Jacketing Technique Research Articles

Flowable nano SiO2 based cementitious mortar for ferrocement jacketed column

Abstract Retrofitting of structures has become an inevitable in the construction activity. It is necessary to improve the load carrying capacity of the damaged structural members and it could be achieved by strengthening externally, through a jacketing technique. Ferrocement Jacketing is preferred as one of the acceptable and viable way for strengthening of structural members. A laboratory experimental investigation was carried out to develop a rich and flowable nano silica based cementitious matrices which could be employed for repair and retrofit the structures. An investigation on nano based cement composite was conducted to obtain the strength and durability properties. Results indicated that the flowable nano silica cementitious mortar showed a significant increase in compressive strength in the range of 7.5–50% than that of the control cement mortar. The splitting tensile strength of cementitious matrices increased from 2.28 to 3.98 MPa. Nano silica with 3% showed a lowest rate of water absorption as compared to all other mortar specimens. From the obtained results, it is revealed that 3% of nano silica could be used as a flowable nano SiO2 based mortar, as it showed a better performance both in strength and durability aspects. Ferrocement jacketed columns has a higher load carrying capacity of about 40% with a higher axial displacement of 95% as compared to the control column. A ductile mode of failure was observed in all the ferrocement jacketed columns.

Condition Assessment and Structural Audit Before and After Repair of Fire Damaged Structure and Ansys Simulation of Column Jacketing

This study give details about the rehab process of fire damaged reinforced concrete buildings in basically three categories; condition evaluation, decision making, rehabilitation & retrofitting. Evaluation process of damaged building is based on understanding of condition survey and condition assessment of fire damaged structure. Condition survey includes detailed visual inspection of building whereas condition assessment includes non-destructive testing of building (such as Rebound Hammer test, Ultrasonic Pulse Velocity test, Carbonation test, pH test, Half Cell Potential test etc.). Based on survey and assessment, various repair and retrofitting schemes have been suggested. RC members often need strengthening to raise their capacity to sustain the applied load. This research investigates the behavior of RC columns strengthened using RC jacket technique. A finite element model was stimulated in ANSYS WORKBENCH to study the performance of these columns with and without jacketing, which has been designed for static loading. Based on ansys simulation and Comparison of test result before and after jacketing, it can be said that structure is safe in static loading condition

Repair of Heavily Damaged RC Beams Failing in Shear Using U-Shaped Mortar Jackets

The effectiveness of slightly reinforced thin U-shaped cementitious mortar jacketing for the repair of damaged shear-critical reinforced concrete beams is experimentally investigated. The test project includes two parts. In the first one, five concrete beams over-reinforced against flexure and under-reinforced against shear with different ratio of closed stirrups were initially subjected to monotonic loading until failure. The initially tested beams have been designed to fail in shear after wide diagonal cracking and to exhibit various strength and deformation capacities along with different levels of damages. In the second experimental part, the heavily damaged beams were jacketed with mild steel small diameter U-shaped transverse stirrups and longitudinal reinforcing bars. The retrofitted specimens using the proposed jacketing technique were tested again following the same four-point-bending load scheme. Based on the overall performance of the beams, it is deduced that the shear strength and deformation capability of the jacketed beams were substantially increased compared to the corresponding capacities of the initial beams. Further, although all beams failed in a shear abrupt manner, the retrofitted ones exhibited reduced brittleness and higher deflections at failure up to six times with respect to the initially tested specimens. The level of the initial damage influences the efficiency of the jacketing. Additional test data derived from relative shear-damaged beam specimens and retrofitted with similar thin jackets is also presented herein in order to establish the effectiveness of this repair system and to clarify the parameters affecting its structural reliability. Comparisons indicated that jacketed beams can alter the failure mode from brittle shear to ductile flexural under certain circumstances.

Full-metal jacket technique using second-generation drug-eluting stent: clinical and angiographic follow-up in 2 years.

