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Nghiên cứu ứng dụng vật liệu cốt thanh polyme sợi thủy tinh cho kết cấu bản mặt cầu trên đường ô tô.Nghiên cứu ứng dụng vật liệu cốt thanh polyme sợi thủy tinh cho kết cấu bản mặt cầu trên đường ô tô.Nghiên cứu ứng dụng vật liệu cốt thanh polyme sợi thủy tinh cho kết cấu bản mặt cầu trên đường ô tô.Nghiên cứu ứng dụng vật liệu cốt thanh polyme sợi thủy tinh cho kết cấu bản mặt cầu trên đường ô tô.Nghiên cứu ứng dụng vật liệu cốt thanh polyme sợi thủy tinh cho kết cấu bản mặt cầu trên đường ô tô.Nghiên cứu ứng dụng vật liệu cốt thanh polyme sợi thủy tinh cho kết cấu bản mặt cầu trên đường ô tô.Nghiên cứu ứng dụng vật liệu cốt thanh polyme sợi thủy tinh cho kết cấu bản mặt cầu trên đường ô tô.Nghiên cứu ứng dụng vật liệu cốt thanh polyme sợi thủy tinh cho kết cấu bản mặt cầu trên đường ô tô.Nghiên cứu ứng dụng vật liệu cốt thanh polyme sợi thủy tinh cho kết cấu bản mặt cầu trên đường ô tô.Nghiên cứu ứng dụng vật liệu cốt thanh polyme sợi thủy tinh cho kết cấu bản mặt cầu trên đường ô tô.Nghiên cứu ứng dụng vật liệu cốt thanh polyme sợi thủy tinh cho kết cấu bản mặt cầu trên đường ô tô.Nghiên cứu ứng dụng vật liệu cốt thanh polyme sợi thủy tinh cho kết cấu bản mặt cầu trên đường ô tô.
MINISTRY OF EDUCATION AND TRAINING UNIVERSITY OF TRANSPORT AND COMMUNICATIONS NGUYEN VAN NGON RESEARCH ON THE APPLICATION OF GLASS FIBER REINFORCED POLYMER BARS MATERIALS FOR rch on the application of glass fiber reinforced polymer rods for bridge deck CONCRETE BRIDGEstructures DECK STRUCTURES ON HIGHWAYS on highways Major: Special Construction Engineering Code: 95.80.2.06 SUMMARY OF ENGINEERING DOCTORAL THESIS HA NOI, 2022 This thesis completed at: UNIVERSITY OF TRANSPORT AND COMMUNICATIONS SUPERVISORS: Prof Dr Nguyen Viet Trung Assoc Prof Dr Pham Duy Anh Reviewer 1: Reviewer 2: Research on the application of glass fiber reinforced polymer rods for bridge deck Reviewer 3: structures on highways This thesis will be defended in front of the University-Graded Committee of thesis evaluation according to Decision …… ./QĐ-ĐHGTVT, on date………… 2022 signed by the Rector of University of Transport and Communications on date…………….… 2022 Readers can find this thesis at: - Vietnam National Library - Library of the University of Transport and Communications PREFACE Why choose the topic The bridge deck is the most rapidly degraded part of the bridge structures due to the direct impact of environmental conditions, chemical agents and vehicle loads, all of which lead to corrosion of the reinforcement Consequences leading to the destruction of the concrete cover give rise to repair costs and cause traffic disruption Due to its strong corrosion resistance, glass fiber reinforced polymer (GFRP) improves the durability of the bridge deck structures and minimizes the cost of repair and replacement Hitherto, the number of studies on the behavior of concrete bridge deck strucrures using GFRP reinforcement is quite limited On the other hand, studies have been conducted using GFRP reinforcing material produced according to European technology, calculation and comparison results based on European, American, Japanese standards, , while no studies have been conducted on GFRP bars material produced in Vietnam to investigate the behavior of the structure based on the relationship between load - deflection, load - strain of concrete, load - strain of reinforcement and load bearing capacity Based on the analysis of experimental results, compare with the theory to propose a suitable load-bearing capacity predict model applied in Vietnam Therefore, the thesis selects the topic "Research on the application of glass fiber reinforced polymer bars materials for bridge deck structures on highways" Purpose of research To study the application of