• Land and Housing Review
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• v.2 no.4
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• pp.509-516
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• 2011

Compared with the traditional RC system, precast stairs can save construction time, reduce the cost of concrete casting, etc. This paper focuses on an investigation of improved continuous longitudinal joint details for PC stair systems. The performance of the precast concrete stair connections subjected to displacement control cyclic loading is compared with that of the monolithic connection. The developed connection is composed of U-rods and clamp joint metals. This paper proposes precast stair connection with improved structural performance and experimentally evaluates the structural performance of the proposed joints in terms of maximum load, displacement ductiliy, strain, crack and failure modes.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.26 no.1
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• pp.89-99
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• 2017

This paper describes the development of a thigh wearable robot for power assistance during stair climbing. In the wearable robot developed in this study, high-power BLDC motors and high-capacity harmonic reduction gears are used to effectively assist the thigh muscle during stair climbing. In particular, normal ground and stair are distinguished accurately by using wireless smart shoes, and the stair climbing assistance is performed by activating the actuators at an appropriate time. Impedance of the hip joint was effectively reduced by performing friction compensation of the gears, and a wearing adjustment mechanism was designed to fit the robot to the thigh by conveniently modifying the width and tilting angle of the robot using set collars. Consequently, the performance of the developed thigh wearable robot was verified through stair climbing experiments with EMG measurement.

• Korean Journal of Applied Biomechanics
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• v.16 no.4
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• pp.31-38
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• 2006

The purpose of this study was to investigate the effect of changing the steps height on the joint moment of lower extremity in stair-descent activity of elderly persons. Data were collected by 3-D cinematography and force platform. 9 male elderly subjects in the 60s and 70s participated in this study. All subjects performed a stair-descent in four different heights of stairs (10, 14, 18, 22cm) having 5 step staircase. The results were as follows. 1. For the step height of 22cm the maximum. plantarflexion moment was the smallest and the largest for the step height of 14cm. 2. There was not a statistical difference shown for the extension moment of the knee joint for the different height of steps. 3. There was not a statistical difference shown for the flexion moment of the hip joint for the varying height of steps but on average for the 18cm step this increased rapidly. 4. The smallest maximum. value for inversion moment was revealed for the step height of 10cm and this increased significantly for the step height of 22cm. 5. The smallest maximum. value for abduction moment of the hip joint was revealed for the step height of 10cm and this increased significantly for the step height of 22cm. 6. There was no significant difference shown for the maximum. abduction moment for the hip joint. The main conclusion is that there is a huge difference in the moment of the lower extremities for the elderly while walking down a stairs with a step height above 18 cm and that this moment increased or decreased rapidly under a condition of step height being 22cm. With the results from this research and related research of elderly walking upstairs it can be shown that the step height has a large role in the safety for the elderly.

• Physical Therapy Korea
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• v.16 no.3
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• pp.24-31
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• 2009

This study aimed to investigate the effect of differing heel heights on the electromyographic (EMG) activity in vastus medialis (VM) and vastus lateralis (VL) during stair ascending and descending activities. A total of 26 healthy women volunteered to perform stair-ascending and stair-descending tasks with 3 heel heights: barefoot, 3 cm, and 7 cm. The EMG activities of the VM and VL were recorded during the tasks. During the stair ascending and descending tasks, the EMG activities of both VM and VL significantly changed with differing the heel heights (p<.05). Moreover, the EMG activities of VM and VL during the stair ascending task were significantly higher than the corresponding values during the stair-descending task (p<.05). However, there were no significant differences between the VM:VL EMG ratios for the 3 heel heights (p>.05). The VM:VL EMG ratios between the 2 tasks differed significantly in the 7 cm high heel condition (p<.05). Despite an increase in the EMG activities in both VM and VL during stair ascending and descending tasks, there was no change in the relative EMG intensities of VM and VL, which was measured by calculating the VM:VL ratio this result indicates that no VM:VL imbalances were elicited. The relative EMG intensities of VM and VL during stair descent were lower than the corresponding values during the ascent, suggesting that VM and VL may show an imbalance in the eccentric activation during the weight-acceptance phase. This study provides useful information that will facilitate future research on how heel height affects muscle activity around the knee joint.

• Korean Journal of Applied Biomechanics
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• v.19 no.2
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• pp.205-215
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• 2009

The purpose of this study is to investigate alterations of pregnant gait by means of 3 different treads of stairs. 9 subjects(body masses; $59.41{\pm}7.49$, $64.03{\pm}6.65$, $67.26{\pm}7.58$, heights; $160.50{\pm}6.35$ ages; $31.22{\pm}2.99$; parity; $1.67{\pm}0.71$) participated in three experiments that were divided by physiological symptoms(the early(0-15 weeks), middle(16-27 weeks) and last(18-39 weeks), and walked at self-selected pace on 4 staircases 3 trials. As extending the pregnancy period, cadence was shorter but cycle time was longer more and more and the difference of maximum and minmum moments between right and left knee joint moment was smaller. With the treads of stair decent lengthening, speed and stride lengths were increased. As extending the treads of stair decent, joint moments of both feet were particular traits, hip joint was asymmetric but joint moments of knee and ankle were symmetric. These findings may account for relation between the treads of stair and moments and suggest that women may adapt their gait to maximize stability and to control gait motion for themselves in pregnant women.

