Cross-sectional Size Research Articles

Mechanical behavior of eccentrically loaded UHPC-encased CFST medium-long columns

To study the eccentric compression performance and failure mechanism of ultra-high performance concrete (UHPC) encased concrete-filled steel tubular (CFST) medium-long columns (UC-CFST medium-long columns), a total of 27 UC-CFST column specimens were tested under eccentric compression with eccentricity and slenderness ratio as the main parameters. After verified by experimental results, the finite element (FE) analysis of UC-CFST medium-long columns with actual structural cross-sectional size under eccentric compression was further carried out. It is found that as the slenderness ratio and eccentricity increased, the bending stiffness and the ultimate bearing capacity of the UC-CFST columns decreased gradually, and the failure mode changed from strength failure to instability failure, and the smaller the proportion of encasing UHPC area, the greater the upper-bound slenderness ratio of strength failure. Moreover, the influence of eccentricity was nonlinearly coupled with slenderness ratio on the eccentric compressive bearing capacity of UC-CFST medium-long columns. Finally, a calculation method of ultimate load-bearing capacity of UC-CFST medium-long columns considering the influence of eccentricity and slenderness ratio was proposed, which had good calculation accuracy with experimental and numerical results.

Behaviour and design of cold-formed high-strength steel built-up beams

The adoption of high-strength steel in the construction sector can provide potential advantages, such as supporting large-scale structures with small cross-sectional sizes leading to decreased self-weight and improved space availability. In this paper, detailed numerical investigations are presented to investigate the nonlinear behaviour of cold-formed high-strength steel (HSS) built-up beams subjected to in-plane flexure along with their bending moment capacities, deformed shapes, and moment-curvature curves. Finite element (FE) models incorporating the initial geometric imperfections of cold-formed sections and material nonlinearities were established and validated against the experiments presented in the literature by comparing the moment-curvature curves, deformed shape, and ultimate bending moment capacities. Following validation, the calibrated FE models were utilized to perform extensive parametric studies to generate further numerical data by varying three different parameters: cross-sectional yield strengths (S700, S900 and S1100), geometries (such that the local slenderness, λl values varied from 1.07 to 4.65) and cold-formed steel (CFS) sheet thicknesses (1.0, 1.5, 2.0, and 2.5 mm). The specimens considered in the present study were restrained to inhibit lateral-torsional buckling and demonstrated failure owing to local buckling. The applicability of the design principles for predicting bending capabilities was assessed using numerical data in accordance with direct strength method (DSM) of AISI codal provisions and continuous strength method (CSM). The obtained numerical results demonstrated that the existing standards lack precise design procedures for cold-formed HSS built-up members and additional research is still required to provide accurate design procedures. Therefore, an improved rational extension of DSM of AISI codal provisions and CSM is recommended to predict the ultimate bending moment resistance.

Determination of longitudinal stability of strip in rolling cage – non-drive dividing device system

In modern industrial and civil construction, various rolled metal products are used in greater volumes. The largest share of them is occupied by rebar profiles produced at small-grade mills. The ever-growing demand for rebar rolling requires an increase in production volumes. The most promising technology in this regard is rolling – separation, which, with relatively low material costs, allows operating rolling mills to significantly increase the production volume of rebar profiles while reducing energy consumption. However, despite the obvious advantages of rolling – separation technology using non-drive dividing devices, it is very difficult to correctly determine the rational modes of conducting the process taking into account the peculiarities of production and equipment layout, which is due to insufficient theoretical knowledge. One of the main problems is determination of the permissible distance in the rolling cage – non-drive dividing device system. The conducted studies allowed us to propose a dependence for determining the maximum permissible distance in the rolling cage – non-drive dividing device system for reasons of longitudinal stability of the strip, taking into account the size and shape of cross-section of the split articulated profile, the nature of pinching, and the backstretch stress. It was experimentally established that when determining the permissible distance between rolling cage and non-drive dividing device, it is advisable to take the length reduction coefficient equal to 0.7.

