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Translation abstract Concrete beam under pure shear load conditionsThe shear force capacity of reinforced concrete components is usually investigated experimentally by subjecting the test specimens to vertical loads. These loads induce internal forces in the form of bending moments and shear forces. However, these internal forces cannot be controlled independently under such loading conditions. This article presents a test set‐up that allows a constant bending moment and a constant shear force of any magnitude to be generated in reinforced concrete beams. The loading situation to generate a constant shear force in a beam with a rectangular cross‐section was realized in three component tests. In addition, an FEM model was developed for comparative calculations. The component tests showed a brittle failure. With regard to the load‐displacement behavior and the calculated load‐bearing capacities, there was good agreement between the component tests and the corresponding FEM simulations. The test setup presented here is generally considered suitable for generating a state of pure shear force in reinforced concrete beams. [ABSTRACT FROM AUTHOR]

In this paper, an experimental, numerical and analytical study is conducted on a 2 × 1 bored pile group on saturated sand under combined loading. Initially, a single-degree-of-freedom system founded on the pile group is tested at the ETH Zurich drum centrifuge under vertical, lateral and pushover loading, gaining insights and deriving benchmark results for validation of finite-element (FE) models. The latter account for non-linear soil–pile interaction, using hypoplasticity for sand and appropriate modelling of interfaces and pile response. Combining centrifuge and FE modelling, the governing resistance mechanisms are identified and quantified. The transition from model to prototype scale is achieved after careful consideration of scale effects. The concrete damaged plasticity model is employed to model the non-linear response of the reinforced concrete (RC) piles, accounting for axial load dependency of bending moment capacity. The prototype problem is studied parametrically, deriving failure envelopes for different levels of vertical loading. Distinguishable failure modes are identified, and the contribution of different resistance mechanisms is quantified. Finally, analytical failure envelopes are derived based on limit equilibrium, expanding Broms' theory to pile groups under combined loading. Accounting for the axial load dependency of RC bending moment capacity, the proposed closed-form solutions provide a useful design tool for engineering practice. [ABSTRACT FROM AUTHOR]

This study examined nine concrete members reinforced with glass fiber–reinforced polymer (GFRP) bars, exploring the impact of combined bending moment and low axial loads. Three reinforcement ratios (1.7%, 2.5%, and 3.3%) were considered under various axial loads (0, 125, and 250 kN). In the absence of a standardized test method for determining the compressive properties of rebars, a simple approach was adopted. GFRP bars demonstrated a compressive modulus of elasticity that was roughly equivalent to their tensile modulus, along with a compressive strength reaching approximately 70% of their tensile strength. The main tests on members showed that increasing the reinforcement ratio to 3.3% resulted in a 4% reduction in bending resistance with a 2% axial load, while a ratio of 2.5% led to a 7% decrease; conversely, a lower ratio of 1.7% showed a 2% increase in bending resistance under the same load. An analytical model incorporating GFRP bar compression contributions was developed for cross-sectional analysis. It was verified against experimental and literature data, to conduct parametric studies on the impact of reinforcement ratio, concrete strength, GFRP modulus, and strength on the interaction diagram shape under low axial loads. The results demonstrated that there are two major cases of interaction diagram slope in the proximity of the pure moment axis. At higher reinforcement ratios, the moment resistance diminishes at low axial loads when compared with pure moment conditions. However, more research is needed to verify the repeatability of the test results and draw conclusive empirical evidence. [ABSTRACT FROM AUTHOR]

Studies on cable-stayed bridges exposed to blast loads encounter significant challenges arising from the complex interaction among different structural elements. Despite extensive investigation into how buildings respond to explosive loads, there is limited literature on the dynamic response of prestressed concrete bridge decks to blast loads. Single plane cable stayed bridges are very sensitive to cable loss or degradation. This study investigates the response of a prestressed concrete cable-stayed bridge with a single plane under blast loads, utilizing a comprehensive Finite Element (FE) model that incorporates nonlinear effects. The investigation considers blast weights of 230 kg, 680 kg, and 2270 kg of TNT. The analysis reveals that even small explosions cause damage to the deck, with more significant effects observed under higher blast loads, resulting in a damaged region measuring 12 m x 10 m with a 2270 kg TNT weight. Forces in cables near the detonation point increase by 19% during a 2270 kg TNT explosion. Notable changes are observed in pylon moments under different explosion charges. Maximum Bending Moment (BM) values are observed at the base under dead loads, while BMs at mid-height increase under various blast weights, with no discernible change at the base. This study provides valuable insights for designers, emphasizing the importance of incorporating explosion-resistant design principles into cable-stayed bridges. [ABSTRACT FROM AUTHOR]

Nonplanar reinforced concrete (RC) core walls form the backbone of millions of mid- and high-rise buildings, resisting both gravity and lateral loads from wind and earthquakes. The latter inevitably induces torsional demands, even in the case of full plan-wise symmetric structures, which add to bending, shear, and axial deformations. Unfortunately, current international building codes are not applicable for the design of nonplanar sections governed by warping torsion rather than circulatory torsion. This lack of information and guidance in building codes has resulted in a very limited number of structures being designed to account for warping stresses, even though the latter can be of a similar order of magnitude to bending stresses and, therefore, of major significance. A simple procedure is herein presented to estimate the ultimate warping moment and ultimate torque of nonplanar RC sections based on "warping-equivalent" ultimate bending moments from sectional analysis. A circular and bilinear bending moment-torque interaction relationship is proposed and compared to the existing, albeit limited, experimental and numerical results available in the literature. [ABSTRACT FROM AUTHOR]

