bluuebunny/crossref_metadata_2025 huggingface dataset:
A review of fatigue strength improvement methods
Authors: Smith Ian F.C. , Hirt Manfred A.
Published: January 2010

Improving the fatigue strength of welded joints may be economically interesting in many situations, especially in those cases where high-strength steels are used. However, widespread use of a method is, in many cases, restricted by a lack of knowledge of its reliability. Previous work has focused only on the effectiveness of improvement methods to increase fatigue strength; cost studies and quality control instructions are rarely given.In this report, several methods for structural steel are summarized. A review of existing test results shows that improved connections made from a high yield strength steel reveal a higher percentage improvement than mild steel connections using the same improvement method. In addition, improved joints may be sensitive to the applied stress ratio. Finally, the most efficient method depends on the type of welded joint.Residual stress methods have relatively inexpensive application costs whereas some grinding methods are very costly. Quality control depends upon fabrication, loading, and environmental conditions. Examination of four types of fillet-welded joints has identified several methods that require further research. A three-dimensional finite element study of these joints predicts that at crack locations, under service loading, a very small plastic zone is formed. Therefore, residual stress methods may remain effective under variable-amplitude load conditions. Key words: structural steel, welded joints, fatigue, improvement methods, fillet welds, finite element analysis.
Fatigue of riveted connections
Authors: Baker K. A. , Kulak G. L.
Published: January 2010

The renovation or replacement of existing steel bridges in North America is a topic of increasing importance. Because most older structures used riveted connections, rather than the bolted or welded connections that are common today, information on the fatigue life of riveted connections is required for a proper evaluation of the structure.The study reported herein provides a summary and evaluation of the existing data on the fatigue strength of riveted connections, and reports on the results of fatigue tests on some highway bridge members taken from service. Fatigue tests were also carried out on new material containing unfilled holes, both as a reference for riveted connections (rivets with zero clamping force) and with respect to new work in which misplaced holes might be present. The beneficial effect of filling misplaced holes with high-strength bolts is noted. Key words: bolts, failure, fatigue, holes, steels.
Response of guyed tower to irregular waves for linear and nonlinear behaviour of mooring cables
Authors: Wishahy Momen A. , Arockiasamy M.
Published: January 2010

The dynamic response of a guyed tower to irregular waves has been studied by the finite element method. Hydrodynamic interaction is taken into account by the added water mass concept, and the fundamental frequencies are determined using (i) a lumped-parameter two-dimensional beam model and (ii) a three-dimensional truss finite element model. The effect of the mooring guy lines is simulated using one-dimensional boundary elements. The example structure analyzed is the Exxon test guyed tower erected in water of 89.3 m depth in the Gulf of Mexico. The measured wave height – time history reported by Exxon is used to determine the wave forces. Irregular wave forces are computed using the linearized Morison's equation. The nonlinearity of the mooring system is computed using an iterative technique in which the cable configuration is corrected using successive solutions. The tower response in terms of offset-time history to wave forces is determined for both linear and nonlinear cable behaviour. The computed frequencies and the responses agree reasonably well with the available measured values. Key words: guyed tower, irregular wave forces, linear and nonlinear mooring cable stiffness, dynamic response.
The strength of fillet welds under longitudinal and transverse shear: a paradox
Authors: Kennedy D. J. Laurie , Kriviak Gary J.
Published: January 2010

Fillet welds loaded only by transverse forces exhibit considerably greater strength than those loaded only by longitudinal forces. Current design standards in North America generally base the strength on the minimum value obtained in the longitudinal direction and consider that the strength is independent of the direction of loading. These standards require as well, that fillet welds loaded simultaneously by both longitudinal and transverse components be designed such that the vector sum of the components does not exceed the longitudinal strength. Experimental data, although limited, indicate that this vector approach is very conservative. Some standards do allow an ultimate strength analysis, although the method is not given. The transverse strength of fillet welds is about 1.45 times the longitudinal strength, and for angles of loading of up to 45° from the longitudinal axis, welds with transverse components have longitudinal capacities in excess of the longitudinal strength. Based on available test data, two alternative interaction relationships are proposed for the design of fillet welds loaded simultaneously by longitudinal and transverse forces. Key words: connections, design, fillet welds, longitudinal strength, transverse strength, steel.
A numerical model for beach profile development
Authors: Swain A. , Houston J. R.
Published: January 2010

A time-dependent numerical model that calculates beach profile development due to offshore sediment transport is developed. The model allows variable wave conditions, water level fluctuations due to tide, arbitrary bathymetry, and sediment size. The accuracy of the model is tested by comparison of calculations with laboratory and with field data. The agreement between calculated and measured beach profiles is good. Key words: numerical model, beach profile, laboratory tests, field data.
An analysis of pipe breakage in urban water distribution networks
Authors: Kettler A. J. , Goulter I. C.
Published: January 2010

