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Translation abstract A modular precast segmental bridge with thermally formed CFRP reinforcement – modularisation approach and precast concrete productionModular construction enables the serial prefabrication of structural elements and transfers manufacturing processes from the construction site to the protected environment of a precast concrete factory. In serial production with sufficient quantities, rationalisation, digitalisation and automation of manufacturing processes becomes viable and economies of scale can be utilised. In the design realisation of modular building structures, the design engineer is faced with the challenge of arranging these into sensible modules and designing robust and durable joints. This article presents a modularisation approach based on the principles of precast segmental construction and discusses the design and precast segment production for an 8.10 m long test bridge. Non‐metallic reinforcement made of carbon fibre reinforced polymers (CFRP) is used in order to create particularly material‐efficient and thin‐walled concrete cross‐sections and to avoid the risk of reinforcement corrosion. The forming of the reinforcement elements, which is currently still a technical challenge in the application of CFRP‐reinforced concrete, was realised by using recently developed processes of thermal forming. With the realisation of a modular segmental bridge with thermally formed CFRP reinforcement, the authors aim to contribute to the development of technical solutions for modular construction and demonstrate new fields of application for non‐metallic reinforcements. [ABSTRACT FROM AUTHOR]

Concrete is a building material with excellent structural and architectural qualities that could be molded into any shape. However, it is responsible for approximately 8% of the world's total greenhouse gas emissions. Therefore, material consumption must be reduced during the design and construction of concrete structures. To achieve this, designers could employ approaches that allow achieving more with less, such as designing structural geometries that use material where it is needed and removing it from elsewhere. In addition, efficient concrete construction methods are a major focus of research in architecture, civil engineering, and material sciences. One area of investigation is the direct digital fabrication of concrete, or three-dimensional concrete printing (3DCP), and another is the indirect digital fabrication by three-dimensional printed formworks (3DPFs). Focusing on 3DPFs, many projects have investigated them using multiple approaches, such as stay-in-place, in situ, or disposable strategies. A number of these approaches are incompatible with economies of scale. Mass production and modular, reusable assemblies currently dominate the market to cut costs, with reusable 3DPFs largely underrepresented in current research. This research presents a case study for a new manufacturing workflow for the design and fabrication of precast facade panels. Structural topology optimization (TO) designs facade panels with optimized material distribution according to the panel's connection to a substructure. Then, flexible thermoplastic polyurethane (TPU) molds are additively manufactured and repeatedly cast. This research demonstrates a proof-of-concept for additively manufactured TPU molds for the repeatable casting of concrete when accommodating undercuts in complex cast geometries. In addition, it investigates a hybrid molding approach that uses a TPU–polylactic acid (PLA) two-part mold. This research is novel because the use of additively manufactured flexible molds made from TPU for the repeatable casting of geometries is in its early stages. In addition, to the best of the author's knowledge, no previous study has looked into creating hybrid molds with TPU and PLA filaments. This research is pioneering because it addresses material savings during the design phase with TO; and during the fabrication phase by creating reusable 3DPFs. [ABSTRACT FROM AUTHOR]

ACI 318-19 and ASCE 7-22 specify code-compliant and emulative seismic force-resisting systems (SFRS) including intermediate precast shear wall systems. For the seismic design of a precast shear wall system, its successful performance heavily depends on the capacity design of inevitable discrete connections between precast wall panels, thus playing a critical role in controlling yielding to occur within steel reinforcements at the vicinity of intended locations or components. This is imperative for achieving not only ductility but also adequate energy dissipation, ensuring the system can effectively withstand seismic forces. To this end, the overstrength is essentially required to prevent any brittle failure, and the connections designed not to yield can be protected by addressing the 1.5Sy condition as specified in ACI 318-19 and ASCE 7-22. However, there can be a blind spot for the precast connections designed to yield. To this end, this study showed some cases based on practical examples from which a reasonable magnitude of overstrength (Sy) was tentatively recommended for better safety in the seismic design of the intermediate precast shear wall system with precast connections designed to be yielded. [ABSTRACT FROM AUTHOR]

This study investigates prestress loss measured on precast, prestressed concrete bridge beams for a bridge in Oklahoma. The research examines the effects of including mild reinforcing steel in the bottom flange of precast concrete girder and the alternative prestressing pattern on the prestressing losses of pretensioned bridge girders. Using solar powered batteries, a structural monitoring system has been providing an ongoing stream of data since beam fabrication and will continue through the service life of the bridge. In addition to the measured data, the prestress losses were predicted at the girder midspan using five different methods for computing prestress loss. Data show that current equations overestimate the concrete elastic modulus at early ages, leading to an underprediction of elastic shortening losses. Results show that prestress losses are reduced by incorporating a combination of fully tensioned top strand plus mild steel in the bottom flanges of the bridge girder. [ABSTRACT FROM AUTHOR]

Strand debonding patterns and release (prestress transfer) practices can result in significant local stresses at prestressed girder ends, which are not accounted for in design. This article presents a numerical and analytic study of various single-webbed prestressed concrete girder shapes for which large amounts of prestressing are necessitated by the use of 0.7 in. (17.8 mm) diameter strands. Shapes with wide bottom flanges are shown to potentially exhibit large stresses that effectively pry, or peel, the portions of the flanges extending from the web away from the web. Such peeling stresses can be mostly mitigated by partially debonding strands in the recommended pattern from the outside in. Similarly, releasing or cutting strands in a uniform manner mitigates peeling stresses. While releasing all strands simultaneously is optimal, it is unlikely to be practical for large prestressed components. For conventional release operations, the results presented in this article indicate that a symmetrical top-down method would not result in significant peeling stress. Moreover, prestressed girder end region detailing requirements aimed at providing adequate flange confinement and strand anchorage at the ultimate limit would be adequate to control peeling stresses, including those resulting from the inadvertent use of a poor release sequence. [ABSTRACT FROM AUTHOR]

