Earticle

연구목적: 본 연구는 자정식 건설장비 전도방지 시스템에 대하여 역학적 메커니즘에 따른 효율도를 수 치해석적인 방법과 실대형 실험체의 하중재하실험결과를 비교하여 거동을 검증 하고자 한다. 연구방 법: 기존 전도방지 가설구조물에 대한 제원을 분석하고 본 연구대상에 대한 모듈식 제원을 도출하였다. 건설장비의 총하중과 충격력을 적용하여 수치해석적 방법으로 해석을 수행하였고 실대형 실험체를 제 작하여 하중재하실험을 수행하였다. 연구결과: 실대형 실험체 하중재하 실험결과 가력하중에 대한 연 직방향 변위는 수치해석 결과를 상회하는 거동 결과이며 가장 불리한 거동의 수직부재는 허용응력 대 비 81.6~82.3%의 응력이 작용하는 것으로 확인하였다. 결론: 건설장비의 전도모멘트와 장비 자중에 의 한 저항모멘트 상호 보완의 역학적 메커니즘을 적용한 전도방지 시스템에 대하여 수치해석적 및 실대 형 실험체의 하중재하 실험을 비교 검토결과 거동의 안전성 확보를 확인하였다.

Purpose: This study verified the behavior of a temporary structure module system for preventing overturning drilling rigs by comparing the efficiency of the mechanical mechanism with the results of a numerical analysis method and load test of a full-scale specimen. Method: The geometric and material specifications of existing a temporary structure were analyzed and the specifications of temporary structure module system of this study were derived. Numerical analysis was performed by applying the total load and impact force of construction equipment, and static loading experiments of a full-scale test specimen using horizontal and vertical loading method was performed. Result: The results of static loading experiments of the full-scale specimen showed that the vertical displacement in response to the applied load exceeded the results of the numerical analysis. It was confirmed that the vertical member with the most unfavorable behavior was subjected to a nominal stress of 81.6 to 82.3% of the allowable stress. Conclusion: The safety of the behavior was confirmed through a comparative result of numerical analysis and static loading experiments on a full-scale specimen for a temporary structure module system for preventing construction equipment from overturning that applies a mechanical mechanism in which the overturning moment of construction equipment and the resistant moment due to the self-weight of equipment complement each other.

In many optimal methods for the structural design, the structural analysis is performed with the given design parameters. Then the design sensitivity is calculated based on its structural anaysis results. There-after, the design parameters are changed iteratively. But genetic algorithm is a optimal searching technique which is not depend on design sensitivity. This method uses for many design para- meter groups which are generated by a designer. The generated design parameter groups are become initial population, and then the fitness of the all design parameters are calculated. According to the fitness of each parameter, the design parameters are optimized through the calculation of reproduction process, degradation and interchange, and mutation. Those are the basic operation of the genetic algorithm. The changing process of population is called a generation. The basic calculation process of genetic algorithm is repeatly accepted to every generation. Then the fitness value of the element of a generation becomes maximum. Therefore, the design parameters converge to the optimal. In this study, the optimal design pro- cess of a machine tool structure for static loading is presented to determine the optimal base supporting points and structure thickness using a genetic algorithm.

It is well-known fact that the stone-mastic asphalt (SMA) mixture has shown superior rut resistance, compared with the dense-graded asphalt (DGA) mixture in highway pavements. However, the SMA is measured to be inferior to DGA mixes when tested by well-known high-temperature test methods, such as the wheel tracking (WT), asphalt pavement analyzer, the Marshall Stability and Kim Test. Therefore, this study examined the reasons why it was measured to be inferior, and devised a potential procedure by which the superiority of SMA could be measured at $60^{\circ}C$. The strength against deformation ($S_D$), which was known to show very high correlation with WT results for DGA mixes, was measured by the Kim Test on the specimen confined in the compacted mold. In standard Kim Test, which used the specimen without confinement, the DGA was measured to show higher $S_D$ than the SMA. But by confining specimen, it was found that the $S_D$ of SMA was measured to be higher than that of DGA. Therefore, the confined static test protocol devised in this study was found to be feasible for evaluating rut resistance of SMA mix.

