Ground Slab Research Articles

High-speed railway-induced ground and building vibration: Numerical validation of a spectral element analysis-based sub-model method

This paper proposes a spectral element method-based analysis procedure to study further the low-frequency responses of the ground and building induced by high-speed railways. Based on an existing scale model building test in Portugal, the properties of the track–ground submodel are calibrated to determine the moving perturbation on the ground surface. In modeling the soil–structure coupled subsystem, multi-objective optimization is employed to estimate the equivalent structural properties to mitigate computational inefficiency when using continuum elements. The accuracy of the numerical prediction is compared with the experimental records at several monitoring points in terms of ground and floor slab vertical vibrations induced by two types of high-speed trains. In addition to the analysis of possible factors related to systematic discrepancies, special attention is paid to investigating the influence of (a) the presence of frame structure as well as (b) the vehicle properties on ground motion in this particular case.

Reliability of depleted cement–ground slab with waste granodiorite dust admixture on semi-saturated substrate

There are many types of pavements for roads. For technical roads, one of the most effective and economically advantageous pavement types is chemically stabilized soil pavement. When designing a pavement made of soil admixed with binders, it is necessary to meet the load-bearing conditions while considering the effects of environmental factors. The aims of this study were to optimize the strength parameters of pavement, minimize negative environmental effects, minimize the carbon footprint, and simultaneously dispose of mineral waste materials from the production of asphalt mixes for roads. After testing the strengths of samples admixed with cement or with reduced cement content and the addition of dust, questions arose as to how both materials affect the reliability of the pavement structure. Samples of soil doped with cement and dust were subjected to reliability analyses. Abaqus software with a three-dimensional subgrade model was used for a comparative analysis. The substrates under soil stabilization slabs were subjected to varying saturation states, which affected their vulnerability. In this study, the changes in the saturation characteristics of the subsoils associated with different types of climatic interactions were simulated. The Darcy–Buckingham law was used to describe the flow of liquids through the subsoil. Pavement reliability calculations were performed for a multidimensional space of random variables. The results served as an interesting starting point for recommendations to decrease the use of energy-intensive materials, increase the reuse of waste, and reduce the effects of the strengthening process on the environment.

Foundation Earthing System – Its Application and Electrical Safety Considerations

Foundation earthing system greatly reduces the resistance to ground as compared to driven earthing rods. Low resistance to ground is desirable to protect lives – it ensures disconnection of power supply by Residual Current Device in the event of leakage current to ground. However, special attention must be given in the application of foundation earthing system to terrace houses and shop lots, where common ground slab steelwork is used throughout the entire row of houses or shop lots. This paper shows the field tests and findings of terrace houses with foundation earthing system, the requirements of the design and installation of foundation earthing system, and the importance of such installation to achieve low resistance to ground, to be able to operate the protective devices for supply disconnection during fault condition.

Case study of waste material 2 development projects

We can interpret the waste material in construction as loss or loss of material resources, time (by looking at labor and equipment), and also capital, this is caused by activities that require costs, either directly or indirectly, but do not add value at all. construction service products. This research compares the material waste that occurs in 2 project case studies, namely the XYZ factory construction project, and the supermarket building project in Jakarta, and compares the causes of material waste in the two projects. The research methodology is by obtaining secondary data from each project and conducting a questionnaire to find out the comparison of the causes of material waste in the two projects. The most waste in the construction of the XYZ factory was: column work at 34%, the second largest was floor slab work at 10% and the third rank was 6% for ground slab main building work while the most supermarket waste building was Steel structure with a percentage of material remaining 14.5765%, concrete Fc 32 F/A with a percentage of remaining material of 11.5912% and iron in diameter 25 with a percentage of remaining material of 9.1921%. The causes of waste in the two projects are different from one another. Even though there are 3 similarities in the causes of waste material.

