Precast Concrete Members Research Articles

Development of Assembled Precast Pier with Crimped Construction by Prestressing─Unit-Type Construction with Factory-Produced Precast Concrete Members─

Development of Assembled Precast Pier with Crimped Construction by Prestressing─Unit-Type Construction with Factory-Produced Precast Concrete Members─

Analysis of CO2 Emission Reduction Effect of On-Site Production Precast Concrete Member according to Factory Production Environment

Precast concrete (PC) method of construction is preferred for excellence in the reduction of construction period, lightweight, and durability and for PC member to be mostly transported to a site after its production in the in-plant production because the in situ production of the PC member is negatively perceived because of the limitation of space or production process being complex and difficult. However, if the PC member is produced on site and installed, it is possible to reduce the carbon dioxide emissions that are generated during shipping and loading and unloading, which are indirectly required for in-plant production. Carbon dioxide emission reduction effect due to the difference between the in situ production and in-plant production process of the PC member was confirmed by the existing studies, but the study of the carbon dioxide reduction effect according to various production environments of the in-plant production has not been performed. Therefore, the purpose of this study is to analyze the CO2 emission reduction effect of the PC member produced in site according to the in-plant production environment. As a result, it was found that when PC members were produced on site, there was an effect of reducing CO2 emissions by an average of 25.64% compared to factory production. In future, the results of this study will be used as basic data for establishing a CO2 emission reduction plan at construction sites.

Integrated management model of production and yard stock for in-situ precast concrete production

ABSTRACT In-situ production of precast concrete (PC) members is affected by various factors, such as cost, time, quantity, lead-time, number of molds, production cycle, number of cranes, and yard stock area. Particularly, the yard stock area constitutes over 84% of the total required area, considerably larger than the production area. This is important because in-situ production is not applicable if the yard stock area is not satisfied. However, most existing studies related to in-situ production of PC members have focused on the production area, and no study has specifically focused on the yard stock area. Therefore, research on in-situ production, considering various influencing factors centering on the yard stock area, is required. This study developed a system dynamics-based integrated management model of production and yard stock for in-situ production. Cost reduction up to 739,000 USD was demonstrated possible in a case project, wherein the yard stock area was 5,941m2. The influencing factors of in-situ production can be numerically controlled in the proposed model. It is thus possible to perform an effective simulation study and obtain appropriate values of the yard stock area, which varies during the project, under various scenarios based on the real site situations.

Experimental investigation on seismic performance of two types of member-panel zone unified joints for precast concrete moment-resisting frame

Recently, precast concrete (PC) moment-resisting frame (MRF) is widely used for lateral load-resisting systems in buildings such as semiconductor factories requiring a short construction period and high quality of materials, but its application is limited to high-seismicity regions due to complex in-situ assembly between PC members and low seismic performance of joints. This paper presents the evaluation on cyclic behavior of two types of member-panel zone unified PC joints, in which the panel zone is unified with a PC beam or column, designed for use in high-seismicity regions. Two specimens of the member-panel zone unified joints and a benchmark specimen of cast-in-place joint (CIP) were tested under cyclic loading and were analyzed about crack patterns, failure mode, hysteretic behavior, shear distortion, and reaction moment of beams to compare the cyclic behaviors of PC joints with the CIP joint. The seismic performance of each specimen was evaluated in terms of allowable drift ratio, strength & stiffness degradation and energy dissipation capacity suggested in the current code. The maximum strength of the beam-panel zone unified PC joint was comparable to that of the CIP joint, and the crack pattern and failure mode were found to be similar to that of the CIP joint with shear failure of the panel zone. The seismic performance of the beam-panel zone unified PC joint satisfied the criteria applicable to special MRF. On the other hand, the column-panel zone unified PC joint exhibited the flexural failure of the PC beam due to a biased distribution with a high bending moment on either beam, which significantly contributed to a low maximum strength than that of the CIP joint. In spite of relatively low strength, the seismic performance of the column-panel zone unified PC joint satisfied the criteria except for the allowable drift ratio. It was shown that the member-panel zone unified PC joint can be applied as the special MRF by improving the workability and securing high seismic performance. • Cyclic tests on two types of member-panel zone unified PC joints were conducted to investigate seismic performance compared to cast-in-place joint. • Two distinct failure modes were observed depending on PC members unified with panel zone. • Gap-opening between PC beam and panel zone significantly reduced strength of joint contrary to gap-opening between PC column and panel zone. • Column-panel zone unified joint showed low strength due to biased bending moment to one side of PC beam generated by gap-opening. • Beam-panel zone unified joint had comparable seismic performance with conventional cast-in-place joint in terms of strength, stiffness, and energy dissipation capacity.

