Rotation Capacity Research Articles

A deformability-based mechanical model for predicting shear strength of FRP-strengthened RC beams failed in concrete cover separation

Concrete cover separation (CCS) is frequently happened prior to the yielding of steel stirrups in FRP-strengthened RC beams. However, the debonding mechanism and criterion have not been fully understood. In this study, the typical crack types associated with CCS are comprehensively summarized and investigated in terms of profiles and kinematics of crack. The dowel action and dowelling cracks are proved to be the dominant factors causing CCS. Based on the cracking features, the simplified local debonding strength and average shear strength of fracture interface, which constitutes the contribution of concrete to shear capacity of strengthened RC beams, are analytically derived and verified against the available experiments and code provisions. Through regression analysis of 179 collected shear tests, a formulation based on the Critical Shear Crack Theory (CSCT) is presented to assess the deformability of strengthened RC beams governed by CCS. The commonly overlooked actual stress level in steel stirrups is considered as a function of the rotation capacity of beams and assessed based on the Modified Compression Field Theory (MCFT). Validation of this analytical approach, involving comparison against the empirical models and experimental results from 107 specimens, confirms its superior effectiveness and consistency in predicting CCS and shear strength.

Numerical investigation on plastic hinge behavior of hybrid steel-FRP reinforced concrete columns

This paper presents a numerical study on the plastic hinge behavior and rotation capacity of concrete columns reinforced with a combination of steel bars and fiber-reinforced polymer (FRP) bars. A meso-scale numerical model, which considers the internal heterogeneity of concrete and bond behavior between concrete and longitudinal reinforcements, was developed and validated. The failure modes, lateral load-displacement responses, and the physical plastic hinge lengths of hybrid steel-FRP reinforced concrete (SFRC) columns were investigated and compared with those of conventional steel-reinforced concrete columns. The results indicated that the steel yielding zone and curvature localization zone of SFRC columns with FRP longitudinal bars were enlarged, due to the relatively low modulus of FRP bars. After that, a parametric analysis was performed to study the plastic hinge length of SFRC columns with respect to the nominal area ratio of FRP longitudinal bars, shear span-to-depth ratio, axial load ratio, and longitudinal reinforcement ratio. A new empirical model was proposed to predict the equivalent plastic hinge length, which was subsequently integrated into an analytical method for predicting the ultimate rotation. The comparison of predictions with simulation and test results demonstrated the accuracy of both the proposed empirical model and analytical method.

Experimental and numerical study on flexural performance of ultra-high performance concrete frame beams reinforced with steel-FRP composite bars

This paper presents the bending tests of four ultra-high performance concrete (UHPC) frame beams and one normal strength concrete (NSC) frame beam, all reinforced with steel-FRP composite bars (SFCBs). A comprehensive analysis was carried out, encompassing evaluation of the failure mode, crack propagation, bearing capacity, deformation, strain response, and plastic rotational capacity of the frame beams. Investigating the effects of concrete type, reinforcement type, and beam-end reinforcement ratio on the flexural performance of the frame beams was a key aspect of this study. A three-dimensional finite element (FE) model of the frame beam was established and rigorously verified. The developed model enabled a detailed parametric analysis involving the steel ratio, the yield strength of the inner core steel bar, the elastic modulus of the FRP, and the ultimate tensile strength of the SFCB. The results indicated a consistent failure mode of all frame beams: crushing of concrete at the beam-end, initiating a sequence of plastic hinge occurrence starting at the beam-end and then progressing to mid-span. The substitution of normal strength concrete with UHPC significantly enhanced various aspects of the frame beams, including the flexural capacity, deformation, ductility, ultimate energy dissipation, and plastic rotational capacity, while inhibiting the generation and expansion of cracks. Notably, the plastic rotation angle of SFCB-UHPC frame beams was 4.9 times greater than those of steel-UHPC frame beams, emphasizing the effectiveness of SFCB in enhancing the beam-end plastic rotational capacity. A decrease in the beam-end reinforcement ratio significantly reduced the flexural capacity, ultimate energy dissipation, and beam-end plastic rotational capacity, while improving ductility. Additionally, the study established a formula for calculating the equivalent plastic hinge length, utilizing the relative compressive zone height and effective section height of the beam-end controlling section as variables, which demonstrated good alignment between predicted and experimental results.

