Cyclic Loading Tests Research Articles

Correlating ballast resilient modulus with particle movement through SmartRock sensing

The resilient modulus of ballast is a key parameter in assessing track quality and is influenced by various loading conditions, such as deviator stress, bulk stress, loading frequency, and confining pressure. These factors, when incorporated into different models, can sometimes complicate their application in track maintenance planning. Therefore, a simplified model that collectively considers these factors would be beneficial in practical applications for estimating the ballast resilient modulus. This study utilizes smart sensing technology, SmartRock, to track particle movement during large-scale triaxial cyclic loading tests, exploring the potential correlation between ballast resilient modulus and particle motion. The findings indicate that the settling acceleration of ballast particles significantly impacts the ballast resilient modulus. This effect is dependent on the applied cyclic loading pulses, an aspect previously overlooked in research. Consequently, an index termed the Cyclic Loading and Acceleration Index (CLAI) has been introduced. CLAI integrates the effects of deviator stress, loading frequency, loading pulses, and settling acceleration. Based on CLAI, a simplified model for ballast resilient modulus has been developed and validated.

Seismic Performance of Precast Double-Skin Composite Shear Wall with Horizontal Connection Region

This paper proposed a novel, precast double-skin composite (DSC) shear wall, which was composed of two precast parts at the factory and welding and pouring grouting material on site. One monolithic cast-in-place DSC shear wall specimen and two precast DSC shear wall specimens with different axial compression ratios were subjected to reverse cyclic loading tests. The results indicated that the failure mode of both the cast-in-place and precast DSC shear wall shear walls were compression-bending failures, and the damage range of specimens within a height range of 100 mm to 200 mm from the bottom of the DSC shear wall. The load-bearing capacity of the precast specimen was 6.3% higher than that of the monolithic counterpart, but its ductility was reduced by 16%. The precast DSC shear wall with better casting quality and easier site installation exhibited a satisfactory seismic performance on a par with that of the monolithic cast-in-place DSC shear wall. Under higher axial compression ratios, the bearing capacity and energy dissipation of the precast DSC shear wall specimen significantly improved due to the enhanced confinement effect. Finite element (FE) models clarified the stress and deformation mechanisms between the exterior steel plate and the infill concrete. Finally, the key parameters affecting the seismic bearing capacity of the precast DSC shear wall were identified through FE parameter analysis.

The Seismic Performance of Self-Centering Ribbed Floor Flat-Beam Frame Joints

To achieve rapid post-earthquake repair of self-centering ribbed floor flat-beam frame structures, a ductile hybrid joint consisting of dog-bone-shaped, weakened, energy-dissipating steel bars connected to the upper and lower column sections through high-strength threads is proposed based on the damage control design concept. By moving the ductile energy-dissipating zone out to the locally weakened section of the energy-dissipating steel bars and the locally unbonded prestressed steel bars in the core area, the residual deformation was limited and the seismic performance improved. Based on the working principle of hybrid joints, low cycle loading tests were conducted on two joint specimens to analyze the influence of lateral prestress on the seismic performance of the hybrid joints. Numerical modeling methods were used to compare the position of the energy-dissipating steel bars in the composite layer and the friction performance of the joints. The research results indicated that the hybrid joint had stable load bearing, deformation, and energy dissipation capabilities, with damage being primarily concentrated in the energy-dissipating steel bars. Even at an inter-story displacement angle of 5.5%, the upper and lower column segments remained elastic. After unloading, the connection seam at the joint was closed, and the self-centering performance was good. When the inter-story displacement angle reached 5.5%, the lateral prestress increased from 150 kN to 250 kN, the ultimate bearing capacity of the joint increased by 16.3%, and the cumulative energy consumption increased by 30.0%. The influence of the friction coefficient of the joint surface on the structural performance was set at a threshold of 0.7. When it was less than the threshold, the ultimate bearing capacity and initial stiffness of the joint increased with the increase in the friction coefficient. After reaching the threshold, the increase in the ultimate bearing capacity of the joint slowed down, and the rate of stiffness degradation gradually accelerated. This joint showed excellent seismic performance and can thus achieve post-earthquake repair of structures.