GFRP bars for concrete bridge deck structures on highways; Objects and scope of the research Subjects of the thesis: Bridge deck structures uses GFRP bars reinforcing with ridges, manufactured in Vietnam (meeting requirements of TCVN 11109:2015) Scope of the study: - Research to determine the behavior of concrete bridge deck structures (with a compressive strength of 45 MPa), GFRP bars manufactured in Vietnam, subjected to concentrated load (laboratory test) - Determination of failure model, load bearing capacity, effect of transverse reinforcement ratio of bottom layer on load bearing capacity, deflection, cracking, strain of concrete on top surface and strain of transverse reinforcement of bottom layer Research methodology The thesis uses a combination of research methods: analytical, statistical, theoretical research; experimental research method; numerical simulation method The meaning of scientific and practical of topics Scientific meaning: - Be able to determine the failure model of bridge deck structures and propose the modify equation for predict of load bearing capacity suitable for calculating concrete bridge deck structures using GFRP reinforcement - Proposing the method of designing GFRP reinforced concrete bridge deck structures and plans to use of GFRP in concrete bridge deck structures in Vietnam - Demonstrate the effectiveness of the application of GFRP bars to replace reinforcement in bridge deck structures through life cycle cost analysis Practical meaning: The thesis proposes the model of forecasting the load-bearing capacity of concrete bridge deck structures using GFRP type bars manufactured in Vietnam and plans to use GFRP in bridge decks, as a basis for research and application of GFRP in bridge construction in Vietnam Thesis organisation The thesis consists of the preamble, main chapters, conclusions, recommendations, proposals for further research, references and calculation appendices CHƯƠNG OVERVIEW OF GLASS FIBER REINFORCED POLYMER BAR REINFORCEMENT MATERIALS AND APPLICATION STUDIES IN BRIDGE DECK STRUCTURE 1.1 Overview of fiber reinforced polymer materials (FRP) A fiber reinforced polymer (FRP) is a composite material formed from at least two different material components Classification by fiber reinforcement FRP is divided into categories: glass fiber reinforced polymer (GFRP), carbon fiber reinforced polymer (CFRP) and aramid fiber reinforced polymer (AFRP) Advantages GFRP bar material is high strength, light weight, low corrosion and non-magnetic Cons GFRP bar has a low modulus of elasticity (45 GPa); is reduced in strength in humid, salt, alkali, UV environment; coefficient of thermal expansion in the direction perpendicular to the fibers is higher than that of concrete, shear strength and strength in the direction of transverse fibers is low; fire resistance is relatively low; there are no yield limits and broken when small deflections; no bending is possible at the site 1.2 Typical mechanical and physical properties of GFRP materials GFRP bar is a material that behaves linearly elastically until failure The compressive strength and compressive elastic modulus are taken to be 45% and 80% respectively from the strength and tensile elastic modulus values [76, 104] Shear behavior is influenced primarily by the properties of the polymer component GFRP bars generally have weak transverse shear resistance Shear strength can be improved by braiding or winding the additional strand in the transverse direction Transverse shear strength of FRP bars ranges from 30 - 50 MPa [58] 1.3 Strength of GFRP bars Studies have demonstrated that factors from the environment that influence the strength of GFRP bars degrade the tensile strength and elastic modulus in GFRP bars Since there are currently no real applications