• Structural Engineering and Mechanics
• /
• v.63 no.4
• /
• pp.429-438
• /
• 2017

Structural design has an imperative role in deciding the failure possibility of a Reinforced Concrete (RC) structure. Recent research works achieved the goal of predicting the structural failure of the RC structure with the assistance of machine learning techniques. Previously, the Artificial Neural Network (ANN) has been trained supported by Particle Swarm Optimization (PSO) to classify RC structures with reasonable accuracy. Though, keeping in mind the sensitivity in predicting the structural failure, more accurate models are still absent in the context of Machine Learning. Since the efficiency of multi-objective optimization over single objective optimization techniques is well established. Thus, the motivation of the current work is to employ a Multi-objective Genetic Algorithm (MOGA) to train the Neural Network (NN) based model. In the present work, the NN has been trained with MOGA to minimize the Root Mean Squared Error (RMSE) and Maximum Error (ME) toward optimizing the weight vector of the NN. The model has been tested by using a dataset consisting of 150 RC structure buildings. The proposed NN-MOGA based model has been compared with Multi-layer perceptron-feed-forward network (MLP-FFN) and NN-PSO based models in terms of several performance metrics. Experimental results suggested that the NN-MOGA has outperformed other existing well known classifiers with a reasonable improvement over them. Meanwhile, the proposed NN-MOGA achieved the superior accuracy of 93.33% and F-measure of 94.44%, which is superior to the other classifiers in the present study.

• Structural Engineering and Mechanics
• /
• v.63 no.4
• /
• pp.509-519
• /
• 2017

Wind field in mountainous regions demonstrates unique distribution characteristic as compared with the wind field of the flat area, wind load and wind effect are the key considerations in structural design of television towers situated in mountainous regions. The television tower to be constructed is located at the top of Xiushan Mountain in Nanjing, China. In order to investigate the impact of terrain factors of hilltops on wind loads, firstly a wind tunnel test was performed for the mountainous area within 800m from the television tower. Then the tower basal forces such as bending moments and shear strength were obtained based on high frequency force balance (HFFB) test. Based on the experiments, the improved method for determining the load combinations was applied to extract the response distribution patterns of foundation internal force and peak acceleration of the tower top, then the equivalent static wind loads were computed under different wind angles, load conditions and equivalent goals. The impact of terrain factors, damping ratio and equivalent goals on the wind load distribution of a television tower was discussed. Finally the equivalent static wind loads of the television tower under the 5 most adverse wind angles and 5 most adverse load conditions were computed. The experimental method, computations and research findings provide important references for the anti-wind design of high-rise structure built on hilltops.

• Structural Engineering and Mechanics
• /
• v.74 no.4
• /
• pp.457-470
• /
• 2020

The force resisting ability of a connection has direct implications on the overall response of a timber framed structure to various actions, thereby governing the integrity and safety of such constructions. The behavior of timber framed structures has been studied by many researchers by testing full-scale-connections in timber frames so as to establish consistent design provisions on the same. However, much emphasis in this approach has been unidirectional, that has focused on a particular connection configuration, with no research output stressing on the refinement of the existing connection details in order to optimize their performance. In this regard, addition of adhesive to dowelled timber connections is an economically effective technique that has a potential to improve their performance. Therefore, a comparative study to evaluate the performance of various full-scale timber frame Nailed connections (Bridled Tenon, Cross Halved, Dovetail Halved and Mortise Tenon) supplemented by adhesive with respect to Nailed-Only counterparts under tensile loading has been investigated in this paper. The load-deformation values measured have been used to calculate stiffness, load capacity and ductility in both the connection forms (with and without adhesion) which in turn have been compared to other configurations along with the observed failure modes. The observed load capacity of the tested models has also been compared to the design strengths predicted by National Design Specifications (NDS-2018) for timber construction. Additionally, the experimental behavior was validated by developing non-linear finite element models in ABAQUS. All the results showed incorporation of adhesive to be an efficient and an economical technique in significantly enhancing the performance of various timber nailed connections under tensile action. Thus, this research is novel in a sense that it not only explores the tensile behavior of different nailed joint configurations common in timber construction but also stresses on improvising the same in a logical manner hence making it distinctive in its approach.

