Search

The initial clamping forces of high strength bolts subjected to different faying surface conditions drop within 500 hours regardless of loading, any other external force or loosening of the nut. This study develops a mathematical model for relaxation confined to creep on a coated faying surface after initial clamping. The quantitative model for estimating relaxation was derived from a regression analysis for the relation between the creep strain of the coated surface and the elapsed time for 744 hours. This study establishes an expected model for estimating the relaxation of bolted joints with diverse coated surfaces. The candidate bolts are dacro-coated tension control bolts, ASTM A490 bolt, and plain tension control bolts. The test parameters were coating thickness, species of coating. As for 96, 128, 168, and 226 μm thick inorganic zinc, when the coating thickness was increased, relaxation after the initial clamping rose to a much higher range from 10% to 18% due to creep of the coating. The amount of relaxation up to 7 days exceeded 85% of the entire relaxation. From this result, the equation for creep strain can be derived from a statistical regression analysis. Based on the acquired creep behavior, it is expected that the clamping force reflecting relaxation after the elapse of constant time can be calculated from the initial clamping force. The manufacturer's recommendation of inorganic zinc on faying surface as 75 μm, appears to be reasonable.

This project is mainly related to evaluation of total energy consumption of low energy house, the exterior envelope of which was wholly composed of structural insulated panels(SIP). The U-value of applied SIP was in the range of 0.189 to 0.269W/ K and the U-value of pair glass from 0.78 to 1.298W/ K was applied for window ㎡· ㎡· dependent to its function respectively. For comparison of total energy performance, the energy simulation for pilot house was performed to compare with the control house having insulation criteria of Korean building regulation in 2009. Based on simulation of dynamic energy performance, the pilot house saved 48.3% of annual energy consumption while the control house in 2009 consumed as 85.7GJ/y. In case of heating, the result showed that the energy saving ratio amounted to 76.7%. For CO emission, the pilot house diminished approximately 35.4% from 6,208.4kgCO to ₂ ₂

There are few technical documents regulated structural performance and engineering criteria in domestic market for Structural insulated panels in Korea. This paper was focused to identify fundamental performance under monotonic loading and cyclic loading for SIPs in shear wall application. Load-displacement responses of total twelve test specimens were recorded based on shear stiffness, strength, ultimate load and displacement. Finally energy dissipation of each specimen was analyzed respectively. Monotonic test results showed that ultimate load was 44.3 kN, allowable shear load was 6.1 kN/m, shear stiffness was 1.2 MN/m, and ductility ratio was 3.6. Cyclic test was conducted by two kinds of specimens: single panel and double panels. Cyclic loading results, which were equivalent to monotonic loading results, showed that ultimate load was 45.4 kN, allowable shear load was 6.3 kN/m. Furthermore the accumulated energy dissipation capability for double panels was as 2.3 times as that for single panel. Based on results of structural performance test, it was recommended that the allowable shear load for panels should be 6.1 kN/m at least.

This paper presents the structural behavior of CFRP (carbon fiber reinforced polymer) strengthened CFT (concrete-filled steel tubes) columns under axial loads. Circular and square specimens were selected to investigate the retrofitting effects of CFRP sheet on CFT columns. Test parameters are cross section of CFT, D/t (B/t) ratios, and the number of CFRP layers. The load and ductility capacities were evaluated for each specimen. Structural behavior comparisons of circular and rectangular section will be represented in the experimental result discussion section. Finally, ultimate load formula of CFRP strengthened CFT will be proposed to calculate the ultimate strength of CFRP strengthened circular CFT. The prediction values are in good agreement with the test results obtained in this study and in the literature.

Professor, The University of Seoul, Department of Architectural EngineeringAbstract:Structural insulated panels, structurally performed panels consisting of a plastic insulation bonded between twostructural panel facings, are one of emerging products with a viewpoint of its energy and construction efficiencies.These components are applicable to fabricated wood structures. In Korea, there are few technical documents regulatedstructural performance and engineering criteria in domestic market. This study was conducted to identify fundamentalperformance of both monotonic load and quasi static cyclic load for SIPs in shear wall application. Static test resultsshowed that maximum load was 44.3kN, allowable shear load was 6.1kN/m, shear stiffness was 1.23 MN/m, andductility ratio was 3.6. Cyclic test was conducted by two kinds of specimens : single panel and double panels. Cyclictest results, which were equivalent to static test results, showed that maximum load was 45.42kN, allowable shearload was 6.3kN/m. Furthermore the accumulated energy dissipation capability for double panels was as 2.3 times asthat for single panel. From performance of structural tests, it was recommended that the allowable shear load for panelswas at least 6.1kN/m.K

