Cramped Conditions Research Articles

Installation of a Pit Fence in Cramped Conditions

The construction of buildings and structures in cramped conditions requires a special approach from hydraulic engineers and builders, requiring the preservation of the surrounding development in a working condition. This circumstance requires a geotechnical forecast of deformations of objects falling into the zone of geotechnical influence of the construction of a building under construction at the design stage and then the organization and implementation of geotechnical monitoring of deformations as a result of construction and installation work. It should be noted that the objects of the surrounding development can be in different categories of technical condition. According this circumstance the permissible deformations may be different. In any geotechnical case, there is an urgent need to install excavation fences that perform a dual task: both ensuring the stability of the soil walls, and reducing the impact of the new construction object on existing buildings. The determination of the bearing capacity of the enclosing structures of the excavation, especially the retaining soil anchors themselves, is of great importance in modern geotechnical construction. The engineering method used in this article to determine the bearing capacity of drilling-injection anchors with sufficient accuracy for technical calculations showed the convergence of calculated and real values based on the results of static tests.

Estimation of stability of lifting equipment during excavation of pits in cramped conditions

Estimation of stability of lifting equipment during excavation of pits in cramped conditions

A Case from the Geotechnical Practice of Construction in Cramped Conditions

A Case from the Geotechnical Practice of Construction in Cramped Conditions

МОДЕЛИРОВАНИЕ СГЛАЖИВАЮЩИХ ТРАЕКТОРИЙ ПЕРЕМЕЩЕНИЯ АВТОНОМНЫХ ЭЛЕКТРИФИЦИРОВАННЫХ ПЛАТФОРМ

Automation of cargo transportation both inside production and warehouse premises and between individual objects of livestock and crop production complexes is a promising direction in saving fuel and energy resources of the agro-industrial complex. The use of autonomous vehicles for these purposes, including electrified platforms with non-operational adaptive control, is especially necessary due to the movement of significant volumes of cargo in cramped conditions of buildings and structures. However, the use of broken lines in the planning of ATU movements leads to the need for a significant reduction in the movement speed during the passage of turning sections of the trajectory. This significantly increases the execution time of technological operations, leads to additional energy consumption for braking and acceleration. Thus, the approach proposed in the work to the analytical determination of smoothing movement trajectories of autonomous vehicles is relevant. (Research Purpose) The research purpose is developing an approach to the construction of smoothing sections of the trajectory of a non-operational vehicle with adaptive control that does not require solving optimization problems. (Materials and methods) For a smoothing curve of polynomial form, a system of equations is derived from geometric conditions that defines its most rational form from the point of view of the maximum speed of passing an obstacle. After its representation in the local coordinate system associated with the bypassed obstacle, the equation of the desired curve is found. For the practical implementation of the method, formulas for the transition from a local coordinate system to an absolute one are given. (Results and discussion) A general method is proposed for smoothing the reference broken trajectories obtained at the initial stage of planning the movement of an autonomous electrified platform in cramped conditions. In the local coordinate system associated with the obstacle, the shape of the smoothing transition curves is found and formulas for the transition to the absolute coordinate system are given. (Conclusions) The obtained analytical solution to the construction of smoothing sections of the trajectory of an autonomous vehicle in cramped conditions of buildings and structures for agricultural purposes does not require complex calculations. This simplifies its practical application, including the implementation of programmable adaptive control systems using microprocessor hardware.

