Lightweight Slabs Research Articles

Quantitative measurements of lightweight timber floors using low-frequency impact source; analysis of the accuracy of 1/3 octave band heavy-hard impact prediction modelling in lightweight structures

This paper analyses heavy weight drops on lightweight structures such as timber frame and mass timber, with particular emphasis on the accuracy of the 1/3 octave band heavy-hard impact prediction modelling. With the increasing popularity of lightweight structures such as mass timber, timber frame and steel frame, this research investigates the behaviour of lightweight slabs when free weights such us kettlebells are dropped on fitness flooring. A comparison of the spectral shapes of various base structures has been carried out, focusing on the low-frequency range and resonance of various base structure types. Third-party laboratory data is utilised to derive design recommendations when free weights or heavy hard impacts are proposed in lightweight structure developments. Previously, the author carried out a case study in the UK which demonstrates the accuracy of the 1/3 octave band prediction model for concrete developments using force pulse data collected at the in-house drop tower. While the prediction method shows good agreement for concrete buildings up to 200 Hz, there is interest in extending the range for use in lightweight structures.

Flexural behaviors of 3D printed lightweight engineered cementitious composites (ECC) slab with hollow sections

3D concrete printing (3DCP) is a form-free construction method that offers the potential to construct load-efficient structures with unique shapes. However, 3DCP currently lacks a compatible reinforcement method. This paper aims to print self-reinforced lightweight slabs using engineered cementitious composites (ECC). By introducing honeycomb-like (HS) and rectangular hollow sections (RS) into printed ECC slabs, the self-weight of HS and RS slabs is reduced by over 30.5% and 35.7%, respectively, compared to that of a solid slab. The flexural behaviors of the printed slabs were investigated via four-point bending test and finite element modeling. Experimental results show that the printed ECC slabs exhibit typical ductile failure even in the absence of steel reinforcement. The maximum flexural strength-to-mass ratio of HS and RS slabs approaches 0.049 MPa/kg, which almost equals to the value of solid slab. The numerical models were validated using the experimental results. Furthermore, parametric analysis reveals that bond strength higher than 1.5 MPa can achieve a stable flexural behavior for HS slab. The findings lay the groundwork for load-efficient and lightweight structural design by using ECC in 3DCP.

The Effect of Voids on Flexural Capacity of Reinforced Concrete Slabs

The voided reinforced concrete slab system is mainly produced with polyester foam placed mostly at the bottom of the slab. The aim of the voids is to reduce the weight of the slab. In this paper behavior of the voided reinforced concrete slabs in which voids placed at the mid-height of the slab cross-section, is examined analytically. A series of models were created to come up with a lightweight slab. Two distinct slab models were analyzed using the ABAQUS software. In the first group, slabs had three layers, in which bottom and top layers were of solid reinforced concrete, but the mid layer was of voided unreinforced concrete. In the second layer, in order to increase the contact between top and bottom layers of the slab, crossties were utilized, and the mid layer was reinforced accordingly. Since all the layers were 5 cm thick, the total thickness of the slabs were 15 cm. Slabs were 100 cm wide and 200 cm long. They were simulated the three-point bending test. Concrete damaged plasticity material model (CDPM) for concrete and elastoplastic material model for steel was selected. From the results it was found that moment capacity decreased with the increase in the volume of the voids. There was a sudden decrease in strength after reaching the yield strength in voided slab without a crosstie. In addition, crossties enabled the reduction of the weight of the slabs without significant decrease in moment capacity.

Strength, stiffness and crack resistance of a lightweight slab structure model with spherical void formers

Precast concrete has been used for many decades with optimized consumption of concrete and reinforcement. The use of monolithic reinforced concrete in the Russian Federation cannot be called balanced in terms of its material consumption. One of the design ideas for creating lightweight slab reinforced concrete structures in monolithic construction is the BubbleDeck technology. Spherical bushings are located in places of the least stresses in the structure, which leads to a significant reduction in the own weight. The article presents the results of assessing the strength, stiffness and crack resistance of a reduced model of a reinforced concrete slab in comparison with similar parameters of a solid section slab.

