Gregor Fischer

INFLUENCE OF MATRIX DUCTILITY ON TENSION-STIFFENING BEHAVIOR OF STEEL REINFORCED ENGINEERED CEMENTITIOUS COMPOSITES (ECC)

In this paper, the interaction of structural steel reinforcement and high-performance fiber-reinforced cement composites (HPFRCC) in uniaxial tension is examined. The effects of cementitious composite ductility on the steel reinforced composite deformation behavior are experimentally studied and contrasted to normal reinforced concrete (RC). The substitution of brittle concrete with an engineered cementitious composite (ECC), a particular type of HPFRCC with strain hardening and multiple cracking properties, has shown to provide improved load-deformation characteristics in terms of RC tensile strength, deformation mode, and energy absorption. Analysis of the deformation mechanisms suggests that combining steel reinforcement and ECC results in composite action, where unlike in RC or regular FRC, both constituent materials deform compatibly in the postcracking and postyielding deformation process. This deformation compatibility results in a more uniform strain distribution in reinforcement and composite matrix, reduced interfacial bond stress, and controlled damage at relatively large inelastic composite deformations. Research described here focuses on the influence of composite ductility on the deformation behavior of the RC and its effects on the strain distribution in the reinforcement, composite matrix, and interfacial bond.

Effect of matrix ductility on deformation behavior of steel Reinforced ECC flexural members under reversed cyclic loading conditions

Summarizes the results of research aimed at investigating the effect of ductile deformation behavior of engineered cementitious composites (ECC) on the response of steel reinforced flexural members to lateral load reversals. The combination of a ductile cementitious matrix and steel reinforcement is found to result in improved energy dissipation capacity, reduction of transverse steel reinforcement requirements, and damage-tolerant inelastic deformation behavior. Basic concepts and composite deformation mechanisms of steel reinforced ECC are provided, experimentally verified, and compared to conventional reinforced concrete using small-scale specimens. Results indicate advantageous synergistic effects between ECC matrix and steel reinforcement with respect to compatible deformation, structural composite integrity, and damage evolution, and suggest integrating advanced materials design into the structural design process.

Performance of Bridge Deck Link Slabs Designed with Ductile Engineered Cementitious Composite

ACI Structural Journal/November-December 2004 ACI Structural Journal, V. 101, No. 6, November-December 2004. MS No. 03-156 received May 5, 2003, and reviewed under Institute publication policies. Copyright

DEFORMATION BEHAVIOR OF FIBER-REINFORCED POLYMER REINFORCED ENGINEERED CEMENTITIOUS COMPOSITE (ECC) FLEXURAL MEMBERS UNDER REVERSED CYCLIC LOADING CONDITIONS

Research provided herein studies the response of fiber-reinforced polymer (FRP) reinforced engineered cementitious composite (ECC) members, focusing on flexural load-deformation behavior, residual deflection, damage evolution, and failure mode. Critical aspects of conventional FRP-reinforced concrete members are reviewed and compared to FRP reinforced ECC. The interaction of linear FRP reinforcement and ECC matrix with ductile stress-strain behavior in tension results in nonlinear elastic flexural response characteristics with stable hysteretic behavior, small residual deflection, and ultimately gradual compression failure. Compatible deformations of reinforcement and matrix lead to low interfacial bond stress and prevent composite disintegration by bond splitting and cover spalling. Flexural stiffness and strength as well as crack formation and widths in FRP-reinforced ECC members are found effectively independent of interfacial bond properties due to the tensile deformation characteristics of the cementitious matrix. A model for the load-deflection envelope based on a nonlinear moment-curvature relationship is suggested.

Intrinsic Response Control of Moment-Resisting Frames Utilizing Advanced Composite Materials and Structural Elements

ACI Structural Journal/March-April 2003 ACI Structural Journal, V. 100, No. 2, March-April 2003. MS No. 01-377 received November 14, 2001, and reviewed under Institute publication policies. Copyright

Mechanical performance of sprayed engineered cementitious composite using wet-mix shotcreting process for repair applications

, V. 101, No. 1, January-February 2004.MS No. 02-473 received December 11, 2002, and reviewed under Institute publicationpolicies. Copyright

Auto-adaptive response modification in moment resisting frame structures

The response of the simplified moment resisting frame structure discussed in this paper is characterized by relatively large elastic deflection capacity with reduced residual deflections, auto-adaptive system stiffness modification, and considerable energy dissipation. The suggested structural system is assembled from particular column and beam elements with elastic and elastic/plastic load-deformation characteristics utilizing advanced composite materials and common construction technology without use of mechanical devices. Conventional frame structures, exclusively utilizing steel reinforced concrete members, ultimately form a collapse mechanism upon formation of plastic hinges in the beam and column members. While the flexural strength of the columns in the proposed system exceeds that of the beam as required in seismic design provisions, the relative stiffness of the frame members changes upon formation of plastic hinges in the beam element. This switching mechanism and the resulting modification of frame stiffness are inherent structural properties of the system, which can be adjusted to specific requirements in the design process. Although extensive inelastic rotation occurs in the beam element, plastic hinges at the column base are not required in order to initiate and utilize the energy dissipation potential of the beam element. In this frame configuration, the auto-adaptive stiffness modification is expected to reduce structural demand in terms of base shear forces under dynamic excitations while the formation of a kinemetic mechanism is prevented.

FRP reinforced ECC structural members under reversed cyclic loading conditions

Publisher Summary This chapter investigates the effect substituting brittle concrete with a ductile, fiber reinforced cementitious composite in combination with structural FRP reinforcement under reverse cyclic loading conditions. The engineered cementitious composite (ECC) represents one type of high performance fiber-reinforced cement composites (HPFRCC), which are designed with the intent of obtaining a high toughness composite material with pseudo strain-hardening and multiple cracking properties. The response of FRP reinforced flexural members to reversed cyclic loading conditions indicates nonlinear elastic load-deformation behavior with relatively small residual deflections. While the overall load-deformation behavior of FRP reinforced concrete and ECC show similarities, detailed differences have been established in terms of their composite deformation mechanism, damage evolution, and ultimate deflection capacity. Deformation compatibility between FRP reinforcement and ECC is found to effectively eliminate interfacial bond stress, and relative slip in the multiple cracking deformation regimes, preventing bond splitting and spalling of ECC cover. The incompatible deformations between reinforcement and concrete cause loss of interfacial bond, and composite action resulting in damage to the reinforcement and limited deflection capacity of the FRP reinforced concrete member.