The concrete-filled tube column has the excellent structural performance. But it is difficult to connect with column and beam because of closed section. It suggests that pipe should be produced by welding two sides together where two shapes are joined after a channel is pre-welded onto the three sides in order to form an internal diaphragm. The upper diaphragm of the connection used the horizontal plate and the lower diaphragm used the Vertical plate. This research performed 6 monotonic tension experiments describing the connection upside and downside in order to evaluate the structural capability of the offered connection. And the cyclic loading experiment was performed about 2 T-Type column to beam connections. As to the experimental result edge cutting geometry, there was no big effect. An increase in the number of holes of the plate ultimate strength was increased by 5% and The thickness of the plate increases, the maximum strength was increased by 4%. T-Type connections until it reaches the plastic moment showed a stable behavior.

The construction of a moment connection for a rectangular hollow section (RHS) column and a H-shaped beam is difficult because the RHS is a closed section. When a inner diaphragm is used for such a connection, in general, it is installed after cutting the HSS columns, which results in increased construction work. This paper suggests a new fabrication method to overcome such problems: An inner diaphragm is welded to inside a C-shaped section first, and then a column is fabricated by welding two C-shaped sections. This fabrication method is superior to a classic method in terms of constructibility. An experimental and a numerical study using Ansys 9.0 were performed in order to compare the strength of connections with respect to the presence of concrete, the corner shape of diaphragm, and the axis of loading. The experimental results including initial stiffness and ultimate loads are reported and the analytical results including load transfer mechanism, degree of stress concentration, and strain distribution are also reported.

This paper investigates an experimental behavior of circular columns and beam-columns made of HSB600 high strength steel as a fundamental study to enhance the applicability of HSB steel. The applicability of the current Standard such as KBC and Eurocode 3 is also evaluated. A total of six specimens are fabricated and tested. The main parameters are slenderness ratio(KLe/r

This paper presents the experimental results of axially loaded stub columns of slender steel hollow square section(SHS) strengthened with carbon fiber reinforced polymers(CFRP) sheets. 6 specimens were fabricated and the main parameters were: width-thickness ratio(b/t) and CFRP retrofitting. From the tests, it was observed that two sides would typically buckle outward and the other two sides would buckle inward. A maximum increase of 33% was achieved in axial-load capacity. Also, stiffness and ductility index(DI) were compared between unretrofitted specimens and retrofitted specimens. In the last section, a prediction formula of the ultimate strength developed using the experimental results is presented.

The concrete-filled tube (CFT) column has the excellent structural performance. But it is difficult to connect with column and beam because of closed section. Its Solution, 2 members of ㄷchennel in which Internal diaphragm is installed were welded beforehand and the method of making Rectangular Steel Tube was proposed. According to upside and downside junction shape, Internal diaphragm suggested as symmetric specimen and asymmetric specimen. The upper and lower diaphragm of the Symmetric specimen used the same horizontal and The upper diaphragm of the Asymmetric specimen used the horizontal plate and the lower diaphragm used the vertically plate. In this research, 4 T-shape column to beam steps connections were tested with cyclic loading experiment in order to evaluate the structural capability of the offered connection. Symmetric specimens be a failure in 0.03rad from beam flange. And Asymmetric specimens be a failure in 0.05rad from column interface. The comparison results of All specimens shown similar to energy absorption capacity in 0.02rad.

Recently, as the height of building is getting higher, the applications of CFST column for high-rise buildings have been increased. In structural system of high-rise building, The RC core and exterior concrete-filled tubular (CFST) column-beam pinned connection is one of the structural systems that support lateral load. If this structural system is used, due to the minimal CFST column thickness compared to that of the CFST column width, the local moment occurred by the eccentric distance between the column flange surface from shear bolts joints degrades the shear strength of the CFST column-beam pinned connections. This study performed a finite element analysis to investigate the shear strength under eccentric moment of the CFST column-beam pinned connections. The column`s width and thickness were used as variables for the analysis. To guarantee the reliability of the finite element analysis, an actual-size specimens were fabricated and tested. The yield line theory was used to formulate an shear strength formula for the CFT column-beam pinned connection. the shear strength formula was suggested through comparison on the results of FEM analysis, test and yield lime theory, the shear strength formula was suggested.

