Hollow Core Slabs Research Articles

Analytical study on fire resistance performance of precast concrete hollow-core slabs for electric vehicle fire in parking structures

This study evaluated the effects of fires that occur in internal combustion engine vehicles (ICEVs) and battery electric vehicles (BEVs) on the structural safety of hollow-core slabs (HCS) installed in parking structures. A fire simulation of a prototype parking structure was performed using the time–heat release rate curves of ICEVs and BEVs derived from fire experiments, and fire behavior and temperature history were derived according to the fire curve. Additionally, nonlinear finite element analysis was conducted using a general-purpose finite element analysis program, and the fire resistance performance of HCS was evaluated according to the fire curve and slab load ratio. In the case of a fire in ICEVs, the performance criteria of ISO 834–1 were met even at a slab load ratio of 0.7. However, in the case of a fire in BEVs, the standard for insulation was not met as the temperature change of the upper surface of HCS exceeded 180 K, and the load-bearing capacity was also not satisfied as the limiting deflection reached a slab load ratio of 0.7.

Contribution to the design of prestressed hollow core purlins without transverse reinforcement

AbstractThe hollow core purlin is a structural element resulting from the sectioning of hollow core slabs into two ribs. This component can be classified as a prestressed hollow core beam without transverse reinforcement. Although this solution offers potential for increasing the productivity of precast concrete element factories, it currently lacks normative guidelines due to the high risk of shear failure. The aim of this study is to highlight an equation to underpin the design of hollow core purlins based on experimental verification. To achieve this objective, six samples of hollow core purlins were analyzed. Initially, the manufacturing characteristics and cross‐sectional geometry of each piece were observed to gather data on the production process. Subsequently, positive bending tests were conducted to characterize stiffness and determine the effective mean tensile strength. Later, shear strength tests were performed to identify the failure mechanisms of the elements. In parallel, the prestressing forces, stiffness, tensile strength, cracking moment, calculated shear strength using the flexural‐shear mechanism, and verification of shear strength due to diagonal tension were computed based on concrete compressive strength values and data provided by the manufacturer. Finally, the experimental values obtained were compared with the theoretical calculated values to establish a correlation that highlights the calculation procedure that best represents the behavior of the studied elements.

Effect of Cast-in-Place Concrete and Stirrups on Shear Capacity of Precast Composite Hollow-Core Slabs

Effect of Cast-in-Place Concrete and Stirrups on Shear Capacity of Precast Composite Hollow-Core Slabs

Experimental and Theoretical Studies on the Vibration Serviceability of Composite HCS Floors with RC Topping

Composite hollow–core slab floor with reinforced concrete topping (i.e. CHFT) is relatively new, which can be applied to various long-span structures. However, these systems are typically lightweight and exhibit low damping, posing potential serviceability concerns related to human vibrations. This paper presents a comprehensive vibration test on a 9[Formula: see text]m-long CHFT system. Natural frequencies, damping ratios, and mode shapes of the floor system were obtained through modal tests. The peak acceleration, root–mean–square acceleration, maximum transient vibration value, and perception factor of the floor under heel-drop excitation were obtained through the perceived vibration test and were checked against the available design codes and standards. Sensitivity studies using the finite element method were made to investigate the vibration performance of the CHFT system. Analytical formulas for the fundamental frequency and peak acceleration were derived, which are therefore suggested for practical use. Additionally, an approach for evaluating the vibration serviceability of CHFTs is described.

Negative bending behavior of prestressed hollow core slab with cast-in-place RC layer in the RC beam-slab joint area

To study the negative bending behavior of the prestressed hollow core slab (HCS) with cast-in-place (CIP) RC layer (HCSPR) in the beam-slab joint area, eight full-scale tests were conducted, covering the following parameters: support length (S), longitudinal reinforcement ratio (ρr), HCS height (h1), and CIP concrete layer height (h2). The mechanical properties of specimens were evaluated including load-deflection relationship, cracking behavior, and strain development. Two distinct failure modes of flexure and shear were observed. An extensive parametric study was also conducted to study the effects of h2, h1, prestressing degree, ρr, and span on negative bending performance. The results from the tests and parametric study indicate that h1, ρr, and h2 significantly affect the failure modes, bearing capacity, and ductility. To ensure robustness, S values no less than 30 mm are recommended for the connection between HCS and RC beam. Moreover, to avoid shear failure of HCS with CIP RC layer (HCSPR) in the joint area under negative moment, the shear span-to-depth ratio [L0/(h1 +h2)] should be restricted to be larger than 4. Lastly, both flexural and shear capacity formulas based on GB50010, EN1168, and ACI318 were compared. The calculated results were compared with the test and parametric analysis results. This research is of great significance for the application of simplified RC beam-HCS connection.

