Design Of Concrete Structures Research Articles

Probabilistic error assessment and correction of design code-based shear strength prediction models for reliability analysis of prestressed concrete girders

Aiming at probabilistic error assessment of design code models for shear strength prediction of prestressed concrete (PC) girders, this study compiled an experimental database containing 369 PC girders that failed in shear. Using the experimental database, this paper first assessed seven well-received shear strength models from five concrete structure and bridge design codes, including ACI 318-19, AASHTO LRFD 2017, CSA A23.3:19, CSA S6:19 and fib MC 2010. In view of the fact that systematic error exists in those models, polynomial correction terms were calibrated for each model together with the remaining error quantified based on the compiled experimental database and Bayesian updating. The resulted models can be used for shear strength predictions with better accuracy and, more importantly, with the model uncertainty quantified probabilistically. In the end, a case study of fragility analysis was conducted to show the benefits of the developed probabilistic models.

Research on Seismic Performance of 735 MPa High-Strength Reinforced Concrete Frame Joints

To study the seismic performance of high-strength reinforced concrete frame joints, cyclic loading tests were carried out on six concrete beam-column joints configured with the new Cold-rolled Ribbed Bar (CRB) 735 high-strength steel reinforcement and one joint with Hot-rolled Ribbed Bar (HRB) 400 ordinary steel reinforcement to obtain the effects of the axial compression ratio and the stirrup ratio in the joint core on the seismic performance of the joints. The test results show that the following: (1) Increasing the axial compression ratio can improve the energy dissipation characteristics of the joints configured with CRB735, but cannot effectively improve the ultimate shear capacity of the joints. Larger axial compression ratio will cause earlier cracks in the core area and reduce the ductility of the specimens by 6.1~27.9%. (2) Increasing the stirrup ratio in the joint core will increase the shear capacity of the joint by 5.3~8.1% while also increasing the failure displacement by 2.8~14.9%. (3) When the joints are configured with CRB735 stirrups, the rate of stiffness degradation from core cracking to the yielding stage of the specimens will be effectively delayed. (4) Compared with the joint configured with HRB400, the ultimate loading process of the joints using CRB735 is shorter, the yield load and yield displacement are higher, and the specimens are close to the ultimate state when they reach yield. Finally, the shear capacity of concrete beam-column joints configured with CRB735 can be calculated using the relevant shear capacity equation in GB50010-2010 Code for Design of Concrete Structures, and has a certain safety reserve. In the equation, the yield strength of CRB735 steel reinforcement is recommended to be 735 MPa.

Contributions of the Future Eurocode for the Assessment of Existing Concrete Structures

This article highlights the most relevant aspects of the new generation of Eurocodes for the assessment of existing structures, and in particular those governing concrete structures. In this respect, Eurocode 0 will include a new section (prEN 1990-2. Basis of assessment and retrofitting of existing structures: general rules and actions) covering the approach and analysis that must be included in this type of assessment, while Eurocode 2 (prEN1992-1-1:2021 Design of concrete structures) includes Annex I: Assessment of existing structures, which is informative and covers particular aspects of the assessment of concrete structures.

Study on Eccentric Compressive Behavior of Concrete Columns Reinforced with NPR735 High-Strength Steel Bars

In this paper, eccentric compressive tests and theoretical studies of grade 735 MPa reinforced concrete columns were conducted. The eccentric distance and strength of the longitudinal reinforcement were used as experimental parameters to investigate the bearing capacity, failure mode, and strength of eccentric compressive behavior of NPR735 high-strength steel bars. When the load eccentricity of the reinforced concrete columns was small or longitudinal, the reinforcement ratio was large, and small eccentricity failure occurred. The results were similar to the failure mode of ordinary concrete columns with traditional steel bars. When the load eccentricity decreased, the bearing capacity increased, but the deflection and ductility of the specimen decreased. When the strength of the longitudinal reinforcement increased, the bearing capacity of the specimen increased slightly. Finally, according to current design methods in the concrete structure design code, the bearing capacity of the eccentric compressive column was obtained, and the calculated results were compared with the experimental results to verify the applicability of the concrete structure design code GB50010-2010 to concrete columns with grade 735 MPa reinforcement.

