Reinforced Concrete Specimens Research Articles

Impact resistance and performance of precast shear walls with various connections under axial and lateral loads

This study conducted pendulum impact tests on three precast concrete (PC) shear wall specimens with various connection types and one cast-in-situ reinforced concrete (RC) shear wall specimen to investigate their behavior under out-of-plane impact loads at a consistent axial compression ratio. The study reported observations on failure patterns, the progression of cracks, the dynamics of impact force over time, relationships between axial force and vertical displacement, deformation behavior, and the strains in concrete and rebars. Through comparative analysis with similar PC columns, the influence of various connections on the impact resistance is analyzed for both shear walls and column specimens. It was found that all PC specimens showed flexural failure modes akin to those of the RC specimen, yet with more extensive cracking and lower stiffness. PC specimens with grouted sleeve connections demonstrated satisfying impact resistance that emulates the performance of cast-in-situ walls. Specimens with grouted corrugated metallic duct connections demonstrated obvious localized damage. Eventually, the study proposes a novel method for rapidly evaluation of the impact resistance of concrete shear walls.

Examination of the stress-strain model for confined concrete considering the impact of corroded spiral bars

To examine the impact of corroded spiral bars on the confinement effect of concrete, a series of dry-wet cyclic accelerated corrosion tests and axial compression tests were performed on 36 RC (Reinforced Concrete) specimens. This study investigated the effects of various factors, including the degree of corrosion in spiral bars, the reinforcement configuration, and the concrete strength grade, on the axial compressive performance of confined concrete. The mechanical behavior of concrete, which was confined by corroded spiral bars, was analyzed by considering the corrosion characteristics, failure patterns, and load-carrying capacity of the specimens. A modified Mander model, which incorporates the influence of corroded spiral bars, was developed. The results indicate that increased corrosion accelerates specimen damage and reduces ductility. Stirrups show pull-off phenomena. A higher stirrup ratio enhances the bearing capacity and deformation capacity of specimen during destruction, while reducing longitudinal reinforcement buckling. Stronger concrete delays vertical cracking, increases bearing capacity, but reduces deformation capacity during destruction. The modified Mander model demonstrates high computational accuracy.

Carbon Fiber Reinforced Polymer (CFRP) for Structural Capacity Enhancement of RC Beams Incorporating Innovative Side Hybrid (SH) Technique

Reinforced concrete (RC) infrastructure is an essential part of modern civilization. However, the serviceability of RC infrastructure in extreme weather has become challenging due to the susceptibility of the initiation of cracks. Hence, the demand for strengthening and retrofitting RC infrastructure is rapidly increasing. The RC specimens strengthened with existing externally bonded reinforcement (EBR) and near-surface mounted (NSM) techniques; however, they suffered a prematurely brittle or debonding failure. Hence, the merging of side near surface mounting (SNSM) and side externally bonded reinforcement (S-EBR) methods ended up resulting in the development of an innovative side hybrid (SH) strengthening approach that is designed to overcome these drawbacks. In this investigation, six rectangular RC beam specimens were flexurally strengthened utilizing carbon fiber-reinforced polymer (CFRP) with the SH technique, and then four-point bending experiments were performed to failure. The beam specimens were categorized into two types: (I) control specimens and (II) specimens strengthened with the SH technique applying CFRP varying bonded length from 1600 mm to 1900 mm. The initial cracking, yield, and ultimate load-bearing capabilities, deflection, failure modes, cracking characteristics, stiffness, energy absorption capacity, and strain on the utmost fiber of concrete, the tensile strain of major steel rebars, SNSM bars, and S-EB plates were assessed from the experimental investigation. The SH technique substantially improved the flexural performance of the beam specimens. The initial cracking load, yield, and ultimate load-bearing capabilities were enhanced remarkably by 387%, 108%, and 163%, respectively, over the reference specimen. The flexural stiffness and energy absorption capacity substantially improved by 120% and 103%, respectively, compared with the reference specimen.

