: As inferred from earthquake engineering literature, considering soil structure interaction (SSI) effects is important in evaluating the response of transmission line towers (TLT) to dynamic loads such as impulse loads. The proposed study investigates the dynamic effects of SSI on TLT behavior. Linear and non-linear models are studied. In the linear model, the soil is represented by complex impedances, dependent of dynamic frequency, determined from numerical simulations. The nonlinear model considers the soil non-linear behavior in its material constitutive law and foundation uplift in a non-linear time history analysis. The simplified structure behavior of a typical lattice transmission tower is assessed. The analysis of frequency and time domain are followed through varying soil stiffness and damping values. Three different shock durations are investigated. The soil-structure system with equivalent dynamic properties is determined. The behaviors achieved utilizing a rigid and a flexible base for the structures is compared to estimate the impact of taking SSI into account in the calculation. The current mainstream approach in structural engineering, emphasizing the importance of the SSI effect, is illustrated using an example where the SSI effect could be detrimental to the structure. Furthermore, the non-linear analysis results are analyzed to show the linear approach’s limitations in the event of grand deformations.

Autonomous truck platoon (ATP) deployment on road networks has recently attracted significant interest for its potential economic and environmental benefits. However, the impact of platooning on bridges is a concern because of the differences in their live load characteristics compared with those in the existing bridge design specifications. One of the primary aspects in the safe deployment of ATP is to evaluate the reliability of bridge designed using the existing provisions for live loads from potential configurations of ATP. An analysis procedure is proposed and demonstrated for a simple span steel composite bridge designed according to the existing design provisions. Given that many characteristics of the live load distribution such as the bias factor, coefficient of variation (CoV), and the dynamic amplification factor are presently not known for ATP, a parametric approach is used. The bias factor, dynamic amplification, and CoV are parametrized to calculate the live load distribution and quantify its impact on the reliability index. A two-truck platoon with different headway spacings constituted by different trucks in a single lane scenario is considered. The results indicate that the two single lane bridges designed according to existing design specifications are generally reliable (i.e., achieved the target reliability for which the bridge was initially designed) for the range of ATP live loads investigated when the CoV is less than 0.07, bias close to one and headway distances are above 17 ft. Future studies are suggested to include bridges with multiple spans, other bridge types, and a larger number of trucks in the platoons. The main contribution of this paper is to quantify the reliability indices of selected steel composite bridges designed using the existing specifications but subjected to various configurations of ATP loads and the influence of different components of the live load model attributed to the latter.

The behaviour of bolted connections in steel lattice transmission line towers affects their load-bearing capacity and failure mode. Bolted connections are commonly modelled as pinned or fixed joints, but their behaviour lies between these two extremes and evolves in a nonlinear manner. Accordingly, an accurate finite element modelling of the structural response of complete steel lattice towers requires the consideration of various nonlinear phenomena involved in bolted connexions, such as bolt slippage. In this study, a practical method is proposed for the modelling of the nonlinear response of steel lattice tower connections involving one or multiple bolts. First, the local load-deformation behaviour of single-bolt lap connections is evaluated analytically depending on various geometric and material parameters and construction details. Then, the predicted nonlinear behaviour for a given configuration serves as an input to a 2D/3D numerical model of the entire assembly of plates in which the bolted joints are represented as discrete elements. For comparison purposes, an extensive experimental study comprising forty-four tests were conducted on steel plates assembled with one or two bolts. This approach is also extended to simulate the behaviour of assemblies including four bolts and the obtained results are checked against experimental datasets from the literature. The obtained results show that the proposed method can predict accurately the response of a variety of multi-bolt connections. A potential application of the strategy developed in this paper could be in the numerical modelling of full-scale steel lattice towers, particularly for a reliable estimation of the displacements.

To be able to perform nonlinear flutter analyses for bridges, time‐domain approaches should be used instead of Scanlan’s formulation of self‐excited forces. Thus, this paper addresses the development and validation of a modified quasi‐steady time‐domain model similar to Scanlan’s approach that is based on the velocity and acceleration of the bridge deck. In this formulation, quasi‐steady time‐domain flutter derivatives measured in the wind tunnel through forced‐vibration tests at absolute constant velocity and acceleration are used. For this, a unique test rig, which can be used either for free‐ or forced‐vibration tests, was utilized. By measuring the time‐domain flutter derivatives of the Great Belt Bridge, their nondimensionalization with respect to the bridge‐deck width, velocity and acceleration of the deck is validated. Then, time‐domain flutter analyses are performed using this new model. They agree with the experimental critical speed and the prediction using Scanlan’s model.