Evaluation of Effectiveness of Application of Horizontal Inertial Barriers to Reduce Vibrations Propagating in Ground Environment

The paper presents calculations of vibrations of the soil mass when a horizontal inertial barrier in the form of a rectangular concrete slab buried in the ground is placed on the propagation path of vibrations. The damping effect of a surface wave upon its contact with an inertial plate is associated with its reflection, refraction and partial absorption. Theoretical studies have been carried out using the finite element method. The ground medium has been considered as an elastic inertial array bounded by non-reflecting boundaries. Various variants of the geometry of the inertial plate and its spatial arrangement on the surface of the soil medium between the vibration source and the considered point behind the barrier are modeled. The effectiveness of each variant of vibration isolation has been quantified by the value showing how many times the speed of vertical oscillations of the ground behind the barrier decreases compared to the free propagation of surface waves. It is shown that an intensive decrease in vertical displacements occurs starting from the side face of the inertial plate. Here, the amplitude of vertical oscillations decreases by 9,8 times for a concrete slab 15 m long, and by 4,2 times for a 3-meter slab. At a distance of 22 m from the point of application of the dynamic load, the amplitudes decrease by factors of 5.48 and 2.95, respectively, for slabs of 15 and 3 m width. This method of reducing vibro-dynamic effects has a simple design and can be used in cramped conditions of urban development to protect existing and planned buildings and structures.

Studying the strength of a small-sized loader working equipment

Problem. The growth in the volume of construction work carried out in the improvement of adjacent territories, playgrounds, and pedestrian paths requires the use of a wide range of small-sized machines for earthwork and road construction, including loaders. The main requirements for small-sized loaders are small dimensions, which makes it possible to perform work in cramped conditions, good maneuverability, light weight, which allows for low pressure on the surfaces on which the equipment moves, ensuring the safety of loading operations, efficiency and economy. These conditions are fully met by a variety of construction equipment that is combined with self-propelled chassis, which have been manufactured for many years at Ukrainian enterprises and used by organizations for the improvement and beautification of urban space. The indisputable advantage of self-propelled chassis over a large number of short wheelbase loaders, which are also widely used in the public utilities sector, is greater stability due to the large wheelbase and the possibility of using additional outriggers installed on the machine, as well as the availability of a self-unloading platform for transporting goods. The operation of small-sized forklifts based on self-propelled chassis in cramped conditions, along with builders performing installation work, requires increased attention to ensuring the strength of the machine's metal structure, so the issue of studying the load of working equipment is an urgent task. Goal. The aim of the study is to develop scientifically based recommendations for reducing the load of small-sized forklift equipment based on the created design scheme, determining the acting forces and stresses, and rational modes of operation of the forklift. Methodology. The design position in which the handle of the working equipment is located horizontally and the maximum load acts on it is considered. The design load is the maximum weight of the cargo, taking into account the dynamic coefficient. The calculated position for the boom is the position of the greatest bending moment, i.e. the position at maximum reach. The center of gravity of the boom and handle, as well as the weight of the metal structure, were determined using a computer model. The loads acting in the boom joints are determined using a simplified, calculated, boom scheme, for which We will discard the handle, replacing its action with the corresponding reaction and consider the handle separately to determine this load. Given that the force of action from the boom on the handle will be equal in modulo to the force of action from the handle on the boom, and the reactions in the hydraulic cylinder joints will also be equal, we will depict the diagram of the forces acting on the boom. Results. Based on the developed design schemes of the boom and arm, we studied the loading of working equipment, which was carried out using the created program at variable values of the load weight from 4000N to 4500N, the coefficient of dynamism equal to 1, 1.1...1.5, and the height of the arm section from 0.14 to 0.16 m. The analysis of the research results showed that an increase in the coefficient of dynamism to a value of 1.5 at a load weight of 4500N leads to an increase in the acting force to 6840N, but the stresses are within the permissible limits. Increasing the load with which the forklift operates to 5000N requires an increase in the height of the handle section to 0.15m to ensure that the stresses are within the permissible limits. The analysis of the dependence of the acting stresses on the weight of the load and the coefficient of dynamism made it possible to propose recommendations for rational modes of operation of the forklift, which consist of limiting the load to 4500N and the coefficient of dynamism within 1.3-1.4 with a handle cross-sectional height of 0.14m and a wall thickness of 0.05m. It is also proposed to work without jerks, smoothly at low lifting speeds, within the range of the coefficient of dynamism up to 1.3-1.4. Practical meaning. The developed research methodology is proposed for use in the operation of a small-sized forklift in various modes, as well as in the design of working equipment for forklifts of a similar class and design.

