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Timber is arguably the oldest construction materials that human have used since the dawn of civilization. Since the last few centuries, the invention of concrete and steel materials has limited timber uses to small and medium structural applications. The renaissance of timber construction has been felt recently due to the emergence of engineered massive timber elements that can perform similar structurally to that of concrete. The main objective of this paper is to study feasibility using massive timber element in building to be constructed in the futuristic city LINE-NEOM, Saudi Arabia. The main motivation of this study is the sustainability aspect of timber that can contribute to zero carbon emission for buildings, which will be one of the major environmentally friendly goals for LINE. Literature survey was conducted to demonstrate that timber is promising construction material for future building. A comparative case study of multi-story building constructed using traditional reinforced concrete and massive timber elements was performed. One particular type of massive timber element called Cross Laminated Timber (CLT) was used in this study. Key structural performance of building was compared using applicable design code criteria. Furthermore, carbon emission of buildings constructed with reinforced concrete and CLT was analyzed and compared. The structural analysis and design results indicated that the CLT building was acceptable in term of lateral deformation or drift under critical combination of lateral and gravity loads. The carbon emission comparison showed that CLT building outperformed the reinforced concrete building significantly. As was anticipated, the CLT building stored significant amount of carbon making it an excellent alternative materials for buildings in LINE that has goal to be zero-net carbon's city. [ABSTRACT FROM AUTHOR]

Externally restraining volume changes of concrete, that is, thermal effects and shrinkage, may result in tensile stresses and eventually cracking. Such cracking risk is controlled/mitigated by the provision of steel reinforcement, which presumes a correct understanding of the cracking patterns under different types of restraint conditions. Reinforced concrete (RC) members may be restrained at their edges or end, or in many cases a combination of the two. Existing guidance on the subject is mostly based on end restrained members, however, it is applied to predict the behavior under edge restraint too. Researchers have identified that the mechanisms of cracking associated with edge and end restraints are quite different. To this purpose, findings from an experimental investigation aiming to understand the behavior of edge restrained RC walls were utilized to validate a finite element (FE) model. Subsequently, this FE model was used to parametrically study walls having different aspect ratios and subjected to different forms of restraint. Cracking patterns, widths, and extent appeared to greatly depend on the type of restraint and wall aspect ratio. The influence of combined restraint, for instance, was found to be more significant in walls with aspect ratio less than 4. The study provides clear evidence on why similar studies, are needed to support engineers in designing against cracking due to restraints. [ABSTRACT FROM AUTHOR]

In recent years, there has been extensive research on detecting damage or identifying changes in stiffness in structures by analyzing their dynamic properties or responses. The fundamental idea is that damage or loss of integrity in a structural system can affect its response to dynamic forces, leading to changes in properties like eigenfrequencies, modal damping ratios, mode shape, and transfer functions. In Vietnam and some other countries in the Southeast Asia region, the prevailing climate conditions, slow economic development, and geographical location have resulted in the construction of predominantly short-span bridges with a limited number of spans. This is primarily because these bridges connect small channels and waterways. This characteristic provides a basis for developing and applying research findings specifically for this group of bridges, as they are seldom encountered and researched in other countries worldwide. This paper presents a damage identification technique for short-span bridges based on changes in the representative power spectral density (RPSD) and the static moment of area (SSM). The proposed method is applied to experimental data obtained from various bridge models, including prestressed concrete, reinforced concrete, and composite steel bridges. It is important to note that changes in RPSD and SSM are independent of traffic conditions on the bridge but instead rely on the structural and material properties of the bridge spans. By utilizing RPSD and SSM, new advancements can be made in assessing the structural condition of bridges using vibration signals. [ABSTRACT FROM AUTHOR]

The nonconventional damping properties of structures, composed of two substructures with different damping ratios along the height, make an exact seismic analysis very complex. Determining an equivalent damping ratio for such structures makes the time‐history analysis (THA) possible through conventional analysis methods. In this study, this issue is addressed using a novel analytical method that computes the equivalent damping ratios of arbitrary mixed structures composed of two different parts with arbitrary damping ratios. The accuracy of the method is verified by two studies already published in the technical literature that are based on the semiempirical analysis methods. Furthermore, the method is applied to two vertically irregular 15‐story frames composed of steel and reinforced concrete substructures. The seismic responses obtained from the THA using the proposed equivalent damping ratios are compared with those from the THA performed on the main structure with a nonclassical damping matrix. The latter analysis is implemented in the state space as a benchmark solution. The results indicate that the proposed formula generates accurate seismic responses. The advantages of the proposed analytical method are its ease of use, accuracy, and the capacity of application to arbitrary mixed structures composed of two parts with arbitrary damping ratios. [ABSTRACT FROM AUTHOR]

Prestressed concrete frames with infill walls (IW‐PC frames) are commonly used in civil engineering as a structural element. The possibility of structures undergoing progressive collapse is a cause for concern due to its severe consequences. This has become a significant topic in the academic community in recent years. However, research on the resistance of IW‐PC frame structures to progressive collapse is still insufficient. Therefore, this paper investigated the dynamic effects of progressive collapse on the IW‐PC frame, reinforced concrete frame with infill walls (IW‐RC), prestressed concrete frame (PC), and common reinforced concrete frame (RC). The study was conducted using the finite element software OpenSees. The study revealed that the vertical displacement during stabilization of the IW‐PC frame increased by 92.5% and 71.7% compared to the IW‐RC frame and decreased by 93.9% and 92.6% compared to the PC frame for middle column and side column failure, respectively. Additionally, the IW‐PC frame exhibited the highest dynamic load carrying capacity, which was 7.67 and 7.56 times higher than that of the RC frame, respectively. The mechanical properties of the frame were altered by the coupling effect of prestressed tendons and infill walls, making the IW‐PC frame more monolithic. [ABSTRACT FROM AUTHOR]

Monitoring and detecting buried pipelines under concrete pavement are often complex and difficult tasks. The time–frequency electromagnetic technology, with the fast information acquisition and strong anti-interference ability, is first applied in the buried pipeline inspection. The purpose is to verify if this method can monitor and detect the pipelines status change effectively, even if covered by concrete pavement. Three representative scenarios (normal, coating-damaged and leaking) and two types of pavement (plain concrete and reinforced concrete) are created and applied in the simulations with the finite element method. The simulated results are processed and analysed with the proposed method. In the frequency domain, the maximum change of the electric and magnetic field signals for the coating-damaged scenario from the normal one are 0.4% and 9.9% respectively, and 97.7% and 157.7% for the leaking scenario. In the time domain, the shifts of the electric and magnetic field signal peak are 6.2 μs and 6.5 μs respectively when the coating damage occurs, and 11.4 μs and 13.1 μs when leakage appears. The results indicate that the above technology is valid for buried pipelines. Moreover, it can be used to locate and identify the abnormalities and types of concrete pavement can be differentiated. [ABSTRACT FROM AUTHOR]

