Types Of Slabs Research Articles

Deflection Analysis of Layered Slabs with Plastic Inserts.

The article deals with experimental and numerical research of the layered reinforced concrete slab with plastic inserts. The investigated layered reinforced concrete slab is made of prefabricated and monolithic reinforced concrete layers. Voids were formed in the plate with spherical plastic inserts. With reference to the built-up bars theory, the paper proposes an analytical method for calculating the deflection of the layered reinforced concrete structures in non-linear stage, when bond between layers is partially rigid. The article also focuses on the numerical simulation of the layered slab, compares the estimated theoretical values of deflection with the experimental values and assesses the shear stiffness of the bond of prefabricated and monolithic concrete layers for calculating the deflection of the reinforced concrete slab. Paper presents the parametric analysis of deflection dependence on shear stiffness and the width of the contact zone of the layers. It was established that proposed analytical method and numerical analysis properly characterise the behaviour of the slab. Calculation results were close to experimental data. Moreover, it was determined that performance of this type of slab is highly influenced by shear stiffness of the bond between the concrete layers. Analysis confirmed that slab fails when bond is damaged, and layers slip in the support zone.

Finite size effect on the existence of the liquid–vapour spinodal curve

Fluids interacting with Lennard-Jones and Square Well potentials reach thermodynamic equilibrium forming two coexisting phases when simulated within the liquid–vapour spinodal region. If molecular dynamics simulations in the NVT ensemble are performed on a fluid kept in a cubic cell with periodic boundary conditions, liquid and vapour phases at equilibrium are separated by a process of spinodal decomposition. In the vapour side of the spinodal curve, spherical, cylindrical, and slab type liquid structures are formed, depending on the total density. Under the mentioned conditions, in the liquid side of the spinodal, vapour bubbles with the same shapes, surrounded by liquid, are formed. Results from this work suggest that as the simulation system size increases, the spinodal curve approaches the orthobaric, but it converges to a position closer to the coexistence curve but separated from it. The same thing happens for both potential models simulated. This is in sharp contrast with previous findings by Errington, McDowell, Binder and coworkers, where they conclude that ‘Only for infinitely large systems does the effective spinodal density converge to the macroscopic coexistence vapor density.’

Comparing the embodied carbon and cost of concrete floor solutions

Multi-objective optimisation of concrete floors for economic and environmental performance is critical in the present context since the building construction sector is responsible for a rising share of the global economy and greenhouse gas emissions. This study explores how the designs with optimum cost and embodied carbon are governed by the selection of a concrete floor system and column spacing. Discrete concrete floor designs were generated parametrically varying the column spacing for eight different construction forms available in practice. Pareto optimal solutions for cost and cradle-to-gate embodied carbon were identified for a range of column spacings. The trends of the sensitivity of the optimum solutions were also investigated due to inherent uncertainty and potential variations in the cost and embodied carbon of different constituents. Column spacings can be increased up to 2 m than the optimum, compromising cost or embodied carbon only up to 10% due to their nonlinear relationship, depending on the slab type. Post-tensioning can reduce embodied carbon of flat slabs for spans longer than 7 m but do not reach Pareto optimality due to available cheaper floor solutions with similar levels of embodied carbon. Flat slabs can be suggested as Pareto optimal for spans within 6 m–8 m when construction time and storey height is considered, due to reduced cost. However, parallelly Pareto optimal two-way slabs on beams have up to only 8% higher cost but up to 37% lower embodied carbon than flat slabs. While the floor designs are optimum for spans within 5–7 m for most of the slab types, two-way slabs on beams and/or hollow-core slabs are the optimum choice for a wide range of spans depending on relevant cost and carbon coefficients.

DETERMINATION OF LOADS FOR CALCULATION OF STRENGTH CHARACTERISTICS OF STRUCTURAL ELEMENTS OF FACADES

This article discusses the possible loads that will affect the elements of the facade coatings of buildings. Various types of facade slabs, claddings, ice, wind loads, loads from various types of guides for fastening the slabs are considered. The standard and design loads were determined, taking into account the Eurocodes, the loads for the calculations were selected.

Experimental Study and Numerical Simulation on Mechanical Properties of the Bottom Plate in the Assembled Composite Slab with Additional Steel Trusses

The composite slab with steel trusses is composed of precast bottom plate and cast-in-place concrete. In engineering applications, cracks often appear in the bottom plate before casting the upper concrete, which even leads to the failure of the composite slab. To improve the crack resistance of the slab, a composite slab with additional steel trusses is proposed; that is, on the basis of the original longitudinal steel trusses, the transverse steel trusses are added. Static test and numerical analysis were carried out on the bottom plate of the new type of composite slab with the additional transverse steel trusses. The experimental and analytical results show that the load level of the plate with additional steel trusses can be increased by 33% under the normal service limit state; the deflection of the plate is significantly reduced and the crack development is effectively controlled, which illustrates that the new type of composite slab can improve the bearing capacity, increase the bending stiffness, and enhance the crack resistance effectively.