Seismic performance of shuttle-shaped double-restrained buckling-restrained brace: Experimental investigation and numerical analysis

To solve the problems of excessive cross-section size and self-weight and buckling instability of super-long buckling-restrained brace, a new lightweight shuttle-shaped double-restrained BRB (SDR-BRB) is proposed in this study. Firstly, cyclic loading experiments are conducted on three SDR-BRB specimens to investigate their failure mode and seismic performance. Then, a finite element model considering geometric, material, and contact nonlinearity is established and verified by experimental results. Finally, the effect of the restraining ratio on the hysteretic performance of SDR-BRB is studied by parameter analysis, and the restraining ratio requirement of the energy-dissipation type of SDR-BRB that meets the ductility requirements is obtained. The results show that SDR-BRB has stable and plump hysteretic curves, excellent energy-dissipation capacity, and low cycle fatigue performance, exhibiting obvious strain-strengthening characteristics. The restraining ratio is an important factor affecting the overall stability and failure mode of SDR-BRB, and it is recommended that the restraining ratio requirements of the SDR-BRB should be 2.25. The above research can provide a design reference for the practical engineering application of SDR-BRB.

A microchip based Z-cell absorbance detector integrating micro-lenses and slits for portable liquid chromatography

A miniaturized microchip-based absorbance detector was developed for portable high-performance liquid chromatography (HPLC) to test glycated hemoglobin (HbA1c). The microchip integrating a Z-shaped cell, two collimating micro-lenses and two ink-filled optical slits is small in size (30 mm × 15 mm × 7 mm). The Z-shaped cell has a cross-sectional size of 500 μm × 500 μm and a physical optical path length of 2 mm. Two collimating micro-lenses were inserted in empty grooves on both sides of the cell, one micro-lens for collimating the initial light and the other for focusing the transmitted light. Optical slits on each end of the cell were used to block the stray light. Therefore, this detector indicated a low stray light level (0.011 %) and noise level (2.5 × 10−4 AU). This detector was applied for the commercial HPLC system to detect HbA1c level, and showed a low limit of detection (0.5 μg/mL) and excellent repeatability (≤ 2.03 %). The sensitivity was enhanced by 3.4 times when the optical path length was increased from 0.5 mm to 2 mm and the stray light was blocked by optical slits. The miniaturized microchip-based absorbance detector developed shows a great potential for application in portable and compact HPLC.

A Case of Transmural Lipoma of the Right Atrium

Primary cardiac tumors are a relatively rare disease. About 75% of primary cardiac tumors are benign. The most common histological type is myxoma, followed by cardiac fibroma, lipoma, etc. We report a case of a 53-year-old female patient admitted to the hospital due to "repeated palpitations and tightness of breath for 5 years, worsened for 2 days." Preoperative transthoracic echocardiography revealed a hypoechoic mass approximately 3.1 cm x 3.0 cm in size within the right atrium, suggesting an intracardiac mass: nature? Chest computed tomography (CT) indicated a fat-density nodule within the right atrium, with a larger cross-sectional size of about 3.0 cm x 2.5 cm, suggesting a lipoma. The patient underwent excision of the right atrial mass under cardiopulmonary bypass. Intraoperative transesophageal echocardiography (TEE) revealed a mass within the right atrium, closely connected to the atrial wall, with no signs of tricuspid valve obstruction. Exploration during surgery revealed a yellow, smooth-surfaced mass approximately 3.0 cm x 3.0 cm in size, penetrating the right atrial wall, from which the mass and an additional 2mm margin of the right atrial wall were completely excised. A suitable-sized bovine pericardial patch was used to repair the defect in the right atrial wall. Postoperative TEE showed the disappearance of the right atrial mass. The postoperative pathological result indicated a lipoma. Cardiac lipoma is a rare benign primary cardiac tumor. The common sites of occurrence of this tumor are the right atrium, left ventricle, and pericardium. Based on their location, cardiac lipomas can be divided into three types: subepicardial, intramyocardial, and subendocardial lipomas, with subendocardial lipomas being the most common, accounting for over 50% of primary cardiac lipomas. Clinical symptoms largely depend on the size and growth location of the tumor, and it is generally believed that most cardiac lipomas are asymptomatic. Symptomatic lipomas can be treated with curative surgical excision. Transmural lipomas of the right atrium are relatively rare, and such lipomas may affect adjacent structures both inside and outside the atrial wall. Although the lipoma in this case did not significantly affect valve function or blood flow, the patient experienced repeated symptoms of palpitations and tightness of breath. Despite being a benign tumor, the lipoma in this case exhibited transmural growth within the right atrium, showing a certain degree of invasiveness, making surgical excision an effective treatment method.