A Dynamic, Self-Tensioning Suture Contracts in Saline to Counteract Changes in Loop Length From Cyclic Loading

To compare the biomechanical performance of a suture with proposed dynamic self-tensioning properties with that of commonly used high-tensile sutures by evaluating suture loop length changes, responses to cyclic loading, and failure testing with intermittent saline soaks. Six knots each of 4 different sutures were studied: 3 high-tensile sutures (ORTHOCORD, FiberWire, and ETHIBOND), and a dynamically self-tensioning suture (DYNACORD). After we measured loop length, knots were soaked in 37°C saline for 24 hours. Loop lengths were remeasured and tensile testing was performed. Cyclic elongation, first-cycle excursion, and elongation amplitude were recorded. Knots were then resoaked and retested. Finally, knots were pulled to failure, and peak load and stiffness were measured. Values were compared using nonparametric statistical tests. DYNACORD loop length decreased by 27% after the first soak (P= .002), whereas the other sutures demonstrated no length change (P > .05). Although DYNACORD loop length increased during cyclic load testing (P= .009), it was still significantly reduced after the second saline soak compared withits initial length (P= .002), whereas all other suture loops had elongated. ETHIBOND (P= .004) and ORTHOCORD (P= .002) had significantly less cyclic elongation from cycle I to cycle II testing compared with the other sutures. ETHIBOND had the lowest peak load at failure (P= .002). FiberWire had the greatest stiffness (P= .006). Compared with other suture types, the self-tensioning suture showed dynamic properties, demonstrating a decrease in loop length when soaked in a saline bath. This length was maintained after a second soak despite increased loop length during interval cyclic loading. Knot and loop security are of paramount importance to arthroscopic soft-tissue procedures. The ability for a suture to self-tension has implications for how it may interact with tissues invivo to increase construct stability after arthroscopic soft tissue repair procedures.

Seismic cyclic test of perforated replaceable link for eccentrically braced frames

This study introduces a design comprising a unweakened link and four variants of perforated replaceable links, denoted as specimens RX1 (unweakened link), RX2 and RX3 (with circular holes of 50 mm diameter on the web), RX4 and RX5 specimens (with elliptical holes on the web), and RX6 and RX7 specimens (with weakened flanges and circular holes of 50 mm and 80 mm diameter on the web). Seven link specimens underwent cyclic loading tests. RX1 ultimately failed due to tearing of the weld at the connection between the flange and the end plate, while RX2 to RX7 exhibited deformation concentrated within the energy dissipating region, ceasing loading upon failure of this region, demonstrating enhanced safety and stability. All specimens exhibited relatively full hysteretic curves, with a decrease in the area of hysteretic curves corresponding to an increase in the web perforation ratio. The overstrength coefficient for specimen RX1 ranged from 1.81 to 1.82, while for specimens RX2 to RX7, it ranged from 1.80 to 3.65. Not only were the overstrength coefficients greater than RX1, but also the cumulative energy dissipation was higher than RX1. This indicates that RX2 to RX7 can accommodate larger plastic deformations, effectively utilizing plastic deformation for energy dissipation, thereby exhibiting superior safety. Moreover, an increase in web perforation ratio and weakening of the flanges resulted in a decrease in the overstrength coefficient, load-bearing capacity, and plastic deformation capacity of the specimens. Ductility decreased with increasing web perforation ratio but increased with flange weakening. Additionally, through analysis of link replacement time and residual rotation of links after unloading, it was observed that perforated replaceable links exhibited favorable replaceability.

