Precast Concrete Panels Research Articles

Modular precast concrete facing for soil-nailed retaining walls: laboratory study and in situ validation

A new concept for constructing the facing of soil-nailed walls is proposed and validated through experimental and numerical approaches. This new process uses precast concrete panels. For each excavation step, the soil reinforcements are first connected to the panels. A slightly cemented 4–6-mm crushed stone is then injected, through the weep holes, between the panels and the excavation vertical cut, applying a confining pressure to the ground and providing continuous high-capacity drainage behind the facing. The structural design of the precast reinforced concrete panel, based on full-scale loading tests in the laboratory and nonlinear numerical simulations, is presented in detail. Crack initiation and failure modes are properly predicted by the model. A full-scale experimental soil-nailed wall 7.5 m high was also built to evaluate the environmental, economic and mechanical performances of the new construction technique compared to the conventional shotcrete technique. The new construction technique greatly improves worker’s safety, significantly reduces construction duration and cost and improves the mechanical behaviour of the soil-nailing technique and drainage of the facing. Compared to the conventional shotcrete technique, the new technique reduces concrete consumption by 64% and greenhouse gases emission by 56%.

Evaluation of high performance cementitious grouts for connecting precast concrete bridge deck panels

The use of full-depth precast concrete panels for rehabilitation of bridge decks allows fast installation and all-weather construction. Typically, precast panels are prefabricated in a well-controlled environment, resulting in strong and durable products. Undoubtedly, they will perform well under the traffic loading and weathering. However, the panel joints that are closed later with grout pour may degrade prematurely, leading to a less desirable composite action. Obviously, the lack of overall system performance causes concerns that limit the wider application of this innovative construction method. Conventionally, cementitious grouts, epoxy mortars or polymer concretes are used for the closure pour. In general, epoxy mortars or polymer concretes have extremely low permeability and dry shrinkage, as well as good adhesion with the substrate; but they are difficult to mix and clean, very sensitive to moisture variations, and incompatible with the substrate under thermal and mechanical loads. As a result, deficient bonding may occur, particularly when longitudinal post-tensioning is not provided, causing leaking and rusting. Oppositely, cementitious grouts are easier to mix and more compatible with the concrete substrate; however, they are more prone to shrinkage. More recently, advances in cementitious materials resulted in the development of Ultra-High Performance Concrete (UHPC). While this material has demonstrated exceptional performance when used for the closure pour; it requires special mixing to well disperse the particles and careful attention must be paid to the construction and curing practices to achieve enhanced mechanical and durability properties. As a result, testing of various types of grout materials is essential to establish the quality and serviceability of these materials. It is the intention of this paper to evaluate the performance of different cement-based grouting materials and to provide bridge engineers with useful database as to what materials are preferred for a specific project.

Lumped GFRP star connector system for partial composite action in insulated precast concrete sandwich panels

This paper introduces a novel composite shear connectors system used to transfer interface shear forces in a precast concrete sandwich panel. The shear connectors consist of non-proprietary non-composite commercial glass fiber reinforced polymer (GFRP) pin connectors that are laid out in a star pattern and clustered at the top and bottom of the panels. The testing program consisted of thirty-four push-off, twenty-three pullout, and eight full-scale flexural specimens was conducted to evaluate the structural performance of the new shear connectors. The effect of concrete wythe thickness, insulation wythe thickness, and concrete compressive strength was investigated throughout these tests. Additionally, the effect of bond between insulation and concrete wythes was investigated using push-off tests. The flexural test results were compared with predicted fully composite, non-composite, and partially composite values to evaluate the overall panel performance. The comparison showed satisfactory performance with a lower bound of 90% composite action for specimens with 100 mm thick insulation wythe and full composite action for most panels with 50 mm thick insulation. Idealized shear load-slip curves were also developed that account for various parameters to assist design engineers in designing insulated sandwich wall panels with the proposed shear connectors system.

