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 Study Regarding Input Data Consideration (Required

Accelerograms) for Experimental Test of The Optimal

Moment Resisting (MR) Reinforced Concrete(RC) Frame Model on The Seismic Platform

Authored by Sococol Ion

A significant number of reinforced concrete (RC) frame models have been studied for seismic (ductile) performance purpose through nonlinear static analyses (using ATENA software). In these conditions, it was chosen the optimal models for experimental test on the seismic platform. In next stage, it was used the existing pushover curves to establish the ground acceleration values for five performance requirements (objectives). Thus, it was generated for each performance requirement an artificial accelerogram with which optimal RC frame model can be tested on the seismic platform. Consequently, it will be possible to study the complex cracking mechanism and failure/ split/ rupture/ expulsion material process of the RC frame model at each experimental test for either performance objective. Also, it will be possible test results superposition proceeding with existing theoretical studies.

Keywords: Static Pushover bilinearization; performance requirements (objectives); response spectra; Fourier spectra

*Corresponding author: Sococol Ion, Doctoral School, Faculty of Civil Engineering

and Building Services, “Gheorghe Asachi” Technical University of Iasi, Nr. 1, 700050,

Romania. Received Date: September 25, 2021 Published Date: October 07, 2021

Introduction

Complex analytical studies it were performed with nonlinear [1-7] static analyses [8-15] for a multitude of pure [16] moment resisting RC frame models (“reduced to ½ scale [17] with the same inter-axis distances and story height” [11] (see Figure 1 - Figure 5 and Table 1) in order to identify the optimal ductile (and realistic) seismic response [18-25].

Global Journal of Engineering Sciences Volume 8-Issue 4Citation: Sococol Ion, Mihai Petru, Budescu Mihai. Study Regarding Input Data Consideration (Required Accelerograms) for Experimental Test of The Optimal Moment Resisting (MR) Reinforced Concrete (RC) Frame Model on The Seismic Platform. Glob J Eng Sci. 8(4): 2021. GJES.MS.ID.000692. DOI: 10.33552/GJES.2021.08.000692. Page 6 of 22 Figure 5: “Representation of steel reinforcement car case in pure MR RC frame models with : (a) longitudinal rigid RC beams (structural system type 1); (c) normal RC beams (structural system type 2); (e) ductile RC beams (structural system type 3). Representation of structural mesh discretization for pure MR RC frame models with: (b) longitudinal rigid RC beams (structural system type 1); (d) normal RC beams (structural system type 2); (f) ductile RC beams (structural system type 3)” [11].

Thus, it has been reached the input data stage for experimental test on the seismic platform [26] of the optimal (unique) RC frame model. In these conditions, it was proposed to “generate artificial ac- celerograms” [27-31] (associated with “target spectra” [30-32]) whose PGA values (see Table 6 - column two (from left to right)) reach the absolute acceleration values assigned for each consid- ered performance requirement [33-43] (see Table 5 - column three (from left to right)) [27,32], [44-51]. Thus, it is desired artificial accelerograms implementation in the pre-test stage of experimental study to verify the structural seis- mic response [18-23], [25,43] in accordance with achieved perfor- mance objectives [52-53] in the post-test stage. Determination of Spectral Acceleration Values For M_8, K_5, K_7 And Z_8 Moment-Resisting RC Frame Models Depending on Performance Objectives Analytical study conducted by Sococol et al. [9] demonstrates the superior concrete strength class effectiveness on ductile seis- mic response for MR RC frame structural models. Thus, it was con- sidered valid for the next research stage M_8, K_5, K_7 and Z_8 RC frame models.

Citation: Sococol Ion, Mihai Petru, Budescu Mihai. Study Regarding Input Data Consideration (Required Accelerograms) for Experimental Test of The Optimal Moment Resisting (MR) Reinforced Concrete (RC) Frame Model on The Seismic Platform. Glob J Eng Sci. 8(4): 2021. GJES.MS.ID.000692. DOI: 10.33552/GJES.2021.08.000692.Global Journal of Engineering Sciences Volume 8-Issue 4 Page 7 of 3 In these conditions, it were drawn the “F-d” capacity curves (where: “F” - Base Shear; “d” - horizontal Roof Displacement) (see Figure 6- Figure 9 and Table 2) in order to establish the absolute spectral accelerations values for this series of RC frame models depending on the performance requirements (objectives) [34-43], [52-53] (see Table 3).

