Papers by Elena Dragomirescu
Water Entry Response of Wall Assemblies to Dynamic Driving Rain Wind Pressure
The pressure difference across a wall assembly arising from the Driving-Rain Wind Pressure (DRWP)... more The pressure difference across a wall assembly arising from the Driving-Rain Wind Pressure (DRWP) produces a driving force that induces water ingress into wall assemblies given the presence of deficiencies on the exterior surface of the wall, and the downward migration of rain water over the wall surface. The extent of water penetration, which has a detrimental effect on the long-term performance of wall assemblies, is affected by the magnitude of the DRWP acting across the wall. In this study, a wall test specimen consists of 3 layers of polycarbonate sheathing has been tested under simulated Wind-Driven Rain (WDR) conditions. Deficiencies of different sizes and configurations were purposely built to the test specimen to investigate the extent of water entry given different DRWPs. To permit investigating the response of water entry under different DRWP conditions, a test protocol having a low cyclic rate was developed such that the water entry rates through the wall deficiencies could be obtained at different magnitudes of DRWP and as well, a variety of cyclic frequencies and amplitudes. Peer-review under the responsibility of the organizing committee of the ICMB21.
Canadian Journal of Civil Engineering
Cable corrosion is among one of the most common damage mechanisms in cable-stayed bridges. A fini... more Cable corrosion is among one of the most common damage mechanisms in cable-stayed bridges. A finite element model of the long-span Stonecutters Cable-Stayed Bridge was built, and its dynamic behaviour was investigated considering localized groups of corroded cables. The reduction in cable cross-sectional area was used to simulate corrosion levels from 25% to 75% cross-sectional loss. The corroded cables were divided into two groups of four cables, arranged in symmetric and asymmetric distributions along both decks. Natural frequencies and mode shapes were compared with a reference case with no corrosion-damaged cables. A recorded wind load was applied on the deck to investigate the time-history response of the mid-span in lateral, vertical, and torsional directions. Frequency analysis was performed on the time-history response, and coupled motions at certain frequencies were observed for certain corrosion cases and were discussed.
Lecture notes in civil engineering, May 18, 2022
Journal of Wind Engineering and Industrial Aerodynamics
Abstract The performance and durability of wall assemblies are greatly affected by the moisture l... more Abstract The performance and durability of wall assemblies are greatly affected by the moisture load to which they may be subjected, in particular those arising from Wind-Driven Rain (WDR). Standard approaches for estimating such moisture loads assume 1% of the WDR load, whereas these loads have also been assessed from watertightness tests, although these assumed loads have been determined based on limited climate information. To more accurately estimate the moisture loads to which wall assemblies may be subjected over their service life, an analysis of historical WDR loads was completed for 11 cities across Canada. The magnitude, probability of occurrence of WDR loads in different cities and correlations between WDR related climate parameters, are discussed in this paper. Also, a novel WDR severity index is introduced, referred to as the Wind-Driven Rain Pressure Index, to permit quantifying the real-time and simultaneously occurring effects of WDR intensity and Driving Rain Wind Pressure (DRWP). To estimate the WDR intensity and DRWP with a specific probability of occurrence, an Extreme Value Analysis (EVA) was completed for a climate dataset of 31 years (1986–2016) using the Generalized Extreme Value and Gumbel distributions.
Buildings, 2021
The moisture load in wall assemblies is typically considered as 1% of the Wind Driving Rain (WDR)... more The moisture load in wall assemblies is typically considered as 1% of the Wind Driving Rain (WDR) load that is deposited on the surface of wall assemblies as specified in the ASHRAE-160 standard whereas this ratio has been shown to be inaccurate as compared to results derived from several watertightness tests. Accurate assessment of moisture loads arising from WDR can be obtained through the watertightness test during which different levels of WDR intensities and Driving Rain Wind Pressures (DRWPs) are applied to a test specimen and water that penetrates wall assembly can thus be quantified. Although many previous studies have included watertightness tests, only a few of these have attempted to correlate the moisture loads to WDR conditions as may occur in specific locations within a country. To improve the assessment of moisture loads for a vinyl-clad wall assembly, a wall test specimen was tested following a test protocol based on local climate data using National Research Council...
