Earticle

연구목적: 본 연구의 목적은 화재가 발생한 교량의 지속적인 사용가능 여부를 결정하고 보수·보강에 대 한 근거자료를 제공하기 위해 교량의 화재 손상여부를 정확하게 분석하는 것이다. 연구방법: 구조물에 전달된 화재온도를 추정하기 위하여 콘크리트의 XRD, SEM 및 EDS 분석 등을 실시하였으며, PSCI Beam 및 바닥판 콘크리트 표면으로부터의 깊이별, 구역별로 분석하였다. 연구결과: 화재구간 콘크리 트에 대한 시험결과 G12,11은 깊이 60mm까지 열에 의한 영향이 미친 것으로 확인되었고 수열온도는 최 대 1000°C 이상인 것으로 나타났다. 그리고 G10,9,8 거더는 G12,11에 비해 상대적으로 약한 피해를 입었으 며 피해 정도는 최대 40mm 깊이까지 열에 의한 영향을 받은 것으로 확인되었다. 결론: 분석된 자료를 근거로 보수‧보강과 정기적인 점검을 시행한다면 본 교량은 화재에 의한 손상을 감안하더라도 충분한 안전성을 확보할 수 있을 것으로 사료된다.

Purpose: The purpose of this study is to accurately analyze the damage of bridges in order to determine whether fire bridges can be used continuously or to provide information on maintenance augmentation data. Method: XRD, SEM and EDS analyzes of concrete were carried out to estimate the fire temperature transferred to the structure, and analyzed by depth and area from PSCI beam and bottom plate concrete surface. Results: Test results G12,11 for the fire zone concrete were confirmed to be affected by heat up to depth of 60mm and the temperature of the hydrothermal heat was above 1000 °C. Also, the girder G10,9,8 was relatively weakly damaged compared to G12,11, and the degree of damage was confirmed to be affected by heat up to a depth of 40 mm. Conclusion: Based on the analyzed data, it is considered that if the repair / reinforcement and periodic inspection are carried out, the bridge can secure sufficient safety even considering the damage caused by the fire.

ABSTRACT Background Pelvic compression belt passively stabilized the sacroiliac joint via application of a compression force, thereby having a possibility to affect hip muscle strength. Purpose We investigated the effects of pelvic compression belts on the strength of hip extensor and the electromyographic (EMG) activities of latissimus dorsi and erector spinae during isometric prone hip extension with knee extension and prone hip extension with knee flexion. Study design Comparative, repeated measures design. Methods We recruited 15 patients with sacroiliac joint pain. All performed isometric prone hip extension with knee extension with and without a pelvic compression belts at a hip extension of 10°. Strength of hip extensor were measured using a load cell, and the muscle activities of the contralateral latissimus dorsi and erector spinae muscles measured using surface EMG. Results Strength of hip extensor with a pelvic compression belts increased significantly compared to without a pelvic compression belts (p<0.001) as did the EMG activity of the contralateral latissimus dorsi (p<0.05). However, the EMG activity of the contralateral erector spinae did not change significantly (p>0.05). Conclusions We recommend using of a pelvic compression belts by sacroiliac joint pain patients increased the strength of hip extensor and muscle activity of contralateral latissimus dorsi.

The compression strength of corrugated fiberboard containers for packaging the agricultural products rapidly decreases because of various environmental conditions during distribution of unitized products. Among various environmental conditions, the main factors affecting the compression strength of corrugated fiberboard are absorption of moisture, long-term accumulative load, and fatigue caused by shock and vibration. An estimated rate of damage for fruit during distribution is about 30~40% owing to the shock and vibration. This study was carried out to characterize the durability of corrugated fiberboard containers for packaging the fruits and vegetables under simulated transportation environment. After the packaging freight was vibrated at various experimental conditions, the compression test for the packaging was performed. The compression strength of corrugated fiberboard containers decreased with loading weight and vibration time. The multiple nonlinear regression equation (R2 = 0.9198) for predicting the decreasing rate of compression strength of corrugated fiberboard containers were developed using four independent variables such as input acceleration level, input frequency, loading weight and vibration time.

