Shahria Alam

Prefabricated wood I-joists with web openings are commonly used in light-frame wood construction. The capacity and the failure pattern of such I-joists in the presence of a circular web opening were experimentally investigated on 100 specimens with various sizes and locations of web openings and two different span lengths of 3.66 m (12 ft) and 6.10 m (20 ft). The control I-joists, i.e., I-joists without any opening, failed in flexure in the midspan, whereas most of the I-joists with an opening failed in a brittle and sudden shear mode. The presence of an opening reduced the capacity up to 54% compared to I-joists without web openings depending on the size and location of the opening. Subsequently, to prevent brittle failure and improve capacity, the I-joists were reinforced using two perpendicular OSB collar layers with a variation in the reinforcement length. The effectiveness of reinforcing the web around openings was investigated on another 100 specimens. After reinforcement, brittle premature failure of I-joists was prevented with an increase in capacity up to 27% compared to the I-joists with openings. Analytical models to calculate the capacity of unreinforced and reinforced I-joists with openings are proposed, validated with results from previous research, which prove to be more accurate compared to existing models from the literature.

Timber I-joist is a common building construction element in North America and Europe due to its availability and easiness of passing the service conduits and ducts through openings in the Oriented Strand
Board (OSB) web of I-joists. However, in order to provide passageway for service conduits and ducts, cuts
and notches in the flange of I-joist are frequently made during construction without considering the
structural integrity of the system. Flange stiffness is very critical as it provides the flexural strength to
the I-joist, hence it is prohibited to cut or notch the I-joist flanges. This study examined ten series of timber I-joists with single flange notch at different locations in two span lengths (12 and 20 ft) and compared
with the uncut I-joists to understand the reduction in load capacity, stiffness and failure mechanism of
the tested I-joists. A total of 100 I-joist specimens, which included uncut and flange notched I-joists, were
tested in this experimental study. It was observed that with the increase in distance of the notch from the
support, the load carrying capacity of notched I-joists can even decrease up to 80% in comparison with
the uncut I-joists. Moreover, the effects of notch location and notch size were also investigated, and it
was found that these notches significantly affect the load carrying capacity of an I-joist.

This paper proposes improved shear strength prediction equations for steel fiber-reinforced concrete (SFRC) beams from a database of 358 test results without web reinforcement. A parametric study was performed to evaluate the contribution of different parameters on the shear strength of SFRC beams. The factorial design identified the most important parameters and their interactions on the shear strength. The results showed that the interactions were significant. Therefore, nonlinear interaction terms were incorporated in the genetic algorithm to develop equations for deep and slender beams. The results showed that the proposed shear equations produced less scatter with a significant improvement in coefficient of variation, standard deviation, and average absolute error. A design example is presented for a reinforced concrete (RC) beam with steel fibers. It was observed that the steel fibers could reduce the stirrups requirements significantly in the RC beams by providing sufficient shear strength in fiber-concrete matrix.

Posttensioned (PT) elements in steel buildings can substantially mitigate permanent seismic damages and the associated post-earthquake repair costs during earthquakes. In this paper, a response surface methodology (RSM) is used to predict and optimize the lateral response characteristics of PT steel beam-column connections with top-and-seat angles. The monotonic lateral response characteristics considered in the study include: initial stiffness, load capacity, and ultimate drift of PT connections, as well as load and drift levels corresponding to the gap-opening (decompression) in PT connections. Based on the results of finite element simulations and extensive sensitivity studies, six influential parameters are considered as input variables in this study. These parameters are posttensioning strand force, beam depth, beam flange thickness and width, span length, and column height. By using a desirability approach, the lateral response of PT steel beam-column connections is optimized. The optimization studies aim at maximizing the initial stiffness, load capacity, and ultimate drift of PT connections and/or minimizing the amount of steel in the beam section, which contributes to the final cost of frame structures. The multi-criteria optimization studies reveal the regions of factor space where optimal conditions are achieved. The optimized solutions are then confirmed by performing simulation runs with the optimal factor combinations. Among the results, it is shown that damage occurs earlier in PT connections with deeper beams and greater posttensioning strand forces. The dominant limit state for the PT connections was beam local buckling starting at early drifts of 1.2%, whereas the first occurrence of angle fracture was at about 4% drifts, and two limit states of strand yielding and bolt extensive yielding were not observed in the analyzed PT connections.

