Special Moment-resisting Frames Research Articles

Probabilistic Seismic Performance Assessment of Tall RC Special Moment-resisting Frame Buildings Equipped with Buckling-restrained Braces under Near-field Excitations

Many tall buildings have already been constructed near faults throughout the world, several of which have sustained casualties and economic losses during strong ground motions. This study investigates the effect of near-fault excitations on the vulnerability of tall, reinforced concrete (RC) special moment-resisting frame (SMRF) buildings equipped with buckling-restrained braces (BRBs) using seismic fragility curves. After attaining the structure’s response modification factor (R), three-dimensional (3D) models of 15-, 25- and 35-story frames were developed by the OpenSees software according to the Iranian code provisions. Thus, the seismic response of the elements was obtained. Subsequently, incremental dynamic analysis (IDA) was conducted by selecting a suitable number of compatible accelerograms in two near-field and far-field groups. Considering the maximum story drift as the demand parameter and selecting the interstory drift ratios (IDR) for the slight, moderate, extensive, and complete collapse seismic performance levels proposed by Hazus, IDA curves were plotted. Then, the seismic fragility curves were produced using the structural reliability relations. The median fragility at complete collapse damage level reduced from 0.73g, 0.62g, and 0.61g to 0.68g, 0.59, and 0.57g for the 15-, 25, and 35-story near-field and far-field earthquake models, respectively. This was attributed to increasing vulnerability and seismic fragility of the structures as a result of both height increase and distance reduction from fault. Based on the results, the most vulnerable structure, i.e., the 35-story near-fault model, experienced a 40, 17, 18, and 6% increase in median fragility at slight, moderate, extensive, and complete collapse damage levels, respectively.

Stiffening of I-section MRF beams against degradation due to local buckling

Moment resisting frame (MRF) beams under cyclic loading are vulnerable to local flange and web buckling. The Seismic Provisions for Structural Steel Buildings (AISC341) prescribe width-to-thickness ratio limits, which are contingent on target rotations during predefined cyclic loadings. Some rolled I-sections available in the market cannot be employed in special MRFs since they fall short of satisfying the AISC341 flange slenderness limit. Moreover, local buckling leads to a decrease in both strength and stiffness in cyclically loaded MRF beams, ultimately increasing the risk of frame side-sway collapse. This paper introduces a stiffening method aimed at improving the behavior of I-section MRF beams. The proposed method involves placing a pair of stiffeners at the plastic hinge regions. A two-phase numerical study was conducted to assess the effectiveness of this approach. In the first phase, nine unstiffened beam cross-sections with varying flange and web slenderness were considered. The slenderness limits specified by AISC341 were evaluated based on cyclic analyses of these beams. In the second phase, a parametric study was conducted on the same cross-sections, with the flange width and the placement of the pair of stiffeners considered as variables. The results revealed a substantial improvement in behavior with the addition of a pair of stiffeners. Cross-sections that failed to meet the flange slenderness limit could be used in MRFs when stiffened. The optimal location for the stiffeners was found to be significantly influenced by the flange width. Design recommendations for the ideal stiffener placement are presented in this paper.

Evaluation of seismic performance of connected adjacent buildings using fragility curves

One of the effective methods to reduce the seismic response of the adjacent buildings is to connect these buildings by passive dampers. In this research, the seismic performance of this type of control system is evaluated using fragility curves. Furthermore, the parameters and arrangement of the connecting viscous dampers are investigated. For this purpose, two 8- and 12-story RC special moment-resisting frame buildings are connected by viscous dampers. After obtaining the appropriate parameters and arrangement of dampers, incremental dynamic analysis was performed under 22 far-field ground motions using OpenSees software. Assuming a log-normal distribution, the probability of exceedance of the performance level is calculated at each maximum ground acceleration value as a fragility curve. The fragility curves show that the connection of adjacent buildings by viscous dampers will improve the seismic performance of both connected buildings compared to the corresponding results of single uncontrolled buildings.

Emulation Evaluation of Interior Beam-Column Connections in PC and RC Moment-Resisting Frames.