The article discusses a research collaboration between PCI and Oak Ridge National Laboratory (ORNL) on next-generation materials for architectural precast insulated wall panels. The project aimed to develop lighter panels with higher thermal performance and a shorter production time. The research focused on developing a concrete mixture with reduced density and early tensile strength, as well as noncorroding inserts for the panels. The collaboration has led to further research opportunities in the precast concrete industry. [Extracted from the article]

Identifying plastic hinge property is one of key the factors in successful modeling and subsequent seismic performance evaluation of precast concrete (PC) moment frame systems. Tight mechanical splices are also essentially required in precast connections, and its residual slip can greatly affect the plastic hinge length and finally the emulative performance level of PC seismic forceresisting system (SFRS). However, most of the existing models are not directly applicable in current forms to estimate the plastic hinge length of precast connections with mechanical splices. To address the effects of the residual slip induced in the mechanically spliced reinforcement system and its nonuniform stiffness due to splicing device (or coupler), a detailed nonlinear finite element (FE) analysis model was developed in this study, where plasticity-based constitutive models and a unique connector element were adopted for concrete and mechanically spliced reinforcements, respectively. Existing test results of column-foundation connections were used to verify the analytical approach. On this basis, a robust macro modeling method was also proposed for nonlinear cyclic analysis of PC moment frame systems with mechanical splices in this study. It appears that the magnitude of the residual slip in mechanical splices can greatly undermine the lateral stiffness, energy dissipation capacity, and equivalent viscous damping ratio of PC moment connections, and the proposed macro modeling approach can reasonably capture their behavioral characteristics. [ABSTRACT FROM AUTHOR]

The side junctions of metal-plastic block frame windows to the walls of residential buildings at different positions of window frames in the wall cavity are analysed. The duration of thermal failure state by the condensate formation criterion was used as a probabilistic indicator of reliability. The units of uninsulated walls, erected in the second half of the 20th century, have a clearly insufficient thermal reliability level. Thermal insulation of walls according to current design standards in most cases ensures an acceptable of the thermal failure state duration. [ABSTRACT FROM AUTHOR]

Summary: A novel proposal for an assembled bolted joint between a precast reinforced concrete beam and column is presented in this paper. In order to evaluate the behavior of the joint, a comprehensive experiment was carried out on a full‐scale precast concrete beam‐column joint based on bolted connection subjected to pseudo‐static loading. The experiment aims to investigate the failure mode, load carrying capacity, and energy dissipation characteristics of the joint. To further understand the performance of the joint, a finite element model was developed using ABAQUS. The difference in failure mode and ultimate bearing capacity between the bolted joints and cast‐in‐situ joints were analyzed in conjunction with the experimental results. Moreover, the impact of various parameters on the performance of the bolted joints was quantified. The characteristics of the bolted joints, such as the span‐depth ratio, reinforcement ratio of the beam, the stirrup ratio at the beam‐column junction, T‐end length, and the bolt strength grade, were meticulously analyzed through an examination of bearing capacity curve, stiffness degradation patterns, and energy dissipation capability. The results show that, in comparison with the traditional cast‐in‐situ joints, the damage failure extent exhibited by the bolted joints is notably smaller, thereby rendering it more advantageous for seismic restoration and replacement. Furthermore, the span‐depth ratio, reinforcement ratio of the beam, and the stirrup ratio have a greater influence on the seismic performance of bolted joints than the T‐end length and bolt strength grade. [ABSTRACT FROM AUTHOR]

The paper portrays a comprehensive computational procedure for determining the global structural resistances of two existing bridges made of I‐73 and KA‐61 precast post‐tensioned concrete girders using advanced statistical assessment methods in combination with nonlinear fracture mechanics‐based finite element method analysis. Although this combination is a powerful tool for realistic modeling of structures, its practical application is still very time consuming. Therefore, a statistical sampling approach for the determination of the structural design resistance is compared to selected efficient semi‐probabilistic methods based on the estimation of coefficient of variation—estimation of coefficient of variation (ECoV) method according to fib Model Code 2010 and improved approach called Eigen ECoV method. Load‐bearing capacity is determined for the ultimate as well as several serviceability limit states. The sensitivity of the input parameters burdened with uncertainties on the response of the structure is quantified using a sensitivity analysis supported by a surrogate model based on polynomial chaos expansion. The paper shows that the applicability of nonlinear modeling with respect to uncertainties is possible when using these ECoV methods and a surrogate model and can be applied in a routine manner. The shortcomings and advantages of all the used safety design/assessment methods are discussed. [ABSTRACT FROM AUTHOR]

The capacity of the circumferential joint of the precast concrete segmental tunnel lining (PCTL) structure in terms of shear performance principally includes the dowel action by connector/bolt as well as friction force, and it is a vital parameter to assess the mechanical response of the circumferential joint. Further, as there was no analytical model available for precise estimation of a circumferential joint in terms of the shear‐bearing capacity considering the dowel action of the bolt in the presence of axial/normal force, therefore in this investigation, an analytical model has been proposed to estimate the shear‐bearing capacity of the circumferential joint. Furthermore, the analytical model's precision and accuracy were validated via large‐scale experimental investigation on a circumferential joint of PCTL. Upon comparing analytical model outcomes with experimental results, absolute error varied between +5% and −9%, with an average value of the coefficient of friction at the yield point of the bolt. Moreover, the formation of hinges on the side of the bolt within the segment was considered a failure of the circumferential joint. Additionally, the parametric investigation revealed that with just a 1% change in axial force, the diameter, pre‐tightening, and yield strength of the bolt and concrete strength improved by 2.85%, 1%, 0.27%, 0.26% and 0.17% shear‐bearing capacity of the circumferential joint respectively. Axial force variation greatly influences the shear‐bearing capacity of circumferential joint followed by diameter, pre‐tightening, yield strength of the bolt, and concrete strength. Conclusively, with analysis of axial force distribution around the ring for the tunnel, the proposed model has been applied to a full ring to estimate shear bearing capacity. [ABSTRACT FROM AUTHOR]

