Concrete Wall Thickness Research Articles

Structural strength and fatigue analyses of large-scale underwater compressed hydrogen energy storage accumulator

Underwater compressed hydrogen energy storage (UWCHES) is a potential solution for offshore energy storage. By taking advantage of the hydrostatic pressure of deep seawater, the compressed hydrogen can be isobarically stored in underwater artificial energy storage accumulators. The accumulator should withstand high pressure and large buoyancy and possess reliable anchoring to the seabed. In this study, the structural strength analysis and fatigue life of the large-scale accumulator is conducted employing the finite element method (FEM). The dimensionless stress prediction model and dimensionless fatigue life prediction model are developed through dimensional analysis and multivariate regression analysis. The performance of the accumulator with operating water depth of 100∼300 m, gas storage volume of 1081∼10128 m³, and concrete wall thickness of 0.1∼0.63 m is investigated. The results show that with an operating water depth of 100 m, gas storage capacity of 10,128 m3, and concrete wall thickness of 0.63 m, the maximum compressive stress is 1.43 MPa (yield strength is 60 MPa) and the maximum tensile stress of the accumulator is 2.55 MPa (yield strength is 6 MPa). The design fatigue life is 106 cycles which is larger than the expected service life of 104 cycles. Therefore, the accumulator structure meets the static strength and fatigue life. As the operating water depth increases with a consistent gas storage capacity, a transition in the stress state shifts from primarily tensile stress to predominantly compressive stress. The accuracy of the dimensionless stress prediction model and the dimensionless fatigue life prediction model were verified, with maximum deviations of 10.3 % and 13.7 %, respectively. Furthermore, the anchoring factor of safety of 1.12 is achieved.

Experimental investigations on the partially concrete-filled steel tubular slender beams

This paper focuses on the flexural behaviour of partially concrete-filled steel tubular (PCFST) beams having slender cross-sections (D/t > 150). PCFST beam is developed by optimising the tension zone concrete in a concrete-filled steel tubular (CFST) beam. Twelve specimens were investigated under a four-point load to understand the flexural behaviour and load transfer mechanism of PCFST slender beams. Parameters considered for the tests are concrete compressive strength, shear-span-to-depth ratio, and concrete wall thickness. The failure mode, load-deflection, strain distribution and moment-rotation data of the test specimens are reported and compared. In general, PCFST beams exhibit the same flexure behaviour as CFST beams in terms of flexural resistance and stiffness, and the weight reduction is around 40 %. However, composite action is lost in PCFST without tension zone concrete, and the beam behaves like an empty steel tube. Therefore, a minimum concrete wall thickness (tc,min) in the tension zone is required in PCFST and an equation for tc,min is proposed based on the test results. Concrete compressive strength is found to have lesser significance in the PCFST beam, whereas a decrease in the shear span-to-depth ratio from 2 to 1 can alter the mode of failure from flexure to shear. A numerical model is developed using ABAQUS to support the test results. This study finds the PCFST beam an optimised replacement for CFST beams in flexure-predominant structural systems. Additionally, a flexure capacity equation is proposed using the plastic stress distribution method, and made good predictions with the experimental and finite element results.

Practical Approach to Nuclear Shelter Wall Thickness Estimation

Abstract In the complex situation in which we live, preventive measures are increasingly being taken against the threat of nuclear attack and ionizing radiation, nuclear shelters are being built for private and public purposes. The purpose of the authors is to provide a practical approach to quickly calculate the thickness of the concrete shelter wall for such cases. The shelter wall thickness is assessed on the basis of published data on radiation dose calculations, corroborated by field data from nuclear tests, and information or calculations of the dose attenuation in the shelter wall. Doses from nuclear tests or simulations are summarized in tables in relation to bomb yield and distance from the explosion point. A dose criterion is chosen as the acceptable dose behind the shield. Neutron dose transmission factors, defined as ratio of the dose criterion to the dose without shielding are calculated. The concrete wall thickness corresponding to the neutron dose transmission factor was taken from reference sources. For gamma rays, the shield thickness is calculated based on an analytical relationship between dose without shield, the dose criterion, and the shield thickness. Data tables are provided with the estimated concrete wall thickness in relation to bomb yield and distance.

