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Convenient Design Loads CheckWe understood that you may have lots of loads to check due to different load cases and load combinations. We don't have any limit on the number of design loads you can input. Besides, you load check results can be sorted in many ways so that you can find what you need with minimal time. When you are running a biaxial bending check, you can view each load's corresponding P-M and Mx-My interaction diagram with only one click.
Concrete Column Interaction Diagram Software
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UltCol computes axial/bending interaction for a circular reinforced concrete column. The nominal moment capacity is computed for various levels of axial force between the compression and tension limits.
UltCol uses a simplified solution for estimating the capacity of a circular reinforced concrete column. Engineering judgment must be used when determining the applicability of this software to a particular situation. The following assumptions have been made:
Press the [Update] button to refresh the analysis results. The results consist of a tabular listing of the nominal moment and axial forces, the capacity reduction factor, and the moment and axial resistance. An interaction diagram is also created.
Vertical members that are part of a building frame are subjected to combined axial loads and bending moments. These forces develop due to external loads, such as dead, live, and wind loads. Simply put, an interaction diagram (or curve) displays the combinations of the acceptable moment and axial capacities of a structural member.
The strength of a column cross-section can be determined from the geometry of the cross-section, the constitutive relationships of the concrete and steel and consideration of equilibrium and strain compatibility. For the calculation of intermediate M-N curve points that describe the strength of section the SkyCiv uses an iterative process. The next steps are involved in this process as per ACI code:
For the design of a column to be considered adequate (safe), the combination of action effects (M, P) must be less than the combination of design strengths (M, P) from the interaction curve. This means that if the position of the M,P point on the plot is outside of the curve it is deemed as not meeting this criterion and considered unsafe.
In SkyCiv RC Design Module, SkyCiv uses both the major and minor axis to calculate the balance point. The module defines the point of intersection with a 3D interaction diagram (green point in the below picture). The coordinates of this point provides the axial and flexure capacities for the section.
SkyCiv offers a fully featured Reinforced Concrete Design software that allows you to check concrete beam and concrete column designs as per ACI 318, AS 3600, and EN2 Design Standards. The software is easy-to-use and fully cloud-based; requiring no installation or downloading to get started!
The 3D interaction diagram is generated by the software by rotating the cross section multiple times. The 2D interaction diagram is then generated at each new rotation angle. The process is extremely long and cumbersome to be done by hand.
Slender reinforced concrete column may fail in material failure or instability failure. Instability failure is a common problem which cannot be analyzed with first-order analysis. So, second-order analysis is required to analyze instability failure of slender RC column. The main objective of this study was to construct uniaxial interaction diagram for slender reinforced concrete column based on nonlinear finite element analysis (FEA) software. The key parameters which were studied in this study were eccentricity, slenderness ratio, steel ratio, and shape of the column. Concrete damage plasticity (CDP) was utilized in modeling the concrete. Material nonlinearity, geometric nonlinearity, effect of cracking, and tension stiffening effect were included in the modeling. The results reveal that, as slenderness ratio increases, the balanced moment also increases, but the corresponding axial load was decreased. However, increasing the amount of steel reinforcement to the column increases the stability of the column and reduces the effect of slenderness ratio. Also, the capacity of square slender RC column is larger than rectangular slender RC column with equivalent cross section. However, the result is close to each other as slenderness ratio increased. Finally, validation was conducted by taking a benchmark experiment, and it shows that FEA result agrees with the experimental by 85.581%.
Reinforced concrete column is a structural member which is used to carry primarily compression loads. It may be short or slender (long) depending on the slenderness ratio of the column. Short column is a column which can resist axial force and moment which is greater than or equal to axial and moment capacity of column cross section. However, slender column is a column which its section resistance is reduced by second-order deformation (buckling) of the column [1]. In addition, previous works showed that the compressive strength, steel reinforcement, and dimensions of cross sections of columns can directly affect the capacity of the column [2]. Slender column may fail either material failure or instability failure. Instability failure will occur as the effect of slenderness of the column increases. The use of slender reinforced concrete column is increasing to keep the aesthetic of the building and get the sufficient space inside of the building [3]. So, analysis and design of this column is considering the second-order deformation necessary. Mac Gregor also recommends that the column should be designed to carry the axial load and moments that account the effect of second-order deformation [1].
Different country codes set on how to consider the second-order effect in the design of slender reinforced concrete column. For example, Euro code-2 recommends second-order nonlinear analysis and simplified methods such as second-order analysis based on the nominal stiffness method based on estimation of the curvature [4]. Other methods such as the long column reduction factor method and the complementary moment design method also could be used. Except second-order nonlinear analysis, the all other methods use approximate empirical equation to account for the second-order deformation of the column. Although some of empirical equation does not account effect of cracking, the others account effect of cracking at location of maximum moment only cracking of the column reduces the flexural stiffness of the column. Since the crack will not form only at the location of the maximum moment, nonlinear analysis of the slender column which accounts the effect cracking throughout the length is needed.
Slender reinforced concrete column may fail in material failure or instability failure. Instability (buckling) failure is a common problem which cannot be analyzed with first-order analysis. Because geometry, material properties (stress-strain relationship) and large deformations are nonlinear, and hence, nonlinear analysis should be performed to get better result [5, 6]. For acceptable analysis and design of slender reinforced concrete columns, detail investigation of second-order effects for taking into account a total bending moment. A recent research indicates that an approximate method for calculating the second-order moment is not always results the safe side of the design. Relatively, a discrete model which take account the x-sectional nonlinearity, nonlinear behavior of concrete in compression, influence of cracking, and tension stiffening provides fair results [7].
In the design of the slender column using the above listed design method, the tensile strength is ignored, though the member carries small tensile stress due to tension stiffening. So, investigating the behavior of slender reinforced concrete column under nonlinear analysis including effect of cracking and tension stiffening effect is very important. Many researchers did different research studies on this area, such as Kim and Kwak did a nonlinear behavior of slender reinforced concrete column [3]. Cleason and Gylltoft also conducted experimental and FE analysis of the slender concrete column subjected to eccentric loading [8]. Rodrigues et al. worked on failure behavior modeling of the slender reinforced concrete column subjected to eccentric loading [5]. However, none of them study construction of uniaxial interaction diagram for slender reinforced concrete column using nonlinear FE analysis.
In this paper, construction of an interaction diagram for uniaxial slender reinforced concrete column using nonlinear finite element software was studied. So, the effect of cracking throughout the length of column and effect of tension stiffening on the uniaxial interaction diagram is also considered in this study.
The shape of the column has an effect on the capacity of the slender reinforced concrete column. In this study, only square and rectangular reinforced concrete column which have an equivalent area was considered. For the rectangular column, the eccentricity was considered in the minor axis direction so that the column will be uniaxial. The capacity of square reinforced concrete column is larger than rectangular one. However, with increasing slenderness ratio, the effect of the shape diminishes, as illustrated in Figure 8. The effect is the same with the increase in the amount of steel.
The structural frame & truss analysis and design program RSTAB 9 contains a similar range of functions as the FEA software RFEM, paying special attention to frames and trusses. Therefore, it is very easy to use and for many years, it has been the best choice for the structural analysis of beam structures consisting of steel, concrete, timber, aluminum, and other materials.
SE::Column is a computer program for reinforced concrete column design. It computes column interaction diagrams (P-M interaction diagram and Mx-My interaction diagram) based on strain compatibility approach. The program combines power and simplicity perfectly. For common regular column sections, the design has been made even easier. For cases other programs can not handle, this program can take care of them for you with sophisticated algorithm. We think it is the best reinforced concrete column design program.
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