EFFECT OF STRAIN-STRESS RELATIONSHIP OF STEEL TUBE ON THE INITIAL STIFFNESS OF SQUARE CFT COLUMNS

2017 ◽  
Vol 4 (1) ◽  
Author(s):  
Ryo Handa ◽  
Masae Kido ◽  
Mao Liu ◽  
Keigo Tsuda
Keyword(s):  
Yield Strength ◽  
Cross Section ◽  
Bending Moment ◽  
Steel Tube ◽  
Force Characteristic ◽  
Initial Stiffness ◽  
Short Term ◽  
Restoring Force ◽  
Strain Stress ◽  
Cft Column

The restoring force characteristic of a concrete filled steel tubular (CFT) column is modeled with three straight lines which show the relation of M-R. The initial stiffness is calculated by assuming that the steel and concrete portions are fully effective and materials are elastic. The first break point is the yield bending moment of the CFT column. The yield bending moment is defined by the bending moment when a part of the cross-section yield or the allowable strength for short-term loading obtained by the superposed strength method. It is supposed that the theoretical initial stiffness obtained by assuming that the whole cross section is effective is different from the real one. This study aims to clarify effects of strain-stress relation on the yield strength and allowable strength for short-term loading and the initial stiffness. Three types of stress-strain relations for steel are used, elastic-perfectly plastic model, Menegotto-Pinto's model and Morino's model. According to the analytical results, the difference between allowable strength and yield strength becomes larger as the axial load ratio, indexes Rh and k which are used in Menegotto-Pinto's model and Morino's model increase.

EVALUATION METHOD FOR ALLOWABLE SHORT-TERM FLEXURAL STRENGTH AND YIELD STRENGTH OF CONCRETE-FILLED STEEL TUBULAR BEAM-COLUMNS

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Takashi Fujinaga ◽  
Tomoya Kawabata
Keyword(s):  
Flexural Strength ◽  
Yield Strength ◽  
Evaluation Method ◽  
Steel Tube ◽  
Superposition Method ◽  
Short Term ◽  
Restoring Force ◽  
Beam Columns ◽  
Slope Factor ◽  
The Moment

According to the Recommendations for Design and Construction of Concrete Filled Steel Tubular Structures from Architectural Institute of Japan, the allowable short-term flexural strength (ASFS) can be used as the yield strength for the restoring force characteristics model of concrete-filled steel tube (CFST) members. Therefore, it is necessary to examine whether the ASFS can be appropriate as an alternative for the yield strength. Furthermore, as the ASFS is typically calculated using the superposition method, the value of the deformation at the superposed strength cannot be evaluated. To address these issues, in this study, numerical analysis was conducted on the moment-curvature relation of CFST column sections using the finite fiber method. The characteristics of the point of ASFS and evaluation method for flexural yield strength in a broad sense were examined using the slope factor and strength satisfaction factor methods. The corresponding slope factor is larger than the value (1/3) that is generally used for the yield strength definition. Therefore, using the ASFS is as the yield strength of the CFST section is reasonable. Additionally, the formula for the curvature at the ASFS was also proposed.

STRESS STATE OF STEEL TUBE OF SQUARE CFT COLUMNS WHICH REACHED SHORT-TERM ALLOWABLE STRENGTH

2019 ◽  
Vol 6 (1) ◽  
Author(s):  
Mao Liu ◽  
Ryo Handa ◽  
Masae Kido ◽  
Keigo Tsuda
Keyword(s):  
Stress State ◽  
Yield Strength ◽  
Axial Force ◽  
Compressive Force ◽  
Steel Tube ◽  
Effective Length ◽  
Short Term ◽  
Damage State ◽  
Short Columns ◽  
Cft Column

The allowable strength was compared with the yield strength of CFT short columns subjected to constant axial force and horizontal force in previous studies. The yield strength of CFT columns is determined by 2/3 of compressive force of concrete in most cases. And the yield strength of CFT columns is smaller than the allowable strength. However, as an important index representing the damage state of CFT column, the stress state of steel tube when the CFT column reaches the short-term allowable strength is not clarified. The objective of this study is to make clear whether the steel tube yielded when the short-term allowable strength of square CFT column is reached by an analytical method. The analytical parameters are the effective length to depth ratio, axial force ratio and width to thickness ratio. The range of parameters in the cases which the steel tubes yield before the CFT columns reaches the allowable strength are shown and the decrease of stiffness in these cases are discussed.

