The Adhesive-Applied Roofing System (AARS) is a new generation of built-up roofs gaining popularity in North American low-slope application. AARS uses no fasteners, and all components (e.g., steel deck, vapor barrier, insulation board, cover board, and membrane) are integrated by application of adhesives. Although AARS has been in use, existing standards address only mechanically attached or bonded roof assemblies. To quantify the wind-uplift performance of the AARS, an industry–university–government collaborative research project, Development of Wind Uplift Standard for Adhesive-Applied Low-Slope Roofing System, has been initiated. The project has three major tasks: experimental investigation, formulation of a numerical model, and development of wind design guide and standards. Task 1 developed test protocols to quantify the uplift and peel resistance of small-scale AARS specimens respectively subjected to tensile and shear loading. Using the standardized tensile test parameters, this paper identifies the effect of material combinations and variation in the adhesive applications on the uplift resistance of AARS subjected to tensile loading. This parametric study not only verified the applicability of the developed tensile test method for variations in the configurations, but it also identified the weakest link in AARS. Data from this small-scale testing can facilitate industries to optimize the material combinations such that it can be correlated with the systems wind uplift resistance.
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Tsunami, meaning “harbor wave” in Japanese, is the outcome of a vertical displacement of a large body of water. It can be triggered by various geological or astronomical phenomena, including: underwater earthquakes occurring along tectonic boundaries, volcanic eruptions, submerged or aerial landslides, and impact from asteroids or comets. In deep, open waters, tsunamis have small amplitudes (wave height), but very long wavelengths. However, as tsunami waves advance toward shorelines they transform.
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This paper presents the results of using distributed Brillouin fibre sensors to detect crack formation in a simply supported reinforced concrete beam subjected to four-point loading. A Brillouin multiple-peak fitting method was used to enhance the spatial and strain resolutions of the measurements. By doing this, the distributed strain profile along the beam was determined with a 5 cm read-out resolution in comparison with the 15 cm spatial resolution of the fibres. The location of the cracks was identified by locating the positions in the strain profile where the strain suddenly changes, by searching for the maximum compressive or tensile peaks in the Brillouin frequency spectrum, as opposed to conventional strain reading, which focuses solely on the maximum Brillouin peak. The amplitude of the Brillouin peak for the suddenly changed strain (crack) was found to be smaller than half of the amplitude of the maximum Brillouin peak at the maximum strain location corresponding to the average strain of the material, which would have been neglected by standard peak or area fitting methods, especially for fine cracks or the initial crack build-up period.
A combined experimental and analytical investigation was conducted at the University of Ottawa to assess the performance of blast-resistant window retention anchors to generate design information. The experimental phase of research involved 46 full-scale window tests with different parameters. The analytical investigation included numerical modeling and dynamic analysis of windows to expand the experimental results and to assess the significance of design parameters. Computer software LS-DYNA was selected for the analyses. Analytical models of selected test windows with aspect ratios of 1.0 and 3.0 anchored on structural steel, reinforced concrete, concrete block masonry, and stone masonry substrates were modeled. The models were validated against experimental data. Additional windows with aspect ratios of 1.5 and 2.0 were also modeled for investigation. The models were used to conduct a parametric investigation with the parameters consisting of substrate flexibility, anchor fixity conditions, window size and aspect ratio, frame rigidity, number and spacing of anchors, and the threat level as defined by reflected pressure-impulse combinations. The significance of each parameter is illustrated with emphasis placed on the magnitude of anchor shear and tension design forces. The distribution of anchor forces is obtained numerically. Anchor forces and distributions are compared with those observed experimentally. Design force distribution along the perimeter of window frames is recommended for use in design. The paper provides the results of numerical simulations illustrating the significance of design parameters on anchor design force levels and their distributions.
The International Union of Laboratories and Experts in Construction Materials, Systems and Structures (RILEM) was founded with the aim to promote scientific cooperation in the area of construction materials and structures worldwide. This mission is achieved through collaboration of leading experts in construction practice and science including academics, researchers, industrialists, testing laboratories and authorities.