Calculation-theoretical justification of the compensation grouting parameters for the metropolitan railway protection from sedimentary deformations

An increase in the volume and scale of underground space development, including the construction of metropolitan railway facilities in large cities, is accompanied by a significant impact on the surrounding urban development, which requires the development and implementation of a set of special measures to protect buildings and structures from excess deformations. At the same time, numerous above-ground and underground structures are involved in the area of influence of the construction, including existing metropolitan railway facilities, as well as residential buildings and above-ground transport facilities. Сurrently, one of the most effective methods that provide reliable facilities protection from sedimentary deformations is the compensation grouting method. The article outlines the theoretical foundations for the use of compensation grouting technology to protect buildings and structures from excess sedimentary deformations during the construction of transport infrastructure facilities in dense urban areas. A mathematical model has been developed that corresponds to the actual geometry of the computational area of the metropolitan railway lobby with a soil base, the actual physical and mechanical characteristics of the materials of its structures, and the soil mass. The article presents the computer modeling results, with its help determined volumes, pressure, sequence, and injection sites. Based on calculated data, the duration of the special solution compensatory injection was determined to maintain a stable position of the foundations of the metropolitan railway escalator tunnels by forming the calculated stress-strain state of the soil mass at the ground slab base of the structure to provide a given preventive lift, the dependences of the lift deformations on pressure and the grouting volumes of special mixtures were established. Based on the obtained data, a procedure was developed for the production of work to maintain the planned-altitude position of metropolitan railway facilities at all construction stages and operation of the multifunctional complex.

Model to Balance an Acceptable Radon Level Indoors

A theoretical model is presented for balancing an acceptable radon concentration in indoor air. The infiltration of radon from the ground to the indoor air can be controlled by barriers or by lowering the air pressure at the lower zone of the ground slab. Indoor air with a radon concentration higher than that of outdoor air can further be controlled through the effective dilution of indoor air with outdoor air. The theory estimates the allowed radon infiltration from the ground to balance radon at an acceptable level indoors for a given ventilation rate, considering the radon contribution to the indoor air from indoor materials, building materials and the interior. A method using this theory is presented, identifying the necessary airtightness required for a radon barrier to balance the acceptable radon concentration for a building. Barriers include commercially used system solutions, such as bitumen-based radon blockers, wet-room membranes, reinforced fixed mortar pastes, and polyethene membranes. An acceptable indoor radon concentration of between 100 and 300 Bq/m3 in indoor air is used. Barriers are evaluated by their ability to prevent soil gas penetration from the ground in combination with their effect on the building durability, as barriers may create a far more vulnerable building.

A Sensitivity Analysis for Thermal Performance of Building Envelope Design Parameters

Sensitivity analysis is crucial in building energy assessments. It is used to determine the major variables influencing building thermal performance, using both observational research and energy simulation models. This study investigates the most influential envelope design parameters on the thermal performance of a typical residential building in Budapest, Hungary. Sensitivity analysis is used in conjunction with the IDA-Indoor and Climate Energy (IDA-ICE 4.8) simulation tool to assess the effects of 33 envelope design parameters for energy consumption and carbon dioxide concentrations. The input parameters include thickness, materials, density, specific heat and thermal conductivity of the basement, exterior floor, interior floor, exterior wall, interior wall, roof, ground slab, glazing type, and infiltration rate. The results show that exterior floor materials have the biggest impact on annual delivered energy for heating and cooling, whereas the density of all structural elements and thickness of the basement, exterior floors, interior floors, and walls have minimal effects on energy consumption. It is also shown that the impact of all investigated parameters is not sensitive to the carbon dioxide concentration in the building. The authors consider that the findings of the paper assist designers to assess the performance of existing buildings and more efficiently generating alternative solutions in the energetic retrofitting of existing and energy design of new residential buildings.

