STR-807: ANSYS MODELING OF POST-TENSIONED STEEL BEAM-COLUMN CONNECTIONS UNDER CYCLIC LOADING

Permanent deformations in a steel moment resisting frame can be eliminated by using post-tensioned (PT) elements. This paper presents the development of three-dimensional finite element models of PT steel beam-column connection subassemblies. Knowing that there is limited experimental data in the literature on PT steel connections with top-and-seat angles, reliable finite element models can be used to investigate the load carrying behaviour of PT steel connections as well as producing more data for these new connections. In this paper, finite element modelling, meshing, and analysis are performed in the commercial software, ANSYS. The analysis includes geometric and material nonlinearities, pre-loaded bolts and strands, gap opening and closing behaviour, in addition to contact and sliding phenomena. The results of finite element simulations are verified against previous test results on five interior PT steel beam-column connections with top-and-seat angles. In addition, parametric studies are conducted to investigate the effects of three factors on the cyclic response of PT steel connections. These factors include the yield strength and strain hardening of steel angles, the amount of initial post-tension force in PT strands, and the use of beam flange reinforcing plates

Hysteresis Behavior of Pre-Strained Shape Memory Alloy Wires Subject to Cyclic Loadings: An Experimental Investigation

Shape memory alloys (SMAs) are a class of smart materials with the ability to recover their initial shape after releasing the applied load and experiencing a relatively large amount of strain. However, sequential loading and unloading which is an unavoidable issue in many applications significantly reduces the strain recovery of SMA wires. In the present work, experimental tests have been performed to study the pre-strain effect of SMA wires on hysteresis behavior of SMA under cyclic loadings. The effects of cyclic loading on austenite and martensite properties have been investigated. SMA wires with diameter of 1.5 mm and length of 560 mm subjected to about 1000 cycles show about 3 mm residual deformation, which is approximately equal to 0.5% residual strain. It is observed that applying 1.7% pre-strain on the SMA wire fully eliminates the residual strain due to cyclic loading

STR-925: BONDING BEHAVIOR IN BRIDGE STEEL-REINFORCED ELASTOMERIC ISOLATORS

Steel-reinforced elastomeric isolators (SREIs) have been shown to be efficient devices to protect structures against moderate and severe earthquakes by isolating them from ground motions. Bridge elastomeric isolators, however, deteriorate when undergone repetitive loading cycles due to either earthquakes or traffic loadings. One major damage type observed dominantly in these devices is delamination or de-bonding between rubber and supporting plates and steel reinforcements, if cold-bonded. This paper investigates potential damage scenarios likely to occur in cold-bonded bridge SREIs. It also looks into bonding properties of rubber and steel in tension and shear, the two important functional characteristics of elastomeric isolators. In this study, experimental tests are employed in order to observe the bonding behavior between rubber and steel. Damage states have been organized and it is observed that the adhesive properties and level of shear deformations govern bonding characteristics

STR-931: TIMBER I-JOISTS WITH WEB OPENINGS: REINFORCEMENT, CAPACITY PREDICTION AND SENSITIVITY ANALYSIS

Timber I-joists are a popular product in light-frame wood construction in North America. The design with timber I-joists, however, has not yet achieved the same level of refinement compared to reinforced concrete or steel structures. One of the reasons is that timber I-joists have higher variability in their material properties than more homogeneous building materials. Additionally, although very commonly applied in practice, engineers and practitioners have limited knowledge and guidance for I-joists with web opening. As a result, in many cases the design of timber I-joists based on manufacturer’s specifications lead to very conservative solutions. The present research predicts the capacity of unreinforced and reinforced timber I-joists with openings from experimental results. A total of 100 unreinforced and 100 reinforced I-joists with opening were tested under four point loading. The capacity of the I-joists with opening was predicted from regression analysis. A sensitivity analysis was performed for the predicted equations using Meta-model of Optimal Prognosis (MOP) to evaluate the contribution of each parameter on the model responses. The research demonstrates that the reinforcement technique was efficient for I-joists with openings and the proposed equations were very accurate to predict the I-joists capacity