Модернизация системы обеспечения устойчивости железнодорожного крана КЖ-971 и оценка её эффективности

The weight of the load hanging on the boom of a railroad hydraulic crane KZH-971 creates a load moment that bends the crane slewing ring. To partially balance the load moment, a stationary counterweight is installed on the crane, rigidly fixed on a slewing platform. With an increase in the boom departure, the unbalanced part of the load moment and tensions in the slewing ring increases. In this article, to ensure a constant value of the unbalanced part of the load moment and reduce bending tensions, it is proposed to install a counterweight on the railroad crane with a telescoping system and the ability to rotate about the vertical axis for a work in cramped conditions. A strength analysis of the slewing ring for the change in maximum tensions from the use of a movable counterweight was carried out. An adaptive control system for the position of a movable counterweight has been modeled, with the help of which it will be possible to develop a device for convenient control from the crane operator’s cabin in the future. The advantages of using a movable counter-weight with the possibility of rotation relative the vertical axis are shown when performing loading and repair work in cramped conditions. The results of the strength analysis of the slewing ring with the location of loads in the main working positions are summarized.

«Парк-ассистент» - система помощи при парковке для автопоезда

Almost daily drivers of road trains (RT) have to maneuver in cramped conditions, including moving in reverse, which is a significant difficulty. The existing electronic parking sensors systems are implemented only for single cars. The available publications concerning the RT are devoted to the search for optimal control algorithms without the driver participation. The purpose of this study is to develop «Park Assistant» (PA) system that helps the driver to maneuver the RT in reverse in difficult conditions. To do this, using the «navigation system», the current situation is estimated and modeled, the initial coordinates of the RT and the planned parking place are determined. Using the mathematical model of the RT, the trajectory of the «optimal movement of the tractor and semi-trailer» is calculated. The optimal trajectory of the RT in reverse and the steering wheel rotation algorithm are calculated using a specially developed program. The actions of the driver to perform the parking maneuver of the RT are reduced to the implementation of recommendations on the screen of the PA. The theoretical and practical results obtained contribute to the development of promising autonomous motor transport.

Management of degradation processes and strengthening of soils and foundations of transport structures

The method of strengthening the soils and foundations of transport structures used for their preservation, especially buildings of architectural and historical value, as well as during mass renovation in large cities in cramped conditions with high density of existing buildings, is considered. The method of constructing a horizontal distributor by pushing through round-section sleepers in the form of steel-reinforced concrete elements made of pipes filled with concrete is considered. In the article, the dependence of the radius of the compacted zone on the initial characteristics of the soil density and the diameter of the pressed pipe concrete element is analyzed. The method of installing a pipe-concrete horizontal distributor for simultaneous strengthening of the foundation and soils is considered, as well as it is the most environmentally friendly and does not negatively affect the surrounding buildings and structures. An assessment of the change in the height of the surface discharge of the foundation soil is presented, which allows to regulate the process of leveling the deformation of the building as a whole.

Preservation of the natural landscape during construction

The issues of preservation of existing green spaces and other elements of the natural landscape during new construction are considered. The methods of preserving perennial plantations throughout the entire progress of construction are proposed. If it is impossible to save the tree on the construction site, a method of transplanting it to another place is proposed. A tree transplant scheme and a method for calculating its weight for the selection of equipment for digging and transportation have been developed. The methods of solving the problems of preserving the landscape needed by a person, maintaining the stability of the created infrastructure, a comfortable urban environment, as well as studying, analysing and predicting human actions on the natural landscape are proposed. The balance of the city’s territories has been developed, which provides a comfortable ratio of different zones of urban development for a person. When building in cramped conditions, it is proposed to lay out gardens on the roofs of houses, apply vertical greening of facades, and use the “garden city” construction method for large areas of development. The possibility of installing playgrounds and sports grounds in an already existing landscape without completely cutting down trees is described. The positive experience of updating the DSTU Student Park is given. The negative experience of the city of Rostov-on-Don is also given: the breakdown of a new park near the stadium built on the left bank of the Don.