The joints between precast reinforced concrete pile segments in deep foundations are typically mechanically lockable. They include anchor bars embedded inside the ends of each segment, forming lap splices with the main bars. Because of their particular technology, these lap splices are somewhat different from traditional lap splices, as shown in the first part of this paper, where the impact of their specific characteristics on the tensile behavior of the joints is discussed. The experimental section presents the results of 19 tensile tests on these lap splices and compares them with established theoretical models. The roles of various parameters (lap length, type and amount of confining reinforcement, type of anchor bars, and concrete cover thickness) are investigated. One of the major findings indicates a significantly lower lap capacity when using plain‐bar spirals compared to closed‐ribbed stirrups. Additionally, at low stress levels, the models tend to be unconservative. Building on this insight, a modified model is proposed for lap splices provided with plain‐bar spirals. [ABSTRACT FROM AUTHOR]

The mechanical characteristics of segmental joints are pivotal in defining the comprehensive stress behavior of prefabricated assembled cover beams. In this research, direct shear tests were conducted on dry key‐tooth joints, and acoustic emission technology was employed for monitoring purposes. The shear failure mechanism was explored under a range of influential parameters. Building upon these observations, the study delved into the mechanical response of joints within segmental cover girders subjected to concurrent bending and shear forces. Specimen K‐3‐3 exhibited a higher shear carrying capacity compared to other specimens, indicating that the shear resistance of dry joints proportionally increases with the height of the specimen and the strength of the concrete. The carrying capacity of Specimen K‐4 was marginally lower than that of Specimens K‐3‐1 and K‐3‐2, suggesting that increasing the number of keys does not significantly impact the shear resistance of dry joints. Notably, Specimen K‐3 demonstrated exceptional shear carrying capacity, exhibiting minimal relative slip during failure, and streamlined the casting process. Consequently, these dry joints featuring large key teeth are deemed more appropriate for use as shear connectors in precast concrete segmental cover beams. Crack patterns in large key tooth precast concrete segmental cover beams propagate along the joints. A damage evolution model for the specimens, based on spatial b‐values and T‐values, visually depicts the damage extent in large key tooth precast concrete segmental cover beams. This model demonstrates excellent agreement with experimental results and provides a solid foundation for theoretical research and practical applications of large key tooth precast concrete segmental cover beams. [ABSTRACT FROM AUTHOR]

The closure section of precast concrete segmental bridges (PCSBs) usually adopts the wet joint of cast‐in‐situ concrete, the width is generally 10–20 cm, and the regular longitudinal reinforcement is discontinuous, which makes the section the vulnerable part of the bridge. To explore the mechanical property of the wet joint in the closure section of PCSB under cyclic load, six wet joint specimens are tested to investigate the influence of loading mode, interface treatment mode, setting of regular reinforcement, and prestress level. The results show that the failure modes of wet joint specimens have similar characteristics, careful roughening of joint surfaces can improve the bonding effect of the new and old concrete and delay the cracking of the specimen, the cracking load of the specimen increases by 10.3% after careful roughening. When the prestress level increases from 6 to 8 MPa and 10 MPa, the stiffness of the specimens increases obviously, and the fracture development of the specimen in the loading process is improved. The cracking load increases by 21.9% and 32.8%, the shear strength increases by 9.9% and 6.6%, respectively, but the ultimate displacement decreases by 5.6% and 11.4%, respectively. Then, the finite element model of the wet joint was established and verified, the influence of shear key, concrete strength, and wet joint width are selected for parameter analysis. It is found that stress concentration is easy to occur after shear key is set, which has adverse effects on structural flexural resistance. The shear capacity of the model decreases by 22.4% and 21.5%, respectively after the setting of single and double‐shear keys, but the stiffness of the wet joint model before cracking is improved. Compared with C50 concrete model, the ultimate bearing capacity of C60 and C70 concrete models is increased by 11.5% and 24.8%, respectively. Wet joint width has little influence on the mechanical properties of wet joints in the closure section. The research results provide references for design and construction of PCSB wet joints in practical engineering. [ABSTRACT FROM AUTHOR]

At present, the connection between the beams and slabs adopting composite layers is cast on-site, which is laborious and time-consuming. In this study, a new type of precast concrete (PC) beam and PC slab connection, which was connected by stud/channel steel connectors, was proposed to enhance the efficiency of prefabricated construction. Push-out tests were carried out on 5 PC beam-slab specimens connected with studs and 3 PC beam-slab specimens with channel steel connectors. The test variables were the connecting methods of beam-slab, the connector reinforcement ratio and the connecting width between two slabs. The failure process, load and slip of the beam-slab connection were recorded. Then, the slip behavior, shear capacity and shear stiffness of the PC beam-slab connection were analyzed. The results showed that the new type of PC beam-slab connection proposed in this study was an effective form for transferring force between the beam and slabs. Based on the push-out test results, the shear mechanism of connectors was analyzed and the calculation formulas for shear strength of stud/channel steel connectors were put forward. The calculated values obtained from the proposed formula demonstrated a strong correlation with the test results, providing an accurate measurement of shear strength of the new type of PC beam-slab connection. This study offers a reference for realizing the fast-full assembly construction of PC frame. [ABSTRACT FROM AUTHOR]

