Stability Design of Cross-Bracing Systems for Frames

In this study, the effects of wind and seismic loads on 5, 10, and 15 story steel buildings with different bracing systems were investigated. Linear static and nonlinear dynamic analyses were performed to assess the base shear, base moment, and story drift for all bracing systems. In addition, the cost analysis was taken into consideration. Five structural configurations were used: V-bracing, inverted V-bracing, one-story X-bracing, and multistory X-bracing. One of the most important features of a building is lateral stiffness, which defines the resistance to displacement under seismic and wind loads, at the same time, the lateral stiffness has a major impact on the natural time of the structure. Reducing displacement and cost in the structures indicates that the design is safe and economical. Therefore, the purpose of this article is to find the best bracing system that causes minimum displacement, which indicates maximum lateral stiffness. From this point of view, the behavior of bracing systems exposed to wind and seismic loads in buildings with different stories was investigated. Static linear analysis results showed that the best bracing systems to reduce lateral displacement were the one-story X-bracing system for 5 and 15 story buildings and the V-bracing system for 10 story buildings. On the other hand, nonlinear dynamic analysis results showed that lateral displacement was minimum in unbraced, V-bracing, and one-story X-bracing systems for 5, 10, and 15 stories, respectively.

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.

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.

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.

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.

이 연구에서는 고강도 철근콘크리트 외부 보-기둥 접합부의 시공성 및 내진성능을 개선하기 위하여 보-기둥 접합부 영역의 스터럽 및 띠철근 유무에 따라 고인성섬유 복합모르타르를 사용하여 내진성능을 평가하였다. 총 5개의 실험체를 제작하고 실험을 수행하여 내진성능을 평가하였으며, 이 연구의 시험 결과를 근거로 다음과 같은 결론을 얻었다. 기존 고강도 철근콘크리트 내부 보-기둥 접합부의 위험단면 영역을 고인성섬유 복합모르타르로 보강한 결과 재하 전 과정을 통하여 섬유의 가교역할로 인한 균열 분산효과로 인하여 균열 제어 효과가 커서 안정적인 파괴형태 및 내력을 나타내었다. 고강도 철근콘크리트 외부보-기둥 접합부의 시공성 및 내진성능을 개선하기 위하여 고인성섬유 복합모르타르를 사용하여 보강한 실험체(BCJNSP 시리즈)는 스터럽과 띠철근이 제거 되었음에도 안정적인 이력거동을 나타내었고, 최대내력이 전단보강근이 없는 실험체 BCJNS의 1.09∼2.03배로 증가하였다. 그리고 고인성섬유 복합모르타르를 사용하여 보강한 실험체(BCJNSP 시리즈)는 표준실험체 BCJC의 최대내력이 0.92∼0.96배로 거의 비슷하였고, 에너지소산능력은 최대 1.62배로 크게 증가하였다.

Tall buildings are categorized as important structures because of the large number of occupants and high construction costs. The choice of competent lateral load resisting systems in tall buildings is of crucial importance. Bracing systems have long been an economic and effective method for resisting lateral loads in steel structures. However, there are some potential adverse aspects to bracing systems such as the limitations they inflict on architectural plans, uplift forces and poor performances in compression. in order to eliminate the mentioned problems and for cost optimization, in this paper, six 20-story steel buildings and frames with different types of bracing, i.e., conventional, mega-scale and buckling-restrained bracing (BRB) were analyzed. Linear and modal push-over analyses were carried out. The results pointed out that Mega-Scale Bracing (MSB) system has significant superiority over the conventional bracing type. The MSB system is 25% more economic. Some other advantages of MSB include: up to 63% less drift ratio, up to 38% better performance in lateral displacement, up to 100% stiffer stories, and about 50% smaller uplift forces. Moreover, MSB equipped with BRB attests even a better seismic behavior in the aforementioned parameters.