To investigate the development of cracks in the walls of reinforced concrete silos under feeding–discharge cycle loading, their causes, and their fatigue life during dynamic loading, a study was conducted using a combination of in situ monitoring and numerical simulation analysis. The following conclusions were drawn: during the loading and unloading process of the silo, the time of occurrence of the minimum pressure points follows a 4:3 ratio; extreme points are approximately 15 min apart; the minimum pressure increases during material addition and decreases during material subtraction; and the load in the non-discharge area is 1.43 times that of the load in the discharge area. That is, at the same elevation, the load borne by the silo wall is uneven, with fluctuations and rotational effects occurring. Under such uneven load conditions, the silo wall experiences significant bending and torsional moments, causing excessive local tension and leading to cracking. Our analysis showed that the most unfavorable load condition occurs when discharge ports 5 and 7 are operating simultaneously, which causes the maximum tensile damage to the silo wall. For the first time, a fatigue life prediction model for reinforced concrete silos was proposed, and the accuracy of this prediction method was verified based on actual conditions. [ABSTRACT FROM AUTHOR]

The assessment of existing reinforced concrete (RC) structures, especially, bridges and viaducts, nowadays is one of the most relevant aspects for infrastructural engineers. Due to the old age of a large part of the railways and roadways assets, their safety, especially, with respect to the Ultimate Limit States (ULS) may result compromised. Safety assessment can be performed following different approaches as well as the most sophisticated methodologies based on the application of safety formats for non‐linear finite element (FE) analyses. This study presents the safety assessment at the ULS of existing prestressed RC bridge decks regarding bending moment and axial force failure mechanism adopting different methodologies. Specifically, the safety assessment will be performed through five different approaches (i.e., Courbon theory, elastic FE analysis, and NLFEAs according to the three global safety formats). The decks are modeled using, first, Courbon theory and then, girder FE model composed only of beam elements. The safety assessment is performed by comparing the design resisting moment and design acting moment in the section of interest, therefore, through a local approach. Within the local approach, design values are calculated using the partial safety factors. Afterwards, the decks are modeled with a 3D non‐linear FE model. Three different global safety formats are implemented within a global approach. The application of the different approaches leads to significantly different conclusions about the safety assessment. The two local approaches are the most conservative, therefore, lead to a lower safety margin. The application of global approaches based on global safety formats leads to a safety margin gain compared to local approaches, with significant variability in terms of safety margin gain depending on the specific global safety format. [ABSTRACT FROM AUTHOR]

This study presents analytical model for the analysis of hybrid (steel and fiber reinforced polymers (FRP)) reinforced concrete (RC) columns at elevated temperature under eccentric compressive loads. The bending moment resistance of the (RC) columns at elevated temperature is formulated based on force equilibrium and strain compatibility of the concrete column section under combined bending moment and axial force. Deterioration the mechanical properties of concrete, steel, and FRP bars due to the rise of temperature has been taken into account using equations proposed by previous studies. Validating the suggested model was carried out by comparing the analytical results with corresponding experimental and numerical results in terms of axial load‐lateral displacement relationships, axial load‐bending resistance interaction diagrams, and failure modes. Validation results have shown the accuracy of the suggested analytical model. A parametric study has also been conducted using the proposed analytical model to investigate the effect of some parameters on the axial load‐bending resistance interaction diagrams of hybrid steel and FRP‐RC columns under elevated temperature. These parameters include the effect of higher temperature values, the effect of reinforcement material, and the effect of reinforcement configuration. Parametric study results have revealed some interesting conclusions that may be implemented in the design of hybrid RC columns at fire. [ABSTRACT FROM AUTHOR]

Hammerhead pier is the preferred option in many bridge sites for its limited ground occupation. Since the bearing reactions act on the short cantilever ends of the cap beam, it is usually treated as stress-disturbed region (D region) in structural concrete. Although finite element model (FEM) can predict the response of such structures, the calculation efficiency will be sharply decreased once it enters nonlinearity. Therefore, strut-and-tie model (STM) has been promoted as an alternative approach for analyzing D regions. In this study, a loading pattern was defined to relate the axial force and bending moment of the pier column with the eccentric load ratio. Sectional analysis method and associated codes were developed to generate the STM. In addition, a full-scale hammerhead pier specimen subject to varying eccentric loads was tested. Besides, nonlinear FEM was also established to numerically investigate the response of the pier. The results indicate that the proposed STM has general applicability for modeling the hammerhead pier and shows better prediction than the FEM. The failure pattern of the hammerhead pier with a prefabricated cap beam was defined. Combining the mechanical analysis of STM and experimental results, the recommended design details for hammerhead piers were proposed. [ABSTRACT FROM AUTHOR]

Bond failure is a crucial element in ascertaining the failure mechanisms of reinforced concrete (RC) structures. The investigation pertaining to the dynamic loading's impact on bond efficacy remains a lacuna within scholarly discourse. Therefore, 138 eccentric pull-out half-beam specimens have been fabricated to probe the intricate degradation mechanisms underlying the bond-slip phenomena between concrete and reinforcement when subjected to high-temperature transients. Initially, a series of experiments were conducted on half-beam specimens possessing different reinforcement diameters and embedded lengths. Subsequently, the transient temperature changes within the bond segment were recorded, and this was pursued by the execution of eccentric pull-out tests. Second, the bond stress-strain curves under transient temperature were measured. The experimental findings revealed that the bond strength peaked at 101°C and showed an upward trend up to 302°C. Beyond this temperature, however, the bond strength exhibited a decline. Specifically, at a target temperature of 400°C, the bond strength increased by 18.1% and 9.3% compared to values at 20°C and 200°C, respectively. In contrast, it decreased by 23.2% and 41.3% in comparison to values at 600°C and 800°C. Additionally, as the reinforcement diameter increased, there was a decrease in bond strength, while the ultimate failure force increased. Finally, a methodology for evaluating bond strength under dynamic temperature was introduced, and a semiempirical constitutive model was formulated, taking into account the interplay between different heating rates. The constitutive model underwent validation through temperature computations, proposing a bending moment calculated methods, thus affirming its accuracy under fluctuating temperature scenarios. [ABSTRACT FROM AUTHOR]