The rates of pipe breakage with increasing pipe diameter and times are investigated. Failure rates for cast-iron pipe are found to decrease with increasing diameter. Changes in pipe failure rates for the various modes of failures are examined in detail. Asbestos-cement and cast-iron pipe overall failure rates are found to increase with time, but for different reasons. Analysis of the modes of failure shows that joint failure is predominant for cast-iron pipe systems with bolted and universal joints whereas the predominant mode of failure for asbestos-cement pipe systems is circumferential cracking. Key words: asbestos cement, cast iron, cracking, diameter, failure rate, joint, regression analysis.
A linear programming screening model for the Grand River Basin
Authors: Fortin Michael , McBean Edward A.
Published: January 2010

A linear programming screening model is developed to formulate a set of comprehensive water resource management plans using individual projects to deal with problems of flooding, water quality impairment, and municipal water supply shortfalls for the Grand River Basin Study. The value of the model is described as being the forcing of a system-wide approach by analysts, identifying interdependencies, directing technical analyses, and the formulation of management plans. Postoptimality procedures are used to test the sensitivity of derived management plans to parameters used to describe the Grand River Basin. Key words: water resources, management modelling, Grand River, linear programming.
Shear-bond resistance of composite deck-slabs
Authors: Seleim S. S. , Schuster R. M.
Published: January 2010

This paper presents an ultimate shear-bond equation for composite deck-slabs failing in shear-bond. The equation is based on recent experimental evidence of composite deck-slabs exhibiting early end-slip prior to ultimate load, and contains the steel deck thickness as a parameter, which other existing equations do not. The presence of the steel deck thickness parameter can result in a reduction of up to 75% of the presently required number of laboratory performance tests. A total of 196 test results was used to substantiate as well as to compare the results of the equation developed. The results of the developed equation were, in general, within the commonly accepted scatter range of ±15% of the corresponding experimental results. Key words: bonding, composite structures, shear strength, shear tests, slabs, structural engineering, ultimate strength, steel decking.
Concrete water tanks in Ontario
Authors: Slater W. M.
Published: January 2010

Since 1981, an Ontario provincial government study has been undertaken on the 53 concrete water tanks built in the province since 1956. Results of mainly external, but some internal, inspections, condition surveys, and ratings on an ascending 0–9 scale revealed a wide range in performance. This varied from failed tanks, rated 0 (two tanks), to very good performance, rated 9. The ratings were generally related to the tank types and construction method used. The best performance was exhibited by posttensioned bonded (PTB) types. The survey results and defects analysed revealed various problems and causes. These varied from specific construction methodology faults, such as slipform jack rods (pipes) left in the walls of certain types of tank, which filled with water and froze, to common defects, such as cold joints, experienced in all types, leading to leakage and freezing, and ice expansion in voids in tank walls during the winter. Actual concrete tensile stresses induced by internal ice formations, thermal gradients, and shrinkage stresses were found to be higher than those used in most designs or allowed in international codes or standards. As a result of the study, a provincial government rehabilitation programme for ministry-built tanks in need of repairs and leakproofing was started in mid-1982 in the order of priority ratings established during the study.
Snow loads on sloping roofs: two pilot studies in the Ottawa area
Authors: Taylor D. A.
Published: January 2010

The results of two pilot studies are presented: one concerning snow on farm roofs in the Ottawa area carried out in 1966, and the other an eight-winter investigation of the influence of surface roughness and slope on snow accumulation on nine 2.4 m × 2.4 m unheated, north-facing experimental roofs built in a sheltered woods at the National Research Council Canada in Ottawa. The results indicate a trend towards reduced snow density as slopes increase and a smaller accumulation of snow on smooth (metal) surfaces than on rough shingled roofs as slopes increase. More data on full-sized roofs across Canada are required to verify this. It is suggested that a less conservative slope-reduction relation might be considered for smooth roofs in the Ottawa area and for other areas with similar climate. Key words: snow loads, sliding snow, sloping roofs, snow depths, snow densities, surface roughness, pilot survey.
Expansive concrete drilled shafts
Authors: Sheikh Shamim A. , O'Neill Michael W. , Mehrazarin M. A.
Published: January 2010

