bluuebunny/crossref_metadata_2025 huggingface dataset:
Canadian use of ground granulated blast-furnace slag as a supplementary cementing material for enhanced performance of concrete
Authors: Hooton R Doug
Published: April 2011

The performance of concrete, in terms of its placeability, physical properties, and its durability, can be enhanced by the use of slag-blended cements or separately added ground granulated blast-furnace slag. It also has advantages for architectural purposes due to the whiteness it imparts to concrete. Properly proportioned and cured slag concretes will control deleterious alkali-silica reactions, impart sulphate resistance, greatly reduce chloride ingress, and reduce heat of hydration. Setting times and early age strengths can be controlled through appropriate proportioning, while later age properties are typically enhanced. CSA and ASTM standards cover both slag-blended cements (CSA A362; ASTM C595; ASTM C1157) and slag as a supplementary cementing material (CSA A23.5; ASTM C989). Since Lafarge introduced the first large-scale slag grinding plant near Hamilton in 1976, slag has become the predominant supplementary cementing material in Ontario. Recently, its availability in the U.S. has expanded dramatically.Key words: blast-furnace slag, concrete performance, supplementary cementing material.
Experimental measurement and finite element analysis of the deformation of a high-pressure sluice gate
Authors: Chou Chuen-Shii , Lou Shou-Chih
Published: April 2011

The deformation of a high-pressure sluice gate under an orthogonal water pressure load of 0.539 MPa (i.e., 55 m water height), acting upon the upstream side of a gate leaf, was studied numerically and experimentally. The sluice gate was installed at the end of a water-release tunnel in the Nan-Hwa Reservoir, Nan-Hwa, Taiwan, R.O.C. The numerical results obtained using the ANSYS 5.5.2 finite element program agreed reasonably well with the experimental data. The deformation of this high-pressure sluice gate under water pressure loads of 0.736 MPa (i.e., 75 m water height) and 0.931 MPa (i.e., 95 m water height) was predicted by ANSYS 5.5.2. The research reported here may provide a method for establishing a safety monitoring system for any high-pressure gate and provide engineers with useful information to evaluate the possibility of increasing the capacity of an existing reservoir.Key words: sluice gate leaf, finite element method (FEM), strain gauge, water pressure.
Design equations for axially loaded reinforced concrete columns strengthened with fibre reinforced polymer wraps
Authors: Thériault Michèle , Neale Kenneth W
Published: April 2011

Step-by-step design procedures are proposed for the axial load capacity enhancement of circular and rectangular reinforced concrete columns confined with fibre reinforced polymer (FRP) wraps. The design methods are intended for practicing engineers in that they are relatively simple to apply and are made readily available in a design code format. Commentaries are presented to explain the design philosophy and rationale leading to the various design equations. For purposes of validation, numerical results based on the proposed design equations are compared against available experimental data. Strengthening limits, as governed by creep and fatigue phenomena, are also proposed. Whenever test data are found to be too limited, conservative approaches are adopted. Various experimental investigations are suggested for future work to further validate and update the design equations.Key words: FRP strengthening, concrete columns, axial loading, confinement, design.
Numerical simulation of A-type hydraulic jumps at positive steps
Authors: Sakarya A Burcu Altan , Tokyay Nuray Denli
Published: April 2011

A numerical simulation of the A-type hydraulic jump at a positive step, which is an example of mixed supercritical-subcritical flow with a discontinuity at the channel bed, is given by using an integral approach. A gradually varied subcritical flow over a rectangular, horizontal, and prismatic channel with an abrupt bottom rise is considered as the initial condition. Then, the upstream depth is decreased to a value producing a supercritical flow and remaining unchanged during computations. The resulting unsteady flow is solved by using both the MacCormack and the dissipative two-four schemes for the one-dimensional, unsteady Saint-Venant equations. In the numerical simulation, the step is treated as an internal boundary. At the downstream and the internal boundaries, the method of characteristics is employed to compute the relevant parameters. The numerical simulation is verified by comparing the results with the available data and analytical methods.Key words: hydraulic jump, positive step, numerical simulation, internal boundary.
Accelerated corrosion and repair of reinforced concrete columns using carbon fibre reinforced polymer sheets
Authors: Lee C , Bonacci J F , Thomas M DA , Maalej M , Khajehpour S , Hearn N , Pantazopoulou S , Sheikh S
Published: April 2011