Understanding Impact Resistance of Hollow Core Slabs Using FRP Retrofitting. A Comparative Analysis of GFRP And CFRP

Abstract Sudden Impact of structural events poses a significant threat to life safety and structural stability. In other words, the local failure(s) of structures can lead to the collapse of other members and eventually a partial or total collapse. Impact load is one of the extreme loads that are not usually taken into design consideration because of its high cost to be prevented unless the usage of the building dictates this extra care. Hollow core slabs, while offering advantages in terms of weight and construction efficiency, are particularly vulnerable to localized damage in comparison with other slab systems to localized damage, which could lead to progressive collapse. This research investigates the effectiveness of Fiber Reinforced Polymer (FRP) retrofitting techniques in enhancing the impact of resistance of hollow core slabs, aiming to mitigate progressive collapse risks and improve structure resilience. In this paper, the significance of FRP retrofitting techniques and properties for different types have been discussed and compared, focusing on Glass Fiber-Reinforced Polymer (GFRP) and carbon Fiber-Reinforced Polymer (CFRP). By evaluating various case studies, experimental analyses, and numerical simulations, the effectiveness, durability, and performance of FRP retrofitting strategies are examined as well to show the most suitable material for resisting impact load. The findings of this study will provide valuable guidance for engineers and designers in selecting the most suitable FRP material for retrofitting hollow core slabs, enhancing structural integrity and safety against impact loading. Furthermore, this research identifies research gaps and potential areas for further investigation, contributing to the development of a more effective and resilient research orientation for enhanced structure systems.

Comparative life cycle assessment (LCA) of the composite prefabricated ultra-shallow slabs (PUSS) and hollow core slabs in the UK

Life cycle assessment studies of precast construction methods highlight their superiority over traditional cast-in-situ construction in reducing buildings’ environmental impacts. Among the extensively used precast structural elements, hollow core precast slabs have proven benefits with their practical implementation in flooring systems across various flooring spans and live loads. This paper presents a case study comparing the global warming potential and embodied energy impacts of a recently developed lightweight prefabricated composite flooring system (PUSS) with zinghollow core precast slabs in the UK. The analysis is based on 16 live load/flooring span scenarios, between 6 and 12m. The study examines the benefits and drawbacks of utilising different concrete types in PUSS flooring, namely normal weight concrete, lightweight aggregates concrete and geopolymer concrete. PUSS with GPC demonstrates potential savings of up to 50 % in GWP compared with hollow core slabs, while PUSS with LWC exhibits potential savings of up to 35 % in total EE compared with hollow core slabs.

Second life for pre-stressed concrete hollow core slabs – time to act

The construction sector contributes to approximately 50% of global carbon dioxide emissions and natural resource consumption, along with generating a significant amount of landfill waste. Thus, there is an urgent need to actively involve our professional community in fostering real environmental change. Embracing circularity in construction presents significant opportunities for decarbonization, particularly in the context of prestressed precast concrete structures. This paper explores the potential for reusing prestressed hollow core slabs already built-in, as well as the principles of designing for future dismantling and reassembly. A second life for hollow core slabs is possible, as has already been confirmed by practical realisations in the Netherlands, Sweden and Finland.

Post-Tensioned Hollow-Core Concrete Slabs with Unbonded Tendons for Truck Scale Platforms: Design Assumptions and Tests.

At Cracow University of Technology, attempts were made to develop national truck scale platforms with a capacity of 60 tons, made from prestressed concrete. For this work, we designed slabs partially prestressed with unbonded tendons featuring a cross-section of 1.00 × 0.28 m and a span of 5.94 m. To reduce the weight of the slabs, four channels made from commonly used ø110 × 2.2 mm PVC pipes were used. In this way, we created post-tensioned hollow-core slabs. Due to the unpredictable behavior of slabs operating in a cracked state under a repetitive load, two slabs were subjected to cyclic loads amounting to 1,000,000 cycles with different load values. This paper presents the basic design principles and design details of the slabs, as well as the methodology and results of the research conducted. Lastly, we provide appropriate conclusions directed at further optimizing the slabs.