In prestressed concrete continuous beams, building code provisions often allow for a reduction in the moment at a critical section (calculated through elastic analysis). This reduction is permitted as long as the moments in all other sections are adjusted to maintain equilibrium and support the designated loads. However, the allowable moment redistribution percentage (MRP) for prestressed concrete beams (PCBs) remains a topic of debate. Many codes currently assign a similar MRP limitation to both PCBs and reinforced concrete beams (RCBs). This approach might be over-simplistic for PCBs due to their unique behaviour. A method for identifying the maximum available MRP is proposed in this article. An in-depth study was conducted on the maximum available MRP of PCBs based on calibrated finite-element models. The results showed that parameters such as the passive reinforcement ratio, steel yield strength, slenderness ratio, eccentricity of prestressing tendons, concrete grade and load pattern, which are not considered in the codes, influence the maximum available MRP to an extent. Using the same permissible MRP as RCBs may thus be inappropriate. An equation is proposed to estimate the maximum available MRP for PCBs. [ABSTRACT FROM AUTHOR]

Chloride penetration is one of the main causes of failure of reinforced concrete structures, especially in undersea tunnels, which is also accompanied by stress and seepage-induced calcium leaching. The chloride penetration resistance of concrete under the single and dual effects of stress and calcium leaching were investigated in this work. The microscopic mechanisms were evaluated using scanning electron microscopy and X-ray diffraction analysis. The results showed that the chloride diffusion depth and chloride content increased linearly with the stress level in the tensile zone and decreased linearly in the compressive zone; the change was more obvious in the tensile zone. At stress levels of 15%, 30% and 45%, the diffusion depth in the tensile zone increased by 11.4%, 36.6% and 43.5%, respectively, while the change ratios of chloride content were 1.2%, 11.2% and 19.4%. No significant synergistic effect between stress and calcium leaching on the chloride diffusion depth was found, but the effect on chloride content was obvious, especially when the tensile stress level was below 15% and the compressive stress level was above 30%, for which the differences caused by considering the synergistic effect or not were approximately 6% and 15%, respectively. [ABSTRACT FROM AUTHOR]

Chloride-induced corrosion is one of the most important causes of the strength degradation of reinforced concrete (RC) bridges. As the piers of RC bridges are important elements for sustaining lateral loads, corrosion of pier columns may lead to significant degradation of the structure. It is thus necessary to have an appropriate evaluation technique to assess the effect of corrosion on the behaviour of RC columns. Numerical modelling approaches based on a concentrated plastic hinge can predict structural behaviour rapidly and with acceptable accuracy, and are highly regarded by engineers. In this study, a numerical approach was conducted to develop an empirical lumped plasticity model (LPM) for corroded RC column elements. In this study, 13 440 RC column specimens, including corroded and uncorroded columns of both rectangular and circular cross-section, were analysed under monotonic and cyclic loading. The LPM was extracted based on regression of the results of cyclic and monotonic analyses. The calibrated model, valid for corroded and uncorroded columns, was assessed using experimental results and numerical models with data out of the range of those used in the parametric study and was found to have high accuracy. The newly developed plastic hinge model can be used to model and analyse corroded bridge columns rapidly. The results are appropriate for use in further assessments such as fragility or rehabilitation analyses. [ABSTRACT FROM AUTHOR]

The leachability of low-level radioactive waste was meticulously evaluated to determine the efficacy of a cement–vermiculite matrix for immobilisation. Laboratory-scale blocks, with a cement-to-vermiculite ratio of 1:0.1, were subjected to the IAEA-recommended semi-dynamic leaching test using rainwater (RW) from the disposal site and demineralised water (DW) for comparative analysis. The experimental data elucidated the transport phenomena governing Cs-137 release from the matrix. A strong positive correlation was observed between pH, conductivity, and Cs-137 activity release, indicating their interdependent dynamics. This research derived mathematical equations for both single-source term models describing the entire leaching process and the most fitting combination models, based on statistical parameters. Key leaching parameters, including a diffusion coefficient of 5.83E-07 cm2/d, a dissolution velocity of 4.93E-05 cm/d, and a first-order kinetic rate constant of 8.00E-05 d−1, were established and used to identify the optimal leaching model. These parameters are crucial for future radiological impact assessments of the area. Various physico-chemical observations during the leaching period were documented, with efforts to elucidate their underlying causes. The cumulative Cs-137 release of less than 1% over the study period and a leachability index of 7.2 confirmed the matrices' suitability for immobilising the studied waste. Research highlights: Cs-137 is the major long-lived radionuclide present in low-level radioactive waste. Waste is immobilized in cement–vermiculite matrix and disposed in reinforced concrete trenches at disposal site, Tarapur. Cs-137 leaching from cement-waste products using rainwater and demineralised water is studied using IAEA standard leaching test. Integrity of block is studied and Leaching parameters are evaluated from observed cumulative leach fraction. Using statistical parameter, Index of agreement, best-fit leaching mechanism for Cs-137 was established. The efficiency of the matrix in immobilising low-level waste is found suitable with Leachability Index > 6. Diffusion is the underlying controlling leaching mechanism. [ABSTRACT FROM AUTHOR]

Basalt fiber–reinforced polymer (BFRP) is widely used to reinforce concrete due to its high strength, lightweight nature, good corrosion resistance, and low cost. Previous studies have shown that the double-helix BFRP macrofiber has better bond behavior with concrete compared with other types of BFRP fibers. This is attributed to its irregular geometry. The bond-slip behavior between double-helix BFRP macrofiber and concrete is further numerically studied in this study. The corresponding finite-element model is established, and the accuracy of the numerical method is validated by the experimental results based on fiber-matrix pullout tests. The effects of twisted pitches, bundle numbers, and cross-section shapes of the fiber on the bond-slip behavior are extensively investigated and discussed. It is shown by the numerical results that the bond stress and energy-dissipating capacity increase with the decrease of twisted pitches (30, 20, 10, and 5 mm). The bond stress of the fiber with a twisted pitch of 5 mm can be increased by 17.0% at most compared with the fiber with a twisted pitch of 30 mm. Furthermore, it is found that the double-helix BFRP fiber has higher bond stress than the fiber with three or four bundles, with corresponding increases of 11.9% and 16.9%, respectively. [ABSTRACT FROM AUTHOR]

Chloride transport is one of the most serious problems facing reinforced concrete structures, and coatings can effectively block the intrusion of chloride ions. In order to evaluate the resistance of coatings to chloride ion erosion more quickly and accurately, based on the transport mechanism of chloride and water in coated concrete, a two-dimensional mesoscale model of concrete containing coating, aggregate, and matrix was established in this paper. In response to the transport mechanism of chloride ions in coated concrete, a coupled convection–diffusion numerical model considering the binding effect of chloride, temperature effect, and hydration effect is established. The idealized service life conditions of the coating are introduced, and the influence of coating type, coating thickness, and coating service life on the distribution of erosive agents inside the coated concrete is analyzed. After analysis and research, it is recommended that coating concrete exposed to 3.5% NaCl erosion use a film-forming coating with an expected life of more than 10 years and a coating thickness of at least 1.5 mm, preferably chlorinated polyvinyl chloride (CPVC) and chlorinated polyethylene (CPE) coatings. [ABSTRACT FROM AUTHOR]