The aims of this study are to evaluate the efficacy of percutaneous coronary intervention (PCI) using full-metal jacket (FMJ) with second-generation drug-eluting stents (DES). A single-center, non-randomized, retrospective study was performed from May 2005 to February 2014 at Miyazaki Medical Association Hospital, Japan. PCI using FMJ with DES was performed to treat 240 very long lesions (> 60mm) in 240 patients. Subjects were divided into a first-generation or second-generation DES group. The primary endpoint was the incidence of major adverse cardiac events (MACE) at 2years. MACE included all-cause death, myocardial infarction (MI), cerebrovascular event, and target vessel revascularization. The secondary endpoint was binary restenosis (> 50% stenosis) assessed by angiography at 1year of follow-up. Second-generation DES were implanted to treat 121 lesions, and the first-generation DES were implanted to treat 119 lesions. Since 35 patients were lost to follow-up, the final analysis included 102 patients with second-generation DES and 103 with first-generation DES. At the 2-year follow-up, the incidence of MACE was significantly less in the second-generation DES group (9.8% vs. 20.4%, p = 0.03). The incidence of binary restenosis at 1year was also significantly lower in the second-generation DES group (6.7% vs 29.1%, p < 0.01). When PCI was performed using FMJ with DES to treat very long lesion, the angiographic and clinical outcomes were better with second-generation than first-generation DES.

Seismic vulnerability and retrofitting scheme for low-to-medium rise reinforced concrete buildings in Nepal

In this paper, seismic capacity assessment is presented for representative low-to-medium rise reinforced concrete (RC) buildings in Nepal. The structural behavior of buildings was studied with different analysis techniques and loading considerations. The non-linear behaviors of nine residential building structures were studied with finite element analysis. Structural performance is presented in terms of strength, stiffness, capacity curves, and inter-story drifts. The building models were analyzed as bare frames, and the drift profiles were compared with some standard drift limits to depict the vulnerability. Buildings noted as vulnerable after the analyses were modified as retrofitted using column jacketing technique, and finite element analyses were carried out again. Comparisons were made in terms of seismic performance of as-built and retrofitted buildings. The sum of observations depicts that column size directly affects the vulnerability of buildings. Moreover, column jacketing significantly ameliorates the seismic performance of low-to-medium rise RC buildings as depicted by the comparison between as-built and retrofitted structures in terms of inter-story drift and fundamental period.

Axial Behaviour of Glass Fibre Reinforced Polymer-Confined Reinforced Concrete Short Columns

Fibre-reinforced polymer (FRP) jacketing is an effective confinement tool for reinforced concrete (RC) columns. To avoid the excessive stress concentration in square-shaped columns, a jacketing technique with rounded column edges needs to be practiced. The load-carrying capacity of RC square short columns wrapped with glass FRP (GFRP) on axial loading was investigated. The effi­ciency of confinement offered by improved jacketing schemes with different corner radii of the column, number of layers of FRP and various vertical distri­bution methods of jacketing are compared. The experimental study was con­ducted on 31 columns of size 140 mm x 140 mm x 1200 mm with one, two and three layers of FRP distributed over one-fourth, one-third and full length of the column. The corner radii of the columns were 0,12.5, 25 and 37.5 mm. Spe­cimens were loaded to the failure modes in concentric uniaxial compression, and the behaviour of the specimens was analysed. An analytical model for the ultimate load-carrying capacity of RC square columns confined by GFRP is proposed from the test results.

Axial Behaviour of Slender RC Circular Columns Strengthened with Circular CFST Jackets

This paper investigates the axial behavior of slender reinforced concrete (RC) columns strengthened with concrete filled steel tube (CFST) jacketing technique. It is realized by pouring self‐compacting concrete (SCC) into the gap between inner original slender RC columns and outer steel tubes. Nine specimens were prepared and tested to failure under axial compression: a control specimen without strengthening and eight specimens with heights ranging between 1240 and 2140 mm strengthened with CFST jacketing. Experimental variables included four different length‐to‐diameter (L/D) ratios, three different diameter‐to‐thickness (D/t) ratios, and three different SCC strengths. The experimental results showed that the outer steel tube provided confinement to the SCC and original slender RC columns and thus effectively improved the behavior of slender RC columns. The failure mode of slender RC columns was changed from brittle failure (concrete peel‐off) into ductile failure (global bending) after strengthening. And, the load‐bearing capacity, material utilization, and ductility of slender RC columns were significantly enhanced. The strengthening effect of CFST jacketing decreased with the increase of L/D ratio and D/t ratio but showed little variation with higher SCC strength. An existing expression of load‐bearing capacity for traditional CFST columns was extended to propose a formula for the load‐bearing capacity of CFST jacketed columns, and the predictions showed good agreement with the experimental results.

