Discussion: Recommendations for nonlinear finite element analyses of reinforced concrete columns under seismic loading up to collapse
Year: 2025
Type: article
Abstract: This is a discussion piece on Dolati SSK, Matamoros A and Ghannoum W (2023)Recommendations for nonlinear finite element analyses of reinforced concrete columns under seismic loading up to collapse. ACI Symposium Paper 358: 230-250, Link to the article of ACI Symposium Paper.While the discusser appreciates the work of Dolati et al. (2023), which helps the engineering community to develop non-linear finite-element (FE) models of reinforced concrete columns using ATENA, there are some points of discussion that are necessary to clarify the work. The work reported by Dolati et al. (2023) is novel and innovative, and clearly required needed dedication, time and effort. However, the discusser has some minor concerns regarding the data collected and used in modelling and some major concerns regarding the results discussed in the paper. This discussion corrects the inaccuracies in the paper and suggests possible solutions for the problems whenever possible. The results are thoroughly discussed, raising some serious questions that need answers to better understand the work. The major points regarding the details of the work and the results are discussed first, and then the minor points are addressed.This article corrects mistakes in the paper by Dolati et al. (2023), which should help engineers better understand the work and model FE models of columns under cyclic loads using ATENA. The results presented are elaborated upon by criticising crucial points, with the aim of helping readers better understand and apply the outcomes of the original paper.When the authors stated that additional information on the columns can be found in the literature, they cited Li and Hwang (2017). The paper by Li and Hwang (2017) is an analytical study on some tests they carried out, which are documented by Li et al. (2014). This is misleading as instead of Li and Hwang (2017), the reference should have been Li et al. (2014). Furthermore, they state that ‘While lateral drift is imparted to the column, axial load for these tests was kept constant (Figure 1)’. In the paper, Figure 1 consists of three distinct undefined figures without any distinct captions. The figure on the left contains numbers 1, 2 and 3, without any definition.Dolati et al. (2023) present data related to the examined columns in Table 1. However, a large portion of the numbers are reported incorrectly if they are compared with the properties of the specimens tested in the original papers. These errors are not from unit conversions as the real numbers in the original papers differ from those reported by Dolati et al. (2023).For instance, the tie spacings of specimens 3CLH18, 3CMH18, SC-2.4-0.2, SC-2.4-0.5, Specimen#1 and Specimen#2 are reported by Dolati et al. (2023) to be 457.2, 457.2, 124.9, 124.9, 457.2 and 203.2 mm, respectively. In the original papers, the spacings for these specimens are reported to be 457, 457, 125, 125, 457 and 203 mm, respectively. Also, the column dimensions of SC-2.4-0.2 and SC-2.4-0.5 in the discussed paper are stated to be 350.5 mm × 350.5 mm, while the dimensions in the original paper (Tran, 2010) are 350 mm × 350 mm. Additionally, Dolati et al. (2023) reported the longitudinal reinforcement ratio of SC-2.4-0.2 to be 0.021, while it is 0.0205 when calculated based on the data given by Tran (2010).Moreover, the clear height of columns 1NL, 2NL and 2NH is reported as 497.8, 1001 and 1001 mm, respectively, in the discussed paper. However, Li et al. (2014) reported the clear height of the same columns to be 500, 1000 and 1000 mm, respectively. It is not obvious why 19.7 inches in the column dimensions of 2NL and 2NH was converted to 500 mm while the same 19.7 inches for the clear height of specimen 1NL was converted to 497.8 mm in the same table. The same applies for the conversion of the dimensions of columns 3CLH18, 3CMH18, Specimen#1 and Specimen#2, in which 18 inches is converted to 457 mm while for the tie spacings of 3CLH18, 3CMH18 and Specimen#1, the same 18 inches is converted to 457.2 mm in the same table.The authors claim that they used the equations of ACI 318-19 (ACI, 2019) to calculate the modulus of elasticity (MoE) of the concrete. However, they only used the imperial system equation then converted it to SI units. Because when the SI equation is used to check the data in Table 2, it yields different numbers than those presented. Despite that, the reported numbers also have inconsistencies. For example, in the discussed paper, the MoE of specimens 3CLH18, SC-2.4-0.2 and SC-2.4-0.5 is reported to be 3559, 3262 and 3376 ksi, respectively. However, the calculated MoE for these same specimens based on the compressive strength of the concrete and the equation provided in the discussed paper is 3122, 3224 and 3372 ksi, respectively. Therefore, the difference between the calculated MoE and the reported values of the MoE is in the range 4–437 ksi.In reporting the material properties of the columns, Table 2 in the discussed paper also shows some discrepancies between the reported data and the data in the original works. For instance, the concrete compressive strengths of specimens 3CLH18, SC-2.4-0.5 and Specimen#1 are reported to be 3.9 ksi, 24.1 MPa and 19.9 MPa respectively – in the original papers they are 3.71 ksi (Lynn et al., 1996), 24.2 MPa and 20 MPa respectively. Additionally, the longitudinal bar diameter of SC-2.4-0.2 is reported as 19.9 mm while the original paper states 20 mm. The tensile strength of longitudinal bars of the same specimen is reported as 606 MPa while it is 606.6 MPa in the original paper. Moreover, the yielding and tensile strengths of the ties for the same specimen are reported as 392 MPa and 580 MPa, respectively, while they are stated as 392.6 MPa and 579.7 MPa in the original papers.The loading is presented in Table 3 in the discussed paper. However, there are substantial differences between the numbers reported by Dolati et al. (2023) and the numbers in the original papers. For example, the maximum load