• Structural Engineering and Mechanics
• /
• v.74 no.6
• /
• pp.789-807
• /
• 2020

Multiple earthquakes that occur during short seismic intervals affect the inelastic behavior of the structures. Sequential ground motions against the single earthquake event cause the building structure to face loss in stiffness and its strength. Although, numerous research studies had been conducted in this research area but still significant limitations exist such as: 1) use of traditional design procedure which usually considers single seismic excitation; 2) selecting a seismic excitation data based on earthquake events occurred at another place and time. Therefore, it is important to study the effects of successive ground motions on the framed structures. The objective of this study is to overcome the aforementioned limitations through testing a two storey RC building structural model scaled down to 1/10 ratio through a similitude relation. The scaled model is examined using a shaking table. Thereafter, the experimental model results are validated with simulated results using ETABS software. The test framed specimen is subjected to sequential five artificial and four real-time earthquake motions. Dynamic response history analysis has been conducted to investigate the i) observed response and crack pattern; ii) maximum displacement; iii) residual displacement; iv) Interstorey drift ratio and damage limitation. The results of the study conclude that the low-rise building model has ability to resist successive artificial ground motion from its strength. Sequential artificial ground motions cause the framed structure to displace each storey twice in correlation with vary first artificial seismic vibration. The displacement parameters showed that real-time successive ground motions have a limited impact on the low-rise reinforced concrete model. The finding shows that traditional seismic design EC8 requires to reconsider the traditional design procedure.

• Structural Engineering and Mechanics
• /
• v.76 no.2
• /
• pp.153-162
• /
• 2020

Aiming at the mechanical and structural characteristics of the contact zone composite rock, the shear tests and numerical studies were carried out. The effects of the differences in mechanical properties of different materials and the normal stress on shear properties of contact zone composite samples were analyzed from a macro-meso level. The results show that the composite samples have high shear strength, and the interface of different materials has strong adhesion. The differences in mechanical properties of materials weakens the shear strength and increase the shear brittleness of the sample, while normal stress will inhibit these effect. Under low/high normal stress, the sample show two failure modes, at the meso-damage level: elastic-shearing-frictional sliding and elastic-extrusion wear. This is mainly controlled by the contact and friction state of the material after damage. The secondary failure of undulating structure under normal-shear stress is the nature of extrusion wear, which is positively correlated to the normal stress and the degree of difference in mechanical properties of different materials. The increase of the mechanical difference of the sample will enhance the shear brittleness under lower normal stress and the shear interaction under higher normal stress.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.2
• /
• pp.443-448
• /
• 2010

Rapid advance in information technology requires high performance devices with compact size. Integrated multi-layer electronic element with different functions enables those compact devices to possess various performances and powerful capabilities. In mass production, the multi-layer electronic element is manufactured as a bulk type with a large number of parts for productivity. However, this may cause the electronic part to be damaged in the cutting process of the bulk elements to separate into each part. Therefore the cutting performance of multi-layer element bulk is playing an important role in the view of production efficiency. This study focuses on the cutting characteristics of multi-layer electronic elements. In order to increase the efficiency, the vibration cutting method was applied to the blade cutting machine. Flexure hinge structure, which is an physical amplifier of increasing displacement, was attached to the vibration cutting device for machining efficiency. The behaviors of flexure hinge were modeled with Lagrange equation and simulated with finite element method (FEM). Performance of hinge structure was verified by experimental modal analysis (EMA) for hinge structure to be tuned to the specific mode of vibrations. Cutting experiments of multi-layer elements were conducted with the proposed vibrating cutting module, and the characteristics was analyzed.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.9
• /
• pp.5434-5439
• /
• 2014

The surface management of metals was performed with a tool microscope or surface roughness measurement instruments. These methods were not efficient for checking the surface status of the die in the production field. For this reason, an analysis system or measurement system to monitor the wear, defects and surface status as a die ages is required. This study, developed surface analysis software for automatic analysis and standardization of a die or processed products. Software was designed to measure the basic features, such as circles, dots, and lines. The captured images were rendered as three-dimensional representations so that the depth of the grooves on the die and segmental profiles could be estimated. As a result of experimental analysis, the surface roughness was measured with an accuracy more than 93.2%, and the maximum deviation in the surface roughness for the brightness of the lighting was within $3{\mu}m$. The confidence in the device's precision was assured. These results show quality control through efficient surface analysis.