To enhance the mechanical properties of concrete and inhibit the development of cracks, this study designed and prepared four kinds of shape memory alloy fiber–reinforced concrete (SMAFRC) with different volume contents (0%, 0.3%, 0.6%, and 0.9%), and carried out cube compression, splitting tensile, and bending tests at two temperatures (20°C and 100°C). The SMAFRC failure samples were analyzed by scanning electron microscopy (SEM) and the failure mechanism was explored. The results showed that the SMAFRC specimen with 0.9% SMA fiber content (S-0.9) had the best mechanical properties at 20°C, and the cube compressive strength, splitting tensile strength, and bending strength were increased by 18.22%, 32.34%, and 33.20%, respectively, compared with the pure specimen (S-0). At 100°C, the strength of concrete decreased compared with that at 20°C and the SMAFRC sample with an SMA fiber content of 0.6% (S-0.6) decreased slightly at 100°C, indicating stable mechanical properties. SEM shows that the presence of SMA fibers not only acts as a bridge in concrete, but also blocks the generation and development of microcracks. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on the progressive collapse behavior of a full-scale three-dimensional (3D) steel frame substructure with cast-in-place reinforced concrete (RC) floor slabs. A full-scale specimen and relatively large-span RC floor slabs were the two main features of the experimental test. The alternate load path (ALP) method was chosen as the research approach, with one external column being removed before testing. A specially designed 12-point loading system was employed to load the specimen quasi-statically, allowing the acquisition of the load-displacement response and failure process of the test specimen from the initiation of loading to the final collapse. Additionally, based on the test, the deformations of structural members, contributions of various load-resisting mechanisms, load redistribution among the remaining parts of the structure, and dynamic response were analyzed. The ultimate collapse resistance of the structure was theoretically predicted based on the yield line and plastic hinge theories. The test and analysis results led to the following findings: One, the typical steel frame structure in this study, designed based on current steel structure codes, withstood the failure of an external column. Two, tensile membrane action (TMA) primarily developed in the floor slab parallel to the double-span beam above the removed column. Three, flexural action (FA) was the main contributor to resisting the vertical loads throughout the loading process. Its contribution reached up to 88% at the structural ultimate load-carrying capacity position. However, before the final failure of the structure, the loads resisted by catenary action (CA) in beams and TMA in floor slabs could not be ignored. The sum of the two accounted for one-third of the total vertical loads. Four, Columns C1 and C2, directly connected to the removed column through the double-span beam B1-B2, sustained the majority of the vertical loads. Five, for steel frame structures with rigid or semi-rigid connections characterized by good moment resistance but limited rotational capacity, strengthening the connection via additional measures to ensure full development of CA in beams at large deformation stage may be the key to enhancing structural resistance to progressive collapse. [ABSTRACT FROM AUTHOR]

Concrete is used as a material in the construction of several types of structures. The structural behavior of concrete is constrained by its lower tensile strength, bending strength, and toughness. Fiber-reinforced concrete is gaining importance in various concrete applications. Research has been carried out to use multiple types of fibers in concrete in different combinations to improve its mechanical characteristics, such as toughness, strength, ductility, and durability. In traditional concrete, microcracks have developed before loading the structure because of volume changes and drying shrinkage. When the load is applied, the microcracks start opening and propagating. Therefore, failure of the concrete member occurs. Hence, the usage of fibers helps arrest the growth of the crack and improves concrete characterization. The goal of this research study is to examine mechanical properties of concrete when used in combination with steel, basalt, and glass fibers. Steel fiber is useful in arresting macrocracks, whereas basalt and glass fibers are effective in preventing microcracks. In this research, the specimens incorporated hybrid (steel, glass, and basalt) fibers in the concrete mix with various percentage proportions at a 0.5% volume fraction. Experiments were carried out to assess the bending strength, compression strength, and splitting tensile strength. Therefore, this research can show comparative analysis for different percentages of fibers to enhance the qualities of concrete and can show the optimum fiber percentage among the proportions selected for this study. [ABSTRACT FROM AUTHOR]

Earthquake catastrophes continue to cause substantial damage and casualties in many parts of the world. Despite design codes and standards having succeeded in reducing life losses during earthquakes, the level of damage in buildings after severe earthquakes still cannot be precisely predicted. Code provisions focus on the safety of buildings with no consideration of the amount of damage expected after an event. Current U.S. guidelines designate three performance levels related to the inelastic rotational demands of RC shear walls––immediate occupancy, life safety, and collapse prevention. The damage corresponding to these performance levels is minor, moderate, and severe, respectively. In the current study, these performance limits were implemented, along with other recognized standards, in order to design four RC ductile shear wall buildings with different heights located in a high seismic hazard zone. Each building was designed based on Canadian building codes to reach the three designated performance levels. For each case, the quantities of the constitutive materials of the RC shear walls were estimated and compared. The impact of the targeted performance level on the building's gravity-load-resisting system was also investigated. The cost effectiveness of using moderately ductile shear walls in high seismic hazard zones was also examined. [ABSTRACT FROM AUTHOR]

Corrosion of steel in reinforced and prestressed concrete members exposed to a marine tidal zone is a serious durability problem. This study presents a methodology for rationally estimating the safe cover thickness for steel in concrete structures exposed to the tidal zone. The proposed methodology was implemented for the case of six Indian coastal stations using 100-year-long simulations of chloride transport in concrete. Real-time meteorological and tidal height data were used for simulating the model boundary conditions. Using simulated results of chloride threshold depths (CTDs), safe cover thickness to steel was assessed. Estimated safe cover thicknesses to steel across coastal stations differed significantly (25–30 mm), indicating a need for corrosion vulnerability zonation of coastlines. Conventionally used tide models were improved by superimposing with an annual component of astronomical tides, which expanded the range of wet-dry regimes simulated by the tide models. The study also compared the chloride ingress predictions from the modified tide models with those from real tides. The superimposed tide model was found to be a better approximation of real tides than the diurnal tide model. The modified tide models very well simulated chloride ingress around the critical sections in the tidal zone. [ABSTRACT FROM AUTHOR]

