Precast Concrete Floor Research Articles

Deflection function of a novel bolt-connected precast concrete floor

Owing to the post-cast procedure and relatively complex joint configuration, composite precast floors limit the full display of advantages of precast concrete systems. The development of fully assembled precast floors is of necessity; therefore, a novel bolt-connected precast concrete floor was proposed in this study to meet the increasing demand for quick assembly, lightweight, and good insulation in flooring systems. The proposed floors consist of precast sandwich unit slabs that are fully assembled to an integral floor with dry-type bolted connectors. Field static loading tests were conducted on four full-scale precast concrete floors. The test results indicate that the floors exhibited a two-way flexural ability due to the involvement of the bolted connectors. The restraining mechanism at anchorage and load-transferring mechanism at joints were investigated through a theoretical analysis. Based on the theory of plates and shells, a simplified theoretical method of solving the deflection function of the floors was established and validated to provide a reference for designing such fully assembled floors. The comparison between the theoretical and experimental results indicates that the arrangement of joint connectors could affect the theoretical calculation accuracy due to its influence on the performed continuity simplification. The application scope of the proposed theoretical method was evaluated through a finite element analysis.

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.

A robustness-oriented procedure for the design of tying reinforcement in precast concrete hollow-core floors

Buildings may be subjected during their service life to extreme events which can trigger progressive collapse. On this front, the role played by tying reinforcement in structural members is crucial for an adequate load redistribution and the avoidance of disproportionate collapse. This work proposes a robustness-oriented procedure for the design of tying reinforcement placed in the hollow-core units and beams of precast concrete buildings, where limited studies are available in scientific literature. In particular, the aim is to provide a simple yet reliable approach for the design of concentrated and distributed ties in precast floors by adopting fundamental input parameters such as the system’s chord rotation capacity and dynamic amplification factor, which are not considered in current design codes. Firstly, a flow-chart of the design procedure is proposed and discussed. Secondly, the input parameters are calculated based on recent analytical approaches - proposed by some of the authors - to optimize the tying reinforcement design. Finally, the efficiency of the design procedure is demonstrated with an application example, and a novel detailing scheme is proposed which is aimed at a significant enhancement of structural robustness. Due to its simplicity, the proposed design procedure is contended to be applicable in robustness assessment and design of building structures with precast concrete hollow-core floors.

Vibration behavior of innovative discretely connected precast concrete sandwich floors

This paper investigates the vertical vibration behavior of an innovative discretely connected precast concrete sandwich floor (DCPCF) in orthogonal slab laying direction (OSLD). An experimental program included the full-scale tests of seven DCPCF specimens and two cast-in-situ floor (CISF) specimens was conducted. In order to evaluate the vertical vibration behavior of the DCPCF, the parameters considered the number of slabs, the number of connectors, the position of slab joints and loading condition were studied according to the vibration mode, fundamental frequency, damping ratio and acceleration response. The test results indicated that the first two vibration modes of DCPCF specimens and CISF specimens were basically the same. The fundamental frequency of the DCPCF was negatively correlated with the number of slab joints and overlying loads, and positively correlated with the number of connectors and the distance of slab joints to the mid-span. The damping ratio of the DCPCF decreased with the decrease of the number of slab joints, the increase of the number of connectors and the distance of slab joints to the mid-span. The vibration response of DCPCF specimens was slightly larger than those of CISF specimens under the same excitation. The peak acceleration increased with the increase of the loading frequency and the number of pedestrians. The closer the loading distribution was to the mid-span, the greater the peak acceleration would be. Based on the vertical vibration theory of elastic thin slab, the calculation methods for predicting the first mode natural frequency and peak acceleration of the DCPCF in OSLD were proposed. The calculated results obtained by the proposed formula showed good agreement with the experiment results.

