Search

This paper proposes a novel nature-inspired meta-heuristic algorithm, named Snow Geese Algorithm. It is inspired by the migratory behavior of snow geese and emulates the distinctive "Herringbone" and "Straight Line" shaped flight patterns observed during their migration. The algorithm is structured into three main phases for benchmark testing. In the first phase, the Snow Geese Algorithm's numerical results are compared with those of several classical meta-heuristic algorithms using the same test functions and original data from these algorithms. In the second phase, in order to minimize potential variations during the comparison, all algorithms undergo evaluation on a standardized testing platform. In the third phase, this paper applies the Snow Geese Algorithm to solve four widely recognized engineering optimization problems: the tubular column design, piston lever optimization design, reinforced concrete beam design and car side impact design. These real-world engineering problems serve as test cases to assess Snow Geese Algorithm problem-solving capabilities. The primary objective of the Snow Geese Algorithm is to provide an alternative perspective for tackling complex optimization problems. Please note that the complete source code for the Snow Geese Algorithm is publicly available at https://github.com/stones3421/SGA-project. • Snow Geese Algorithm: A novel meta-heuristic approach inspired by snow geese flight behavior, tackling optimization problems. • Two-stage Strategy: Mimics snow geese exploration and exploitation patterns, setting it apart from traditional methods. • Performance Evaluation: Multiple algorithms are assessed on different problems. • Algorithm Features: Experimental results validate the effectiveness of the Snow Geese Algorithm. • Practical Applications: Snow Geese Algorithm shows potential in engineering optimization, aiding accurate decision-making. [ABSTRACT FROM AUTHOR]

Cold-formed steel, prized for its affordability and durability, gains enhanced structural performance through perforated patterns on beams. This study explores the impact of perforation on load-carrying capacity and capability-to-weight ratio in cold-formed steel cantilever beams, specifically focusing on "C" sections. Assessing beams of varying lengths under uniform loading, the investigation, employing ABAQUS software, reveals significant load-carrying capability reductions of 35% to 95% for beams subjected to minor-axis bends, depending on hole quantity and placement. The findings stress the imperative precision needed when incorporating perforated sections into load-bearing structural systems. Flange perforations result in substantial drops, up to 90%, in load-carrying capacity, while web holes in beams bent about the major axis cause only minor reductions. This study informs the establishment of innovative design standards for perforated cold-formed steel beams, enhancing efficiency in construction and minimizing environmental impact. The proposed cold-formed steel cantilever beam exhibits a substantial load-bearing capacity of 185.4 kg/KN, surpassing capacities of simply-supported RC beams (119 kg/KN) and fixed beams (165 kg/KN), suggesting its potential advantages in structural applications. Bridging structural engineering and material science, this research pioneers sustainable and cost-effective construction approaches for the future. [ABSTRACT FROM AUTHOR]

• Decoupling of physical phenomena reduces complexity in the calibration process • Assuming creep nonlinearity as a result of damage agrees with experimental tests • Numerical results can reproduce load level and specimen size effects • The proposed model represents well the residual capacity after high load creep This work presents a methodology to model the basic creep of concrete, considering aging and damage. Continuum elements with viscoelastic material represent the basic creep with aging using the solidification theory; interface elements with a cohesive zone model describe damage behavior through a linear softening law. Given the challenges of obtaining a unique set of parameters from experimental tests, a calibration process based on decoupling the physical phenomena is adopted. In addition, an inverse analysis is used when characterization tests are not available, allowing an indirect model calibration. Afterward, numerical results are compared with experimental data from bending creep tests. These results show that the proposed methodology can accurately represent concrete creep behavior at different load levels and specimen sizes besides predicting the beams' residual capacity observed in tests with high load levels. [ABSTRACT FROM AUTHOR]

Low-density Zeolite Aggregate (LDZA) is obtained by thermally treated zeolite in a furnace under 500°C. Thus, the water evaporates, and zeolite aggregates (ZA) are obtained with porous structures in which water molecules that make LDZA have endogenous processing properties. In this research, experimental behavior using ZA is used as a replacement portion of fine and Coarse-grained aggregate to obtain Low-density concrete (LDC) beams. The performance of normal reinforced concrete beams was contrasted with that of LDC beams based on their load-deflection behavior, ultimate load capacity, deformation profile, and crack pattern Under the effect of static load. In addition, apertures of different diameters (25, 38,50,60) mm were made in the tensile region along the aperture length of beams to minimize the self-weight of the beams. As a result of the use of zeolite aggregates, there was a decrease in the weight and density of the concrete used in casting the beams, and the results for the Normal Concrete (NC) beam were close to the results from the beam LDC. However, using Apertures in LDC beams in the tensile zone gradually reduced ultimate loads and mid-span deflection. Therefore, it is recommended to use zeolite aggregates to make LDC for use in reinforced concrete elements. [ABSTRACT FROM AUTHOR]

Shear resistance by beams without stirrups presents the transfer of shear and normal principal stresses across the open cracks within reinforced concrete (RC) beams. The complexity of the shear mechanism is further complicated by the distorted structure of RCA, which is composed of hardened adhered surface mortar and virgin aggregate. Compression field theory (CFT) postulates a series of curves for shear-loaded beams to signify the transfer of tensile and compressive stresses in concrete beams across developed shear cracks. Special attention is given to beams with recycled materials, which do not necessarily give the same strength as virgin aggregate. A numerical shear model is developed that accounted for the fracture characteristics, modes I and II of the beam containing RCA along the primary crack path from dowel action, aggregate interlock, and uncracked compression zone of the beam. The model captures the correlation of shear arm ratio, longitudinal reinforcement ratio, maximum coarse aggregate size, and concrete strength. The study model was validated using experimental results from 139 concrete beams containing RCA without stirrups. The strength ratio resulted in mean of 1.32 with a standard deviation of 0.48, a coefficient of variation of 36.8% and R-squared value of 0.65. The statistical evaluations of the model were compared with the other nine (9) theoretical models by authors and codes of practice. The developed model predicted a relatively higher shear strength value due to the inclusion of contribution from dowel action, aggregate interlock and compression zone. [ABSTRACT FROM AUTHOR]

Seven ultra high-performance concrete (UHPC) beams without shear reinforcement are tested in this work to examine their structural behavior as shear failure is a major concern in such members. Coarse aggregate was not used in two of the beams while the other five are made with coarse aggregate as 50% replacement of fine sand. Three longitudinal steel reinforcement ratios (1.14%, 1.64% and 2.46%) and three steel fiber ratios (0, 1% and 2%) are used. Results show that UHPC beams with coarse aggregate show higher ultimate loads (4.7% − 11.5%) than UHPC beams without coarse aggregate and incorporating 1% and 2% steel fiber raises ultimate loads by 60% and 131%, respectively for beams with coarse aggregate. Also, using 2% steel fiber changes failure mode from brittle shear failure by diagonal crack in beams of 0 or 1% steel fiber to ductile flexural failure by yielding of longitudinal reinforcement. Higher stiffness and toughness and lower deflections are observed with the increase of longitudinal reinforcement, steel fiber or coarse aggregate. Using 2% steel fiber highly improved toughness by more than 17 times. Lower rates of improvement are recorded for longitudinal reinforcement and coarse aggregate. However, it is recommended to perform more research to examine more parameters such as fiber types. [ABSTRACT FROM AUTHOR]

This research studies the flexural behavior of concrete beams reinforced with biaxial geogrids, distributed short glass and steel fibers. No longitudinal steel reinforcement bars were used. Therefore, an amount of short glass and steel fibers was used to improve the concrete beam behavior against flexural failure. Eleven specimens of single reinforced (flexural reinforcement) concrete beams and double reinforced (compression and flexural reinforced) concrete beams using two biaxial geogrids sheet layers, with randomly distributed short glass and steel fibers were cast. The samples were tested using two points of load along the beam specimen span with an increment of loading by 5 KN to evaluate several parameters. The studied parameters are using geogrids as a main flexural reinforcement, using geogrid sheet layers as a flexural and compression reinforcement, using short glass and steel fibers as an additional reinforcement of concrete with various ratios 0.25 %, and 0.75 %. The test results indicated that the use of geogrid layers as the main flexural reinforcement improved the behavior of the concrete beam specimens at failure. As well as; more enhancement of beam specimens at failure was observed when using short glass and steel fibers with geogrid reinforcement in concrete beams. The tested beam specimens which were reinforced by geogrids in the flexural and compression zone using 0.75 % of steel fibers gave better results due to modes of failure, toughness, failure load capacity, crack width, and post cracking stiffness. [ABSTRACT FROM AUTHOR]

Cracks will inevitably occur in concrete structural during the normal use phase due to load action, fatigue effect, and environmental corrosion. Concrete resistance can reflect some internal concrete damage. In this work, three-point bending tests were performed on concrete beams. We simultaneously measured the concrete beam resistance before and after cracking to investigate the feasibility of resistance measurement for achieving self-monitoring of concrete cracking and crack development. This work provides a methodology for the monitoring of engineering structures. It establishes a quantitative reference for the relationship between the number of steel fibers used and their conductive and mechanically sensitive properties. [ABSTRACT FROM AUTHOR]

