Reinforced Concrete Slabs Research Articles

Design and Construction Technology of Prefabricated Reinforced Concrete Slab Culverts

Compared with traditional cast-in-situ concrete slab culverts, prefabricated reinforced concrete slab culverts can be produced more quickly and has strong quality controllability, strong earthquake resistance, and repeatability. They will be the primary production method of slab culverts in the future. This article offers a comprehensive review of the design and construction technology associated with prefabricated reinforced concrete slab culverts. The objective is to provide a valuable reference for related enterprises, enhance the quality of design and construction in precast pile configuration, and, in turn, contribute to the advancement of construction projects within our country.

Yield Line Analysis of a Three-Side Supported Two-Way Reinforced Concrete Slab by Various Location of Concentrated loading

Yield Line Analysis of a Three-Side Supported Two-Way Reinforced Concrete Slab by Various Location of Concentrated loading

Monotonic and cyclic behaviour of deficient reinforced concrete slabs retrofitted with externally bonded carbon fibre reinforced polymer

Fibre reinforced polymer (FRP) retrofitting of reinforced concrete (RC) slabs has been widely investigated; however, the flexural behaviour of deficient RC slabs retrofitted with FRP under cyclic loading are limitedly explored. Towards this aim, this study experimentally and theoretically investigated the behaviour of RC slabs retrofitted with carbon fibre reinforced polymer (CFRP) under monotonic/cyclic loadings. Seven full-scale RC slabs, including one control slab and six slabs retrofitted by 1/2 and one CFRP layer, namely retrofitting types I and II, were tested under monotonic and cyclic loadings until failure. The results indicated that FRP retrofitted slabs failed by CFRP debonding while the control slab failed by steel yielding. CFRP retrofitted slabs exhibited tri-linear behaviour. CFRP retrofitting types I and II improved the yield load-carrying capacity by 43.5% and 83.5%, and the maximum load-carrying capacity by 81.9% and 217.4% compared with the capacity of the control slab, respectively. The stiffness of the retrofitted slabs increased significantly, leading to a substantial reduction in the deflection capacity. Although the ductility decreased, the safety factors based on load-carrying capacity of CFRP retrofitted slabs were much higher than the safety factor of the control slab. Cyclic loading caused a marginal strength degradation while it slightly reduced the ultimate deflections. Finally, a model to compute the moment capacity of CFRP retrofitted slabs was proposed, which can be useful for engineers in practice due to its simplicity and reasonable accuracy.

Structural evaluation of RC overhang cantilever slab strengthened with FRP near‐surface mounted (NSM) composites for bridge applications

AbstractThis paper presents the findings of a large‐scale experimental study that focus on assessing structural behavior of reinforced concrete (RC) cantilever slabs with carbon/epoxy fiber‐reinforced polymer (CFRP) composite strips using a near‐surface‐mounted (NSM) approach. The NSM/CFRP system evaluated in this study was implemented in strengthening the shoulders of the Slide Canyon Bridge in California, USA. The experimental phase is divided into two main parts: (i) determining the design parameters for NSM, including the bondline strength through pull‐out tests, and (ii) conducting a practical evaluation of the bending behavior of original and retrofitted RC cantilever slabs, each with varying NSM reinforcement and three different development lengths. Results of this study indicated that the use of NSM‐CFRP has a considerable benefit in that it significantly improves ductility and changes the failure mode of the unstrengthened RC slab from the typical brittle shear‐based failure mode to a more ductile flexural‐based failure mode. The large‐scale slab specimens' performances, which had different development lengths, showed little variance, except for the slab specimen with a development length of 457.0 mm that exhibited an appreciable flexural stiffness as compared to other specimens evaluated in this study. In order to simulate the serviceability and ultimate behavior of the RC slab specimens, linear and nonlinear finite element analyses were performed. A satisfactory agreement between numerical and experimental results was achieved especially at load level prior the initiation of large‐size cracks.

