Reinforced Concrete Plates Research Articles

Optimized analysis and reinforcement design model for RC/SCC box-section bridges using developed advanced design framework

In recent years, there has been a significant rise in the construction of reinforced concrete (RC) and steel-concrete composite (SCC) box-section bridges. However, design codes do not provide specific design methods for the RC plates of such bridges where the plates experience both intricate forces and moments. The current design approaches are primarily based on conventional one-dimensional beam element theory, which neglects the complex spatial force characteristics of the structural elements, potentially leading to unsafe design. Therefore, it is imperative to address this issue. To bridge this gap, a comprehensive analysis and reinforcement design procedure named as the developed advanced design framework (DADF) is proposed in this study. The spatial analysis of bridges was performed using a refined numerical model, called the spatial grid model (SGM), to consider the structural spatial effects with limited model scales. Subsequently, the internal force corresponding matrix (IFCM) was implemented through Python scripts to determine the most critical internal force combination for an RC plate element. Additionally, the three-layered sandwich model (T-LSM) was employed with limit analysis to automatically design reinforcement for all elements, serving as a practical tool for design. This research demonstrates that the implementation of the DADF can significantly reduce steel reinforcement in the RC plates of such bridges by up to 48 %, and 23 % in total, showcasing the efficiency of the developed framework. Overall, the findings emphasize that the proposed DADF offers a robust procedure for steel reinforcement design of RC/SCC box-section bridges.

Identifying the effect of thickness on crack width in one-way reinforced concrete slab structures

This paper presents an evaluation study of crack limit states according to design codes and previous research. It aims primarily to relate research findings to design code similarities. Cracks in reinforced concrete structures are still a challenging problem for researchers, especially in one-way plate structures where there is still a lot of damage and corrosion in the reinforcement due to cracks. Finding the right formula will make it easier for practitioners to design these structures, and the problem of durability in reinforced concrete plates can be overcome. From this research, an approach is proposed on how to predict the maximum crack width formula in one-way reinforced concrete slabs with different thicknesses. Plates use a variety of thicknesses, including 125 mm, 150 mm, 175 mm, and 200 mm. The test specimens have the same dimensions and steel reinforcement, a slab width of 0.6 m and a length of 2 m. From a literature study of prediction formulas from previous research works and codes, namely wmax(prop)=7.5*10-3 fsh-0.333, it was found that thickness (h) has little influence on maximum crack width. The results from both approaches in this analysis are overall in accordance with the observed experimental tests and the proposed formula. Based on these observations, increasing the thickness of the reinforced concrete slab has significantly reduced the maximum crack width so that the experimental formula is obtained, namely wmax(exp)=0.32*fsh-1.113. Therefore, a constant is needed to evaluate the influence of thickness parameters for slabs with a thickness less than 200 mm on the maximum crack width formula for reinforced concrete slabs, and a special approximation formula has been obtained. In practical use, the crack width formula can only be used for one-way slabs

Modeling the initiation and propagation of complex networks of cracks in reinforced concrete plates

The present paper proposes a new finite element formulation for the analysis of RC slabs, accounting for concrete cracking and reinforcement yielding. The proposed formulation, developed within the framework of Lumped Damage Mechanics, considers that all inelastic effects are localized in lines and relates all numerical parameters to the mechanical properties of the slab. The proposed variational approach is presented as a Nash noncooperative equilibrium point. It is verified, numerically, that the proposed FE leads to mesh-independent results. Numerical simulations of some experimental tests are also presented. The results in terms of collapse mechanism, cracking network, and force-deflection curves showed that the model has significant accuracy, even for non-symmetric free clamped and simple supported boundary conditions. It is also shown, through the confrontation with experimental results, that the model correctly characterizes the initiation and development of complex networks of cracks.

