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This paper investigates the use of glass fiber reinforced polymer (GFRP) bar bents as stirrups at the joint between the steel posts of a bridge guardrail system with a deck slab cantilever. In addition, GFRP bars with headed ends are used for better anchorage at the postdeck slab joint. Four full-scale cantilever post specimens were erected and tested to collapse. Two specimens were reinforced with steel bars as control specimens, whereas the other two specimens were reinforced with GFRP straight bars, bent bars, and headed bars at applicable locations. Similar failure modes were observed in all specimens because of curb external side face breakout. Failure occurred in unconfined concrete cover because of significant compressive and frictional shear stresses and also torsional effects, resulting in concrete spalling at the side face of the cantilever at the bottom of the posts. Although it is recommended to consider larger edge distance of the post to prevent premature failure in the unconfined concrete cover, the obtained experimental capacity of the postcurb region was concluded to be sufficient to resist design loads. To calculate the share of the design lateral loads received by each post, a linear finite-element analysis (FEA) and a simplified FEA were used. The analysis showed that the share of each post decreases with decrease in spacing between posts. [ABSTRACT FROM AUTHOR]

Ground anchorages are the main means of support used for safety aspects in mining and tunnelling industry. Poor installation of ground anchorages can result in partial debonding between the tendon and the grout. The effects of debonding on the load carrying capacity of a model anchorage are examined by pull out tests. The load carrying capacity is found to decrease with increasing length of pre-existing debonding at the tendon-grout interface. The fracture toughness of the tendon-grout and of the ground-grout interfaces is measured over a wide range of mixed-mode loading and the results are used to assess the likelihood of debonding at the interfaces in a ground anchorage system. [ABSTRACT FROM AUTHOR]

An experimental program was conducted to investigate the application of headed glass fiber-reinforced polymer (GFRP) ribbed bars at the barrier wall-deck anchorage. Six full-scale barrier models of 1,200 mm in length were erected and tested under static monotonic loading to determine their ultimate load-carrying capacities and failure modes with respect to the barrier wall-deck anchorage. Four PL-2 barrier specimens were cast: two of them were of tapered face and the other two specimens were of parapet type with constant thickness. Each set had a steel-reinforced specimen as the control model and a GFRP-reinforced specimen. In addition, two PL-3 GFRP-reinforced specimens were erected with different spacing of GFRP bars. Each specimen was loaded laterally until collapse. This paper presents the results from these tests in the form of crack pattern, deflection history, and ultimate load-carrying capacity. Experimental results were compared with the design values specified in the Canadian bridge code for barrier anchorage into the deck slabs, showing a large margin of safety for the proposed GFRP-reinforced barriers. In addition, a parametric study was undertaken using finite-element analysis to investigate the applicability of resultant design loads prescribed by the Canadian bridge code for the design of the barrier wall-deck anchorage. The key parameters considered in this study were deck overhang length and thickness and barrier length. The data generated from this parametric study were used to develop set of empirical expressions for the factored applied moment at the barrier-deck interface, as well as the factored tensile force required to design the deck slab cantilever. [ABSTRACT FROM AUTHOR]

Numerical simulations using the nonlinear finite-element method (FEM) have been successfully used to predict the full nonlinear response of reinforced concrete (RC) members strengthened with fiber-reinforced polymers (FRPs). Calibrated numerical models have the potential to reduce the number of experimental tests through the use of parametric studies that can provide further data on the influence of key parameters. A relatively new area of research is the use of FRP anchorage systems to improve the efficiency of FRP-strengthened members by preventing the various modes of deboning failure. Although FRP anchorage systems have shown exceptional potential for widespread use, further experimental and numerical data are required before establishing theoretical models and design guidelines. The focus of the present work is to develop and validate an FE modeling approach to expand the available data on FRP-to-concrete joints anchored using unidirectional and bidirectional fiber patch anchorages. The critical bond properties among multiple layers of FRP sheet, laminate, and concrete are simulated using interface elements and a calibrated interface bond law. The proposed modeling approach and calibration techniques have resulted in replication of prepeak and postpeak response with a reasonable level of accuracy. Numerical parametric studies have also been conducted to expand the experimental data to encompass variations in concrete strength and the overall effect on anchorage effectiveness. [ABSTRACT FROM AUTHOR]

Fiber-reinforced polymer (FRP) strengthening systems for infill-masonry walls are typically designed to resist flexural stresses caused by out-of-plane pressure. Previous research has shown that there are potential premature failure mechanisms caused by shear sliding of the infill, which could reduce the effectiveness of the strengthening system. Current design guidelines for strengthening of masonry walls with FRP do not include guidelines for infill-masonry. This paper presents a rational approach for the design and analysis of FRP-strengthened infill-masonry walls subjected to out-of-plane loading, including the effect of using FRP end anchorage. The approach is based on consideration of four potential mechanisms: arching, shear sliding, debonding of the FRP in the overlap region, and failure of the FRP end-anchorage system. The predictions based on the proposed rational approach agree well with the measured values from two experimental programs. [ABSTRACT FROM AUTHOR]

