Precast Slabs Research Articles

An Investigation of the Effects of Drill Operator Posture on Vibration Exposure and Temporary Threshold Shift of Vibrotactile Perception Threshold

The present study involved performing an experiment to clarify whether vibration measurement values on the tool handle, in accordance with ISO 5349-1, can assess risk from workplace environments. The study investigated the relationship between the vibration magnitude of a hand-held electric drill with different operating postures. The experiment included the determination of the participant’s temporary threshold shift (TTS) of vibrotactile perception threshold (VPT) at the tip of the index finger. The experimental hypothesis was that the vibration measurement values on the tool handle, in accordance with the ISO 5349-1 standard, include the effect of posture on the vibration measurements obtained despite the variation in posture and test participants. The hand-transmitted vibration (HTV) was applied using a hand-held electric drill applied to a pre-cast concrete paving slab substrate (600 × 600 × 50 mm, 55 MPa) using a 10 mm diameter masonry drill bit (without hammer action). The tool was operated using the right hand on twelve male subjects with three working postures (n = 36). Vibration was measured in three orthogonal directions according to the international standard ISO 5349-1 procedure. Vibration magnitudes were expressed as root-mean-square (r.m.s.) acceleration, frequency-weighted using the Wh frequency weighting. Clause 4.3 states that the characterisation of the vibration exposure is assessed from the acceleration of the surface in contact with the hand as the primary quantity. The experimental results indicate that the TTS following vibration exposure is not related to the measured vibration magnitude on the tool handle. Therefore, the automatic inclusion of posture and test participant variation is not proven. The results suggest that the vibration measurement values on the tool handle do not predict the TTS after hand-transmitted vibration in varying posture across the test participants. The research concludes that tool handle vibration measurement, in accordance with ISO 5349-1, does not properly assess the potential hazard from authentic workplace tool usage conditions of varying postures.

Developing a Sustainable Concrete using Waste Glass and Rubber for Application in Precast Pedestrian Slabs

In this piece of research, n attempt was made to produce a sustainable concrete with the partial replacement of both fine and coarse natural aggregates with two different non-biodegradable wastes. The selected wastes were fine glass and shredded rubber tires. Fine glass passing through 4.75 mm BS sieve was utilised for the partial replacement of fine natural aggregates. Coarse natural aggregates were partially replaced with shredded rubber passing through 20 mm sieve and retained on 6.30 mm sieve. Several mixes with varying % of fine glass but with a fixed 10 % of shredded rubber were tested. Optimum fine glass content was determined to be in the order of 20 %. The resulting concrete exhibited lower plastic and hardened densities (2040 and 2117 kg/m3 respectively) in comparison to normal plain concrete. The static modulus of elasticity was found to be 18.3 GPa (mean value), while the splitting tensile strength was 2.37 MPa. The flexural strength showed a significant increase of 20.3% compared to the control mix. The results concluded that the concrete thus produced is a viable means of disposing of such non-biodegradable wastes (rubber and glass), thus reducing the loads at landfills. This new genre of concrete was produced at a lower cost than normal concrete because of the very low pre-treatment costs of the recycled wastes used. Furthermore, the properties tend to indicate that the concrete could be applied where lower strength and high durability properties are warranted. Hence precast slabs were made from the new design concrete and were tested along a stretch of a highly trafficable pedestrian walkway on the University campus. The slabs were continuously monitored for defects such as cracks, broken corners and slabs for a period of 24 consecutive weeks. After the test period it was observed that only 4 out of the 80 precast slabs had hairline cracks. Hence concluding the enhanced durability properties of the new design concrete. Doi: 10.28991/cej-2021-03091690 Full Text: PDF

Practical application of a novel prefabricated curling ice rink supported by steel–concrete composite floors: In situ measurements of static and dynamic response