Though box compression strength (BCS) is commonly used as a performance criterion for shipping containers, estimating BCS remains a challenge. In this study, artificial neural networks (ANN) are implemented as a new tool, with a focus on building up ANN architectures for BCS estimation. An Artificial Neural Network (ANN) model can be constructed by adjusting four modeling factors: hidden neuron numbers, epochs, number of modeling cycles, and number of data points. The four factors interact with each other to influence model accuracy and can be optimized by minimizing model’s Mean Squared Error (MSE). Using both data from the literature and “synthetic” data based on the McKee equation, we find that model estimation accuracy remains limited due to the uncertainty in both the input parameters and the ANN process itself. The population size to build an ANN model has been identified based on different data sets. This study provides a methodology guide for future research exploring the applicability of ANN to address problems and answer questions in the corrugated industry.

The objective of this study is to find the electrical properties of Bottom ash from thermoelectric power plants in Korea. By using Parallel Plate Method, the electrical resistivity and dielectric constant were measured at the frequency from 20 Hz to 10 MHz. Also, unconfined strength test, XRF and sieve analysis were performed for finding the relationship between strength, physiochemical properties and electrical properties. In the result, the change of electrical resistivity and dielectric constant of bottom ash against frequency was similar to that of general soil. The proportion of fine grain in bottom ash had the positive correlation with dielectric constant and negative correlation with electrical resistivity. Chloride and sulfur trioxide were proportional to dielectric constant and the more bottom ash had chloride content, the lower electrical resistivity appeared in bottom ash. Unconfined strength of bottom ashes had a range from 200 kPa to 780 kPa and strength was inverse proportional to electrical resistivity.

PURPOSES : It is difficult to estimate tunnel stability because of lack of timely information during tunnel excavation. Tunnel deformability refers to the capacity of rock to strain under applied loads or unloads during tunnel excavation. This study was conducted to analyze a methods of pre-evaluation of stability during tunnel construction using the critical strain concept, which is applied to the results of tunnel settlement data and unconfined compression strength of intact rock or rock mass at the tunnel construction site. METHODS : Based on the critical strain concept, the pre-evaluation of stability of a tunnel was performed in the Daegu region, at a tunnel through andesite and granite rock. The critical strain concept is a method of predicting tunnel behavior from tunnel crown settlement data using the critical strain chart that is obtained from the relationship between strain and the unconfined compression strength of intact rock in a laboratory. RESULTS : In a pre-evaluation of stability of a tunnel, only actually measured crown settlement data is plotted on the lower position of the critical strain chart, to be compared with the total displacement of crown settlement, including precedent settlement and displacement data from before the settlement measurement. However, both cases show almost the same tunnel behavior. In an evaluation using rock mass instead of intact rock, the data for the rock mass strength is plotted on the lower portion of the critical strain chart, as a way to compare to the data for intact rock strength. CONCLUSIONS : From the results of the pre-evaluation of stability of the tunnel using the critical strain chart, we reaffirmed that it is possible to promptly evaluate the stability of a tunnel under construction. Moreover, this research shows that a safety evaluation using the actual instrumented crown settlement data with the unconfined compression strength of intact rock, rather than with the unconfined compression strength of a rock mass in the tunnel working face, is more conservative.

Background : To assess the effect of a pelvic compression belt on the strength of hip flexor in healthy young individuals. Study design: Pre- and post-treatment measurement design on one factor was used. Methods : 30 healthy volunteers (male: 15, female: 15) participated in this study. Dynamometer was used to measure the strength of hip flexor, and measurements were performed before and after the application of the pelvic compression belt at neutral position of hip joint and at 30 cm raised position from floor with straight leg in supine. Results : After the application of the pelvic compression belt, the strengths of hip flexor measured at both positions were significantly increased when compared with before the application (p<.05). However, at neutral position of hip joint and at 30cm raised position from floor, there were significantly different in the changing patterns in the strengths of hip flexor between men and women (p>.05). Conclusion : The findings suggest that the pelvic compression belt is helpful in strengthening hip muscles. With easy application, it is sufficiently feasible for clinical use.

