A Comparative Study of Seismic Performance Evaluation of Reinforced Concrete Frame Structures Using Chinese and African Seismic Codes

Suliman, Musaab; Lu, Liang

doi:https://doi.org/10.1155/2024/5588833

Advances in Civil Engineering

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Abstract Introduction Discussion Conclusions Data Availability Conflicts of Interest Acknowledgments References Copyright Related Articles

Research Article | Open Access

Volume 2024 | Article ID 5588833 | https://doi.org/10.1155/2024/5588833

A Comparative Study of Seismic Performance Evaluation of Reinforced Concrete Frame Structures Using Chinese and African Seismic Codes

Musaab Suliman¹and Liang Lu¹

Academic Editor: Chunfeng Wan

Received04 Dec 2023

Revised16 Jan 2024

Accepted09 Feb 2024

Published22 Feb 2024

Abstract

The evaluation of various earthquake codes, it is one of the significant challenges in the study area of earthquake engineering. However, according to the literature review, most research works have not addressed comparing Chinese and African seismic codes. Therefore, the purpose of this study is to identify each code’s advantages by comparing assessment of the seismic efficacy of moment resistance frame reinforced concrete (MRF-RC) frames using four different codes: the Ethiopian Building Code Standard (EBCS-8), the Egyptian Code for Design and Construction of Reinforced Concrete Structures (ECP-201), the Algerian Seismic Regulations (RPA-99), and the Chinese Code for Seismic Design of Buildings (GB-50011), the first three are the major codes used in Africa. The seismic provisions of these codes are compared and evaluated using nonlinear time-history analysis (NL-THA) and nonlinear static pushover to validate the results. These analyses are performed on four MRF-RC frame models with different heights. The results include various parameters that reflect the seismic performance of the structures. The study revealed that the Chinese code is more conservative and overestimates seismic performance compared with African codes. However, the Chinese code can be applied in African projects considering the African soil classifications, and seismic weight are adjusted to meet the African design criteria.

1. Introduction

With the promotion of the “One Belt and Road Initiatives” proposal, Chinese engineering firms are more involved in international projects. This means that domestic designers have to understand international design standards. A key area of focus is the earthquake resistance requirements, which are essential for structure configuration. Therefore, this area is getting more attention [1]. Due to its high seismic activity, China has updated its seismic code GB-50011-2010 [2] several times since 1959 to ensure safety and resilience [3].

Africa has moderate seismic activity compared to other parts of the world [4]. However, some areas are more prone to earthquakes than others, while others are almost free. The northern part of Africa, especially Egypt and Algeria, has experienced several strong earthquakes. The most powerful was a 7.3 local magnitude quake that hit El Asnam in Algeria’s Tell Atlas in 1980. Before the 1990s [5], some minor earthquakes were reported in northern Egypt with local magnitude of 5 or less [6, 7]. Recently, a 4.4 body wave magnitude quake was also felt in the Hawassa region of Ethiopia. This earthquake happened in 2016 [8], and many adjacent cities and towns felt the tremors [9].

Egypt published its first seismic code (ECP-1989) in 1989 [10]. It was revised in 1993 (ECP-1993) and 2003 (ECP-2003) to address the shortcomings of the previous versions [11]. The ECP-2003 seismic code considers the building’s response spectra and soil modulus seismic regions [10, 12]. Algeria established its first seismic regulation (RPA-81) in 1980. It was revised several times, most recently to RPA-99/Version 2003 [13] after the 2003 Zemori earthquake [14]. Ethiopia modified its code (ESCP1–83) in 1983 and revised it to EBCS 8 : 1995 [15] based on recent earthquake records. A council to revise the code was established in 2013 [16].

The earthquake response of reinforced concrete (RC) structures planned by modern regulations has been studied by various researchers, focusing on American and European structures. A numerical analysis of a 4-story RC structure according to the International Building Code 2003 was conducted by Kueht and Hueste [17]. The European standard was used by Panagiotakos and Fardis [18] to evaluate the behavior of RC buildings. Ile and Reynouard [19] proposed a constitutive model with fixed orthogonal cracks and the smear crack method to evaluate the periodic behavior of RC structures. Studies [20, 21] examined the earthquake behavior of typical RC frames designed according to the Chinese standard (GB-50011-2010) [2]. Young et al. [22] compared the seismic behavior of RC structures designed based on GB-50011 and European standards.