On the basis of not destroying the original function, the non-curling field is transformed into a new curling ice rink that meets certain professional requirements through the detachable and prefabricated structure. This curling ice rink is an innovative type of prefabricated curling rink compared with the traditional rink, which has excellent advantages in terms of functional transformation and refrigerating efficiency. However, due to the vibration of the supporting structure and the deformation of the insulation foam under the ice layer, the annoying vibration and ice surface cracking are easy to occur. The static and dynamic performance of the new type of prefabricated curling ice rink located in Beijing, China, in the National Aquatics Center (Water Cube) was analyzed by a series of in situ tests. The field test consisted of two phases: the steel-framed concrete slab prefabricated structure test before ice making and the curling ice rink test after ice making. Phase 1 consisted of graded static load test and dynamic characteristic test as well as analytical frequency predictions. Phase 2 included static load test and dynamic test, long-term vertical deformation at the center point of column grid region on the precast concrete slabs for 19 days, and horizontal deformation at key points of the curling rink during 2019 China Junior Curling Open. A 3D finite element model was established using ABAQUS software, and the natural frequency and key deformation values obtained by modeling were compared with the corresponding ones from experiments. According to the proposed evaluation criteria, the results show that the mechanical properties and deformation ability of this new type of functional transformation curling rink are suitable for application in large international competitions.

Assessment of Structural Dynamic Response and Vehicle-Track Interaction of Precast Slab Track Systems

Recently, precast slab tracks have been used widely in railway applications, especially in conventional urban railway lines. These types of tracks are rapidly constructed and limit interruptions to train operation. However, the problems of dynamic stability when the trains run on the discontinuous type of tracks must be seriously considered. This paper focuses on analyzing the train-track interaction in two types of tracks under the dynamic load by using the numerical analysis program (APATSI) to evaluate the structural response as well as the running safety to precisely understand the load transfer efficiency of precast slab track systems.

Steel-Concrete Composite Beams with Precast Hollow-Core Slabs: A Sustainable Solution

Industrialization of construction makes building operation more environmental friendly and sustainable. This change is necessary as it is an industry that demands large consumption of water and energy, as well as being responsible for the disposal of a high volume of waste. However, the transformation of the construction sector is a big challenge worldwide. It is also well known that the largest proportion of the material used in multistory buildings, and thus its carbon impact, is attributed to their slabs being the main contributor of weight. Steel-Concrete composite beams with precast hollow-core slabs (PCHCSs) were developed due to their technical and economic benefits, owing to their high strength and concrete self-weight reduction, making this system economical and with lower environmental footprint, thus reducing carbon emissions. Significant research has been carried out on deep hollow-core slabs due to the need to overcome larger spans that resist high loads. The publication SCI P401, in accordance with Eurocode 4, is however limited to hollow-core slabs with depths from 150 to 250 mm, with or without a concrete topping. This paper aims to investigate hollow-core slabs with a concrete topping to understand their effect on the flexural behavior of Steel-Concrete composite beams, considering the hollow-core-slab depth is greater than the SCI P401 recommendation. Consequently, 150 mm and 265 mm hollow-core units with a concrete topping were considered to assess the increase of the hollow core unit depth. A comprehensive computational parametric study was conducted by varying the in situ infill concrete strength, the transverse reinforcement rate, the shear connector spacing, and the cross-section of steel. Both full and partial interaction models were examined, and in some cases similar resistances were obtained, meaning that the same strength can be obtained for a smaller number of shear studs, i.e., less energy consumption, thus a reduction in the embodied energy. The calculation procedure, according to Eurocode 4 was in favor of safety for the partial-interaction hypothesis.

Effect of bottom flange cleat on integrated precast slab and column panel using cold-formed steel

Effect of bottom flange cleat on integrated precast slab and column panel using cold-formed steel

Impacto da ausência de compatibilização de projetos na execução de uma obra residencial

Para execução de uma obra residencial é necessário primeiramente a etapa de desenvolvimento de projetos, projetando cada disciplina sequencialmente ou paralelamente. A interação de mais de um profissional na elaboração de um projeto é o caminho certo para uma boa elaboração, entretanto, a centralização de dados permite melhor gestão das informações mitigando problemas de incompatibilidade, que refletem na separação sequencial dos projetos, uma vez que compatibilização fornece uma visão holística do processo. O objetivo deste artigo é analisar erros de execução na construção de uma edificação habitacional em estruturas de concreto armado com lajes pré-moldadas de concreto e vedação em alvenaria, devido à incompatibilidade entre projetos. Para o desenvolvimento da pesquisa foi desenvolvido o acompanhamento das fases de construção por meio de visitas técnicas regulares e registro fotográfico. Sendo uma obra de pequeno porte, os projetos foram realizados de maneira independente e sem o estudo prévio das etapas da construção, o que favoreceu as inconformidades neste estudo de caso. Foram verificados erros de execução causados por incompatibilidade entre projetos arquitetônico, estrutural, elétrico e hidráulico que impactaram negativamente durante a execução do projeto. Desta maneira ressalta-se a importância da compatibilidade entre projetos independente do porte da obra.