Pengaruh Audit Firm Rotation, Komite Audit, dan Audit Capacity Stress Terhadap Kualitas Audit: Studi Empiris pada Perusahaan Sub Sektor Bank yang Terdaftar di BEI Periode 2018-2022

This research aims to empirically prove the influence of audit firm rotation, audit committee and audit capacity stress on audit quality in banking sub-sector companies on the Indonesian Stock Exchange. In this research, 30 banking companies were used. The sampling technique used was purposive sampling. The data analysis method used in hypothesis testing is binary logistic regression and Wald test. In accordance with the results of hypothesis testing processed using the SPSS program, it was found that audit firm rotation had no significant effect on audit quality in banking sub-sector companies on the Indonesia Stock Exchange. In the second hypothesis testing stage, it was found that the audit committee had a positive and significant effect on audit quality in banking sub-sector companies on the Indonesia Stock Exchange, while in the third hypothesis testing results it was successfully proven that audit capacity stress had a negative and significant effect on audit quality in sub-sector companies. Banking on the Indonesian Stock Exchange. In accordance with the results of hypothesis testing obtained, it is recommended that companies continue to optimize the role of the audit committee as part of the monitoring instruments within the company. When the role of the audit committee runs well and consistently, the quality of the audit will be better. Through strict supervision, the possibility of fraud will be smaller so that the quality of the resulting audit will be higher and beneficial for stakeholders, especially investors.

Changes in Shoulder Rotation Based on Elevation in Children With Brachial Plexus Birth Injury

Lack of shoulder external rotation is common in children with brachial plexus birth injuries. Development of glenohumeral (GH) dysplasia is associated with progressive loss of passive external rotation. Some authors recommend measuring external rotation with the arm adducted, whereas others recommend measurement with the arm in 90° of abduction. The purpose of this study was to compare active and passive external rotation and internal rotation measured in adduction versus abduction. Fifteen children with brachial plexus birth injuries held their affected arms in maximal external and internal rotation with the arm adducted and the arm at approximately 90° of abduction. Active and passive rotations were measured with three-dimensional motion capture. Scapulothoracic (ST) internal/external rotation and GH internal/external rotation joint angles were calculated and compared using multivariable, one-way repeated measures analyses of variance. There were no significant differences for active or passive ST rotation in external rotation in adduction versus abduction. Glenohumeral external rotation was significantly increased with the arm in abduction compared with adduction both actively and passively. There were no differences in ST rotation in active versus passive conditions, but all GH rotations were significantly greater passively. Shoulder internal/external rotation in abduction and adduction is not interchangeable. Comprehensive assessment of shoulder external and internal rotation should include both adduction and abduction. For children with brachial plexus birth injuries, both active and passive GH external rotations were greater in abduction. Therefore, early GH joint dysplasia may be missed if GH external rotation is measured in abduction. Additionally, consistency in arm position is important for comparison over time. The entire ST rotation capacity was used to perform maximal internal and external rotation, but the entire passive GH range of motion was not actively used. This highlights an area for potential surgical intervention to improve motion.

Progressive Collapse and Post Impact Damage Assessment in a Regular Beam-Slab Building & Flat-Slab Building on the Intermediate Floor

