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This paper presents a numerical and experimental study aimed at the modeling and dynamic characterization of the reinforced concrete structure of the Palazzetto dello Sport in Rome, designed and by Pier Luigi Nervi with Annibale Vitellozzi, and built by Nervi & Bartoli contractors in 1956‐57. An experimental dynamic testing campaign has been performed to obtain the modal properties of the structure, identified using operational modal analysis (OMA). The axial symmetry of the Palazzetto's dome, expected to exist in an idealized perfect dome, has been observed to occur experimentally by noting that rotated modes possessed nearly identical frequencies, evidenced by closely spaced double peaks in the power spectral density. This observation recognizes the remarkable precision of Nervi's construction methodology. A numerical 3D model has been developed by relying on detailed information about the structure gathered from various sources, including archival documents, on‐site testing, and surveying. The model has been calibrated by means of modal updating based on the experimental measurements collected in this study. The reconstruction of the dome using laser‐scanning and aerophotogrammetry has revealed a slight asymmetry in its thickness distribution (and consequently its mass distribution) that, when incorporated in the numerical model, has been shown to contribute to the experimentally observed frequency split. It is expected that, by tracking these closely spaced frequencies on top of the typical variations of natural frequencies in a health monitoring approach, further insight might be gained into the detection of possible damages and/or degradation of the structure and its components. [ABSTRACT FROM AUTHOR]

Reinforced concrete (RC) structures are mainly designed to withstand both static and dynamic loads. However, due to the highly nonlinear behavior of RC structures subjected to extreme dynamic loads, these structures have a very complex damage behavior under dynamic impact loading. In fact, current existing methods for damage‐simulation and prediction are generally based on either empirical data, simplified mechanical approaches or complex numerical simulations mainly using the finite element method. In this regard, empirical and semi‐empirical models can be considered to calculate the load‐bearing capacity in a simplified way with only a few input parameters. Hence, using current experimental test data, this paper aims to analyze and assess existing empirical and semi‐analytical approaches that are established in standards and guidelines. Accordingly, a functional relationship in terms of an impact factor is found. Based on the obtained results, different approaches are also developed to describe the resistance to projectile penetration of RC structures as well as the force interaction between projectile and RC structures. [ABSTRACT FROM AUTHOR]

The study examines the early incorporation of reinforced concrete in the architecture of Historicism in Austria–Hungary. Spanning the late 19th to early 20th centuries, the research illuminates the period's stylistic pluralism and the transformative impact of reinforced concrete. The paper examines the integration of reinforced concrete into traditional forms, providing detailed case studies and architectural examples. It navigates through various aspects, including the evolution of reinforced concrete during the historicist period, its adoption in notable structures, and its documentation in contemporary literature. Case studies, such as the Lutheran Church in Battyánd (now Puconci, Slovenia), the Roman Catholic Church in Topolya (now Bačka Topola, Serbia), and the former Synagogue in Český Krumlov, Czechia, showcase the innovative ways reinforced concrete addressed structural challenges while adhering to historicist aesthetics. The research concludes by reflecting on the transformative role of reinforced concrete in challenging the conventions of Historicism, paving the way for modern architectural expressions. [ABSTRACT FROM AUTHOR]

The paper investigates the behavior of glass‐fiber reinforced polymer (GFRP) reinforced concrete columns with integrated steel spirals (hybrid reinforcement). Six concrete columns were tested under eccentric axial loading, resulting in failure due to bending. Columns with outer steel longitudinal bars experienced steel yielding at peak loads, while those with GFRP outer rebars failed due to concrete crushing. The results revealed that using GFRP as outer longitudinal bars led to peak loads 3–10% lower compared to columns with steel rebars. Inner confinement by steel spirals increased the load‐carrying capacity. Additionally, columns with inner tubular steel exhibited greater strength than those with steel spirals, indicating a slightly enhanced confinement effect. A finite element model was developed to analyze structural behavior, considering both material and geometric nonlinearity. The model's accuracy was validated by comparing predictions with test results. Parametric analysis from the nonlinear FE model showed that eccentricity significantly impacted column load‐carrying capacity. Increasing inner confinement area and the number of inner longitudinal bars improved structural stiffness and load‐carrying capacity. Furthermore, a simplified theoretical method was proposed. Comparison between experimental failure loads and theoretical predictions revealed differences within 20%, indicating satisfactory reliability of the proposed method. [ABSTRACT FROM AUTHOR]

This paper presents the experimental results of six full‐scale one‐way reinforced concrete slabs with variations in reinforcement detailing. Test specimens consisted of two reference concrete slabs reinforced fully with glass fiber reinforced polymer (GFRP) rebars or with steel rebars and four hybrid‐reinforced slabs. The variables included the arrangement of rebars, mechanical reinforcing ratio, and the ratio of steel rebar area to GFRP rebar area. The fabricated specimens were subjected to four‐point loading until failure in the strong floor laboratory. Experimental results indicated that hybrid reinforcement enhances stiffness compared to FRP reinforcement and provides a higher load‐bearing capacity than steel reinforcement. Also, it was observed that FRP bars placed as tensile reinforcement, similar in number and diameter size to steel bars placed as compressive reinforcement in a slab result in the highest ultimate capacity. Moreover, it was observed that while the mechanical reinforcing ratio contributes to the overall behavior of hybrid‐reinforced concrete slabs, the ratio of steel rebar area to GFRP rebar area is not considerably effective. Furthermore, image processing was employed to determine the exact crack widths of specimens after failure. Finally, finite element modeling results showed good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

Alkali silica reaction (ASR) is an undesirable phenomenon that occurs between alkalis that usually originate from cement and certain types of siliceous aggregates in concrete. The result of this reaction is delayed expansion of hardened concrete in the presence of moisture, which may cause cracking and damage in an existing structure. The present paper investigates the general behavior and shear strength of pretensioned concrete bridge girders affected by ASR. Four identical pretensioned concrete AASHTO Type I girders were fabricated using reactive concrete and subjected to environmental conditioning at a relative humidity of 100% and a temperature of 45 degrees Celsius for up to 296 days to accelerate the development of ASR. During this period, ASR‐induced expansions, changes in surface strains of concrete, transfer lengths, and patterns of damage and cracking were monitored. Each specimen was subjected to shear‐critical loading until failure upon reaching the desired expansion level. The results showed that the existence of prestressing force played a significant role in limiting the ASR‐induced in‐plane expansion and cracking. Progress of ASR caused a reduction in the load corresponding to the first detected flexural crack but an increase by up to 14% in the load corresponding to the first diagonal cracking compared to the control specimen, likely due to the additional prestress caused by restrained ASR‐induced expansions. The ultimate shear strength of ASR‐affected girders was generally within 5% of the control specimens, and all specimens exceeded their nominal shear strengths according to AASHTO LRFD 2020 specifications. Until the unrestrained uniaxial expansion of 0.2%, no significant concerns were identified regarding the shear strength of the ASR‐affected pretensioned concrete specimens. [ABSTRACT FROM AUTHOR]

