Akanshu Sharma

Purdue University | Purdue · Lyles School of Civil Engineering

Haunch retrofit solution (HRS) has been relatively recently investigated as a viable alternative for retrofitting of beam-column joints of reinforced concrete (RC) frame structures. For connecting the haunch elements to the frame members, partially prestressed rods were used. However, this solution makes it difficult for implementation in practice...

The paper presents experimental and numerical work carried out on a full-scale four storey reinforced concrete (RC) structure for seismic assessment by pushover method. For practicality, a portion of an existing structure having certain eccentricities was replicated for the experimental setup. The structure was detailed as per non-seismic reinforce...

Fully fastened haunch retrofit solution (FFHRS) has been proven to be an efficient and effective retrofitting technique to safeguard the beam-column joints by modifying the hierarchy of strength converting the undesirable joint shear failure mode to a desirable beam flexure failure mode. Experiments at joint sub-assemblies under cyclic loads as wel...

Inelasticity in RC frame structures, due to seismic loads, is generally considered to be concentrated in the form of hinges in beams, columns and joints. In this paper, the parameters for rectangular RC beams, columns and non-seismically detailed beam-column joints are suggested keeping the simplicity of the original pivot hysteresis model. With th...

The behavior of bond between reinforcement and concrete at high temperature is numerically investigated considering both pure bond failure and splitting of concrete. To this end, a transient three-dimensional thermo-mechanical model utilizing temperature dependent microplane model as the constitutive law for concrete is employed. Two heating types...

Anchor channels are a common fastening system for attaching highly loaded base plates of non-structural and structural components to reinforced concrete structures using channel bolts. The reliability and robustness makes this fastening system also populär for seismic applications. An innovative gap filier set was developed to eliminate the gap bet...

The concrete capacity design (CCD) method for the design of anchorages comes with a prerequisite that the base plate connecting the anchors of a group should be "sufficiently stiff." This article addresses a frequently and vastly discussed topic in fastening technology, namely "What a sufficiently stiff base plate actually means?" The qualitative d...

Fully fastened haunch retrofit solution (FFHRS) is a low-invasive method for seismic retrofitting of substandard beam-column joints. The method is quite effective provided a good performance of the anchors used for connecting the haunch elements and structural members is ensured. Therefore, to assess the performance of the joints retrofitted with F...

Current formulas to assess the shear capacity of headed steel stud anchors and post-installed (PI) anchors in case of pryout failure (sometimes known as pull-rear failure) have been derived either based on the indirect-tension resistance model or are fully empirical based on push-out test results. In both cases, the predicted pryout capacity is cle...

Multiple anchor groups with small intergroup spacing, are inevitable to solve complex engineering construction problems. Anchor groups subjected to external tension loads where concrete cone break-out failure mode is dominant, the behavior of an individual anchor group is affected by the presence of other closely spaced anchor group. The current st...

The failure of anchorages placed close to the concrete edge and loaded in shear perpendicular towards the edge is often governed by the concrete edge breakout failure. The current design provisions for such anchorages are limited in their scope to rectangular and maximum of 3 × 3 anchor patterns. This paper provides an overview of a new nonlinear s...

The current provisions for the design of headed reinforcement are not very clear. Three approaches are given in fib Model Code 2010 to calculate the capacity of a headed bar, namely (i) considering it as an equivalent hooked bar, (ii) considering it as a headed stud ignoring any bond along the bar, and (iii) by performing a test. The actual behavio...

This paper investigates the behaviour of single bonded anchors in uncracked steel fibre reinforced concrete (SFRC) undergoing concrete cone breakout failure under tension loads. Experimental investigations are carried out on bonded anchors installed in SFRC under tension loads while varying different parameters, namely, concrete grade, fibre conten...

The failure of anchorages placed close to the concrete edge and loaded in shear perpendicular towards the edge is often governed by the concrete edge breakout failure. Several assumptions are made in the current design methods to calculate the anchorage resistance, which simplify the calculations but may also lead to over-conservative or even uncon...