ratios (P/(f′cAg)) of columns 3CLH18, 3CMH18, Specimen#1 and Specimen#2 are reported to be 0.08, 0.26, 0.36 and 0.37, respectively – in the original papers they are 0.12, 0.35, 0.37 and 0.38, respectively. Therefore, the question is: Were the ratios reported in Table 3 or the actual values used for applying axial loads in the modelling?Regarding the maximum applied lateral load (Vpeak), the reported numbers in Table 3 are also incorrect when compared with the original papers. For instance, the values of Vpeak for specimens 3CLH18, 3CMH18, SC-2.4-0.2, SC-2.4-0.5, Specimen#1, Specimen#2, 1NL, 2NL and 2NH are reported to be 62.6 kips, 73.7 kips, 218.7 kN, 237.2 kN, 566.2 kN, 521.6 kN, 600.1 kN, 408 kN and 457.1 kN respectively. In the original papers, the values are stated to be 61 kips, 76 kips, 218.9 kN, 237.6 kN, 565 kN, 520 kN, 660 kN, 402 kN and 460 kN. Therefore, the question is: Were the loads stated in Table 3 used in calculating errors or the actual lateral loads?Additionally, the entire column labelled “Peak shear stress” in Table 3 of the discussed paper yields incorrect numbers if the equation provided in the column heading is used. All the numbers in that column are at least multiplied by ten if the provided equation is used. For example, the peak shear stress of specimen 3CLH18 is 0.33 if the SI unit properties are used in the equation, while using the same equation and material properties in imperial units yields a value of approximately 0.13. In both cases, the result is far from the value of 3.1 reported in Table 3. This is true for all the other specimens. Furthermore, in the same table, the displacement at initiation of axial degradation for specimens 2NL and 2NH is reported as 2.27 inches and 1.16 inches and 67.6 mm and 40.6 mm, respectively. If the displacements in inches are converted to millimetres, the values should be 57.66 and 29.46 mm. respectively. The source of all these inaccuracies is not clear.Regarding the results presented by Dolati et al. (2023), there are several points to be discussed.In the first paragraph, the authors state that many buildings in the USA are at risk of exhibiting low seismic behaviour, citing Inel et al. (2008). However, the cited document is on re-evaluation of buildings in Turkey. For the same statement, Dolati et al. (2023) also cite Galvis et al. (2017), who actually studied buildings in Mexico City, Mexico. Next, they cite Tran (2010) for reasoning that those buildings in the USA were designed not following modern building codes; however, Tran (2010) emphasise that buildings in Singapore lack sufficient confinement. Moreover, in the same section, Ghannoum and Sivaramakrishnan (2012) is cited for a database on rectangular columns; however, based on the bibliography provided in the discussed paper, there are more than two authors for that database, so the citation should be written as Ghannoum et al. (2012). The authors claim that a database of 689 concrete column tests was developed by Suselo (2021); however, the database was actually developed by Ghannoum and Sivaramakrishnan (2012) as the work of Suselo (2021) is a PhD dissertation. Additionally, the sentence ‘Out of a database of 689 concrete columns tests developed by Suselo (2021) and Ghannoum and Sivaramakrishnan (2012), the effect of different lateral loading protocols, such as monotonic pushover and fully reversed cyclic loading protocols, with varying the number of cycles, were explored on only eight experimental tests, despite evidence that axial and lateral load histories can influence significantly the seismic behaviour of non-ductile concrete columns (Nakamura and Yoshimura, 2002)’ lacks clarity as it is not obvious who conducted the eight experimental tests. Are the authors referring to Suselo (2021) or Nakamura and Yoshimura (2002)?In the second paragraph, the authors introduce FEA without definition, although the abstract reveals that FE refers to finite elements. In this paragraph, the authors cite two papers that are not directly relevant to the work (Khedmatgozar Dolati et al., 2021, 2022) – the former is on the application of rubber bearing pads for bridges and the latter is on the application of VD-LRBP system for bridges.In the third paragraph, the authors state that the modelled columns, including the columns studied by Tran (2010), were full-scale columns. However, Tran (2010) state that they tested ten half scale columns. Additionally, the sentence ‘Also, the comparison of shear capacity derived from the FE models and estimated by standards are compared (ASCE/SEI 41-17, ACI 369.1-17 (American Concrete Institute (ACI) Committee 369 2017))’ lacks clarity. Is the comparison compared? Or the shear capacity from the FE models and the estimated shear capacities from the standards? Also, why are the standards cited at the end of the sentence? Is this statement mentioned in those standards or were these standards used to estimate the shear capacity?The authors state that ‘numerous studies have looked at’ – the word choice of ‘looked at’ is informal and, when used, it means the study examined, analysed or reviewed an existing study, result or data. Also, the sentence ‘that not only depends on columns material and geometric properties but also on loading history’ should have been ‘that depends on not only columns material and geometric properties but also on loading history’. Additionally, the authors cite Haselton and Pacific Earthquake Engineering Research Center (2008), but this is a report by Haselton et al. (2007). Moreover, they also cite Rajae et al. (2022), which is on the inspection of bridges using digital image correlation (DIC) systems and it is not directly related to the topic of the paper. Moreover, the authors cite Hagen (2012) to justify that columns that tend to yield in flexure prior to failure generally have larger deformation before shear degradation. However, the work of Hagen (2012) is concerned with shear walls not columns.
Author: Wrya Abdullah
Institution: University of Sulaimani
Language: English
Subfield: Building and Construction
Field: Engineering
Domain: Physical Sciences
Open Access status: bronze
OpenAlex ID: W4415956626