A Vibration and Crack Assessment on Precast Pre-stressed Hollow-Core Floor

Hollow core concrete floors are usually used in high-rise buildings, shopping malls and parking garages due to their sustainability advantage in the construction industry. However, in certain conditions, hollow core concrete floors can be sensitive towards vibration due to long span. The floor vibration issue is crucial and must be managed properly during the building design phase, as addressing this issue becomes significantly more challenging after the structure has been constructed completely. Thus, this study aims to determine the vibration and crack behaviour of precast hollow core concrete floors. 3D finite element models of the floor were developed using SAP2000 software to obtain the vibration parameters of the hollow core concrete floor subjected to vehicle-induced vibration. The specifications of the floor materials are based on the hollow core concrete floor manufacturer, Eastern Pretech, and the acceleration time history from testing was applied to the analysis. Modal analysis and time history analysis were analysed to investigate the vibration behaviour of the hollow core concrete floor. Modal analysis revealed a fundamental frequency of 23.52 Hz for the floor with actual dimensions. The fundamental frequency of the floor was compared to the standard guideline for human vibration sensitivity, which is 10 Hz. Time history analysis was employed to assess floor deformation based on the vibration waves generated by vehicle movement on the floor.The crack assessment analysis on concrete topping of precast hollow core slab in the warehouse flooring system was carried out. The cracks that appeared on the concrete topping were investigated using vibration testing and finite element analysis. Acceleration data from the damaged area was captured and transformed into the frequency domain using ME’Scope to analyse the natural frequency behaviour. The preliminary finite element analysis was performed by SAP 2000 software. Normal attenuation was observed on the surface with a crack at 50 mm, as the pattern of the time series data at this location was similar to other sensor positions. Analysis of the frequency domain of the wave confirmed this observation, revealing a dominant frequency of 23.741 Hz and no abnormal event occurred during testingon the surface crack.

Data-driven shear strength predictions of prestressed concrete hollow-core slabs

Although providing sufficient shear strength is crucial in the design of hollow-core slabs (HCS) to prevent shear failure, conventional shear equations for HCS could not always represent the non-linear relationship between the shear strength and influencing parameters, especially for deep HCS. Back-propagation-neural-network- (BPNN)-based models could be a possible solution since they have been widely used in predicting structural behaviour of other concrete structures. However, the feasibility of such an application has not been examined previously. Therefore, a set of BPNN-based models with and without optimisation algorithms were proposed for predicting the shear strength of prestressed HCS. The proposed BPNN-based models were trained and verified against a database of 227 HCS tested in shear. Comparisons between BPNN-based and mechanics-based models were also performed. The corresponding performances of different models were evaluated by the mean Vut/Vpre, R2, RMSE, MAE and MAPE criteria. To the author's best knowledge, this is the first study to apply hybrid-BPNN-based models for shear strength prediction of HCS. The study found that all proposed BPNN models were effective in predicting the shear strength, while the ACO-BPNN model yielded the best predictions among all the BPNNs. It was also shown that the ACO-BPNN model provided better predictions than the ACI 318 code provisions with/without the size effect factor. Besides, the well-trained ACO-BPNN model could present the size effect of slab thickness on shear strength, which was not explicitly considered in ACI 318. In summary, the ACO-BPNN-based model could a rational tool for predicting shear strength for HCS.

Reducing the Cooling Energy Demand by Optimizing the Airflow Distribution in a Ventilated Roof: Numerical Study for an Existing Residential Building and Applicability Map

This work presents a study of a ventilated hollow core slab system (VHCS) that obviates the need to completely replace the slab of an existing residential building. It is assimilated to a heat exchanger to allow its effectiveness to be studied as a function of the area and airflow rate. The balance between the energy consumed by the fan and the heat evacuated by the system is also studied through the use of the thermo-hydraulic performance factor (THPF), for which a series of cases were simulated by CFD following a methodology in which a configuration is achieved by means of the sequential analysis of cases in which both the thermal effectiveness and the THPF are maximized. The configuration chosen in this study was found to benefit from high airflow rates since, although this implies an increase in fan energy consumption, the increase in heat removed is proportionally greater. It has also been found that the design of the airflow distribution through the slab is of high importance as it affects both the heat exchanged with the slab and the pressure losses. An applicability map has been developed as a function of the temperature of the space below and the air temperature at the inlet of the ventilated roof. The heat flux per unit area that the studied envelope is able to evacuate is about 20 W/m2 K.

