RC BEAMS SHEAR-STRENGTHENED WITH FABRIC-REINFORCED-CEMENTITIOUS-MATRIX (FRCM) COMPOSITE

The interest in retrofit/rehabilitation of existing concrete structures has increased due to degradation and/or introduction of more stringent design requirements. Among the externally-bonded strengthening systems fiber-reinforced polymers is the most widely known technology. Despite its effectiveness as a material system, the presence of an organic binder has some drawbacks that could be addressed by using in its place a cementitious binder as in fabric- reinforced cementitious matrix (FRCM) systems. The pur- pose of this paper is to evaluate the behavior of reinforced concrete (RC) beams strengthened in shear with U-wraps made of FRCM. An extensive experimental program was undertaken in order to understand and characterize this composite when used as a strengthening system. The labo- ratory results demonstrate the technical viability of FRCM for shear strengthening of RC beams. Based on the experi- mental and analytical results, FRCM increases shear strength but not proportionally to the number of fabric plies installed. On the other hand, FRCM failure modes are related with a high consistency to the amount of external reinforcement applied. Design considerations based on the algorithms proposed by ACI guidelines are also provided

Destructive and Non-Destructive Testing of Bridge J857 Phelps County, Missouri : Feasibility Study on Damage Detection of RC Structures using Dynamic Signature Tests

This report presents the results of a research program aimed at investigating the constructability and effectiveness of externally bonded FRP strengthening systems for improving the flexural capacity of bridge decks and piers. The joint effort of two universities, industry, and a state DOT provided the premise for a successful outcome. Bridge J857 was constructed in 1932 and was scheduled for demolition in the fall of 1998 due to highway realignment. Two of the three solid reinforced concrete (RC) decks were strengthened using two FRP systems namely, near-surface mounted carbon FRP (CFRP) rods and surface bonded CFRP sheets. Bridge decks were tested to failure under quasi-static loading cycles. Flexural strengthening of bridge columns was achieved by mounting CFRP rods on two opposite sides of the columns. Columns were also jacketed with carbon and glass FRP laminates. The experimental moment capacities of the decks compared well with theoretical values. Strengthened decks exhibited ductile behavior prior to FRP failure. The columns were tested to failure by applying lateral load cycles. The proposed strengthening technique for the bridge columns is feasible and effective for improving the flexural capacity of RC columns. The capacity of the strengthened column sections could be predicted using classical methods of analysis. Dynamic tests were conducted on the deck strengthened with CFRP sheets. The objective of dynamic tests was to relate the change in fundamental frequency to the induced damage, which could be used as a tool to assess the damage level of RC structural members. An effective damage indicator was identified that requires no baseline for damage level detection

Destructive and Non-Destructive Testing of Bridge J857 Phelps County, Missouri : Strengthening and Testing to Failure of Bridge Decks

