고인성섬유 복합모르타르를 활용한 고강도 철근콘크리트 외부 보-기둥 접합부의 내진성능평가

Numerical investigation on the shear behavior of slender reinforced concrete beams without shear reinforcement differed by various boundary and loading conditions

This paper investigated the eccentricity ratio, relative clearance, and length to diameter ratio under different load carrying capacities and journal rotation speeds, aiming to provide design reference of eccentricity ratio, relative clearance, and length to diameter ratio in water-lubricated bearing design process. The computer fluid dynamics was adopted to analyze eccentricity ratio, relative clearance, and length to diameter ratio of water-lubricated bearing. The cavitation effect of water was considered in the analysis. The simulation results of eccentricity ratio were verified by experiments. In different journal rotation speeds, the relative clearance had little influence on the maximum water film pressure and load carrying capacity. The numerical number of maximum water film pressure and load carrying capacity was in a small range. Designing chart of eccentricity ratio, relative clearance, and length to diameter ratio was provided.

The hybrid concrete frame investigated herein was composed of precast concrete T beams and cast-in-place concrete columns. This study presents the results of experimental investigations on 1/4-scale six-story two-bay hybrid concrete frames under cyclic loading and monotonic loading, respectively. Behavior of the specimens was evaluated in terms of failure pattern, failure mechanism, stiffness degradation, energy dissipation, and displacement ductility. The results revealed that the plastic hinge first occurred in the second story beam end. Both specimens, as expected, exhibited a mixed sideway mechanism. The hysteresis loops of the test specimen were globally stable and exhibited some pinching. The maximum load-carrying capacity under cyclic loading was about 6% higher than that under monotonic loading. Both specimens behaved in a ductile manner, and the global displacement ductility under cyclic loading was 38% lower than that under monotonic loading. An overview of damage observations and the local and global behaviors were provided.

A computational technique for obtaining the maximum load-carrying capacity for a robotic manipulator with joint elasticity, subject to accuracy and actuator constraints, is described. Full load motions and increased productivity are linked in the industrial applications of many robotic manipulators; the maximum load carrying capacity which can be achieved by a manipulator during a given trajectory is limited by a number of factors. The dynamic properties of a manipulator, its actuator limitations, and joint elasticity (transmissions, reducers, and servo drive system) are probably the most important factors. This paper presents a strategy for determining dynamic load carrying capacity (DLCC), subject to both accuracy and actuator constraints, where a series of cubical bounds centred at the desired trajectory is used in the end-effector oscillation constraint while a typical d.c. motor speed-torque characteristics curve is used in the actuator constraint. The technique which considers the full nonlinear manipulator dynamics, actuator constraints, and accuracy constraints permits the manipulator user to specify the trajectory completely. Finally, a numerical example involving a two-link manipulator with joint flexibility using this method is presented and the results are discussed.

This paper presents calculating the maximum load capacity of 2-link mechanical manipulator using evolutionary algorithms, PSO and GA, applied to the system's dynamic model. GA and PSO are two techniques that have received a lot of attention in recent years, owing to their parallel characteristics and their ability in searching for optimal solutions in irregular and high dimensional solution spaces. As a 2-link mechanical manipulator is a system with high dimensionsthat calculating its maximum load carrying capacity is an important issue, PSO and GA can be of great help in determining this capacity easily and efficiently.

In this study, experimental research was carried out to investigate the seismic and structural performance of precast concrete exterior beam-column joints using bolt type connection and prestressing method. A total of five full-scale exterior beam-column joints were constructed and tested under reversed cyclic loading, controlled by displacement. Results of the test are as follows: Energy dissipation capacity and pinching phenomenon of PC beam-column joints showed disadvantageous behavior compared to RC beam-column joints. However, drift capacity of the PC joint was excellent. Also, yield mechanism concentrated on embedded nuts was suitable as an exterior beam-column joint of lateral load resistance frame. Additional application of prestressing method was also very effective to control excessive pinching and cracking in the joint region, and thus improved an overall seismic performance of the PC joint.

In this study, the inelastic load-carrying capacity of the compression diagonal of a typical cross-bracing system used in concentrically braced frames under gravity and wind loads is investigated, taking into consideration its interaction effect with the tension diagonal. Depending on the lateral stiffness of the tension diagonal, the compression diagonal can be fully or partially braced by the tension diagonal at their intersection point. An expression for the transition lateral stiffness, kst, that demarcates the fully and partially braced conditions is derived. When the compression diagonal is fully braced, its maximum load-carrying capacity is a function of its member slenderness, L/r, only. However, when the compression diagonal is partially braced, its load capacity is dependent upon both its member slenderness, L/r, and the lateral stiffness, ks, of the tension diagonal. Once the equations for the maximum load-carrying capacity of the compression diagonal are established, design guidelines are proposed and design examples are given to demonstrate how the proposed guidelines can be used for the design of cross-bracing systems in steel frames. The consideration of the lateral bracing effect will result in a more economical and logical design for such bracing systems.

