Concrete Floor Systems Research Articles

Modeling of in-plane floor flexibility in existing reinforced concrete buildings

The paper addresses the problem of determining the mechanical characteristics of an orthotropic slab that best represents the in-plane behavior of a complex reinforced concrete (RC) floor system. To represent the structural behavior of the real RC floor, a reference model composed of solid finite elements is developed. The mechanical parameters of the equivalent orthotropic slab are determined by different homogenization techniques. In particular, two numerical algorithms and an analytical procedure to derive the elastic parameters of the equivalent slab representing the in-plane behavior of a single floor cell are proposed. Then, to determine which homogenization technique best predicts the structural behavior, representative one-story and six-story structures are modeled using both the equivalent slabs obtained using the three proposed techniques and the reference floor model. A discussion of the suitability of modeling floor in-plane flexibility taking account of only the top RC slab, for the considered case studies, is also provided.

Conceptual design of a modular Expanded Polystyrene (EPS) formwork for sustainable prefabricated concrete slab

European policymakers emphasize the critical need for a substantial renovation of the current European building stock, stressing the imperative to sustainably integrate energy and structural design. Consistent with the European objectives, industrialized construction and precast/offsite methods offer potential advantages in terms of time, cost, and quality for building renovation; along with the possibility of utilizing secondary raw materials, they enhance the energy performance of building products and advocate for environmentally sustainable solutions. This study presents the initial stage in designing a prefabricated concrete floor system, thermally and structurally high-performing, to be integrated into new and existing buildings. Specifically, the study outlines the design development of a modular element made with expanded polystyrene (EPS) for the construction of insulated floor systems with EPS lost-formwork (ICF - Insulated Concrete Form). This element ensures high and continuous thermal insulation without contributing to the structural resistance of the finished floor system. The process of designing, optimizing, and testing various design iterations is described. Materials and finished product requirements were identified, and numerical analyses and experimental tests were conducted. The main step involved the formwork mould, focusing on the shaping of joints, and evaluating the performance from a mechanical and thermal perspective. Field tests were also conducted, first on virgin EPS formwork and subsequently on a formwork containing a percentage of recycled EPS.

Optimal Design of a Novel Large-Span Cable-Supported Steel–Concrete Composite Floor System

This paper optimizes the design of a novel large-span cable-supported steel–concrete composite floor system in a simply supported single-span, single-strut configuration, aiming for cost-effective solutions and minimal steel consumption. The optimization considers various cross-sectional dimensions, adhering to building standards and engineering practices, and is based on a non-linear programming (NLP) algorithm. Parameters of live loads ranging from 2 to 10 kN/m2 and spans from 20 to 100 m are considered. The optimization results show that cable-supported composite floors with a single strut exhibit robust economic feasibility for spans of less than 80 m and live loads under 8 kN/m2. Compared to conventional composite floors with welded I-beams, the cable-supported system offers more cost-effective cross-sections and reduces steel consumption. The savings in economically equivalent steel consumption range from 20% to 60%. Discussion on the area ratio of cables to steel beam in the optimal cross-section reveals that the secondary load-bearing system (i.e., bending of the main beam with an effective span length of L/2) may require more steel in cases of ultra-large spans. Therefore, the economical efficiency of cable-supported composite beams with multiple struts and smaller effective span lengths warrants further exploration in future studies.

Flexural behavior of modular steel channel–concrete composite floor systems with bolted connections