EFFICIENCY RESEARCH OF MONOLITHIC LIFT- SLABS IN MULTISTOREY SKELETON BUILDSNGS

One of the priority directions of modern construction is the construction of framemonolithic multi-story buildings with beamless ceilings. The use of a frame-monolithic scheme of house construction makes it possible to diversify thearchitectural and planning solutions of apartments and houses, as well as to significantly shorten the terms of their construction.The experience of construction and operation of frame-monolithic buildings shows that floor slabs are the most material-intensive element of the frame. At the same time, the consumption of concrete is more than 30.0% of the total volume of concrete in the building. Therefore, the problem of reducing the mass of the ceiling is urgent.The search for a reserve for reducing the consumption of concrete in floor slabs is accompanied by an increase in the deformability of lightweight slabs, as well as an additional concentration of compressive stresses in the places where the slabs reston vertical elements. The indicated zone of butt connection needs additional reinforcement in order to ensure compressive strength.The article examines ways to reduce the material consumption of floor slabs, and gives an assessment of the above-mentioned factors that affect the workof slabs as part of the building frame. Numerical studies of the calculation model of the building in Kyiv were carried out using PC LIRA CAD, on the basis of which the parameters of the stress-strain state of the experimental plates were established, aswell as the justified conditions of their use for further operation in the practice of frame-monolithic house construction.

Innovative prefabricated lightweight slab system of high structural performance

This paper presents a new pre-fabricated lightweight slab system where the relatively high post-cracking tensile capacity of steel fibre reinforced concrete (SFRC) is combined with the high ductility and tensile strength of optimized shape profiles made by cold formed steel sheets for a synergetic result in terms of structural performance. The SFRC fills the longitudinal steel profiles (girders) that have openings in the web for materializing SFRC shear mechanisms that provide very high shear resistance to the slab. This slab system (designated by PreSlabTec) includes a SFRC deck of 40 mm thickness and lightweight blocks serving as permanent moulds to the SFRC and thermal insulation. The transversal stiffness is assured by thin wall tubular steel profiles that remained anchored in the girders due to their openings. PreSlabTec is simple and fast of executing and was conceived for being produced in an automation process of prefabrication industry.For assessing the performance of the PreSlabTec in serviceability and ultimate limit state conditions, an extensive program with almost real scale prototypes was executed and tested under loading configurations for flexural and shear failures. For the flexural loading configurations, the PreSlabTec demonstrated a very high load carrying capacity and ductility performance. The PreSlabTec never failed in shear, despite the very exigent shear loading configurations adopted. The long-term deflection was also experimentally evaluated for the standard design requirement for slabs of residential buildings, and a relatively low average creep coefficient of 0.13 was obtained.Finally, the theoretical approach for the design of PreSlabTec is described and its good predictive performance is demonstrated.

INVESTIGATION OF THE EFFECTIVENESS OF REINFORCED CONCRETE MONOLITHIC OVERLAP WITH HOLLOW LINERS

The use of floors with hollow linersis one of the possible ways to reduce the materialconsumption and weight of buildings made ofmonolithic concrete, almost without reducing theirreliability. Reducing the weight of structures is animportant advantage in the construction of facilities in seismically active regions.However, the introduction of such plates inconstruction is constrained by the lack of theoretical research and the necessary regulatory framework and experience in designing these structures.The article considers the problems of calculations and construction of a lightweight monosummer floor on the example of a specific 18-storey residential building. The basic principlesand methods of construction and calculation ofhollow monolithic floors are given.The method of modeling a slab of reducedstiffness is the most expedient for the constructionof a spatial calculation model of a building withdifferent floor slabs.According to the results of the study, it wasfound that the hollow floor has advantages over thesolid typical in many parameters. The key differences are in the consumption of concrete -18.6%,the consumption of steel - 24.2% and the ownweight of the floor - 32.9%.Lightweight slabs are best suited for buildingswith large spans and low payloads, but their usewill be effective for buildings with large spans andsignificant payloads.

Multi-criteria decision-making applied to the sustainability of building structures based on Modern Methods of Construction

Since the establishment of the Sustainable Development Goals, great concern has arisen on how to diminish the impacts that result from construction activities. In such context, Modern Methods of Construction (MMC) rise as a powerful way to reduce life cycle impacts through optimizing the consumption of materials. This paper focuses on the sustainability assessment of different modern construction techniques applied to concrete structures of single-family houses. The life cycle performance in terms of sustainability is compared between a conventional reference design, a precast design, a lightweight slab design with pressurized hollow discs, and a design based on double-wall structural elements. The sustainability is assessed through a set of 38 indicators that address not only the economic and environmental response of the designs, but also their social impacts as well. Five of the best known Multi-Criteria Decision-Making (MCDM) techniques (SAW, COPRAS, TOPSIS, VIKOR and MIVES) are applied to derive the life-cycle performance of each design into a single sustainability score. Since there is no consensus on which MCDM method works best in sustainability assessments, a Global Structural Sustainability Index (GSSI) combining and weighting the above is proposed here to aid the analysis of the results obtained. The results show that consideration of the three dimensions of sustainability leads to balanced designs whose preference need not coincide with those derived from each one-dimensional life cycle approach.