Precast concrete (PC) structures have many advantages, but their use in the construction of middle- to high-rise buildings is limited. The construction of PC structures requires skills in various operations such as transportation, assembly, lifting, and structural soundness. In particular, regarding the seismic design of PC structures, it is necessary to clearly evaluate whether they have the same structural performance and usability as integral RC (cast-in-place) structures. In this paper, an experimental study was conducted to investigate whether PC members can achieve a seismic performance equivalent to that of RC members in beam-column joints, which are representative moment-resisting frames. The main variables are the two types of structural systems (intermediate and special moment-resisting frames) and the design flexural strength ratio of the columns and beams. The experimental and analytical results showed that the seismic performance of the PC specimens was equivalent to that of the RC specimens in terms of strength, stiffness, energy dissipation, and strain distribution, except for the specimen with splice sleeve bond failure of the column reinforcement (poor filling of the internal mortar). In addition, the I series satisfied the present emulation evaluation criteria for special moment-resisting frames of PC structures, confirming the possibility of applying intermediate moment-resisting frames.

Seismic performance of bidirectional bolted drilled cut RBS-CFT connections under cyclic loads

Welded connections were widely used in different regions of the world for ease of fabrication and good performance under gravity load. However, Northridge (1994) and Kobe (1995) earthquakes demonstrated that seismic performance of welded connections has been inferior as compared to that of bolted connections. Reduced beam section (RBS) has been one of the effective methods to enhance seismic performance in terms of energy dissipation capacity and ductility. Drilled-cut RBS-CFT connections have been gaining acceptance for enhancing overall seismic performance of steel moment resisting frames. However, no comparative study has been reported in the literature on RBS-CFT connection with bidirectional bolts for evaluation of their seismic performance. In view of the above, experimental study has been carried out for evaluation of seismic performance of two variants of RBS-CFT connections with constant drilled cut (CD-cut) and varied drilled cut (VD-cut) RBS. Both the drilled cut RBS-CFT connections are found to be semi-rigid in nature and exhibited stable hysteretic behavior. Test results showed that the cumulative energy dissipation capacity in the VD-cut connections is marginally higher than CD-cut connection. VD-cut RBS-CFT connections effectively reduced the lateral-torsional deformation. The load-carrying capacity and stiffness degradation ratio of VD-cut RBS-CFT connection is higher than CD-cut RBS-CFT connection. Damping of the both connections are nearly of similar order. Recorded strain data of both connections showed that plastic hinge confined only on drilled zone of the beam. Further, a detailed numerical simulation of force-deformation envelope curve of RBS-CFT connections was carried out using ABAQUS software. Simulated force-deformation envelope curves are found to be in close agreement with those obtained from experimental investigation. Both connections meet the seismic requirements of the AISC specified for composite special moment-resisting frames (SMRFs) by achieving rotational capacity of 0.04 radians without any damage in the joint panel region.

A Comparative Study on Seismic Analysis of Multistorey Buildings in Different Seismic Zones

The multi-story buildings are constructed to accommodate numerous residents in confined spaces due to the growing population and lack of available land. The population growth and industrial revolution caused a migration of people from rural to urban areas resulting in the need for the construction of multi-story buildings for both residential and commercial uses. The tall buildings, which are not adequately constructed to resist lateral stresses, result in the total collapse of the structure. Buildings that can withstand earthquake forces are created by considering different criteria such as the building’s inherent frequency, damping factor, kind of base, significance of the building and ductility of the structure. Because they have better moment distribution properties, structures designed for ductility need to be designed for lower lateral loads. To ensure safety against the seismic stresses of multi-story buildings, it is essential to understand seismic analysis in order to develop earthquake-resistant structures. Both a regular moment resisting frame and a special moment-resisting frame were taken into account for the seismic study. In the present study, a G + 8 storey reinforced concrete (RC) structure in three different seismic zones was compared in terms of percentage longitudinal steel, reinforcement details, and design base shear. The structure was examined for seismic zones III, IV, and V in accordance with the guidelines of IS 1893 (Part 1): 2016. Results showed that base shear increased with the change in the seismic zone from III to V.

Seismic Assessment of RC Frame Building using Gross and Cracked Section as per IS 1893: 2016 and IS 16700: 2017

The primary objective of this research is to investigate the behaviour of tall concrete buildings featuring structural walls combined with Special Moment Resisting Frames (SMRF) when subjected to seismic loads, as defined by the IS 1893:2016 and IS 16700:2017 codes. To achieve this, a comprehensive seismic analysis was conducted using the Linear Dynamic Response Spectrum Method in ETABS 2020 software.