Flexural behaviour of optimised steel tubular beams partially filled with concrete

A partially concrete-filled steel tubular beam (PCFST) is proposed in this study to optimise the design and construction of the concrete-filled steel tubular beams (CFST). Concrete filling prevents the local buckling of the slender tubes. However, it is not needed in the beam’s tension zone. Therefore, in PCFST, concrete is filled in the compression zone while the tension zone is kept empty. In this paper, the flexural behaviour of the PCFST beam is studied experimentally and numerically. The ultimate moment resistance and flexural stiffness of PCFST are the same as CFST beams, while the weight reduction in PCFST is up to 60%. A finite element (FE) model is developed using ABAQUS software to investigate the effect of geometric and material properties of the PCFST beam on flexural behaviour. The FE model is validated by the present test results and the literature reports on CFST beams. Next, a parametric study is conducted to study the effect of concrete wall thickness in the web region, length-to-depth ratio, steel yield strength, concrete compressive strength, and beam shear span-to-depth ratio. The results show that the concrete filling is useful for slender steel tubular cross-sections rather than compact ones. A higher grade of concrete increases the beam ductility, while high-strength steel reduces the ductility. The results also show that the PCFST beam is more suitable for beam lengths where flexure is predominant than shear. Further, a flexural capacity equation is proposed for PCFST beams, and it agrees well with the test and numerical results. The reliability of the proposed equation is checked as per the recommendation in EN:1994–2004 and AISC 360–2016 code provisions.

MONTE CARLO NEUTRON DOSE MEASUREMENT IN PROTON THERAPY FOR HEALTHCARE WORKER RADIATION SAFETY

Background: Proton therapy is an innovative and highly advanced external radiation therapy modality for cancer treatment that uses positively charged atomic particles. The usage of proton therapy facilities in Asia has been increasing and will be followed by Indonesia in the short-coming years. In line with its significant benefits, the application of proton therapy also requires radiation protection awareness due to its higher energy used by protons produces scattered photon and neutron radiation in proton interactions. Therefore, optimal verification is needed in the commissioning process for designing proton therapy shielding bunkers. Objective: This research aims to examine the effect of concrete density on proton shielding by calculating the equivalent dose H*(10) of neutrons in the treatment control room (TCR) and the door of the compact proton therapy facility (CPTC) using Particle and Heavy Ion Transport code System (PHITS) simulation software. Method: The proton facility modeled for this simulation uses a compact proton therapy type planned to be built at one of the radiotherapy facilities in Indonesia. The proton therapy bunker model consists of a synchrocyclotron accelerator room and an examination room with standard configurations, wall thicknesses, and modeling areas under compact proton therapy standards. The analysis is focused on assessing the suitability of concrete materials and wall thicknesses and determining the neutron exposure dose values in the TCR and CPTC doors. The geometry, radiation source, and type of concrete in the wall are simulated from a conservative assumption to a more realistic model. Result: At the designated points in the TCR and CPTC door, measurements are taken from the simulation, which indicates that the equivalent dose H*(10) value is below one mSv/year. Conclusion: This value indicates that the dose rate passing through the wall does not exceed the dose limit value already set at one mSv/year for the general public.

Seismic performance of pretensioned centrifugal spun concrete piles with steel strands

Pretensioned centrifugal spun concrete piles with steel strands (PSC piles) have been developed to improve the seismic performance of the piles by using higher strength and more ductile prestressing steel strands, instead of the more traditional high strength steel bars. This paper presents a systematic evaluation of the seismic behavior of PSC piles by means of full-scale test and finite element (FE) simulation. Lateral cyclic loading tests have been carried out on three full-scale PSC pile specimens subjected to different axial compressive forces. The performances of test specimens, including cracking pattern, lateral bearing and deformation capacities, stiffness degradation, energy dissipation and failure mode are examined. The performances of PSC piles are subsequently compared with piles reinforced by high strength steel bars (referred as PHC piles) tested in a previous study. A detailed FE model was developed to simulate the hysteretic behavior of PSC piles using DIANA. This model was validated against test results and then used for parametric analyses. The effects of four key design parameters, in terms of axial force ratio, steel strand ratio, prestressing level of steel strands and concrete wall thickness, on the cyclic behavior of PSC piles have been investigated. The results show that all PSC pile specimens are dominated by the bending damage, and their cyclic behavior and failure mode are influenced significantly by the axial force. The lateral bearing capacity increases remarkably while the deformation capacity generally decreases with the increase of the axial force ratio. The PSC pile failure is mainly dominated by the tensile rupture of steel strands under lower axial force ratios, while concrete crushing under higher axial force ratios. Compared with PHC piles, PSC piles with a smaller reinforcement ratio demonstrate better overall seismic performance, especially ductility, under low to medium axial force ratios, as in such cases the high ductility of steel strands can be fully utilized. Further improvement of the seismic performance of PSC piles under higher axial force ratios can generally be achieved by increasing concrete wall thickness.