Structure Insulated Panel (SIP) is an wooden structure material with which structure and insulation functions are satisfied. Hence, it would be a cost-effective model to implement low energy house which has higher insulation and structure performance and which the wall thickness is able to be reduced. In this study, performance of thermal insulation and fire resistance were evaluated in order to verify applicability to low energy house. Fire resistance test is performed on vertical load bearing members for partitions, and the test results satisfy one hour of fire resistance condition according to KS F 2257. The members include two layers of fireproof gypsum board with thicknesses of 12.5mm attached to SIP. Thermal insulation performance is satisfied with the 2012 standard (0.225W/㎡·K). As the performance of resistance and thermal insulation are satisfied, SIP is expected to be applied to low energy building materials. In the future, the structural safety will be confirmed by structural performance and seismic performance test and the guidelines for distribution will be drawn up.

Structural insulated panels, which are structurally performed panels consisting of a plastic insulation bonded between two structural panel facings are one of emerging products with a viewpoint of its energy and construction efficiencies. These components are applicable to fabricated wood structures. By now, there are few technical documents regulated structural performance and engineering criteria in domestic market. This study was conducted to suggest fundamental reports such as racking resistance, axial capacity, transverse load capacity, and lintel load capacity for SIPs. Test results showed that maximum load was 44.3kN, allowable load was 14.7kN for racking resistance, and that maximum load was 137.6kN, allowable load was 37.4kN/m for axial compression capacity. For transverse load capacity, test results showed of maximum load, of allowable load. For lintel load capacity for SIPs dependent to lengths, allowable loads were 20.4kN for 600mm long lintel, 23.9kN for 1,200mm long lintel, 19.3kN for 1,800mm long lintel, and 2,400mm long lintel had 14.1kN of allowable load. In the near future, when the allowable load for wall application is established, SIPs is considered to substitute the existent post-and-lintel construction to bearing wall structure.

The initial clamping forces of high strength bolts depending on different faying surface conditions drop within 1,000 hours regardless of loading, any other external force or loosening of the nut. This study is focused on an expectation model for relaxation of high strength bolt, which is confined to creep on coated faying surfaces after initial clamping. The range of this experiment is limited to estimate the relaxation of bolted joints coated by inorganic zinc primer. The candidate bolts were dacro-coated tension control bolts. The parameters of coated thickness for the faying surface were 96, 168,and respectively. From experiments, it exhibited that the logarithmic function for creep strain was derived due to the parameter of coating thickness. By using the creep strain, subsequently the quantitative model for estimating long term relaxation of high strength bolt can be taken with the elapsed time. The experimental results showed that the relaxation after the initial clamping of high strength bolt rose to a much higher range from 10% to 18% due to creep of the coating as the coating thickness was increased. This study showed that the clamping force reflecting relaxation after the elapse of constant time can be calculated from the initial clamping force of high strength bolt.

A welded built-up square tube is made by flare welding 4 thin steel plates, which are bent to form L-shape. When it is used for a CFST column, the ribs placed at the center of concrete and steel tube width prevent local buckling and the tube confines concrete to improve its structural load capacity. In this study to introduce how to build welded built-up square columns and to evaluate the structural capacities of welded built-up square steel tubes and CFST columns, 15 full-size specimens were fabricated for structural test with various types of steel tubes (welded built-up square tube and generic steel tube), width–thickness ratio (B/t=50, 58 and 67) and concrete strength (Fck=10 MPa and 40 MPa) to verify sectional efficiency and structural superiority inherent in welded built-up square columns.

This study seeks to devise a design application for a beam structure with partially restrained composite connection to a CFT column. A cost-efficient and stable component is applied by adjusting the stiffness ratio of the column connection through partially restrained composite connection. Based on a review of the structure`s stability, it was confirmed that in the case of a low-rise building as a moment frame, resistance without bracing is feasible because stiffness increased by virtue of the partial restrained composite connection by composite action. In the case of a high-rise building, lateral resistance load of moment frame was approximately 10% when proper partial restrained rate was at around 60%. With considerations related to economic efficiency, the partial restriction effect of the beam component was significantly activated by the uniform load, but that of the beam activated by concentrated load was not significantly indicative. The analysis indicated that 60% partial restrained girder at the connection was the most economical in the case of uniform load. It also showed that end moments can be reduced by approximately 25%.

The concrete-filled tubular square column is superior to steel frame column in terms of fire resistance because of the thermal storage provided by the concrete. Studies have been conducted on CFT column reinforcement with steel bars or with the use of an internal tube to improve its structural load capacity and fire resistance. In fact, reinforced CFT columns have been increasingly used to deal with high axial force. The functional deterioration of columns due to fire damage needs to be measured precisely. In this study, the temperature distribution inside the columns in case of a fire was evaluated and the degree of deterioration in the load capacity of the concrete and reinforcing members associated with temperature distribution was identified in order to evaluate the overall residual strength of the columns.