This research investigates the application of plastic fiber reinforcement in pre-tensioned reinforced concrete railway sleepers, conducting an in-depth examination in both experimental and computational aspects. Utilizing 3-point bending tests and the GOM ARAMIS system for Digital Image Correlation, this study meticulously evaluates the structural responses and crack development in conventional and plastic fiber-reinforced sleepers under varying bending moments. Complementing these tests, the investigation employs ABAQUS' advanced finite element modeling to enhance the analysis, ensuring precise calibration and validation of the numerical models. This dual approach comprehensively explains the mechanical behavior differences and stresses within the examined structures. The incorporation of plastic fibers not only demonstrates a significant improvement in mechanical strength and crack resistance but paves the way for advancements in railway sleeper technology. By shedding light on the enhanced durability and performance of reinforced concrete structures, this study makes a significant contribution to civil engineering materials science, highlighting the potential for innovative material applications in the construction industry. [ABSTRACT FROM AUTHOR]

A possible way to improve the structural safety and robustness of precast building structures is to develop effective precast frame systems with layered beams, which combine prefabricated parts with cast-in situ ordinary concrete, high-performance concrete, fiber concrete, or FRP. The paper provides a new type of precast reinforced concrete frame system with layered beams for rapidly erected multi-story buildings resistant to accidental actions. Using a combination of the variational method and two-level design schemes, a simplified analytical model has been developed for structural analysis of the precast reinforced concrete frame system, both for serviceable and ultimate limit states as well as for accidental actions. The proposed model allows for determining shear deformations and the formation and opening of longitudinal cracks in the intermediate contact zone between precast and monolithic parts of reinforced concrete structural elements of the frame, as well as the formation and opening of normal cracks because of the action of axial tensile force or bending moment in these elements. The design model was validated by comparing the calculated and experimental data obtained from testing scaled models of the precast reinforced concrete frame system with layered beams. The paper investigates and thoroughly analyzes the factors affecting the stiffness and bearing capacity of the intermediate contact zone, discusses the criteria for the formation of shear cracks along the contact zone of precast and monolithic concrete, and examines the change in the stiffness and dissipative properties of layered elements at different stages of their static–dynamic loading. The robustness of the experimental models of the structural system was not ensured under the specified load, section dimensions, and reinforcement scheme. Following an accidental action, longitudinal cracks were observed in the contact joint between the monolithic and prefabricated parts in the layered beams. This occurred almost simultaneously with the opening of normal cracks in adjacent sections. A comprehensive analysis of the results indicated a satisfactory degree of agreement between the proposed semi-analytical model and the test data. [ABSTRACT FROM AUTHOR]

There exist various methods for computing reactions in reinforced concrete slabs in buildings, but the most precise approaches involve solving differential equations that are challenging to apply, rendering their practical application infeasible. Consequently, practical methods adopt simplifications in the equations to ensure their practicality. The use of rigid supports is one of the commonly adopted simplifications in calculating displacements and support reactions. The grid theory assumes that the supports are rigid, which does not accurately represent reality in design practice since the beams supporting the slab deform, often causing considerable displacements in the calculation. In this study, a new extension to the grid theory is proposed, which considers the flexibility of slab supports in calculating displacements and support reactions. An analysis of bending moments and displacements of slabs was carried out on 20 numerical models with support flexibility and different boundary conditions. The analyzed loading was static and uniformly distributed, and the boundary conditions adopted in the analytical model included both simply supported and fixed slabs. The numerical analysis showed that the proposed model, which considers the flexibility of slab supports, produced results that were in good agreement with the numerical analysis. [ABSTRACT FROM AUTHOR]

Reinforced concrete frame-wall (RC frame-Wall) structures are generally solved in a global manner by modeling the entire structure by assembling the RC frame and wall stiffness matrices into a global matrix. The bar-wall element interface is modeled at the mean line of the beam-column element, according to RPA 99, which limits the interaction to the axial and transverse components of the forces (mechanical and kinematic) thus neglecting the effects of section rotations. In order to take into account, the rotational components of the mechanical behavior of the beams (section rotation and bending moment), the interaction between the RC frame and the wall must take place at the real interface of the two substructures, i.e. at the extreme fiber of the bar elements (beams and columns). The transmission of force from the wall to the RC frame is done by transforming the tangent stresses of the wall into moment in the beam. [ABSTRACT FROM AUTHOR]

The practical application of BFRPB (Basalt Fiber-Reinforced Polymer Bars) as a support structure in foundation pit and slope engineering is relatively under-researched. The indoor tensile test presented in this paper is carried out on the bond between BFRPB and different labelled concrete. The mechanical characteristics of BFRPB, the failure characteristics, and the load-carrying capacity were analyzed. The results of this study demonstrate that the normal section stress of concrete cylindrical components with BFRP has a good linear relationship and supports the rationality of the flat section assumption. In circular reinforced concrete BFRP structures, the failure of the pile load occurs in four phases, and the cracking load is in the range of 51% to 67% of the normal yield load. The main bars increase in strain with load but become attenuated in the compression zone. The deformation of the main bars increases with the load but becomes muted in the compression zone. Based on the method of calculating the load-carrying capacity of GFRP-reinforced RC piles and the normal limit load-carrying moment obtained from in-door tests, the bending moment correction coefficient in the calculation formula for the load-carrying capacity of BFRP-reinforced RC piles was then obtained. [ABSTRACT FROM AUTHOR]