Static and dynamic load test on concrete hollow-core slab bridge

In this paper, dynamic and static load test were carried out on a multi-span reinforced concrete simply supported hollow core slab bridge in Shenyang, Liaoning Province. Through the static load test, the quality and reliability of the project are evaluated, and the results show that under the action of 0.88 times of highway-classⅠload, the deflection and strain check coefficients of the control section of the tested condition are less than 1, which meets the specification requirements, and the measured relative residual deformation and relative residual strain are less than 20%, and the bridge structure is basically in the elastic working state. And combined with the finite element analysis model, the comparison between measured data and calculated data is carried out. Through the dynamic load test, the self-oscillation frequency and damping ratio of the superstructure were tested, and the results showed that the measured damping ratio was 0.690%, the first-order measured vibration pattern conformed to the variation rule of the vibration pattern of the simply supported girder bridge, and the measured self-oscillation frequency was 13.594 Hz, and the measured self-oscillation frequency (fundamental frequency) was greater than the calculated frequency, and the structural actual stiffness was greater than the theoretical stiffness, and the working condition was good. This study is of great significance for the assessment of bearing capacity and quality control of concrete hollow core slab bridge, and provides a useful reference for bridge design and operation.

Analytical Evaluation of Natural Frequencies in Hollow-Core Slabs: A Practical Methodology for Civil Engineering Applications

Analytical Evaluation of Natural Frequencies in Hollow-Core Slabs: A Practical Methodology for Civil Engineering Applications

Improving building energy efficiency through ventilated hollow core slab systems

The increasing desire for comfort and healthy indoor environment, as well as improvements in energy standards in recent years, have stressed the need to make an active use of the building mass to achieve the maximum energy saving This is why the application of ventilated hollow-core slab systems (VHCS) can be considered as one of the innovative approaches. These systems have precast concrete slabs with tubular voids directing ventilation air on its length. In the present study Solving this system numerically using the ANSYS fluent program to study the temperature distribution and air flow in the 3-D test model of the present study to determine the feasibility of applying this system in an arid climate especially in Iraq by checking the inlet velocity and temperature and to predict the impact of these operating parameters on human comfort and energy savings. The study aimed to provide a numerical analysis of a conditioned zone's temperature distribution using VHCS. The investigation was carried out on a scale model room of size (1 m × 1.2 m × 1 m) with a scale factor of ¼. Four distinct scenarios were examined: the first two cases occurred during a no-load time in the night when there were no internal or external loads and examined the effects of changes in inlet temperatures and air velocities. The remaining two scenarios were conducted during an occupied period with internal heat gain of 630 W/m2 and external heat gain of 800 W/m2 based on the SHGC for the summer season of Iraq. As previously demonstrated, setting the inlet velocity to 1 m/s resulted in an optimal temperature and velocity distribution in the main flow, irrespective of changes in the external and internal loads and temperatures of the supply core. The findings shown that input air velocity and temperature affect heat remove efficiency. In addition, numerical outcomes have also illustrated that the Thermal Active VHCS System, while used in combination with ventilation strategies, could indeed regulate the space conditions by cooling down the building's ceiling, thus eradicating stored heat. All investigations found VHCS systems suitable for air conditioning in dry and hot locations. The systems are known for their ease of use, simplicity, high performance, comfort, and energy savings. They can also reduce peak loads to boost structural energy efficiency.

Analysis of the Application of Hollow Core Slab to Cost and Time Efficiency in High Rise Building Construction Project

The floor slab is one of the factors that affect the cost and duration of construction projects because it has the largest volume of work among other jobs. The selection of the method of implementation of floor slab work also affects the efficiency of development. The use of precast slabs can be an alternative to conventional floor slabs because of their potential to increase cost efficiency, speed up implementation time, and increase structural durability. In this study, a comparative analysis of cost efficiency and scheduling time of precast hollow core slab (HCS) method as an alternative to conventional slabs was conducted, using primary data obtained from the project and in accordance with government regulations. Time analysis and scheduling were calculated with the help of Microsoft Project software and determination of plate work items. As for the cost analysis, it is calculated based on the literature and applicable regulations to get real results by field conditions. Based on the analysis, it is known that the implementation of the 4-storey building slab work with the alternative precast slab method takes 8 days and costs Rp. 1,691,887,497. While the conventional slab method takes 38 days with a total cost of Rp. 2,276,920,601.