Objective. To understand the meaning of the experiences of sexual incestuous abuse (SIA) that three families have built, as well as the conceptions, beliefs and values that perpetuate or transform the above-mentioned experience inside the family intimacy. Method. Phenomenological hermeneutical research with narrative methodology, which implied an information generation process through the stories narrated by the families about their lives. Three families who are being attended by the Acercamiento (Reconciliation)-Asperla program in the city of Medellin were interviewed. Interviews were conducted with the girls who were victims and a significant figure, whether their father or mother. Results and conclusions. The biographical events on the family narratives did not determine the causes of abuse in a continuous and uni-causal line, but as metaphors that contributed to generate comprehension of the meaning that the family built around this experience. Among the most relevant are cultural and familiar anchorages of the abuse and mistreatment; disintegration and reconfiguration on the family; reflections on the interference of the State and the law; the position of parents facing sexual abuse of their daughters; and finally, the meaning constructed by the girls about the experience of abuse. [ABSTRACT FROM AUTHOR]

A new type of combined cable-stayed bridge, named the extradosed and intradosed cable-stayed bridge with continuous cables, is presented to improve the mechanical behavior of the traditional extradosed bridges. The cable-girder anchorage is innovated to be suited for traditional extradosed bridges, which makes the girder supported by a group of continuous cables with larger eccentricity above and under the deck simultaneously. This paper evaluates the structural performance of the innovative structural scheme through parametric studies and detailed comparisons with traditional ones. Preliminary analyses show the advantages of the innovative structure, such as decreased bending response and deflection of the deck because of larger stiffness, smaller cable forces and increments, better dynamic resistance, and less amount of material. [ABSTRACT FROM AUTHOR]

The requirements for the anchorage of beam longitudinal reinforcement at interior beam-column joints in earthquake-resistant RC moment-resisting frames are reevaluated. An introductory comparison of international design criteria shows that a broad disparity currently exists between these requirements. The suitability of existing criteria was assessed by assembling a database of more than 90 interior beam-column joint tests and comparing the assessed test performance with the performance that was predicted by each design criterion. This comparison showed that none of the existing design criteria were adequately able to predict experimental performance. To improve the design of earthquake-resistant RC frame structures, an improved design criterion was developed by parametrically determining the influence of important variables on anchorage performance. [ABSTRACT FROM AUTHOR]

Connections with glued-in rods are very efficient, high-strength joints and can be successfully used, for example, for the anchorage of vertical timber elements to a foundation. Although extensive research was done on the pullout strength of single rods, few references can be found on the behavior of multiple glued-in rods. This paper presents the results of an experimental program carried out on timber-to-steel connections with multiple glued-in rods. Two series of 10 specimens with four large-diameter, glued-in rods made from mild steel (Series GB) and 10 specimens with 12 small-diameter, high-grade glued-in rods (Series GS) were tested to failure under monotonic tensile load. Both types of connections ultimately failed in a brittle manner; however, the GB series developed some plastic deformations prior to failure which was caused by the pullout of two rods and longitudinal splitting of the timber member. By comparing the experimental results with the analytical predictions, no significant group effect could be detected in the GB test series, and an overall acceptable approximation was found. In the GS test series, no final conclusion on the group effect could be drawn as several rods failed by nut-stripping. A parametric study using analytical formulas was carried out to investigate the effect of rod strength, rod diameter, glued length, and timber density on the connection performance. Based on the results of the parametric study and experimental tests, it can be concluded that the use of mild steel as well as more rods of larger diameter, properly spaced from each other, and from the edges are all effective measures to increase the connection ductility. Furthermore, by leaving a suitable length of rod unbonded between the steel plate and the glued length, it is possible to control ductility, providing all brittle failure modes have a higher strength capacity than the rod-yielding force. Special care should be taken during the manufacturing process to ensure good quality of gluing (required glued length and amount of adhesive) and rod alignment. [ABSTRACT FROM AUTHOR]

The distribution of bond on the lateral surface of steel reinforcement embedded in concrete is explored through systematic solution of the governing field equations of the associated mechanical problem. By separating the variables, the state of stress in the concrete surrounding the bar is represented by coupling two independent solutions, each describing attenuation of bond stresses either in the longitudinal direction or in the radial direction of the cover, respectively. Kinematic considerations are used to couple longitudinal slip with the radial translation of the cover, whereas the corresponding stress components developing along the lateral bar surface over the anchorage (radial pressure and bond stress) are related through a frictional relationship. Using the derived solution, various experimentally documented trends and phenomena pertaining to the study of bond, as represented by the international experimental databank, are reproduced analytically and interpreted. These include the processes of debonding and yield penetration and the sensitivity of the development capacity to important design variables such as the related rib area, cover to bar diameter ratio, concrete strength, bar yield strength, bar hardening characteristics, and confinement. A model representing the envelope curve of the local bond-slip relationship suitable for analysis and simulation is presented and calibrated in the paper. [ABSTRACT FROM AUTHOR]