In this study, the prestressed composite beam with corrugated web has been developed, which is suitable for the long-span structure that enables a reduction in story height as well. Utilizing the corrugated steel web improves the efficiency of prestress introduced into the top and bottom flanges due to the accordion effect, which also provides better deflection control and greater resistance against local and out-of-plane buckling. Additionally, when the corrugated steel web becomes composite with concrete, the slanting plate of the corrugated web induces bearing stress that can improve composite action between the steel beam and the surrounding concrete. In this study, a parametric study on the accordion effect has been performed by a total of 24 corrugated webbed steel beams utilizing the finite element analysis. Based on the analysis result, a simple approach for the estimation of the accordion effect has been proposed. In addition, this study introduces a flexural behavior model for the prestressed composite beams with corrugated web. The verification of the proposed methods in this study is presented in a separated paper.

Welding process and throat depth are essential to reduce construction costs of steel tubes. However, the resulting welds should be checked to ensure construction safety especially when wet concrete is to be pumped into the tubes. In the past, tests (Mock-up Test) using actual size specimens were conducted to verify the feasibility of welding throat depth (WTD) during the concrete casting stage on site. However more than often, this is inapplicable owing to the high testing costs, difficulties in disposing of test specimens with wet concrete, and lack of suitable places to conduct tests. Accordingly, this study suggested a water pressure test method and carried out 6 tests on welded built-up square concrete-filled steel tubular (CFST) columns to evaluate the WTD safety. Recommendations are made for the WTD selection.

This study investigates the axial behavior of CFRP strengthened circular CFT columns and proposes the design formula of CFRP strengthened circular CFT columns. 10 specimens were prepared and axial loading test were conducted to investigate the retrofitting effects of CFRP composites on CFT columns. The main parameters are the number of FRP sheets and D/t ratio. Test results showed that the CFRP retrofitting enhanced the load bearing capacity of the circular CFT columns. Finally, A ACI 440 code applied ultimate axial strength formula is proposed to predict the ultimate strength of CFRP strengthened circular CFT columns. The proposed formula are good agreement with the test results.

Thin Walled Cold-Formed Concrete Filled Tubular Square Column are manufactured by flare welding at center of column width for cold formed L shape plates of 4 piece and improved composite effect of concrete and steel by vertical inner anchor. Also, Axial resistance of concrete is increased by confine effect of steel tube and steel prevent local buckling of steel column. In this study, we introduced manufacture method of thin walled cold-formed square column steel square concrete filled tubular column and structural performance of the welded built-up square stub column was verified by structural test for ten specimens with parameters of concrete strength, type of steel tube, width to thickness ratio of steel tube.

H-beams set up between columns are widely used to support building slabs. However, H-beams have fixed joints and the bending moment at both ends of the beam under uniformly distributed load is twice as great as the moment at its center. Because beam design is based on ultimate moment, its depth gets to be larger, which leads to the problem of smaller available space on each floor. If the ends of H-beam which are vulnerable to ultimate bending moment are additionally reinforced, beam design based on the bending moment at beam center is feasible. In this study, 4 specimens were fabricated for structural experiment with variables of the purpose of end-reinforcing steel plates, bar reinforcement and load transfer method in order to analyze the structural performance of end-reinforced steel frame beams (hereinafter Eco-girder system).

This study presents the development of an improved detail for a Concrete Filled Steel Tube (CFT) square column-to-beam partially restrained composite connection (PR-CC) and the evaluation of its hysteresis behavior under cyclic loading. The detail of the connection was designed to prevent brittle failure at the bottom of the connection due to the composite effect and to simplify its fabrication process. The suggested connection is a welded type of bottom beam flange connection and the existing PR-CC is a bolted type with a seat-angle. To evaluate their hysteresis behavior, specimens were fabricated at full scale and tested under cyclic loading. Results revealed that the suggested type fractured at the welding zone without a drop in capacity due to the anchors inside the steel tube, and reached over 0.04 radian of the plastic rotational angle. The stiffness of the suggested type was about 10% greater than the existing type because the bolted connection allowed more deformation than the welded connection. Both connections were classified as Semi-rigid connections by stiffness analysis according to Eurocode3. The suggested type can be classified as a partially restrained connection overall under cyclic loading because it reached more than 0.03 rad of an inelastic rotation angle 80% capacity of the maximum moment capacity. This type was evaluated to exhibit equal or more ductility than the existing type. As a result, it is concluded that the welded bottom beam flange connection type can be used in practice for the CFT column–beam connection instead of the existing bolt connection using a seat-angle.