An experimental study on the simulation of corrosion in large-scale reinforced concrete columns and their repair using carbon fibre reinforced polymer (CFRP) sheets is presented. Seven columns were subjected to an accelerated corrosion regime, wrapped using CFRP sheets, then tested to structural failure and (or) subjected to further post-repair accelerated corrosion, monitoring, and testing. Accelerated corrosion was achieved by adding sodium chloride to the mixing water, applying a current to the reinforcement cage, and subjecting the specimens to cyclic wetting and drying. Results showed that the CFRP repair greatly improved the strength of the repaired member and retarded the rate of post-repair corrosion. Moreover, subjecting the repaired column to extensive, post-repair corrosion resulted in no loss of strength or stiffness and only a slight reduction in the ductility of the repaired member.Key words: accelerated corrosion, carbon fibre reinforced polymer, composites, corrosion damage, corrosion rate, external confinement, reinforced concrete columns.
Pultruded fibre reinforced polymer reinforcements with embedded fibre optic sensors
Authors: Kalamkarov Alexander L , Georgiades Anastasis V , MacDonald Douglas O , Fitzgerald Stephen B
Published: April 2011

The use of the pultrusion process for the manufacture of fibre reinforced polymer (FRP) composites with embedded fibre optic sensors is discussed. The specific application is the use of smart composite reinforcements for strain monitoring in innovative concrete bridges and structures. The Bragg grating and Fabry-Perot fibre optic sensors are embedded during the pultrusion of FRP rods and the process-induced residual strains are evaluated using these sensors. The behaviour of optic sensors during pultrusion is assessed, and the effect of the embeddment of optical fibres and their surface coatings on the mechanical properties of the composite material is investigated. To verify the operation of the optic sensors embedded in the smart pultruded rods, mechanical tests were conducted and the output of the fibre optic sensors was compared to that of an extensometer. These mechanical tests were performed at room temperature as well as under conditions of low and high temperature extremes. The reliability assessment of the fibre optic sensors further entailed the study of their fatigue and creep behaviour as well as their performance when the rods in which they are embedded are placed in a severe environment (e.g., alkaline solutions) that may simulate conditions encountered in concrete structures wherein the composite rods will be used as prestressing tendons or rebars.Key words: smart composite reinforcements, fibre optic sensors, pultrusion, residual strain, fatigue and creep behaviour, reliability assessment.
A direct integration method for computation of gradually varied flow profiles
Authors: Ramamurthy A S , Saghravani S F , Balachandar R
Published: April 2011

A simple procedure to compute the length of gradually varied flow profiles is presented. It is based on the direct integration of the dynamic equation for gradually varied flow, which forms the bases for existing methods of computing flow profiles. In these methods, a long reach for which the profile length is needed gets divided into several subsections, to ensure that the hydraulic exponents do not vary very much in the subsections. Since the proposed analytical method does not use the hydraulic exponent in its development, the flow profiles can be computed in one step and one can still get accurate results. The results of the profile computations based on existing methods are compared with the corresponding results of the present method. The results find direct application in hydraulic engineering practice, where flow profile lengths are needed for design purposes. Key words: gradually varied flow, flow profile computation, open channel flow, backwater curve, drawdown curve.
Two-year deflections of the Confederation Bridge
Authors: Ghali Amin , Elbadry Mamdouh , Megally Sami
Published: April 2011

A comprehensive research program is currently in progress to monitor and study the behavior and performance of the Confederation Bridge. Part of this program is on monitoring short- and long-term deflections to evaluate the deflection prediction techniques employed in the design of concrete structures in general and this bridge in particular. The investigation comprises measurements of parameters related to the materials used in the bridge. This paper presents some field measurements of vertical deflection as well as the results of computer analysis. Short-term deflections are measured at the time of installation of precast units and also in truck-loading tests. After completion of construction, the deflections are measured at specified intervals. The last readings reported in this paper have been taken 27 months after completion of construction. The computer program CPF (Cracked Plane Frames in prestressed concrete) is employed for analysis of the monitored part of the Confederation Bridge. The bridge is modeled as a plane frame in which the nonprestressed and prestressed steels are considered. Several analyses are performed employing the actual time-dependent concrete properties measured in the field and those calculated from the ACI Committee 209 equations and CEB-FIP Model Code. Comparisons are made between the measured and the predicted deflections. The predicted deflections are found to be in close agreement with the measured values, which indicates that the deflection prediction techniques used in design of this bridge are adequate.Key words: computer analysis, concrete bridges, Confederation Bridge, creep, deflections, field measurements, long-term, prestressed steel, segmental construction, short-term, shrinkage, time-dependent.
Evaluation of the seismic response coefficient introduced in the Canadian Highway Bridge Design Code
Authors: Naumoski Nove , Cheung M S , Foo S
Published: April 2011

This paper describes results from an evaluation study of the elastic seismic response coefficient introduced in the Canadian Highway Bridge Design Code. The evaluation is conducted by comparing the seismic response coefficient with (i) uniform hazard spectra for selected cities in eastern and western Canada, (ii) spectra of numerically simulated ground motions for sites in British Columbia for scenario earthquakes on the Cascadia subduction zone, (iii) spectra of the 1988 Saguenay, Quebec, earthquake records and selected ensembles of recorded accelerograms from strong earthquakes around the world, and (iv) bridge design spectra of other countries. The results from this study show that the seismic response coefficient of the Canadian Highway Bridge Design Code is conservative in terms of the Canadian seismic hazard, with the exception of (i) sites close to the Cascadia subduction zone and (ii) sites for which the seismic hazard is governed by the effects of strong earthquakes at large epicentral distances. Key words: seismic, response, coefficient, acceleration, spectra, bridge, design, code.
Seismic design of low- and medium-rise chevron braced steel frames
Authors: Tremblay Robert , Robert Nathalie
Published: April 2011