Previous tests of structural walls have routinely used continuous reinforcement extending from the foundation to the top of the specimen. This detailing is consistently different from that of multistory walls in the field, which incorporate splices in the wall longitudinal reinforcement above the wall-foundation interface. As a result, the performance of walls incorporating continuous reinforcement in the laboratory may not be representative of walls in the field that use lap splices or mechanical couplers near the wall base. This paper investigates lateral load behavior of three nominally identical structural walls with continuous reinforcement, lap splices, and mechanical couplers in the plastic hinge region, and quantifies the differences in their responses using force-displacement response, lateral deformation components, and energy dissipation estimated using equivalent viscous damping. [ABSTRACT FROM AUTHOR]

The study presents the results of an experimental program aimed at investigating the flexural behavior of externally plated RC beams. A total of 13 full-scale rectangular RC beams were tested. The effects on the behavior of the plate thickness, the anchorage of the plate to the beam through anchor bolts or side plates (collars), and the use of perforated plates instead of solid ones were investigated. The experiments indicated that the beam ductility increases as the plate thickness decreases, and the anchorage of the plate to the beam through bolts or collars proves to be an efficient method for preventing the premature plate peeling failure and achieving sufficient ductility in beams strengthened with thick solid plates. Anchor bolts had adverse effects on the ductilities of the beams with thin plates, and the use of perforated steel plates was found to be an efficient method for increasing the ductility of a strengthened beam. The beams repaired with perforated plates anchored to the beam with collars had load-carrying capacities close to those of the undamaged beams. [ABSTRACT FROM AUTHOR]

It is not uncommon that cover cracking, spalling, and delamination occur in many corroding RC structures. Previous research has mainly been concerned with corrosion levels leading to cover cracking along the main reinforcement, whereas corrosion of stirrups is often overlooked. Corrosion phenomena, including stirrup corrosion, were studied in an experimental investigation presented in this paper. High levels of corrosion were reached, up to 20% of the main bars and 34% of the stirrups legs. The occurrence of crack initiation, propagation, and cover delamination were examined. The specimens had the shape of a beam end and were corroded with an accelerated method; an imposed current was used, taking care to keep the current density as low as practically possible for the duration of the laboratory testing. The effects of this process were compared with those of natural corrosion using models from the literature. The location of the bar, middle and corner placement, the amount of transverse reinforcement, and the corrosion level of longitudinal reinforcement and of transverse reinforcement were studied. The results concerning the concrete cracking in the experimental campaign are presented. The crack patterns and widths were analyzed, showing differences between specimens with or without stirrups and whether stirrups were corroding. Finally, the effect of corrosion was simulated as the expansion of corrosion products in a finite-element (FE) model, and the results, mainly the crack pattern and width, were compared with the test results. The conclusions addressed the importance of taking into consideration both high corrosion levels and corrosion of stirrups for the assessment of deteriorated structures. [ABSTRACT FROM AUTHOR]

The paper describes a numerical model to analyze the fatigue behavior of RC anchorage zones. The model takes into account the cycle-dependent bond-slip behavior at the steel-concrete interface and is able to reproduce the experimental increase of the relative slip developed with number of load cycles, as well as the process of redistribution of stresses that takes place over the anchorage length as a result of fatigue damage. The results compare satisfactorily with existing experimental results. The model has been used to derive curves to provide the fatigue strength of anchorage zones under different confinement conditions and various values of the anchorage length-to-diameter ratio and the steel diameter. The results indicate that the confinement degree plays a significant role in the fatigue bond strength: no fatigue problems are found for the well-confined concrete condition, but significantly short fatigue strength is obtained under the moderately confined and unconfined concrete conditions. [ABSTRACT FROM AUTHOR]

The existing wood-diaphragm-to-masonry-wall connections in unreinforced masonry (URM) buildings provided very little or insufficient resistance in past earthquakes. Recent strengthening techniques for the connections between URM walls and flexible diaphragms concentrate only on the installation of wall anchorages for out-of-plane tension forces and shear bolts for in-plane shear forces. Strengthened chord elements, however, are also essential parts of URM buildings to resist earthquakes. This paper proposes seismic rehabilitation techniques where steel angles are used as chord reinforcement. A practical design example is presented, where chord axial forces caused by in-plane diaphragm deflections and chord shear flows caused by transverse seismic forces are computed. The computed axial forces and shear flows are to be used in the design of the chord reinforcement and the chord shear connections, respectively. [ABSTRACT FROM AUTHOR]