Segmental tunnel is widely adopted in the urban transportation system, thereby its seismic resilience is a cornerstone for resilient cities. The segmental tunnel is an assembly of reinforced concrete segments, bolts, gaskets, gaps, etc., and exhibits highly nonlinear behavior when subjected to external loadings. Yet, in practice, its seismic response is generally estimated via a holistic modeling approach where the segmental tunnel is represented by a homogeneous beam or shell element with equivalent stiffness. Here, a multi-contact joint-based model is developed for a segmental tunnel, incorporating the nonlinearities embedded in the assembly with acceptable computational costs. The reinforced concrete segment is represented as the displacement-based fiber beam element, whereas the complex interaction among the configurations of the joint, i.e. bolt, gasket, and contacting concrete, is modeled via the zero-length section element. The proposed model's accuracy is validated via a series of experimental data under three loading scenarios. A sensitivity analysis demonstrates that the mechanical response of segmental tunnels highly relies on the assembly configurations. The proposed model is implemented to investigate the seismic response of a typical segmental tunnel under various ground motions, demonstrating its applicability in seismic safety assessments, particularly in capturing the nonlinear response of segmental tunnels under high-intensity earthquakes. [ABSTRACT FROM AUTHOR]

In this study, Recycled Concrete Aggregate (RCA) was employed as a sandwich technique around the geogrid to enhance the pullout resistance of the geogrid in clayey backfills. Large-scale pullout tests were conducted on three configurations: geogrid-reinforced clay, geogrid-reinforced RCA, and geogrid sandwiched between layers of RCA, aimed at investigating pullout resistance and deformation. The experiments encompassed two different geogrid types (designated as G1 and G2), varying normal pressures ranging from 10 to 50 kPa, and RCA layers with thicknesses of 40, 80, 160, and 320 mm. Results from the experiments revealed that the inclusion of RCA layers around the geogrid substantially enhanced pullout resistance, with improvements ranging from 1.5 to 3 times compared to clay specimens. Optimal RCA thicknesses were determined in order to enhance soil-geogrid bonding and pullout resistance. For G1 geogrid, a thickness of 160 mm (equivalent to replacing 25% of clay volume with RCA) was identified as optimal, while for G2 geogrid, an 80 mm thickness (equivalent to replacing 15% of clay volume with RCA) was found to be sufficient. These thicknesses were established to achieve over 80% of the pullout force compared to full RCA specimens. • Large-scale pullout tests were performed on two types of geogrids. • Recycled Concrete Aggregate (RCA) was utilized at various thicknesses within a sandwich technique to enhance geogrid pullout resistance in clayey backfills. • The optimum thickness of RCA layer in sandwich technique was determined. [ABSTRACT FROM AUTHOR]

The article presents the results of adapting the digital image correlation method for the possibility of diagnosing reinforced concrete structures. Reinforced concrete (RC) bending elements are the most widely used in construction practice, which determines the importance of reliable estimation of their stress-strain state. The purpose of this study includes reliable theoretical and experimental investigation of the strength and deformability parameters of the RC beam. The experimental study was conducted using digital image correlation and sub-micron contactless gauges. Experimental data was verified with the calculation of the stress-strain state of the RC beam according to DBN V.2.6-98:2009 and Eurocode 2 and the finite-element modelling (FEM). As a result, the values of deflections, concrete and rebar strains were obtained and presented as corresponding diagrams. The results of all the methods are within the same ranges. Also, the form and character of corresponding diagrams are very similar. The indicated deviations were within acceptable limits. It was noted that the theoretical calculation generally provides lower strain values, which is a satisfactory result, as it indicates the bearing capacity reserves provided by the current regulations. The propagation of cracks was monitored during the experiment and the measured cracks opening was compared with theoretical assumptions. Theoretical values are higher than experimental, which shows certain conservativity of valid normative regulations. The experimental and theoretical results were in good correspondence, which confirms their reliability. It was concluded, that the proposed in the study complex theoretic-experimental approach provides essential information about the strength and deformability of the structure. [ABSTRACT FROM AUTHOR]

Rapid population growth and the need for sustainable land use have led to a remarkable increase in the construction of tall buildings. To accommodate the increasing need for floor space, high‐rise structural systems are being developed aiming to improve building performance against lateral loads. This paper introduces a novel steel‐infilled Reinforced Concrete Frame (SP‐RCF) outrigger and compares its structural performance against other systems, such as the Concrete Wall‐infilled Reinforced Concrete Frame and the Steel Truss‐infilled Reinforced Concrete Frame. A geometrically and materially non‐linear analysis was applied to these systems and validated through existing experimental and analytical data. Subsequently, a case study on a prototype tall building was conducted. The results indicate that the SP‐RCF outrigger shows superior performance compared to the other systems in terms of ultimate strength, stiffness, and ductility; demonstrating its potential to enhance the structural integrity of high‐rise buildings. [ABSTRACT FROM AUTHOR]

In the study, flexural performances of FRP reinforced concrete (RC) slabs with different fiber and bar surface properties were investigated. Glass fiber reinforced polymer (GFRP), Carbon fiber reinforced polymer (CFRP), Aramid fiber reinforced polymer (AFRP) and Basalt fiber reinforced polymer (BFRP) steel reinforcements were used in the reinforcement of the slabs. A total of 27 slabs were produced in the dimensions of 1100–1100–100 mm and with the same reinforcement ratios as FRP and steel reinforcement and were tested with the four-point flexural test method. The flexural strength, moment capacity, toughness and ductility values of the slabs were calculated by determining their flexural behaviour, and the average values were compared. In the comparison, the behaviour of the FRP RC slabs was analysed by taking the steel RC slabs as reference. The effects of FRP fiber type and bar surface properties on slab behaviour were evaluated. The bending load-carrying capacity of AFRP and GFRP RC slabs with ribbed surfaces was 4% higher than those with sand-coated surfaces. In addition, the bending load-carrying capacity of BFRP and CFRP RC slabs with sand-coated surfaces was 13% and 16% higher than those with ribbed surfaces, respectively. The type of failure in slabs varies based on the type of reinforcement and the surface properties of the reinforcement. Three types of failures have been identified: flexural failure, shear failure, and flexural-shear failure. The ductility performance of steel RC slabs has been determined to be the highest, with a value of 9.45. When comparing toughness, sand-coated FRP bars exhibit toughness levels 8–40% higher than ribbed ones. Among the FRP RC slabs, sand-coated CFRP RC slabs provide the greatest contribution to flexural load-carrying capacities. [ABSTRACT FROM AUTHOR]

This study presents a critical historical review of one century of methods, results and regulations concerned with permeability testing of concrete and other stone building materials, keeping under a magnifying glass the triad of factors invasiveness-reliability-insight with the objective of scouting the feasibility of a near-zero-invasiveness practice, alternative to some recent standards. This practice is herein proposed for integrating actions of surveying, sampling and watertightness testing of a concrete cover object of a life cycle appraisal in a reinforced concrete structure for possible replacement from a perspective of sustainability and evaluated on a historical documental basis. Two main conclusions of this study are: the feasibility, on a historical documental basis, of cutting specimens for permeability testing from thin regions of concrete cover, and the great importance for the decision-maker to have access to sufficient diagnostic data suitable to let her/him discern the self-sealing or self-unsealing nature of the concretes under investigation. [ABSTRACT FROM AUTHOR]