This paper presents two different seismic design approaches for multistorey chevron (inverted V) steel braced frames. The first method complies with current Canadian code provisions in which the beams in the bracing bents must be designed to sustain the forces expected to develop up to buckling of the bracing members. In the second approach, the beams must also resist the gravity loads together with a fraction of the brace loads that are induced after buckling of the braces. This second approach aims at minimizing the degradation in storey shear resistance typically exhibited by chevron bracing subjected to strong ground motions, and it is proposed that such braced frames with reinforced beams be designed for reduced seismic loads. Both design procedures are applied to typical multistorey braced frames to examine their economical impacts. Three different beam strength levels were considered for the second design method. The results show that the saving expected from reducing the seismic loads in the second design approach is generally offset by the increase in beam sizes required by this method. However, the braced frames with stronger beams exhibit a much higher storey shear resistance after buckling of the bracing members has occurred.Key words: earthquakes, seismic, design, steel, structures, braced frames, bracing members, beams, columns, connections.
Study of tunnel outlet head-loss coefficient
Authors: Liu Minnan , Zhu David Z
Published: April 2011

In the design of diversion tunnels, culverts, and pressurized conduits, the outlet head-loss coefficient is generally assumed to be 1.0. However, the head loss can be reduced if a transitional expansion is added to the conduit outlet. This paper studies the reduction in the outlet loss coefficient by using the wingwalls at the tunnel outlet. The best wingwall diffusion angle is found to be 8°, which gives an outlet loss coefficient of 0.62-0.81 with a wingwall length of 2D, with D being the height of the tunnel. A wingwall length of 2D is also found to be suitable, as further increase in length only reduces the outlet loss coefficient marginally. An illustrating example shows that by adding wingwalls of 8° and a length of 2D the headwater level is decreased by 9-22% compared to the case without wingwalls for the same discharge.Key words: outlet, loss coefficient, diversion tunnel, wingwall, diffusion angle.
Analysis of cycle excavation and productivity of large-scale rock tunnel projects - lesson learned in Taiwan
Authors: Guo Sy-Jye
Published: April 2011

Tunnel construction has become a major part of infrastructure development in Taiwan in the 1990s. This study compares and analyzes the productivity difference in the construction of two large-scale long rock tunnels, i.e., the Pengshan and Nangkang No. 2 tunnels. These two tunnels, which are 3.8 and 2.7 km in length, respectively, are part of the Taipei-Ilan Expressway. The cross section, construction method, and contract type are all similar. Both projects utilized multi-skilled working crews for improving productivity. However, essential differences in productivity and monthly progress were recorded. This study analyzes the key factors for these differences regarding the geological condition, working crews, equipment and facilities, and management approach. Based on the productivity data analysis of the two tunnels, the key points for productivity improvement of large-scale rock tunnel projects are then pinpointed.Key words: cycle excavation, productivity, rock tunnel, Taiwan.
A methodology to estimate remaining service life of grey cast iron water mains
Authors: Rajani Balvant , Makar Jon
Published: April 2011

The decision to repair, renew, or replace existing old grey cast iron mains is typically based on performance indicators such as structural integrity, hydraulic efficiency, system reliability, and water quality. Structural integrity (often quantified as the number of main breaks per kilometre or mile per year) is the most common performance indicator. However, these indicators represent past performance, rather than expected future performance. Decisions based on performance indicators may not, therefore, accurately meet the real needs of the utility owner of the water distribution system. A preferred approach to make decisions on pipe repair and replacement is to determine the expected remaining service (residual) life of each pipe segment and ensure that the necessary work is performed before failure occurs. Past efforts to estimate remaining service life of water mains have been based on corrosion pit depth and estimated corrosion rate with no regard to the influence of corrosion on the structural resistance capacity of water mains. This paper describes a methodology to estimate the remaining service life of grey cast iron mains that takes corrosion pit induced changes in the structural resistance capacity into account. The methodology combines the residual resistance capacity of grey cast iron mains, anticipated corrosion rates, and the measurement of corrosion pits by direct inspection or non-destructive evaluation technology to predict when the factor of safety of an individual pipe segment will fall below a minimum acceptable value set by the utility owner, i.e., remaining service life. The estimate of remaining service life may then be used to schedule appropriate maintenance or replacement of grey cast iron mains.Key words: water mains, remaining service life, residual life, repair, renew, or rehabilitate water mains, corrosion models, pit and spun grey cast iron.
Effects of shrinkage on tension stiffening and cracking in reinforced concrete
Authors: Bischoff Peter H
Published: April 2011