In railway tracks, additional stresses occur in rails due to interaction between the rail and the bridge superstructure, which is a phenomenon known as track–bridge interaction (TBI). The additional rail stresses (ARSs) develop primarily as a result of temperature effect, vertical bending of bridge superstructure, and braking/acceleration of trains traveling over the bridge. One of the major parameters affecting the TBI response is the behavior of interface elements simulating the coupling between the bridge superstructure and the rail. In TBI analysis this coupling is defined by the so-called longitudinal resistance-displacement curves (RDCs). The present study deals with the longitudinal aspect of TBI though a numerical investigation. The numerical modeling approach was verified with available analytical solutions and data obtained from bridge monitoring. The primary interest was to illustrate how sensitive the TBI response is to changes in RDCs with both separate and sequential analysis approaches, which has not been investigated thoroughly earlier. The parametric study was extended to investigate the effects of expansion length and substructure stiffness, in addition to RDC type. For simply supported precast girder bridges, RDCs that are experimentally proven specific to ballastless railway bridges can be used as an economic alternative to those specified by provisions. [ABSTRACT FROM AUTHOR]

A novel concept of hybrid reinforcement in the form of glass fiber‒reinforced polymer (GFRP) longitudinal column bars combined with steel longitudinal column bars and high-strength post-tensioning all-threaded rods is investigated in this research to construct bridge columns for seismic regions. Two half-scale specimens were constructed using grouted ducts to connect the columns to the footings as an accelerated bridge construction method. The first column was reinforced with a combination of mild steel and GFRP longitudinal bars (hybrid column) and the second with all-mild steel longitudinal bars, and both columns were confined with a double layer of GFRP spirals; this arrangement improves column longevity since GFRP materials do not corrode. Both specimens utilized high-strength all-threaded rods for post-tensioning. Carbon fiber‒reinforced polymer jackets were externally wrapped at the column bottom to confine the concrete in the plastic hinge region. The seismic behavior of both precast concrete specimens was assessed through quasi-static cyclic tests. Both columns exhibited satisfactory strength and deformability. The combination of post-tensioning bars with GFRP longitudinal bars improved the self-centering capability. The residual displacement of the hybrid column was decreased by 46% compared with the all-steel-reinforced column at 6.0% drift ratio. The elastic nature of the GFRP longitudinal bars provided substantial self-centering by reducing the residual displacement of the hybrid specimen thereby enhancing seismic resilience. [ABSTRACT FROM AUTHOR]

Non-sintered cement (NSC) mortar was developed using only industrial by-products, such as ground granulated blast furnace slag, classes C and F fly ashes, and slaked lime. The characteristics of different NSC mortar formulations were investigated, as well as their applicability for use in forming precast concrete products. X-ray diffraction and scanning electron microscope analyses were performed to examine the internal structure of the different formulations. Overall, the developed NSC mortar satisfied the existing quality standards in terms of strength performance and absorption rate. Therefore, it is expected to be highly applicable as a raw material for production of the desired cement products. [ABSTRACT FROM AUTHOR]

Precast concrete (PC) shear wall members are essential components of the precast concrete shear wall structural system. Therefore, it is crucial to research their materials, and seismic performance is an important and vital indicator to promote the development of prefabricated buildings. This study introduced a new type of precast concrete sandwich shear wall, the precast high-titanium heavy slag concrete sandwich panel wall (PHCSPW), by replacing ordinary concrete coarse and fine aggregates with high-titanium heavy slag and adding insulation boards. This study constructed a cast-in-place high-titanium heavy slag concrete wall (CHCW) for comparative pseudo-static tests to validate its seismic performance. Finite element simulation analysis was conducted to compare and validate the reliability of the test. Considering the limitations of the test conditions, it also researched the seismic performance of PHCSPW by simulating different parameters such as reinforcement ratio, concrete strength, and axial compression ratio. It concludes the following: (1) The failure mode, stress-strain distribution, and ultimate bearing capacity values of PHCSPW and CHCW were consistent with theoretical and experimental analysis results. (2) PHCSPW exhibited high stiffness before cracking but experienced a rapid stiffness degradation rate after cracking. (3) The development trend of the PHCSPW and CHCW hysteresis curve is the same as the skeleton curve. There is little difference between the bearing capacity and deformation capacity after cracking. Comparing the hysteresis loops of CHCW and PHCSPW, it is found that PHCSPW has a larger hysteresis loop area, which indicates that PHCSPW has better energy dissipation capacity. The value of the yield load of the specimen compared with the peak load is between 0.636 and 0.888; that is, the difference inthe early-stage stiffness of the specimen is small. The yield load of PHCSPW is slightly larger than that of CHCW. The maximum carrying capacity of CHCW is about 68.31% of that of PHCSPW. (4) The simulation of different parameters revealed that the energy dissipation capacity of the members increased within a specific range with an increasing reinforcement ratio. PHCSPW demonstrated superior energy dissipation capacity. The influence of concrete strength on the energy dissipation capacity of the members was relatively small. The energy dissipation capacity of the members decreased with increasing axial compression ratio. [ABSTRACT FROM AUTHOR]