PurposeTo investigate the feasibility of using artificial neural networks for conceptual design of bracings systems for tall steel buildings.Design/methodology/approachDatabase of 234 design examples has been developed using commercially available detailed design software. These examples represent building up to 20 storeys. Feed forward back‐propagation neural network is trained on these examples. The results obtained from the artificial neural network are evaluated by re‐substitution, hold‐out and ten‐fold cross‐validation techniques.FindingsResults indicate that artificial neural network would give a performance of 97.91 percent (ten‐fold cross‐validation). The performance of this system is benchmarked by developing a binary logistic regression model from the same data. Performance of the two models has been compared using McNemar's test and receiver operation characteristics curves. Artificial neural network shows a better performance. The difference is found to be statically significant.Research limitations/implicationsThe developed model is applicable only to steel building up to 20 storeys. The feasibility of using artificial neural networks for conceptual design of bracings systems for tall steel buildings more than 20 storeys has not been investigated.Practical implicationsImplementation of the broad methodology outlined for the use of neural networks can be accomplished by conducting short training courses. This will provide personnel with flexibility in addressing buildings‐specifics bracing conditions and limitations.Originality/valueIn tall building design a lot of progress has been made in the development of software tools for numerical intensive tasks of analysis, design and optimization, however, professional software tools are not available to help the designer to choose an optimum building configuration at the conceptual design stage. The presented research provides a methodology to investigate the feasibility of using artificial neural networks for conceptual design of bracings systems for tall buildings. It is found that this approach for the selection of bracings in tall buildings is a better and cost effective option compared with database generated on the basis of expert opinion. It also correctly classifies and recommends the type of trussed bracing system.

Theoretical and experimental research on the rocking truss system with post-tensioned rocking connection

Viscosity is the most important lubricant parameter as lubricant requires suitable values to ensure its performance in industrial applications under a high pressure and temperature. In this study, the effects of viscosity on temperature for engine oil (SAE 20W40) and palm oil were studied in journal bearing application using the ANSYS FLUENT CFD (computational fluid dynamic) method. In addition, this study also compared the effects of constant viscosity and viscosities that dependent on temperature for engine oil (SAE 20W40) for an application of journal bearing at a different rotational speed of journal bearing start from 200 rpm, 400 rpm, 600 rpm, 800 rpm, and 1000 rpm. The results show that the pressure distribution in journal bearing is in agreement with the experiment by using the correct method in ANSYS FLUENT. Finally, under the hydrodynamic lubrication regime, the lubricant viscosity has a significant impact on the improvement of a journal bearing’s most essential aspects (maximum pressure and load carrying capacity). Hence decision to consider constant viscosity conditions or viscosities that dependent on temperature cases will give a different result that will affect the overall performance of journal bearing. The numerical validation study was done to validate data from simulation and experimental studies.KeywordsJournal bearingPalm oilCFDANSYS FLUENTViscosityTribology

Wind resistant size optimization of geometrically nonlinear lattice structures using a modified optimality criterion method

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.

This paper aims to evaluate seismic response modification factor, overall ductility factor, and overstrength factor of ordinary moment steel frames with different concentrically bracing systems (X-bracing, V-bracing, and inverted V-bracing). The effects of bracing type and number of stories have been considered in the course of this study. Such factors effects on seismic parameters are not considered in seismic codes such as International Building Code (IBC, 2012) and European Standards (EN). Linear time history analysis has been performed using multiple earthquake records selected to include the variability in ground motion characteristics for 4-, 8-, 12-, and 16-story steel frame buildings. Nonlinear pushover analysis was then carried out by assigning nonlinear material behaviour and plastic hinges to steel elements according to code. It has found that each bracing system has a unique behaviour as well as different seismic parameters than other types, which are not differentiated in seismic codes such as IBC and EN. Also, it was found that the overall ductility factor, decreased with increasing the number of stories, while response modification factor (except for the inverted V-braced system) and overstrength factor increased with increasing the number of stories.

Cyclic behavior of autoclaved aerated concrete block infill walls strengthened by basalt and glass fiber composites

This study addresses the effect of pre-stressed cables on a pre-stressed mega-braced steel frame through employing static analysis and pushover analysis. The performances of a pre-stressed mega-braced steel frame and a pure steel frame without mega-braces are compared in terms of base shear, ductility, and failure mode. The influence of the cable parameters is also analyzed. Numerical results show that cable braces can effectively improve the lateral stiffness of a pure frame. However, it reduces structural ductility and degenerates structural pre-failure lateral stiffness greatly. Furthermore, it is found that 20% fluctuation in the cable pretension has little effect on structural ultimate bearing capacity and lateral stiffness. As comparison, 20% fluctuation in the cable diameter has much greater impact.