Steel Jacket Research Articles

Axial compressive behavior of predamaged RC columns retrofitted with precast steel-reinforced grout jackets

Steel jacketing and concrete jacketing are popular retrofitting techniques to strengthen the axial compressive behavior of reinforced concrete (RC) columns. However, these retrofitting methods lack efficiency in practical application due to intensive labor and time-consuming installation. In order to improve the retrofit efficiency of damaged RC columns, this study proposed a novel precast steel-reinforced grout jacket (PSRGJ) consisting of early-strength cementitious grout and a steel frame. Ten columns were tested to investigate the axial compressive behavior of predamaged RC columns retrofitted with PSRGJ. The tested parameters were the stirrup reinforcement ratio, the transverse reinforcement ratio of PSRGJ, and the predamage level. The results indicated that the columns’ peak load and ductility index I10 were significantly improved by PSRGJ retrofitting and increased with the increase of transverse reinforcement ratio of PSRGJ. Besides, the peak load and the initial stiffness of PSRGJ-retrofitted RC columns decreased with the predamage level, while the ductility index I10 increased. In addition to the confinement effect, PSRGJ carried 11%−17% of the peak load through the interfacial bonding effect. Based on the test results, the actual confinement pressure model and interfacial bonding strength model were proposed. Further, peak load models considering the size effect were developed for PSRGJ-retrofitted intact and predamaged RC columns. The predictions of the proposed models agreed well with the test results from this study and the literature.

Numerical Analysis of Reinforced Concrete Columns Strengthened With Steel Jacket

Numerical Analysis of Reinforced Concrete Columns Strengthened With Steel Jacket

Numerical Study of Strengthened Spun Pile with Concrete Infill and Steel Jacket

The confinements in a spun pile in Indonesia are below the minimum requirement mentioned in ASCE 7-16. Since Indonesia still adopts the linear elastic concept for foundation design, where the pile should be designed strongly without damage, the deficiency does not matter. However, enormous piles are required to keep it elastically under severe earthquakes. Hence, a transition to performance-based design (PBD) should be prepared since the seismic acceleration tends to increase. PBD requires sufficient transverse reinforcement to ensure flexural failure. Steel jacket is proposed to overcome the lack of confinements, particularly on the pile cap connection where the largest curvature occurs. Experimental and numerical studies have been conducted on a full-scale spun pile-to-pile cap connection with a steel jacket under cyclic loading. A monotonic pushover analysis with Opensees Navigator open-source software was performed for further study.

Effects of UHPFRC jacketing and axial loading on the blast behaviour of reinforced concrete beams and columns

The objective of this study was to characterize the effects of axial loading and UHPFRC (ultra-high performance fiber-reinforced concrete) jacketing on the blast performance of reinforced concrete beams and columns. The test group included two as-built and strengthened columns with UHPFRC jacketing applied over the full span (FJ). The companion group included three as-built and UHPFRC-strengthened beams, with jacketing applied either over the full span (FJ) or in the middle hinge region (FJ-Mid). With the exception of axial load, the specimens in both groups had the same dimensions, reinforcement properties and boundary conditions. In both groups, the UHPFRC jacketing improved control of blast-induced displacements and damage when compared to the as-built specimens. Under equivalent blasts, axial loading was also confirmed to reduce the magnitude of the displacements in both the as-built and retrofit specimens. In addition, applying UHPFRC jacketing increased the blast capacity of the columns, but ultimately led to rupture of the tension steel bars. As part of the numerical study, finite element (FE) modelling was used to predict the blast behaviour of the test specimens, and to study the effects of parameters not considered in the experiments, including the effects of axial load ratio, boundary conditions, longitudinal steel ratio and jacket design on blast performance and failure mode.

The Steel Jacket: Antecedents of Trauma A Pilot Nurse-Led Study to Examine Trauma Patients Existential Experience and the Impact of Empathic Nursing Care

This nurse-led, institutional review board-approved pilot study describes basic nursing research from the phenomenon of interest through institutional review board submission and approval process, study protocol development, study execution, and reporting both qualitative and quantitative finding. This study is underpinned with a novel nursing theory, The Steel Jacket: Antecedents of Trauma, inspired by the work of physicist David Bohm and nursing theorist Martha Rogers. The study involved 2 distinct sets of subject: nurses and trauma patients. Nurses were recruited to participate in a prestudy and poststudy of The Steel Jacket Theory. Trauma patients were interviewed to understand their lived experience of the meaning of trauma 1 year after the event. One hundred acute care nurses in a level 1 trauma center were emailed a survey about their level of empathic care and existential nursing approaches toward trauma patients. The intervention included a short module on The Steel Jacket Theory and an accompanying original 6-minute video. Simple statistics were used to tabulate findings. The second set of subjects were trauma patients who were consented and participated in 30-minute interviews. Spielberg's Phenomenological framework was used to describe themes from trauma patient's lived experiences: feeling lost, engaging in self-blame, internally fighting vulnerability and fear, marshalling inner resources to survive, and knowing that a moment in time changed their life forever. Trauma patients can benefit from Trauma Survivorship clinics and nurses need protected time to appreciate and cultivate the space to listen for what is said, perceive what is not said, and co-create a path of healing.