This paper develops the pressure-impulse (P-I) diagram to conduct damage assessment of simply supported reinforced concrete (RC) beams under close-in explosion based on the equivalent single-degree-of-freedom (SDOF) model. Firstly, eleven close-in explosion tests are carried out with different charge weight, scaled distances and offset distances of explosives relative to the mid-span of RC beams. Test results show that the maximum rotation angle can characterize the comprehensive spalling/bending damage under asymmetric load, therefore it is selected as the damage criteria. Then, the equivalent SDOF model is improved by considering the influence of asymmetric load on flexural resistance, and is verified through the test results. Both test results and SDOF model show that increasing the offset distance results in asymmetric bending failure and reduces peak deflection. Through comparative analysis, the equivalent uniform load is chosen to be the axis of P-I diagram. The asymptotes and shape parameters of P-I curves are related to the offset distance and load uniformity. The relationship is derived through curve fitting and validated with the test results and the calculated results of SDOF model. This work expands the application scope of P-I diagram, which contributes to a more comprehensive damage assessment of RC structures under close-in explosion. [ABSTRACT FROM AUTHOR]

Besides the common modes of failure including compressive, tensile, and bending in concrete structures, cracking and failure due to the shear is also considered as a significant and hazardous mode of failure. The shear failure mode can be observed in structural elements such as deep beams, locations having high point loads, connection cores of beams and concrete columns, short columns, punching shear in slabs and foundations, etc. However, the direct shear strength of the fiber-reinforced concretes has seen limited studied. Hereupon, this study aims to experimentally investigate the influences of the type, length, and various volumetric fractions of the steel fiber (SF) and polypropylene (PP) fiber on the compressive strength, the tensile strength, and specifically on the direct shear strength of the fiber-reinforced concretes. To this end, four different mixture design schemes of the plain concrete were examined by adding PP and SF with lengths of 3 cm, 5 cm, and their half-half combination with volumetric fractions of 0.5 %, 1 %, and 1.5 % to measure the compressive strength (the cubic sample), the tensile strength (the cylindrical sample), and the direct shear strength (the prismatic sample) of the concrete specimens. In addition, the plain concrete specimens as the witness specimens were built to compare with fiber-reinforced ones. The experiments were not only performed for 20–25 MPa concrete strength category, but were also executed for 25–30 MPa. The constructed concrete specimens were exhaustively surveyed in terms of the contribution of the fibers, the failure patterns in various specimens, the force-displacement diagrams in shear, the maximum displacement in specimens, the aspect ratio of the fibers, and the shear ductility index in various specimens. The obtained results indicated that, with increasing the length and volumetric fraction of the fibers (i.e., the aspect ratios), the compressive, tensile, and direct shear strengths have been subsequently augmented in the concrete specimens. Moreover, the strain and ductility of the concrete specimens have also been enhanced. Remarkably, in most tests, the SF-reinforced specimens have excellent performance compared with other specimens. However, the specimens containing the PP fibers have not considerably improved the compressive and direct shear strengths of the concrete specimens. • Influences of SF and PP on the concrete specimens were experimentally investigated. • Experiments were performed for both 20–25 and 25–30 MPa concrete strength categories. • Variations of type, length, and volumetric fraction of SF and PP were applied. • Both length and volumetric fraction of SF have remarkable effect on the compressive, tensile, and direct shear strengths. • Moreover, the strain and ductility of the concrete specimens have also been increased. [ABSTRACT FROM AUTHOR]

This research investigated the behavior of RC slabs subjected to four points loading with five different CFRP sheet numbers (1, 2, 3, 4, 5) and three different anchorage systems (Type 1 used CFRP strips in the transverse direction, Type 2 used galvanized steel end plates without grooving, Type 3 used galvanized steel end plates with grooving). A total of twenty reinforced concrete (RC) solid slabs were cast to fulfill the study objectives. Results showed that the presence of CFRP strips enhanced the slab's ultimate load capacity by 102 %, reduced mid-span deflection by 12 %, also improved energy absorption capacity and stiffness by 36 % and 32 %, respectively. Type 2 anchorage system without grooves and type 3 anchorage system with grooves both used galvanized steel end plates and enhanced the flexural capacity of the slabs by 119 % and 125 %, respectively, also improved the RC slab properties and shifted the failure mode from delamination to a CFRP strips rupture. The introduced anchorage system without grooving was found to be an efficient and easily applied technique with high efficiency in terms of capacity and serviceability. • The noticed mode of failure of the control RC slab was due to flexural failure. • The debonding between concrete parent and fiber is a significant major failure mode for FRP. • Develop effective strengthening techniques for RC slabs. • Increasing the number of CFRP strips increased the toughness. [ABSTRACT FROM AUTHOR]

Due to the increasingly prominent issue of corrosion damage to the concrete structures of in-service port terminals built 30 years ago in South China, low-carbon and efficient strengthening technologies for these corrosion-damaged components have received considerable interest. In this study, a green strengthening method in which a small-diameter carbon fiber-reinforced polymer (CFRP) bar-reinforced geopolymer matrix (FRGM) system was used to retrofit damaged reinforced concrete (RC) beams exposed to chloride corrosion was developed, with a focus on the durability of the strengthened beams in a wet-dry cycling chloride environment. Electrochemically accelerated corrosion tests were performed on the RC beams, wet-dry cycling chloride environmental exposure tests were performed on the strengthened RC beams, and three-point bending tests were successively conducted using digital image correlation on the exposed beams. The various tested parameters included the following: (1) corrosion–damage ratio (10% and 20%), (2) strengthening matrix type (geopolymer (inorganic) and epoxy resin (organic)), and (3) exposure time (0, 90, 180, and 360 d). The results showed that the FRGM strengthening system effectively promoted the rehabilitation of corrosion-damaged RC beams. The substitution of the geopolymer for epoxy resin in the strengthening system with small-diameter CFRP bars had a similar short-term strengthening effectiveness and improved the ultimate loads of corrosion-damaged beams by more than 100%. However, the interface between the FRGM and old concrete in the damaged RC beam was vulnerable to chloride exposure, especially for beams with higher corrosion–damage ratios. This resulted in interface debonding, which dominated the failure modes of the FRGM-strengthened beams with increasing exposure time. Although the postexposure ultimate load of the strengthened beams with epoxy resin was greater than that with FRGM, the former exhibited greater brittleness at failure. • An FRGM strengthening system was used for retrofitting corrosion-damaged RC beams. • The postexposure behavior of the strengthened beams in a seawater environment was investigated. • The FRGM system enabled good rehabilitation of the corrosion-damaged beams. [ABSTRACT FROM AUTHOR]

guidelines require an adequate overlap length for reinforcing bars, especially in extended spans of elements constructed from Reinforced Concrete (RC). Insufficient overlap can have adverse effects on key characteristics like bending strength and deformability of RC beams. The potential danger of failure in such elements is a significant concern as is considered a potential threat, and this study addresses it through experimental identification and numerical analysis to be mitigated carefully in this study to enhance the safety and sustainability of buildings to mitigate the risk of failure. The current investigation is centered on investigating the structural behavior of cantilevered RC beams exhibiting inadequate overlap between reinforcing bars in the hogging moment region. These beams have been strengthened through the application of ferrocement layers of Engineered Cementitious Composite (ECC). The experimental study consisted of eleven beams, which were categorized into four groups and subjected to bending loads until they reached failure. The research assessed various factors, such as the casting method (whether cast-in-situ or precast), the installation technique (involving the use of epoxy, or epoxy with anchors), and the length of the ECC layer. This layer was configured to have a length of 30Ø, 40Ø, and 50Ø, with Ø representing the diameter of the reinforcing bars along the zone subjected to hogging moments. According to findings, strengthening of specimens exhibiting insufficient steel overlap through an ferrocement ECC layer exhibited an improved overall structural behavior compared to the defective control beam. The most significant enhancement in both failure mode and load-deflection behavior was observed in beams strengthened through the incorporation of a cast-in-situ ECC layer with anchor bolts. Additionally, augmenting the strengthening length not only increased the initial stiffness of the reinforced beams but also enhanced their energy absorption capacity. Furthermore, the study involved the construction of a numerical simulation employing the Finite Element Method (FEM) simulating the observed behavior in experimentally tested beams. The model's precision was validated through a comparison of its results with the experimental data, revealing a satisfactory level of accuracy. • ECC layers enhance cantilevered RC beams with inadequate lap spliced reinforcement. • Beams strengthened with ECC layers exhibit enhanced failure mode and load-deflection behavior. • Anchor bolts with cast-in-situ ECC layers improves failure mode. • FE Models accurately predict beam behavior, offering insights for further research. [ABSTRACT FROM AUTHOR]

Monitoring flexural stiffness variations of cracked reinforced concrete (r/c) structures is one of the most challenging problems of the dynamics of these structures. In this article, the application of rotation rate sensors for structural health monitoring of reinforced concrete beams is proposed as an alternative SHM method to, e.g. those utilising more expensive and laborious fiber optics. This subject was investigated with progressively damaged 6 m long reinforced concrete beams. During each damage state, the cracks were located and described in detail. Experimental modal analyses were carried out. Translational and rotational vibration modes were acquired using translational accelerometers and rotation rate sensors. The stiffness distributions of the damaged reinforced concrete beams were identified from the modal properties using model-updating techniques. It is demonstrated that stiffness distributions calculated using rotational modes are more accurate than those obtained from the familiar translational natural modes of vibrations. Further improvement of stiffness identification of r/c beams from their vibrations was obtained by combining the directly measured rotational modes and their approximations from translational modes by the central difference method. • The stiffness of cracked beams can be identified with rotation rate sensors. • Stiffness identification or concrete beams is improved with rotation rate sensors. • Only fundamental rotational mode is needed to identify the stiffness of a beam. • A sparser measurement grid can be used with translational-rotational measurements. [ABSTRACT FROM AUTHOR]