In Situ Investigation of the Dynamic Response and Settlement in the Expressway Culvert–Subgrade Transition Section Using a Vibration Exciter

During the operational phase of the expressway, a significant challenge arises concerning substantial differential settlement in the transition zone connecting the culvert and the general subgrade, affecting its smoothness. In order to address the issue of abrupt stiffness variations within the transition section and to mitigate the occurrence of differential settlement, a gradient pile–reinforced-concrete slab composite foundation was implemented for the first time within an expressway culvert–subgrade transition section. At the same time, an in situ vibration test was conducted through the SBZ30 vibration exciter to comprehensively understand the vertical dynamic responses in the culvert–subgrade transition section under various axle loads and speed conditions. Furthermore, continuous monitoring was conducted to track the long-term settlement of the roadbed. The findings indicate that the utilization of gradient pile–reinforced-concrete slab composite foundations can significantly mitigate the amplitude of the dynamic response parameters. Moreover, dynamic parameters and attenuation coefficients exhibit a gradual reduction as the depth increases. Dynamic stresses, acceleration, and displacements on the roadbed surface exhibited positive correlations with both the axle weight and vehicle speed. However, at deeper depths, the load weight exerted a more pronounced influence. As the speed rose, acceleration decayed faster, affecting a shallower depth. Conversely, the increased load slowed the acceleration decay. The cumulative deformation of the roadbed and the number of excitations followed exponential function characteristics. Settlement values progressively increased while the settlement rate gradually diminished, eventually reaching a stable state, ultimately stabilizing within 4.7 mm. These research outcomes offer valuable guidance and serve as a reference for the implementation of gradient pile–reinforced-concrete slab composite foundations within the culvert–subgrade transition section.

Innovative approaches to deflection analysis in strengthened reinforced concrete Slabs: Combining experiments and theoretical research

Structures often experience high-stress conditions, leading to premature deterioration and costly replacements before their intended design life ends. To address this issue, strengthening techniques are employed to mitigate the degradation of reinforced concrete (RC) slabs. This study focuses on investigating the flexural strengthening of RC slabs. Specifically, it examines the impact of different externally bonded plates and slab thickness on the deflection of RC slabs during the pre-crack elastic stage. Additionally, the study seeks to predict measured displacement values using approximate methods like the Classical Laminated Plate Theory (CLPT) and the First-order Shear Deformation Theory (FSDT). The experiment utilized six square slabs measuring 1100 mm by 1100 mm, with thicknesses of 60 mm and 90 mm. For the slabs with a thickness of 60 mm, two-way flexural reinforcing bars, each with a 10 mm diameter, were placed at 150 mm intervals, while the slabs with a thickness of 90 mm had reinforcing bars spaced at 100 mm intervals. Two of the RC slabs were strengthened with carbon plates, two with steel plates, and the remaining two served as control samples. The results indicated that steel plate strengthening improved RC slabs by 47 %, while carbon plates achieved a 43 % enhancement. Furthermore, increasing the slab thickness significantly reduced the deflection of RC slabs. A good agreement was noted when the deflection capacities predicted by the analytical model were compared to the experimental findings.

Low-Code Application and Practical Implications of Common Machine Learning Models for Predicting Punching Shear Strength of Concrete Reinforced Slabs

This paper investigates the effectiveness of machine learning (ML) models available in MATLAB Regression Learner app and MATLAB App Designer, both low-code applications, for accurately predicting punching shear strength (PSS) in reinforced concrete (RC) slabs. A database of 379 RC slab samples without transverse reinforcement was compiled from renowned publications. RandomSearch and Bayesian optimisation were employed for tuning hyperparameters. The performance of these models was compared with six empirical models, which included three current design codes, three equations from other researchers, and 227 finite-element simulations conducted by the authors. The ML models and finite-element method (FEM) demonstrated superior performance compared with the literature and practical codes. Furthermore, the results emphasised the exceptional performance of the Gaussian process regression (GPR) with optimised hyperparameters, exhibiting the best performance in validation, training, and testing datasets with R2 values of 0.95, 0.99, and 0.98, respectively. A user-friendly standalone application was developed, providing real-time predictions of the PSS using the two best-developed ML models, GPR and support vector machine (SVM), as well as six empirical models from the literature. This tool offers users flexibility in choosing the most appropriate model for their specific needs, delivering reliable, and accurate results for estimating the PSS of RC slabs.