The shear wall system with cast‐in situ concrete infilled walls has been widely used in high‐rise buildings due to its significant advantages in construction. In this paper, quasi‐static tests were conducted on the shear walls with and without cast‐in situ concrete infilled walls to analyze their failure modes, load‐bearing capacity, stiffness, energy dissipation capacity, and ductility. A simplified model of the shear wall with cast‐in situ concrete infilled walls was proposed based on the fiber element model in OpenSees. The test results showed that the shear wall specimens with cast‐in situ concrete infilled walls exhibited full‐section compression or tension failure, and the cast‐in situ concrete infilled walls did not show obvious damage. Compared with the shear wall without infilled walls, the overall stiffness, load bearing capacity, and energy dissipation capacity of the shear wall specimens with cast‐in situ concrete infilled walls improved, indicating better seismic performance than those without infilled walls. Comparison between the hysteresis and skeleton curves derived from the tests and those simulated by the proposed simplified model revealed errors within 15% for stiffness, yield bearing capacity, and ultimate bearing capacity for shear walls with cast‐in situ concrete infill walls, affirming the effectiveness and accuracy of the model. [ABSTRACT FROM AUTHOR]

The mechanical behavior of cable pylon anchorage zone in a cable‐stayed bridge is complex due to high localized stresses. A strut‐and‐tie model (STM) has been introduced in this paper, which is recommended as an efficient way to analyze the disturbed region. However, predicting the internal forces in the tie members in the STM by integrating stresses was time‐consuming and inefficient. To address this issue, the principle of minimum strain energy was used to analyze the STM of the cable pylon anchorage zone. A simplified method was presented to assess the internal forces in the cable pylon anchorage zone. Moreover, an actual bridge (Cao'e River Bridge) was employed to be analyzed, and the prestressed steel strands in the bridge were obtained by the simplified method. A full‐scale test model of the bridge was fabricated to validate the accuracy of the simplified method. Furthermore, based on the simplified method, the effect of the thickness of front wall, the length of inner opening straight section, the thickness of side wall, the thickness of inner wall and the width of inner opening straight section on the internal force in the tie members in the STM was studied. The results show that the length of inner opening straight section has negligible effect on the internal forces in all tie members. Compared with the thickness of the side wall, the thickness of inner wall and the width of inner opening straight section have limited effect on the internal force of tie members. This study was expected to promote the design of cable pylon anchorage zone. [ABSTRACT FROM AUTHOR]

This paper aims at assessing the failure time of a 7‐story reinforced concrete (RC) frame in a post‐earthquake fire (PEF) event probabilistically. Cumulative distribution functions (CDF) of the studied frame's failure time in various seismic load intensities have been calculated and presented with the aid of Monte Carlo analysis. Seismic load intensity, failure time, and failure probability are three parameters that are correlated through probabilistic analysis. The effects of cracking, spalling, and residual deformations resulted from the seismic load are considered in the strength of structure against the fire load. Seismic load intensity, materials properties, gravity load, and geometry are considered as random variables and one probabilistic analysis has been carried out for each seismic load intensity. The results have illustrated that in low seismic load intensities, probabilistic values of failure time in a structure subjected to pure fire load are equal to the one exposed to PEF. With the increase of seismic load intensity, the effects of cracking, spalling, and residual deformations would lead to a decline in the strength of structural elements against PEF scenario. The failure time in 50% failure probability for Sa = 0.2 g, Sa = 1 g, and Sa = 2 g intensities has been calculated as 14,300, 12,200, and 5100 s, respectively. The analysis results have shown that in an unspecified seismic load intensity, the failure time of the 7‐story RC frame for the 50% occurrence probability is equal to 9750 s. [ABSTRACT FROM AUTHOR]

This paper presents experimental and numerical investigations on the behavior of eccentrically loaded lightweight aggregate concrete encased steel (LWACES) columns after exposing to elevated temperatures. Sixteen concrete encased steel (CES) columns were considered in the study, 12 of which were exposed to elevated temperature then eccentrically loaded up to failure at different eccentricity ratios. The effect of temperature on the load–displacement relationships, failure load, and failure modes of the concrete encased steel (CES) columns was monitored and evaluated. Experimental results have shown that as the temperature increases, the load bearing capacity of the CES columns decreased. It has also been showed that, at high temperature, the normal‐weight concrete encased steel (NWCES) columns experienced larger degradation of the load bearing capacity compared to that of LWACES columns. Also, this study presents a numerical simulation of the behavior of LWACES columns at elevated temperatures with eccentric compressive load. The numerical model was implemented in conducting parametric study to understand the effect of temperature distribution, concrete cover, eccentricity ratio, and high temperature levels on the behavior of the thermally exposed (CES) columns. Numerical results have revealed that, at temperature value of 500°C, the ultimate capacity of LWACES with eccentricity ratios of 0.75, and 1 has decreased by 17%, and 23%, respectively, compared to that of the column with eccentricity ratio of 0.5. [ABSTRACT FROM AUTHOR]

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

In typical reinforced concrete design, reinforcement is designed to carry axial forces, but it can also resist transversal forces by dowel action. This is usually neglected for simplicity's sake in the design phase, but it can be accounted for either explicitly in mechanical models or implicitly in empirical relationships. Furthermore, there are cases where the connection between various concrete elements explicitly depends on dowel action, as for example, in connections between precast elements or between two concrete parts cast at different times. On the other side, dowel action can have a negative impact on the fatigue resistance of reinforcing bars subjected to cyclic loading, because of the local stress concentrations near interfaces due to relative movements, either in sliding or in opening of cracks not perpendicular to the bar. For the assessment of the remaining capacity of existing structures, improved models of the behavior are needed, including realistic models of the behavior of concrete, steel and their interfaces. The aim of the present paper is to provide a contribution to a better understanding of dowel action by two test series. The first series focused on the behavior of the dowel: the concrete specimens with the embedded bars were placed in a custom‐made test setup and subjected to monotonic or low stress‐level cyclic actions with a longitudinal and a transversal crack opening component, up to developing the full plastic capacity of the dowel and rupture at the peak of catenary action. The measurement system included tracking the displacement field at the surface of the concrete and the strains in the dowel by optical fibers glued on its surface. The latter measurements allow to derive the internal forces in the reinforcing bar and deformed shape of the bar as well as the contact pressure between the bar and the surrounding concrete. The results show a strong dependency on the test variables: diameter of the bar, imposed crack kinematics and angle between the bar and the crack. The second test series looked more closely at the behavior of concrete underneath the bar, in the presence of a point load introduced at various locations into concrete through a reinforcing bar. A comparison of the test results with existing models shows a general good agreement and some aspects that deserve to be improved. [ABSTRACT FROM AUTHOR]

