Publications

Performance of Structures During the 2004 Indian Ocean Tsunami and Tsunami Induced Forces for Structural Design

No abstract is provided for this article.

DESIGN OF FRP JACKETS FOR SEISMIC RETROFIT OF CIRCULAR CONCRETE COLUMNS

Analytical and experimental research was conducted to develop a design procedure for seismic retrofit of existing circular concrete columns using carbon fiber reinforced polymer (CFRP) jackets. The analytical research is an extension of earlier work on the development of a displacement based design procedure for column confinement. The experimental work involves full-size bridge columns tested under simulated seismic loading, consisting of constant axial compression and incrementally increasing lateral deformation reversals. The specimens are representatives of typical bridge columns between the footing and the point of inflection. One of the columns tested represents as-built conditions in practice with longitudinal reinforcement spliced near the base, providing an assessment of the deformability of existing columns. The test results indicate that the deformability of this column is limited to 1% lateral drift ratio. Companion columns with identical properties and CFRP jackets show that the deformability can be improved significantly through jacketing. CFRP jacketing of circular columns is effective in improving bond between reinforcement and concrete within the plastic hinge region while also confining the compression concrete. The lateral deformability of retrofitted columns shows improvements beyond 5% drift ratio. It is shown that columns satisfying the proposed design expressions develop ductile behavior, meeting the performance criterion adopted in design.

Preliminary evaluation of Pier cap from an ASR affected bridge in Central Canada

The Bridge, a highway bridge structure, was built using a suspected alkali-silica reactive aggregate in the 1960’s in a city in central Canada. Its concrete elements experienced rapid deterioration resulting in the need for costly increased repairs and rehabilitations. Alkali-silica reaction (ASR) is one of several damage mechanisms which might be contributing to damage of concrete elements. Infrastructure in central Canada experiences frequent freeze-thaw cycles, and heavy use of de-icing salts in winter as well as high heat and humidity in summer which might intensify distress. In recent years several concrete elements were selected for further assessment. Among them, five segments of a decommissioned Pier cap were selected for preliminary evaluation through visual inspection (conventional, semi-quantitative and quantitative using the cracking index) and non-destructive techniques (Schmidt hammer, ultrasonic pulse velocity and surface resistivity). Preliminary assessment results will be used to determine the appropriate locations (i.e., demonstrating the lowest/ highest deterioration) to extract cores for further assessment. Future work will be conducted on extracted cores using a multi-level assessment technique consisting of mechanical (compressive testing and stiffness-damage test) and microscopic procedures (the damage rating index and SEM) to assess the condition of the Pier cap.

Performance of Reinforced Concrete Structures During the 1992 Erzincan Earthquake

No abstract is provided for this article.

Combined Effects of Freeze-Thaw and Corrosion on Performance of RC Structures: State-of-the-Art Review

Freezing and thawing cycles (FTC) on RC columns are a significant problem for vulnerable infrastructure exposed to extreme climate conditions. This problem is exacerbated by the presence of deicing agents that lead to reinforcement corrosion and overall concrete deterioration. Current research has mainly focused on studying the mechanical properties of concrete when exposed to cyclic conditions of freezing and thawing. Few studies have analyzed FTC’s influence or the dual action of FTC and steel corrosion on the structural performance of RC. This paper surveys available literature on the synergistic effects of one or multiple environmental exposures on RC columns and methodologies for inducing frost damage according to current standards. The literature survey is organized as follows: (1) frost damage mechanism; (2) test methods to evaluate frost damage; (3) effect of FTC on concrete mechanical properties; (4) effect of FTC on the structural performance of RC columns; and (5) effect of dual action of FTC and steel corrosion on RC columns. Finally, this paper draws a series of conclusions and recommendations for future work.

ACI design handbook : design of structural reinforced concrete elements in accordance with ACI 318-05

No abstract is provided for this article.