A hypothesis is presented in this paper that states that expansive cement concrete produces a stronger bond between the concrete in a drilled shaft (bored pile) and the surrounding soil than does normal cement; this results in an increase in the frictional component of capacity and a reduction in the settlement of the shaft at working load levels.Four types of expansive cement, type "K" cement (the expansive cement available commercially) and three made from commercially available materials, were tested for their expansion characteristics; two of them were selected to be used in two instrumented drilled shafts in stiff clay. Normal (type 1) cement was used in a third shaft to serve as a reference. The three shafts were tested to failure after essentially all the expansion was deemed to have taken place in the two expansive concrete shafts. Lateral and longitudinal expansion of the shafts were monitored during the curing period. Load–settlement behaviour and load transfer between shafts and soil during the tests were studied.The test results permitted the preliminary conclusion that expansive cement concrete can increase the frictional capacity of drilled shafts in stiff clay by as much as 50% and reduce the settlement by about 50%. The results are valid for short-term behaviour of drilled shafts made of expansive cement. The long-term behaviour of such shafts remains to be studied. Key words: base bearing capacity, bored pile, cement (expansive), concrete (structural), drilled shaft, ettringite, expansion, frictional capacity, settlement, stress path.
Photoelastic study of postbuckled shear webs
Authors: Marsh Cedric
Published: January 2010

A model for the stress system in a stiffened shear web after initial buckling has been proposed that does not require the presence of diagonal tension. A square panel with thin edge flanges, composed of photoelastic material, was loaded in shear to study the stress distribution up to failure. The results showed that at a force some eight times the value causing initial buckling the shear stress along the boundary followed a hyperbolic distribution, with no normal boundary stresses. Web failure occurred when the ultimate shear stress was reached at the corners. The flanges were straight throughout, and remained intact after failure. Key words: plates, shear, buckling, postbuckling, photoelastic, plate girders, shear webs.
Snow loads in the 1985 National Building Code of Canada: Curved roofs
Authors: Kennedy Timothy H. R. , Kennedy D. J. Laurie , MacGregor James G. , Taylor Donald A.
Published: January 2010

In the 1985 edition of the National Building Code of Canada (NBCC) the intensity of the specified snow load at any location on a roof is obtained by multiplying the ground snow load for the building locale by a series of factors. These factors reflect the overall reduction in average snow loads on roofs as compared with that on the ground, the effect of exposure to wind, the effect of roof slope, and the effect of drifting, sliding, creep, and drainage.The four loading cases for the design of curved roofs suggested in the Commentary on snow loads accompanying the 1980 NBCC were examined by determining, for roofs of circular cross section, the variation across the span of load intensity, shear force, and bending moment for a wide range of spans, ground snow loads, and roof edge slopes. The purpose of the examination was to fully describe known inconsistencies arising from these loading cases.A new case for drift loading was developed (case III) that, when used with "full" or "uniform" loading and with the unbalanced loading developed for the 1977 NBCC (case II), eliminates or at least reduces the inconsistencies. With this new loading case and the derivation of a formula to define when to switch from loading case II to the new case III the designer now has to consider only one unbalanced loading condition rather than three as before.A simplified method for establishing specified load intensities, shear forces, and bending moments, suitable at least for preliminary design, is also presented. Key words: bending moments, curved roofs, drifts, load intensity, shear force, snow load factors, wind.
Recent advances in the computation of nonlinear wave effects on offshore structures
Authors: Isaacson Michael de St. Q.
Published: January 2010

The present paper provides a review of recent research on various nonlinearities that arise in ocean wave interactions with offshore structures. These include nonlinearities associated with the incident waves alone, the response of slender structural members to waves, and the nonlinear diffraction problem involving wave interactions with large structures. Emphasis is given to areas of current research into two particular nonlinear problems. One concerns an investigation into alternative approximations to the Morison equation for flexible structures and the other concerns the numerical simulation of nonlinear wave diffraction around large structures. Key words: diffraction, hydrodynamics, nonlinear flow, ocean engineering, offshore structures, waves.
Simulation of particle concentration distribution in primary clarifiers
Authors: Abdel-Gawad Sameh , McCorquodale John A.
Published: January 2010

A numerical model to simulate the performance of both rectangular and circular primary clarifiers is presented. The proposed model is restricted to those mean steady flows that are isothermal, of neutral density, low in solids concentration, and nearly two-dimensional.The strip integral technique is used to reduce the partial differential equations of continuity, momentum, and mass transport to a set of ordinary differential equations. The resulting set of equations is numerically integrated using a fifth-order, Runge–Kutta method.The full numerical model contains a hydrodynamic submodel and a transport submodel. The hydrodynamic submodel predicts the velocity field and dispersion characteristics within the clarifier, which are prerequisite for the transport submodel.The model, as presented here, was used to simulate the circular tanks used in the cities of Windsor, Ontario and Waterloo, Ontario. The predicted concentration profiles and removal efficiency were in good agreement with the measured values. Key words: numerical model, primary clarifiers, strip integral technique, transport model, concentration profiles, removal efficiency.
Annacis cable-stayed bridge—design for earthquake
Authors: Taylor P. R. , Selst A. M. van , Hodge W. E. , Sexsmith R. G.
Published: January 2010

