Horizontal Bridge Research Articles

Experimental Study on Shear Lag Effect of Long-Span Wide Prestressed Concrete Cable-Stayed Bridge Box Girder under Eccentric Load

Based on the engineering background of the wide-width single cable-stayed bridge, the shear lag effects of the cross-section of these bridge box girders under the action of the eccentric load were experimentally studied. The behavior of shear lag effects in the horizontal and longitudinal bridge directions under eccentric load in the operational stage of a single cable-stayed bridge was analyzed by a model testing method and a finite element (FE) analytical method. The results showed that the plane stress calculation under unidirectional live load was similar to the results from spatial FE analysis and structural calculations performed according to the effective flange width described in the design specification. At the position of the main beam near the cable force point of action, the positive stress at its upper wing edge was greatest. At a distance from the cable tension point, the maximum positive stress position trend showed that from the center of the top flange to the junction of the top flange and the middle web to the junction of the top flange and the middle web and the side web. Under eccentric load, the positive and negative shear lag effects on the end fulcrum existed at the same time, and the shear lag coefficient on the web plate was larger than the shear lag coefficient on the unforced side. Due to the influence of constraint at the middle fulcrum near the middle pivot point, positive and negative shear lag effects were significant, and the coefficient variation range was large, resulting in large tensile stress on the roof plate in this area. According to FE analytical results, stress and shear forces of a single box three-chamber box girder under eccentric load were theoretically analyzed, the bending load decomposed into the accumulation of bending moment and axial force, using the bar simulation method, and the overall shear lag effect coefficient λ was obtained and verified.

Research of stamping of unequal channels. Part 7. Kinematic and stress states of the workpiece under constrained extrusion. 4. Fully constrained extrusion

The problem is being solved of determining the kinematic and stress states of the workpiece with a completely constrained extrusion of unequal channels under plane strain conditions with a misaligned punch and matrix. The force and geometrical parameters of the process are determined. Formulas are obtained for determining the main technological parameters of the process of extrusion of channels with a relatively thin horizontal bridge. Keywords: die forging, extrusion, misalignment of punch and matrix, plane strain, plastic flow rates, stresses. mt13@bmstu.ru

Effect of Yoga and Pilates exercises on lumbar spine physical parameters in healthy women

Purpose: In this study, it was aimed to examine the physical effects of participation in a Yoga and Pilates-based exercise program on the endurance and flexibility of the spine in order to protect the health of the lumbar region in healthy women.
 Methods: A total of 40 healthy women with a mean age of 41.62±6.91 years were included in the study. Participants were divided into two groups as Yoga and Pilates groups randomly. Both groups participated in an exercise program for 45 minutes a day, two days a week for 12 weeks. Sit and reach test was used to evaluate flexibility, and curl up, Static back endurance test and horizontal side bridge building test were used to evaluate endurance. 
 Results: When both exercise groups were compared before and after treatment, statistically significant difference was found in favor of post-treatment in all measurements (p0.05). 
 Conclusion: According to the results of our study, it was determined that both exercise types improved both flexibility and muscle endurance performance. However, it was seen that Yoga and Pilates exercises were not superior to each other in terms of flexibility and endurance. Both Yoga and Pilates exercise methods can be used safely to protect and improve general health and especially lumbar region health.

Research of stamping of unequal channels. Part 7. Kinematic and stress states of the workpiece under constrained extrusion. 3. Force and geometric parameters

The problem of determining the kinematic and stress states of the workpiece with partially constrained extrusion of channels under plane strain conditions with a misaligned punch and die is solved. The force and geometrical parameters of the process are determined. Formulas are obtained for determining the main technological parameters of the process of extrusion of unequal-shelf channels with a relatively thin horizontal bridge. Keywords: die forging, extrusion, misalignment of punch and die, plane strain, plastic flow rates, stresses. mt13@bmstu.ru

Research of stamping of unequal channels. Part 7. Kinematic and stress states of the workpiece under constrained extrusion. 2. Plastic area under the punch end near the formed thick wall

The problem of determining the kinematic and stressed states of the workpiece under partially constrained extrusion of channels under plane strain conditions with a misaligned location of the punch and matrix is considered. The flow velocities and stresses in the plastic deformation zone under the punch end near the formed thick wall of the channel are determined. Formulas for the extrusion process parameters of unequal-shelf channels with a thin horizontal bridge are obtained. Keywords: die forging, extrusion, misalignment of punch and matrix, plane strain, plastic flow rate, stresses.mt13@bmstu.ru

Study of stamping of unequal channels. Part 7. Kinematic and stress states of the workpiece under constrained extrusion. 1. Plastic area under the resulting thick wall

