Lateral Stiffness Research Articles

Quay Quarter Tower, Sydney – conservation, life extension and upgrade using live digital twinning

This article describes the feasibility studies, investigations, analysis, structural health monitoring, digital twinning, and structural adequacy verification of the repurposed 50-storey Quay Quarter Tower in Sydney, Australia. The design life of the retained building was extended by 50 years with minimum structural intervention. The adaptive reuse increased the net lettable area from 45 000m2 to 90 000m2. The 45-year-old retained components provided structural integrity for the accelerated construction programme and 80% of the lateral strength and stiffness with minimum intervention for the upgraded building. The digital twinning technology facilitated safe and speedy construction and conserved 12 079t of embodied carbon, with a carbon footprint for the gross internal area of 247kgCO2e/m2. The innovative engineering processes enabled the client, AMP, to achieve its aspirations for a unique world-class commercial building using a comprehensive approach to reducing embodied and operational carbon.

Seismic Behavior of an Inter-story Hinged Lateral Resistance Braced Frame

Based on the deflection behavior of structural components occurring at the lateral deformation of moment frames, a new lateral force-resisting system, the R-BRACE Frame (RBF) system, was proposed. This system is capable of effectively limiting the inter-story drift response of tall buildings. An evaluation was conducted using the finite element method program SAP2000 to simulate the internal force distribution and deformation of the system. The equivalent lateral force procedure (ELFP), the capacity spectrum method (CSM), a linear time-history analysis and the pushover method were applied to assess the yielding mechanism of the structure under different earthquake intensity levels. The findings revealed that the sub-unit, referred to as an R-BRACE, had a major impact on improving a structure's lateral stiffness. The placement of R-BRACE units could guarantee controllable stiffness degradation and enhanced seismic ductility, but would not alter the vertical load transfer path of the initial structure, which makes the RBF system an ideal option for seismic retrofitting. KEYWORDS: Lateral force-resisting system, R-BRACE frame, Enhanced lateral stiffness resistance, Seismic ductility

Lumped Plasticity Model and Hysteretic Performance of Ultra-High-Performance Concrete Rocking Pier.

Rocking piers using ultra-high-performance concrete (UHPC) have high damage-control capacity and self-centering characteristics that can limit the post-earthquake recovery time of bridges. To study the hysteretic behavior of UHPC rocking piers, a lumped plasticity model is proposed that comprises two parallel rotational springs and which can accurately calculate their force-displacement hysteretic behavior. Three states of the rocking piers, decompression, yield, and large deformation, are considered in this study. The model is verified based on existing experimental results, and the hysteretic characteristics of the UHPC rocking piers, such as strength, stiffness, and energy dissipation, are further analyzed. The research results show that the lumped plasticity analysis model proposed in this study can predict the force-displacement hysteretic behavior of the rocking piers accurately. Moreover, the hysteretic performance of the UHPC rocking piers is better than that of rocking piers using normal-strength concrete. An increase in the energy dissipation reinforcement ratio, pre-stressed tendon ratio, and initial pre-stress improves the lateral stiffness and strength of the UHPC rocking piers. However, the increase in the pre-stressed tendon ratio and initial pre-stress reduces their energy-dissipation capacity.

Experimental testing of post-tensioned steel-timber hybrid frames equipped with energy-dissipating braces

The weak properties of wood in perpendicular-to-grain direction have imposed significant design challenges for post-tensioned (PT) timber frame structures. To resolve the challenges, the authors of this study have introduced a novel solution, the steel-timber hybrid PT frame. To further enhance its lateral performance, additional damping and stiffness (ADAS) braces were integrated into the hybrid frame. In this study, the feasibility of the combination was experimentally examined at the system level. Cyclic tests were conducted to evaluate the performance of two 2/3 scaled frame specimens: a conventional PT timber frame and a PT steel-timber hybrid frame with ADAS braces. The combination of a hybrid frame with ADAS braces showed substantial enhancements in lateral strength, initial stiffness, system ductility, and energy dissipation compared to the conventional PT timber frame. The experimental results highlighted the significant role of ADAS braces in enhancing energy dissipation, while their contribution to stiffness was less dominant. Analytical analysis further revealed an inverse relationship between the increase in ADAS contribution to lateral stiffness and the self-centering competence of the frame. A design equation was proposed to assist practitioners in achieving an optimal balance between the self-centering capacity of the PT hybrid frame and the stiffness enhancement provided by ADAS braces.