Effect of corrosion on steel piles embedded in soils: State-of-the art review

Steel piles are widely used in the construction of civil infrastructure to support heavy loads from the superstructure in various types of soils and limit settlements. A key challenge associated with the design of buried steel piles is their gradual deterioration that can be predominantly attributed to corrosion. While corrosion mechanisms in atmospheric conditions are well understood, the long-term impact on the performance of buried steel piles in soils considering complex corrosion processes is less explored. Corrosion-induced degradation is of growing interest to both structural and geotechnical engineers because there is limited understanding of long-term performance and reliability of corroded steel piles behavior as infrastructure ages. This paper provides a comprehensive state-of-the-art literature review on the effect of corrosion on steel piles considering different scenarios of soil environments, focusing on experimental studies, prediction models, and numerical simulations. Current design methods for estimating pile bearing capacity are reviewed comprehensively, highlighting gaps in research and offering suggestions for future work. This review aims to guide the development of improved design approaches that account for corrosion, ensuring the long-term reliability and durability of steel pile foundations.

Quantification of Uplift Resistance of Adhesive-Applied Low-Slope Roof Configurations Subjected to Tensile Loading Test Protocol

The Adhesive-Applied Roofing System (AARS) is a new generation of built-up roofs gaining popularity in North American low-slope application. AARS uses no fasteners, and all components (e.g., steel deck, vapor barrier, insulation board, cover board, and membrane) are integrated by application of adhesives. Although AARS has been in use, existing standards address only mechanically attached or bonded roof assemblies. To quantify the wind-uplift performance of the AARS, an industry–university–government collaborative research project, Development of Wind Uplift Standard for Adhesive-Applied Low-Slope Roofing System, has been initiated. The project has three major tasks: experimental investigation, formulation of a numerical model, and development of wind design guide and standards. Task 1 developed test protocols to quantify the uplift and peel resistance of small-scale AARS specimens respectively subjected to tensile and shear loading. Using the standardized tensile test parameters, this paper identifies the effect of material combinations and variation in the adhesive applications on the uplift resistance of AARS subjected to tensile loading. This parametric study not only verified the applicability of the developed tensile test method for variations in the configurations, but it also identified the weakest link in AARS. Data from this small-scale testing can facilitate industries to optimize the material combinations such that it can be correlated with the systems wind uplift resistance.

STRESS-STRAIN MODEL FOR CONFINED REINFORCED CONCRETE IN BRIDGE PIERS. DISCUSSIONS AND CLOSURE

Two discussions of a paper with the aforementioned title by J. Hoshikuma, K. Kawashima, K. Nagaya, and A.W. Taylor, published in this journal (Volume 123, Number 5, May 1997), are presented. The first discusser presents a model that he proposed in 1991, which was developed on the basis of a large database including 63 column specimens with rectangular hoops from five different experimental programs. He also proposes that the effect of hook shape, the relationship between the strength of the unconfined specimens the authors tested to the cylinder strength, and the possible effect of longitudinal reinforcement warrant further investigation. The last two discussers present eight points that they believe deserve further attention before the authors' approach for confined concrete columns can be utilized. Discussions are followed by closure from the authors.

Comparison of Seismic Performance of HSC Columns Confined by FRP Tubes and Steel Reinforcement

No abstract is provided for this article.

Damage to concrete structures due to the 1994 Northridge earthquake

Observations on damage to concrete structures, due to the 1994 Northridge earthquake, are reported from a Canadian code perspective. Most of the damaged structures were older, nonductile, structures that do not conform to current design and detailing requirements. Concern is expressed about the seismic hazard of older Canadian structures having similar deficiencies. A significant number of parking structures suffered extensive damage and a number of precast concrete parking structures collapsed. Deficiencies in these structures include lack of proper diaphragm connections, a mix of gravity load columns with ductile framing, inappropriate number and distribution of shear walls, torsional effects caused by ramps, and the creation of short columns due to geometric features. This earthquake also demonstrated the deficiencies in connections of pre-1973 tilt-up structures. Key words: seismic design, earthquake, Northridge, structures, codes, concrete, precast concrete.

