Reinforced Concrete Plates Research Articles

An experimental investigation on the effect of steel reinforcement on impact response of reinforced concrete plates

An experimental investigation has been conducted to collect fundamental data and to develop more understanding of the effect of steel reinforcement distribution on the dynamic response of reinforced concrete plates. Five high strength concrete (HSC) plates are tested using free-fall low-velocity impact technique. A total of 10 impact tests are conducted, including two tests on each specimen. The impact loads are applied at the mid-point of the HSC plates by dropping a 475 kg steel weight from a constant height of 4.15 m. Two parameters are investigated namely: the main bottom steel reinforcement ratio (1.0, 2.0, and 3.0%); and the steel reinforcement arrangement (single or doubly reinforced plates). The top reinforcement of all doubly reinforced plates is kept constant as shrinkage reinforcement of 10 mm diameter spaced at 210 mm. The experimental results are evaluated focusing on the impact force characteristics and the impact behaviors of reinforced concrete plates. The test program was successful in providing a simple method for validating impact test setup using impulse–momentum theorem. Results showed that the change of reinforcement ratio and/or reinforcement arrangement has no significant effect on impulse and absorbed energy values for same impact loading condition. Additionally crack pattern and failure mode are found to be more dependent on the reinforcement arrangement rather than reinforcement ratio.

Dissipative Homogenised Reinforced Concrete (DHRC) constitutive model dedicated to reinforced concrete plates under seismic loading

A new stress resultant nonlinear dissipative constitutive model for reinforced concrete (RC) plates under cyclic solicitations is presented. This constitutive model, named DHRC for Dissipative Homogenised Reinforced Concrete, is expressed within the usual thin plate kinematics framework. It is built by a periodic homogenisation approach using the averaging method and it couples concrete damage and periodic debonding between steel rebar and surrounding concrete. The generality of the proposed method leads to a generic closed-form for the Helmholtz strain energy density function and the two dissipation pseudo-potentials that can be adapted to any material with an internal structure similar to the RC structural element one. A restricted number of geometric and material characteristics are needed from which the whole set of model parameters are identified through an automatic numeric procedure performed on a Representative Volume Elements (RVEs) of the RC plate. Finally, comparisons of finite element simulations with experimental results concerning the seismic behaviour of reinforced concrete wall made structures are proposed and discussed.

Experimental analysis and modeling of two-way reinforced concrete slabs over different kinds of yielding supports under short-term dynamic loading

This paper presents the experimental and theoretical results of an investigation carried on reinforced concrete plates placed on yielding supports along their perimeter under short-term dynamic loading. The yielding supports are made of elements with annular cross-section. Their functionality allows operations in elastic and elasto-plastic stages with a further turning to hardening stage. This particular support scheme has been adopted in order to simulate the different boundary conditions that r.c. slabs subjected to impacts may encounter in practical applications of civil engineering (e.g. roofs, vertical panels, retaining walls, guardrails, etc.). The experimental results showed that influence of support deformability on the structural response under impact depends on their rigidity and on the deformation stage. The results of numerical simulations based on a simple mechanical model qualitatively agree with the experimental results. Therefore the model can be adopted for simulation and design of reinforced concrete panels under impact or high-strain loading situations.

Analysis on formulas of concrete plate under contact explosion

Based on many test data of concrete plates of several thicknesses, this paper presents some new simple engineering formulas for computing critical thickness of scabbing and perforation, the front explosion diameter and the rear scabbing diameter of reinforced concrete plates under contact explosion. For the damage problem of a 20 cm thick concrete target under contact explosion of 1.25 kg TNT charge, the paper gives the numerical simulation results of LS-DYNA software for comparison. The damage zone of concrete plate in numerical simulation is determined by analysis of tension pressure resulted from shock wave reflection on the free boundary. And the numerical simulation results are in basic agreement on the results of these engineering formulas.