Lateral strength evaluation of innovative and traditional composite shear wall systems

This paper proposes formulations for predicting lateral load-bearing capacity of two types of composite shear wall (CSW) systems, which consist of a steel frame and a reinforced concrete (RC) plate attached to one side using bolts. Due to the high out-of-plane stiffness of the RC plate, it can effectively provide out-of-plane constraint to prevent out-of-plane deformation of the steel plate in CSW systems. However, in traditional CSW systems, direct contact between the RC plate and the frame often results in crushing at the former under seismic loading, thereby providing insufficient restraint against out-of-plane deformation of the steel plate. In contrast, the innovative CSW system with a gap maintained at the steel frame and RC plate exhibited superior seismic behavior than its traditional counterpart. While previous studies have investigated cyclic behavior and parameter effects of CSW systems, there remains a gap in evaluating their lateral strength. The proposed formulations show a mean distinction among theoretically determined and actual lateral load-bearing capacity less than three percent.

Numerical Prediction of Ballistic Performance of Thin Concrete Plate

This research explores the ability of 60[Formula: see text]mm thick reinforced concrete (RC) plates to resist impacts from ogive-nosed hard steel projectiles. The projectiles used in the present study have a diameter of 19[Formula: see text]mm, a length of 200[Formula: see text]mm, and a mass of 0.4[Formula: see text]kg impacted on the RC plates with incident velocities ranging from 92[Formula: see text]m/s to 161[Formula: see text]m/s. Numerical simulations were conducted using ABAQUS/Explicit finite element software to validate the experimental results. The Holmquist–Johnson–Cook (HJC) material model was employed to simulate the constitutive behavior of concrete, while the Johnson–Cook (JC) material model was used to simulate the material response of reinforcing steel bars. The residual velocities obtained from the simulations closely matched the actual experimental results, showing a polynomial correlation with the incidence velocities of the projectiles. Moreover, the experimentally and numerically determined ballistic limit for the 60[Formula: see text]mm thick RC plate was found to be 108[Formula: see text]m/s and 109.5[Formula: see text]m/s, respectively. In contrast, the ballistic limit calculated using empirical mathematical expressions was 107.4[Formula: see text]m/s. This alignment between predicted, calculated, and actual ballistic limits underscores the reliability and accuracy of both numerical and empirical approaches.

Study on the relationship of design parameters and damage modes for RC slabs subjected to large-scale hard missile impacts base on task-driven approach

This study proposes a novel hybrid ensemble learning (EL) model that integrates CatBoost and SMOTE-NC algorithms to evaluate the damage modes of reinforced concrete (RC) slabs under large-scale hard missile impacts, overcoming the limitations of conventional approaches. To develop the optimization model, a database was constructed using publicly published experimental data from 304 large-scale missile impact tests conducted on RC plates. Furthermore, the SMOTE-NC oversampling algorithm is employed to optimize the database and address the issue of class imbalance. Subsequently, four ensemble machine learning models and empirical formulas are assessed. The findings indicate that the hybrid ensemble learning model combining CatBoost and SMOTE-NC exhibits superior performance, showcasing robustness and efficacy. Furthermore, through the application of SHAP analysis, it was revealed that velocity, thickness, concrete compressive strength, missile mass, reinforcement ratio, and missile diameter are the most influential variables, and they interact with each other in significant ways. Notably, the analysis indicated that once the concrete compressive strength reaches a certain value, further improvements may have a detrimental effect on penetration resistance. Additionally, the impact of yield strength on slab performance becomes more pronounced as the slab thickness decreases. Drawing upon these findings, a proposed approach for damage assessment and protection design utilizing an interpretable hybrid EL model was introduced. However, it is crucial to acknowledge that the applicability of this model is confined to RC targets with finite thickness, specifically engineered to withstand large-scale hard missile impacts.