Database of tall pre-Northridge steel moment frames for earthquake performance evaluations

This article describes a detailed database of tall steel moment frame buildings that are representative of the construction practices in San Francisco prior to the 1994 Northridge earthquake. The database contains design details that affect the structural performance of steel moment frames, including frame geometry, member cross-section sizes, and gravity system characteristics. This database also captures irregularities that might impact seismic response, such as podiums, setbacks, mass concentrations (mechanical, electrical, and plumbing (MEP) floors), interrupted column lines, and atriums. The database includes information on 89 moment frame buildings, 14 of which were built before 1960 and are constructed with riveted connections, while the remaining 75 have welded flange connections like those that suffered brittle fracture during the 1994 Northridge earthquake. The buildings are further distinguished between space frame, perimeter frame, and partial space frame systems. For about half (41/89) of the buildings in the database, section sizes of representative structural members were collected, which enabled the evaluation of the seismic design, elastic, and inelastic response using computational workflows. The design diagnostics indicate that most of the buildings meet the minimum seismic strength and strong-column weak-beam requirements of modern building codes, even though they were not necessarily designed with this intent. On the contrary, about one-third of the buildings do not meet the seismic design drift limit of current codes, and about half of them have weak beam-column panel zones. This database, associated structural analysis models, and processing scripts are published at DesignSafe https://doi.org/10.17603/ds2-wjad-r340 to facilitate collaboration and continued development of open-source data for high-resolution simulations to inform risk mitigation strategies on a regional scale.

Response Modification Factor of High-Strength Steel Frames with D-Eccentric Brace Using the IDA Method

The design innovation of high-strength steel frames paired with D-eccentric bracing exhibits remarkable resistance to plastic deformation during seismic events. This method strategically combines regular steel connections (with yield strengths below 345 MPa) and high-strength steel beams and columns (such as Q460 or Q690, with yield strengths over 460 MPa), effectively reducing cross-sectional sizes while preserving the elasticity of non-energy-dissipating members. This configuration results in substantial ductility and superior energy dissipation capabilities. The response modification factor (R) is vital for achieving both effective and economical seismic resilience, particularly in the development of efficient and cost-effective seismic designs. However, the 2016 edition of the Code for Seismic Design of Buildings (GB50011-2010) fails to incorporate the concept of R, opting instead to apply a uniform value to all structural systems. This oversight is fundamentally flawed, necessitating a comprehensive investigation into the R value specifically for the high-strength steel frame with a D-eccentric brace. This research primarily aims to improve structural performance design, provide guidance for future projects, and encourage the adoption of this advanced seismic performance structure in earthquake-prone areas. To achieve these objectives, a performance-based seismic design approach is employed. This method involves designing structures with varying numbers of stories (4, 8, and 12), different link lengths (900, 1000, and 1100 mm), and various steel strengths (Q460 and Q690). This study uses the Incremental Dynamic Analysis (IDA) method to determine the R values for each prototype. The derived performance coefficients act as crucial references for the development of future innovative structural designs. This research greatly enhances seismic design practices and facilitates the wider adoption of high-strength steel frames with D-eccentric braces due to their outstanding seismic performance.

Thermally Drawn-Based Microtubule Soft Continuum Robot for Cardiovascular Intervention.