This paper studies the development of the through-type concrete-filled square steel tube column-to-beam connection, reinforced with an asymmetric lower diaphragm. This type of connection can be used in weak-earthquake regions such as Korea. A simple tension test was performed on the suggested lower diaphragms and the combined cross diaphragm in order to confirm their tensile behavior. Subsequently, four types of concrete-filled square steel tube column-to-beam connection (with combined cross diaphragm, nothing, horizontal T-bar and vertical plate as lower diaphragm) were fabricated in actual size and tested according to the ANSI/AISC SSPEC 2002 cyclic loading program. The horizontal T-bar and stud bolts in the vertical plates were designed to transmit the tensile stress from the bottom flange of the beam to the filled concrete. All the test specimens satisfied the 0.01 radian inelastic rotation capacity requirements for the composite ordinary moment frame (C-OMF) of the AISC seismic provisions. It was concluded that the suggested simplified lower diaphragms have sufficient strength, stiffness and plastic deformation capacity to be used in the field.

The existing CFT columns present the deterioration in confining effect after the yield of steel tube, local buckling and the deterioration in load capacity. If lateral load such as earthquake load is applied to CFT columns, strong shearing force and moment are generated at the lower part of the columns and local buckling appears at the column. In this study, axial compression test and beam-column test were conducted for existing CFT square column specimens and those reinforced with carbon fiber sheets (CFS). The variables for axial compression test were width-thickness ratio and the number of CFS layers and those for beamcolumn test were concrete strength and the number of CFS layers. The results of the compression test showed that local buckling was delayed and maximum load capacity improved slightly as the number of layers increased. The specimens` ductility capacity improved due to the additional confinement by carbon fiber sheets which delayed local buckling. In the beam-column test, maximum load capacity improved slightly as the number of CFS layers increased. However, ductility capacity improved greatly as the increased number of CFS layers delayed the local buckling at the lower part of the columns. It was observed that the CFT structure reinforced with carbon fiber sheets controlled the local buckling at columns and thus improved seismic performance. Consequently, it was deduced that the confinement of CFT columns by carbon fiber sheets suggested in this study would be widely used for reinforcing CFT columns.

This paper presents the results of an experiment comparing the current circular CFT columns and circular CFT columns that were additionally confined by carbon fiber sheets (CFS) under axial loading. The main experimental parameters are the numbers of CFS layers and the diameter-to-thickness ratio. 10 specimens were prepared according to the experimental parameter plans, and axial compression tests were conducted. From the tests, the failure procedure, load-axial deformation curve, maximum axial strength, and deformation capacity of the CFT columns and confined CFT columns were compared. The test results showed that the maximum axial strengths of CFT columns additionally confined by CFS are increased higher than those of the current CFT columns, and that local buckling can be delayed due to the confinement effect of CFS.

The strength and behavior of split-tee connections that are applicable to all tensile connections with high-strength bolts have been studied in many countries. The design code of each country (AISC, Eurocode 3) does not consider various field conditions, however, such as the painting of the connection surface, the length of the bolt shank, and the preload. Moreover, the previous studies (Bahaari) that used the link element on the preload of the bolt could not predict the correct behavior of high-strength bolts. In this study, to evaluate the tensile capability of split-tee connections, a total of 20 split-tee specimens with two bolts each were fabricated and tested. The experiment parameters that were used were the thickness of the T-flanges, painting, preload, and the length of the bolt shank. The joint stiffness of split-tee connections was compared with the stiffness equation of Faella et al., and finite-element method analysis with Ansys 8.0 was conducted. Further, to verify the reliability of the highstrength-bolt model, the load-to-bolt stress relation in the experiment test and the analysis results were compared.

The fire resistance of concrete filled square steel tube columns (CFT columns) without fire protection under a constant axial load has been previously examined. The purpose of this present study is to investigate the fire resistance of CFT columns when they are subjected to combined loads. This paper presents a nonlinear thermal stress analysis method for predicting the mechanical behavior and fire resistance of CFT columns under eccentric axial load (axial load and flexure moment). This method is based on the stress-strain characteristics of materials at high temperatures and on the mechanics of column deflection curves. From the results of the developed computational technique, it was demonstrated that as the yield stress and rigidity of the steel tube rapidly decreased for approximately 30 minutes, the decrease of flexure moment capacity increased significantly more than that of the axial load capacity. In addition, as the load eccentricity ratio increased, the fire resistance time drastically decreased. However, the time of maximum expansion under eccentric axial load was independent of the load eccentricity ratio.