Flexural Strengthening of Two-Way RC Slabs with Textile Reinforced Mortar: Experimental Study and Calculation Model

Textile reinforced mortar (TRM) strengthening can improve the anti-aging performance of reinforced concrete (RC) slabs, and significantly improve the rust problem of steel plates and bending performance of RC slabs. To study the effect of TRM on the flexural capacity of two-way RC slab, four sided simply supported bending tests were conducted on two TRM strengthened concrete slabs and an unstrengthened control slab. And the effects of different strengthening techniques on the flexural capacity and bending deformation capacity of the two-way RC slabs were investigated. It was concluded that the application of TRM to strengthen the two-way RC slabs can effectively improve its bending bearing capacity and bending deformation capacity. Compared with the unstrengthened control slab, the bending bearing capacity of the two strengthened slabs increased by 54.2% and 43.8%, respectively, and the energy absorption value increased by 75.5% and 49.1%, respectively. In addition, compared with control slab, the post-cracking stiffness of TRM reinforced slabs treated with and without interface agents increased by 145.2% and 83.4%, respectively. This indicated that using interface agents for interface treatment could improve the adhesion between the TRM and the original RC slab, thereby preventing the initiation and development of cracks between the new and old interfaces. The strength utilization rate of textile was proposed, and the relationship between strength utilization rate of textile and maximum or minimum distribution network rate was analyzed. Based on the plastic hinge theory a simple calculation formula for the bending bearing capacity of the two-way RC slab strengthened with TRM was proposed, which provided the reference for the application of TRM for strengthening projects.

A time and cost-effective strengthening of RC half joint bridges exposed to brittle failure: application to a case study

This paper addresses the strengthening of a reinforced concrete (RC) road bridge with Gerber-type beams, prompted by the recent collapses of some Italian bridges. The study discusses the characteristics of half-joint bridges, also known as Gerber beam types. These designs, originating in the late 1800s and commonly utilized from the 1950s to the 1970s, exhibit an isostatic structure. While they are easy to design, typically featuring pairs of piers with symmetrical cantilevers and two or more suspended spans, they often suffer from weakening of the half joints (saddles), necessitating structural consolidation. Designers have proposed several solutions to strengthen this type of bridges and the approach presented in this paper focuses on cost-effectiveness and efficiency. It involves a gradual demolition of longitudinal strips on the RC slab of suspended beams, followed by the installation of new steel beams to create a mixed RC-steel system. The application of this method is illustrated in a double-pier bridge spanning the Arno River, Italy. The bridge’s rehabilitation required a complete closure of the traffic road for twelve weeks, followed by alternating traffic for twenty-four weeks. The paper discusses both the design and construction aspects of the proposed intervention, considering costs and implementation time. Furthermore, a low-cost health monitoring procedure is briefly introduced.

Fire behaviour of reinforced concrete slab strips strengthened with prestressed NSM-CFRP laminates

Carbon fibre reinforced polymer (CFRP) composites are now widely used to strengthen reinforced concrete (RC) structures. Among the strengthening systems available, near-surface mounted (NSM)-prestressed CFRP laminates offer several advantages, as they significantly increase the load carrying capacity and also the serviceability performance of RC structures. However, as for other CFRP systems, there is a concern about their behaviour at elevated temperature and under fire exposure due to the glass transition process undergone by their polymeric components. Nevertheless, the fire performance of NSM-prestressed-CFRP strengthening systems has not yet been investigated. This paper presents an experimental study about the fire resistance behaviour of RC slab strips strengthened with prestressed NSM-CFRP laminates; the slabs were simultaneously subjected to a mechanical (fire) load and the ISO 834 fire curve, and the influence of the following parameters on their fire resistance behaviour was assessed: (i) the prestress level (0 %, 25 % and 50 % of the CFRP tensile strength), and (ii) the presence of passive fire protection, comprising up to 48 mm thick calcium silicate (CS) boards. The results obtained showed that: (i) without fire protection, the strengthening system remained effective during a very low period of fire exposure, which significantly decreased with the prestress level, from 16 min (0 %) to less than 5 min (50 %); (ii) with fire protection, even with 50 % of prestress, the strengthening system remained effective for more than 120 min; and (iii) the “critical” temperatures in the anchorages of the strengthening systems were found to be about 2.5Tg, 2.0Tg and 1.5Tg, for the prestress levels of 0 %, 25 % and 50 %, respectively, with Tg being the glass transition temperature of the adhesive.