Interface Mechanical Properties and Damage Behavior of CRTS II Slab Track considering Differential Subgrade Settlement

To analyze the effects of differential subgrade settlement on the interface mechanical properties and damage behavior of the China Railway Track System (CRTS) II slab track, a three-dimensional finite element (FE) model considering the uneven support of the subgrade was developed. A cohesive zone model was used to simulate the interface damage between the precast slab and the cement asphalt (CA) mortar layer. The effects of settlement amplitude, wavelength, and temperature gradient were analyzed. The results indicated that the interface stress is significantly affected by the settlement amplitude. There exists a particular settlement wavelength that results in the maximum interface stresses. Considerable attention should be paid to the effect of the temperature gradient load, which may cause interface damage in the differential settlement region.

Study on Bending Performance of Epoxy Adhesive Prefabricated UHPC-Steel Composite Bridge Deck

UHPC has high strength, high toughness, and excellent durability. For orthotropic steel bridge deck pavement, UHPC can significantly increase the bridge deck’s stiffness and then solve the problems of fatigue cracking and pavement damage of the bridge deck. However, if UHPC adopts cast-in-place construction, its self-shrinkage can easily cause shrinkage cracks, and it requires high maintenance conditions. Meanwhile, the traditional stud connection will bring a great deal of welding work and cause welding fatigue. In contrast, prefabricated UHPC pavement and orthotropic steel bridge deck can greatly reduce the amount of welding of studs on the bridge deck through epoxy bonding, thus speeding up the construction process and avoiding the risk of cracking caused by UHPC self-shrinkage. In order to consider the influence of the surface state of interface and ratio of shear span to depth on flexural behavior of epoxy adhesive prefabricated UHPC-steel composite bridge deck, positive bending moment loading test with different ratios of shear span to depth was carried out, and the failure mode, load-deflection curve, interface slip, and strain distribution of the specimens were obtained. Finally, based on the cohesive interface element, the prefabricated UHPC-steel epoxy bonding interface was successfully simulated. The test results show that each specimen’s loading stage can be divided into the elastic stage, crack initiation stage, interfacial crack propagation stage, interface failure stage, and yield stage. The specimen’s ultimate failure is that the interface failure is prior to the yield at the bottom of the steel plate. During the loading process, the bending performance shows that the ultimate load P B i and growth deflection Δ δ B i C i of CD-ERA-P-λ4.44 are higher than those of other specimens in terms of the load-deflection curve. The ultimate load of CD-ERA-P-λ3.33 is lower than that of CD-ERG-P-λ3.33, which decreases by 4.6%, but the increasing deflection increases by 75%. Simultaneously, the interface slip of the specimen is similar, which further shows that the specimen has the best bending performance when the surface of the steel plate is rough (R) and the surface of the prefabricated UHPC plate is grooved (A). No matter what kind of surface is used at the interface, the reduction of the ratio of shear span to depth will aggravate the ultimate failure of the interface and the cracking of the precast UHPC slab. Finally, the bending performance of epoxy adhesive prefabricated UHPC-steel composite bridge deck is successfully simulated based on the cohesive interface element, which is verified by the test results.

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.

Seismic behaviour of steel plate shear wall with non-welded oblique multi-ribs

This paper presents a comparative study on the seismic behaviour of steel plate shear wall (SPSW) stiffened by non-welded oblique multi-ribs and reinforced concrete. Two 1/3-scale one-bay, two-storey SPSWs specimens, namely oblique multi-ribbed buckling-restrained plate (OR-BRP) and concrete buckling-restrained plate (Con-BRP), were tested under cyclic loading. The failure mode, load-carrying capacity, energy dissipation, stiffness degradation, beam-column connections rotation of SPSW structures were examined and compared. Although the stiffeners in specimen OR-BRP are more than two-thirds lighter than those in specimen Con-BRP, the results indicate that specimens OR-BRP and Con-BRP exhibit similar hysteresis behaviour in terms of stiffness degradation, energy dissipation, and load-carrying capacity. The SPSW with oblique multi ribs exhibits smaller beam-column connection deformation than that with concrete slabs. Besides, both oblique multi ribs and precast concrete slabs have similar influence on the overall deformation of columns in the SPSWs. Therefore, it is beneficial to use oblique multi-rib stiffeners in SPSW as compared with traditional concrete slabs.