Experimental and numerical investigation of the seismic performance of concrete-filled steel tubular composite columns with UHPC plates

To study the seismic performance of concrete-filled steel tubular composite columns with UHPC plates. The pseudo-static tests were carried out on five specimens with the longitudinal distance of the column limbs and thickness of the UHPC plates as test parameters. Subsequently, a nonlinear finite element model of such composite columns was established based on OpenSees, and the calculation method of lateral bearing capacity of the specimen under compression-bending load was proposed. The results showed that the longitudinal distance of the column limbs significantly influenced the lateral bearing capacity as well as the initial stiffness of the specimens. The longitudinal distance of column limbs was increased from 250 mm to 650 mm, and the lateral bearing capacity as well as the initial stiffness of the specimens were increased by 246.0 % and 488.5 %, respectively. The thickness of the UHPC plate was increased from 50 mm to 100 mm, the lateral bearing capacity of the specimen was increased by 32.2 %, while the cumulative hysteretic energy consumption was reduced by 45.05 %. Keeping the same axial pressure ratio, the initial stresses in the column limb steel tubes of the concrete-filled steel tubular composite columns with UHPC plates specimens were higher compared to those of the concrete-filled steel tubular composite columns with ordinary reinforced concrete plates specimens, resulting in poorer ductility. The established nonlinear numerical model accurately captured the hysteretic performance of the specimen. Moreover, the proposed lateral bearing capacity calculation method has high accuracy and can predict the lateral bearing capacity of such structures well.

Shaking table tests of a full-scale base-isolated flat-bottom steel silo equipped with curved surface slider bearings

This paper presents a series of shaking table tests on a full-scale flat-bottom steel silo filled with soft wheat, under isolated-base conditions. The tested specimen is a 3.64 m-diameter 5.50 m-height corrugated-wall cylindrical silo, representing the smallest manufactured silo available in the catalogue of an Italian commercial silo provider. Curved Surface Slider isolators were introduced between the shaking table and the reinforced-concrete plate, on which the silo was mounted, to realize the isolated configuration where the main results have been investigated and compared with other results for the same silo specimen under fixed-base conditions. A detailed description of the silo components, the filling bulk material properties as well as the test setup is provided, including the full testing protocol. Multiple sensors were used to monitor the dynamic response of the filled silo system, including accelerometers, pressure cells, LVDT displacement transducers. Numerous unidirectional dynamic tests were conducted consisting of random signals, sinusoidal inputs, pulse-like inputs, and both artificial and real earthquake records. The results were processed to evaluate the performance of the isolators and their effectiveness on the silo response in terms of measured accelerations and dynamic overpressures. The efficiency of the isolation on the reduction of both acceleration amplifications over the silo wall height as well as the captured dynamic overpressures were detected in the range 30%–80% depending on the input type and magnitude.

Projectile impact-induced spalling damage on carbon fiber reinforced polymer strengthened RC plates

As the most widely used material in protective structures, a better understanding of the resistance of reinforced concrete (RC) to high-speed projectile striking is needed. It has been accepted that concrete material possesses limited impact resistance in virtue of its poor energy absorption capacity. To improve the performance of RC structures under impulsive loading, affixing externally-bonded Fiber Reinforced Polymer (FRP) sheets on structural elements is a practical method. Due to the emphasis of most existing literature on the penetration behavior of projectiles, the studies of impact-induced spalling damage on normal and FRP strengthened RC plates are not sufficient and in-depth. In this paper, the local response of un-strengthened and FRP strengthened RC plates under projectile impact is systematically investigated with experimental approaches. In consideration of the complexity of transient behavior as well as multiply parameters involved, empirical approaches based on dimensionless analysis are proposed to predict the diameter and depth of spalling craters on normal RC plates and strengthened ones with frontal CFRP layers, which fill current research gap and are potential tools for damage assessment and repair. The validity of the proposed approaches is verified by test results from the present and published studies.

Dynamic analysis of reinforced concrete plate resting on elastic foundation using state space method and refined plate theory

This paper studies the dynamic response of rectangular reinforced concrete plates on an elastic foundation by state space method. The system of differential equations of vibration of the plate is developed by using Hamilton's principle. With a single-link rectangular plate, the displacements are represented through a double trigonometric series. Use the state space method to find the plate vibrational responses. The calculation examples are performed to calculate the displacement and stress of the plate with different structural parameters, thereby evaluating the influence of these parameters.