This paper presents an innovative modular steel channel–concrete composite floor system designed for rapid assembly. This system, compared to traditional steel–concrete composite floors, connects adjacent modules solely through the use of high-strength bolts. This design eliminates the need for on-site wet construction, thereby yielding superior economic benefits. To investigate the proposed system’s mechanical behavior, bending tests were conducted on four composite floors with various support conditions, the numbers of bolts, and the degrees of shear connection. The load–displacement responses, torsional behavior of the channel beams, interfacial slip, and strain development of the composite floor systems were analyzed. The test results show that the simply supported composite floor, without bolted connections, undergoes flexural failure. In contrast, the semi-continuous composite floors, with bolted connections, display punching shear-flexural failure. The pre-tension forces applied to the bolts can effectively mitigate the torsional deformation of the channels and module separation, ensuring that the system maintains excellent structural integrity, sufficient load-bearing capacity, and adequate ductility. The semi-continuous composite floors, when fitted with high-strength bolts, demonstrate an increase in ultimate load-bearing capacity by 13–15%. However, there is a corresponding decrease in ductility by 18–23% when compared to the simply supported composite floor without bolts. The use of perforated steel plates as shear connectors offers efficient shear resistance between the steel channels and concrete slabs, facilitating full composite action of the system throughout the loading process. The paper concludes with the development of a model that calculates the flexural strength and punching shear strength of the composite floors based on the yield-line theory.

ANALYSIS AND DESIGN OF BUILDING (B+G+10) WITH FLAT SLABS IN ZONE ‘II’ USING ETABS AND SAFE SOFTWARE

Structural Engineering is a Branch of civil engineering which deals in the determination of behaviour of structures in order to predict the responses of real structures like bridges, Buildings, etc. under the improvement of expected loading and external environment during the service life of the structure. Structural Engineers these days are up against the challenging task of striving for the most efficient and most economical design with accuracy in solution while guaranteeing the final design of a building is serviceable for its design lifetime. In reality it’s very difficult to predict with certainty how much damage a building will experience for a given level of ground motion, because there are number of factors that affect the behaviour of the structural systems. The objective is to emphasize on structural behaviour of a commercial building (basement + ground+10 stories) installed with flat slabs for Bangalore (Zone 2) pertaining to medium soil. The building model is designed and analysed using ETABS (Extended Three dimensional analysis of Building System) and SAFE. ETABS is the ultimate integrated software package for the structural analysis and design of buildings. SAFE is the ultimate tool for designing concrete floor and foundation systems. The lateral loads induced from wind and earthquakes in the design and analysis of building is considered. The dead loads are calculated as per IS 875(part 1)-1987, live load is taken as per IS 875(part 2)-1987, earthquake load has been taken as per IS 1893-2002(part 1) and wind load has been taken from IS 875 (part 3)1987. The manual calculations for the design of structural members were compared with the software results which were found to be satisfactory. All the design and detailing procedures for structural members were carried out as per the guidelines of Bureau of Indian Standard code books.

Assessment of the embodied carbon performance of post-tensioned voided concrete plates as a sustainable floor solution in multi-story buildings

With growing concerns for the building industry’s contribution to climate change, designers are considering the global warming potential and corresponding embodied carbon (EC) emissions of building structures. However, conventional reinforced concrete (RC) floors are one of the highest contributors to the EC in a multi-story building. A solution to reduce EC that combines proven construction technologies is post-tensioned (PT) voided plates, where void formers are placed in areas where less material is required, therefore increasing the effectiveness of the pre-stressing, and reducing substantial structural material. This paper assesses the EC of PT voided plates for three different tendon layouts and compares them to RC flat plates, RC voided plates, and PT flat plates. 3280 different design conditions are assessed to replicate the range of common applications of each concrete floor system. The minimum required material quantities were determined for each design condition, which were used to calculate and compare the corresponding EC. The EC results for the floor systems were also compared to other sustainable floor designs. This paper found that PT voided plates have an EC savings up to 51 % compared to conventional floors and are a sustainable floor system that can be built worldwide using current construction practices.

Selection of a Sustainable Structural Floor System for an Office Building Using the Analytic Hierarchy Process and the Multi-Attribute Utility Theory