Also, it was obtained the ultimate lateral forces “Fu” and later- al displacement requirements “du” of the structural systems [54], [21-25] (see Table 2) following nonlinear static analyses performed with ATENA software [13-14]. Lateral forces “F*y” and lateral dis- placements “d*y” corresponding to the global yielding mechanism [18-22], [25], were obtained after bilinearization process (method, procedure) [19-20] of the pushover curves for equivalent SDOF sys- tems [53]. Thus, it were established elastic - perfectly plastic fits com- patible with EC8 indications [20] (see Figure 10 - Figure 13) using SPO2FRAG software [55] (where “SPO2FRAG (Static Push-Over to FRAGility) is introduced, a MATLAB® [56] - coded software tool for estimating structure-specific seismic fragility curves of buildings, using the results of static pushover analysis” [53]). In these conditions, it was indicated position of the perfor-
mance requirements (Figure 14 - Figure 17) through “RDR” indica-
tor (Roof Drift Ratio) (see Equation 1) for each “F-d” capacity curve,
establishing the absolute spectral accelerations values (see Table) where: “RDR - Roof Drift Ratio [%]; hi - denotes the height of the i-th storey [m]; Γeff - effective modal participation factor; μ = δmax/δy - displacement ductility (structural ductility) [18]; * Y δ – equivalent SDOF yield displacement [m]” [53]. In current seismic design norms [19-20], [57] and engineer- ing literature [21-25], [52,58] is practiced performance objectives consideration in different forms (with qualitative implications and quantitative enumeration [59]). Thus, five performance objectives are considered in current research (analytical) study (see Table 3). Four performance objectives were considered according to SEAOC recommendations [52]. The fifth limit state, labeled “side- sway collapse”, is added by SPO2FRAG [53,55] when the SPO.

(Push-Over) curve exhibits strength degradation in the form of a negative-stiffness branch (this limit state corresponds to dynamic instability) [53,55] (Table 3). Generation of Target Spectra and Artificial Accelerograms for K_7 Moment Resisting RC Frame Model Depending on Performance Objectives The principal parameters regarding optimal RC frame model determination for target spectra [30-32] generation process with the corresponding artificial accelerograms [27-31] (depending on performance objectives) are:

• “F-d” capacity curves values (with focused attention on the ul- timate lateral displacements “du” and structural yielding dis-placements “d*

y” [19-20], [53]);

• bilinearized curves [19-20], [53];

• “RDR” (%) values for five performance objectives [52-53];

• MR RC frame deformation mechanisms

 [19-25] for either lat- eral loading stage or absolute spectral acceleration values “Sa” (see Table 4). In these conditions, Z_8 MR RC frame model presents optimal results, without inclusion in a legal design norm [19]. Thus, it was performed the generation of the artificial accelerograms [27-31] according to the performance objectives for K_7 MR RC frame model. The analytical process of artificial accelerograms generation [27-31] (in correspondence with performance objectives [52-53]) for K_7 moment resisting RC frame model includes the knowledge of the “normalized elastic response spectrum of absolute accelera- tions for horizontal components of the ground motion with Tc=0.7 s” (according to P100-1 [19] norm - Iasi area) (see Figure 18), in addition to knowing the absolute spectral acceleration values for each performance objective (see Table 4 and Table 5).

Thus, it was calculated (with Equation 3) the absolute acceleration values necessary for target spectra generation and comparison of these values with subsequently PGA values related to generated artificial accelerograms. An important condition in the comparison process is the proximity of the PGA values in Table 6 to the GA values in Table 5, preferably being as PGA>GA.

The elastic response spectrum of absolute accelerations for horizontal components of the site ground motion, Se(T)=Sa(T), is defined according to P100-1 norm [19] (see Equation 2):

Accelerogram sets compatible with target acceleration spectra (Figure 19), it was generated with (using) MSIMQKE software [62-63]. Graphical representation of these artificial accelerograms and their elastic response spectra, was performed through PRISM soft- ware [64] (where: “PRISM® is a free program for seismic response analysis of structures idealized as single-degree-of-freedom systems. The main features of the program include modification of earthquake records, calculation of response time histories of various hysteresis models, and generation of elastic and inelastic response spectra” [65]). In these conditions, it was generated a number of artificial accelerograms (Figure 20 - Figure 24) for K_7 moment resisting RC frame model, depending on performance objectives.

Accelerogram PGA values presented in Table 6, reach the absolute acceleration values enumerated (listed) in Table 5. Elasticspectra of these artificial accelerograms are represented in Figure 25, Figure 26, Figure 27, Figure 28, Figure 29, following the form

Conclusion

In current research practice exist a major necessity for clear methodology regarding required accelerograms consideration for experimental moment resisting RC frame structures/ systems/ prototypes/ models in experimental tests on seismic platforms.

In these conditions, it was presented a method of the input data consideration for the experimental test, have as a reference point the performance objectives necessary to be achieved in terms of the global seismic response of the RC frame structure. Thus, it was considered this form of input data for experimental seismic analysis of the K_7 moment-resisting RC frame model (system). Basically, it can be verified the theoretical considerations in RC seismo-engineering literature through the real seismic response of the reinforced concrete frame structure. If artificial accelerograms cannot be used for any technical reason, it can be used PGA values for a standard lateral loading protocol.

Acknowledgement

None.

Conflict of Interest

This research paper is sponsored by “Gheorghe Asachi” Technical University of Iasi with grant number GI/R16_Drd/2021.

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