This paper describes the structural aspects of the Wieselburg Bridge collapse in Austria. The original design and reinforcing details for this integral concrete bridge are discussed. The collapse of the bridge is re‐constructed based on forensic documentation of the failure. The results of structural analysis carried out using material properties obtained after failure are compared to the shear capacity obtained from various models and from test results from literature. The results are used to explain the cause of failure of the integral bridge under dead load. [ABSTRACT FROM AUTHOR]

In this paper, a numerical critical shear crack model, in which the shear‐flexural coupling effect is considered and the full process of stress and strain is captured, is proposed to evaluate the post‐peak behavior of reinforced concrete (RC) and steel fiber reinforced concrete (SFRC) beams. The shape of critical shear crack is identified by combining the modified compression field theory considering the bridge effect of steel fibers and the section analysis method. Based on the shape of critical shear crack, the shear capacity of beam members is provided by the shear tension zone and the shear compression zone. The shear capacity of the shear tension zone is calculated by the modified compression field theory and that of the shear compression zone is determined by multiaxial strength criterion of concrete. The vertical displacements caused by the flexure deformation and shear deformation are deduced by the moment area method and integration of shear strain. To verify the proposed numerical approach, a test database of 486 RC beams and 313 SFRC beams was established to predict the shear strength, and the force‐displacement relationships of twelve beam members are used to validate the feasibility for full process analysis. The stochastic analysis of beams with different failure modes is conducted via GF‐discrepancy‐based point selection method and probability density evolution method. The limitation between different failure modes is defined according to the degradation percent of shear capacity and it is taken as threshold value of failure domain, and the failure probability analysis indicates that the designed flexure beam member suffered severe degradation of shear capacity, resulting in a significant decline in safety probability. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation of the use of composite polymer mortar (CPM) and steel strands wire mesh (SSWM) to strengthen reinforced concrete (RC) beams in shear. In order to maximize the shear resistance of the steel strands, a new type of anchor device called wedge‐shaped steel plate hoops (WSSPHs) was developed. And the study aimed to examine the effect of shear‐to‐span ratio and prestressing level on the mechanical properties of the beams. A total of nine beams were constructed and tested under four‐point bending monotonic load, comprising three control beams and six strengthened beams. The study analyzed the damage modes, load‐deflection curves, strength, stiffness, and ductility of the beams. The test results indicated that (1) the mechanical properties of the strengthened beams were improved, with the shear capacity improving by 38.47%–71.37% after strengthening. (2) It was observed that SSWM could be utilized more effectively in high shear‐to‐span ratio beams among the strengthened beams with the same prestressing level. (3) Additionally, the larger prestressing level was found to change the design damage mode of the test beams, with RB‐2.5‐0.5 failing in bending. Finally, a model was proposed to predict the shear capacity of the test beams based on the specification GB 50011‐2010. The model considered the effect of the initial prestressing of the steel strands. [ABSTRACT FROM AUTHOR]

Alkali‐aggregate reaction (AAR) is a detrimental reaction between alkalis originating from cement and aggregates that contain reactive minerals. This reaction produces an expansive gel in hardened concrete that may cause internal stresses and cracking, after which it would be critical to evaluate the safety of the AAR‐affected structure. This paper presents a calculation framework primarily using the finite element method to simulate the structural behavior of reinforced concrete members affected by AAR. Numerical subroutines are used to calculate the anisotropic distribution of AAR‐induced expansions at each integration point, considering the stress field at each time step, whereas changes in the properties of concrete due to the progression of AAR are also considered. The modeling approach is successfully validated based on experimental data from several studies on AAR‐affected members that were reinforced in 1, 2, and 3 orthogonal directions in terms of load–deflection behavior and damage patterns. The mechanical properties of concrete were found to negligibly affect the distribution of AAR expansions. A better correlation was observed with experimental data if compressive and tensile strengths of concrete are assumed unchanged and only the modulus of elasticity of concrete is reduced as a function of AAR‐induced expansion. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to use the data‐driven approach to predict and evaluate the mechanical properties of concrete made with recycled concrete aggregate (RCA), including compressive strength and elastic modulus. Using 358 data samples, including 10 input variables, 10 popular machine learning (ML) algorithms are introduced to select the best ML performance model for predicting RCA concrete's compressive strength and elastic modulus. Gradient Boosting and Categorial Boosting have the best performance in predicting the compressive strength of RCA concrete, with R2 = 0.9112, RMSE = 5.3464 MPa, MAE = 4.0845 MPa, and R2 = 0.9175, RMSE = 5.1520 MPa, MAE = 3.7567 MPa, respectively. Light Gradient Boosting and Categorial Boosting have the best performance in predicting the elastic modulus of RCA concrete, with R2 = 0.8775, RMSE = 2.3560 GPa, MAE = 1.8330 GPa, and R2 = 0.9300, RMSE = 2.3560 MPa, MAE = 1.2589 MPa, respectively. Based on the Shapley Additive Explanation analysis, the influence of main factors on compressive strength and elastic modulus of RCA concrete values has been analyzed qualitatively and quantitatively. RCA replacement level and cement/sand ratio slightly affect compressive strength but have a dominant influence on the elastic modulus of RCA concrete. [ABSTRACT FROM AUTHOR]

This paper presents an experimental shear test performed to investigate the web‐shear capacity of composite hollow‐core slabs (HCS) with cast‐in‐place (CIP) concrete. Five HCS specimens are fabricated, and the presence of a topping slab and number of cores strengthened by core‐filling concrete are set as key test variables. The shear force–displacement responses of the specimens, patterns of cracks occurring in the HCS and filled cores, strain behavior of stirrups, and composite action between the HCS and CIP concrete are measured and analyzed comprehensively. In addition, the web‐shear capacity of the composite HCS with CIP concrete is calculated based on elasticity theory and the transformed area method, in which the residual stress ratio factor is introduced to reflect the shear contribution of the core‐filling concrete after its shear cracking. Moreover, a practical equation is proposed to allow structural engineers to easily perform the shear‐strengthening design of HCS via the core‐filling method. The detailed model and the simplified equation accurately evaluate the web‐shear capacities of the HCS specimens. [ABSTRACT FROM AUTHOR]

The bond behavior between reinforcement and concrete has a significant influence on the load‐bearing behavior and serviceability of the composite material. This paper focuses on the characterization of the bond behavior between fine‐grained concrete and mineral‐impregnated carbon‐fiber reinforcement. In this study, the influence of different bond lengths on local bond behavior was experimentally investigated. To predict the bond stress along the bond length, an analytical bond stress‐slip model was specified, and its model parameters were determined based on the experimental tests using an iterative approximation approach. Based on the defined bond stress‐slip model, a numerical bond model was developed and adjusted for the first time. A three‐dimensional (3D) finite element analysis (FEA) allows the simulation of the local bond stress along the bond length. Finally, the results of the 3D FEA were compared with the results of the experimental investigations to validate the developed numerical model. [ABSTRACT FROM AUTHOR]