Identification of defects in underground structures using machine learning aided distributed fiber optic sensing

Despite the extensive use of distributed fiber optic sensing (DFOS) in monitoring underground structures, its potential in detecting structural anomalies, such as cracks and cavities, is still not fully understood. To contribute to the identification of defects in underground structures, this study conducted a four-point bending test of a reinforced concrete (RC) beam and uniaxial loading tests of an RC specimen with local cavities. The experimental results revealed the disparity in DFOS strain spike profiles between these two structural anomalies. The effectiveness of DFOS in the quantification of crack opening displacement (COD) was also demonstrated, even in cases where perfect bonding was not achievable between the cable and structures. In addition, DFOS strain spikes observed in two diaphragm wall panels of a twin circular shaft were also reported. The most probable cause of those spikes was identified as the mechanical behavior associated with local concrete contamination. With the utilization of the strain profiles obtained from laboratory tests and field monitoring, three types of multi-classifiers, based on support vector machine (SVM), random forest (RF), and backpropagation neural network (BP), were employed to classify strain profiles, including crack-induced spikes, non-crack-induced spikes, and non-spike strain profiles. Among these classifiers, the SVM-based classifier exhibited superior performance in terms of accuracy and model robustness. This finding suggests that the SVM-based classifier holds promise as a potential solution for the automatic detection and classification of defects in underground structures during long-term monitoring.

Rehabilitation of reinforced concrete slab using ultra high-performance concrete and fiber reinforced polymer

Rehabilitation the flexural capacity of reinforced concrete structures has been the subject of many studies. However, there is currently limited research on repairing such structures using Ultra-High-Performance Concrete (UHPC) and the combination of UHPC with Fiber-Reinforced Polymer (FRP) materials. This article presents the results of an experimental study on the flexural behavior of 4 specimens: 1 specimen of reinforced concrete (RC), 1 specimen strengthened with FRP sheets, and 02 specimens with the same height as the RC specimen but with a replacement of 3 cm of the protective concrete layer with a UHPC layer, either bonded or not bonded to the existing concrete, with or without the reinforcement of FRP sheets. The experimental results of the 4-point bending tests indicate that, while maintaining the height of the RC specimen constant, replacing the protective concrete layer with a UHPC layer and incorporating FRP in the tension zone led to an increase of approximately 83.35% in flexural capacity, with the deflection at the failure stage rising by only 12.8%. This research opens up a new and promising direction for improving and extending the service life of RC bridges using UHPC and FRP

Study on seismic performance of steel fiber reinforced concrete shear walls with hybrid steel strands and HRB400 bars in the boundary elements

The paper proposed a type of reinforced concrete (RC) shear walls both replacing steel bars in boundary elements with steel strands and adding steel fibers. Four specimens, including one RC specimen, one steel strands RC (SRC) specimen, and two SSFRC specimens referred to SRC specimens using SFRC, were designed and tested to investigate the influences of steel strands in the boundary elements and steel fiber volume ratios (SFVRs) on the seismic performance of proposed shear walls. The results showed adding steel fibers could significantly reduce the damage level of shear walls. Both reinforcing steel strands in the boundary elements and using SFRC could efficiently enhance the bearing capacity and resilient capacity of shear walls, and increased with the increasing SFVRs. Compared with RC shear wall, the peak loads of the SSFRC shear walls with 0%, 0.75% and 1.50% SFVRs increased by 15.8%, 27.7% and 34.5%, and the residual displacement of them decreased by 49.3%, 59.0% and 63.1% at 2.00% loading level, respectively. In addition, reinforcing steel strands in the boundary elements significantly reduced the energy dissipation of shear walls, but using SFRC could enhance the energy dissipation. As the SFVRs increased to 1.50%, the final cumulative energy dissipation of SSFRC shear walls was similar to that of RC shear walls. Finally, the calculation methods for cracking load, steel yielding load and peak load of the SSFRC shear walls were proposed, and the acceptable accuracy was verified by comparing the calculated and experimental results.

Quantitative image analysis on the filling proportion of corrosion products in reinforced concrete using X-ray computed tomography

Corrosion-product filling inhibits corrosion-induced cracking in reinforced concrete (RC) structures, thereby affecting structural deterioration. However, the accurate quantification of corrosion-product filling has challenged the scientific and engineering communities. In this study, a novel method for quantifying the filling proportion of corrosion products βF at the macro- and meso-scales using X-ray computed tomography and image segmentation algorithms was proposed. This method was applied to RC specimens exposed to chloride-rich environments and compared with conventional methods. The results showed that conventional quantitative methods underestimated βF owing to a lack of understanding of the corrosion products filling into air voids and the aggregate–mortar interface, and those overflowing from the specimen. A positive correlation between βF and corrosion propagation as well as moisture content in the environment was observed, whereas βF was negatively associated with concrete cover thickness.