Experimental study on the shrinkage behaviour of steel concrete composite slab

AbstractSteel concrete composite slabs are widely adopted in civil engineering and their numbers are rapidly increasing in Japan. A steel concrete composite slab is connected between concrete and a bottom steel plate by a shear connector. FaB‐Tec Japan Corporation developed a rigid type of shear connecter with a pipe that passes through the long hole on the steel rib. The load‐carrying capacity and durability of this design have been confirmed to be equal to or more than those of the headed stud and perfobond‐rib because the long hole of the steel pipe is filled with concrete. However, the time‐dependent behaviour, especially drying shrinkage, of this type of slab remains unclear. A steel concrete composite slab contains more steel than reinforced and prestressed concrete slabs; the effect of drying shrinkage is therefore expected to be greater owing to the steel restraint. To address this question, drying shrinkage tests were performed on steel concrete composite slabs and reinforced slabs. The change of stress resultants induced on the concrete, reinforcing bar and bottom steel plate was obtained by solving the simultaneous equation derived from the equilibrium conditions for stress resultants and the compatibility condition of strain and curvature.

A Bayesian group lasso classification for ADNI volumetrics data.

The primary objective of this paper is to develop a statistically valid classification procedure for analyzing brain image volumetrics data obtained from the Alzheimer's Disease Neuroimaging Initiative (ADNI) in elderly subjects with cognitive impairments. The Bayesian group lasso method thereby proposed for logistic regression efficiently selects an optimal model with the use of a spike and slab type prior. This method selects groups of attributes of a brain subregion encouraged by the group lasso penalty. We conduct simulation studies for high- and low-dimensional scenarios where our method is always able to select the true parameters that are truly predictive among a large number of parameters. The method is then applied on dichotomous response ADNI data which selects predictive atrophied brain regions and classifies Alzheimer's disease patients from healthy controls. Our analysis is able to give an accuracy rate of 80% for classifying Alzheimer's disease. The suggested method selects 29 brain subregions. The medical literature indicates that all these regions are associated with Alzheimer's patients. The Bayesian method of model selection further helps selecting only the subregions that are statistically significant, thus obtaining an optimal model.

Behaviour of simply supported RC skew slabs stiffened with shallow beams

Skew slab is the most common structural element that finds numerous applications in practice, especially when there is any space constraint that prevents the selection of either square or rectangular slab. Due to its geometry, this type of slab behaves differently in comparison to the rectangular slabs and it is a very time-consuming process to predict the moment field in such type of slabs. It becomes still more complicated when some beam system is used to meet the prescribed serviceability criterion. A set of mathematical expressions is presented in the paper that could be of help to predict the moment field being induced in skew slabs under external loads. The outcome of the proposed expressions is validated experimentally as well as numerically; a good agreement is observed in the results. An illustrative example is also presented in the paper to demonstrate the efficiency of the proposed expressions.

Research on the fatigue performance of self-compacting concrete structure in CRTSIII slab ballastless track under the action of heavy haul train

To further explore the fatigue characteristics of the CRTS (China Railway Track System) type III slab ballastless track structure generally used for high-speed railways, the fatigue damage of CRTS III type slab ballastless track structure system under the action of heavy-haul trains was studied. Based on the three-stage model, the CRTS III slab ballastless track structural system fatigue finite element numerical model was established, with particular emphasis on the fatigue characteristics of the self-compacting concrete of the CRTS III slab ballastless track under a load of heavy haul trains. To verify the reliability of the established model, the track structure displacement and stress under static load and fatigue load were analyzed and compared. The results shows that the model can be used to explore the fatigue damage law of the structural system of the CRTS III slab ballastless track under the action of heavy-haul trains. The results of further analysis showed that: (1) For self-compacting concrete, the maximum longitudinal tensile stress is greater than the maximum lateral tensile stress (2) For the longitudinal direction of the lower surface of the self-compacting concrete, once the tensile stress reaches the tensile strength of concrete, the self-compacting concrete cracks; as the number of fatigue loads further increases, more cracks will develop from the sides of the slab centre in the self-compacting concrete (3) The larger the axle load, the higher the stress level of each layer of the track structure, the faster the concrete damage rate, and the earlier the concrete cracks. As axle load is greater than 35 t, the damage of self-compacting concrete is more pronounced.