Full-scale experimental study of the seismic performance of pretensioned spun high-strength concrete piles

Pretensioned spun high-strength concrete (PHC) piles have been widely used in the pile foundations of buildings in soft soil areas due to their high axial bearing capacity and good economic benefit. However, the behavior of PHC piles under lateral loading is generally poor and this restricts their application in high-intensity seismic regions, especially for high-rise buildings. The existing research on the performance of PHC piles under cyclic lateral loading and with the presence of axial force is scarce. In this paper, the seismic performance of PHC piles is systematically evaluated through full-scale tests and numerical simulations. Lateral cyclic loading tests for two full-scale PHC pile specimens were conducted under different axial force ratios, and their performances were examined in terms of cracking pattern, failure mode, hysteretic characteristics, lateral bearing capacity, ductility, stiffness degradation and energy dissipation capacity. A dedicated finite element (FE) model was then developed using the software DIANA to compute the cyclic behavior of PHC piles, and the model was verified against the experimental results. Using the verified FE model, parametric analyses have been carried out to study the effects of axial force ratio, prestressing level of prestressing tendons, longitudinal reinforcement ratio, concrete wall thickness of the pile body and distributed pattern of prestressing tendons on the seismic performance of the PHC piles. The results show that the axial force ratio has a significant effect on the cyclic behavior and failure mode of PHC piles; an increase in the axial force ratio leads to an increase in the lateral bearing capacity but generally a decrease in the deformation capacity. The failure mode of the PHC piles is controlled by the rupture of prestressing tendons under lower axial force ratios (less than 0.15) but crushing of concrete under higher axial force ratios (greater than 0.15). Increasing the concrete wall thickness tends to improve the overall performance of the PHC piles, especially under higher axial force ratios.

Evaluation and Numerical Investigations of the Cyclic Behavior of Smart Composite Steel-Concrete Shear Wall: Comprehensive Study of Finite Element Model.

The composite shear wall has various merits over the traditional reinforced concrete walls. Thus, several experimental studies have been reported in the literature in order to study the seismic behavior of composite shear walls. However, few numerical investigations were found in the previous literature because of difficulties in the interaction behavior of steel and concrete. This study aimed to present a numerical analysis of smart composite shear walls, which use an infilled steel plate and concrete. The study was carried out using the ANSYS software. The mechanical mechanisms between the web plate and concrete were investigated thoroughly. The results obtained from the finite element (FE) analysis show excellent agreement with the experimental test results in terms of the hysteresis curves, failure behavior, ultimate strength, initial stiffness, and ductility. The present numerical investigations were focused on the effects of the gap, thickness of infill steel plate, thickness of the concrete wall, and distance between shear studs on the composite steel plate shear wall (CSPSW) behavior. The results indicate that increasing the gap between steel plate and concrete wall from 0 mm to 40 mm improved the stiffness by 18% as compared to the reference model, which led to delay failures of this model. Expanding the infill steel plate thickness to 12 mm enhanced the stiffness and energy absorption with a ratio of 95% and 58%, respectively. This resulted in a gradual drop in the strength capacity of this model. Meanwhile, increasing concrete wall thickness to 150 mm enhanced the ductility and energy absorption with a ratio of 52% and 32%, respectively, which led to restricting the model and reduced lateral offset. Changing the distance between shear studs from 20% to 25% enhanced the ductility and energy absorption by about 66% and 32%, respectively.