Based on the complete system of equations of the theory of plastic flow, the beginning of solving the problem of determining the kinematic and stressed states of the workpiece under constrained extrusion of channels under conditions of plane strain with a misaligned location of the punch and matrix is outlined. The flow rates and stresses in the area of plastic deformation under the forming thick channel wall are determined. Formulas are obtained for determining the technological parameters of extrusion of unequal channels with a thin horizontal bridge. Keywords: die forging, extrusion, misalignment of punch and matrix, plane strain, plastic flow rates, stresses. mt13@bmstu.ru

THE KINEMATIC AND STRESS STATE OF THE WORKPIECE AT CONSTRAINED EXTRUSION OF RECTANGULAR BRACKETS. Part 4

On the basis of the complete system of equations of the theory of plastic flow, a solution to the problem of determining the kinematic and stress states of a workpiece with a completely constrained extrusion of rectangular brackets under conditions of plane deformation in the general case of misaligned arrangement of the punch and matrix is presented. The determination of the power and geometric parameters of the process has been carried out. Formulas are obtained that are necessary to determine the main technological parameters of the process of extrusion of rectangular brackets with a relatively thin horizontal bridge.

THE KINEMATIC AND STRESS STATE OF THE WORKPIECE AT CONSTRAINED EXTRUSION OF RECTANGULAR BRACKETS. Part 1

On the basis of the complete system of equations of the theory of plastic flow, the beginning of solving the problem of determining the kinematic and stress states of the workpiece with constrained extrusion of rectangular brackets under conditions of plane deformation in the general case of misaligned position of the punch and matrix is presented. The determination of the flow rates and stresses in the area of plastic deformation located under the forming thick wall of the rectangular bracket has been carried out. Formulas are obtained that are necessary to determine the main technological parameters of the process of extrusion of rectangular brackets with a relatively thin horizontal bridge.

THE KINEMATIC AND STRESS STATE OF THE WORKPIECE AT CONSTRAINED EXTRUSION OF RECTANGULAR BRACKETS. Part 3

On the basis of the complete system of equations of the theory of plastic flow, the beginning of solving the problem of determining the kinematic and stress states of the workpiece with constrained extrusion of rectangular brackets under conditions of plane deformation in the general case of misaligned position of the punch and matrix is presented. The determination of the flow rates and stresses in the area of plastic deformation located under the forming thick wall of the rectangular bracket has been carried out. Formulas are obtained that are necessary to determine the main technological parameters of the process of extrusion of rectangular brackets with a relatively thin horizontal bridge.

THE KINEMATIC AND STRESS STATE OF THE WORKPIECE AT CONSTRAINED EXTRUSION OF RECTANGULAR BRACKETS. Part 2

On the basis of the complete system of equations of the theory of plastic flow, the beginning of solving the problem of determining the kinematic and stress states of the workpiece with constrained extrusion of rectangular brackets under conditions of plane deformation in the general case of misaligned position of the punch and matrix is presented. The determination of the flow rates and stresses in the area of plastic deformation located under the forming thick wall of the rectangular bracket has been carried out. Formulas are obtained that are necessary to determine the main technological parameters of the process of extrusion of rectangular brackets with a relatively thin horizontal bridge.

Experimental study on the freezing process of a supercooled horizontal water bridge between cold fins

In this study, a series of experiments were conducted to comprehensively investigate the freezing process of a static supercooled horizontal water bridge between cold fins. How cold surface temperatures, water bridge volumes, and air relative humidities with a wide range of variation effects on water bridge freezing were further explored. The dynamic evolutions of internal temperature, ice-water interface, and freezing time were revealed. Some particular deformation phenomena, such as ice rings and protruding droplets, were observed during the freezing process of the water bridge. The results indicate stable nucleation temperatures in the recalescence stage. It was found that whether nucleation and crystal growth occur depends on the nuclear energy barrier, and whether the nucleation temperature changes when nucleation occurs is determined by the stable nucleation temperatures. When the cold surface temperature is constant, the nucleation temperature decreases with the increase of water bridge volume and air relative humidity, respectively. Compared with water bridge volume, cold surface temperature and air relative humidity have a more significant effect on water bridge freezing. Furthermore, the lower the cold surface temperature, water bridge volume, and air relative humidity, respectively, the shorter the freezing time and the faster the movement velocity of the ice-water interface. In addition, a semi-empirical correlation is proposed to predict the movement distance of the ice-water interface, which can accurately predict 95% of the considered experimental data with a deviation of ±25%.