Shaking table test and numerical simulation of a precast frame-shear wall structure with innovative untopped precast concrete floors

An innovative discretely connected precast concrete floor (DCPCF) was presented, in which the adjacent precast concrete hollow or sandwich flat slabs were connected by mechanical connectors embedded in the precast concrete slabs and beams. This paper summarized the seismic performance observed during the shaking table test of a precast frame-shear wall structure adopting DCPCF. A 1/4-scale model of a 4-storey 2-bay single-span frame-shear wall structure was designed and tested on the shaking table to evaluate the dynamic characteristics and seismic responses of building structures adopting DCPCF. In addition, a finite element model, including detailed modeling of beam-column joint and slab joint connections, was established using nonlinear dynamic modeling program. The predictions on the seismic performance using the finite element model agreed well with the test results for the designed frame-shear wall structure. The precast concrete frame-shear wall structure adopting DCPCF had satisfactory seismic performance during the test process. The in-plane deformation of DCPCF was observed under the horizontal earthquakes, and DCPCF could not satisfy the requirements of rigid diaphragm assumption in most cases under design basis seismic intensity. The seismic design method based on semi-rigid floor diaphragm had large error and safety risk in calculating the seismic shear force of building structure adopting DCPCF. Additionally, design suggestions for multi-storey and high-rise building structures using DCPCF were proposed based on the observed seismic responses.

An analytical framework for the evaluation of the progressive collapse resistance of precast concrete hollow-core floors

Buildings may be subjected to extreme events such as earthquakes, tsunamis, explosions, fires, or terroristic attacks during their service life. The current codes and guidelines provide three methods for the structural robustness assessment of buildings subjected to unidentified accidental actions: (i) the Tie Force, (ii) the Alternate Load Path and (iii) the Key Element methods. In particular, the Alternate Load Path is a direct method based on the evaluation of the ability of the structure and/or sub-assembly to effectively redistribute the applied loads and develop alternate load paths after the loss of a load-bearing element. In the literature, several studies aimed to investigate the progressive collapse performance of monolithic reinforced concrete structures, with almost no attention paid to precast concrete structures. In this work, in the context of the Alternate Load Path methods, an analytical framework is proposed and validated for the assessment of the progressive collapse resistance of precast concrete floors composed of hollow-core units and precast concrete beams, where the role played by tying reinforcement is analysed. Firstly, the study focuses on double-span hollow-core floor units by providing: (i) the static pushdown response, (ii) the dynamic capacity curve as well as the dynamic amplification factor and (iii) a practical robustness indicator, based on geometrical and mechanical features through the calculation of the chord rotation capacity, a fundamental parameter to be adopted for progressive collapse resistance. Finally, the method is extended to an entire hollow-core floor system, where both distributed ties in slab units and concentrated ties in beams are considered in the system resistance. Due to its simplicity, the analytical framework is considered useful for practical purposes, as reported with an example in the Appendix.

PELAKSANAAN PEKERJAAN PLAT LANTAI DENGAN BETON PRECAST PADA PROYEK PENATAAN GGM TAHAP 1

Abstract
 The building structure is one of the most important elements in a building construction. So the selection of the right implementation method is very important to be able to get the best and maximum results. Replacing conventional methods to become more modern is one of the efforts that can be done by managers. As in the implementation of the skywalk work, it also uses a more modern method, namely by applying a precast concrete system to the floor slab.
 The purpose of this study: (1) to know and understand how to carry out the work of preparing/installing precast concrete floor slabs. (2) knowing and understanding how to carry out precast concrete connection work. From this it will be known the method of implementation, the stages of implementation carried out, the specifications of the precast concrete used, as well as the types and specifications of the heavy equipment used.The results of this study are: the implementation stage starting from the mobilization of materials, preparation work, HCS work and the last stage is the connection stage. The precast used are: Width 1,200 mm, Length 3,720 mm, Weight 932.14 kg. The iron used in the connection is D10 in size.
 Keywords: Precast concrete, Implementation Method, floor slab