Experimental study on factors influencing the connection performance of grouted welded sleeves under uniaxial tensile loads

Grouted-sleeve connections are widely used to connect precast concrete members. In this study, a new type of grouted sleeve was presented. The sleeve was fabricated with a new method of forming ribs on the inner wall of a seamless steel pipe by using surfacing welding. Based on this sleeve and slotted rebar, 33 splice specimens with different parameters were designed and manufactured. Uniaxial tensile tests and a comparative analysis were carried out to study the influence of parameters such as the inner cavity of sleeves, the anchorage length, and the grout strength on the mechanical properties of grouted sleeve splices. Test results show that the rib spacing has an effect on the failure mode of the joint. The effect of increasing grout strength on the tensile strength of the joint is significant. However, it is not easier to reach and less reliable than increasing the anchorage length. • A new type of grouted sleeve by using surfacing welding. • Use of slotted rebar to measure the strain of the rebar in the sleeve. • Parametric research and comparative analysis.

Numerical study on the influence of defects in grouting on the mechanical properties of a full grouted sleeve connector

ABSTRACT The present article analyses the influence of defects in the bonding zone between the reinforcement bar and the grout on the mechanical performance of the full-grouted sleeve connector. Grouted sleeve connections are widely used for horizontal and vertical connections of precast concrete members. This work establishes a friction-based interfacial model to simulate the bond between the reinforcement and the grouting materials when the connection is subjected to tensile loading and conducts a Parametric Analysis to study how the confinement effect and contact surface interact with defects in various mechanical and geometric configurations of the connector on 50 different setups of the models in Abaqus. It is found that the influence of defects is non-homogeneous and additional partial grouting improves the bond strength, which increases the tensile capacity of the connector by up to 70% in some specimens. The effect of the sleeve diameter’s reduction is proven to improve the performance of the connector due to the confinement effect, and the safe minimum anchorage of the bar required for adequate bonding in the weakest configuration is eight times the diameter of the bar.

Experimental study on bond behavior between high-strength grout and deformed steel bars

Engineers use high-strength grout to connect precast concrete members for its low shrinkage and good fluidity. This paper designed 87 central pull-out specimens using the control variable method to investigate the influence of factors on the rebar-grout bond property such as compressive strength, steel grade, bar diameter, transverse stirrups, and bond length. The test result showed that improving grout compressive strength (85.8 MPa–122.7 MPa) cannot improve the bond strength, which was different from the previous conclusions of concrete pull-out tests. Simplified formulas were presented for calculating the characteristic values of bond strength, residual strength, peak slip, and relative slip of load-holding platform based on parameter analysis. Then, a constitutive model was proposed to predict the full-range bond stress-slip curve of high-strength grout and steel bar specimens from bearing to failure. Finally, FEA models were established to evaluate the applicability and accuracy of the constitutive model.

The effect of combined carbonation and steam curing on the microstructural evolution and mechanical properties of Portland cement concrete

The present study investigated the effect of the combined carbonation and steam curing on the physicochemical properties and CO2 uptake of the Portland cement concrete. Four different curing regimes were adopted during the initial 10 h of curing to evaluate the potential of carbonation curing as an alternative to conventional steam curing in the precast concrete industry from environmental and practical viewpoints. Four combinations of carbonation and steam curing conditions were applied as curing regimes to the samples at an early age. The test results indicated that the samples treated with the combined carbonation and steam curing exhibited higher early strength development compared to the other samples, signifying that carbonation curing can reduce the production time of precast concrete. Furthermore, the CO2 uptake capacity of the samples was calculated and found to be as high as 18% with respect to the mass of the paste samples. Hence, the simultaneous utilization of steam and CO2 for the fabrication of precast concrete members has the potential to make precast concrete greener and more costeffective.

