Reinforced Concrete Panels Research Articles

Development of CSMM-based shell element for reinforced concrete structures

Reinforced concrete shell structures have been widely used in a variety of modern engineering applications. It is found from earthquake reconnaissance that reinforced concrete (RC) shell structures, such as nuclear containments, cooling towers, roof domes, shear walls, etc., are the key elements in resisting earthquake disturbances. This paper presents the development of a finite element analysis (FEA) program, SCS-3D, to predict the inelastic behavior of RC shell structures. In the program, a Cyclic Softened Membrane Model (CSMM)-based shell element is developed based on the degenerated shell theory with a layered approach and taking into account the CSMM developed at the University of Houston. To form the FEA program, the constitutive relation modules and the analysis procedure were implemented into a finite element program development framework, OpenSees developed at UC Berkeley. Several large-scale structural tests were employed to validate the developed FEA program, including RC panels subjected to a combination of shear and bending, three-dimensional RC shear wall and cylindrical RC tanks subjected to reversed cyclic loading.

Behavior of Reinforced Concrete Panels Strengthened with Carbon Fiber-Reinforced Polymers

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Comparative assessment of impact resistance of SC and RC panels using finite element analysis

In this paper, the impact resistance of steel-plate concrete (SC) and reinforced concrete (RC) panels is evaluated using the commercial software LS-DYNA. The structural components and their contacts are fully modeled in the analysis, and the material nonlinearity and strain rate effect for concrete and steel are considered. The analysis results of SC and half steel-plate concrete (HSC) panels under impact loading are compared with the test results conducted in previous research in order to determine the main factors influencing the analysis. The impact analyses as per four different concrete thicknesses with five different steel ratios are performed in order to compare the impact resistance of the SC and RC panels. Failure mode, damage size, and displacement of the SC and RC panels are investigated. The results show that the SC panel has better impact resistance than the RC panel. Finally, the impact analyses for optimal panel design are performed, and the optimal concrete thickness and steel ratio are recommended.

Influence of Fiber-Reinforced Polymer Sheets on the Constitutive Relationships of Reinforced Concrete Elements

Fiber-reinforced polymer (FRP) started to find its way as an economical alternative material in civil engineering in the early 1970s. The behavior and failure modes for FRP composite structures were studied through extensive experimental and analytical investigations. Although research related to the flexural behavior of FRP-strengthened elements has reached a mature phase, studies related to FRP shear strengthening are less advanced. In all proposed models to predict shear capacity, the constitutive behaviors of concrete and FRP are described independently. The true behavior, however, should account for the high level of interaction between the two materials. Constitutive relations for FRP-strengthened reinforced concrete (RC) elements should provide a better understanding of the shear behavior of the composite structure. To generate these relations, large-scale tests of a series of FRP-strengthened RC panel elements subjected to pure shear were conducted. This paper presents the results of the test program and the calibration of the parameters of the constitutive model. These constitutive laws could easily be implemented in finite-element models to predict the behavior of externally bonded FRP-strengthened beams. The focus in this work is on elements failing because of concrete crushing and not because of FRP debonding. The newly developed model provides a good level of accuracy when compared with experimental results.

Impact of composite materials on performance of reinforced concrete panels

The use of composite materials to strengthen reinforced concrete (RC) structures against blast terror has great interests from engineering experts in structural retrofitting. The composite materials used in this study are rigid polyurethane foam (RPF) and aluminum foam (ALF). The aim of this study is to use the RPF and the ALF to strengthen the RC panels under blast load. The RC panel is considered to study the RPF and the ALF as structural retrofitting. Field blast test is conducted. The finite element analysis (FEA) is also used to model the RC panel under shock wave. The RC panel performance is studied based on detonating different TNT explosive charges. There is a good agreement between the results obtained by both the field blast test and the proposed numerical model. The composite materials improve the RC panel performance under the blast wave propagation.

Reinforced concrete and fiber reinforced concrete panels subjected to blast detonations and post-blast static tests

Results of an experimental study of reinforced concrete panels under blast detonations are presented. The primary purpose of the tests was to collect data for validating simulation methods for blast loads. The scaled distance ranged from 0.41m/(kg)1/3 to 0.57m/(kg)1/3 and hence the tests are close-in detonations. Four types of 1.2m square panels were subjected to blast to investigate the performance of new walls: reinforced concrete (RC) panels; fiber reinforced concrete (FRC) panels without additional reinforcement; FRC panels reinforced with steel bars; and RC panels reinforced with glass fiber reinforced polymer (GFRP) bars. Another RC panel type was built which was retrofitted with external GFRP laminates on both faces. The performance of the panels is classified into three categories as medium protection, very low protection, and protection below antiterrorism standards. FRC panels reinforced with steel bars had the best performance for new construction. Panels that survived the blast detonation without sustaining a breach were tested under monotonic static loads to determine their static post-blast load resistance.