Correlation of Student Attainment for Civil Engineering Design Project and Structural Concrete and Steel Design for Undergraduate Students in Concurrent Semester

Structural Concrete and Steel Design(ECSXXX) and Civil Engineering Design Project(ECSYYY) are two (2) compulsory subjects in most studies of Diploma of Civil Engineering in Malaysia. These subjects have been associated with each other as the structural concrete and steel design has carried the theory and fundamentals to the design project subject. ECSXXX which indicates the study on the reinforced concrete of beam, slabs, column, and foundation. Complementary to these, the design of steel beam, column and connections are also included in the syllabus. All the topics will imply in the subject of ECSYYY, whereby students are required to design manually and software for a two-story house. The previous study plan for Diploma Civil Engineering in UiTM Johor was designed that the subject of ECSXXX was under semester 5 and the subject ECSYYY was at semester 6. However, to fulfill the requirement of the Engineering Technology Accreditation Council (ETAC), current study plan was established which combined the two subjects in semester 5. As a result, a single semester 6 will be allocated for the Industrial Training. Due to this system, student attainment based on grade and PO should be analysed. Data recorded all students pass the minimum indicator for PO2,P03,PO4,PO5,PO8 and PO10 using i-Ras. Hence, correlation of overlapping PO such as PO3 and PO4 were analysed for betterment of continual quality improvement can be done in future. Students scored better grades for ECSYYY compared to ECSXXX.

Design and assessment of concrete structures with strut‐and‐tie models and stress fields: From simple calculations to detailed numerical analysis

AbstractThe introduction of strut‐and‐tie models in fib Model Code 1990 as a design basis for discontinuity regions constituted a significant step toward promoting consistent design methods for reinforced concrete structures. In fib Model Code 2010, the scope was broadened through the stress field method that was introduced as a complementary tool. The present article summarizes subsequent evolutions in both methods, which will be incorporated in the upcoming fib Model Code 2020. Besides emphasizing their suitability for the structural design and assessment, their adaptability to the “Levels‐of‐approximation” approach is also depicted. This article presents the theoretical ground of both methods and looks on their potential for computer‐modeling implementation. With this respect, several strategies are presented by discussing their advantages and optimum field of application.

(S)FRC in EC2 and in Model Code 2020

The current Eurocodes are under revision and estimated to be available in 2025. For the first time in the European history, Eurocode 2: “Design of concrete structures” will be extended with a European-wide harmonized annex, covering steel fibre reinforced concrete. The work on Annex L – Steel Fibre Reinforced Concrete has already started in 2012 and significantly benefitted from the work carried out for the fib Model Code of Concrete Structures 2010. The use of performance classes of Model Code 2010 as well as parts of the design approach were the basis for the new steel fibre reinforced concrete annex. In addition, the latest state of science has been used to prepare a powerful but, in the same way, easy-to-use design document for structural engineers, covering both ultimate and serviceability limit states for steel fibre reinforced structures, with or without reinforcement. At the same time the new Model Code 2020, mainly concentrated on existing structures and sustainability, extended to all types of fibres as the previous Model Code, has tried to look at FRC as to a generalized concrete, able to exhibit a significant toughness in uniaxial tension, integrating its resistance equations to those of conventional concrete, guaranteeing in many structural cases a sustainable choice for the reinforcement and paying more attention to high- and Ultra-high performance materials and at the same time to hybrid solutions for the reinforcement.

Dimensionamento de estruturas de concreto armado a partir de campos de tensão tridimensionais

abstract: The design of reinforced concrete structures starting from a linear analysis is allowed by design codes and leads to safe solutions. The structural model built for the analysis may be composed not only of bar and shell elements, but also solid elements. In the present work, the formulation of the Reinforced Solid Method (RSM) was reviewed and applied to the Ultimate Limit State design of a reinforced concrete member, with the computation of the required reinforcement and concrete check of each individual solid element within the structural model. The results were visualized in a post-processor and validated by numerical simulations. The RSM effectively allows for the design of concrete structures with general geometry and loading conditions, whilst identifying local effects throughout the volume of the structure.