For assessment and design of post installed reinforcing bar (rebar) anchorages in reinforced concrete (RC) construction, two different approaches (i) conventional RC approach and (ii) fastening technology approach, coexist. For high strength adhesive systems, it is likely that the design anchorage lengths obtained using the fastening technology app...

Structural behavior of reinforced concrete elements strongly depends on the interaction between the reinforcing bars and the surrounding concrete, which is generally referred as “bond in concrete”. In service conditions, the reinforcement-to-concrete bond governs deformability through the tension stiffening of concrete surrounding the bar as well t...

Structural behavior of reinforced concrete elements strongly depends on the interaction between the reinforcing bars and the surrounding concrete, which is generally referred as “bond in concrete”. In service conditions, the reinforcement-to-concrete bond governs deformability through the tension stiffening of concrete surrounding the bar as well t...

Bond deterioration in reinforced concrete due to cyclic loads is a significant factor, which has to be considered in the seismic design and assessment procedure of reinforced concrete (RC) structures. Most studies so far have analyzed the cyclic bond behavior in well-confined conditions, where bond pull-out was the governing failure mode. Based on...

The design of anchorages according to current standards in fastening technology is limited to strict boundaries. The main reason for the limitations can be attributed to the semi-empirical and force-based nature of the design provisions, which are generally sufficient for the design of non-structural connections. Furthermore, unless otherwise prove...

TR-069 (2019) provides for the design of post-installed rebar end anchorages taking in to account the product specific bond resistance of the system. The design is based on product specific evaluation of the combined bond and splitting resistance of the PIR system using EAD-332402. The design in TR-069 is based on consideration of three failure mod...

Concrete cone breakout failure based on the tensile behavior of concrete is duly considered in design and analyses of fastening systems. The design of end anchorage in reinforcement bars is largely empirical in nature, and typically based on combined bond and splitting actions resulting in the rebar anchorage zone. The mechanics of end anchorage of...

Die Digitalisierung hält zunehmend Einzug in die Bauindustrie und entsprechend muss auch die Befestigungstechnik mit diesem Tempo Schritt halten. Je mehr Informationen zur Verfügung stehen und je präziser das Verhalten der einzelnen Komponenten eines Tragwerks beschrieben werden kann, desto genauer entsteht ein Bild über das Verhalten der Gesamtkon...

Existing anchorages in concrete structures may need strengthening due to an increase in the applied load during its lifetime. In certain cases, due to limited dimensions of the structural member, the size of anchorages is also limited, and the standard design may not be enough to provide required load-carrying capacity. In such cases, a method to s...

Chloride-induced corrosion is one of the most important reasons for the strength degradation of reinforced concrete (RC) bridges. As the piers of RC bridges are important element to sustain lateral loads, corrosion of columns in pier may lead to significant degradation. So it is necessary to have an appropriate evaluation technique to assess the ef...

This study investigates the effectiveness of hybrid fibers (steel and macro-synthetic) on the shear behavior of prestressed concrete beams. The hybrid fiber combination was selected to avoid workability issues at high volume dosages and ensure effective crack arresting over the crack opening range. Fracture studies included testing notched concrete...

This paper presents the results of comprehensive and systematic experimental investigations carried out on anchorages (single anchors and groups) of bonded anchors supplemented with post-installed reinforcement subjected to tension loading. Until now, the use of supplementary reinforcement is allowed in the codes only for anchorages with cast-in he...

As the construction industry increasingly moves toward digitalization, anchor technology will need to keep up. In structural design, displacement-based approaches are being incorporated for better and more realistic assessment of structural behavior. From the perspective of anchorage, there is a need for displacement-based approaches for design tha...

This study investigates the possibility of replacing the minimum web reinforcement in deep beams with discrete fibers. Additionally, the equivalent dosage of fibers required to obtain similar performance of the deep beam with minimum web reinforcement is investigated. Deep beams made of plain concrete with no fibers, beams with minimum web reinforc...