Investigating seismic behavior of a modified widened flange beam-column connection in SMRF utilizing experimental, numerical and hybrid simulation

This manuscript presents the seismic performance of a modified widened flange beam-column connection in a special moment-resisting frame (SMRF). The beam-column connection has been modified by two cover plates welded to the top and bottom flanges of the beam and investigated under earthquake acceleration. One-story one-bay special moment resisting frame with an increased beam flange at the vicinity of column was analyzed in accordance with the Iranian Code of Practice for Seismic Resistance Design of Buildings (Standard 2800). Experimental investigation was carried out in which a cyclic displacement history was applied. Numerical finite element analysis was carried out using ABAQUS and its results validated by experimental test results. A hybrid simulation was conducted utilizing OpenSees as the finite element software, OpenFresco as the middleware and LabVIEW as data collector and actuator motion controller. Results comparison of three above mentioned methods (experimental test, numerical analysis and hybrid simulation) indicate that the hysteresis curves are in great compatibility with each other. As expected, results demonstrate that the yielding occurred immediately beyond cover plates at arc shaped areas of beam. On the other hand, the experimental and numerical results show that the specimen reached at least 0.07 rad drift angle before experiencing strength degradation. Furthermore, parametric studies on ‘c’ and ‘R’ which are two key parameters of modified widened flange beam represent that for a constant dimensions of cover plate, increasing ‘c’ and decreasing ‘R’ will reduce plastic strain and stress demands in beam.

Earthquake-induced loss assessment of steel dual concentrically braced structures subjected to near-field ground motions

Steel structures with dual systems, including special moment-resisting frames (SMRFs) and special concentrically braced frames (SCBFs), have found extensive applications in seismically active regions due to their considerable lateral stiffness and ductility. However, the seismic performance of such system has not been investigated subjected to near-field ground motion records. To address this research gap, this paper evaluates collapse risk and earthquake-induced loss of multi-story steel structures with dual concentrically braced frames. A comprehensive seismic performance assessment is conducted on selected five-, 10-, and 15-story structures subjected to near-field ground motions (NF-GMs) with and without pulses based on the methodology provided in FEMA P-58. The results are also used to assess the effect of NF-GMs with pulses on the seismic performance measures, such as life-cycle cost and repair time of the studied structures at different seismic intensity levels. Finally, the contribution rate of collapse and demolition of structures, and contribution of structural and nonstructural members in the repair cost and time of the steel structures are estimated and compared subjected to NF-GMs. It is concluded that collapse and demolition loss play significant roles for NF-GMs with and without pulses, respectively, while the seismic collapse behavior is governed by the ratio of the pulse period of the GM to the period of the first mode of the structure.

Life cycle cost‐based optimization framework for seismic design and target safety quantification of dual steel buildings with buckling‐restrained braces

AbstractThis study proposes an efficient risk‐targeted framework for integrated optimal seismic design and quantifying target safety of Special Moment‐Resisting Frames (SMRFs) with Buckling‐Restrained Braces (BRBs) in the typical dual steel buildings. This framework provides an automated design procedure formulated as a constrained single‐objective optimization problem to achieve the minimum Life Cycle Cost (LCC) within the Particle Swarm Optimization (PSO) algorithm and can be the basis of current seismic codes for target safety calibration. LCC includes initial construction cost and lifetime seismic losses such as repair cost, repair time, and casualties. FEMA P‐58 methodology is employed for the LCC analysis of the building under possible earthquakes during its lifetime, which is able to take into account potential uncertainties in the hazard‐response‐damage‐loss relationship. An appropriate cost model is developed to estimate the initial and repair cost of the studied BRBs. Minimum requirements of ASCE and AISC codes are considered as design constraints. Nonlinear response history analysis through the Endurance Time (ET) method is utilized to estimate the structural responses versus seismic intensity. Three 4‐, 8‐, and 12‐story steel buildings with dual seismic force‐resisting system consisting of SMRF and BRB (called steel SMRF‐BRB) are selected as the case study. Each building is optimally designed with two approaches: (1) LCC‐based design within the proposed framework and (2) code‐based design to minimize initial construction cost. Comparison of optimized buildings with the two design approaches in terms of structural responses and seismic consequences demonstrates that fulfilling the minimum code requirements at a given seismic hazard level is not sufficient to minimize lifetime seismic losses of steel SMRF‐BRBs. This is because the optimal designs obtained from the code‐based approach are associated with damage concentration, irreparability, and high collapse probability, especially in seismic events more severe than the design level. The proposed LCC‐based approach provides useful information for improving the lifetime seismic performance of steel SMRF‐BRBs.

