Publications

Analysis of Masonry Infill Panels Retrofitted with FRP Sheets in R/C Frames

Masonry infill walls are often used as non-structural elements. According to the past structural failure, ignorance of interaction between infill walls and enclosed frame may lead to the different seismic response for non-ductile building frames. The main contribution of this paper is to analytically investigate the behavior of reinforced concrete with masonry infill panels as participating structural. In doing so, a finite element model based on an equivalent strut method is conducted to represent the behavior of masonry panels. The strut model is calibrated using the results of the companion experimental program, which examined the cyclic behavior of infill panels with and without FRP sheets. Accordingly, a nonlinear spring element and a shell element are used to simulate the behavior of masonry strut elements and FRP sheets, respectively. The nonlinear static analysis (Push over analysis) is accomplished using SAP2000 [1] structural analysis software for a 10-story building with FRP sheets subjec

Urban RAT: New Tool for Virtual and Site-Specific Mobile Rapid Data Collection for Seismic Risk Assessment

The Urban Rapid Assessment Tool (RAT) integrates recent advances in virtual environments and mobile smart devices to facilitate the rapid visual screening (RVS) of building structural parameters outlined in FEMA 154 and FEMA 310. These advanced parameters support Tier-1 and Tier-2 earthquake loss estimations in programs such as Hazus and CanRisk. Urban RAT includes two software components that use a common database schema: Urban RAT Desktop integrates the virtual environment of Street View within the geographic information system ArcGIS and, Urban RAT mobile, an equivalent on-site data collection application for the Android operating system. Structural parameters observed on a sample of 113 buildings using both Urban RAT Desktop and Urban RAT Mobile show significant agreement. As such, virtual assessment is a viable proxy for field-based RVS, making Urban RAT effective and efficient for rapid structural data collection to support detailed loss estimation studies in urban regions. Developed and tested during 2011–2013, the advantages of the Urban RAT tool are defined and discussed in the context of traditional sidewalk surveys and contrasted with other existing data collection solutions.

Seismic Behavior and Design of Reinforced Concrete Columns Confined with FRP Stay-in-Place Formwork

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Seismic fragility analysis of pre-1975 conventional concrete frame buildings in Canada

Fragility analysis was conducted for reinforced concrete frame buildings in Canada designed based on the 1965 National Building Code of Canada as representative of pre-1975 era of seismic design practice. Two-, five-, and ten-storey buildings were designed for Vancouver and Ottawa, representing buildings in high and medium seismic regions. They were modelled for inelastic response time history analysis, with respective inelastic hysteretic models for flexure and shear. Software PERFORM-3D was used to conduct incremental dynamic analysis under incrementally increasing earthquake intensity. Probabilistic analysis of the results of incremental dynamic analysis led to the development of fragility functions, which can be used as seismic vulnerability assessment tools. The results are compared with those generated for frame buildings designed on the basis of the 2010 NBCC. The comparison indicates that the probabilities of exceeding performance levels are significantly higher for older buildings relative to recently built fully ductile and moderately ductile buildings, respectively.

Seismic flexural behavior of concrete connections reinforced with CFRP bars and grids

The corrosion of steel reinforcement in concrete and the resulting deterioration of structures prompted research on fiber reinforced polymers (FRP) as potential reinforcement for concrete members, for use in new construction. FRPs have more favorable advantages for new concrete buildings subjected to seismic loads particularly in corrosive environment. A comprehensive experimental research program was conducted at Ottawa University in Canada to investigate the behavior of FRP reinforced concrete joints to develop design and detailing requirements for FRP reinforced concrete joints under seismic loading. Three large-scale FRP reinforced concrete structural joints were designed, constructed, and tested under cyclic loading. The specimens were T-shape joints consisting of two columns and one beam representing half portion of the first and the second floor of one-bay reinforced concrete frame, or exterior joint of frames with more than one bay. The columns were subjected to the constant axial load and the beams were under reversed cyclic loading. The reinforcement cage was consisted of CFRP bars as longitudinal reinforcement and CFRP grids as transverse reinforcement. The paper presents the details and results of the experimental programs. The results indicate that FRP reinforcement can be used effectively in new concrete buildings. Photographs taken at the selected stages of loading illustrated the performance of each joint. The hysteretic behavior was presented in terms of force–displacement and moment–drift relationships and other hysteretic relationships. Spacing of CFRP grids and arrangement of longitudinal CFRP bars were the main test parameters.

A study of the effect of chloride binding on service life predictions

The August 17, 1999, Kocaeli (Turkey) earthquake — damage to structures

The 1975 Turkish code provisions are first reviewed to provide the background for design and detailing of structures prior to the earthquake. The performance of reinforced concrete and masonry structures is described indicating many of the deficiencies in design, detailing, and construction execution. The behaviour of precast concrete structures, steel structures, and industrial facilities is also presented. The provisions of the 1997 Turkish building code are summarized and a description of new construction provides evidence of both excellent and poor construction practice. Some examples of retrofitting of damaged structures soon after the earthquake are also presented.Key words: seismic design, earthquake, Kocaeli, structures, codes, concrete, precast concrete.

High-Strength Concrete Columns: State of the Knowledge

This paper consists of reported information divided into two general categories, performance of High-Strength Concrete (HSC) columns under concentric loads, and combined axial and bending moments. Presented is a brief summary of the highlights of the reported data.

