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Recent studies show that rotational components of earthquakes can amplify the floor acceleration in a base-isolated structure. As a result, the seismic force of nonstructural components could be significantly increased. In this paper, a simple rectangular deck with various geometrical properties mounted on triple concave friction pendulum (TCFP) bearings is examined. At first a set of three translational components from 25 near-fault ground motion records are considered. Then, three rotational components, i.e., torsional and two rocking motions are computed for each earthquake. The results of nonlinear dynamic analysis in a rectangular structure with an aspect ratio in plan equal to 3, demonstrate that the acceleration approximately intensifies 3.4 times in presence of all six ground motion components compared to three translational ones. Finally, a new formula is proposed to determine the maximum acceleration of base-isolated structure without performing the dynamic analysis due to rotational components of ground motions. [ABSTRACT FROM AUTHOR]

Compressing project schedule using activity accelerating and overlapping requires that an intensive time-cost trade-off analysis be carried out, to determine costs and benefits for each day of compression. However, the cost elements and implications of compression techniques differ significantly, since activity accelerating imposes extra direct cost whereas activity overlapping adds a risk of changes and rework. Such a trade-off becomes even more complicated in capital projects comprised of a large number of schedule activities and relationships. The variety of combinations of accelerating and overlapping of different activities in these complex networks can offer numerous possibilities for compression with various costs and potential risks. The lack of a reliable analytical tool for performing a precise cost-benefit analysis causes this critical task to be performed in a subjective manner during the planning stage of projects. The purpose of this paper is to present an advanced method using a multi-objective evolutionary optimization tool seeking the optimum degree of accelerating and overlapping during the schedule compression process. This optimization technique would be beneficial in maximizing project benefits while meeting the intended target dates. [ABSTRACT FROM AUTHOR]

Schedule compression is an attempt to reduce project durations for early delivery, or to catch up on occurred delays. This is usually performed using 'crashing', 'overlapping' and 'substitution' of activities. 'Crashing' is shortening task duration by adding more resource hours. 'Substitution' is changing the method or tool by which the activity is performed. 'Overlapping' is performing sequential activities in parallel. Few studies can be found in the literature that compare costs and benefits of each technique and recommend the optimum combination of these techniques in project schedules. In fact, the implications of each technique are inherently different since crashing and substitution impose extra cost whereas overlapping adds the risk of changes and rework. Therefore, it is a challenge to develop a reliable analytical tool for performing time-cost trade-offs using the three methods. There are also few studies in the literature to propose a practical method for performing schedule compression by combining these techniques. The purpose of this paper is to discuss these schedule compression techniques in detail, and present and validate a heuristic method to perform the combination of crashing, overlapping and substitution in a project schedule, to reach the maximum benefit while meeting the project target dates. [ABSTRACT FROM AUTHOR]

A simplified method is presented in this paper for the estimation of forces at the base of telecommunication towers mounted on building rooftops due to seismic excitation. Although some codes and standards propose simplified methods for the evaluation of base shear forces for towers founded on ground, no method yet exists for the evaluation of overturning moments. The proposed simplified method is based on numerical simulations using truncated modal superposition, which is widely used for seismic analysis of linear structures. The method requires the prediction of input seismic acceleration at the building–tower interface, the definition of an acceleration profile along the building-mounted tower, and the determination or evaluation of the mass distribution of the tower along its height. The method was developed on the basis of detailed dynamic analyses of three existing towers assumed to be mounted separately on three buildings. It was found that the method yields conservative results, especially for the overturning moments. [ABSTRACT FROM AUTHOR]

This paper presents a comparison of the two main regional damage estimation methodologies currently in use, namely the modified Mercalli intensity (MMI) based approach and the spectral parameter based approach. In the first methodology, expected damage is related to ground shaking intensity in terms of MMI through damage probability matrices. In the second methodology, the ground motion intensity is described in terms of spectral acceleration (SA), and building response in terms of spectral displacement (SD). Both methodologies were applied to buildings in Vancouver of three different construction types: single-family wood-frame houses, low-rise unreinforced masonry buildings, and high-rise concrete frame structures with concrete shear walls. The two methodologies predict damage that lies in the same general damage categories of light and moderate, which are defined by fairly broad ranges in mean damage factors. The specific mean damage factors predicted by the two methods for a given location are significantly different, however. The significant differences in mean damage factors imply significant differences in damage costs and hence in seismic risk. [ABSTRACT FROM AUTHOR]

This paper describes results from a study of the dynamic performance of the Confederation Bridge during traffic load tests and a storm with high winds that occurred at the bridge site on 7 November 2001. The traffic load tests were conducted over a three-span segment of the bridge and consisted of single and double truck configurations at different speeds. The winds during the storm of 7 November 2001 were the strongest that have ever been measured at the bridge site since the opening of the bridge. The vibrations of the bridge during both the load tests and the storm were recorded by a network of 76 accelerometers. By processing the recorded vibrations, vertical deflections and dynamic amplification factors due to the traffic load tests and vertical and lateral deflections due to the wind during the storm were computed. The computed values were compared with those used in the design. It was found that both the deflections and the dynamic amplification factors were much smaller than the design values. [ABSTRACT FROM AUTHOR]

Many models have been developed to evaluate the operating speeds on two-lane rural highways. However, provided information usually lacks details essential to assess their applicability at locations other than where they were developed. This paper presents a procedure to interpret raw data collected on three horizontal curve sites of different two-lane rural highway classes in Ontario. The speed observations were categorized into three vehicle classes (passenger car, light truck, and multi-axle heavy truck) and four light condition categories (day, night, and two transition periods). The minimum headway and percentile value to define the operating speed were examined, and a revision of the current practice deemed not warranted. The findings also indicated that operating speeds do not depend on the time or vehicle class. Finally, the horizontal alignment affects the operating speed, but the speeds of the two travel directions on a horizontal curve may differ even with little contribution of the vertical alignment. [ABSTRACT FROM AUTHOR]

This paper presents a simple iterative method for structural static reanalysis. A preconditioned Richardson’s iterative method is developed and the relaxation parameter is determined by a very simple formula derived from the corresponding potential energy function. Based on the iteration method, an acceleration technique is also established. The proposed method is intended to utilize the existing stiffness matrix factorization completed for the initial design, require matrix-by-vector products only, preserve the ease of implementation and improve significantly the quality of the results. The method is suitable for general finite element systems. Calculation of derivatives is not required. The computational time is considerably reduced. A numerical example is used to validate the effectiveness of the proposed reanalysis method. [ABSTRACT FROM AUTHOR]