• PNF and Movement
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• v.22 no.1
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• pp.31-41
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• 2024

Purpose: The purpose of this study is to compare lower extremity muscle activities and ankle joint angles between different foot strike patterns (forefoot strike, heelfoot strike) during stair ascent walking. Methods: The subjects of this study were 22 males who walked in each foot strike pattern on ascent stairs at a speed of 85 beats/min. During stair walking with the two types of foot strike patterns, the muscle activities of the rectus femoris, tibialis anterior, medial gastrocnemius, hamstring, and gluteus medius were measured. Additionally, ankle joint angles for inversion, eversion, dorsi flexion, and plantar flexion were recorded. Each participant underwent the experiment three times, with the foot strike pattern randomized. Results were averaged according to the foot strike pattern. Results: Significant differences in ankle angles were observed across all phases according to foot strike pattern. Muscle activities in the lower extremities showed significant differences in all phases except the swing 1 phase. Moreover, differences in foot movement trajectory were noted depending on the foot strike pattern. Conclusion: Walking on ascent stairs elicited differences in lower extremity muscle activities and ankle joint angles based on foot strike pattern. These findings can serve as foundational data for selecting a suitable foot strike pattern tailored to individual patient conditions when training patients in walking on ascent stairs.

• Journal of the Korea Concrete Institute
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• v.20 no.6
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• pp.833-840
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• 2008

The time and cost can be reduced when applying partial precast concrete to the stair system in comparison to the cast-in-place or precast method. Because the performance of staircase which is used for evacuation can be largely different from connection types of precast concrete member, we tried to know structural behavior and performance evaluation according to each type of stair joints by experimental study. In the cast-in-place rigid joint, much reinforcement is needed in the end portion because much stress is concentrated in the middle portion. Also, in the pin joint which is used in the connection point, the maximum stress occurs in the middle point, so not only the amount of re-bar is increased but also the serviceability is largely decreased. The bolt type of semi-rigid joints proposed in this study had been increased strength and serviceability which is similar to the rigid joints. Also, its ductility was shown about 0.7 times in comparison to the rigid type and was about 2.8 times for the pin joint type. According to the classification of joint in Eurocode, it can be considered that it is one of the semi-rigid joints which are in the semi-rigid-full strength, and the structural behavior can be expected by using a model which applied to stiffness value decreased by 40 percent.

• Journal of muscle and joint health
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• v.18 no.2
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• pp.249-256
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• 2011

Purpose: The purpose of this study was to investigate electromyographic(EMG) activity of vastus medialis oblique(VMO) and vastus lateralis(VL) following the application of patellar taping during stair stepping. Methods: Both VMO-VL onset timing and VMO/VL ratio of 15 participants with patellofemoral pain syndrome (PFPS) were measured using an surface EMG uint(Myosystem 1400A, Noraxon Inc., USA). The measurements were taken under three conditions in random order of patellar taping, placebo taping, and no-taping. Data were analysed using $1{\times}3$ repeated measures ANOVA. Results: There was a significant difference with patellar taping on VMO/VL amplitude compared with the placebo taping and no-taping conditions during stair stepping, but no significant difference on VMO-VL onset timing. Conclusion: These result indicate that patellar taping on the vastus medialis oblique has effect on the VMO/VL ratio. Increased values of VMO/VL ratio may contribute to patellar realignment and explain the mechanism of pain reduction following patellar taping in participants with PFPS.

• The Journal of Korean Physical Therapy
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• v.25 no.5
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• pp.297-302
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• 2013

Purpose: This study was conducted in order to investigate the kinematic gait parameter of lower extremities with different gait conditions (level walking, stair, ramp) in hemiplegic patients. Methods: Ten hemiplegic patients participated in this study and kinematic data were measured using a 3D motion analysis system (LUKOtronic AS202, Lutz-kovacs-Electronics, Innsbruk, Austria). Statistical analysis was performed using one-way repeated measure of ANOVA in order to determine the difference of lower extremity angle at each gait phase with different gait conditions. Results: Affected degree of ankle joint in the heel strike phase showed significant difference between level walking and climbing stairs, and toe off phase showed significant difference between level walking and climbing stairs, ramps, and climbing stairs. Affected degree of knee joint showed no significant difference in all attempts. Affected degree of hip joint in the toe off phase showed significant difference between level walking, ramps and stairs, and climbing ramps. Swing phase showed significant difference between sides for level walking and stairs, climbing ramps. Affected ankle joint of heel strike and toe off, and affected hip joint of toe off and the maximum angle of swing phase in the angle was increased. Unaffected side of the ankle joint, knee joint, and hip joint showed a significant increase in walking phase. Conclusion: These findings indicate that compared with level walking, different results were obtained for joint angle of lower extremity when climbing stairs and ramps. In hemiplegia patient's climbing ramps, stairs, more movement was observed not only for the non-affected side but also the ankle joint of the affected side and hip joint. According to these findings of hemiplegic patients when climbing stairs or ramps, more joint motion was observed not only on the unaffected side but also on the affected side compared with flat walking.

• The Journal of Korea Robotics Society
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• v.4 no.4
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• pp.265-272
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• 2009

IVarious driving mechanisms to adapt to uneven environment have been developed for many urban search and rescue (USAR) missions. A tracked mechanism has been widely used to maintain the stability of robot's pose and to produce large traction force on uneven terrain in this research area. However, it has a drawback of low energy efficiency due to friction force when rotating. Moreover, single tracked mechanism can be in trouble when the body gets caught with high projections, so the track doesn't contact on the ground. A transformable tracked mechanism is proposed to solve these problems. The mechanism is designed with several articulations surrounded by tracks, used to generate an attack angle when the robot comes near obstacles. The stair climbing ability of proposed robot was analyzed since stairs are one of the most difficult obstacles in USAR mission. Stair climbing process is divided into four separate static analysis phases. Design parameters are optimized according to geometric limitations from the static analysis. The proposed mechanism was produced from optimized design parameters, and demonstrated in artificially constructed uneven environment and the actual stairway.