Numerical Study Regarding the Seismic Response of a Moment-Resisting (MR) Reinforced Concrete (RC) Frame Structure with Reduced Cross-Sections of the RC Slabs

In the first part of the current study, the effectiveness of the transversal cross-section reduction method for RC beams in marginal areas (by means of mechanical drilling) was validated. The said method “encourages” the formation of plastic hinges at the beam ends and, at the same time, allows for taking into account the bending stiffness of RC slabs, which is exerted upon the RC beams. In these conditions, the second part of the current research study (i.e., the current manuscript) highlights the real mode of reducing the lateral stiffness of the slabs upon the RC beams. These elements form a common body, together with the beam–column frame node. The same method as in the first part of the study—“weakening” the plates in the corner area through vertical drilling, without affecting the integrity of the reinforcing elements—was used. The analytical MR RC frame model, studied by means of the comparative method, highlights the efficiency of the transversal cross-section reduction method for RC slabs. Basically, the directing of the plastic deformations from the weakened slab areas towards the marginal areas of the reinforced concrete beams takes place. The beams rotate as far as the weakened slab areas allow its plastic deformation, thus being possible to observe the partial conservation effect of the beam–column frame joint. Furthermore, for the analytical model with the maximum number of vertical holes in the corner areas of the concrete plate, minimal plastic deformations are recorded for the marginal areas of the concrete columns. A partial conservation of the formation mechanism of the “beam-slab-frame node” common rigid block is also noted. Consequently, the dissipation of the seismic energy is made in a partially controlled and directed manner, in the “desired” areas, according to the “Strong Columns—Weak Beams” (SCWB) ductile mechanism of the lateral behavior to seismic actions for reinforced concrete frame structures. The mechanism is specified in current design norms for RC frame systems. The effectiveness of the method for reducing the transversal section of the RC plates in the corner areas by means of transversal drilling is highlighted and validated from the perspective of the local and global ductile seismic response of reinforced concrete frame structures. A significant reduction in the bending stiffness of the slabs upon the beams and a real development of the plastic hinges in the marginal areas of the beams (together with partial implications and plastic deformations) were observed.

Artificial intelligence - finite element method - hybrids for efficient nonlinear analysis of concrete structures

Realistic structural analyses and optimisations using the non-linear finite element method are possible today yet suffer from being very time-consuming, particularly in case of reinforced concrete plates and shells. Hence such investigations are currently dismissed in the vast majority of cases in practice. The "Artificial Intelligence - Finite Element - Hybrids" project addresses the current unsatisfactory situation with an approach that combines non-linear finite element models for reinforced concrete shells with scientific machine learning algorithms to create hybrid AI-FEM models. The AI-based surrogate material model provides the material stiffness as well as the stress tensor for given concrete design parameters and the strain tensor. This paper reports on the current status of the project and findings of the calibration of the AI-based reinforced concrete material model. We successfully calibrated and evaluated k-nearest-neighbour, LGBM and ResNet algorithms and report their predictive capabilities. Finally, some light is shed on the future work of integrating the AI surrogate material models back into the finite element method in the course of the numerical analysis of reinforced concrete structures.

Improvement of Calculation Technique for Flexible Orthotropic Plates on Elastic Base. Part 2. Calculation Results

