Effects of Variation of Axial Load on Seismic Performance of Shear Deficient RC Exterior BCJs

Mohammed Ali Al?Osta,Umais Khan,Mohammed Hussain Baluch,Muhammad Kalimur Rahman 한국콘크리트학회 2018 International Journal of Concrete Structures and M Vol.12 No.5

The focus of this paper is to investigate the effect of column axial load levels on the performance of shear deficient reinforced concrete beam column joints (BCJs) under monotonic and cyclic loading. The problem of interaction between shear stress in BCJ and axial load on column has been addressed in this work by initially postulating a mechanistic model and substantiated by an experimental test program. This was achieved by conducting appropriate tests on seven BCJ sub-assemblies subjected to monotonic and reversed cyclic loading, with varying levels of the column axial load. Experimental results were further validated using a finite element model in an ABAQUS environment. The effect of variation of compressive strength of concrete was considered in a subsequent parametric study, in order to obtain sufficient data, and utilized to develop a new shear strength model for BCJs which includes influences of all the important parameters required to predict the shear strength of BCJs. The results showed that column axial load affects the seismic performance of BCJs significantly. Experimental results demonstrated that at initial stages of loading, increase in axial load enhances the shear capacity of the joint and reduces its ductility. However, when the column axial load/axial strength ratio increases to about 0.6–0.7, shear strength starts to decrease rapidly, leading to pure axial failure of the joint. The magnitude of axial load/axial capacity ratio also dictates the failure mode and development of crack patterns in BCJs. Results of reverse cyclic tests on BCJs showed that high value of axial load/axial capacity ratio increases the initial stiffness of BCJ but rate of stiffness degradation is accelerated after peak strength attenuation.

Fire Resistance of Concrete Filled Square Steel Tube Columns Subjected to Eccentric Axial Load

정경수,박수희,최성모 한국강구조학회 2009 International Journal of Steel Structures Vol.9 No.1

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 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.

축부하가 요추부 자기공명영상에서 미치는 영향 -신경학적 파행 유무에 따른 효과 비교-

이진영,이정길,오범석,이효범,구본재 대한척추외과학회 2012 대한척추외과학회지 Vol.19 No.4

Study Design: This study intended to find out differences of effects by axial loading in MRI examination in a patient group with neurologic claudication and a group without neurologic claudication Objectives: It was intended to understand in which group the effects of axial loading can be expected when taking MRI on the lumbar spine. Summary of Literature Review: The study of Willen and Danielson found spinal canal stenosis, which cannot be found by existing methods comparing an MRI taken in bended posture of lumbar without axial loading implementation by MRI taken with axial loading implementation. Hiwatashi et al. also reported that there was a change of treatment direction by laminectomy after axial loading in patients who were intended to take a conservational treatment before the axial loading. Materials and Methods: A total of 39 patients and 54 intervertebral discs were compared. The distances from a sagittal plane before and after intervertebral discs were compared by measuring a sectional area of dura mater in a horizontal plane image and two groups were compared by existence of patients’ neurologic claudication. Results: The AP diameter before and after a intervertebral discs increased into 41.98 mm from 41.1 mm on the average and the sectional area of dura mater showed 137.47mm2 before loading and 119.86mm2 after loading on the average. There was not a significant difference in the distances before and after axial loading implementation, but a significant difference was found in the sectional area of dura mater. Conclusion: Axial loading would contribute to diagnose spinal disease, and especially, spinal canal stenosis in a patient group with claudication. 연구 계획: 신경학적 파행이 있는 환자 군과 없는 환자 군에서 자기공명영상 촬영 시 축부하에 의한 효과의 차이를 알아보고자 하였다. 목적: 요추부 자기 공명 영상을 시행할 때, 어떠한 군에서 축부하에 의한 효과를 기대할 수 있는지 알아보고자 하였다. 선행 문헌의 요약: Willen과 Danielson의 연구에서는 축부하를 시행하지 않은 요추부의 굴곡된 자세에서 시행한 자기공명 영상과 축부하 후 시행한 자기공명 영상을 비교하여 기존의 검사방법으로 찾을 수 없었던 척추관 협착증을 발견할 수 있었고 Hiwatashi등은 축부하 이전에는 보존적 치료를 하려 했던 환자에서 축부하 후 척추궁 절제술로 치료 방향의 변화가 있었다는 발표도 있었다. 대상 및 방법: 39 명의 환자, 54개의 추간판이 비교대상이 되었다. 시상면에서 추간판의 전 후 거리를, 수평면 영상에서 경막의 단면적을 측정하여 비교하였고, 환자의 신경학정 파행 유무에 따라 두 군을 비교하였다. 결과: 추간판 전후 거리는 평균 41.1mm, 에서 41.98mm로 증가, 척추관 협착은 경막의 단면적이 부하 전 평균 137.47mm2, 부하 후 평균 119.86mm2로 차이를 보였다. 신경학적 파행 유무에 따라 두 군을 비교하였을 때 두군간의 추간판 전후 거리에서는 유의한 차이를 보이지 않았으며, 경막의 단면적부분에서는 유의한 차이를 확인할 수 있었다. 결론: 축부하는 척추 질환의 진단에 도움이 될 것으로 생각되며, 특히 파행이 있는 환자 군에서 척추관 협착증의 진단에 도움을 줄 것으로 생각된다.