This investigation considered the usability of ceramic waste powder (CWP) in altered quantities in reinforced concrete beams (RCBs). In this way, it was aimed to reduce the environmental impacts of concrete by using CWP as a raw material in RCBs. 12 small-scale shear RCBs with the dimensions of 100 × 150 × 1000 mm were tested in this study. The variations of stirrups spacing and CWP ratio were examined in these specimens. The percentages of CWP by weight utilized in RCBs were 10%, 20%, and 30%, and stirrups spacings were adopted as 270 mm, 200 mm, and 160 mm. At the end of the study, it was determined that more than 10% CWP additive negatively affected the RCBs' compressive strength. The load-carrying capacity reduced between 30.3% and 59.4% when CWP increased from 0% to 30% as compared to RCB with stirrups spacing of 270 mm without CWP. However, compared to RCB with stirrups spacings of 200 mm and 160 mm without CWP, there were decreases in the load-carrying capacity as 21.4%–54.3% and 18.6%–54.6%, respectively. While the CWP ratio increased, the specimens with 160 mm, 200 mm, and 270 mm stirrups spacings obtained a lower maximum load value. However, with the increase of the CWP ratio in the specimens with 160 mm stirrups spacing, RCBs reached the maximum load-carrying capacity at an earlier displacement value. When stirrups spacing was selected as 270 mm, it was observed that the maximum load-carrying capacity of RCBs reached at a similar displacement value as the CWP ratio increased. Besides, it was resulted that the bending stiffness of RCBs reduced as the quantity of CWP enhanced. The bending stiffness decreased by 29.1% to 66.4% in the specimens with 270 mm stirrups spacing, 36.3% to 20.2% with 200 mm stirrups spacing, and 10.3% to 36.9% with 160 mm stirrups spacing. As an implication of the experiments, the use of CWP up to 10% in RCBs was realized as an economical and environmental approach and is suggested. There is some evidence to report that making use of CWP may be considered to be ecologically benign. This is due to the fact that reusing CWP may significantly reduce CO2 emissions, save energy, and reduce total power consumption. Furthermore, the experimental results were compared to the analytical calculations.

In this study, a series of investigations have been planned to examine the altered mechanical properties of reinforced concrete beams that have experienced different levels of shear damage under vertical loads, through the application of Carbon Fiber-Reinforced Polymer (CFRP) strengthening. Both experimental and numerical approaches will be utilized to analyze these effects comprehensively. Within the scope of this study, four reinforced concrete beams with rectangular cross-sections and inadequate shear strength were subjected to vertical loads. One of these beams was designated as the reference beam, while the other three beams were loaded to induce varying levels of damage, corresponding to 50%, 65%, and 85% of the reference beam's shear capacity. Subsequently, these beams were strengtheningwith CFRP strips at shear spans of 12.5/10 cm width and spacing. The experiments were then repeated with this strengthening. Models were created using the ABAQUS finite element program, considering support, load, and material conditions, to simulate the experiments accurately. At the conclusion of the study, the maximum load-carrying capacity obtained from the Finite Element Model (FEM) was found to be between 95% to 105% of the maximum experimental Load-Carrying Capacity (Pu). Additionally, the study demonstrated that the crack mechanisms occurring in the beams during the experiments were in perfect agreement with those predicted by the finite element analysis.

The article presents the design of Complibot, a robot with a novel gripper for pipe climbing. The mechanism of the gripper involves the use of a bistable buckled beam, which is a type of bistable compliant mechanism. The bistable buckled beam in the gripper is alternately actuated between its gripped and ungripped states using a camshaft and lever mechanism, which is powered by a single DC motor. The design parameters associated with the gripper are obtained both experimentally and numerically. A proper selection of design parameters helps in the efficient functioning of the gripper. After the design of the gripper, two such grippers are fabricated and attached to each other by two stepper motor-driven lead screws to make a pipe climbing robot with inchworm locomotion. The mobility of the robot is controlled by an Arduino Uno microcontroller after the electronic components have been integrated. Finally, Complibot is subjected to a series of tests to establish its maximum load-carrying capacity when climbing a polyvinyl chloride (PVC) pipe. Complibot is found to perform satisfactorily without slipping while climbing a PVC pipe with a diameter of 105–115 mm, a velocity of 0.2 m/min, a power consumption of 18.58 W, a maximum load-carrying capacity of 114.64 N, and a payload to weight ratio of 0.52.