with long durations, information on the durability of FRP bars in these applications is often extrapolated based on the results of short-term accelerated aging tests 1.4 Overview of GFRP reinforcement research and application 1.4.1 Overview of current design standards and guidelines While the AASHTO LRFD 2009 design guidelines include only bridge deck and traffic railings, the 2nd version of the AASHTO LRFD 2018 already includes all parts of the bridge works This document guides the design of GFRP bridge deck according to the flexural design method on the basis of the calculation theory of steel reinforced concrete bridge deck and includes the coefficients considering the difference in behavior of GFRP reinforcement compared to steel reinforcement In addition, the Canadian Bridge Design Standard (CAN/CSA S6) allows the design of GFRP reinforcement bridge decks in two methods: flexural design method and empirical method 1.4.2 Some studies use FRP reinforcement for bridge slab structure Studies on actual bridge works Benmokrane et al [29], Ahmed et al [23] conducted a survey on actual bridge works with bridge deck using GFRP reinforcement The obtained results show that the structure satisfies the specified limit conditions Based on the measurement results, Ahmed considers that the flexural design method of AASHTO and CHBDC (CAN/CSA S6) gives the expected result that the design bending moment is greater than actual This result is due to the effect of the compression arch effect in the restrained slab structure [23], [29] The test results also show that the bridge deck using a combination of steel and GFRP bars reinforcement has the same behavior as in the case of use entirely with GFRP bars or steel reinforcement [23] Studies on the bridge deck model in the laboratory El-Gamal et al [50], Bouguerra et al [30] conducted experiments on GFRP reinforced concrete bridge deck model The slabs are 3,0 m long, 2,5 m wide and 0,2 m depth, arranged GFRP with different ratio The test specimen is connected to two steel beams spaced 2,0 m apart by bolts The test load placed in the middle of the span is transmitted onto a steel plate (600x250)mm in size to simulate the wheel tracks Experimental results show that all test specimens have punching shear failure, with a load capacity of about times as much as the factored design load according to CHBDC (CAN/CSA S6) The crack width and the maximum deflection measured corresponding to the load used are both less than the allowable limit Compared to experimental, the results of load-bearing capacity prediction according to ACI 440.1R give values 2,66 to 3,17 times lower on average Study on compression arch effect in bridge deck structure Zheng et al [108] experimental study a 1/3 scale GFRP deck slab model, with the investigation of the influence of parameters such as supporting beam width (100, 150, 200)mm, type of reinforcement (GFRP, steel) and reinforcement ratio (0,5 - 1,0)% on deck slab behavior Based on experimental results, Zheng argues that the load bearing capacity of the bridge deck slab structure is determined by the sum of the flexural resistance of the material (Mb) and the flexural strength due to the compression arch effect (Ma) formed from the boundary conditions between the bridge deck slab and the support beams The reinforcement ratio has a negligible effect on the load bearing capacity of the bridge deck structure, while the support beam width has a significant effect on (Ma) Numerical simulation load bearing prediction study El-Gamal [47] surveyed the behavior of the bridge deck structure by nonlinear analysis of finite element, using the ANATECH 3.0 concrete structure analysis software (ANATECH Corp., San Diego - USA) The analysis results compared with the experimental results are quite