This paper presents an analytical investigation of glass fiber–reinforced polymer (GFRP) reinforced concrete knee joints subjected to closing moments, with a focus on reinforcement ratio, joint geometry, and confinement stirrups. The study uses the finite-element method with a commercially available code to verify experimental tests and examines the behavior of the knee joints through a parametric study. The concrete damaged plasticity model was used to define the material behavior of concrete, and the effects of different dilation angles were also studied. The average test-to-predicted ratios between finite-element analyses and test results fall within a range of 2% for moment capacities and 5% for deflections at peak. The results indicate that the dilation angle significantly influences the moment capacity and the ultimate deflection of specimens. Proper reinforcement detailing and concrete confinement are found to be important in knee joints, as unconfined specimens failed at significantly lower strengths than their confined counterparts. Incorporating diagonal stirrups in the knee joints is shown to be more effective than utilizing lateral stirrups in enhancing both moment capacity and deflections of the specimens under closing moments. However, placement of lateral stirrups is more practical than diagonal stirrups and it is shown that lateral stirrups increase the capacity of the joints to acceptable levels. [ABSTRACT FROM AUTHOR]

Determination of the maximum shear capacity of reinforced concrete (RC) beams and slabs has been a challenging task for over 100 years. Recently, the shear crack propagation theory (SCPT) was developed as a unified mechanics-based solution to determine the ultimate capacity and to explain the phenomenon of one-way shear in RC members without shear reinforcement. The proposed theory is not limited to steel-RC members and can be applied to members with nonmetallic reinforcement accounting for their material parameters and constitutive relationships. Further, the SCPT does not focus only on the ultimate state but also on the behavior during the entire loading process up to failure. In this paper, the application of the SCPT is extended to RC members with longitudinal fiber-reinforced polymer (FRP) reinforcement without stirrups for the first time. A parametric study is first presented to explore the effect of FRP bar properties on shear behavior and shear transfer mechanisms in RC beams. Subsequently, the experimental results of 44 beam tests reported in the literature are used for validation. The results showed that the SCPT provided accurate estimates of the shear strength of FRP-RC beams that compared favorably with those from current design codes. [ABSTRACT FROM AUTHOR]

A steel strand wire mesh (SSWM)–reinforced engineered cementitious composite (ECC), referred to as SSWM-ECC, is a promising composite material for structural strengthening owing to the combination of the high strength of SSWM and the high ductility of ECC. This paper presents an application of SSWM-ECC for shear strengthening of reinforced concrete (RC) beams subjected to cyclic loading. First, cyclic loading tests were conducted on two control beams and five strengthened beams, considering various shear span-to-effective depth ratios, reinforcement ratios of the SSWM, and strengthening schemes. The test results showed that brittle failure and degradation of the shear properties of the strengthened beams were effectively mitigated. Compared to the control beams, the ultimate load, cracking load, service load, ductility, and energy absorption of the strengthened beams increased by 18%–40%, 145%–208%, 35%–126%, 20%–65%, and 58%–96%, respectively. The improvement in shear performance increased with increasing reinforcement ratio of the SSWM and shear span-to-effective depth ratio. In addition, the fully wrapped strengthening method effectively confined the concrete, resulting in a more significant increase in the shear performance of the beams compared to the U-wrapped and both-sided methods. Furthermore, a modified truss arch model was developed to predict the shear strength of the strengthened beams. The results predicted by the proposed model exhibited greater accuracy than those generated by various existing models, including those commonly utilized in the field. Practical Applications: The experimental study presented in this paper demonstrates a significant improvement in the shear performance of RC beams subjected to cyclic loading using a novel composite called SSWM-ECC. This method is expected to be useful for structural strengthening. The fully wrapped, U-wrapped, and both-sided SSWM-ECC strengthening methods introduced in this paper are applicable to a wide range of engineering projects. In particular, an economical and convenient method for strengthening RC beams using externally bonded prefabricated SSWM-ECC plates is presented. The SSWM-ECC can effectively mitigate the shear brittleness of RC beams subjected to cyclic loading and significantly increase their shear strength, stiffness, cracking resistance, energy absorption, and ductility. Furthermore, the strengthening efficiency increased with increasing shear span-to-effective depth ratio and reinforcement ratio of the SSWM. Finally, a calculation method for predicting the shear strength of strengthened beams is proposed, which provides a basis for the design and application of shear strengthening of RC beams with SSWM-ECC under cyclic loading. [ABSTRACT FROM AUTHOR]

The significant influence of the geometric properties of the rebar surface on the bond behavior of fiber-reinforced polymer (FRP)-reinforced concrete (RC) members is not adequately covered in current design provisions. Twenty-four hinged-type glass FRP (GFRP)-RC specimens have been tested in the present study to investigate the effect of concrete strength, embedment length, confinement conditions, and surface geometric properties of GFRP rebars on the flexural bond behavior of the specimens. It has been observed that the bond strength between the GFRP rebars and the concrete can be increased (up to 15%) by altering the surface geometric properties of the GFRP rebars. The effect of surface geometry is more pronounced in higher-strength confined concrete specimens with an embedment length of GFRP rebars equal to five times the diameter (d) of the rebar as compared to the other tested specimens. Confinement reinforcement has also been observed to increase the bond strength of the tested specimens by 10%–18%. Furthermore, the effect of the test variables on the mode of failure and the postpeak behavior of the specimens under flexural loading has also been investigated in this study. The findings of the present study strongly demonstrate the necessity of a contribution factor that considers the surface characteristics of GFRP rebars in the estimation of the bond strengths of GFRP-RC members. An equation for bond strength estimation, which considers contributions from bar surface geometry, has also been proposed from the findings of this study. It is imperative that similar factors are incorporated into future versions of design provisions in order to integrate the contributions of bar surface geometries to the bond strength of GFRP-RC members. Practical Applications: The research findings highlight the importance of considering the geometric properties of fiber-reinforced polymer (FRP) rebar surfaces in the design of FRP-reinforced concrete (RC) members. The bond strength between the rebar and the concrete can be significantly increased and the overall performance of FRP-RC members can be improved by adequately selecting the surface geometry of FRP rebars. This study also demonstrates the influence of concrete strength, embedment length, and confinement conditions on the bond behavior of FRP-RC members. It is recommended to implement a contribution factor that considers the effect of the surface characteristics in design provisions. A new equation has been proposed for engineers and designers to consider the surface geometry in the calculation of the bond strength of FRP-RC members. Implementing the findings of the present study in future design provisions will enhance the safety and effectiveness of FRP-RC structures, through improved performance and durability in various applications. [ABSTRACT FROM AUTHOR]