Research on seismic behaviour of shear walls with high-strength steel is limited. A combined experimental and analytical investigation was conducted to assess seismic behaviour of flexure-dominant shear walls. A large-scale concrete shear wall with Grade 690 MPa (ASTM A1035) reinforcement and 84 MPa concrete was tested under simulated seismic loading. The wall represented a 6-story building shear wall with 4.53 m height and 1.45 m length. It sustained a lateral drift of 1.8% prior to developing failure due to the rupturing of longitudinal reinforcement. This is 35% less than the drift capacity of a companion wall reinforced with 400 MPa reinforcement tested earlier. VecTor2 software was used to conduct an analytical parametric study to expand the experimental findings. The results indicate that the reinforcement grade has a significant impact on strength, ductility, and hysteretic behaviour of shear walls.
Damage to structures and infrastructure due to the Chile tsunami of 27 February 2010, is presented. Robust, modern engineered structures performed well during this tsunami and, generally, damage only to non-structural components was evident. The majority of damage was sustained by non-engineered residential homes located within the inundation zone. These dwellings consisted of either light timber frame construction or concrete frame construction with brick masonry infill walls. Many of the dwellings incorporated sheet metal as exterior cladding or roofing. The hydrodynamic (drag) forces, impulsive loading, hydrostatic forces, buoyant forces, and debris impact loading were probable sources during the tsunami causing the observed damage. Failures included punching of brick masonry infill walls, partial and complete collapse of load bearing elements such as columns, and sliding and unseating failures of second storey levels and roofs. A discussion of the state of the art in tsunami design practice is also provided.
Performance-based vulnerability assessment of buildings requires dynamic inelastic analysis, which cannot be conducted without reliable analytical models. An important aspect of analytical building models involves hysteretic modeling of force-deformation relationships. PERFORM-3D software was used to generate fragility curves for moderately ductile buildings in Eastern Canada using hysteretic models with different features reflecting the recommendations of different North American standards. Two-story and five-story reinforced concrete (RC) frame buildings were considered for this purpose. The parameters that define rotational limits, as specified in ASCE 41-13 and ACI 369R-11 as well as the National Building Code of Canada (NBCC), were assessed. The results indicate that the variations in modeling parameters did not result in significant differences in fragility response at immediate occupancy and life safety performance levels, whereas the fragilities at the collapse performance level were affected. The probability of exceeding collapse prevention in buildings modeled as per NBCC was higher than those modeled using the ASCE 41-13 and ACI 369R-11 requirements.
The corrosion of reinforcing steel in reinforced concrete (RC) bridge decks due to the application of de-icing salts in winter has been recognized as one of the major causes of highway bridge deterioration in North America. Corrosion-induced damage is usually manifested by longitudinal cracking, spalling, and/or delamination of the concrete cover due to the expansion of corrosion products accumulating around the reinforcement. This damage leads to reduction or loss of serviceability, safety, and service life of RC bridge decks. This paper presents finite element analyses of the behaviour of the concrete bridge deck cover subjected to reinforcing steel corrosion. The prediction of the damage caused by corroding reinforcing bars is established by calculating the induced stresses in the surrounding concrete. The numerical model is used to conduct a parametric investigation of several design variables. It is found from the analyses that different failure mechanisms govern depending on the geometry and configuration of the reinforcing bars in the concrete cover of the bridge deck. Finally, the impact of concrete overlays on the governing failure modes of cracking, spalling and/or delamination of the concrete cover is investigated by using the model. (A)
This study introduces a slack free connection (SFC) by which pinching would be removed from hysteretic behavior of tension-only braces (TOBs). SFC through its mono-directional behavior, eliminates undesirable pinching of the tension-only bracing and changes it to a reliable lateral load resisting system with high energy dissipation capability. A Matlab/Simulink-based model, called Macro-Simulink model, is developed to simulate hysteretic behavior of TOBs with or without SFC. Derived Macro-Simulink model is also able to account for hysteretic behavior of the frame. The frame itself can have either deteriorated or non-deteriorated hysteretic behaviors. The Macro-Simulink model is verified through different techniques including earlier experimental results, explicit finite element modeling, and other pre-verified analytical/numerical tools. It is observed that initial pre-tension load only affects initial stiffness of the TOB and has no contribution on its nonlinear hysteretic behavior. Obtained results of this study indicate that energy dissipation capacity of TOBs with SFC would be improved up to 6 times compared with that of conventional TOBs. Moreover contribution of SFC is more pronounced in the case of frames with highly deteriorated behaviors. As a result TOB with SFC can be considered for retrofit purposes as well.