Agricultural corrugated fiberboard packaging boxes frequently experience damage due to loading and unloading, vibration during transport, and shock by dynamic distribution condition change. This study was carried out to estimate effect of vibration during distribution process on compression strength of corrugated fiberboard boxes for agricultural products. In order to identify the degradation caused by vibration, after box packaging the agricultural products( tangerine or cucumber), the natural frequencies of the packaging boxes were measured by varying the relative humidity(50, 70 and 90%) at 25oC temperature. Various types of corrugated fiberboard boxes were packed with tangerines and cucumbers, and the PSD plot vibration tests were conducted by utilizing the actual vibration recording results of the Gyeongbu Expressway section between Seoul and Gimcheon. As a result of the experiment, the decrease in compression strength of the box was relatively low in DW-AB, and the decrease in compression strength of the SW-A 0201(RSC) type box was the highest at 20.49%. In particular, both SW-A and DW-AB showed low compression strength degradation rates for open folder type boxes. The moisture content varies depending on the type of the box or agricultural products, and the enclosed 0201(RSC) type box was generally higher than the open folder or bliss type box, which is believed to be the reason for the decrease in compression strength of RSC type box due to humidity. By the agricultural product, the percentage of decrease in compression strength of box packed with cucumbers was especially high.

본 연구에서는 국내 모래의 공학적 특성을 파악하기 위하여 표준사, 욕지사, 낙동강사를 이용하여 구속압 조건, $K_0$ 조건, 과압밀 조건, 상대밀도 조건을 다르게하여 삼축압축시험을 실시하였다. 삼축압축시험 결과, 변형률 ${\epsilon}_1$에 따른 축차응력 $\acute{q}$의 변화는 구속압 ${\sigma}_3$와 상대밀도 $D_r$이 클수록 크게 변화하였으나, $K_0$ 조건과 과압밀 조건변화와 크게 상관이 없었다. 모래의 최대 내부마찰각(${\phi}_{max}$)은 구속압이 클수록 입자간의 접촉력이 크게 되어 작아지는 경향을 나타내었고, $K_0$ 조건과 과압밀 조건에 따라서는 거의 변화가 없는 것으로 나타났으며, 상대밀도에 따라서는 상대밀도가 감소함에 따라 내부마찰각도 작아지는 경향을 나타내었다. 체적변형률(${\epsilon}_u$)은 구속압이 클수록 입자의 파쇄성과 입자간의 재배열에 의해 체적 팽창이 작게 나타났으며, $K_0$ 조건과 과압밀 조건에서는 조건에 상관없이 거의 같은 거동을 보였고, 상대밀도에 따라서는 상대밀도가 커질수록 초기에는 압축되다가 축변형률(${\epsilon}_1$)이 증가할수록 팽창하는 경향이 뚜렷하게 나타났다. 변형률 변화에 따른 탄성계수 $E_{sec}$는 변형률이 커질수록 차츰 수렴하는 경향을 나타내었고, 축차응력($\acute{q}$)-변형률(${\epsilon}_1$) 관계에서 초기할선 탄성계수($E_{ini}$)>할선 탄성계수($E_{sec}$)>접선 탄성계수($E_{tan}$) 순으로 탄성계수의 크기가 산정되었으며, 구속압 및 상대밀도가 증가함에 따라 탄성계수가 증가하는 경향을 보였고, $K_0$ 및 과압밀에 따라서는 거의 비슷한 탄성계수를 나타내었다. 접선 탄성계수에 의한 정규화에 대해서는 다양한 증가비로 증가하는 경향을 보였다. 한계상태선의 기울기 M은 구속압이 증가함에 따라 감소하는 경향을 나타내었고, $K_0$ 및 구속압, 상대밀도에 따라서는 동일선상에 표현되며, 상대밀도가 증가할수록 한계상태선의 기울기 M도 증가하는 경향을 보였다.

