• Steel and Composite Structures
• /
• v.52 no.2
• /
• pp.199-215
• /
• 2024

The Caynarachi Bridge is a 130 m long posttensioned steel-concrete composite bridge built in Peru. The structural performance of this bridge under construction loads is reviewed in this paper using numerical simulation. Hence, a numerical model using shell finite elements to trace its deformational behavior at service conditions is proposed. The geometry and boundary conditions of the superstructure are updated according to the construction schedule. Firstly, the adequacy of the proposed model is validated with the field measurements obtained from the static truck load test. Secondly, the study of other scenarios less explored in research are performed to investigate the effect of some variables on bridge performance such as time effects, sequence of execution of concrete slabs and type of supports conditions at the abutments. The obtained results show that the original sequence of execution of the superstructure better behaves mechanically in relation to the other studied scenarios, yielding smaller stresses at critical cross sections with staging. It is also demonstrated that an improper slab staging may lead to more critical stresses at the studied cross sections and that casting the concrete slab at the negative moment regions first can lead to an optimal design. Also, the long-term displacements can be accurately predicted using an equivalent composite resistance cross section defined by a steel to concrete modulus ratio equal to three. This article gives some insights into the potential shortcomings or advantages of the original design through high-fidelity finite element simulations and reinforces the understating of posttensioned composite bridges with staging.

• Journal of Korea Multimedia Society
• /
• v.13 no.7
• /
• pp.1000-1015
• /
• 2010

In this paper, we propose a novel algorithm for hand gesture recognition. The hand detection method is based on human skin color, and we use the boundary energy information to locate the hand region accurately, then the moment method will be employed to locate the hand palm center. Hand gesture recognition can be separated into 2 step: firstly, the hand posture recognition: we employ the parallel NNs to deal with problem of hand posture recognition, pattern of a hand posture can be extracted by utilize the fitting ellipses method, which separates the detected hand region by 12 ellipses and calculates the white pixels rate in ellipse line. the pattern will be input to the NNs with 12 input nodes, the NNs contains 4 output nodes, each output node out a value within 0~1, the posture is then represented by composed of the 4 output codes. Secondly, the hand gesture tracking and recognition: we employed the Kalman filter to predict the position information of gesture to create the position sequence, distance relationship between positions will be used to confirm the gesture. The simulation have been performed on Windows XP to evaluate the efficiency of the algorithm, for recognizing the hand posture, we used 300 training images to train the recognizing machine and used 200 images to test the machine, the correct number is up to 194. And for testing the hand tracking recognition part, we make 1200 times gesture (each gesture 400 times), the total correct number is 1002 times. These results shows that the proposed gesture recognition algorithm can achieve an endurable job for detecting the hand and its' gesture.

• Journal of the Korean Chemical Society
• /
• v.41 no.9
• /
• pp.449-459
• /
• 1997

The bonded state polarizabilities of ions in the alkali halides are estimated by using the Seitz and Ruffa (SR) energy level analysis relation. The effective number of electrons $(N_{eff})$ in the Slater-Kirkwood formula are used for all members of an isoelectronic sequence. The effective dispersion coefficients $(C_6^{eff})$ are calculated by the use of the empirical formula (J. Chem. Phys. 1991, 95, 1852) estimating $(N_{eff})$ values to reproduce the experimental $(C_6^{eff})$ for atom-atom (or molecule) interactions. In the framework of the T-Rittner model the model potential is constructed and used to calculate the values of dissociation energy and dipole moment. The results obtained in the present study are in good agreement with the experiment one.

• Journal of the Korea Institute of Building Construction
• /
• v.7 no.1 s.23
• /
• pp.91-98
• /
• 2007

In this study, the property and plastic cracking pattern of concrete were compared and analyzed with the replacement ratio of fly ash 0, 5, 10, 15, 20% by cement weight. And curing conditions of concrete were given variously such as indoors(with wind speed as 0, 300, 500m/min), outdoors and chamber. The hydration temperature had a tendency to decrease as the replacement ratio of fly ash increased, and in the case of the wind speed 0m/min, it was showed that the moment that the amount of evaporation of water from surface of reference concrete was more than the volume of bleeding was 90 min since casting concrete. The time that the crack initiated had a tendency to be more quickly as the replacement ratio of fly ash increased. The number, length, width and area of crack in the indoor curing, exposed outdoor curing, enclosed outdoor curing had a tendency to decrease as the replacement ratio of fly ash increased. The crack had a tendency to decrease in sequence of exposed outdoor, enclosed outdoor curing, indoors curing. The outbreak of cracking by the change of temperature and humidity was affected by relative humidity more than temperature and the cracking had a tendency to increase as relative humidity lowered.

• Ocean Systems Engineering
• /
• v.4 no.3
• /
• pp.201-213
• /
• 2014

Wave run-up is an important issue in offshore engineering, which is tightly related to the loads on the marine structures. In this study, a series of physical experiments have been performed to investigate the wave run-up around a vertical cylinder in transitional water depth. The wave run-ups of regular waves, irregular waves and focused waves have been presented and the characteristics in frequency domain have been investigated with the FFT and wavelet transform methods. This study focuses on the nonlinear features of the wave run-up and the interaction between the wave run-up and the cylinder. The results show that the nonlinear interaction between the waves and the structures might result wave run-up components of higher frequencies. The wave run-ups of the moderate irregular waves exhibit 2nd order nonlinear characteristics. For the focused waves, the incident waves are of strong nonlinearity and the wavelet coherence analysis reveals that the wave run-up at focal moment contains combined contributions from almost all the frequency components of the focused wave sequence and the contributions of frequency components up to 4th order harmonic levels are recommended to be included.