Experimental study on seismic performance of frame with steel-hollow core partially encased composite spliced beam

This paper conducted design and experimental study on frame specimen equipped with steel-HPEC (Hollow-core partially encased composite) spliced beams (SHS beam in short). SHS beams are comprised of two bare steel beams and an HPEC beam with thinner flange plates, present similar deformation and bearing capacity to traditional I-shaped steel structure, in addition to the benefits of good lateral stiffness and steel saving. Lateral low-cyclic loading tests were conducted on a bare steel frame and a frame with SHS beams to investigate their failure modes, seismic performance, and evaluate the feasibility of implementing SHS beams in frame structures. The frame specimen with SHS beams exhibited similar failure modes as those observed in steel frame specimen. Due to the higher stiffness of SHS beams, which effectively limited out-of-plane deformation in frame, SHS beam frame presented higher initial lateral stiffness, ultimate bearing capacity and energy dissipation capacity when contrast with bare steel frame. For calculations, SHS beams could be construed as stepped beams with variable rigidity. Finally, the calculation methods and formulas for initial lateral stiffness and ultimate bearing capacity of both the frames with SHS beams and bare steel frames were proposed, and the calculated results agreed well with the experimental values.

Behavior of a Multi-Story Steel Structure with Eccentric X-Brace

Eccentrically Braced Frames (EBFs) outperform moment-resisting frames in seismically active regions because of their strength, stiffness, energy dissipation, and ductility. Conventional bracing systems, such as X, Y, V, or K types, are utilized to enhance structural integrity. This study employs computational modelling to analyze multi-story steel buildings featuring an eccentric X-brace system. In this investigation, 120 multi-story steel frame buildings were selected. These multi-story structures comprise six-, nine-, and twelve-story geometries. ETABS built a full-scale FE model of multi-story structures. The study's parametric variables are the X-brace eccentricity, steel X-brace section size, and X-braced placement. Steel X-braces may have an eccentricity of 500, 1000, or 1500 millimeters. The ETABS model was validated when its findings matched experimental data. According to the data, the eccentric X-brace increases top-story displacement more for 6-story multi-story structures than for 9- and 12-story ones. Eccentric X-braces reduced lateral stiffness, allowing more significant floor movement. Eccentric and diagonal braces offer less lateral rigidity than concentrically braced frames due to their flexibility. Eccentricity reduces stiffness, even if the X-braced component has a larger cross-section. EBFs may migrate horizontally. Since the EBF absorbs more energy, changing the X-brace section size and eccentricity affects its ductility.

Dynamic Response of an Elastic Tube-like Nanostructure Embedded in a Vibrating Medium and under the Action of Moving Nano-Objects

In recent years, researchers have looked at how tube-like nanostructures respond to moving loads and masses. However, no one has explored the scenario of a nanostructure embedded in a vibrating medium used for moving nano-objects. In this study, the governing equations of the problem are methodically derived using the nonlocal elasticity of Eringen as well as the Rayleigh and Reddy–Bickford beam theories. Analytical and numerical solutions are developed for capturing the nonlocal dynamic deflection of the nanostructure based on the moving nanoforce approach (excluding the inertia effect) and the moving nanomass approach (including the inertia effect), respectively. The results predicted by the established models are successfully verified with those of other researchers in some special cases. The results reveal that for low velocities of the moving nano-object in the absence of the medium excitation, the midspan deflection of the simply supported nanotube exhibits an almost symmetric time-history curve; however, by increasing the nano-object velocity or the medium excitation amplitude, such symmetry is violated, mainly due to the lateral inertia of the moving nano-object, as displayed by the corresponding three-dimensional plots. The study addresses the effects of the mass and velocity of the moving nano-object, amplitude, and frequency of the medium excitation, and the lateral and rotational stiffness of the nearby medium in contact with the nanostructure on the maximum dynamic deflection. The achieved results underscore the significance of considering both the inertial effect of the moving nano-object and the shear effect of stocky nanotubes embedded in vibrating media. This research can serve as a strong basis for conducting further investigations into the vibrational properties of more intricate tube-shaped nanosystems that are embedded in a vibrating medium, with the aim of delivering nano-objects.