Post-installed anchors can offer a low-invasive and practical solution to connect strengthening elements with the existing reinforced concrete structure in seismic retrofitting applications. Such a connection formed with multiple-anchor groups is faced with several challenges due to high demands and structural or architectural features. In the fram...

The paper investigates the seismic performance of non-seismically designed reinforced concrete exterior and interior beam-column joints. The study focuses on the influence of transverse beams and slab on the sub-assemblies which are failing due to a joint shear failure. In the case of exterior joints, top and bottom longitudinal deformed bars of th...

Anchorages are often required at the corners of frame structures. For example, when diagonal steel bracings are attached to the corner of a reinforced concrete frame to strengthen it against seismic actions. However, there are no guidelines or standards available which provide a design solution for such a corner configuration. To this end, a numeri...

Increasing worldwide urbanization pushes city centers to grow in height. The skylines of cosmopolitan cities are increasingly dominated by tall buildings clad with curtain wall façade panels. In many cases, these panels are attached to the structure by anchor channels. One of the challenges of this is that the concrete decks are becoming thinner an...

Anchorages of non-rectangular configuration, though not covered by current design codes, are often used in practice due to functional or architectural needs. Frequently, such anchor groups are placed close to a concrete edge and are subjected to shear loads. The design of such anchorages requires engineering judgement and no clear rules are given i...

In this paper, numerical simulations are performed to investigate the performance of post-installed anchors used to connect a gusset plate in corner configuration. Thereby, the complete connection is both fully and partly fastened to the concrete specimen to determine the effect of the concrete corner. It is found that the stiffness and ultimate lo...

Due to notch effect of the holes, the anchors installed in concrete are highly likely to be intercepted by cracks that may form due to thermal and/or mechanical loads on the structure. The presence of cracks, alters the behaviour of anchors by reducing their stiffness and load carrying capacity. The behaviour of anchors in steel fiber reinforced co...

In recent years, the use of post-installed anchors to connect the haunch elements with the structural members has been investigated proficiently. It represents a promising alternative for strengthening of joints of existing reinforce concrete (RC) structures (moment resisting frames) with low invasion. The efficacy of the fully-fastened-haunch-retr...

In der Ingenieurpraxis steigt die Nachfrage nach Befestigungsmitteln im stahlfaserverstärkten Beton (Steel Fibre Reinforced Concrete: SFRC), was ein tiefes Verständnis über das Tragverhalten erfordert. Zu typischen Anwendungen zählen Fußpunktkonstruktionen von Schwerlastregalsystemen, Schwermaschinen in Industrieböden, Stahlbetonfertigteilbau, Indu...

The increasing demand on the use of cast-in and post-installed anchors in steel fibre reinforced concrete (SFRC) requires a better understanding for the load bearing behaviour. Typical applications of anchorages in SFRC include baseplate connections of high rack systems, heavy machines in industrial floors, precast reinforced concrete structures, i...

During earthquakes, buildings are subjected to loads well beyond their usual demands, resulting in high stresses in the structural components and additional inertial forces coming from the non-structural elements. When post-installed anchors are used to form the connection between non-structural or structural members and the primary reinforced conc...

Beam-column-joints (BCJ) in reinforced concrete (RC) frames are known to be critical against seismic actions. Hence, several researchers have conducted related investigations. The loading history used in the experimental investigations must be a sufficiently accurate and conservative representation of seismic loading on the structure and should tri...

The paper presents and discusses the results of a numerical study on post-fire (residual) behavior of reinforced concrete (RC) beams with critical tension lap splices. It is based on the experimental findings and the validation of the numerical approach in the accompanying paper (Part I) and further analyzes the residual performance by varying most...

This paper presents the efficiency of the fiber-reinforced polymer (FRP) composites as internal reinforcement in rescue the structural performance and controlling the mode of failure of the sulfate damaged reinforced concrete (RC) beam-column joint by nonlinear finite element analysis (NLFEA). Firstly, the RC beam-column model was validated against...