This research aimed to compare the seismic codes for concrete frame structures in China and Africa, considering the increasing influence of Chinese construction companies in Africa. These companies have funded and built many tall buildings in Africa, such as the Iconic Tower in Egypt, which is 385 m high [23, 24]. These projects may use the Chinese building standards, which have been developed based on their previous construction experience [25]. Therefore, this study aims to identify code differences by comparing the assessment of the seismic efficacy of moment resistance frame reinforced concrete (MRF-RC) using Chinese and African codes. The study aims to fill the research gap in the literature on comparing and evaluating Chinese and African seismic codes by measuring the seismic performance of MRF-RC frames.

2. Methodology

The designs of RC buildings with 2-, 4-, 8-, and 12-story with moment resisting systems are compared under different seismic intensity levels. The comparison includes member sizes, vibrational properties, earthquake design loads, and material usage. Next, nonlinear finite element analysis models are created to assess the earthquake behavior of the designs. Seismic design codes were compared based on permitted analysis methods, zoning scheme, site class, the dynamic baseline period of the building, response reduction factor, importance factor, minimum lateral design force, allowable interstory drifts, and design response spectrum. A nonlinear behavior time-history analysis was performed on each building, and several key indicators were conducted to evaluate the performance of the four buildings.

2.1. Structure Model

The structure type chosen here is the RC moment-resistant frame structure, a common building structure. Based on the HAZUS Directory [26], building ties are categorized by height or the number of stories. Therefore, buildings with 2, 4, 8, and 12 stories have been selected to model low-rise, mid-rise, and high-rise buildings. The structures have a regular shape in layout and elevation, with four spans along the X-axis and four spans along the Y-axis, as shown in Figure 1(a) direction, and a story height of 3.5 m, as demonstrated in Figure 1(b). These structures are being designed as office buildings. The dead load of the floors is 3 kN/m², not including the self-weight of the building’s members. The live load of the roof floor is 0.75 kN/m², and the live load of the other floors is 2.5 kN/m². This study adopts HRB400 steel with E and ∂ values of 210 GPa and 0.02 and concrete with 30 MPa compressive capacity.

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The frames are designed using the standard Chinese GB-50011 and African norms following the Eurocode to design concrete structures [25]. The structural analysis and design were conducted with the assistance of ETABS software [27]. ETABS is widely used in engineering design offices and was endorsed by Abdo [28] to analyze RC multistory buildings. Shell elements are used for the panels, and frame components are used for the beams and columns. The supports are located at the foundation level. The total beam and column stiffness are considered in the analysis of all models. The complete quadratic combination (CQC) was applied to integrate the behavior of different modes according to the recommendations of EBCS-8, ECP-201, RPA-99, and GB-50011-2010. Tables 1 and 2 show the section and reinforcement design of the form frame. For each axis (X or Y), the center of mass was allocated an accidental eccentricity of 5% (relative to the corresponding level dimension).

2.2. Nonlinear Dynamic Analysis (NL-DA)

A powerful tool for this purpose is incremental dynamic analysis (IDA), which involves performing the nonlinear time-history analysis (NL-THA) for a range of ground acceleration intensities and recording the structural response. NL-THA provides more realistic results about how a specific structure performs under seismic excitation [29], accounting for the structural element’s nonlinear behavior and the ground acceleration dynamic characteristics. However, NL-THA requires a suitable intensity measure (IM) to characterize the ground motion [30]. Nazri and Alexander [31] highlighted that peak ground acceleration (PGA) is a frequently utilized parameter, the IDA curve can be generated through the correlation between the interstory drift ratio and PGA.

Nine pairs of seismic ground motions acceleration with various seismicity levels are chosen for each building is showed in Table 3. These ground motion pairs are employed for NL-THA. A total of 36 pairs of raw seismic data are obtained from the PEER NGA website, whose response spectrum agrees with the response spectra for the four-character scheme. SeismoMatch uses spectral matching to transform accelerometer data into an analogous response spectrum. The program depends on the wavelet method several authors proposed [32–34]. The wavelet algorithm method for aligning response spectra is employed in earthquake engineering to customize recorded ground movements to match desired seismic parameters. This process entails breaking down the motion into components specific to certain frequencies using wavelet transformation. These components are then optimized using algorithms such as enhanced colliding bodies optimization (ECBO) to reduce the difference between the actual and target spectra. The components are subsequently modified and recompiled into a fresh ground motion time history. This approach guarantees that the altered ground motion adheres to design specifications while maintaining the original motion’s traits [35]. The period range for spectral alignment using wavelet algorithms generally encompasses the range of periods that are pertinent to the design and analysis of structures under seismic loading. For this study, the intermediate period range is set between 0.2 and 2 s, during which the spectral shape exhibits a linear decrease. These ground motions were scaled to 0.2 g for time history analysis. Figure 2 illustrates the matched response spectrum of chosen records with the design response spectra of the four codes.