Analysis of The Most Affecting Factors in The Selection of Conventional and Precast Concrete Floor Slabs on Time Performance

One of the efforts to achieve the goals of construction project in terms of cost, quality and time is to replace conventional methods with more modern ones, namely by applying precast concrete. Precast concrete products, especially for buildings, are quite varied, one of them is Hollow Core Slab (HCS). Supported by previous research which explains that precast concrete floor slabs can save processing time compared to conventional floor slabs. Therefore, it is necessary to identify factors and variables that affecting the selection of conventional and precast
 floor plates on time performance and how the influence of the X variable (Factors) on the Y variable (Time performance).The results showed that the most affecting factors in the selection of conventional floor slabs on time performance were manpower factor with variable number of workers (41.3%), location factor with variable distance of batching plant to project site (19.8%), and also technical factors with shop drawing revision variable (by 41.8%). As for, the most affecting factors in the selection of precast concrete floor slabs on time performance include manpower factors with worker’s expertise variable (29.7%), and technical factors with shop drawing revision variable (by 38.4%).

Highlighting the need for multiple loading protocols in bi-directional testing

Major earthquakes, such as the Canterbury and Kaikoura events recorded in New Zealand in 2010-2011 and 2016 respectively, highlighted that floor systems can be heavily damaged. Quasi-static cyclic experimental tests of structural sub-assemblies can help to establish the seismic performance of structural systems. However, the experimental performance obtained with such tests is likely to be dependent on the loading protocol adopted. This paper provides an overview of the loading protocols which have been assumed in previous experimental activities, with emphasis on those adopted for testing floor systems. The paper also describes the procedure used to define the loading protocol applied in the testing of a large precast concrete floor diaphragm as part of the ReCast floor project jointly conducted by the University of Canterbury, the University of Auckland and BRANZ. Subsequently the limitations of current loading protocols for bi-directional testing are discussed. The relevance of local seismicity on bidirectional demand is demonstrated by examining a large dataset of records from the RESORCE database. It is concluded that bi-directional experimental testing be undertaken using at least two loading protocols that impose different ratios of demand in orthogonal directions.

Preliminary investigation on the bending capacity of a novel connection between the concrete slab and steel beam

Using precast concrete floors can greatly improve the construction efficiency of steel structures, and the development of the connection between precast slabs affects the application of precast concrete floors in steel structures. In this paper, a new connection between the precast concrete floor and steel beam is proposed. The bending capacity of the connection was investigated through experiments, and compared with that of the cast-in-place floor. The test results showed that the reliability of the new connection was excellent, and the bending capacity of the floor with this connection is basically the same as that of the cast-in-place floor. The finite element software ABAQUS was employed to simulate the bending behavior of the new connection floor and cast-in-place floor, and the feasibility of the model was verified by comparing it with the experimental results. The model was used to analyze the structural response of the two types of composite beams composed of new connections and precast floor, cast-in-place floor, and steel beam, respectively. The load-bearing capacity and failure modes of the two composite beams were compared. The results showed that the bearing capacity of the composite beam fabricated with the new connection can reach that of the cast-in-place floor composite beam. This is only a preliminary investigation about the new connection and there are some limitations as well.

Investigate the carbon footprints of three intermediate flooring systems: Cross-laminated timber, solid concrete, and hollow-core precast concrete

This paper evaluates and compares the embodied energy and embodied carbon using a Life Cycle Assessment (LCA) approach for three different intermediate floor structures, all of which use prefabricated materials-cross-laminated timber (CLT), precast hollow-core concrete, and solid concrete-to decide which floor construction materials have less environmental impact for use in the construction of a semi-detached house in the UK. The Inventory of Carbon & Energy (ICE) and the Carbon Calculator tool were used to calculate the carbon footprint from "cradle to grave" to determine whether the use of a CLT solution provides improved environmental performance over the traditional concrete solutions. The carbon footprint results indicate that the use of a hollow-core precast concrete floor system emits less carbon than the other two systems, although the concrete requires more fossil fuel input than the timber during the manufacturing process, so based on this, the footprint from cradle to gate for the timber was expected to be the less than that of the concrete. However, the results show the opposite; this is because of the differences in the material quantities needed in each system.