In this paper we derive the theory of multiple peeling, extending the pioneering energy-based single peeling theory of Kendall, including large deformations and pre-stretching. We can thus treat a complex system of films, adhering over a substrate and having a common hinge where the pulling force is applied. Two case studies are investigated: the asymmetric V-shape double peeling and the symmetric cone-shape configuration with N peeling tapes, both requiring the solution of six nonlinear coupled equations (instead of the one needed in the simpler single peeling problem). Remarkable implications emerge: (1) for moderate deformations, the critical strain of a tape is identical to that of the single peeling; (2) an optimal peeling angle, at which adhesion is maximal, is discovered; (3) an additional optimization, even for hierarchical structures, is introduced by imposing the delamination force equal to the intrinsic fracture of the tape. Also, the length of the peeling process zone is calculated, suggesting different optimal values for flaw-tolerant peeling at different angles. Applications to gecko adhesion, for which the flaw-tolerant peeling is demonstrated, and spider silk anchors, that we are going to discuss in details in subsequent papers, are envisioned (including a new pre-stretching mechanism for adhesion control) and suggested by the evidence of a smart mechanism capable of maximizing adhesion simply by increasing the applied tension. [ABSTRACT FROM AUTHOR]

The results of an experimental investigation for the retrofitting of shear-damaged RC beams using diagonal CFRP strips are presented in this article. The experimental study consisted of seven shear-deficient, T-cross-sectioned, ½-scale, simply supported beam specimens. One beam is used as the reference specimen. The remaining six specimens are tested in two stages. At the first stage, specimens are shear damaged severely and the shear-damaged RC beams are retrofitted using diagonal CFRP strips by wrapping them around the beam in the shape of a ‘U’. Then, retrofitted beams are tested to failure. In this study, 50 mm wide CFRP strips are used with three different spacings such as sf = 125, 150, and 200 mm. One of the two specimens with the same spacing is tested with anchorages at the ends of the CFRP strips. Although the strips without anchorages improved the shear strength of the shear-damaged beam, they could not prevent the shear failure. Shear-damaged specimens that are retrofitted with anchoraged CFRP strips showed to improve the shear strength, and ductile flexural behavior was observed in them. When the CFRP strains of the strips with and without anchorages are compared, maximum strains at anchoraged strips are approximately 1.55 times larger than those without anchorages. Calculated shear load carrying capacity of the specimens, according to ACI 440 and FIB regulations, are approximately 2% larger than the experimental one. [ABSTRACT FROM PUBLISHER]

The deterioration attributable to corrosion of concrete structures reinforced with unbonded, posttensioned tendons is a costly problem. Recent research has shown composite materials such as fiber-reinforced polymers (FRP) to be suitable alternatives to steel because they provide similar strength without susceptibility to electrochemical corrosion. Carbon-FRP (CFRP) in particular has great promise for prestressed applications because it shows resistance to corrosion in environments that might be encountered in concrete and experiences less relaxation than steel. This paper outlines the testing and implementation of a posttensioned system that uses CFRP tendons to replace corroded, unbonded posttensioned steel tendons. This system was then implemented in a parking garage in downtown Toronto. To the writers' knowledge, this is the first example of an unbonded, posttensioned tendon replacement using FRP tendons. The system used split-wedge anchors designed specifically for CFRP tendons. The dead end was anchored by directly bonding the tendon to the concrete slab. The CFRP tendon was successfully inserted in the opening created by the removal of the corroded tendon and stressed. Although the system was shown to be feasible, the current anchorage configuration results in load losses of up to 60% during the transfer. Changing the orientation of the anchor was found to reduce the load loss to an acceptable range of 1-9%. [ABSTRACT FROM AUTHOR]

The results of an experimental investigation are presented in this paper for retrofitting of shear damaged reinforced concrete beams by using U shaped CFRP strips. The experimental program is consisted of seven shear deficient T cross sectioned 1/2 scale simply supported beam specimens. One beam was used as reference specimen, and the remaining six specimens were tested in two stages. At the first stage, specimens were shear damaged severely, and then were retrofitted by using CFRP strips with or without fan type anchorages. Finally, retrofitted beams were tested up to failure. Three different CFRP strip spacing were used such as 125 mm, 150 mm, and 200 mm. The effect of anchorages on shear strength and behavior of the retrofitted specimens is investigated. CFRP strips without anchorages improved the shear strength, but no flexural failure mode was observed. Specimens showed brittle shear failure due to peeling of CFRP strip from RC beam surface. Shear damaged specimens retrofitted with anchoraged CFRP strips showed improved shear strength and ductile flexural failure. Maximum strains at anchoraged strips were approximately 68% larger than that of strips without anchorages. [ABSTRACT FROM AUTHOR]