연구목적: 본 연구에서는 공용년수 20년이 경과된 콘크리트 단순 슬래브교를 대상으로 하여 대상교량 구조물의 내하성능을 평가하는 것을 목적으로 하였다. 연구방법: 정적재하시험 및 동적재해시험을 수 행함으로써 변위, 변형율, 충격계수, 고유진동수 값을 실측하였으며, 해석방법을 통해 평가하였다. 연 구결과: 본 연구를 통해 나타난 주요 결과는 다음과 같다. 첫째, S1 최대 변위 및 최대 변형률은 각각 2.917 mm, 44.720 με(인장), -13.760 με(압축)로 평가되었으며, S2 최대 변위 및 최대 변형률은 각각 2.100 mm, 4.870 με(인장)로 나타났다. 둘째, 최대 실측충격계수는 S1 A-A단면에서 0.242로 나타났으 며, 최대 실측충격계수는 S2 C-C단면에서 0.198로 나타났다. 셋째, 고유진동수를 해석결과, 6.086Hz로 평가되었고, 측정결과 6.152Hz∼6.738Hz의 범위로 나타났다. 결론: 시험대상 교량은 설계하중에 대하 여 양호한 거동 및 특성을 보이는 것으로 평가할 수 있다.

Purpose: The objective of this study is to evaluate the load carrying capacity of a target bridge structure based on the simple slab bridge of concrete over 20 years of public service. Method: By performing static loading test and dynamic loading test, the displacement, strain, impact factor, and natural frequency values were measured and evaluated through analysis method. Result: The main results of this study are as follows. First, the maximum displacement and maximum strain of S1 were assessed at 2.917 mm and 44.720 με( tensile) and -13.760 με(compression), respectively, with S2 maximum displacement and maximum strain being 2.100 mm and 4.870 με(tensile), respectively. Second, the maximum measured impact factor was 0.191 in section S1 A-A, and the maximum measured impact factor was 0.155 in section S2 C-C. Third, the natural frequency was assessed at 6.086 Hz, and the measurement was found to be within the range of 6.152 Hz to 6.738 Hz. Conclusion: The tested bridge may be evaluated to show good behavior and characteristics for the design load.

연구목적: 본 연구는 기존 라멘교의 경간장 제약을 극복하고 시공성을 개선하기 위해 개발된 T형 확폭 부를 적용한 강합성 라멘 거더의 구조적 거동과 안전성을 실증적으로 규명하는 데 목적이 있다. 이를 위 해 연구방법: 실물 크기의 실험체를 제작하여 PS 강봉을 이용한 긴장력 도입 효과를 분석하고, 파괴 시 까지의 단계별 정적 재하 실험을 수행하여 하중-변위 및 하중-변형률 관계를 평가하였다. 연구결과: 강 봉 긴장을 통해 거더 중앙부에 6.83mm의 초기 솟음(Camber)이 효과적으로 도입됨을 확인하였으며, 재 하 실험 시 하중 524.7kN에서 최종 파괴될 때까지 급격한 하중 저하 없이 충분한 연성 거동을 나타내었 다. 결론: T형 확폭부를 적용한 강합성 라멘거더는 처짐 제어 능력과 휨 내하력이 우수하고 비틀림 저항 성능 또한 확보되어, 중소경간 교량에서의 구조적 효율성과 현장 적용성이 타당함을 확인하였다.

Purpose: The purpose of this study is to empirically investigate the structural behavior and safety of the ‘Composite Rahmen Girder with T-shaped Widened Ends,’ which was developed to overcome the span length limitations of conventional Rahmen bridges and improve constructability. Method: To achieve this, a full-scale specimen was fabricated to analyze the effect of prestressing force introduced by PS bars, and step-by-step static loading tests were performed up to failure to evaluate the loaddisplacement and load-strain relationships. Result: It was confirmed that an initial camber of 6.83mm was effectively introduced at the mid-span through the tensioning of the bars. During the loading test, the specimen exhibited sufficient ductile behavior without a sudden drop in load until the final failure at 524.7kN. Conclusion: It was confirmed that the Composite Rahmen Girder with T-shaped Widened Ends possesses excellent deflection control capability and flexural load-carrying capacity, as well as secured torsional resistance performance. Consequently, the structural efficiency and field applicability of this system for medium and small-span bridges were verified to be valid.

