presents a state‐of‐the‐art review of diagrid structures. First, various diagrid configurations, main factors affecting their behaviors, and related design parameters and approaches are discussed. Then, diagrid applications for free‐form steel and concrete structures are introduced showing the diagrid applicability for complex structures followed by recent advances in structural design of diagrid connections, diagrid nonlinear behavior, and structural control of diagrids. Recent studies about a new variation of tubular and diagrid systems, hexagrids, are discussed briefly. Finally, the diagrid potential in design of sustainable buildings is delineated.     

Concurrent Optimization of Large Structures. I: Algorithms

Parallel algorithms are presented for optimization of structures on shared‐memory multiprocessor computers. Structures subjected to multiple loading cases with limitations on nodal displacements, element stresses, and member sizes are optimized using the optimality‐criteria approach in a concurrent‐processing environment. Emphasis is directed toward parallelizing each computational step of the solution process. Parallel algorithms are developed to assure the best concurrent performance and speed‐up within each step. A substructuring algorithm is used to achieve the best work‐load balance during the solution of the generalized displacements. Concurrency is achieved through the use of the notion of cheap concurrency and the concept of threads. (A companion paper demonstrates the efficiency of the parallel algorithms through optimization of several truss and frame problems on an Encore Multimax shared‐memory computer for a variable number of processors.) The algorithms are particularly suitable for optimization of large structures such as space stations.     

Global optimum design of cold-formed steel hat-shape beams

Using the computational neural network model developed recently by the authors, a comprehensive parametric study is performed for global optimization of cold-formed steel hat-shape beams based on the AISI Specifications. Design curves are presented for global optimum values of the thickness, the web-depth-to-thickness ratio, and the flange width-to-thickness ratio for unbraced beams having steel yield strengths of 250 and 345 N/mm². The computational neural network model guarantees a local optimum solution. The global optimum is found by an exhaustive search that is guided by a heuristic approach to reduce the search effort. An extensive parametric study yielded insights into the behavior of cold-formed steel beams that are then used as rules to reduce the search space and guide the exhaustive search. The procedure for finding the global optimum design of cold-formed steel beams is presented in a few recursive steps. The optimum design curves presented in this article can be of great value to structural design engineers.     

Web-Based Interactive Courseware for Structural Steel Design Using Java

The recent resurgence of the World Wide Web and Internet technologies has provided fresh opportunities to enhance the educational environment. Issues in developing courseware for Web-based education and potential solutions are discussed. Building on the synergistic human-machine approach of interactive computer-aided design developed by Adeli in 1987, a new Web-based approach and courseware are presented to complement teaching of structural steel design. The courseware has been developed in Java, an object-oriented, platform-independent computer language. Example applets for interactive design of beams and different types of connections are presented. The user can modify or limit any design parameter and request a new design without the need to start all over again. This is an effective tutorial feature considering the open-ended nature of the design problems. The student can find the answers to a lot of what-if scenarios in a very short period of time. Not only does this boost the learning experience in the design course significantly, but it also makes it more interesting.     

Stock exchange trading optimization algorithm: a human-inspired method for global optimization

The Journal of Supercomputing - In this paper, a human-inspired optimization algorithm called stock exchange trading optimization (SETO) for solving numerical and engineering problems is...