Structural Behavior of Hollow-core One Way Slabs of High Strength Self-compacting Concrete

Reinforced concrete hollow-core slab (HCS) is a new type of lightweight slabs in which the longitudinal voids provide the ability to reduce the concrete amount. Reducing the concrete amount causes a reduction of the dead loads which consequently leads to cost-saving, fast construction, and getting long-span. The experimental program includes constructing and testing slab species with dimensions 1700×435×125mm to investigate the effect of eliminating concrete ratio by changing the size of the longitudinal void and the number of longitudinal voids on the performance of HCS. The experimental results showed that elimination of the concrete with percentages 10.83, 17.20 and 24.37% from the hollow-core high strength slabs using three longitudinal voids of diameters 50, 63, and 75mm, respectively, resulted in saving the ultimate strength by 90.06, 87.84 and 85.07%, and increasing the ultimate deflection by 5.48, 10.80 and 17.44%. While, elimination of the concrete with percentages 16.25, 24.37 and 32.50% from the hollow-core high strength slabs using two, three, and four longitudinal voids of 75mm diameter resulted in saving the ultimate strength with percentages 89.29, 85.07 and 80.61%, and increasing the ultimate deflection with percentages 7.57, 17.44 and 22.81% respectively when compared with the reference solid slab.

Cyclic behavior tests and evaluation of CFS truss composite floors

The cold-formed steel (CFS) composite floors have used widely in engineering practice owing to their benefits of lightweight, high strength and fast construction. Previously published literatures mainly focused on the flexural behavior of this type of composite floor, while there was little guidance on the cyclic behavior and design method. Therefore, it was necessary to study the cyclic behaviors of CFS composite floors with various lightweight slabs. This paper employed the CFS truss beam, commonly used profiled steel sheeting-concrete (PSSC) slab and novel type of autoclaved lightweight concrete (ALC) slab. A series of experimental and analytical studies on the hysteretic behaviors of CFS truss composite floors with PSSC slab and ALC slab were reported in this paper. The typical failure modes, hysteresis curves, envelope curves, characteristic values, ductility ratios, stiffness, and energy dissipation capacities of this composite floor type were systematically studied and estimated. The results indicated that the using of shear connectors could restrict the separation of concrete slab and profiled steel sheet, and improve the shear capacity and ductility ratio of CFS truss composite floor with PSSC slab. Besides, the CFS truss composite floor with ALC slab exhibited reliable hysteretic behavior accompanied by relatively poor integral rigidity owing to its assembly. Finally, the shear capacity and initial stiffness of CFS truss composite floor with PSSC slab were predicted based on a simplified model. The predicted results were agreed well with the experimental data. The studies in this paper could be adopted in the design and application of the CFS composite floor.

Mechanical Behavior of a Composite Lightweight Slab, Consisting of a Laminated Wooden Joist and Ecological Mortar.

The investigation reported in this paper is an evaluation of the mechanical behavior of full-scale ecological mortar slabs manufactured with a mixture of expanded clay and recycled concrete aggregates. The composite mortars form a compressive layer over laminated wooden joists to form a single construction unit. To do so, full-scale flexural tests are conducted of the composite laminated wood-ecological mortar slabs with different types of mortar designs: reference mortar (MR), lightweight mortar dosed with recycled concrete aggregates (MLC), and lightweight mortar dosed with recycled mixed aggregates (MLM). The test results showed that the mortar forming the compression layer and the laminated wooden joists worked in unison and withstood a higher maximum failure load under flexion than the failure load of the wooden joists in isolation. Moreover, the laboratory test results were compared with the simulated values of the theoretical model, generated in accordance with the technical specifications for structural calculations contained in the Spanish building code, and with the results calculated by a computer software package. From the analysis of the results of the calculation methods and the full-scale laboratory test results, it was concluded that the safety margin yielded by the calculations validated the use of those methods on this type of composite slab. In this way, a strong mixed wood–mortar slab was designed, contributing little dead-load to the building structure and its manufacture with recycled aggregate, also contributes to the circular economy of construction materials.