Basic concepts of tension stiffening behaviour of reinforced concrete members under tension are reviewed, and different approaches to account for this behaviour are linked together. This includes a "load sharing" approach, where the average load carried by the cracked concrete is used to determine the post-cracking stressstrain response of concrete in tension, and a "tension stiffening strain" approach, which evaluates changes in member stiffness to obtain a reduction in member deformation by including the stiffening effect of the tension carried by concrete between cracks. Shrinkage strains are then included in an analysis of tension stiffening and the results of this analysis are validated with experimental data. The experimental study was carried out for symmetrically reinforced axial tension members having reinforcing percentages between 1% and 2% and shrinkage strain values up to 230 µε. Failure to account for initial member shortening caused by shrinkage leads to an apparent reduction in tension stiffening, which becomes more predominant as the percentage of reinforcement increases. Corrected results indicate that tension stiffening is independent of the reinforcing steel ratio, ρ (within the studied field for 1% < ρ < 2%) and continues to decrease during loading after cracking has stabilized. Test results are also compared with a number of proposals made by other researchers in the past. Prediction of crack widths based on results from axial tension member tests is not significantly affected by shrinkage.Key words: bond, cracking, crack widths, reinforced concrete, shrinkage, stress-strain response, tension, tension stiffening.
A probabilistic approach to analysis of ice loads for the Confederation Bridge
Authors: Brown T G , Jordaan I J , Croasdale K R
Published: April 2011

The main focus of the paper is the framework for analysing ice loads on the Confederation Bridge across the Northumberland Strait, using probabilistic methods. Safety targets were given as a beta factor of 4.0 for a 100-year lifetime, amounting to a probability of failure of about 3 × 10-7 per year. The ice regime comprises rafted and ridged ice, and peak loads are expected during March and April of each year. A simulation method was developed, in which loads are calculated corresponding to individual interactions associated with ridges in the ice floes that traverse the strait. The floes are driven by environmental driving forces, and the highest loads occur when these exceed the ridge failure loads. The load results from failure of the consolidated layer and rubble keel. Methods for the analysis of this are described. The determination of extreme loads depends on the number of interactions per year. Difficulties in modelling are described, together with techniques for analysis, such as updating of probability distributions given an interaction. Many of these techniques were derived from work related to the Beaufort Sea oil exploration. The results reflect a best-estimate approach to those parameters for which information was sketchy, or unavailable. They are therefore conditional on those estimates, but as the results are largely insensitive to these, the potential for error is minimal. There are a number of parameters (e.g., friction coefficient) that do have a significant effect and for which all those involved in the effort would have wished better definition. This sensitivity is reflected in the two sets of results presented in the paper.Key words: ice, forces, probabilistic, safety, bridges, modelling.
Hydrodynamic damping due to baffles in a rectangular tank
Authors: Isaacson Michael , Premasiri Sundaralingam
Published: April 2011

The present paper describes the prediction of hydrodynamic damping due to baffles in a fluid-filled rectangular tank or reservoir undergoing horizontal oscillations. The estimation of hydrodynamic damping involves an assessment of the total energy in the fluid associated with sloshing motions and the average rate of energy dissipation due to flow separation around the baffles. Experimental measurements of hydrodynamic damping have been carried out to validate the theoretical model and to investigate the effectiveness of various baffle configurations. Recommendations are made regarding the assessment of hydrodynamic damping in earthquake engineering applications.Key words: baffles, hydrodynamic damping, sloshing, tanks.
Seismic performance of low- and medium-rise chevron braced steel frames
Authors: Tremblay Robert , Robert Nathalie
Published: April 2011

This paper describes the seismic behaviour of chevron steel braced frames for 2-, 4-, 8-, and 12-storey steel building structures. Two different design approaches were considered: one that corresponds to current CSA-S16.1 seismic provisions for braced frames with nominal ductility with an R factor of 2.0, and one in which the beams are sized to develop a fraction of the yield tension capacity of the bracing members. In this second approach, an R factor of 3.0 was used for determining the seismic loads and chevron bracing with stronger beams capable of developing 100%, 80%, and 60% of the brace yield load were examined. The results show that current S16.1 provisions for chevron braced frames may lead to systems that are prone to dynamic instability for 4-storey and taller structures. Chevron bracing with stronger beams exhibits a more stable inelastic response and can be used for structures up to 8 storeys in height. For 2- and 4-storey buildings, chevron braced frames with beams designed to develop only 60% of the brace yield resistance can be used. The analyses also show that the force demand in brace connections, beams, and columns as determined from capacity design provisions agree well with that anticipated under strong ground motions.Key words: earthquakes, seismic design, steel, structures, braced frames, bracing members, beams, columns, connections.
An overview on the activation of reactivity of natural pozzolans
Authors: Shi Caijun
Published: April 2011