Experimental Study on Monitoring Damage Progression of Basalt-FRP Reinforced Concrete Slabs Using Acoustic Emission and Machine Learning.

Basalt fiber-reinforced polymer (BFRP) reinforced concrete is a new alternative to conventional steel-reinforced concrete due to its high tensile strength and corrosion resistance characteristics. However, as BFRP is a brittle material, unexpected failure of concrete structures reinforced with BFRP may occur. In this study, the damage initiation and progression of BFRP-reinforced concrete slabs were monitored using the acoustic emission (AE) method as a structural health monitoring (SHM) solution. Two simply supported slabs were instrumented with an array of AE sensors in addition to a high-resolution camera, strain, and displacement sensors and then loaded until failure. The dominant damage mechanism was concrete cracking due to the over-reinforced design and adequate BFRP bar-concrete bonding. The AE method was evaluated in terms of identifying the damage initiation, progression from tensile to shear cracks, and the evolution of crack width. Unsupervised machine learning was applied to the AE data obtained from the first slab testing to develop the clusters of the damage mechanisms. The cluster results were validated using the k-means supervised learning model applied to the data obtained from the second slab. The accuracy of the K-NN model trained on the first slab was 99.2% in predicting three clusters (tensile crack, shear crack, and noise). Due to the limitation of a single indicator to characterize complex damage properties, a Statistical SHapley Additive exPlanation (SHAP) analysis was conducted to quantify the contribution of each AE feature to crack width. Based on the SHAP analysis, the AE duration had the highest correlation with the crack width. The cumulative duration of the AE sensor near the crack had close to 100% accuracy to track the crack width. It was concluded that the AE sensors positioned at the mid-span of slabs can be used as an effective SHM solution to monitor the initiation of tensile cracks, sudden changes in structural response due to major damage, damage evolution from tensile to shear cracks, and the progression of crack width.

A rate-dependent peridynamic model of reinforced concrete subjected to explosive loading

Explosive loads caused by various factors seriously threaten the security of reinforced concrete (RC) structures. To explore the dynamic damage and failure patterns of RC structures under explosive loads, new rate-dependent peridynamic (PD) models for concrete and reinforcement are proposed. For concrete, the behavior of progressive damage and the compressive deformation limit are also taken into account. The ideal microplastic PD model is adopted for reinforcement. Then, this paper investigated the failure process of RC slabs under close-in explosive loads and obtained crack propagation paths and central bending deflections consistent with the test results. The results manifest the established PD model can correctly calculate the damage process of RC structures under explosive conditions.

Structural Performance of Reinforced Concrete Double Layer Bamboo Bubble Slab Under Uniformly Distributed Load

The architectural use areas in the structure are formed by reinforced concrete (RC) slabs, which transport vertical loads to the beams, columns, load-bearing walls, and shear walls. The slab is an important structural member of reinforced concrete building structures and concrete-intensive parts of structural members. . The slab deflects significantly when the load acting on the slab or the clear span between columns is large. As a result, the slab's thickness increases to accommodate the load received. Since this slab's self-weight increases as the thickness increases, the slabs get heavier and causes the slab unable to withstand the load and to produce cracks on the surface. At the turn of the twentieth and twenty-first centuries, the creation of the bubble deck slab became an innovation to replace conventional slab. This study used bamboo as the bubble material in reinforced concrete bubble slab. This study examined and assessed the mechanical properties and structural behaviour of bamboo as a bubble in supported reinforced concrete double-layer bamboo bubble slab under a uniformly distributed load. In this research, 500 mm x 1250 mm x 175 mm supported reinforced concrete slabs C25 (1 sample) and C30 (1 sample) with double layer (DL) bamboo bubble slabs were constructed. Both samples were compared with the control sample (CS) for each slab type. It was found that the maximum displacement occurred at the centre of the slab, with 6.45 mm for DL25 and 6.89 mm for DL30. According to stress-strain analysis, the double layer bamboo slab produced a lower stress value than the control sample. Since the values were smaller than 2, DL25 and DL30 slab performed better for the ductility factor than CS25 and CS30. As a result, the displacement, ductility and section capacity were improved by employing bamboo as a bubble material in a reinforced concrete slab.