As the frequency and scale of earthquakes in Korea increase, the government has enacted the risk assessment of earthquake-damaged buildings to quickly respond to earthquakes and prevent the spread of earthquake damage. Among the earthquake damage risk assessment contents, the risk of vertical structural members, such as columns and walls, is evaluated according to the damage assessment criteria for damage occurring on the surface of the member by structural type. Currently, the domestic damage evaluation standard of reinforced concrete(RC) wall members borrowed from Japan's damage evaluation standard, and there is insufficient reflection of the structural characteristics of domestic RC wall members such as piloti buildings and non-seismic details. Therefore, in this paper, based on the test results of RC wall members with different aspect ratios subjected to eccentric axial force, qualitative and quantitative damage evaluation criteria for wall members were derived. Specifically, the damage level of the wall member was divided into 5 stages, and qualitative evaluation criteria based on the visible damage conditions such as cracks, crushing and spalling of covered concrete, exposure, buckling and fracture of rebara, etc for each damage level and quantitative evaluation criteria based on the maximum residual crack width were derived. The damage evaluation criteria derived in this paper showed that some qualitative and quantitative evaluation criteria were smaller at the same level of damage compared to the existing domestic damage evaluation criteria.

Many piloti-type RC buildings were damaged by Pohang earthquake. It is necessary to reflect the characteristics of domestic buildings and failure mode by an earthquake to the post-earthquake safety evaluation criteria. In this study, the behavior characteristics and failure mode of RC walls of piloti-type buildings subjected to eccentric axial load was investigated by the reversal cyclic test. The variables were the aspect ratio(height to length) of the wall and the eccentricity which was different because the axial force was applied at the same position from the center of the wall specimens. As a result of the experiment, the slender wall was dominated by the flexure behavior. On the other hand, flexure-shear cracks occurred predominantly in the wall with a small aspect ratio. The crack patterns in the positive and negative loading directions were different due to the influence of eccentricity. The number of crack increased, and the rotation of the wall increased while the maximum horizontal strength decreased when the shear moment and the eccentric moment acted in the same direction by the eccentric axial force.

In the process of full-scale static loading test of wind turbine blades, the loading forces all had relatively strong coupling effect, which seriously affected the accuracy of the test result. In order to eliminate this effect, firstly, a vertical static loading device for 10MW wind turbine blades was established and the coupling rule of loading force was obtained. Then, a control algorithm was put forward based on fuzzy theory. This algorithm took the error of loading force, error’s change rate as the input variables and the opening degree of proportional valve as the output variable. A control strategy based on this algorithm was constructed. In the end, the static device took the max flapwise of aeroblade5.0-62 wind turbine blade as example to conduct loading test. The result suggested the algorithm in this paper could ensure that the loading forces on five nodes always kept uniform changing and the control errors were respectively less than±2KN, ±2KN,± 2KN,± 2KN and±1KN. When in the 100% phase, the loading force could be finely maintained at the set value. The statistical results showed that the error rates of loading force with control algorithm were smaller than those without control algorithm. The test results verified the feasibility of control strategy applying to full-scale static loading test for wind turbine blades.

The paper reports the physical and mechanical properties of hand-woven carpets, which have been put under static force. Two groups of wool fibres, from two parts of Iran, were prepared to spin pile yams for the carpets. Each group of the fibres included both conventional and tanned wool. Then two yam counts, $N_m$ = 4/2 and 6/2, were spun for two different knot densities. After weaving the carpets, they were put under static force and their thickness variations were measured and plotted against time, in logarithm scale. The resiliency of the carpets piles after eliminating the static force, were measured and plotted against time, in logarithm scale, too. The results were compared to each other and analysed with respect to parameters such as the type and quality of the wool fibres as well as knot density of the carpets.

Bone is a living material with a complex hierarchical structure that gives it remarkable mechanical properties. Bone constantly undergoes mechanical. Its quality and resistance to fracture is constantly changing over time through the process of bone remodeling. Numerical modeling allows the study of the bone mechanical behavior and the prediction of different trauma caused by accidents without expose humans to real tests. The aim of this work is the modeling of the femur fracture under static solicitation to create a numerical model to simulate this element fracture. This modeling will contribute to improve the design of the indoor environment to be better safe for the passengers' transportation means. Results show that vertical loading leads to the femur neck fracture and horizontal loading leads to the fracture of the femur diaphysis. The isotropic consideration of the bone leads to bone fracture by crack propagation but the orthotropic consideration leads to the fragmentation of the bone.

In this paper, several different fracture criteria using the Eftis and Subramanian's stress solutions [1] are compared with the printed experimental results under different loading conditions. The analytical results of using the solution with non-singular term show better than without non-singular in comparison with the experimental data. And maximum tangential stress criterion (MTS) and maximum tangential strain energy density criterion (MTSE) can get useful results for several loading conditions.