Corrosion in Reinforced Concrete Panels: Wireless Monitoring and Wavelet-Based Analysis

To realize the efficient data capture and accurate analysis of pitting corrosion of the reinforced concrete (RC) structures, we first design and implement a wireless sensor and network (WSN) to monitor the pitting corrosion of RC panels, and then, we propose a wavelet-based algorithm to analyze the corrosion state with the corrosion data collected by the wireless platform. We design a novel pitting corrosion-detecting mote and a communication protocol such that the monitoring platform can sample the electrochemical emission signals of corrosion process with a configured period, and send these signals to a central computer for the analysis. The proposed algorithm, based on the wavelet domain analysis, returns the energy distribution of the electrochemical emission data, from which close observation and understanding can be further achieved. We also conducted test-bed experiments based on RC panels. The results verify the feasibility and efficiency of the proposed WSN system and algorithms.

Crack propagation analysis of reinforced concrete wall under cyclic loading using RBSM

This paper presents the numerical simulations of the reinforced concrete (RC) panels and the RC shear walls under monotonic and cyclic loading in order to validate the ability of the proposed model which is based on the Rigid-Body-Spring Model (RBSM) to predict the crack propagation behaviours. The authors have already developed constitutive models for the three-dimensional RBSM with random geometry in order to quantitatively evaluate the mechanical responses including softening and localization fractures, and have shown that the model can well simulate the cracking and failure behaviours of RC members. In this study, the constitutive models were extended to include cyclic effects and the model was validated through the simulations of the RC panel tests under cyclic loadings, which were reported in the literatures. Furthermore, the simulations of the RC shear wall tests, which were tested in the context of the international benchmark ConCrack (http://www.concrack.org/) were carried out, and the capability of the model to predict the detailed cracking information, such as crack width, spacing and direction of propagation is discussed.

Performance of Simplified Damage Assessment Tools for Reinforced Concrete Panels under Blast Loading

Pressure-impulse (P-I) and charge weight-distance (CW-D) diagrams are widely used as quick damage assessment tools for reinforced concrete (RC) elements exposed to blast loading. Depending on the loading and element properties, the blast loading can induce different patterns of response and damage. Appropriate application of different simplified damage assessment tools for both far-field and near-field blast effects can be significantly challenging. This paper presents the comparison of the performances of two commonly used simplified damage assessment methods for RC elements exposed to explosive loading. Different aspects of the simplified damage assessment methods related to their construction and application for damage assessment are investigated. Some specific limitations of construction and use of P-I and CW-D diagrams are explored. Suitability of P-I diagrams for far-field and near-field blast effects is also explored. P-I diagrams are found to provide misleading damage assessment when applied for near-field blast effects.

Design methodologies for one way spanning eccentrically loaded minimally or centrally reinforced pre-cast RC panels

This paper examines and evaluates design methodologies applicable to pre-cast reinforced concrete (RC) panels subjected to eccentric axial load. Theoretical capacities derived from existing regulatory guidance are compared against those determined from experimental investigations, showing that slender RC walls have load capacities significantly higher than the estimates based on current design equations.A simple computational procedure incorporating lumped plasticity is presented and experimentally validated. It is shown that by utilising a non-linear hinge at the critical cross section, it is possible to effectively simulate the buckling response of the slender walls considered with a modest computational effort. The proposed design strategy emerges as a viable alternative to traditional methodologies by being able to capture the main effects of geometrical and material nonlinearities. It is therefore suggested that this approach, used in conjunction with a probabilistic, semi-empirical design procedure, will lead to design capacities more representative of actual experimental findings.

Nuclear radiation effect on the behavior of reinforced concrete elements

This paper investigates the effects of radiation on structural strength of reinforced concrete (RC) 2-D panels, which represent typical elements of nuclear power plants (NPPs) structures. Reduction in concrete compressive and tensile strength due to radiation exposure was determined based on extensive literature review. Material properties, geometry, and load cases are selected based on structural characteristics of the components in the existing nuclear power plants. A nonlinear analysis program, Membrane-2000, based on the Modified Compression Field Theory (MCFT) is used to compute the response of RC elements, which include ultimate strength capacity, and ductility index. The results show that ultimate shear capacity of highly reinforced elements subjected to combinations of shear and tension loading are reduced significantly in the highest radiation exposure category. The RC panels under shear-biaxial and uniaxial compression show significant reduction in strength in high and moderate radiation levels. Failure modes of the elements change from yielding of steel to shear failure with increasing radiation exposure. Also, ductility of the RC panels is reduced when they are exposed to the high levels of radiation.