Hybrid fiber-reinforced polymer (FRP)–concrete–steel double-skin tubular members (DSTMs) yield much higher strength-to-weight ratios and much better corrosion resistance than traditional reinforced concrete members. The steel tube and the FRP tube in DSTMs act as propping and formwork for concrete casting, thus significantly reducing construction efforts. DSTMs have been extensively studied as columns and beams. This paper presents a study aimed at understanding the benefit of using the double-skin tubular cross section in arches. Five double-skin tubular arches (DSTAs) with a span length of 3.6 m were fabricated and tested to investigate their behavior. The test program examined the effects of section load eccentricity, eccentricity of the steel tube position in the section, thickness of the FRP tube, and diameter of the steel tube on the behavior of the DSTAs. All the DSTA specimens displayed ductile behavior. The DSTAs were found to provide a significantly higher ultimate load than corresponding steel–concrete composite arches of a similar cross section. A higher cross-sectional load eccentricity was found to reduce the ultimate load of a DSTA. A numerical model was also developed in OpenSees (2019) version 3.2.2 to predict the behavior of the DSTAs. The numerical predictions were found to agree with the experimental results reasonably well. [ABSTRACT FROM AUTHOR]

Steel-reinforced concrete (RC) columns typically exhibit significant residual displacements and low postyield stiffness when subjected to seismic loads, which may complicate subsequent repairs. This paper investigated the effects of different reinforcement methods on the seismic performance of concrete columns by using glass fiber–reinforced polymer (GFRP) and basalt fiber–reinforced polymer (BFRP) bars. Five samples were subjected to low-cycle horizontal loading tests to compare the corresponding seismic performance indices. The results showed that fully FRP-reinforced concrete columns had a lower energy dissipation capacity and ductility coefficient than RC columns but had other clear advantages in terms of ultimate displacement and a postyield stiffness increase by 100%. Compared to RC columns, the concrete columns with half FRP bars exhibited comparable energy dissipation, greater ultimate displacements and ductility coefficients, and a 60% increase in postyield stiffness. Incorporating FRP bars significantly reduced the residual deformation of FRP-reinforced concrete columns compared to RC columns under the same loading cycle, enabling structural repairs and continued use after an earthquake. Practical Applications: During the 2008 Wenchuan earthquake, many traditional reinforced concrete structures were severely damaged, causing significant economic losses and threatening lives and property. Related investigations verified that the deformation of reinforced concrete columns was the most serious under the same displacement level, and adding fiber-reinforced polymer materials greatly reduced the deformation of the concrete columns, which can improve the reparability of the structure after an earthquake. Additionally, the peak load-carrying capacity of fiber-reinforced polymer materials is similar to that of reinforced concrete columns, giving the former a certain application value. In the coastal areas of traditional reinforced concrete structures, because of corrosion, which leads to a significant reduction in the service life of the environment, it is proposed that the introduction of fiber-reinforced polymer materials with excellent corrosion resistance will largely improve the service life of the corrosive environment of the components while ensuring similar seismic performance. [ABSTRACT FROM AUTHOR]

Bridges situated in northern climate regions, which face severe environmental conditions and daily fatigue loading, are prone to accelerated deterioration and corrosion of their components. The application of carbon fiber–reinforced polymer (CFRP) sheets bonding to the surface of bridge elements has emerged as an attractive solution for enhancing bridge strength. Past studies and field implementations have effectively showcased the viability of this approach in strengthening bridges. An exceptional opportunity arises with the deconstruction of a bridge in Canada, providing a unique chance to assess and study the condition of reinforced concrete elements strengthened with CFRP. These elements have endured real service conditions, including fatigue loads and exposure to aggressive environmental factors. This paper presents the experimental results of a research program that aimed to investigate the residual fatigue life and capacity of 60-year-old reinforced concrete bridge girders, which were strengthened using CFRP sheets. The study focuses on assessing the performance of these girders under different test conditions, providing valuable insights into their remaining fatigue life and load-carrying capabilities. The two 60-year-old girders have been strengthened with CFRP for the last 10 years of the service life of the bridge. The two full-scale girders were tested under 2 million fatigue load cycles and then tested monotonically until failure at the structural lab of the University of Sherbrooke. The test results revealed that the CFRP-strengthening technique can extend the service life of the bridge element and enhance its shear capacity. The CFRP–concrete interface and CFRP sheets showed excellent bonding behavior, as no damage-debonding failure or tensile rupture occurred until the formation of the diagonal shear crack. [ABSTRACT FROM AUTHOR]

The steel plate shear walls (SPSWs) have been proven effective in reinforced concrete frames (RCFs) as a lateral force‐resistant structure. Despite of advancements, accurately predicting the ultimate shear capacity of RCFs with SPSWs remains challenging using current simplified models. Additionally, the flexural capacity design procedure for the boundary elements (beams and columns) in previous studies of RCF‐SPSWs involved intricate iterative procedures, hindering its widespread implementation. To address the two issues, this paper investigates the pushover responses and the plate‐frame interaction (PFI) of an RCF‐SPSWs system using theoretical and numerical methods. There are three main contributions. First, a theoretical model of ultimate shear capacity for RCF‐SPSWs is proposed, which can also be used to predict shear contributions of boundary frames in RCF‐SPSWs. Calculation errors for ultimate shear capacity of RCF‐SPSWs and shear contribution from the boundary frame are only 3.7% and 6.7% respectively, which are reduced dramatically compared with the traditional model. A simplified schematic diagram for the global collapse mechanism (uniform distribution of plastic hinges within a structure) of RCF‐SPSWs is developed to facilitate the calculation of internal work and reaction forces. Secondly, a flexural capacity design method for the boundary elements to avoid in‐span plastic hinges is proposed. The proposed method enables the achievement of direct estimation of the flexural demands that could trigger a global collapse mechanism, all without intricate iterative procedures. The applicability of current assumptions for the design of steel boundary frame in RCF‐SPSWs system is discussed, and engineering suggestions are provided to ensure safer and more economic designs. Comparison results confirmed the applicability of the proposed design method, which can be adopted to achieve the global collapse mechanism for RCF‐SPSW system. Thirdly, impacts of yielding panel actions on the flexural capacity of boundary elements of RCF‐SPSWs are clarified. Comparison results demonstrated that adding SPSWs to an RCF alters the axial force on boundary elements and significantly impacts the flexural capacity. A design suggestion is made to emphasize the importance of avoiding the balanced failure of boundary elements. The proposed theoretical model can be used to economize the cross‐section of boundary elements in RCF‐SPSWs system under seismic loads due to accurate prediction of their shear contribution; the proposed flexural capacity design method can achieve a global collapse mechanism, and thus the structural safety and energy dissipation capacity are improved; moreover, the building design efficiency is also improved due to avoidance of intricate iterative procedures. [ABSTRACT FROM AUTHOR]