PURPOSE. This in vitro study aimed to compare the failure load and failure characteristics of two different zirconia framework designs of premolar crowns when subjected to static loading. MATERIALS AND METHODS. Two types of zirconia frameworks, conventional 0.5 mm even thickness framework design (EV) and 0.8 mm cutback of full contour crown anatomy design (CB), were made for 10 samples each. The veneer porcelain was added on under polycarbonate shell crown made by vacuum of full contour crown to obtain the same total thickness of the experiment crowns. The crowns were cemented onto the Cobalt-Chromium die. The dies were tilted 45 degrees from the vertical plane to obtain the shear force to the cusp when loading. All crowns were loaded at the lingual incline of the buccal cusp until fracture using a universal testing machine with cross-head speed 0.5 mm/min. The load to fracture values (N) was recorded and statistically analyzed by independent sample t-test. RESULTS. The mean and standard deviations of the failure load were $1,170.1{\pm}90.9$ N for EV design and $1,450.4{\pm}175.7$ N for CB design. A significant difference in the compressive failure load was found (P<.05). For the failure characteristic, the EV design was found only cohesive failures within veneering porcelain, while the CB design found more failures through the zirconia framework (8 from 10 samples). CONCLUSION. There was a significant difference in the failure load between two designs, and the design of the framework influences failure characteristic of zirconia crown.

PURPOSE. The purpose of this study was to evaluate the resistance to deformation under static overloading by measuring yield and fracture strength, and to analyze the failure characteristics of implant assemblies made of different titanium grades and connections. MATERIALS AND METHODS. Six groups of implant assemblies were fabricated according to ISO 14801 (n=10). These consisted of the combinations of 3 platform connections (external, internal, and morse tapered) and 2 materials (titanium grade 2 and titanium grade 4). Yield strength and fracture strength were evaluated with a computer-controlled Universal Testing Machine, and failed implant assemblies were classified and analyzed by optical microscopy. The data were analyzed using the One-way analysis of variance (ANOVA) and Student's t-test with the level of significance at P=.05. RESULTS. The group $IT4_S$ had the significantly highest values and group IT2 the lowest, for both yield strength and fracture strength. Groups $IT4_N$ and ET4 had similar yield and fracture strengths despite having different connection designs. Group MT2 and group IT2 had significant differences in yield and fracture strength although they were made by the same material as titanium grade 2. The implant system of the similar fixture-abutment interfaces and the same materials showed the similar characteristics of deformation. CONCLUSION. A longer internal connection and titanium grade 4 of the implant system is advantageous for static overloading condition. However, it is not only the connection design that affects the stability. The strength of the titanium grade as material is also important since it affects the implant stability. When using the implant system made of titanium grade 2, a larger diameter fixture should be selected in order to provide enough strength to withstand overloading.

The number of fabrication shop for spherical type LNG tank is proportional to that of the tank radius to be constructed. Due to limitation of facility investment including building sites, it is practically difficult to fabricate various size tanks with perfectly spherical shape in the yards. The efficient method to be capable of increasing cargo tank volume is to extend vertically the conventional spherical type LNG tank by inserting a cylindrical shell structure. The main purpose of this study is to derive related equations on forces generated on spherical type LNG tank with central cylindrical part under various static loadings in order to establish the simplified analysis method for the initial estimate. In this study, equations on circumferential and meridional force have been derived and verified by relations with the reaction forces per unit length of equator.

In the present study, a CPT-based p-y analysis method was proposed for offshore mono-piles embedded in sands. Static and cyclic loading conditions were both taken into account for the proposed method. The continuous soil profiling capability of CPT was an important consideration for the proposed method, where detailed soil profile condition with depth can be readily incorporated into the analysis. The hyperbolic function was adopted to describe the non-linear p-y curves. For the proposed hyperbolic p-y relationship, the ultimate lateral soil resistance $p_u$ was given as a function of the cone resistance, which is directly introduced into the analysis as an input data. For cyclic loading condition, two different cyclic modification factors were considered and compared. Case examples were selected to check the validity of the proposed CPT-based method. Calculated lateral displacements and bending moments from the proposed method were in good agreement with measured results for lateral displacement and bending moment profiles. It was observed the accuracy of calculated results for the conventional approach was largely dependent on the selection of friction angle that is to be adopted into the analysis.