Influence of Yield Strength Variability over Cross-Section to Steel Beam Load-Carrying Capacity

2005 ◽  
Vol 10 (2) ◽  
pp. 151-160 ◽  
Author(s):  
J. Kala ◽  
Z. Kala
Keyword(s):  
Yield Strength ◽  
Cross Section ◽  
Carrying Capacity ◽  
Bending Moment ◽  
Statistical Characteristics ◽  
Load Carrying Capacity ◽  
Load Carrying ◽  
Strength Variability ◽  
Hot Rolled ◽  
Hot Rolled Steel

Authors of article analysed influence of variability of yield strength over cross-section of hot rolled steel member to its load-carrying capacity. In calculation models, the yield strength is usually taken as constant. But yield strength of a steel hot-rolled beam is generally a random quantity. Not only the whole beam but also its parts have slightly different material characteristics. According to the results of more accurate measurements, the statistical characteristics of the material taken from various cross-section points (e.g. from a web and a flange) are, however, more or less different. This variation is described by one dimensional random field. The load-carrying capacity of the beam IPE300 under bending moment at its ends with the lateral buckling influence included is analysed, nondimensional slenderness according to EC3 is λ¯ = 0.6. For this relatively low slender beam the influence of the yield strength on the load-carrying capacity is large. Also the influence of all the other imperfections as accurately as possible, the load-carrying capacity was determined by geometrically and materially nonlinear solution of very accurate FEM model by the ANSYS programme.

Experimental Study on the Influence of Boundary Condition on the Behavioral Characteristics of CFT Square Columns under Constant Axial Load upon a Fire

2011 ◽  
Vol 82 ◽  
pp. 521-526 ◽  
Author(s):  
Heung Youl Kim ◽  
Kyung Hoon Park ◽  
Ki Hyuk Kwon
Keyword(s):  
Boundary Condition ◽  
Cross Section ◽  
Fire Resistance ◽  
Axial Load ◽  
Load Ratio ◽  
Steel Tube ◽  
Section Size ◽  
Cft Column ◽  
Major Factors ◽  
Resistance Performance

The temperature of the steel tube of a CFT column rises rapidly upon a fire causing the deterioration of its strength, while the concrete inside of the tube having large heat capacity provides fire-resistance performance. In order to employ CFT columns as fire-resistant structure, it is necessary to conduct studies on the factors exerting influence on structural capacities and the influence associated with each condition. Concrete’s compressive strength, cross-section size, axial load ratio and boundary condition are the major factors which are influential in fire-resistance performance. In particular, boundary condition between columns and beams is one of the major factors which decide fire-resistance performance because it exerts influence on load carrying capacity. The result of the test conducted in this study showed that fire-resistance time of 106 minutes was secured in the specimens with clamped ends and that of 89 minutes in those with pinned ends when cross-section size was 360mm by 360mm. In the specimens with cross-section size of 280 mm × 280mm, fire-resistance time of 113 minutes was secured under the condition of clamped ends and that of 78 minutes was secured under the condition of pinned ends.

scholarly journals Axial behaviour of concrete filled steel tube stub columns: a review

2018 ◽  
Author(s):  
Soner Güler ◽  
Fuat Korkut ◽  
Namik Yaltay ◽  
Demet Yavuz
Keyword(s):  
Cross Section ◽  
Axial Load ◽  
Load Capacity ◽  
Local Buckling ◽  
Bending Moment ◽  
Steel Tube ◽  
High Rise ◽  
Axial Load Capacity ◽  
The Cross ◽  
Cfst Columns