The stabilisation of shallow translational landslides can be carried out by using large diameter concrete piles, with the aim of increasing the available strength along the slip surface. In the following article, 3D numerical models of a free-head flexible pile embedded into a translational type of landslide are studied. The landslide model has a given inclination angle, β, and a thickness, D, while the reinforced concrete pile has a fixed diameter, d, and a length, D + L, in the perspective of studying the failure modes B1, BY and B2 of free-head flexible piles. In this category of piles, collapse is reached with the formation of plastic hinges. Both the soil and the concrete are modelled with simple constitutive models, such as Mohr–Coulomb for soil and the elastic-perfectly plastic for the concrete pile, in order to carry out the design approaches provided by Eurocode, as well as to highlight some practical aspects of soil–structure interaction during the landslide displacements. The results highlight how the achievement of the shear strength in a flexible free-head concrete pile generally precedes the achievement of the ultimate bending moment associated with the development of plastic hinges. Furthermore, the axial load supported by the pile may itself contribute to the overall strength available along the slip surface. [ABSTRACT FROM AUTHOR]

This article presents a review of state of the art on nonmetallic reinforcement in terms of bending moment redistribution in double‐span elements. The authors present a summary of existing research programs focused on moment redistribution in FRP (Fiber Reinforced Polymer) reinforced concrete (RC). On this basis authors created a database of concrete elements with all the important construction properties of the elements. Gathered data are presented with quantitative analysis of several variables effecting moment redistribution in published articles. In the following publication authors show a research review which includes an analysis of the influence of variable parameters from the point of view of the database, concerning: degrees of longitudinal reinforcement, ratio between degrees of reinforcement in span and over the support, type of reinforcement (FRP/steel/hybrid), concrete class and transverse reinforcement. [ABSTRACT FROM AUTHOR]

In this study, without using any uniaxial force and bending moment (N-M) interaction diagrams, designs were carried out on thick columns subjected to uniaxial bending and compression by a novel 1 dimensional (1D) Fuzzy Inverse Logic (FIL) method. For this purpose, firstly, a Fuzzy Logic (FL) model was developed and the FIL method was applied to it thereafter. While, the cross-section width (b), the cross-section height (h), the rebar diameter(f), the numbers of reinforcement rows (Rx and Ry) placed into the cross-section in X and Y directions, the characteristic concrete compressive strength(fck) and the axial force ratio Nr=N/(b.h.(fck/1.5)) were taken as variable parameters, concrete cover thickness (c), rebar strength (fyd) and k1 parameter defined for the concrete pressure block were kept constant in the developed FL model. After designs were performed on 15 columns having different variable variations by the 1D FIL method, moment bearing capacities of the obtained 9737 alternative designs determined conventionally were compared with the desired moment values. The evaluations made on the comparisons show that the FIL method is not only a very effective artificial intelligence method for the design of reinforced concrete thick columns but also a promising method for many other problems such as control, optimization, design, etc. [ABSTRACT FROM AUTHOR]

This experimental study investigates the effects of carbon fiber reinforced polymer (CFRP) strengthening on eccentrically loaded and corrosion-damaged reinforced concrete (RC) columns. The experimental program comprises two main phases: (1) inducing accelerated electrochemical corrosion in steel-bar RC column specimens and (2) subjecting both undamaged and corroded specimens to eccentric compression until failure. Five RC column specimens, sharing identical geometry, reinforcement detailing, and concrete mix, were fabricated. One served as an undamaged control, while the remaining four underwent corrosion induced by electrochemical means. Two of the corroded specimens were strengthened with CFRP sheets after repairing their concrete covers with non-shrink grout, while the other two received neither repair nor strengthening. The study examines the structural behavior of the corrosion-damaged RC columns and evaluates the effects of repair and strengthening solutions, including non-shrink grout and CFRP sheets, under eccentric loading conditions. The experimental results reveal a significant enhancement in the performance of the corrosion-damaged RC columns after applying non-shrink grout and CFRP sheet wrapping. In comparison to the undamaged control RC column, the ultimate bending moment decreases by 16.8% for corrosion-damaged RC columns, while it increases by 15.2% for strengthened RC columns. Furthermore, in accordance with the guidelines outlined in ACI 440.2R-17, a calculation is presented to establish the axial load-bending moment interaction diagram for the strengthened RC columns. This calculation provided a deeper understanding of how CFRP sheet strengthening improves the strength of corroded RC columns subjected to eccentric loading. [ABSTRACT FROM AUTHOR]

In reinforced concrete flat slab buildings, the transference of unbalanced moments in the slab–column connections usually results from the asymmetry of spans, vertical loads, and horizontal forces from the wind. The punching strength of the slab–column connections can limit the load-carrying capacity of the structure in these cases, leading to structural collapse. The design code provisions are still based on empirical or semi-empirical equations; as the punching shear failure mechanisms are complex, and the ultimate strength is affected by several parameters. In this context, this paper presents the results of the computational investigation of the mechanical behaviour of flat slabs subjected to balanced and unbalanced moments using numerical Finite Element models. The numerical models were calibrated and accurately reproduced the behaviour and the punching resistance for concentric and eccentric loading. Furthermore, a parametric study was conducted to evaluate the mechanical behaviour of flat slabs under different load eccentricities, confirming that the increase in the unbalanced moment negatively impacts the load-carrying capacity of the slab–column connection. Furthermore, it was observed that all computational results obtained from models with unbalanced bending moments were higher than those estimated by the design codes. [ABSTRACT FROM AUTHOR]