The 465 m span Annacis cable-stayed bridge, currently under construction near Vancouver, British Columbia, will be the longest cable-stayed span in the world when it is completed in 1986. As this bridge is partially founded on soft delta deposits and is located within 80 km of a seismic source zone, its design has required careful consideration of earthquake effects. This paper reports the seismic analytical and design approaches adopted for the foundations and superstructure of the bridge. Details covered include dynamic modelling of the subsoil layers, correlation of measured surface accelerations with those predicted by computer modelling from nearby rock accelerations, earthquake risk analysis, assessment of the soil liquefaction potential, compliance of deep piles and pier translation during ground shaking, dynamic modelling of the superstructure, ductility and displacement demands in the superstructure, and details for construction. Key words: bridges, earthquake.
Erosion of unconsolidated gravel beds
Authors: Chee S. P. , Yuen E. M.
Published: January 2010

In any riverbed degradation phenomenon, the vertical dimension of the deepest part of the scour hole is a pertinent parameter since all the other erosion parameters describing the configuration of the scour hole depend on its numerical value. Hence, it is necessary to be able to evaluate the maximum depth of the scour hole.For most practical situations, the impingement of submerged water jets on a granular riverbed occurs at an angle, and it is the object of this study to include the effects of obliqueness in the analysis. Some examples of the effects of impingement by water jets are the erosion problems caused by plunging water jets from hydraulic control structures as they discharge into the tail-water downstream.Basic to an understanding of the mechanism of local scour is the concept of "initiation of motion." Hence, the analytical study will use this concept to derive generalized relations that will link the incipient motion condition at the deepest point of the scour hole with the numerical value of the scoured depth. In addition, care was taken to ensure that only those hydraulic variables that are frequently used in hydraulic engineering design are included in the analysis in order to make the results useful to practicing engineers. Key words: local scour, maximum erosion, river bed, plunge basin, diving jets, energy dissipation, riverbed degradation.
Rotational ground motion and seismic codes
Authors: Rutenberg A. , Heidebrecht A. C.
Published: January 2010

The primary purpose of this paper is to discuss the separation of travelling wave effects from the mass center to resistance center eccentricity effects, and to propose means by which the torsional spectrum (or a torsional seismic factor) could be incorporated in the seismic provisions of the National Building Code of Canada. The paper begins the treatment of the subject matter by presenting a detailed review of previous work on the effects of torsional ground motion, emphasizing the methods which have been proposed to develop torsional response spectra. The travelling wave assumption is critically reviewed and the effective phase velocities applicable for design purposes are discussed. This is followed by a simple analysis showing how the torsional spectra can be derived directly from the corresponding translational response spectra. Formulae separating the torsional input effects from the accidental eccentricity effects are presented and discussed. Finally, it is shown how the torsional spectrum can be incorporated within the framework of the response spectrum procedure of the 1985 edition of the National Building Code of Canada. Key words: seismic, earthquake, structure, dynamic, rotation, code, torsion, foundation, eccentricity, response spectrum, acceleration, velocity, design.
Behaviour of truss plate and metal web joints in machine-stress-rated lumber trusses
Authors: Keenan F. J. , Lepper M. M. , Quaile A. T. , Aplin E. N.
Published: January 2010

In project A, 1500 pieces of 38 × 89 mm spruce–pine–fir lumber from three mills, in two machine-stress-rated (MSR) grades, 1650f–1.5E and 2100f–1.8E, were proof-loaded to obtain the mean modulus of elasticity, the fifth percentile modulus of elasticity, and the fifth percentile modulus of rupture. Relative density was measured for each piece, and values of the 33.3 and 52.3 percentiles of the relative density ranges were determined for each species/grade category and related to the minimum values stipulated by the National Lumber Grades Authority (NLGA) Special Product Standard SPS-2-82 for machine-stress-rated lumber. The values of relative density at the 33.3 and 52.3 percentiles that will cause the NLGA mean modulus of elasticity MOE (mean), criterion to be just barely satisfied were estimated.In project B, the lateral resistances of 480 truss plate joints were determined. The variables were two common types of truss plates (thicknesses of 0.91 mm and 1.5 mm) in two grades of MSR lumber (1650f–1.5E and 2100f–1.8E) subdivided into two species groups (pine alone and spruce–fir combined), tested at four orientations of load to grain and load to plate axis. These tests showed that, in most cases, an increase in the design capacity of truss plates in MSR lumber over the values now used for spruce–pine–fir lumber is justified.In project C, 30 commercially designed metal web floor trusses of three span/depth combinations were tested to determine their stiffnesses and strengths. Trusses with 2100f grade lumber in the chords were stiffer than the trusses with 1650f chords. In both grades, larger trusses are relatively less stiff than smaller trusses. With respect to strength, the results indicate that higher design values may be used with higher grades of MSR lumber provided that design is governed by either tooth withdrawal at the joints or by chord strength. An improved analytical model, taking into account four distinct failure modes, is required for the behaviour of floor trusses. Key words: machine-stress-rated lumber, truss plates, trusses, metal webs, strength, density.
Influence of flow contraction on solids removal in a small circular clarifier
Authors: Wigglesworth Joseph , Silveston P. L. , Hudgins R. R.
Published: January 2010