Cardiovascular disease is becoming the leading cause of human mortality. In order to address this, flexible continuum robots have emerged as a promising solution for miniaturizing and automating vascular interventional equipment for diagnosing and treating cardiovascular diseases. However, existing continuum robots used for vascular intervention face challenges such as large cross-sectional sizes, inadequate driving force, and lack of navigation control, preventing them from accessing cerebral blood vessels or capillaries for medical procedures. Additionally, the complex manufacturing process and high cost of soft continuum robots hinder their widespread clinical application. In this study, we propose a thermally drawn-based microtubule soft continuum robot that overcomes these limitations. The proposed robot has cross-sectional dimensions several orders of magnitude smaller than the smallest commercially available conduits, and it can be manufactured without any length restrictions. By utilizing a driving strategy based on liquid kinetic energy advancement and external magnetic field for steering, the robot can easily navigate within blood vessels and accurately reach the site of the lesion. This innovation holds the potential to achieve controlled navigation of the robot throughout the entire blood vessel, enabling in situ diagnosis and treatment of cardiovascular diseases.

Cross-Sectional Melt Pool Geometry of Laser Scanned Tracks and Pads on Nickel Alloy 718 for the 2022 Additive Manufacturing Benchmark Challenges

The Additive Manufacturing Benchmark Series (AM Bench) is a NIST-led organization that provides a continuing series of additive manufacturing benchmark measurements, challenge problems, and conferences with the primary goal of enabling modelers to test their simulations against rigorous, highly controlled additive manufacturing benchmark measurement data. To this end, single-track (1D) and pad (2D) scans on bare plate nickel alloy 718 were completed with thermography, cross-sectional grain orientation and local chemical composition maps, and cross-sectional melt pool size measurements. The laser power, scan speed, and laser spot size were varied for single tracks, and the scan direction was varied for pads. This article focuses on the cross-sectional melt pool size measurements and presents the predictions from challenge problems. Single-track depth correlated with volumetric energy density while width did not (within the studied parameters). The melt pool size for pad scans was greater than single tracks due to heat buildup. Pad scan melt pool depth was reduced when the laser scan direction and gas flow direction were parallel. The melt pool size in pad scans showed little to no trend against position within the pads. Uncertainty budgets for cross-sectional melt pool size from optical micrographs are provided for the purpose of model validation.

Fracture mechanics analysis of gas pipeline with circumferential crack under the action of transverse landslide

The whole process of pipeline–soil interactions between a landslide and a gas pipeline was simulated using the strength reduction method. The main purpose is to investigate how pipeline internal pressure, landslide displacement, crack depth ratio (the ratio of crack depth to wall thickness), crack aspect ratio (the ratio of crack depth to crack half-length), and reinforcement with anti-slide piles influence the J-integral of a circumferential crack in the pipeline under landslide impact. The simulation showed that increases in the landslide displacement, crack depth ratio, and pipeline internal pressure led to an increase in the maximum value of the J-integral at the crack leading edge. An increase in the crack aspect ratio reduced the maximum value of the J-integral. In addition, in the process in which the crack shape changed from semi-elliptical to semicircular, there was a critical crack aspect ratio at which the J-integral at the deepest point of the crack was equal to the J-integral at a point on the surface. The study also found that an increase in the number of anti-slide piles affected the location and distribution of the zone of maximum slippage and effectively reduced the maximum von mises stress and the J-integral at the crack tip. However, when the number and cross-sectional size of anti-slide piles exceed a certain threshold, further increasing or enlarging them barely affects the J-integral.

Ultrasonic vibration-assisted electrical discharge machining of enclosed microgrooves with laminated electrodes