AN INNOVATIVE BOUNDARY ELEMENT FORMULATION FOR BUILDING SLABS

Slab supported by beams (i.e. beam-slab floor) is a common practice in the construction of buildings. Modeling this slab type using the boundary element method (BEM) is an essential step to provide seamless frameworks for the analysis of buildings with complex geometries. However, one of the most challenging difficulties that have been facing research efforts in this area is its theoretical setting with limited applicability to practical building slabs. This limitation is addressed in this research work and a practical BEM-based formulation for the slab-beam floor is presented. The presented formulation discretizes the connection area between the slab, and beams and columns into cells (supporting cells). The centroids of these cells are used to carry out an additional collocation scheme which is required to solve the resulting system of equations. To generate the slab stiffness matrix, the generalized displacements that correspond to the supporting cells’ degrees of freedom are set to unity (one at a time). By assembling the generated slab stiffness matrix with beams and columns stiffness matrices using the stiffness analysis method, the overall stiffness matrix is obtained. Hooke’s law is then applied to calculate the generalized displacements and straining actions are obtained in the post-processing phase. The developed formulation is applied to an example to validate its results by comparing it with the analytical solution.

Evaluating the effects of different slab types on static and dynamic characteristics of structures

In this study, the effect of different types of slabs on dynamic characteristics of structures under the lateral loading was investigated. For this purpose, four different types of slabs namely, beamed slab, flat slab, one way ribbed (hollow core) slab and waffle slab have been modeled in buildings having 3, 4 and 5 storeys with the same geometric dimensions, in accordance to design and construction requirements (TS 500) and Turkish building seismic codes (TBDY, 2018). Seismic analysis calculations of the modeled buildings were done using the equivalent seismic load method. The assumed local soil class was taken from the geotechnical report as ZD. As a result of the analysis, natural periods, base shear forces, maximum horizontal displacements and relative storey drifts of the buildings were compared. Seismic analysis and calculations of the buildings were completed using SAP2000 finite element software.

Structural performance and failure analysis of bubbledeck concrete slabs in construction

In this research paper, as the concrete material is eliminated from the locations situated around the middle of the cross-sections of bubbledecks (BDs), the BD type slabs are lighter than the traditional slabs. In the recent researches, the performance analysis (PA) is generally determined for the reinforced concrete (RC) structures with the moment-resisting frame (MRF) and dual systems. The dual system comprises mainly the MRF with shear wall of building under construction, as well as the flat slab having chiefly the BD system. In this paper, the evaluation of values of the performance and failure analysis of RC structures using BD system are submitted. We recorded a maximum load of 6.48, maximum stress of 75.00, macimum strain of 7.80, with minimum force of 0.83, while minimum slab length of 9.62 and lastly the maximum slab span of 27 for our bubbledeck concrete slab experiment in comparison with reinforced concrete slab to get the best results. The obtained results indicate that the lateral strengths of buildings increase by increasing the span length to story height ratio. Besides, the variations of the span length and the number of the story have more effects than the variation of the usage category buildings on the performance of structures. Furthermore, the span length has more effect than the number of stories in determining performance in an MRF. We observed that the bubbledeck concrete slabs are more lightweight and resistant in comparison with reinforced concrete.

Structural performance and failure analysis of bubbledeck concrete slabs in construction

In this research paper, as the concrete material is eliminated from the locations situated around the middle of the cross-sections of bubbledecks (BDs), the BD type slabs are lighter than the traditional slabs. In the recent researches, the performance analysis (PA) is generally determined for the reinforced concrete (RC) structures with the moment-resisting frame (MRF) and dual systems. The dual system comprises mainly the MRF with shear wall of building under construction, as well as the flat slab having chiefly the BD system. In this paper, the evaluation of values of the performance and failure analysis of RC structures using BD system are submitted. We recorded a maximum load of 6.48, maximum stress of 75.00, macimum strain of 7.80, with minimum force of 0.83, while minimum slab length of 9.62 and lastly the maximum slab span of 27 for our bubbledeck concrete slab experiment in comparison with reinforced concrete slab to get the best results. The obtained results indicate that the lateral strengths of buildings increase by increasing the span length to story height ratio. Besides, the variations of the span length and the number of the story have more effects than the variation of the usage category buildings on the performance of structures. Furthermore, the span length has more effect than the number of stories in determining performance in an MRF. We observed that the bubbledeck concrete slabs are more lightweight and resistant in comparison with reinforced concrete.