Posttensioning is an effective method for the construction of different types of bridge girders such as those used in segmentally erected bridges. Available nonlinear analysis programs for bridge girders under severe loading conditions are computationally expensive though. In addition, they neglect important phenomena such as bond-slip, friction, and anchorage losses. The objective of the proposed work is to develop a new nonlinear finite-element program for analysis of posttensioned bridge girders. The new model overcomes most of the difficulties associated with existing models. The model is based on the computationally efficient mixed formulation and considers bond, friction, and anchorage loss effects. The mixed formulation is characterized by its fast convergence, usually with very few finite elements and its robustness even under severe loading conditions. The posttensioning operation is accurately simulated using a phased-analysis technique, in which each stage of the posttensioning operation is simulated through a complete nonlinear analysis procedure. Correlation studies of the proposed model with experimental results of posttensioned specimens are conducted. These studies confirmed the accuracy and efficiency of the newly developed software program, which represents an advancement over existing commercial software packages for evaluating posttensioned bridge girders, in particular those subjected to severe loading conditions. [ABSTRACT FROM AUTHOR]

The results of an experimental investigation are presented in this article for improving the shear capacity and ductility of reinforced concrete beams by using CFRP strips. The purpose of this study is to obtain ductile flexural behavior for shear-deficient reinforced concrete beams. The experimental program consisted of 10 T cross-sectioned half scale simply supported beam specimens, seven of which were constructed with deficient shear reinforcement and the remaining three without any shear reinforcement. One beam was used as a reference and nine beams were strengthened using U-shaped CFRP strips with or without fan type anchorage. Three different CFRP strip spacing such as sf = 125 mm, 150 mm, and 200 mm were used. The effect of anchorages that were used at the ends of the strips on shear strength and behavior of the strengthened specimens was investigated. CFRP strips without anchorages improved the shear strength, but no flexural behavior was observed. specimens failed with brittle shear failure due to peeling of CFRP strip from RC beam surfaces. specimens with deficient shear reinforcement that were strengthened with anchored CFRP strips showed improved shear strength and ductile flexural behavior was observed. Similar behaviors were observed for specimens even without any shear reinforcement. When the CFRP strip strains of the specimens with anchorages and without anchorages were compared, maximum strains at anchored strips were approximately 56% larger than that of without anchorages. [ABSTRACT FROM PUBLISHER]

Every year, several prestressed concrete (PC) bridge girders are accidentally damaged by overheight vehicles or construction equipment impact. Although complete replacement is sometimes deemed necessary, repair and rehabilitation can be far more economical, especially when the time and the installation cost of the repair system are drastically reduced. The use of fiber-reinforced polymer (FRP) composites to restore the original capacity of impacted PC girders are being increasingly considered for bridge applications due to their high strength-to-weight ratios, corrosion and fatigue resistance, their ease of transport and handling and their potential for tailorability. Experimental data on full-scale PC girders strengthened by using FRP laminates are very limited; the present paper is intended as an extension of a previous experimental work conducted by writers [as reported by M. Di Ludovico et al. ACI Struct. J. 102(5), 97-109 (2005)] on three full-scale PC specimens. In particular, tests on five full-scale (1,300 mm long, 1,050 mm high) PC I-shaped girders with RC slabs, designed according to ANAS (Italian Transportation Institute) standard specifications, are presented. One beam was used as control and the other four were intentionally damaged in order to simulate a vehicle impact by removing the concrete cover and by cutting a different percentage of tendons (17% on two specimens and 33% on the remaining two). The repair, by using externally bonded carbon FRP (CFRP) laminates installed by wet manual layup, was aimed at restoring the ultimate flexural capacity of the member, taking particular attention to the laminate's anchoring system. Main experimental phases along with the comparison of tests results in terms of flexural capacity, deflections, strains, and failure modes are herein presented and discussed with reference to control, damaged, and CFRP strengthened specimens. The effectiveness of the adopted anchorage systems is also evaluated. [ABSTRACT FROM AUTHOR]

Use of anchoring devices can be useful to avoid or delay end debonding failure in reinforced concrete elements externally bonded with fiber-reinforced plastic materials. Many theoretical formulations are now available to predict bond strength, but no design provisions have been suggested to take into account the beneficial effect of anchorage devices. This paper presents the results of experimental bond tests performed on concrete blocks externally strengthened with carbon fiber sheets. The prime focus is the evaluation of effect given by three different types of anchorage systems upon increasing debonding load. A simple model is introduced to predict the influence of the examined anchorage systems on the debonding load. Its accuracy is confirmed by comparisons with the experimental results. [ABSTRACT FROM AUTHOR]

