• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.28 no.6
• /
• pp.675-682
• /
• 2015

Current design codes such as AASHTO LRFD or Korean Highway Bridge Design Code recommend of using static force for designing bridge column against vehicle collisions. However, there was an accident that the bridge was collapsed shortly after vehicle impact on bridge pier in Nebraska(near Big Spring, 2003). It was found that the second largest cause of bridge collapse is collision after hydraulic causes. It can be thought that the possibility of truck-bridge collision are getting increasing as the size of truck increases and traffic condition are becoming improved. However, dynamic behavior under the impact loading seldom considered in bridge design procedure due to computational cost and time. In this study, in order to reduce the computational cost for dynamic impact analysis, model reduction method was developed. Obtained results of residual displacement were compared with the results of direct impact simulations.

• Journal of the Korean Geotechnical Society
• /
• v.20 no.5
• /
• pp.67-78
• /
• 2004

Soil-steel bridges are made of flexible corrugated steel plates buried in the well-compacted granular soil. One kind of possible collapses of these structures could be initiated by shear or tension failure in the soil cover subjected to vehicle loads. Current design codes provide the requirements for the minimum depth of the soil cover to avoid problems associated with soil cover failures. However, these requirements were developed for short span (less than 7.7 m) structures which are made of unstiffened plates of standard corrugation (150$\times$50 m). Numerical analyses were carried out to investigate the behavior of long span soil steel bridges according to thickness of the soil cover. The span of structures were up to 20 m and deep corrugated plates (381$\times$140 m) were used. The analysis showed that the minimum cover depth of 1.5 m could be sufficient to prevent the soil cover failure in the structures with a span exceeding 10 m. Additional analyses were performed to verify the reinforcement effect of the concrete relieving slab which can be a special feature to reduce the live-load effects. Analyses revealed that the bending moment of the conduit wall with a relieving slab was less than 20% of that without a relieving slab in a case of shallow soil cover conditions.

• Journal of Korean Society of Steel Construction
• /
• v.29 no.2
• /
• pp.147-158
• /
• 2017

The present study focused on the structural performance of newly developed prefabricated composite columns (PSRC composite column) using bolt-connected steel angles. Concentric axial loading tests were performed for four 2/3 scaled PSRC column specimens and two conventional SRC column specimens. The test parameters were the spacing and sectional configurations of lateral reinforcement, and width-to-thickness ratio of steel angles. The test results showed that the axial load-carrying capacity and deformation capacity of the PSRC column specimens were comparable to those of the conventional SRC column specimens. Closely spaced steel plates and Z-shaped steel plates for lateral reinforcement increased the deformation capacity of the PSRC column specimens. The load-carrying capacity was greater than the prediction by current design codes. Numerical analysis was performed for the specimens. The results agreed well with the test results in terms of initial stiffness, load-carrying capacity, except for strength degradation due to cover concrete spalling.

• Journal of the Earthquake Engineering Society of Korea
• /
• v.3 no.1
• /
• pp.113-122
• /
• 1999

The importance of the vertical response of a structure was well recognized after the Hyogoken-Nanbu earthquake of Japan. However, most of the seismic design codes does not specified the site sail profiles, and the sail and foundations conditions were mostly neglected in the vertical seismic analyses of a structure. In this paper, the effects of foundation size, sail layer depth under the foundation, foundation embedment and pile foundation on the vertical seismic response spectra for both surface and embedded mat foundation were studied to investigate the effects of the soft soil layer on the vertical response of a structure excited with the vertical components of Taft and El Centro earthquakes, considering the sail profile types of $S_A,S_C,S_E$ in UBC-97, the medium and large size foundations, the soil layer depth under the foundation of 30 and 60m, the foundation embedment of 0 and 15m, and the precast reinforced concrete bearing piles installed in the soft soil deposit. According to the study results, the foundation size has a little effect on the vertical seismic response, However, the soil layer depth under the foundation of 60m has to be considered for the vertical seismic analysis of a structure as for the horizontal one. The embedded pile foundations as well as the surface ones built on the soft soil layer amplified the vertical seismic response of a structure very much.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.2 no.3
• /
• pp.87-99
• /
• 1982

This study proposes a reliability based design criteria for the R.C. superstructures of highway bridges. Uncertainties associated with the resistance of T or rectangular sections are investigated, and a set of appropriate uncertainties associated with the bridge dead and traffic live loads are proposed by reflecting our level of practice. Major 2nd moment reliability analysis and design theories including both Cornell's MFOSM(Mean First Order 2nd Moment) Methods and Lind-Hasofer's AFOSM(Advanced First Order 2nd Moment) Methods are summarized and compared, and it has been found that Ellingwood's algorithm and an approximate log-normal type reliability formula are well suited for the proposed reliability study. A target reliability index (${\beta}_0=3.5$) is selected as an optimal value considering our practice based on the calibration with the current R.C. bridge design safety provisions. A set of load and resistance factors is derived by the proposed uncertainties and the methods corresponding to the target reliability. Furthermore, a set of nominal safety factors and allowable stresses are proposed for the current W.S.D. design provisions. It may be asserted that the proposed L.R.F.D. reliability based design criteria for the R.C. highway bridges may have to be incorporated into the current R.C. bridge design codes as a design provision corresponding to the U.S.D. provisions of the current R.C. design code.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.6 no.4
• /
• pp.53-60
• /
• 1986