Simplified test method for evaluating progressive collapse resistance of precast concrete frame structures

To evaluate the progressive collapse resistance of precast concrete (PC) structures, various test methods have been used in existing experimental studies. However, verification of whether the progressive collapse resistance can be evaluated equivalently by different test methods has been limitedly investigated. In this study, three simplified and three half-frame test specimens were tested under monotonic vertical loading to investigate the effects of the test method on their progressive collapse resistance. As the test parameters, types of test specimens (i.e., sub-frame, simplified, and half-frame specimens), and joint details (i.e., reinforced concrete (RC) continuous joint, PC with continuous joint, and PC with pinned joint) were directly compared. The test results showed that the progressive collapse resistance was primarily affected by the overall lateral stiffness of the exterior columns (Kh) rather than the test setup. When Kh increased in the simplified specimens, the axial force transferred by the beams increased, resulting in an increase in the peak strength (PCAA). Further, the effect of Kh on the peak strength was greater in PC specimens with pinned joints than in RC and PC specimens with continuous joints. To investigate the effect of Kh on the PCAA, a parametric study was conducted using the existing CAA strength model. The parametric study results also indicated that the relationship between the increase in Kh and PCAA was not significantly governed by the test setup for the same joint details. These results indicated that various simplified test methods can be used to evaluate the progressive collapse resistance of PC structures when an adequate range of Kh is provided. Based on the test and parametric study results, recommendations for progressive collapse tests were discussed.

Exploring chloride-induced corrosion in reinforced concrete structures through embedded piezo sensor technology: an experimental and numerical study

Corrosion of steel in concrete is one of the major problems with respect to the durability of reinforced concrete (RC) structures. Thus, monitoring the corrosion in real-time is essential to prevent structural damage. However, one of the main challenges is to simulate the real-time development of corrosion in the RC structure. In recent years, smart aggregates, also called embedded piezo sensors (EPS), have become increasingly popular for monitoring localized and corrosion damage in RC structures using electro-mechanical impedance (EMI). This paper presents the experimental and numerical investigation of corrosion in RC structures subjected to the chloride-laden environment using EPS via the EMI technique. To fulfil this objective, the study has been carried out in two stages such as; in the first stage, the experiments are conducted on the RC specimen, and the EMI response was obtained both in a pristine state and when accelerated corrosion progressed. In the second step, a numerical model of the RC specimen has been developed based on the experimental data in the COMSOL software, and the effect of corrosion in the form of varying mass loss percentages has been simulated. Based on the results, it is concluded that the experimental and numerical conductance signatures before and after corrosion are matched. The deterioration in terms of stiffness loss in the RC specimen was 18.20% at 30% mass loss.

Simulation of the degraded (steel - concrete) bond strength due to corrosion via modeling pull out tests

Steel corrosion is recognised as major degradation factor of structural capacity and durability of reinforced concrete (RC) structures, especially in marine environment. RC structures with corroded reinforcement present reduced performance due to loss of the cross-sectional area of reinforcement, cracks in concrete and loss of bond between steel and the surrounding concrete. In the present study, simulation of the degraded bond strength on corroded RC elements was elaborated developing a three-dimensional (3D) model through finite element analysis (FEA) in ABAQUS, taking into account the recommendations of fib Model Code 2010. As a basis for the model validation, an existing experimental study on the effect of corrosion and stirrups spacing on bond behavior was considered. In the abovementioned study the bond mechanism of two groups of corroded RC specimens in confined (stirrups Φ8/120mm) and unconfined (without stirrups) conditions were examined upon the completion of eccentric pull-out tests. In order to model the complex conditions of the corroded steel-concrete interface, the cohesive behavior was adopted by appropriately modificated parameters, for each corrosion level. The bond-slip curves extracted from the developed model were shown to be in a good agreement with the relevant experimental results. In particular, the bond strength of confined RC specimens deviates at about 10% among the analytical and experimental outcomes, for both uncorroded and corroded conditions up to 8.3% corrosion level. In case of the unconfined specimens, the bond strength prediction was satisfactory up to 5% corrosion level, whereas for greater corrosion level, large deviation was observed. Regarding the prediction of the relative slip between steel and concrete, further investigation is required as the development of slip is influenced by a plethora of factors.

