Precast Hollow Core Research Articles

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.

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.

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

Vertical load distribution in precast hollow core floors: State of the art and future perspectives

AbstractPrecast prestressed hollow core (HC) floors are widely used in various applications within the construction sector. Such floors are usually designed as single, simply supported elements, although it is known that individual elements forming the floor interact with each other. This article presents the state of the art regarding load redistribution in HC floors in the light of experimental data, current analytical models and code provisions. While this phenomenon is widely known and recognized, only sparse, and often poorly documented experimental data are available, which represent the basis for the assessment and calibration of analytical models. Moreover, even though the available models and code provisions share similar assumptions, their outcomes are in some cases conflicting. Having recognized the existing knowledge gap, the authors outline future perspectives for the development of consistent analytical and numerical approaches supplemented by new experimental data.

Comparative Life-Cycle Assessment of Steel and GFRP Rebars for Procurement Sustainability in the Construction Industry

This research examines the potential impact on the procurement sustainability of replacing steel rebars with Glass Fiber-Reinforced Polymer (GFRP) rebars in the construction industry, focusing on screed pre-cast hollow core topping in a project in the Kingdom of Saudi Arabia. A comparative life cycle assessment (LCA) is conducted using One Click LCA (Version 0.26.0) software for cradle-to-grave analysis. The assessment covers various stages, including raw material extraction, manufacturing, transportation, usage, and recycling. The comprehensive LCA highlights GFRP rebars as a more sustainable alternative to steel, emitting 17% less CO2 equivalent (2e) per kilogram throughout its life cycle. Additionally, GFRP requires substantially less mass compared to steel, resulting in a dramatic reduction in CO2e emissions ranging from 77.89% to 85.26% across different spacing configurations in real-world construction scenarios, as presented in this research case study. These findings suggest that GFRP rebars offer a promising solution for reducing the environmental impact of construction activities while potentially yielding significant cost savings over the project’s life cycle. Integrating environmental considerations into material selection processes can prioritize sustainability without compromising performance or safety, contributing to a more sustainable future for the construction industry globally.

In-plane seismic performance of precast concrete hollow-core slab panels for basement walls

In building structures, exterior basement walls should resist the soil pressure type earthquake load transmitted by the ground. Thus, the structural performance of the exterior basement walls is affected by in-plane seismic performance as well as out-of-plane load resistance. In the present study, for better constructability and cost-effectiveness of the exterior basement walls, conventional reinforced concrete walls were replaced with precast hollow core slab (HCS) panels. To investigate the in-plane earthquake load resistance of HCS for exterior basement walls, cyclic lateral loading test and numerical analysis were performed on four HCS panels with in-plane double curvature. The test and analysis results showed that the structural behavior of the HCS panels was significantly affected by the panel layout. In the test specimens using a single panel, flexural compression failure occurred at the bottom of the panel, and shear friction damage occurred at the upper and lower parts of the panel. In the test specimens using double panels, failure mode was governed by direct shear. The load-carrying capacity of the test specimens using double panels was greater than two times that of the test specimens using a single panel, because the load transfer changed from flexure into direct shear in the wall specimens using double panels. Further, to use HCS panels for exterior basement walls, a design method for prediction of in-plane seismic performance and yield displacement of HCS panels was proposed.

Application of Artificial Neural Networks to Numerical Homogenization of the Precast Hollow-Core Concrete Slabs

The main goal of this work is to combine the usage of the numerical homogenization technique for determining the effective properties of representative volume elements with artificial neural networks. The effective properties are defined according to the classical laminate theory. The purpose is to create and train a rapid surrogate model for the quick calculation of the mechanical properties of hollow concrete slabs. First, the homogenization algorithm was implemented, which determines membrane, bending and transverse shearing properties of a given parametrized hollow-core precast slab reinforced with steel bars. The algorithm uses the finite element mesh but does not require a formal solution of the finite element method problem. Second, the learning and training artificial intelligence framework was created and fed with a dataset obtained by optimal Latin hypercube sampling. In the study, a multilayer perceptron type of artificial neural network was used. This allows for obtaining rapid calculations of the effective properties of a particular hollow-core precast slab by using a surrogate model. In the paper, it has been proven that such a model, obtained via complex numerical calculations, gives a very accurate estimation of the properties and can be used in many practical tasks, such as optimization problems or computer-aided design decisions. Above all, the efficient setup of the artificial neural network has been sought and presented.