This study is directed to propose a probability based LRFD design code, which could possibly replace the traditional USD provisions of the current code, based on the AFOSM reliability theory. The uncertainties of resistances and load effects for each R.C. structural elements are evaluated and adopted considering our practice, and a set of rational target reliability indices are selected based on the calibration with the reliability of the current R.C. design code and by considering the desired hierarchy of safety level. Then, a set of common load factors are chosen from the results of load and resistance factors which are computed by AFOSM method using the Rackwitz-Fiessler's efficient practical algorithm which is to transform the non-normal variables into the equivalent normal variables. It may be asserted that the proposed LRFD code for the R.C. building structures may have to be incorporated into the current RC. design codes as a design provision corresponding to the USD provisions of the current R.C. design code.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.14 no.6
• /
• pp.188-197
• /
• 2010

This paper presents research result to study the change of structural capacity of reinforced concrete beams with various shear reinforcement ratios after damage by fire load. In addition, fundamental data are given in order to predict the strength variation of RC member due to fire damage by evaluating the previous calculation method codified in codes. Nine RC beam specimens were made and exposed to the fire controled by the standard fire curve. And the structural capacity was evaluated through a failure test under simple support condition. Previous code formula, ACI code and Eurocode were reviewed and used for the calculation of the strength of specimens damaged by fire. From the test, RC beam specimens exhibited very brittle failure when it exposed to fire controled by standard fire curve during more than one hour. And this failure pattern tended to be more serious when shear reinforcement ratio decreased or fire loading duration increased. From the evaluation of the calculation process in code, the change of strength due to fire can be properly predicted if the damage of materials is well defined.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.29 no.3
• /
• pp.322-335
• /
• 2019

Objectives: The goal of this study is to standardize industry, process, and job within work environment measurement information. Methods: We selected 180 work environment measurement reports on 30 industries from a database monitored from 2014 to 2016 by the Korea Industrial Health Association. Ten industrial hygienists, each with over five years of experience in measurement, conducted a primary standardization of 180 reports. Two professional industrial hygienists with more than 20 years of experience each reviewed and revised the results of the primary standardization. We also examined the validity on the usefulness of the standardized database by the two industrial hygienists. Results: The final standardization results were classified into eight major categories, 23 sub-major categories, 39 minor categories, 53 unit categories and 70 sub-unit categories in the Korean Standard Industrial Classification (KSIC) 10th revision. A total of 161 processes were standardized, and there were 148 processes with K2B codes. Standard job was coded into 13 job groups including operator, automobile maintenance, nurse, maintenance, manager, excavating machine operator, forklift driver, radiologist, clinical pathologist, signer, researcher, kitchen assistant, and concrete reinforcement ironworker. Conclusions: Although the standardized information in this study may be only a part of the total information, it can be useful for improvement of the K2B system. Additional research is needed for an ongoing clean-up of data in the K2B and re-calibration and reclassification of standard processes until the future national exposure monitoring system is fully established.

• Cross-Cultural Studies
• /
• v.52
• /
• pp.1-29
• /
• 2018

The notion of 'gift' is one of the effective and fruitful codes for understanding Western civilization. In this study, we will shed light on several meanings, especially by comparing among the three French philosophers that expressed interest in this notion: they are Mauss, Derrida and $Ric{\oe}ur$. Called "father of French ethnography", Mauss claims, in his famous article "Essay on the Gift", that the gift is paradoxically a kind of economic exchange dominated by three obligations: to give, receive, and return. But he strives to establish a moral theory based on the obligation to give. Under the influence of Mauss, Derrida deconstructs the theory of Mauss by devoting attention to 'time', one of the determining elements in studies on the gift. Derrida observes that the gift is established just at the extremely short moment of emergence of the act of giving and that this act is transformed into an economic exchange with passing of time. From it, the impossibility of the gift is derived despite its concrete and real emergence and existence. Under the influence of Mauss, $Ric{\oe}ur$, for his part, is interested in the notion of giving as part of the dialectic between 'love' and 'justice'. According to him, whereas justice is dominated by the economy of gift, namely the logic of equivalence, love, by the logic of 'superabundance'. He focuses on establishing 'Supra-ethics' by considering the fact that the gift is at the core of his religious and philosophical vision. Finally, let us point out that in $Ric{\oe}ur$, this notion of gift ('don') is closely linked to forgiveness ('pardon'), that holds in it the secret of understanding regarding the 'fallible' and 'capable' man.

• Nuclear Engineering and Technology
• /
• v.55 no.5
• /
• pp.1593-1603
• /
• 2023

In deterministic and Monte Carlo transport codes, b-delayed emission is included using a group structure where all of the precursors are grouped together in 6 groups or families, but given the increase in computational power, nowadays there is no reason to keep this structure. Furthermore, there have been recent efforts to compile and evaluate all the available b-delayed neutron emission data and to measure new and improved data on individual precursors. In order to be able to perform a transient Monte Carlo simulation, data from individual precursors needs to be implemented in a transport code. This work is the first step towards the development of a tool to explore the effect of individual precursors in a fissile system. In concrete, individual precursor data is included by expanding the capabilities of the open source Monte Carlo code OpenMC. In the modified code - named Time Dependent OpenMC or OpenMC(TD)- time dependency related to β-delayed neutron emission was handled by using forced decay of precursors and combing of the particle population. The data for continuous energy neutron cross-sections was taken from JEFF-3.1.1 library. Regarding the data needed to include the individual precursors, cumulative yields were taken from JEFF-3.1.1 and delayed neutron emission probabilities and delayed neutron spectra were taken from ENDF-B/VIII.0. OpenMC(TD) was tested in a monoenergetic system, an energy dependent unmoderated system where the precursors were taken individually or in a group structure, and in a light-water moderated energy dependent system, using 6-groups, 50 and 40 individual precursors. Neutron flux as a function of time was obtained for each of the systems studied. These results show the potential of OpenMC(TD) as a tool to study the impact of individual precursor data on fissile systems, thus motivating further research to simulate more complex fissile systems.