STR-930: CROSS LAMINATED TIMBER WALLS WITH OPENINGS: IN-PLANE STIFFNESS PREDICTION AND SENSITIVITY ANALYSIS

Cross-laminated timber (CLT) is gaining popularity in residential and non-residential applications in the North American construction market. An accurate quantification of in-plane stiffness of the CLT walls with openings is required to design a CLT structure subjected to lateral loads. Nevertheless, till today, no general approach is available for the design of CLT-members loaded in plane and there are no standardized methods for determining the stiffness of CLT shearwalls in the respective material design standards: the CSA O86 in Canada, and the NDS in the US. This study aims to quantify the stiffness of CLT walls with openings under in-plane loading. A finite element (FE) model of CLT walls was developed modelling wood as orthotropic elastic material and the glue-lines between layers using non-linear contact elements. The FE model was verified from test results of CLT panels under in-plane loading. A parametric study was performed to evaluate the change in stiffness of CLT walls with the variation of opening size and shape. A simplified equation to predict the in-plane stiffness of CLT walls with openings was proposed. Subsequently, a sensitivity analysis was performed using Meta-model of Optimal Prognosis (MOP) to evaluate the contribution of each parameter on the model response

STR-978: A HYSTERESIS MODEL FOR THE PISTON-BASED SELF-CENTERING BRACING SYSTEM CONSIDERING RESIDUAL DEFORMATION

A load deformation hysteresis model has been developed for the piston based self-centering (PBSC) bracing system. This bracing system utilizes shaft-piston mechanism for transferring load to its core energy dissipating elements, which are made of Nickel Titanium alloy (NiTinol) bars. These bars provide the brace its strength as well as the self-centering capability. Although in theory, the NiTinol based shape memory alloy bars are supposed to come back to their original shape after large nonlinear deformations, in reality, they experience residual deformation. The hysteresis models, which are currently available for capturing the behavior of self-centering systems, are known as flag shaped hysteresis. Unfortunately, these flag shaped hysteresis models cannot capture residual deformation. In order to solve this issue a novel hysteresis model has been developed for the PBSC bracing system. This model will enable researchers to capture the PBSC brace behavior in detail during quasi-static and dynamic time history analysis. This hysteresis model is developed using the results of nonlinear static analysis in MATLAB. The resultant plots were thoroughly examined to determine loading/unloading rules. These rules were coded and implemented in the S-FRAME software’s nonlinear analysis solver. A building frame model was built with PBSC bracing system and it was tested using ten earthquake records scaled to Vancouver soil class “C” response spectrum. It was observed that the PBSC brace has an excellent re-centering capability

Highway Bridge Infrastructure in the Province of British Columbia (BC), Canada

Some recent catastrophic impacts on highway bridges around the world have raised concerns for assessing the vulnerability of existing highway bridges in Canada. Rapid aging of bridge infrastructure coupled with increased traffic volume has made it crucial to establish an advanced Bridge Management System (BMS) for highway bridges. This paper aims at developing a highway bridge inventory for the province of British Columbia (BC) which is critical for efficient assessment of the existing structural health condition of the bridges, predicting their future deterioration, and prioritizing their maintenance and retrofitting works. This inventory is an extensive assemblage of data on highway bridges in BC under the responsibility of the BC Ministry of Transportation and Infrastructure (BC MoT) that includes more than 2500 highway bridges. It includes identification of the most common bridge types along with their location, structural and geometric parameters such as construction materials, bridge length, number of spans, deck width, skew angle, bridge pier, and foundation type, structural health condition rating and construction period. This information is of paramount importance for effective infrastructure management, proper rehabilitation solutions, and efficient design of a Structural Health Monitoring (SHM) and Control System for enhancing structural resilience of highway bridges in BC. Several statistical analyses have been carried out for efficient utilization of the information available in the inventory for further research and analyses, as well as for developing a proper BMS for the province’s bridges.Applied Science, Faculty ofEngineering, School of (Okanagan)ReviewedFacult