Self-centering concrete-filled steel tubular column-steel beam joint: Experiment and numerical modeling

This paper studied the seismic behavior of a novel self-centering concrete-filled steel tubular column-steel beam (SCSTCSB) joint. The restoring force was provided by the post-tensioned tendons arranged in the CFST columns. Cyclic loading tests were performed on five 1/3 scaled specimens by varying the parameters of steel tendon type, concrete strength (fc), and axial compression ratio (n). The failure modes, hysteresis behavior, stiffness and strength degradation, energy dissipation, post-tensioned tendons response, residual deformation, and strain distribution were studied in detail. The finite element models were established to capture the stress distribution of the joints. In addition, parameter analysis was performed by expanding 17 finite element models. The results show that the ratio of residual deformation to beam rotation angle of the specimens ranged from 0.068 to 0.172. And the proposed joints demonstrated excellent self-centering ability. The self-centering (SC) performance of joints with ordinary steel tendons was better than that of joints with high-strength steel tendons. With the increase of n, the SC performance of the joints intensified at the lower ratio (n from 0.1 to 0.3) and weakened after n = 0.3. The flexural capacity of the joints improved with the increase of axial compression ratio (n), width-thickness ratio (D/t), diameter of steel tendons (d), and assembly part strength (fy,a).

Biomechanical Comparison of Fixation Methods for Posterior Wall Fractures of the Acetabulum: Conventional Reconstruction Plate vs. Spring Plate vs. Variable Angle Locking Compression Plate.

Background and Objectives: Acetabular fractures, though infrequent, present considerable challenges in treatment due to their association with high-energy trauma and poor prognoses. Posterior wall fractures, the most common type among them, typically have a more favorable prognosis compared to other types. Anatomical reduction and stable fixation of the posterior wall are crucial for optimal treatment outcomes. This study aimed to biomechanically compare three commonly used fixation methods for posterior wall fractures of the acetabulum-a conventional reconstruction plate, a spring plate, and a 2.7 mm variable angle locking compression plate (VA-LCP). Materials and Methods: The study utilized 6 fresh-frozen cadavers, yielding 12 hemipelvises free from prior trauma or surgery. Three fixation methods were compared using a simple acetabulum posterior wall fracture model. Fixation was performed by an orthopedic specialist, with prebending of plates to minimize errors. Hemipelvises were subjected to quasi-static and cyclic loading tests, measuring fracture gap, stiffness, and displacement under load. Results: It showed no significant differences in fracture gap among the three fixation methods under cyclic loading conditions simulating walking. However, the conventional reconstruction plate exhibited a greater stiffness compared to the spring and variable angle plates. Fatigue analysis revealed no significant differences among the plates, indicating a similar stability throughout cyclic loading. Despite differences in stiffness, all three fixation methods demonstrated adequate stability under loading conditions. Conclusions: While the conventional reconstruction plate demonstrated a superior stiffness, all three fixation methods provided sufficient stability under cyclic loading conditions similar to walking. This suggests that postoperative limitations are unlikely with any of the three methods, provided excessive activities are avoided. Furthermore, the variable angle plate-like the spring plate-offers an appropriate stability for fragment-specific fixation, supporting its use in surgical applications. These findings contribute to understanding the biomechanical performance of different fixation methods for acetabular fractures, facilitating improved surgical outcomes in challenging cases.

Experimental Investigation on Mechanical, Electrical, and Fatigue Properties of Entangled Metal Wires under Cyclic Dynamic Load Test

Experimental Investigation on Mechanical, Electrical, and Fatigue Properties of Entangled Metal Wires under Cyclic Dynamic Load Test

Composite patch with negative Poisson's ratio mimicking cardiac mechanical properties: Design, experiment and simulation