A growing body of research has shown that reversed cyclic shear loading of reinforced concrete (RC) causes effects that are not accounted for in monotonic behavioral models. Notable among these effects are a reduction in shear strength and significant plastic offsets. This paper presents the General Crack Component Model, a rational, mechanics‐based model that explicitly considers the constitutive behavior of cracks in RC. Cracked RC is treated as a series–parallel system of bonded and unbonded regions, where the crack interfaces have both crack closing hysteresis and a kinematic contact constraint. Validation was performed using data from monotonic and reversed cyclic experiments on panel elements, and has shown that this analytical model is able to accurately capture the salient features of reversed cyclic shear behavior. [ABSTRACT FROM AUTHOR]

This paper investigates the behaviors of different types of prestressed concrete beams utilizing fully encased cold‐ or hot‐formed steel joists. Twelve types divided into two sets of composite beams are assessed. Set 1 is composed of six beams utilizing cold‐formed steel (CFS) joists distinguished by the cross‐sectional steel‐to‐concrete ratios of 1%, 2%, and 3%, and the presence or absence of web openings. Set 2 has the similar composition but utilizes hot‐formed steel joists. Four‐point and three‐point bending tests were conducted at the mid‐span of the composite concrete beams. Key properties, such as strength, stiffness, flexural load capacity, ductility, energy absorption capacity, and failure modes, were used in the analysis. It was found that the specimens with CFS I‐beam joists provided better performance compared to those with hot‐formed steel joists. Also, the existence of web openings in the encased CFS beams enhances the ductility and energy absorption of the composite concrete beams. [ABSTRACT FROM AUTHOR]

To enhance the mechanical and constructional performance of the ultra‐high performance concrete (UHPC) beams, the steel plate placed at the bottom surface of the UHPC beam is utilized to replace the ordinary steel rebars. In this paper, four 3.2 m UHPC T‐shaped beams with different reinforcement patterns of ordinary steel rebars and external steel plate were fabricated and comparatively tested under flexure loading. Their damage patterns, load versus deflection behavior, flexural capacity, load versus strain behavior, moment versus curvature behavior, stiffness, and crack development were investigated. The flexural experiments indicated that the external steel plate, positioned at the bottom surface of the UHPC members, could resolve the difficulty of installing ordinary steel rebars in slender UHPC components and improve its constructional performance. Compared with the inside steel rebar reinforcement, the employment of the steel plate at the bottom surface of the UHPC beam can effectively increase the distance from the neutral axis to the tensile reinforcement at the serviceability and ultimate states, thereby improving its flexural capacity and stiffness. Additionally, the configuration of the external steel plate was beneficial to reduce the tensile stress level of the tensile reinforcement and limit the opening of UHPC crack width, and thus their crack resistance can be effectively enhanced. Moreover, increasing the thickness of the steel plate or rebar ratio can also significantly improve the flexural capacity, stiffness, and cracking resistance of UHPC beams. [ABSTRACT FROM AUTHOR]

The paper investigates the effect of high temperature exposure on the performance of concrete confined through textile/fabric‐reinforced composites. Small‐scale cylindrical specimens (150 × 300 mm) were confined using two types of carbon fibers (dry and epoxy‐resin coated). For the sake of comparison, two confining layers were applied to all specimens. After curing, cylinders were exposed to four ranges of increasing temperatures—being 20°C (ambient), 80°C, 100°C, and 250°C and, after cooling down, were tested under compressive cyclic loading. The experimental results show that thermal stress significantly influences the confinement effectiveness of textile‐reinforced composites. Exposure to high temperatures reduces the ultimate confined strength and significantly influences the overall axial stress–strain behavior. [ABSTRACT FROM AUTHOR]

This paper describes the 3rd Blind Simulation Competition (BSC) organized by the fib WP 2.4.1 which aims to assess the predictive performance of models based on the finite element method (FEM) for analysis and design of fiber reinforced concrete (FRC) structures submitted to loading and support conditions that promote punching failure mode. Fiber reinforcement is used in an attempt to eliminate conventional punching reinforcement and provide technical and economic advantages. The two tested real‐size prototypes represent a column‐slab interior region of an elevated steel‐fiber reinforced concrete (E‐SFRC) slab where anti‐progressive collapse reinforcement is disposed in the alignment of columns/piles. Despite a punching failure surface being formed in both experimentally tested prototypes at the rupture stage, fiber reinforcement was able to mobilize the yield capacity of the conventional flexural reinforcement, providing high deformation capacity, and ductility to the prototypes. The average post‐peak load‐carrying capacity of the tested prototypes at a deflection seven times higher than the deflection at yield initiation of the conventional reinforcement was still 90% of the average peak load. Regarding the BSC, a total of 26 proposals were received and involved 94 participants from 29 institutions and 17 countries, with 53.9% using smeared crack models (SCMs), 30.8% a concrete damage plasticity (CDP) model, 3.8% discrete crack models (DCMs) and 11.5% considered as “other models.” From these simulations it was verified, in average terms, that SCM assured the best predictive performance apart from the average strain in the SFRC and the maximum crack width which were better predicted by DCM. More accurate predictions were obtained by using in‐house software than by adopting commercial software. [ABSTRACT FROM AUTHOR]

During the cantilever casting process of reinforced concrete arch bridges with cantilever cast‐in‐situ method, it is difficult to select representative training samples for reliability analysis due to its complex structural system. Many random variables and large computational sample size, this paper proposes to solve the reliability indexes based on the combination of the improved sparrow search algorithm (LGSSA) and the support vector regression (SVR) method. Firstly, random variables are selected according to the actual situation of the bridge structure. Then representative training samples are designed to be substituted into the finite element model through the homogeneous method. The resultant data samples are used to fit the functional function by the support vector regression. Then combined with the penalized function method to transform the nonlinear optimization into the problem of solving the extreme value of the function. Based on the improved SSA to solve the extreme value of the final function. Finally the reliability index of the structure is obtained. With the background of reinforced concrete arch bridge of 200 m, the method is used to analyze the reliability of its buckling cable stress, arch stress, buckling tower deviation and structural system reliability during the cantilever casting process. The results show that the overall structural reliability of the arch ring during cantilever casting is 3.502–3.608. The indexes of buckling cable stress reliability are 3.806–6.784. The indexes of arch ring stress reliability are 4.379–7.562, and the indexes of buckling tower deflection reliability are 3.608–8.123. [ABSTRACT FROM AUTHOR]