Seismic retrofitting of beam to double-I built-up column moment connections by lateral T-stiffeners: Experimental and numerical study

In the present paper, the retrofitting of welded flange plate moment connections joined to double-I built-up columns is discussed by presenting the design method and details of construction retrofitting. Some of the usual construction problems of this connection include the defective complete joint penetration groove weld at the connection of the flange plate and the column, the large out-of-plane deformations of the column cover plate at the level of the beam-to-column connection, and as a result, its inappropriate seismic performance and the connection's partially restrained behavior. Thus, an attempt is made to evaluate the advantages of strengthening this defective connection with the help of lateral T-stiffeners using analytical and experimental studies. For this purpose, the experimental specimen and the high-fidelity finite element model are considered for both retrofitted and defective connections by evaluating the proposed design method, cyclic behavior of connection, collapse potential of weld fasteners, and failure modes. The results indicate that by using the proposed retrofitting method, the connection is classified in the group of fully restrained connections, while also having the necessary strength and ductility to accept the conditions of the special moment-resisting frames according to AISC seismic provisions. By performing a sensitivity analysis on the T-stiffener, changing its dimensions and examining the damage indices, the accuracy of the proposed design method is proven. The examinations indicate that the aforementioned retrofitting method is a proper method for the introduced defective connection.

Structural behaviour of RC-ECC beam-column connections under quasi-static loading

This research investigates the quasi-static cyclic behaviour of a special moment-resisting frame (SMRF) structure with the application of engineered cementitious composites (ECC) in the beam-column joint. For this purpose, three full-scale beam-column connections were cast and tested under quasi-static loading conditions. The control specimen was cast with the conventional concrete having 21 MPa compressive strength and detailed as per special moment resisting frame (SMRF) requirement. On the contrary, transverse reinforcement was removed from the remaining two (02) specimens with ECC replacing concrete in the joint region and the interface portion of the beam-column connection. Strain gauges and LVDTs were installed at appropriate locations to record the connection's response. After the careful acquisition of data, hysteresis loops, load-displacement envelop and energy dissipation curves were obtained. The test results demonstrated that models with ECC in the joint outperformed the control specimen in ductility, load-carrying capacity and energy dissipation. As compared to the control specimen, the use of ECC in beam-column connection increased the peak displacements by 28.44 %, peak load carrying capacity by 27.13 % and energy dissipation by 58.06 %. Due to high shear strength and ductility, the use of ECC in the joint region was found to address the shear stress requirements without using any transverse reinforcement.

Design and Comparative Study of Overhead Tank Subjected to Seismic Forces in Different Zones

Overhead tank are generally classified as Ordinary Moment Resisting Frame (OMRF) and Special Moment Resisting Frame (SMRF) supported response reduction factor. Generally, the Overhead tank consists of structural members like slabs, beams, columns, and footings, where the subjected loads are transferred between the structural members and eventually transferred to the Sub-grade of the soil. The behavior of the Overhead tank is different for various sorts of loadings (Dead, Live, Wind, and Seismic) within the analysis and of overhead tank usefully Indian standards codes suggest various loads combinations supported probability of Occurrence. There are around 52 load combinations and IS codes suggest the lateral load (wind and seismic) acts independently but the load governing the planning of structural members is to be acknowledged. and therefore the present study to research the consequences of wind and seismic forces on Overhead tank structures of heights (15m) are considered in seismic zones II, III, IV, V where length and width of the structures are kept constant. An earthquake load is calculated as per IS and wind pressure calculated as per IS 875-1987. The analysis is done the use of STAAD.pro software.