An Experimental Study on Reinforced Concrete Infilled Frames with Openings

In the last decade, seven major earthquakes caused significant casualties and extensive structural failures. Thousands of RC buildings were severely damaged or collapsed in Turkey due to various deficiencies. This has initiated experimental studies on strengthening methods and intensive researches regarding the rehabilitation of reinforced concrete structures by introducing reinforced concrete infill walls were carried out. Strengthening of reinforced concrete frames by cast-in-place reinforced concrete infills is commonly used in practice. Many structures were also repaired using this technique after the recent earthquakes. In this experimental research, six, one-bay/two-story, 1/3-scaled non-ductile, undamaged reinforced concrete (RC) frames were constructed and tested to investigate the behavior of frames strengthened by introducing infills with or without openings. The test specimens were subjected to reversed cyclic quasi-static lateral loading. The specimens were constructed with the most commonly observed deficiencies in residential RC buildings in Turkey. The first specimen was the reference bare specimen and contained no strengthening. The other specimens were infilled with RC panels with openings having different ratios and configurations. Strength, stiffness and storey drifts of the test specimens were measured and compared. Test results indicated that infilled RC frames displayed significantly higher lateral strength and stiffness than the non-ductile bare frame considerably.

Numerical Simulation of Masonry Walls Retrofitted by Prefabricated Reinforced Concrete Panels

Assembly technology using prefabricated reinforced concrete (RC) members can effectively improve the seismic performance of existing masonry buildings. In this study, an existing masonry wall is enhanced by two pieces of prefabricated RC panels bonded on both surfaces of the wall. In order to guarantee the co-action between RC panels and the masonry wall, three techniques are employed, specifically, RC dowelling keys, grouting agent, and post-cast concrete bands. To investigate the interaction and force transmission between the two components, this study builds sophisticated finite element models and conducts nonlinear analyses to simulate the quasi-static cyclic tests. It is demonstrated that the proposed retrofitting technology effectively improves the seismic performance of existing masonry walls. The strength of existing walls increases 3-4 times and the stiffness increases 2-3 times, so that the requirement of current seismic design code is satisfied.

Effect of Reinforcement Ratio and Distribution on Penetration Resistance of Reinforced Concrete Panels: Numerical Simulation

Reinforced concrete protective layers of fortified structures are considered key points in resisting missiles penetration. Ferrocement is a highly versatile form of concrete reinforced with wire mesh reinforced in two directions. This type of reinforcement provides isotropic properties in two directions, high tensile strength, and high modulus of rupture. It also results in larger bond forces and reduces crack spacing and width compared to conventional reinforced concrete. Accordingly, concrete panels (550 x 550 x 300 mm) are reinforced with expanded steel mesh instead of the conventional steel bars and tested through numerical simulation to study the parameters affecting penetration resistance. A Nonlinearthree-dimensional hydrocode numerical simulation was carried out using AUTODYN 3D, which is an extensive code dealing with penetration problems. In the simulation, steel ogivenose projectile with a diameter of 23 mm is fired against concrete panels with striking velocity 990 m/s. Twelve numerical tests were carried out to study the parameters that significantly affect the penetration resistance of reinforced concrete panels. The parameters included are the reinforcement ratio; reinforcement position; and reinforcement distribution. The results showed that using the ferrocement wired mesh decreases the size of damage in the front and rear face of the panels. Increasing the reinforcement ratio has insignificant impact on the penetration resistance while the position and the distribution pattern of reinforcement proved to relatively enhance the penetration resistance.

Influence of Test Machine Control Method on Apparent Performance of ASTM C1550 Fiber Reinforced Concrete Panels

Abstract The ASTM C1550 round panel test is used to assess the post-crack performance of fiber reinforced concrete (FRC) and fiber reinforced shotcrete (FRS) and has become firmly established as the most repeatable means of post-crack performance assessment available for these materials. When the test method was first published, two methods of test machine control were permitted: displacement control, in which the displacement of the loading actuator is used as the control parameter in the test, and strain control, in which the central deflection of the specimen is used as the controlling parameter. Both these methods of control, however, require expensive testing machines, with the result that some operators have used cheaper open-loop machines to test ASTM C1550 round panels. Doubts have arisen among specifiers of FRC and FRS in tunneling and mining projects as to whether specimens tested using open-loop machines result in the same apparent performance as would be expected using displacement- or strain-controlled testing machines. This investigation has established that under certain circumstances, an open-loop testing machine can produce results for ASTM C1550 panels that are similar to results obtained using a strain- or displacement-controlled testing machine. It was also found that the measurement of specimen deflection on the underside of the panel is problematic at large deformations and can lead to substantial variations in apparent performance.

