11 research outputs found
Optimum design for sustainable 'green' bonded concrete overlays:failure due to sheer and delamination
Evaluation of equivalent delamination driving coefficient in bonded concrete overlays
This study investigates failure due to interfacial delamination in a bonded concrete overlay system comprising Polymer Modifies Roller Compacted Concrete (PMRCC) overlay and substrate Ordinary Portland Concrete (OPC). Optimum overlay mix was designed using Composite Desirability Analysis (CDA). Intrinsic complex stresses along the plane of the interface resulting from differential length change and elastic mismatched properties between the two bonded layers were investigated. Distinct delamination cases involving variable structural scales were investigated using both laboratory determined fracture parameters and ANSYS zero-thickness Interface Cohesive Zone Model (ICZM) concept. The FEA results showed that the restraint capacity of the interface varies as a function of overlay structural scale and its associated mismatched elastic parameters
Numerical investigation of tension reinforcement lap length of eurocode 2 using a four-point beam loading system
© 2019 Latin American Journal of Solids and Structures. All rights reserved. This report presents a computational research on Eurocode 2 (EC2) tension lap lengths (lo) design in a normally reinforced concrete beam, using ANSYS Workbench simulation software program by simulating a laboratory 4-point beam loading test system under static loading(discrete model approach). A typical 4-point laboratory setup loading system was modelled using an innovative and sustainable Finite Element Analysis (FEA) approach. In order to investigate the EC2 tension lap lengths (lo) design recommendation, a total of 100 analysis cases of lap lengths were considered for different reinforcement bar diameters of 10mm, 12mm, 16mm, 20mm and 25mm. The study has considered beam failure types, effects of failure load on the various lap length reduction cases and effects of steel reinforcement bar size changes on the design lap lengths. The analysis of results revealed that the yield strength of steel (fyk), diameter of tension reinforcement bar, (db), tensile strength of concrete (fctd) and concrete cover (cd) are the main parameters for a tension lap length design according to EC2. While a linear relationship exists between tension steel reinforcement bar sizes (db) and the obtained lap lengths (lo). The study reveals a potential use of 15% and 20% reduction in lap length (lo) for tension steel reinforcement bar sizes of 10mm, 16mm and 12mm and 20mm in comparison with the recommended design lap length of EC2. It was concluded that EC2 tension lap length design recommendation is conservative
Structural performance of a modified shear-head assembly for edge steel column embedded in reinforced concrete slab
© 2018 by the authors; licensee Growing Science, Canada. This paper presents a study on the structural performance of a modified shear-head assembly for edge steel column embedded in reinforced concrete slab. The structural performance was investigated in terms of punching shear capacity of the reinforced concrete flat slab. The study consisted of a laboratory punching shear test on the contra-flexure bound slab of dimension 1060mm × 1250mm by 130mm thick in a reactant test frame using a 500kN load cell. Results of the experimental study was validated using finite element based numerical method. Both experimental and numerical results show that increase in tensile strength of concrete, increases punching shear capacity of the connection. It was also observed that punching shear failure of the connection depended largely on concrete shear strength. This study has also revealed that punching shear occurs when concrete shear strength is reached, irrespective of the robustness of the shearhead connection
Investigation of intrinsic de-bonding in bonded concrete overlays: Material characterisation and numerical study
© 2018 Growing Science Ltd. All rights reserved. This study investigates the evolution of intrinsic interfacial de-bonding of Roller Compacted Steel Fibre Reinforced Polymer Modified Concrete (RC-SFR-PMC) bonded on substrate Ordinary Portland Cement Concrete (OPCC), using both experimental and numerical techniques. The relative effects of evolving material inhomogeneity and composite dimensional stability during curing was studied as a function of overlay structural scale, using a 2D plane strain Interface Cohesive Zone Model (ICZM). The effects of creep coefficient on interface restraint capacity and ensuing cohesive zone length were clearly evaluated. The results showed that the applied curvature due to the measured shrinkage strain was inadequate to cause critical de-bonding. In the FEA results, while the rate of interface energy release generally varies as a function of the bi-material relative stiffness and overlay structural scale, it is also evident that the two variables lose effects as the overlay structural scale approaches 0.50. The overall indicative trend shows that the rate of energy release in compliant overlay when relative stiffness (α0. Therefore, a more compliant overlay typically exhibits less relative restraint to bending induced de-bonding
Potential and current distribution across different layers of reinforcement in reinforced concrete cathodic protection system- A numerical study
Applied mixture optimization techniques for paste design of bonded roller-compacted fibre reinforced polymer modified concrete (BRCFRPMC) overlays
Effect of overlap distance and chord angle on performance of overlapping soil-cement columns
The stress distribution in deep mixing improved columns is affected by cement content and in-situ soil properties of the surrounding soil. Group of cement improved soil column can be overlapped to form a shear wall which can support side slopes of embankments to enhance stability of the supported structure. The overlap distance of these columns is one factor that influences the efficacy of the columns and their overall effect on performance of the supported structure. This paper presents a numerical investigation on the effect of overlap distance and chord angle of overlap on the performance of soil-cement columns. The analysis of results show that the total stress on the columns decreases initially from 89.9kPa to 83.1kPa at 0 and 0.16m overlap distance due to development of discontinuities and stress concentration at corners of overlapping columns. The total stress on the column also increases between 0.16 and 0.32m overlaps corresponding to e/d ratio of 0.2 to 0.4m. This implies that values between 0.2-0.4 can be adopted for ratio of overlap distance and column diameter in design of overlapping column
Strength and Hydraulic Conductivity of Cement and By -Product Cementitious Materials Improved Soil
This paper presents an experimental investigation on strength and hydraulic conductivity of a fine grained soil mixed with cement, Pulverised Fly Ash and Ground Granulated Blast Slag. Strength and permeability are important properties that defines the engineering behaviour of deep mixing improved soils. Cement contents of 4%, 8%, 12% and 16% by weight of dry soil were added using wet soil mixing technique. The percentages of cement were reduced and replaced with PFA, GGBS and Bentonite at 33.3% and 50% reductions respectively. Unconfined compressive strength (UCS) and permeability tests were conducted on cement, PFA/GGBS and Cement/Bentonite mixtures prepared at their respective optimum moisture content (OMC) and maximum dry density (MDD) and cured for different periods. The results show that an increase in % of additives causes decrease in porosity and increase in density of cement and cement/PFA stabilised soil and hence, increase in UCS. Except at some optimum values of 12% and 16% of additives in C+PFA combinations where the density of the improved soil decreases at fairly constant porosity resulting to an increase in UCS. This implies that % of additive and the type of additive controls the UCS of improved soils more than the influence of porosity and density on UCS. Decrease in porosity of samples improved using C+PFA+GGBS and C+B with increase in % of additives, resulted to increase in UCS but however, the reduction in density and increase in UCS also shows dominance of % and type of additive on strength over porosity and density. Cement-Bentonite and combination of PFA /GGBS with reduced amount of cement were observed to better improved permeability of the soil. This study has also defined the functional relationships between hydraulic conductivity and additive type based on the investigated % of additives and combinations