Reinforced concrete members strengthened with Fibre-Reinforced Polymer will suffer degradation when exposed to elevated temperatures or fire without an external insulation. Textile Reinforced Mortars (TRMs) can alleviate these problems posed by Fibre Reinforced Polymer epoxies at elevated temperatures. The present study deals with the thermo-mechanical behaviour of reinforced concrete beams strengthened with Textile Reinforced Mortar at elevated temperatures. Reinforced concrete beams were strengthened with Basalt and Carbon textiles and tested while the specimens were maintained in hot conditions. Carbon and Basalt TRMs were applied as one-layer and one- and three-layer, respectively. All the test specimens were heated to 200 °C, 400 °C, 600 °C, and 800 °C, followed by mechanical loading to evaluate their flexural behaviours. Strengthened members experienced common degradation of flexural strength when subjected to higher temperatures except at 400 °C. The test results revealed that Textile Reinforced Mortars can sustain temperatures up to 600 °C, but the concrete and steel underwent degradation at this temperature. At 800 °C, the Basalt textile showed signs of annealing, whereas the carbon textile oxidised from the textile reinforced mortar matrix. The study also evaluated strengthened members' thermal response and mechanical failure patterns at elevated temperatures. • Thermo-mechanical investigation of TRM strengthened RC beams. • Performance of Basalt and Carbon Textile Reinforced mortars evaluated at elevated temperatures. • RC beams were tested to failure at 200 °C, 400 °C, and 600 °C. • Noticeable flexural strength improvement at 400 °C and fibre degradation at 800 °C. • Basalt and Carbon Textile Reinforced mortars can withstand temperatures up to 600 °C. [ABSTRACT FROM AUTHOR]

The purpose of this paper is to test ten identical reinforced concrete haunched beams (RCHBs) to determine the effectiveness of pre-cast strain-hardening cementitious composite (PSHCC) plates for shear strengthening. For this purpose, the PSHCC plates have been manufactured in accordance with the test parameters, let to cure for roughly 30 days, and then dipped into the strengthened RCHBs' concrete cover at the critical shear span. The used PSHCC plates are rectangular in shape with a 20 mm thickness and a 100 mm width, and they are reinforced with a single layer of steel wire mesh. The considered key parameters were the effect of shear reinforcement in the test region, the PSHCC plate orientation angle (450, 600, or 900), and the spacing between PSHCC plates (200, 250, or 300 mm). In addition, it was interesting to observe how the strengthening plates, if they exist, are positioned in relation to the inner stirrups (aligned, un-aligned, or inclined). The application of PSHCC substantially enhanced the ultimate shear capacity of the strengthened beams, according to the results of experimental tests. Moreover, the inclined configuration of the PSHCC demonstrated higher shear performance than the vertical configuration, both in terms of the shear cracks characteristics and ultimate capacity. As well, the ductility and serviceability characteristics of the strengthened RCHBs were obviously affected by the application of PSHCC plates. Finally, a proposed analytical model was developed to estimate the shear capacity of the strengthened RCHBs using PSHCC plates. • PSHCC plates were investigated for shear strengthening of RC haunched beams. • The effect of web reinforcement, plates orientation angle and spacing were investigated. • Ten RC haunched beams under four-point loading have been experimentally tested. • A shear capacity increase of 48.8-148.5% was achieved. • A proposed analytical model was developed for predicting the ultimate shear capacity of the strengthened RCHBs. [ABSTRACT FROM AUTHOR]

This research addresses the pressing issue of horizontal crack initiation in ledge girders of post-tensioned concrete (PTC) bridges, which is a significant concern for the safety and longevity of long-span bridges. With field observations and advanced engineering computations, the study identifies the primary causes of these cracks and explores potential mitigation strategies. The research pinpoints the primary causes of horizontal crack initiation in PTC girders by analyzing 3D finite element modeling and comparing the results with the analytical solution suggested by a design code. The study also probes the potential of using external prestressing with a post-tensioning bar to mitigate horizontal cracking. The findings underscore the significance of adhering to the design code requirements for hanger reinforcement, which notably mitigates crack width in PTC girders. The research also highlights that higher prestress losses correspond to increased crack width, emphasizing the need to consider prestress losses for maintaining structural resilience. Furthermore, the study reveals that in all strengthening cases, the maximum crack width is notably reduced at the point of failure, albeit less effectively than when using rebar as per the design code. These findings underscore the potential of post-tensioning as a strengthening technique and the importance of adhering to design standards. • Investigated horizontal cracking in ledge girders of a PTC bridge designed based on the 1973 AASHTO code. • Field observations revealed uniform horizontal crack development at the ledge region of half-joints. • The 2012 AASHTO code's hanger reinforcement requirements were not met by the girder designed under the 1973 code. • 3D FE analysis validated the analytical findings, emphasizing the role of hanger reinforcement and prestress losses. • External prestressing with high-strength steel rods proposed as a strengthening technique. [ABSTRACT FROM AUTHOR]

Glulam beams reinforced with bonded steel bars are a common form. The study describes theoretical models of unbonded reinforced and prestressed reinforced glulam beams for assessing the reinforcement ratio and prestress level range, and for predicting the effect of unbonded steel bars on the flexural capacity of the beam. Considering the stress changes of beam cracking and cross-sectional stress, the minimum and maximum reinforcement ratios were determined. On this basis, the influence of the service load on the beam in the actual engineering was explored, and the force equilibrium equation was established to derive a reasonable prestress range related to the reinforcement ratio. Combined with the glulam constitutive model, and analyzed the strain distribution of unbonded steel bars was to establish the flexural capacity prediction model. The accuracy of the model was verified by the relative error between the prediction and test values ranging from-11.78% to 8.84%. • By analyzing the stress of beam cross-section in different states, the maximum and minimum reinforcement ratio calculation method for reinforced glulam beams was proposed systematically. • Considering whether the beams are subjected to service load in the construction state, the reasonable prestressing level range of glulam beams was deduced. • A flexural capacity prediction model of unbonded reinforced and prestressed glulam beams was developed. [ABSTRACT FROM AUTHOR]

Most of the current methods for estimating the shear contribution of CFRP are based on laboratory testing of small-sized specimens. The applicability of the current codes on large-sized FRP-strengthened shear walls remains debatable. The present study addresses the problem by investigating the combined effects of structural sizes and CFRP ratios on the shear contribution of CFRP. Through experiments, a series of geometrically similar CFRP-strengthened RC shear walls were designed and subjected to a cyclic horizontal loading. From the experiments, the following results can be obtained. The application of the externally bonded CFRP strips alters the failure mode and enhances remarkably the seismic resistance by suppressing crack propagation and increasing the energy dissipation. The increasing specimen size reduces the enhancement effects of CFRP on the nominal shear strength, ductility, and energy dissipation. These findings indicate that without considering the size effect, the effective strain that reflects the shear contribution of CFRP strips are greatly overestimated by the current codes. Therefore, the present study proposed and validated an effective strain factor capturing the combined effects of the structural size and the CFRP ratio on the shear contribution of CFRP strips, serving in assessing the shear strengthening effect of CFRP on shear walls. • Investigated size-dependent seismic performance of CFRP-strengthened shear walls. • Larger structure size reduced strengthening effectiveness. • Combined effects of structural sizes and CFRP ratios were investigated. • Derived a factor quantifying combined effects on CFRP shear contribution. [ABSTRACT FROM AUTHOR]

• Crack initiation load P i has been predicted using the maximum fracture load P max and FPZ length. • Analytical predictions of P i have been confirmed by experiments reported in literature. • The corresponding toughness K i and K un at P i and P max are obtained analytically. • The size-independent fracture toughness K IC are compared with K i and K un. • Simple approximation of the tensile stress at the notch tip is provided. The initial cracking load (P i) of a notched concrete beam, difficult to measure, has been predicted from the maximum fracture load (P max) together with the notch-tip fracture process zone (FPZ) at P max. A simple analytical model is used to link P i and P max together through the FPZ. The corresponding initiation and unstable fracture toughness, K i and K un , have also been determined. The model assumes that the lower limit of P max from a group of identical notched concrete beams corresponds to the lower limit of the FPZ length FPZ L , so that the lowest limit P max = P i is established for FPZ L = 0. Detailed FPZ measurements before and at P max using a digital image correlation technique were analysed and used to predict the initial cracking load P i. Six different specimens with various sizes (W = 40, 60 and 80 mm), initial notches (a 0 = 12 to 48 mm) and FPZ L (7 to 13 mm) at P max showed the average ratio of FPZ L /(W – a 0) was around 0.25, indicating the P i / P max ratio was around 0.67 based on the analytical model. The crack growth resistance K R -curve between the crack initiation toughness K i at P i and the unstable fracture toughness K un at P max was also established approximately by the simple model. Estimated intrinsic fracture toughness K IC was compared with K i and K un. The influence of average aggregate size d av on P i and FPZ L at P max was also discussed. [ABSTRACT FROM AUTHOR]

