Yes / The flexural performance of geopolymer concrete (GPC) T-beams reinforced longitudinally with GFRP bars under a four-point static bending test was investigated. Six full-scale simply supported T-beams were cast and tested; one control specimen was made with ordinary Portland cement concrete (OPCC), while the other five beams were made of geopolymer concrete. The G-GPC2 was designed to attain the same theoretical moment capacity as the G-OPCC6 control beam. The main parameters investigated were the reinforcement ratio of ρ_f/ρ_b= 0.75, 1.05, 1.12, 1.34 and 1.34 for G-GPC1, G-GPC2, G-GPC3, G-GPC4, and G-GPC5, respectively, and compressive strength of geopolymer concrete. Based on the results of the experiments, the ultimate strain of GPC did not show the same behaviour as that of OPCC, which affects the mode of failure. The beam capacity and deflection were, respectively, overestimated and underestimated using the ACI 440 2R-17 predictive equations.

Yes / This paper numerically investigates flexural performance of Ultra-High Performance Concrete (UHPC) beam reinforced with Steel-Fibre-Reinforced Polymer (FRP) Composite Bars (SFCBs) in terms of flexural stiffness, moment capacity, deflection, ductility and energy dissipation. The effect of various parameters, include the inner steel core area ratio of SFCB, yield strength of inner steel core, elastic modulus and ultimate strength of outer-wrapped FRP, reinforcement ratio, type and strength of concrete were studied. The results demonstrate that the inner steel core area ratio of SFCB, reinforcement ratio and the elastic modulus of SFCB's outer FRP have significant effect on the overall flexural performance of SFCB reinforced UHPC beam. The overall flexural performance of SFCB reinforced UHPC beam is slightly improved by increasing the yield strength of inner steel core of SFCB, but not affected by the ultimate strength of SFCB's outer FRP when specimen occurred compression failure. The results also exhibit that the flexural performance of UHPC beam reinforced with SFCBs is significantly improved when compared to those of reinforced high strength concrete (HSC) beam and normal strength concrete (NSC) beam. The flexural stiffness and the moment capacity of SFCB reinforced UHPC beam at the ultimate point were 2.0 and 2.4 times, respectively, of those of reinforced NSC counterpart. / Natural Science Foundation of Jiangsu Province, China (BK20201436), the China Postdoctoral Science Foundation (2018M642335), the Science and Technology Project of Jiangsu Construction System, China (2018ZD047, 2021ZD06), the Science and Technology Project of Gansu Construction System, China (JK2021-19), the National Natural Science Foundation of China (51678514), the Science and Technology Innovation Fund of Yangzhou University, China (2020-65), the Open Foundation of Jiangsu Province Engineering Research Center of Prefabricated Building and Intelligent Construction, China (2021), the Science and Technology Cooperation Fund Project of Yangzhou City and Yangzhou University, China (YZU212105), the Practice and Innovation Plan for Postgraduates in Jiangsu Province, China (SJCX21_1589), the Blue Project Youth Academic Leader of Colleges and Universities in Jiangsu Province, China (2020) and the Deputy General Manager Science and Technology Project of Jiangsu Province, China (FZ20200869). References

This paper presents test results and code predictions of four continuously and two simply supported concrete slabs reinforced with basalt fibre reinforced polymer (BFRP) bars. One continuously supported steel reinforced concrete slab was also tested for comparison purposes. All slabs tested were 500 mm in width and 150 mm in depth. The simply supported slabs had a span of 2000 mm, whereas the continuous slabs had two equal spans, each of 2000 mm. Different combinations of under and over BFRP reinforcement at the top and bottom layers of slabs were investigated. The continuously supported BFRP reinforced concrete slabs exhibited larger deflections and wider cracks than the counterpart reinforced with steel. Furthermore, the over reinforced BFRP reinforced concrete slab at the top and bottom layers showed the highest load capacity and the least deflection of all BFRP slabs tested. All continuous BFRP reinforced concrete slabs failed owing to combined shear and flexure at the middle support region. ISIS-M03-07 and CSA S806-06 design guidelines reasonably predicted the deflection of the BFRP slabs tested. However, ACI 440-1R-06 underestimated the BFRP slab deflections and overestimated the moment capacities at mid-span and over support sections.