This study conducted experiment for understanding engineering characteristics of domestic sands by examining standard sand and sand from Yokji Island and Nakdong River in terms of confining pressure, $K_0$, over consolidation and relative density factors through triaxial compression test. The test showed that deviator stress by strain positively changed as confining pressure and relative density grow while $K_0$ and over consolidation factors do not directly correlated with it. Angle of internal friction decreases as confining pressure increases which strengthens contact force between particles, and declines as relative density drops, whereas $K_0$ and over consolidation factors hardly affect the results. When it comes to volumetric strain, volume expansion decreases as confining pressure increase due to crushability and rearrangement of particles while $K_0$ and over consolidation shows same movement unconditionally, and relative density appears compressed as it grows at the beginning however it expands as axial strain increases. Modulus of elasticity ($E_{sec}$) by strain has tendency into convergence resulting in initial secant modulus of elasticity ($E_{ini}$) > secant modulus of elasticity($E_{sec}$) > tangent modulus of elasticity ($E_{tan}$). On the other hand, it grows as confining pressure and relative density increase while indicating similar modulus of elasticity ($E_{sec}$) regarding on $K_0$ and over consolidation. Slope of critical line (M) tended to decrease as confining pressure increases, follow same line according to $K_0$, confining pressure and relative density, and increase as relative density grows.

Background: Lumbopelvic stability is highly important for exercise therapy for patients with low back pain and shoulder dysfunction. It can be attained using a pelvic compression belt. Previous studies showed that external pelvic compression (EPC) enhances form closure by reducing sacroiliac joint laxity and selectively strengthens force closure and motor control by reducing the compensatory activity of the stabilizer. In addition, when the pelvic compression belt was placed directly on the anterior superior iliac spine, the laxity of the sacroiliac cephalic joint could be significantly reduced. Objects: This study aimed to compare the effects of EPC on lumbopelvic and shoulder muscle surface electromyography (EMG) activities during push-up plus (PUP) and deadlift (DL) exercise, trunk extensor strength during DL exercise. Methods: Thirty-eight subjects (21 men and 17 women) volunteered to participate in this study. The subjects were instructed to perform PUP and DL with and without the EPC. EMG data were collect from serratus anterior (SA), pectoralis major (PM), erector spinae (ES), and multifidus (MF). Trunk extensor strength were tested in DL exercise. The data were collected during 3 repetitions of all exercise and the mean of root mean square was used for analysis. Results: The EMG activities of the SA and PM were significantly increased in PUP with pelvic compression as compared with PUP without pelvic compression (p<.05). In DL exercise, a significant improvement in trunk extensor strength was observed during DL exercise with pelvic compression (p<.05). Conclusion: The results of this study indicate that lumbopelvic stabilization reinforced with external pelvic compression may be propitious to strengthen PUP in more-active SA and PM muscles. Applying EPC can improve the trunk extensor strength during DL exercise. Our study shows that EPC was beneficial to improve the PUP and DL exercise efficiency.

In order to determine safety factor of corrugated fiberboard boxes for agricultural products, relationship with effect of relative humidity and structure of box types must be defined. The results obtained from the study were summarized as follows; 1. Results show a detrimental effect on bursting strength of corrugated boards with increasing relative humidity of environment. 2. Compression strength of corrugated boards were decreased rapidly after the relative humidity was over 70 percent. 3. Compression strength of corrugated board boxes were greatly depending on the box types. Folder type showed the best performance at higher humidity environment while bliss type was the worst. 4. Further studies are needed in order to expect box compression strength in real distribution environment.

Determination of safety factor of corrugated fiberboard boxes used for agricultural products is very complicated process due to nature of living products. Moisture content is one of the most critical factors to determine overall physical strength of paper, so its influences on strength properties of corrugated board made from different raw materials must be quantified. The results obtained from the study were summarized as follows; 1. Results show a detrimental effect on bursting strength and compressive strength of liners with increasing relative humidity of environment and moisture content of liners. 2. The relevance of equilibrium moisture content at varying relative humidity levels was proved and its relationship was used as an important factor to estimate box compression strength. 3. Test results was statistically used for establish the relationship between relative humidity and moisture content of liners. Estimated compression strength of boxes at varying moisture content was similar to results of theoretical equations such as Kellicutt`s. Further study could be carried out in order to determine a optimum safety factors of various corrugated board boxes for agricultural products.