Download link: http://authors.elsevier.com/a/1Tv59W4G4Bj1I

ABSTRACT In the past earthquakes, steel moment resisting frames suffered damage. Earthquake-induced damage in the main structural members, such as beams, and columns, leads to permanent deformations in buildings. The resulting permanent damage following earthquakes substantially increases repair costs. The repair of damaged buildings with extensive permanent deformations may not be economically feasible. Therefore, it is essential to eliminate the residual deformations while designing ductile beam—to—column connections. The seismic performance of steel buildings can be improved by allocating pre-specified elements in the building so as to dissipate the input energy and also provide self-centering (the ability to return the structure to its undeformed position). This paper presents a feasibility study of utilizing superelastic Shape Memory Alloy (SMA) plates in steel beam—column connections. Three-dimensional finite element models of steel beam—column subassemblies are generated to assess the efficiency of SMA-plates on the seismic behavior of connections. In this new application, SMA-plates are used in the plastic hinge region of the beam. The results of these finite element simulations are promising. The proposed connections with SMA plates could return to their original positions, while exhibiting a ductile behavior with good energy dissipation. Furthermore, the occurrence of local buckling in beam flanges was prevented in the new connections with SMA-plates. Read More: http://ascelibrary.org.ezproxy.library.ubc.ca/doi/abs/10.1061/9780784479117.180

The use of Fibre-Reinforced Polymer (FRP) as reinforcement in concrete structures has received much attention owing to its higher resistance to corrosion compared to that of regular steel reinforcement. Since FRP is a brittle material, its use in seismic resisting structural elements has been a concern. FRP RC structures can be made ductile by utilizing a ductile material such as

ABSTRACT Conventional steel-based rubber bearings are being replaced by fiber reinforced elastomeric isolators (FREI) due to their high weight and manufacturing cost. Compared to existing rubber bearings, FREIs have superior performance and as a result can control the seismic response of structures more efficiently. This study aims to simulate the performance of rectangular carbon FREIs (C-FREIs) produced through a simple and cost-effective manufacturing process. Additionally, the effect of different factors including the number and the thickness of rubber layers, as well as the thickness of carbon fiber reinforced sheets are investigated on the performance of C-FREIs through sensitivity analyses based on the results obtained from finite element simulations. The results show that by increasing the number and thickness of rubber layers, the efficiency of C-FREIs degrades in terms of vertical strength and damping capacity, however, the performance improves in terms of lateral flexibility. Another important observation is that the increasing thickness of fiber-reinforced layers can increase the vertical rigidity of the base isolator. The vertical stiffness has the most sensitivity to the thickness of elastomeric layers and the thickness of CFR sheets while, when the number of rubber layers increases, the effective lateral stiffness is mostly affected.

The present research investigates the polymer/cement (P/C) ratios (0, 5, 10, 15, and 20%) on mechanical and durability properties of modified mortar exposed to different curing conditions. These properties include compressive and flexural strengths, flow spread test, water absorption, density, coefficient of water absorption, sorptivity, and salt/sulfate resistance tests. The results show that combining seven days of water submergence and 21 days of ambient temperature curing (7W21D) along with 15% polymer content is more helpful to improve the mortar properties compared to other
mix proportions and curing conditions. Interestingly, the same combination resulted in a better performance in terms of water absorption, the coefficient of water absorption, sorptivity, toughness and salt/sulfate resistance as compared to polymer-modified mortars (PMMs) containing 0, 5, 10, and 20% polymer.

Substantial amount of glass wastes are being generated all around the world. In most cases, they end up in the landfill without considering recycling option. Since it is an inert material, they occupy the landfill space for considerable amount of time unless there is a potential for recycling. Such glass wastes in the crushed form have a good potential in the infrastructure industry. In this research we investigate the possibility of utilizing recycled glass powder (RGP) in along with supplementary cementitious materials (SCMs), such as fly ash (FA) and silica fume (SF) as partial replacements of cement. The physical and mechanical properties of fresh and hardened cement mortar with such combinations are investigated. In order to improve the physical and mechanical properties of hardened mortar, styrene butadiene rubber (SBR) was also added in the mortar mix. The result shows that the addition of fine RGP, FA and SF significantly improved the bond between the SBR and cement matrix which leads to an increase in the compressive and flexural strengths. Moreover, the addition of RGP, SF and FA considerably reduced the alkali silica reaction (ASR) expansions, percentage of water absorption, and the rate of water absorption than those of the control mix. This study shows that the RGP can be successfully utilized as an effective mineral admixture in cement mortar with 25% optimal replacement of cement.