Slender steel sections are widely used in the construction of steel structures such as lattice structures for transmission line and telecommunication towers. Local buckling may be the observed failure mode under compression loads for these slender sections, and many experimental studies have been conducted to evaluate their resistance. All steel design codes include equations to account for local buckling. In numerical models, local buckling can be reproduced using 2D shell or 3D elements. Nonlinear numerical models have been developed in the last decades that can capture the complex behavior of lattice structures up to failure. These models typically use beam elements that consider correctly the global buckling and yielding of sections but do not consider the local buckling of angles due to geometrical limitations. This article proposes a method that modifies the material behavior of sections to involve the local buckling failure in the analysis. Forty-two experimental tests were conducted on short angles and a general stress-strain formula was defined based on the test results. The formula relates the local buckling slenderness ratio of the members to a material constitutive law that accounts for the local buckling. To evaluate the method, the numerical results were compared to those of four x-braced frame configurations using slender angle sections. The results demonstrate that the proposed method can accurately model the local buckling failure of fiber beam elements.

Using seismic isolation systems for highway bridges modifies the structure's principal vibration modes and effectively reduces the seismic base shear conveyed from the superstructure to the substructure. However, for some low-damping rubber isolation bearings, large displacements can be a problem. Supplemental hysteretic dampers can be introduced into the base-isolated bridge, which might nevertheless increase the structure base shear, and the merit of adding dampers has to be evaluated properly. In this paper, a simplified method was implemented for the design of a low-cost hysteretic damper, and the resulting isolator-damper system was tested experimentally. The design method used is based on an equivalent linearization approach. A full-scale elastomeric isolation bearing was characterized and used in the design of a hysteretic damper. Both the isolator and the damper went through cyclic testing and real-time dynamic substructuring (RTDS) methods to verify the capacity of the method to design base isolation-damping systems. The study was further extended to extreme seismic loading by nonlinear time-history analysis. The results reveal that the simplified method is adequate for use in the performance optimization of isolated-damped bridges. (C) 2016 American Society of Civil Engineers.

The response of concentrated photovoltaic (CPV) structures under wind loading has to be carefully predicted to optimize the design of these structures. Designers normally, rely on wind tunnel tests and equivalent static approaches as recommended by codes for the design of this type of nonconventional structures. This paper aims to evaluate the full scale wind response of a concentrated photovoltaic (CPV) prototype with mirror surface of 8 (*) 16 m(2) and correlate it with wind measurements made near the solar structure. The full-scale wind response of the structure was evaluated with continuous 10 min measurements of deformations on tower leg members during moderate wind events. The utility of this work derives from enriching field measurement data in order to understand the behavior of this type of structure and to validate the previous wind tunnel testing works, Standard wind design process based on the analytical method, which is adopted by ASCE 7, is also revisited in the light of the full scale observations. (C) 2017 Elsevier Ltd. All rights reserved.

This paper describes a novel application of statistical learning theory to structural reliability analysis of transmission lines considering the uncertainties of climatic variables such as, wind speed, ice thickness and wind angle, and of the resistance of structural elements. The problem of reliability analysis of complex structural systems with implicit limit state functions is addressed by statistical model selection, where the goal is to select a surrogate model of the finite element solver that provides the value of the performance function for each conductor, insulator or tower element. After determining the performance function for each structural element, Monte Carlo simulation is used to calculate their failure probabilities. The failure probabilities of towers and the entire line are then estimated from the failure probabilities of their elements/components considering the correlation between failure events. In order to quantify the relative importance of line components and provide the engineers with a practical decision tool, the paper presents the calculation of two types of component importance measures. The presented methodology can be used to achieve optimised design, and to assess upgrading strategies to increase the line capacity.

In this paper, the aerodynamic loads on simplified lattice structures are evaluated as the sum of the force on each individual member rather than using conventional methods accounting for the overall truss through solidity ratio and global shielding coefficients. Wind tunnel tests were conducted on a single cylinder to determine the aerodynamic force coefficients and the velocity profile in its wake. Aerodynamic forces were measured on 5 models of regular lattices made of round bars. An empirical local method was developed in order to calculate the wind forces on lattice tower based on the forces acting on each individual members and considering the shielding effect. The wind forces on the 5 truss models calculated with this method compare very well to the results from wind tunnel tests and the difference with experimental tests is similar or smaller to the one obtained with the various design documents. Because it accounts for the shielding effect on each member individually, the approach presented appears to be promising for the calculation of wind forces on complex lattice structures at various angles of attack.