A hybrid strengthening system, comprising a carbon fiber reinforced polymer (CFRP) sheet combined with fiber reinforced concrete (FRC) layer is proposed in this study as a mitigatory solution to brittle debonding problems. Five reinforced concrete (RC) beams, comprising both control cases and those strengthened with the hybrid CFRP-FRC system at various FRP reinforcement ratios, were fabricated and tested to assess the system's effectiveness. A comprehensive finite element (FE) model was also developed to complement the experimental campaign and extend it into a parametric investigation on the effects of FRP reinforcement ratio (ρ f), fiber percentage in FRC (v f), and FRC layer thickness (t FRC). Compared with beams strengthened with FRP alone, using the FRC layer increased the ultimate load (P ult.) of FRP-strengthened beams by 29–59%, depending on ρ f and v f. The ductility of the hybrid FRP-FRC strengthened beams also increased by more than twice compared to the beams strengthened with only FRP. For the FRP reinforcement ratio (ρ f) of 0.18%, use of an FRC layer with v f = 2% yields the highest increase in P ult. and ductility for the hybrid system. Ultimately, the brittle FRP debonding failure was successfully eliminated using the FRC layer, leading to desirable FRP rupture. Built with capabilities to capture material nonlinearity, contact, and debonding phenomena, the FE model predictions excellently matched those of the test results in terms of the beam's capacity, failure modes as well as load-deflection and load-strain responses. • A hybrid strengthening using CFRP sheets combined with FRC layer is proposed. • Performance was evaluated using tests on RC beams at various FRP reinforcement ratios. • A comprehensive finite element model was developed to complement the experiment. • FRC layer serves as a mitigatory solution to brittle FRP debonding and leads to desirable FRP rupture. • Compared with FRP only strengthening, FRC layer increased the capacity by 29–59% along with up to twice the ductility realized by using FRP alone. [ABSTRACT FROM AUTHOR]

This paper investigates the behavior of reinforced concrete (RC) arch beams with shear weaknesses strengthened with fiber-reinforced polymer (FRP) composites, using two different methods: the externally bonded reinforcement (EBR) and grooving method (GM) in the form of externally bonded reinforcement on grooves (EBROG) method. Additionally, two different patterns of shear strengthening including two-sided and U-shaped were utilized. Nine arch beam specimens were tested, each having a square cross-section of 150 mm and a span length of 947 mm. Among these, two specimens were strengthened using the EBR method, while six specimens were strengthened using the EBROG method. The paper explores the impact of the strengthening method and pattern on the load-carrying capacity, failure mode, energy dissipation, and strain distribution of the specimens. The results indicate that the EBROG method significantly increased the load-carrying capacity of the arch beams compared to the EBR method in both patterns. The results also show that the U-shaped pattern was more effective than the two-sided pattern in increasing the load-carrying capacity of the specimens. The specimen with intermittent U-shaped FRP demonstrated 34.8% and 47.3% higher load-carrying capacity than the non-strengthened specimen when using the EBR and EBROG methods, respectively. The paper also introduces an analytical approach to estimating internal forces, such as flexural moment, axial force, and shear force, along the arch beam. The comparison between the experimental and theoretical results confirms the accuracy of the analytical approach. • The behavior of RC arch beam with shear weakness was investigated. • EBR and EBROG methods were adopted for strengthening of the arch beam. • PIV method was utilized to obtain the strain distribution, validate the displacements, etc. • An analytical procedure was conducted to validate the experimental results and investigate the performance of the strengthening methods. [ABSTRACT FROM AUTHOR]

In this investigation, crumb rubber (CR) was a viable substitute for concrete's conventional natural fine aggregate (FNA). This approach carries dual advantages: the conservation of natural resources and the environmentally conscious recycling of rubber waste, diverting it from traditional disposal methods. The study incorporated varying proportions of CR (5%, 10%, and 20%) by volume of the sand used in the mixtures. The primary study objective is to enhance the bond between CR particles and the surrounding concrete components by coating the CR with cement or fly ash slurry (CTR and FATR). For the limitation of the previous research discussed the CR effect on the beam's behavior, fourteen beams were poured with different rubberized concrete (RuC) and tested in flexure. This comprehensive approach sought to assess the influence of diverse factors, including rubber content, treatment materials, and the nature of internal reinforcement, on the overall performance and characteristics of the beams. The results assumed that the compressive strength was raised by 6.0–11.0% and 13.0–22.0% for the mixes cast with CTR and FATR, respectively, compared to the corresponding mixes cast with UR. Consequently, the tensile strength of the RuC-integrated CTR and FATR was raised by 5.9–11.0% and 14.0–22.0%, respectively, compared to the mixes integrating uncoating CR. Moreover, the beams cast with FATR concrete experienced the highest flexural capacities among all the steel RC beams. Furthermore, using the carbon fiber reinforced polymer (CFRP) bars as internal reinforcement for the RC beams showed the highest load capacities. • The coated and uncoated crumb rubber wastes were a viable substitute for the fine aggregate. • The compressive strength was raised by 6.0–11.0% for the CTR mixes. • The compressive strength was raised by 13.0–22.0% for the FATR mixes. • The beams cast with FATR concrete experienced the highest flexural capacities. [ABSTRACT FROM AUTHOR]

With the ongoing advancement in the construction and development of intelligent infrastructures, there has been a significant integration of sensors within structures. Portland Cement Concrete (PCC) pavement, being a predominant form of transportation infrastructures, necessitates comprehensive analysis due to its critical role. Given that flexural strength is a paramount design criterion for PCC pavements, concrete beams are selected as the primary focus for this study. Initially, a sophisticated three-dimensional numerical model is constructed. This model intricately incorporates the concepts of concrete damaged plasticity (CDP) and the cohesive zone model (CZM) to examine the interaction between the sensor and the concrete beam. The veracity of the numerical model is rigorously validated through methodical three-point bending tests, ensuring its reliability and accuracy. Subsequently, an innovative method for the synergistic design and assessment of the mechanical properties of the implantable sensor in conjunction with the concrete component is introduced. This methodology is underpinned by a novel synergistic performance index system. The system is stratified into different layers, with synergy degree as the target layer, and bearing performance, deformation coordination, and damage control as the criterion layer. In the final phase of the research, the study delves into the impacts of various factors such as size parameters, packaging materials, and positioning of the sensor on its synergistic performance with the concrete. The insights derived from this research are poised to offer valuable guidance for the integrated synergistic design of sensors. This is envisioned to facilitate optimal integration, ensuring long-term and precise monitoring of concrete structures, thereby contributing significantly to the field of intelligent infrastructure construction and maintenance. • A three-dimensional refined numerical model considering concrete damaged plasticity (CDP) and cohesive zone model (CZM) between sensor and concrete beam is established. • A synergistic design and evaluation method for the mechanical properties of implantable sensor and concrete component is proposed. • A synergistic performance index system is constructed with the synergy degree as the target layer. • A synergistic optimization design scheme of sensor is proposed. [ABSTRACT FROM AUTHOR]

• Three-point bending tests of notched beams reinforced with a GFRP bar are conducted. • A larger width of the beam was associated with a slightly greater FPZ length. • Cracked hinge model was used to study the GFRP-reinforced beam flexural behavior. • Results of pull-out tests represent an upper bound compared to beam test results. In this study, three-point bending fracture tests of notched beams reinforced with a glass fiber-reinforced polymer bar are conducted. Plain concrete beams are also tested for comparison. Two different widths are considered for the beams. Digital image correlation (DIC) is used on the lateral surface of the beam to study the fracture process zone (FPZ) and neutral axis depths at different load stages. A non-linear analytical model named cracked hinge model and cross-sectional analysis are used to obtain the force in the bar and the interfacial slip between bar and concrete, which are compared to the results from pull-out tests. [ABSTRACT FROM AUTHOR]

• The radial force generated by the prestressing of curved bottom slabs within tapered girders exerts a substantial influence on the safety, applicability, and durability of bridges. • The radial force effect is more prominent in long span box girder bridges with corrugated steel webs compared to conventional bridges due to the accordion effect of the corrugated steel webs. • A simplified analytical formula is proposed for accurately calculating the magnitude of radial forces induced by curved prestressing tendons in the bottom slab. • An optimized design approach using horizontal bottom slab with prestressing tendons positioned at the midspan of box girders, which effectively mitigates the radial force effects. The study numerically and theoretically investigates the radial force effect of long span prestressed concrete (PC) box girders with trapezoidally corrugated steel webs (TCSWs). It reveals that under the influence of radial forces, the curved prestressing tendons in the bottom slab in long span box girder bridges with TCSWs exhibited higher levels of stress and deflection compared to conventional concrete box girder bridges due to the accordion effect of the TCSWs. Furthermore, this study simplifies the radial forces as concentrated forces of PC box girder with TCSWs. Based on this simplification, a formula is derived to accurately calculate the magnitude of these radial forces. Through parameter analysis of the power exponent in the equation defining the curve profile of the bottom slab, it was observed that lower power exponents result in more significant radial force effects. Finally, to eliminate the radial force effect, the study innovatively proposed an optimized structural scheme by adopting horizontal bottom slab at midspan and arranging horizontal diaphragms uniformly across the entire longitudinal span of the bridge. A contrastive study suggested that the horizontal arrangement of internal prestressing tendons in the bottom slab at midspan could effectively eliminate the negative impact of the radial force effects and greatly improve the overall bearing capacity of the box girders with TCSWs. [ABSTRACT FROM AUTHOR]