Effect of Steel Jacketing Thickness on Seismic Performance of Bridge

The bridges of Nepal are getting older and old bridges were designed without considering the seismic forces, hence have low seismic capacity. The capacity of these bridges needs to be enhanced and should perform well during seismic events. The jacketing technique can be used to upgrade the bridge's structural performance. This research paper mostly focuses on the seismic performance enhancement after the application of steel jacketing on the bridge pier. The variable that has been varied is the thickness of the steel jacket. The capacity of a bridge pier is evaluated using displacement-controlled nonlinear static analysis (Pushover). The time history load is applied to the structure to determine the seismic demand of the bridge. The quantification of the enhancement of the bridge structure after the application of Steel Jacketing is evaluated by plotting the fragility curve. The modeling of the bridge is done in CSI Bridge V20.2.0. The different damage state is defined using the strain values obtained from the pushover analysis. For different damage states, the capacity and demand value are used to obtain the probability of exceeding at different PGA levels. The fragility curve is developed using the First Order Second Order Method (FOSM). From the study, it is found, that the vulnerability of the bridge after the use of jacketing for extensive damage state, the probability of failure reduced from 28.22% to 14.24% at 1.0g PGA. Similarly, the vulnerability of the bridge after the use of jacketing for collapse damage state, the probability of failure decreased from 16.93% to 7.22% at 1.0 PGA

Experimental Study of Reinforced Concrete T-Beam Retrofitted with Ultra-High-Performance Concrete under Cyclic and Ultimate Flexural Loading.

Structurally deficient bridges are commonly retrofitted using conventional methodologies, including reinforced concrete, steel jackets, and fiber-reinforced polymers. Although these retrofit methods aim to improve structural performance, exposure to aggressive environments may undermine the durability performance of the retrofit material. More recently, ultra-high-performance concrete (UHPC) has provided an alternative to conventional construction methods, with its superior material characteristics favoring its use in retrofit applications. In this study, a large-scale reinforced concrete (RC) T-beam is constructed and artificially damaged. The T-beam is then retrofitted with an external envelope of UHPC on all faces. Sandblasting is introduced to the surface, providing partially exposed reinforcement in the T-beam to simulate material deterioration. Additional reinforcement is placed in the web and flange, followed by casting the enveloping layer of UHPC around the specimen. The feasibility of this method is discussed, and the structural performance of the beam is assessed by subjecting the beam to cyclic and ultimate flexural loading. This paper presents the results of cyclic and ultimate testing on the RC-UHPC composite T-beam regarding load-displacement, failure mode, and strain responses. The retrofitted T-beam specimen is subjected to a cyclic loading range of 131 kN for 1.576 million cycles. Despite no visible cracks in the cyclic testing, the specimen experiences a 12.22% degradation in stiffness. During the ultimate flexural testing, the specimen shows no relative slip between the two concretes, and the typical flexural failure mode is observed. By increasing the longitudinal reinforcement ratio in the web, the failure mode can shift from localized cracking, predominantly observed in the UHPC shell, toward a more distributed cracking pattern along the length of the beam, which is similar to conventional reinforced concrete beams.

Hybrid strengthening scheme for reinforced concrete beams: Flexural behaviour and large-scale testing