Ultimate Strength of Orthogonal Stiffened Plates Subjected to Axial and Lateral Loads

M. Suneel Kumar,C. Lavana Kumar,P. Alagusundaramoorthy,R. Sundaravadivelu 대한토목학회 2010 KSCE Journal of Civil Engineering Vol.14 No.2

Orthogonal stiffened plates present in the ship deck are subjected to axial compression due to hogging and sagging bending moments and, lateral load due to cargo load. The main objective of this investigation is to determine the ultimate load carrying capacity and study the interactive behaviour of orthogonal stiffened plates under axial and lateral loads. Tests were conducted on six stiffened plates with plate slenderness ratios of 80 and 64, and corresponding column slenderness ratios of 24 and 26. Hydraulic jacks and inflatable air balloon with load control mechanism were fabricated to apply axial and lateral loads on the test specimens respectively. All the specimens were tested up to ultimate load and the mode of failure was determined based on the initial yielding observed in the plate and/or stiffener. Nonlinear finite element analysis of test specimens was performed using the general purpose FE software ANSYS®. Both material and geometric nonlinearities were considered in the FE analysis of test specimens. The ultimate loads obtained from the finite element analysis were compared with experimental data and found to be satisfactory. It was also observed that the mode of failure obtained from finite element analysis is similar as observed from experiments. It was concluded that the increase in lateral load beyond two thirds of ultimate lateral load significantly reduces the axial ultimate load carrying capacity of stiffened panels. The interactive effect of stiffened plates subjected to combined action of axial and lateral loads is determined as nonlinear.

브레이크용 모터의 축 방향 하중에 따른 기계적 손실을 고려한 특성 분석

원태준(Tae-Juu Weon),정재식(Jae-Sik Jung),박현진(Hyun-Jin Park),홍정표(Jung-Pyo Hong) 한국자동차공학회 2018 한국자동차공학회 부문종합 학술대회 Vol.2018 No.6

This paper presents characteristic analysis of surface permanent magnet synchronous motor(SPMSM) considering mechanical loss according to rotor axial load by oil pressure in brake system. If rotor is forced in axial direction, mechanical loss increases. Mechanical loss is one of major components which affect on efficiency. To consider mechanical loss, no load loss is measured at axial load condition. Mechanical loss is calculated by subtracting core loss from no load loss. Mechanical loss is increased as rotor axis is forced and rotates more quickly. Motor characteristic comparison between model with axial load and model without axial load is done. In case of model with axial load, motor performance decreases compared to model without axial load. In conclusion, Mechanical loss by axial load reduces torque and efficiency in high speed region.