This paper discusses an experimental program aimed at comparing different reinforcing bar (rebar) anchorage systems in reinforced concrete (RC) column-to-foundation joints (CFJ). A total of 13 tests on full scale CFJ are presented. Within the test matrix, cast-in straight (CIS), cast-in with bent-in hook (CIH) and post-installed rebar (PI) systems...

The behaviour of anchor groups arranged parallel to the concrete edge in one single anchor row and loaded in shear perpendicular to the concrete edge is experimentally investigated. A comprehensive test program was performed to obtain information on the group behaviour, influence of the displacement behaviour of single anchors, influence of load ec...

The circumferential (hoop) stresses and the corresponding radial micro-cracks induced by tension-loaded adjacent and closely spaced anchor groups may interact with each other, resulting in a reduced concrete cone capacity of the individual anchor groups. If the adjacent anchor groups are not connected by a common rigid base plate, the design of the...

The paper presents a series of tests conducted to study the post-fire (residual) performance of the reinforced concrete beams with critical (under-designed) lap splices. Furthermore, a 3D numerical modelling approach is validated against the experimental results. Two types of beams namely, Type 1 - with continuous reinforcement, and Type 2 – with c...

The paper investigates the influence of the joint aspect ratio (ratio between beam depth to column depth) on the shear strength of exterior non-seismically designed reinforced concrete beam-column joint sub-assemblies with transverse beams and slab. Three-dimensional numerical (FE) analysis is performed employing the microplane model for concrete....

Channel bolts installed in cast-in anchor channels are a convenient and reliable way to anchor high loads in reinforced concrete structures. The system is in particular handy when a fast connection or a tolerance compensation is important, e.g. for curtain wall elements or hanger works of cable trays (for power and data lines) and pipes (for water...

Anchor channels are cast in concrete and allow the connection of components using channel bolts. In recent years, the design to value resulted in ever thinner concrete elements, which often cannot accommodate the required embedment depth of standard anchor channels. For this reason, channels may be fitted with short anchors. While existing design p...

The world becomes ever smaller and thus the global construction industry moves closer together. For this reason, civil engineers are looking for possibilities to harmonize design-for example, in the field of reinforced concrete structures. The streamlining would ease working in an international context and could offer opportunities for optimization...

Fire safety is a critical performance aspect of construction products, and post-installed anchors and rebars are no exemption in that regard. During their service life, anchors and rebars are subjected to different kinds of load actions, so they have to be qualified and designed for critical safety performance. While the qualification guidelines fo...

Past earthquakes have highlighted the seismic vulnerability of non-seismically designed reinforced concrete (RC) frame structures worldwide. It is documented that the mechanics under seismic loads and the poor reinforcement detailing of beam to column connections may result in highly inelastic joint shear distortions thus resulting in non-ductile r...

The presence of in-situ cast slabs and transverse beams in reinforced-concrete (RC) beamcolumn joints is usually neglected in RC design practice concerning frames subjected to seismic actions for at least two reasons: (i) the need of simplification in the design process and (ii) the limited experimental studies which are mainly focused on two-dimen...

Reinforced concrete (RC) frame structures designed before the introduction of modern seismic codes are particularly susceptible to seismic events. The risk of a complete collapse during an earthquake and the related damage caused due to such disasters can be significantly reduced by retrofitting the RC frame structures. Hence, different methods hav...

Post-installed anchors are often used to form a connection between the non-structural or structural component with the primary reinforced concrete (RC) structure. Especially when it comes to structural connections, one major field of application of the anchorages is in seismic retrofitting. In order to overcome the structural deficiencies and to en...

The use of post-installed reinforcement (PIR) systems in reinforced concrete (RC) construction has gained popularity over the last few decades, since the solution offers a way to anchor reinforcement in the least invasive manner. Researchers have in the past, investigated monotonic and/or cyclic behaviour of structural joints formed using postinsta...

Tension loaded anchorages far from the concrete edge may fail due to concrete cone failure, steel failure, pull-out failure or splitting of the concrete member. In the case of concrete cone failure, a conical concrete breakout body forms, where the angle of the initial crack of the concrete cone to the concrete surface is approximately 35° and the...