The integration of green building technology is currently regarded as a critical step towards a sustainable future because it is a means of attaining sustainable development. It takes skill to combine a sustainable ecosystem with comfortable living areas to create eco-friendly building designs. The use of modern technologies can also enhance traditional methods for developing greener structures and thereby help maintain sustainable built environments. This research paper is intended to develop a selection framework to evaluate three different structural floor systems for a high-rise office building in Alhasa, the Kingdom of Saudi Arabia. The three structural floor systems are as follows: a two-way ribbed slab system, a post-tension slab system, and a hollow core slab system. The main selection criteria used for the investigation in this paper are as follows: initial cost, running costs (operating and maintenance costs), salvage value, self-structural weight, and the possibility of utilities passage. A questionnaire survey was designed to collect the opinions of experts (project managers) regarding the relative importance of the different selection criteria, and these were used to determine the most suitable structural system for the office building. The analytic hierarchy process (AHP) was the tool used to determine the weights of the different criteria, and it was applied in combination with an Eigenvector analysis. Another objective of the investigation was to determine the utility preference values of the selection criteria by employing the multi-attribute utility theory (MAUT) technique. The results showed that the most important criterion is utilities passage, which is followed by structural weight and then initial cost, salvage value, and running costs. From the results of this research, we conclude that the system with the highest total value is the post-tension slab system. The limitations of the study include the fact that it only investigated three concrete floor systems commonly used in office buildings in Saudi Arabia, and that it included only five selection criteria that were identified and evaluated by the experts.

Validated Finite Element Modeling of Lightweight Concrete Floors Stiffened and Strengthened with FRP

The main challenge in designing Light-Weight Concrete (LWC) is to adapt most of the design, production, and execution rules from normal-weight concrete. Carbon Fiber-Reinforced Polymer (CFRP) composites provide strength and stiffness to the composite system. This study investigated the stiffness of an LWC flat slab with CFRP when subjected to human-induced vibration. This was determined by finding the natural frequency of the slab and comparing it with the acceleration limit ratio (human perception of vibration) of 0.5% g. In most cases, vibration characteristics are examined using commercial software based on Finite Element Analysis (FEA) methods that are powerful tools, but the user needs to understand the underlying assumptions and methods implemented, especially for reinforced concrete floor systems where inherent attributes, such as cracking, play an important role in the determination of vibration characteristics. This study used Abaqus CAE. The main idea of this study was that such software cannot detect the behavior of cracks in structures over the years and the effect on frequencies, as stiffness depends on the modulus of elasticity and not on the moment of inertia. Therefore, the natural frequency equation has a component that constantly accounts for the level of cracking on concrete slabs. This component was theoretically determined with detailed calculations that are not provided in the Design Guide for Vibrations of Reinforced Concrete Floor Systems. Then, the constant that accounts for the level of cracking k1 was multiplied by the modulus of elasticity E and substituted in the latter's place in Abaqus to ensure the right behavior of the slab with and without CFRP. This study also investigated the properties of CFRP and how to represent it in the Abaqus. The numerical results showed good agreement with FEA and the acceptance criteria for walking excitations increased when using CFRP on a floor system.

Experimental Investigation on Strengthening of Geo-Polymer Concrete Slab with Bubble Technology

The bubble deck technology developed in Europe makes use of high-viscosity concave polyethene spheres to replace the ineffective concrete in the centre of the slab, therefore dwindling the dead weight and adding the effects of the bottom. This system is used in the concrete floor system. Concrete is good in contraction and hence is more useful in the contraction region than in the pressure region. The reduction in concrete can be done by replacing the pressure zone concrete. An experiment has been carried out to find out the effectiveness of plastic bubbles by replacing concrete in the pressure zone of Ordinary Portland Cement Concrete (OPCC) and Geo-Polymer Concrete (GPC) slab. Constituents named are cement, sand, and coarse aggregate for OPCC and for GPC cement is fully replaced with 70% fly ash, 15% GGBS and 15% glass powder. NaOH(12M) alkaline solution is added instead of water for GPC. In this design, M45 concrete blend is used to prepare both OPCC and GPC slabs. The trial blend is tested for compressive strength in 7 days and 28 days. A flexure test is done for 7 days and 28 days of curing of the beams. The procedure is repeated for beam samples with bubble mesh and bubble mesh along with shear underpinning. Relative analysis of the OPCC and GPC slabs is done to observe the chance reduction in tone-weight and cost-effectiveness. Analysis of the geste of the GPC beam in comparison with that of the OPCC beam is also carried out.