Revision of design standards, new regulations, and planned/unplanned increases in loadings potentially make buildings vulnerable to changes in capacity demands. This may result in some structural components of an existing structure requiring strength or stiffness improvement. Strengthening of capacity deficit members is widely recognised as the preferred and sustainable choice in terms of conserving resources and minimising the carbon footprint. Strengthening techniques such as Reinforced Concrete (RC) jacketing, steel jacketing and Fibre Reinforced Polymer (FRP) wrapping have been explored and widely used. However, when adopted solely, each scheme has its drawbacks. RC jacketing results in a considerable rise in the dead load, influencing the loading on the foundation and restricting the functional space available post-jacketing. Steel jacketing often lacks flexibility as a significant effort is required for installation. FRP improves the flexural strength response but produces low stiffness enhancement and lesser ductility. A hybrid strengthening option, i.e. a combination of the above strengthening methods, presents a viable option to address the limitations cost-effectively. This paper presents a pioneering attempt focused on improving the flexural performance of RC beams using a hybrid strengthening scheme comprising of RC jacketing and FRP. Four large-scale RC beams were prepared, and three of them were strengthened. The first was strengthened by RC jacketing, the second by a combination of RC jacketing and flexural FRP, and the last by the combination of RC jacketing, flexural FRP and FRP ‘U wrap’ in the shear zones. The specimens were tested using the four-point bending test. The flexural behaviour was assessed in terms of the peak moment capacity, flexural stiffness, load-displacement response, crack pattern and failure modes. The test results confirmed that hybrid strengthening leads to strength gain and stiffness gains of 105% and 90% respectively, as compared with the unstrengthened beam. The efficacy of the theoretically predicted strengths against the test strengths is assessed.

Retrofitting Techniques of Columns: A Comprehensive Review of Methods and Materials

Column retrofitting is a critical aspect of structural maintenance and improvement. It ensures that existing structures remain safe, resilient, and adaptable to evolving needs, contributing to the longevity and sustainability of the built environment. It is essential to maintain or enhance the structural integrity of buildings and infrastructure, ensuring their continued safety, resilience, and functionality. In such cases, columns may not meet current safety codes, and it becomes essential to bring them up to contemporary standards and ensure compliance with building codes. The purpose of this paper is to provide a brief overview of the methods of retrofitting, like steel jacketing, wrapping, concrete jacketing and bracing. For these advanced methods materials used in retrofitting techniques and advanced methods for column retrofitting, as it addresses various challenges associated with existing structures. Key Words: Retrofitting, Steel Jacketing, CFRP Wrapping, concrete jacketing.

Rehabilitation of RC Structure by Using Ferrocement Jacketing

Many structures fail or deteriorate before completion of its intended life span due to poor quality of material used, lack of mix design, poor workmanship, attacked by environmental agencies, etc. Sometimes due to slenderness of column or less reinforcement provided than actual requirements, less depth/thickness provided in flexural members, etc. feels excessive vibration during walking on floor ultimately develops cracks. Strength of such structural elements can be found by using non-destructive tests like Rebound hammer test, ultrasonic pulse velocity test, etc. If strength of existing structural elements is less than desired strength then structural consultant suggested strengthening of structural elements. There are various methods used in strengthening of existing structural elements like pressure grouting, fibre wrapping, chemical treatment, structural steel support, jacketing, etc. But these techniques are very costly and need precise quality control activity. In the present of investigation, strengthening of beam and column elements of a building by ferrocement techniques and steel jacketing were carried out and cost and cost comparison and strength results before and after strengthening are presented. It is observed that the strength og structural by ferrocement technique is cost effective than steel jacketing technique. And also has increase in the strength of RCC elements

Lateral ring compression test applied to a small caliber steel jacket: Identification of a constitutive model

The evolution of threats and scenarios requires continuous performance improvements of ballistic protections for armed forces. From a modeling point of view, it is necessary to use sufficiently precise material behavior models to accurately describe the phenomena observed during the impact of a projectile on a protective equipment. In this context, the goal of this paper is to characterize the behavior of a small caliber steel jacket by combining experimental and numerical approaches. The experimental method is based on the lateral compression of ring specimens directly machined from the thin and small ammunition. Various speeds and temperatures are considered in a quasi-static regime in order to reveal the strain rate and temperature dependencies of the tested material. The Finite Element Updating Method (FEMU) is used. Experimental results are coupled with an inverse optimization method and a finite element numerical model in order to determine the parameters of a constitutive model representative of the jacket material. Predictions of the present model are verified against experimental results and a parametric study as well as a discussion on the identified material parameters are proposed. The results indicate that the strain hardening parameter can be neglected and the behavior of the thin steel jacket can be described by a modeling without strain hardening sensitivity.

Study of Spun Pile to Pile Cap Connection with Steel Jacket Strengthening

Spun piles in Indonesia are designed to behave as an elastic structure according to SNI8460:2017. The piles are designed with low confinement where the amount does not meet ASCE 7-16 requirements. Indonesia should apply a performance-based design for the bottom structure someday since the seismic demand tends to increase based on the current seismic risk map. Steel jackets are proposed to fulfill the need for transverse reinforcement, particularly at the connection region where the curvature demand is higher. The steel jacket was made from high-quality zincalume steel, a high-quality rolled steel that is customizable following the size of the spun pile and has a low cost. Experimental and numerical studies were conducted. A 500mm diameter spun pile was retrofitted with a steel jacket loaded vertically and horizontally. The experimental study applied the cyclic loading according to ACI374.2r, and 0.1fc'Ag vertical load was applied. The experimental study applied the cyclic loading according to ACI374.2r, and 0.1fc'Ag vertical load was applied. The experimental study found that the spun pile and grouted concrete interaction was not perfectly bonded. A further finite element study was conducted to understand the connection's performance thoroughly. Two parameters were investigated, the steel jacket's height and thickness. A numerical study performed pushover analysis on the 3D model using the ABAQUS software to see the effect of the height and moment-curvature analysis obtained from fiber section element from SAP software to study the impact of the thickness. The results were presented in terms of its strength and ductility.