Developing patches that effectively merge intrinsic deformation characteristics of cardiac with superior tunable mechanical properties remains a crucial biomedical pursuit. Currently used traditional block-shaped or mesh patches, typically incorporating a positive Poisson's ratio, often fall short of matching the deformation characteristics of cardiac tissue satisfactorily, thus often diminishing their repairing capability. By introducing auxeticity into the cardiac patches, this study is trying to present a beneficial approach to address these shortcomings of the traditional patches. The patches, featuring the auxetic effect, offer unparalleled conformity to the cardiac complex mechanical challenges. Initially, scaffolds demonstrating the auxetic effect were designed by merging chiral rotation and concave angle units, followed by integrating scaffolds with a composite hydrogel through thermally triggering, ensuring excellent biocompatibility closely mirroring heart tissue. Tensile tests revealed that auxetic patches possessed superior elasticity and strain capacity exceeding cardiac tissue's physiological activity. Notably, Model III showed an equivalent modulus ratio and Poisson's ratio closely toward cardiac tissue, underscoring its outstanding mechanical potential as cardiac patches. Cyclic tensile loading tests demonstrated that Model III withstood continuous heartbeats, showcasing outstanding cyclic loading and recovery capabilities. Numerical simulations further elucidated the deformation and failure mechanisms of these patches, leading to an exploration of influence on mechanical properties with alternative design parameters, which enabled the customization of mechanical strength and Poisson's ratio. Therefore, this research presents substantial potential for designing cardiac auxetic patches that can emulate the deformation properties of cardiac tissue and possess adjustable mechanical parameters.

Shape Optimisation of Grooves in Grooved Gusset Plate Damper used in X-Braced Frame

The X-braced frame represents a specialized variation of concentric-braced frames. It can be used as a resistance towards the lateral load acting on the structural system. X-braced frames generally exhibit lower flexibility when compared to eccentrically braced and moment frames, which is often perceived as a drawback of this structural system. To address this limitation, energy dissipation devices can be integrated into the system with X-bracings to absorb the plastic action and safeguard other structural elements, such as columns, beams and connections from earthquake forces. Specifically, X-concentrically braced frames are tailored through variations in groove shapes. Furthermore, the investigation determines the dampers' load-bearing and energy dissipation capacities. The assessment commences with cyclic load testing conducted using the ANSYS software. The grooves present in GGPD help dissipate seismic energy. The energy dissipation and load-bearing capacity of the X-concentrically braced frame equipped with a grooved gusset plate damper were compared based on different groove shapes. The different shapes used for the analysis were L shape, oval, rectangular and stadium shape. It was observed that oval-shaped grooves have more energy dissipation capacity among four groove shapes, with an increase of 10.74%.

Influence of precast microbial reinforcement on lateral responses of monopiles

Microbially Induced Calcium Carbonate Precipitation (MICP) provides an environmentally friendly solution for reinforcing large diameter monopiles for offshore wind turbines (OWTs). This study presents an investigation into the lateral responses of monopiles with precast microbial reinforcement using a low-pH one-phase method. Both static and cyclic loading tests were carried out. The results of static loading tests show that the failure mode of the bio-reinforced monopile was an overall overturn failure. The lateral bearing capacity was increased by 50% and the bending moment was reduced by about 25% with the bio-reinforcement. Further investigation was conducted on the secant stiffness, damping ratio, and accumulated deformation of the bio-reinforced monopile under various cyclic loadings. With the bio-reinforcement, the accumulated deformation under one-way cyclic loading can be reduced by 30%–60%. The influences of cyclic loading parameters and loading sequence on pile stiffness were clarified. The growth ratio of pile stiffness due to bio-reinforcement under one-way loading was between 1.65 and 2.82, and decreased with increasing load amplitude. The ratio was smaller under two-way loading. Three competing factors on pile stiffness were identified: cyclic compaction of the unreinforced sandy soil, weakening of the bio-reinforced soil and soil subsidence around the bio-reinforced soil.