Economical Design Comparison of Large-Span Composite Floor Systems with I Beams and Corrugated Web Beams

A comparative study of composite floor systems with I-beams and corrugated web beams is performed based on non-linear programming (NLP) algorithm. The optimization is conducted to find the most economical design with minimum steel consumption considering variables associated with the cross-sectional dimensions and multiple constraints from standards, specifications and engineering practices. Various parameters of live loads ranging from 2 to 10 kN/m2 and spans ranging from 20 to 100 m are considered. The optimization results reveal that composite floors with corrugated web beams have reasonable and economical cross-sections with less steel consumption, owing to the high performance of the corrugated web in shear resistance and stability. Further comparative studies show that composite floors with corrugated web beams are economically competitive for spans larger than 30 m with a steel saving of 20–60%, and composite floors with welded I-beams can be applicable for spans less than 30 m considering the simpler configuration and construction. In addition, a spatially structured cable-supported steel–concrete composite floor system is proposed and recommended for super-large-span floor structures considering the cost-effectiveness of the analyzed floor systems reduces as the span further increases.

Structural behaviour of steel fibre-reinforced concrete floor system for modular construction

Steel fibre-reinforced concrete (SFRC) slabs are ideal for modular construction owing to the shorter span of slab in standardised modules. To investigate the structural behaviours of SFRC floor system designed for modular construction, nine full-scale slab specimens were tested both at ambient temperature and under fire conditions. The crack pattern, failure mode, concrete spalling phenomenon, deformation capacity, load-carrying capacity and fire resistance time of the SFRC slabs are reported and compared with those of conventional steel rebar-reinforced concrete slabs. The experimental results showed that SFRC slabs achieved sufficient load carrying-capacity and fire resistance time for the application in modular buildings. A fibre-element model is proposed for computing the temperature distribution and cross-sectional moment resistance of SFRC slabs under fire conditions. Based on the experimental findings, design recommendations are provided to determine the fire resistance of SFRC floor system in modular construction.

Effect of Deep Bedded Pack System in Manure Management for Reducing Heat Stress of Cattle in Bangladesh

Background: Heat stress has a considerable effect both on animal welfare and production. Animals in heat stressreduceproductivity and reproductive performances and in extreme cases, it causes death. Methods: The experiment was carried out in Satkhira, a South-Western part of Bangladesh from July 2019 to June 2020 for12 monthsperiod to investigate the year-round heat stress experienced by cattle raised in a Deep Bedded Pack System (DBP) compared to that raised on a concrete floor (CF) system in an open barn. A total of six dry cows (2.5 to 3 yearsold, Holstein-Friesian crossbred) were allotted into two groups with three replications. The deep bedded pack was prepared with rice husk. The heat stress was calculated by following an equation using temperature and humidity data. Result: Animals raised on a concrete floor were suffered moderate to severe heat stress for eight months in a year from March to October. Otherwise, animals on the DBP floor were suffered from moderate heat stress only for five months, from June to October in a year. No severe case was found on the DBP floor but severe heat stress was shown by animals on the concrete floor from July to September. Therefore, animals feel more comfortable in the DBP management system.

Computational design exploration of a segmented concrete shell building floor system

The construction industry is responsible for nearly half of the UK's carbon dioxide emissions and the use of an extremely large volume of concrete – the world's most widely used man-made material – accounts for more than 7% of global carbon dioxide emissions. The scale of this problem spawned research to explore the potential for structurally efficient non-prismatic geometries to reduce the amount of concrete used in building elements substantially, thus also reducing their embodied carbon dioxide footprint. In particular, the research focused on segmented thin concrete shells as floor slabs, leveraging computational design and digital fabrication methodologies to automate their production off site. An important part of this research was the development of a computational framework for the design of thin concrete shells in order to make such a construction methodology accessible to building designers in practice. The framework combines solutions for parametric modelling, finite-element analysis, isogeometric analysis, form-finding and optimisation, along with embedded fabrication constraints specific to the project's automated manufacturing system. The application of the developed computational framework in the design of a 4.5 m × 4.5 m prototype is documented in this paper, illustrating how automating concrete construction can transform the industry towards net-zero.