The structure of an edge flame in a mixing layer of two uniformly flowing pure CH4 and pure O2 streams has been investigated numerically by employing a detailed methane–oxidation mechanism in order to investigate the influence of using pure oxygen, instead of air, as the oxidizing agent. The results exhibited similar behaviour to the CH4-air counterpart in the premixed-flame front, through which the carbon-containing compound leaked mainly in the form of CO and H2 instead of HC compounds. However, while passing through the rich premixed-flame region, the most pronounced distinction of using pure oxygen was that the major route for CO production, in addition to the direct CH4 decomposition, is C2H m compound formation followed by their decomposition into CO, thereby giving continuous CO production, contrary to the rich CH4-air premixed-flame region in which CO consumption existed. In the downstream region from the rich premixed flame front, CO is further oxidized into CO2 in a broad diffusion-flame-like re...

This paper presents a plan and guidelines that were drawn for Korean based research carried out on the fire-resistance of CFT columns. This research was carried out by reviewing the Korean regulations related to the fire-resistance of CFT columns and examining studies which had been made in Korea as well as overseas. The first phase of the study plan was to compare the fire-resistance of square CFT columns without fire protection (obtained through fire-resistance tests and numerical analyses) with estimated values (obtained through fire-resistance design formulas proposed in Korea and overseas). This comparison provided conclusions as outlined below. Fire-resistance tests conducted in this study proved that, when the actual design load is taken into consideration, square CFT columns without fire protection are able to resist a fire for more than one hour. A comparison was made of test and analysis results with the fire-resistance time based on the AIJ code, the AISC design formula and the estimation formula suggested for Korea. The results of this comparison showed that the test and analysis results for specimens SAH1, SAH2-1, SAH2-2 and SAH3 were almost identical with the AIJ code, the AISC design formula and estimation formula. For specimens SAH4 and SAH5, the estimation formula was more conservative than the AIJ code and the AISC design formula. It was necessary to identify the factors that have an influence on the fire-resistance of CFT columns without fire protection and to draw fire-resistance design formulas for these columns. To achieve this, it is proposed that numerical analyses and tests be conducted in order to evaluate the fire-resistance of circular CFT columns, the influence of eccentricity existing as an additional factor and the influence of the slenderness ratio of the columns. It is also suggested that the overall behavior of CFT structures without fire protection within a fire be evaluated through analysis simulation.

This paper presents a critical review of the performance of the currently available material models with regard to the mechanical behaviour of a concrete-filled steel tube (CFT) column at elevated temperatures. For this purpose, numerical heat transfer analysis and nonlinear thermal stress analysis were carried out by taking into account the existing material properties, such as the thermal and mechanical properties of concrete and steel. In addition, ten CFT column specimens with rectangular cross-sections of 300–350 mm in size were heated for two hours in accordance with KSF 2257 (equivalent to ASTM E119 and JIS A 1304). On comparing the numerical analysis and experimental results, it can be observed that we can validate and employ the existing material models such as EUROCODE, AIJ CODE, Lie’s material model, and Yin’s material model.

In December 2005, one(A) of the two pre-engineered warehouse buildings in the port of K City of Korea was completely destroyed and the other(B) was seriously damaged to be demolished. Over-loaded snow and unexpected blast of wind were the causes of the accident and destructive behavior was brittle fracture caused by web local buckling and lateral torsional buckling at the flange below rafter. However, the architectural design technology of today based on material non-linear method does not consider the tolerances to solve the problem of such brittle fracture. So, geometric non-linear evaluation which includes initial deformation, width-thickness ratio, web stiffener and unbraced length is required. This study evaluates the structural safety of 4 models in terms of width-thickness ratio and unbraced length using ANSYS 9.0 with parameters such as width-thickness ratio of web, existence/non-existence of stiffener and unbraced length. The purpose of this study is to analyze destructive mechanism of the above-mentioned two warehouse buildings and to provide ways to promote the safety of pre-engineered buildings.

This paper presents the development of an improved detail in partially restrained beam-to-column composite connections in concrete filled square tubes and the evaluation of its structural characteristics and behaviour under monotonic and cyclic loading. Studies for the bolted seat-angle connections of existing partially restrained composite connection (PR-CC) details have been conducted mostly on shallow beam-to-column connections. In case of deep beam-to-column connections, the fabrication becomes complicated because the sizes of the seat-angles are larger than the connections, and the number of bolts and welding length are increased. This study suggests a new detail of PR-CC which can be applied to concrete-filled tubular structures incorporating the effect of composite slabs and the performance for construction work. A welded bottom beam flange connection is proposed to enhance the capacity of the bottom of the connection and to improve ductility and fabrication. In addition, a reduced beam section (RBS) is adapted for the bottom beam flange to examine its effect on ductility. A seat-angle connection with penetrating bolts is also suggested and compared with the welded bottom beam flange connection. Both monotonic and cyclic loading tests are conducted on the five full scale specimens to compare and evaluate their ductility characteristics.