Experimental evaluation of performance of geo-mat system on weak to intermediate subgrade

Geo-mat system is considered as an alternative to a flexible or rigid pavement that can be used for fire lanes, parking areas, or roadway shoulders for cars, pickup trucks, utility/delivery trucks, and fire trucks. Also, it can be used to reduce the thickness of the base course in unpaved roads. In this investigation, six cyclic loading tests were conducted to assess the efficacy of the geo-mat system on weak to intermediate subgrade layers, characterized by California Bearing Ratios (CBR) of 2%, 3%, and 4%. Control sections, consisting of a 300-mm thick base course over subgrade layers with CBR values of 2% or 4%, were compared against the test sections comprising a geo-mat system placed atop aggregates of varied thickness (150 or 50 mm) on a geotextile layer over the same subgrade layers. Each test section underwent cyclic loading, progressively increasing from 17.8 to 71.2 kN using a 300-mm diameter steel plate. The results demonstrate that the geo-mat system, particularly when placed over a 150 mm-thick aggregate base, exhibited comparable or superior performance to the control sections with a 300 mm thickness, especially under substantial cyclic loading. This was evidenced by the reduced permanent deformations beneath the loading plate and a wider load distribution. The increase of the subgrade CBR value reduced the permanent deformation significantly. When the intermediate subgrade with a 4% CBR was used, the geo-mat system played a more important role than the aggregate base and the base thickness had a minor effect on the performance.

Seismic responses and loss evaluation of RC frame with slotted infill walls

Infill walls are a primary source of structural loss under service level and design basis earthquakes, so developing high-performance infill wall is an effective strategy to reduce seismic loss. While several high-performance infill walls have been proposed, most studies only reveal the damage characteristics of infill walls at the component level. However, the interaction between infill walls and structures can alter the seismic response of structures and consequently affect the loss of infill walls under earthquakes. Therefore, it is necessary to investigate the seismic responses and loss of high-performance infill wall at the structural level. In this paper, the working mechanism and damage characteristics of the slotted infill wall (SIW) are firstly introduced and verified through cyclic loading test. Then, an in-plane hysteresis model of SIW is developed, and the calculation method of key parameters is proposed. Finally, a numerical analysis model of a 10-story frame with slotted infill wall (SIW-F) is developed to study the seismic response and seismic losses. The results indicate that SIW-F’s displacement response is larger than that of the frame with ordinary infill wall (OIW-F) on most floors. However, the floor acceleration response is less. The seismic loss of SIW-F is less than that of OIW-F, particularly under design basis earthquakes. The repair cost ratio of infill wall decreases from 19% to 8%, the total repair cost of the SIW-F decreases by 41%, and the total repair time also reduces by 25%.

Experimental Study on the Microfabrication and Mechanical Properties of Freeze-Thaw Fractured Sandstone under Cyclic Loading and Unloading Effects.

A series of freeze-thaw cycling tests, as well as cyclic loading and unloading tests, have been conducted on nodular sandstones to investigate the effect of fatigue loading and freeze-thaw cycling on the damage evolution of fractured sandstones based on damage mechanics theory, the microstructure and sandstone pore fractal theory. The results show that the number of freeze-thaw cycles, the cyclic loading level, the pore distribution and the complex program are important factors affecting the damage evolution of rocks. As the number of freeze-thaw cycles rises, the peak strength, modulus of elasticity, modulus of deformation and damping ratio of the sandstone all declined. Additionally, the modulus of elasticity and deformation increase nonlinearly as the cyclic load level rises. With the rate of increase decreasing, while the dissipation energy due to hysteresis increases gradually and at an increasing rate, and the damping ratio as a whole shows a gradual decrease, with a tendency to increase at a later stage. The NRM (Nuclear Magnetic Resonance) demonstrated that the total porosity and micro-pores of the sandstone increased linearly with the number of freeze-thaw cycles and that the micro-porosity was more sensitive to freeze-thaw, gradually shifting towards meso-pores and macro-pores; simultaneously, the SEM (Scanning Electron Microscope) indicated that the more freeze-thaw cycles there are, the more micro-fractures and holes grow and penetrate each other and the more loose the structure is, with an overall nest-like appearance. To explore the mechanical behavior and mechanism of cracked rock in high-altitude and alpine areas, a damage model under the coupling of freeze-thaw-fatigue loading was established based on the loading and unloading response ratio theory and strain equivalence principle.