Abstract: Ballast stone deposits are a common feature of sediments in ancient harbour basins but are often overlooked as a potential source of archaeological information. Recent geophysical investigations at Caesarea Maritima in Israel have discovered a thick, laterally extensive ballast layer in the area seaward of the 1st c. BC Roman harbour. The ballast deposits were identified by low-relief mounds on the seabed with elevated magnetic intensities. Jet probing and excavation of magnetic anomalies at several locations revealed a 20–60cm thick rubble layer containing large quantities of Late Roman and Byzantine pottery, local sedimentary boulders (kurkar sandstone, limestone cobbles) and foreign igneous and metamorphic boulders (granite, schist, volcanics; ca. 50%). The foreign boulders and pottery identify the rubble layer as ballast and ships refuse jettisoned by merchant ships outside the harbour. The strong magnetic contrast between the ballast deposits and the natural seabed sediments is attributed to the high magnetic susceptibility (>10−3 SI) of crystalline boulders and pottery materials within the ballast rubble. AMS 14C and OSL dates and pottery evidence indicate the ballast accumulation began in the Late Roman period (ca. 200–330 AD) and continued well into the Late Byzantine (ca. 7th c. AD). The main phase of ballast deposition (ca. 4th–5th c. AD) coincided with a decline in the state of Caesarea''s harbour following a destructive tsunami event in the early 2nd c. AD and records a shift to a more intensive use of the area seaward of the harbour as an anchorage and ballast lightening area. [Copyright &y& Elsevier]

To assess the viability of the external confinement of normal-strength concrete beam–column joints with carbon fiber-reinforced polymer (CFRP) sheets in increasing the bond strength of hooked bars anchored in the joints, 12 hooked bar specimens were tested. The variables were beam tensile bar size, anchorage length, mode of confinement of the beam hooked bars in the beam–column joint (whether the hooked bars were anchored within or outside the column reinforcement cage, denoted as “confined specimens” or “unconfined specimens”), and presence or absence of FRP wraps. The specimen simulated the rigid connection of a cantilever beam to a column. The tensile beam reinforcement consisted of two bars anchored in the base column using hooked-bar anchorages. Test results indicated that FRP sheets were effective in increasing the anchorage capacity and the ductility of the load–deflection history for both unconfined and confined specimens. However, FRP sheets had a more significant influence on unconfined specimens than companion confined specimens. As compared with unconfined specimens without FRP wrapping, unconfined FRP specimens had an average of a 23% increase in bond strength, confined non-FRP specimens had an average 30% increase in bond strength, and confined FRP specimens had an increase of 54%. [ABSTRACT FROM AUTHOR]

Abstract: Debonding of the fixed length of ground anchorages is presented, concentrating on the failure behaviour of the bond at the proximal end of the fixed length. The dynamic effects of debonding along the fixed length are discussed in particular, with specific reference to dynamic testing. The static effects in terms of load distribution are also reviewed by comparing pull out tests undertaken on laboratory anchorages bonded using resin grout to results from a bond model included in a dynamic model. Bond models, which allow the dynamic effect of the debonding to be observed, are proposed for inclusion in the dynamic model. These models are an elastic–plastic yielding model with some residual load capacity and a model with reduced stiffness once the plastic-yielding regime has been entered. Simulations of an anchorage system including these bond models show both a change in load distribution and a drop in the first natural frequency due to debonding. Simulation of a case study is undertaken using the model and the results show good agreement with the measured field data. [Copyright &y& Elsevier]

The behavior of bridge monolithic connections is modeled using a simplified mathematical model that accounts for stress equilibrium, compatibility of deformations, and the state of bond of longitudinal column bars anchored through the joint panel. In this regard, a stress gradient factor is introduced, to model the profile of bar stresses along the anchorage. To establish this factor, two independent mechanisms of stress transfer are considered: a bond mechanism between the anchored bars and the surrounding concrete and a friction mechanism between the anchored bars and the transverse bars that enclose and restrain the anchorages. The model is used for calculation of the shear stress–shear strain relationship of all tests found in the international literature on bridge monolithic connections that showed shear type of failure under simulated seismic loading. Joint strength values calculated with the proposed model are compared with the experimental results. Based on this comparison the proposed model is verified for use in interpretation of bridge monolithic connection behavior and design. [ABSTRACT FROM AUTHOR]

Performance of near-surface mounted (NSM) bars as additional reinforcement in strengthening of existing reinforced-concrete construction largely depends on the development capacity of the bar inside the groove. This is controlled primarily by the surface characteristics of the bar and its interaction with the surrounding groove filler and the cover concrete. In this paper, the bond strength of short NSM-bar anchorages is explored experimentally, using a modified eccentric pullout test specimen designed to alleviate some of the deficiencies associated with bond testing. A total of 45 tests were conducted to study the influence of the most important technological parameters of this upgrading method, namely the groove dimensions, the embedment length, and the surface pattern of the bars. NSM bars were 12 mm diameter rods: CFRP bars used had a sandblasted surface and winding helical lengthwise indentations. Steel bars were either standard deformed bars or smooth reinforcement. The variety of bar type considered was intended to highlight and to quantify through the tests the bond strength that may be mobilized by postinstalled reinforcement according to surface profile and stiffness. Test results are used to establish a limit-state bond-slip model for near-surface mounted bars, so as to enable implementation of this emerging technology in practical design. [ABSTRACT FROM AUTHOR]