Progressive collapse, where a localized member failure causes widespread structural collapse, has become a critical concern nowadays, due to its potential to cause significant financial losses and loss of human life. Triggers include natural disasters like earthquakes and floods, as well as accidents, attacks and explosions. Reinforced concrete flat slab structures, which are eminent for their architectural flexibility and have larger spans, are particularly susceptible to disproportionate collapse, due to the lack of floor beams, which can redistribute loads after a column failure, unlike moment frame buildings. This research examines how multi-story reinforced concrete flat slab buildings behave, under prescribed gravity load combinations, compared to conventional framed buildings. The effects of removing columns at specified locations from an intermediate floor of the multistorey building are also examined. However, this investigation covers both the column removal approaches to check a possibility of disproportionate collapse which are; static removal and dynamic instantaneous removal. Furthermore, the research also assesses the efficacy of perimeter beams, in minimising the risk of gradual collapse in flat slab structures, by scrutinising their ability to reduce joint displacement, chord rotation, and demand capacity ratio. ETABS v18 was used to analyze all the 18 models. The findings revealed that buildings are more prone to progressive collapse when corner columns are removed, as opposed to edge and interior columns, due to higher Demand-Capacity Ratios (DCR) and joint displacement. In comparison to dynamic analysis, the static evaluation exhibited greater DCR values and vertical joint displacement. Furthermore, since they have a more efficient load redistribution mechanism, traditional framed structures performed better than flat slab models. The simulations additionally indicated that, adding edge perimeter beams, substantially lowered the possibility of progressive collapse in flat slab structures. Moreover, the tested flat slab building models, with and without perimeter beams showed no indications of progressive collapse, when specified columns were removed from the intermediate floors, since the DCR values of the crucial columns stayed within the permissible range of 2.0. In conclusion, structures built in compliance with IS 1893:2016 code and designed to withstand seismic loads demonstrate stronger resistance against significant damage, brought about by column failures.

Capacity design assessment of composite reduced web section (RWS) connections

A gap in current design approaches demands explicitly introducing a capacity design approach when designing steel-concrete composite reduced web section (RWS) connections. This paper addresses this gap by presenting test-validated finite element models and parametric investigations, focusing on the presence and absence of composite action over the web opening, the diameter, and the end-distance of the web opening. Additionally, the first-ever comprehensive experimental and numerical database from the literature on bare steel and composite RWS connections is compiled and thoroughly analysed to develop the capacity design assessment for such connections. Both parametric investigations and the database highlight the significance of the capacity design ratio between the connected components in achieving a desirable ductile mechanism. This is crucial, as evidenced by the results: a 15 % increase in the connection's moment capacity led to an average 21 % difference in dissipated energy, favouring the web opening with a diameter of 50do over 80do, in RWS connections with the presence of composite action. The results show that proper consideration of the capacity design approach in designing RWS connections ensures a stable yield mechanism is developed, resulting in the redistribution of global action and capping deformation demands on non-ductile elements. This enhances connections' rotational capacity and ductility by forming the Vierendeel mechanism. Lastly, the paper presents a detailing recommendation for employing RWS connections in both existing and new structures for seismic purposes.

Study on the Nodal Composite Bearing Performance of Nontruncated PHC Pipe Pile and Bearing Platform.

In this paper, low circumferential reciprocating load foot-scale tests were performed on two nontruncated PHC B 600 130 tubular piles with bearing nodes to characterize the damage process and morphology of the specimens and to investigate the load-carrying performance of the members. The test results reveal that under the action of tensile-bending-shear loading, the bearing concrete in the node area buckles and is damaged, the anchored reinforcement in the node area yields, the constraint is weakened, an articulation point is formed, and the node rotational capacity increases. When the embedment depth increases from 200 mm to 300 mm, the ultimate bearing capacities of the positive and negative nodes increase by 31.04% and 36.16%, respectively. A numerical simulation is used to verify the test results. Considering the four types of piles without truncated nodes, the numerical simulation is used to analyze the node-bearing capacity at different embedment depths. Finally, a preferred node type is proposed as follows: a terminal plate welded anchor bar and pipe pile core-filled longitudinal reinforcement anchored into the bearing node, with a preferred embedment depth of 250 mm.

Inelastic behavior of diagonally reinforced coupling beams confined with steel fibers

Experimental studies were conducted to analyze the plastic rotation capacity and the effect of replacing transverse reinforcements with steel fibers in diagonal reinforced concrete coupling beams. Six specimens were planned, and the steel fiber reinforcing index and total area of transverse reinforcements were the main variables. Reverse cyclic loading tests were conducted to confirm the seismic performance of the coupling beam. The results showed that the plastic hinge rotation capacity increased and the buckling point of the diagonal reinforcing bars was delayed as the steel fiber reinforcing index increased. An analysis of 78 specimens and the results of previous studies confirmed that ductility improved when the confinement effect of the steel fiber was considered. Application of an equation for ductility requirements reflecting the confining stress of steel fiber reinforced concrete confirmed that the amount of transverse reinforcement could be reduced.