• The failure models and collapse mechanisms of self-centering PC frames were analyzed. • Effects of different design parameters on failure modes were evaluated. • Reasonable optimization measures were suggested to reduce the concrete damage. • Collapse mechanism of self-centering PC frames were compared with RC frames. • Calculation model was proposed to predict the progressive collapse resistance. In this study, the refined finite element (FE) models for the collapse resistance of self-centering precast concrete (PC) frames with and without infill walls were established. Based on the validated FE models, the effects of different design parameters on the failure modes at the beam ends as well as the collapse resistance of the structures were evaluated. Correspondingly, the reasonable optimization measures were suggested to reduce the concrete damage at the beam ends. The results indicated that the insufficient stirrup spacing may cause the concrete failed prematurely along the edge of the steel jackets due to stress concentration. Decreasing the thickness of steel angles could reduce the failure area of concrete at the beam ends, but also caused a significant reduction in the initial stiffness and vertical resistance of the structures. The thickness of steel jackets mainly influenced the size of failure area at the beam ends. The position of horizontal bolts and longitudinal bolts had effects on the failure modes of concrete at the beam ends as well as the collapse resistance of the structures, while the latter was particularly evident. Compared to the cast-in-place reinforced concrete (RC) frames with the same size and reinforcement ratio, the damage extent at crucial locations of the optimized self-centering PC frame structures was lower, while exhibiting similar collapse resistance. A calculation model considering the resistance contribution of structural and non-structural infill wall members was proposed to predict the vertical resistance of self-centering PC frame structures in the compressive arch action (CAA) stage. The accuracy of the calculation model was verified by comparing 23 FE models with different design parameters. [ABSTRACT FROM AUTHOR]

When eccentric loadings are applied to girders with corrugated steel webs (CSWs), the longitudinal bending moments resulting from these eccentric loadings induce normal stresses on the top and bottom slabs. In addition to these stresses, the eccentric loadings also generate transverse bending moments, giving rise to warping normal stresses on the top and bottom slabs of the girders. Specifically, for long-span tapered box girders with CSWs constructed using the cantilever casting method, eccentric construction loadings induce significant warping normal stresses on both the top and bottom slabs. Notably, existing design standards solely consider bending and torsional normal stresses when addressing concrete crack resistance in girders with CSWs. In contrast, this research highlights that under eccentric loadings, distortional loading significantly amplifies normal stresses on the concrete slabs of the girders. This phenomenon is attributed to the accordion effect and the comparatively lower torsional stiffness of CSWs. Conversely, current standards do not provide formulas for calculating the normal stresses in tapered girders with CSWs under eccentric loadings. In this study, for the first time, a theoretical calculation model was proposed to evaluate normal stresses in tapered box girders with CSWs under eccentric loadings, considering the combined effects of bending, torsional and distortional effects. Through experimental investigations and finite element (FE) simulation, this study demonstrates the high accuracy of the proposed theoretical model. Additionally, this study introduces the concept of normal stress amplification factors to quantitatively analyse the composition and magnitude of normal stresses in tapered girders with CSWs under eccentric loadings. • A normal stress analysis model for tapered girders with corrugated steel webs under eccentric loadings is proposed. • The bending normal stress and warping normal stresses on the girder with corrugated steel webs are calculated separately. • The normal stress amplification factors are introduced to reveal the magnitude and patterns of normal stresses. [ABSTRACT FROM AUTHOR]

Conventional reinforced concrete coupling beams are subject to severe damage after earthquakes, resulting in costly repairs or even the need for complete demolition. In order to improve the seismic resilience of coupled wall structure, a new self-centering coupling beam (SCCB) incorporating self-centering friction dampers (SCFDs) is proposed. The proposed coupling beam consists of an elastic beam segment and a fuse part. The fuse parts consist of four SCFDs arranged in a diamond shape and two chord members. The SCFD is the core component, which provides strength and stiffness to the coupling beam and reduces the residual deformation of the coupling beam. Since the damper and chord members are joined by dowels, they are easily removed and replaced after an earthquake. In addition, the SCCB can eliminate the beam elongation effect. The working principle and design methodology of the SCCB are described in detail. Cyclic loading experiments were carried out on the SCCB, and the results showed that the SCCB had good self-centering and energy dissipation capabilities. The influence of friction force and loading rates on the seismic performance of SCCB was investigated. Among all the tested specimens, the maximum residual rotation is 0.0095 rad and the minimum residual rotation is 0.0035 rad. Finally, the SCCB was tested for replacement to assess its replaceability. Experimental results show that the damaged components can be replaced by two workers within 30 min, and the seismic performance of SCCB after replacement is basically the same as before. • An innovative self-centering coupling beam incorporating self-centering friction dampers is proposed. • The effects of friction force of the damper and loading rate on the coupling beam was investigated experimentally. • Replacement tests were conducted to assess the seismic resilience of the self-centering coupling beam. [ABSTRACT FROM AUTHOR]

Corrosion of reinforcement in concrete civil structures poses a significant challenge to their integrity and durability. To ensure the safety and longevity of such structures, effective monitoring strategies that can accurately detect, localise and assess the progression of damage are crucial. For most existing concrete structures, this is often challenging, as damage is already present when the monitoring campaign starts. In addition, reinforced concrete structures can be subject to a combination (or a succession) of corrosion and load-induced damage. By combining multiple measurement techniques, a more accurate and reliable condition assessment of concrete civil structures can be aimed for. This paper presents a comprehensive experimental study of the combination of vibration-based monitoring (VBM) and acoustic emission (AE) sensing techniques during progressive load tests of corroded reinforced concrete beams. Five beams were subjected to a cyclic four-point bending test, three of which were previously corroded while two beams remained undamaged prior to the mechanical loading. The influence of pre-existing corrosion damage and corresponding longitudinal concrete cracking on the modal characteristics (natural frequencies and strain mode shapes) and AE outcomes is investigated during the four-point bending test. The monitoring results obtained by both techniques are shown to be influenced by the pre-existing longitudinal concrete cracking caused by the reinforcement corrosion. Lower AE activity and a lower reduction in natural frequencies is observed for corroded RC beams during load bending tests when compared to uncorroded specimens. In addition, bending cracks occurring within the corroded zones appear to have a very limited effect on the identified strain mode shapes. These observations could possibly result in an underestimation of the damage and corresponding overestimation of the load-carrying capacity, as the corrosion damage conceals the occurrence of bending cracking on the AE and VBM outcomes. • Combined approach of AE and VBM is employed to assess mechanical damage in previously corroded RC beams. • AE signals during load testing and during reinforcement corrosion are compared. • Pre-existing corrosion damage shows a significant influence on the AE and VBM outcomes. • AE localisation and strain mode shapes can detect and localise early concrete cracking. [ABSTRACT FROM AUTHOR]

In this study, the gradually anchored technique is combined with the prestressed near-surface-mounted (NSM) carbon fiber-reinforced polymer (CFRP) strengthening technique to reduce the stress concentration caused by prestress transfer at the CFRP end section and improve the failure mode and bearing capacity of strengthened beams. Flexural performance tests are conducted on one fully prestressed and six gradually prestressed NSM CFRP-strengthened reinforced concrete beams under static loads. The influencing factors include the gradient prestress, CFRP bond length, concrete cover thickness, and steel reinforcement type. The failure mode, characteristic load, shear stress distribution at the CFRP end section, as well as the crack development under prestress and load are analyzed. The test results indicate that the gradually prestressed beam is superior to the fully prestressed beam in reducing the stress concentration at the CFRP end, thereby inhibiting the development of cracks at the CFRP end, improving the bearing capacity, and delaying the separation of concrete cover. The bearing capacity and ductility of the strengthened beams are significantly improved, with a maximum increase of 35% and 100.33% for them respectively, confirming the effectiveness of the gradually prestressed NSM CFRP strengthening technique. Finite element analysis is conducted to further investigate the effect of gradient prestress on flexural performance of strengthened beams and propose design suggestions. • Static load tests were performed on RC beams strengthened with gradually anchored prestresses NSM CFRP. • Prestress setting parameters and reinforcement layout of RC beams were studied. • Finite element model was established, and the recommended parameters of gradient prestress were given. [ABSTRACT FROM AUTHOR]