Selection of seismic excitations for nonlinear analysis of reinforced concrete frame buildings

The selection of seismic motions is one of the most important issues for the time-history analysis of buildings. This paper discusses four different methods for obtaining spectrum-compatible acceleration time histories (i.e., accelerograms) of seismic motions. Based on these methods, four sets of accelerograms compatible with the design spectrum for Vancouver were selected for this study. These included (i) scaled real accelerograms, (ii) modified real accelerograms, (iii) simulated accelerograms, and (iv) artificial accelerograms. The selected sets were used as excitation motions in the nonlinear analysis of three reinforced concrete frame buildings designed for Vancouver. The buildings included a 4-storey, a 10-storey, and a 16-storey building, which can be considered representative of low-rise, medium-rise, and high-rise buildings, respectively. The storey shears, interstorey drifts, and curvature ductilities for beams and columns obtained from the analysis were used for the evaluation of the effects of the selected sets on the responses of the buildings. Based on the results from the analysis, scaled real accelerograms are recommended for use in time-history analysis of reinforced concrete frame buildings.

Performance of Structures in Indonesia during the December 2004 Great Sumatra Earthquake and Indian Ocean Tsunami

A reconnaissance was conducted in Indonesia to investigate the effects of the 26 December 2004 earthquake and tsunami on buildings, bridges, and other physical infrastructure. The infrastructure in the coastal regions of Banda Aceh was completely devastated by both tsunami wave pressures and seismic ground excitations. The damaging effects of the tsunami were most pronounced in unreinforced masonry walls, nonengineered reinforced concrete buildings, and low-rise timber-framed buildings. Engineered structures survived the tsunami pressure, but many suffered extensive damage due to seismic forces. The majority of the seismic damage was attributed to poor design and detailing of nonductile buildings. Specific observations made during the reconnaissance indicate the engineering significance of the disaster.

Coupled walls in earthquake-resistant building: Parametric investigation and design procedure

Evaluation of Residual Load Carrying Capacity of Aging Multi-span Slab-on-Steel Girders Bridge in Changing Climate

The effect of cable corrosion on dynamic response of Stonecutters Cable-Stayed Bridge model

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.

Ductility and seismic behavior

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Capabilities of a Shock Tube to Simulate Blast Loading on Structures

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Seismic behavior of concrete bridge columns confined with fiber-reinforced polymer stay-in-place formwork

One of the applications of fiber-reinforced polymers in bridge construction is stay-in-place formwork. Fiber-reinforced polymer stay-in-place formwork, in the form of preformed tubes, provides easy form assembly, protection of steel reinforcement and concrete against corrosion and chemical attacks while also improving the strength and ductility of structural elements in earthquake resistant construction. Experimental research was conducted to investigate the seismic performance of fiber-reinforced polymer stay-in-place formwork for bridge columns. Tests of large-scale specimens were conducted under simulated seismic loading. The experimental program included circular and square columns confined with carbon fiber–reinforced polymer tubes. The results indicate that the use of carbon fiber–reinforced polymer tubes increases column inelastic deformability significantly. Bridge columns under low levels of axial compression exhibit inelastic drift capacities in excess of 4% before failing in flexural tension due to the rupturing of longitudinal reinforcement. These observations and experimental results were used to develop a displacement-based design procedure for concrete confinement for fiber-reinforced polymer–encased concrete columns. This article presents an overview of the experimental program and the design approach developed.

Modelling hysteretic behaviour of coupled walls for dynamic analysis

Modelling techniques for dynamic inelastic response analysis of coupled wall structures are investigated. Emphasis is placed on effects of parameters defining the force‐displacement hysteresis loop. Specifically, effects of axial force‐moment interaction, strength reduction, shear yielding, pinching, reloading and unloading branches of hysteresis loops are considered. Effects of modelling parameters on selected response quantities are investigated and discussed in detail. A 20‐storey coupled wall structure was selected for dynamic analysis. Ranges of parameters characterizing force‐displacement hysteresis loops were obtained from laboratory tests under slowly reversed static loading. Previously recorded strong motion accelerograms were used as input motions. Results indicate that wall axial forces and beam strength reduction can have significant effects on response envelopes. Moderate variations in unloading and reloading branches of hysteresis loops and pinching appear to have little effect on dynamic response.

Hysteretic Behavior of Anchorage Slip in R/C Members

Large‐scale reinforced concrete columns were tested to investigate hysteretic behavior of anchorage slip in reinforced concrete structures. The columns were subjected to constant axial compression and unidirectional and bidirectional lateral‐deformation reversals. The results indicate a significant increase in column rotation due to anchorage slip. Penetration of yielding into the column footing was observed in the tension reinforcement, while the compression yielding was localized at the column‐footing interface. Axial compression resulted in early closure of the crack associated with anchorage slip, reducing related deformations. An analytical model was developed for hysteretic moment‐anchorage slip‐rotation relationship. The model consists of a primary curve and a set of rules defining unloading and reloading branches. The primary curve is constructed by computing the extension and slippage of tension reinforcement in the adjoining member. This is accomplished by considering inelastic strain distribution along the embedment length of reinforcement, as well as the local bond‐slip relationship. Hysteretic rules are obtained from experimental observations, and incorporate pinching of hysteresis loops as well as the effect of axial compression. Comparisons of experimental and analytical hysteretic relationships indicate excellent agreement.