The use of UHPC enables reducing the height of composite slabs, which may decrease the punching shear capacity. This paper investigates the punching shear behavior of steel‐normal concrete‐UHPC composite slabs with experiments and theoretical analyses. Results indicated that a 50 mm UHPC layer makes the nominal punching shear strength increase by 24.91%. Utilizing UHPC and increasing loading area can effectively enhance the punching shear capacity. Besides, theoretical punching shear model proposed based on rigid‐plastic theory can reliably predict the punching shear capacity of composite slabs. The punching shear angle derived from strength theory closely matches the experimental values. [ABSTRACT FROM AUTHOR]

The paper presents an experimental study for the evaluation of the flexural response and failure mode of a prestressed concrete (PC) beam subjected to simultaneous sustained loads and corrosion. The obtained results are judged and discussed also through a comparison with the experimental outcomes on a reference sound PC beam, and a companion specimen subjected to artificial corrosion first, and then tested in bending. The three specimens are characterized by a 200 × 300 mm rectangular cross section, a total length of 3700 mm, and a clear span of 2700 mm. The value of the sustained load, applied with a simultaneous accelerated corrosion process of the strands, was chosen, based on the result of the uncorroded reference beam, to achieve a scenario that can occur in a real structure in situ. The flexural response of the tested element was monitored over a period of 70 days, up to failure, and showed to be highly dependent on the localization of the corrosion phenomena affecting the strands, especially when coinciding with the maximum bending moment position. The obtained results are finally compared with the ones obtained on a PC beam with the same geometry and material properties, first subjected to corrosion and then tested in bending. The differences in corrosion morphology and location and in the failure mode of the strand confirm the importance of accounting for the combined effect of reinforcement corrosion and loading when assessing the structural performance of PC beams. [ABSTRACT FROM AUTHOR]

This paper investigates the effects of pozzolanic substitutions for ordinary Portland cement (OPC) with silica fume (SF) and metakaolin (MK) on the mechanical and toughness performances of steel fiber reinforced concrete (SFRC). Initially, a reference concrete mix with a water‐to‐binder ratio of 0.4 is blended with different volume fractions of steel fibers with varying geometry: crimped steel (CS) and straight steel (SS), both individually and in combination, to examine their mechanical properties. In the subsequent phase, the study investigates the impact of combining macro‐ and microsteel fibers on flexural toughness, to determine potential synergy for suitable combinations. Also, the possible influence of pozzolans in the variation of flexural toughness of hybrid steel fiber reinforced concrete (Hy‐SFRC) was evaluated. Hybridization of steel fibers was found effective in improving the workability of the concrete mix up to 11%. SFRC mixes containing pozzolans exhibited a significant enhancement in compressive strength, modulus of rupture, and modulus of elasticity compared to non‐pozzolanic SFRC. The hybrid combination of CS 1.5% and SS 0.5% was considered the best in terms of mechanical properties. Additionally, the results of synergy assessment showed that hybridization of steel fibers in the pozzolanic concrete mix was particularly effective in the post‐cracking stages with a positive 14% compared to a negative 8% in the pre‐cracking stage. The pozzolanic addition improved the flexural toughness of Hy‐SFRC to about 10%–20%. Blending of SF and MK in Hy‐SFRC was found effective in enhancing the toughness mechanism of concrete compared to Hy‐SFRC mixes containing binary SF and MK, indicating a stronger bond between the fibers and the matrix resulting from the pore refinement and hydration products developed at the interface. Hy‐SFRC containing a ternary pozzolanic mix of SF 10% and MK 10% gave the best results in flexural toughness, and the corresponding synergy values were found to be the maximum. The results were consistent with the morphology analysis, which revealed an increase in hydration products at the interface between the aggregate and concrete matrix, as well as between the steel fiber and concrete matrix, due to the ternary blending of SF and MK. [ABSTRACT FROM AUTHOR]

In this paper, seven half‐scale specimens are used to investigate the effects of the beam–column width ratio, concrete strength, and axial load on the seismic performance of wide exterior beam–column joints. The test results show that all the specimens undergo bending damage at the beam end. The concrete damage in the core column is not significant, meeting the seismic requirements of strong column–weak beams and strong joint–weak members. For specimens with small beam widths, the increase in axial load can effectively reduce the damage to the concrete in the outer joint and increase the strength of the specimen. Increasing the beam width and concrete strength reduces the ductility of the specimen while increasing the strength of the specimen. The bonding performance of the longitudinal bars anchored outside the core column is poor, as bond–slip with the concrete is observed during the test. In addition, compared with ACI 318‐19, GB 50011‐2010 is more conservative for calculating the shear strength of exterior wide beam–column joints. Finally, a corresponding finite element model is established by MSC Marc and verified based on the experimental results. [ABSTRACT FROM AUTHOR]

This paper proposes a new design code formulation for calculating crack widths for regular and more special reinforced concrete (RC) members. The more comprehensive Modified Tension Chord Model (MTCM) has been simplified (SMTCM) to facilitate an alternative method for calculating crack widths to Eurocode 2 and fib Model Codes. The model is based on mechanical principles without empirical modifications and is benchmarked against a previously published experimental crack width database. The SMTCM predicts crack widths quite as accurately as the MTCM and provides a broader range of applicability, such as for large covers and RC ties having arbitrary rebar configurations and thus a better crack width model than the current design codes for RC ties. In addition, there are no openings for ambiguous interpretations of the calculations, which can increase the risk of obtaining two different crack widths from two different designers. To further justify the SMTCM code formulation and concept, several RC ties with experimental crack width profiles were used and discussed. The results show a considerable difference between the crack width profile at the surface and at the reinforcement location, depending on the concrete cover and rebar size. These observations are interesting regarding durability design and requirements and show that the approach using a maximum design crack width at a specific surface as a decisive parameter should be further investigated, especially for large concrete covers. [ABSTRACT FROM AUTHOR]

This paper investigated the blast behavior of a low‐rise composite steel structure of three stories subjected to internal and external explosions for the same explosive charge of 250 kg TNT. A comparison of three various blast scenarios is aimed at better understanding how blast waves propagate in confined risk zones and their damage effects on far and exposed elements to an explosive charge. Evaluation of the damage level and the overall response of the proposed numerical model is done by estimating the adequacy of structural members subjected to blast loading using general limits in attempting to check the structure's strength and regularity. The analysis was based on load combinations and damage criteria according to the Unified Facilities Criteria which are general design approaches suitable for civil design applications in forecasting blast loads and structural system responses. The overall behavior of this structure was simulated based on a dynamic analysis by the direct simulation approach, which was chosen for modeling blast loads using the Friedlander blast load equation, and the simpler, less expensive, more accurate, and realistic A.T.‐BLAST model to deduce the simplified blast‐wave overpressure profile. The material nonlinearity at a high strain rate using the Johnson‐Cook strength and concrete plasticity damage model is studied dynamically using ABAQUS finite element code to simulate the explicit dynamic nonlinear analysis. The overall response of the proposed numerical model was evaluated by estimating the adequacy of structural members, considering the blast load as the initial cause of failure, such as axial plastic strain, internal forces limits, maximum deformation, support rotation, demand‐capacity‐ratio (DCRshear/moment), drift index and material damage model. The position of the explosive charge played an important role in determining the rate at which the structural element begins to plastic strains, displacements, moments, or rotations beyond the limits, and then key elements should be considered in structural design against progressive collapse. Results showed that steel members exhibit early indicators of failure, such as buckling necking, shear tearing, or plastic hinges, whereas concrete slabs break up immediately due to brittleness. DCRmoment values successfully showed the columns in which the first plastic joint can occur, whereas DCRshear values signaled the onset of shear failure at connections. Besides, plastic hinges played an important role in dissipating energy and preventing total structural collapse via the Strong Column‐Weak Beam design concept, which appears repeatedly in this study. The structure is a well‐designed and ductile building capable of supporting higher loads and is considered to be repairable and intact. [ABSTRACT FROM AUTHOR]