Thermal investigation of thin precast concrete sandwich panels

Thin, lightweight alternatives to standard precast concrete sandwich panels have received much research and design focus in recent years. Some designs have been structurally tested and validated. Much less focus has, however, been given to their thermal performance. This study thermally investigates thin, lightweight precast concrete sandwich cladding panels that embed high performance insulation between two thin concrete wythes. A sample thin design is experimentally tested using a hot plate apparatus to evaluate its thermal performance. Finite element modelling is then used to further investigate the common features of thin panel designs and potential areas of heat loss. The analysed representative thin sample sandwich panel (150 mm thick) achieves an average U-value of 0.324 W m−2 K−1; this is 16% lower than that of a typical 315 mm thick sandwich panel with 100 mm of polystyrene foam insulation. Thermal bridging is identified as a major source of heat loss in the thin wall design, accounting for up to 71% of the total thermal transmittance of the tested thin sandwich panel. In standard walls this is usually less than 20%. Some of the features of the tested design can be improved to significantly reduce the effect of the thermal bridging and reduce the U-value by 59% to 0.13 W m−2 K−1 in an optimised panel design.

Cyclic behaviour of bolted shear connectors in steel-concrete composite beams

An experimental study of the cyclic behaviour of steel-concrete composite connections using mechanical shear connectors subjected to a low-cycle high-amplitude loading regime is presented in this study. The ductility, strength degradation and absorbed energy which characterise the performance of a mechanical shear connector under cyclic loading conditions in steel-concrete composite connections are assessed. Nine steel-concrete composite connection specimens were designed and tested in order to investigate the cyclic behaviour of the proposed composite connections, and to elucidate the structural behaviour of the demountable bolt shear connectors between the precast concrete panels and steel beams. In addition, three monotonic tests on steel-concrete composite connection were conducted to evaluate the yield slip, yield load, ultimate slip, and ultimate shear strength capacity. The size of the bolted shear connector and the strength of the bolted shear connectors are the main variables in this study. The preparation and construction of the specimens, the testing procedure, the test set-up, and the instrumentation used are described and the results of the monotonic and cyclic tests are reported in detail.

Composite behaviour of fibre-reinforced concrete sandwich panels with FRP shear connectors

The flexural behaviour of a precast concrete sandwich panel constructed of high performance fibre reinforced concrete wythes and foam insulation, connected together with carbon fibre reinforced polymer grid connectors, is investigated in this paper. This study tests and analyses the thin concrete cladding system which omits conventional steel reinforcement, the use of which requires concrete cover to the reinforcement layer that typically dictates the minimum thickness of the concrete wythes. A total of four full height panels are constructed in a precast concrete facility and are tested by way of three point bending. To complement the experimental study, finite element analysis is used to better understand the bending behaviour beyond what was discerned from the results obtained through experimentation. The experimental results showed that the thin concrete sandwich panel is a plausible solution for precast cladding systems with ultimate moment capacities in excess of those required to meet design wind loads. Ductile behaviour was observed in all of the four tested panels as a result of the high dosage of small 24 mm coated glass fibres used in the mix design for the concrete wythes. The experimental results showed no evidence of the FRP grid connector providing any significant degree of composite action. Finite element analysis suggests that this is due to, one or a combination of, the insulation′s stiffness being too low or because the tensile members in the grid connector being under an initial compressive strain and not fully engaged during initial loading.

Application of High-Resolution Terrestrial Laser Scanning to Monitor the Performance of Mechanically Stabilized Earth Walls with Precast Concrete Panels

AbstractMechanically stabilized earth (MSE) walls are extensively used in civil infrastructure projects, particularly in areas with tight right-of-way constraints. Traditional geotechnical design o...

Shear strength at the interface of precast bridge concrete decks and girders subjected to cyclic loading with varying speeds

Since its inception, the full-depth precast concrete deck panel system has attracted the attention of the bridge construction community. This alternative system constitutes a cost-effective solution that solves some of the issues associated with the traditional cast-in-place concrete decks. To ensure an adequate composite action, shear connectors are required at the interface deck-girders. Previous studies dealt mostly with the shear behavior of the interface between precast girders and cast-in place decks. Studies dealing with the alternative system are limited and were based on static push-off tests. In this paper, 12 cyclic loading tests were carried out to understand the cyclic behavior of the interface deck-girder of the alternative system and estimate its shear strength. Test variables included the number of shear connectors and speed of loading (i.e., loading rate). We observed that the common mode of failure of the interface is due to debonding of the deck from the girder. Test results showed that the shear strength increases with the number of shear connectors but decreases with the speed of loading. Moreover, the test results of specimens without shear connectors were used to estimate the cohesion factor at different loading speeds. Comparison between AASHTO LRFD code provisions and test results showed that the code provides an acceptable estimate of the shear strength provided that the cohesion factor is accurate.