The purpose of this study is to propose simplified strength equations that can be conveniently used to establish a P–M interaction curve of square concrete filled tubes (CFTs) with concrete strength of up to 100 MPa. The method presented in the author's previous study [Choi Y-H, Foutch DA, LaFave JM. New approach to AISC P–M interaction curve for concrete filled tube beam-columns. Eng Struct 2006;28(11):1586–98] was used as a basic unified formula for pure steel members and CFT ones, and a parametric study was performed to determine the contribution of the concrete, which were expressed by two variables: a normalized maximum moment, α, and the axial load ratio at the maximum moment, β. The two variables were formulated with respect to tube width-to-thickness ratio (b/t) and relative concrete compressive strength to yield strength of the steel tube (f′c/Fy). Then, the proposed method were compared to experimental data found in literatures, which showed greatly improved results in terms of accuracy and amount of computation, when compared to the current AISC design methods.

The purpose of this study is to suggest a new CFT column-to-beam connection type, which will have an axis direction that takes into consideration the asymmetry of connections. Through experimental study and finite element analysis, the study also compares the structural capacities of the new CFT column-to-beam connection type with those of existing connection types. Existing connection types for comparative study are those with an interior diaphragm and through diaphragm. The new connection type suggested uses a combined-cross diaphragm, featuring a column flange penetration in the major-axis direction and an interior diaphragm in the minor-axis direction. In order to analyze and compare the initial stiffness and strengths of the connections considered simple tension tests along with finite element analysis were performed on the specimens, while idealizing the tension-applied beam flange. Stress concentrations, according to the geometric configurations and load transfer mechanisms of diaphragms, were analyzed through finite element analysis. The results show that the existing connection types, in terms of initial stiffness and ultimate strength, do not precede the combined-cross diaphragm, and that the stress concentration on the connection can be relieved by improvement to the detail.

Dept. of Architectural Engineering, University of Seoul, Seoul 130-743, KoreaABSTRACT Analytical probabilistic vulnerability analysis requires extensive computing effort as a result of the randomness inboth input motion and response characteristics. In this study, a new methodology whereby a set of vulnerability curves are derivedbased on the fundamental response quantities of stiffness, strength and ductility is presented. A response database of coefficientsdescribing lognormal vulnerability relationships is constructed by employing aclosed-form solution for a generalized single-degree-of-freedom system. Once the three fundamental quantities of a wide range of structural systems are defined, the vulnerability curvesfor various limit states can be derived without recourse to further simulation. Examples of application are given and demonstratethe extreme efficiency of the proposed approach in deriving vulnerability relationships.Keywords : vulnerability curve, nonlinear static procedure, fast demand estimation, response parameters, response database

Fires in buildings cause not only economic losses but also many casualties. A prolonged fire involves the possibility of the damage to structural members, which calls for the repair or reinforcement of the building. Since it is critical to decide whether structural members need reinforcement, the technique to determine the degree of the damage to structural members caused by a fire should be established. CFT columns are superior to generic steel columns in terms of fire resistance performance thanks to the thermal storage effect of the concrete inside the columns. Studies have suggested how to reinforce the concrete to further improve the structural strength and fire resistance performance of CFT columns. When CFT columns of a building are damaged by a fire, it is required to determine preciously how serious the structural deterioration of the members is. The purpose of this study is to evaluate the residual strength of CFT columns damaged by a fire by evaluating the temperature distribution inside the columns and determining the degree of deterioration in the load capacity of concrete and steel in relation to temperature distribution.

The cyclic load–deformation relationships of columns in the post-peak region need to be investigated in the prevention of collapse of the buildings under earthquake excitation. This paper provides an efficient method of prediction of the pre- and post-peak hysteretic behavior of concrete-filled square steel tube columns subjected to a combination of constant axial load and cyclic lateral load. For this purpose, the simplified nonlinear fiber element method is used to obtain the uni-axial stress and strain relationship of materials in terms of the composite action between the steel tube and the concrete. The accuracy of the proposed computational technique is verified by comparing the results from this technique with existing experimental results, which are briefly reviewed in this paper.

