This paper presents a summary of current practice and recent developments in the application of passive energy dissipation systems for seismic protection of structures. The emphasis is on the application of passive energy dissipation systems within the framing of building structures. Major topics that are presented include basic principles of energy dissipation systems, descriptions of the mechanical behavior and mathematical modeling of selected passive energy dissipation devices, advantages and disadvantages of these devices, development of guidelines and design philosophy for analysis and design of structures employing energy dissipation devices, and design considerations that are unique to structures with energy dissipation devices. A selection of recent applications of passive energy dissipation systems is also presented.

Energy dissipation systems for seismic applications: Current practice and recent developments

A simple numerical model to predict the load-displacement response and energy dissipation characteristics of wood shear walls under general quasi-static cyclic loading is presented. In this model the shear wall is comprised of three structural components: rigid framing members, linear elastic sheathing panels, and nonlinear sheathing-to-framing connectors. The hysteretic model for the sheathing-to-framing connector takes account of pinching behavior and strength and stiffness degradation under cyclic loading. A robust displacement control solution strategy is utilized to predict the wall response under general cyclic loading protocols. The shear wall model has been incorporated into the computer program CASHEW (Cyclic Analysis of SHEar Walls). The predictive capabilities of this program are compared with monotonic and cyclic tests of full-scale wood shear walls. It is shown that this model can accurately predict the load-displacement response and energy dissipation characteristic of wood shear walls under general cyclic loading. As an application of the CASHEW program, a procedure is presented for calibrating a single degree-of-freedom system to predict the complete nonlinear dynamic response of shear walls under seismic loading.

Cyclic Analysis of Wood Shear Walls

This paper provides a critical evaluation of equations commonly used to compute short-term deflection for steel and fiber reinforced polymer (FRP) reinforced concrete beams Numerous proposals have been made for FRP in particular, and the different approaches are linked together by comparing the tension-stiffening component of each method Tension stiffening reflects the participation of concrete between cracks in stiffening the member response The Branson equation used in North America and other parts of the world is based on an empirically derived effective moment of inertia to calculate deflection The tension-stiffening component with this method is highly dependent on the applied level of loading relative to the cracking load as well as the ratio of uncracked-to-cracked transformed moment of inertia ( Ig ∕ Icr ) for the beam section Tension stiffening is overestimated for the high Ig ∕ Icr ratios typical with FRP concrete, leading to a much stiffer response and underprediction of member deflection

Reevaluation of Deflection Prediction for Concrete Beams Reinforced with Steel and Fiber Reinforced Polymer Bars

The aims of this research were to develop a simple method for the design of fiber-reinforced polymer (FRP)-reinforced beams and to determine if a common approach for steel and FRP-reinforced members is possible. A model is presented for calculating the concrete contribution to shear strength of reinforced concrete beams. The applicability of the model is supported by comparing the computed shear strengths with the experimental strengths of 370 specimens. The shear strength equation developed from the model is simplified to yield a design equation applicable for both steel and FRP-reinforced beams. The design equation is demonstrated to provide conservative results across the range of variables known to affect shear strength.

Concrete shear strength: another perspective

This paper presents a review of research on shear strength of reinforced concrete members without stirrups (shear reinforcement). A database of 1849 available experimental results from over the past 60 years is examined and these results are compared to predictions from current North American shear design procedures. Special attention is paid to the behavior of beams ranging from short span deep beams to members controlled by flexure. The findings from the review indicate that using the current ACI shear provisions to decide where shear reinforcement is required can be unconservative for members with larger effective depths, or higher stresses in the longitudinal reinforcement. Improvements to the ACI Code are proposed to mitigate these weaknesses. The AASHTO-LRFD and Canadian CSA sectional and strut-and-tie provisions are found to provide a more uniform level of safety for all member types. The results from this review can allow engineers to identify members in their own structure where a more conservative shear design procedure is appropriate.