With the convenient and fast requirements for construction in bridge engineering, prefabricated assembly technology is widely applied in engineering construction. Typically, prefabricated bridge decks are connected through cast-in-place wet joints. Wet joints, as the primary load-bearing parts of bridge decks, undergo complex stress and are prone to cracking and damage. Particularly in the negative bending moment region of bridges, the influence of tensile stress on wet joints is more severe, thus enhancing the mechanical performance and crack resistance of joints becomes crucial. This paper investigates the mechanical behavior of prefabricated reinforced concrete bridge deck panels with variable cross-sections under negative bending moments, focusing on the performance of Ultra High-Performance Concrete (UHPC) wet joints. Full-scale experimental tests were conducted on a 176 m steel truss composite continuous rigid bridge, employing C50 concrete panels with UHPC wet joints. Results show three distinct stages: elastic, crack initiation and propagation, and failure. The maximum failure load reached 822 kN, with a maximum displacement of 21.64 mm. Concrete strains indicate compressive stress near the wet joint and tensile stress near the loading positions. Cracks primarily develop at the wet joint interface and propagate under increasing load, ultimately leading to flexural–shear failure near the variable cross-section of the wet joint. Numerical simulations using ABAQUS/CAE (2020) corroborate experimental findings, closely matching load-displacement curves and identifying damage locations. The study demonstrates that UHPC wet joints significantly enhance crack resistance, meeting design requirements for improved mechanical performance in bridge structures subjected to negative bending moments. [ABSTRACT FROM AUTHOR]

A half-slab precast concrete (HSPC) system with precast bottom layers and in-situ cast top layers has been widely applied in various constructions. It generally behaves as a one-way slab due to the absence of positiveflexural reinforcements in the perpendicular direction to the precast component. However, in some cases, the HSPC was also applied in a two-way slab system. Consequently, a particular design and treatment in the connection between precast members was required, so that the bending moment in two orthogonal directions could be accommodated. In the present study, an innovative rectangular rigid connection (RRC) in a two-way HSPC system was investigated through an experimental test. It was found that the RRC-HSPC presented only a 9.13% reduction of the load at the crack, a 16.44% reduction of the ultimate load, and a 6.06% increase of the deflection at the crack when compared to the monolithic one. [ABSTRACT FROM AUTHOR]

The article presents an analysis of the results obtained from the testing of simply supported reinforced concrete beams subjected to four-point bending. The beams, with two levels of steel reinforcement (ρs1 = 1.26%, ρs 2= 0.71%), and dimensions of 0.12x0.30x3.30 m, were subjected to loading involving a sudden increase in force with multiple unloading cycles to zero. The study included comparative analysis of deflection results obtained from experimental tests (calculated based on the curvature of the element and readings from measurement devices) with deflection values obtained through calculations based on two selected standards. Real values of ultimate bending moments were also compared with theoretical values. Additionally, compressive strength tests were conducted on eight cubic concrete specimens with a side length of b = 150 mm, obtained for each concrete batch. They constitute accompanying studies. Using standard procedures, strength and statistical parameters were estimated and evaluated, taking into account the assessment of the quality of the concrete production used to make the reinforced concrete beams. Ensuring compliance with the process of producing full-sized reinforced concrete beams with existing standard procedures, as well as attention to the quality of concrete production, contributed to achieving satisfactory results in the experimental tests. Knowledge about the impact of loading on mechanical properties enables effective management of factors shaping quality to obtain a construction material with optimal parameters. [ABSTRACT FROM AUTHOR]

This study presents an overview of the design of reinforced concrete (RC) structures (moment frames, shear walls and large panels) for Romania and the impact on seismic exposure and vulnerability within the context of the recent European Seismic Risk Model 2020 (ESRM20). The overview is focused on the design of structural elements for bending moment and shear force, as well as on the constructive and detailing requirements imposed by various codes. The design of RC structures in Romania over the past century involved the use of material- and element-oriented design codes, besides the seismic design code. In addition, economic constraints regarding the material (steel) consumption influenced considerably the design process. The observations made from various literature sources regarding the design and construction practice in Romania are used for a better understanding and evaluation of the seismic exposure and vulnerability. In addition, the key observations regarding the seismic behaviour of each particular structural type are also presented. [ABSTRACT FROM AUTHOR]

In this paper, we present an investigation of the performance of reinforced concrete (RC) columns under combined bending loads and various axial forces using a finite element method (FEM) model developed with the ABAQUS finite element program, verified with actual experimental values. In the experimental study, we applied combined bending loads and various axial forces to four RC members. Two RC members were subjected to vertical cyclic loads using displacement control with 0% axial force, while the other two were tested with vertical cyclic loads, one with 10% axial force, and the other with 20% axial force. The axial force load was applied using a specially designed setup. The experimental results of the RC members include observations of final failure mode, ductility, and axial load–bending moment interaction curves (P–M correlation curves). The experimental study confirmed that as the axial force increased, cracks in the RC columns concentrated at the center of the column. The yield strength increased by 55% when the axial force ratio was 10%, and 106% when the axial force ratio was 20%. The maximum strength increased by 28% with a 10% axial force ratio, and 50% with a 20% axial force ratio. However, ductility tended to decrease as the axial force increased, reducing by 26% with a 10% axial force ratio and 60% with a 20% axial force ratio. The analytical study produced results consistent with the experimental research, showing similar numerical trends. Finally, when comparing theoretical values, experimental results, and analytical results using P–M correlation curves, we found that the experimental value has a safety rate of 18% compared to the theoretical value. The experimental and theoretical result values were similar. Therefore, it has been demonstrated experimentally and analytically that the current design has a safety value of about 18% for the performance of the actual structure. [ABSTRACT FROM AUTHOR]