Strengthening of RCC Beams in Shear by Using SBR Polymer‐Modified Ferrocement Jacketing Technique

There is a common phenomenon of shear failure in RCC beams, especially in old buildings and bridges. Any possible strengthening of such beams is needed to be explored that could strengthen and make them fit for serviceable conditions. The present research has been made to determine the performance of predamaged beams strengthened with three‐layered wire mesh polymer‐modified ferrocement (PMF) with 15% styrene‐butadiene‐rubber latex (SBR) polymer. Forty‐eight shear‐designed and shear‐deficient real‐size beams were used in this experimental work. Ultimate shear load‐carrying capacity of control beams was found at two different shear‐span (a/d) ratios 1 and 3. The sets of remaining beams were loaded with different predetermined damage levels of 45%, 75%, and 95% of the ultimate load values and then strengthened with 20 mm thick PMF. The strengthened beams were then again tested for ultimate load‐carrying capacity by conducting the shear load test at a/d = 1 and 3. As a result, the PMF‐strengthened beams showed restoration and enhancement of ultimate shear load‐carrying capacity by 5.90% to 12.03%. The ductility of strengthened beams was improved, and hence, the corresponding deflections were prolonged. On the other hand, the cracking pattern of PMF‐strengthened beams was also improved remarkably.

Experimental evaluation of energy dissipation and viscous damping of repaired and strengthened RC columns with CFRP jacketing under biaxial load

Abstract The seismic repair and retrofitting of reinforced concrete (RC) columns have been the focus of innumerous studies and from the literature it can be concluded that the biaxial horizontal loading can reduce considerably the strength capacity, ductility and energy dissipation of the columns when compared with the corresponding response to uniaxial loading tests. However, reduced information regarding the influence of the retrofit strategies in the energy dissipation capacity and the viscous damping of the columns were obtained. Thus the main goal of the present work is to evaluate the efficiency of the Carbon Fiber Reinforced Polymer (CFRP) jacketing technique to improve the behaviour of three damaged columns subjected to repair procedures and four “as built” columns behaviour and evaluate their influence in the energy dissipation capacity and viscous damping of the columns when compared with the original response. From the test results a good efficiency of the CFRP jacketing improved about 20% the original energy dissipation capacity. Regarding the viscous damping it was obtained about 10% lower values for the repaired columns and to 20% higher values for the strengthened ones.

Numerical Study on the Local Buckling Behaviour of Bolted Steel Plates in Steel Jacketing

A numerical simulation was conducted to investigate the local buckling behaviour of the bolted steel plates in steel jacketing technique. The numerical model was firstly validated by the results of a previous experimental study. Then a parametric study was conducted to investigate the influence of different restraint measures on the local buckling behaviour and the sensitivity of the buckling behaviour to the initial imperfection. Fitted formulae were developed to calculate the structural field capacity of the bolted steel plates, and recommended values of stiffener size were also provided to facilitate the strengthening design of steel jacketing.

Numerical cyclic behaviour of un-corroded and corroded RC columns reinforced with HPFRC jacket

The possibility of using high performance fiber reinforced concrete (HPFRC) jacketing for strengthening and repairing sound or corroded column, was experimentally investigated by some of the authors in previous studies. Once assessed the feasibility and the effectiveness of this technique, in the present paper, a numerical three-dimensional model is developed, with the FEM software Diana, in order to simulate the cyclic behaviour of RC columns reinforced with the HPFRC jacket. All phenomena governing the structural response are suitably simulated, and the effect of the external jacket on the local and global behaviour is highlighted and discussed. Finally, two case studies available in literature, related to both cases of sound and corroded existing columns, are analysed in order to clarify and validate the procedure and to suggest some improvements of the HPFRC jacket technique.