The objective of this study is to clarify the structural features of members consisting of connection, as a series of the previous study on the CFT column-to-beam tensile connection with combined cross diaphragm. This connection has the merits that the stress is distributed evenly on the beam flange and the diaphragm and the stress concentration is reduced, by improving the stress transfer route and restraining abrupt deformation of diaphragm. The finite element analysis was performed to find out the stress transfer through sleeve which is an important member of the connection with combined cross diaphragm. The length and thickness of sleeve were used as variables for the analysis. As the analysis results, the length and thickness of sleeve didn

The connection with combined cross diaphragm is developed for the connection of square CFT column and steel beam and proposed to be used for the frame with asymmetric span length. The structural characteristics of this connection lie in the penetration of the beam flange in the direction of major axis through the column for the smooth flow of stress. The purpose of this study is to analyze the dynamic behavior and stress flow of suggested connection and to evaluate the resistance to shock of connection. Four T-type CFT column-to-beam specimens; two with combined cross diaphragm and the others with interior and through diaphragms, the existing connection types, were made for cyclic load test guided by the load program of ANSI/AISC SSPEC 2002. The results show that the proposed connection is more efficient than existing ones in terms of strength, stress flow and energy absorption and satisfies the seismic performance required in the region of weak/moderate earthquakes.

Objective : This study was designed to show the possible functional groups from the herb medicine in boiling water. Results : The results are summarized as follows: 1. the new functional groups can be synthesized in water solution for herb medicine. 2. The boiling water solution may change the poison materials into harmless materials. 3. The multiplication, the offset, the contradiction, etc. in terms of mixed herb medicine can be explainable by these reactions. 4. After finding the new medicinal substances for the specific disease, we can synthesize, modify, and mass produce those for that disease.

Purpose: To elucidate radiogenomics association beween magnetic resonance (MR) imaging signatures and expression level of branched-chain amino acid trasaminase1 (BCAT1) messenger RNA (mRNA) in the isocitrate dehydrogenase 1 (IDH1)-wildtype glioblastoma multiforme (GBM). Materials and Methods: Radiogenomic analysis was performed by using MR imaging in 69 patients with GBM in this retrospective study, which was approved by institutional review board in our institute. To evaluate the BCAT1 expression level, quantitative RT-PCR, immunohistochemistry and western blot were performed with GBM patient tissues. Eight MR imaging parameters were evaluated from DSC perfusion imaging (mean CBV, and 95% nCBV) and diffusion weighted imaging (mean ADC1000, and 5 % ADC1000), of which segmentation was based on both contrast-enhanced (CE) T1WI and FLAIR imaging. MR imaging was obtained at 3T scanner (Verio; Siemens Healthcare Sector) and post-processing was performed by using a dedicated commercialized software (Nordic ICE, NordicNeuroLab). The expression level of BCAT1 was compared, and correlated with quantitative MR imaging features by using t-test and Pearson correlation analysis, respectively. Progression-free survival (PFS) associated with interested BCAT1 mRNA and miRNA was performed by Kaplan-Meier survival analysis. Results: The expression level of BCAT1 RNA was significantly higher in IDH1-wildtype patients (n = 60) than in IDH1-mutant patients (n = 9) (P = 0.0021). Similar to this RNA expression results, immunohistochemistry and western blot showed that the BCAT1 protein expression was also higher in IDH1-wildtype patients than in IDH1-mutant patients. In MR imaging features, nCBV based on FLAIR (R2 = 0.08291, P = 0.0164) and 95 % nCBV based on CE T1WI (R2 = 0.07232, P = 0.0255) were significantly correlated with BCAT1 expression level in GBM patients. Moreover, median PFS in patients with BCAT1 expressing of ≤150 was longer than those with BCAT1 expressing of 150≤ (12 vs 43 months, P = 0.004). Conclusion: We found that high BCAT1 expression level was observed in IDH1-wildtype GBM, which was correlated with high CBV value. Thus, we believe that DSC-perfusion MR imaging could be helpful in predicting the prognosis related BCAT1 expression, which seems to be crucial in selecting future tailored treatment for IDH1-wildtype GBM patients.

Recently, in recognition of their outstanding structural performance, the use of Concrete Filled Steel Tube (CFT) columns has been increased. New shape welded built-up square tube was developed by the authors for broader usability using thin steel plates which were bent to be L-shaped (Channel) and each unit members were welded to form square steel tube as an cost-efficient use of expensive steel. In addition, since the rib placed at the center of the tube width acts as an anchor; higher load capacity of buckling is achievable. In order to apply the new shape built-up square columns, the structural behavior and stress distribution with parameter width of thickness (b/t), with and without rib were predicted. The New shape welded built-up square tube effectively delayed the local buckling of the steel tube, which led to a greater strength and ductility than regular HSS.

The ability of allylic and homoallylic 2°-amides to direct nitrile oxide cycloaddition reactions has been studied. For N-cyclopentenyl amides, good regio- and stereochemical control are observed and mechanistic studies suggest that hydrogen bonding in the transition state selectively accelerates formation of one isomer. Acyclic allylic and homoallylic 2°-amides do not exhibit high regio- or stereoselectivity