摘要:

The object of this paper is to share the experience gained from an investigation of prestressed concrete box beams of the elevated roadway of the F. G. Gardiner Expressway in Toronto, 16 years after construction. The 18–30 m long, simply supported beams, which are either pretensioned or posttensioned with prestressing strands, are covered by concrete topping and asphalt. Methods of investigation include coring, chloride-content tests, and power chipping of soffit areas. Rusted reinforcing steel, rusted prestressing strands, and delaminated or spalled concrete were found at transverse joints and at beam soffits. Concrete damage due to bird droppings, as well as a beam with nearly 60% strand loss, were discovered. Causes for deterioration are discussed and proposed repair methods are described.

ISSN:0315-1468    

DOI:10.1139/l85-001

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

A study is made on the hydrodynamic effect caused by seismic ground motions on the design of cylindrical on-ground liquid-storage tanks. The current techniques for determining the design base shear and overturning moment of the tank are reviewed, first treating the tank wall as rigid and then including the wall flexibility effect. By means of examples, these calculations are compared with those suggested by the National Building Code of Canada (NBCC). In addition, theoretically predicted values are compared with experimental data.It was found that in the case of tanks of high height to radius ratio and small wall thickness to radius ratio, the interaction of the fluid and wall flexibility can cause responses as high as two to three times those calculated based on rigid tank wall assumptions. The range of tank geometries under which the tank can be considered rigid is given. It is shown that the NBCC formula to establish seismic loads for tanks on ground is in general conservative, provided the acceleration ratio in the NBCC formulae takes on the value of maximum peak ground acceleration of the site.Key words: seismic, earthquake, hydrodynamic force, response, cylindrical tanks, design code.

ISSN:0315-1468    

DOI:10.1139/l85-002

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The analysis of multibeam bridge decks is seriously complicated by the effect of skew. Conventional methods invoke grillage solutions, which have inherent difficulties. This paper proposes an extension of the transfer matrix solution for right decks to include the effects of skew without detracting from the simplicity of the method. Both the flexural and torsional flexibility coefficients need to be modified for the skew support conditions and a new flexure–torsion coefficient is introduced to represent the cross-coupling that occurs between these flexibilities because of skew. The assumption of load transference through a single-point hinge between adjacent beams is retained, but the spanwise location of this point is varied from beam to beam according to the degree of skew. Results are presented for a range of skew angles and span/width ratios and compared with those from a modified grillage solution; excellent agreement was demonstrated up to and including 45° skew.Key words: highway bridges, skew, transfer matrix analysis, grillage modelling, multibeam decks, single span, comparative solutions.

ISSN:0315-1468    

DOI:10.1139/l85-003

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

A rational procedure for determining the strength of spaced timber columns is presented. The effect of interlayer slip, characteristic of layered systems with nonrigid connections, is considered in the theoretical development. A good agreement is observed between the theoretical predictions and experimental results of some 110 spaced columns. The effect of number of spacer blocks on column strength is investigated, and efficiency of various types of spaced columns is compared, first with respect to each other and then with respect to equivalent solid and layered systems. Finally, the theory is compared with design specifications given by CSA Standard CAN3-086-M80, "Code for engineering design in wood."Key words: bolts, buckling, columns (supports), design practice, efficiency, nails, nonrigid connection, spaced columns, split ring connectors, strength, structural engineering, tests, theory, timber construction.

ISSN:0315-1468    

DOI:10.1139/l85-004

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

In the last decade, software engineering has emerged as a discipline very useful for computer application programmers in various engineering fields. In this paper the author considers the programming and management techniques for developing useful and commercially viable engineering software that may be used in the analysis and design of civil engineering projects. The issue of utilizing existing software effectively and efficiently is also discussed. At the conclusion of the presentation, several recommendations are made to encourage engineering software development in Canada.Key words: engineering, software engineering, software, computers, computer service bureaus, software directories.

ISSN:0315-1468    

DOI:10.1139/l85-005

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

A unified degree-day method for simulating the thermal growth, decay, and breakup of river ice covers is developed and applied to ice covers in the St. Lawrence River between Lake Ontario and Cornwall, Ontario. In the simulation model, the variation of the ice cover thickness is related to the ambient air temperature by the formulain whichh = ice cover thickness;h0 = initial ice cover thickness;S = degree-days of freezing since the formation of the ice cover;t = number of days since the formation of the initial ice cover; and α, β, θ = empirical coefficients.Key words: breakup, degree-day method, ice cover thickness, river, simulation, St. Lawrence River.