Self-Centering Precast Unit as Energy Dissipation Members in Precast Segmental Bridge Columns

This research aims to present a new generation of seismic-resisting systems designed for precast reinforced concrete (RC) bridge piers in modern sustainable cities to withstand moderate to high seismic activity. The proposed system consists of two self-centering (SC) systems operating in parallel to bring together all features of the required resiliency during a seismic action. The first/main system is a hollow core precast segmental bridge column, and the second is composed of an SC precast unit and energy dissipation (ED) steel reinforcements positioned in the main pier segment’s hollow core. To study the performance of the proposed system, a finite element model was first developed to capture the behavior of experimentally tested precast bridge columns. After validation, the created model was systematically studied to investigate the performance of the entire proposed system under cyclic loading. The effects of three parameters related to the ED system were investigated, including the reinforcement ratio, the unbonded length of ED bars, and the SC post-tensioned force ratio. Furthermore, the impact of FRP wrapping on the lower part of the core column of the ED system was also investigated. An analytical model predicting the characteristic points of the lateral response of the proposed system based on the superposition concept is also proposed. The FE results showed that the entire proposed system is a new design-based resilient system with the ability to dissipate energy without compromising the SC capacity of the main resisting system. Compared to the typical precast hollow core segmental column, a 6% reinforcement ratio of the ED unit can cause a 60% increase in lateral resistance and a 220% increase in the ED capacity. The analytical model can successfully be applied in the design of the proposed system to provide customized ED capabilities and controlled lateral resistance.

Seismic performance of confined prestressed hollow core wall panels part II: Numerical simulation and analysis

In Part I of this research, confined prestressed hollow core wall structures were proposed and experimental tests of 19 specimens were conducted to study its mechanical behaviors. In this part, a detailed finite element model was developed in ANSYS to provide a tool for further investigating the seismic behaviors of confined prestressed hollow core wall structures. Contact elements were applied to simulate the interaction between material interfaces. Techniques in ANSYS including coupling of degrees of freedom (CP) of overlapped nodes and deactivation of concrete elements (EKILL) were adopted, along with restart analysis (REST) to simulate nonlinear mechanical behaviors of the structural system. The developed modeling method was verified by the experimental test results and was shown to accurately predict the global and local behaviors such as failure modes and load bearing capacities of precast hollow core walls. Parametric analysis on shear span ratio, axial load ratio, rigidity of floor systems as well as strength of vertical wall-wall joints was conducted, and relevant design recommendations were provided for prestressed hollow core wall structures. Results show that for a ductile prestressed hollow core wall structure, the axial load ratio is recommended to be smaller than 0.06 and the story number less than 5. Influence of rigidity of floor systems requires further study with dynamic tests, but low-strength vertical wall-wall joint is highly recommended for this system. Two analytical mechanisms that are shear-flexural mechanism and truss mechanism were proposed for calculation of load bearing capacities. These two mechanisms provide good predictions for an upper bound and a lower bound for load bearing capacities of prestressed hollow core walls, respectively. From Part I and II of this research, the mechanical behaviors of prestressed hollow core wall structures are verified experimentally, numerically, and theoretically, and it is concluded that they can be used as a potential choice for low-rise buildings in rural areas.

Shear Behavior of Prestressed Hollow Core One-Way Slabs with Openings: Experimental, Numerical, and Standard Formulation Verification

The use of prestressed precast hollow core slabs has intensified as technological advances. However, the knowledge of the structural behavior when openings are inserted into this element is still limited, mainly due to the shear force. Therefore, the present study aims to analyze the structural behavior of the shear test of prestressed hollow core slabs with openings. In this paper, three types of hollow core slabs were tested: no openings, a central opening and side openings; using experimental and numerical methodology. The experimental test was carried out in the Federal University of São Carlos, and the numerical analysis used the software ABAQUS. All results were compared with three standard formulations (i.e., NBR, ACI and Eurocode), in order to verify its accuracy. In the end, the numerical results demonstrated that the developed model (CDP) presented results close to the experimental results. For the hollow core slab with a central opening, a rupture occurred in the web adjacent to the opening. On the other hand, for the hollow core slab with side openings, the rupture occurred at the edge of the web. Therefore, it was possible to conclude that the openings influence the main web tensions, being responsible for the diagonal model stress rupture. Finally, the Brazilian and Eurocode standard formulations proved to be good estimators of the resistant shear force.

Capacity and failure modes of restrained hollow core slabs taking into account compressive membrane action

AbstractThe formation of compressive membrane action in restrained precast concrete hollow core slabs is investigated, and how it affects the load bearing capacity and failure mode under excessive loading. To this end, attention is oriented to a recently completed experimental campaign specifically aimed at quantifying this phenomenon in real‐scale hollow core slabs. The outcomes of this experimental campaign are then analyzed using a validated finite element model, to further study the effects of compressive membrane action on the structural behavior of hollow core slabs. From the numerical evaluations, it can be concluded that the ultimate capacity and failure mode of restrained hollow core slabs strongly depend on the restraint conditions, as well as the span‐to‐depth ratio. The results also indicate that in some cases the failure is caused by crushing of concrete in the top flange, which is typically not observed in case of simply supported boundary conditions. Additionally, the influence of the inherent uncertainties associated with material properties and geometry on the ultimate capacity and failure mode of restrained hollow core slabs is investigated. Probabilistic model evaluations are performed for a wide range of boundary conditions. The results indicate a very high influence of the uncertainty on the concrete tensile strength on the membrane action in precast hollow core slabs.