On the Effective Concrete Compressive Strength in the Theory of Plasticity

In his fundamental book Nielsen (1984) summarized the basics of application of plastic theories to the design of concrete structures. Since that time extended experimental and theoretical works were carried out. Models based on plastic theories were developed for bending, shear, for beams, plates, etc. The strut-andtie-, the stress field models and the Modified Compression Field Theory perform further developments of application of the theory of plasticity. Crucial point (the governing material characteristic) of these models is the effective concrete compressive strength. This paper critically reviews its different theoretical origins and despairs of its existence. It reveals that the main source of plastic behavior of structural concrete structures is the reinforcement. In design for shear instead of a preposterous effective concrete strength the effective web thickness and (a maybe slightly reduced) concrete compressive strength should be taken into account. Neither the concrete compressive strength nor any reduced (effective) value of it are applicable as governing material characteristic of any plasticity model for structural concrete structures.

Research on the Construction of Course Evaluation System Based on OBE Concept and the Background of Curriculum Thinking and Politics

Curriculum thinking politics is becoming more and more important in the ideological and political work of colleges and universities, and the development of engineering curriculum thinking politics is a difficult point in the process of promoting curriculum thinking politics in colleges and universities. In this paper, we selected the course of concrete structure design principles for research and analysis, and found that the course thinking politics of engineering majors is facing real difficulties such as insufficient attention, the cognitive bias, of course, thinking politics among teachers of professional courses, and the complexity, of course, thinking politics increased by the diversified development of students. Through the practice of the reform of the curriculum of the principle of concrete structure design, we summarize the paths of the effect of the curriculum of engineering courses in colleges and universities, deepen the importance of the curriculum of engineering courses, enhance the coupling of engineering professional education and the curriculum of political education, and provide reference significance for the curriculum of engineering majors to carry out the reform of the curriculum of political thinking.

Comparative Study of Reinforced Concrete Beams in School Buildings Using Prestressed Concrete Beams

Building construction in Indonesia generally uses concrete. The concrete used for building structures, such as beams, generally utilizes reinforced concrete. It is very rare to see the use of prestressed concrete for building structures such as beams, especially in Batam City. This study aims to analyze the comparison between the beam structure with reinforced concrete that has been existing and prestressed concrete in the Kaliban School project. The stages in this research included prestressed concrete beam design and comparative analysis. The design of prestressed concrete beams was planned to be composite prestressed concrete blocks using the pre-tension method with a fully prestressed system, and was cast with the floor slabs and also supported during the casting period. Comparative analysis conducted by the researcher of this study was a comparison of the materials used in reinforced concrete beams and prestressed concrete beams. The results of the prestressed concrete structure design obtained a beam dimension of 200 × 400 with a diameter of 12.7 mm, in which 4 pieces were installed 125 mm below the beam. The results of the comparison analysis of the total material prices between prestressed concrete beams with dimensions of 200 × 400 and existing reinforced concrete beams with dimensions of 200 × 500 showed that prestressed concrete beams were 24.28% cheaper than reinforced concrete beams.

Structural Design Optimization of Flat Slab Hospital Buildings Using Genetic Algorithms

The construction costs of hospital buildings are relatively high due to the need to fulfill their complex functions and avoid mishaps. In this context, this study aims to minimize the total construction costs of hospitals while still satisfying the special architectural, practical, and structural requirements specified by design codes. To this end, 48 design alternatives with two floor systems (flat slabs with and without drop panels), three column spacings, and eight concrete grades were optimized using genetic algorithms provided by Palisade Evolver. The objective function included the materials and labor costs per square meter of the floor plan. The decision variables involved the concrete dimensions and steel bars of floors and columns. The hospital buildings were subjected to gravity, earthquake, and wind loads to thoroughly examine the realistic loading conditions. The design was performed in accordance with the Egyptian code for the design and construction of concrete structures and the Egyptian guidelines for hospitals and healthcare facilities. The results revealed that using low-strength concrete, and flat slabs without drop panels could achieve the best design. The slab thickness had a governing impact on the total cost of both floor systems.