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The Takeda model [36], as shown in Figure 3, is employed in the incremental nonlinear dynamic analysis to simulate the flexural response’s hysteretic behavior. This approach effectively mimics the cyclic behavior observed in plastic hinges and is key to reproducing the decreasing strength and stiffness commonly seen in concrete structural components [38].

where K_i: initial stiffness, Δ_y: yield displacement, and Δ_m: maximum displacement.

2.3. Nonlinear Static Analysis (NL-SA)

The study employs nonlinear static analysis to assess a structure’s capability of withstanding a powerful earthquake. The nonlinear static analysis refers to the pushover analysis. This well-established technique generates a capacity curve representing the structure’s capacity in force and deformation before failure. This approach aims to plot a curve illustrating the force and deformation a building can tolerate before collapse. This technique helps engineers design or retrofit existing buildings to resist seismic damage. The pushover analysis reveals crucial information about the structure’s strength, stiffness, and ductility, which can then be used to determine potential deficiencies and propose remedies. Improving these response parameters tends to enhance the earthquake resilience of the structure.

The pushover analysis method was used, specifically employing the SPO2IDA tool to estimate the strength ratio (R) and ductility (μ) curve of the frames [39], which presents an effective approach to estimate the seismic demand and capacity of systems dominated by the first mode of vibration across a range from semielasticity behavior to total failure, as shown in Figure 4. It correlates the curve of static pushover (SPO) empirically with its associated for IDA. This method uses empirical formulas to link the R strength ratio of the one degree of freedom (1DOF) system to the elastic spectrum for a specific ground acceleration, T its seismic period, and μ its ductile ratio. Those formulas between the R, T, and were already derived for different types of SPO basis curves and incorporated into the tools. The outcome is to transform the pushover curve variables for the multiple degrees of freedom (MDOF) into a comparable 1DOF system and then calculate the (IDA) curves.

is the elastic spectrum demand on an 1DOF system with period under ground acceleration excitation, and represents the yield force of that system, denotes the maximum displacement response and signifies the yield displacement. Put simply, R signifies the ratio of strength for the first mode spectrum acceleration of a particular ground acceleration or design spectra, , and the spectrum acceleration yield of the equivalent 1DOF, . As illustrated in Figure 4, the relationship pushover analysis curve and its corresponding IDA percentiles (i.e. 16^th, 50^th, or median and 84^th) were quantified empirically. The SPO–IDA approach allows the translation of the basic parameters of an MDOF system into an equivalent SDOF oscillator, thus facilitating the estimation of seismic demand (i.e. IDA traces) based on well-established empirical R-T-μ relationships.

In the pushover analysis conducted using ETABS, the characteristics of concentrated plastic hinges are key. As illustrated in Figure 4, Point A represents the initial yielding of structural elements, which is determined by their moment–curvature relationship. At Point C, hinge deformation signifies a reduction in strength, potentially leading to sudden structural collapse [40]. In this analysis, beams are assumed to carry no axial load. However, for columns, the axial load is calculated as the permanent load plus 0.25 or 0.5 of the live load, in line with African and Chinese standards, respectively. The length of the plastic hinge is crucial in determining the maximum rotation, derived from the peak curvature. The plastic rotation for each hinge is determined by Equation (3) [41]:

Here, and denote the yield and ultimate moment curvatures, and is the length of the plastic hinge.

According to ATC-40 [42], the length of the plastic hinge should be half the depth of the section in the load direction, a guideline known to produce conservative results. This approach is adopted in this study to calculate the hinge length. Thus,h: section depth of the element, beam, or column.

As a result, with gravity loads uniformly distributed across the beam, potential plastic hinges are considered at both ends of columns and beams. In ETABS, similar to FEMA 356’s plastic hinges, column axial-moment hinges (P-M3) and beam bending moment hinges (M3) are defined at the extremities of these elements.

