Short-leg shear wall structures are a new form of building structure that combine the merits of both frame and shear wall structures. Its architectural features, structure bearing and engineering cost are reasonable. ...Short-leg shear wall structures are a new form of building structure that combine the merits of both frame and shear wall structures. Its architectural features, structure bearing and engineering cost are reasonable. To analyze the elastic-plastic response of a short-leg shear wall structure during an earthquake, this study modified the multiple-vertical-rod element model of the shear wall, considered the shear lag effect and proposed a multiple-vertical-rod element coupling beam model with a new local stiffness domain. Based on the principle of minimum potential energy and the variational principle, the stiffness matrixes of a short-leg shear wall and a coupling beam are derived in this study. Furthermore, the bending shear correlation for the analysis of different parameters to describe the structure, such as the beam height to span ratio, short-leg shear wall height to thickness ratio, and steel ratio are introduced. The results show that the height to span ratio directly affects the structural integrity; and the short-leg shear wall height to thickness ratio should be limited to a range of approximately 6.0 to 7.0. The design of short-leg shear walls should be in accordance with the ＂strong wall and weak beam＂ principle.展开更多
Short-leg walking boots are a common intervention for acute and chronic lower extremity injury.Few studies have examined the neuromuscular adaptations associated with short-leg walking boots and no previous study has ...Short-leg walking boots are a common intervention for acute and chronic lower extremity injury.Few studies have examined the neuromuscular adaptations associated with short-leg walking boots and no previous study has investigated timing characteristics of muscle activation during gait.The purpose of the current study was to examine the timing and amplitudes of muscle activation of the extrinsic ankle musculature during walking in two types of short-leg walking boots.Methods:Eleven healthy young adults performed five level walking trials at a self-selected pace in each of three conditions:normal walking,Gait Walker and Equalizer short-leg walking boots.Ground reaction forces were collected from a force platform while surface electromyography (EMG)was collected from the tibialis anterior,peroneus longus and medial gastrocnemius.EMG signals were rectified and smoothed using the root mean squared with a 20-ms smoothing window and were normalized to the largest mean of the normal walking trials.A repeated measures analysis of variance was used to assess the effect of short-leg walking boots on the onset,duration and amplitude of muscle activation.Results:Short-leg walking boots were generally associated with earlier onsets of muscle activation and longer durations of muscle activation.However,there was no reduction in EMG amplitude.Conclusion:The findings of this study show that the induced alterations in muscle activation patterns may limit the short-leg walking boots.Copyright(C)2012,Shanghai University of Sport.Production and hosting by Elsevier B.V.All rights reserved.展开更多
文摘Short-leg shear wall structures are a new form of building structure that combine the merits of both frame and shear wall structures. Its architectural features, structure bearing and engineering cost are reasonable. To analyze the elastic-plastic response of a short-leg shear wall structure during an earthquake, this study modified the multiple-vertical-rod element model of the shear wall, considered the shear lag effect and proposed a multiple-vertical-rod element coupling beam model with a new local stiffness domain. Based on the principle of minimum potential energy and the variational principle, the stiffness matrixes of a short-leg shear wall and a coupling beam are derived in this study. Furthermore, the bending shear correlation for the analysis of different parameters to describe the structure, such as the beam height to span ratio, short-leg shear wall height to thickness ratio, and steel ratio are introduced. The results show that the height to span ratio directly affects the structural integrity; and the short-leg shear wall height to thickness ratio should be limited to a range of approximately 6.0 to 7.0. The design of short-leg shear walls should be in accordance with the ＂strong wall and weak beam＂ principle.
基金funded in part by a grant from DeRoyal Industries,Inc.,Powell,TN,USA
文摘Short-leg walking boots are a common intervention for acute and chronic lower extremity injury.Few studies have examined the neuromuscular adaptations associated with short-leg walking boots and no previous study has investigated timing characteristics of muscle activation during gait.The purpose of the current study was to examine the timing and amplitudes of muscle activation of the extrinsic ankle musculature during walking in two types of short-leg walking boots.Methods:Eleven healthy young adults performed five level walking trials at a self-selected pace in each of three conditions:normal walking,Gait Walker and Equalizer short-leg walking boots.Ground reaction forces were collected from a force platform while surface electromyography (EMG)was collected from the tibialis anterior,peroneus longus and medial gastrocnemius.EMG signals were rectified and smoothed using the root mean squared with a 20-ms smoothing window and were normalized to the largest mean of the normal walking trials.A repeated measures analysis of variance was used to assess the effect of short-leg walking boots on the onset,duration and amplitude of muscle activation.Results:Short-leg walking boots were generally associated with earlier onsets of muscle activation and longer durations of muscle activation.However,there was no reduction in EMG amplitude.Conclusion:The findings of this study show that the induced alterations in muscle activation patterns may limit the short-leg walking boots.Copyright(C)2012,Shanghai University of Sport.Production and hosting by Elsevier B.V.All rights reserved.