This paper proposes a FE modeling strategy for multilayered strands subjected to multiaxial loads. The approach takes advantage of beam elements and incorporates 3D inter-wire contacts. While reducing mesh sizes, it handles any strand configuration. Comparisons with experimental results validate its precision. The analysis shows that friction forces control the hysteresis and the bending stiffness. The paper develops a multi-level friction coefficient better representing the stick and slip zones, and to account for indentation, the model incorporates a friction orthogonality concept; the axial direction is controlled by adhesion, while the orthogonal direction is associated with adhesion and deformation contributions.

Through an experimental study, this paper describes the behavior of single-lap bonded and bolted–bonded connections for configurations with minimum geometric parameters proposed in design references. Two types of multi-material connections are considered: glass fiber reinforced polymer (GFRP)–steel and aluminum–steel. At first, the behavior of bonded connections using methacrylate and epoxy adhesives is evaluated. Then, the contribution of adhesive in bolted connections is investigated. Test results show that on bonded joints, failures mostly occur at the substrate to adhesive interface. Sanding the GFRP plate was found to improve the connection strength. Despite their lower elastic modulus, methacrylate adhesives with larger capacity to undergo plastic deformation provide better strength than other methacrylate and epoxy adhesives. For bolted–bonded joints, the adhesive was found to improve the elastic behavior and the strength of GFRP–steel joints while its effect for aluminum–steel joints was not apparent due to reduced bonded surface and the high strength performance of the bolted plates.

Climate change is anticipated to influence the reliability of overhead transmission and distribution lines through impacts on extreme weather events. Changes in the frequency and intensity of wind and ice storms may have a considerable effect on applied loads and can consequently affect the probability of structural failure of different components of the line. This study examines the reliability of transmission lines under a range of assumed changes in the mean and standard deviation of climatic variables affecting transmission lines such as annual extreme wind speed and ice thickness. The methodology used for the reliability analysis of transmission lines under current and future climatic conditions is based on the concepts of statistical learning theory. The sensitivity study provides the information required to improve the capacity of transmission lines and mitigate long-term risks from the effects of a changing climate. The results indicate that climate change as predicted by many researchers can significantly affect the reliability of existing transmission line systems. Hence, relying on the historic climatic data may not be sufficient to ensure an adequate reliability of transmission line systems in the future. The specification of design loads for the evaluation of existing lines or the design of new lines should consider both future climate models and historical climate data. (C) 2016 Elsevier Ltd. All rights reserved.

This paper presents the effect of geometric parameters on the behavior of bolted glass fibre reinforced polymer (GFRP) pultruded plates for civil engineering applications. After a literature review, results of an experimental analysis investigating the behavior of GFRP-to-steel single-lap bolted connections are presented. Then, a finite element analysis validated by experimental data is used to evaluate the effects of the end-distance, side-distance, pitch, and plate properties on the strength and failure mode of the connection. A critical examination of geometric recommendations proposed in design references is presented. Bearing failure caused by contact of the bolt on the GFRP plate is usually defined as the preferred failure mode. With highly orthotropic plate, this type of failure was found to be less likely to occur when loading is applied in the pultruded direction. The investigation showed that the minimum end-distance and pitch-distance recommended by design references usually produce a connection with the maximum capacity. However, it was found that the minimum side-distance recommended by these references does not necessarily lead to the maximum capacity for one bolt and for two bolt in a column connections.

Seismic bridge design codes require that bridge piers designed according to prescribed design rules should attain specified multiple seismic performance objectives. However, design codes do not explicitly require checking the attainment of specified performance objectives for designed bridge piers. In this article, seismic performance levels have been correlated with engineering damage parameters. A checking method for multiple seismic performance objectives of bridge piers has been outlined and validated with experimental results. The application of the method has been demonstrated by checking the performance of a bridge pier designed according to a code provision for a wide range earthquake ground motions.