For inelastic material as shown Figure 5(a) illustrates the constitutive material models for steel and concrete. The bilinear rubbery model with kinematic strain reinforcement was employed to stiffen steel. The model requires three parameters: modulus of elasticity (E), yield strength (), and strain-hardening coefficient (). This study adopts HRB400 steel with E and values of 210 GPa and 0.02, respectively. The longitudinal and annular yield strengths are 570 and 400 MPa, respectively. Figure 5(b) shows that the uniaxial static confined model was used to represent the concrete material. The model needs four parameters: compressive capacity (), tensile capacity (), maximum strain () corresponding to (). The , , and values are 30, 2.4 MPa, and 0.002, respectively.

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2.4. Fragility Curve

Seismic impact hazards on structural models can be estimated analytically using fragility curves, which are beneficial methods for estimating the likelihood of failure to any structural system. Fragility curves can also help in making retrofit decisions. The fragility of buildings is evaluated using time-history IDA, and drifts will be used to track severe damage that could cause structural collapse. The deflection percentage can then be computed as shown in Equation (5).

Fragility curves are developed based on several seismic parameters, among which the PGA parameter is used in both IDA and fragility curve development. The damage condition for the four models is determined by the performance levels: operational phase OP, immediate occupancy IO, damage control DC, life safety LS, and collapse prevention CP, which correspond to drift values of 0.5%, 1%, 1.5%, 2%, and 2.5%, respectively, based in FEMA-P-695 process [44]. Two main factors are required to create fragility curves: the average () and standard deviation (). The following equation in Equation (6), which Ibrahim and El-Shami [45] have used.where is the standard normal cumulative distribution function, is the standard deviation of the logarithm, is the average value, and D is the damage state.

3. Comparison of Seismic Provisions

All buildings were assumed to have rigid subsoil. The properties of rigid soil include a shear wave velocity between 180 and 360 m/s, a standard penetration strength between 15 and 50, and an unconsolidated shear resistance between 70 and 100 KPa. Comparing the two investigated codes reveals that rigid soil corresponds to Soil C in ECP-201 and EBCS-8, to Soil D in the GB-50011 code, and S3 in the RPA-99 code. The soil factor S in ECP-201, EBCS-8, and RPA-99 is identical and varies according to soil type and building proximity to the Mediterranean Seashore. For the buildings under investigation, S is 1.5. On the other hand, the soil factor in GB-50011, it is dependent on soil type and has a value of 1.3. The intended use of office buildings. All four codes classify them as standard occupancy. Each code assigns a different identification to the standard occupancy category, but they all have the same importance factor (1.0), as shown in Table 4 [46]. The African codes adopt some European standards for certain specifications [47] and apply a simplified time approach (STA) and the comparable static load analysis method (ESL) to calculate the base shear of the building and distribute it among the stories. STA is given by T = 0.05 H^0.75, where T is the structure’s natural period and H is the building’s height. In GB-50011, the fundamental period depends on the roof type and span, as shown in Table 4.

The nonlinearity correction coefficient (ECP-201 and RPA-99) and the ductility reduction factor (EBCS-8) modify the forces obtained from the linear analysis to reflect the nonlinear behavior. GB-50011-2010 does not apply a nonlinear response modification factor to seismic demand. Instead, it uses the equivalent factor to evaluate the possible seismic ductility of the structural element [43].

The response spectrum (for the four codes) was calculated using the soil classification and earthquake moduli values from Table 4 and are displayed in Figure 6, respectively. Schematic representations of the four-code horizontal design response spectra are also included in Table 4. The diagrams show the limit, lowest, maximum, and intermediate T values. Three intervals can be separated out of Figure 6: (1) The first varies from 0.2 to 0.7 s, and the coding sequence is ECP-201, EBCS-8, RPA-99, GB-50011, depending on the degree of conservatism. Finally, the third interval, which starts at 2 s and shows a striking disparity of the bottom bounds of the four codes where ECP-201 conservatism outperformed the other codes, ranges from 0.7 to 2 s. This comparison of design response spectra, according to El-Kholy et al. [48] may be misleading if other elements, including time T, seismic weights W, and cracking stiffness ratios, are not considered. As observed in Figure 6, the response spectrum of ECP-201 surpasses that of the other codes. As observed in Figure 6, the response spectrum of ECP-201 surpasses that of the other codes. This is attributed to ECP-201’s implementation of the response spectrum method, which features pseudo acceleration linked to the PGA. Additionally, the soil parameter significantly impacts the shape of the response spectrum curve, further influencing the results. This highlights the importance of considering soil parameters in seismic analysis [10].