Tests were conducted on a 1.22 m (4 ft) diameter clarifier in which a flow contraction baffle had been installed. This baffle accelerated the flow towards the overflow weir at the outer diameter of the tank. Removal rates for suspended solids were improved by 18–20% by the use of flow contraction in comparison with a conventional clarifier of the same size. A partial flow contraction baffle gave similar results. Results suggest that the capacity of large-scale clarifiers might be extended by retrofitting them with flow contraction baffles. Key words: clarifier, flow contraction, internal waves.
Column design methods for timber engineering
Authors: Buchanan Andrew H. , Johns Kenneth C. , Madsen Borg
Published: January 2010

Combined bending and axial loading is often encountered in lumber and timber members. Existing design methods are based on studies carried out many years ago, and are no longer appropriate because they do not recognize that wood with defects behaves in compression as a nonlinear ductile material and in tension as an elastic brittle material subject to size effects.This paper summarizes the findings of a comprehensive investigation into the behaviour of lumber subjected to eccentric axial loading, which was carried out at two Canadian universities. The study included analytical modelling and an extensive experimental program using full-size lumber.The results of the investigation have been used in this paper to propose improved design methods, using design charts and approximate formulae for in-plane behaviour. The discussion is extended to general loading cases and biaxial behaviour. Input information required for the design process is also discussed.
Field assessment of a floating tire breakwater
Authors: Bishop Craig T.
Published: January 2010

A field monitoring program of a Goodyear floating tire breakwater (FTB) was undertaken at La Salle Park, Burlington, Ontario, during 1981 and 1982. Incident and transmitted waves were measured with underwater pressure transducers. The resulting wave height transmission data compares favourably with previous results from model studies. Mooring loads on some anchor lines were measured with two electronic and four mechanical gauges. The resulting peak load data, corresponding to incident wave heights up to 0.65 m, are in good agreement with previous results from prototype scale model studies. Key words: coastal engineering, floating tire breakwaters, marinas, pressure gauges, mooring forces, waves.
Wastewater treatment alternatives for municipalities along a stream system
Authors: Pineau M. , Villeneuve J. P. , Boudreault P.
Published: January 2010

Since 1978, the government of the province of Quebec has undertaken an important water pollution control program. Under this program, new wastewater treatment plants are to be constructed in many municipalities of the Yamaska watershed (Quebec) by 1990. From an engineering point of view, one of the major issues in planning the construction of these treatment facilities is the selection of the wastewater treatment alternatives to be implemented at each municipality of the watershed. Using case studies from the Yamaska watershed, the present study illustrates the role and importance of three factors for the analysis and the selection of wastewater treatment alternatives. These factors are (1) the standards, as related to the receiving stream, (2) the discharge point interactions through the receiving stream system, and (3) the various possibilities for joint or separate treatment of municipal and industrial wastewater. Examples are given of the economical implications that may result from these factors. While each factor was dealt with separately for the purpose of this study, it is clear that they are strongly related and that they interact. As a result, the selection of wastewater treatment alternatives is fundamentally a system-based problem rather than a case-by-case problem. Key words: wastewater treatment alternatives, treatment process, standards, receiving stream, stream system, joint treatment, separate treatment, wastewater treatment costs, decision analysis, systems analysis, Yamaska River, urban wastewater, industrial wastewater, economical implication.
Plastic behaviour of unstiffened symmetrical beam-to-column flange connections
Authors: El-Ghazaly Hany A. , Sherbourne Archibald N.
Published: January 2010

Present specifications to prevent premature elastic–plastic buckling of the column web in symmetric moment connections are based on limited semiempirical evidence because costs of a total experimental investigation are prohibitive and an accepted generalized theory for elastoplastic plate bifurcation is lacking. Finite element formulations, based on an incremental version of a deformation theory combined with appropriate iterative techniques, have been recently developed and displayed both accuracy and adaptability to elastoplastic plate buckling problems for general loading–unloading–reloading history.In the present paper the developed numerical technique has been used to conduct a limited parametric investigation studying the effects of a column axial load on the interaction between beam tension and compression zones as reflected in the stability of symmetrical moment connections. Both quantitative and qualitative measurements have been obtained but, more importantly, the behaviour and capacity of symmetrical moment connections as governed by elastic–plastic buckling of the column web are examined. The paper concludes by emphasizing the necessity to reconsider the present specifications controlling the buckling capacity of the column web in connections since parameters such as those considered in the present paper may have significant effects on the plastic buckling capacity. Key words: symmetrical moment connections, plastic buckling, column web, finite element, axial load, beam depth.
Effects of agricultural drainage on streamflow in the Middle Thames River, Ontario, 1949–1980
Authors: Serrano Sergio E. , Whiteley Hugh R. , Irwin Ross W.
Published: January 2010