Summarized in this article are the major findings from a detailed damage investigation of an instrumented ductile reinforced concrete moment frame building subjected to a design-level earthquake. The building sustained widespread damage during the 2016 M-7.8 Kaikoura earthquake and was subsequently demolished. Prior to demolition, the structural system was extensively surveyed to document the severity and distribution of the damage sustained in the reinforced concrete frames and the flooring system. Furthermore, the building response during the earthquake was reconstructed from the acceleration records obtained from instruments installed throughout the building. The site seismic demands were also obtained from a local free-field instrument. The data collected from this damage investigation provide a high-quality dataset that is valuable to researchers investigating different parameters related to the seismic performance of reinforced concrete moment frame buildings. The dataset is published and publicly available on DesignSafe-CI (project PRJ-3444); https://www.designsafe-ci.org/data/browser/public/designsafe.storage.published/PRJ-3444v2. The data collection methodology is described, and a roadmap for navigating the dataset is presented to support future use of the archived dataset. [ABSTRACT FROM AUTHOR]

In this study, we utilized unmanned aerial vehicle (UAV) and high-precision 3D light detection and ranging (LiDAR) scanning to collect data before and after an earthquake-resistant behavior test on a reinforced concrete hybrid frame. We analyzed the deformation of the hybrid frame before and after the test and determined the specific deformation, scale, and change rule. The UAV image data was transformed into a 3D true-color model using the structure from motion (SfM) algorithm. Additionally, the 3D Delaunay surface reconstruction algorithm was used to create a 3D point cloud model and Rodriguez matrix, which are then used to align the two-phase model. Subsequently, a comparison was made in three dimensions between the distribution of the hybrid frame's photographic and 3D point cloud models before and after undergoing earthquake-resistant behavior tests. This method allows for a precise analysis of the local deformation degree of the hybrid frame structure compared with the sensors. While the sensors can only analyze internal structural changes, this method provides results for both local and surface deformation degrees, which are not available in the sensor data. The comprehensive experimental comparison results demonstrate that the reinforced concrete hybrid frame structure had a collective rightward displacement before and after the earthquake-resistant behavior test. Moreover, nodes and edges exhibited more significant deformation, and the test resulted in a more stable overall framework. [ABSTRACT FROM AUTHOR]

The interfacial cohesion between precast normal concrete (NC) and cast‐in‐place ultra‐high performance concrete (UHPC) is an important index to evaluate their interfacial bond strength, which is of great importance for the application of UHPC as a connection material for precast structural bridges. Interfacial cohesion is related to several influencing factors. However, there needs to be more research on the interrelationship model between multiple influencing factors and interfacial cohesion. This study took the UHPC wet joint in a precast concrete structure as the object. First, the relationship between the interface cohesion of UHPC wet joint and substrate strength, UHPC age, interfacial roughness, interfacial moisture content, and curing method was studied; The result shows that the key factors affecting interfacial cohesion include UHPC age, interface roughness, and substrate strength, with interfacial moisture content potentially playing a secondary role. Second, the failure types of the interface zone surface by using digital image correlation (DIC) are divided into three categories. Finally, the quantitative mathematical model of interfacial cohesion under the coupling effect of multiple factors was established based on the above four factors. The model is in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

The main objective of the transverse joint between prefabricated full-depth precast concrete deck panels is to prevent the relative vertical movement between the panels and to transfer the loads between adjacent panels without cracking. The most common failure mode for these types of joints during their service life are the interface cracks. Such cracks serve as a conduit for ingress of water into the superstructure, leading to further deterioration requiring frequent maintenance. UHPC is known for its high tensile and bond strengths and is often considered as a joint fill material that has the potential to make this connection more durable. This research has been initiated to investigate if closure joints cast using UHPC material can compete with the performance of monolithic deck systems. The experimental program consisted of two full-scale concrete bridge decks that were statically tested until failure. One bridge deck was a jointed panel deck (JPD) consisting of two half-size panels connected by UHPC closure joint, while the control deck was a full panel deck (FPD) cast as one monolithic specimen. Both decks were connected to the steel girders with UHPC shear pockets that contained four to six shear studs welded to the girder flange. The JPD had rectangular tapered shear pockets and the FPD had circular shaped pockets. The results indicated that the JPD and FPD reached the same ultimate loads, and both failed via concrete punching at the load point situated adjacent to the closure joint of JPD. The results demonstrated that using UHPC closure joint resulted in similar performance and behaviour under loading as the monolithic deck. The interfacial failure was not indicated even at ultimate loads. This confirms the ability of the UHPC closure joint to transfer the load to the adjacent panel. The results also indicated the use of circular or rectangular pockets led to similar behaviours. [ABSTRACT FROM AUTHOR]

I-shaped concrete girders are widely used in precast bridge and roof construction, making them a common structural component in existing infrastructure. Despite well-established strengthening techniques using various innovative materials, such as externally bonded carbon fibre reinforced polymer (CFRP) reinforcement, the shear strengthening of an I-shaped concrete girder is not straightforward. Several research studies have shown that externally bonded CFRP reinforcement might exhibit early debonding at the concave corners of the I-shape, resulting in a marginal increase in shear capacity. This research study aims to assess the performance of two different CFRP shear strengthening strategies for I-shaped concrete cross-sections. In the first strategy, CFRP was bonded along the I-shape of the cross-section with the provision of additional anchorage. In the second strategy, the I-shape was transformed into a rectangular shape by using in-fill blocks over which the CFRP was bonded in a U-configuration. In addition to the strengthening strategies, the investigated parameters included two different materials for the in-fill blocks (conventional and aerated concrete) and two different anchoring schemes (bolted steel plate anchor and CFRP spike anchor). To avoid testing on large-scale girders, a new test methodology has been implemented on concrete I-sections. The test results demonstrate the feasibility of comparing different shear strengthening configurations dedicated to I-sections. Among other findings, the results showed that the local transformation of the I-shape to an equivalent rectangular shape could be a viable solution, resulting in shear strength enhancement of 12% to 53% without and with the anchorages, respectively. [ABSTRACT FROM AUTHOR]