The probability that ground motions will cause damage depends on several variables, including the ground motion’s acceleration, period, and amplitude, the structures’ dynamic properties, and the ground acceleration’s frequency content. Due to the characteristics of ground motion records, ground acceleration factors might differ greatly. Different sets of seismic records that correspond to the design response spectra of the structure site are used to estimate this discrepancy. As illustrated in Table 4.

where : behavior factor;

: the basic value of the behavior factor dependent on the structural type;

: ductility factor;

: structural regularity in elevation factor;

: factor reflecting the prevailing failure made in structural type;

: the roof-type building;

: span of the building;

: coefficient, the function of the lateral force-resisting system;

H: height measured in meters from the basis of the structure to the top of the last level (N);

, , ;

W_Gi weight due to the dead loads and loads of the eventually fixed equipment attached to the structure;

W_Qi live loads;

β weighting coefficient, depending on the nature and the duration of the live load;

correction factor; and

equivalent gravity loads.

The four standards specify that the seismic mass represents the dead load plus a fraction of the live load based on the occupation category. ECP-201, EBCS-8, and RPA-99 correlate the relationship between occupied levels and the occupancy category. ECP-201 and EBCS-8 stipulate w = 0.25 for office buildings with independently occupied floors. RPA-99 is multiple live loads by weight factor based on the natural duration of the live load. In GB-50011, the total dead load of the building plus 0.5 times the live load is shown in Table 4.

Table 4 contains the basic shear base resistance formulae for the Chinese and African standards. The basic shear computation can be used for shorter vertically homogenous constructions in GB-50011-2010 (i.e., where mass and stiffness are distributed uniformly in the vertical direction). The seismic impact coefficient affects the earthquake strength, site categorization, peak acceleration, and damping ratio.

4. Seismic Performance Assessment

4.1. Vibration Modes

The Ritz method [49] was used to analyze the models of the four structures. The Ritz method is a direct numerical method for finding eigenvalues linked to a structure’s modal shapes and natural frequencies. The analysis included the effects of crack flexural rigidity, specific seismic mass, and shear diaphragms on the structure’s dynamic behavior. Figure 7 shows the modal shapes in the X direction (short span) for different frames. Figure 7(a) shows two mode shapes for the 2-story frame. Figure 7(b)–7(d) show the first four modal shapes for the 4-, 8-, and 12-story frames, respectively. There is a very small difference between frames designed by Chinese and African codes due to mass and the cross-section of the members, which changed their stiffness and mass properties.

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4.2. Base Shear

Base shear refers to the maximal lateral force exerted at the base of a building by the ground motion, as shown in Figure 8. illustrates the time history of the base shear due to the Coalinga ground motion. Specifically, Figure 8(a)–8(d) represent the base shear for 2-, 4-, 8-, and 12-story frames, respectively. These frames are designed according to four different seismic codes: EBCS-8, ECP 201, RPA 99, and GB-50011.The results for African code are almost same. Figure 8(d) shows that for the 12-story frame, the peak base shear values obtained from ECP-201, EBCS-8, and RPA-99 codes are 6,073 kN, and the peak base shear for GB-50011 is 7,445 kN. A similar trend is observed for other frames, where the GB-50011 code gives the highest base shear estimation compared to other regulations. This indicates that the GB-50011 code is more conservative and may result in the overdesign of structures due to the design of the response spectrum, as shown in Figure 6, and the seismic weight.

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4.3. Story Shear Force

This section examined how frame rigidity affects the shear distribution in buildings of different heights. The frames were analyzed using time history for nine earthquake records. The time history method integrates the equations of motion for a multidegree of freedom using nine ground motion acceleration records. Figure 9 shows the results of the analysis. It reveals that the story shear demands depend on the lateral stiffness of the frames, which increases with higher stiffness. Figures 9(c) and 9(d) also indicate that the story shear values for GB-50011 are overestimated. The African code has the same results suggesting that these codes have comparable assumptions and criteria for the frame design.

