摘要:

An experimental program was undertaken on single wythe and cavity concrete block masonry walls to evaluate the effect of the veneer on the vertical load-carrying capacity of the wall. Twelve unreinforced, ungrouted, and relatively slender single wythe and cavity walls were tested to failure under quasi-static, monotonic, axial loading. Three values of equal end load eccentricity were used in the test program. A review of published test data associated with the behavior of single and double wythe concrete block masonry walls indicates a scarcity of data regarding the magnitude and type of effect of the veneer on the stiffness, strength, and stability of such walls. To examine the performance of axially loaded slender masonry walls, and to isolate any effect of the veneer in modifying that performance, the plain masonry walls of the present program were chosen to be quite slender (height-to-thickness ratio of 30) and relatively thin (thickness = 140 mm). This study used a microcomputer spreadsheet program to evaluate the theoretical capacity of the walls and to generate load –moment interaction diagrams. The program is based on a moment–area analysis and incorporates the effects of finite deflections, nonlinear constitutive laws, and cracked section behavior. The walls exhibited material failure in the case of centrally loaded walls, whereas stability failure governed for eccentrically loaded specimens. The contribution of the veneer to the lateral stiffness of the cavity wall system was found to vary with the eccentricity of the applied end load. The contribution to strength seemed to be negligible for central loading, but was quite significant for the case of the eccentrically loaded walls. More tests covering different loadings, slenderness values, and end conditions are needed to quantify the behavior.Key words: masonry, slenderness, stiffness, stability, capacity, veneer, cavity wall, ties, eccentric loading.

ISSN:0315-1468    

DOI:10.1139/l91-090

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

This paper presents an experimental investigation into the seismic behaviour of timber shear walls fastened with nails alone or with nails in combination with wood adhesive. The responses of both types of shear walls were determined under slow, quasi-static racking loads and also under dynamic, earthquake-induced conditions. The experimental results showed that the introduction of the adhesive makes shear walls much stronger but also more brittle than conventional nailed walls. It was observed that shear walls incorporating nails and adhesive behaved almost linearly to failure. To obtain the most out of the adhesive capacity, however, the wood framing should be designed with special attention to the connections between framing members and the anchoring of the wall's base plate. These details control the capacity of the frame to sustain the loads induced by the stiffer adhesive joints.Key words: adhesive, earthquake, tests, timber construction, shear walls, wood.

ISSN:0315-1468    

DOI:10.1139/l91-091

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Two depth-averaged circulation models were applied to a distorted physical model of the Windermere Basin of Hamilton Harbour. One of the models, which includes the nonlinear advective terms, was successful in reproducing the hydraulically induced steady-state circulation. Using a Lagrangian model and the above circulation, trajectories observed in the physical model were replicated. Model sensitivity to changes in the bottom friction and horizontal diffusion of momentum were studied. An increase in each was found to decrease the size of zones of recirculation.Key words: distorted physical model, circulation model, bottom friction, horizontal diffusion.

ISSN:0315-1468    

DOI:10.1139/l91-092

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

High-strength concretes are being increasingly used in the columns of high-rise buildings. Analytical studies of the slenderness effects in these columns have been very limited. The behavior of slender columns with normal- and high-strength concretes is studied using a finite element program. Differences and similarities in long-term and short-term behaviors between high-strength and normal-strength slender concrete columns are noted and discussed.Key words: columns, slenderness, high-strength concrete, creep, finite elements.

ISSN:0315-1468    

DOI:10.1139/l91-093

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

A new mobile-bed mathematical model for simulating sediment transport in river networks under unsteady flow conditions is presented. The new model,ONE-D-SED, is an extended version of the extensively validated fixed-bed, one-dimensional hydrodynamic modelONE-D. This paper reports the results of an application ofONE-D-SEDto simulate bed profile development along a 43-km-long tidal channel network of the Lower Fraser River in British Columbia. The sand-bed study reach has been undergoing degradation caused by navigational dredging and river training works in lower channel reaches and by borrow dredging within the study reach itself,ONE-D-SEDwas used to simulate bed degradation in the study reach during the 1979–1984 period. The simulated annual change in bed elevation at the downstream end of the study reach showed good agreement with that observed during 1968, the data year used to calibrate the model. The predicted cumulative change in bed profile from 1979 to 1984 also compared favourably with the overall degradation pattern observed during that same period.Key words: mathematical model, simulation, sediment transport, river network, finite difference, model validation.