NEW EUROCODE 4 DESIGN RULES FOR COMPOSITE BEAMS WITH PRECAST CONCRETE SLABS

AbstractAs members of Project Team SC4.T5, the authors of this paper present the main outcomes from the work that is intended for implementation within the second generation of Eurocode 4. General design and application rules for composite design of precast concrete elements will be presented, with a particular focus on: the effective width of flanges using precast concrete elements for shear lag; design resistance to longitudinal shear; and the design resistance of headed stud connectors in the presence of precast hollow core slabs.

Vibration Serviceability of Large-Span Steel–Concrete Composite Beam with Precast Hollow Core Slabs Under Walking Impact

A large-span steel–concrete composite beam with precast hollow core slabs (CBHCSs) is a relatively new floor structure that can be applied to various long-span structures. However, human-induced vibrations may present serviceability issues in such structures. To alleviate vibrations, both the walking forces excited by humans and the associated floor responses must be elucidated. In this study, 150 load–time histories of walking, excited by 25 test participants, are obtained using a force measuring plate. The dynamic loading factors and phase angles in the Fourier series functions for one-step walking are determined. Subsequently, walking tests are performed on seven CBHCS specimens to capture the essential dynamic properties of mode shapes, natural frequencies, damping ratios, and acceleration time histories. The CBHCS floor system generally exhibits a high frequency (> 10 Hz) and low damping (damping ratio < 2%). Sensitivity studies using the finite element method are conducted to investigate the vibration performance of the CBHCS floor system, where the floor thickness, steel beam type, contact time, and human weight are considered. Finally, analytical expressions derived for the fundamental frequency and peak acceleration agree well with the experimental results and are hence proposed for practical use.

Structural reliability of hollow core slabs considering compressive membrane action

Compressive membrane action can considerably improve the load bearing capacity of concrete slabs and beams in case of excessive loaded due to an accidental event. Currently, only limited research has been focusing on compressive membrane action in prestressed concrete elements, or on concrete elements with large cavities, such as precast concrete hollow core slabs. Therefore, a novel real-scale test setup has been developed in order to assess this effect in precast hollow core slabs, and how it can enhance the load-carrying capacity in accidental events. In parallel with these tests, a numerical finite element model has been developed in order to perform a more detailed structural analysis of this phenomenon, and to study the influence of various input parameters. The details of this test setup are briefly explained, and some relevant experimental test results are provided. Considering the experimental findings and validated numerical model, this contribution aims to quantify the influence of compressive membrane action on the structural reliability of precast concrete hollow core slabs. To this end, probabilistic models for the most important material and geometric variables are gathered, and the structural reliability is assessed using Latin Hypercube sampling. Overall, the results indicate that considering the formation of compressive membrane action strongly influences the variability of the ultimate load-carrying capacity of precast concrete hollow core slabs.

Shear forces transfer in steel-concrete slim floor with circular web opening and PCHCS

An experimental study was developed to investigate the mechanisms responsible for the transfer of shear forces at the steel-concrete interface in slim floor beams with circular web openings and precast hollow core slab (PCHCS). For this purpose, four specimens were made and subjected to push-out test. The presence of the steel bar through the opening, the concrete compressive strength and the diameter of the steel bar were studied. It was observed that the presence of the steel bar contributed significantly to both the resistance of the connection and for the reduction of the relative slip values of steel-concrete. While the specimen without steel bar presented a post-peak behavior with a drop of resistant capacity, in the specimens with steel bar the load-slip relationship was quite ductile. The variation in steel bar diameter and concrete strength influenced both load-slip relationship and resistant capacity. It was observed that regardless of the presence of steel bar, until the concrete dowel rupture, the load-slip behavior of the specimens with and without steel bar was almost identical. The experimental results were compared to analytical models proposed by other researchers. However, none of the analytical models found in the literature were able to satisfactorily represent the resistant capacity of the specimens with and without steel bar. A good estimate of the theoretical results was obtained using the friction-shear theory for concrete corbels.