The objective of the work presented here is to improve estimates of atmospheric icing hazards, specifically for equivalent radial ice accumulation (Req) on electrical transmission lines, by solving CRREL empirical icing model as a function of random variables using reliability methods. The propagation of uncertainty in the model is preformed using first-order reliability methods (FORM) and Monte Carlo simulations. This methodology is used on clustered freezing rainstorms that form the basis of a de-aggregate hazard analysis. In this paper, freezing rain storms were clustered based on anomaly maps constructed using NCEP reanalysis data of 1000–500 hPa geopotential heights or SLP. The procedure is demonstrated with data from Montreal. The physical meanings of the different clusters were also presented in terms of wind speed, total precipitation, air mass positions, and compare with Rauber’s archetypical patterns. For single population results, the design point identified by FORM analysis for high values of Req corresponds to high total precipitation, high freezing ratios, but only slightly higher than average wind speed. For the de-aggregated analysis, different design points are associated with each clusters. These results correspond to the measured physical characteristics of extreme storms associated with the clusters. In particular, the design point associated with the cluster containing the 1961 ice storm has relatively higher equivalent wind speeds then the other clusters. The performance function being nonlinear, the results from FORM are approximate making Monte Carlo simulations more appropriate for calculating return periods. The hazard function for Req derived from reliability methods for Montreal produces results similar to those of Jones and White in The estimation and application of extremes, electrical. Transmission in a New Age, ASCE, pp 32–47, (2002) using a superstation and extreme value analysis. For the 50-year return period, de-aggregate and single population reliability analysis gives similar results. The analysis indicates Req of approximately 35, 45 and 55 mm for return periods of 50, 100 and 200 years, respectively.

Through experimental and numerical studies, this research work aims to provide directions on the optimal geometric configuration for single-lap and double-lap bolted connection between aluminum alloy 6061-T6 and steel. From experimental test results, the effects of different geometric parameters on the joint strength were discussed. These parameters include the end-distance, the side-distance, the pitch-distance, the plate thickness and the joint eccentricity. Then, the experimental results were compared to predicted results using design references and geometric recommendations proposed by design references were critically examined. The experimental study was complemented by finite element (FE) analysis to extend the study to a larger range of parameters. In addition to the analysis of the geometric parameters listed above, the effects of the gage-distance on the joint strength were studied in the FE analysis. The experimental and finite element results show that a careful selection of geometric parameters can result in the high improvement of the connection strength and failure mode. Limiting the side-distance to the minimum recommended value was found to limit the strength of a connection with two bolts in a column to that of the one-bolt connection. In most cases, bearing was found to govern the strength of the connections. The calculated bearing strengths were found to underestimate significantly the connection strength. Based on these analyses, maximum geometric parameters beyond which there is no further increase of the joint capacity were evaluated and optimum geometric parameters were proposed. (C) 2015 Elsevier Ltd. All rights reserved.

This paper evaluates the possibility of replacing minimum shear reinforcement by steel fibers in both prestressed and non-prestressed thick concrete slab. Due to brittle behavior of plain concrete in tension, shear failure of thick slab is generally catastrophic. The use of minimum shear reinforcement is recommended in many instances to avoid such failure. This paper presents an alternative solution realising that the use of optimum steel fibers can give ductility performance equivalent to the slab with minimum shear reinforcement. To evaluate the effect of steel fibers on shear performance, eight full-scale tests are carried out. The influence of fibers on shear performance is evaluated and its potential to replace the minimum transverse steel of thick slab is discussed. Finally a procedure for predicting the shear capacity of such slab is presented. (C) 2015 Elsevier Ltd. All rights reserved.

Bridge stability is typically investigated based on 2 DOF wind tunnel measurements and very few wind tunnel facilities are available to simulate 3 DOF flutter of sectional model. In the absence of experimental capacity for extracting the flutter derivatives related to the sway, the quasi-steady approach is generally used for their evaluations. Also, the change of angle of attack is generally achieved by rotating the model relatively to the balance, forcing then the model to move according to the wind׳s axis as opposed to the section׳s principal axis. The impact of this experimental limitation needs to be studied. This paper presents a new 3 DOF dynamic force balance and its use to investigate the stability of a typical bridge deck section. The effect of the axis of motion is also studied. An interaction between sway and twist was observed during flutter and, for some angles of attack, the results show that the speed at which the flutter is reached might be influenced by the sway and the direction of motion as compared to principal axis of the section. Further research is needed to properly asses these effects.