An enclosed microgroove is a vital surface microstructure that is difficult to prepare on the surfaces of difficult-to-machine electrically conductive materials using conventional methods. Electrical discharge machining (EDM) is suitable for this task. It is obtained primarily through layer-by-layer scanning EDM with micro-column electrodes or reciprocating EDM with foil electrodes. However, owing to the small cross-sectional size of the electrodes, a stable machining process is challenging to achieve, which seriously reduces the machining efficiency. To solve these problems, this study proposed ultrasonic vibration-assisted EDM using a laminated electrode possessed strong anti-interference properties for enclosed microgrooves. The effects of ultrasonic vibration on the EDM of microgrooves with single foil and laminated electrodes were investigated. The results show that ultrasonic vibration could improve the machining efficiency of the two types of electrodes and significantly improve the profile quality of the microgrooves prepared using laminated electrodes. When the amplitude was 3 μm and the frequency was 30 kHz, the bottom sidewall corner radius of microgrooves machined by brass foils in laminated electrodes was 28 μm, the width, depth, and roughness of microgrooves machined by copper foils in laminated electrodes were approximately 78 μm, 229 μm and 0.7 μm, the material removal rate was 0.0072 mm3/min. Based on the optimized parameters, inverted “convex” microgrooves with fine consistency were successfully prepared using laminated electrodes on Ti–6Al–4V alloy surfaces. The machining time was reduced by 40% for each microgroove compared with using the single foil electrode. This study provides a new method for preparing complex microgrooves.

High cooling and power generation performance of α-MgAgSb with intrinsic low lattice thermal conductivity

α-MgAgSb is a promising near-room temperature thermoelectric material, characterized by its intrinsically low lattice thermal conductivity, a feature attributed to the significant atomic mass contrast and complex crystal structure. In this work, we achieved respective zTavg values of 0.58 in the temperature range of 150–300 K and 1.22 in the range of 300–550 K for α-MgAgSb, indicating exceptional potential for both cooling and power generation applications. Additionally, through the reduction of cross-sectional size, the stability of MgAgSb/Ag interface was enhanced under high temperature, which is crucial for the practical application of thermoelectric module. To verify the property of α-MgAgSb material, a 7-pair MgAgSb/Bi2Te3 module was fabricated, demonstrating a maximum cooling temperature difference ΔTmax of 60 K at hot-side temperature of 300 K and a power generation efficiency ηmax of 7.2 % with ΔT of 275 K. This work paves the way for the application of Mg-based thermoelectric materials.

Analysis of Tool Load Concerning the Cross-Sectional Size of Removed Material

High-feed milling (HFM) represents a progressive manufacturing technology that has recently found widespread application across various industries. HFM is characterized by high machining speed, reduced cycle times, increased overall productivity, and increased tool life. Due to its versatility, HFM is a suitable technology for the application of various materials. The study deals with experimental analysis of cutting forces, machined surface integrity, and statistical evaluation in high-feed machining. In the present study, nickel-copper-based alloy (Monel) was chosen as the machined material, employing HFM with a monolithic ceramic milling cutter. The Monel material is characterized by its excellent mechanical properties and chemical resistance in harsh environments. During machining, cutting forces were recorded in three mutually perpendicular directions. This paper delves into the analysis of the impact of the depth of cut (ap), width of cut (ae), and lead-in angle (ε). The chosen evaluation characteristics encompass the tool load, primary profile, and the attained roughness of the machined surface. It is noteworthy that the technology under consideration predominantly aligns with the roughing phase of the manufacturing process. Additionally, the investigation incorporates a statistical analysis of the response surface pertaining to the cutting force components, namely Fx, Fy, Fz, and the resultant cutting force F.

Shape-Sensing Robotic-Assisted Bronchoscopy in the Multiple Pulmonary Nodule Diagnosis during a Single Anesthetic Event

Introduction: The widespread use of computed tomography as a screening tool for early lung cancer has increased detection of pulmonary lesions. It is common to encounter patients with more than one peripheral pulmonary nodule (PPN) of uncertain etiology. Shape-sensing robotic-assisted bronchoscopy (ssRAB) emerges as a potential alternative to biopsy multiple PPN, in addition to mediastinal staging in single anesthetic procedure. Methods: This is a single-center, retrospective review of 22 patients who underwent ssRAB for evaluation of two or more PPN, between November 2021 and April 2023 at Mayo Clinic, FL, USA. Results: A total of 46 PPNs were biopsied in 22 patients. All lesions were ≤2 cm with a median minimum and maximum cross-sectional lesion size of 1.40 cm and 1.05 cm, respectively. Diagnostic yield was 86.9% (n = 40), and target reach was 91.3% (n = 42). Most lesions were in the upper lobes, a solid pattern was found in 78.3% (n = 36), bronchus sign was present in 82.6% of cases (n = 38), 54.4% (n = 25) were malignant nodules, and 32.6% (n = 15) were benign. Fourteen patients had at least one malignant lesion out of two or more nodules sampled, and 10 patients had a malignant diagnosis for all sampled lesions. The complication rate was 9% (n = 2) with one case of bleeding and one of pneumothorax. Conclusion: This study is, to our knowledge, the first to assess the use and safety of ssRAB for diagnosis of multiple PPN in a single anesthetic event. This procedure will mainly impact management decisions and subsequently shorten the time from diagnosis to treatment.