Unbonded Post-tensioned Precast Concrete Walls With Rocking Connections: Modeling Approaches and Impact Damping

Over the past two decades, precast concrete members have been utilized in seismically resilient structures. In developing these structures, different techniques have been used for connecting the precast members to the foundation. In building construction, unbonded post-tensioning (PT) tendons can anchor a precast wall to the foundation, resulting in the so-called rocking wall system. The rocking wall system develops a dry connection with the foundation and provides moment resistance by means of the PT tendons. The PT tendons remain elastic when the wall is subjected to design-level ground motions to preserve the re-centering capability of the wall. Moreover, the structural damage is concentrated near the wall toes and can be minimized with proper detailing of the toes. Rocking wall systems can consist of a Single precast Rocking Wall (SRW), which uses no supplemental damping, or walls with supplemental damping in the form of viscous or hysteretic energy dissipating devices. In addition to the supplemental damping, rocking walls dissipate the seismic energy through their impacts on the foundation base, their inherent viscous damping, and the hysteresis of concrete near the wall base. While the investigation of rocking walls continues to gain interest, there is no widely accepted means of modeling their dynamic behavior. This paper investigates two popular approaches for modeling rocking walls with and without supplemental damping: the finite element method and analytical modeling. The ability of the two approaches to capture the local and global responses of the walls is evaluated against shake table tests of walls with multiple-level intensity base motions. Next, the behavior characteristics of the two modeling approaches and their ability to simulate impact damping are discussed.

Effects of expansive filler and headed rebar on the shortening of development length of mortar-filled joints

In this paper, the shortening of the development length of mortar-filled joints that connect precast concrete members is studied focusing on the use of expansion fillers and headed rebars. Rebars with a diameter of 13 mm are used. First, specimens are prepared with different dosages of lime-based expansive additive containing calcium oxide as the main component in commercial high-strength-non-shrink mortar or low-viscosity grout. It is found that the load-bearing performance of the mortar-filled joint is improved when the expansive additive is added to the high-strength-non-shrink mortar. However, in all cases, pullout failure occurs and rebar failure cannot be achieved. Second, a cement-based-highly-expansive filler mainly composed of calcium oxide and silicate with a swelling pressure of 40 N/mm2 or more at 3 days is employed. As a result, it is found that the rebar failure can be achieved for a development length of 4 d (52 mm). To further shorten the development length, headed rebar is then used as an inserted rebar. The test results show that rebar failure can be achieved when using a comparatively short development length of 3.5 d (45.5 mm). It is concluded that the use of a cement-based-highly-expansive filler and a headed rebar is effective in shortening the development length of mortar-filled joints.

Production Scheduling Optimization of Prefabricated Building Components Based on DDE Algorithm

At present, the prefabricated construction industry is in a situation of increasing types of prefabricated components and generally high production costs. A hybrid optimization model considering continuity and discreteness for the production of fabricated concrete members is established to minimize production costs through the analysis of the production characteristics of precast concrete members. Under the premise of fully considering the staffing constraints, process constraints, construction period constraints, process constraints, and special process time limits for component production, the production arrangement and staffing of the components are rationalized and optimized. A discrete differential evolution (DDE) algorithm is introduced for such NP-hard problems. The double genetic chromosome coding mode and the active scheduling decoding method are adopted. Based on the improved POX (Precedence Operation Crossover) cross-evolution method, the global evolution operation is carried out, and an interchange-based local search method and continuous work penalty mechanism are designed to find the global optimal solution. The experimental results verify the practicality and effectiveness of the optimization model and algorithm.