consistent with the experimental results with deviations < 4% for cracking load, failure load For CFRP reinforced concrete slab, deflections correspond to design factored loads and failure loads with deviations of 1%, strain of reinforcement correspond to design loads and failure loads with deviations of 11% and 3%, respectively For GFRP reinforced concrete slab, deflection corresponds to design factored load and failure load with deviations of 6% and 1% respectively, strain of reinforcement corresponds to design factored load and failure load with deviations of 4% and 7% respectively Study on the durability of GFRP bars GFRP reinforced concrete structure after 15 years of exploitation period has not been corroded [61] With the analysis, the researchers considered that GFRP reinforced concrete structures will have a durability of up to more than 100 years [110] and have superior fatigue load capacity compared to the case of using steel reinforcement [53] Studies in Vietnam In Vietnam, there are only studies on beam structures, such as those of Vu Ngoc Anh et al [5], Cheng Por Eng [6], Nguyen Hung Phong [11], Nguyen Minh Long et al [19], Pham Thi Loan et al [9], Cu Thi Hong Yen et al [13] The above studies confirm the differential behavior of GFRP reinforced concrete beam structure compared to steel reinforcement in terms of deflection, cracking, corrosion Research by Dang Vu Hiep et al [7] on the change of deflection of GFRP reinforced concrete floor size (2200x650x60)mm in 90 days The results show the deflection prediction value in accordance with ACI.440 is suitable for uncracked floors but is much larger than the measured deflection of cracked floors subjected to long-term loads 1.4.3 Application of GFRP bars In the world, GFRP bars have been applied to a number of items, including: roofs, bridge decks; sea overpasses bridge, coastal retaining walls; railings structures on bridges, railways, railway stations, in the construction of tunnels, … In Vietnam, GFRP bars have been used such as: Warrior's house to protect the memorial site of General Vo Nguyen Giap (Vung Chua, Quang Binh provine); the section of Ho Tung Mau road (Cau Giay, Ha Noi); application in the manufacture of sheet piles using super high strength concrete and GFRP bars; Vingroup has used GFRP bars in combination with steel as basement ramps for trucks transporting excavated soil; BUSADCO Company (Vung Tau) is applying GFRP rods for production of manhole covers and reinforced concrete piles; Phu Dong park project (Tran Phu, Nha Trang) uses GFRP bars as the basement slab; Ca Mau sea dike works use GFRP bars for the construction and testing of gabion systems for sea embankments 1.5 Research orientation Study the theory of calculating the structure of the bridge deck according to the methods such as Canadian and American Experimental study of the concrete slab structure simulating the working conditions of the bridge deck using GFRP reinforcement, under the effect of wheel load The test results identify the characteristics including: the failure model and the bearing capacity of the structure; the relationship between the load and the deflection; the cracking load and the crack width; the relationship between the load with the strain of the concrete of the top surface and the strain of the reinforcement of the bottom layer; Analyze and evaluate the expected results according to the theoretical formulas, compare with the experimental formulas, thereby proposing appropriate adjustment formulas to apply structural design calculations of bridge decks using GFRP bars in Vietnam Analysis of effectiveness when applying GFRP bars as an alternative to reinforcement in bridge deck slab structures It is proposed that some adjustments be made when GFRP bars and current bridge design