ISSN:0315-1468    

DOI:10.1139/l85-006

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

The destructive testing of three reinforced concrete highway bridges, recently made redundant by road realignment, is summarized. The procedure used to test the bridges to ultimate conditions is described and load capacities of about 20 times class 1 axle loads are reported for all structures. Analyses based on conventional ultimate strength theory can account for only two-thirds of these ultimate loads and then only if second order effects are included. A nonlinear finite element computer program has been developed and used to analyze one of these structures. Excellent prediction of the ultimate load is made by the program. It is therefore suggested that compressive membrane action, which is automatically modelled in the finite element solution, plays a significant role in the enhancement of load capacity.The paper concludes that a more sophisticated approach to the assessment of bridge load capacity is necessary if realistic estimates of actual strength are to be made. Limited experience with a nonlinear finite element program suggests one such approach. If used with care, some relief to the bridge replacement program can be expected.Key words: highway bridges, ultimate load capacity, finite element analysis, reinforced concrete, field testing, compressive membrane action.

ISSN:0315-1468    

DOI:10.1139/l85-007

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

Base isolation is a strategy for a design of buildings in areas where seismic loads govern. It enables the reduction of earthquake excitation to an acceptable level, without an increase of structural acceleration. This paper presents the results of the experimental investigations of various schemes of first-storey designs for steel buildings with base isolation.A scaled-down steel frame building was used for the shaking table tests, which were conducted in the Earthquake Simulator Laboratory of the University of British Columbia. The base-storey design was altered while the dynamic response of the frame was recorded. The base isolation consisted of steel roller bearings with parallel steel yield rings, to limit excessive displacements and provide wind restraint.The proposed base storey is substantially different from conventional solutions. The variation in the base-storey design was aimed at the elimination of the blind base storey or double foundation in order to increase the economy of the base-isolation system. The experimental tests showed suitable design approaches, and analytical studies to optimize them will follow.It was verified that uncoupling of buildings from the earthquake ground motion is relatively simple to achieve. Certain restraint is required to resist wind and other horizontal loads. This is usually achieved by mechanical fuses or energy absorbers. A solid state energy absorber was used in the described tests.Key words: base-isolation system for buildings, earthquake-resistant steel structures, experimental investigations, retrofit system.

ISSN:0315-1468    

DOI:10.1139/l85-008

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

This paper presents an analytic (algorithmic) method for determining the optimum proportions of aggregates that satisfy specific gradation, design, and cost requirements of the blend. The gradation requirements include the specification limits and mean deviation from the midpoint of specifications limits. The design requirements include fineness modulus, plasticity index, and specific gravity. The optimum proportions may correspond to minimum mean deviation or minimum cost. In addition to providing the optimum solutions, the method provides the entire feasible region of proportions that may be useful if adjustments of proportions are deemed necessary.The paper first reviews existing aggregate blending methods, classifies them, and describes how the proposed method fits into that classification system. The method is then described along with its graphical interpretation. The method may be regarded as a simulation process and as such is not subjected to any type of constraints. Application of the method to a numerical aggregate blending problem was made to illustrate its use.While existing methods consider minimizing mean deviation (with no consideration of cost) or minimizing cost (with no consideration of mean deviation) the proposed method considers both mean deviation and cost as well as the physical properties. Other advantages of the method include adaptability to linear or stepwise cost functions of aggregates, automatic elimination of negative solutions, and provision for different weights (importance levels) of sieve specifications.Key words: blending, aggregate proportions, cost, mean deviation, gradation, specific gravity, plasticity index, fineness modulus, asphaltic concrete.

ISSN:0315-1468    

DOI:10.1139/l85-009

出版商:NRC Research Press    

年代:1985

数据来源: NRC

摘要:

In many truss joints consisting of double-angle web members welded to stems of inverted lower chord tee sections, adequate fillet weld lengths may be provided without the need for gusset plates. In such cases where a joint may also be subjected to high combinations of shear and tension, the possibility of overstressing of a tee stem exists. In the investigation of this problem, four analytical techniques, including two proposed herein, and experimental results of 30 full-scale specimen tests, 22 of which were conducted during the investigation presented herein, are presented and evaluated. Analytical and experimental results indicate that the interaction of shear and normal stresses is an important consideration in the design of such joints and that an interaction check is required.Of the many parameters investigated as part of the experimental investigation, the two that most significantly influence the magnitude of tension force that a lower chord can simultaneously carry are the magnitude of applied shear force averaged over the available web shear area and the joint configuration itself. The inclination of a diagonal web member as well as intentional joint eccentricities have little effect on the strength of these joints, although joint ductility appears to be affected by eccentricities.Although all four analytical techniques have similar overall accuracies of prediction, a method based on applying a von Mises criterion at ultimate to determine an equivalent shear area in a tee chord is recommended as being the most suitable. Based on this method, as verified and validated by comparison with extensive experimental results of tests on full-scale specimens, a simplified design curve and associated equations are developed and proposed for design office use.Key words: connection, interaction, shear, tension, welded, truss.

ISSN:0315-1468    

DOI:10.1139/l85-010

出版商:NRC Research Press    

年代:1985

数据来源: NRC