IABSE Symposium, Shanghai 2004: Metropolitan Habitats and Infrastructure, 2004
ABSTRACT
A new wind testing facility, the Wind-induced Damage Simulator (WDS), was designed and built at t... more A new wind testing facility, the Wind-induced Damage Simulator (WDS), was designed and built at the University of Ottawa. The new facility is capable of generating extreme wind conditions and can achieve high pressure testing environment for scaled models as well as for full-scale structural elements such as: roofs, windows and curtain walls. The WDS system has dimensions of 3.65 m x 3.65 m x 3.0 m and has 20 circular inlet openings on the four lateral walls. The outlet of the box has a diameter of 300 mm, is at the center of the roof and it is connecting to a powerful industrial blower through a steel duct. Scaled models, 1:30 and 1:40 of the Silsoe cube, which is a basic shape structure was and a total of 42 pressure taps were installed on its surface. Pressure measurements were performed for unidirectional and shear wind flow conditions determined by activating the first and second inlets at the corner of the WDS. Also, different positions of the Silsoe cube model were investigat...
Wind-induced vibrations of slender high rise buildings are always an instability cause of concern... more Wind-induced vibrations of slender high rise buildings are always an instability cause of concern. Several passive and active mitigation methods have been proposed and some of them were found to be very successful such as: dampers, wind shields and aerodynamic geometric optimization. A slender, tall sculpture entitled the Endless Column which is situated in the city of Tg. Jiu, Romania, was reported to have an extraordinary stability to wind, which might be due to its modular shape, consisting of 15 pyramidal blocks of dimensions 45 x 90 x 45 cm, plus two halves-blocks at the extremities, totaling a length of 30 m. Wind tunnel experiments performed for the aerolastic model of the Column showed that for reduced wind speeds of Ur = 7 to 75 and angles of attack of 0°, 5°, 10°, 15°, 30° and 45 the Endless Column model is very stable especially at Ur =75, where galloping was expected (Dragomirescu et al, 2009). A CFD simulation employing the LES algorithm for a model of the Column with t...
Wind and Structures, 2020
A new type of bridge deck section consisting of four-box decks, two side decks for vehicular traf... more A new type of bridge deck section consisting of four-box decks, two side decks for vehicular traffic lanes and two middle decks for railway traffic, has been experimentally investigated for determining its aerodynamic properties. The eight flutter derivatives were determined by the Iterative Least Squares (ILS) method for this new type of four-box deck model, with two windshields of 30 mm and 50 mm height respectively. Wind tunnel experiments were performed for angles of attack α=±6° ±4° ±2° and 0° and Re numbers of 4.85 x105 to 6.06x105 and it was found that the four-box deck with the 50 mm windshields had a better aerodynamic performance. Also, the results showed that the installation of the windshields reduced the values of the lift coefficient CL for the negative angles attack in the range of -6° to 0° but the drag coefficient CD increased in the positive angle of attack range. However, galloping instability was not encountered for the tested reduced wind speeds, of up to 9.8. T...
Wind-induced loads on photovoltaic (PV) solar panels installed on roof tops, are of main concern ... more Wind-induced loads on photovoltaic (PV) solar panels installed on roof tops, are of main concern when designing the system; a detailed comparison between the guidelines and design codes ASCE7-05 (2005) and SEAOC (2013) and field measurements were conducted for a PV solar panel installed on the Mann Parking Building of the University of Ottawa. The PV panel was instrumented with a total of 26 strain gauges, on both surfaces of the panel and data was collected for 5 months. It was noticed that the roof wind zone, building edge and the parapet were the main elements affecting the estimated wind load value on each PV panel. The maximum wind load of 1,208 N was obtained on the northwest corner of the PV solar panel arrays, and the minimum wind load of 806 N was determined for the center of PV solar panel arrays. The field measurements indicated that the highest wind induced stresses are on the lower edge of the PV panel and the lowest stresses are on the middle point of the front surface...
Journal of Structural Engineering, 2021
AbstractWind tunnel tests were carried employing two different free-stream turbulent flow fields ... more AbstractWind tunnel tests were carried employing two different free-stream turbulent flow fields and one harmonic vertical gust profile conditions, and pressure measurements of the buffeting force ...