Experimental Investigation of the Seismic Performance of a Novel Bolt-Assembled Precast Panel Building Structure

In this study, the authors investigated the behavior of the proposed bolt-assembled precast panel building (BPPB) system under the simulated seismic loading through a large experimental campaign. A pseudo-static test was carried out on a two-story half-scale building specimen constructed by many individual precast components which were properly joined together with bolted connections. The results show that the building specimen had the good seismic performance with high bearing capacity, comparable energy dissipation capacity and perfect structural integrity. The crack pattern and failure mode of the building specimen are different from those of traditional cast-in-situ concrete structures and equivalent cast-in-situ precast concrete structures. The final damage was concentrated in the bolted joint zones, a shear failure occurred in the edge of concrete panel near the bolt holes. It results in that the traditional design approaches of concrete shear wall cannot be applied to this new system. Therefore, the design philosophy and design formulas were proposed for the bolt-connected precast concrete panels to ensure the ductility of the panels and further improving the seismic performance of the BPPB system. The design theory of the bolt-connected precast concrete panels was validated by the successful prediction of the building specimen’s flexural capacity.

Comparative study of steel plate shear walls with different types of unbonded stiffeners

This paper presents a comparative study of the steel plate shear walls (SPSWs) with different types of unbonded stiffeners. Multiple ribs and precast concrete panels are installed for restraining the out-of-plane deformation of steel plates. The effect of spacing of unbonded ribs on the behaviour of SPSWs is first investigated through a finite element analysis. Subsequently, three 1/3-scale one-bay, two-storey SPSW specimens, namely unstiffened SPSW (US-SPSW), partially restrained SPSW (PR-SPSW) and completely restrained SPSW (CR-SPSW), are tested under cyclic loading. Test results indicate that specimens PR-SPSW and CR-SPSW exhibit similar load-carrying capacity, energy dissipation capacity, and stiffness degradation. Out-of-plane deformations of infilled steel plates, inward deformation of columns, and rotation of beam-column connections in both specimens PR-SPSW and CR-SPSW are effectively restrained, which alleviates the pinching phenomenon of hysteretic curves and stiffness degradation. As compared to the complete restraints for steel plates, partial restraints can increase the buckling area of the infilled steel plates and subsequently enhance the ductility of SPSW structure. They can also convert the deformation mode of infilled steel panels from the high-wave-low order to the low-wave-high order. In general, specimen PR-SPSW stiffened by unbonded multiple ribs with an appropriate spacing shows the excellent structural behaviour and constructability.

Effects of u-shaped subgrade concrete panel on subgrade deformation

California Bearing Ratio of subgrade lesser than 5% requires a treatment work either by stabilisation or strengthening method. In this study, the latter concept was chosen for the application of U-shaped Subgrade Concrete Panel as it is a method that has less disturbance to the native soil. As the name suggested, this U-shaped Subgrade Concrete Panel is a precast U-shaped concrete panel to be installed into the subgrade soil in an inverted direction. It is divided into two sections; the horizontal panel and vertical webs beneath the panel. Hence, the objective of this paper is to present the effect of applying the U-shaped Subgrade Concrete Panel into subgrade soil with a CBR value of less than 3%. There are 3 sizes of control panel used; square panel with dimension of 150 mm x 150 mm x 50 mm, 300 mm x 300 mm x 50 mm, and 600 mm x 600 mm x 70 mm, and 6 types of U-shaped Subgrade Concrete Panel; square area of 150 mm x 150 mm, 300 mm x 300 mm, and 600 mm x 600 mm. While the depth of the U-shaped Subgrade Concrete Panel varies from 100 mm, 125 mm, 150 mm, 200 mm, 270 mm, and 370 mm. The static load test was applied to centre, edge, and corner point of the panel, as to study the interlocking effect when it is subjected to a localised load. As the study was conducted in the laboratory, the condition of the subgrade soil fully controlled by monitoring the moisture content and the density of the soil in the test box. Settlement of the subgrade soil after compactions was observed and recorded as part of the initial conditions before the static load test was applied to the panel. After the compaction of the subgrade, it shows that a longer web section had caused lesser settlement compared to the control panel, indicating better resistance towards lateral movement under the U-shaped Subgrade Concrete Panel.