Flexural behavior of assembled monolithic long-span composite beams with CIP reinforced concrete layer atop precast hollow core slabs

Steel-concrete composite beams (CB) with precast hollow-core slabs (HCSs) have been widely used in long-span structures for its high bending capacity, good ductility, lightweight, and fast construction. A novel assembled monolithic CB with a cast-in-place (CIP) reinforced concrete layer poured on the precast HCSs (CBCH) was proposed in this study. Eight full-scale flexural tests were conducted majoring in the parameters of span (L = 6.0 m and 8.4 m), degree of shear connection (λDS = 100%, 70%, and 30%), width of CBCH (B = 2100 mm and 1800 mm), and thickness of CIP concrete layer (hCIP = 60 mm and 20 mm). Three typical failure modes were observed: i.e. flexural failure, longitudinal shear failure in the shear span, and peeling failure occurring between the precast HCS and CIP concrete layer. The results indicate that the λDS and hCIP can significantly affect the failure modes, flexural capacity, and ductility; the B has a slight influence on the bending behavior of CBCH. In addition, an extensive parametric study was conducted according to the test results. To elevate the bending capacity of CBCH, relative formulas are proposed, and agree well with the results of test and parametric study. Based on the theoretical and FE analysis, the partial shear specimens with λDS ≥ 85% can achieve almost the same performances as the full shear specimens (λDS = 100%). However, a λDS = 100% and the minimum hCIP = 60 mm are recommended to ensure the integrity of the CBCH in engineering practice.

Composite action on web-post buckling shear resistance of composite cellular beams with PCHCS and PCHCSCT

This paper aims to study the composite action on web-post buckling (WPB) resistance of composite cellular beams with precast hollow core slab (PCHCS) units and with precast hollow core slab units with concrete topping (PCHCSCT). Geometrical and material non-linear analyses are performed. A parametric study is developed, varying the opening diameter, the web-post width and the shear stud spacing, with single and double row. It was found that the models with double row of shear studs showed global shear resistance greater than or equal to the models with only one row. For models with PCHCS, there was a reduction in global shear resistance in some analyses due to the absence of shear studs in the second opening, close to the support. For PCHCSCT models, there was an increase in the global shear resistance, in comparison with PCHCS models. However, in most of these models, shear stud rupture occurred. Finally, the WPB models were compared with a simplified equation that takes into account the global shear resistance due to buckling, composite action and Vierendeel bending. The average, standard deviation and variation value of the ratio between the analytical and numerical models were 0.833, 12.47% and 1.55%, respectively.

Prestressed hollow core slabs for topped slim floors – Theory and research of the shear capacity

This research paper discusses the influence of the flexibility of girders in Slim Floor structures on the reduced load capacity of prestressed HC slabs. The current state of knowledge in the field of the transverse behaviour of hollow core slabs is presented. Contradictory information provided in the literature as well as the computational comparative analysis of the existing theoretical models has demonstrated the need for better recognition of the issue of the effect of reinforced concrete topping layer on the load capacity of HC slabs. The paper includes the presentation of experimental tests, the purpose of which was to reproduce the actual work conditions of hollow core slabs depending on their location on the floor and the numerical analyses supplemented these studies. As a result of the conducted tests and analyses, it was found that the increased flexibility of the support beam resulted in an adverse change in the stress state of the hollow core slab, which may lead to the exceedance of the limit state of shear capacity, while laying an additional layer of structural topping on precast hollow core slabs significantly increased the shear capacity of the floor, and thus safety of the structure. The research also indicates that in all the tested topped elements full composite action up to the failure was shown.

Ultimate strength prediction of steel–concrete composite cellular beams with PCHCS

This paper aims to predict the ultimate behavior of steel–concrete composite cellular beams using precast hollow core slabs. A finite element model is developed by geometrical non-linear analysis. A parametric study is carried out, considering symmetric and asymmetric sections with precast hollow core slabs. The key parameters such as the web-post width and the opening diameter are varied, as well as the presence of the concrete topping. A total of 120 analyses were performed. The results are compared with typical composite slab models using cast in-situ concrete. For symmetrical sections, considering the hollow core slabs, although some observations occurred with the formation of the plastic mechanism, the predominant failure mode was the web-post buckling. For asymmetric sections, the predominant failure mode was the combination of the plastic mechanism with the web-post buckling accompanied by the shear connector rupture. In both cases, considering symmetrical and asymmetrical sections, excessive cracking was observed in the upper part of the hollow core slab. In cases where the end-post was greater than the web-post, there was damage at the upper region of the hollow core slab/concrete topping, close to the support. The numerical models of composite cellular beams with hollow core slabs, when compared with the models of composite cellular beams with composite slabs, showed greater efficiency in structural behavior. The results imply that the strength of the composite cellular beams was not limited only by the strength of the steel cellular beam, but also, of the slab, due to the resistance to shear stress.