Vibration of Simplified Prestressed Pavement Model Under Moving Two-Axle Harmonic Loads

김성민,정원석 대한토목학회 2009 KSCE Journal of Civil Engineering Vol.13 No.6

The dynamic displacement response of a simplified prestressed concrete pavement model has been investigated comprehensively when the system is subjected to two-axle moving loads of harmonic amplitude variations. The axially loaded beam resting on a Winkler-type elastic foundation was employed as a simplified prestressed pavement model. The distributed loads with a constant advance velocity and damping of a linear hysteretic nature for the foundation were considered. Formulations were developed in the transformed field domains of time and moving space, and the steady-state responses to moving harmonic loads were obtained using a Fourier transform. Analyses were performed to investigate the effects of various parameters, such as the load distance, load phase, axial compression, damping, load velocity, and load frequency, on the displacement amplitude distribution and maximum displacement. The analysis results showed that the displacement responses were much affected by the load distance and load phase between two moving loads. However, the critical (resonance) values of the axial compression and load velocity were not affected by the load distance and phase. The first critical frequency was independent of those parameters, but the second critical frequency was dependent on them. The dynamic displacement response of a simplified prestressed concrete pavement model has been investigated comprehensively when the system is subjected to two-axle moving loads of harmonic amplitude variations. The axially loaded beam resting on a Winkler-type elastic foundation was employed as a simplified prestressed pavement model. The distributed loads with a constant advance velocity and damping of a linear hysteretic nature for the foundation were considered. Formulations were developed in the transformed field domains of time and moving space, and the steady-state responses to moving harmonic loads were obtained using a Fourier transform. Analyses were performed to investigate the effects of various parameters, such as the load distance, load phase, axial compression, damping, load velocity, and load frequency, on the displacement amplitude distribution and maximum displacement. The analysis results showed that the displacement responses were much affected by the load distance and load phase between two moving loads. However, the critical (resonance) values of the axial compression and load velocity were not affected by the load distance and phase. The first critical frequency was independent of those parameters, but the second critical frequency was dependent on them.

비선형 동적해석을 이용한 축하중과 폭발하중을 동시에 받는 철근콘크리트 부재의 구조 거동 분석

이승훈,김한수 한국전산구조공학회 2022 한국전산구조공학회논문집 Vol.35 No.3

In this study, the structural behavior of reinforced concrete members under simultaneous axial and blast loads was analyzed. Nonlineardynamic analysis verification was performed using the experimental data of panels under fundamental blast load as well as those of reinforcedconcrete columns subjected to axial and blast loads. Because Autodyn is a program designed only for dynamic analysis, an analysis process isdevised to simulate the initial stress state of members under static loads, such as axial loads. A total of 80 nonlinear dynamic finite elementanalysis procedures were conducted by selecting parameters corresponding to axial load ratios and scaled distances ranging 0%-70% and1.1-2.0 (depending on the equivalent of TNT), respectively. The structural behavior was compared and analyzed with the correspondingdegree of damage and maximum lateral displacement through the changes in axial load ratio and scaled distance. The results show that themaximum lateral displacement decreases due to the increase in column stiffness under axial loads. In view of the foregoing, the formulatedanalysis process is anticipated to be used in developing blast-resistant design models where structural behavior can be classified into threeareas considering axial load ratios of 10%-30%, 30%-50%, and more than 50%. 본 논문에서는 축하중과 폭발하중을 동시에 받는 철근콘크리트 부재의 구조 거동을 분석하였다. 기본적인 폭발하중을 받는 패널실험 데이터, 축하중과 폭발하중을 받는 철근콘크리트 기둥 실험데이터를 이용하여 비선형 동적해석 모델링을 검증하였다. 축하중의적용에 있어서 Autodyn은 동적해석만을 위한 프로그램이기 때문에 축하중과 같은 정적 하중에 대한 초기 응력 상태를 모사하는 해석절차를 제시하였다. 축하중비 0%~70% 구간과 TNT 등가량에 의존한 환산거리 1.1~2.0에 해당하는 매개변수를 선정하여 총 80개의비선형 동적 유한요소해석을 진행하였다. 축하중비와 환산거리의 변화를 통해 손상정도와 최대 변위 및 회전각으로 구조 거동을 비교 분석한 결과로 원거리 폭발하중에서 축하중을 받는 기둥의 강성 증가로 최대 변위가 감소한다. 결과적으로 축하중비 10%~30%,30%~50%, 50% 이상의 영역 3가지로 구조적 거동 분류가 가능함에 따라 내폭 설계 모델 개발에 활용될 수 있을 것으로 보인다.