Performance and strength analysis of shear walls with vertical steel encased profiles under tensile-shear load

This study investigates the behavior of composite steel reinforced concrete (SRC) walls under tension-shear (TS) coupled stress state during earthquakes. Quasi-static tests on five SRC shear walls with a shear span ratio of 1.42 were conducted. The experimental results demonstrated that the SRC shear wall retained its high shear capacity and good ductility in shear failure mode. The stiffness analysis revealed that the concrete provided most axial stiffness before cracking but gradually withdrew from the work as the cracks developed and extended rapidly in the tension loading phase. And the effective lateral stiffness was approximately 10%–15% of the elastic lateral stiffness. Parametric analysis was conducted on the shear capacity, including the axial tensile ratio, steel profiles content, concrete strength grade, and horizontal distributed bar diameter. Additionally, the predictive formulas for the shear capacity in the codes of various countries were compared. It was found that the European and American code inadequately predict the shear capacity of specimens, and the Chinese code has higher safety. These findings can provide references for the practical engineering applications of SRC shear walls in earthquake-prone regions.

Comparing the mechanical characteristics between leg lengthening using only an Ilizarov external fixator and leg lengthening over a nail using an external fixator manufactured in Vietnam.

The mechanical characteristics of leg lengthening over a nail (LON) using an external fixator are not well known; specifically, the number of rings and K-wires required for this method has not been determined. This study aimed to compare the mechanical characteristics of leg LON using the simplest configuration for a domestic frame and those of leg lengthening using the Ilizarov frame alone. The mechanical characteristics of cow tibial samples for lengthening over an intramedullary nail in combination with a domestic external fixator (LON samples) and for lengthening with the Ilizarov frame (Ilizarov samples) were evaluated by assessing axial compression, bending load, and torsional load. The research indices were compression stiffness, bending stiffness, torsion stiffness, yield axial load, ultimate axial load, yield bending load, and ultimate bending load. No statistically significant differences were observed in the compression stiffness, ultimate axial load, bending stiffness, and ultimate, yield bending forces between the Ilizarov samples and LON samples. The compressive stiffness, yield axial load, and ultimate axial load of the LON samples were 98 ± 1.31 N/mm, 915 ± 23.89 N, and 1032 ± 29.86 N, respectively. The anterior-posterior bending stiffness and lateral bending stiffness of the LON samples were 122.48 ± 2.92 N/mm and 116.34 ± 3.95 N/mm, respectively. The yield anterior-posterior bending and ultimate anterior-posterior bending forces of the LON samples were 616.4 ± 3.64 N and 753.2 ± 3.49 N, respectively. The yield lateral bending and ultimate lateral bending forces of the LON samples were 624.6 ± 4.04 N and 759.0 ± 3.39 N, respectively. The axial torsional stiffness of the LON samples was 1.73 ± 0.05 N m/°, which was significantly lower than that of the Ilizarov samples (2.63 ± 0.03 N m/°). No statistically significant differences were observed in the mechanical fixation characteristics of axial compression and bending between the Ilizarov samples and LON samples. However, the axial torsional stiffness of the Ilizarov samples was statistically greater than that of the LON samples. We recommend using the simplest configuration for domestic frames in combination with LON for limb lengthening. Partial weight-bearing is permitted in the distraction stage. Case-control study.

Effect of Soil-Structure interaction on energy dissipation and shock absorption of swing column control devizce

The role of the bridge piers is mainly to bear the load of the superstructure and transfer the load to the foundation. Excessive lateral displacement of the bridge piers under earthquake action can lead to the overall destruction of the bridge structure. In this paper, an improved Swing Column Control Device (SCCD), which is mainly composed of a swing column and Tuned Viscous Mass Damper (TVMD), is proposed to improve the lateral movement stiffness and energy dissipation capacity of the bridge piers and protect the bridge structures from damage under external loads (seismic waves and wind loads). The impact of Soil-Structure Interaction (SSI) on the energy dissipation and shock absorption of the SCCD is not negligible due to the large mass of inertia coming from TVMD. To verify the correctness and effectiveness of this control strategy, based on the theory of elastic half-space and swing-rotation model, the motion equation of the bridge piers with SCCD was established and solved by programming. The case study provided in this paper shows that the bridge pier with SCCD installed on a rigid foundation has a significant absorbing vibration under unidirectional seismic wave. The displacement reduction rate of SCCD for bridge piers built on flexible foundations (category Ⅱ sites) ranges 10% to 16%, even with partial enlargement of displacements on other types of sites. The effects of SSI have weakened the absorbing vibration effect of bridge pier with SCCD constructed on flexible foundations. Therefore, it is necessary to consider SSI when using SCCD to strengthen the bridge piers. Another interesting finding in this paper is that flexible foundations also reduce the displacement response of the superstructure, but the acceleration response of the superstructure is affected by the nature of the seismic waves demonstrating the reverse absorbing vibration.