The double strap joint splicing of glass fiber reinforced polymer (GFRP) bars for reinforced concrete (RC) beams strengthening, applying the near surface mounting (NSM) method, has been proposed in the paper. The proposed method consists of application of the supplementary GFRP bars symmetrically positioned in the cut-off zone of the main GFRP reinforcement. The performances of this splicing method have been experimentally tested for the most unfavorable case of the GFRP reinforcement cut-off in the maximal bending moment zones. During the experiment, the varied parameter has been overlapping length of the bars, taking values of 20Ø and 40Ø. Evaluation of the splicing technique is done comparing the experimental results with the results of the behavior of beams strengthened by GFRP bars without cut-off and with cut-off, but without splicing. Experimental research encompassed analysis of strength, stiffness, ductility, crack pattern, strains in the steel, GFRP reinforcement and concrete, and the failure modes of the beams. It has been shown that in case of the cut-off of the GFRP bar, strengthening effectivity decreases for 39%, and that in the case of bypassing the cut-off using double strap 20Ø and 40Ø long, strengthening effectivity decreased 23%, and 14% respectively, compared to the beam without GFRP bar cut-off. Using extrapolation, it has been shown that double strap with length of 60Ø provided strength equivalent to the case without cut-off. The result of application of this splicing method of the additional GFRP bars is significant increase of strength and serviceability of the strengthened RC beams. [ABSTRACT FROM AUTHOR]

In this paper, a new type of assembled RC beam–column joint with a beam-end steel cover-plate connection is proposed to achieve seismic toughness and damage control of the joint. Energy-dissipation plates with different structural forms are proposed, and a series of seismic performance indexes of the joints are calculated and analyzed by using the finite element method. The energy-dissipation plate with an arc notch can reach the yield condition faster, and the ultimate bearing capacity of the joint reaches the maximum. The bending design of energy-dissipation plates is carried out by calculating the demand bending moment, and energy-dissipation plates of different structural forms are simulated and verified. The results show that the proposed design formula can ensure that the bending moment at the beam end still maintains elastic deformation when the energy-dissipation plate yields. The important parameters affecting the bending moment of the weakened part in the middle of the energy-dissipation plate are analyzed. Finally, this paper also analyzes the important parameters affecting the seismic performance of the joints. The results show that the seismic performance of the newly assembled RC beam–column joints proposed in this paper is better than that of cast-in-place joints. Increasing the longitudinal reinforcement ratio appropriately can greatly improve the ultimate bearing capacity and ductility of the joints. Increasing the thickness of the energy-dissipation plate, increasing the strength of the energy-dissipation plate, increasing the axial compression ratio of the column, increasing the strength of the concrete, and increasing the strength of the shear web can improve the ultimate bearing capacity of the joints but also reduce their ductility. Under different axial compression ratios, the strain in the core area of the joints is low, and the compressive damage of the concrete is zero, which verifies the effectiveness of the damage-control design of the proposed model. [ABSTRACT FROM AUTHOR]

A new and unified approach is proposed toward accurately analyzing overall elastoplastic responses of axially loaded bars and finite bending beams until failure. Results are presented for various constituent materials such as metals, reinforced concretes and reinforced composites, etc. Novelties in three respects are incorporated: (a) new uniaxial stress–strain functions are first presented in explicit forms for the purpose of accurately characterizing non-symmetric tensile and compressive behaviors of axially loaded bars from hardening to softening; (b) explicit solutions to both the varying neutral axis and the flexural moment of finite bending beams are then obtained directly in terms of these two uniaxial functions; and, hence, (c) the complex bending problem of various beams until failure is in a unified manner reduced to a simple issue of fitting two uniaxial functions to tension and compression data from uniaxial testing, thus bypassing the analytical and numerical complexity of various existing approaches. Numerical examples of model predictions are provided for typical constituent materials, including aluminium, meso-scopic heterogeneous concrete and ultra-high performance fiber-reinforced concrete with reinforcing rebars. Good agreement is achieved simultaneously with all experimental data for bars and beams made of these materials. [ABSTRACT FROM AUTHOR]

Occurrence of progressive collapse events invariably leads to significant economic and human-life losses. Progressive collapse analysis and design of building structures have become a research hotspot worldwide. Existing studies have proved that development of extra load-carrying mechanisms could significantly improve the resistance of structures to progressive collapse. However, limited research has been conducted to quantitatively analyze these mechanisms. This study proposed a new and unified division method for mechanisms for resisting progressive collapse; furthermore, it provides a basis for their quantitative analysis. In addition, the progressive collapse behavior of a 1/3-scaled two-story, one-bay-by-two-bay reinforced concrete (beam–slab–column) frame with an edge column lost was experimentally investigated. Additionally, a 3 D solid finite element model was established and validated based on the test results. The effects of different extensive parameters, including ideal lateral constraints, slab thickness, and beam–slab interaction, on each resisting mechanism were quantitatively investigated. Finally, a new simple method for predicting the first peak load was proposed based on the contribution of each mechanism. The results from the simple method were in agreement with the simulation results of beam–slab–column structures. [ABSTRACT FROM AUTHOR]

In an actual structure, torsion seldom acts alone; rather, a complex load combination acts together. Members subjected to a complex loading condition--that is, shear, bending, torsion, and so on-show lower strength compared to the members under torsion only. However, when structural members exhibit ductile behavior, the force-deformation correlation of shear force, bending, and torsional moment may change due to the redistribution of internal forces. In this study, the interaction of bending and torsional moments was evaluated by analyzing the test results of 123 reinforced concrete (RC) members subjected to combined loading. Additionally, 13 RC beams subjected to combined actions of bending and torsional moments were tested to investigate the effect of force redistribution. The results indicate that the post-yielding behavior of actual members subjected to combined loading significantly differs from the theoretically predicted one. This is because the theoretically induced bending and torsional moment interaction curves are based on strengths corresponding to the yield point of reinforcement. However, the experimental results show that the force redistribution mechanism develops after the first reinforcement yielding. Consequently, the torsional strength does not decrease as sharply as theoretically assumed, even when the bending moment increases. [ABSTRACT FROM AUTHOR]