The proposed paper is a continuation of the author's theoretical work presented earlier in the development of the theory and methodology for calculating flexible orthotropic reinforced concrete plates on an elastic foundation, taking into account the physical nonlinearity of the plate material. The paper presents numerical results of elastic and nonlinear calculations of an isolated rectangular orthotropic plate on an elastic foundation, modeled by an elastic homogeneous isotropic layer rigidly connected to a non-deformable foundation under the action of an external static load, taking into account the own weight of the reinforced concrete plate. The change in its stiffness at the time of cracking and further active opening of cracks has been taken into account in the calculation of the structure under study. The nonlinear calculation of the studied structure takes into account the change in its rigidity at the time of cracking and further active crack opening. The calculation of a flexible orthotropic plate on an elastic foundation in a nonlinear formulation is performed iteratively by the method of B. N. Zhemochkin. A mixed method of structural mechanics has been used to determine the coefficients of canonical equations and free terms. At the first iteration, the reinforced concrete plate is calculated as linearly elastic, homogeneous, and orthotropic; at the subsequent ones – as linearly elastic, inhomogeneous, and orthotropic at each Zhemochkin site. Camber plates with a clamped normal in the primary system of mixed method due to the action of a concentrated force are determined by the Ritz method when the deflections were represented as a power polynomial in a new original expression that has been proposed for the first time in the Part 1 of the paper. The solution algorithm has been implemented using the Wolfram Mathematica 11.3 computer program. Numerical and graphical results of elastic and non-linear calculations of sediment concrete road plate, contact stresses and bending moment diagrams on the plate are presented in the paper.

The ballistic evaluation of plain, reinforced and reinforced–prestressed concrete

The ballistic experiments have been performed on plain, reinforced and reinforced–prestressed concrete plates of unconfined compressive strength 48MPa against ogival nosed steel projectiles of mass 0.4 kg and diameter 19 mm at incidence velocities close to ballistic limit. The reinforced concrete targets had two different configurations of reinforcement; first configuration had 0.5% reinforcement in both the orthogonal directions and the second configuration had different percentage of reinforcement (0.5% and 0.8%) in the two orthogonal directions. The prestressing force of 4 MPa was induced in the concrete through pre-tensioning method using 4 mm diameter wires at 40 mm c/c spacing. The reinforcement in the prestressed concrete was provided as 0.5% in one orthogonal direction and 0.8% in the other one. The volume of scabbing and spalling of concrete in the perforated concrete plates was obtained by measurement and calculation using the concept of an equivalent crater. The volume of scabbing has also reduced due to introduction of prestress in the concrete. The penetration depth and perforation limit in the non-perforated reinforced concrete plates were calculated using the ACE expression. The ACE expression was also modified for obtaining the penetration depth in the non-perforated reinforced–prestressed concrete plates and a close correlation between the calculation and the measurement was noticed. The prestressing force is seen to have enhanced the penetration resistance of concrete. The ballistic limit of the reinforced–prestressed concrete plate was 6.6, 8.9 and 22.7% higher than the second configuration reinforced, first configuration reinforced and plain concrete plate, respectively.

Improving the dependability of light vented foundations exposed to vibration load on frost soils

Aim. Today, dynamically-loaded foundations of process equipment often prove to be oversized with significantly overestimated values of stiffness, mass and material consumption. Therefore, reducing the costs and time of construction of gas pipeline facilities, especially on permafrost, is of relevance to PJSC Gazprom. One of the primary ways of solving this problem is installing gas pumping equipment on light vented support structures. The disadvantage of such structures is the low vibration rigidity. A method [1] is proposed for improving the vibration rigidity of a foundation subjected to vibration load. The simulation aims to improve the dependability of light vented foundations by studying vibration displacements of foundations with attached reinforced concrete panels depending on the thermal state of frost soils, parameters of the attached panels and connectors. Methods. Vibration displacements of a foundation with an attached device were identified using the finite element method and the improved computational model of the foundation – GCU – soil system. Results. Computational experiments identified the vibration displacements of the foundation in the cold and warm seasons for the following cases of reinforced concrete plates attached to the foundation: symmetrical and non-symmetrical; at different distances; through connectors with different stiffness parameters; with additional weights; frozen to the ground. Conclusions were made based on the results of simulation of vibration displacements of foundations with an attached device in cold and warm seasons. Conclusion. The presented results of computational experiments aimed at improving the vibration rigidity of light foundations by using method [1] show sufficiently good indicators of reduced vibration displacements of the foundation. Thus, in the case of symmetrical connection of four reinforced concrete panels in summer, the reduction of vibration displacements is 42.4%, while increased stiffness of the connectors, attachment of additional weights and freezing of reinforced concrete panels into the ground will allow reducing the vibration displacements of the foundation up to 2.5 times. However, it should be noted, that applying the findings in the process of development of project documentation and construction of foundations requires R&D activities involving verification and comparison of the obtained results of numerical simulation with a natural experiment.