Ambient Vibration Response of Precast Hollow Core Flooring System

Prestressed precast hollow core is known as a long span slab with a void along its length. The void has a big influence on the weight of the slab. In vibration theory, a lightweight slab with a long span is very sensitive to vibration. In this study, the ambient vibration response of precast hollow core is investigated using the finite element method and modal analysis. Numerical analysis is used to predict the floor vibration and modal testing is used to test the vibration performance of floors on the actual site. The prediction data is obtained by using SAP2000 to determine the vibration behaviour and compared with the modal testing result of the floor located in Kuala Lumpur. The 1st mode shape appeared for 12 natural frequencies between 8.36 Hz to 9.29Hz in the prediction analysis. For modal testing, the vibration behaviour of the actual hollow core floor is determined using an ambient test. The data was obtained using an accelerometer and analysed using Artermis software to determine natural frequencies, damping ratio and mode shape. The 1st mode of natural frequencies for floor area A and area B were 8.45Hz and 9.34Hz. The results from the analysis show that the range of natural frequency between the predicted analysis and that of the modal testing is acceptable. The limitation stated that 10Hz is the cut-off frequency to determine the class of the floor. From the analysis, it is shown that the prediction and the modal testing results are accepted where both floors are classified as low-frequency floors.

РЕЗУЛЬТАТЫ ЭКСПЕРИМЕНТАЛЬНЫХ ИССЛЕДОВАНИЙ ОБЛЕГЧЕННЫХ МОНОЛИТНЫХ ПЛИТ ПЕРЕКРЫТИЙ С КОМБИНИРОВАННЫМ АРМИРОВАНИЕМ

The cutting-edge technologies have touched upon all aspects of human activity, as well as modern construction. If earlier the construction process meant great economic and labor costs, now modern construction reduces these costs by many times. One of the state-of-the-art technologies in modern construction is lightweight monolithic floor slab, which significantly reduces the consump-tion of materials. That is why this article examines the lightweight monolithic floor slabs and coatings with steel and combined reinforcement under the uniformly distributed load. In total, three series of samples have been investigated. The first sample, for comparison with other samples, has been fully reinforced with various-diameter steel bars. For the second and third samples, fiber-glass reinforcement has been used. Within the course of the research the results of studying the lightweight monolithic slabs fitted with metal and fiberglass reinforcement have been obtained. Ex-perimental dependences have been obtained for the deflection change, elongation and shortening in the span sections, the moment of occurrence, the cracking moment and crack width in the light-weight slab on the applied load at the loading steps. The stress in the span of the tension region of the slab, and the stress in the compressed surface of the slab during the failure of structure are given.

Horizontal Shear Behaviors of Normal Weight and Lightweight Concrete Composite T-Beams

This paper presents the results of recent research on the interface shear behavior of normal weight and lightweight concrete composite T-beams. In the experimental program 12 beams and necessary control cylinders were tested to provide experimental cases with the variables of interface preparation, clamping stress and lightweight slab concrete strength. Compared with 7 equations developed previously, it has been found that those formulas, especially the ones from current AASHTO and ACI design codes, give a conservative theoretical prediction of horizontal shear capacity of composite T-beams. Based on the experimental results, a more accurate equation was developed to predict the interface shear transfer strength of composite concrete T-beam. By comparing the experimental results of previous beam tests and shear-friction push-off tests for different types of concrete with both rough and smooth interface published in literature, it has been found that the proposed formula is reliable in predicting the horizontal shear strength of concrete composite T-beams.

Interface shear behavior between high-strength precast girders and lightweight cast-in-place slabs

The overall purpose of this study is to examine the shear-friction behavior of shear interface with transverse reinforcement between precast girder using high-strength concrete and cast-in-place slab with lightweight concrete. Eighteen push-off specimens, with testing parameters of lightweight coarse aggregate size, slab concrete type and shear reinforcement ratio, were tested in this investigation. Based on the analysis of the experiment, this study suggests that the granular size of lightweight coarse aggregate did not play a significant role in the shear strength of interface and the shear transfer strength of lightweight slab concrete specimens are greater than that of normal weight slab concrete specimens having the same concrete compressive strength, interface reinforcement ratio and interface treatment. Additional, the transfer reinforcing steel can improve shear capacity and residual resistance obviously. For both sand-lightweight and normal weight cast-in-place slab concretes, the interface shear strengths predicted by the design equations given in AASHTO LRFD 2014 and ACI 318-14 are conservative.