• Structural Engineering and Mechanics
• /
• v.63 no.1
• /
• pp.77-88
• /
• 2017

Correction Factor Method (CFM) is one of the earliest methods for simulating the actual behavior of structure according to construction sequences and practical implementation steps of the construction process which corrects the results of the conventional analysis just by the application of correction factors. The most important advantages of CFM are the simplicity and time-efficiency of the computations in estimating the final modified forces of the beams. However, considerable inaccuracy in evaluating the internal forces of the other structural members obtained by the moment equilibrium equation in the connection joints is the biggest disadvantage of the method. This paper proposes a novel method to eliminate the aforementioned defect of CFM by using the column shortening correction factors of the CFM to modify the axial stiffness of columns. In this method, the effects of construction sequences are considered by performing a single step analysis which is more time-efficient when compared to the staged analysis especially in tall buildings with higher number of elements. In order to validate the proposed method, three structures with different properties are chosen and their behaviors are investigated by application of all four methods of: conventional one-step analysis, sequential construction analysis (SCA), CFM, and currently proposed method.

• The Journal of Engineering Research
• /
• v.6 no.1
• /
• pp.83-96
• /
• 2004

A soil mailed wall is adapted as road widening measure and is constructed under a miniature abutment built on steel pipe piles. The soil nailed wall called for removal of the existing embankment slope to permanently retain the fill behind the abutment. The soil nailed wall is fully instrumented and is monitored. A 3D finite element analysis is used to study further the behavior of the soil nailed wall. The complete sequence of construction is simulated. The numerical model is calibrated against the instrumented nailed wall. Then a parametric study is conducted. The results provide valuable information related to the effect of the excavation and nailing on the following: axial load and bending moment in the piles, load in the nails, and wall deflections.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2005.03a
• /
• pp.932-939
• /
• 2005

Recently, the lateral displacement of the passive piles which installed under the revetment on soft ground is very important during the land reclamation work along the coastal line. The revetment on the soft clay develops the lateral displacement of the ground when the revetment loading is exceeded a certain limit. The lateral displacement of ground causes an excessive deformation of under structure itself and develops lateral earth pressure against the pile foundation as well. Especially passive piles subjected to lateral earth pressures are likely to have excessive horizontal displacement and large bending moment, which induces structural failure of pile foundation and harmful effects on superstructure. The subject of study is to investigate the later displacement of pile foundation during the construction of container terminal at the south port of Incheon. Actual field measurement data and finite element method(FEM) by AFFIMEX Ver 3.4 were used to analyze the displacement of pile and the vertical settlement of soft ground. This analysis was carried out at each sequence of construction work.

• Computers and Concrete
• /
• v.21 no.1
• /
• pp.55-66
• /
• 2018

A large main shock may consist of numerous aftershocks with a short period. The aftershocks induced by a large main shock can cause the collapse of a structure that has been already damaged by the preceding main shock. These aftershocks are important factors in structural damages. Furthermore, despite what is often assumed in seismic design codes, earthquakes do not usually occur as a single event, but as a series of strong aftershocks and even fore shocks. For this reason, this study investigates the effect and potential of consecutive earthquakes on the response and behavior of concrete structures. At first, six moment resisting concrete frames with 3, 5, 7, 10, 12 and 15 stories are designed and analyzed under two different records with seismic sequences from real and artificial cases. The damage states of the model frames were then measured by the Park and Ang's damage index. From the results of this investigation, it is observed that the sequences of ground motions can almost double the accumulated damage and increased response of structures. Therefore, it is certainly insufficient to ignore this effect in the design procedure of structures. Also, the use of artificial seismic sequences as design earthquake can lead to non-conservative prediction of behavior and damage of structures under real seismic sequences.

• Earthquakes and Structures
• /
• v.14 no.2
• /
• pp.129-142
• /
• 2018

The current paper introduces a new approach for development of damage index to obtain the maximum damage in the reinforced concrete frames caused by as-recorded single and consecutive earthquakes. To do so, two sets of strong ground motions are selected based on maximum and approximately maximum peak ground acceleration (PGA) from "PEER" and "USGS" centers. Consecutive earthquakes in the first and second groups, not only occurred in similar directions and same stations, but also their real time gaps between successive shocks are less than 10 minutes and 10 days, respectively. In the following, a suite of six concrete moment resisting frames, including 3, 5, 7, 10, 12 and 15 stories, are designed in OpenSees software and analyzed for more than 850 times under two groups of as-recorded strong ground motion records with/without seismic sequences phenomena. The idealized multilayer artificial neural networks, with the least value of Mean Square Error (MSE) and maximum value of regression (R) between outputs and targets were then employed to generate the empirical charts and several correction equations for design utilization. To investigate the effectiveness of the proposed damage index, calibration of the new approach to existing real data (the result of Park-Ang damage index 1985), were conducted. The obtained results show good precision of the developed ANNs-based model in predicting the maximum damage of regular reinforced concrete frames.