Steel Jacketing Technique used in Strengthening Reinforced Concrete Rectangular Columns under Eccentricity for Practical Design Applications

Steel Jacketing Technique used in Strengthening Reinforced Concrete Rectangular Columns under Eccentricity for Practical Design Applications

Numerical modelling of RC strengthened columns under biaxial loading

During an earthquake, the reinforced concrete (RC) structures are subjected to deformations that may lead their structural elements to exceed the corresponding resistance limit state, forcing them to have nonlinear responses. The application of realistic numerical models that can represent the non-linearity of each structural element requires full examination and calibration. Furthermore, simplified numerical approaches that can represent the seismic behaviour of original and strengthened RC elements are of full importance. For this, the experimental tests are useful to calibrate the numerical models, and thus to capture as well as possible the real response of the elements. The main goal of this work is to evaluate the efficiency of a simplified numerical approach to represent strengthened RC columns with steel and CFRP jacketing, subjected to biaxial horizontal loading. The numerical modelling efficiency will be evaluated by comparing the numerical results with the experimental ones in terms of shear-drift hysteretic behaviour, initial stiffness and stiffness degradation, maximum strength and energy dissipation. The results shows a good performance of the numerical models, mainly for the RC columns strengthened with CFRP jacketing technique.

Innovative ECC jacketing for retrofitting shear-deficient RC members

Engineered Cementitious Composite (ECC) is distinguished from conventional fiber reinforced concrete by its ductile tensile strain-hardening behavior and crack width control ability. This study investigates the performance of ECC jacketing for retrofitting shear-deficient reinforced concrete (RC) members. Six RC cantilever structural beams are prepared, and five of them are retrofitted with jackets. The experimental parameters involve the properties of the jacket, i.e., (1) ECC or mortar as the matrix, (2) presence or absence of steel meshes, and (3) welded wire or bar meshes. The performance of the various schemes of ECC jacketing is evaluated using the test results of the cantilever beams under cyclic loading. In particular, this study explores whether the appealing properties of ECC shown on the material scale can translate into better performance of the ECC jacket on the structural scale. Multiple performance measures of the beams are employed, including damage patterns, hysteretic loops, energy dissipation capacities, rebar strain profiles, shear distortions, and failure modes. The test results show that the ECC jacket without steel meshes is able to improve the cyclic behavior of the original shear-deficient beam considerably. The behavior of the retrofitted beam at the performance level of the ultimate limit state can be further enhanced by reinforcing the ECC jacket with steel meshes. In addition, the multiple performance measures suggest that the ECC jacket with a single layer of bar meshes be the best retrofitting scheme. Based on the test results, both the advantages and disadvantages of the ECC jacketing technique are reported.

Influence of the cross section shape on the behaviour of SRG-confined prismatic concrete specimens

The effectiveness of the steel-reinforced grout (SRG) jacketing technique in increasing both strength and deformation capacity has been substantiated by experimental evidence (Thermou and Pantazopoulou in Fib Struct Concr J 8: 35–46, 2007; Thermou et al. in ECCOMAS Thematic Conference, 2013; Thermou et al. in Mater Struct J, 2013). What it has not been addressed yet is the influence of the cross section shape on the behaviour of SRG-confined prismatic unreinforced concrete specimens. An experimental study was carried out where 18 concrete small scale specimens were tested to failure under concentric uniaxial compression load. A single layer of the steel-reinforced fabric was applied to circular, square and square specimens with rounded edges. Test results demonstrated that both strength and deformation capacity increased as the shape of the cross section changed from square to circular. In case of the square specimens, the gain in compressive strength was satisfying, whereas the ductility increase was more significant compared to that of the square specimens with rounded edges. An analytical expression for the lateral confining pressure exerted by the composite system was derived based on the assumption that the steel cords were treated as well-anchored steel stirrups placed at a distance equal to the spacing between the steel cords. The ability of the various steel and fiber-reinforced polymer confinement models from literature to predict the normalized compressive strength of non-circular specimens confined with SRG jackets was also explored.