Development and test of a combined radon sub-slab suction and sub-slab drainage system

To ensure a healthy indoor environment, the indoor air level of the radioactive gas radon must be kept low according to the WHO. This can be achieved by installing a radon sub-slab suction system. In buildings with a basement at the same time a sub-slab drainage system is often necessary. This paper describes results from a project, aiming to combine a radon sub-slab suction system with a sub-slab drainage system. A combined system will minimize the number of pipes when constructing new buildings and will also provide an easier retrofitting method for adding a radon sub-slab suction system to buildings with an existing sub-slab drainage system. In the project, it was found that the combination of the two functionalities required an airtight system to lower the pressure under the ground slab, an unhampered drainage of ground water and a prevention of odour from the drains. To meet these requirements, a prototype of a well with a water trap, a water outlet and a separate suction pipe for the air outlet was developed. A low voltage fan was installed in the suction pipe. The system was installed in a detached house with a 104 m2 basement. After installation, the pressure reduction over the ground slab in the basement was measured to be able to investigate the effect of the suction system independently of the radon exposure. The results showed a reduction of the pressure in the farthest corners under the ground slab by approximately 0.6 to 1.9 Pa compared to the pressure over the ground slab. We concluded that a combined radon sub-slab suction and sub-slab drainage system is possible with the designed well, although the use of a stronger fan will be necessary to meet the identified test objective of pressure reduction ΔP ≥ 1-3 Pa.

THE ENGINEERING METHOD FOR UNIFYING GROUND FLOOR SLAB SETTLEMENTS

For industrial buildings and logistics centres truck lifts are usually used. Therefore, there are special requirements for flatness tolerance of ground floor. The ground floor settlements differences in selected distances are limited. The article reviews the behaviour of soils and the importance of the actual behaviour assessment of soils during the design of floor slab on elastic subgrade. Particular attention is given to the behaviour of floor slab areas above pile foundations that support the building’s columns. Calculation results show the impact of subgrade stiffness on the behaviour of the floor slab, especially in areas above pile foundations, where the stiffness of subgrade is much higher. The article presents a solution for achieving the required level of settlements’ differences in areas where pile foundations for the building’s columns under the ground slab are used. The paper proposes an efficient engineering method to reduce ground slab settlements differences. The results of performed calculations confirm the efficiency of presented method.

Resistance of building foundation to radon penetration

Two-dimensional model of the steady-state diffusion radon transport from the soil to the ground floor of the building is developed. Radon concentration distributions in the soil and the living space are calculated at different foundation geometries. The model considers radon entry from enclosing structures, outside air, and diffusion from the soil. The radon field under the building is described. The quantitative criteria for the resistance of the building foundation to radon penetration from the soil are defined. It is found that the resistance of the ground slab to radon penetration and radon concentration in the plane of the soil structure contact have a decisive influence on indoor radon, and that the initial distribution of radon concentration in the soil changes significantly after the building erection. These changes depend on the radon potential in the soil, its radon permeability, resistance of the floor structure to radon penetration, and building geometry.

Efficiency of the chimney effect controlling radon levels indoor

According to the WHO the radioactive gas radon must be controlled indoors. E.g. by naturally driven suction systems based on thermal buoyancy, also denoted the chimney effect, which exploits the difference of indoor- and outdoor temperature to lower radon levels indoor. This paper presents four case studies showing that the efficiency of such systems to control radon level indoors varies, as the outdoor temperature varies throughout the year. The chimney effect was the driving force in the four single-family houses used as case studies. In two cases it was used to increase the indoor air change rate to dilute the radon concentration indoor, in one case it was used to drive a suction system under the ground slab to prevent radon from infiltrating through the ground slab, and in one case both techniques were used in combination. Measurements showed a correlation between a low radon level indoors and an increased difference between the indoor- and outdoor temperature, with the highest temperature indoor. Likely, the temperature difference can provide the needed suction in such systems. Without this driving force – out of the heating season – an increase of the indoor radon level was seen to occur. The needed suction to lower the radon level indoor did not occur in all cases. However, the efficiency of the system was seen to vary throughout the year, and was limited in periods with little difference between the indoor- and the outdoor temperature. Such needs to be taken into account, when the effect of naturally driven suction systems to reduce the radon level indoor are evaluated.