Crack Spacing and Width of Thick High Strength Reinforced Concrete Panels

Experimental program involved testing of eighteen panels to study the cracking behavior of thick high strength concrete panels subjected to in-plane tensile forces, was conducted. The influence of different parameters such as concrete strength fc′, reinforcement ratio ρeff, concrete cover to bar diameter ratio ( Cc/ db), and applying axial or biaxial loading, was critically examined. Model equations developed for predicting crack spacing and width of thick concrete plates were discussed. Using high strength concrete reduced the average crack width measured at every steel stress level. The bar spacing and the concrete cover showed a significant influence on the crack spacing and consequently on the measured crack width. Panels tested under biaxial loading triggered higher crack spacing and crack width compared with the corresponding panels subjected to axial loading. Design equations for predicting the crack spacing and width of thick concrete members are presented parallel with the available code provisions.

Behavior of Reinforced Concrete Membrane Elements Subjected to Bidirectional Shear Loads

The shear design and behavior of a typical membrane reinforced concrete (RC) element has been extensively studied in the past several decades. Such design requires knowledge of the constitutive behavior of RC elements subjected to a shear stress acting along its plane (in-plane shear). These constitutive models were accurately derived from experimental test data on representative RC panel elements. The true behavior of many large, complex structures, however, involves interaction between the in-plane and out-of-plane shear stresses acting on the RC element. To investigate this interaction, large-scale tests on representative concrete panels need to be conducted. The University of Houston is equipped with a unique universal panel testing machine that was used for this purpose. The panel tester enhanced the understanding of the in-plane shear behavior of RC elements. Recently, 10 additional hydraulic jacks were mounted in the out-of-plane direction of the universal panel tester to facilitate testing of concrete elements subjected to bidirectional and tridirectional shear stresses. The experimental program included designing, fabricating, instrumenting, and testing full-scale RC elements. The elements were subjected to different combinations of in-plane and out-of-plane shear loads. A strong interaction between in-plane shear strength and out-of-plane shear stresses was observed.

Qualitative and Quantitative Sensors Based on Electrochemical Techniques for the Corrosion Assessment of RC Panels

Corrosion assessment of the steel bar in reinforced concrete (RC) structures is a very urgent for the structural health monitoring and life-cycle design in civil engineering. Half-cell potential map and guard ring techniques are applied as typical qualitative and quantitative methods to assess the corrosion status, respectively. A RC panel has been formed to be an actual testbed to verify the effectiveness of these techniques. Its potential map and corrosion rate have been investigated by the electrochemical sensors before and after NaCl solution injected, respectively. The results indicate the corrosion status of RC panels can be identified effectively.

Structural behavior of RC membranes having inclined steel bars

In seismic design, special care is needed when the shear force governs the response of a reinforced concrete (RC) element because this element undergoes stiffness degradation, strength deterioration and reduction in the energy dissipation capacity, as the cyclic loading increases beyond the yielding level. Experimental and analytical research has shown that this undesirable response can be controlled and even eliminated in the hysteretic load–deformation curves of a shear-dominant element if the steel orientation within the element is aligned in the direction of the applied principal stresses. However, in practice, it is quite difficult to orient the steel bars parallel to the principal stress directions due to geometric and construction limitations. In this study, the effectiveness of the steel reinforcement orientation on the structural response of RC shear membrane elements was investigated by analyzing the test results of four panels previously reported in the technical literature. The test results were also analyzed by using a compatibility-aided truss model. The experimental and analytical results indicated that the ductility and energy dissipation capacity of RC panels strongly depended on the reinforcement orientation. The results also showed that the hysteretic response of an RC panel did not vary linearly with the steel grid’s orientation within the panel and there was a boundary where the deformability and energy dissipation of the RC panel increased rapidly.

Using Ferrocement to Resist Penetration of Hyper-Velocity Objects

Protective layers of fortified structures are considered key points in resisting missiles. Most of these protective layers are made from plain concrete. Due to the progressive development of military destructive weapons such as hyper-velocity missiles, plain concrete protective layers are not sufficient to resist the effect of hyper-velocity objects. So it is essential to have a new generation of protective layers to able to resist this kind of weapons. The objective of this paper is to enhance the protective layer material through designing a special concrete mixture with high reliability to resist the penetration of hyper-velocity object. Ferrocement technique is used to enhance the concrete panels’ penetration resistance. A parametric study is performed on the effect of changing number of the steel wire mesh layers inside the concrete panels on its penetration resistance. The study in this paper is based on the finite element model verification conducted by M.E. Mohamed et al. using AUTODYN-3D on “Numerical Simulation of Projectile Penetration in Reinforced Concrete Panels” [1].Also, plain concrete and ferrocement panels’ penetration resistance was studied under the effect of hypervelocity objects. This Hyper-velocity projectile was presented in experimental work conducted by Dawson [2]. The main findings of this paper were that there is an enhancement in the penetration resistance for ferrocement panels rather than plain concreteonce. Also increasing of steel layers mesh number have slight influence on the penetration resistance of the ferrocement panels.