International Concrete Abstracts Portal

This paper suggests design guidelines for seismic retrofit of non-seismically designed reinforced concrete frames using High Performance Fiber Reinforced Concretes (HPFRCs), I.e., Slurry Infiltrated Mat Concrete (SIMCON) and Slurry Infiltrated Fiber Concrete (SIFCON). The following retrofit schemes are addressed: (1) column retrofit with either discontinuous or continuous SIMCON jackets, and (2) joint retrofit by either "internal" retrofit with prestressing bars or "external" SIMCON jacketing. Validity of the suggested guidelines was experimentally verified by testing a series of seismically retrofitted non-ductile beam-column sub-assemblages. Experimental data indicate that the suggested design procedure was appropriate for the retrofit design of the specimens. Additional experimental and analytical investigations are suggested to confirm the validity of proposed design approach for different beam-column connections. The paper focuses on the design procedure. Key pieces of information on the experimental investigation are only reviewed here and are presented in detail elsewhere [1].

SP-185 Up until now there has been very little information on the use of high-performance fiber-reinforced concrete (HPFRC). But recent laboratory studies and field applications show that HPFRC improves performance of civil engineering infrastructure in a cost-effective manner. This publication includes 11 papers on the mechanical properties of HPFRC for infrastructural repair and retrofit.

Following a brief introduction on the definition of high-performance fiber reinforced cement composites (HPFRCCs), this paper suggests that HPFRCCs are very well suited for repair and rehabilitation applications. It describes the range of tensile properties currently achievable using HPFRCCs, focusing in particular on the trade-off between strength and strain capacity and the importance of large strains, as evidenced by quasi-strain hardening behavior and multiple cracking. Particular attention is given to describing the tensile stress-strain response of slurry infiltrated fiber concrete (SIFCON), and the parameters influencing that response such as type of fiber, type of matrix, fiber orientation, fiber length, and fiber bond. Also a brief summary of three representative applications involving the use of HPFRCCs in repair and rehabilitation is given, namely: the use of fibers in the tensile zone area of reinforced concrete beams to control cracking and improve durability; the use of SIMCON for repair and rehabilitation of reinforced concrete beams and columns to satisfy seismic requirements; and the use of SIMCON as a jacket in reinforced concrete columns, also to improve seismic resistance. It is concluded that exceptional structural performance such as strength and ductility, particularly in reinforced and prestressed concrete structures, can be achieved if the matrix material is an HPFRC composite.

High performance fiber reinforced cement composites (HPFRC) are defined as the materials which exhibit a postpeak strain hardening type of response with a multiple crack pattern. Such a ductile behavior makes the HPFRC an ideal material to be used in structural repair and retrofit for dimensional stability, tensile-load carrying capacity, impact resistance, flexibility and long term impermeability. The critical parameter for continuous fiber reinforced cementitious materials to obtain the high performance response is the minimum fiber volume ratio with well dispersed fibers. As long as continuous fiber composites have a sufficient number of fibers to bridge the cracks, strain hardening and multiple cracking can always happen. However, there is no single dominant parameter which can control the multiple cracking process in discontinuous fiber composites. Various parameters can affect the postpeak response of discontinuous fiber reinforced cementitious materials. They are related to fibers, matrix and the processing methods. Parameters relating to the reinforcement include the type of fiber, fiber length, fiber volume ratio, fiber orientation, state of fiber dispersion and the degree of adhesion to the matrix. These primary variables are in turn influenced by selection of the matrix type, presence of additives, and the processing conditions. The latter acts through controlling the state of dispersion, establishing a fiber design a high performance fiber reinforced cementitious repair material, the approach in which the repair will be carried out should be considered simultaneously.

This paper reports the results of an investigation on the performance of FRC-encased open web steel joists under cyclic loading. The system completely eliminates the need for any shear connectors between steel joists and surrounding FRC as well as that for conventional longitudinal and transverse reinforcing bars, all of which are quite labor intensive. Cyclic load test on some half-scale specimens consisting of composite beams with end connections were carried out. The parameters included the configuration of web steel elements, and the amount of steel in longitudinal and web elements of the joists. The results are most encouraging. interact in a y so as to provide stable hysteretic behavior with excellent energy dissipation and ductuility. The study indicates that shear strength of the composite beam can be remarkably enhanced by addition of structures. The flexural capacity is also considerably increased. It can be quite accurately calculated by analytical models based on full composite action.