Prestress concrete composite girders with full‐depth precast bridge deck panels (PC composite girders) have been widely utilized in civil engineering due to their high production quality, reduced construction duration, potential weight reduction, and lower life‐cycle cost. The interface shear behavior in ultra high‐performance concrete (UHPC)–normal concrete (NC) connection interface of full‐depth deck PC composite girder has been extensively studied. This study conducted seven push‐off tests to examine the shear performance of UHPC‐filled joints between precast I‐girders and full‐depth precast concrete slabs. The testing variables included the quantity, and spacing of the Ubars, as well as the type of UHPC‐filled joints (longitudinal trough connector or pocket connector). The experimental results show the quantity and spacing of Ubars have a significant impact on both the interface shear capacity and residual shear resistance. For continuous shear connectors with reserved notches specimens, the ultimate load of the 4Ubar and 6Ubar specimens increased by 93% and 194%, respectively, compared with the 2Ubar specimens. With the increase of the spacing of the Ubar, the ultimate load will decrease. When the spacing between Ubars increases from 100 to 150 mm, the normalized ultimate load decreases by 51 kN. The type of joints also plays a crucial role in determining the ultimate shear‐bearing capacity of the specimens. The Ubars in pocket connector specimens will provide a greater contribution to the ultimate shear bearing capacity than longitudinal trough connector specimens and the ultimate stress of the 4Ubar and 6Ubar pocket connector specimens are greater than that of the longitudinal trough connector specimens by 232% and 323%. The study introduces the concept of pulling angle. In the experiment, the specimen with a large length is less affected by the pulling force. The experimental results in this study can rarely be predicted well by typical equations developed in current design codes and previous studies. Therefore, a more accurate equation was developed to predict the interface shear transfer stress between precast common concrete I‐girder and full‐depth precast concrete slab with UHPC‐filled joints. [ABSTRACT FROM AUTHOR]

This study investigates the behavior of hybrid beam-column connections with numerous detailing methods to be incorporated into precast concrete moment-resisting frames under simulated reversed cyclic loading, and ultimately develops a design procedure. Seismic performance of moment-resisting precast concrete beam-column connections was investigated through simulated reversed cyclic load tests. In addition, nonlinear finite element analysis (FEA) of typical monolithic and precast concrete connections was carried out using a modified concrete damage plasticity model. Good agreement was achieved between experimental and numerical results, which indicates that the FEA model is capable of capturing failure modes of the investigated precast concrete connections. Simple detailing modifications resulted in major improvements in the performance of connections in terms of load-displacement curves, stiffness, and energy dissipation. Finally, a design procedure was developed for the investigated connections based on failure modes and investigated limit states. [ABSTRACT FROM AUTHOR]

This paper presents field measurements of the rotational stiffness of three transport vehicles equipped with different types of suspensions: leaf, combined air and leaf, and hydraulic suspensions. The rotational stiffness was determined by measuring the tilts of the vehicles when a girder or known weights were placed on them at various eccentricities. One of the tested vehicles, which featured transversely expandable wheel spacings varying from 6 to 18 ft (1.8 to 5.5 m), exhibited an increase in rotational stiffness from 78,181 to 134,584 kip-in./radian (8833 to 15,206 kN-m/radian). This paper summarizes the rotational stiffness for all the vehicles tested by the authors. The field measurements conducted have enriched the existing database on vehicle rotational stiffness in the United States. [ABSTRACT FROM AUTHOR]

This paper presents a comparison between three numerical models developed for the structural analysis of composite precast concrete sandwich panels under lateral loading. The first model is based on a full finite element analysis where “slip” between the layers is obtained from the elastic deformability of the various components. The second model is based on a simplified finite element analysis where the effect of the shear connectors is smeared and modeled through an effective shear stiffness of the insulation layer. The third approach provides closed-form expressions for evaluating the deflection and is based on the classical sandwich beam theory where the shear connectors are considered through the effective stiffness of the insulation, similar to the second model. The structural response obtained from the three models was compared for various panel configurations and good correlation was obtained. A reasonable agreement with test results from the literature was also demonstrated. Therefore, both the simplified finite element model and the classical sandwich beam theory (closed-form solution) are recommended for the elastic structural analysis and for estimating the degree of composite action at the serviceability limit state of precast concrete sandwich panels. [ABSTRACT FROM AUTHOR]

Precast slab bridges are an attractive option for short- to medium-span bridges; however, the presence of longitudinal joints and concrete overlays adds great complexity to the transverse load distribution (TLD) analysis. Currently, one of the most commonly used methods for simplified analysis relies on the semiempirical formulas provided in AASHTO LRFD Bridge Design Specifications; yet, these formulas have certain limitations in their applicability. This study presents an algorithm based on the transfer matrix method (TMM) to determine the TLD of precast slab bridges. A connection model utilizing shear-and-torsion spring hinges (STSHs) is proposed to simulate the structural behavior of shear keys and the overlay of precast slab bridges in TLD calculations. The transfer matrices and transfer equations between slabs and between joints are established. The TLD for slabs is then computed by introducing boundary conditions and solving transfer equations. In addition, the finite-element method (FEM), along with the existing field tests of two different bridges, is used to verify the accuracy and validity of the proposed method. The study concludes that the TMM shows high algorithmic efficiency compared to the FEM modeling procedure and better precision and applicability than the semiempirical equations provided in AASHTO LRFD. Moreover, extended parametric studies are conducted on the effects of the thickness of concrete overlay and the relative flexibility coefficients of slabs on the TLD of bridges. [ABSTRACT FROM AUTHOR]