Comparative assessment of insulated concrete wall technologies and wood-frame walls in residential buildings: a multi-criteria analysis of hygrothermal performance, cost, and environmental footprints

ABSTRACT Utilizing appropriate materials and assemblies in building envelope components could lead to energy savings, increased durability, and sustainability gains. This study aims at providing an integrated assessment framework to compare three different types of exterior wall systems: wood frame, insulated concrete forms (ICFs), and pre-cast insulated concrete panel (PICP). The focus will be on building envelope performance, cost efficiency, and environmental impacts of these technologies. Such an assessment contributes to decisions on design characteristics of exterior walls as well as the selection of required materials. First, the exterior wall technologies will be compared in terms of hygrothermal performance according to ASHREA standards and other relevant literature. Then, a whole life cost analysis is conducted in order to establish the cost profile of each technology in buildings including capital costs as well as space heating costs over their service life. Finally, we will turn to assessing the environmental footprints of each technology and its components through life cycle assessment (LCA). The proposed framework incorporates multiple performance assessment criteria including well-being aspects, hygrothermal performance, life cycle assessment (LCA), and life-cycle cost (LCC). A multiple criteria decision-making framework is proposed to rank the alternative exterior wall technologies for a case study building.

Seismic Performance of Underwater Bridge Columns Strengthened with Prestressed-Concrete Panels and FRP Reinforcement

AbstractThis paper presents an experimental study on the seismic performance of underwater bridge columns retrofitted with the combination of prestressed precast concrete panels (PPCP) and embedded...

Visual damage at flexural response milestones for blast-resistant precast concrete panels with varying reinforcement

Current blast design practices correlate the flexural performance of reinforced concrete façade panels to empirically developed component response milestones. These milestones were correlated with observed progressions of visual damage from experimental tests. Selection of these performance metrics is based on the component classification and construction type but are not sensitive to variations in cross-section design parameters. This study examines the flexural performance of singly-reinforced solid precast concrete panels (i.e. single wythe, non-insulated) with varying reinforcement indices to evaluate the correlation of mechanical response with the progression of visual damage. Experimental tests are performed using a set of panels designed to similar flexural strengths and the results show that visually graded damage at each flexural milestone is not reliably consistent with visual damage guidelines from previously published design standards. Rather, the experimental results show that the progression of visual damage and component plasticity are dependent on net tensile strain and reinforcement index. The results of experimental testing are used as the basis for a parametric study which highlights the deviations in performance from current state of practice approaches when incorporating realistic material response of the panels.

Experimental studies on through-thickness shear behavior of EPS based precast concrete sandwich panels with truss shear connectors

Effective use of building materials for achieving sustainable construction is of prime importance today due to fast depletion of the natural resources by the construction industries for obtaining raw materials and aggregates. Precast insulated concrete sandwich panels (CSPs) consisting of two reinforced concrete wythes, an Expanded Poly-Styrene (EPS) core and truss-type shear connectors can be considered as an innovative construction material for acting as load bearing walls and floors in building systems. The two wythes are connected by the shear connectors through the EPS core for transferring shear forces (henceforth called as through-thickness shear) between the wythes and achieving composite action in the panels. In this paper, details of experimental studies conducted on small-scale precast CSP specimens under through-thickness shear loading are presented. The major parameters considered in the experimental program were the thickness of EPS core, gap between the wythes (in CSPs without EPS core), presence/absence of EPS core and number of shear connector lines. The effect of the major parameters on the failure mode, through-thickness shear strength, load vs relative displacement (between top and bottom wythes) behavior and load vs strain behavior of the CSPs are presented and discussed. The test results indicate that the through-thickness shear strength and behavior of the CSPs are significantly influenced by the parameters considered. Reduction in thickness of the EPS core and presence of the EPS core improved the through-thickness shear strength of the CSPs.

Static and dynamic analysis of two mechanically stabilized earth walls

The behavior of mechanically stabilized earth walls (MSEW), with vertical precast concrete facing panels and polymeric strips, was analyzed under harmonic loading to investigate dynamic wall performance. To this end, finite element method (FEM) analyses were carried out. The numerical model was based on a full-scale test of a 6 m-high wall built in Jundiai, Brazil. The wall was reinforced with polymeric strips made from high tenacity polyester and heavily-coated with low linear density polypropylene. The accuracy of the numerical model was verified first by comparing numerical and experimental results under static loading. The same 2D FEM model was then subjected to harmonic loading to analyze stress and deformation of the geostrips under dynamic loading conditions. In this case, it was found that the axial forces in the reinforcement strips deduced from the numerical analyses are less than those predicted using the American Association of State Highway and Transportation Officials (AASHTO) load and resistance factor design (LRFD) code under both static and harmonic loading. Under harmonic loading, and for the accelerations chosen in the simulations, the resulting active wedge was larger than for the static case.