Study on Corrosion Monitoring of Reinforced Concrete Based on Longitudinal Guided Ultrasonic Waves

The corrosion of reinforced concrete (RC) is one of the most serious durability problems in civil engineering structures, and the corrosion detection of internal reinforcements is an important basis for structural durability assessment. In this paper, the appropriate frequency required to cause excitation signals in the specimen is first analyzed by means of frequency dispersion curves. Subsequently, the effectiveness of five damage indexes (DIs) is discussed using random corrosion in finite elements. Finally, guided ultrasonic wave (GUW) tests are conducted on reinforcement and RC specimens at different corrosion degrees, and the test results are verified using a theoretical corrosion model. The results show that the larger the covered thickness is at the same frequency, the higher the modal order of the GUW in the frequency dispersion curve is, and the smaller the group velocity is. The SAD is the most sensitive to the corrosion state of the reinforcement compared with the other DIs, and it shows a linear increasing trend with the increase in the corrosion degree of the reinforcement. The SAD values of the RC specimens showed a three-stage change with the increase in the corrosion time, and the time until the appearance of corrosion cracks was increased with the increase in the covered thickness. It can be seen that increasing the covered thickness is an effective method to delay the time until the appearance of corrosion cracks in RC specimens.

Modelling and Simulation of the Strength Properties of Ultra-High Performance Fiber Reinforced Concrete Specimens

The strength performance of UHPFRC with micro and hooked-ends steel fibers was studied in this paper using Finite Element (FE) modelling and simulation. The specimens were modelled in geometry, material, constraints, load and boundary conditions using ABAQUS package and dynamic explicit analysis was used to investigate the crack pattern, failure mode and stress-stain behaviour of the UHPFRC specimens when subjected to uniaxial compression and tension loading. Results from the FE simulation revealed that the surfaces of the UHPFRC specimens were still in good shape after attaining their ultimate resistance against compression and tension loading. The UHPFRC’s ultimate compressive strength of 260N/mm2 was just 7% higher than the experimental compressive strength. The UHPFRC exhibited both linear compressive stress-strain behaviour up to 89% of its peak strength and non-linear stress-strain behaviour with strain hardening and strain softening phases. Further findings also showed that the UHPFRC despite having ultra-high tensile strength did not undergo strain hardening phase as the vertical direction stresses were mainly distributed around the loaded section of the specimen. The FE UHPFRC models’ strength in compression and tension only has slight and negligible variations from the experimental strengths. The deformation and strength performance of the FE specimens are in perfect agreement with the experimental specimens. Therefore, FE modelling and simulation can be used as a reliable method of carrying out extensive studies on UHPFRC properties and performances.

Autonomous detection of steel corrosion spatial variability in reinforced concrete using X-ray technology and deep learning-based semantic segmentation

Correctly determining the spatial distribution of steel corrosion within a structural member is critical for estimating the remaining service life of deteriorating reinforced concrete (RC) structures. While X-ray technology serves as a nondestructive inspection method, existing challenges persist, particularly in semi-automated corrosion boundary detection. This paper describes a deep learning-based semantic segmentation framework to autonomously detect X-ray images associated with RC, facilitating the visualization of nonuniform steel corrosion distribution. X-ray images were collected from a comprehensive experiment using RC specimens with various structural details by two accelerated corrosion methods. Four deep learning models were constructed, trained, and compared based on the database containing the original X-ray images and the corresponding pixel-level labels. The results demonstrate that the proposed autonomous detection method can segment uncorroded steel at a very high level of global accuracy without time-consuming work, outperforming traditional methods in terms of both accuracy and efficiency.

Experimental study on seismic behavior of RC beams confined by corroded stirrups

PurposeTo understand the seismic behavior of reinforced concrete (RC) beams confined by corroded stirrups, low-reversed cyclic loading tests were carried out on seven RC beam specimens with different stirrup corrosion levels and stirrup ratios to investigate their mechanical characteristics.Design/methodology/approachThe failure mode, hysteresis behavior, skeleton curves, ductility, stiffness degradation and energy dissipation behavior of RC specimens are compared and discussed. The experimental results showed that the restraint of concrete provided by corroded stirrups is reduced, which leads to a decline in seismic performance.FindingsFor the specimens with the same ratios of stirrup, as the corrosion level increased, the load-carrying capacity, stiffness, plastic deformation capacity and energy-dissipation capacity dropped significantly. Compared with the uncorroded specimen, the failure modes of specimens with high corrosion level changed from ductile bending failure to brittle failure. For the specimens with the same levels of corrosion, the higher the stirrup ratio was, the stronger the restraint effect of the stirrups on the concrete, and the seismic behavior of the specimens was obviously improved.Originality/valueIn this paper, a total of seven full-size RC beam specimens at joints with different stirrup corrosion levels and stirrup ratios were designed and constructed to explore the influences of corrosion levels and stirrup ratios of stirrups on the seismic performances. The failure modes, strain of reinforcement, hysteretic curves, skeleton curves, stiffness degradation and ductility factor of RC specimens are compared and discussed.