This study investigates the bending and stress behavior of functionally graded material (FGM) microplates and shell panels under thermomechanical loading, using the rule of mixtures (ROM) and local representative volume elements (LRVE). The formulation integrates first-order shear deformation theory (FSDT) with the modified couple-stress theory (MCST) to establish a size-dependent framework, and the governing equations are rigorously derived from Hamilton's principle. A neutral surface approach, along with an exact shear correction factor, is used to improve analysis accuracy. A finite element model is developed using an eight-noded isoparametric element with five degrees of freedom per node. The model represents an FGM panel with a pure ceramic upper layer and a pure metal lower layer, where temperature-dependent material properties are graded through the thickness. The effective properties are calculated using the ROM and LRVE. Aluminum oxide (Al2O3) and titanium alloy (Ti-6Al-4V) are selected as the ceramic and metallic constituents, respectively. The accuracy of the proposed formulation is first established by validating it against existing results. Subsequently, a comprehensive parametric analysis explores the effects of key parameters, including the material length-scale ratio, shear correction factor, panel geometry, and boundary conditions, on the structural performance. The findings of this study reveal that size-dependent effects significantly influence the bending behavior and stress distribution of FGM microplates and shell panels under thermomechanical loading. It is also observed that with the use of the exact shear correction factor, the results for bending and stress for FGM microplates and shell panels under thermo-mechanical loading obtained using ROM and LRVE are more accurate than those obtained using the conventional shear correction factor. Notably, the study is useful for microstructural applications involving the thermomechanical analysis of advanced micro-scale engineering structures, such as MEMS devices, sensors, actuators, and resonators, operating under coupled mechanical and thermal conditions.

The ocean tide loading (OTL) is an important factor for the GPS positioning, especially in the height direction. The shorter of the distance to the ocean, the larger of the error by the OTL. The influence will be changed when we measure in different place and the order of magnitude is from few centimeters to ten centimeters. In this study, more than ten kinds of the OTL models were collected and applied on the GPS static relative positioning in Taiwan. The GPS observations including five stations were obtained from Nov. 9, 2004 to Feb. 23, 2005 and we used the Bernese GPS software to execute the data processing. In this period, the average amplitudes of the 3-D coordinates are as follows: N is 0.4 cm, E is 0.7 cm, h is 1.8 cm at Kinmen station; N is 0.7 cm, E is 1.3 cm, h is 2.3 cm at Lanyu station; N is 0.5 cm, E is 0.7 cm, h is 2.0 cm at Matsu station; N is 0.6 cm, E is 0.6 cm, h is 2.0 cm at Penghu station and N is 0.5 cm, E is 1.2 cm, h is 1.7 cm at Hsinchu station. Moreover, we will analyze the advantage and disadvantage of every kind of the OTL models in different environments to offer some information to the GPS users and enhance the precision of the GPS positioning.

In this article, static analysis of a magneto-electro-elastic (MEE) beam subjected to various thermal loading and boundary conditions has been investigated. Influence of pyroeffects (pyroelectric and pyromagnetic) on the direct quantities (displacements and the potentials) of the MEE beam under different boundary conditions is studied. The finite element (FE) formulation of the MEE beam is developed using the total potential energy principle and the constitutive equations of the MEE material taking into account the coupling between elastic, electric, magnetic and thermal properties. Using the Maxwell electrostatic and electromagnetic relations, variation of stresses, displacements, electric and magnetic potentials along the length of the MEE beam are investigated. Effect of volume fractions, aspect ratio and boundary conditions on the direct quantities in thermal environment has been determined. The present investigation may be useful in design and analysis of magnetoelectroelastic smart structures and sensor applications.

Structural behavior of R/C deep beams was investigated and compared to those of specimens with CFRP Grids. Test results show that the crushing of compression strut for the unstrengthened R/C deep beams is changed to the group of several diagonal cracks at mid-depth within the sheat span. Strengthened specimens grow to be more ductile after the redistribution of internal force on the CFRP Grids. The failure mode and variations of strains in the specimens are dependent on the shear span-to-depth ratio. The lower the shear span-to-depth ratio, the bigger failure load and the less variations in strain are observed. Additional anchorage of CFRP Grids does not only cause the improvement in the internal resistance, but also control the brittle shear failure of specimen after reaching the maximum loads.