In the present seismic design philosophy, the structures are designed to remain within the specified displacement limits for multiple earthquake hazard levels expected during their design life. Accordingly, the estimation of maximum inelastic displacement demand in a structure consistent with a given hazard level is of primary importance. Considering the complexity and inconvenience associated with the nonlinear response history analyses for a suite of hazard‐consistent ground motions, it is preferred to estimate the maximum inelastic displacement demand by using the scaling models available for the inelastic displacement ratio C$C$ in the single‐degree‐of‐freedom (SDOF) structures. In this study, a new scaling model is developed for the inelastic displacement ratio CR(T)${C}_R(T)$ spectrum for a given response reduction factor R in the case of 5%‐initial damping Bouc‐Wen‐Baber‐Noori (BWBN) oscillators with stiffness and strength degradations and pinching. This model is based on the observed similarities between the CR(T)${C}_R(T)$ spectrum and the reciprocal of given displacement response SD(T$T$) spectrum in most cases, and thus, this indirectly accounts for the effects of seismological and site parameters. A new strong‐motion duration definition is also proposed to identify shorter strong‐motion segments of comparable relevance, and on using this definition, it is shown that the dependence of the mean CR(T)${C}_R(T)$ spectrum on strong‐motion duration may be considered negligible. Accordingly, the regression parameters of the proposed scaling model for CR(T)${C}_R(T)$ spectrum are estimated as the exponential functions of only five governing BWBN parameters. The best‐fit estimates of the regression coefficients of the resulting prediction equations are obtained for three values of R. The residual error spectra are also modeled to estimate the CR(T)${C}_R(T)$ spectrum for a given confidence level. The proposed scaling model can be applied to a wide range of existing reinforced concrete (RC) structures with 5% initial damping by using the input of the design displacement spectrum and BWBN parameters. [ABSTRACT FROM AUTHOR]

A circular reinforced concrete (RC) bridge column with two layers of longitudinal and spiral reinforcements is becoming a common structural form in high-seismic regions because they are expected to have improved seismic performance compared to conventional bridge piers. In seismic hazard zones, a large amount of transverse reinforcement is commonly required to satisfy the so-called antibuckling requirements. Accordingly, the double-confined steel (DCS) RC bridge pier is a simple and effective way to achieve high ductility levels and postyield stiffness for bridge piers in seismic regions. In DCS, the longitudinal steel rebars are well distributed inside the cross section; at the same time, the two layers of transverse reinforcement outline different levels of confinement for concrete, including unconfined (cover), singly confined (positioned between two spiral layers), and doubly confined (found inside the inner spiral layer or the core). The adopted reinforcement details, layout, and scale were unprecedented for lateral testing of large-scale DCS. Therefore, this experimental program investigated the effectiveness of DCS as an alternative to typical RC bridge piers. The behavior of large-scale DCS was compared with the performance of conventional RC bridge pier. During the quasi-static cyclic lateral displacement-controlled loading, the onset of cracking, concrete cover spalling, damage progression, plastic hinge length development, lateral load–displacement relationship, and strain in the steel reinforcements were observed. Overall, the curvature, stiffness degradation, and energy dissipation capacity all revealed that the DCS could significantly enhance the seismic performance of a bridge pier. A fiber-based finite-element model was generated to predict the experimental response of the piers under cyclic loading. Charts depicting the relationship between the ratio of elastic stiffness and axial load were developed to serve as a valuable design resource for bridge piers. The charts were created by conducting moment–curvature (M−Φ) analyses on DCS sections. These analyses involved varying the longitudinal reinforcement ratios, reinforcement layouts, and other parameters while also considering different axial load ratios. Subsequently, the performance-based design (PBD) approach was employed to assess the extent of damage relative to engineering demand parameters. Furthermore, a comprehensive example was provided to showcase the design of DCS within the framework of PBD. The findings revealed that DCS successfully met the performance objectives outlined in the PBD guidelines, making it an attractive design option for conventional RC bridge piers. [ABSTRACT FROM AUTHOR]

Reinforced concrete (RC) single-column piers (SCPs) and double-column piers (DCPs) are widely used in highway girder bridges. However, the seismic behavior of conventional RC DCPs has not received sufficient attention. This study aimed to investigate the seismic behavior of DCPs, especially the comparison of the failure mechanism, hysteretic behavior, and dynamic response between SCPs and DCPs. To this end, the critical performance parameters between SCPs and DCPs in the elastic phase were first calculated according to the simplified calculation formulas. Eight 1/3 scaled SCPs and DCPs were then fabricated and tested under quasi-static cyclic loading, and the effective height of the DCPs was twice that of the SCPs. The test results showed that the failure modes and damage mechanisms between the SCPs and DCPs are obviously different. In particular, the plastic damage states at the top and bottom of each column in the DCP were asymmetric, and this behavior was also observed on both sides of each plastic hinge region. Subsequently, the relationship between the performance parameters of SCP and DCP in the plastic phase differed from that of the elastic phase and was not proportional. Existing formulas for calculating the plastic hinge length of SCPs cannot effectively predict DCPs and may even underestimate it. Furthermore, numerical simulations were analyzed to investigate the effects of various design parameters and ground motions on the seismic behavior of the SCPs and DCPs. [ABSTRACT FROM AUTHOR]

This study focused on evaluating the confinement requirements for glass fiber–reinforced polymer (GFRP) reinforcement in circular reinforced concrete (RC) columns subjected to seismic forces, including torsional effects. Seven large-scale GFRP-RC columns were tested under axial and quasi-static cyclic lateral loading. The test parameters included torsion-to-bending moment ratio (tm) and transverse reinforcement spacing and configuration (spiral and hoops). The experimental results revealed that introducing torsion to the loading scheme reduced the lateral load resistance and drift capacity of the columns. The study recommends adopting a spiral pitch equal to one-sixth of the effective core diameter, as per the Canadian provisions for FRP-RC structures. This spiral pitch significantly enhanced peak lateral load, torque, drift, and twist capacities while ensuring column stability at high drift ratios and preventing complex modes of failure under seismic loading, including torsion. The GFRP spirally reinforced columns consistently surpassed the drift threshold requirements specified by the Canadian provisions for FRP-RC structures. In contrast, hoop-reinforced columns failed at lower drifts, with a notable lap-splice failure observed in columns under tm of 0.4. It was concluded that using GFRP hoops with a lap splice length of 40 times the bar diameter is inadequate for columns subjected to seismic conditions with torsional effects. [ABSTRACT FROM AUTHOR]

Using composite precast concrete bridge girders supporting cast-in-place bridge-deck slabs is a cost-efficient method because it merges precast and cast-in-place elements while maintaining the monolithic construction's integrity and continuity. In terms of horizontal shear transfer in composite girders, there is a lack of experimental data on the performance of full-scale fiber-reinforced polymer (FRP)-reinforced composite girders. This study explored an innovative and sustainable approach using noncorroding basalt fiber–reinforced polymer (BFRP) as shear transfer reinforcement in precast concrete bridge girders supporting cast-in-place concrete bridge-deck slabs. Five full-scale composite reinforced concrete T-beams measuring 4,200 mm in length, 420 mm in depth, and 250 mm in width were designed, cast, and tested until failure. The main experimental variables evaluated were the interface shear reinforcement type (BFRP versus steel stirrups), the interface shear reinforcement ratio (0.32% versus 0.48%), and the interface shear reinforcement shape (stirrups versus bent bars). The test results were analyzed in terms of ultimate horizontal shear stress, deflection, slippage, and shear reinforcement strain. The experimental results indicated that the BFRP shear reinforcement provided reasonable shear transfer capacities compared to steel when provided across rough concrete interfaces. In addition, the existing equations in North American bridge design guidelines yielded overly cautious predictions of the BFRP bars' interface shear strength. The study conclusively demonstrates the viability and potential of using BFRP bars as shear connectors in composite precast concrete girders supporting cast-in-place bridge-deck slab applications. [ABSTRACT FROM AUTHOR]

