• Steel and Composite Structures
• /
• v.12 no.3
• /
• pp.183-205
• /
• 2012

This paper presents an investigation of the effect of inclined stiffeners on the load-carrying capacity of simply-supported hot-rolled steel I-beams under various load conditions. The study is carried out using finite element analysis. A series of beams modeled using 3-D solid finite elements with consideration of initial geometric imperfections, residual stresses, and material nonlinearity are analyzed with and without inclined stiffeners to show how the application of inclined stiffeners can offer a noticeable increase in their lateral-torsional buckling (LTB) capacity. The analysis results have shown that the amount of increase in LTB capacity is primarily dependent on the location of the inclined stiffeners and the lateral unsupported length of the beam. The width, thickness and inclination angle of the stiffeners do not have as much an effect on the beam's lateral-torsional buckling capacity when compared to the stiffeners' location and beam length. Once the optimal location for the stiffeners is determined, parametric studies are performed for different beam lengths and load cases and a design equation is developed for the design of such stiffeners. A design example is given to demonstrate how the proposed equation can be used for the design of inclined stiffeners not only to enhance the beam's bearing capacity but its lateral-torsional buckling strength.

• Steel and Composite Structures
• /
• v.39 no.3
• /
• pp.319-335
• /
• 2021

This study proposes a new and highly-accurate artificial intelligence model, namely ANN-IP, which combines an interior-point (IP) algorithm and artificial neural network (ANN), to improve the axial compression capacity prediction of elliptical concrete-filled steel tubular (CFST) columns. For this purpose, 145 tests of elliptical CFST columns extracted from the literature are used to develop the ANN-IP model. In this regard, axial compression capacity is considered as a function of the column length, the major axis diameter, the minor axis diameter, the thickness of the steel tube, the yield strength of the steel tube, and the compressive strength of concrete. The performance of the ANN-IP model is compared with the ANN-LM model, which uses the robust Levenberg-Marquardt (LM) algorithm to train the ANN model. The comparative results show that the ANN-IP model obtains more magnificent precision (R² = 0.983, RMSE = 59.963 kN, a20 - index = 0.979) than the ANN-LM model (R² = 0.938, RMSE = 116.634 kN, a20 - index = 0.890). Finally, a new Graphical User Interface (GUI) tool is developed to use the ANN-IP model for the practical design. In conclusion, this study reveals that the proposed ANN-IP model can properly predict the axial compression capacity of elliptical CFST columns and eliminate the need for conducting costly experiments to some extent.

• Advances in Computational Design
• /
• v.4 no.3
• /
• pp.251-272
• /
• 2019

This study performed lateral load testing on seventeen wood wall frames in two sections. Section one included eight tests studying structural foam sheathing of shear walls subjected to monotonic loads following the ASTM E564 test method. In this section, the wood frame was sheathed with four different types of structural foam sheathing on one side and gypsum wallboard (GWB) on the opposite side of the wall frame, with Simpson HDQ8 hold down anchors at the terminal studs. Section two included nine tests studying wall constructed with oriented strand board (OSB) only on one side of the wall frame subjected to gradually applied monotonic loads. Three of the OSB walls were tied to the baseplate with Simpson LSTA 9 tie on each stud. From the test results for Section one; the monotonic tests showed an 11 to 27 percent reduction in capacity from the published design values and for Section two; doubling baseplates, reducing anchor bolt spacing, using bearing plate washers and LSTA 9 ties effectively improved the OSB wall capacity. In comparison of sections one and two, it is expected the walls with structural foam sheathing without hold downs and GWB have a lower wall capacity as hold down and GWB improved the capacity.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.3
• /
• pp.1123-1130
• /
• 2013

This paper aims to estimate work zone base capacity by the number of lanes for urban freeway. To do this, data were collected from the field survey and the database system maintained by traffic control center, and analyzed with four different methods such as the average maximum observation flow rate, headway, regression analysis, and parameter inspection. The work zone base capacity for urban freeway is estimated based on the average maximum observation flow rate and headway method, which are more reliable methods compared to others. The average capacity is 1,650pcphpl when the design speed is 80km/h. The capacity of four lanes one-way work zones was about 1,700pcphpl, while one of 2 lanes one-way work zones was about 1,600pcphpl. The capacity reduction rates for each are 0.15 and 0.2, respectively. The smaller the number of lane is, the more base capacity is reduced. For verification of results, we estimate the capacity by simulation analysis using PARAMICS, and compare with analytical results by a statistical method. This research can be used for efficient and systemic management of work zone in the urban freeway.

• Journal of the Korean Geotechnical Society
• /
• v.35 no.8
• /
• pp.31-42
• /
• 2019

A total of 73 pile design data for prebored PHC piles was analyzed to study the current design method. Based on the design data, a ratio of skin friction to total capacity from the pile design data was about 20~53%. Such low ratio of skin friction to total capacity tends to underestimate skin friction. Considering this tendency, the current design method should be improved. Also, an average design efficiency of PHC pile capacity was 70% and an average design efficiency for bearing capacity of soil or weathered rock was 80%, which shows slightly higher value than the former. This is probably due to the fact that the allowable bearing capacity is estimated to be equal to or slightly higher than the design load. Hence, the allowable bearing capacity should be estimated to be higher than the long-term allowable compressive force of the PHC pile. In the current design method, skin friction is calculated to be about 2.2 times lower than end bearing. The current design method for prebored PHC piles applied foreign design methods without any verification of applicability to the domestic soil or rock condition. Therefore, the current design method for prebored PHC piles should be improved.