Natural pozzolan is one of the oldest construction materials. Lime-pozzolan cements have been used for several thousands of years and have an excellent reputation for their durability. Pozzolans are being widely used as a cement replacement in Portland cement concrete. The use of pozzolans has the advantage of lower costs and better durability, but the disadvantage of a longer setting time and a slower early strength development. Different techniques have been tried to increase the reactivity of natural pozzolans to overcome these disadvantages. This paper has reviewed various methods used to activate the pozzolanic activity of natural pozzolans. All activation methods can be classified into three catalogues: thermal, mechanical, and chemical activation. A comparison based on strengthcost relationship indicates that the chemical activation method is the most effective and cheapest one.Key words: activation, reactivity, natural pozzolans, pozzolanic reaction, calcination, elevated temperature curing, chemical activators, strength, cost.
Adequate data collection frequency and gauging length for surface condition rating in Alberta
Authors: El-Assaly Ashraf , AbouRizk Simaan , Stoeck Jane
Published: April 2011

In order to ensure safe and comfortable riding, increase network serviceability, and slow pavement deterioration rate, two different strategies are being used simultaneously by transportation departments: routine maintenance and major rehabilitation. Within Alberta Infrastructure, the decision between these alternatives is made based on the pavement condition. Data are collected frequently for the purpose of pavement evaluation. Experienced engineers and technicians normally decide the most appropriate data collection procedure and gauging length associated with it.Key words: pavement, data collection, evaluation, gauging length, condition rating.
Creep deformation of clay masonry structures: a parametric study
Authors: Sayed-Ahmed Ezzeldin Y , Shrive Nigel G , Tilleman Dan
Published: April 2011

When loads are applied to a masonry structure, viscoelastic behaviour is exhibited where the response can be divided into two distinct parts: an instantaneous elastic part and a time-dependent part. With the change in masonry construction during the last century, the latter portion of the response is becoming more important in the design of masonry structures. The effects of mortar type, stress level, age at loading, moisture condition, and masonry strength on the creep behaviour of clay masonry structures are examined. The results of a continuing experimental programme, begun in 1988, were used to evaluate the variations in specific creep of clay masonry with the different parameters considered. The test setup and the effect of moisture content on the creep behaviour of clay masonry are also described briefly.Key words: masonry, creep, specific creep, creep ratio, mortar type, moisture condition.
Effect of mechanical restraint on the rate of corrosion in concrete
Authors: Hearn N , Aiello J
Published: April 2011

Experimental work on prismatic concrete specimens was conducted to determine the relationship between mechanical restraint and the rate of corrosion. The current together with the changes in strain of the confining frame were monitored during the accelerated corrosion tests. The effect of mix design and cracking on the corrosion rates was also investigated. The results show that one-dimensional mechanical restraint retards the corrosion process, as indicated by the reduction in the steel loss. Improved quality of the matrix, with and without cracking, reduces the rate of steel loss. In the inferior quality concrete, the effect of cracking on the corrosion rate is minimal.Key words: corrosion, concrete, repair.
Construction project simulation using CYCLONE
Authors: Sawhney Anil , AbouRizk Simaan M , Halpin Daniel W
Published: April 2011

Construction simulation is a powerful tool that can be used by a construction company for a number of tasks such as productivity measurement, risk analysis, resource planning, design and analysis of construction methods, and site planning. The success of simulation at the construction-process level has led to a natural attempt to use simulation at the construction-project level. Cyclic Operations Network (CYCLONE) and related simulation methodologies have provided the fundamental basis of these developments. This paper describes the enhancements made to the CYCLONE modeling methodology to allow simultaneous simulation of processes involved in a construction project. The objective of these enhancements is to allow development of individual models for all the processes that constitute a project and then to link them so as to simulate them simultaneously using a common resource pool. Such a simulation experiment will allow the construction manager to realistically model, analyze, and plan construction projects. This paper provides the specifications required to perform a project-level simulation using the CYCLONE modeling concepts.Key words: construction planning, construction simulation, modeling, discrete-event simulation, resource management, process interaction.
A new steel anchorage system for post-tensioning applications using carbon fibre reinforced plastic tendons
Authors: Sayed-Ahmed Ezzeldin Y , Shrive Nigel G
Published: April 2011