Experimental study of self-tightening high-strength single-side bolted joints under low cyclic loading

Single-side bolts can be installed on one operating surface and are very suitable for closed cross-section connections. Based on the forming mechanism of materials, a new type of self-tightening high-strength single-side bolt, named SHSB-PRO (Progressed version), was developed herein. The SHSB-PRO was successfully applied to the assembled steel structure joints, with a range of low cyclic loading tests executed. In this test, three assembled steel structure joints were designed. Two of them were connected using SHSB-PRO, while the third was connected using traditional torsional shear high-strength bolt. Different bolt types and axial compression ratios of the steel column were examined to explore their impact on the seismic behavior of the joints. Through the low cyclic loading test, data such as hysteresis curves, skeleton curves, and strain in key parts of the joints were obtained. The mechanical properties, energy dissipation characteristics, failure mechanisms, and seismic performance of these assembled joints were elucidated. The test results indicate that the forming quality of the SHSB-PRO is stable within the joint, and a fine stress condition is maintained. The joints connected by the SHSB-PRO exhibit seismic performance comparable to those with torshear high-strength bolted connection. All joints failed due to the formation of the plastic hinge of the steel beam above the stiffener, and the joints connected by SHSB-PRO belong to the rigid joint. The influence of the axial compression ratio on the load-bearing capacity, ductility, and stiffness of the joints connected using SHSB-PRO is virtually minimal when the ratio is no more than 0.2. The finite element model was rigorously validated against the experimental results, demonstrating its accuracy and reliability in capturing the behavior of SHSB-PRO joints. The research herein lays a foundation for the design and improvement of SHSB-PRO, and promotes its wide application in civil engineering.

Experimental study of mechanical properties of artificial dam for coal mine underground reservoir under cyclic loading and unloading

This study investigates the stability of an artificial dam used in an underground reservoir in a coal mine under periodic weighting imposed by overlying rock strata. For this purpose, cyclic loading and unloading tests with different stress amplitudes were designed. Differences in the mechanical performance of the artificial dam with and without overlying strata were analyzed using a uniaxial compression test. The mechanical properties of the structure under constant-amplitude cyclic loading and unloading were characterized. Further, the law of influence of stress amplitude on stability was discussed. A formula for predicting the mechanical performance of the artificial dam with its overlying rocks (hereafter referred to as the complex) was finally derived and was suitable for clarifying the law of damage in the complex under cyclic loading and unloading. The results showed that the complex had changed the internal structure of rocks. The strength and deformation of the complex were intermediate to that of either single structure. All three underwent brittle failure. During the constant-amplitude loading and unloading tests, the hysteresis loop could be divided into three phases, namely, sparse, dense, and sparse again, with a shift in the turning point in rock deformation memory effect. As the stress amplitude increased during the test, the damping ratio of the specimens decreased, and the area of the hysteresis loop increased non-linearly. The dynamic elastic modulus decreased first and then increased. The confidence interval for the formula fitted based on the test results was above 97%. Damage to the complex caused by constant-amplitude loading and unloading could be divided into three stages. An increase in peak stress served as a catalyst for the evolution of small cracks within the specimens into median and large cracks, thereby accelerating the damage process.

Experimental and Numerical Simulation Investigation of Cement Sheath Integrity during Multi-Stage Fracturing in Offshore Tight Oil Reservoir