Seismic performance evaluation and strengthening of RC beam-column joints adopted in Nepal

Beam-column joints are a crucial component of the reinforced concrete (RC) moment-resisting frame (MRF) as the behavior of the joints significantly influences the strength and ductility of the overall framing system. This study is performed to explore the seismic behavior of interior and exterior beam-column joints designed based on NBC 205:1994 (NBC1), NBC 205:2012 (NBC2), and the revised seismic design standard NBC 105:2020, defined as a well-designed joint (NBC3) which are the building standards used for designing low-rise RC buildings in Nepal and compares the results from the numerical simulations quantitatively. Three possible retrofit options (CFRP, steel and RC jacketing) were explored. Finally, retrofitting options were suggested for the joint of NBC1 and NBC2 with consideration of a well-designed joint (NBC3) as the currently required capacity of the joint based on the demand of revised seismic design standard NBC 105:2020.

Behaviour of polymer-filled–concrete–steel double-skin tubular columns under combined lateral impact and axial compression loading

The paper presents a study on the suitability of using a Polymer as a protective layer for critical structural elements prone to impact damage. Conventional damage mitigation methods include using an outer steel jacket with a void, protecting the inner concrete-steel composite column. Whilst it is usually found that the outer steel jacket can partially negate the impact load, the inner column still experiences a significant brunt of the impact load. In order to minimise the damage to the overall critical structural element, a concept of a Polyurethane Polymer-Filled–Concrete–Steel Double-Skin Tubular Column is proposed. Scaled-down versions of two polymer-filled double-skin column configurations were tested under low-velocity impact using a drop tower. The pre and post-damage columns were tested for their axial capacities. These polymer-filled columns were critically compared to their nominal samples without the Polyurethane fill. It was shown that the mid-span deflection and localised indentations were reduced by 17%, and the localised deformations (at the point of impact) were reduced by up to 70% overall. The columns with Polyurethane also showcased retention of 70% of axial capacity post-impact, whilst the nominal sample was only capable of retaining 48%. Finally, the intrinsic properties of Polyurethane were discussed along with a critical discussion on its ability and mechanism on how energy is dissipated by comparing mechanical and chemical properties.

Behavior of RC columns strengthened with steel jacket under static axial load

Behavior of RC columns strengthened with steel jacket under static axial load

Assessment for behavior of axially loaded reinforced concrete columns strengthened by different patterns of steel-framed jacket

Abstract Rehabilitation, upgrading, or strengthening of structural members, especially columns, has become the target of many researchers because columns are the most important members in a building and the failure of columns causes direct collapse in the building. This study aims to get an assessment of the best pattern of steel-framed jacket used for strengthening axially loaded concrete columns by numerically studying the behavior of the column for different cases of the same amount of steel jacket. The jacket consists of four angles and/or battens, lacings, or battens with lacings. The nonlinear analysis program designated as ARCC-SSJ (Analysis of Reinforced Concrete Columns Strengthened by Steel Jacket) is used to compare different patterns with the same and different cross-sections of battens and single lacing, as well as battens and lacing with battens taken into account. It is found that lacing with battens is the best pattern for the same amount of steel jacket with different cross-sectional areas. It is observed that the load-carrying capacity of the column increased by approximately 1.8 and 1.15% over that of battens alone in the case of a lacing angle of 60.83 2 ∘ 60.83{2}^{\circ } and 74.40 7 ∘ 74.40{7}^{\circ } with the vertical axis of the column, respectively.