Punching Shear Failure Analysis of Reinforced Concrete Slabs under Close-in Explosion.

The susceptibility of reinforced concrete (RC) slabs to punching shear failure is heightened when subjected to close-in explosion loads, leading to a wider range of damage caused by the resultant leakage shock wave through the punching hole. Consequently, it is crucial to analyze the conditions for punching shear failure and the size of the punching hole in RC slabs. This study investigates the punching shear failure of RC slabs under close-in explosions through numerical simulation and theoretical analysis. Initially, a finite element model is developed to examine the distribution of the explosion load on the slab's surface. Subsequently, the critical explosion load for punching shear failure is determined using a damage criterion specific to RC slabs. Additionally, a calculation model based on the twin shear stress yield criterion is established to predict the punching hole's radius. To validate the accuracy of this method, a comparison is conducted with existing test results.

Calculation of the Constructive Nonlinearity of Ribbed Reinforced Concrete Slabs of Self-Stressed Covering Panels

Abstract Precast reinforced concrete constructions meet the requirements of industrialization, high manufacturability, and cost-effectiveness at a reasonably high level. The ribs in constructions perform load-bearing functions, and the slab part performs enclosing functions. Often before the installation of such structures at a construction site, they are mounted from assembly elements. The overall dimensions of the elements are limited by transportation requirements. During such an aggregated mounting, the assembly units work according to a calculation scheme that differs from an operational scheme. The structural nonlinearity of ribbed reinforced concrete slabs during transportation, mounting, and installation, and the operation of a combined spatial covering panel were investigated in this paper. The effects were identified, and a rational design of nodes connecting the individual prefabricated units into a spatial structure was developed. With the help of these nodes, it is possible to create unloading support moments, which will reduce the internal forces in the design cross-sections. The effects of changes in the width of the reinforced concrete slab shelves on the internal forces of the load-bearing ribs of a wall and a roof panel were investigated.

Assessment of Blast-Induced Damage in Reinforced Concrete Slabs: A Comparative Study between Numerical Simulation and Advanced Structural Analysis Software

This research paper presents a comparative study on the assessment of blast-induced damage in reinforced concrete slabs, focusing on the comparison between numerical simulation and advanced structural analysis software. The objective is to evaluate the accuracy and reliability of both approaches in predicting structural damage caused by blast loading. The study utilizes numerical simulation techniques to model the dynamic behaviour of reinforced concrete slabs subjected to blast loading. Material properties, reinforcement details, and blast loading characteristics are incorporated into the simulations. The resulting structural response and damage are evaluated. In parallel, advanced structural analysis software, specifically MIDAS Civil software selected for its capabilities in blast analysis, is employed to analyse the same set of reinforced concrete slabs under blast loading. The software provides advanced modelling and analysis tools for assessing structural response and calculating blast-induced damage. By comparing the results obtained from the numerical simulations and the advanced structural analysis software, the study evaluates the agreement and capabilities of both approaches. Parameters such as displacements, strains, stress distributions, and damage patterns are examined. The findings contribute to the understanding of the accuracy and limitations of numerical simulation and advanced structural analysis software for blast-induced damage assessment. The results of this comparative study provide valuable insights for practitioners and researchers in blast engineering and structural assessment. The implications for blast-resistant design and recommendations for future research are discussed, aiding in the advancement of effective strategies for assessing and mitigating blast-induced damage in reinforced concrete structures. Keywords: Blast Analysis, Dynamic Linear Analysis, Response Spectrum Analysis, Prestressed Concrete.