Application of Laminated Plate Construction Technology in Prefabricated Building Structure

With the development of China's construction field, prefabricated building structure has gradually become a very common building structure in the current construction engineering by virtue of its many advantages in the actual construction field. Combined with the engineering practice, this paper summarizes the hoisting technology of precast composite slab and precast staircase in prefabricated building structure. This paper focuses on the optimization design of laminated plate support under the conditions of wood formwork and aluminum formwork system and the key and difficult points in the construction process, and puts forward a set of practical and feasible construction methods for prefabricated components. This paper focuses on the analysis of the design concept, materials, structural form, manufacturing technology, hoisting and installation, and construction technology of M-type light steel concrete composite slab. This paper discusses and summarizes the advantages and disadvantages of M-type light steel reinforced concrete composite slab at present, and analyzes its development and application prospects. At the same time, in order to determine the reasonable type of laminated plate, the material budget analysis of assembled laminated plates with different structural forms is carried out. The conclusions are as follows: PK prestressed concrete composite slab has great advantages in the whole material budget cost, which is suitable for all kinds of span buildings. One way steel truss slab and YH prestressed concrete composite slab are suitable for small span buildings.

Experimental and Numerical Study of Lattice Girder Composite Slabs with Monolithic Joint

This paper studies the behavior of lattice girder composite slabs with monolithic joint under bending. A full-scale experiment is performed to investigate the overall bending resistance, deflection and the final crack distribution of latticed girder composite slab under uniformly distributed load. A finite element model is given for the analysis of the latticed girder composite slabs. The effectiveness and correctness of the numerical simulations are verified against experimental results. The experimental and numerical studies conclude that the lattice girder composite slabs conform to the requirement of existing design codes. A parametric study is provided to investigate the effects of lattice girder with following conclusions: (a) the lattice girder significantly increases the stiffness of the slab when comparing with the precast slab without reinforcement crossing the interface; (b) the additional reinforcement near the joint slightly increases the stiffness and resistance, while it prevents damage near the joint.

Ultimate flexural strength analysis of composite slim floor beam

This paper presents a new type of composite slim floor beam, determined by combining the results of an experimental study and theoretical analysis of the ultimate flexural strength of slim floor beams. The shear connectors play a significant role in the mechanical properties of this type of composite slim floor beam, because the precast concrete slab is laid on the bottom flange of the steel section and because the upper portion of the steel beam is encased in the cast-in-place concrete slab. To investigate the ultimate flexural strength, three specimens, which included headed studs, transverse steel bar shear connectors and no shear connectors, were tested. Additionally, a detailed numerical analysis was performed to verify the experimental results, which indicated that a higher-strength steel beam and thicker concrete slab can effectively enhance the stiffness and flexural capacity of the composite slim floor beam. Based on plastic mechanics and limit analysis theory, a calculation method was derived to estimate the ultimate flexural strength of a composite slim floor beam, and a comparison between the calculation and experimental results shows that the theoretical results exhibit good agreement with the experimental results, and the proposed analysis method can be used in future studies to gain a better understanding of the ultimate flexural strength of composite slim floor beams.

Comparative response of rocking-wall systems with cast-in-place and precast floor systems in buildings

Two large-scale structural assemblages, which had equivalent PreWEC (Precast Wall with End Columns) rocking-wall systems but different surrounding structures, were tested under quasi-static cyclic loading to study the impact of wall-floor interaction on the performance of rocking-wall buildings. The first specimen (PFS1) included cast-in-place (CIP) edge columns and a CIP unbonded post-tensioned slab with rigid wall-floor connections, which maximized wall-floor interaction. The second specimen (PFS2) included precast edge columns and a precast slab with special vertical-isolation wall-floor connectors, which minimized wall-floor interaction. Test results showed that both structural assemblages demonstrated great seismic performance with limited damage and self-centering behavior. The strength of PFS1 was more than twice that of PFS2; PFS2 encountered less damage and had better self-centering performance than PFS1, but it possessed less energy-dissipation capacity. The difference in the performance of the two assemblages was mainly attributed to the different gravity load transfer paths and constraint effects of the surrounding structures. Contributions to the strength and the self-centering behavior of the two assemblages from different structural elements were quantified and compared.