Iron-based shape memory alloys (Fe-SMAs), which are emerging as a novel class of self-prestressing materials dispensed with in situ tensioning, have been studied primarily in the field of structural strengthening. In addition, the self-prestressing characteristics of the Fe-SMA rebars are extremely promising for new concrete bridges that are seriously affected by prestress loss during their service life. Therefore, the effect of self-prestress generated by embedded Fe-SMA rebar was experimentally investigated by six concrete T-beam. The influence of factors such as the activation status, prestress value, and diameter of the Fe-SMA rebar on the flexural performance was investigated. The variation laws of the cracking load, yield load, ultimate load, and stiffness were analyzed. The results illustrated that the activation of the Fe-SMA rebar had a remarkable influence on delaying beam cracking. Under the same load (130 kN), the specimens with an activated Fe-SMA rebar exhibited a remarkable reduction exceed 30% in crack width compared to those with an unactivated Fe-SMA rebar. Following the activation, the cracking load, yield load, ultimate load, and stiffness increased to varying extents,. The Fe-SMA, characterized by its remarkable ductility, exerted a beneficial influence on the deformation capability of the beams. This enhancement became notably conspicuous following Fe-SMA activation. Analysis of the cracking load and concrete strain during the activation process indicated that the prestress of the embedded Fe-SMA rebar closely approximated the values observed in the rigid confinement. The calculated flexural capacity agreed with the experimental data, and the proposed calculation method can provide a reference for subsequent research. • The flexural properties of T-shaped concrete beams reinforced with Fe-SMA rebar were investigated. • The activation of the Fe-SMA rebar had a remarkable influence on delaying beam cracking • The Fe-SMA exerted a beneficial influence on the deformation capability of the beams. • The method for calculating the flexural capacity of a T-beam with a Fe-SMA rebar is proposed. [ABSTRACT FROM AUTHOR]

This paper presents the results of an extensive experimental campaign aimed at evaluating the feasibility of using steel-reinforced earthen materials for load-bearing structural applications, with a focus on a new category termed "shot-earth". Addressing excavated soil, a major source of construction waste, shot-earth demonstrates remarkable properties, such as notable green strength and reduced water sensitivity. The experimental program includes four-point bending tests on steel-reinforced shot-earth beams, along with pull-out tests to assess the adherence between ribbed steel bars and shot-earth. A flexural design approach, traditionally suited for reinforced concrete, is presented and validated to establish a reliable model for reinforced shot-earth elements in bending state. These findings suggest that leveraging existing models for reinforced concrete can overcome some traditional challenges associated with earth-based constructions, promoting them as a viable and ecological alternative to conventional construction materials. • Shot-earth material is studied here to realize load bearing structural elements for the first time. • Single span beams reinforced with steel rebars have been experimentally investigated. • Four-point loading bending tests equipped with a LVDT system have been performed. • A sectional constitute law has been adopted to predict the moment-curvature response of the beam cross sections. • It has been shown that the ultimate strength of the shot-earth beam reaches values comparable with those exhibited by concrete beams keeping fixed the geometric data. [ABSTRACT FROM AUTHOR]

Hybrid reinforced concrete steel (RCS) frames consisting of reinforced concrete (RC) column and steel (S) are used frequently in practice for mid-to-high-rise buildings. RCS frames possess several advantages from structural, economical and construction view points compared to either traditional RC or steel frames. One of the key elements in RCS frames is the beam-to-column joint. This paper suggests a design method to evaluate the mechanical behaviour of a novel type of exterior RCS beam-column connection in which a steel profile totally encased into a RC column is used to connect the beam through the steelwork part of composite section. The proposed design model is developed considering experimental test results and finite element (FE) analyses. In the first part of the paper, an experimental investigation on the static behaviour of the hybrid joint is presented. Four full-scale specimens were tested under monotonic loading. The primary differences between the specimens are the concrete class and the anchorage length of the embedded steel profile in the RC column. The experimental results indicated that the overall behaviour of the specimens was significantly affected by the shear panel deformations of the embedded profile. Next, a finite element model was created. The FE model predictions compared favourably against experimental tests and confirmed the order of yielding/cracking of joint components. Finally a design method based on Eurocodes 2, 3 and 4 is proposed to determine the initial rotational stiffness and the bending resistance of the joint. • Experimental tests on hybrid steel beam to RC column joints with encased steel profile. • Limited impact of long encased steel profile on mechanical characteristics. • Order of yielding/cracking of components evaluated experimentally and by finite elements. • An Eurocode model for the initial rotational stiffness and bending resistance. [ABSTRACT FROM AUTHOR]

• The effect of bond length of NSM FRPs was examined on the performance of strengthened RC beams. • The effect of mechanical grooves was examined on the performance of strengthened RC beams. • An advanced FE model was developed to optimize the bond length of NSM FRPs. The near-surface-mounted (NSM) fiber-reinforced polymer (FRP) technique is effective for enhancing the load carrying capacity of strengthened reinforced concrete (RC) beams. However, this technique significantly reduces the deformability of strengthened RC beams. To overcome this, the present study combines the NSM strengthening method with the partial bonding technique: the strengthening FRP reinforcement is partially bonded onto the concrete substrate). Six full-scale 4.3 m long RC beams strengthened with NSM FRPs using various bonding patterns were tested. The results indicated that mechanical interlocking grooves slightly improve the load carrying capacity, but have a negligible effect on the deformability of the strengthened beams. A decrease in the bond length increased deformability by 27.2 %, with only a 7.6 % drop in load capacity compared to that of the beam with full bonding. An advanced finite element model was developed and validated to confirm an optimal bond length of 930 mm for maximum flexural performance. [ABSTRACT FROM AUTHOR]

This research study investigates the potential of using Calcium Sulfoaluminate (CSA) binder as a sustainable alternative to ordinary Portland cement (OPC) in the production of precast concrete tunnel lining (PCTL) segments. The effectiveness of CSA-based concrete, reinforced with Glass Fiber-Reinforced Polymer (GFRP) bars, was examined through an experimental program. Comparative analyses, including analytical, experimental, and Life Cycle Assessment (LCA) comparisons, were conducted with OPC-based segments reinforced with traditional steel. The results indicate that the proposed CSA/GFRP solution has the potential to improve sustainability in mechanized tunnelling and prefabrication. A case study is also presented to support these findings. • Eco-sustainable process for mechanized tunnel lining construction. • Calcium Sulfoaluminate binder and GFRP bars in the production of tunnel segments. • Full-scale performances of CSA cement-based precast segments with GFRP bars. • LCA and carbon footprint comparison of OPC/steel and CSA/GFRP tunnel segments. • Case study with theoretical prediction of the construction phases. [ABSTRACT FROM AUTHOR]

A new type of stay-in-place formwork (SIPF) concrete beam was proposed; this beam consists of a U-shaped shell made of basic magnesium sulfate cement-based composite (BMSCC), a perforated square steel pipe and core concrete. The prefabricated shell and square steel pipe form a composite SIPF, the steel pipe replaces the longitudinal reinforcement and hoop reinforcement, and the combination beam can be formed after pouring the core concrete inside. Four-point bending tests of two SIPF beams and one reinforced concrete (RC) comparison beam were conducted using longitudinal steel consumption as a parameter. The results showed that the SIPF beams exhibited a typical ductile damage pattern and that the precast shell was reliably bonded to the core concrete without spalling. The cracking load was increased by 198.25 %, the yield load by 66.3 %, and the ultimate load by 64.7 % for the same amount of steel used in the steel pipe instead of the reinforcing cage. After the equivalent longitudinal reinforcement rate of 1 % at the bottom of the SIPF beam was increased to 1.25 %, the flexural capacity increased by 9.65 %. By introducing the restraining stress coefficient and stiffness contribution coefficient, a formula for calculating the flexural capacity of the positive section of the SIPF beam was established. • A new type of SIPF concrete beam was proposed. • BMSCC is environmentally friendly, high strength and durable. • The precast shell was reliably bonded to the core concrete without spalling • The SIP beam can significantly increase the cracking load and ultimate load. [ABSTRACT FROM AUTHOR]

Modular Integrated Construction (MiC) has gained prominence as a construction method, and the integrity of its structural connections plays a critical role in ensuring the overall stability and safety of buildings. This paper presents an experimental investigation into the static and hysteretic performance of grouted steel beam-column inter-connections designed for MiC. The study examines eight full-scale specimens subjected to both monotonic and cyclic loading conditions, with a focus on failure characteristics, deformation behavior, loading-displacement curves, loading-strain curves, skeleton curves of hysteretic loops, stiffness degradation, and energy dissipation. Key findings of the study include the observation of weld cracking between beam flanges and columns in all specimens, highlighting the necessity of welding quality control to prevent such issues. Grouted connections exhibited superior integrity, with no gap opening or misalignment between upper and lower columns. Additionally, it was found that grouting could enhance the stiffness of certain connections. Removal of diagonal stiffeners significantly decreased peak bearing capacity, emphasizing their importance. The composite action brought about by bolts connecting ceiling and floor beams also proved influential. According to Eurocode 3, all grouted specimens fall under the classification of semi-rigid connections, with a distinction made for partial and full-strength connections. This research contributes valuable insights into the static behavior and hysteretic performance of grouted steel beam-column inter-connections for MiC, providing essential knowledge for the structural design and safety of buildings utilizing this innovative construction method. • Propose novel grouted steel beam-column inter-connections for MiC. • Conduct static monotonic and quasi-static cyclic loading tests on grouted connection. • Explore the static behavior of grouted connection considering different factors. • Investigate the effect of diagonal stiffeners, grouting and bolts on the hysteretic performance. • Conduct the joint classification. [ABSTRACT FROM AUTHOR]