Short-time numerical analysis of steel–concrete composite beams

The objective of this work is to provide a reliable numerical model using the finite element method for the analysis of steel–concrete composite beams for short-time loads. For this purpose, a computer program was developed in this study. The reinforced concrete (RC) slab is modeled using degenerated curved shell elements based on Mindlin theory, while plane shell elements based on Kirchhoff theory were used for modeling the steel beam. Stud shear connectors were modeled using 3D beam elements with special characteristics to take into account partial interaction at the slab–beam interface. Within the theory of plasticity, properly yield functions were considered for the concrete slab and the steel beam. A nonlinear elastic law proved to be adequate for treating the tangential forces in the stud shear connectors. Finally, some typical numerical examples of steel shells, RC plates and steel–concrete composite beams found in the literature are reproduced with the present numerical model and the obtained results are compared with the experimental data. The present numerical model is able to reproduce the path failure, collapse loads and failure mechanism with an acceptable level of accuracy.

Experimental evaluation of the efficiency of trenches for the mitigation of train-induced vibrations

In this work, the efficiency of absorbing barriers for the mitigation of ground vibrations induced by railway traffic has been evaluated by means of two different experimental campaigns conducted in situ, along the newly-built, high-speed railway line that connects the Italian cities of Milan and Bologna. In the first stage of testing, a series of ideal barriers created from unsupported empty trenches were tested to assess the effects of barrier depth on their efficiency in reducing vertical ground accelerations. The second stage of testing was performed to investigate the efficiency of a full-scale prototype barrier, made of a 2-meter-deep trench supported by two precast reinforced concrete plates connected by steel bars, during transit of an ETR 500 train at a speed of 120km/h.

Uncertainties Concerning the Free Vibration of Inhomogeneous Orthotropic Reinforced Concrete Plates

Abstract Analyzing nearly collapsed and broken structures gives good insights into possible architectural and engineering design mistakes and faults in the detailing and mismanagement of a construction by building contractors. Harmful vibration effects of construction operations occur frequently. The background reviews have demonstrated that the problem of the vibration serviceability of long-span concrete floors in buildings is complex and interdisciplinary in nature. In public buildings, floor vibration control is required in order to meet Serviceability Limit States that ensure the comfort of the users of a building. In industrial buildings, machines are often placed on floors. Machines generate vibrations of various frequencies, which are transferred to supporting constructions. Precision machines require a stable floor with defined and known dynamic characteristics. In recent years there has been increasing interest in the motion of elastic bodies whose material properties (density, elastic moduli, etc.) are not constant, but vary with their position, perhaps in a random manner. Concrete is a non-homogeneous and anisotropic material. Modeling the mechanical behavior of reinforced concrete (RC) is still one of the most difficult challenges in the field of structural engineering. One of several methods for determining the dynamic modulus of the elasticity of engineering materials is the vibration frequency procedure. In this method, the required variables except for the modulus of elasticity are accurately and certainly determined. In this research, the uncertainly analysis of the free vibration of inhomogeneous orthotropic reinforced concrete plates has been investigated. Due to the numerous outputs obtained, the software package has been written in Matlab, and an analysis of the data and drawing related charts has been done.

Analysis of reinforced concrete plates subjected to impact employing the truss‐like discrete element method

ABSTRACTThe prediction of the response of reinforced concrete structures subjected to projectiles impact still presents open questions. These include the rate dependence of material properties, the interaction between concrete and steel reinforcement and the simulation of fracture and fragmentation. Because the appearance of discontinuities in the target structure is difficult to account using a continuum approach, the application of discrete models was developed as an appealing alternative. A version of the discrete model in which nodal masses are linked by an array of uniaxial elements, herein called discrete element method, is used in this study. This method was implemented in the system Abaqus to take advantage of its numerical and post‐processing capabilities. A reinforced concrete rectangular plate subjected to impact of a projectile is examined in detail. Comparisons between experimental and numerical results are shown with the aim of validating the proposed method.