This paper presents a novel anchoring technique for strengthening reinforced concrete beams with prestressed carbon fiber- reinforced polymer (CFRP) sheets. Permanent steel anchors are commonly used for the application of prestressed CFRP sheets. The steel anchors are, however, susceptible to corrosion and may not blend into the aesthetics of the original structure. As a result, it may be preferable to remove the steel anchors after transferring the required prestress to the structure with minimal losses of sustained prestress. A technique for replacing the steel anchors with nonmetallic anchors is investigated and reported herein. Nine doubly reinforced concrete beams are tested with various types of nonmetallic anchor systems such as nonanchored U-wraps, mechanically anchored U-wraps, and CFRP sheet-anchored U-wraps. The developed nonmetallic anchorages successfully transfer the sustained prestress in the CFRP sheets with insignificant prestress losses. A closed-form solution for the transfer of prestress is developed and compared to the experimental results. [ABSTRACT FROM AUTHOR]

Four prestressed concrete beams were constructed and tested to investigate the effectiveness of flexural post-strengthening with prestressed carbon fiber-reinforced polymer (CFRP) strips. One of the beams served as a reference beam, another was bonded with an unstressed CFRP strip, and the remaining two specimens were strengthened with prestressed CFRP strips at two prestressing levels. The gradient method was used for the anchorage of the prestressed CFRP strips. Experimental and analytical calculations are compared with the test results. Further, different failure modes are explained. On the basis of this investigation, recommendations for the use of prestressed CFRP strips anchored with the gradient method are given. [ABSTRACT FROM AUTHOR]

This paper presents the flexural behavior of reinforced concrete beams strengthened with prestressed carbon fiber-reinforced polymer (CFRP) sheets using nonmetallic anchor systems. The developed nonmetallic anchor systems replace the permanent steel anchorage. Nine doubly reinforced concrete beams are tested with various types of nonmetallic anchor systems such as nonanchored U-wraps, mechanically anchored U-wraps, and CFRP sheet-anchored U-wraps. The flexural behavior of the tested beams, including detailed failure modes of each nonmetallic anchor system, is investigated. The study shows that the developed nonmetallic anchors are more effective in resisting peeling-off cracks compared to the permanent steel anchors and the beams strengthened with the nonmetallic anchors provide comparable load-carrying capacity with respect to the steel anchored control beam. [ABSTRACT FROM AUTHOR]

An experimental and analytical investigation of bond durability of E-glass fiber-reinforced polymer reinforcement bars in concrete beams is presented. Beams were conditioned with sustained flexural loads in indoor, outdoor, 60°C alkaline solution, or freeze/thaw environments for up to 3 years, after which they were subjected to eccentric three-point flexure tests to evaluate bond. Experimental bar force and slip were used to draw direct conclusions on bond durability, and also to calibrate a proposed local bond–slip model that incorporates concrete cover splitting. Experimental bar force at the onset of free-end slip varied little after any of the conditionings, although the characteristic of bond failure was noted to be less ductile in the moister environments. The interfacial fracture energy associated with bond–slip did not change with conditioning time in any of the environments except freeze/thaw, where a monotonic reduction versus time was seen. The effective bond length of the bar under various conditionings varied roughly in proportion to the local slip at complete local bond failure. [ABSTRACT FROM AUTHOR]

A proprietary product such as a post-installed concrete anchor has a unique place in the engineering community that includes product design, manufacturing, testing, evaluation and design for expected service conditions. An economic model in a non-linear integer programming form is proposed for selection of concrete anchors in order to minimize connection cost. It is shown that the model can be easily incorporated with available computer software packages and generalized when different parameters and constraints are imposed to handle a variety of material selections. The information from recent testing conducted by CEL Consulting for a major engineering, procurement and construction (EPC) contractor is used to provide computational results. The method introduced here adds practical value to these types of industrial problems because it considers points of view from both structural engineers and project managers. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on the bond behavior of longitudinal reinforcements in the hanging region (i.e., the part of the beam outside the support) of a simply supported reinforced concrete beam. Twenty-three reinforced concrete beams were tested to failure. Carbon fiber-reinforced polymer (CFRP) bars were used as longitudinal reinforcements in place of ordinary steel bars. The main test variables were (1) stirrup ratio in the hanging region; (2) stirrup ratio in the shear span; and (3) bond length in the hanging region. The test results showed that, even though the beam had a sufficient stirrup ratio in the shear span, bond-splitting failure occurred in the shear span of the beam with insufficient bond length in the hanging region. Based on the test results, the provision of ACI and AIJ codes on the additional anchorage length in the hanging region was evaluated, and a model for predicting tension force at the support was presented. [ABSTRACT FROM AUTHOR]