Numerical investigation of plastic hinge length and lateral displacement capacity in precast concrete columns reinforced with SFCBs

Basalt fiber-reinforced polymer (BFRP) presents several advantages, including a moderate elastic modulus, cost-effectiveness, and a substantial fracture strain. A steel-FRP composite bar (SFCB) is a composite bar consisting of an inner steel bar and outer longitudinal BFRP, and it offers favorable initial modulus, high durability, and controllable post-yield stiffness. This study aims to address the issue associated with poor corrosion resistance, connection defects, and low integrity in traditional precast concrete columns with grouted sleeves (PCC-GSs) by employing bond- and post-yield-controlled precast concrete columns reinforced with SFCBs (PCC-SFs). The 3D finite element analysis (FEA) modeling was validated by comparing the results with those of six PCC-SFs and three precast reinforced concrete (RC) columns obtained from the experiment. The results encompass failure modes, load-displacement responses, strain distributions of SFCBs, and section curvature along the columns. The predicted errors for the peak load of S10B85–1P, S10B85–2P, and S10B85–3P are 6.4%, 0.1%, and 1.9%, with a mean error of 2.8%. The predicted errors for the ultimate deformation of S10B85-3PL and ST10B85–3P are within 20%, with a value of 6.0% and 18.7%. Subsequently, a series of FEA models were developed to analyze the effects of various on the development mechanism of plastic hinge length (PHL) for the PCC-SFs under lateral loading. The parameters included the post-yield stiffness ratio, equal-stiffness reinforcement ratio, axial force ratio, concrete strength, and bond strength. The longest plastic hinge length can reach 1.91D (D is the width of the column). An adjusted prediction model for the equivalent PHL in PCC-SFs was proposed and evaluated following a discussion of existing empirical models. Finally, the study explored the effects of these parameters on the load-displacement response, and the rationality of Priestley's shear-strength degradation model in PCC-SFs was validated. Based on the CEN model, an improved prediction model of the total chord rotation capacity was proposed.

Design and Analysis of a New Non-Parasitic Parallel Mechanism for 2T1R Motion

Abstract Two-limb parallel mechanisms (PMs) can have several advantages, such as avoidance of mechanical collision, fairly simple architecture, easy assembly, and large workspace. The paper presents a novel two-limb three-degree-of-freedom (DOF) PM with two translations and one-rotation (2T1R) that are actuated by two sliders. The manipulator runs with decoupled position and orientation with forward position solution without parasitic motions. The main topological characteristics of the PM such as position and orientation characteristic (POC), DOF, and coupling degree are analyzed. Second, using the kinematic modeling method based on topological characteristics, the unified symbolic forward and inverse position solutions of the two configurations of the PM (I and II) are derived together with the workspace, rotational capacity, and singularity. Finally, a comparative analysis regarding the kinematics of two configurations (I and II) is carried out to find an optimal design configuration I of a PM for 2T1R motion.

Performance Assessment of Base Plate Connections with Anchor Rod Sleeves

This research presents findings from a study focused on evaluating the performance of exposed base plate connections featuring anchor rods under cyclic loading conditions. The study introduces an innovative sleeve system approach designed to enhance the ductility of column base connections. The inclusion of a steel sleeve with defined geometric characteristics between the base plate and the anchor rod washer modifies the load path within the connection, resulting in a more ductile response. The study utilizes a validated finite element (FE) model to analyze exposed base plate connections featuring different sleeve shapes, illustrating the concept behind this novel method. The innovative approach discussed in this research has the potential to significantly increase the rotational capacity of connections without compromising their inherent strength.

Exterior weak-axis beam-to-column bolted connections between GFRP I-shaped pultruded profiles using stainless steel cleats

This paper presents an experimental investigation on the mechanical behaviour of bolted GFRP pultruded profiles beam-to-column connections, using I-shaped profiles and stainless-steel cleats, rotating around the weak-axis of the column. Using metallic cleats increases resistance, by comparison with composite cleats, using straightforward connection systems, unlike cuff connections, that can be readily used in construction. The campaign included web-cleated and flange-cleated connections, using different cleat thicknesses (4 mm, 6 mm and 8 mm), investigating the influence of the edge end distance (w.r.t. the beam end). The specimens were tested under monotonic and cyclic loads. The results show that the thickness of the cleats influences the behaviour of the flange-cleated configuration, but not that of the web-cleated connections. Additionally, while the former configuration can be considered as semi-rigid, for design, web-cleated connections should be considered as pinned. Both configurations presented significant resistance and rotation capacity, unlike connections using GFRP cleats, reported in previous research. On the other hand, the cyclic tests indicate that these connections present limited energy dissipation capacity, therefore they are not expected to contribute to dissipate energy under seismic actions. Overall, the results show that these weak-axis connections can support load bearing beams, although global structural design must avoid their (brittle) column failure modes.