Optimization of Design Variables of a Phase Change Material Storage Tank and Comparison of a 2D Implicit vs. 2D Explicit Model

In this study, a thermal energy storage tank filled with commercial phase change material flat slabs is investigated. The tank provides heat at around 15 °C to the evaporator of a seasonal thermal energy storage system developed under the EU-funded project SWS-Heating. A 2D numerical model of the phase changed material storage tank based on the finite control volume approach was developed and validated with experimental data. Based on the validated model, an optimization was performed to identify the number, type and configuration of slabs. The final goal of the phase change material tank model is to be implemented into the whole generic heating system model. A trade-off between results’ accuracy and computational time of the phase change material model is needed. Therefore, a comparison between a 2D implicit and 2D explicit scheme of the model was performed. The results showed that using an explicit scheme instead of an implicit scheme with a reasonable number of nodes (15 to 25) in the heat transfer fluid direction allowed a considerable decrease in the computational time (7 times for the best case) with only a slight reduction in the accuracy in terms on mean average percentage error (0.44%).

Analytical Investigation of the Load-Bearing Behavior of Light Weight Hollow Core Composite Slabs*

Slabs are considered the most important structural member but also the heaviest one. Therefore, in the last few years a new type of slabs was introduced, hollow core slabs with steel decks. On the other hand, the use of light weight concrete that has got a density less than (1850 kg/m3 ) reduces the self-weight of structures considerably. This paper conducts an analytical study of the flexural behavior of five slabs, a solid slab that acts as a reference, a hollow core slab with elliptical voids, a composite slab and two hollow core composite slabs using normal weight and light weight concrete using ANSYS software. All the slabs share the same size (2600 x 1200 x 140) mm. The results show that the use of hollow core slabs increases the load carrying capacity by about 32% while using light weight concrete reduces it by about 34% but it also decreases the self- weight and the deformation considerably. The use of light weight hollow core slabs promises with a wide horizon of privileges and improvements in the construction and research domain

Experimental analysis on the structural continuity effect in steel decking concrete slabs subjected to fire

Composite steel decking concrete slabs are an important structural member in building construction. Nevertheless, the behavior of these slabs in case of fire are not yet well characterized and the corresponding fire design methods need improvements. Several parameters that affect the behavior of these slabs in case of fire and that are not taken into account in the fire design at the moment have to be included. One of these parameters, is the continuity effect between slab panels. This study evaluated the structural performance of continuous steel decking concrete slabs subjected to fire. For this purpose, 8 real-scale slabs, with 2.56 × 4.60 m, were subjected to the ISO 834 standard fire curve for a duration of 180 min. The structural continuity of the slab, and thus the induced hogging moment, was studied by introducing at mid-span a thermally-protected intermediate beam. In these tests the following parameters were registered: temperature distribution in the cross-section; temperatures in the unexposed slab’s surface (thermal insulation); mid-span deflections; concrete cracking occurrence; longitudinal elongation of the rebars and relative slip between the steel decking and the concrete. It was observed that the composite behavior of the slab was lost at nearly 5 min of fire exposure, the structural continuity at 10 min and the membrane effect at a time between 30 and 50 min, depending of the slab’s characteristics. The negative rebars didn’t show an effectiveness in the structural continuity of the slab. The steel decking did not have a great contribution in the loadbearing capacity of the slab because it loses resistance and detaches from the concrete in the first minutes of the fire. However, embossments in the web can enhance the shear strength between the steel deking and the concrete and improve the composite action of the slab in case of fire. This research demonstrated the need of further research on the adhesion of the steel decking to the concrete in this type of slabs in case of fire.

GEOPOLYMERS SYNTHESIZED FROM PHILIPPINE COAL ASH AS SUSTAINABLE ALTERNATIVE LOW HEAT TRANSMISSION AND FIRE-RESISTANT MATERIAL FOR BUILDINGS