Experimental research on seismic behavior of +-shaped columns reinforced with high-strength steel bars under cyclic loading

Studying the seismic performance of assembled beam–column joints is essential for the development of assembled frame structures. In this paper, a novel dry connection beam–column joint with a high degree of modularity and a simple structure is proposed and tested using a pseudostatic test. The joint is composed of a precast concrete beam with a steel axillary plate at the end and a precast concrete column connected by long bolts. By analyzing the characteristics of the hysteresis curve, skeleton curve, and stiffness degradation curve, we were able to investigate the seismic performance of this novel new joint under low circumferential reciprocating load as well as the impact of bolts of various strength grades on the joint’s seismic performance. The results illustrated the robust overall bearing performance of the newly assembled beam–column joint. However, when connected with common bolts, the joint deforms more, exhibits good ductility, clearly displays semi-rigid characteristics, and performs better in terms of energy dissipation. This contrasts with connecting with low-strength bolts, which cause the joint to deform little and have poor energy dissipation capacity. The prefabricated columns and beams remain undamaged, making it possible to quickly repair the assembled building structure after an earthquake; however, the joints are harmed due to the bending and fracture of the connection bolts. It has been suggested that researchers add damping energy dissipation devices to the new joint to increase its energy dissipation capacity and control the joint’s overall deformation because the joint’s energy dissipation capacity is insufficient under the low circumferential reciprocating load.

Seismic performance of glulam timber post and beam structures with and without light frame timber shear wall infill

A total of five ultra-high-performance concrete (UHPC)-strengthened reinforced concrete (RC) columns and one RC column were built and subjected to eccentric compression testing to examine the force performance of UHPC-strengthened eccentrically compressed plain RC columns. This experimental study examined the crack progression, the damage morphology, the deformation ability, the maximum load-carrying capacity, and the ductile properties of the eccentrically compressed columns. It also investigated the impacts of eccentricity, the reinforcement thickness, and the addition of steel fibers on the effectiveness of reinforcement. The cracking load, peak load, and ductility coefficient of the UHPC-reinforced specimens were increased by 100.28%, 172.30%, and 56.30%, respectively, compared with the RC column at an initial eccentricity of 50 mm. As the eccentricity distance increased, the bearing capacity of the UHPC eccentrically compressed specimens decreased, and the deformation capacity increased. Increasing the steel fiber dosage within the appropriate range decreased the crack width of the specimen. The addition of 2% steel fiber resulted in a 24.8% increase in cracking load, an 8.96% increase in peak load, and a 2.60% increase in ductility coefficient compared to the addition of 1% steel fiber. However, the reinforcing effect of UHPC was weakened under high eccentric pressures. Based on the theory of concrete structure and mechanical principles, the formula for calculating the compressive bearing capacity of RC columns strengthened with high-performance concrete was proposed. The results of calculating the positive section bearing capacity of eccentrically compressed RC columns reinforced with high-performance concrete are in good agreement with the test values. The results of this paper provide an experimental basis and theoretical foundation for the cross-sectional design of UHPC eccentrically compressed columns.

In accelerated bridge construction (ABC), precast segmental piers (PSPs) have shown significant progress in shortening the construction period and reducing the cost. By combining multiple segments with post-tensioned (PT) tendons, the desired self-centering ability can be introduced; however, this may lead to a lower energy dissipation (ED) capacity and concentrated damage. To address this concern, the present study proposes a design concept that promotes multiple joint openings to achieve a better energy dissipation capacity and decentralized damage without compromising the self-centering ability. Two main approaches for this objective are discussed in detail. The first approach incorporates different arrangements of ED rebars at various joints, while the second introduces innovative damage control rubber joints (DCRJs) with varying stiffness beneath each segment. Four scaled specimens designed using these two approaches were quasi-statically tested. The observed damage, final failure mode, energy dissipation capacity, resilience index, and damage decentralization were further examined. The results revealed that for PSPs designed using the first approach, the joint openings were successfully decentralized only up to a certain level, after which they were still predominantly concentrated at a single joint, leading to strength degradation and damage concentration. PSPs designed using the second approach demonstrated decentralized joint openings, improved displacement ductility, and damage mitigation, resulting in both superior seismic and post-seismic performance.