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4.4. Interstory Drift

Interstory drift ratio (IDR) reflects the degree of structural damage that can occur during an earthquake. The data obtained from the time-history response was used to determine the greatest relative displacements between each floor (for every story level). Following this, the interstory drifts ratio were computed by taking the ratio of these maximum relative displacements to their corresponding story heights. Figure 10 shows the IDR values for the model frames under different seismic codes. The lateral load pattern causes a significant soft-story effect, particularly for the building based on the GB-50011 standard. This effect is more pronounced for the 2-, 4-, 8-, and 12-story frames, which have a maximum IDR of 0.44%, which is still within the allowable limit. It can also be observed that the largest IDR values are located in the middle stories of the frames. On the contrary, the other codes, namely ECP-201, RPA-99, and EBCS-8, tend to underestimate the IDR values compared to the GB-50011 code.

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4.5. Pushover Analysis

The criteria pushover analysis used to compare the performances are the strength ratio, R, and the ductility, μ, of the frames. The strength ratio is defined as the ratio of the base shear force to the structure’s weight, and the ductility refers to the ratio of the maximum displacement to the elastic displacement of the structure. These metrics are calculated from the nonlinear static analysis of the frames under different seismic intensity levels. Figure 11 visually compares the strength ratio and ductility curves for two of the 4-story frame structures considered in this study designed by the African and Chinese codes. The method a tends to overestimate the structure’s strength and ductility for a given seismic intensity, resulting in a conservative design. In Figure 11, 16%, 50%, and 84% are typically indicative of statistical metrics employed in probabilistic seismic demand models. The 16% fractile signifies a lower limit, the 50% fractile corresponds to the median, and the 84% fractile denotes an upper limit. These fractiles serve as critical markers in understanding the distribution and potential variability of seismic demands. Especially, Figure 11 indicates that frame design by African code has more probability of seismic demand compared to the frame design by the GB-50011 is more effective and reliable for designing RC frames under seismic loading.

4.6. Fragility Curves

Fragility curves are graphical tools used to evaluate the potentiality of structural damage under various levels of earthquake intensity. In seismic fragility analysis, the mean and standard deviation values are derived from a statistical examination of the outcomes from the time-history IDA. This process involves calculating the roof drift associated with various damage states—namely; OP, IO, DC, LS, and CP. These states correspond to specific values: 0.5%, 1%, 1.5%, 2%, and 2.5%, respectively. The fragility curves are shown in Figure 12 for four performance levels (OP, IO, DC, LS, and CP). The results indicate that all the model frames have a full probability (100%) to reach or exceed the OP-level under certain ground motion intensities. These intensities are 0.8, 0.77, 0.7, and 0.3 g for the frames designed by EBCS-8, ECP-201, RPA-99, and GB-50011 codes, respectively. The frame designed by the GB-50011 code will experience at least IO-level damage when a 0.75 g ground motion is applied. Similarly, the results show that the probability reach or exceed the LS-level varies among the frames under a 1.5 g ground motion. The frame designed by the GB-50011 code has a full probability (100%) to reach or exceed the DC-level, while the frames designed by EBCS-8, RPA-99, and GB-50011 codes have lower possibilities of 38%, 34%, and 35%, respectively. Figure 12 observe that the buildings designed according to GB-50011 exhibited different standard deviations in the fragility curves. This is attributed to the greater roof drifts observed for these buildings. The IDA outcomes indicated that the response of the GB-50011 designed buildings, in terms of both interstory drifts and story shear, was greater when compared to those designed by African codes. This finding is consistent with the observed ductility capabilities of the structures, as illustrated in Figure 11, where GB-50011 designed buildings show a smaller ductility capability.

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4.7. Total Energy Components

Total energy components show how energy is divided among different structure parts during seismic analysis. The energy components are input energy, kinetic energy, potential energy, and damping energy, Table 5 shows the maximum value of the energy components. Input energy is the energy given to the structure by an external seismic load [50]. Kinetic energy is the energy related to the movement of the structure, this indicates the possibility of structural damage [51]. Potential energy is the energy saved in the structure due to the elastic stress that can be released when the load is removed. The damping energy is the energy the structure loses because of damping mechanisms, such as material damping or Rayleigh damping [51].