Investigation of Linear and Nonlinear Behaviour of Reinforced Concrete Column Exposed to Corrosion Effect for Different Damage Limit Levels

The high performance of reinforced concrete structural elements under the effects of lateral loads such as earthquakes is of great importance in terms of minimizing the loss of life and property that may occur due to earthquakes. One of the parameters affecting the earthquake behavior of a reinforced concrete structure is the corrosion effect. The aim of this study is to investigate the behavior of reinforced concrete columns exposed to different corrosion levels for different durations within the damage limits. In this direction, it is aimed to perform linear and nonlinear analysis of reinforced concrete columns in 5 different corrosion scenarios. In the study, nonlinear analyzes of the column were made using ANSYS software, the data obtained were determined for different damage limit levels and compared with the section analysis. Because of the study, moment-curvature relations, lateral load-horizontal displacement relations, bending ductility and plastic rotation capacity of the reinforced concrete column were determined for each corrosion scenario.

Overstrength and Rotation Capacity of Short and Very Short Links Made of ASTM A992 Steel and Subjected to AISC 341-22 Loading Protocol

Overstrength and Rotation Capacity of Short and Very Short Links Made of ASTM A992 Steel and Subjected to AISC 341-22 Loading Protocol

Evolution characteristics and performance evaluation of extended end-plate joints with single and double side connections under cyclic loading

Experimental studies were conducted on four extended end-plate joints subjected to cyclic loading at the column top, investigating the evolving patterns of the joints' mechanical performance. The paper provides a detailed analysis and discussion of the test joints' failure modes, ductility, stiffness degradation, and energy dissipation capacity. The Mann-Kendall (M − K) trend analysis tool was applied to the mechanical response curves, identifying key performance evolution points (evolution initiation point P and overall yield point Q). The trends in bolt forces, deformations, and strains at critical joints were effectively validated, revealing the transition of the energy system from quantitative to qualitative changes and the component's failure process from stability to instability. Additionally, based on the experimental joints' hysteresis curves and energy dissipation capacity, a theoretical hysteresis model was established to predict the joint's hysteresis curve and cumulative dissipated energy accurately. According to EC3 requirements, joints were classified as partially rigid connections. The experimental results of the initial rotational stiffness and plastic moment were further used to evaluate the calculated values in existing standards EN 1993-1-8, ANSI/AISC 358-16, and GB 51017-2017. The results indicate that extended end-plate connections possess sufficient strength, joint rotational stiffness, ductility, and energy dissipation capacity, making them suitable for seismic moment frames.

Experimental study on edge cell partially-replaced joint for I-beam to multi-celled CFST walls under cyclic loading

The multi-celled concreted-filled steel tubular walls (MCCFSTWs) are widely used in practice, especially in apartment constructions. The use of thin steel tubes in MCCFSTWs makes it weak at the joint zone, therefore the connections between the MCCFSTWs and steel beams become an important issue for the application of MCCFSTWs. A novel joint for the connection between the MCCFSTWs and I-beams is proposed in this study. The main feature of the proposed joint is that the edge cell of the MCCFSTW is partially replaced using a welded C-section, where two partial internal diaphragms are set to transfer the bending moment from the I-beam. With this treatment, the edge cell of MCCFSTWs near the joint zone can be significantly strengthened to satisfy the requirements of the seismic design, while the compactness of concrete at the joint zone can be guaranteed by using the partial internal diaphragms. The design philosophy of the proposed joint is first introduced in this study. Three specimens are then designed and tested under the cyclic lateral loading. Subsequently, the behaviors of the proposed joints are discussed based on the test results, including the failure mode, the hysteresis curve, the ductility, the ultimate load and the initial stiffness. The stress states at the joint zone obtained from tests are also analyzed and compared with those using simplified analytical model. According to Eurocode 3, all tested specimens can be classified as rigid and full-strength joints. Moreover, the rotation capacity of this novel joint meets the requirements of GB50011. The investigation of this paper is believed to be meaningful for the application of the novel joints in the practice.