Seismic behavior of reinforced concrete slender walls subjected to variable axial loads

Reinforced concrete (RC) shear walls are the major lateral load-carrying structural components in high-rise buildings. Under strong earthquake motions, the axial loads of RC walls are not constant axial compression, but may be in tension, resulting in the axial load of RC walls varying from compression to tension. In this study, three RC slender wall specimens (shear-to-span ratio λ = 2.0) were tested to study the effect of the fluctuating range and loading patterns of variable axial forces on their cyclic behavior, including failure modes, hysteretic response, strength and deformation capacity. Test results indicated that the final failure of RC slender walls subjected to variable axial forces was controlled by flexural failure in the compressive-flexural direction. The hysteretic curves of RC slender walls were asymmetric and substantively different from the hysteretic curves of RC slender walls with constant axial loads. The fluctuating range of axial forces had a limited influence on the shape of hysteretic curves, while the loading patterns significantly changed the shape of these hysteretic curves. Under the variable axial forces, the lateral strength and deformation capacity of RC slender walls depended on the fluctuating range of axial forces, while loading patterns had limited influence when the fluctuating range of axial forces kept constant. The loading patterns had a limited influence on the lateral stiffness of RC slender walls, while the increase of fluctuating range of axial forces increased the difference between compressive-flexural and tensile-flexural lateral stiffness. No matter in tensile-flexural or compressive-flexural directions, the assumption that the wall section remains plane after deformation is suitable for RC slender walls under the variable axial forces, and enables reasonable estimations of yielding and peak strength. Finally, a finite element model was developed for predicting the cyclic behavior of RC walls under the variable axial loads.

Dynamic model, performance analysis and evaluation of frame-distributed rocking-core tube structure

To obtain adequate lateral stiffness for frame-core tube (FCT) structures, the core tube area proportion is often increased and/or overly reinforced which often limits the layout flexibility and economy of the structure. A new high-rise configuration named frame-distributed-core tube (FDCT) is proposed to reduce the tube area proportion of the FCT structure. Combined with a rocking system, the frame-distributed rocking-core tube (FDRCT) structure is further proposed, which aims to reduce the damage caused by soft-stories due to by the weakening of the stiffness of the FDCT structure. Simplified models are built, and the structural dynamics are derived based on the Lagrangian equation. Through numerical simulation of three structures under ground motions, it is shown that the FDRCT structure has good energy dissipation and damping performance. The inter-story drift ratios of the structure decreases with the increase of the distributed rocking tubes mass. Under different site conditions and long-period ground motions, numerical simulations and shaking table tests show that the distributed rocking tubes can effectively reduce the structural response and improve the seismic performance. The FDRCT configuration gives better damping performance under long-period ground motions. A performance-profit evaluation shows that the proposed high-rise structure system of FDRCT provides a safe and cost-effective design solution.

Shake table tests to compare the seismic response of concrete frames with conventional and high‐strength reinforcement

AbstractReported test results suggest reinforcement grade can have an important effect on the seismic displacement demands of reinforced concrete (RC) structures. Two one‐story one‐bay RC frames (Specimens C1 and H1) were mounted in parallel on the NCREE‐Taiwan shake table and simultaneously subjected to 16 base motions, each representing a horizontal component of recorded earthquakes. The dynamic tests were followed by quasi‐static large‐amplitude cyclic testing. The specimens had the same nominal dimensions and base shear strengths with longitudinal reinforcement that was Grade 60 (60 ksi [420 MPa]) in C1 and Grade 100 (100 ksi [690 MPa]) in H1. Maximum drifts of H1 were 1.3 to 2.3 times larger than for C1. The lateral stiffness of H1 was consistently lower than C1, with stiffness ratios (H1 to C1) ranging from 0.78 after Run 1 to 0.45 after Run 16. Drift estimates using stiffness values based on gross‐section properties provided a reasonable upper bound for C1 but were unconservative for H1. Drift estimates based on the secant‐to‐yield stiffnesses, which were inversely proportional to reinforcement grade, provided an upper bound for both specimens. Preliminary recommendations are made for accounting for these effects in design.