Energy and environmental impact of recycled end of life tires applied in building envelopes

This paper presents an initial investigation into the application of end of life vehicle tires as building envelope materials for a residential building design in Calgary, Canada. Two applications of tires are investigated: shredded tire chip insulation and structural whole tires filled with earth, in two envelope locations: walls and floors. Thermal properties such as thickness and conductivity, and the effective energy performance are analysed in EnergyPlus. OpenLCA is employed to assess the embodied energy benefits against conventional materials.Earth-filled whole tires constituting floor slabs are the most efficient application, performing equivalently to an energy efficient code case (0.03% decrease in annual energy use intensity (EUI)). Tire chip insulation performs more efficiently in floors than walls with EUI deviations of 28–67% in walls and 0–6% in floors. Whole earth-filled tires performed similarly to the structural concrete components in both walls and floors (3% and 0.6% EUI increase respectively). The most efficient application, whole tire floor slab, is shown to require 74% less embodied energy at 6.13MJ and 89% less global warming potential at 0.43kgCO2eq for one tire as compared to a precast concrete floor slab of the same area, with effects predominantly due to transportation and excavation of on-site earth.

Experimental and analytical investigation on the in-plane mechanical property of discretely connected precast RC floor diaphragm

Discretely connected precast reinforced concrete floor diaphragm (DCPCD) is a new-type untopped precast concrete floor system. Using slab joint connectors, instead of cast-in-situ concrete overlap layers on precast slab, to transmit slab joints inner forces caused by vertical and horizontal loads eliminates the need for wet works in construction site, thus leading to economical designs and high efficiency in installation. This paper presents the development and experimental evaluation of DCPCD subjected to in-plane low-cyclic reversed loading. Performance of the tested specimen was evaluated in terms of failure mode, in-plane deformation pattern, hysteretic curves, stiffness, ductility and energy dissipation capacity. The results show that DCPCD had high in-plane stiffness and good integrity, and the beam-to-slab connections and slab joints perform well during the test process. The ductility of the specimen is acceptable, while the energy dissipation is not that satisfactory, confirming that the elastic design method of precast RC diaphragms is rational. The shear and axial force distribution regularity of the tested specimen was analyzed, and the results indicate that internal force distribution is similar to that of the simply supported beam. The equivalent beam model theory was modified based on the measured tensile (compressive) stiffness of slab joint connectors and the actual load effect in the floor et al. It is demonstrated that the in-plane deformations determined by the modified calculation method agree well with the test results. Hence, the proposed in-plane stiffness analysis method is reliable and can be used for designing buildings adopting DCPCD.

Design Aids for Prestressed Concrete Double Tee Beam with Web Opening Associated With the Variation of Its Compressive Strength

Precast prestressed concrete double tee beams are one of the most popular precast concrete floor framing system, which it’s being from necessity to carry out many researche’s studies to predict a powerful tool to simulate its full behavior. Herein, an investigating studies have been carried out to check the validity of increasing span length by increasing concrete compressive strength with the existence of web opening. The main advantage of these openings is that mechanical equipment can pass through the webs of double tees instead of under them. This reduces the floor-to- floor height and the overall cost of the building. Another advantage is a slight reduction in double tee weight that would improve the demand on the supporting frame both under gravity loading and seismic excitation. All of that advantage will be more benefit with larger span length, that will be limited within the existence of web opening. A numerical model was prepared checked to simulate the nonlinear behavior of prestressed concrete beams under monotonically increasing load. Within such numerical model, tested programs were made to predict longer span in considerable concrete compressive strength, that chosen from practical available values can be achieved in the site. After all of that a design charts were prepared to be a guide tool to engineers when double tee beams with web opening required to cover more span length. Curves are classified and presented considering the most common typical sections of the double tee beams modified to show the flexibility could be obtained when changing concrete compressive strength.