yes / This paper presents experimental results of three continuously supported concrete slabs reinforced with basalt-fibre-reinforced polymer (BFRP) bars. Three different BFRP reinforcement combinations of over and under reinforcement ratios were applied at the top and bottom layers of continuous concrete slabs tested. One additional concrete continuous slab reinforced with steel bars and two simply supported slabs reinforced with under and over BFRP reinforcements were also tested for comparison purposes. All slabs sections tested had the same width and depth but different amounts of BFRP reinforcement. The experimental results were used to validate the existing design guidance for the predictions of moment and shear capacities, and deflections of continuous concrete elements reinforced with BFRP bars. The continuously supported BFRP reinforced concrete slabs illustrated wider cracks and larger deflections than the control steel reinforced concrete slab. All continuous BFRP reinforced concrete slabs exhibited a combined shear–flexure failure mode. ACI 440-1R-15 equations give reasonable predictions for the deflections of continuous slabs (after first cracking) but stiffer behaviour for the simply supported slabs, whereas CNR DT203 reasonably predicted the deflections of all BFRP slabs tested. On the other hand, ISIS-M03-07 provided the most accurate shear capacity prediction for continuously supported BFRP reinforced concrete slabs among the current shear design equations.

Yes / This paper presents the experimental results of five large-scale hybrid glass fiber reinforced polymer (GFRP)-steel reinforced concrete continuous beams compared with two concrete continuous beams reinforced with either steel or GFRP bars as reference beams. In addition, two simply supported concrete beams reinforced with hybrid GFRP/steel were tested. The amount of longitudinal GFRP, steel reinforcements and area of steel bars to GFRP bars were the main investigated parameter in this study. The experimental results showed that increasing the GFRP reinforcement ratio simultaneously at the sagging and hogging zones resulted in an increase in the load capacity, however, less ductile behaviour. On the other hand, increasing the steel reinforcement ratio at critical sections resulted in more ductile behaviour, however, less load capacity increase after yielding of steel. The test results were compared with code equations and available theoretical models for predicting the beam load capacity and load-deflection response. It was concluded that Yoon's model reasonably predicted the deflection of the hybrid beams tested, whereas, the ACI.440.1R-15 equation underestimated the hybrid beam deflections. It was also shown that the load capacity prediction for hybrid reinforced concrete continuous beams based on a collapse mechanism with plastic hinges at mid-span and central support sections was reasonably close to the experimental failure load. / Higher Education of Libya (972/2007).

Yes / Geopolymer concrete is a promising candidate to replace conventional concrete as geopolymer concrete depends on alkali-activated binders instead of Portland cement. The elimination of cement from the mixture results in the reduction of the greenhouse gas release. From the literature, it is known that the micro-scale characteristics of the geopolymer concrete are similar to its counterparts. However, the structural performance of geopolymer elements should be investigated in detail. Therefore, in this study, the structural performance of reinforced geopolymer concrete beams is compared by conducting bending tests to determine the shear behavior of new generation geopolymer concrete produced from entirely construction and demolition wastes (CDW). In these tests, geopolymer concrete with recycled aggregates, geopolymer concrete with natural aggregates, conventional concrete with recycled aggregates, and conventional concrete with natural aggregates are used in order to study the possibility of reaching fully-recycled construction materials. Three different shear-span-to-depth ratios (a/d) are utilized to investigate the different modes of failure. Therefore, the structural performance of beams was, firstly, compared for mixtures without recycled aggregates to control the possible side effects of 100% recycled concrete construction. Load-deflection curves, moment-curvature curves, and crack patterns were utilized to conclude the performance of geopolymer concrete. Test results revealed that geopolymer concrete beams exhibited similar performance to the conventional concrete beams of the same grade. However, the inclusion of recycled aggregates caused a shift in the failure mechanism from shear-dominated to flexure-dominated, especially in specimens with larger a/d ratios. Finally, the capacity prediction performance of current codes, i.e., TS500 and ACI318, are also examined, and the calculations resulted that the current code equations have a percentage error of approximately 55% on average, although TS500 equations performed slightly better. / The authors gratefully acknowledge the financial assistance of the Scientific and Technical Research Council (TUBITAK) of Turkey and the British Council provided under projects: 218M102 and European Union’s Horizon 2020 research and innovation programme under grant agreement No: 869336, ICEBERG (Innovative Circular Economy Based solutions demonstrating the Efficient recovery of valuable material Resources from the Generation of representative End-of-Life building material).