Where is Shear Reinforcement Required? Review of Research Results and Design Procedures

This paper evaluates the shear strength, Vc, of intermediate length (2.5 ρb, were tested with three replicate beams per design. All samples failed as a result of diagonal-tension shear. Measured shear strengths at failure are compared with theoretical predictions calculated according to traditional steel-reinforced concrete procedures and recently published expressions intended for beams reinforced with GFRP. Recommendations are made regarding the adequacy of shear strength prediction equations for GFRP-reinforced members. The study concludes that shear capacity is significantly overestimated by the “Building Code Requirements for Structural Concrete and Commentary” (ACI 318-99) expression for, Vc, as a result of the large crack widths, small compression block, and reduced dowel action in ...

Shear Strength of Normal Strength Concrete Beams Reinforced with Deformed GFRP Bars

This paper investigates deflection behavior of concrete flexural members reinforced with glass fiber-reinforced polymer (GFRP) reinforcing bars. It is recognized that serviceability plays a major role in the design of GFRP-reinforced concrete beams. Therefore, accurate modeling of flexural stiffness is critical and the effect of influencing parameters must be considered. This study accounts for variations in concrete strength, reinforcement density, and shear span-depth ratio. Experimental results from 48 simply supported concrete beams reinforced with GFRP are compared with ACI Committee 440's published deflection model. The ACI 440.1R model is found to overestimate the effective moment of inertia, and an appropriate modification is presented.

Effective Moment of Inertia for Glass Fiber-Reinforced Polymer-Reinforced Concrete Beams

Engineers have proposed relocating externally bonded strengthening fiber reinforced polymer (FRP) material from the unprotected exterior of the concrete to the protected interior. This technology is known as near-surface mounted (NSM) strengthening. In NSM reinforcement, the FRP is surrounded by concrete on three sides so the bond and damage problems associated with externally bonded FRP strengthening systems are reduced or eliminated. This paper presents experimental results from 12 full-scale concrete beams strengthened with NSM carbon FRP (CFRP) strips. Three companion unstrengthened specimens were also tested to serve as a control. Experimental variables include three different ratios of steel reinforcement and two different ratios of CFRP reinforcement. Yield and ultimate strengths, flexural failure modes, and ductility are discussed based on measured load, deflection, and strain data. Test results show measurable increases in yield and ultimate strengths in all beams strengthened with CFRP as well as predictable nominal strengths and failure modes. Force transfer between the CFRP, epoxy grout, and surrounding concrete was able to develop the full tensile strength of the CFRP strips. Energy and deflection ductilities were reduced for CFRP strengthened beams. Future research needs are addressed.

Flexural behavior of concrete beams strengthened with near-surface-mounted cfrp strips

This paper evaluates the shear strength for normal and high strength concrete beams reinforced with longitudinal glass fiber reinforced polymer (GFRP) reinforcing bars and no web reinforcement The effect of reinforcement ratio is examined, and experimental data is compared with values predicted by FRP shear strength expressions found in the literature, including the new design expression recommended by ACI Committee 440 (2001)

Shear Strength of Normal and High Strength Concrete Beams Reinforced with GFRP Bars

Static and dynamic tests were conducted on wood frame shear walls to (1) determine the wall resistance to lateral loading; (2) examine the wall performance under fully reversed cycles of dynamic loading; and (3) compare the static and dynamic performance as measured using the same test facility. Tests were conducted on standard 2.44 by 2.44 m (8 by 8 ft) walls, constructed of plywood or oriented strand board sheathing. Four specimens were tested statically using the traditional ASTM E-564 test procedure: three half-cycles, loading monotonically to failure. Eight specimens were tested dynamically, using a proposed test standard that was recently developed by the Structural Engineers Association of Southern California. A comparison of the static and dynamic test results demonstrates several key differences. The ultimate loads measured in the dynamic tests are slightly less than those measured in the static tests; however, the ductility of the wall, when measured dynamically, is between 34 and 42% less than ...

David W. Dinehart

Papers

Shear Strength of Normal Strength Concrete Beams Reinforced with Deformed GFRP Bars

Effective Moment of Inertia for Glass Fiber-Reinforced Polymer-Reinforced Concrete Beams

Flexural behavior of concrete beams strengthened with near-surface-mounted cfrp strips

Shear Strength of Normal and High Strength Concrete Beams Reinforced with GFRP Bars

Comparison of static and dynamic response of timber shear walls