Temperature action in analysis of thermal stressed state of massive concrete and reinforced concrete structures

The work is dedicated to research of the thermal stresses state of massive concrete and reinforced concrete structures in construction period. The article examines the results of the analysis of the thermal stress state, which occurs in massive concrete ground slab with thickness of 1 m. The study was conducted with using analytical models, which include the factor of diurnal temperature range in comparison with simplified methods. Authors established that solving the problem of thermal stressed state of the massive foundation slabs in the building period without taking into account the influence temperature changing during the month might not cause to significant deviation of the real diagram of the thermal stresses and elongation deformations in the structures body: error is less than 0.5%.

Comparative Evaluation of Mechanical Properties of Fibre-Reinforced Concrete and Approach to Modelling of Bearing Capacity Ground Slab

The use of steel fibre-reinforced concrete is becoming gradually widespread in the engineering design of buildings. Typical cases include concrete foundations or floors. The actual design approach is often different. The proposal significantly encompasses the knowledge and range of the material properties of steel fibre-reinforced concrete. This article presents a comprehensive research programme, which has been focused on extensive laboratory testing, in situ testing and advanced numerical modelling using computing models and nonlinear models of concrete. It aims at a comprehensive description of the material properties of concrete, according to the degree of reinforcement, using 8 types of laboratory tests for description. In total, over 74 specified laboratory tests and four slab tests in situ are carried out. Selected evaluated material properties are also provided for the regression curve according to the degree of reinforcement, 0 to 3%. Subsequently, the detailed description of steel fibre is used in advanced modelling of tests of concrete slabs in situ. Numerical models simulate the behaviour of the steel fibre-reinforced concrete base structure in the interaction with the subsoil, where the objective was to verify the total carrying capacity of the slab structure.

A linear polarization converter with near unity efficiency in microwave regime

In this paper, we present a linear polarization converter in the reflective mode with near unity conversion efficiency. The converter is designed in an array form on the basis of a pair of orthogonally arranged three-dimensional split-loop resonators sharing a common terminal coaxial port and a continuous metallic ground slab. It converts the linearly polarized incident electromagnetic wave at resonance to its orthogonal counterpart upon the reflection mode. The conversion mechanism is explained by an equivalent circuit model, and the conversion efficiency can be tuned by changing the impedance of the terminal port. Such a scheme of the linear polarization converter has potential applications in microwave communications, remote sensing, and imaging.

Split-loop resonator array for microwave energy harvesting

In this paper, we propose a three-dimensional split-loop resonator composed of a bended wire, a metallic ground slab, and a coaxial line loaded with a lumped matching resistor to mimic the input impedance of a rectifier. An ensemble of such resonators can function as an efficient energy harvester. The energy capture mechanism is explained by an equivalent circuit model. A 20 × 20 resonator array is fabricated to resonate around 2.45 GHz. The simulated and measured results indicate that the proposed resonator array has nearly unity energy conversion efficiency at the resonant frequency and is quite promising as an energy harvester in the microwave wireless power transmission system.

Effect of Extending Hot Weather Periods on Approach to Floor Construction in Moderate Climate Residential Buildings / Wpływ Przedłużających Się Okresów Występowania Wysokich Temperatur Letnich Na Podejście Do Projektowania Podłogi Na Gruncie w Budynkach Mieszkalnych w Krajach Klimatu Umiarkowanego

Abstract The effects of changes in Global climate on the prolonging time and the frequency of the periods of very high outside air temperature at summer were shown in the paper with particular emphasis on European moderate climate countries. In these countries, residential buildings, are usually equipped neither in air conditioning equipment, nor in ordinary window blinds. As the most promising solution it is suggested to resign completely or partially from ground slab thermal insulation, directly utilizing ground heat storage capacity. The paper includes detailed simulations on potential effect of various kind of floor construction and actions preventing high indoor air temperatures in building approach on air temperature inside the one-storey, passive residential buildings during consecutive days of very high outdoor temperature and total energy used yearly for additional heating and air conditioning.