Introducing a multi-layer pendulum isolator and investigating its effect on structures' responses during some earthquakes

To protect structures from earthquakes, various systems called base isolation are used, which reduce the force applied to the structure during ground movement by reducing the lateral stiffness of the structure. This makes the structure follow the movement of the earth, but softly and with a delay in response. In this research, an isolator with a new shape is proposed without having permanent displacement, similar to a pendulum, and can be used as an isolation system in structures. This system is called a multi-layer pendulum isolator. The system has the same period as a tall pendulum but is much smaller in size. The equations of the isolator were derived and solved by MATLAB software. Examples of frames were modeled in Abaqus under several earthquakes, and the responses of the system were obtained. Results showed that the proposed isolator reduced acceleration, drift, and base shear very effectively. For example, by using a multi-layer pendulum isolator in a six-story frame, it was found that the base shear and drift created in the first floor were reduced by more than sixty percent. The multi-layer pendulum isolator introduced showed that it was an efficient isolator system capable of reducing the destructive effects of an earthquake. The results of the system responses showed that the system reduced the maximum acceleration of the earthquake by more than seventy percent. The results of the FFT analysis showed that by using a suitable damper with a damping coefficient of more than ten percent, no resonance would occur in the system. Two different heights of the multi-layer isolators were compared. It was shown that for the isolator with a height of eighty centimeters, about twice as much material was used as for the isolator with a height of forty centimeters, but no significant improvement was observed in the results.

Investigating the deformation characteristics of balloon-type CLT shearwall

Balloon-type cross-laminated timber (CLT) shearwalls represent a valuable alternative to traditional platform-type construction for use as lateral load resisting systems in mid-rise mass timber buildings. Limited information is available on the behaviour of balloon-type shearwalls, and the system is not included in design codes and standards. The research aims to investigate the lateral deformation contribution and kinematic behaviour of balloon-type CLT shearwall system. A simplified analytical model to establish the lateral displacement of shearwalls is presented and discussed. The methodology involves a validated finite element model, and the result of sensitivity analysis is used to develop the analytical model. The study revealed that the stiffness of hold-downs and vertical joints, and aspect ratio of panels and vertical loads are contributing factors influencing lateral stiffness. The proposed analytical model was verified against 45 cases implemented in numerical models yielding an average error in the prediction of top lateral displacement of less than 4.7%.

Impact of lower muscle stiffness on ankle dorsiflexion restriction in children with cerebral palsy evaluated using ultrasound elastography

BackgroundPlantar flexor muscles always contribute to limiting the range of motion of ankle dorsiflexion in children with spastic cerebral palsy, but the individual contributions of these muscles are not well defined. This study aimed to identify which muscles' stiffness impacts the dorsiflexion range of motion in children with cerebral palsy. MethodsTwenty-five children with cerebral palsy were included. The maximum passive dorsiflexion range of motion was measured in two positions: hip and knee joints in flexion, and both joints in full extension. Strain ratios indicating muscle stiffness were measured using strain elastography of the lateral and medial gastrocnemius, soleus, flexor hallucis longus, peroneus longus, peroneus brevis, and tibialis posterior muscles. To analyze which muscles impact the limitation of the dorsiflexion range, multiple regression analyses were conducted. The values of muscle stiffness were included as independent valuables, and the values of the dorsiflexion range were included as dependent valuables. A p-value <0.05 was considered statistically significant. FindingsIn the analyses, the soleus and flexor hallucis longus muscle stiffness were significant independent factors for the dorsiflexion range of motion of hip and knee flexion (adjusted R2: 0.50). The lateral gastrocnemius muscle stiffness was a significant independent factor for the dorsiflexion range of motion with both joints in full extension (adjusted R2: 0.61). InterpretationFlexor hallucis longus muscle stiffness, in addition to triceps surae muscle stiffness, was shown to impact dorsiflexion range; attention should be paid to muscle stiffness in children with cerebral palsy.

Experimental and analytical investigation of WT‐shapes stiffened steel panel dampers