Structural performance of novel SCARC column under axial and eccentric loads

Chunheng Zhou,Zongping Chen,Junhua Li,Liping Cai,Zhenhua Huang 국제구조공학회 2020 Steel and Composite Structures, An International J Vol.37 No.5

A novel spiral confined angle-steel reinforced concrete (SCARC) column was developed in this study. A total of 16 specimens were prepared and tested (eight of them were tested under axial loading, the other eight were tested under eccentric loading). The failure processes and load-displacement relationships of specimens under axial and eccentric loads were examined, respectively. The load-carrying capacity and ductility were evaluated by parametric analysis. A calculation approach was developed to predict the axial and eccentric load-carrying capacity of these novel columns. Results showed that the spiral reinforcement provided enough confinement in SCARC columns under axial and low eccentric loads, but was not effective in that under high eccentric loads. The axial load-carrying capacity and ductility of SCARC columns were improved significantly due to the satisfactory confinement from spirals. The outer reinforcement and other construction measures were necessary for SCARC columns to prevent premature spalling of the concrete cover. The proposed calculation approach provided a reliable prediction of the load-carrying capacity of SCARC columns.

기둥 軸力의 變化에 따른 鐵筋콘크리트造 外部 보-기둥 接合部의 剪斷强度에 관한 實驗的 硏究

이철주,이상호 부산대학교 도시문제연구소 2000 都市硏究報 Vol.9 No.-

The purpose of this study is to experimentally investigate the shear strength of reinforced concrete exterior beam-column joints with varying of axial column load. Reinforced concrete exterior beam-column joints are able to be weaken when axial column load has been changed to tensile load by seismic load. In order to investigate the effect of axial column load for joint shear strength, we have tested three reinforced concrete exterior beam-column joint specimens in relation to varying axial column load(axial column load ratio : 0.1,0.0,-0.1). The test under the displacement control(cyclic loading) on the beam member and the load control on column member simultaneously was performed. The experimental results show that the maximum joint shear strength and joint shear crack angle of specimen are affected by axial-column load.

An equivalent stress parameter for multi-axial fatigue evaluation of welded components including non-proportional loading effects

Mei, J.,Dong, P. IPC Science and Technology Press ; Elsevier Scienc 2017 International journal of fatigue Vol.101 No.2

This paper presents a comprehensive investigation into non-proportional multi-axial fatigue of welded components by introducing an equivalent structural stress parameter that takes into account of load-path non-proportionality in addition to plate thickness and stress state effects. This is accomplished by formulating a ''moment of load path'' or ''MLP'' based fatigue damage parameter that provides a consistent treatment of load-path non-proportionality under arbitrary multi-axial loading conditions for which cycle counting can be consistently performed by means of a previously developed path-dependent maximum range (PDMR) cycle counting procedure. To examine its broad applicability and effectiveness, non-proportional multi-axial test data obtained using different components, joint types, and loading conditions from various sources are analyzed using the newly developed equivalent stress parameter. The results show that the new equivalent stress parameter enables not only an effective consolidation of all multi-axial test data (up to about 300 tests) analyzed in this paper into a narrow band, but also the demonstrated transferability between the master S-N curve (dominated by test data under uniaxial cyclic loading conditions) adopted by the 2007 ASME Div 2 and API 579 RP/ASME FFS-1 Codes and the consolidated S-N curve dominated by severe non-proportional multi-axial cyclic loading conditions. As a result of the present development, a unified fatigue evaluation procedure based on the newly proposed effective stress parameter and a single master S-N curve can be implemented for arbitrary cyclic loading conditions regardless of stress multi-axiality or load path proportionality.