Journal of Wind Engineering and Industrial Aerodynamics, 2020
The current study attempts to investigate the characteristic of aerodynamic admittance of twin-bo... more The current study attempts to investigate the characteristic of aerodynamic admittance of twin-box bridge decks via wind tunnel test. Pressure measurement has been carried out on three twin-box bridge models and one closedbox bridge model, for two different turbulent flow-fields. The aerodynamic admittances of those bridge models and the buffeting force coherences along the spanwise direction are obtained to clarify the difference between twin-box bridge deck and conventional closed-box bridge deck in unsteady aerodynamic force, and it is found that the aerodynamic admittance of twin-box girders at low reduced frequencies is significantly higher than that of the conventional closed-box girder, the coherence of fluctuating force on twin-box girders is lower than that for a conventional closed-box girder due to the existence of the central gap. The distributions of the fluctuating pressure on bridge models are presented and discussed, which reveal that the three-dimensional effect of the incident wind velocity depends not only on the ratio of turbulence integral scale to the width of the bridge deck, but also on the flow separation pattern. Finally, empirical models for determining the fluctuating force coherence and aerodynamic admittance of twin-box bridge decks are proposed based on in-depth data analysis and are proved to be effective for fitting the experimental data, while the fitting parameters can be applied to flow-fields with different turbulence integral scales.
Shock and Vibration, 2018
During the past decades, wind-induced vibrations of bridge stay cables were reported to occur und... more During the past decades, wind-induced vibrations of bridge stay cables were reported to occur under various incipient conditions. The ice formation on stay cables is one of these conditions, which causes the ice-accreted stay cables to alter their cross section geometry, thus modifying their aerodynamic characteristics. Wind tunnel tests and several CFD simulations were performed for ice-accreted inclined bridge stay cables with two ice-accretion profiles dimensions, 0.5D and 1D, where D is the diameter of the cable. Wind-induced vibrations were analyzed experimentally for cable models with yaw inclination angles of 0°, 30°, and 60° and vertical inclination angles of 0° and 15°, for Reynolds numbers of up to 4 × 105. The aerodynamic drag and lift coefficients of the cable models and the pressure coefficients were determined from the CFD-LES simulations. The experimental results indicated that the vertical and torsional vibrations of the ice-accreted stay cables increased with the in...
Engineering Structures, 2018
This paper presents the results of reverse cyclic load testing of a repaired slender concrete she... more This paper presents the results of reverse cyclic load testing of a repaired slender concrete shear wall reinforced internally with superelastic Shape Memory Alloys (SMAs) in the boundary zones within the plastic hinge region. In addition, a companion-repaired wall reinforced with deformed mild steel was also tested. Provided herein is an assessment of the performance of the repaired walls against the same set of walls previously tested in their original condition. The repair strategy included removing heavily damaged concrete within the plastic hinge region, replacing ruptured and buckled reinforcing steel, and shortening of the SMA bars in the boundary zones. High-strength, self-consolidating concrete replaced the removed concrete. The concrete above the plastic hinge region remained intact given the negligible damage (hairline cracking) of the original walls in this zone. The test results demonstrated that SMA-reinforced concrete structural components are self-centering, permitting repair of damaged areas. Furthermore, the SMA bars were re-usable for the repair application due to their capacity to reset to their original state within the range of inelastic strains of up to 6%. The repaired walls were capable of restoring the yield and ultimate lateral load capacities, but sustained lower drift capacities. The repaired SMA wall was capable of recovering the imposed lateral drifts up to 2%, after which residual displacements accumulated due to rupturing of the SMA bars in the boundary zone. The repaired walls dissipated up to 7.8% more energy than their original walls for a significant portion of the loading range. The length of the SMA bars and the presence of starter bars in the original walls were influencing factors in the location of failure of the SMA-and steel-reinforced walls.
Computers & Structures, 2019
The recently developed integrated finite strip method (IFSM) is extended to the aerodynamic flutt... more The recently developed integrated finite strip method (IFSM) is extended to the aerodynamic flutter analysis of bridges under wind effects. The methodology is capable of performing a three-dimensional (3D) flutter analysis in the IFSM environment, and the solution falls into the category of both multi-mode and full-mode flutter analysis. Aerodynamic stiffness and damping matrices, as well as structural property matrices, are derived by IFSM. In addition, an optimal scheme is proposed for solving the flutter eigenvalue problem. Furthermore, a simple technique has been developed in order to handle different end boundary conditions. The proposed finite strip solution is very straightforward in terms of amount of input data, boundary conditions, modeling, and the flutter analysis process. Moreover, the convergence rate of the method is very high due to the semi-analytical and localization nature of the IFSM. Benchmark numerical investigations are presented, including the study of a simply supported thin flat shell and a model of the Kap Shui Mun Bridge, an existing long-span cable-stayed bridge. The numerical results show that IFSM significantly improves the convergence of the critical flutter frequencies, and therefore leads to smaller storage requirements and faster flutter eigenvalue extraction.