During the past half century, the use of prestressing in different structures has increased tremendously. One of the most important techniques of prestressing is post-tensioning. The main problem associated with post-tensioning in different structures is the corrosion of the prestressing steel tendons even with well-protected steel. New materials, fibre reinforced plastics or polymers (FRP), which are more durable than steel, can be used for these tendons/strands and thus overcome the corrosion problem. However, different shortcomings appear when FRP tendons are introduced to post-tensioning prestressing applications. For carbon fibre plastic tendons (CFRP), there is no suitable anchorage system for post-tensioning applications. Some of the anchorages developed by others for use with FRPs are therefore described and assessed. A new anchorage system developed by the authors, which can be used with bonded or unbonded CFRP tendons in post-tensioning applications, is described. The results of direct tension and fatigue tests on CFRPs anchored with the new system are presented.Key words: anchorage system, cyclic loading, fatigue, fibre reinforced plastics, finite element analysis, post-tension, prestressed concrete, prestressed masonry, strands, tendons.
Stress concentration factors for non-90° X-connections made of square hollow sections
Authors: Packer J A , Wardenier J
Published: April 2011

A number of fatigue experiments and stress concentration factor measurements on non-90°, square hollow section X-connections have been carried out. Comparison of the measured stress concentration factors with those derived from existing parametric formulae for 90° T- and X-connections showed a strong influence of the brace angle. A tentative extension of the range of validity of the parametric formulae for 90° T- and X-connections for other brace angles has been derived.Key words: steel structures, connections, fatigue, hollow structural sections, hot spot stress, stress concentration factors.
Influence of cyclic test protocols on performance of wood-based shear walls
Authors: He Ming , Lam Frank , Prion Helmut GL
Published: April 2011

This paper compares the test results obtained from three cyclic test protocols in a series of studies on lateral resistance of wood-based shear walls built with oriented strand board panels. When the shear walls were subjected to a long sequence of cycle groups, the failure mode was dominated by low cycle fatigue failure of nail connectors which was rarely observed under seismic conditions. Alternate cyclic loading protocols with large amplitude but short sequence allowed shear walls to avoid this type of nail failure. The results also indicate that under the high amplitude short sequence cyclic test protocol, a higher racking resistance of the shear wall can be achieved which approaches the peak loads from monotonic tests.Key words: wood shear wall, oriented strand board, oversized panel, cyclic lateral loading, earthquake, connector failure mode, energy dissipation.
Estimation of bridge static response and vehicle weights by frequency response analysis
Authors: Thater G , Chang P , Schelling D R , Fu C C
Published: April 2011

A methodology is developed to more accurately estimate the static response of bridges due to moving vehicles. The method can also be used to predict dynamic responses induced by moving vehicles using weigh-in-motion (WIM) techniques. Historically, WIM is a well-developed technology used in highway research, since it has the advantage of allowing for the stealthy automatic collection of weight data for heavy trucks. However, the lack of accuracy in determining the dynamic effect in bridges has limited the potential for its use in estimating the fatigue life of bridge structures and their components. The method developed herein amends the current WIM procedures by filtering the dynamic responses accurately using the Fast Fourier Transform (FFT). Example applications of the proposed method are shown by using computer-generated data. The method is fast and improves the predicted truck weight up to 5% of the actual weight, as compared to errors up to 10% using the current WIM methods.Key words: weigh-in-motion, digital filters, FFT, bridge dynamics, in-service testing.
Strengthening of reinforced concrete beams with externally bonded fiber-reinforced-plastic plates: design guidelines for shear and flexure
Authors: Chaallal O , Nollet M -J , Perraton D
Published: April 2011

This paper presents a comprehensive design approach for reinforced concrete flexural beams and unidirectional slabs strengthened with externally bonded fiber-reinforced-plastic (FRP) plates. The approach complies with the Canadian Concrete Standard. The paper is divided into two parts, namely flexural strengthening and shear strengthening. In the first part, analytical models are presented for two families of failure modes: classical modes such as crushing of concrete in compression and tensile failure of the laminate, and premature modes such as debonding of the plate and ripping off of the concrete cover. These models are based on the common principles of compatibility of deformations and equilibrium of forces. They can be used to predict the ultimate strength in flexure that can be achieved by such elements, given the FRP cross-sectional area, or conversely, the required FRP cross-sectional area to achieve a targeted resisting moment for rehabilitated flexural elements. In the second part, design equations are derived to enable calculation of the required cross-sectional area of shear lateral FRP plates or strips for four plating patterns: vertical strips, inclined strips, wings, and U sheet jackets. A step by step procedure is also presented along with an easy to use flow chart. Finally, a numerical design example is provided to demonstrate the applicability of the approach. This study is believed to be timely and very useful for the practicing engineer.Key words: reinforced concrete, beams, slabs, strengthening, FRP, plates, design, flexure, shear, mode of failure, adhesive.
Supercritical flow at an abrupt drop: flow patterns and aeration
Authors: Chanson H , Toombes L
Published: April 2011