Yes / Concrete requires a vast amount of aggregate and cement production. Although there are some efforts in the literature to reduce the amount of Portland cement in the concrete mixture to lessen the greenhouse gas release, a limited number of studies were conducted to investigate the possibility of using this geopolymer mixtures to serve as a structural component. Therefore, this study firstly aimed to produce geopolymer concrete from construction and demolition waste-based precursors, including masonry units (red clay brick, roof tile, hollow brick, etc.) and glass. In addition, recycled aggregates produced from the concrete waste portion of the CDW were used to obtain 100% recycled construction material on the scale of the binder and aggregate phase. Then, this study investigated the possible use of this proposed geopolymer concrete to produce structural components that perform similar to conventional concrete. Therefore, the structural properties of reinforced geopolymer concrete beams produced from the recycled construction demolition wastes were evaluated in this study by conducting laboratory experiments. To this end, bending tests were performed on reinforced conventional concrete beam specimens and reinforced geopolymer concrete beam specimens. The test observations clearly showed that construction demolition waste could be recycled to produce new constructional components, considering its advantage of promoted sustainability. / The authors gratefully acknowledge the European Union’s Horizon 2020 Research and Innovation Programme’s financial assistance under Grant Agreement No: 869336 and Acronym: ICEBERG and the financial assistance of the Scientific and Technical Research Council (TUBITAK) of Turkey and the British Council under Grant no:218M102. This work was also supported by Newton Prize 2020.

Minimally invasive surgery (MIS) has several advantages over traditional methods. Scaling MIS instruments to smaller sizes and increasing their performance will enable surgeons to offer new procedures to a wider range of patients. In this work, two compliant mechanism-based minimally invasive surgical instrument wrist or gripper mechanisms are designed and analyzed.The cylindrical cross-axis flexural pivot (CCAFP) is a single-degree-of-freedom wrist mechanism that could be combined with existing gripper mechanisms to create a multi-degree-of freedom instrument. The simplicity of the CCAFP mechanism facilitates analysis and implementation. The flexures of the CCAFP are integral with the instrument shaft, enabling accessories to be passed through the lumen. The CCAFP is analyzed and determined to be a viable wrist mechanism for MIS instruments based on research results. A finite element (FE) model of the mechanism is created to analyze the force-deflection and strain-deflection relationships. Experimental results are used to verify the FE model. A 3 mm design is created that could undergo an angular deflection of +/- 90 degrees. The addition of cam surfaces to help guide the flexures and limit the maximum stress during deflection is explored. These cam surfaces can be integral to the instrument shaft along with the flexures. A 2 degree-of-freedom (DoF) CCAFP with intersecting axes of rotation is also introduced. The inverted L-Arm gripper compliant mechanism has 2 DoF, one wrist and one gripping. Three challenges associated with using compliant mechanisms in MIS instruments are considered: inadequate performance in compression, large flexure deformations, and a highly variable mechanical advantage. These challenges were resolved in the L-Arm design by inverting the flexures, tailoring flexure geometry and employing nitinol, and integrating pulleys into each jaw of the mechanism. The L-Arm was prototyped at several sizes to demonstrate functionality and scalability. A finite element model of the L-Arm flexure was created to determine the strain-deflection relationship. A fatigue test was completed to characterize nitinol for use in compliant mechanism MIS instruments.These concepts demonstrate the ability of compliant mechanisms to overcome the design and manufacturing challenges associated with MIS instruments at the 3 mm scale. The models and principles included in this work could be used in the application of compliant mechanisms to design new MIS instruments as well as in other areas that employ compliant mechanisms in a cylindrical form factor.