Application of waste tire rubber and recycled aggregates in concrete products: A new compression casting approach

The inferior performance of eco-friendly concrete owing to the addition of waste materials is a big hurdle in its practical adaptation. This study focuses on developing eco-friendly and green concrete, having performance similar to normal aggregate concrete (NAC). For this purpose, two waste products, including recycled aggregates (RA) and waste tire chipped rubber (CR), were used during the study. Furthermore, green concrete was also manufactured using RA treated through techniques such as lime immersion with carbonation and acetic acid immersion with mechanical rubbing. To achieve the strength of green concrete similar to NAC, an innovative concrete casting approach was followed. Green concrete specimens were cast and then compressed in the fresh state using specially designed molds. Results show that the compressive strength of recycled aggregate concrete (RAC) incorporating 20% CR in replacement of coarse aggregates is noticed 49% lower than NAC. However, the compressive strength and elastic modulus of compressed RAC and treated RAC incorporating 10-20% of CR in replacement of coarse aggregates are quite close to traditional concrete specimens without CR. No such method is available in the current literature through which green concrete incorporating RA and CR can achieve properties similar to NAC. Furthermore, the cost comparison and cement strength contribution index calculated in this study also show the industrial application potential of the new casting approach. Therefore, the developed concrete casting approach promotes the efficient utilization of RA and CR in the production of precast concrete members resulting in eco-friendly and sustainable construction.

Review of Mechanical Bar Couplers for Splicing Precast Concrete Members

One of the methods for connecting precast concrete members is the application of grouted sleeve couplers. The use of this type of connection is becoming more common over the years and in many cases provides for a time-effective, labor-friendly, and economic alternative to other connection types. However, their application has been limited to non- or low-seismic regions due to the reduction in the ductility capacity attributed to these connections. Recent studies have shown that they can be implemented in the moderate and high seismic zones providing that they are placed in the locations away from damage protected members or arranged to allow yielding of connected bars. This paper aims at reviewing the performance of grouted sleeve couplers under tensile and bending loads as well as gathering in one place recent approaches in improving their ductility behavior. The results of this study are expected to pave the way for researchers to apply this type of connection in seismic areas and motivate new ideas for improving their performance.

Use of unstressed strands for connections of precast concrete members

Precast concrete members need to be connected effectively to form an integral structural system. Use of unstressed strands provides a cost-effective and practical solution to reinforce the connection regions of precast concrete members, especially for precast concrete bridge girder applications. With the limited understanding of bonding characteristics for unstressed strands, a combination of experimental and analytical programs, which focused on unstressed strands as a connection between precast concrete girders and cap beams for seismic applications, was designed to investigate the fundamental load-transfer characteristics of unstressed strands anchored in grout and concrete based on pullout tests. The relationship between strand stress and loaded-end displacement was developed, and the bond stress of unstressed strands embedded in concrete and grouted duct was examined. The average bond stress of unstressed strands anchored in concrete and grouted duct is recommended to be five and seven times the square root of concrete compressive strength, respectively. The results of this research provide qualitative embedment length requirements to design connections between precast concrete members using unstressed strands.

Foam-void precast concrete double-tee members

Foam-void precast concrete double-tee members

Seismic behavior of unbonded post-tensioned precast concrete members with thin rubber layers at the jointed connection

Seismic behavior of unbonded post-tensioned precast concrete members with thin rubber layers at the jointed connection

Influence of compression casting technique and chipped rubber usage on the strength parameters of concrete

Recycled rubber is not considered as an option for the production of recycled concrete as it decreases the strength parameters of concrete in a major outsource. In this research work, a new kind of testing method is taken into consideration for the production of precast members. Compression casting is mainly considered for the production of compressed concrete precast members. Chipped rubber is used as an option over natural coarse aggregate. Chipped rubber at normal instance decreases the durable properties of concrete but the combination of compression testing as well as chipped rubber replacement can note be neglected. Chipped rubber is replaced at 0–50% with natural coarse aggregate. The freshly prepared concrete is condensed in a specially designed mould and after that compression, casting technique is applied over it. Samples of both compressed chipped rubber as well as uncompressed chipped rubber are prepared and then tested further for compressive strength test, modulus of elasticity test, water absorption test. Scanning electron microscopy, as well as cost analysis of controlled concrete, compressed rubber concrete and uncompressed rubber concrete, is performed to get the ultimate benefits of this type of concrete. Compressive strength test results show that the mix with 30% replaced of ripped rubber under compression gives the maximum results of all. Also, the results of elastic modulus were maximum for the same. Cost analysis shows that compressed rubber concrete shows major benefits in the case of precast concrete members. This proposed method should be implemented by the concrete industry from an environmental point of view .