An experimental program was conducted to examine the seismic performance of flexural beam members strengthened with carbon fiber-reinforced polymer (CFRP) sheet and anchored using carbon fiber splay anchors. This research study extends the use of carbon fiber anchors to secure the top and bottom CFRP flexural sheets under cyclic loading. In this study, low strength concrete is examined, with lightly reinforced steel ratio (0.0034) to test full-scale rectangular beams. Five reinforced concrete beams were cast, strengthened, and tested under reversed cycles of four-point bending to failure. The beams were categorized into a control specimen, strengthened specimens with thin sheets with and without fiber anchors, and strengthened specimens with thick sheets with and without fiber anchors. They were tested cyclically under displacement control according to the AC 125 loading protocol. The failure modes ranged from classical ultimate failure for the control beam to rupture and intermediate crack (IC) debonding for the beam with unanchored thin CFRP sheets. On the other hand, debonding took place for the thicker sheets with no anchors, while the thicker sheets with fiber anchors underwent cover delamination failure mode despite the fact that the sheets were extended very close to the simple supports. The hysteresis response loops were compared for the different specimens and the analytical envelop curves were predicted resulting in a close agreement to the experimental finding. • Seismic performance of flexural beams CFRP strengthened with and without carbon fiber anchors is successfully examined. • Thicker CFRP sheets yield lower energy dissipation, ductility, but higher strength and seismic pinching. • Failure modes varied from sheet debonding to CFRP rupture and cover delamination. • The use of anchors at sheet ends was not very effective in extending the hysteretic cycles beyond those without anchors. • The need to apply fiber anchors along the entire shear span to harness improved behavior is clearly evident. [ABSTRACT FROM AUTHOR]

Longitudinal cracks at the bottom of the deck are a common form of hidden damage in box girder bridges. Timely detection of deck cracking is critical to ensure the safe operation of box girder bridges. This paper proposes a damage detection method for the deck of box girder bridges using mode shapes constructed from a moving vehicle. One stationary excitation vehicle excites the local bending modes of the deck, and the other vehicle moves along the planned path. The moving vehicle acceleration is collected to construct mode shapes on the driving path. First, generalized beam theory is used to analyze the dynamic behavior of the box girder bridge. The theoretical model of the proposed approach is built to analyze the response of the vehicle-bridge system under shaker excitation, and mapping relationship between the instantaneous amplitude of the vehicle response and the local bending mode of the deck is deduced. The damage indicator based on the mode curvature is used to determine the crack position. Then, a damage detection process for field testing is proposed. Technical details such as excitation parameters, driving path, and narrowband filtering are explained. Finally, factors that affect damage detection, including road roughness, crack length, and crack height are investigated via numerical analysis. Results show that the proposed method can detect medium damage. • Dynamic characteristics of the box girder bridge are analyzed through generalized beam theory (GBT). • Vibration characteristics of the deck are clarified based on the proportion of each GBT deformation mode. • Relation between the vehicle response and the bending mode of the deck is revealed by Hilbert transform. • Damage detection process for field testing of bridges is proposed, and technical details are explained. • Influence of road roughness, crack length and crack height, are investigated via numerical analysis. [ABSTRACT FROM AUTHOR]

Fire is an accidental disaster resulting in disastrous consequences for building. Post-earthquake fire is a secondary disaster induced by earthquake, triggering off larger destruction in a higher probability of occurrence. The potential severity of consequences to structures makes fire and post-earthquake fire safety imperative in the design of any new structures. Self-centering concrete joints are introduced as a promoting alternative to traditional reinforced concrete (RC) joints. They always exhibit excellent seismic performance and self-centering capacity, available in high-seismic zone. However, the current lack of experimental data on fire response of self-centering concrete joints means that they remain an open issue in current design codes. In this paper, full-scale quasi-static cyclic test and fire tests were conducted on two self-centering concrete joints connected with bolted angles and posttensioned (PT) tendons. The experiments aimed to explore the performance of self-centering joint in fire situations, and the impact of post-earthquake damages on fire response of self-centering joint. The deformation patterns and thermal responses of self-centering joints including temperature distribution, prestress force of PT tendons, displacements at beam ends and duration were recorded and analyzed. The results show that both self-centering joints exhibited satisfactory fire resistance with endurance over 170 min. Generally, the bolted angles and PT tendons in self-centering concrete joints showed acceptable working performance in fire. The findings unveil the actual response of self-centering concrete joints during the fire and post-earthquake fire conditions, providing experimental data for further numerical simulation and analysis. It can be used to calibrate the design approach for self-centering joints under fire and seismic-induced fire exposure. • Fire resistance of self-centering concrete joint was reported. • Structural and thermal response of self-centering joint exposed to post-earthquake fire identified for the first time. • The damages in RC beam and column were controlled in earthquake to enhance the post-earthquake fire resistance. • The fire resistance of self-centering concrete joints was over 170 min even after cyclic loading of a 2% drift ratio. [ABSTRACT FROM AUTHOR]

With the construction and development of intelligent roads, an increasing number of sensors are being embedded into the road structures. Portland cement concrete (PCC) pavement is one of the main forms of road pavement, but the mechanical behaviors of the PCC pavement with sensor embedding are less studied. In this study, the damage mechanism of PCC pavement is investigated by using the three-point beam bending test, considering the sensor embedding and the coating of the sensor surface. The effect of sensor embedding on the flexural mechanical properties and the damage failure modes of concrete beams are evaluated by using the acoustic emission (AE) technique and the digital image correlation (DIC) technique. Moreover, the concept of degree of coupling (DC) is introduced to reveal the collaborative bearing mechanism between sensor and concrete, and is characterized by an evaluation model considering ultimate bearing capacity, critical instability point, collaborative bearing capacity, AE ring counts, and AE energy. The findings can provide valuable insights in the packaging design of sensor to guarantee the coupling between the sensor and the surrounding concrete for accurately monitoring the long-term performance of road infrastructure. • The damage evolution of concrete beam implanted with sensor with different surface coating were conducted through three-point bending test. • The acoustic emission (AE) data and digital image correlation (DIC) data of concrete beam embedded with sensor or not were discussed. • The degree of coupling (DC) is introduced to reveal the collaborative bearing mechanism between sensor and concrete. [ABSTRACT FROM AUTHOR]

A redesign was attempted for the concrete-filled double-skin tube subjected to bending, and by adjusting the core tube position and applying carbon fiber-reinforced polymer (CFRP) sheets or steel bars in the tensile region, it was hoped to delay the cracking of the concrete in the tensile region. Epoxy mortar was used to modify the interface. Seawater and sea sand has been successfully applied from reinforced concrete beams to concrete-filled steel tube beams, benefiting from the corrosion-resistant properties of CFRP and epoxy mortar. The four-point bending test parameters included the type of core tube, the number of CFRP layers, and the diameter of the steel bars. The beams with FRP sheets exhibited better flexural capacity and residual stiffness, while the brittle fracture of FRP led to major crack in concrete. The beams with steel bars exhibited better initial stiffness and the cracks in concrete were more uniform in width. When the layers of CFRP or the diameter of the steel bars was increased, the flexural capacity of the composite beams increased by 11.0%-13.6% and 7.0%-9.1%, respectively. The enhancements provided by the core tubes were small, and the design of the composite beams should be considered from various perspectives. The moment-curvature relationships, ultimate states, and flexural stiffness were defined by considering concrete cracking, FRP fracturing, and steel buckling. Several formulas for calculating flexural stiffness in the code were evaluated in combination with the test data. • CFRP-steel composite beams with seawater sea sand concrete core were presented. • Flexural performance, strain and deflection curve distribution were evaluated. • Designing FRP in tensile region is more effective in improving mechanical properties. • A flexural stiffness calculation model for the composite beams was established. [ABSTRACT FROM AUTHOR]

• A 3D meso-scale numerical simulation method of CFRP strengthened RC beams is established. • The coupling effect between shear-span ratio and CFRP fiber ratio is explored. • The quantitative relationship between the contribution of CFRP and shear-span ratio is analyzed. • The effect of shear-span ratio and CFRP fiber ratio on the size effect is investigated. • The shear strength size effect law of CFRP strengthened RC beams is proposed. In this study, a 3D meso-scale numerical simulation method is established for analyzing the shear failure of carbon fiber reinforced polymer (CFRP) strengthened RC beams without stirrups. The inhomogeneity of concrete, the bond-slip relationship between steel bars and concrete, and the interaction between CFRP and concrete are considered. Based on this method, effects of shear-span ratio and CFRP fiber ratio on the shear performance and nominal shear strength size effect of CFRP strengthened RC beams are investigated. Results indicate that the size effect of CFRP strengthened RC beams is obvious, however, the shear-span ratio has little impact on the size effect of nominal shear strength of RC beams. The CFRP fiber ratio enhances the shear strength of RC beams on the one hand, while weakens the shear size effect of RC beams on the other hand. However, its influence on the shear performance of RC beams remains basically unchanged with varying shear-span ratios, indicating that there is no coupling effect between the shear-span ratio and CFRP fiber ratio. The shear-span ratio significantly influences both the shear bearing capacity of RC beams and the shear contribution of CFRP sheets, with the increase in the shear-span ratio, the shear bearing capacity of RC beams decreases to varying degrees, and the shear contribution of CFRP sheets increases initially and then decreases. Finally, the shear strength size effect law (SEL) of CFRP strengthened RC beams is proposed, which can quantitatively describe the effects of the shear-span ratio and the CFRP fiber ratio. [Display omitted] [ABSTRACT FROM AUTHOR]