Comparison of backscattered photons from various thicknesses of ordinary and baryte concretes using FLUKA code for energies 0.25–20 MeV

With the advancement of medical technology and increased radiation technologies, the main material in radiation building construction is concrete, either ordinary or, more recently, heavy-weight concrete called baryte concrete (BaSO4). Numerous studies were performed on calculating and measuring linear attenuation coefficients μ (cm−1) for ordinary and baryte concrete, but few for backscattered photons and reflection coefficients. As a result, determining the photon reflection coefficient and backscattered photon data for ordinary and baryte concrete has become more commonplace. The ability to provide precise reflection coefficient data has consequences in various fields, including radiation protection, industry, and radiotherapy room design. As a result, the purpose of this study is to determine photon reflection coefficients for different thicknesses of ordinary and baryte concrete. This new information might be applied to various uses, such as saving money and space by enhancing the design of mazes used in radiation facilities. The FLUKA Monte Carlo code was used to calculate photon reflection coefficients with different energies and for varying thicknesses of ordinary and baryte concrete to investigate the impact of concrete wall thicknesses. The reflection coefficient as a function of various energies has been tabulated and figured to study the dose reduction factor compared to ordinary concrete. Recent research reveals that baryte concrete with a high density is beneficial as a shield for constructing radiation facilities to minimise the backscattered photon exposure in the incident energy range below 2 MeV. This new data has been presented in many applications, such as improving the mazes used for radiotherapy rooms; reducing cost and space requirements. In addition, the Monte Carlo method enables calculating the energy distribution of reflected photons, and these were shown for a range of angles.

Performance of steel-reinforced square CFST stub columns loaded in axial compression: Experiments

A steel-reinforced concrete-filled steel tubular column is a type of concrete-filled steel tubular (CFST) column reinforced by embedded steel profile. The inner carbon steel tube reinforced square concrete-filled stainless steel tubular column (SR-CFSST) has not been systematically investigated. In this project, stub composite columns with various experimental parameters were tested as loaded in axial monotonic compression, considering the effects of the concrete strength, column size and wall thickness of the steel tubes. The mechanical behaviour of stub columns was analysed in terms of ultimate load-bearing capacity, strength index, ductility, and failure modes. The calculation methods in five codes, including GB 50936, DBJ/T 13–51, Eurocode 4, ANSI/AISC 360 and AIJ, which are widely used for ordinary CFST stub columns, were compared. Finally, a simplified calculation method for the SR-CFSST stub columns was proposed for predicting the ultimate bearing capacity. The predicted results agree well with test results and the simplified calculation method can be used to design SR-CFSST stub columns loaded monotonically in axial compression.

Experimental study on torsional behavior of thin- and thick-walled RC box-girders using BFRP bars and steel stirrups under combined torsion-shear-moment

Experiments on hollow FRP-RC members subjected to combined torsion are uncommon. Six specimens of identical size and length, five rectangular and one trapezoidal, were constructed and tested in this investigation. About 2.5 percent reinforcement is included in all of the specimens. The study variables were the effect of shape (rectangular vs trapezoidal), concrete wall thickness (thin vs thick), cover thickness, and reinforcement layout (single-layer vs double-layer). Strength and stiffness, deflection and angle of twist, cracking pattern, and modes of failure were all evaluated. It is discovered that a trapezoidal thin-walled box-girder can attain around 85% of the ultimate strength of its rectangular counterpart, with 9% less deflection and 11% more twist. Thin-walled box-girders have a 17 percent higher ultimate torsional capacity than thick-walled members with thick covers. Thin-walled box-girders have the least deflection and twist, but their ultimate torsional capacity is limited compared to thick-walled counterparts. In thick-walled members, utilizing a double layer of reinforcement instead of a single-layer, can result in just a 4% increase in ultimate strengths, while deflection and twist both drop by 23%; in addition, a double-layer reinforced box-girder with thicker webs than flanges can reach the largest ultimate strength with the least angle of twist at failure.