Performance of bridges in the 1994 Northridge earthquake

This paper describes damage to bridges caused by the 1994 earthquake at Northridge, California. A description of the damage and the probable causes are presented for the seven bridges that suffered some form of collapse. The majority of damage was due to column shear or combined shear and flexure failures, but restrainer failure was the cause of collapse in one bridge. The lack of damage to other bridges and to foundations is discussed. Key words: Northridge, earthquake, seismic, bridges, damage, performance.

Chloride ingress in pre-tensioned prestressed concrete beams and the effect of corrosion on their structural behaviour

Dynamic analysis of buildings for earthquake-resistant design

The proposed 2005 edition of the National Building Code of Canada specifies dynamic analysis as the preferred method for computing seismic design forces and deflections, while maintaining the equivalent static force method for areas of low seismicity and for buildings with certain height limitations. Dynamic analysis procedures are categorized as either linear (elastic) dynamic analysis, consisting of the elastic modal response spectrum method or the numerical integration linear time history method, or nonlinear (inelastic) response history analysis. While both linear and nonlinear analyses require careful analytical modelling, the latter requires additional considerations for proper simulation of hysteretic response and necessitates a special study that involves detailed review of design and supporting analyses by an independent team of engineers. The paper provides an overview of dynamic analysis procedures for use in seismic design, with discussions on mathematical modelling of structures, structural elements, and hysteretic response. A discussion of the determination of structural period to be used in association with the equivalent static force method is presented.Key words: dynamic analysis, earthquake engineering, elastic analysis, fundamental period, hysteretic modelling, inelastic analysis, National Building Code of Canada, seismic design, structural analysis, structural design.

High-Strength Concrete Columns: State of the Knowledge

This paper consists of reported information divided into two general categories, performance of High-Strength Concrete (HSC) columns under concentric loads, and combined axial and bending moments. Presented is a brief summary of the highlights of the reported data.

Response of Reinforced Concrete Columns to Simulated Seismic Loading

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Bond-slip modelling of reinforced concrete lap splices subjected to low and high strain rates

This paper presents an analytical model developed to predict the flexural load-deformation behavior of reinforced concrete members containing tension lap splices. The proposed model incorporates the effect of reinforcement slip of the lap splice and the effect of high strain rates on bond characteristics and material properties of concrete and steel. The main advantages of the proposed model are that bond-slip phenomena are captured through the use of pseudo-material stress-strain relationships, rather than giving consideration to the continuum of reinforcement and slippage over the entire structural element. Material properties and associated dynamic increase factors (DIF) are defined using accepted formulations. A suitable bond-slip law is presented and modified to account for the influence of strain rates on bond characteristics. Beam failure criteria are expressed in terms of a flexural failure of the member or a bond splitting failure of the splice. A comparison of the analytical predictions with experimental data demonstrated that the proposed analysis technique can reasonably predict the flexural response of beams with tension lap splices. The results also show that the model is equally applicable for use at low- and high- strain rate loading, such as those generated during blast and impact loading.

Generalized Schmertmann Equation for settlement estimation of shallow footings in saturated and unsaturated sands

Simple relationships are proposed in this paper by modifying the Schmertmann's equation for settlement estimations of footings (i.e., <TEX>$B/L{\approx}1$</TEX>) carrying vertical loads in saturated and unsaturated sandy soils. The modified method is developed using model plate load tests (PLTs) and cone penetration tests (CPTs) results conducted in saturated and unsaturated sand in a controlled laboratory environment. Seven in-situ large-scale footings tested under both saturated and unsaturated conditions in sands were used to validate the proposed technique. The results of the study are encouraging as they provide reliable estimates of the settlement of shallow footings in both saturated and unsaturated sands using the conventional CPT results.