Behavior of reinforced concrete columns strengthened by steel jacket

RC columns often need strengthening to increase their capacity to sustain the applied load. This research investigates the behavior of RC columns strengthened using steel jacket technique. Three variables were considered; shape of main strengthening system (using angles, C-sections and plates), size and number of batten plates. Behavior and failure load of the strengthened columns were experimentally investigated on seven specimens divided into two un-strengthened specimen and five strengthened ones. A finite element model was developed to study the behavior of these columns. The model was verified and tuned using the experimental results. The research demonstrated that the different strengthening schemes have a major impact on the column capacity. The size of the batten plates had significant effect on the failure load for specimens strengthened with angles, whereas the number of batten plates was more effective for specimens strengthened with C-channels. Then, by using finite element (F.E) package ANSYS 12.0 [1] their behavior was investigated, analyzed and verified. Test result showed a good match between both experimental tests and F.E models.

Experimental Study of Eccentrically Loaded Columns Strengthened Using a Steel Jacketing Technique

Experimental Study of Eccentrically Loaded Columns Strengthened Using a Steel Jacketing Technique

Ferrocement Jacketing for Restrengthening of Square Reinforced Concrete Column under Concentric Compressive Load

Abstract This study focuses on the improvement of square jacketing technique in effective restrengthening of existing RC building column. Square jacketing technique can’t effectively provide lateral confinement due to stress concentration and subsequent cracking at the corners. In order to overcome this problem, two different approaches are taken into account; i.e. (a) strengthen all the corners, and (b) reducing stress concentrations at corners. Three types of square jacketing techniques under these two approaches are considered in this study. Test results and crack pattern shows that, both approaches are effective to overcome the stress concentration problem of square jacketing. However, the first approach is practically more suitable than the second one.

Application of a Reinforced Self-Compacting Concrete Jacket in Damaged Reinforced Concrete Beams under Monotonic and Repeated Loading

This paper presents the findings of an experimental study on the application of a reinforced self-compacting concrete jacketing technique in damaged reinforced concrete beams. Test results of 12 specimens subjected to monotonic loading up to failure or under repeated loading steps prior to total failure are included. First, 6 beams were designed to be shear dominated, constructed by commonly used concrete, were initially tested, damaged, and failed in a brittle manner. Afterwards, the shear-damaged beams were retrofitted using a self-compacting concrete U-formed jacket that consisted of small diameter steel bars and U-formed stirrups in order to increase their shear resistance and potentially to alter their initially observed shear response to a more ductile one. The jacketed beams were retested under the same loading. Test results indicated that the application of reinforced self-compacting concrete jacketing in damaged reinforced concrete beams is a promising rehabilitation technique. All the jacketed beams showed enhanced overall structural response and 35% to 50% increased load bearing capacities. The ultimate shear load of the jacketed beams varied from 39.7 to 42.0 kN, whereas the capacity of the original beams was approximately 30% lower. Further, all the retrofitted specimens exhibited typical flexural response with high values of deflection ductility.

Rehabilitation of Shear-Damaged Reinforced Concrete Beams Using Self-Compacting Concrete Jacketing

The application of a reinforced self-compacting concrete jacket for the structural rehabilitation of shear damaged reinforced concrete beams is experimentally investigated. Five beams were constructed and subjected to monotonic loading in order to exhibit shear failure. The damaged specimens were restored using relatively thin reinforced jackets and retested by the same four-point bending loading. The self-compacting concrete jacket applied, encasing the bottom width and both vertical sides of the initially tested beams (U-formed jacketing), has a small thickness (25 mm) and includes small (5) steel bars and U-formed stirrups. Test results and comparisons between the experimental behaviour of the beams indicated that the examined jacketing technique is a reliable rehabilitation method since the capacity of the retrofitted beams was fully restored or ameliorated with respect to the initial specimens. Discussion of the ability of the applied jacket to enhance the overall structural performance of the examined beams and, potentially, to alter their failure mode to a more ductile one is also included. Calculations of the flexural and shear strength of the tested beams and evaluation of the monolithic factors for the capacity at yield and at ultimate of the jacketed beams were also performed and are commented on.