Frieder Seible

USE OF FRP COMPOSITES IN CIVIL STRUCTURAL APPLICATIONS

Abstract Fiber reinforced polymer (FRP) composites or advanced composite materials are very attractive for use in civil engineering applications due to their high strength-to-weight and stiffness-to-weight ratios, corrosion resistance, light weight and potentially high durability. Their application is of most importance in the renewal of constructed facilities infrastructure such as buildings, bridges, pipelines, etc. Recently, their use has increased in the rehabilitation of concrete structures, mainly due to their tailorable performance characteristics, ease of application and low life cycle costs. These characteristics and the success of structural rehabilitation measures have led to the development of new lightweight structural concepts utilizing all FRP systems or new FRP/concrete composite systems. This paper presents an overview of the research and development of applications of advanced composites to civil infrastructure renewal at the University of California, San Diego (UCSD).

Design of seismic retrofit measures for concrete and masonry structures

Abstract The concept of seismic retrofit of older concrete and masonry structures possessing substandard seismic resistance using jackets or skins of composite fibres bonded with a polymer matrix to the surface is discussed. Results from extensive experimental research are presented to support simple design models enabling retrofit measures to be designed for enhanced shear strength, flexural ductility or lap-slice performance.

PIVOT HYSTERESIS MODEL FOR REINFORCED CONCRETE MEMBERS

For nonlinear dynamic seismic analysis of bridge structures to be practical, only the dominant nonlinear characteristics of the structure should be included. Based on capacity design principles, the current seismic bridge design philosophy is generally to force all member nonlinearities into the ends of ductile columns. Therefore, nonlinear characteristics of the columns must be adequately defined. In this paper, a hysteresis model is presented that accurately captures the nonlinear behavior of reinforced concrete members in terms of a force-displacement, or moment-rotation, response. What makes this model attractive, when compared with other hysteresis models, is that unsymmetric sections (nonsymmetric cross-section geometry and/or tension reinforcement amounts in the two loading directions), a cyclic axial load, and strength degradation may be included. The model is based on a few simple rules. Results based on the proposed hysteresis model show close agreement with various experiments on reinforced concrete members.

STRUCTURAL CHARACTERIZATION OF FIBER-REINFORCED COMPOSITE SHORT- AND MEDIUM-SPAN BRIDGE SYSTEMS

The paper describes the development of a new structural system for short and medium span bridges wherein use is made of both advanced composites and conventional materials such as concrete. The concept uses prefabricated composite tubes as girders which are then filled with concrete, after which a conventional precast or cast-in-place, or advanced composite, deck system is integrated to form the bridge superstructure. The paper presents experimental results of large-scale tests aimed towards the structural characterization of the girders, anchorages, and girder-deck assemblies for both serviceability and ultimate limit states.

Fiber Reinforced Composites – Advanced Materials for the Renewal of Civil Infrastructure

Fiber reinforced polymer matrix composite materials hitherto used predominantly in aerospace and marine applications are increasingly being considered for use in the renewal of civil infrastructure ranging from the seismic retrofit of bridge columns and the strengthening of parking garage floor slabs to their use in replacement bridge decks and in new bridge structures. Their corrosion resistance, potentially high overall durability, light weight, tailorability and high specific performance attributes enable their use in areas in which the use of conventional materials might be constrained due to durability, weight or lack of design flexibility. This paper provides an overview of the use of composites in the renewal of civil structures with particular emphasis on bridges and pipelines. Examples of large scale testing for the validation of structural effectiveness are given and future design and research advances are presented.

Experimental dynamic characterization of an FRP composite bridge superstructure assembly

A system comprised of concrete filled, filament wound, circular carbon/epoxy girders and an E-glass/polyester deck, representative of a bridge section in the positive moment region was tested at large scale to assess the overall and component structural response. The system was characterized for stiffness and overall response under monotonic and cyclic fatigue loads. Forced vibration testing was conducted as part of a level I non-destructive evaluation (NDE) procedure at each of the test stages, including after failure. Experimental results from the tests were seen to correspond well with analytical results for mode shapes and frequencies obtained through an eigenvalue analysis of a plane-grillage finite element model. The test method was shown to be effective in indicating changes in response as a function of load level and damage accumulation, and is expected to have significant potential for eventual routine health monitoring and damage detection of such structural systems in the field.

Development of a performance evaluation database for concrete bridge components and systems under simulated seismic loads

Through lessons learned in recent earthquakes, the need for new seismic bridge design methodologies that consider structural performance explicitly and address the inelastic response of bridge structures more directly is recognized. Efforts are in progress to define and quantify limit states and associated performance goals to develop a multi-level bridge design methodology. A multi-level design approach can only be implemented, however, when structural behavior or limit states can accurately be characterized and assessed for the wide range of probable input or demands. The outlined capacity assessment database addresses the response determination and parameterization of bridge components, sub-assemblages, and systems in direct support of the development of multi-level performance design and evaluation procedures for bridges. Through the use of a standardized template, a performance library for bridge structures, which is open for access and expansion to the entire practicing bridge engineering community, has been initiated.

FORCE-DISPLACEMENT CHARACTERIZATION OF WELL-CONFINED BRIDGE PIERS

This paper outlines an approach to estimating the horizontal force-displacement response of well-confined reinforced concrete bridge piers. Special attention is paid to the hollow rectangular piers designed to support 3 new toll bridges in the San Francisco Bay Area. This approach accurately assesses a piers elastic displacement, its spread of plasticity and plastic displacement, and its shear displacement for most ductility levels. The shear transfer mechanism inside a piers plastic hinge region is key to this assessment. This mechanism appears as a fanning crack pattern and results in concentrated compression strains at the base of a pier. These concentrated strains oppose the traditional notion of curvature that assumes plane sections remain plane. The assumption that there is a linear distribution of plastic curvatures inside the plastic hinge region, however, largely overcomes the problem of relating plastic curvatures to plastic rotations, both experimentally and analytically. At most levels of ductility, the mean difference between analytical assessments of the spread of plasticity and results from 12 large-scale structural tests is 16% with a 12% coefficient of variation.

Kings Stormwater Channel and I-5/Gilman Bridges, USA

Advanced composite materials, or fiber-reinforced polymer (FRP) composites, have found wide application in recent years in the rehabilitation of structures. Most of the primary structure applicatio...

Shear and Flexural Behavior of Lightweight Concrete Bridge Columns in Seismic Regions

This paper describes research related to the use of lightweight concrete for bridge column construction in seismic regions. Of interest is the behavior of columns dominated by shear as well as those dominated by flexure. A series of large-scale experimental tests was performed to assess the response of reinforced lightweight concrete columns in the inelastic range. Results indicate that a reduction in shear and flexural strength is appropriate for lightweight concrete, while displacement capacity and energy dissipation are not affected in a significant manner.