Machine-learning-assisted design of high strength steel I-section columns

High strength steel has been attracting attention in the building industry due to its superior mechanical properties. The accurate design of high strength steel structures is crucial to boost its wide application. In this paper, an accurate and unified design approach for high strength steel I-section columns with different material grades, boundary conditions, geometric dimensions (including cross-section sizes and member lengths) and failure modes is proposed based on machine learning. Firstly, 871 experimental and numerical data were collected from the literature to establish a database. Then, seven machine learning algorithms, including Decision Tree, Random Forest, Support Vector Machine, K-Nearest Neighbour, Adaptive Boosting, Extreme Gradient Boosting and Categorical Boosting, were applied to establish machine learning regression models to predict buckling resistances of high strength steel I-section columns. The model performance was then evaluated through statistic indices, with the evaluation results indicating that the Categorical Boosting trained model yields the highest level of accuracy. Based on the data in the collected database, the regression model trained by Categorical Boosting and existing codified design provisions, as given in the European code and American specification, were assessed and compared. The European code and American specification were found to yield scattered and inaccurate failure load predictions, while the Categorical Boosting trained model led to substantially more accurate and consistent failure load predictions for high strength steel I-section columns with different material grades, boundary conditions, geometric dimensions and failure modes.

Close-in blast performance of RC beams with varying cross-sectional sizes and damage assessment based on the dynamic load carrying capacity

Aiming to investigate the impact of cross-sectional size on the close-in blast performance of reinforced concrete (RC) beams, the local damage features and structural responses of RC beams with varying cross-sectional widths and depths subjected to close-in explosions were investigated experimentally and numerically. Experiments were conducted on ten RC beams with a cross-sectional size of 25 cm × 12.5 cm to study the influence of scaled distance and charge mass on the local damage size and structural responses (displacement and reaction force). The results indicate that the blasting face damage to tested beams, such as the crushing crater of concrete cover and side peeling-off damage, is more sensitive to the scaled distance (intensity of applied blast loads) compared to the rear spalling damage. And the peak reaction force exhibited a gradual increase within the range of 0.5 m/kg1/3, eventually reaching an average maximum value of 93.5 kN, and remained unchanged after the scaled distance was greater than 0.5 m/kg1/3, indicating that the dynamic load-carrying capacity of tested beams increased with the increasing scaled distance and the maximum dynamic load-carrying capacity of these beams is around 93.5 kN. Furthermore, a numerical model of RC beams subjected to close-in explosions was established based on the Fluid-Structure-Interaction (FSI) method. For validation, the local damage morphology and sizes of RC beams and their dynamic responses (displacement and reaction force) were computed and compared with the corresponding experimental results, concluding that the numerical results are in good agreement with the experimental findings. A parametric analysis was conducted to study the impact of cross-sectional size on the development process of initial local damage, stress distribution in cross sections, local damage sizes, and structural responses. Moreover, a damage index of the dynamic load-carrying capacity was derived from the relationship between the normalized maximum reaction force and the normalized maximum displacement to assess the damage degree of RC beams with varying cross-sectional sizes. This work can serve as a partial reference for relevant research.