Seismic behavior of self-centering prestressed precast concrete frame subassembly using steel top and seat angles

In order to improve the seismic resilience of the precast concrete structures, a novel prestressed self-centering concrete frame structure is proposed in this study. The beam-column and the column-foundation connections are all assembled using the post-tensioning (PT) tendons and steel angles. Both the experimental and numerical studies were conducted on a 1/2-scaled frame subassembly to investigate the seismic behavior of the specimen. The test results showed that the precast beam/column members and the PT tendons behaved almost elastically during the course of tests. The steel angles provided energy dissipation capacity for the subassembly through significant plastic deformation. The use of PT tendons ensured a good self-centering capacity of the specimen. The seismic performance of the repaired specimen was also evaluated through experiments and showed comparable load-carrying and energy dissipation capacities that were comparable to the original specimen. The good repairability of the specimen was due to the low damage and residual deformation that was induced to the precast concrete members. Based upon the finite element platform OpenSees, numerical modeling was performed to investigate the effects of various design parameters, including initial PT force, area of the PT tendons, geometry of the steel angles, on the cyclic response of the subassembly. The numerical results indicated that an increase in the initial PT force and the area of PT tendons improved the stiffness and the load-carrying capacity of the specimen. A decrease in the thickness, or an increase in the column gage length of the steel angle may result in a reduction in the energy dissipation capacity of the subassembly.

Structural Performance of PC Double Beam\u2013Column Connection Under Gravity and Seismic Loading

Recently, as a new precast concrete (PC) construction method for increasing economy and constructability, the PC double-beam system has been developed for factories or logistic centers, where construction duration is particularly important. In this study, half-scaled PC double beam–column connection was tested under gravity loading and cyclic lateral loading. The major test parameters included the use of the spliced PC column and the addition of reinforcement at the beam–column joint. In the gravity loading test, the flexural behavior of the PC double beam was investigated. The test results showed satisfactory flexural capacity at the PC double-beam section, validating the composite action between the PC and RC members. In the cyclic lateral loading test, the seismic performance of the PC double beam–column connection was investigated. Based on the test results, the failure mode, load-carrying capacity, deformation capacity, energy dissipation capacity, secant stiffness, and shear strength of the PC double-beam system were evaluated and compared with those of a conventional RC double beam–column connection. According to the test results, the structural performance of the PC double beam–column connection was comparable to that of the RC double beam–column connection and satisfied the acceptance criteria of moment frame in the ACI 374.1-05 provision.

Development of a double-tee flange connection using shape memory alloy rods

This study investigated the out-of-plane shear performance of a newly developed shape memory alloy (SMA) connector and a commonly used shear/alignment connector. The innovation lies in developing a durable and easily installed and maintained flange-to-flange connector between precast concrete double-tee members. The proposed connector consists of a superelastic SMA curved bolt inserted into a duct that is then cast into the precast concrete member. Two types of sealant materials were used: polyurethane elastomeric sealant and nonshrink cementitious grout. The shear/alignment and SMA connectors were tested under monotonic vertical shear. The tests were conducted on 4 ft × 4 ft × 4 in. (1.2 m × 1.2 m × 100 mm) slab specimens. The resulting capacities and associated damage were summarized. Higher stiffness and lower ductility were observed for the SMA connector with nonshrink grout compared with the shear/alignment connector with polyurethane elastomeric sealant. The average stiffnesses of the SMA and shear/alignment connector specimens were 116,681 lb/in. (20,434 kN/m) and 31,300 lb/in. (5481 kN/m), respectively. The ductility of the SMA connector was improved when using polyurethane elastomeric sealant; however, more tests should be done to confirm this behavior. The SMA rod was reused in several tests through reheating of the SMA element. The shear/alignment connector cannot be reused.