Khaled Galal

Shear Strengthening of RC T-Beams Using Mechanically Anchored Unbonded Dry Carbon Fiber Sheets

This research studies the feasibility and effectiveness of a new method of strengthening existing RC T-beams in shear by using mechanically anchored unbonded dry carbon fiber (CF) sheets. This method eliminates the debonding of epoxy-bonded carbon-fiber-reinforced polymer (CFRP) sheets and utilizes the full capacity of dry CF sheets. In this method, dry CF sheets are wrapped around and bonded to two steel rods. Then the rods are anchored to the corners of the web-flange intersection of the T-beam with mechanical bolts. This makes a U-shaped dry CF jacket around the web which increases the shear strength of the T-beam using the privilege of higher tensile strength and modulus of elasticity of dry CF compared to composite CFRP. A total of three RC T-beams with shear span-to-depth ratio of 2.0 were tested under increasing monotonic load till failure. The pilot tests were done as a proof-of-concept of the effectiveness of the proposed method in increasing the shear capacity of the RC T-beams. The first T-beam, which was tested as the control beam, failed in shear. The second beam was strengthened by using a U-shaped CFRP sheet that was externally bonded to the web of the beam in the shear zones. The third beam was strengthened by using anchored U-shaped dry CF sheet. The test results showed that the beam strengthened by the new mechanically anchored dry CF had about 48% increase in shear capacity as compared to the control beam and 16% increase in shear capacity as compared to the beam strengthened by CFRP epoxy-bonding method.

Strengthening RC Beams in Flexure Using New Hybrid FRP Sheet/Ductile Anchor System

This paper explores a new hybrid fiber-reinforced polymer FRP sheet/ductile anchor system for rehabilitation of reinforced concrete RC beams. The advantages of the proposed strengthening method is that it overcomes the problem of low ductility that is associated with brittle failure mode in conventional methods of strengthening beams using epoxy-bonded FRP sheets. The proposed system leads to a ductile failure mode by triggering yielding to occur in a steel anchor system steel links rather than by rupture or debonding of FRP sheets, which is sudden in nature. Four half-scale RC T-beams were tested under four-point bending. Three retrofitted beams were strengthened using one layer of carbon FRP sheet. The results of the two beams that were strengthened with the new hybrid FRP sheet/ductile anchor system were compared with the results from the beam strengthened with conventional FRP bonding method and the control beam. The results show the effectiveness of the proposed strengthening system in increasing flexural capacity and ductility of RC beams.

Out-of-Plane Flexural Performance of GFRP-Reinforced Masonry Walls

The objective of this paper is to assess the out-of-plane flexural performance of masonry walls that are reinforced with glass fiber-reinforced polymers (GFRPs) rods, as an alternative for steel rebars. Eight 1 m×3 m full-scale walls were constructed using hollow concrete masonry units and tested in four-point bending with an effective span of 2.4 m between the supports. The walls were tested when subjected to increasing monotonic loads up to failure. The applied loads would represent out-of-plane loads arising from wind, soil pressure, or inertia force during earthquakes. One wall is unreinforced; another wall is reinforced with customary steel rebars; and the other six walls are reinforced with different amounts of GFRP reinforcement. Two of the GFRP-reinforced walls were grouted only in the cells where the rods were placed to investigate the effect of grouting the empty cells. The force-deformation relationship of the walls and the associated strains in the reinforcement were monitored throughout the t...

Design and Simulation for a Solar House with Building Integrated Photovoltaic-Thermal System and Thermal Storage

Building integrated photovoltaic-thermal systems (BIPV/T) that pre-heat ambient air may be used in combination with ventilated concrete slabs for thermal storage purposes. This is one of many feasible ways to maximize solar energy utilization. This paper describes the design and simulation of a solar house with an innovative BIPV/T system and ventilated concrete slab. This house is to be built by a Canadian prefabricated-home manufacturer for Canada’s EQuilibrium Housing demonstration initiative. The BIPV/T system can harvest a considerable amount of useful heat; however, some of this energy typically needs to be stored for later use with an appropriate thermal storage design. A concrete thermal storage system is utilized for this purpose. Simulation results are presented from a transient finite difference model for the house, including the BIPV/T system and ventilated concrete slab.

Shake Table Tests on FRP-Rehabilitated RC Shear Walls

This paper investigates the behavior of two 8-story cantilevered RC shear walls rehabilitated using carbon fiber-reinforced polymer (CFRP) composite sheets when subjected to base excitations from a shake table. The two original reduced size walls (1:0.429) were tested on the shake table of Ecole Polytechnique de Montreal to investigate the effect of higher modes of vibration on the behavior of multistory RC walls. The walls were subjected to several levels of ground motion excitation that matches the design spectrum of Montreal city in Quebec, Canada. The original walls showed significant inelastic deformations at the 6th-story level in addition to those at the base plastic hinge. After the shake table tests on each of the two original walls, the damaged walls were rehabilitated and resubjected to the same levels of the ground motion excitations. This paper focuses on the FRP-rehabilitation of the original walls. The rehabilitation scheme for the two walls aimed to increase the flexural and shear capacities of the wall at the 6th-story panel because of the observed increase in demand at that level, whereas the base panel was confined using CFRP sheets to increase the ductility capacity without increasing strength. The rehabilitated walls showed satisfactory performance with improved flexural strength at the 6th-story panel. The rehabilitation scheme resulted in a reduced wall rotation and lower strain values of the flexural steel rebars at the 6th-story panel. The shear demands and bending moments on the FRP-rehabilitated walls were higher than those of the original ones.