Experimental study of hybrid precast concrete lattice girder floor at construction stage

As part of an on-going research project on the hybrid precast lattice girder floor system, a series of six specimens were physically tested in the laboratory to investigate the behaviour of the floor at construction stage. The purpose of the experimental tests was to improve the understanding of the floor system at construction stage and examine the key parameters which influence its behaviour at both serviceability and ultimate limit states. The results suggest that there is scope for further optimisation of the lattice girder floor system and that the current design methods may be overly conservative.The lack of comprehensive test data on this floor system limits the development of accurate models which can predict the behaviour of the floor during construction. In this paper, the developments of strain in the various components of the floor system (lattice girder, concrete plank and reinforcement) are measured for a range of lattice girder planks. The use of the transformed area method and Eurocode 3 to predict the behaviour of the plank are investigated in this paper. The analytical model developed is shown to be relatively accurate for predicting the initial stiffness and deflection of planks with tall girders but is not appropriate for planks with low height girders. Areas requiring further research are recommended in this paper to allow formulation of a generic model which would predict the behaviour of the floor system accurately at construction stage.

Investigation into Resilience of Precast Concrete Floors against Progressive Collapse

Investigation into Resilience of Precast Concrete Floors against Progressive Collapse

Can a precast pit latrine concrete floor withstand emptying operations? An investigation from Malawi.

For fecal sludge from households in low- and middle-income countries to be treated offsite it needs to be removed, which can be greatly affected by the pit latrine floor design. However, it is unclear whether precast pit latrine concrete floors (latrine slabs) can withstand emptiers and their equipment. To investigate this issue, 28 prefabricated latrine slabs were purchased in two cities of Malawi. They were first visually evaluated, and then their compression strength was tested. Additionally, each seller was asked a series of questions to better understand their business, training, and construction practices. Results showed that households should perform due diligence to ensure that they are purchasing a safe precast latrine slab. Commonly reported problems included nonstandard reinforcement material and spacing, in addition to slabs that were not thick enough or were not large enough in diameter. The results of this research illustrate the inherent complexity in ensuring high-quality decentralized sanitation solutionsand how one component, the user interface, if implemented poorly, can affect the rest of the value chain. The findings from this work can help inform training and initiatives that engage artisans and suppliers who play a role in the provision of onsite sanitation service delivery.

Design of precast concrete floors in steel-framed buildings. Part 3: Disproportionate collapse

Design of precast concrete floors in steel-framed buildings. Part 3: Disproportionate collapse

Design of precast concrete floors in steel-framed buildings. Part 2: Beam design

In the UK, steel-framed buildings with precast concrete floors are a common form of multistorey building. Such structures may be used for car parking, for commercial, retail or residential property developments, and for public buildings, such as schools and hospitals. This hybrid form of construction has many benefits, including the provision of an early, secure and broad platform from which subsequent site activities can be undertaken. This article is the second in a series of three addressing aspects of designing steel-framed buildings with precast concrete floors. The article describes aspects of the design of steel or composite beams which will support precast prestressed concrete planks.

Design of precast concrete floors in steel-framed buildings. Part 1: Slab design

In the UK, steel-framed buildings with precast concrete floors are a common form of multistorey building. Such structures may be used for car parking, for commercial, retail or residential property developments, and for public buildings, such as schools and hospitals. This hybrid form of construction has many benefits, including the provision of an early, secure and broad platform from which subsequent site activities can be undertaken. This article is the first in a series of three addressing aspects of designing steel-framed buildings with precast concrete floors. The first article describes aspects of the slab design of precast prestressed concrete planks which will be installed in a steel frame.