Experimental and numerical studies of circular sandwiched concrete axially loaded CFDST short columns

This paper aims to experimentally and numerically investigate the compressive behavior of circular concrete-filled double-skin steel tubular (CFDST) short columns, in which only the sandwiched concrete is under axial compression. In total, 28 CFDST columns were loaded axially, and their axial load-shortening curves, ultimate strength and failure modes were briefly discussed. Results suggest that the wall thickness and yield stress of outer steel tube have a significant effect on the failure modes, while the concrete strength shows an insignificant effect. The tested columns exhibited good ductility concerned by seismic resistant design. The ultimate strength of the columns using STK490 outer steel tubes was about 20–26% than that of ones with STK400 outer steel tubes. With an increase in the concrete strength and wall thickness of outer steel tube, the ultimate strength of the columns was improved by 32% and 43%, respectively. Moreover, finite element (FE) models were established and verified by comparing with the test results, and then an extensive parametric analysis was carried out to ascertain the effects of key variables on the compressive behaviour of the studied CFDST short columns. Finally, based on the numerical and test results, a novel formula was proposed to estimate the ultimate strength of CFDST columns, and high prediction performance was found in the proposed formula. The proposed formula is not only applicable for the strength prediction of CFDST columns, but also for that of steel tube confined concrete (STCC) columns.

Shielding design for high-intensity Co-60 and Ir-192 gamma sources used in industrial radiography based on PHITS Monte Carlo simulations

Protection in industrial radiography facilities has been a worldwide concern for decades and the most appropriate protection for the public and operators in small scale facilities is the engineering protection including shielding first, time and distance. Monte Carlo methods were used for thickness determination in shielding design for gamma imaging using gamma sources in fixed facilities. Computation was done to develop the concrete design that can slow down the effective dose rate of the gamma rays from 100 Ci (or less) of Co-60 and 50 Ci (or less) of Ir-192 less than the value of 2.5 μSv/h (the limit for Public area) as required by the ALARA principle and regulation of different countries. The minimum concrete wall thickness necessary to achieve the ALARA principle in the previous conditions was found to be 120 cm for Co-60 source and 70 cm for the Ir-192 source. From the optimized design using a single corner maze, it was found that the central source position gives rise to high exposure and should not be used as a source position. Only the left and right positions of the source are preferred depending on the facility’s dimensions. For Co-60 with a maze corridor less than 7 m, the right position of the source is the most appropriate while the left position is preferred for larger dimensions. For Ir-192, the right position if preferred if the corridor length is less than 5 m and the left otherwise. Double-corner maze design was found to be the most appropriate shielding design for gamma radiation with the left and right position of the sources the best for both sources used. The double-corner maze required only 4 m maze length to achieve 2.5 µSv/h or less ALARA principle while single corner design requires 12 m or 14 m for left and right positions, respectively.

Electromagnetic Shielding Performance of Carbon Black Mixed Concrete with Zn-Al Metal Thermal Spray Coating.

The electromagnetic pulse (EMP) is a destructive phenomenon which harms the building, telecommunication, and IT based infrastructure. Thus, it is required to reduce the effect of EMP using shielding materials. In the present study, we have used different thickness of concrete walls by incorporating 1 and 5 wt% of carbon black, as well as 100 µm thick Zn–Al coating using the arc thermal metal spraying method (ATMSM). The EMP was evaluated using waveguide measurement fixture for shielding performance of the concrete wall in the range of 0.85 to 1 GHz frequency. The results reveal that the maximum value, i.e., 41.60 dB is shown by the 5-300-N specimen before application of Zn–Al coating where the thickness of concrete wall was 300 mm and 5% carbon black. However, once the 100 µm thick Zn–Al coating was applied on concrete specimen, this value was increased up to 89.75 dB. The increase in shielding values around 48 dB after using the Zn–Al coating is attributed to the reflection loss of the metal thermal spray coating. Thus, the Zn–Al coating can be used for EMP application instead of metallic plate.

Dependence of Lamé transformation for concrete pipeline design calculation

Determination of concrete strength and wall thickness for low pressure concrete pipe underground pipeline by possible way to identifications of the known dependencies by entering the correlation “wall diameter/wall thickness” and transformation of the Lamé formula. The conversion of the known dependencies, allowing to determine the normal hoop stress from the external equivalent load and internal pressure according to the Lamé dependence, allowed us to obtain new transformed dependencies for calculating the stresses in pipes under the combined action of internal pressure and external (reduced) load. Using the obtained equations allows you to determine the range of application of concrete (without metal reinforcement) pipes and select the concrete composition for the pipe production. It was determined in this study the stresses in the walls of concrete pipes under the combined action of an external (compressing pipe) load (the pipeline depth – the magnitude of the working fluid pressure) and internal pressure from the fluid transported under pressure.