Lateral Movements of a Bridge Abutment Due to Compressible Foundation Soils

Highway approach embankments are often constructed over weak and compressible soils. The consolidation settlements induced by the embankment loads are known to result in downdrag forces and lateral forces on the piles supporting the bridge abutments. Several approaches are commonly employed during construction of highway bridges in Ontario in order to reduce these forces. These approaches include: preloading and surcharging to achieve the anticipated settlements prior to the installation of abutment piles; application of lightweight fill materials such as expanded polystyrene and expanded pelletized blast furnace to reduce embankment loads; and measures to expedite pore water pressure dissipation such as wick drains. This paper presents a case history where the abutments of seven bridges on the Macdonald-Cartier Freeway between Carnwall and the Quebec border experienced excessive movements, which resulted in extensive repair work in three of these structures. A series of numerical analyses are conducted to provide an explanation for abutment movements in Brookdale Avenue underpass structure. Two-dimensional nonlinear finite element analyses were conducted using commercial software package, PLAXIS 2D to evaluate the forces and moments acting on the abutments as a result of embankment loading. The behavior of compressible soils is modeled using Soft Soil Model (SSM). The results indicated that the consolidation settlements and their impact on the abutment piles were estimated with an acceptable accuracy using FE model. The results presented in this study are considered to be of interest to researchers and practitioners

Seismic fragility assessment of multi-span concrete highway bridges in British Columbia considering soil–structure interaction

Fragility curve is an effective tool for identifying the potential seismic risk and consequences during and after an earthquake. Recent seismic events have shown that bridges are highly sensitive and vulnerable during earthquakes. There has been limited research to evaluate the seismic vulnerability of the existing bridges in British Columbia (BC), which could help in the decision-making process for seismic upgrade. This study focuses on developing seismic fragility curves for typical multi-span continuous concrete girder bridges in BC. Ground motions compatible with the seismic hazard were used as input excitations for vulnerability assessment. Uncertainties in material and geometric properties were considered to represent the bridges with similar structural characteristics and construction period. The fragility of the bridge is largely attributable to the fragilities of the columns, and to a lesser extent, the abutment and bearing components. The results of this study show that, although not very significant, the soil–structure interaction has some effect on the component fragility where this effect is not very significant at the bridge system level.The accepted manuscript in pdf format is listed with the files at the bottom of this page. The presentation of the authors' names and (or) special characters in the title of the manuscript may differ slightly between what is listed on this page and what is listed in the pdf file of the accepted manuscript; that in the pdf file of the accepted manuscript is what was submitted by the author

Experiment-Based Sensitivity Analysis of Scaled Carbon-Fiber-Reinforced Elastomeric Isolators in Bonded Applications

Fiber-reinforced elastomeric isolators (FREIs) are a new type of elastomeric base isolation systems. Producing FREIs in the form of long laminated pads and cutting them to the required size significantly reduces the time and cost of the manufacturing process. Due to the lack of adequate information on the performance of FREIs in bonded applications, the goal of this study is to assess the performance sensitivity of 1/4-scale carbon-FREIs based on the experimental tests. The scaled carbon-FREIs are manufactured using a fast cold-vulcanization process. The effect of several factors including the vertical pressure, the lateral cyclic rate, the number of rubber layers, and the thickness of carbon fiber-reinforced layers are explored on the cyclic behavior of rubber bearings. Results show that the effect of vertical pressure on the lateral response of base isolators is negligible. However, decreasing the cyclic loading rate increases the lateral flexibility and the damping capacity. Additionally, carbon fiber-reinforced layers can be considered as a minor source of energy dissipation.Applied Science, Faculty ofEngineering, School of (Okanagan)ReviewedFacult