Although plain round or square section reinforcement is no longer used in new construction, there are many older structures still in service built with such bars. In recognition of the need for guidance on the assessment of load‐carrying capacity of structures reinforced with such bars, design codes are now introducing or re‐introducing provisions to assess the capacity of laps and anchorages of such reinforcement. The authors have contributed to the introduction of design rules in the fib Model Code 2020. This paper describes the derivation of these provisions. Starting from the form of expression proposed earlier by the authors, the data from which these proposals are derived is specified and modifications in interpretation preparatory to a statistical analysis are outlined. A rigorous multivariate statistical procedure is then employed firstly to determine a mean strength expression for the capacity of anchorages and laps which is then validated against test data. Further statistical analysis is subsequently used to determine a design expression using the approach outlined in EN 1990, taking appropriate account scatter in test data. Finally, some comparisons are presented between the assessment expressions proposed and design provisions that were in place when these types of bars were in common use. Areas where earlier design provisions may be non‐conservative are identified. [ABSTRACT FROM AUTHOR]

Post‐installed and cast‐in‐place anchors are widely used to connect structural or nonstructural elements using a steel baseplate at the concrete structure. Generally, concrete anchors must be qualified if their failure would compromise the safety or result in substantial economic damage. Concrete anchor qualification results in technical approvals forming the basis for a code‐compliant design. In Europe, anchor design is governed by the new standard EN 1992‐4, and in the United States by ACI 318. Qualification and design regulations are predominately similar between Europe and the United States; however, there are still some notable differences. To this end, this paper introduces the basics of anchor design and underlying product qualification. Then, it describes some of the boundary conditions with special attention to the baseplate as well as discusses the critical design parameters. Later, the paper provides a comprehensive overview of the complex design rules. This paper includes identification of the differences between EN 1992‐4 and ACI 318 and their resultant effect on anchor design. [ABSTRACT FROM AUTHOR]

The influence of microstructural changes on concrete properties at elevated temperatures is presented and discussed in this paper, as the exposure to elevated temperatures brings in marked changes in concrete thermal, mechanical and kinematic properties owing to the heat‐induced evolution of material's microstructure. The major microstructural changes consist in increasing pore size, occurrence of microcracking and activation of chemo‐physical processes in the hardened cement‐paste. These processes (like portlandite dissociation and crystalline change in quartzitic aggregate) occur above 400°C and are more pronounced in high‐strength than in normal‐strength concrete. Increasing pore size and microcracking, however, yield the largest contribution to concrete strength‐loss, that occurs mainly between 400 and 800°C, depending on aggregate type and initial moisture content in the mix. On the whole, calcareous (or carbonate) aggregate behaves better than siliceous aggregate face to increasing temperatures. Initial moisture content favors concrete thermal spalling, mostly between 200 and 400°C, but such a complex phenomenon is still open to investigation, as demonstrated by the various theories found in the literature, each with its chemo‐physical mechanisms and limitations. Three theories are discussed in this paper, and these theories together with other critical issues allow to focus on future work. [ABSTRACT FROM AUTHOR]

The effect of the boundary conditions, defined as the thermal expansion restraint imposed by the external uniaxial compressive load in plain concrete subjected to high temperatures, is discussed. A numerical mesoscopic investigation uncoupled the load induced thermal strain (LITS) into three main components (aggregates and matrix strain contributions and the effect of the thermal expansion restraint). The analyses demonstrate that LITS depends on the materials properties (viscous‐plastic behavior) and also on the boundary conditions, which is function of the test setup and seems to be not related to the material properties. In this paper, the role of the boundary conditions on 1‐phase (homogeneous) and 2‐phase (matrix + aggregates) numerical analyses are investigated. A LITS semi‐empirical model is incorporated in the numerical modeling to account for the stiffness degradation. It is demonstrated that in 1‐phase models, the effect of the boundary conditions is absent, which is not true for mesoscale analyses. In this case, the effect of the boundary conditions should be taken into account and subtracted from the results to avoid an overestimation of the material response. It is important mentioning that the analyses of concrete behavior at elevated temperatures and transient creep experimental procedures completely neglect the role of the boundary conditions. [ABSTRACT FROM AUTHOR]

This paper introduces the conservation and intervention provisions included in the latest edition of the fib Model Code for Concrete Structures (MC2020). This is the first international code which addresses life‐cycle management issues for both new and existing concrete structures. Accordingly, the contents relating to conservation (maintenance and interventions) have been extensively enhanced compared with the provisions included in the previous MC2010, with these now including monitoring. Much of the contents on interventions are newly‐added provisions in MC2020. A new chapter (19) is introduced to show the available materials/systems and the properties necessary for these materials. The necessary properties required to make successful interventions also include consideration of the long‐term performance of materials/systems and compatibility with the substrate concrete. All the processes for interventions, including intervention strategies, selection of intervention methods, survey for interventions, design of interventions and execution of interventions are explained in chapter (38) on conservation and a new chapter (37) on execution of interventions. Selection of intervention methods should be made according to the intervention strategies and the causes and extent of deterioration/damage. In the future the issues of repairability and the standardization of intervention methods are expected to have greater importance. Repairability is the ability to physically repair a structure or structural element which has deteriorated or been damaged by the effects of the considered actions, thus restoring its functionality, but while incurring acceptably low economic cost, environmental burdens and societal disruption. [ABSTRACT FROM AUTHOR]