Advances in Civil Engineering, 2016
The bridge deck sections used for long-span suspension bridges have evolved through the years, fr... more The bridge deck sections used for long-span suspension bridges have evolved through the years, from the compact box deck girders geometrical configurations to twin-box and three-box bridge decks sections. The latest generation of split and multiple-box bridge decks proved to have better aerodynamic behavior; thus further optimization methods are sought for such geometrical configurations. A new type of multibox bridge deck, consisting of four aerodynamically shaped deck boxes, two side decks for the traffic lanes and two middle decks for the railway traffic, connected between them by stabilizing beams, was tested in the wind tunnel for identifying the flutter derivatives and to verify the aerodynamic performance of the proposed multibox deck. Aerodynamic static force coefficients were measured for the multibox bridge deck model, scaled 1 : 80, for Reynolds numbers up to 5.1 × 105, under angles of attack between −8° and 8°. Iterative Least Squares (ILS) method was employed for identi...
Wind and Structures, 2016
Long-span suspension bridges have evolved through the years and with them, the bridge girder deck... more Long-span suspension bridges have evolved through the years and with them, the bridge girder decks improved as well, changing their shapes from standard box-deck girders to twin box and multi-box decks sections. The aerodynamic characteristics of the new generation of twin and multiple-decks are investigated nowadays, to provide the best design wind speeds and the optimum dimensions such bridges could achieve. The multi-box Megane bridge deck is one of the new generation bridge decks, consisting of two side decks for traffic lanes and two middle decks for railways, linked between them with connecting beams. Three-dimensional CFD simulations were performed by employing the Large Eddy Simulation (LES) algorithm with a standard Smagorinsky subgrid-scale model, for $Re
Journal of Bridge Engineering, 2016
This paper provides a very efficient, integrated framework for seismic analyses of long-span cabl... more This paper provides a very efficient, integrated framework for seismic analyses of long-span cable-stayed bridges. The efficiency comes from the dramatic reduction in formation time and the degrees of freedom (DOF) associated with the structure, using the integrated finite strip method (IFSM) along with the application of a very robust and efficient time history method (THM) using the Newmark scheme for dynamic analysis of the bridge structure. The previous versions of the finite strip method are limited to modeling the bridge deck only, whereas other structural components are replaced by assumed boundary conditions. Using the IFSM, all components of the long-span cable-stayed bridge can be modeled in a unified system, and consequently, the real dynamic behavior including the interactions between deck, piers, and cables can be perfectly considered. To verify the solution, the geometric and dynamic properties of the Kap Shui Mun (KSM) Bridge, as a real example of a long-span cable-stayed bridge, are derived by the proposed finite strip method. Then, the seismic response of KSM Bridge under uniform and nonuniform earthquake loadings is investigated by using the THM. The results show that the IFSM can be applied successfully for seismic analysis of long-span cable-stayed bridges, and the analysis can be performed in a minimal amount of time.
This paper introduces a total integrated analytical solution for multi-span, continuous slab-on-g... more This paper introduces a total integrated analytical solution for multi-span, continuous slab-on-girder and box girder bridges by modelling the bridge deck and the piers together, using finite strip method (FSM). FSM has been well accredited for its efficiency in the structural analysis of bridges, reducing the time required for data input and analysis without affecting the degree of accuracy. By using a continuously differentiable smooth series in the longitudinal direction, a complex 3D problem is reduced to a 2D problem using the FSM. However, difficulties are encountered when components of different orientation, such as the piers, are being added to the formulation. Thus, the analytical model developed using the conventional FSM is limited to the superstructures without proper consideration of the interactions between the bridge deck (super-structure) and piers (sub-structure).In this regard, the cantilever type of pier strip element is formulated by the authors, base on the spline finite strip concept, which is compatible with the well developed spline finite strip bridge deck. In addition, by combining the piers and the bridge deck together in a single finite strip formulation, with some appropriate connecting boundary conditions, the time required for both static and dynamic analysis can be significantly reduced. In this paper, the development and verification of the vertical cantilever strip is introduced and the overall integrated method of analysis is presented with the aid of numerical examples. In addition, the efficiency of the proposed approach in seismic analysis using the Pseudo Excitation Method (PEM) is also demonstrated as an extension of its application.
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Papers by Elena Dragomirescu