The combined effects of thermal mass and insulation on energy performance in concrete office buildings

ABSTRACT Considering the use of concrete in structural and cladding applications, and energy code requirements for inclusion of thermal insulation in building envelopes, an investigative study was carried out to determine how the interaction between thermal mass properties of concrete and thermal insulation in the building envelope affects the building energy performance. This study examines how the combination of thermal mass and insulation influences building energy use in eight U.S. climate zones through Energy Plus simulation. The measuring parameters include the concrete wall thickness and relative location of thermal insulation with respect to the thermal mass wall. Building energy consumption is measured in terms of annual heating and cooling energy demands, as well as total energy use. The paper presents conclusions about the potential benefits of thermal mass and insulation for office occupancy. The results have shown that in cold climates the addition of thermal insulation to a concrete enclosure provides significant further benefits beyond those provided by thermal mass alone, whereas in hot locations those benefits are fewer. These results also indicate that other influential design variables such as occupancy type could also demonstrate broader implications of the integration of thermal mass and insulation in different climate zones.

Development of effective precast concrete barrier wall thickness for existing bridge

Development of effective precast concrete barrier wall thickness for existing bridge

Estimation of Indoor Temperature for a Passive Solar Residential Building with an Attached Sunspace during the Heating Period

The study presents the effects of the passive solar heating incorporated in an individual residential building located in Nis, brought about by the application of a passive solar system consisting of a sunspace and a thermo‐accumulative concrete wall thickness of 0.2 and 0.45 m. The building is not additionally heated by conventional fuels. A mathematical model was developed to investigate dynamic behavior of the thermo‐insulated building with attached sunspace and to investigate inner temperatures of the sunspace and of the room divided by thermo‐accumulative concrete partition wall with windows for direct collection of solar radiation. The diagrams are given for interior temperatures of the sunspace and of the room, taking into account the sunspace's various orientations: ψ = 0 ° (south‐orientated sunspace), ψ = +80° (east‐orientated sunspace), ψ = −80 °(west‐orientated sunspace). ψ stands for an angle that determines the position of the wall in relation to sunrays. The results shown in the study were derived using the mathematical model presented in the study. The highest room temperatures are achieved in the case of a thermo‐accumulative concrete wall with a thickness of 0.20 m for a south oriented building with sunspace (ψ = 0 °). This case requires the least additional heating by conventional fuels. The applied mathematical model can be used for the design and materialization of newly built buildings with attached sunspace. © 2018 American Institute of Chemical Engineers Environ Prog, 38:e13127, 2019

A study on the cost of concrete shielding in a conventional radiotherapy facility room

Ionizing radiations produced by particle accelerators is widely used for the treatment of cancer. In particular high-energy photon beams generated by electron linear accelerators play an important role in external beam radiation therapy, provided that millions of people will undergo cancer in the next decades and radiotherapy is the major kind of treatment used worldwide. An interesting question is how to estimate the thicknesses of the walls of the facility room in order to prevent their vicinities to receive a radiation dose above the permissible levels. In this work we present a simplified general formalism for the estimation of the concrete wall thicknesses of a facility room housing linear accelerators that produce photon beams of high-energies varying from 4 up to 30 MeV. A computer code based on FORTRAN programming language was developed, which allow us to handle with all the input parameters in a fast and simple way. The overall results have shown a slight linear growth of the total volume and associated cost of concrete shielding with the surface available to construct the facility vault.

Modeling fiber reinforced polymer (FRP) coating in retrofitting concrete walls against explosive loads

One of the issues considered in the design and dynamic resistance of structures (as seismic or explosive) is the use of materials which cause reduction in the force applied on the structure. With regard to the fact that greater loading is on the wall of concrete structures, the use of materials that reduce explosive force on the structure wall are among explosive force reduction methods.One of the viscose and damping materials of polymers is FRP, and in this study the FLAC3D software is used to evaluate the effect of this material on reducing force implemented on the walls and hence reduction of wall movement due to explosion. The concrete wall along with the FRP layer is modeled under dynamic loading. The effect of damping coefficient, number of FRP layers and concrete wall thickness has been evaluated.