AbstractThe three‐segment steel panel damper (TSPD) is a type of shear panel damper (SPD) used for dissipating seismic energy. TSPDs consist of an inelastic core (IC) and two outer elastic joints (EJs), with the IC having a weaker shear strength than the EJs. Buckling restraining stiffeners delay shear buckling, and end stiffeners stabilize the IC to facilitate force transfer. However, the fabrication of TSPDs may be costly due to the use of built‐up shapes. This prompted the investigation of a more cost‐effective option, namely the WT‐shapes stiffened steel panel damper (WSPD). The WSPD can be built from a single hot rolled wide flange steel shape with four WT‐shapes cut from it. A practical procedure for seismic design using this method is developed in this study. The design procedure for IC web stiffeners is also considered. We propose elastic stiffness calculation methods for WSPDs, which match the analytical results of the proposed model using commercial software. Two full‐scale 2.6 m tall WSPD specimens were fabricated and tested. Different target IC buckling shear deformations of 0.08 and 0.12 radians resulted in two different stiffener designs for specimen WSPD‐0L2T and WSPD‐1L2T, respectively. The specimens had excellent energy dissipation performance. WSPD‐0L2T IC web buckled later than predicted, while WSPD‐1L2T IC web buckled slightly earlier than expected. The elastic lateral stiffness and maximum shear strength computed from the proposed procedures agree with the experimental results within 5%. The experimental responses of the two specimens can also be accurately simulated using Abaqus finite element model analysis.

Monopile Foundation Stiffness Estimation of an Instrumented Offshore Wind Turbine through Model Updating

Rapid development of offshore wind foundation models has resulted in a large number of built structures with generally underestimated foundation stiffness properties and a need to update and validate both the individual structural models and the underlying foundation design frameworks. This paper outlines a structural health monitoring approach, based on the combination of output only structural health monitoring methods and model updating, to estimate foundation stiffness parameters using field monitored data. Field monitoring data from an offshore wind turbine under idling conditions, over a large monitoring period, are presented and operational modal analysis is applied to estimate the modal parameters. Those are compared to modal properties predicted by finite element models, employing either old (API/DNVGL) or new (PISA) foundation design properties, which are calibrated using geotechnical site investigation data. A new approach to interpret seabed level statically equivalent foundation stiffness, in terms of effective lateral and rotational stiffness against load eccentricity, is presented. Seabed level statically equivalent foundation properties are updated by comparison against the observed modal behaviour and the optimised foundation parameters are presented, demonstrating a close match to the predictions of the PISA method.

Identification of Damage in Planar Multistory Reinforced Concrete Frames Developing a Beam-Sway Plastic Mechanism Using the “M and P” Technique

The effectiveness of a recently proposed methodology for the identification of damage in planar, multistory, reinforced concrete (RC) moment frames, which develop a plastic yield mechanism on their beams, is showcased here via the examining of a group of such existing multistory frames with three or more unequal spans. According to the methodology, the diagram of the instantaneous eigenfrequencies of the frame in the nonlinear regime is drawn as a function of the inelastic seismic roof displacement by the performance of a sequence of pushover and instantaneous modal analyses with gradually increasing target displacement. Using this key diagram, the locations of severe seismic damage in an existing moment frame can be evaluated if the instantaneous fundamental eigenfrequency of the damaged frame, at an analysis step within the nonlinear area, is known in advance by “the monitoring and the identification of frequencies” using a local network of uniaxial accelerometers. This is a hybrid technique because both procedures, the instrumental monitoring of the structure and the pushover analysis on the frame (M and P technique), are combined. A ductile, five-story, planar RC moment frame with three unequal spans is evaluated in this paper by the M and P technique. The results show that the seismic roof displacement, the lateral stiffness matrix, and, finally, the damage image of this existing frame, are fully compatible with the eigenfrequencies identified by the monitoring and are calculated with high accuracy.

Experimental cyclic response of heat-damaged RC beam-column joints strengthened with CFRP strings

Reinforced concrete (RC) buildings may be subjected to high temperatures during their service life, which causes significant deterioration in the mechanical and physical characteristics of several structural members (i.e., joints), making it necessary to upgrade their overall performance to withstand the additional stresses. Therefore, the effectiveness of carbon fiber reinforced polymer (CFRP) strings used as near-surface mounted (NSM) reinforcement in restoring the structural performance and minimizing the failure mechanism of heat-damaged RC beam-column (B-C) joints is examined in this study through experimental work. The experimental research consists of twelve RC beam-column joint sub-assemblages divided into three groups: four joints were kept at room temperature, four were heated to 400 °C, and four were heated to 600 °C. Three joints from each batch were tested under a quasi-static cyclic load after adding one, two, or three strings of CFRP reinforcement. The cyclic response of joints was evaluated by determining the ultimate load capacity in pulling and pushing and its corresponding lateral displacement, energy dissipation, displacement ductility, and stiffness degradation. The experimental results showed that the upgraded joints with CFRP strings experienced a significant increase in energy dissipation, initial stiffness, displacement ductility, and ultimate load capacity in pulling and pushing over reference joints.