ISSN:0315-1468    

DOI:10.1139/l91-094

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Reliability, defined as the probability of survival in a given period of time, forms the basis of most design codes. In this work, the use of reliability concepts to make informed decisions regarding in-service monitoring and maintenance is demonstrated. Parking garages are used as an example application. The degradation of the driving surface, as defined by the percentage of floor surface delaminated, was used to describe the deterioration process. The delamination is related to corrosion of the reinforcing steel accelerated by Cl−ions deposited in the concrete lattice from deicing salt laden vehicles. The time at which deterioration commences and the rate at which it proceeds are related to the depth of cover to the top level of the reinforcing steel, the water-to-cement ratio of the concrete, the concentration of Cl−ion in the deicing salt mixture, the treatments used to prevent Cl−ion attack, the crack size, and the garage temperature. A limit-state function relating to the degree of delamination to the garage age and other influencing parameters was developed and used in a first-order reliability method algorithm to evaluate repair intervals and treatments such as polymer impregnation, vacuum treatments, boiled linseed oil, and absorptive form liners. Considerable savings in maintenance costs may be achieved through optimum scheduling and choice of garage surface treatment.Key words: reliability, maintenance, parking garages, monitoring, repair, inspection.

ISSN:0315-1468    

DOI:10.1139/l91-095

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

Under a moving load, a bridge undergoes deflections and stresses which significantly exceed those caused by the same load when applied statically. These dynamic deflections can cause discomfort to pedestrians using the bridge, since human response is sensitive to accelerations and to the rate of change of acceleration. Another factor affecting human response is the type of vibration in the dominant mode. People tend to react more adversely to torsional modes of vibration than to flexural modes. This paper summarizes the results of an extensive analytical investigation, which was conducted to identify key parameters affecting the changes of dominant mode types and to study the influence of diaphragms and cross bracings on dynamic responses of a twin box girder bridge. The finite element method was used to carry out these analyses. The analytical results indicate that the provision of diaphragms within the boxes at each support, or of a cross-bracing system in-between boxes, can effectively reduce peak accelerations when the dominant mode of vibration is torsional. As a result, the human discomfort and perception to vibration can be improved.Key words: vibration, human response, torsion, flexure, box girder bridge, diaphragm, cross bracing, finite element analysis.

ISSN:0315-1468    

DOI:10.1139/l91-096

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

This paper describes the results of an accelerated laboratory investigation to measure the rate of deterioration of a newly developed filled plastic composite exposed to acidic (sewage) environments. The specific objective was to compare the relative rates of deterioration of an experimental filled filament wound (FFW) polyester composite immersed in sulfuric (pH 2.23) and acetic (pH 2.22) acid environments at 45 °C. Deterioration was measured in terms of changes in wet specimen weight, loss in dried (soluble) material weight and mechanical properties, the extent of chemical dissolution, and the depth of penetration. Based on regression analyses of these parameters, it was found that the rate of deterioration was a function of the square root of immersion time. Deterioration of the FFW composite in acetic acid was 1.6–3.9 times greater than in the sulfuric acid environment. The loss in wet flexural properties and the dissolution behavior of aluminum trihydrate were not influenced by the type of acid environment. Based on the findings of this study, sulfuric acid is recommended as a standard laboratory test medium for fiberglass reinforced plastic composites used in construction of sewage facilities and pipelines where deterioration due to sulfur oxidizing bacteria is anticipated.Key words: accelerated, polyester, fillers, filament-wound, environment, acidic, durability, composite, septic tanks.

ISSN:0315-1468    

DOI:10.1139/l91-097

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

This paper describes the development of a prototype knowledged-based expert system for predicting the cost – time profiles of various construction activities in New Brunswick. Knowledge, both quantitative and qualitative, about the cost – time patterns of various activities in educational, office, and apartment building projects in New Brunswick are stored in an expert system shell (Personal Consultant Plus). The system simulates a consultation between an expert and a user, where the microcomputer represents the expert and the user is the prospective building contractor or owner. The output of the consultation shows how the total cost of the various trades will most likely be distributed over time. This will enable the contractor and the client to anticipate the probable financial commitments each month, even before any schedule is available, once an investment decision has been made. Funds can then be arranged in such a way as to match the progress of work and therefore meet the financial demands of each individual building activity.Key words: cost – time profiles prediction, expert system, shell, knowledge base, buildings, construction, rules, parameters.

ISSN:0315-1468    

DOI:10.1139/l91-098

出版商:NRC Research Press    

年代:1991

数据来源: NRC

摘要:

The shear behaviour of both conventional end plate connections and clipped end plate connections, in which the upper corner of the end plate was removed, was examined in a laboratory investigation of 29 full-scale test specimens. The study included connections of varying geometry, bolt diameter, and end plate depth. The majority of the connections failed in one of two modes: a failure of the bolt group component or a web-tear failure. For connections failing through the bolt group, the ratio of the shear capacity of the clipped connection to that of the conventional connection is the ratio of the number of bolts in the clipped and conventional connections. Even when failure is not through the bolt group, the shear capacity of an end plate connection is reduced when the upper corner of the end plate is clipped. The experimentally determined shear capacities are compared with the calculated resistances determined using the resistance equations in CAN3-S16.1 in conjunction with the assumptions of load transfer mechanisms and stress distributions embodied in the design aid for end plate connections in theHandbook of Steel Construction.Key words: beams, connections, bolts, end plates, shear strength.

ISSN:0315-1468    

DOI:10.1139/l91-099

出版商:NRC Research Press    

年代:1991

数据来源: NRC