Direct shear strength (DSS) of the precast concrete dry joints (PCDJs) is one of the critical issues for ensuring the structural integrity and performance of the precast segmental concrete bridges (PSCBs). However, the effects of shear key configurations, such as size, shape, spacing, and number of the PCDJs, were studied within narrow value ranges and were not well considered in the widely used AASHTO formula, resulting in unconservative predictions of the formula for multiple-keyed PCDJs. This study investigated the effect of shear key configurations within wider value ranges and incorporated a reduction factor into the AASHTO formula through a newly established parametric finite-element (FE) simulation. The simulation included an automatic procedure of model generation and calculation to derive the DSS of PCDJs based on 13 input parameters of the joint and was validated by a comprehensive database including 111 DSS results of PCDJs collected from existing literature. A parametric study was then conducted on a customized joint, which allows for exploring the PCDJs with large key sizes or numbers. Finally, a reduction factor was proposed to the AASHTO formula based on the test and simulation data considering the effects of key configurations. Results demonstrate that the proposed FE simulation is able to consider the reduction effect from the key configurations and reaches an excellent agreement in predicting the DSS of PCDJs in the database with more accurate mean values (MVs) (0.95 and 0.98), higher R2 values (0.63 and 0.69), and lower root-mean-squared error (RMSE) values (1.00 and 0.79 MPa) for both single-keyed and multiple-keyed joints compared with the results of the AASHTO formula. The parametric study revealed that the ASSHTO formula becomes increasingly unconservative with the increase of key numbers. The reduction factor needs to be included in the formula when multiple-keyed or large-size keyed joints are considered. The AASHTO formula with the reduction factor leads to a conservative prediction performance in the multiple-keyed joints, which is similar to that in the single-keyed joints. [ABSTRACT FROM AUTHOR]

Early CO2 curing acting as a new curing technique is an effective way to cut down on carbon footprint in cement industry. It also improves the strength development and long-term durability of concrete without reinforcement. Given the fact that reinforcement concrete is most widely used in construction and building fields, the carbon sequestration potential will be enhanced remarkably if this curing technology can be used in reinforced concrete. However, the impacts of early CO2 curing on the corrosion behavior of steels, which is the major concern for reinforced concrete exposure to chloride, is unclear yet. In this work, the permeability of chloride, threshold chloride value and corrosion behaviors of steels in cement mortar were determined to comprehensively study the effect of early CO2 curing on the chloride induced corrosion of steels. Early CO2 curing lowers the chloride ions permeability of mortars, in particular for the mortars with 28 day curing ages. Steels take longer time to form stable passive films in early CO2-cured mortar than in conventional moist-cured ones. Early CO2 curing reduces the chloride threshold concentration of mortar, in particular for the mortars that the whole cross section is carbonated, the reduction reaches ∼50%. However, it exerts few effects on corrosion induction phase of steel rebar. Moreover, early CO2 curing decreases the corrosion rate of steel bars in corrosion propagation phase and thus the overall corrosion rate of steels during the whole testing process due to slower chloride ingress rate. Thus, early CO2 curing can act as an alternative curing technique in the production of pre-cast reinforced concrete exposed to chloride. [ABSTRACT FROM AUTHOR]

Accelerated bridge construction (ABC) has emerged as a faster method of bridge construction. Reinforced concrete (RC) columns in bridges constructed using ABC methods remain vulnerable to corrosion, which impacts their performance during large earthquakes. Three specimens were constructed using ABC methods to investigate the effects of corrosion; two of these specimens were subjected to accelerated corrosion procedures to simulate moderate and severe corrosion levels. The longitudinal steel bars experienced 11% and 24% mass loss, while the steel spirals experienced 18% and 40% mass loss for moderately and severely corroded specimens, respectively. The severely corroded specimen experienced buckling of longitudinal bars at 5.0% drift ratio. Corrosion severity impacted column displacement capacity; the first reinforcing bar fractured at lower drift ratios in the corroded specimens, both of which experienced reduced displacement ductility and hysteretic energy dissipation. The importance of considering corrosion in evaluating seismic performance of RC bridges constructed using ABC methods is demonstrated. [ABSTRACT FROM AUTHOR]

The behavior of precast concrete tunnel lining (PCTL) segments reinforced with glass fiber-reinforced polymer (GFRP) bars under punching loads is one area in which no research work has been conducted. This paper reports on an investigation of the punching-shear behavior of GFRP-reinforced PCTL segments induced by soil conditions, such as rock expansion or the geotechnical conditions surrounding a tunnel. Six full-scale rhomboidal PCTL specimens measuring 1500 mm (59 in.) in width and 250 mm (9.8 in.) in thickness were constructed and tested up to failure. The investigated parameters were: 1) reinforcement type (GFRP or steel); 2) reinforcement ratio (0.46 or 0.86%); 3) stirrups as shear reinforcement; and 4) segment length (2100 or 3100 mm [82.7 or 122 in.]). The experimental results are reported in terms of cracking behavior, punching-shear capacity, deflection, strain in the reinforcement and concrete, and failure modes. The results reveal that the GFRP-reinforced PCTL segment was comparable with its steel counterpart with the same reinforcement ratio and satisfied serviceability limits. Increasing the reinforcement ratio and decreasing the segment length enhanced the punching-shear strength. The shear stirrups improved the structural performance and increased the punching and deformation capacities of the GFRP-reinforced PCTL segments. In addition, theoretical predictions of the punching-shear capacity using the current design provisions were compared to the experimental results obtained herein. The theoretical outcomes show the suitability of using current FRP design provisions for predicting the punching capacity of PCTL segments reinforced with GFRP bars. [ABSTRACT FROM AUTHOR]