Sensitivity of structural responses to the processing of near-fault ground motion records containing fling-step

Fling-step is one of the important characteristics of near-fault ground motions that is caused by a permanent static offset of the ground and appears as a one-sided velocity pulse and a large residual displacement at the end of the motion. Due to baseline errors in many ground motion records, they are processed (processing is a combination of baseline correction and filtering) before adding accelerograms to some earthquake databases whereby the residual displacements ( i.e., the permanent static offsets) in the fling records are typically eliminated. It is not clear to what extent the record processing can affect the nonlinear responses of structures subjected to fling-step records. To address this issue, the current study is conducted to investigate the sensitivity of the nonlinear structural responses to record processing. To achieve this goal, the seismic responses of three code-conforming reinforced concrete (RC) special moment-resisting frames with different heights subjected to two versions of fling-step ground motions including a processed version that static offsets are removed, and a baseline-corrected version with static offsets preserved are evaluated. The findings of this assessment indicate that even though the processing procedure does not preserve the static offsets of the fling-step ground motions, the seismic responses of the structures to the processed records may resemble those obtained under only the baseline-corrected ground motions (with static offsets preserved).

Performance Assessment of Ductile Detailing Code-Based Reinforced Concrete Special Moment Resisting Frames

Reinforced concrete (RC) buildings make up the majority of Indian building stocks. Structural elements of these buildings are often designed limited to non-ductile detailing. With a very low building replacement rate, many Indian buildings are vulnerable to earthquakes and pose a significant risk to lives, properties and economic activities. This paper examines the effectiveness of ductile-detailing in mitigating the seismic collapse risk by analyzing the behaviour of a four-storey RC Special Moment Resisting Frame (RC SMRF) using the latest codes of ductile detailing. It also aims to quantify the impact of lateral force resisting system detailing on the performance and cost of RC SMRF buildings and its benefits. The present study emphasizes the effect of ductile detailing on three fundamental aspects of the structure – safety, stability and economy. Two four-storeyed building models – one without ductile detailing and the other with ductile detailing are designed and then analyzed using non-linear static analysis. The results of this study represent the behaviour of ductile-detailed and non-ductile-detailed buildings in terms of pushover curves, and hinge behaviour and identify the mode of final failure. In extension to that, a cost-benefit analysis is done to study the benefits of ductile detailing with the increased cost. The marginal increase in initial cost associated with ductile detailing is significantly outweighed by the resulting savings in the repair and downtime costs during the service life of the building.

Analiza postupnog guranja za procjenu seizmičkih zahtjeva okvira s eliptičnim vezovima

In this paper, an innovative steel bracing system, known as the seismic response of elliptic braced moment resisting frame (ELBRF), is evaluated. ELBRF has a better structural behavior comparing to the other bracing systems and it has an architectural advantage allowing to place openings in walls with less interference. The demand for seismic performance of ELBRF is estimated through different loading patterns by adopting the conventional pushover methods. The pushover results are verified through nonlinear time history analysis (NTHAs) of 3, 5, 7, and 10-story ELBRF frames, which are on type II soil and are affected by 10 scaled earthquake records. These results are also with special moment resisting frames (SMRF) and X-Braced CBF and Inverted V-Braced CBF concentrically braced frames. Story drifts, displacements, and story shears are evaluated. A proportionally accurate estimation is observed through the pushover methods in comparison with NTHAs. Modal Pushover Analysis (MPA) can estimate the seismic demands by overcoming the shortcomings of FEMA load distributions when the higher mode effects are of concern. The seismic performance of the ELBRF system against earthquakes has improved, failure is transmitted to the upper stories, and the response modification factor is increased in ELBRF.

Development of Near-Field Earthquake Loading Protocols for the Steel Moment Connections in Iran

Steel moment frame buildings are widely used in Iran and around the world. The observations from major earthquakes underscored the importance of the beam-to-column connections in seismic force-resisting systems and their influence on such building’s performance. Since the most catastrophic earthquakes that occurred in Iran contained the characteristics of near-field earthquakes, hence understanding the behavior of these connections under such earthquakes is needed. This study proposed loading protocols for special steel moment-resisting frame systems under near-field earthquakes in Iran. Each of them had 23 damage half-cycles with a maximum inter-story drift of 0.065 radians. The proposed loading protocols were compared numerically to each other. The most influential one was chosen as the main loading protocol since it has the most destructive effect on the connection. The main loading protocol showed a faster rate of increase in the plastic strain and imposed the highest amount of dissipated energy at a former loading stage compared to other near-field earthquake loading protocols related to other countries such as SAC and Fang et al.