Impact of lateral force-resisting system and design/construction practices on seismic performance and cost of tall buildings in Dubai, UAE

The local design and construction practices in the United Arab Emirates (UAE), together with Dubai’s unique rate of development, warrant special attention to the selection of Lateral Force-Resisting Systems (LFRS). This research proposes four different feasible solutions for the selection of the LFRS for tall buildings and quantifies the impact of these selections on seismic performance and cost. The systems considered are: Steel Special Moment-Resisting Frame (SMRF), Concrete SMRF, Steel Dual System (SMRF with Special Steel Plates Shear Wall, SPSW), and Concrete Dual System (SMRF with Special Concrete Shear Wall, SCSW). The LFRS selection is driven by seismic setup as well as the adopted design and construction practices in Dubai. It is found that the concrete design alternatives are consistently less expensive than their steel counterparts. The steel dual system is expected to have the least damage based on its relatively lesser interstory drifts. However, this preferred performance comes at a higher initial construction cost. Conversely, the steel SMRF system is expected to have the most damage and associated repair cost due to its excessive flexibility. The two concrete alternatives are expected to have relatively moderate damage and repair costs in addition to their lesser initial construction cost.

Impact of Seismicity on Performance and Cost of RC Shear Wall Buildings in Dubai, United Arab Emirates

AbstractUnfortunately, available probabilistic seismic hazard studies are reporting significantly varying estimates for seismicity of Dubai. Given Dubai’s rapid economic growth, it is crucial to as...

Corrosion-Fatigue Strain-Life Model for Steel Bridge Girders under Various Weathering Conditions

Corrosion of existing infrastructure, such as steel bridges, would significantly reduce its anticipated fatigue life. There are very few corrosion-fatigue models that address civil engineering applications. To account for corrosion in the fatigue life prediction of steel bridges, a new fatigue strain-life model based on the Smith-Watson-Topper model is proposed. The proposed model provides the fatigue life predictions in the form of ranges with a minimum and a maximum value. The model takes into account the corrosivity of the environment, the stress level, and the corrosive behavior of the material used. The resulting fatigue life predictions using the proposed model matched well with the experimental results reported in the literature for 24 steel beams that were subjected to various fatigue and weathering conditions. The analytical predictions show that the proposed model is accurate, simple, and practical and can be easily calibrated for different materials.

Upgrading the Seismic Performance of Reinforced Masonry Columns Using CFRP Wraps

Compared with reinforced concrete, relatively fewer experimental studies address the behavior of masonry columns under com- bined axial load and cyclic flexure. There exist reinforced concrete masonry (RCM) columns that are part of the moment resisting system of masonry structures that are in need of seismic upgrade. Wrapping such susceptible RCM columns with carbon fiber-reinforced polymers (CFRP) is expected to enhance the seismic behavior of reinforced masonry columns considerably. This paper focuses on assessing the seismic performance of RCM columns wrapped with CFRP. In this experimental study, six 1.4-m reinforced masonry columns were constructed and tested when subjected to constant axial force and cyclic lateral excitations. The columns had a cross-section of 390 mm × 390 mm and were constructed using bull-nosed concrete units. The first column had no CFRP wraps and was used as a control specimen whereas the other five columns werewrapped using different layers of CFRP sheets or different wrapping schemes. From the tests, it was observed that wrapping the masonry columns with CFRP wraps enhanced the seismic performance of the columns by offering more ductile behavior, increasing both strength and energy dissipation capacity. DOI: 10.1061/(ASCE)CC.1943-5614.0000252.

Optimal bracing type and position to minimize lateral drift in high-rise buildings

Selection of high-rise bracing type and position is based on many factors: their degree of resistance to lateral forces, cost, complexity of connection and assembly, and the integration with Architectural objectives. This paper includes selection of the optimal bracing type and position for a high-raise office building in Dammam Saudi Arabia. This 900 square meters per floor prototype is used as case study to compare four bracing types: single diagonal bracing, chevron shape bracing, cross (X) bracing and eccentric bracing; as well as two positions: bracing at the core and external parameter bracing (building facade). The case study building height is 40 stories in an area of high wind velocity (145 km/h) where no critical seismic force is recorded. The STAAD Pro 2005 software is used to analyze these systems according to allowable stress requirements for an objective function to minimize drift for wind speed of 145 kilometers per hour. The result of this study shows that adding bracing members to the moment frame structure increases stability and reduces drift. Chevron bracing and cross bracing have the highest resistance to the lateral drift compared to the others; but cross bracing is more costly due to more joints. Therefore chevron is the optimal bracing type. Also this study shows that adding the braces to the core of building reduces the drift much more than adding them to the building facades.