standards (TCVN 11823: 2017) are used in the bridge deck design CONCLUSION OF CHAPTER GFRP bars with higher corrosion resistance and durability than steel reinforcement have been studied and applied in bridge construction, railway stations, coastal retaining walls, Up to now, the instructions for calculation and structural design of GFRP reinforcing bridge deck have been issued and applied in some countries such as the US, Japan, Canada, Studies and applications have been carried out in the world demonstrating the use of GFRP bars to replace part or all of the reinforcement in the bridge deck to meet the design requirements and increase the durability of the works CHƯƠNG THEORETICAL BASIS FOR STRUCTURAL DESIGN OF CONCRETE BRIDGE DECKS REINFORCED WITH GFRP BARS 2.1 Introduction This chapter presents the theoretical basis and sequence of bridge deck design using GFRP reinforcement according to the guidelines of AASHTO LRFD 2018 [16], and according to Canadian Bridge Design Standards CAN/CSA S6.1S1-10 [44] In addition, in order to have a basis for proposing the formula for predicting the bearing capacity applied in the design of bridge deck structures using GFRP reinforcement, an analysis, evaluating the theoretical models according to CSA - 2012 [43], ACI 440.1R - 15 [18], AASHTO LRFD 2018 [16]; JSCE - 97 [69]; El-Gamal et al [50], Ospina et al [86], British Standard BS 8110 [35], TCVN 11823: 2017 [2], combining nonlinear regression analysis on experimental data [30, 46, 49, 50, 52, 62, 63, 72, 92, 105] will be conducted 2.2 Design method of GFRP reinforcing bridge deck according to AASHTO LRFD 2018 AASHTO LRFD 2018 guides the design of bridge deck structure using GFRP reinforcement by the same flexural method as for steel reinforced concrete bridge deck specified in TCVN 11823: 2017, with the calculation formula adjusted to suit the behaviour characteristics of GFRP reinforcement 2.3 Design method of GFRP reinforcing bridge deck according to Canadian Bridge Design Standards (CAN/CSA S6.1S1-10) The Canadian Bridge Design Standard allows for the design of GFRP reinforcement bridge deck slabs in two methods The design method of bending resistance is similar to the steel reinforced concrete bridge deck specified in section 5.7 (CAN/CSA S6.1S1-10) and the empirical design method with the condition that the structure must ensure the structural conditions as prescribed and only apply to the deck slab between girders According to the empirical method, the bridge deck is arranged with reinforced grids, with the clearance between the top and bottom grids not less than 55 mm The transverse bottom GFRP reinforcement layer has a minimum area defined by (2.70) Af = 500ds / E f (2.70) With ds being the distance from the top surface of the slab to the center of gravity of the transversely placed FRP reinforcement in the lower layer, mm; Ef is the elasticity modulus of GFRP bars, MPa The remaining GFRP bar layers in the top layer transverse and longitudinal reinforcement in both the bottom and top layers are arranged with minimum content (f = 0,0035) 2.4 Evaluation of the formulas used to calculate the load bearing capacity of GFRP reinforced concrete bridge deck structure 2.4.1 Overview of predicting formulas The load bearing capacity of GFRP reinforced concrete slab structures can be estimated using the formulas of ACI 440.1R 2015 [18], AASHTO LRFD 2018 [16]; JSCE - 97 [69]; El-Gamal et al [50], Ospina et al [86], British Standard BS 8110 (BSI 1997) [35] In addition, in order to notice the difference in load bearing capacity when using GFRP to replace the reinforcement in the bridge structure, the forecast formula of the Road Bridge Design Standard TCVN 11823: 2017 [2] is also included in the analysis ACI 440.1R - 2015 [18] ' k = 2 f n f + f n f − f n f