The failure mode of anchorages placed close to the concrete edge and loaded in shear perpendicular towards the edge is often governed by the concrete edge breakout failure. The design provisions for concrete edge failure given in the current codes are limited in their application for anchor groups with rectangular anchor configurations only. The nu...

The development of a proper bond between steel and concrete in a reinforced concrete structure is essential for a safe and effective transfer of stresses between them. In case of realistic concrete covers, failure of bond between reinforcement and concrete can be limited by the premature splitting of concrete cover prior to bond pull-out failure. M...

Use of organic resins such as epoxy and vinyl esters as bonding materials in fibre reinforced polymer (FRP) strengthening of concrete members is widely accepted. However, the performance of organic resins is compromised when exposed to high temperature and extreme weather conditions leading to reduced durability of the strengthened systems. The pre...

The usage of post-installed anchors in structural applications and seismic retrofit solutions has become more and more popular over the past decades. The current approaches for seismic assessment of post-installed anchors follow primarily a force-based approach and were developed focusing on non-structural applications. On the structural level, per...

Steel fibre reinforced concretes (SFRC) is known to have significantly improved mechanical properties compared to the normal concrete. The addition of steel fibre has a positive influence e.g. on the load-bearing capacity, crack formation, ductility. In the recent past, a great emphasis is being laid upon the behaviour of cast-in and post-installed...

This paper presents the results of nonlinear finite element (FE) analysis of fiber reinforced polymer (FRP) strengthened reinforced concrete (RC) columns under different combinations of axial compression (P) and bending (M) loads. Three-dimensional FE models of RC columns were analyzed for different eccentricity (e) to depth (h) ratios as (a) axial...

Hinterschnittdübel werden in kerntechnischen Anlagen zur nachträglichen Befestigung von maschinentechnischen Komponenten an Stahlbetontragwerken eingesetzt. Um die Integrität der Komponenten auch bei außergewöhnlichen Einwirkungen wie Erdbeben zu garantieren, müssen die Dübel eine ausreichende Tragfähigkeit aufweisen. Für die Annahme einer ausreich...

Concrete pryout failure mode of a group of relatively shallow embedded anchors welded to a steel base plate has not been extensively investigated in the past. Therefore, the failure mechanism and resistance of such anchor groups needs to be clarified. In this paper a three‐dimensional (3D) finite element parametric study for quadruple (2 × 2) ancho...

Post installed rebars offer a convenient and robust solution for rehabilitation, retrofit and strengthening of reinforced concrete structures, whenever additional structural members might be required. Although certain post installed rebars have significantly higher bond strength as compared to cast in systems, presently they are considered equivale...

In this work a tension loaded 2 x 1 anchor group is investigated numerically. The numerical analysis is performed within the framework of a 3D FE analysis using microplane model with relaxed kinematic constraint as the material model for concrete. The anchor group includes two bonded anchors, a fixture connecting the anchors and a concrete slab in...

The design of anchorages according to the current codes and guidelines is limited to rectangular configurations and a sufficiently rigid base plate is required. However, due to technical, functional or architectural requirements, anchorages are also used in industry, for which the design is not covered by the current provisions. Furthermore, with t...

EN 1992-4 [1] regulates the design of fastenings in concrete. It contains provisions for fastenings at an edge with supplementary reinforcement to take up shear forces perpendicular to the edge. The model given in [1] is very conservative. Therefore tests were performed at the University of Stuttgart to investigate the behavior of fastenings with u...

In this work, experimental and numerical studies are performed to investigate the influence of elevated temperature on the residual (post-heating) behaviour of masonry. Two different types of solid brick units namely, clay bricks and calcium silicate bricks, were used in the study. The tests were performed on the individual brick units, the cement...

Corrosion is one of the most important causes of degradation in reinforced concrete structures. It endangers the serviceability of the structure, requires a vast amount of effort, and consumes considerable financial resources towards repair and retrofitting of the damaged part of structures. Therefore recognizing this phenomenon and its effects on...