전단마찰 시험체는 재하형태에 따라 압축재하와 인장재하 시험으로 구분된다. 인장재하 시험의 경우에는 외력으로 작용하는 수직방향 인장력에 의하여 전단응력 및 수직방향 인장응력이 유발된다. 이 연구에서는 압축장 이론을 이용하여 인장재하 시험체의 전단전달강도를 평가하였으며, 2축-응력 상태의 콘크리트 최대 압축강도의 변화를 고려하기 위하여 수정압축장이론, 연화트러스모델의 구성방정식을 사용하였다. 타당성 검증을 위하여 과거 연구자들에 의해 수행된 직접전단강도 실험값들과 압축장 이론을 이용하여 구한 값들을 비교한 결과, 비균열 인장재하 시험체의 경우 예측값과 실측치가 대체적으로 잘 일치함을 확인하였다. 또한 콘크리트 스트럿의 유효압축강도를 고려한 전단강도 평가식을 제안하고, 기존 문헌에 수록된 실험결과와 비교함으로써 제안식의 적용 가능성을 검증하였다.

Two different types of shear-friction tests were classified by external loadings and referred to as a push-off and a pull-off test. In a pull-off test, a tension force is applied in the transverse direction of the test specimen to produce a shear stress at the shear plane. This paper presents a method to evaluate shear transfer strengths of uncracked pull-off specimens. The method is based on the compression field theory and different constitutive laws are applied in some ways to gain accurate shear strengths considering softening effects of concrete struts based on Modified Compression Field Theory (MCFT) and Softened Truss Model (STM). The validity of the proposed method is examined by applying to some selected test specimens in literatures and results are compared with the predicted values. A general agreement is observed between predicted and measured values at ultimate loading stages in initially uncracked pull-off test specimens. A shear strength evaluation formula considering the effective compressive strength of a concrete strut was proposed, and the applicability of the proposed formula was verified by comparing with the experimental results in the literature.

본 연구는 공중낙하법으로 만든 공기건조 상태의 일본의 표준사인 풍포사(豊浦砂)(Toyoura sand)와 영국의 표준사인 Silver Leighton Buzzard sand 공시체를 배수상태에서 평면 변형율 압축시험을 실시하여, 구속압이 모래의 변형 강도특성에 미치는 영향을 조사하였다. 축방향 변위와 수평방향의 변위는 변형율수준(strain level) $10^{-6}$에서 파괴상태까지를 연속적으로 구할 수 있는 장치를 사용하여 정도 높게 측정함으로써 미소변형에서 파괴상태까지의 응력 변형율 특성을 상세히 연구하였다. 그 결과, 극저구속압에서는 구속압이 작아져도 내부마찰각 ${\sigma}^{\prime}{_{max}}=arcsin\{({\sigma}{_1}^{\prime}-{\sigma}{_3}^{\prime})/({\sigma}{_1}^{\prime}+{\sigma}{_3}^{\prime})\}_{max}$가 급격히 크게 되지는 않아, Bolton의 경험식을 사용할 시는 어느 정도 구속압이 클 때만 적용 가능하다는 것을 알았다. 또, 모래의 강성률은 근사적으로 구속압의 m승에 비례하는데(G or $E{\propto}{\sigma}{_3}^{{\prime}m}$), 이때 m은 변형율수준 $10^{-4}$이하에서는 약 0.4 정도이고 변형율=$10^{-1}$에서는 $m{\fallingdotseq}0.9$ 정도이었다. 이러한 경향은 모래의 종류, 혹은 시험종류에 따라 거의 변화하지 않음을 알았다. 이것은 구속압이 작을수록 강성률의 변형율수준 의존성, 응력수준 의존성이 크게 되는 것과 대응한다. 끝으로, Rowe의 응력-다이러턴시 관계는 미소 변형율수준($10^{-4}$ 이하)에서 파괴까지 거의 직선적으로 성립하고, 구속압의 영향을 거의 받지 않는다는 것을 알았다.