Model Code 2010 made a step forward in introducing durability models for the probabilistic calculation of design service life. The accumulated experience has allowed the improvement of these models and the introduction of some advances in MC2020. In particular their application to not only new structures, but also to existing ones, with the models serving both circumstances. MC2020 sets the traditional requirements concerning safety and serviceability within an overarching sustainability and performance‐based approach framework, which are major requirements. The main novelties concerning durability design introduced in MC2020 can be summarized as: (a) Guidance on the treatment of a wider range of mechanisms of deterioration which may potentially affect concrete structures, including the simultaneous action of some of these, (b) The classification of the ways of verification into "Levels of Approximation" (LoA), and (c) The definition of what has been called the "Condition or Deterioration" Limit state (CLS or DLS). The paper explains these aspects and chloride penetration is illustrated as a case example. [ABSTRACT FROM AUTHOR]

A beam‐end test is proposed in this paper and in the new fib Model Code 2020 to determine the effects of concrete type, confinement effects, and casting position on the anchorage strength of reinforcing bars. Two bars are cast in each specimen (in the two opposite corners), one in a "good" casting position and the other in "poor" casting position. The proposed test aims to be an economical bond test capable to represent actual conditions of anchored bars in real design practice. The test is also intended to verify whether existing provisions for bond and anchorage in the fib Model Code are suitable in nonconventional concrete. The validity of the proposed beam end type bond test is assessed by the results of more 60 tests on rebars having anchorage length of about 20 times the bar diameter in plain concrete, in fiber reinforced concrete, and in recycled aggregate concrete. Experimental results provide information both on the "top cast effect" in three types of concrete and on the effectiveness of fib Model Code provisions for anchorage when nonconventional concrete is used. [ABSTRACT FROM AUTHOR]

The paper presents a synthesis of an extensive experimental campaign on linear and two‐dimensional steel fiber reinforced concrete (SFRC) structural elements carried out to check the ductility requirements aimed at guaranteeing limit analysis approaches for the computation of ultimate load‐bearing capacity of SFRC structures; special attention is devoted to the role of the degree of redundancy of the structure. In particular, full‐scale shallow beams and slabs reinforced with steel fibers (with or without conventional longitudinal reinforcement) were tested in two different laboratories: the Politecnico di Milano (PoliMI) and the University of Brescia (UniBS). In this experimental campaign, two different fiber contents and fiber types were considered. The experimental investigation, carried out within the activities to support Annex L of Eurocode 2, was fundamental also for developing the design rules included in the fib Model Code 2020 and allowed to formulate conclusions regarding optimization of the mix design, ductility, and design prediction at the ultimate capacity. [ABSTRACT FROM AUTHOR]

Precast segmental construction can shorten the construction time of the bridge and reduce the impacts on traffic and environment. Thus, this approach has been widely used in many countries. The relevant literature suggests that in the existing segmental precast bridges, nearly all of the centerlines of the girders are aligned with the centerline of the bridge piers. This paper introduces a wide urban viaduct comprising twin separate box girder cells using segmental prefabrication. To save space under the bridge, the bridge has only one row of piers and long cantilever crossbeams are set at the top of each pier. Additionally, the centerline of the girder and the centerline of the pier do not overlap. To prevent eccentric loading and improve the construction speed, two bridge erection gantries are used for synchronous construction. This study is a pioneering attempt at bridge construction with a precast segmental twin‐deck box girder bridge simultaneously erected with double gantries. To investigate the stress state of the whole system (crossbeam, gantries, and box girder segments) during construction and demonstrate the feasibility of the construction method, a real bridge was used. The test results provide a reference for the design and construction of similar projects. [ABSTRACT FROM AUTHOR]

Existing structures often no longer meet the demands formulated in contemporary design codes with respect to structural safety and serviceability. This occurs, for instance, if the loads on existing structures, like traffic loads on bridges, are larger than assumed in the original design. A second potential reason is that structures are subject to deterioration, like alkali–silica reaction within the concrete or corrosion of the reinforcement due to chloride attack or carbonation. A third possible reason is that in recent codes, additional criteria have been introduced based on new theories and/or negative experiences with older structures. The new fib Model Code for Concrete Structures 2020 will be valid both for the design of new structures and the assessment of existing structures. This paper shows how the design and assessment of concrete structures are integrated into this new code concept. [ABSTRACT FROM AUTHOR]

This paper presents a modeling approach to analyze the flexural response of hybrid reinforced concrete beams with localized corrosion. A new mechanical model based on extensive uniaxial testing is proposed to describe the stress–strain relationship of corroded bars with a single pit. The proposed mechanical model is then incorporated into a sectional analysis to determine the moment curvature relationship of hybrid reinforced concrete sections with pitting corrosion. The actual crack pattern is used to divide a beam into discrete hinge elements which are then combined to compute the load–deflection response of statically determinate beams. The modeling approach is evaluated with available experimental data showing good predictive capabilities. A parametric study revealed the importance of the interaction between the tensile reinforcement ratio and the concrete postcracking residual stress. Furthermore, the deformation capacity of reinforcement bars with pitting corrosion levels beyond 0.25 was shown to have a dominant effect on the ultimate deflection of hybrid reinforced concrete beams. [ABSTRACT FROM AUTHOR]

Sustainability is a global goal of sustainable development aimed at ensuring a quality life on the Earth for the future generations. Buildings, infrastructure and the entire built environment should be better prepared for the new conditions—they should be sustainable, resilient and adaptable to new situations. This requires new technical solutions for the construction, reconstruction, and modernization of buildings and all other engineering structures. Concrete is gradually becoming a building material with great potential for realizing technical solutions that meet new requirements, leading to the necessary reduction of environmental impacts and consequent improvement of social and economic conditions. The paper presents implementation of sustainability principles in the new fib Model Code 2020 (MC2020). This represents a contribution of the International Federation for Structural Concrete (fib) to the achievements of the Sustainable Development Goals (SDGs), set by the United Nations in 2015 as an action plan for the period up to 2030. [ABSTRACT FROM AUTHOR]

Accurate information from monitoring of structures plays a critical role in making informed decisions regarding structural safety control and maintenance needs. Unfortunately, there are several gaps in the existing standards and the monitoring practices at local, national, and transnational (e.g., European) levels. The wide diversity of assets and their respective environments further complicates the development of standardized monitoring approaches. Despite the constantly increasing number of examples and intensive knowledge exchange on the use of information from inspection, testing, and monitoring to support the safety and risk assessment of existing structures, major challenges are being faced in establishing consensus on standardization in this domain. At the same time, the need for robust standardization that enables integrating structural monitoring with the assessment of existing structures is generally acknowledged by public authorities and industrial stakeholders. Extending the lifespan of structures to enhance sustainability is a critical imperative of our time and monitoring is expected to be key element of reliable service life extension of existing structures. However, development and adoption of new standards involve complex processes that require multi‐level dialogues, consensus, and commitment from political and industrial stakeholders to move forward from legacy procedures. The fib Model Code 2020 (MC2020) serves as a significant milestone in the development of new standards for monitoring and maintenance of concrete structures. It addresses the existing gaps in knowledge and seeks to close the gap between the practice and the standards with regard to the monitoring of structures. The important objectives of the MC2020 are to support the standardization bodies in formulating new standards in monitoring, maintenance, and safety of existing concrete structures. This paper presents the fundamental/basis for shaping the methodology of data‐driven assessment and the methodologies proposed in the ModelCode. [ABSTRACT FROM AUTHOR]