The effects of surface and subsurface agricultural drainage on streamflow in the Middle Thames River have been studied through the analysis of changes in the volumetric response, changes in the seasonal distribution of streamflow volumes, and changes in the time distribution of runoff response of the Middle Thames in the period 1949–1980.The results indicated that only small changes in streamflow behaviour occurred in the Middle Thames for the period studied. There is evidence of a reduction of less than 25% in the time-to-peak of storm hydrographs on the watershed, but with little change in peak flow rate or centroid-to-centroid lag time. This is consistent with increased channel velocities in hydraulically improved municipal drains, coupled with an increased proportion of storm flow being diverted from overland runoff to rapid subsurface runoff through subsurface pipe drainage. There is no evidence of appreciable changes in volumes of runoff for individual storms or as annual total streamflow or changes in seasonal distribution of streamflow. Key words: agricultural drainage, streamflow, unit hydrograph, storm runoff.
Mechanical stabilization for the control of frost heave
Authors: Kettle R. J. , McCabe E. Y.
Published: January 2010

This paper is concerned with the role of mechanical stabilization in controlling frost susceptibility. This has been assessed in terms of the heave, developed over a 250 h period, of cylindrical specimens subjected to the Transport and Road Research Laboratory (United Kingdom) frost heave test. The basic soil matrix consisted of a highly susceptible mixture of sand and ground chalk. Three types of coarse particle (slag, basalt, limestone) were used as the stabilizing agent, and these were each subdivided into two particle groups: 20−3.35 mm and 37.5−20 mm.The introduction of up to 50% of the selected coarse aggregates produced various non-frost-susceptible mixtures. The influence of the coarse aggregate was very dependent on aggregate type but less dependent on aggregate size. The data have been examined to assess the role of these coarser particles in the freezing process, including the effects of their individual characteristics. This clearly demonstrated the possibility of using mechanical stabilization to control frost susceptibility and this was supported by the results of additional tests on natural soil. Heaving pressures are also reported and are examined in relation to the amount of aggregate added, nature of the aggregate, and particle size. The addition of coarse aggregate to the matrix is shown to reduce the measured heaving pressures. Key words: frost heave, heaving pressure, granular materials, mechanical stabilization.
Seismic liquefaction probability for Canadian offshore regions
Authors: Atkinson Gail M.
Published: January 2010

Seismically induced liquefaction is a potential hazard to petroleum developments in Canadian offshore regions. This paper addresses the hazard to eastern Canada's continental margin and the Beaufort Sea. To indicate the probability of seismically induced liquefaction, maps have been produced that contour the minimum value of soil resistant (N1) required in order that the probability be less than 0.001/a. Expected acceleration levels for this probability level are also provided. For many areas, liquefaction is a greater hazard to offshore structures than that directly attributable to vibratory ground shaking. Key words: seismic hazards, liquefaction, offshore structures, Beaufort Sea, continental shelf, probability, Canadian offshore, ground motion, soil stability.
Reliability-based design criteria for timber bridges in Ontario
Authors: Nowak Andrzej S. , Taylor Raymond J.
Published: January 2010

The new Ontario Highway Bridge Design Code (OHBDC) is based on limit states theory and therefore uses a load and resistance factor format. This paper deals with the development of the basis for the timber bridge design provisions (OHBDC). Three structural systems are considered: sawn timber stringers, laminated nailed decks, and prestressed laminated decks. The latter system has been successfully used in Ontario for the last 7 years.The acceptance criterion in calculation of load and resistance factors is structural reliability. It is required that bridges designed using the new code must have a reliability equal to or greater than a preselected target value. Reliability is measured in terms of the reliability index. The safety analysis is performed for a structural system rather than for individual members. The live load model was developed on the basis of available truck survey data. Material properties are based on extensive in-grade test results. Numerical examples are included to demonstrate the presented approach. Key words: bridge deck, design code, prestressed timber, reliability, reliability index, stringers, structural safety, timber bridges.
The influence of the energy stored in the test apparatus on the strength of lumber
Authors: Madsen Borg , Mindess Sidney
Published: January 2010

The problem of the behaviour of lumber at the low end of the strength distribution is slowly being unravelled. It appears that this lumber behaves more like a brittle material than had been previously assumed. This paper describes a test program in which matched samples (N = 88) of lumber were tested using different loading systems. It was found that the systems in which energy was stored in the testing machine gave apparent strengths that were lower than those obtained in a deformation-controlled setup. Since failure is caused by crack growth, it is postulated that the available stored energy is the cause of the observed strength differences. The difference between the two systems was found to be strength dependent (larger for the weaker pieces), and at the 5th percentile amounted to about 30%. The implications for the development of characteristic strength and design data are outlined.
Effects of phosphorus removal chemicals upon methane production during anaerobic sludge digestion
Authors: Kindzierski Warren B. , Hrudey Steve E.
Published: January 2010