Concrete bridges are conventionally reinforced with steel bars and/or prestressed with steel tendons. When subjected to aggressive environments, corrosion of the reinforcing and prestressing steel occurs and eventually leads to premature structural deterioration and loss of serviceability. In addition, the increasing service loads as well as seismic upgrade requirements result in a need to strengthen many of these bridges. The use of externally bonded steel plates for flexural and shear strengthening of concrete members is well established. However, corrosion related problems have limited the use of this technique for outdoor application. Fiber reinforced polymer (FRP) composites are corrosion resistant and exhibit several properties that make them suitable for repair/strengthening of reinforced concrete (RC) structures. However, the database for performance of FRP strengthened RC members is based on small-scale specimens that do not account for the variation of boundary conditions of a real structure. Fullscale field tests can demonstrate the actual behavior of a structure and can lead to a better understanding of the performance of the system and therefore strengthening design requirements. This part of the research program aimed at demonstrating the feasibility and effectiveness of strengthening bridge RC decks with two systems of externally bonded FRP reinforcement to increase their flexural strengths as well as verify design methodology and capacity improvement. Two of the three simply supported decks were strengthened and tested to failure. One span was strengthened using near-surface mounted (NSM) CFRP rods while the second span was strengthened using externally bonded CFRP strips. The objective of the strengthening scheme was to increase the flexural capacity by approximately 30%. Each of the three spans was tested to failure by applying quasi-static load cycles. Test results indicate that the actual capacity of the bridge decks were higher than anticipated due to higher actual material strengths. In addition, the decks had end fixities that were estimated by comparison of experimental and theoretical results. The experimental moment capacities compared well with theoretical values based on the actual material properties obtained from laboratory testing and the determined end fixity. Strengthened decks exhibited ductile behavior prior to FRP failure. The short-term behavior of FRP strengthening system applications has been experimentally evaluated. Research into longterm performance should be conducted even though FRP used in highway bridges is expected to perform for a long time. The final report consists of three volumes. Volume I depicts the strengthening and testing to failure of the three bridge decks. Volume II focuses on the laboratory and field dynamic tests. Volume III focuses on the strengthening and testing to failure of the bridge piers

Analytical and experimental shear evaluation of GFRP-reinforced concrete beams

Reinforced Concrete (RC) technology is advancing towards new frontiers enhancing its sustainability and durability through innovative materials. In particular, the application of Glass Fiber Reinforced Polymer (GFRP) bars, in lieu of steel reinforcement, shows excellent performance, especially in aggressive environments. Nevertheless, current international design guidelines and standards tend to be rather conservative, especially concerning shear reinforcement. This element hinders the technology’s competitiveness, not only in terms of material consumption but also in construction efficiency. This research aims to conduct an analytical comparison and experimental validation of the formulations found in some international standards pertaining to shear capacity in a specific case. The focus is on scenarios involving reduced shear reinforcement and cases where the number of stirrups falls below the minimum recommended by these standards. In the sample beam tests, two distinct flexural GFRP reinforcement ratios were employed to evaluate their influence on shear capacity, leading to diverse failure mechanisms: rupture of longitudinal GFRP bars and concrete crushing. The experimental results were used to compare the North American ACI, French AFGC, and Italian CNR shear capacity design approaches in the case of reduced transversal reinforced ratio. Analytical capacity expressions of the standards above are discussed with some remarks aiming at structural optimization

Can partial splenectomy preserve humoral immunity in pediatric patients? Risks and benefts of partial splenectomy

Te spleen plays an important role in removing normal and abnormal cells from the blood and in providing an immunologic response to encapsulated bacteria. Surgical splenectomy provides efective treatment for several pediatric disorders, such as congenital and acquired hemolytic anemias, abdominal traumas and immunological and metabolic disorders, but it is associated with an immediate and lifelong risk of overwhelming infection. An alternative to conventional splenectomy is partial splenectomy, recommended especially in children younger than 5 years of age. Recommendations for the prevention of overwhelming post-total splenectomy infection include: Pneumococcal, Haemophilus infuenzae type B and Meningococcal immunizations, antimicrobial prophylaxis and prompt antibiotic treatment of acute febrile illness; conversely, there is no clear evidence indicating which prevention measures are to be performed in patients undergoing partial splenectomy

Response to Snodgrass and Bush

We sincerely appreciate the comments made by Warren Snodgrass and Nicol Bush regarding our paper. First of all, we need to clarify that of our population of 130 patients only 66 have already reached pubertal development (55 in the preputial flap group and 11 in the staged repair). The aim of the published paper, as already clearly stated in our discussion, was limited to a retrospective analysis of the potential risk of development of megalourethra and fistula in this population. We fully agree that there is indeed a potential large amount of very important data retained in these series which may help to better understand some of the still unresolved questions on long-term outcome of hypospadias repair. Unfortunately we will need a few more years of follow-up before we will be able to fulfill these requests. Regarding the multiple questions mentioned we will try to provide some specific answers