Engineering design of optimized reinforced concrete floor grillages

A new reinforced concrete beam grillage floor system is proposed as a lightweight alternative to traditional solid flat or waffle slabs used in construction. For the first time, beam grillage optimization has been paired with design code compliant floor plate design, for single and multi-bays of a building. The investigated floor slabs are novel, in that the depths of the grillage T-beams and their reinforcement are tailored for the local strength demands. This engineering efficiency gives rise to significant savings of approximately 40–50% in the quantities of concrete and steel needed compared to flat slabs. For the multi-bay studies, it was found that moving the location of the supporting columns could further decrease the volume of material required, by over 50% compared to a standard grid layout. Given the urgent need to reduce the volume of material consumed in construction projects, this appears to challenge traditional floorplate layouts. The research shows that digital optimization tools can be paired with standard design code rules to deliver significantly more sustainable building designs, though these benefits need to be balanced against the construction challenges associated with the more complex geometries that generally result.

A prototype low-carbon segmented concrete shell building floor system

Concrete shell structures offer a mechanically efficient solution as a building floor system to reduce the environmental impact of our buildings. Although the curved geometry of shells can be an obstacle to their fabrication and implementation, digital fabrication and affordable robotics provide a means for the automation of their construction in a sustainable manner at an industrial scale. The applicability of such structures is demonstrated in this paper with the realisation of a large-scale concrete shell floor system, completed by columns, tie rods, and a levelled floor. The shell was prefabricated off-site in segments that can be transported and assembled on-site, and which can be disassembled to enable a circular economy of construction. This paper presents the conceptual and structural design; the automation of fabrication, thanks to an actuated, reconfigurable, reusable mould and a robotic concrete spraying process; the strategy and sequence of assembly and disassembly on-site using standard scaffold elements; and the sustainability assessment using life-cycle analysis. This prototype offers a reduction of about 50% of cradle-to-gate embodied carbon benchmarked against regular flat slabs before further improvement and optimisation.

Digitally fabricated ribbed concrete floor slabs: a sustainable solution for construction

The concrete used in floor slabs accounts for large greenhouse gas emissions in building construction. Solid slabs, often used today, consume much more concrete than ribbed slabs built by pioneer structural engineers like Hennebique, Arcangeli and Nervi. The first part of this paper analyses the evolution of slab systems over the last century and their carbon footprint, highlighting that ribbed slabs have been abandoned mainly for the sake of construction time and cost efficiency. However, highly material-efficient two-way ribbed slabs are essential to reduce the environmental impact of construction. Hence, the second part of this paper discusses how digital fabrication can help to tackle this challenge and presents four concrete floor systems built with digitally fabricated formwork. The digital fabrication technologies employed to produce these slab systems are digital cutting, binder-jetting, polymer extrusion and 3D concrete printing. The presented applications showcase a reduction in concrete use of approximately 50% compared to solid slabs. However, the digitally fabricated complex formworks produced were wasteful and/or labour-intensive. Further developments are required to make the digital processes sustainable and competitive by streamlining the production, using low carbon concrete mixes as well as reusing and recycling the formwork or structurally activating stay-in-place formwork.

Strength of RC Beam Using Geo Polymer Concrete and Adoption Bubble Technology

Abstract: Bubble Deck technology first time in European countries provide consumption of high-density polyethylene hollow spheres to replicate the unproductive material in the mid of the slab, consequently diminishing the deceased burden and escalating the competence of the flooring. This process be used in the concrete floor system. Concrete is superior in firmness and thus is further constructive in the compression section than in the tension section. The diminution in concrete can be done by replacing the tension region concrete. Keeping the equal design in intellect, an effort has been ended to discover out the efficiency of plastic bubbles by replacing concrete in the tension region of Ordinary Portland Cement Concrete (OPCC) and Geo polymer Concrete (GPC) beam. Geo polymer Concrete does not figure calcium- silicate-hydrates (CSHs) for matrix configuration and potency like OPCC however utilizes the poly condensation of silica with alumina precursors to achieve structural potency. In this job, M25 concrete mix is used to practice both OPCC and GPC beams. The trial mix is experienced for compressive potency. Flexure test is completed for 28 days of curing of the beams.