Aluminum sulphate (alum) and ferric chloride are commonly employed to aid phosphorus removal in wastewater treatment. Previous studies have indicated that these chemical coagulants produce sludges that adversely affect anaerobic digestion. The objective of this study was to assess the magnitude of the effects chemical coagulants have upon methane generation in anaerobic digestion. Methane production was monitored and concentrations of aluminum or iron present during batch digestion of chemically precipitated sludge were measured.Both alum and ferric chloride addition to activated sludge produced a sludge that demonstrated reduced methane production in batch anaerobic digestion. Neither metal inhibited methanogenesis of an acetate supplement, suggesting that chemical toxicity was not a likely explanation for overall reductions in methane formation. Considering the experimental results and the findings of others, reduced methane generation is most likely caused by physical isolation of degradable substrate by the coagulant floc, which causes an overall reduction in conversion of sludge volatile solids to methane.
Development of a simulation model for the Port of Thunder Bay
Authors: Easa Said M.
Published: January 2010

This paper presents a computer simulation model, PORTSIM, that was developed for the grain terminals of the Port of Thunder Bay. In addition to simulating ship arrival and grain loading characteristics, the model incorporates two distinct features of the port. These features are the movements of ships between berths to load different grades of grain and the impact of the rail-side operation on port performance.The paper first reviews existing simulation models and presents an overview of the operations of the port. Model details are then presented and include its logic and structure, design of experiments, measures of performance, and model input/output. In particular, the model provides several measures of performance, including average waiting time of ships, average queue length, berth utilization, port throughput, and maximum queue length. These measures are useful in assessing future improvements in the port. Some practical applications of the model and areas of future expansion of its capabilities are discussed. Key words: port, grain terminals, simulation model, ship arrival, grain loading, performance measures, practical applications.
Storm water pollution modelling: first-order atmospheric dustfall processes that affect runoff quality
Authors: Shivalingaiah Boregowda , James William
Published: January 2010

The buildup of surface pollutants has been shown to be a controlling factor in the quality of storm water runoff. In industrial areas particularly, atmospheric fallout is an important component of surface pollutant loadings. Storm water runoff models presently in use do not consider the physics of atmospheric dustfall.Industries, vehicle exhausts, and blowing of wind over unprotected surfaces all introduce pollutants to the atmosphere. Redistribution of this material on the ground depends on local topography and prevailing meteorological conditions. The location of the industrial areas; the direction, velocity, and duration of wind; total precipitation; and source concentrations are important parameters in the prediction of atmospheric dustfall. The paper describes the physical processes of atmospheric fallout that are relevant to water quality modelling. A new model, called ATMDST, to predict dustfall on individual subcatchments in a metropolitan area using prevailing meteorological conditions is developed based on statistical methods. Results from average, one-variable and two-variable linear regression models were statistically compared with observed data. Finally, ATMDST is interfaced with the storm water management model version 3 (SWMM3) to compute runoff water quality. The model is applied to Hamilton, Ontario. Key words: atmospheric dustfall, air pollution, urban runoff, water quality, pollutant buildup, environmental modelling.
Winter ice regime in the tidal estuaries of the northeastern portion of the Bay of Fundy, New Brunswick
Authors: Desplanque Con , Bray Dale I.
Published: January 2010

As more engineering works are constructed in the upper sections of tidal estuaries in northern regions, it is imperative that engineers become aware of the primary processes related to ice formation, degradation, and breakup in such environments. Since the tidal behaviour can be estimated from astronomical considerations, it is possible to make reasonable estimates concerning the timing and the relative significance of the ice buildup in a particular estuary. A classification system for the ice regime of well-mixed estuaries with a large tidal range is presented. Five distinct zones within the estuary are identified by considering the primary ice-related processes in such estuaries. The worst case for the formation of significant ice accumulations in these estuaries is considered to be that associated with a sequence of freezing temperatures occurring when the difference between the neap tide and the subsequent spring tide is greatest. During this period, significant vertical ice walls can form in a few days. The ice walls that form in the upper portion of the estuaries of the Memramcook River and the Petitcodiac River can reach a height of about 5 m. As the vertical ice walls are formed they significantly reduce the normal trapezoidal cross section, which has side slopes in the order of 1.0V:3.5H, to a rectangular cross section having about the same bottom width. Key words: ice, estuaries, processes, ice walls, classification system, Bay of Fundy, engineering works.
Ice pressures and behaviour at Adams Island, winter 1983/1984
Authors: Frederking R. , Wessels E. , Maxwell J. B. , Prinsenberg S. , Sayed M.
Published: January 2010