Cyclic performance of precast hollow core slab to beam connections using innovative assembling technique

This study emphasizes the performance of novel assembling technique using anchored continuity bars as a connection detail between precast hollow core slab and beam, aiming to achieve faster assembly and increased efficiency. The study further conducts a detailed analysis of core rebar impact on the hollow core slab to beam connection, examining both the assembly technique and core rebar influence. Effectiveness assessment of newly introduced anchored continuity bars and core rebars utilized five full scale half span prototypes under reverse cyclic loading. Findings indicate that connections incorporating anchored continuity and core rebar exhibit high strength, less stiffness deterioration, high ductility, and substantial energy dissipation, thereby meeting seismic load requirements. All connections met ACI 374.1–05 criteria, demonstrating satisfactory performance in seismic tests concerning relative energy dissipation ratio and stiffness ratio criteria. Notably, the continuity bar anchored to beam reinforcement-core reinforcement anchored to beam with ties connection surpasses the continuity bar anchored to beam reinforcement connection, demonstrates a superior average peak load carrying capacity of 149.8 % and cumulative energy dissipation of 288.78 %. The study concluded that the innovative assembly using anchored continuity bar with the inclusion of core rebar in the voids contributes to the improvement of connection performance under positive drift moment capacity and partly enhances negative drift moment capacity, thereby enhancing the overall stability of floor units in the event of seat loss.

RESEARCH OF THE STRESS-STRAIN STATE OF PRECAST REINFORCED CONCRETE HOLLOW CORE SLABS UNDER THE ACTION OF A CONCENTRATED AND UNIFORMLY DISTRIBUTED LOAD

The scientific work is devoted to a comprehensive study of the stress-strain state of prefabricated hollow-core floor slabs, establishing the nature of deformation, as well as determining the characteristics of crack resistance, deformability and load-bearing capacity experimentally under short-term loads. The experimental data obtained were confirmed by theoretical calculations. The scientific novelty of the experiments carried out within the framework of the presented work lies in the improvement of the principles of direct design of floor slabs from commercially produced beam slabs, the possibility of determining the stress-strain behavior of a slab structure using the formed ends. The method of monitoring the stressed behavior of a slab structure was also further developed. For the first time, the results of full-scale experimental studies of the stress-strain behavior of a prefabricated slab, carried out using the hydraulic loading method, have been obtained, and the features of the deformation of a slab embedded in the wall of a multi-story building have been experimentally established. The article provides recommendations for the practical use of the research results obtained, and also develops technical specifications for the production of concrete slabs during design and construction. The developed proposals were used in the construction of residential buildings in Kharkiv. When using the recommended grade of concrete C25/30 (instead of the actual grade C20/25 tested), the rigidity of the slab increases and its deflections will be smaller. Based on the data obtained from the experimental testing of the slabs, a generally positive test result should be stated. During further serial production of slabs, periodic testing of batches of slabs should be carried out in accordance with DSTU B V.2.6-53:2008. In this case, the slabs are accepted according to the indicators of strength, rigidity, crack resistance, fire resistance limits, frost resistance limits, as well as water resistance of slabs intended for use in aggressive environments. Keywords: concentrated load, testing, concrete, calculation, deflection, transverse force.

Evaluation of Maximum Shear Strength of Prestressed Concrete (PSC) Hollow Core Slab (HCS)

In this study, four-point load tests were conducted to evaluate the shear performance of factory-produced precast prestressed concrete hollow core slabs (HCS) assembled on-site. The test specimens were fabricated using compression molding and comprised six samples, with variables being the presence or absence of topping concrete and the shear reinforcement. According to the experimental variables, experiments were conducted using simple support beams to evaluate the shear performance and ultimate strength of HCSs. The results showed that HCSs, regardless of whether they included topping concrete or not, exhibited average values of shear strength more than 10% higher than the factored shear strength specified by concrete structure standards, confirming that these materials satisfy existing design standards. According to current standards, the overall reinforcement length should be increased to meet the minimum shear rebar placement requirements. However, the nominal shear strength of PS concrete hollow slabs exceeded the hollow design, with the ratio of experimental results ranging from 1.26 to 1.87 on average, satisfying the required performance.

An experimental assessment on the seismic behaviour of precast hollowcore slab to beam connection with different connection details

An experimental assessment on the seismic behaviour of precast hollowcore slab to beam connection with different connection details