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This paper presents the outcomes of a comprehensive experimental investigation aimed at characterizing the in-plane shear strength of Unreinforced Masonry (URM) wallettes subjected to diagonal compression. The study focuses on the strengthening of these wallettes using precast Ultra-High Performance Concrete (UHPC) diagonal strips, externally bonded onto the wall substrates through high-strength epoxy mortar. Twenty-three wallettes, each measuring 1000 mm × 1000 mm × 70 mm, were meticulously constructed and subjected to in-plane diagonal compression. Among these, eighteen wallettes underwent strengthening utilizing various configurations of UHPC, with a key emphasis on variables such as UHPC strip width and thickness, substrate nature, and corner confinement with enlarged UHPC rectangular plates. Findings from the experimental program highlighted the significant influence of UHPC retrofit parameters on the wallettes performance. Notably, corner confinement emerged as an effective strategy against premature toe crushing failure, enhancing the wallettes ability to withstand higher in-plane compressive loads. While UHPC strip width exhibited moderate impact, UHPC strip thickness emerged as a dominant factor. Increasing strip width from 100 to 250 mm yielded an approximate 8% shear strength improvement, whereas doubling strip thickness from 10 to 20 mm led to a substantial 27% enhancement. Notably, enhanced strip width demonstrated pronounced benefits in terms of ductility and energy dissipation capacity. Excessive UHPC retrofit thickness induced brittle failure despite escalating shear strength. Conversely, thinner UHPC retrofits achieved a favorable balance between strength, ductility, and energy dissipation. Wallettes retrofitted with 5 mm UHPC exhibited an impressive 2.36-fold shear strength increase compared to reference walls, while those with 10 mm and 20 mm UHPC retrofits experienced 2.14 and 2.78-fold improvements, respectively. Furthermore, the manner of UHPC application significantly influenced the strengthening system's behaviour. For identical strengthening layouts, the direct bonding of UHPC onto masonry substrates resulted in a 25% increase in shear strength compared to UHPC bonding onto plaster overlays. [ABSTRACT FROM AUTHOR]

The use of recycled concrete aggregate instead of natural coarse aggregate is of great interest from a sustainability perspective. The present study investigates the flexural design of unbonded, post-tensioned, precast recycled concrete beams. It also evaluates the application of unbonded prestressed tendons in recycled concrete beams. Flexural behavior tests were performed on 13 beams with different prestressed reinforcement indices, section heights, and comprehensive reinforcement indices. We thoroughly investigated stress changes in prestressed steel strands, beam failure forms, and crack development during loading. The results demonstrate that under the same load level, the average crack width of recycled concrete beams is 36% higher than that of conventional concrete beams. A theoretical analysis indicates that the factors affecting the stress increment of unbonded prestressed tendons are the comprehensive and prestressed reinforcement indexes. A theoretical model of stress increment during loading of prestressed reinforcement was obtained, allowing derivation of an ultimate bearing capacity formula for unbonded, post-tensioned, precast, recycled concrete beams. An influence coefficient for recycled coarse aggregate is introduced and set to 1.14, the experimental data is fitted to derive the calculation formula for the average crack spacing and width. The theoretical model of the stress increment in prestressed steel strands and the proposed crack width model provide a valuable design reference and theoretical support for engineering applications. [ABSTRACT FROM AUTHOR]

Recycled concrete aggregates are potentially interesting for the precast concrete industry as they provide a new use for high-quality waste from its products' life cycle. In precast concrete structures, it is common to use headed bars in several connection types between structural members. This paper presents the results of experimental tests to investigate the impact of replacing coarse natural aggregates with coarse recycled concrete aggregates in the concrete breakout strength of cast-in headed bars embedded in slender structural elements. Results of 12 tests on 16 mm headed bars embedded in 500 × 200 × 900 mm concrete members with an effective embedment depth of 110 mm are presented. The percentage of replacement of natural aggregates by recycled concrete aggregates was 0%, 30%, and 100%, and the flexural reinforcement ratio of the structural elements varied from 0.5% to 3.5%. The behavior and strength of the tested specimens are discussed, and comparisons with theoretical strength estimates are presented. The results showed that the concrete breakout strength of the headed bars was not affected by the use of recycled concrete aggregates and that the flexural reinforcement ratio significantly impacts the load-carrying capacity of the headed bars as they control the crack widths before failure. [ABSTRACT FROM AUTHOR]

In this study, four-point load tests were conducted to evaluate the shear performance of factory-produced precast prestressed concrete hollow core slabs (HCS) assembled on-site. The test specimens were fabricated using compression molding and comprised six samples, with variables being the presence or absence of topping concrete and the shear reinforcement. According to the experimental variables, experiments were conducted using simple support beams to evaluate the shear performance and ultimate strength of HCSs. The results showed that HCSs, regardless of whether they included topping concrete or not, exhibited average values of shear strength more than 10% higher than the factored shear strength specified by concrete structure standards, confirming that these materials satisfy existing design standards. According to current standards, the overall reinforcement length should be increased to meet the minimum shear rebar placement requirements. However, the nominal shear strength of PS concrete hollow slabs exceeded the hollow design, with the ratio of experimental results ranging from 1.26 to 1.87 on average, satisfying the required performance. [ABSTRACT FROM AUTHOR]

Abstract Non-sintered cement (NSC) mortar was developed using only industrial by-products, such as ground granulated blast furnace slag, classes C and F fly ashes, and slaked lime. The characteristics of different NSC mortar formulations were investigated, as well as their applicability for use in forming precast concrete products. X-ray diffraction and scanning electron microscope analyses were performed to examine the internal structure of the different formulations. Overall, the developed NSC mortar satisfied the existing quality standards in terms of strength performance and absorption rate. Therefore, it is expected to be highly applicable as a raw material for production of the desired cement products.