• Structural Engineering and Mechanics
• /
• v.58 no.2
• /
• pp.277-300
• /
• 2016

Cold-formed steel (CFS) sections are becoming an increasingly popular solution for constructing floors in residential, healthcare and education buildings. Their reduced weight, however, makes them prone to excessive vibrations, increasing the need for accurate prediction of CFS floor modal properties. By combining experimental modal analysis of a full-scale CFS framed building and its floors and their numerical finite element (FE) modelling this paper demonstrates that the existing methods (based on the best engineering judgement) for predicting CFS floor modal properties are unreliable. They can yield over 40% difference between the predicted and measured natural frequencies for important modes of vibration. This is because the methods were adopted from other floor types (e.g., timber or standard steel-concrete composite floors) and do not take into account specific features of CFS floors. Using the adjusted and then updated FE model, featuring semi-rigid connections led to markedly improved results. The first four measured and calculated CFS floor natural frequencies matched exactly and all relevant modal assurance criterion (MAC) values were above 90%. The introduction of flexible supports and more realistic modelling of the floor boundary conditions, as well as non-structural $fa{\c{c}}ade$ walls, proved to be crucial in the development of the new more successful modelling strategy. The process used to develop 10 identified and experimentally verified FE modelling parameters is based on published information and parameter adjustment resulting from FE model updating. This can be utilised for future design of similar lightweight steel floors in prefabricated buildings when checking their vibration serviceability, likely to be their governing design criterion.

• Structural Engineering and Mechanics
• /
• v.39 no.3
• /
• pp.383-398
• /
• 2011

This paper investigates the nonlinear analysis of concrete-filled steel composite columns subjected to axial loading to predict the ultimate load capacity and behaviour of the columns. Finite element software LUSAS is used to conduct the nonlinear analyses. The accuracy of the finite element modelling is verified by comparing the result with the corresponding experimental result reported by other researchers. Nonlinear analyses are done to study and develop different shapes and number of cold-formed steel sheeting stiffeners with various thicknesses of cold-formed steel sheets. Effects of the parameters on the ultimate axial load capacity and ductility of the concrete-filled steel composite columns are examined. Effects of variables such as concrete compressive strength $f_c$ and cold-formed steel sheet yield stress $f_{yp}$ on the ultimate axial load capacity of the columns are also investigated. The results are shown in the form of axial load-normalized axial shortening plots. It is concluded from the study that the ultimate axial load capacity and behaviour of the concrete-filled steel composite columns can be accurately predicted by the proposed finite element modelling. Results in this study demonstrate that the ultimate axial load capacity and ductility of the columns are affected with various thicknesses of steel sheets and different shapes and number of stiffeners. Also, compressive strength $f_c$ of the concrete and yield stress $f_{yp}$ of the cold-formed steel sheet influence the performance of the columns significantly.

• Structural Engineering and Mechanics
• /
• v.40 no.3
• /
• pp.411-429
• /
• 2011

In the past decades, recycling use of demolished concrete was almost limited to the types of recycled coarse aggregate with a size of about 5-40 mm and recycled fine aggregate with a size of about 0-5 mm for concrete structures, and reuse of demolished concrete lumps (DCLs) with a size much larger than that of recycled aggregate, e.g., 50-300 mm, has been limited to roadbed, backfilling materials, or discarded to landfills. Treatment processes of DCLs are much simpler than those of recycled aggregate, leading to less cost and more energy-saving. In the future, the amount of demolished concrete is estimated to be much higher, so reuse of DCLs for concrete structures will become necessary. The objectives of this paper are to document the process of making reinforced concrete beams with DCLs, and to discuss the flexural and shear behaviors of those reinforced DCL beams through an experimental program, which includes three beams filled with DCLs and one conventional beam for investigating the flexural strengths and deformations, and 12 beams filled with DCLs and two conventional beams for investigating the shear strengths and deformations. The authors hope that the proposed concept offers another sustainable solution to the concrete industry.