Loading Capacity Calculation of Integrated Precast Slab and Column Panel Using Cold-formed Steel

In the current study, the precast panel using a cold-formed steel section integrated with a cold-formed steel section integrated with self-compacting concrete was connected to the precast column panel. A T-shaped plate was used as a joint connector. Point loading applied onto the free-side of the slab panel. The material used to form a composite slab panel was C12524-type of cold-formed steel section as the reinforcements and it was integrated with self-compacting concrete. The connection in this research was divided into two-part. It was the side part and the middle part. The quality of cold-formed steel was fy = 530 MPa and fu = 590 MPa, the quality of the T-shaped plate connector grade was S355. The bolt diameter was variated with 10 mm, 12 mm, 14 mm, and 16 mm. The bolt quality was grade 8.8 (fy = 800 MPa). The calculation was the moment joint capacity of the connection and the stiffness. The moment joint capacity was increased within the bolt diameter increased. The side part of the specimen had the highest stiffness value; the bolts that could be used were M10, M12, and M14. To use the M16 bolt, configure the bolt spacing to be compatible with the standard BS EN 1-8:2005 [1].

Hollow-core precast and two-way solid slabs: Cost estimation and time duration comparison

Time and cost are important factors affecting the successful completion of the construction building project. This study analyses and examines the cost and time comparison of precast and cast-in-situ slabs of a particular building. Taking into account that slab is one of the important structural members, this study will take the hollow core slab in particular which can define as precast prestressed concrete elements contain an empty void inside of it which mostly used for floor, roof slabs and wall panels. The results demonstrate that the precast slab construction time is extremely faster in comparison with the cast-in-situ slab as it took around 31 of working days and 43 days in total after considering the holidays while the precast slab took around 9 working days only and 13 days in total. The results also show that the cast-in-situ slab is inferior in both cost and time duration. As cast-in-situ cost is 3.76 times higher than the precast slab, and the time duration is 3.31 times longer.

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.

Flexural behaviors assessment of Hidden boundary Rib precast concrete Slab (HRS) with bi-tensional prestress: Experiments, analyses, and formulations

This study presents overviews of a first proposed Hidden boundary one-way Rib precast concrete Slab, so-called HRS. In order to investigate bending behaviors of the novel structural system, three specimens manufactured in factory are tested by corresponding static loading protocol experiments. Four-points bending tests in both cases of the presence and absence of topping concrete slabs are performed. Results of the experiment scrutinize how each structural component such as rebars, topping concretes, strand wires can affect the bending behavior of HRS. As regards the main originality of this paper, approximate equations showing flexural strengths for a partially prestressed concrete flagged section, like HRS, are proposed in accordance with several current global and local design standards such as ACI 318, EN: Eurocode 2, PCI, AASHTO 2002, KCI 2012 and CSA A.23. Moreover, this study provides another predicting approach using finite element analysis of MIDAS FEA for analytical performances of specimens. Through these experimental and analytical results, the general characteristic of HRS may be observed and studied for realization in the field of prestressed precast concrete industries for construction.

Repair of local damages to precast prestressed slab elements at a parking garage

The durability of precast structures often depends on quality of execution of the connections between the structural elements. Essential also is their design and proper exploitation. This paper focuses on the magnitude of damages as well as repair methods used for a precast slab, which consists of prestressed double T slab elements supported on prestressed inverted T girders. It was found that during execution, the girders were forced to fit dowel bars, which resulted in their initial deformation. Moreover, those connection zones were subjected to unpredicted loading coming from delivery trucks. It resulted in crushing of the elastomeric bearings, uncontrolled rotation of double T precast elements, and further deformation of dowel bars. Numerous cracks, splits, concrete spalling, surface rust stains, and efflorescence were observed. To prevent failure, a project for repair was developed. The slab was lifted with the use of a jacks to provide necessary space for work. Damaged dowel bars and elastomeric bearings were removed. The concrete surface of double T beams and the inverted T girder was cleaned, refilled, prepared, and strengthened with FRP wraps. Additionally, steel angles were used to protect the edges of the inverted T girder.