COMPARISON OF WIND INDUCED RESPONSE OF HIGH-RISE BUILDINGS WITH REINFORCED CONCRETE AND CROSS LAMINATED TIMBER

The main objective of this paper is to examine the wind-induced structural response of high–rise buildings constructed in the Kingdom of Saudi Arabia using reinforced concrete and lightweight cross-laminated timber (CLT) floor systems. Two major analyses were performed on two regular reinforced concrete (RC) buildings of 200 m height located in Dhahran and Jeddah. In the first instance, numerical simulations to obtain wind induced displacements and accelerations were conducted using computer software ETABS, SAP2000 and analytical model derived from building code. Then, another simulation of the building models was performed under similar wind conditions and same design criteria but by replacing the RC slabs of the buildings by cross laminated slabs. The wind data used for simulation was based on hourly wind data collection for the last 11 years (2009 – 2019). The results revealed higher story drift for both floor systems, whenever the wind speed is higher. The comparative analysis of the wind induced structural responses of traditional RC and CLT slabs showed greater accelerations at the top of the buildings with CLT floor system. However, the usage of CLT slab seems to be more feasible in the KSA considering adjusting designing lighter beam, column, and shear wall elements due to inherent CLT lightness.

LONG TERM PERFORMANCE OF REHABILITATED CONCRETE BEAMS STRENGTHENED FOR TORSION USING CFRP

The paper presents long term performance of reinforced concrete floor beams that were rehabilitated in 2007 for torsion using carbon fiber reinforced polymer (CFRP). The two rehabilitated beams were members of the concrete beam and slab floor system of a new parking garage near Boston in Massachusetts, USA. Without this rehabilitation, the new garage could not be accepted. The paper recapitulates the causes that led to the cracking and the rehabilitation of the beams for torsion, and the choice between strengthening by reinforced concrete jacket and by CFRP wrap. It was probably the first time and ahead of the Codes of Practice that CFRP was used to resist torsion in real as-built concrete structure and for total torsion. In previous practices, CFRP was ever used for flexure and shear strengthening in partial supplement to the original strength, not for total strength. The methodology for CFRP for torsion was given. Pictures depicting the rehabilitation in 2007 are illustrated. The recent pictures of the beams taken in December 2021 are given. The long term monitoring and observation, on the author’s own time and duty of care, for the past 14 years on this real structure confirms the reliability, durability and efficiency of CFRP wrap for torsion of concrete beams under sustained dynamic live loading and vibration from motor vehicles. The paper concludes with discussion of the advantages of CFRP wrap over the reinforced concrete jacket strengthening.

Shape optimization of chilled concrete ceilings – Reduced embodied carbon and enhanced operational performance

The design of lightweight, thermally activated concrete floor systems offers the opportunity to simultaneously tackle two of the most urgent challenges currently faced by the built environment: reducing the use of concrete, responsible for 5–8% of global carbon emissions, and implementing energy-efficient cooling strategies to mitigate the consequences of extreme heat events. This paper introduces a novel chilled concrete ceiling technology integrated into the structural floor slab. This system reduces embodied carbon and enhances operational performance through rigorous structural-thermal shape optimization. As a radiant ceiling with embedded water pipes, the system's cooling capacity improves due to the extended exposed surface provided by the shaping. Additionally, condensation risk decreases as thermal comfort is reached through warmer surface temperatures.Two cooling-dominated climates and five slab geometries are analyzed using a multi-objective optimization approach, achieving Pareto optimal designs that reduce their embodied carbon by up to 52.5% while achieving 12–14% operational savings relative to conventional prismatic floors. The latter can be reduced by as much as 22–32% at the expense of lowering the embodied savings to 30%. Further, this work introduces a novel method for simulating shaped thermally activated surfaces in Building Energy Modeling (BEM) platforms. An equivalent flat slab model is proposed to transfer the complex 3-D heat transfer processes captured by numerical Conjugate Heat Transfer (CHT) methods into annual, climate-specific simulations. This solution offers a flexible and modular framework that allows architects and engineers to replicate the structural-thermal analysis conducted in this work for other locations and geometries of interest.