Stepped waterways and cascades are common features of storm waterways, at dam outlets, and in water treatment plants. At an abrupt drop, open channel flows are characterized by the presence of shock waves and a substantial flow aeration. There is, however, little information on the basic flow characteristics. The study presents new experimental data obtained in a 0.5-m-wide stepped flume with an unventilated nappe. The investigations describe the three-dimensional flow patterns, including shock waves, standing waves, and spray, downstream of the nappe impact. The characteristics of the flow patterns are similar to those observed with abrupt expansion supercritical flows. Downstream of the drop brink, substantial aeration takes place along the nappe interfaces and the flow downstream of the impact is deaerated.Key words: abrupt drop, supercritical flow, shock waves, flow patterns, cascade.
Ultimate strength of a box girder simulating the hull of a ship
Authors: Akhras Georges , Gibson Stephen , Yang Stephen , Morchat Richard
Published: April 2011

An important feature of ship design is the ability to describe the structural behaviour of the hull and to accurately predict its ultimate strength. Research on the ultimate strength of hulls has been carried out by many experimental research groups. Recently, the consensus reached is to simulate the behaviour of the hull by loading a box girder up to its ultimate strength. A box girder was tested at the Royal Military College of Canada. The objective of this experiment is to study the structural behaviour and compare the experimental results with the predictions of two computer codes. The construction of the model follows typical hull construction methods. The girder was subjected to pure bending until failure occurred. Provisions were taken so that collapse would occur due to buckling and not to plastic failure. Residual stresses and initial geometrical imperfections were measured and considered in the analysis. In previous publications, details of the design, fabrication, and loading were presented. In this paper, the experimental results are described and discussed.Key words: box girder, ship's hull, bending, ultimate strength, residual strength, residual stresses, initial imperfections.
Development of load and resistance factor design format for flexible pavements
Authors: Kim Hyung Bae , Harichandran Ronald S , Buch Neeraj
Published: April 2011

The objective of pavement design, just as with the design of other structures, is to provide economical designs at specified levels of reliability. Methods that yield designs with different levels of reliability are undesirable, and over the course of time design approaches in the United States have converged toward the load and resistance factor design (LRFD) format in order to assure uniform reliability. At present the LRFD format has been implemented in concrete, steel, wood, and bridge design specifications. In this paper, reliability concepts are used to illustrate the development of an LRFD format for fatigue design of flexible pavements. It is shown that 10 candidate pavement sections designed against premature fatigue failure according to standard practice using the DNPS86 software do not have uniform reliability. It is demonstrated that uniform reliability can be achieved by using the LRFD format. The work reported is based on assumed variations of pavement layer properties and on analytical formulation; field verification was not attempted.Key words: LRFD, reliability index, fatigue, partial safety factors, flexible pavement design.
Management of rubber dams in Hong Kong
Authors: Tam Paul Wing Ming , Zhang Xue-qing
Published: April 2011

The rubber dam is a relatively recent technological breakthrough. It was introduced to Hong Kong in the early 1960s. To date, a total of 20 rubber dams have been installed in Hong Kong. Most of the dams are used to impound water for irrigation. Due to its inflatable and deflatable characteristics, the rubber dam is excellent for flood mitigation and environmental protection. When a dam is inflated, it blocks water. When the river level reaches a preset value, the dam deflates automatically and the flood risk is reduced. Furthermore, silt deposits, debris, garbage, and animal wastes behind the dam can be removed by regular deflation. Much of the maintenance work required for rubber dams is related to punctures, which are simple to repair. The vulnerability of a rubber dam to damage by sharp objects or vandalism is the major disadvantage. Ceramic chips coating and stainless steel mesh have been used to strengthen the dam body against damage by sharp objects. Continual technological innovation is vital to the improvement of rubber dam performance. This paper highlights the various issues connected with rubber dam applications in Hong Kong, including procurement, construction, operation, maintenance, problems, and countermeasures.Key words: rubber dam, management, technological innovation, application, construction, operation, maintenance.
A survey of the bidding practices of Canadian civil engineering construction contractors
Authors: Fayek Aminah , Ghoshal Indrani , AbouRizk Simaan
Published: April 2011

This paper presents the findings of a survey of the bidding practices of Canadian civil engineering construction contractors. The results of the survey provide insight into the most important factors that contractors consider in making four bid decisions: the decision to bid, the risk allowance, the opportunity allowance, and the markup-size decision. The survey methodology is described to illustrate its effectiveness. Common practices in assessing risks and opportunities, the competition, and markup are discussed. A major conclusion of this paper is that the decision-making process used in bidding is largely subjective and based on experienced judgement. The assessment of the competition is done on an informal basis in most cases, with little use of historical competitor data. Risk and opportunity assessment is subjective and largely based on experience. Although the markup-size decision is critical to the success of a company in achieving its objectives and realizing a profit, markup setting is usually based on experience, with little or no formal methods of analysis.Key words: bidding, markup, risk analysis, surveys, tendering.
On the behaviour of low-volume unpaved resource access roads: effects of rehabilitation
Authors: Gnanendran C T , Beaulieu C
Published: April 2011