Taking the typical brick–wood structure houses in northern China as the research object, two 1/2‐scale brick–wood structure house models with the same size and layout were tested using large‐scale shaking table test technology. Model 1 has seismic measures of ring beams, structural columns, wall tie bars, reinforced concrete lintels for doors and windows, and purlin bottom plates. Model 2 has the same structural layout, dimensions, and construction technical conditions as Model 1 but lacks the seismic measures of ring beams and structural columns as Model 1, and the other construction measures are the same. In the test, the Wenchuan record, EL‐Centro record, and Lanzhou artificial record were selected to simulate the horizontal seismic action on the models. Through the analysis and comparison of the seismic damage process and seismic response characteristics of the two models, the results showed that horizontal shear failure was the main failure mode of single‐story brick–wood houses, and the protruding gable wall parts of the crosswall were the weak points for seismic resistance. The seismic measures adopted in the test effectively improved the seismic performance of the houses, with Model 1 and Model 2 achieving the basic seismic fortification of intensity VIII and IX, respectively. The relevant research results presented in this paper clarify the seismic response law and seismic failure mechanism of brick–wood houses. Meanwhile, the corresponding seismic technical measures proposed based on these results have certain guiding significance for the construction of suburban or rural houses. [ABSTRACT FROM AUTHOR]

Translation abstract Strut‐and‐tie models for indirectly supported structural concrete beamsFor indirectly supported r.c.‐beams it is recommended to place the required hanging up stirrups within the intersection area of both beam webs. This follows from a clear strut‐and‐tie model. However, about 50 years ago it was discussed to partly place stirrups outside this direct intersection area, and this was eventually allowed in codes. Yet, no strut‐and‐tie model was presented for this case, but only detailing rules were given for placing the hanging up stirrups. In the following two variants for strut‐and‐tie models will be presented for this case. The result is that one cannot really talk of distributing hanging up stirrups in regions outside the direct intersection area of the webs, because altogether the triple amount of stirrups is required. [ABSTRACT FROM AUTHOR]

Translation abstract High performance aerogel concrete – flexural behaviour with GFRP reinforcementHigh Performance Aerogel Concrete (HPAC) is a new type of structural lightweight concrete based on a combination of lightweight aggregates made from silica aerogels and HPC matrices. To produce HPAC components subjected to bending, as with normal weight and other structural lightweight concretes, internal reinforcement is required on the bending tension side. For reasons of building physics and durability, reinforcement made of fibre‐reinforced plastics (FRP), such as GFRP reinforcement, should preferably be used for this purpose. To investigate the bending behaviour of FRP‐reinforced HPAC components, 16 four‐point bending tests were carried out on HPAC beams of different strengths and with different amounts of reinforcement. For a better understanding of the failure mechanisms, physically non‐linear finite element simulations were carried out and validated based on the test results. The results of the experimental and numerical investigations were used to derive a model for the bending design of FRP‐reinforced HPAC components. This work on the bending behaviour of HPAC components with FRP reinforcement is presented below. [ABSTRACT FROM AUTHOR]

A comprehensive 3D imaging analysis was conducted to investigate the corrosion process in reinforced concrete (RC) samples at various stages of the accelerated galvanostatic corrosion process. A state-of-the-art X-ray computed tomography (CT) scan technology was utilized to collect high-resolution 3D images of the specimen. The CT imaging was complemented and validated using a multi-faceted approach utilizing Scanning electron microscopy (SEM) and Raman spectrometry techniques. The distribution and evolution of voids, corrosion products, and cracks were investigated. A localized corrosion was observed that has some similarity to pitted corrosion but not as wide spread along the bar. The micro-scale imaging investigations revealed a gradual increase in the diameter of voids as the time of corrosion increased, especially after 8 days of accelerated corrosion process at which a significant decrease in small-sized voids (≤0.11 mm) accompanied by an increase in other void sizes was observed. At 10 and 12 days of accelerated corrosion process, the volume of larger-sized voids (≥0.35 mm) continued to increase, indicating a rapid corrosion progress and the formation of corrosion-induced cracks. In addition, a thorough X-ray CT analysis allowed us to differentiate between various categories of corrosion products. Notably, iron oxides and iron hydroxides were found to dominate the corrosion products. Understanding the composition and distribution of these corrosion products is essential as they play a significant role in the degradation and deterioration of the concrete structure. The coexistence of iron oxides and iron hydroxides in the region of corrosion products were confirmed using Raman spectroscopy analysis. The CT scan images captured the evolution of cracks at different time intervals, revealing a strong correlation between the initiation of cracks and the presence of corrosion products. Subsequently, during the cracking in the matrix, while the propagation of corrosion products within the matrix contributed to the expansion of cracks. SEM images and elemental analysis confirmed that these cracks were filled with corrosion products. [ABSTRACT FROM AUTHOR]

In order to study the deformation behavior of reinforced concrete frame beam–column joints under high‐temperature fire and the variation of their mutual constraint with temperature, structural tests were conducted on the entire process of temperature rise and fall of reinforced concrete frame beams under high‐temperature coupling load. Innovatively, based on structural testing, the Vulcan program was used to conduct numerical analysis of the fire response of the moment–angle relationship between beam–column nodes under constant load when the frame beam is subjected to high temperature alone or when both beams and columns are subjected to high temperature simultaneously. The results show that the rotational deformation and restrained bending moment of the beam–column joints in reinforced concrete frames increase first and then decrease with the increase of fire temperature, and the peak rotation angle of the beam–column joints has a lag effect compared to the peak bending moment. As the temperature continues to rise, the beam end angle begins to decrease after reaching its peak value, and the peak value of the beam end angle appears later than the constrained bending moment. Based on the thermal mechanical coupling test, a fire response calculation model for reinforced concrete beam–column joints was established using the Vulcan program; when the beam is subjected to high temperature alone and when the beam–column is subjected to high temperature simultaneously, the rotation angle shows an increasing trend within 80 min and 120 min, respectively, and the structural bearing capacity of the latter decreases more severely than the former. The bending moment and rotation angle of beams under high‐temperature conditions alone and beams–columns under high‐temperature conditions exhibit synchronous changes with the development of fire temperature within 60 min before fire exposure. After the fire exposure time is extended, the deformation of the rotation angle continues to increase, while the bending moment begins to decrease until it stabilizes. The structural response of beams and columns subjected to high temperature simultaneously is stronger than that of beams subjected to high temperature alone, and their peak moment appears earlier. The deformation and constraint force of beam–column joints during high‐temperature fire are nonsynchronous. [ABSTRACT FROM AUTHOR]