5. Discussion

(1)Different codes and standards have different methods and criteria for estimating the base shear. The paper shows that among the four codes considered, GB-50011 gives the highest base shear estimation for all frames, regardless of their height or number of stories. This means that the GB-50011 code is more conservative and may result in the overdesign of structures. On the other hand, the peak base shear values obtained from ECP-201, ECBS-8, and RPA-99 are relatively close, indicating that these codes have similar assumptions and factors for estimating the base shear.(2)The story shear demands four frames of different heights using time-history analysis methods. The paragraph shows that the story shear demands increase with the frame stiffness and that the ECP-201, RPA-99, and EBCS-8 codes give similar results, while the GB-50011 code gives higher results.(3)The buildings’ IDR values using different seismic codes. The paragraph shows that GB-50011 gives the highest IDR values, as expected due to the design response spectrum seismic weight estimation, which indicates a soft-story effect, while the ECP-201, RPA-99, and EBCS-8 codes tend to underestimate the IDR values compared to the GB-50011 code.(4)This study developed fragility curves for four model frames based on four seismic codes. The results of the fragility analysis indicate that the GB-50011 code is the most conservative, as it gives the highest probability of damage for all performance levels. This means that the frame designed by this code is more likely to experience structural damage than the other frames under the same ground acceleration intensity. On the other hand, the African codes are the least conservative, as they give the lowest probability of damage for all performance levels. This means the frame designed by these codes is more resilient and can withstand higher ground motion intensities without significant structural damage.(5)Based on this study, we discovered that the seismic design codes of Africa are derived from the European code 8, and most of the provisions of the African code follow the same procedures. The main differences between these codes lie in the soil classifications and the design response spectrum. We obtained similar results for these codes when we performed the same ground motion scaling for time-history analysis.(6)This research reveals that China’s seismic design code exceeds the African code by 20%. Since the Chinese companies have engineering projects in Africa, they can apply the Chinese code by considering the soil classifications in Africa. This excess results from the fact that the estimation of seismic weight needs to be adjusted to meet the African design criteria.

6. Conclusions

This paper compares the earthquake performance evaluation of MRF-RC frame buildings using four different codes: Ethiopian Building Code Standard (EBCS-8), Egyptian Code for Design and Construction of Reinforced Concrete Structures (ECP-201), Algerian Seismic Monitoring Code Regulations (RPA 99), and the Chinese Code for Seismic Design of Buildings (GB-50011). The study designs 2-, 4-, 8-, and 12-story RC model frames according to the four-code amplitude design principle. It then compares and presents the four-code seismic criteria for soil classification, seismic zone, response modification, response spectrum, story drift, seismic weight, and base shear. The study also evaluates the earthquake behavior of the model frames by IDA and NL-THA using different ground acceleration levels and provisions given in EBCS-8, ECP-201, RPA-99, and GB-50011. Moreover, the study identifies and summarizes some major differences among the four codes:(1)The African code for seismic design: EBCS-8, ECP-201, and RPA-99, these standards are based on the European seismic code (Eurocode-8), which provides general principles and rules for designing structures to resist earthquakes. Most of the equations and provisions in the African codes are the same as those in Eurocode-8, with only minor modifications. The main differences between the three codes lie in the soil classification and seismic zonation. The African codes adopt a different system of classifying soil types according to their geotechnical properties and seismic response. The African codes also divide the continent into different seismic zones depending on the expected earthquake hazard level and ground acceleration. This would facilitate the unification process of seismic design codes for African countries.(2)Based on preliminary research, developing a unified African seismic design code is essential. Since the existing African codes are derived from the European code, this would facilitate the unification process by considering the soil classification and seismic zones for the whole of Africa. This would bring significant benefits to African countries and reduce costs compared to creating standards for individual countries. Moreover, some African countries lack codes for seismic design.(3)This study has compared the seismic performance of moment resisting frames designed based on Chinese and African codes using different metrics, such as base shear, story shear, IDR, and fragility curves. The results show significant differences between these codes regarding the safety and resilience of structures under seismic actions. This is an important finding for Chinese engineering firms increasingly involved in international projects under the “One Belt and Road Initiatives” proposal, as they need to understand and comply with international design standards. Based on this research, the Chinese engineering frame can use the Chinese seismic design code in their projects in Africa for some parameters like soil classifications in Africa. However, this study has some limitations, as it only considers one type of structure. Therefore, future research could extend such comparison to different structures, such as steel frames, shear walls, or braced frames, to further investigate the strengths and weaknesses of Chinese and African codes for seismic design.

Data Availability

The data that have been used to support the results of this study are contained in the article.

Conflicts of Interest

The authors declare that they have no conflicts of interest.

Acknowledgments

The authors greatly appreciate the support from the Chinese Scholarship Council (CSC).

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Copyright © 2024 Musaab Suliman and Liang Lu. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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