Supplementary reinforcement can be used to increase the concrete edge resistance of the anchorages with headed studs according to current norms. However , the utilization of post-installed reinforcement to improve the behaviour of anchorages against concrete edge failure has not been investigated yet. In this work, experimental investigations are c...

The behaviour of anchor groups under tension loading depends on a number of parameters such as anchor type, anchor configuration, concrete strength, base plate geometry and stiffness, vicinity of the concrete edge and load eccentricity. In order to calculate the resultant anchor forces and the group resistance, several assumptions are made in the c...

Steel bracing has proven to be a very powerful method to improve the seismic behaviour of reinforced concrete frame structures. In general the steel braces are indirectly connected to the RC frame via additional steel frames that are in turn fixed to the RC frame using post-installed anchors or reinforcing bars. However, this method comes with seve...

The effectiveness of hybrid fibre-reinforced polymer (FRP) strengthening is evaluated for rapid repair of the pre-damaged plain concrete (PC) and reinforced concrete (RC) columns. The objective of this study is to understand the efficiency of hybrid technique for completely restoring the initial stiffness, load carrying capacity and ductility of pr...

Concrete edge failure often governs the failure of anchorages, which are installed close to the concrete edge and are loaded in shear perpendicular towards the edge. The design provisions for concrete edge failure given in the current codes are rather limited in applicability. Only anchorages arranged in a rectangular pattern are allowed. For ancho...

The existing anchorages in reinforced concrete structures may need strengthening due to an increase in the applied load during its lifetime. In certain cases, due to limited dimensions of the structural member (e.g. concrete slab or beam), the size of the anchorages that can be used is also limited and the standard design of anchorages may not be e...

In this work, experimental and numerical studies are performed to investigate the influence of elevated temperature on the residual (post-heating) behavior of masonry. Two different types of solid brick units namely, clay bricks and calcium silicate bricks, were used in the study. The tests were performed on the individual brick units, the mortar a...

This work experimentally investigates the efficacy of hybrid strengthening technique using a combination of near surface mounted (NSM) carbon fiber laminates and externally bonded (EB) carbon fiber reinforced polymer (CFRP) wraps for short reinforced concrete (RC) columns under eccentric loads. The performance of the hybrid FRP strengthened column...

Strengthening with steel bracing is one of the popular retrofitting methods used to improve the seismic performance of reinforced concrete frame structures. Commonly the steel braces are connected to additional steel frames which in turn are fixed to the RC frames using post-installed anchors or reinforcing bars. This method of connection leads to...

Zusammenfassung Die Bemessung von zugbeanspruchten Befestigungen in Beton nach den aktuellsten Normen und Richtlinien weist viele grundlegende Einschränkungen zur Anwendung der Konzepte auf. Sie beschränkt sich beispielsweise auf rechteckige Dübelanordnungen und setzt die Verwendung einer ausreichend steifen Ankerplatte voraus. Definitionen und Reg...

The current recommendations given in the codes and guidelines for design of anchorages to concrete are limited in scope to rectangular and regular anchor groups with a maximum of three anchors in a row. Furthermore, several assumptions are made, which may render the designs conservative but may also lead to unconservative results such as the requir...

This paper discusses the efficacy of different fiber-reinforced polymer (FRP) techniques on the behavior of RC columns under uniaxial high eccentric compression. Eight RC columns were strengthened using three FRP strengthening schemes: (1) near surface mounting (NSM), (2) external bonding (EB), and (3) hybrid strengthening, which uses a combination...

The current recommendations given in the codes and guidelines for design of anchorages to concrete are limited in scope to rectangular and regular anchor groups with a maximum of three anchors in a row. Furthermore, several assumptions are made, which may render the designs conservative but may also lead to unconservative results such as the requir...

Though anchor channels with channel bolts are used in practice since long time, the codification of their design rules was just recently finalized in Europe with the issuing of the new EN 1992-4. In the United States, full consolidation of the design rules for anchor channels with channel bolts in ACI 318 is yet to be included. The design requires...