Effects of sustained load and reinforcement spacing on the evolution and spatial characteristics of corrosion damages in RC segmental specimens

Because of the combined actions of sustained load and corrosive agents, premature steel corrosion and rapid material deterioration can be extensively observed in the reinforced concrete (RC) shield tunnels in an aggressive environment. Such a degradation accompanies with diverse corrosion damages in segmental lining, such as nonuniform steel corrosion and crisscrossed cracks on concrete surface, which shall be exacerbated due to congested steel arrangements and complex stress states in segment. In this paper, a corrosion-accelerated experiment on RC specimens in a tunnel segment was conducted by employing galvanostatic method and a designed loading system. Multiple rebars with different spacing distances were considered in two types of RC specimen. Deterioration damage evolution of RC specimens, including deterioration deformation and surface cracking patterns, has been investigated with an emphasis on the influence of sustained load and interaction of corroded rebars. Both visual inspection and distributed optical fiber sensing technology were applied to track the surface concrete cracking of bearing specimens. Meanwhile, the spatial variability of steel corrosion in bearing specimens was elaborated. The impacts of applied tensile load and reinforcement spacing on the spatial correlation of steel corrosion in longitudinal and transverse directions of rebars were experimentally illustrated. The experimental findings can help in improving the probabilistic model associated with nonuniform steel corrosion of several spaced rebars in tension and identifying the extent of corrosion damages in the load-bearing RC segments.

Corrosion damage detection in reinforced concrete using Rayleigh wave-based method

Corrosion of reinforcing bars is a dominant cause of degradation of reinforced concrete (RC) structures. Over time, expansive products of corrosion build up tensile stresses within the concrete, leading to cracks on the exterior surface and spalling of concrete cover. To extend the service life of RC structures, a reliable non-destructive inspection method is required to detect and evaluate corrosion-induced internal cracks in concrete before spalling, so that timely repair can be conducted. Ultrasonic Rayleigh waves have been employed to detect near-surface cracks in concrete based on their transmission coefficient in frequency domain or their time-of-flight information. However, due to heterogeneity of concrete materials, the ill-defined Rayleigh wave component and the sensor coupling on the rough surface of concrete have a significant influence on accuracy of the method. In this study, an improved method using Rayleigh waves has been investigated to detect corrosion-induced internal cracks in concrete. In the method, energy spectrum of the Rayleigh wave is analysed using the continuous wavelet transform and correlated to locations of internal cracks. This method is not sensitive to surface roughness of concrete members and does not need accurate identification of the Rayleigh wave components. Performance of the method was examined using corroded RC specimens with different cover depths and aggregate sizes. As a comparison, electrochemical tests were performed to map the corrosion current density. The test results showed very good agreement with the corrosion damage map generated from the proposed Rayleigh wave-based method.

Steel corrosion in precast reinforced concrete column-beam joint with grouted sleeve connections under chloride-rich environment

Due to the existence of pump and vent holes, precast reinforced concrete (RC) structure with grouted sleeve connections may have serious durability issues, which have almost never been studied. In this paper, a precast RC column-beam joint specimen with grouted sleeve (GS) connections, as a comparison of a cast-in-place specimen, was exposed to chloride-rich environments for 4 years. The steel corrosion and its impacts on specimen were investigated by visual inspections, X-ray computed tomography (X-ray CT) and data analysis. The test results showed that the precast RC specimen exhibited porous and loose interfaces between PVC tubes, sleeve and cement-based materials within the GS connections, leading to more severe stirrup corrosion compared to the cast-in-place specimen. In contrast, the sleeve, grouting material and their interfaces were dense so that the longitudinal bars inside had been well protected. Besides, the chloride diffusion coefficient of concrete cover in the two specimens were quantified. The corrosion level of precast RC structures with GS connections was found to grow more rapidly versus service year. On this basis, several precautions for alleviating the negative impact of GS connections on steel corrosion were proposed.

