Structural dynamic response analysis on structure under tsunami bore impact

The forefront of the tsunami bore has extremely strong turbulent intensity, vorticity, and impact force. It generates tremendous impact effect on the coastal structures, which is the direct reason of the damage and destruction of the structures. On the basis of the computational fluid dynamic theory, this paper applied fluid volume method to capture the free surface motion of the tsunami waves and developed a 3D wave numerical model of an experiment of dam-break tsunami bore impact on a structure. The effectiveness of the model was also validated. The model was then applied to numerically analyze the dynamic impact effect of a tsunami bore on the structure of a full-scale reinforced concrete frame. It resolved the dynamic impact force of the tsunami bore on the structure and their interaction process. This study also employed finite element analysis to compare the static and dynamic response of the frame structure under the impact effect of the tsunami bore. The structural vibration characteristic and dynamic magnification factor of the structure under tsunami bore impact are confirmed, which could provide a reference for the design of anti-tsunami buildings

Investigation on dynamic effects of frame with specially shaped columns subjected to column failure

Dynamic effects caused by sudden failure of the vertical load-bearing component are an important factor affecting the progressive collapse of building. In order to study the influence of dynamic effects on structure, a collapse experiment of a 1/3-scale, 2×3-bay and 2-story reinforced concrete frame with specially shaped columns with sudden column removal were carried out. The displacement response, reinforcement and concrete strains during the collapse of the frame were studied to reveal the dynamic response of structure such as deformation and internal force redistribution. Experimental results show that the influence of dynamic effects on structure at the moment of component failure was not significant. The structure was still in the elastic stage and collapse did not occur, indicating that reinforced concrete frame designed according to Chinese codes has a good behavior against progressive collapse caused by sudden loss of a first floor column. A progressive collapse dynamic analysis model was established using the alternate path method based on the test frame, and the relationship between the dynamic amplification factors and failure time were derived. Transient time history analysis was carried out on the finite element model of experimental frame using OpenSees to obtain the variation of dynamic amplification factor with the failure time

Seismic performance of cross-shaped columns with 500 MPa grade reinforcing steel bars

Na temelju eksperimentalnog istraživanja provedenog na tri križna stupa s armirnim čeličnim šipkama od 500 MPa, izvršena je kontrastivna analiza u odnosu na kvar, nosivost i duktilnost pomaka probnog uzorka svakog stupa s različitim razmakom metalnih spona uz identičan omjer aksijalnog stupnja kompresije. Istraživanje pokazuje da uzdužne šipke popuštaju prije raspadanja betonske jezgre, a da spone visoke čvrstoće mogu osigurati značajno oganičenje. Smanjenjem razmaka između spona može se znatno poboljšati duktilnost probnih uzoraka. U međuvremenu, na osnovu vlaknastog elementa u OpenSees softveru, stimuliraju se mehaničke karakteristike uzoraka poboljšanim odnosom sastavnih materijala. Rezultati ispitivanja dobro se slažu s rezultatima dobivenim proračunom. U radu su istraženi učinci čvrstoće uzdužne šipke, čvrstoće i razmaka spona na mehaničke karakteristike uzoraka, a rezultati pokazuju da se smanjenjem razmaka između spona i povećanjem čvrstoće spona može znatno poboljšati nosivost, krajnji pomak i duktilnost uzoraka, ali je učinak na pomicanje granice popuštanja malen. Povećanje čvrstoće uzdužne šipke može znatno povećati nosivost, pomicanje granice popuštanja i krajnji pomak uzoraka, ali će neznatno biti smanjen faktor duktilnosti pomaka.Based on the experimental research on three cross-shaped columns with 500 MPa grade reinforcing steel bars, the contrastive analysis is made on failure mode, bearing capacity and displacement ductility of each column specimens with different stirrup spacing under the identical axial compression ratio. The research shows that the longitudinal bars yield before spalling of core concrete and high-strength stirrups can provide significant confinement. Decreasing stirrup spacing can significantly improve the ductility of the specimens. Meanwhile, based on the fibre element in the OpenSees software, the mechanical characteristics of the specimens are stimulated using fined constitutive relation of materials. The test results are well consistent with the calculated results. The effects of the longitudinal bar strength, the stirrup strength and stirrup spacing on the mechanical performance of the specimens are investigated in this paper, and the results show that the decrease of the stirrup spacing and increase of the stirrup strength can significantly improve the bearing capacity, ultimate displacement and ductility of the specimens but has little effect on the yield displacement. The increase of the longitudinal bar strength can significantly increase the bearing capacity, yield displacement and ultimate displacement of specimens, but the displacement ductility factor will be decreased slightly

Linearly Sweeping Leaky-Wave Antenna with High Scanning Rate

Leaky wave antenna is known as a type of travelling antenna with dispersive frequency responses, which has found important applications in modern communication, imaging and radar systems. The beam scanning rate is a key consideration in some applications, since it can minimize the bandwidth requirement of the system, during the scanning in broad angular regions. However, the sweeping linearity, namely the scanning angular range per unit frequency, is seldom taken into account at the same time in the published literature. In this article, we propose a waveguide-type leaky-wave antenna working from 11.1 GHz to 12 GHz. By loading periodical pins with glide symmetry in the waveguide, it is possible to manipulate the dispersion properties of the fast wave mode, hereby giving rise to a good balance between the scanning rate and sweeping linearity. This scenario has been validated by numerical simulation and experiment with excellent agreement. The measurement results reveal that the scanning angles have been increased to range from 16.7° ~67.5° varying the frequency from 11.1 to 12.1 GHz. The relative average scanning rate is enhanced up to 589.3°, with high sweeping linearity

An Improved Multiobjective Particle Swarm Optimization Algorithm Using Minimum Distance of Point to Line

In a multiobjective particle swarm optimization algorithm, selection of the global best particle for each particle of the population from a set of Pareto optimal solutions has a significant impact on the convergence and diversity of solutions, especially when optimizing problems with a large number of objectives. In this paper, a new method is introduced for selecting the global best particle, which is minimum distance of point to line multiobjective particle swarm optimization (MDPL-MOPSO). Using the basic concept of minimum distance of point to line and objective, the global best particle among archive members can be selected. Different test functions were used to test and compare MDPL-MOPSO with CD-MOPSO. The result shows that the convergence and diversity of MDPL-MOPSO are relatively better than CD-MOPSO. Finally, the proposed multiobjective particle swarm optimization algorithm is used for the Pareto optimal design of a five-degree-of-freedom vehicle vibration model, which resulted in numerous effective trade-offs among conflicting objectives, including seat acceleration, front tire velocity, rear tire velocity, relative displacement between sprung mass and front tire, and relative displacement between sprung mass and rear tire. The superiority of this work is demonstrated by comparing the obtained results with the literature