The vision for fib MC2020 is to go beyond the point reached by fib MC2010, recent ISO codes, such as ISO 16311, and the current Eurocode activities to extend the application of Eurocodes to existing structures. The contents of fib MC2020 suit these forward‐looking objectives, dealing both with the design of new structures and all the activities associated with the life‐cycle management of existing concrete structures including matters, such as in‐service assessment and interventions upon them, including situations where new structural members are incorporated as parts of existing structures. With the fib MC2020 adaptations taking sustainability as a fundamental requirement, defining implications for subsidiary performance requirements critical to structural design and assessment procedures, it is logical that Model Code 2020 explicitly introduces and consequently seeks to make use of performance‐based concepts. A focus on performance provides a potential way to better align the interests of owners, users, technical consultants (such as structural engineers, material engineers, etc.), contractors, as well as material suppliers and manufacturers. It is envisaged that implementing the concept of the performance‐based approach in design and assessment will encourage rational design and technological progress which will facilitate the creation of superior structures for future generations, by removing constraints to the use of novel types of concrete and reinforcing materials and offering possibilities for optimization of solutions that better fit the needs of stakeholders. This paper addresses the principles of the performance‐based approach to design and assessment and discusses the manner in which it has been introduced in fib MC2020. The benefits and burdens associated with the performance‐based approach and the traditional prescriptive approach to engineering specification are discussed, both from a technical and process/commercial/contractual point of view, to describe the overall benefits of the performance‐based approach. Finally, the future outlook for a coherent integration of the performance‐based approach in design and assessment is addressed, paving the way for further work on standardization for sustainable concrete structures. [ABSTRACT FROM AUTHOR]

The fib Model Code 2020 (MC2020) is developed to serve as the basis for future international codes and standards for the design of concrete structures by summarizing international research and experience and converting this knowledge into a practical document. The chapter "Concretes" contained therein provides a clear set of application rules in combination with sufficient background information and related references. This paper gives a concise overview of the contents of the Chapter 14 "Concretes" in the 2nd draft of MC2020. Instead of presenting numerous details on changes in the text and equations compared with the previous MC2010, major fundamentals on modeling concrete behavior are indicated. New sections in MC2020 on non‐conventional concretes, durability specifications and environmental performance are covered. Extended state‐of‐the‐art chapters on concrete transport properties and durability design conclude this contribution. [ABSTRACT FROM AUTHOR]

The annual global building demolition is burdensome due to the rapid development of cities. The pollution associated with building demolition severely endangers the urban environment. Soundless chemical demolition agents (SCDAs) can effectively avoid environmental hazards in the demolition of concrete buildings. However, related literature on optimal hole layout design is still vacant. The demolition of reinforced concrete slabs was therefore explored in this paper. In total, 18 slab specimens were tested. Results showed that the slab specimens were demolished into several blocks due to sufficient development of cracks. Following this, a set of complete evaluation system was proposed. First, the volumetric expansion ratio of SCDAs was provided as a new evaluation index. Based on this evaluation index, the influences of critical parameters and the influence mechanism of reinforcements were investigated. Second, a novel multi‐parameter hole layout computational model was established. With this model, an optimal hole layout scheme could be obtained. Finally, the application prospect of SCDAs was discussed. This work can open up a new vision for the demolition industry. [ABSTRACT FROM AUTHOR]

High‐performance fibre reinforced concrete represents a promising alternative to conventional reinforced concrete for the construction of prestressed precast girders for road bridges. Specifically, all shear reinforcement is replaced by the use of steel fibres, which leads to important savings from the material and economical perspectives. Therefore, reliable shear formulations are required for these specific cases. In an effort to evaluate the accuracy of code expressions, this paper presents a database collecting 80 experimental shear tests on prestressed fibre reinforced concrete beams without stirrups. After illustrating its main characteristics, this database is used to verify the conservativeness and accuracy of shear formulation according to several codes and recommendations: i) Model Code 2010, ii) draft version of Model Code 2020, iii) draft version of the new Eurocode 2, and iv) Spanish National Code. The evaluation, carried out through the calculation of the model safety factor, indicated that the application of all shear formulations is largely conservative, leading to less unsafe tests than the desired 5% fractile. The relation between model safety factors and mechanical parameters is then investigated. Finally, the results obtained for the developed database are compared with those achieved from two larger databases of beams with similar features but without prestress. The comparison clearly proves the greater conservatism of code expressions when beams are prestressed. [ABSTRACT FROM AUTHOR]

The next edition of the fib Model Code for concrete structures, Model Code 2020 (MC2020), is under development with the aim of issuing a first partially harmonized draft for comment in early 2023. MC2020 is a single code dealing with both new and existing concrete structures, that is both the design of new structures and the various activities associated with the assessment, interventions upon and life‐cycle management (LCM) of existing concrete structures. The paper outlines the overarching sustainability framework and the performance‐based or outcomes‐based approaches (PBA) adopted by MC2020. There is a pressing need to reduce barriers to the evolution in concrete construction materials and the technical aspects of design and the LCM of existing structures, in order to meet pressing climate change drivers and the goal of achieving lower carbon construction. MC2020 also addresses significant advances made on a wide range of issues including those relating to structural design and analysis methods, seismic design and assessment procedures, durability, structural monitoring, service life design, structural assessment through‐life and making interventions to adapt existing structures or enhance their performance or extend their useful life. [ABSTRACT FROM AUTHOR]

Despite their successful applications in practice for over a century, the design of concrete hinges still entails considerable modeling uncertainty. Their dimensioning still relies on semi‐empirical recommendations originally proposed for admissible stress design, based on limited experimental data and generalized with engineering judgment. This presumably results in overly conservative designs in many cases, particularly when applied with modern design codes based on partial safety factors. This paper addresses these issues by revisiting the analytical modeling for one‐way Freyssinet concrete hinges under general loading based on approaches compatible with current design codes. A cross‐sectional analysis with confined concrete properties is proposed for the behavior under axial forces and bending moments, where the strength of the triaxially compressed concrete in the hinge throat is determined with a discontinuous stress field. The hinge resistance to shear forces is investigated with failure mechanisms inspired by failure modes observed in experiments. Based on the shear strength, a simple approach to estimate the torsional resistance of the throat is proposed. Remarks are also made on the analysis of combined actions. The predictions of the proposed models are validated against a wide range of test data, including a series of recently conducted own experiments. Overall, the proposed models agree better with the available experimental data than the existing approaches, potentially allowing for a more efficient design of new and assessment of existing concrete hinges. [ABSTRACT FROM AUTHOR]