Assessing the importance of artificial canopy bridge design for Costa Rican monkeys in an experimental setting

Abstract Although artificial crossing structures are increasingly implemented by conservationists and wildlife managers to connect fragmented wildlife habitat, the study of artificial crossing structure design, particularly of canopy bridges, is an emerging field of study in primatology. We address this issue by evaluating five competing bridge models with varying width, material stiffness, and substrate spacing. We assessed bridge preference and performance by sampling the behavior of three species of Costa Rican monkeys (Alouatta palliata: n = 4, Ateles geoffroyi: n = 3, Cebus imitator: n = 3). In a semi-wild setting, we used focal individual sampling with instantaneous recording once every minute for ten-minute intervals and all occurrences sampling whenever study subjects used the bridge. We hypothesized that monkeys prefer bridges that are more stable, and that are made of materials that resemble tree branches. During nearly 37 sampling hours we observed 119 crossing events. We found that study subjects prefer bridge models that are built using more rigid materials, such as the bamboo pole bridge, or wider bridges that offer more stability than narrower bridges. The bridge type and the materials used to build the bridges are both significant predictors of bridge use. While preference for bridges and their performance varies by species, the bamboo pole bridge model and the horizontal mesh bridge were preferred and performed best in our study. The simple liana bridge model was the least preferred by all species and performed poorly in comparison to the other models. Our findings will help us better understand how design and materials impact the use of canopy bridges by monkeys, which can help improve biological corridors and offer new information for the management and conservation of primates living near infrastructure corridors and other kinds of dangerous matrix.

3D printable ceramic pastes design: Correlating rheology & printability

Binder-free ceramic pastes based on TiO2 nanoparticles (64 wt%) with different solvent:co-solvent volumetric ratios (water:glycol, W:G) are disclosed for the first time. Ceramic pastes were prepared without binders (polymers or gel-precursors) using a straightforward, and environmentally respectful method. Two criteria to achieve three-dimensional and complex structures were proposed. 1.- shear-thinning ability and 2.- G' = G'' > 1 × 103 Pa. Pseudoplastic behaviors were found and were suitably modeled for all pastes analyzed, fulfilling the first criterion. Nonetheless, only those pastes with 60:40, 50:50, and 40:60 (W:G) fulfilled the second criterion. These latter exhibited a good balance between rigidity to form long and horizontal bridges but fluid enough to avoid flow cuts or clogs. Thus, 3D structures (20 layers of stacking) were obtained with outstanding self-supporting and excellent shape-retention. The complex structures were dried at 400 °C, thus obtaining binder-free and mechanically stable ceramic structures preserving their printed shape.

TYPOLOGY OF BRIDGES-TRANSITIONS BETWEEN BUILDINGS

Considered are prerequisites and development features of bridges-transitions between buildings in the world architecture. With the rapid development of construction technologies, the widespread use of metal in the construction of public and residential buildings, as well as the strong aesthetic and functional demand from developers and residents, there is a need for open and closed multi-storey, multifunctional bridges between buildings.
 The term "bridge-transition" has been used only recently to refer to bridge structures placed between high-rise buildings. This term is commonly used to refer to urban pedestrian bridges installed at height and bridges located in mountain gorges. As the term "bridge-transition" is ambiguous and has several different meanings, it is necessary to define the term "bridge-transition" for the purposes of this study. In this study, a bridge-transition is defined as "a part of a building that allows pedestrians to pass into another building at a height."
 Based on the existing understanding of the communications spread inside a building, we can divide such bridges-transitions into point-communicative and multi-communicative. In each of these types, there are closed, open and mixed point-communicative or multi-communicative bridge-transitions between buildings. Multi-communicative bridges-transitions and their subsequent types can be further divided into bridges in one horizontal projection, e.g. one-level, and bridges in different horizontal projections, e.g. multi-level. The analysis of existing types of bridge-transitions allows to define a separate type of bridges-transitions as bridge-planes.
 The use of bridges-transitions in various building designs for various purposes is prompting more and more specialists-designers to incorporate these solutions into their projects, which fuels the public interest in the application of these solutions.

Circuit network theory of n-horizontal bridge structure

This research investigates a complex n order cascading circuit network with embedded horizontal bridge circuits with the N-RT method. The contents of the study include equivalent resistance analytical formula and complex impedance characteristics of the circuit network. The research idea is as follows. Firstly the equivalent model of n-order resistance network is established, and a fractional difference equation model is derived using Kirchhoff’s law. Secondly, the equivalent transformation method is employed to transform the fractional equation into a simple linear difference equation, and its particular solution is computed. Then the solution to the difference equation is used to derive the effective resistance of the resistance network of the embedded horizontal bridge circuit, and various special cases of equivalent resistance formula are analyzed and the correctness of the analysis model gets verified. Finally, as an expanded application, the equivalent complex impedance of LC network is studied, and Matlab drawing tool is employed to offer the equivalent impedance with various variables of the graph. Our results provide new research ideas and theoretical basis for relevant scientific researches and practical applications.