A new resurfacing method has been proposed recently for rehabilitating low-cost unpaved resource access (forest) roads using a mobile crusher. The quality and performance of the road rehabilitated using this new method have been a concern for some forestry companies and a study was initiated to compare it with the traditional resurfacing method where pit-run material is used. Two selected forest roads in New Brunswick, Canada, one resurfaced with the mobile crusher and the other resurfaced with pit-run material from a stationary crusher, were examined to assess the relative merits and deficiencies of the two methods. The particle-size distribution, maximum dry unit weight, and optimum water content for standard Proctor compaction were similar for the resurfacing materials derived from each method. The Benkelman beam deflection data suggest that the resulting roads from the two resurfacing methods were of similar structural capacity but the thickness of the gravel added and the level of compaction applied during resurfacing were different. Moreover, the materials from both methods contained a significant proportion of larger size particles exceeding 25.4 mm (1 in.) and failed to contain the required cohesive (binder) component.Key words: road rehabilitation, road resurfacing, mobile crusher, Benkelman beam, unpaved low volume road, forest road.
Impacts of full cost pricing on the sustainability of urban transportation: towards Canada's Kyoto commitments
Authors: Soberman Richard M , Miller Eric J
Published: April 2011

Certain concerns about sustainable transportation derive from the premise that significant atmospheric concentrations of carbon dioxide (CO2) and other greenhouse gases which contribute to global warming can be attributed to automotive emissions. Among measures considered to curtail automobile dependency and increase transit modal split, "full cost pricing" → a means of extracting both environmental costs and hidden subsidies which road users allegedly impose on society → has emerged as an increasingly popular suggestion. This paper examines the potential impact of full cost pricing on the "sustainability" of urban transportation, using Toronto as a case study. The analysis deals with the direct effects on mode choice and vehicle utilization resulting from increased user costs as might be achieved through fuel taxes or road pricing, as well as the indirect, longer term effects on location decisions. To investigate the land-use impacts, population distributions were altered to reflect more compact development and less urban sprawl as a proxy for relocations that might result from an increase in the costs of automobile use. Impacts are presented in terms of changes in total peak period vehicle-kilometres, mode split, and CO2 emissions. Despite several qualifications related to modelling techniques used in the case study, the analysis suggests that, overall, the impacts of large increases in road user costs appear to be less than proponents of full cost pricing would expect. In addition, the analysis suggests the fairly obvious, namely, that the greatest impacts of pricing occur within those choice markets where reasonable alternatives to the private automobile actually exist.Key words: sustainable transportation, road pricing, full cost pricing, urban transportation, emissions.
Indirect estimates of flexural strain in concrete sidewalks induced by vertical movement
Authors: Rajani B , Zhan C
Published: April 2011

This paper examines different numerical methods to estimate flexural strain from surface elevation measurements on concrete sidewalks. Surface elevations, along a typical concrete sidewalk cross section, were monitored on a monthly basis as part of a study to determine the cracking mechanism of concrete sidewalks. These measurements were carried out in Calgary, Edmonton, and Camrose, Alberta, between 1993 and mid-1995. Finite difference, cubic spline, polynomial fit, and Fourier series methods of analyses are described for an indirect estimation of flexural strains in sidewalks. The sensitivity of these methods to measurement error is discussed. The Fourier series method is found to be the best procedure to analyse sidewalk surface elevation data for flexural strains estimates. The numerical methods to indirectly determine strain are best suited for those circumstances where installation of strain gauges is difficult, expensive, or impossible.Key words: concrete sidewalks, indirect estimates of flexural strain.
An efficient analysis of continuum shear wall models
Authors: Ha Kinh H , Tan TMH
Published: April 2011

This paper formulates the stiffness matrix and a procedure for the analysis of a general class of coupled shear walls subjected to arbitrary loading and boundary conditions. The computed solutions for both deflections and stresses are exact in the sense that they satisfy the governing differential equation of the continuum shear theory, as well as all boundary conditions and inter-element compatibility. Explicit expressions are given for the formulation of the stiffness matrix and of the fixed-end forces for common loading conditions. The theory is also applicable to shear walls having variable stiffnesses and multiple bands of opening.Key words: coupled shear walls, stiffness matrix, finite element, structural analysis, structural design.
Connection of infill panels in steel plate shear walls
Authors: Schumacher A , Grondin G Y , Kulak G L
Published: April 2011

The behaviour under cyclic loading of unstiffened steel plate shear wall panels at their connection to the bounding beams and columns was investigated on full-size panel corner details. Four different infill panel connection details were tested to examine and compare their response to quasi-static cyclic loading. The load versus displacement response of the details showed gradual and stable deterioration at higher loads. The formation of tears in the connection details did not result in a loss of load-carrying capacity. In addition to the experimental program, a finite element model was developed to model the behaviour of one of the infill plate corner connection specimens. Results from the analysis showed that the finite element method can be used to obtain the load versus displacement behaviour of an infill panel-to-boundary member arrangement.Key words: cyclic loading, hysteresis, shear wall, steel, welded connection.