Conceptual model of noise monitoring system for construction projects in cramped conditions, based on sensors and GIS

Existing sound measuring equipment are mostly designed for indoor use, and those of outdoor are costly and demands human involvement multiple times. This study proposes the concept of a compact and cheap sensor and GIS-based system that runs algorithms of sound distribution and visualizes interpolated and extrapolated data as heatmaps in an interactive map. According to the concept, the system consists of several noise measuring devises wirelessly connected to a data collector that transmits the measurement data real-time through internet to a server, where the data is analyzed and visualized. The integrated into GIS algorithms are designed to identify the sound sources and locations where the sound level exceeded its daytime or nighttime standard limits. The implementation of proposed concept may make noise issues related to construction activities more transparent.

Who Makes the City? Beijing's Urban Villages as Sites of Ideological Contestation

Abstract Inside Beijing are hundreds of urban villages. Originally farming villages, now engulfed by urban expansion, they persist due to China's segregated urban-rural property system. Inhabitants are often still classed as peasants, despite being inside the city. Since most have had their agricultural land requisitioned for urban construction, they instead build multiple extensions to their houses to rent to rural migrants seeking cheap accommodation. In some cases, village populations have increased tenfold as migrants have flooded in, causing cramped conditions and overloading village infrastructure. Urban villages have in recent years emerged as key sites of ideological and political contestation. For local officials and planners envisioning gleaming world cities brimming with advanced technology and highly skilled workers, these are dirty and backward “urban cancers,” enclaves of the “low-end population,” and obstacles to their visions of the city as embodiment of global modernity. An opposing set of scholars and policy makers view these villages as essential to city life, channels for low-cost labor to service urban elites, and gateways to modernity for those formerly excluded. Within the urban villages, groups of migrant-activists defy the statist vision of the city. Through cultural performances and visual representations, they struggle to promote an urban modernity in which they are included as active participants. This article explores how Beijing's urban villages constitute a key site of ideological contestation over what the city should be, and whom urban life is for.

Analysis of organizational features of the work of assembly cranes in cramped conditions construction

The possibilities of placing erection cranes in cramped conditions are considered. The factors for determining the type of crane and the conditions for its operation at the construction site are given. The principles of determining the conditions of tightness of the construction site in accordance with the regulatory documentation are shown. The possibilities of limiting the boundaries of the dangerous zone of the crane are considered. The designs of various cranes are analyzed from the point of view of their placement in cramped conditions. Data are given on the features of the use of bottom-slewing and top-slewing tower cranes in the construction of civil buildings of different heights. The possibility of replacing tower cranes with fast-mounted ones during the construction of low-rise public buildings is being considered. Recommendations are given on the placement of cranes of various designs, the definition of the technological sequence of the construction of the building.

Installation of Pit Fencing in Cramped Conditions

What is the contribution of circular economy in the effort to meet Paris agreement and slow down global warming? How circular is our planet, and which is the circularity gap in order to meet the Paris agreement? What is the role of cities in circular green transformation? This short communication communicates briefly finding of the URGE: Circular Building Cities Network that is financed by the URBACT programme, aiming to promote the role of cities in boosting circularity, specifically in the construction sector.