ВСЕСТОРОННЕЕ ИССЛЕДОВАНИЕ ВЫДАВЛИВАНИЯ П-ОБРАЗНЫХ КРОНШТЕЙНОВ. СООБЩЕНИЕ 6. КИНЕМАТИЧЕСКОЕ И НАПРЯЖЕННОЕ СОСТОЯНИЯ ЗАГОТОВКИ ПРИ СТЕСНЕННОМ ВЫДАВЛИВАНИИ. Ч. 2

On the basis of the complete equation system of the plastic flow theory, the solution continuation of the determination problem of the kinematic and stressed states of a blanket during restricted extrusion of П-shaped brackets under conditions of plane deformation in the general case of a nonaligned placement of the punch and the die is stated. The determination of flow velocities and stresses in the area of plastic deformation, located under the punch end near the formed thick wall of the bracket has been carried out. The formulae were obtained, which are required for identification of the main parameters of the extrusion process of П-shaped products with a relatively thin horizontal bridge.

ВСЕСТОРОННЕЕ ИССЛЕДОВАНИЕ ВЫДАВЛИВАНИЯ П-ОБРАЗНЫХ КРОНШТЕЙНОВ. СООБЩЕНИЕ 6. КИНЕМАТИЧЕСКОЕ И НАПРЯЖЕННОЕ СОСТОЯНИЯ ЗАГОТОВКИ ПРИ СТЕСНЕННОМ ВЫДАВЛИВАНИИ. Ч. 3

On the basis of the complete equation system of the plastic flow theory, the solution continuation of the determination problem of the kinematic and stressed states of a blanket during partially restricted extrusion of П-shaped brackets under the conditions of plane deformation in the general case of a nonaligned placement of the punch and the die is stated. The determination of the force and geometric parameter of the process was carried out. The formulae were obtained, which are required for identification of the main technological parameters of the extrusion process of П-shaped products with a relatively thin horizontal bridge.

ВСЕСТОРОННЕЕ ИССЛЕДОВАНИЕ ВЫДАВЛИВАНИЯ П-ОБРАЗНЫХ КРОНШТЕЙНОВ. СООБЩЕНИЕ 6. КИНЕМАТИЧЕСКОЕ И НАПРЯЖЕННОЕ СОСТОЯНИЯ ЗАГОТОВКИ ПРИ СТЕСНЕННОМ ВЫДАВЛИВАНИИ. Ч. 4

On the basis of the complete equation system of the plastic flow theory, the solution of the determination problem of the kinematic and stressed states of a blanket during completely restricted extrusion of П-shaped brackets under the conditions of plane deformation in the general case of a nonaligned placement of the punch and the die is stated. The determination of the force and geometric parameter of the process was carried out. The formulae were obtained, which are required for determination of the main technological parameters of the extrusion process of П-shaped products with a relatively thin horizontal bridge.

ВСЕСТОРОННЕЕ ИССЛЕДОВАНИЕ ВЫДАВЛИВАНИЯ П-ОБРАЗНЫХ КРОНШТЕЙНОВ. СООБЩЕНИЕ 6. КИНЕМАТИЧЕСКОЕ И НАПРЯЖЕННОЕ СОСТОЯНИЯ ЗАГОТОВКИ ПРИ СТЕСНЕННОМ ВЫДАВЛИВАНИИ. Ч. 1

On the basis of the complete equation system of the plastic flow theory, the solution origination of the determination problem of the kinematic and stressed states of a blanket during restricted extrusion of П-shaped brackets under conditions of plane deformation in the general case of a nonaligned placement of a punch and a die is stated. The determination of flow velocities and stresses in the area of plastic deformation, located under a formed thick wall of the bracket has been carried out. The formulae were obtained, which are required for identification of the main parameters of the extrusion process of П-shaped products with a relatively thin horizontal bridge.

Formation and Deformation of Liquid Drops in Microchannels

The laws of drop formation are experimentally studied in narrow horizontal microchannels with rectangular section with heights from 50 to 150 μm. It is shown that there exists a new flow regime when the drops in the form of vertical liquid bridges move along the microchannel. Three mechanisms of formation of such drops are distinguished: formation directly near the liquid nozzle, departure of drops from liquid moving at the lateral sides of channel, and drop formation due to destruction of severely deformed drops and horizontal liquid bridges. It is established that the deformation of drops increases with increasing Weber number. It is demonstrated that the drops begin to deform when the first critical value of the Weber number is achieved and begin to be destroyed when the second one is achieved.