The use of cold-formed steel (CFS) structures has become increasingly popular in different fields of building technology. For example, small housing systems using cold-formed steel for wall structures, framing systems and roof structures, including trusses and shielding materials, have been developed during recent years. The reasons behind the growing popularity of these products include their ease of fabrication, high strength/weight ratio and suitability for a wide range of applications. These advantages can result in more cost-effective designs, as compared with hot-rolled steel, especially in short-span applications. It has been common practice in cold-formed steel construction to cut openings in the web of beams for the passage of service ducts and piping. The provision of such openings reduces the story heights and consequently can result in saving of considerable amount of construction materials. On the other hand, the presence of a large web opening causes localized redistribution of stress around the opening region. The large opening causes loss of strength and changes the buckling characteristics of an entire member. It also affects the flexural stiffness, resulting in poor performance of member under serviceability. It is common practice to reinforce the opening of hot-rolled steel members, but proper reinforcement schemes for CFS perforated members has not been established yet. Various reinforcement schemes for cold-formed steel sections were investigated during this study. Two types of reinforcement schemes (for flexural zones and shear zones) were developed. Fifty-four flexural tests and 33 shear tests were conducted. Two types of sections (lipped channel joists with h/t ratio 180 and 118) were tested in flexure and one type of section (lipped channel joists with h/t ratio 180) was tested in shear. The study also included a finite element based numerical investigation, consisting of parametric studies on the size (web depth and thickness) of joists, size and shape of web openings, reinforcement and associated fastening schemes. It was observed that a 75 percent of opening in the web of CFS channel joist causes up to 25 percent reduction in flexural strength and up to 60 percent reduction in shear strength. Such reduced flexural and shear strengths were re-captured by providing proper reinforcement schemes. The flexural reinforcement schemes recommended by the current AISI Standard were found to be ineffective for the sections having low w /t ratios. Bridging channel reinforcement scheme was also considered in this study. Bridging channel reinforcement scheme was capable of restoring the flexural strength of cold formed steel joist having w /t ratios 118 and 180. Similarly, the reinforcement schemes recommended in AISI Standard were not adequate to restore the shear strength of joist sections. A newly developed Virendeel type reinforcement system was capable of restoring the original shear strength of a cold-formed steel joist section. / Thesis / Doctor of Philosophy (PhD)

Yes / In order to promote the utilization of high strength materials and application of prefabricated structures, flexural behaviour of section steel-precast UHPC (Ultra-High performance concrete) slab composite beams prefabricated with bolt shear connectors are numerically simulated by the finite element (FE) software ABAQUS. The model is verified by three prefabricated steel-concrete composite beams tested. Numerical analysis results are in good accordance with experimental results. Furthermore, parametric studies are conducted to investigate the effects of strength of section steel and concrete of precast slab, thickness of section steel, width and height of precast concrete slab, diameters of steel bars and bolt shear connectors. The flexural behaviour of composite beams, in terms of bearing capacity, deflection, ductility and energy dissipation, are compared. The numerical results indicate that the improvement of strength of section steel results in a decrease of ductility, but a significant increase of the ultimate load and energy dissipation. Compared with composite beam made of section steel with thickness of 10 mm, the ultimate load of beams made of section steel with thickness of 14 and 18 mm improve by 29.0% and 58.8%, respectively, the ductility enhance by 2.8% and 8.3%, respectively, and the energy dissipation improve by 8.0% and 12.3%, respectively. With the increase of concrete strength, the ultimate load, deflection and energy dissipation gradually increase. The ductility of steel-UHPC composite beam is the highest, that of steel-HSC composite beam is the lowest. The effect of reinforcement ratio of concrete slab and diameter of shear bolts on the ultimate load of composite beam is limited. Simplified formulae for two different sectional types of proper-reinforced section steel-precast UHPC slab composite beams occurred bending failure are proposed, and the predicted results fit well with the simulated results. The results can be taken as a reference for the design and construction of section steel-precast UHPC slab composite beams.