A series of drained plane strain compression tests was performed on dried samples of dense Toyoura sand and Silver Leighton Buzzard sand prepared by air-pluviation method to find out the deformation and strength characteristics on the value of confining pressure ${\sigma}{_3}^{\prime}({\sigma}{_3}^{\prime}=0.05{\sim}4.0kgf/cm^2)$. The axial and lateral strains measured in this apparatus ranged from $10^{-6}$ up to the failure of the specimen. So the stress-strain characteristics would be investigated from very small to very large strain levels. It was found that the change of the angle of internal friction ${\phi}^{\prime}{_{max}}=arcsin\{({\sigma}{_1}^{\prime}-{\sigma}{_3}^{\prime})/({\sigma}{_1}^{\prime}+{\sigma}{_3}^{\prime})\}_{max}$ with the change of ${\sigma}{_3}^{\prime}$ is very small when ${\sigma}{_3}^{\prime}$ is lower than higher. Furthermore, the effect of confining pressure on stiffness of sands was evaluated. It was also found that for the range of shear strain ${\gamma}$ from $10^{-6}$ to those at peak, the Rowe's stress-dilatancy relation seems to be a good approximation for air-dried Toyoura sand and Silver Leighton Buzzard sand, irrespective of the change of ${\sigma}{_3}^{\prime}$.

Background: This study is goal to explore the effects of swiss ball exercise on muscular strength, flexibility, and balance in healthy adults with and without pelvic compression belts. Design: Randomized Controlled Trial. Methods: This study randomly divided the experimental and control groups in 24 healthy adults wearing pelvic compression belts, and they conducted Swiss ball exercise programs, 5 times for 40 minutes a week during 3 weeks in conclusion 15 times. Results: The results showed that the experimental groups have increased significantly in muscle strength and flexibility (p<.05). Conclusion: This study showed that pelvic compression belts and Swiss ball exercise programs will help health improvements such as muscle strength, flexibility, and balance in normal adults, and it is also thought to be worth applying to patients with back pain.

Purpose : The purpose of the study is to investigate the quality and relevance of back strength or chest compression which is applied by isotonic exercise of hip joint. Methods : Subjects were 37 students who participated in the BLS course and accepted the informed consent from December 7 to 8, 2012. During CPR performance, back strength was measured by the researcher. CPR was used the manikin for practical training with using PC, conducted by standard CPR for 2 minutes,Quality of chest compressions included average chest compression depth, rate, and recoil ratio. Results : Back strength (kg) is related to the chest compression depth (mm) (r =.746, p <.001). The high quality CPR is the most important factor so high quality is full chest recoil of chest compression and chest compression depth (mm) (β=.831, p <.001). In this study, chest compression rate and recoil ration were not influenced by back muscle strength. Conclusion : It is necessary to implement the CPR program to improve physical strength and effective performance of CPR.

The purpose of this study is to investigate the effects of wearing elastic compression stockings and lower leg strength exercise on lower extremity edema and pain scale of female office worker. We divided 30 subjects into 3 groups: control group(GC, n=8), exercise group(EG, n=10), and stocking group(SG, n=10). After dividing groups, we measured body composition, ankle and calf circumference and lower body pain scale by visual analogue scale bar for previous test. During experimental period of 8 weeks, EG was performed modified leg strength exercise for 50 minutes per 1 time and 3 days per week and SG was worn elastic compressive stockings in proportion to the height and weight of each subjects. When the experimental period finished, we measured the same factors of previous things. For results, the ankle circumference and pain scale was improved significantly in both EG and SG compared to the CG(p<.05, p<.001). But a significant differences between EG and SG was not observed. Theses results show that leg strength exercise and wearing stockings may be a therapeutic factors for lower extremity edema and pain scale of female office workers.

Recently, Korea design codes about CFT columns were indicated. Such are the Specifications and Codes for Allowable Stress Design by Korean Society of Steel Construction in 2003 and Korean Building Codes for Limit State Design by Architectural Institute of Korea in 2005, which was revised in 2009. However, KBC/LSD provision underestimate the strength of CFT columns. Therefore, more accurate estimation of strength of CFT columns is needed. Current research performs column tests under eccentric axial load and investigates buckling loads of the columns in inelastic range. It also compares the test results to KBC/LSD provision. This paper suggests new design method of CFT columns for KBC/LSD provision.

In this study, to consider practical compressive zone of hollow slab, the equation for its flexural strength is proposed by the volume of compressive stress block according to neutral axis location in hollow section assumed. Existing estimation method of flexural strength of hollow slab considering only compressive zone above hollow part is evaluated as the most conservative method and the method estimating flexural strength by two alternative cross-section of hollow slab is evaluated as more practical method.