The integrity of the cement sheath is susceptible to failure during multi-stage fracturing. In this study, the failure mechanisms of cement sheath integrity during multi-stage fracturing in the A offshore tight oil reservoir wells were investigated. The cement samples were subject to triaxial compression test (TCT), triaxial cyclic loading test (TCLT), and permeability test. A full-scale device was constructed for cement sheath integrity experiments. Additionally, a 3-D finite element model was developed to simulate the interface debonding and the subsequent growth of micro-annuli throughout multi-stage fracturing. The results revealed that TCLT induced cumulative plastic deformation in the cement samples, resulting in a 10.7% decrease in triaxial compressive strength, an 8.3% decrease in elastic modulus, and a 150% increase in permeability. Despite these significant variations, no serious damage was caused to the cement sheath matrix. It was observed that gas leakage occurred at the 8th, 10th, and 14th cycles under cyclic loading with upper limits of 70 MPa, 80 MPa, and 90 MPa, respectively. After 15 cycles, the experimentally measured widths of micro-annuli were 117 μm, 178 μm, and 212 μm, which were in good agreement with simulation results of 130 μm, 165 μm, and 205 μm, respectively. These findings elucidate the causes of cement sheath integrity failure, providing insights into the failure mechanisms of cement sheath integrity during multi-stage fracturing.

Hysteretic behavior of the segmented buckling‐resistant braces with LYP160

AbstractThe goal was to evaluate the hysteretic performance of buckling‐resistant braces with low yield point steel LYP160, the monotonic tensile and cyclic loading tests of LYP160 test specimens were conducted and the cyclic constitutive relationship was obtained. According to the load–displacement curves of the specimens, the low‐yield point steel was characterized by good ductility and energy absorption ability. With consideration of the Chaboche model for the materials, the cyclic hardening parameters of low‐yield point steel were obtained. On this basis, the hysteretic properties of buckling‐resistant braces under cyclic loads were simulated and analyzed. After the analysis and comparison of buckling‐resistant braces specimens with isotropic core plate and segmented variable section core plate, it can be found that: when the conventional buckling‐resistant braces with an isotropic core plate were loaded to L/100, the lateral deformation of the buckling‐resistant brace (BRB) would reach 17 mm. Additionally, serious squeezing could be observed on the lateral restraining members. The conventional BRB would become ineffective due to the accumulation of deformation at both ends of the BRB. When the segmented buckling‐resistant brace was applied, the core plate with variable section would buckle first in the middle area, other parts could continue to consume energy thanks to the action of the limit plate. It would avoid the situation that other areas would be unable to consume energy after the core plate yields at one area first. Under the action of cyclic loads, no stiffness degradation was noted in the segmented buckling‐resistant brace. Segmented buckling‐resistant braces demonstrated superior ductility and energy dissipation capacity.

Performance of an EBR CFRP-strengthened RC slab using 24-h and cyclic load tests: a real case study

Performance of an EBR CFRP-strengthened RC slab using 24-h and cyclic load tests: a real case study

Evaluation of Rotation Capacity and Bauschinger Effect Coefficient of I-Shaped Beams Considering Loading Protocol Influences

Recent catastrophic earthquake events have reinforced the necessity of evaluating the seismic performance of buildings. Notably, the buildings can go into the plastic phase during a striking earthquake disaster. Under this condition, the current design codes assume seismic response reduction by virtue of the energy dissipation capacity of the structural members. In the strong-column–weak-beam design, which involves I-shaped beams and boxed columns, the mechanism is defined as a standard design scheme to prevent the building from collapsing. Therefore, energy dissipation relies highly on the I-shaped beam performance. However, the I-shaped beam performance can differ depending on the loading history experienced, whereas this effect is untouched in the prevailing evaluation equation. Hence, this study first performs cyclic loading tests of 11 specimens using different loading protocols. The experimental results clarify the fluctuation in the structural performance of I-shaped beams depending on the applied loading hysteresis, proving the necessity of considering the stress history for proper assessment. Furthermore, the database of experimental results is constructed based on the previous experimental studies. Ultimately, the novel evaluation equation is proposed to reflect the influences of the loading protocol. This equation is demonstrated to effectively assess the member performance retrieved from the experiment of 65 specimens, comprising 11 specimens from this investigation and 54 specimens from the database. The width–thickness ratio, shear span-to-depth ratio, and loading protocols are utilized as the evaluation parameters. Moreover, the prediction equation of the Bauschinger effect coefficient is newly established to convert the energy dissipation capacity under monotonically applied force into hysteretic energy dissipation under the cyclic forces.