Failure Behavior and Numerical Simulation of the Local Damage of Ultra High Strength Fiber Reinforced Concrete Subjected to High Velocity Impact

This study presents the local damage of ultra high strength fiber reinforced concrete plates. Impact test of the reinforced concrete plates using two different short fibers are conducted to examine the failure behavior and impact resistant performance. Material models are discussed and proposed by simulating the high speed tri-compressive and uni-tensile tests. Numerical simulations of the impact tests are carried out. Numerical results show good agreements with the test results.

Limits to the strength design of reinforced concrete shells and slabs

One of the most important works in the ultimate limit state design of reinforced concrete plates or shells subjected to flexure and membrane actions is the one provided by Brondum-Nielsen (1974). Therein, the author divides the shell element into three layers; the outer layers withstand a state of membrane forces located on their middle surfaces. The forces at the centroid of the reinforcement, in both directions, have been obtained from equilibrium, and the steel area needed is computed by dividing these tension forces by the steel yield stress, fy. An extension to the strain plane hypothesis widely used in the strength design of RC beams and columns is presented, aiming at RC strength design of shells and slabs. As a result, limits to the application of the Bromdum-Nielsen procedure are given in this work since it cannot always be guaranteed that the stress in the steel is fy as the original method proposes. A new method based on the computation of the balance point in the beam flexure design is developed to check the limits of application of Brondum-Nielsen’s approach. The Upper Bound Theorem of plasticity guaranties that the obtained forces are on the safe side. Examples are provided.

Study on Thermal Conductivity of Reinforced Concrete Plate

By the heat flow meter method, the thermal conductivity of reinforced concrete was experimental studied for the energy conservation design of reinforced concrete composite wall as building envelop. The steel bars were arranged as horizontal one-way, horizontal two-way and vertical in the reinforced concrete plates with different reinforcement volume ratio. Based on the test results, the effects of arrangement of steel bar and reinforcement volume ratio on thermal conductivity of reinforced concrete were analyzed. It can be concluded that the thermal conductivity of reinforced concrete was higher than that of concrete and increased with the reinforcement volume fraction, the steel bars in horizontal two-way arrangement brought the reinforced concrete with greater thermal conductivity than that in one-way arrangement, the vertical steel bar made the reinforced concrete with significantly higher thermal conductivity. The series-parallel model and parallel-series model are proposed for predicating the thermal conductivity of reinforced concrete with horizontal steel bars.

Homogenised constitutive model coupling damage and debonding for reinforced concrete structures under cyclic solicitations

A new stress resultant constitutive model for reinforced concrete plates under cyclic solicitations is presented. This model is built by the periodic homogenisation approach using the averaging method and couples damage of concrete and periodic debonding between concrete and steel rebar. In one-dimensional situations, we derive a closed-form solution of the local problem useful to verify and set up the plate problem. The one dimensional macroscopic constitutive model involves a limited number of parameters, the sensibility of which is studied. Comparison to experimental results underlines the pertinence of the model by considering internal debonding in order to properly represent the mechanical dissipation occurring during cyclic loadings on reinforced concrete panels.

Numerical analysis of square reinforced concrete plates strengthened by fiber-reinforced plastics with various patterns

Abaqus finite element program is employed to analyze the ultimate load capacities of square reinforced concrete plates strengthened by fiber-reinforced plastics. Appropriate constitutive models are introduced and validated to stimulate nonlinear material behavior of reinforced concrete and fiber-reinforced plastics. The influences of FRP reinforcement, steel reinforcement, and concrete properties on the ultimate strengths of the reinforced concrete plates are investigated. Finally, based on the numerical results, empirical equations are proposed to predict increment of ultimate load capacities of the square reinforced concrete plates strengthened by fiber-reinforced plastics, which would be useful for practical engineering applications.

Minimum shear reinforcement for thick plates and two-way slabs

Thick reinforced concrete plates of over 250mm thickness usually exhibit brittle shear failure under concentrated loads. Potential punching failures in the vicinity of concentrated loads have already been taken into consideration by conventional design methods. The current research is a continuation to previous work published by the authors on minimum flexural reinforcement for thick plates. The main focus of this research is to design adequate shear reinforcement for thick concrete plates. In this paper, new models are developed to calculate minimum shear reinforcements for thick plates, concrete plates and two-way slabs. Design guidelines as well as a design example for minimum shear reinforcement that the design engineers can follow are given. A comparison between the proposed formulae with experimental tests carried by different researchers is conducted. A comprehensive review of different design codes formulae is discussed and compared with the proposed formulae. The proposed formulae are simple and account for member size effect through fracture mechanics concepts. For all equations, (MPa) is used for stresses and (mm) for lengths unless otherwise noted.