In-plane cyclic testing of precast concrete wall panels with grouted metal duct base connections

In order to achieve satisfactory seismic performance the connections between precast concrete wall panels and other structural elements should be well-designed to avoid brittle connection failure during an earthquake. Following the 2010/2011 Canterbury (New Zealand) earthquakes it was observed that brittle failure had occurred in some grouted metal duct connections used for precast concrete wall panels, resulting in recommendations for more robust detailing of this connection type. A set of experimental tests was subsequently performed to investigate the in-plane seismic behaviour of both existing and newly recommended detailing for precast concrete wall panel connections, with this testing comprised of seven reversed cyclic in-plane tests of full-scale precast concrete wall panels having wall-to-foundation grouted metal duct connections. Walls with existing connection detailing were found to perform adequately when carrying low axial loads, but performance was found to be less satisfactory as the axial load and wall panel length increased. The use of transverse confinement reinforcement around the grouted metal ducts was observed to prevent brittle connection response and to improve the robustness of the reinforcement splice.

Optimum design for unbonded posttensioned precast split shear wall system using genetic algorithm

SummaryPrecast concrete structures are increasingly being adopted by building designers in regions of high seismicity. An unbonded posttensioned (PT) precast split shear wall system (UPPSSW) was proposed by the Precast Seismic Structural Systems (PRESSS). The UPPSSW system is composed of two or more single precast concrete wall panels that are connected together with energy‐dissipating shear connectors and anchored to the foundation with unbonded PT tendons located at the panel center. In this paper, an optimum design program has been developed for designing this system. The objective of the optimum process is to find the optimum combination between PT tendons and shear connectors while keeping the moment capacity of the wall equal to the applied design moment and achieving zero residual drift simultaneously. In addition, MATLAB was employed to explore an optimization program using genetic algorithm. Compared with the existing design methods for the system, the optimum design program proposed in this research is accurate, efficient, and direct. Moreover, it can yield the optimum design automatically and quickly. As a result, the existing lengthy and manual design process of trial and error for the system can be avoided.

Experimental investigation of buckling-restrained steel plate shear walls with inclined-slots

A buckling-restrained steel plate shear wall with inclined slots (simply referred as “slotted SPSW”) consisting of an inner steel plate sandwiched between two precast concrete panels, has been developed as an energy dissipation device of structures. The steel strips between inclined slots behave like a series of buckling-restrained braces to dissipate the energy through inelastic axial deformation when subjected to cyclic loading. This paper experimentally investigated the seismic behavior of slotted SPSWs. Three half-scale specimens were fabricated and tested under quasi-static cyclic loading. Details for proper fabrication of slotted SPSWs were firstly configured. The results illustrated that the slotted SPSW could sustain the target lateral drift ratio (2%) without a reduction of shear force and energy dissipation capacity. Moreover, the tested specimens exhibited stable fatigue hysteresis loops when the cyclic loadings were repeated 30 times at 1.5% peak lateral drift ratio. The maximum drift ratio of tested specimens reached 3.5%, and the cumulative plastic ductility factor was larger than 200. The experimental results indicate that the slotted SPSW is capable of providing high lateral force-resisting and energy dissipation, which can be widely used in engineering structures.

Nonlinear finite element analysis of composite precast concrete sandwich panels made with diagonal FRP bar connectors

Composite precast concrete sandwich panels made with diagonal FRP bar connectors have increasingly been used in the last few decades mainly due to their excellent thermal insulating properties. However, there is a lack of standards, design guidelines and reliable models that can be used for their analysis and design. In this paper, a finite element model is developed for investigating their structural behaviour, which aims to clarify their response and to provide a basis for establishing design guidelines. The model accounts for cracking and tension stiffening, material nonlinearity of concrete in compression, and geometric nonlinearity. The modelling challenges and assumptions are investigated, and the model is validated by comparing with other models and test results from the literature. The results explain the structural behaviour of these panels, which exhibit a partial composite action. The results also show that the failure mode of typical panels is ductile and dominated by yielding of the flexural steel reinforcement. A preliminarily investigation of the thermal effects shows that temperature gradients can lead to significant arching action in the panel and can affect its stability. The influence of the diameter and shape of the shear connectors and the stiffness of the insulation are investigated.