This study presents the performance of reinforced concrete (RC) slender columns (structural elements with a shear span-to-depth ratio larger than 2) under lateral loading using finite element analysis (FEA). The FEA model was first validated with an experimental result. To observe the effect of various parameters and their interactions on the performance of slender columns, design of experiments (full factorial design and regression analysis) were performed. The parameters considered were concrete strength, reinforcement ratio, slenderness ratio, steel strength, axial load and transverse reinforcement. The performance was evaluated in terms of capacity and ductility ratio of the slender column. Finally, two regression models for capacity and ductility ratio were proposed, which are based on the important factors and interactions where both models were validated with the FEA model.

This study presents the performance of reinforced concrete (RC) slender columns (structural elements with a shear span-to-depth ratio larger than 2) under lateral loading using finite element analysis (FEA). The FEA model was first validated with an experimental result. To observe the effect of various parameters and their interactions on the performance of slender columns, design of experiments (full factorial design and regression analysis) were performed. The parameters considered were concrete strength, reinforcement ratio, slenderness ratio, steel strength, axial load and transverse reinforcement. The performance was evaluated in terms of capacity and ductility ratio of the slender column. Finally, two regression models for capacity and ductility ratio were proposed, which are based on the important factors and interactions where both models were validated with the FEA model.

In this study, the seismic performance of a newly proposed seismic-force-resisting system, consisting of superelastic shape memory alloy (SMA) reinforced concrete building, was evaluated. Thirteen different reinforced concrete (RC) ductile moment resisting frames having two different storey heights (3 and 8) were analyzed. The frames were designed according to the recent Canadian building code NBCC (2005) and assumed to be located in the seismic zone of Western Canada. The control frame in each building height was reinforced with steel rebars. For the other 11 frames, the steel rebars were replaced by SMA rebars in the plastic hinge region of the beams starting with the first level and then gradually increasing the use of SMA to the upper levels while keeping steel rebars in other regions of the beams and columns. The seismic performance of steel and SMA frames were evaluated from nonlinear incremental dynamic analyses (IDA) performed using 20 earthquake records. The seismic performance was measured in terms of the maximum inter-storey drift ratio (Max.ISDR), and maximum residual inter-storey drift ratio (Max.RISDR). Results have shown that SMA-reinforced concrete frames experienced 2.5% to 50% higher drift ratio and 3.3% to 100% lower residual drift ratio compared to the steel-RC frames.

In this study, the performance of newly proposed seismic-force-resisting systems, concrete reinforced with superelastic shape memory alloy (SMA) rebars, was evaluated. A trial value of the response modification coefficient, � factor was assessed and the appropriate values of system overstrength,
Ω0 and the ductility related force modification factor, 𝑅 were determined. The FEMA P695 (2009) methodology was followed for this purpose. A total of 13 frames, varying in two parameters, building height (3 and 8) and replacement of steel by SMA starting from level 1 and moving up to the top level sequentially were analyzed. Different reinforcement detailing used for each frame were: (i) steel reinforcement in all the levels (steel-RC) and (ii) replacement of steel by SMA rebars used in the plastic hinge region of the beams in the first level and then gradually increasing the use of SMA to the upper levels and keeping steel rebar in other regions (steel-SMA-RC). For both cases, columns were reinforced with only regular steel. The frames were designed according to CSA A23.3 (2004) and assumed to be located in the high seismic zone of Western Canada. Nonlinear static pushover analyses and nonlinear incremental dynamic analyses considering 20 earthquake records were performed to investigate the seismic performance factors (𝑆���. The) obtained results on 𝑆�� of all individual frames represent that the proposed seismic factors were within the range of permissible limit and when subjected to maximum considered earthquake a sufficient
margin could be provided against collapse. Steel-SMA-RC frames experienced 4%-17% lower probability of collapse compared to the steel-RC frames. This will encourage the structural and material engineers along with the builders to consider SMA as one of reinforcing materials especially in the earthquake prone areas.