Shear design and life cycle assessment of novel limestone calcined clay cement reinforced concrete beams

AbstractTo reduce the impact on global warming, many countries and regions are advocating the use of low‐carbon and green supplementary cementitious materials (SCMs) to improve the cement industry. This study investigates the shear behavior of reinforced concrete (RC) beams made with a novel green concrete, limestone, calcined clay, and cement clinker (LC3). Full‐scale shear tests were conducted on RC and LC3‐RC beams to evaluate their fundamental behavior for structural applications. The shear resistance of LC3 concrete beams was evaluated using Chinese, American, and Eurocode codes, while carbon emission and environmental impact were analyzed by life cycle assessment (LCA). Results showed that LC3‐RC and RC beams exhibited similar shear behavior in terms of crack initiation, propagation, and development. The increase in concrete strength improved the stiffness of LC3‐RC specimens, while RC specimens remained unchanged. The ductility of RC specimens was inversely proportional to concrete strength, while LC3‐RC beams exhibited optimal ductility. The increase in stirrup ratio significantly improved the shear resistance of both LC3‐RC and RC beams. With increased shear‐span ratio, the failure mode of LC3 specimens improved, changing from diagonal‐compression to shear compression or diagonal tension failure. The shear resistance of both LC3‐RC and RC beams was underestimated by GB 50010‐2010, ACI 318‐19, and Eurocode 2. LC3 concrete significantly reduced energy consumption and carbon emissions and achieved favorable environmental benefits in terms of GWP, PMFP, POFP, TAP, and TETP. Increasing usage of limestone in LC3 may further decrease environmental potential without sacrificing mechanical properties. The findings of this study contribute to the development of sustainable and environmentally friendly structures in engineering.

Experimental and analytical studies on shrinkage and creep behavior of RC walls and prisms

AbstractA component level experimental study has been carried out on four reinforced concrete (RC) walls subjected to a sustained compressive load for a period of 1 year and shrinkage tests on 10 prisms under ambient environmental conditions. Two extreme longitudinal reinforcement percentages and two grades of concrete were considered and their influence on the time‐dependent behavior studied. It was observed that both longitudinal percentage of steel and concrete grade have a significant influence on the time‐dependent strains. The evolution of time‐dependent strain in RC member was also predicted, adequately accounting for the effect of reinforcement, using a theoretical model which can employ any linear viscoelastic constitutive law for concrete and a linear elastic constitutive law for reinforcing steel. The ACI 209 and fib MC 10 recommendations for creep and shrinkage of plain concrete have been used for the prediction of long‐term strains. It is demonstrated that the analysis predicts the time‐dependent strains reasonably well (with a statistical mean deviation error of 1.16 and 1.00) for the creep tests on RC walls, when the compliance function proposed by ACI and fib is used. However, in the case of shrinkage tests, the accuracy with both ACI and fib models was limited (1.64 and 1.66, respectively). It is further demonstrated that by suitably recalibrating the compliance and shrinkage parameters in both ACI and fib models, the accuracy of shrinkage prediction in the companion RC specimens improves significantly with mean deviation error of 1.07 and 1.05 for ACI and fib models, respectively.

Assessing the performance of subspace-based modal identification procedures for systems subjected to structural damage and Coulomb-friction non-linearities

In this paper, the robustness of subspace-based identification methods for modal analysis is assessed for damaging systems including local Coulomb-friction mechanisms (or equivalently elasto-plasticity). The underlying objective is to capture damage-induced modal feature changes of structures, mainly frequency drop-off and damping increase, knowing that the presence of components with participating friction forces also affects modal signature. The performance of several modal detection procedures is assessed using the data acquired during the JVP (french for ‘Jonction Voile-Plancher’) test campaign during which a reinforced-concrete specimen, anchored to a shaking table by the means of swivels, is submitted to several kind of ground motion inputs of varied level. A comparison between Input/Output versus Output-Only identification is made using both seismic and broad-band random inputs and the potentialities of the modal selection procedures are highlighted for different cases where the two kind of non-linearities (damage occurrence and friction at swivels) are activated in different proportions. Regarding the presence of friction forces when conducting modal analysis, experimental results are backed up by a numerical study that enables a theoretical quantification of the apparent frequency and damping ratio values that should be expected after modal analysis for varied input-to-nonlinear forces ratios.