Mass Concrete with EAF Steel Slag Aggregate: Workability, Strength, Temperature Rise, and Environmental Performance

Temperature control is the primary concern during the design and construction process of mass concrete structures. As the concrete production has an enormous negative environmental impact, the development of green mass concretes will eventually become as important as the thermal characteristics. Therefore, this paper investigates the use of Electric Arc Furnace (EAF) steel slag aggregate for the partial replacement of the natural aggregate in the production of mass concrete. The impact of EAF steel aggregate on mass concrete workability, strength, and thermal behaviour was analysed. In addition, a cradle-to-gate LCA study was conducted to evaluate the environmental footprint and sustainability potential of the tested mass concrete mixtures. The study results suggest that the use of EAF steel slag aggregate in combination with a low-heat cement with a high content of blast furnace slag can significantly lower the temperature, reduce the environmental impact, and increase the sustainability potential of mass concrete, while at the same time providing sufficient workability and compressive strength. The study results indicate that EAF steel slag can be upcycled into an aggregate for the production of green mass concrete mixtures.

Experimental Study on Flexural Behaviour of Prestressed Specified Density Concrete Composite Beams

To solve the problem of poor seismic resistance due to the disadvantages of traditional concrete composite beams, such as heavy self-weight in prefabricated buildings, prestressed specified-density concrete composite beams are proposed herein. First, a mix ratio test of specified-density concrete was performed. Second, five prestressed specified-density composite beams, a prestressed ordinary concrete composite beam, and a prestressed semi lightweight concrete cast-in-situ beam were tested. The influence of the precast concrete height, reinforcement ratio, and concrete materials on the failure mechanism, flexural bearing capacity, and short-term stiffness of the composite beams were analysed. From the results, the specified-density concrete composite beams and the ordinary composite beam had similar ultimate bearing capacities, but the average distance between crack spacings of the former was smaller. The precast concrete height affected the bending performance of the prestressed specified density concrete composite beam insignificantly, but the maximum ultimate bearing capacity of the composite beam could be increased by 35.6% by increasing the reinforcement ratio. The composite beam and the cast-in-place beam exhibited similar load-carrying capabilities and deformation properties. The average crack spacing, cracking load, and ultimate load value of the specified density concrete composite beams calculated according to the China national standard “Code for design of concrete structures” were consistent with the measured values.

Damage evolution models of static pre-loaded concrete under impact load based on the Weibull distribution

Affected by static loads, ahead of the dynamic loads such as blasting, flowage, and earthquakes, concrete structures are already in various degrees of damage. Against this engineering backdrop, the damage degree should be considered in seismic design and disaster mitigation for concrete structures. To investigate the dynamic mechanical properties, energy evolution, and fracture mechanism of damaged concrete under dynamic load. The damage models of the dynamic compressive strength, energy dissipation density, and fragmentation characteristics related to the damage degree based on the Weibull distribution are theoretically studied and demonstrated by experiment. Uniaxial loading with diverse pre-loads is employed to make the concrete in varying damage degrees. The Split Hopkinson Pressure Bar (SHPB) is employed to investigate the damaged concrete's dynamic mechanical properties, energy evolution, and fracture characteristics. The experiment demonstrates the rationality of the theoretical study, the growth ratio of energy dissipation density, reduction rates of dynamic strength, and the average diameter of the fractured concrete all follow the Weibull distribution. The energy dissipation density and fragmentation degree of the damaged concrete under impact load increase with pre-load rise, while the dynamic strength and transmission energy are opposites.

Creep damage coupling model of concrete based on the statistical damage theory

The creep behavior is one of the key issues in the design and construction of hydraulic concrete structures. However, it is an enormous challenge to accurately predict the development of creep deformation in concrete structures. Since the creep deformation behavior of concrete under long-term load action originates from the interaction between creep and damage, a new creep damage coupling model was developed by introducing the damage variable into the creep constitutive equation. This model utilized the statistical damage theory framework and assumed that the damage variable follows the random distribution described by the Weibull function. Then Weibull distribution parameters F0 and m were derived to determine the evolution equation of the damage variable D. Considering stress under complex stress conditions may change, the stress-strain correlation of concrete under complex stress conditions was deduced using the elastic creep theory. Moreover, the results of uniaxial compressive concrete creep tests with the corresponding numerical simulations under different levels of sustained loads, and the accuracy and applicability of the creep damage coupling model were verified. Consequently, the nonlinear creep properties of hydraulic concrete were analyzed by combining it with acoustic emission techniques.