Experimental evaluation and numerical investigation on the anti-collapse performance of beam-to-column connections in the minor-axis direction

This study examined the effects of structural resistance in both major- and minor-axis directions on the anti-collapse performance of a fully bolted composite frame. Current research in the field has focused predominantly on the anti-collapse performance of H-columns in the major-axis direction, potentially hindering accurate determination of anti-collapse transmission path within a structure. Herein, monotonic static loading experiments were conducted on two substructures in the minor-axis direction: one equipped with welded flange and bolted web connections and the other with fully bolted connections. The ductility development curve, dynamic collapse response curve, and resistance mechanism correlation curve were employed to evaluate the test results. Fully bolted connections exhibited superior nonlinear rotation capacity, which is essential for the development of a structure's catenary resistance The failure mechanisms and resistance development processes of the structures were reproduced using the ABAQUS/Explicit dynamic quasi-static modeling technique. A full-scale finite element model was developed for the frame with fully bolted connections loaded in the minor-axis direction. This research will contribute to the robust design of fully bolted structural frames that considers the effects of the column stiffness, thickness of the splicing cover plate, number of bolt rows, and bolt apertures of flange connections on deformation and resistance to loading in the minor-axis direction.

A robustness-oriented procedure for the design of tying reinforcement in precast concrete hollow-core floors

Buildings may be subjected during their service life to extreme events which can trigger progressive collapse. On this front, the role played by tying reinforcement in structural members is crucial for an adequate load redistribution and the avoidance of disproportionate collapse. This work proposes a robustness-oriented procedure for the design of tying reinforcement placed in the hollow-core units and beams of precast concrete buildings, where limited studies are available in scientific literature. In particular, the aim is to provide a simple yet reliable approach for the design of concentrated and distributed ties in precast floors by adopting fundamental input parameters such as the system’s chord rotation capacity and dynamic amplification factor, which are not considered in current design codes. Firstly, a flow-chart of the design procedure is proposed and discussed. Secondly, the input parameters are calculated based on recent analytical approaches - proposed by some of the authors - to optimize the tying reinforcement design. Finally, the efficiency of the design procedure is demonstrated with an application example, and a novel detailing scheme is proposed which is aimed at a significant enhancement of structural robustness. Due to its simplicity, the proposed design procedure is contended to be applicable in robustness assessment and design of building structures with precast concrete hollow-core floors.

Theoretical investigation of the structural performance of multi–span reinforced concrete beams strengthened with FRCM systems

Few studies have reported on the flexural behavior of multi–span reinforced concrete (RC) structures strengthened using externally–bonded (EB) systems such as fiber–reinforced polymer (FRP) and fiber–reinforced cementitious matrix (FRCM) systems. This paper introduces a theoretical model that can accurately predict the flexural behavior of such structures with a focus on their rotational capacity (curvature) and their moment redistribution response between critical sections. Unlike the available models, the proposed model accounts for the variation in the structure’s stiffness during loading including that of the strengthened section. The model can precisely determine the failure mode, the rotational capacity of the formed plastic hinges and estimate the moment redistribution ratio (MRR) between the critical sections at any applied load. The efficiency of the model was validated against the experimental results of eleven FRCM–strengthened two–span RC beams (including two control beams) previously tested by the authors. A good agreement between the experimental and the theoretical results was obtained with average experimental–to–theoretical ratios of 1.0 and 0.99 for the load carrying–capacity and MRR, respectively. To accurately determine the mid–span deflections of continuous EB–strengthened structures, a new reduction parameter was incorporated in the CSA–A23.3–19 (2019) formulations to account for the variation in stiffness of the strengthened section. The new formulations substantially enhanced the prediction of the deflection capacity of the strengthened structures with an average experimental–to–theoretical ratio of 1.02 versus 1.7 when CSA formulations were used.