An improved 2DOF system for predicting the seismic performance of isolated steel moment frames

This paper proposes an improved two-degree-of-freedom (i2DOF) system with an incorporated effective base-level mass (EBLM) for evaluating the P-Delta and cyclic deterioration effects of nonlinear isolated superstructures. This study verifies the dynamic response and collapse accuracy of the i2DOF system for actual isolated buildings. The case study buildings are the National Institute of Standards and Technology’s (NIST) steel special moment-resisting frames (MRFs) of 4, 8, and 12-stories base-isolated by a friction pendulum bearing (FPB) system. Nonlinear time-history analyses of 22 coupled horizontal–vertical ground motions are performed to verify the i2DOF maximum response when subjected to uplift and pounding effects. The collapse fragility curves of the i2DOF system are compared to those of each corresponding isolated MRF using incremental dynamic analyses (IDA). The results indicate that MRF corner uplifts occur rapidly and do not significantly differ between the i2DOF system and maximum MRF results. The i2DOF system obtains median collapse intensities slightlyhigher than isolated MRFs, indicating that the i2DOF system somewhat overestimates the accurate collapse results. All types of symmetrical and regular low-to-medium-rise isolated steel MRFs with FPBs are designed using a simplified design procedure based on the proposed i2DOF system with a reasonable seismic response precision.

Effect of interior gravity framing system and composite floor slab action on the lifetime seismic risk assessment of steel frame buildings subjected to mainshock–aftershock sequence

The structural analysis practices of steel moment-resisting frame buildings often neglect the participation of the interior gravity frames and composite floor slab action in their lateral strength and stiffness. In addition, the effects of aftershocks are frequently omitted in steel frame buildings’ seismic performance evaluations. This study investigates the effects of structural modeling assumptions and the incorporation of aftershocks on the seismic vulnerability and time-dependent lifetime seismic risk for a group of steel moment-resisting frame buildings. Three ductile steel moment-resisting frame buildings of four, eight, and twelve stories are examined in this study. The results indicate that the seismic performance of steel special moment-resisting frame buildings is substantially underestimated when based on structural models that ignore additional sources of lateral stiffness and strength owing to the interior gravity frame system and the composite floor slab action. In addition, when ignoring aftershocks from the seismic performance assessment, the possibility of catastrophic failure could be underestimated by a factor of 11 at the end of an assumed 50-year lifetime for the steel frame buildings, underscoring the need to account for aftershock effects in evaluating the collapse safety of the selected buildings.

A recurrent-neural-network-based generalized ground-motion model for the Chilean subduction seismic environment

This paper proposes a deep learning-based generalized ground motion model (GGMM) for interface and intraslab subduction earthquakes recorded in Chile. A total of ∼7000 ground-motion records from ∼1700 events are used to train the proposed GGMM. Unlike common ground-motion models (GMMs), which generally consider individual ground-motion intensity measures such as peak ground acceleration and spectral accelerations at given structural periods, the proposed GGMM is based on a data-driven framework that coherently uses recurrent neural networks (RNNs) and hierarchical mixed-effects regression to output a cross-dependent vector of 35 ground-motion intensity measures (denoted as IM). The IM vector includes geometric mean of Arias intensity, peak ground velocity, peak ground acceleration, and significant duration (denoted as Iageom, PGVgeom, PGAgeom, and D5-95geom, respectively), and RotD50 spectral accelerations at 31 periods between 0.05 and 5 s for a 5 % damped oscillator (denoted as Sa(T)). The inputs to the GGMM include six causal seismic source and site parameters, including fault slab mechanism, moment magnitude, closest rupture distance, Joyne-Boore distance, soil shear-wave velocity, and hypocentral depth. The statistical evaluation of the proposed GGMM shows high prediction power with R2 > 0.7 for most IMs while maintaining the cross-IM dependencies. Furthermore, the GGMM is carefully compared against two state-of-the-art Chilean GMMs, showing that the proposed GGMM leads to better goodness of fit for all periods of Sa(T) compared to the two considered GMMs (on average 0.2 higher R2). Finally, the GGMM is implemented to select hazard-consistent ground motions for nonlinear time history analysis of a sophisticated finite-element model of a 20-story steel special moment-resisting frame. Results of this analysis are statistically compared against those for hazard-consistent ground motions selected based on the conditional mean spectrum (CMS) approach. In general, it is observed that the drift demands computed using the two approaches cannot be considered statistically similar and the GGMM leads to higher demands.