The use of balanced lowering method technology for bridge construction in cramped urban environments

The main trends in bridge building are: the implementation of new materials, the assimilation of novel technologies, and the construction time reduction. The new technologies assimilation is often associated with the need to build bridge structures in cramped conditions. Considered by the author balanced lowering method technology corresponds to these trends. The technology was developed at the Vienna Technical University, the main idea is to assemble the supporting elements in a vertical position with subsequent deployment to the design horizontal position. To reduce the weight of the mounted elements, this technology uses thin-walled prestressed precast concrete units. After installing it in the design position, they perform the function of leave-in-place form and are cast in place directly on the construction site. This technology was invented for high pier bridges to eliminate the erection and dismantling of temporary support but has recently been shown to be cost-effective for low pier bridges. The advantage of this method is not only the construction time reduction and the free underbridge clearance presence but also the fact that the braces are not only a mechanism for turning the span into a horizontal position but also allow to reduce the estimated span length. The article discusses the bridge projects across the Lafnitz and Lahnbach rivers in Austria, as well as previous options for bridge projects. Particular emphasis in the work is placed on the bridge construction technology consideration, the main technological stages identification, as well as the performance features of certain works. The author presents recommendations on the application of this construction method.

Age and activity take their toll on house fly wings

Choosing a name can be stressful, so some creatures have simply ended up with literal monikers. Sloths, dung beetles and anteaters pretty much do what their names suggest; or at least they do in English. And then there's the humble fly. Where would these insects be without their wings? This is a question that Fritz-Olaf Lehmann from the University of Rostock, Germany keeps asking. How does the wear and tear that fly wings endure come about? Do the delicate structures simply become more fragile and disintegrate with age, or are they vulnerable to the knockabout of flight and collisions, accumulating damage over time? To find out where and how house flies accumulate damage to their wings, Henja-Niniane Wehmann, Thomas Engels (both from the University of Rostock) and Lehmann teamed up to identify which factors take the greatest toll on house fly wings and how much damage individuals can sustain before they can no longer remain aloft. Initially, Wehmann placed groups of four house flies (Musca domestica) together in small (130 cm3) plastic tubes for their entire lives, monitoring their activity by listening in as the insects buzzed while flying. In addition, she anaesthetised the tiny inhabitants three times a week to trace the outline of their wings and check their deterioration under a microscope. As well as cramming flies together, Wehmann also kept 20 of the insects in a larger mesh enclosure – providing 2000 times more space – regularly photographing them to find out how much of a toll the alternative lifestyle took on their wings.Recording almost 7.7 million flights, ranging from as little as 0.03 s (five wing beats) to 0.92 s for females, but only up to 0.79 s for the males, Wehmann and Engels realised that the insects’ wings first began incurring damage at the tips and rear edges of the fragile transparent membrane, becoming more ragged. However, after about 6 h of flight, the wings began showing signs of really catastrophic damage, fracturing along the front edge and losing larger portions. One fly lost almost 90% of a wing over one calamitous 3 day period.Yet, while there were some clear losers, there were also winners. Some of the closely caged insects lost only 15% of their wing area over their lifetime, while others were left with almost non-existent stubs by the time they died. Also, the flies that were living in the most cramped conditions suffered damage 20 times faster than the insects that had a spacious cage to explore, confirming that impacts contribute significantly to incurred wing damage.In contrast, some of the grounded flies appeared to have lost only 10% of their wing area, while others still managed to remain aloft, having lost as much as 34% of their initial wing area. And when Wehmann plotted the insects’ ages against their ability to fly, it was clear that the most elderly flies were the most likely to have lost the power of flight; age in addition to wear and tear, is a clear risk for wings.So, use and getting old both take a toll on the fragile structures that carry flies through the air, but the team suspects that other factors also play a role. For example, once a vein has become damaged, the wing may dry out faster, leaving it more vulnerable to damage from even the gentlest knock, accelerating the process. Wehmann also warns researchers that they shouldn't rely on the state of an insect's wings to estimate its age: ‘the variability between wings and individuals is too great’, she explains.