The Influence of Transformational Leadership on Work Stress in Banking: Unveiling the Mediating Role of Emotional Intelligence

The objective of this research is to conduct a comprehensive investigation into the factors that contribute to job stress among banking employees in Karachi. This study aims to elucidate the relationship between transformational leadership and work stress, in the social exchange theory. The study collected data from multiple individuals employed at various banks in Karachi. A questionnaire was employed to gather information from a total of 380 employees. The analysis of this study was conducted using the SMART-PLS4. For this quantitative research study, convenient sampling was employed, along with a cross-sectional technique. The findings suggest that transformational leadership and work stress are positively correlated. Additionally, emotional intelligence factors, including self-awareness, self-regulation, motivation, and empathy, were found to mediate the relationship between transformational leadership and job stress. However, the study did not find evidence to support the mediating effect of social skills on this relationship. In Karachi's banking sector, putting transformational leadership into practice and giving emotional intelligence training top priority can greatly lower workplace stress, improve the well-being of workers, and create a more optimistic and successful work atmosphere. The cross-sectional approach and sample size of this study restrict the findings to the banking industry in Karachi. For a more comprehensive knowledge of the evolution of work stress and wider generalizability, future studies should make use of longitudinal approaches and take into account other mediators and moderators. The research examines the relationship between transformational leadership and work stress through the novel mediator, emotional intelligence. The five components of emotional intelligence enable a more thorough investigation to gain a deeper understanding of workplace dynamics. Utilizing the study's structure to deliver valuable insights to the organizations.

Plastic hinge behavior of rectangular CFRP-confined RC columns: Meso-scale modelling and formulation

The ultimate rotation capacity, depending on the plastic hinge length, is a vital factor in the seismic design of flexural members. This paper focuses on the investigation of the plastic hinge length and size effect of rectangular carbon fiber-reinforced polymer (CFRP)-confined reinforced concrete (RC) columns. Firstly, considerable scatter and evident bias of the calculation results were found after evaluating existing models for calculating the plastic hinge length of FRP-confined RC columns. Accordingly, a meso-scale numerical approach was developed, with concrete heterogeneity considered, to investigate the influences of the confinement ratio and corner radius on the plastic hinge length and size effect of rectangular CFRP-confined RC columns. Results show that columns having different cross-sectional sizes exhibit similar failure patterns, and the region of lateral crack propagation for columns with lower confinement ratios is larger than that for columns with higher confinement ratios. The actual plastic hinge length is determined based on the yielding zone of reinforcement, the crushing zone of concrete, and the localization zone of curvature, while the localization zone of curvature is employed to determine the real plastic hinge zone. The size effect is found to exist in the plastic hinge length ratio, and it is weakened with the increase of the corner radius, which can be attributed to the fact that columns with higher corner ratios have more effective confinement. Taking into account the size effect, a new model for calculating the ultimate drift ratio of CFRP-confined RC columns was proposed based on an assumption of curvature distribution and presented accurate predictions.

A New Moment-Resisting Glulam Beam-End Connection Utilizing Mechanically Fastened Steel Rods—An Experimental Study

A new moment-resisting mass timber connection was designed based on the principles of force equilibrium in applied mechanics. The connection configuration utilizing two mechanically fastened threaded steel rods embedded into the end of a glulam beam section was experimentally investigated in this study. A gradually increasing transverse load was applied to the free end of a cantilevered beam, causing a bending moment on the beam-end connection until failure. Four different connection configurations were examined, each replicated twice to verify results. The beam connection parameters investigated were rod anchorage length (200 and 250 mm) and square washer size (38.1 and 50.8 mm). Test results show that increasing the washer size increased the connection bending strength by increments more significantly than those due to increasing the rod anchorage length. However, the connection configurations with the smaller-size washer, which failed mainly due to wood crushing under the washer, had higher ductility ratios than those with the larger-size washer, which failed due to steel rod yielding. In a real-life scenario, a structural element such as a glulam beam is usually loaded to approximately 50% to 70% of its design capacity, considering a reasonable margin of safety. The study estimates a maximum possible bending moment utilization factor for the strongest connection configuration that ranged between 34% and 48% compared to the maximum moment resistance of a supported glulam beam spanning an average length of 4.0 m to 6.0 m (a common span length in framed timber buildings) and has a cross-section size same as the one utilized in this study. This utilization factor is quite large for a timber connection, and thus, confirms a considerable moment-resisting capability of the new configuration developed in this study.