• Progress in Superconductivity and Cryogenics
• /
• v.20 no.2
• /
• pp.1-5
• /
• 2018

Arsenic (As) is one of the elements having most harmful impact on the human health. Arsenic is a known carcinogen and arsenic contamination of drinking water is affecting on humans in many regions of the world. Adsorption has been proved most preferable technique for the removal of arsenic. Many researchers have studied various types of solid materials as arsenic adsorbent, and iron oxide and its modified forms are considered as the most effective adsorbent in terms of adsorption capacity, recovery, and economics. However, most of all iron oxides have small surface area in comparing with common adsorbents in environmental application such as activated carbon but the activated carbon has weak sorption affinity for arsenic. We have used an activated carbon as base adsorbent and iron oxide coating on the activated carbon as high affinity sorption sites and giving magnetic attraction ability. In this study, adsorption properties of arsenic and magnetic separation efficiency of the magnetized activated carbon (MAC) were evaluated with variable iron oxide content. As the iron oxide content of the MAC increased, adsorption capacity has also gradually increased up to a point where clogging by iron oxide in the pore of activated carbon compensate the increased sorption capacity. The increase of iron oxide content of the MAC also affected magnetic properties, which resulted in greater magnetic separation efficiency. Current results show that magnetically modified common adsorbent can be an efficiency improved adsorbent and a feasible environmental process if it is combined with the magnetic separation.

• Journal of the Korean GEO-environmental Society
• /
• v.4 no.3
• /
• pp.19-26
• /
• 2003

Recently, for the design of pile foundations on the soft ground condition, it is recognized that set-up effects are another important factor which influence the characteristics of bearing capacity of pile. In this paper, the thirteen dynamic pile loading tests were performed at the two different construction sites and the end of initial driving(EOID) were also performed and then restrike tests were performed after certain time lag. The H-pile, pipe pile, PHC pile are installed by driving into the loose silty soil and then restrike tests were performed. Nine days after pile driving, the bearing capacity of H and pipe pile were increased whereas there is not bearing capacity increasement with PHC pile. When the dense silty soil, the restrike test results showed that the bearing capacity of H and pipe pile increased up to 1.17 times. The 1-st and 2-nd restrike tests performed after 6 and 12 day, respectively. The results showed that the bearing capacity of PHC pile was decreased but the bearing capacity of piles were increased up to 1.38 times after 13 days with the third restrike test.

• Journal of Environmental Science International
• /
• v.7 no.6
• /
• pp.735-744
• /
• 1998

This research emphasizes the necessity of building a multilateral environmental cooperation. The Process and Problems of multilateral environmental cooperation system are discussed, and some policy proposals are suggested. Especially for Northeast Asia, a comprehensive multilateral environmental cooperation system is required because of transborder pollutions. Within the contractual environment, international institutions can help the parties of conference to build up national capacity to cope with environmental threat.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.15 no.7
• /
• pp.4675-4681
• /
• 2014

This study examined the $H_2S$ removal characteristics, such as breakthrough time, adsorption capacity, and adsorption rate of adsorbents between Zeolite 3A and DETOX in terms of the $H_2S$ inflow concentration and adsorption temperature. The adsorption capacity of Zeolite 3A increased with increasing mass flow rate of hydrogen sulfide($H_2S$) inflow, but the breakthrough time decreased. On the other hand, both the adsorption capacity and breakthrough time of DETOX decreased with increasing mass flow rate of $H_2S$ inflow. The adsorption capacity and breakthrough time of Zeolite 3A decreased with increasing adsorption temperature but those of DETOX increased. The adsorption capacity of DETOX was higher than that of Zeolite 3A by a factor of 2.5 - 16.4 because the collision frequency that overcomes the activation energy barrier increased with increasing adsorption temperature. For Zeolite 3A and DETOX, the adsorption rate of $H_2S$ increased with increasing mass flow rate of $H_2S$ inflow and adsorption temperature. The adsorption rate of $H_2S$ for Zeolite 3A was 4 times as much as that for DETOX. For the removal of $H_2S$ in biogas, DETOX had an advantage over Zeolite 3A because DETOX had a much longer breakthrough time and greater adsorption capacity in the temperature range of 308~318K than Zeolite 3A.

• Korean Journal of Environmental Biology
• /
• v.21 no.4
• /
• pp.405-409
• /
• 2003

To study the tolerant capacity of anaerobic granular sludge (AGS) to oxygen using semi -dynamic batch experiment, the aerating time, pH of the basal media, reductive inorganic materials, microorganism, and microorganism metabolite were investigated. When the aerating time was higher or lower than 0.5 h, the producing gas activity of sludge was lower than that of the control. The oxygen tolerance of the experimental sludge was the highest at the initial pH 7.2. The producing gas activity of sludge I was higher than that of sludge II. And storage at $4^{\circ}C$ can low the lose of the oxygen tolerance capacity of granular sludge. The producing gas activity of sludge was the highest when KI was added. The growth of aerobic microorganisms and some metabolite could increase the producing gas activity of granular sludge.