Exploring Analytical Hierarchy Process for Multicriteria Assessment of Reinforced Concrete Slabs

The decision regarding which slab type should be used in a building is generally made by the structural engineer, considering structural efficiency and compatibility with the architectural design, as well as the costs related to the amount of material used in each option. Because of the technical responsibilities inherent to this specialty, the decision-making process neglects to encompass various other factors of consequence that influence the construction process. These considerations include productivity, the visual and aesthetic characteristics of the slab, waste generation, and thermal and acoustic comfort. This paper aims to develop a multicriteria method to assist stakeholders in selecting the most suitable structural system for slabs based on project needs and objectives. The study utilized the Analytic Hierarchy Process (AHP) and information from bibliographic research, expert opinion using the Delphi Method, and machine learning on a dataset of over 2000 previously constructed slabs to achieve this goal. The analysis showed that the conventional solid slab type was the top priority, followed by the two-way waffle slab, one-way waffle slab, solid flat slab, and waffle slab. Additionally, the proposed AHP method was effective in developing a decision-making model for companies and the construction sector.

Nonlinear analysis of reinforced concrete slabs using a quasi-3D mixed finite element formulation

This study presents an efficient quasi-3D mixed finite element (MFE) formulation for the materially nonlinear analysis of reinforced concrete (RC) slabs based on a refined layered global–local plate theory. The cross-section of the RC slab is divided into a series of concrete and steel layers. Each layer is treated as a plate structure and mechanical properties of the steel and concrete materials are individually applied to each layer. In addition to unknown variables of the displacement field, out-of-plane stress components are also assumed as independent field variables in the presented MFE formulation. It makes it possible to obtain the out-of-plane shear stresses at each node directly from constitutive equations with the enough accuracy. A four‐node rectangular element ensuring the C1‐continuity is used for discretizing the domain of the RC slab. The governing equations are derived based on a partially mixed-field variational principle. The accuracy and efficiency of the presented MFE have been investigated through some benchmark examples. Numerical tests show that the presented MFE yields results with sufficient accuracy at a low computational cost.

Sensitivity Analysis of Factors Influencing Blast-like Loading on Reinforced Concrete Slabs Based on Grey Correlation Degree.

Blast simulators are capable of applying blast-like loading to components in a safe and controlled laboratory environment, overcoming the inherent shortcomings of blast testing in terms of data acquisition, test cycle time, and cost. In this paper, reasonable assumptions and refinements are made to the components and shape of the impact module, a key component of the blast simulator, to achieve diversity in simulated blast loading. By designing four rubber shapes, the importance of ellipsoid rubber as an elastic cushion for simulating blast loading was determined. In order to assess the effectiveness of this optimization, numerical calculations based on a calibrated finite element model were performed around four factors: flat rubber thickness, ellipsoid rubber thickness, impact velocity, and impact modulus mass. Additionally, a grey correlation sensitivity analysis was carried out to evaluate the effect of these factors on the impact loading on the reinforced concrete (RC) slab. The results indicate that peak pressure and impulse had opposite sensitivities to velocity and mass. Changes in ellipsoid rubber thickness had a more positive effect on the impact loading than flat rubber thickness. An in-depth study of the role of these influencing factors is important for the design and improvement of impact modules.

Experimental and analytical investigation on the use of NSM–BFRP and NSM–GFRP bars in strengthening corrosion–damaged RC slabs

This paper presents the results of an experimental and analytical study on the flexural behavior of corrosion–damaged reinforced concrete (RC) slabs strengthened with different near–surface mounted fiber–reinforced polymer (NSM–FRP) bars. An accelerated corrosion technique was used to induce corrosion in the steel reinforcing bars of the tested slabs. The investigated parameters comprised the number of NSM–FRP bars (two and four bars), the type of the NSM–FRP reinforcement (basalt B and glass G bars), and the mass loss in the steel rebars due to corrosion (10 and 20%). The yielding and ultimate capacity of the strengthened slabs was not only restored but surpassed those of the virgin control slab. Slabs strengthened with two and four NSM–BFRP bars showed 32–42% increase in their yielding load and 45–50% in their ultimate loads, respectively, as compared to the unstrengthened corroded slab. Similarly, the strengthened slabs showed 5–50% increase in their ductility index as compared to the virgin slab. The strengthened slabs failed due to the yielding of the steel reinforcing bars followed by compression concrete crushing. ACI–440 formulations reasonably predicted the performance of the strengthened slabs with conservative capacities when ACI strain limit of 0.7 εfu was considered.