STRUCTURAL FEATURES OF THE ASSEMBLIES OF THE JOINING OF TRAM RAILS TO ROAD COVERAGE

In the modern world, the priority is the development of clean urban electric transport. The constructive solutions used in the construction of the tram wheel in the past years are outdated and do not meet modern requirements. One of these problems is the destruction of asphalt coating in the places of road coverage to tram rails, which worsens the operational characteristics of tram crossings. The reasons for this problem can be attributed to the following: Not enough asphalt concrete near the rails; low adhesion of asphalt and metal from which rails are made; dynamic loads and vibrations arising from trams and motor transport; bad base of tram train and others. One of the options for increasing reliability and durability is to use as a road covering of tram plates. This solution is used in Ukraine and the European Union. German company RailBeton developed solutions for railway crossings - BetoCross. This system is a modular construction of reinforced concrete slabs, which are pulled together by steel strips. With the help of a system of fastenings and bearings, the flooring is fastened to rails, which provides vertical and horizontal stability of their position and stabilization under the influence of loading. To reduce the dynamic influence, the plates are based on reinforced concrete sleepers through the intermediate layers of the elastostomer. The load from the automobile transport is transferred to the broken beam. In addition to the positive features, the BetoCross system, due to the large number of connections, ties and bearings, requires frequent maintenance and maintenance. The Ukrainian state enterprise "Starokostiantyniv plant ZBSH" developed a similar technology, reinforced concrete plates with the help of a screw fastening through rubber gasket fixed to a special bridge type wallpaper. At a step of wallpaper 0,6 m the plate is attached to each wallpaper from two sides, with the length of the plate itself is 2,7 m. that is, on one plate there are five points of fastening on each side. Loads from the automobile transport, similar to the German technology, are transferred to the rubble balast and the basis. These technological solutions have found their application on railway crossings, and need some improvement for use in urban electric transport. The article reviews the constructive decision on the organization of the mentioned site, which is proposed by RS ENGINEERING in Kharkov. In the proposed solution instead of the crushed balast used monolithic reinforced concrete slab with supporting elements. The arising loads from the rolling stock and transport are transferred through the supporting elements to the concrete slab, which redistributes them on the rubble basis. As a road cover are used reinforced concrete plates covering RS-Slab. The plates are divided into 3 types: Road, interroad and external, which in turn have several sizes. The plates are bound to the supporting elements by means of screws in four points. To reduce dynamic influence between the film and the reference element, a rubber elastomer is laid. Depending on the size of the plates have different number of cutting sites. Also because of the design features possible option when the slab simultaneously relies not on all the supporting sites, these options should be taken into account when calculating the scale and choosing a class of concrete. This solution allows to solve the problems of road surface destruction on the side of the rails, keeps more load from transport, compared to asphalt. At the same time, there are factors that need to be studied in detail when designing and before implementing the solution in mass production. These include: Investigation of the influence of violation of standard assembly plates on the stress-deformed state of the element; determination of thickness and acceptable physical characteristics of the gasket on the plate supports; detailed development of a node for fixing plates. The use of reinforced concrete plates as a road coating has a number of advantages before asphalt concrete: Resistance to destruction on the rails; installation regardless of weather and temperature conditions; resistance to loads from trucks. At the same time, this decision has certain peculiarities that require detailed study, which is a branch of further research.