Shear behavior of light weight ferrocement concrete slabs

The objective of the work presented in this research was to develop light weight composite slab subjected to punching load by using column slab connection at the center of the slab which comprises polystyrene block of thickness 80 mm reinforced with welded galvanized steel mesh or expanded steel mesh. The use of expanded metal mesh and welded steel mesh was proposed as a viable alternative to ordinary steel bars in reinforcing ferrocement plates, also it was proposed to use it with ordinary steel bars to enhance the mechanical behavior of the composite slab. For light weight sandwich elements, light weight polystyrene of density 12Kg/m3 is used as a core material and welded wire meshes or expanded steel meshes are to be used as steel reinforcement at the two thin skin layers. Twelve squares composite light weight slabs were developed having the dimensions of 1200mm x 1200mm and overall thickness of 140mm were tested simply supported along all four sides under central column slab connection until failure. This research presents the behavior of ferrocement lightweight slabs under punching shear. The effects of various types of reinforcing materials were investigated. Using such lightweight materials will contribute to decreasing the weight of the elements and consequently decreasing the overall dead load of the building. Moreover, the study aimed at improving some other characteristics like flexural strength, crack pattern, first crack load, crack width, and deflection.

AAC-concrete light weight precast composite floor slab

In this study, the use of Autoclaved Aerated Concrete (AAC) as an in fill material for semi precast panel is investigated experimentally. The effectiveness of proposed light weight slab is reached by comparing the behavior of specimens with that of conventional solid precast slab. The comparisons were based on structural performance and total weight reduction. The composite AAC slabs section chosen are one way slabs with a size of 1m×3m×0.130m (Width×Length×Depth). The specimens vary in the AAC blocks layouts and total weight reduction ratio. The test results showed that the AAC composite precast panel provides reasonable weight reduction without sacrificing the structural capacity.

Three-dimensional broadband and high-directivity lens antenna made of metamaterials

We present the theoretical modeling and prototype demonstration of a three-dimensional broadband, low-loss, dual-polarization, and high-directivity lens antenna using gradient index (GRIN) metamaterials, which is composed of multi-layer microstrip square-ring arrays. The elements of metamaterials, closed square-ring units of variable sizes, are distributed on the planar substrate to satisfy the radial gradient index function and the axial impedance matching layer configuration of the lens. The gradient-index metamaterials are designed to transform the spherical wave-front into the planar wave-front and to minimize the reflection loss. A prototype lens antenna, which consists of a metal conical horn and the gradient-index lens, are simulated, constructed, and measured. The resemblance of simulation and measurement results shows that the prototype lens antenna maintains low return loss and high directivity on the whole X-band (from 8 GHz to 12 GHz). Compared to the traditional horn antenna, the metamaterial GRIN lens antenna has much superior performance—for instance, the gain increases by 6 dBi at 12 GHz. These results demonstrate the feasibility of such a light weight slab metamaterial lens for broadband and high-directivity antenna applications, such as in radar and communication systems. We have used the lens antennas in the measurements of a three-dimensional invisibility cloak due to the high directivity.

Limit states of cracking in beam-and-block floor systems using pretensioned ribs

Beam-and-block floor systems using pretensioned ribs enable very efficient industrialised production. By ensuring that the ribs are produced under a strict quality assurance programme and that they are safely transported, assembled and properly detailed, an equally monolithic structural performance is achieved. However, calculation methods to control cracking in these structural elements must ensure the durability according to the surrounding environment's severity and predefined exposure classes. The design of beam-and-block floor systems is particularly affected by serviceability limit states. This fact is closely linked to the verification conditions for crack control. Therefore, new design models have been developed to take into account the peculiarities and characteristics of these floor systems. The aim is to find practical and effective crack-control methods for composite beam-and-block floor systems with pretensioned ribs or beams. The verification of the limit state of crack widths has so far been disregarded in the design of this type of lightweight slab. In fact, the current procedure is simply to compare the tensile stress in the lower fibre of the beams with the characteristic strength of the rib's concrete. This paper presents a method to assess crack control. The procedure implies the quantification of a limit bending moment depending on the physical and geometric characteristics of the sections. Simplified calculation methods and verification rules are presented, which allow the establishment of tables and design charts for the indirect verification of this limit state through bar size and spacing limits.

El «Edificio Central» en las Palmas de Gran Canaria – España

A description is given of the program, characteristics, and building solutions for this unique building, situated in downtown Las Palmas. The building complex is composed of two underground levels for parking, a ground-floor and mezzanine for commercial purposes, and open plaza with swimming pool, dressing rooms, cafeteria, restaurant, dance spot, playground, and a block of 15 floors containing 137 apartments of varying size arranged so as to minimize sun overexposure and maximize privacy. The structure is of reinforced concrete and lightweight slabs, and enjoys quality fixtures which assure excellent functioning.