In the DEMO power plant design, the bioshield roof above the tokamak is a steel structure with radial beams and concrete inserts. A contamination protection structure (CPS) is placed on the bioshield roof to protect other areas against the potential release of any radioactive materials from inside the reactor during maintenance. It also provides support to the cask, which is used to transfer the heavy blanket segments to the active maintenance facility (AMF). Herewith, the structural design of the CPS and the bioshield roof is investigated using parametrized FE models in the Ansys APDL environment. The results of the linear static analysis show that the stress in the CPS as well as in the structure of the bioshield roof is within the acceptable range. However, linear buckling analysis shows that the CPS may lose stability due to buckling. The proposed design modifications resulted in a structure that is sufficiently strong and rigid to withstand all load conditions. The analyses revealed that the actual loads acting on the bioshield roof structure, due to the CPS and its handling structures, are lower than assumed during its preliminary design, therefore it is possible to reduce the dimensions of the bioshield roof beams and girders in the future. [ABSTRACT FROM AUTHOR]

• A new type of the connection of the S-CSC column and the U-SCC beam was developed. • Seismic performance of the connection was systematically evaluated. • The force transmission path and force mechanism of the connection were presented through FE model. • The influence of each part of on the bearing capacity of the connection was analyzed. • The formula for calculating the shear capacity of the connection was proposed. The steel tubular-corrugated steel plate confined concrete composite column (S-CSC column) and the reinforced concrete beam with U-shaped corrugated steel webs (U-SCC beam) have recently been developed as efficient steel-concrete composite construction. The connection method of the S-CSC column and U-SCC beam with convenient construction and clear force transmission was proposed based on the design principle of "strong connection and weak member". A cyclic loading test was conducted on the S-CSC column and U-SCC beam connection to analyze failure modes, load-displacement curves, strains in the core region of the connection, energy dissipation capacity, and stiffness degradation. Experimental results revealed that the connection's ultimate failure occurred at the beam, where the plastic hinge zone underwent outward relocation, while the core region of the connection remained undamaged. The load-displacement curves exhibited full, indicating a good energy dissipation capacity and strains in the core region of the connection were uniformly distributed across various positions. To elucidate the force transmission path and force mechanism of each component within the core region of the connection, a finite element model was established. Additionally, parametric analyses were conducted to examine the impact of different parameters on the connection's bearing capacity. Lastly, based on a shear model that considers the concrete and steel in the core region of the connection, a calculation method for shear capacity was proposed. [ABSTRACT FROM AUTHOR]

Round-ended concrete-filled steel tubular (CFST) columns have numerous benefits, including easy construction, aesthetic appearance, and variable section arrangement. This study experimentally and numerically investigated the flexural behavior of round-ended CFST columns. The six testing results showed that as the aspect ratio increased from 1.38 to 1.86, the flexural resistance and stiffness increased by 82.0% and 159.9%, respectively. Every round-ended CFST specimen had excellent ductility. Concrete can be adequately confined by the round-ended steel tube. Mechanistic and parametric analyses were carried out using a finite element model. Mechanistic analysis demonstrated that the round segment of the steel tube can effectively confine the concrete, resulting in a considerable strength gain near the edge of the compression zone. The parametric analyses showed that as the concrete strength increased from 24 to 110 MPa, the flexural resistance increased by average 20.4%; as the steel strength improved from 235 to 700 MPa, the flexural resistance increased by average 155.4%; as the steel ratio enhanced from 0.05 to 0.2, the flexural resistance increased by average 179.7%; and as the aspect ratio increased from 1 to 3, the flexural resistance of the major (minor) axis increased (decreased) by about 59.9% (36.5%). The analysis showed that the flexural stiffness of this composite specimen can be accurately predicted by AISC 360–2016. Finally, a simplified model was proposed for estimating the flexural resistance of the round-ended CFST specimens. • Flexural tests of six round-ended CFST specimens with higher strength concrete were conducted. • A finite element model was developed for the round-ended CFST beam. • Parameters analysis about the round-ended CFST beams was carried out. • Simplified models for its flexural resistance and stiffness were evaluated. • A simplified model for its flexural resistance was proposed. [ABSTRACT FROM AUTHOR]

The influence of steel reinforcement corrosion on both the bond strength between steel reinforcement and concrete and the mechanical properties of steel reinforcement has been a subject of continuous investigation, with significant implications for the durability and failure of reinforced concrete (RC) structures. This paper introduces Cohesive elements between the steel reinforcement and concrete to propose a new method to present their bond–slip behavior. Then, this paper focuses on corroded RC beams and establishes refined finite element (FE) models that effectively captures the degradation of steel reinforcement due to corrosion. the effects of longitudinal reinforcement and stirrups with different corrosion extents on the degradation of the mechanical behavior of RC beams are discussed in detail. Comparative analyses of the flexural and shear load-carrying capacities between the FE models and experimental models are conducted. The results illustrate that the FE models established by the proposed method in this paper accurately reflects the load-carrying capacity of RC beams affected by corrosion. The corrosion of steel reinforcement has a great influence on the failure mechanisms of RC beams. As the stirrup corrosion extent increased, the RC beam gradually changed to brittle failure. • Show the failure mechanisms of corroded reinforced concrete (RC) beams in detail. • Consider the effects of rebars corrosion on the mechanical behavior of RC beams. • Propose a method to present the bond-slip behavior of corroded RC beams. [ABSTRACT FROM AUTHOR]

This paper proposes a direct analytical model to evaluate compressive arch action (CAA) of reinforced concrete (RC) beam-column sub-assemblages under middle column removal scenario (MCRS), incorporating bending curvature of the double-span beam, and different horizontal and rotational restraint conditions at the beam ends. Based on the proposed approach, the structural engineer can easily obtain the CAA peak capacity and the corresponding CAA displacement by hand calculations. Unlike the previous models in which the accuracy highly relies on pre-assumed CAA displacement, this prediction approach directly derives the CAA displacement and CAA capacity through force equilibrium, geometric relationship, compatibility and boundary conditions, incorporating various horizontal restraint conditions, span-to-depth ratio and section profile of the bridging beam. Comparison with existing test results in available literature indicates that this model not only gives good predictions of peak capacity, displacement and maximum axial beam force in CAA, but also incorporates the effect of horizontal restraint stiffness and working stress of compression reinforcement. Besides, a further simplified explicit model is proposed to enhance usability in practical design, and sensitive studies are conducted to study how the simplification affects the prediction accuracy of vertical CAA capacity and displacement. Thereafter, the proposed model is extended to substructures with orthogonal beams in X- and Y- directions to predict CAA capacity under different column removal scenarios such as interior, penultimate, edge and corner column removal cases. • An easy-to-use analytical model to predict compressive arch action of RC beams under middle column removal. • Bending curvature, horizontal and rotational restraint conditions of beam are considered. • The model does not rely on pre-assumed CAA displacement. • Effect of horizontal restraint condition on CAA displacement and capacity can be well considered. • The model is extended to two-way framed substructures under different column removal scenarios. [ABSTRACT FROM AUTHOR]

This research has investigated the ability of ultra-high performance concrete (UHPC) to improve the blast performance of high-strength concrete (HSC) beams. As part of the study 4 shear-deficient HSC beams built without stirrups and with dimensions of 125 mm × 250 mm × 2440 mm were retrofitted with a UHPC jacket and tested under simulated blast loads using a shock-tube. The retrofit involved replacing the existing cover with a cast in-situ UHPC jacket (with thickness of 20–40 mm). A companion set of beams was also tested under quasi-static four-point bending. The results from the blast and static tests are compared to a control set of HSC beams built without and with stirrups to examine the ability of UHPC to increase shear and flexural resistance, respectively. The effect of steel ratio (ρ = 1.6% or 2.4%), an important parameter which affects the behavior of HSC and UHPC beams, was also investigated in beams with 15M and 20M bars. Under static loading, the results show that the UHPC jacket was able to prevent shear failure, and improve flexural performance by increasing strength by 40–125%, stiffness by 80–100% and overall toughness by 56–144%, when compared to the companion HSC beams. Under blast loading, the UHPC increased shear capacity, prevented shear failure and improved blast performance by reducing displacements, increasing overall blast capacity and improving damage tolerance. For example, in the 20M set, the UHPC-retrofitted beam showed reductions of 26–63% in maximum displacements, and 88–100% in residual displacements under varying blast intensities. The steel ratio was found to play an important role on the failure mode of the retrofitted beams under static loading, with bar fracture observed in the beam with lower steel ratio of 1.6%. As part of the numerical study, the blast response of the UHPC retrofitted beams was predicted using 3D finite element (FE) modeling. The FE models were able to predict the failure modes and maximum displacements of the control and UHPC retrofitted beams, with an average numerical-to-experimental displacement ratio of 1.03 and an average error of 8%. • Ability of UHPC to improve shear/flexural response of HSC beams under static/blast loads is investigated. • UHPC prevented shear failure and promoted flexural response in shear-deficient beams under static and static/blast loads. • Compared to beams with stirrups, the UHPC retrofit increased blast capacity and reduced blast-displacements. • The UHPC further increased damage tolerance and prevented formation of blast fragments. • FE modeling of the beams was conducted with LS-DYNA with good predictions of displacements and damage modes. [ABSTRACT FROM AUTHOR]