Estimate of Cracking and Bond Splitting Stresses of Reinforced Concrete Plates under Uniaxial and Biaxial Tension

Estimate of Cracking and Bond Splitting Stresses of Reinforced Concrete Plates under Uniaxial and Biaxial Tension

Crack width model for thick reinforced concrete plates subjected to in-plane forces

An extensive experimental program is conducted in the present study to investigate the cracking behavior of two normal strength concrete plates and thirteen high strength concrete plates. The results raise questions about the applicability of the present code approaches to predict the crack width of thick concrete plates used for offshore structures and containment structures for nuclear power plants. The main objective is to provide a simple equation for crack width prediction of a concrete plate to ensure the control of crack openings in designing thick high strength reinforced concrete structures. The model predictions are compared with the results of the tests of reinforced concrete panels subjected to in-plane tension forces along with the code approaches for predicting the crack width.

Nonlinear finite element analysis of reinforced concrete plates modeled by layered composites

In this study, finite elements method (FEM) was used for the nonlinear analysis of reinforced concrete (R/C) plates under incremental loading up to failure load. Layered composite material model (LCMM) was used for the modeling of reinforced concrete plates. This approach differs from the other approaches since it considers the effect of tensile stiffness of concrete between cracks and uses a criterion based on the fracture energy concept considering the effect of finite element mesh size. Load-displacement relationships were determined according to the ‘layered composite material approach’. The results of the analyses were compared and found to be in agreement with the experimental results and the results of past studies. A computer program prepared with Fortran PowerStation 4.0 programming language was used in this study. Key words: Non-linear plate analysis, finite elements method, layered composite materials.

SDOF Models for RC and FRC Circular Plates under Blast Loads

This work presents simplified models, in the form of single degree of freedom (SDOF)elasto-plastic systems, for the dynamic analysis of traditional reinforced concrete (RC) and fibre-reinforced concrete (FRC) circular plates under blast loads. Two cases have been examined inthis study: simply supported and resting on Winkler-type soil plates. Both cases intend toprovide a simplified tool for predicting the response respectively for specimens subjected toblast pressure wave inside shock-tube facilities and for slabs on ground under blast loads. Thesecond case also represents the loading conditions inside a new shock tube facility specificallyintended for the investigation of underground tunnel lining subjected to blast loads.

Prediction of time-dependent structural behaviour with recurrent neural networks for fuzzy data

In the paper, an approach is described which permits the numerical, model-free prediction of uncertain time-dependent structural responses. Uncertain time-dependent structural actions and responses are modelled by means of fuzzy processes. The prediction approach is based on recurrent neural networks for fuzzy data trained by time-dependent results of measurements or numerical analyses. An efficient solution for network training and prediction is developed utilizing α-cuts and fuzzy arithmetic. The approach is verified using a fractional rheological model. The capability of the approach is demonstrated by predicting the long-term structural behaviour of reinforced concrete plates strengthened by textile reinforced concrete layers.

DEFORMATION MEASUREMENT OF A STRUCTURE WITH CALCULATION OF INTERMEDIATE LOAD PHASES

At the Centre for Geodesy of the University of Maribor, Slovenia, we engaged in the measurement and analysis of displacements for the last ten years. We wanted to find the connections between the displacements and the applied loads. Therefore, reliable and accurate results were needed. A reinforced-concrete plate was loaded to 42 kN in pre-calculated steps and the resulting deformations measured by three independent methods. The results were compared to analytical ones. The analyses and calculations of the most suitable method were implemented. An electronic tacheometer, photogrammetry and a pressure length transducer on the hydraulic cylinder were used.