The secondary spiral and skin reinforcement in the anchorage zone of prestressed posttensioned girders causes congestion and poses difficulty in the placement of concrete. It is also labor intensive to produce and place secondary anchorage reinforcement. The objective of this study was to determine the feasibility of reducing the secondary reinforcement with steel fibers for posttensioned anchor zones. The AASHTO Special Anchorage Device Acceptance Test was performed in this study. Variations of spiral and skin reinforcement, with concrete strengths ranging from 37.9 MPa (5,500 psi) to 52 MPa (7,500 psi), were utilized to investigate the performance of the two types of steel fibers with various amounts. The experimental results indicated that 1% hooked-end steel fibers could eliminate all secondary reinforcement for a minimum concrete strength of 40.7 MPa (5,900 psi). Lower volumes of steel fibers may also be used to reduce secondary reinforcements. [ABSTRACT FROM AUTHOR]

This paper presents laboratory tests on a bond-type anchorage system and a full-scale ground anchor with fiber-reinforced polymer 9-bar tendons. A cement-based mortar filled steel tube was used to simulate a rock mass environment. Resistance strain gauges, fiber optic sensors, embedded strain gauges, and linear variable displacement transducers were used to monitor the behavior of the anchor and to study load transfer mechanism of the tendon to surrounding rock mass. The test results show that the developed bond-type anchorage performs well for post-tensing applications with the tendons. The tested anchor presents an acceptable tensile behavior for each loading stage investigated (up to a load level of 0.6ffu, where ffu=guaranteed capacity of the tendon) in accordance with existing codes. The anchor is similar in strain distribution profile to conventional steel anchors, except giving a shorter load transfer length. It is expected that the anchor require a minimum anchor bonded length of 2,000 mm with plain cement grouts. [ABSTRACT FROM AUTHOR]

Abstract: Modelling of existing reinforced concrete (r.c.) frames designed without specific seismic rules is a key problem for maintenance, structural upgrading and seismic assessment. In many European countries a very large percentage of reinforced concrete buildings are 40 years old, or even older; thus reinforcement consists of smooth rebars, since only in the 1970’s did early applications of deformed rebars appear. Technical literature on mechanical performances of anchored smooth rebars is non-comprehensive, mainly from the deformation standpoint, despite the relevance of this aspect to the response of critical regions, i.e. beam to column joints and column bases. In the present paper a series of experimental tests on smooth rebars are presented; they are aimed at describing in detail the force–slip relation for the bond mechanism for straight rebars and for anchoring end details, i.e. circular hooks with a 180∘ opening angle. [Copyright &y& Elsevier]

Thirty masonry walls strengthened using three different fiber-reinforced polymer (FRP) systems, with three anchorage methods, were fabricated and tested under a concentrated load over a 100 mm square area or a patch load over a 500 mm square area. The test results indicated a significant increase in the out-of-plane wall strength over the unstrengthened wall. While failure occurred in the unstrengthened wall by bending, four different modes of failure, that is, punching shear through the bricks, debonding of FRP reinforcement from the masonry substrate, crushing of brick in compression, and tensile rupture of the FRP reinforcement, were observed in the strengthened walls, depending on the types and configurations of FRP and anchorage systems. With appropriate surface preparation and anchorage systems, premature failure due to FRP debonding is prevented. Based on the principles of strain compatibility and force equilibrium, simple analytical models are presented to predict the ultimate load-carrying capacity of the strengthened walls. The test results compared well with the analytical predictions. [ABSTRACT FROM AUTHOR]

Deterioration of antenna tower foundations is fast becoming an issue of critical importance. A great effort has been carried out to develop the international standards for design and construction of antenna towers and antenna-supporting structures. Comparatively little attention has been directed toward the design against failure of buried tower components. In this paper a case study is introduced for the investigation of 51 defective foundations of self-supported and guyed antenna towers. Factors affecting the durability of tower anchorages and foundations are discussed. These include corrosion of tower parts in direct contact with soil, inadequate reinforcement detailing of tower foundations, and lack of maintenance of concrete footings. Repair methods of tower foundations are introduced along with tower shoring systems used to maintain the structural capacity during the repair process. Furthermore, precautions necessary for preventing failure due to corrosion of buried tower components and deterioration of anchor blocks and foundations are also discussed. An innovative system of surface anchor blocks for guyed towers is evaluated and compared to the conventional anchoring systems. [Copyright &y& Elsevier]