Concrete-filled steel tubular (CFST) columns are widely used in construction of high-rise buildings and peers of bridges to increase the lateral stiffness of the buildings, the axial load capacity, ductility, toughness, and resistance of corrosion of the columns. The CFST columns have much superior characteristics compared with traditionally reinforced concrete columns. The position of the concrete and steel tube in the cross-section of the CFST column is the most appropriate solution in terms of the strength and ductility. The steel tube, which is placed outside of the cross-section of the column, withstand the bending moment effectively. The concrete that is placed into the steel tube delay the local buckling of the steel tube and increase the axial load capacity of the column due to continually lateral confining. This paper presents a review on experimental results of the axial behavior of CFST columns performed by various researchers.

scholarly journals Flexural Behavior of Innovative Posttensioned Composite Beams with Corrugated Steel Webs

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Xiang Li ◽  
Tao Yang ◽  
Yongbing Zhang ◽  
Yun Zhang ◽  
Taosheng Shen
Keyword(s):  
Yield Strength ◽  
Bending Moment ◽  
Composite Beams ◽  
Considerable Effect ◽  
Steel Tube ◽  
Numerical Results ◽  
Flexural Behavior ◽  
Steel Tubes ◽  
Depth Ratio ◽  
Ultimate Load Carrying Capacity

Steel-concrete composite beams with corrugated steel webs (CSWs) usually have concrete flanges that are prone to crack under tension, and an innovative posttensioned composite beam (IPCB) with CSWs has been proposed previously to overcome this shortcoming. Here, an IPCB with CSWs is manufactured and submitted to a flexural test to investigate its flexural behavior, based on which finite element (FE) models with different parameters are developed and analyzed using the ANSYS software. The effects of the span-to-depth ratio, concrete compressive strength, initial effective prestress, width of the upper concrete flange, and yield strength of the steel tubes on the flexural behavior of the IPCBs with CSWs are discussed. Numerical results show that the span-to-depth ratio of the beam and the yield strength of the steel tube have a considerable effect on the ultimate load-carrying capacity of the IPCB, which increases by 48.2% when the depth of the CSWs is increased from 240 to 400 mm and by 21.8% when the yield strength of the steel tubes is increased from 295 to 395 MPa. The plane-section assumption is unsuitable for IPCBs. Almost all the unbonded posttensioning strands in the beams yield for the specimens at ultimate state. The normal stress is distributed unevenly across the width of the upper concrete flange, and the maximum shear lag coefficient is 1.17. Based on the numerical results, a calculation method is established to evaluate the bending moment resistance of an IPCB with CSWs. Comparison shows that the theoretical results in accordance with the proposed method agree well with the numerical results.

FLEXURAL STRENGTH OF SQUARE CFT BEAMCOLUMNS WHEN DAMAGED WITH CONCRETE CRACKS

2018 ◽  
Vol 5 (2) ◽  
Author(s):  
Daijiro Fujioka ◽  
Masae Kido ◽  
Mao Liu ◽  
Hiroki Ikeda
Keyword(s):  
Yield Strength ◽  
Axial Force ◽  
Tensile Strain ◽  
Bending Moment ◽  
Steel Tube ◽  
Lateral Stiffness ◽  
Beam Columns ◽  
Concrete Crack ◽  
Force Ratio ◽  
The Relationship

The lateral stiffness of CFT beam-columns is considered to decrease because of the damage by the concrete crack or yielding of the materials however the relationship between two phenomena is not clear. It is necessary to clarify the strength when the CFT columns damaged by the concrete crack for evaluating the lateral stiffness of CFT beam-columns properly. The purposes of this study are to calculate the flexural crack strength of a square CFT section and to compare them with the yield strength. The analysis is carried out as follows; 1) assuming the stress-strain relationships of materials and the strain and stress distribution of the cross-section, 2) setting the limit of the tensile strain of concrete and 3) calculating the relation between the axial force and the bending moment when the strain of concrete reaches the limit tensile strain. Parameters are width-thickness ratio, the yield strength of a steel tube and compressive strength of concrete. As a result of the analysis, we showed that the axial force ratio is 0.2 ~0.3 when the flexural crack strength and the yield strength are the same. It is concluded that the lateral stiffness decreases because of the crack of concrete-and not from the yielding of materials--when the axial force ratio is smaller than 0.2~0.3.

Sign in / Sign up

Export Citation Format

Share Document