Geopolymers are formed from alumina and silica rich materials by alkali dissolution and subsequent polycondensation into a polymeric network. Geopolymerization technology presents a great potential for positive environmental impact since many alumina- and silica- rich industrial waste materials, such as coal ashes, blast furnace slags, mine tailings, etc., can be used as its precursor materials in a process that requires less energy and gives up less emissions vis-à-vis the current conventional OPC (ordinary Portland cement) technology. In this study, geopolymer samples were prepared using an 85% coal fly ash (CFA) - 10% coal bottom ash (CBA) - 5% rice hull ash (RHA) wt/wt mix proportion and activated using an alkali solution of NaOH-Na2SiO3 at an 80%-20% wt/wt solid-to-liquid ratio. With this mix proportion, two types of specimens were used, a slab type with 50 mm thickness, and a cube type, 50 mm x 50 mm x 50 mm. The slab type specimens were used for evaluating fire resistance using ASTM E119, Standard Test Methods for Fire Tests of Building Construction and Materials, and the cube type specimens were used to study the effect of foaming agents on the strength and thermal conductivity of the geopolymers formed. Two types of foaming agents, hydrogen peroxide and sodium perborate, at an amount of 0.1% to 0.4% of dry mass mixture, were used. Results from the foamed geopolymers gave compressive strength values ranging from 0.37 to 0.71 MPa and densities of 1430-1560 kg/m3 at 0.3% to 0.4% peroxide added. Values of thermal conductivity of the foamed geopolymers were within 0.033-0.037 W/m-K for all foamed geopolymer samples tested which is a significant reduction compared to the thermal conductivity of the unfoamed geopolymer sample at 0.48 W/m-K. The fire resistance tests show that the unfoamed geopolymer samples perform better than OPC concrete. However, the foamed geopolymers have very low strength compared to the unfoamed sample compressive strength of 18.1 MPa and, thus, are suitable for non-load bearing, insulation applications.

Investigation of the behavior factor of Reinforced Concrete Moment Frame with concrete Voided slab constructed by Spherical and Cubic Balls

In order to prevent damage caused by earthquakes in different types of structures including concrete structures, various methods are used by structural engineers considering terms of design and working conditions. Simple slabs, bubble hollow slabs (Spherical) and Cubic hollow slabs may be used to meet the structural requirements and also to increase performance level of the structures against earthquakes. This research aimed to evaluate the performance of these structures in different conditions and evaluate their impact on the structural behaviour coefficient. For this purpose, ABAQUS finite element software has been utilized to model a concrete moment frame with one span in one floor equipped with simple concrete slab, Spherical and Cubic hollow slabs in different conditions. Then the required analysis has been performed to evaluate the behaviour of these different type slabs. Verification of the model is implemented According to the study of Leimam et al. Then, in different models, the coefficient of structural behaviour is calculated and studied. The results show that using Cubic and Spherical slab could increase the behaviour coefficient of concrete moment frame in comparison with simple slabs. In the case of concrete moment frame with Cubic and Spherical slab, behaviour coefficient increases 32.79% and 46.3% respectively.

Experimental Study on the Flexural Behavior of Concrete-Filled Steel Box Slabs

Different to conventional reinforced concrete or steel material, a new type of concrete-filled steel box slab has been proposed by effectively integrating the combined benefits of both steel and concrete. By filling concrete, this type of slab could avoid the local bucking of steel plate and then could provide a high moment capacity. Therefore, this study aims to investigate the flexural behavior of concrete-filled steel box slabs through testing seven specimens and characterize their failure characteristics, stress distribution and ultimate moment capacity. A comprehensive parametric study focuses on the influence of the steel plate thickness, the stud and stiffening plate on the slab flexural behavior. The results show that concrete-filled steel box slabs had a high moment capacity and good ductility. The thickness of the steel plate had a significant influence on the moment capacity of the specimen. The stud led to the reduction of the moment capacity of the slab. The stiffening plate effectively improved the flexural behavior of the specimen. Moreover, a calculation method was formulated to describe the moment capacity of the slab and compared with experimental results. The results show that the proposed method for the moment capacity of the slab was conservative and reasonable.

Finite element analysis of two-way hollow core reinforced concrete slab under punching repeated load

This research provides informationabout the finite element analysis of the structural behavior of an innovative new type of two-wayhollow reinforced concrete (RC) slabs of two-way plastic piping system under the effects of concentratedpunching repeated loads. This new type of two-way hollow slab could be constructedbyreplacing part of the concrete volume by a continuous network of two-way plastic piping systemsto cutportion of the dead loads by reducing the self-weight of the createdslabsas well as offering networks of voids inside the RC slab which could be valuable for passing utility lines. The reliability of elements forms, material characteristics, types of constantsand the convergence study of the proposed finite element model of the new type of two-way hollow RC slabswas confirmed by the outcomes of the numerical study and the experimental results using five different parametric studies. The proposed FE modeshowed satisfactoryaccuracy with a maximum varianceratio of about 0.11in comparison with the ultimate loading capacity of the experimental behavior. The results weredemonstratingthe efficiency of the new methodology of producing two-way hollow RC slabs using the two-way piping system by reducing the self-weight by about 24% with maintaining about 79% of the total strength. Moreover, the reduction in the strength could be eliminated by locating the networks of plastic pipes out of the locations of the maximum stresses, adding micro steel fiber, using high strength concrete or increasing the reinforcement ratio.