The results of the study are aimed at developing a nonlinear strain model for reinforced concrete beam elements in the general case of force actions and temperature effects for different durations. As a rule, temperature effects on structures involve temperature drops, causing heterogeneity of mechanical and rheological properties of concrete and reinforcement. The article has approximating expressions needed to take into account the effects of temperature and heating time on the values of temperature-induced strain and mechanical and rheological properties of heavy concretes with C30–C60 strength classes. The properties of concrete and rebars are heterogeneous from top to bottom and across the width of the cross section. A physically nonlinear problem is solved using the method of elastic solutions combined with the method of stepwise increases in temperature and force loading. The cooling of a heated reinforced concrete element to normal temperature is considered a short-term effect. Strength criteria of portions of a concrete cross section, crack closure conditions, and the ability of cracked sections to take loads in compression amid a change in the sign of stresses are determined. The stress–strain state (SSS) analysis of reinforced concrete beams, made according to the proposed method, is compared with the experimental studies using (i) values of thermal bending moments in statically indeterminate structures, (ii) cracking forces, and (iii) values of deformations (elongations and curvatures) of the elements in the longitudinal axis. Good agreement between the calculated and experimental values of controllable criteria confirms the reliability of physical relationships (i) developed for heterogeneous reinforced concrete beam elements and (ii) applied to the complex cases of temperature and force effects. [ABSTRACT FROM AUTHOR]

Reinforced concrete pipes are usually designed to attend a three-edged-bearing test (TEBT) using the partial safety factors from building structures. This study presents an alternative approach to designing RC pipes based on simplified reliability analyses. The procedure consists of providing curves of failure probability according to the reinforcement areas used in the pipes. The results indicate that RC pipes with simple reinforcement show a failure probability of around 1% with the most traditional design method, even using the partial safety factors from buildings, due to the higher dispersion of the concrete cover and the use of a single reinforcement layer to satisfy different control sections. Meanwhile, RC pipes with double reinforcement show a significantly lower failure probability as each reinforcement layer is designed to satisfy the bending moments from different control sections and due to the larger pipe thickness. In summary, the large randomness of the reinforcement position increases the failure probability of these members compared to traditional building structures. [ABSTRACT FROM AUTHOR]

Since reinforced concrete members suffer from different types of loads during their service life, the steel bars embedded in reinforced concrete members can be easily corroded in chloride‐laden environment. To investigate the influence of combined effect of load and steel corrosion on the flexural stiffness of recycled aggregate concrete (RAC) beams, 12 RAC beams were prepared and tested. The effects of load level (i.e., the ratio of the load applied to beams to the ultimate load) and recycled coarse aggregate (RCA) replacement ratio (i.e., the ratio of RCAs to replace natural coarse aggregates) on the internal force arm coefficient of cracking cross‐section, the elastoplastic resistance moment coefficient of cross‐section, and the strain incongruity coefficient of corroded tensile steel bars were analyzed, and a calculation model for flexural stiffness of RAC beams under combined effect of load and steel corrosion was established. The results showed that when the ratio of bending moment to ultimate bending moment of the pure bending part of beams was within 0.55–0.80 and the average mass loss of tensile steel bars was less than 3.23%, 0.85 could be adopted as the internal force arm coefficient of cracking cross‐section. The elastoplastic resistance moment coefficient of cross‐section was approximately a constant when the corroded RAC beams were in the service stage, while it increased obviously with the load level. There was a strong linear relationship between strain incongruity coefficient and average mass loss of tensile steel bars during the service stage of corroded RAC beams, and the strain incongruity coefficient increased linearly with the load level. The calculated values of the model of flexural stiffness proposed in this paper were in reasonable agreement with the experimental values. [ABSTRACT FROM AUTHOR]

The use of concrete incorporating slag is necessary due to global environmental concerns, but the decrease in concrete durability caused by environments rich in chloride ions requires more advanced concrete mix designs, especially in coastal areas. The aim of this study was thus to assess the influence of slag addition on the transport of chloride ions in reinforced concrete (RC) beams under sustained bending moments, considering two conditions of environmental chlorine exposure: drying–wetting cycles and soaking. The results showed that the chloride diffusion coefficient (CDC) increased in tension zones and decreased in compression zones when the sustained bending load in the concrete beam was increased. However, it was also found that the addition of slag can significantly reduce the chloride diffusion depth and CDC for both environmental conditions, with a more significant effect under drying–wetting cycles. The chloride concentration on the surface of slag concrete in the compression zone was greater than that in the tension zone and greater than that in both the tension and compression zones of the ordinary concrete. A prediction model was established for describing the chloride penetration characteristics of concrete beams subjected to sustained bending moment. The proposed model is a reasonable approach for predicting chloride distribution in RC beams with slag addition subjected to bending moments. [ABSTRACT FROM AUTHOR]

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This paper investigates the seismic behavior of high-rise buildings having transfer elements. Three constructed reinforced concrete (RC) buildings having either transfer slabs or transfer girders were analyzed using the response spectrum (RS) and time-history (TH) methods. For each building, the story shear, bending moment, displacement, drift, and time period were obtained. Furthermore, pushover analysis (POA) method was conducted to evaluate the capability of these buildings to resist the expected seismic loads. Results of the studied buildings showed that, the base shears obtained using pushover analysis are ranging between 50% to 83% of those calculated using the static approach. In addition, the response modification factors (R) for these buildings were calculated to show their sensitivity due to the irregularity of buildings. For the studied cases in this research, the R values given in the building codes were overestimated for the cases with transfer slabs and underestimated for cases with transfer girders. [ABSTRACT FROM AUTHOR]