Mechanical and Structural Characteristics of PET Fiber Reinforced Concrete Plates

ABSTRACT The growth of plastic generation has increased exponentially with time, in particular the polyethylene terephthalate (PET) that is widely used in the human consumer industry. The objective of this study is focused on sustainability principles by minimizing the environmental pollution through reusing the plastic bottles by cutting them into small fibers to reinforce the concrete matrix to boost the performance of reinforced concrete plates. To investigate the effect of the PET fiber content on the behavior of the two-way reinforced concrete plates, four two-way reinforced concrete plates. PET fiber percentages were (0.5, 1, 1.5, 2) %, with one reference plate without fiber tested up to failure under monotonic load. All concrete plates are simply supported and tested at age 28 days and with dimensions of (800 × 800 × 50) mm. The ultimate load, load-deflection relationships, and cracking patterns of all plates are reported. The findings reveal that employing PET fibers for strengthening could boost the ultimate strength and flexural stiffness of the plates considerably. Besides, the mechanical test results reveal a decrease in compression strength with increasing PET fiber content. On the contrary, the splitting tensile strength exhibited a clear improvement with the increase in PET.

Combination of the finite element method and particle-based methods for predicting the failure of reinforced concrete structures under extreme water forces

We present a combination of the Finite Element Method (FEM), the Particle Finite Element Method (PFEM), and the Discrete Element Method (DEM) for modeling and analyzing the failure of reinforced concrete structures under impulsive wave forces originating from free-surface flows in critical water hazards. The free-surface water flow is modeled with the PFEM, while the structural behavior and the fractures induced by the water forces in the structure are modeled with a coupled FEM–DEM technique. The concrete material behavior is simulated with a standard isotropic damage model. The reinforcing bars are modeled by a rule of mixtures procedure, for simplicity. The possibilities of the new integrated PDFEM approach for predicting the evolution of free-surface tsunami-type waves and their devastating effect on constructions are validated with experiments on the failure of reinforced concrete plates under large impacting waves, performed in a laboratory facility in Japan.

Experimental Study of the Effect of Cavities on the Load Capacity of Two-Way Reinforced Concrete Plates on Fixed Concrete Thickness

The study aims to determine the effect of cavities on the load capacity of reinforced concrete slabs when compared to massive reinforced concrete slabs that have the same thickness, with the hope of reducing the structure’s weight and the use of concrete materials. The modified PVC pipes, as cavity formers, will be placed in the tensile area without reducing the flexural strength that is caused by the weak nature of concrete against tensile strength. The test is carried out on a full scale against 14 cm thick solid plates (PP-1), and hollow plates, which use modified PVC pipes (PB-2), with a cavity diameter of 7.6 cm that has the same thickness. The test uses joint supports on all four sides and the loading pattern is evenly distributed. All slabs are made, on the spot, of cast concrete with the same size and distance between the reinforcement. PVC hollow plate (PB-2) has the same effective thickness as solid plate but has 14% less concrete volume. The maximum load capacity on the solid plate (PP-1) is 522.66 kN and on the hollow plate (PB-2) is 444.33 kN. The melting capacity on the solid plate (PP-1) is 373,515 kN and on the hollow plate (PB-2) is 325,935 kN. Initial crack load capacity on the solid plate (PP-1) is 19.5 kN and on the hollow plate (PB-2) is 16.75 kN

Torsional behavior of reinforced concrete plates under pure torsion

The present study investigated experimentally and numerically the behavior of reinforced concrete plates subjected to pure torsion. The main parameters examined were: steel reinforcement ratio or spacing and plate width. A pure torsion test was carried out on nine reinforced concrete plate with different dimensions and reinforcement. A 3D numerical analysis by the finite element method and a torsion theories were adopted for all specimens tested. The finite element results overestimate the cracking torque, accurate of ultimate torque. Skew-bending theory calculate the cracking torque more accurate compared to FE and other theories. Moreover, ACI318-14 building code is unconservative for cracking torque, conservative of ultimate torque.