УСИЛЕНИЕ ОСНОВАНИЙ ФУНДАМЕНТОВ ФИЗИЧЕСКИ УСТАРЕВШИХ ЗДАНИЙ

The problems and prospects of existing methods of strengthening the foundations of physically obsolete buildings are outlined, which is relevant for the preservation of buildings of architectural and historical value, as well as for mass renovation in large cities in cramped conditions with a high density of existing buildings. Method of calculation of hollow rectangular and round sections filled with concrete during bending is considered. In this article the dependence of compacted zone radius on initial characteristic of soil density and diameter of pressed pipe concrete element is analyzed. The conclusion is formed that the method of arrangement of the pipe-concrete horizontal distributor for simultaneous reinforcement of soil of the base and foundations chosen for the study allows to regulate the process of leveling the building settlement as a whole, and is also the most environmentally safe and does not negatively affect the surrounding buildings and structures.

Errors in Construction of Facilities in Restricted Conditions

The construction of facilities in cramped conditions requires a special approach to the need to develop and implement measures to ensure the safe operation of the buildings surrounding the building within the limits of geotechnical influence. Builders often neglect the impact of the new facility technology on the possible negative effects (cracks on facades due to uneven precipitation, heels, etc.) of the buildings in use. The term «minimum price» is still used when part of a building is erected below zero. This approach completely disregards the notion of «technical utility». At the same time the builders go to any tricks to reduce the cost. This «irrational» way of construction may eventually result in a substantial increase in the cost of constructing a zero part of a building and, as a general rule, in a longer construction period (agreement on a new project as a result of substitution of another geotechnical technology, passing of new construction expertise). This article examines one negative case from the geotechnical practice of constructing 16 storey dwellings next to an existing five-storey dwelling house.

Common mistakes made under facility construction in cramped conditions

Construction of facilities in cramped conditions requires a special approach connected with the development and implementation of measures to ensure safe operation of the surrounding buildings within the geotechnical influence. Builders often neglect the impact of a new facility construction technology on possible negative effects resulted in the existing buildings (cracks on the facades due to uneven settlement, tilts, etc.). So far the concept of a minimum price has been used when erecting a building part below the zero mark. This approach completely ignores the notion of engineering viability. At the same time builders resort to every kind of trick to reduce the cost of construction. Such an irrational method may eventually result in a substantial increase in the cost of the zero building part construction. As a rule, it can increase the construction time (agreement on a new project when replacing it with another geotechnical technology, and undergoing new expert review). This paper examines a negative case from the geotechnical practice of constructing a 16-storey residential house next to the existing five-storey one.

Аnalysis Catalytic Hydrogen Recombiner Capacity Calculation Taking into Account Conditions Inside Sealed Enclosure of Containment Safety System of Nuclear Power Plants with Water-Water Energetic Reactor

Localizing safety systems are provided to contain radioactive substances in an accident and attenuate ionizing radiation at a modern nuclear power plant. Together with radioactive substances, hydrogen is also retained, which is formed during the decomposition of the primary coolant. The accumulation of hydrogen in the presence of oxygen from the atmosphere in the accident localization zone carries the danger of the formation of flammable and explosive concentrations of these components. Nuclear power plant (NPP) deigns with water-water energetic reactor (WWER) provides for a hydrogen removal system including passive catalytic hydrogen recombiners. The device capacity is confirmed experimentally under reference conditions (lean air-hydrogen mixture, pressure and temperature close to normal, no interference with gas exchange). Capacity is an important safety parameter. In the event of an accident, conditions inside the ealed enclosure of the localizing system of NPP with WWER can differ from the reference ones and affect the capacity. On the basis of calculations, the operation of recombiners with lack of oxygen and with hindered gas exchange has been investigated in the paper. The decrease in capacity with lack of oxygen reaches 50 %, which is mainly caused by an increase in underburning. Compared to the reference conditions, the effect is more pronounced in the event of an accident – 60–70 %. The hindered gas exchange is modeled by a decrease in the height of recombiner traction channel. This case can be reduced to the placement of the device in cramped conditions and the effect of the atmosphere speed inside the enclosure. Regardless of the hydrogen concentration, the operating characteristic of the device remains linear, with a two-fold decrease in height leads to a decrease in capacity by 20 %. The results can be used to substantiate the safety of NPPs with WWER and to review on the safety subtantiation of power units.