Optimization of Steel Jackets to Support Offshore Wind Turbines Using Evolutionary Algorithms

Abstract This paper presents an optimization tool for jacket structures to support Offshore Wind Turbines (OWTs). The tool incorporates several combinations of optimization algorithms and constraint-handling techniques (CHTs): Genetic Algorithm; Differential Evolution (DE); Tournament Selection Method; Multiple Constraint Ranking (MCR); Adaptive Penalty Method, and Helper-and-Equivalent Optimization. The objective function regards the minimization of the jacket weight; the design variables are the diameter and thickness of the tubular members. The constraints are related to natural frequencies and Ultimate Limit State criteria. The candidate solutions are evaluated by full nonlinear time-domain Finite Element coupled analyses. To assess the optimization algorithms and CHTs, a case study is presented for the standardized OWT/jacket structure from the Offshore Code Comparison Collaboration Continuation project. First, a numerical model is built and validated, in terms of masses, natural frequencies, and vibration modes; then, this model is employed to run the optimization tool for all combinations of optimization algorithms and CHTs. The results indicate that, while all methods lead to feasible optimal solutions that comply with the constraints and present considerable weight reductions, the best performer is the combination of the DE algorithm with the MCR constraint-handling technique.

Influence of UHPFRC jacketing on the static, blast and post-blast behaviour of doubly-reinforced concrete beams

This paper investigates the effects of ultra-high performance fiber-reinforced concrete (UHPFRC) jacketing on the static and blast behavior of reinforced beams. The test program included a total of six beams with dimensions of 150 mm × 200 mm × 2440 mm, including three replicate control beams, and three replicate beams retrofitted with a 20 mm UHPFRC jacket. The beams were doubly-reinforced, with provision of compression bars and ties spaced at 75 mm throughout the beam span. Each beam type included specimens tested under quasi-static four-point bending, and repeated or singly-applied blast loads applied using a shock-tube. Under static loading the UHPFRC is shown to increase beam stiffness and capacity, however the high bond capacity of the UHPFRC, crack localization effect, and relatively low steel ratio resulted in bar rupture, thereby reducing ductility. Under repeated blast loading the UHPFRC effectively reduced maximum and residual displacements at equivalent blasts, but the crack localization which initiated at the earlier blasts eventually led to bar rupture. Under the singly-applied blast, the UHPFRC was found to reduce displacements, and better control damage when compared to the companion RC beam, without bar rupture. As part of the numerical study, finite element (FE) modelling was used to predict the blast response and damage in the test beams. A parametric study is also used to examine the effects of steel ratio, jacket thickness and jacket interface location on blast behavior.

Enhancement of the Lateral Performance of RC Columns Using Steel Jacketing: A Numerical Approach

Steel jacketing has become an attractive strengthening technique for reinforced concrete (RC) columns due to ease of construction and less space requirement. The steel cage consists of angle sections placed at corners and held together by battens at intervals along the RC column height. A numerical investigation of the effective use of steel jackets as a strengthening technique in RC columns is presented in this paper. First, the finite element models of the strengthened column were developed and validated using past experimental data. Then, with the validated model, six sets of steel jacket sections with modified cross-sections such as batten spacing, batten thickness, batten width, end batten width, L angle thickness and steel jacket height were tested under constant axial and lateral loading to understand the effectiveness of steel jackets as the strengthening technique. AnunstrengthenRC column were also analysed to compare the performance of a similar column strengthened by steel jackets with modified parameters. It was shown that strengthening RC columns with steel jackets was effective in enhancing the lateral performance of the columns and resulted in a more stable load-displacement curve with lower strength degradations as compared with the un-strengthened ones. Additionally, it was found that the most effective method to increase the lateral strength and ductility is increasing the L angle thickness. On the other hand, increasing the steel jacket height also increases the lateral performance, however, it was identified that increasing the jacket height is effective only up to 1/3rd of the RC column height. Finally, the obtained results for each parameter were compared to study the behaviour of each component of the steel jacket towards lateral strength and ductility improvements.

Partially restrained seismic isolation system to retrofit a continuous girder RC bridge

The present paper proposes a partially restrained seismic isolation (PRSI) system to retrofit existing continuous girder reinforced concrete (RC) bridges. It involves a pure-friction system with a self-centring force provided by the stiffness of the deck and the frictional forces generated at the area of contact acting as an energy dissipation mechanism. The advantage is that the very small height of the system allows its application to existing bridges. The dynamic response until the collapse of an existing bridge subjected to seismic accelerations was assessed through a detailed 3D numerical model. This numerical model employed an explicit integration scheme that avoids numerical convergence drawbacks as a result of the strength and stiffness degradation of concrete structures. It was able to identify collapse mechanisms such as the development of cracks in the concrete elements. The seismic response of the original bridge was compared with that resulting from structural rehabilitation through implementation of a P-F type isolator in combination with the PRSI technique, which provided the system with a restitutive mechanism minimizing residual deformations. In addition, a classic structural reinforcement was incorporated by means of steel jacketing of the column. Both structural rehabilitation strategies were compared under the same seismic actions, assessing their efficiency and highlighting their benefits.