Service Life Design for Concrete Engineering in Marine Environments of Northern China Based on a Modified Theoretical Model of Chloride Diffusion and Large Datasets of Ocean Parameters

In this study, through experimental research and an investigation on large datasets of the durability parameters in ocean engineering, the values, ranges, and types of distribution of the durability parameters employed for the durability design in ocean engineering in northern China were confirmed. Based on a modified theoretical model of chloride diffusion and the reliability theory, the service lives of concrete structures exposed to the splash, tidal, and underwater zones were calculated. Mixed concrete proportions meeting the requirement of a service life of 100 or 120 years were designed, and a cover thickness requirement was proposed. In addition, the effects of the different time-varying relationships of the boundary condition ( C s ) and diffusion coefficient ( D f ) on the service life were compared; the results showed that the time-varying relationships used in this study (i.e., C s continuously increased and then remained stable, and D f continuously decreased and then remained stable) were beneficial for the durability design of concrete structures in marine environment.

Finite Element Analysis of Punching Shear of Reinforced Concrete Slab–Column Connections with Shear Reinforcement

Shear reinforcement is one of the common measures used to strengthen slab–column connections. It can make the joint’s load capacity increase. However, when the connection is subjected to an unbalanced bending moment, the reduction effect of the shear reinforcement on the bending moment is worth investigating. Nonlinear finite element analysis was performed on reinforced concrete slabs with shear reinforcement for various moment-to-shear (M/V) ratios. The effects of the number and diameter of shear reinforcement and different loading methods on the slab were investigated, as along with a correction to the ACI-318 and China Concrete Structure Design code GB50010 formula for the moment transfer coefficient. The 3D finite element modeling was performed using appropriate element types and a constitutive model for concrete. The concrete damage plasticity model parameters were calibrated using the experimental results of a specimen. The amount of shear reinforcement had a certain contribution to the strength of the slab, but the diameter of the shear reinforcement had little effect. The plate’s bearing capacity decreased as the M/V increased. The corrected moment transfer coefficient formula demonstrates that M/V is positively correlated with the coefficient and that the calculated values specified in ACI-318 and GB50010 are overly conservative.

Shear strength of concrete beams using stay-in-place flexible formworks with integrated transverse textile reinforcement

This study investigates the fabrication and the structural performance of concrete beams using weft-knitted tubular fabrics as stay-in-place formworks with integrated textile reinforcement. The use of non-corrosive high-strength textile materials for flexible formworks offers great potential for efficient construction processes and a bespoke design of material-efficient concrete structures. To this end, an experimental campaign consisting of ten three-point bending tests on beams with rectangular cross-sections made with flexible stay-in-place formworks was conducted, where aramid rovings were integrated within the textile as transverse reinforcement to withstand the shear forces while the longitudinal reinforcement consisted of conventional deformed steel bars. The use of digital image correlation measurements and distributed fibre optical sensing allowed the refined analysis of the deformations, including the strains in the textile reinforcement and the estimation of the crack kinematics, which were used to assess various contributions from the reinforcement and the concrete to the shear strength in the governing crack. The amount of textile reinforcement proved to be a decisive parameter in increasing the shear strength, although the full tensile capacity of the rovings could not be exploited due to the lack of ductility in the material behaviour. The thorough consideration of the shear transfer mechanisms revealed a strong dependence of the concrete contribution, specifically aggregate interlock and the formation of a direct strut, on the crack patterns. The combination of the brittle aramid rovings as shear reinforcement and conventional steel reinforcing bars in the tension chord provided a large deformation capacity if the shear reinforcement was able to sustain the load until a bending failure was reached.

A short overview of reinforced concrete frame structure design methodology and problems

A short overview of reinforced concrete frame structure design methodology and problems