Steel profiles are often embedded in reinforced concrete (RC) members (specially columns) to achieve higher performance in a localised manner. Although the RC and steel‐concrete composite zones of such members can be respectively designed according to the Eurocodes 2 and 4, the transition zone between the steel profile and its surrounding concrete needs to be adequately designed to ensure an effective transmission of the axial force, shear and bending moments carried by the interrupted steel component. This is currently not covered by the design standards and is only partially covered by the current literature. This article proposes a design procedure for such transition zones relying on a 2‐steps approach: (1) Definition of the transverse load to be transferred from the steel part of the composite zone to the RC part, based on a reasonable distribution of the contact pressure between the profile and the surrounding concrete; and (2) Evaluation of a suitable "strut & tie" mechanism to ensure the appropriate transfer of this load and consecutive design of the transverse reinforcement. In order to evaluate the efficiency of the design approach, the transition zone between a composite and a pure RC part of a locally composite column was investigated experimentally. Four test specimens were designed and tested in order to study the influence of certain parameters, e.g. length of the assumed transfer zone, presence of one or two lateral beams at the level of the transfer zone, compression level in the column, etc. [ABSTRACT FROM AUTHOR]

The seismic performance of hybrid coupled walls (HCWs) made of a single reinforced concrete (RC) wall connected to two steel side columns by means of steel links is studied in this article. Steel links are designed as dissipative elements while the RC wall and the steel side columns should remain elastic. Given that previous studies highlighted the difficulties in avoiding damage at the base of the RC wall due to the concentration of bending moment, the scheme with fixed base is modified in this study with the adoption of a hinged connection and vertical steel elements called corner components. A ductile design methodology is proposed and applied to the design of case studies with different building heights (three and six stories) and different base conditions (fixed base and hinged base with corner components). Moreover, the influence of uniform and variable distributions of links along the building height is assessed. Results of pushover analyses are presented to validate the design methodology and provide insight into the structural response of the proposed solution, showing the benefits of a hinged base with corner components. [ABSTRACT FROM AUTHOR]

Thermally induced ratcheting of a thermo-active pile is the accumulation of net and irreversible pile head displacement upon heating–cooling cycles. Although this kind of phenomenon has been observed in vertically loaded piles in sand, it is unknown whether this exists in laterally loaded cases, and also what underlying mechanisms occur under the thermomechanical flexural soil–pile interaction. This study presents a series of centrifuge tests and finite-element simulations of the thermomechanical behaviour of a laterally loaded thermo-active pile in sand. A new model reinforced concrete (RC) was used in the centrifuge tests to mimic the thermal and mechanical properties of a prototype RC pile realistically. Ratcheting was evident in laterally loaded piles and its extent was more significant when the working horizontal load was higher. The ratcheting phenomenon was attributed to the accumulation of soil plastic strain due to the cyclic mechanical loading induced by pile thermal horizontal expansion and contraction, soil dilation upon soil–pile interface shearing and creep. The additional bending moment induced by the thermal action did not induce yielding within the pile. A subsequent numerical sensitivity study suggested that ignoring the softening behaviour of the sand would lead to underestimation of the magnitude of the accumulative thermally induced pile head lateral displacement. [ABSTRACT FROM AUTHOR]

Using the limit state method, it is challenging to precisely study Reinforced Concrete (RC) column sections subjected to axial compression and bending moments because the neutral axis in biaxial bending is inclined to the resulting bending axis. Many design standards, like the IS-456:2000, use the Bresler-invented constant load contour method as an approximation when designing rectangular RC columns that are biaxially loaded. However, the 'precise' load contours deviate from the 'approximated' load contours due to the simplifying approximations imposed. This work examines the degree to which the aforementioned approximations lead to inaccuracies by analyzing 336 column sections. Based on the analysis, new values of exponent α, which defines the shape of the normalized load contour, are provided, which improves the estimation of load contours. Lastly, reliability analysis is performed for different combinations of dead load and imposed load effects and for the whole range of axial load levels and load eccentricity values to validate if the proposed exponent α results in a uniform design conservatism. [ABSTRACT FROM AUTHOR]

Solving engineering design tasks requires the use of analytical formulas and dependencies. The direct inclusion of mathematical expressions in the artificial neural network (ANN) is not possible. This research studies the possibility of applying the neural networks method for designing of single or double-side reinforced concrete sections. A Visual Basic for Applications (VBA) macro was developed in the MS Excel environment to solve the task of determining the required area of the reinforcement by given geometric dimensions and bending moment and applying classical analytical formulas for reinforced concrete sections design. The training of the pre-configured neural network is performed by approximately 34000 sets of matching input parameters. The presented results from the trained ANN are compared and analysed against the exact analytical solutions. The study presents an approach to the application of structural design calculations. The results suggest that the approach is applicable to more complicated structural design problems. [ABSTRACT FROM AUTHOR]

Minimizing construction cost while simultaneously meeting structural requirements has been an important topic. This study addresses the application of grey wolf optimization (GWO) to the cost minimization of T-beams subjected to ultimate loading. Both the objective and constraints functions take the self-weight of T-beams into account. Due to their section modulus, T-beams have a high ultimate bending moment capacity, especially over long spans. The objective function has been split into three subobjectives: concrete, steel, and formwork costs. Standard design constraints were followed. The constraint functions include the nonlinear behavior of concrete and steel. Ten T-beams of varied lengths were evaluated, and corresponding low-cost design solutions were provided. The relationship between the length of the T-beam and the efficiency of GWO was demonstrated. Comparisons between optimal solutions attained and standard design solution demonstrated conclusively that the proposed method typically results in large reductions in the quantity of building materials needed. This method can be easily adaptable to various types of RC frame construction and other building codes. [ABSTRACT FROM AUTHOR]