As a continuation of an ongoing project, measurements of environmental conditions and ice cover responses were made around Adams Island over the winter of 1983/1984. These included current, tide, speed and direction of wind, air temperature, and thickness, temperature, and salinity of the ice. Wind profiles were measured over the ice surface; from these, drag coefficients of 0.001–0.005 were calculated. Horizontal movement rates of the ice cover varied from 20 to 300 mm/day. No direct correlation was found between ice cover movement and the wind and current measurements. In situ ice pressures measured around the island averaged 250 kPa. Key words: ice pressures, environmental forces, ice behaviour, field instrumentation.
LAVSED-I — Un modèle pour prédire l'érosion des bassins et le transfert de sédiments fins dans les cours d'eau nordiques
Authors: Frenette M. , Julien P. Y.
Published: January 2010

Computer modeling techniques are used for predicting soil losses from overland flow and subsequent suspended sediment yield from large watersheds. The model LAVSED-I (LAVal SEDidentological model No. 1) is based on the universal soil-loss equation of Wischmeier and Smith and the equation of Kiline and Richardson. The model subdivides the watershed into square units varying in size from 0.3 to 3000 km2 and the computational procedure is subdivided in four components: precipitation, physical characteristics of watersheds, erosion/sedimentation, and land use. This paper describes the operational development and the application of the model to a prototype-scale watershed. A map for the annual soil loss is presented for the Chaudière watershed (area = 5830 km2). Results of mapping compared with the sediment yield observed are shown in the paper.
Duration of load tests for shear strength
Authors: Spencer R. A. , Madsen Borg
Published: January 2010

The strength of wood falls with time under load, and in current design codes the short-term strength of wood is reduced by about 40% to account for duration of load effects. This figure is based on tests made on small bending specimens. In this paper are described tests made on wooden torque tubes to investigate the effect of duration of load on shear strength. A control sample was tested to establish a curve for short-term strength, and four groups of 80 specimens each were then tested under various levels of constant long-term load. Stress ratio at failure was estimated by assuming that the short-term strength of each group could be represented by the control curve, and that under long-term loading specimens would fail in the order of their short-term strength. In each group the stress ratio at failure fell with time under load, and this reduction appears to be related to that predicted by a viscoelastic plastic model. It is concluded that the Madison curve presently used to predict duration of load effects may be conservative at normal levels of applied stress. Key words: wood, shear, long-term loading, duration of load.
Long-term behavior of expansive concrete drilled shafts
Authors: Sheikh Shamim A. , O'Neill Michael W.
Published: January 2010

The research reported here is a continuation of work reported earlier in which it was concluded that the use of expansive cement concrete increased the side resistance of drilled shafts (bored piles) in stiff clay by as much as 50% over that in normal concrete shafts and reduced the settlement by about 50%. The conclusions were based on tests conducted at a concrete age of about 2 months. A year and a half later, the three shafts (one made with normal concrete and two made with expansive concrete) were tested again and the same comparatively better behavior of expansive concrete shafts was observed. The base capacities of all the shafts increased over this period owing to the consolidation of soil caused by residual base stresses following the initial tests. The shafts were later extracted for visual observation and coring. The compression tests on concrete cores obtained from various depths along the shafts indicated that expansive concrete behaves as a sound structural material in the long term. The gains in strength and stiffness of expansive concrete over normal concrete over a period of 2 years were found to be significant. Key words: base bearing capacity, bored pile, cement (expansive), concrete (structural), drilled shaft, expansion, frictional capacity, long-term behavior, settlement.
Trace element leaching in bench-scale recirculating ash transport systems
Authors: Constable Thomas W. , Ross Geoff
Published: January 2010

Fly and bottom ash from coal-fired power generating stations are commonly disposed by transporting the ash in a water slurry to a lagoon. The recently developed "Environmental codes of practice for steam electric power generation" recommend the use of recycled lagoon decant water rather than fresh makeup water for these sluicing operations. To provide background information during the development of these environmental codes of practice, bench-scale studies were conducted to simulate the operation of recirculating bottom ash and combined fly/bottom ash lagoon systems, and data were collected on the concentrations of trace elements in the ash sluice waters. The ashes were obtained from seven Canadian coal-fuelled power generating stations. For most ash systems, the pH of the slurry water remained relatively constant after the first two recirculation cycles, and generally was lower in a bottom ash system than in the corresponding fly/bottom ash system. The major dissolved species in the slurry waters were sulphate, calcium, and sodium. Concentrations in bottom ash systems usually increased linearly with increasing cycles of concentration, whereas concentrations in fly/bottom ash systems generally increased during the first several cycles, then either remained constant or decreased. Scaling was observed only in studies involving fly/bottom ash from stations burning western Canadian coal or a mixture of western Canadian and U.S. bituminous coals. Key words: ash handling, fly ash, lagoons, leaching.