강섬유 보강 콘크리트 인장성능 평가방법에 따른 지반 바닥슬래브의 설계

Flexural strength of concrete ground slab reinforced with steel fiber is evaluated using the equivalent flexural strength ratio of steel fiber reinforced concrete based on the yield line theory. Recently, the European standard specifies that the tensile performance of the steel fiber reinforced concrete be evaluated directly from the residual flexural strength after the cracking of concrete. Thus, in the study, an experiment was carried out to evaluate the conventional equivalent flexural strength ratio and the residual flexural strength of the steel fiber reinforced concrete. Then the design flexural strength was investigated according to the location of a point load, based on the ratio of the radius of contact area of the load to the radius of relative stiffness. Design flexural capacity obtained from ACI 360R-10 was smaller than that from TR 34 (2003 & 2013). In addition, TR 34 (2013), which evaluates the design flexural capacity based on the residual flexural strength, showed slightly smaller value than TR 34 (2003).

Mechanical Properties of Steel-polypropylene Fibre Reinforced Concrete Under Elevated Temperature

Fibre reinforced concrete (FRC) has been found to improve strength, ductility, toughness, and durability of the structures. The application of FRC includes tunnel lining, ground slab, façade and many more. However, when exposing them to high temperature such as fire, there is still little information on the impact on its mechanical properties. The main objective of the study is to understand the fundamental behaviour of FRC when it is exposed to elevated temperature. However, rather than relying on one type of fibre, this study proposed of mixing two different types of fibre in concrete which will then be exposed to elevated temperature at normal temperature i.e. 27°C (room temperature), 200°C, and 400°C. The two types of fibres i.e. steel and propylene has different characteristics. The study is mainly focused on the experimental work. The fibre dosage will also be varied with percentage of steel-to-propylene of (100-0), (75-25), (50-50), (25-75) and (0-100) at 1.5% of fibres proportion from the volume of the concrete. Therefore this research is expected to answer the fundamental question whether if one type is vulnerable to fire, the other one will take place to avoid catastrophic failure of the whole structure. Experimental work will be carried out to study the impact of elevated temperature on the compressive strength, tensile strength, and flexural strength.

Collapse Behaviour Assessment of Precast Soft Storey Building

Soft-storey buildings are considered to be particularly vulnerable because the rigid block formed by upper levels has limited energy absorption and displacement capacity, thus leaving the columns in the soft-storey to deflect and absorb the seismic energy whilst resisting the axial gravity loading. To investigate collapse mechanism of such structures, a unique experimental field testing of a precast soft storey building in Melbourne was then undertaken. Four pull-over tests were conducted to measure the drift capacity and load-deflection behaviour of such buildings. Detailed theoretical models were developed that considered rocking behaviour, connection behaviour, P-Delta effects and ground slab interaction effects. The experimental results together with a comparison with theoretical model predictions showed that the precast soft storey structure had considerable displacement capacity beyond the traditional definition of failure used in high seismic regions, where failure is deemed to occur when the horizontal resistance capacity of the system is reduced to 80% of the nominal capacity. It is recommended that the nominal failure point could be reduced to a displacement limit set at the lesser of the displacement associated with 40% of the peak strength or 60% of the column width to allow for some conservatism. This preliminary definition is considered more realistic, particularly for regions of lower seismicity where the ground shaking is more modest in terms of displacement demand and duration and P-delta effects are not as significant.

Construction of Buckden's living stones rooms, Cambridgeshire, UK

Faced with a set of daunting technical, conservation and budget challenges, in building a small extension onto a medieval church to serve the local community of Buckden, Cambridgeshire, UK, a group of retired civil engineers combined their experience to achieve a successful project outcome. Visitor and user facilities were squeezed into an extremely confined site, producing a development of exceptional quality. Using an innovative procurement route, the client formed its own limited company, directly employing the professional consultants on a design and build basis and taking on the project risks itself. Substantial savings were achieved by eliminating contractors' overhead costs and making extensive use of volunteer labour and expertise. The fact that the end user and contractor were the same people, having a deep understanding of client needs, helped in resolving a number of issues. These included the presence of ancient monuments, a diversity of interested parties and other complications. Work also included risk management, traditional external materials of stonework, lead and glazing for longevity, foundations of reinforced concrete ground slab and steel shell piles, temporary works, recycling and reuse of materials.