Vc ACI = fc bo c (2.71); (2.72) where: c is the neutral axis height of the converted cracking section, c = k.d, mm; bo is the circumference of the integral section at a distance of d/2 from the concentrated load, mm; nf is the elastic modulus ratio; f is the ratio of GFRP reinforcement; AASHTO LRFD 2018 [16] ( Vc LRFD = 0,84 where: f’c in (MPa) f c' bo c ) (2.73) JSCE - 97 [69] Vc JSCE = d p r f pcd bo d (2.74) 1/ with: d = 100 ,1.5 d u = 2(cx + cy) ( f pcd = 0.2 fc' ,1.2 (2.75); 100 f E f 1/3 p = ,1.5 Es (2.77); r = + ) (2.76) (2.78) u + 0.25 d (2.79) Ospina et al [86] ( Vc.Osp = 2, 77 f f c' ) 1/3 Ef (2.80) b1.5 d Es where: b1.5 is the circumferential section of the piercing tower at a depth of 1,5d from the load bearing surface, mm El-Gamal et al [50] Vc El = 0.33 f c' bo d (1.2) N (2.81) 1/3 E 8d with: = 0.62 f f 1 + bo 1000 (2.82) N: is the continuity factor taken as for one-panel deck slabs, for deck slabs continuous long one axis, and for deck slabs continuous along their two axes British Standard BS 8110 (BSI 1997) [35] 1/3 Vc BS E f = 0, 79 100 f Es 1/3 f c' 25 1/ 400 d (2.83) b1.5 d TCVN 11823: 2017 [2] 0,33 ' ' Vc.TCVN = 0,17 + f c bo d v 0,33 f c bo d v c (2.84) where: c is the ratio of the long edge to the short edge of the rectangle through which the load is transmitted; dv is the effective shear height (dv = d), mm 2.4.2 Evaluation of forecasting formulas Evaluate the theoretical formulas based on the conducted experimental data of the authors [30, 46, 49, 50, 52, 62, 63, 72, 92, 105] The results are summarized and evaluated in Table 2.5 and Figure 2.3 Table 2.5 Evaluate the suitability of theoretical formulas VTN/ VTN/ VTN/ VTN/ VTN/ VTN/ VTN/ No Slabs Vc.TCVN Vc.ACI Vc.LRFD Vc.JSCE Vc.Op Vc.El Vc.BS G-200-N 0,87 2,05 1,95 1,27 1,10 1,04 1,52 G-175-N 0,82 1,85 1,76 1,07 1,06 1,04 1,39 G-150-N 0,78 1,75 1,67 1,05 1,05 1,04 1,31 G-175-H 0,88 2,28 2,17 1,54 1,25 1,11 1,65 G-175-N-0,7 0,76 2,41 2,29 1,44 1,25 1,15 1,64 G-175-N-0,35 0,69 3,06 2,91 1,66 1,44 1,32 1,89 G-S1 0,92 2,35 2,24 1,43 1,25 1,17 1,70 G-S2 0,94 1,81 1,73 1,15 1,06 1,41 1,41 G-S3 0,94 2,21 2,10 1,38 1,21 1,64 1,64 10 C-S1 0,80 2,11 2,01 1,27 0,93 1,51 1,51 11 C-S2 1,00 1,88 1,79 1,19 0,91 1,48 1,48 12 D1 1,07 3,06 2,91 1,62 1,47 2,11 2,11 13 D2 1,23 2,57 2,45 1,48 1,35 1,93 1,93 14 1,17 2,27 2,16 1,54 1,03 1,72 1,72 15 1,40 2,72 2,59 1,85 1,23 2,07 2,07 16 1,55 3,01 2,87 2,05 1,36 2,29 2,29 17 G-S4 0,95 2,19 2,08 1,33 1,20 1,63 1,63 18 G-S5 0,99 2,27 2,17 1,38 1,25 1,70 1,70 19 1,37 2,41 2,29 1,49 1,45 1,89 1,89 20 1,24 4,38 4,17 2,07 1,58 2,42 2,42 21 1,39 4,91 4,68 2,32 1,77 2,71 2,71 22 1,15 4,05 3,85 1,91 1,46 2,23 2,23 23 1,06 3,76 3,58 1,78 1,36 2,07 2,07 24 0,72 2,53 2,41 1,36 1,12 1,71 1,71 25 SG1 0,46 2,33 2,22 0,97 0,87 1,16 1,16 26 SC1 0,61 2,23 2,13 1,02 0,79 1,22 1,22 27 SG2 0,62 2,37 2,26 1,16 0,96 1,28 1,28 28 SG3 0,67 2,32 2,21 1,10 0,97 1,29 1,29 29 SC2 0,91 2,16 2,05 1,14 0,86 1,33 1,33 30 G(0.7)30/20 0,68 1,93 1,84 1,02 0,94 1,26 1,26 31 G(1.6)30/20 0,85 1,73 1,65 1,01 0,92 1,24 1,24 32 G(1.6)30/20-H 0,77 1,68 1,60 1,21 0,85 1,18 1,18 33 G(1.2)30/20 0,87 1,74 1,65 1,01 0,89 1,25 1,25 34 G(0.7)30/20-B 0,81 2,37 2,25 1,27 1,16 1,54 1,54 35 G(0.7)45/20 0,78 2,35 2,24 1,31 1,14 1,52 1,52 36 G(0.7)45/20-B 1,09 2,25 2,14 1,34 1,22 1,61 1,61 37 G(1.6)30/20-B 1,06 2,09 1,99 1,24 1,15 1,51 1,51 38 G(1.6)45/20 0,90 1,78 1,69 1,12 1,07 1,41 1,41 Average 0,94 2,45 2,34 1,38 1,16 1,08 1,64 Standard deviation (SD) 0,244 0,734 0,699 0,330 0,227 0,153 0,373 Figure 2.3 Comparing the relevance of theoretical formulas to experimental results Table 2.5 and Figure 2.3 show the forecast results according to El-Gamal's formula closest to the experimental value with a mean difference of 8%, safety bias and with the lowest standard deviation (0.153) The formulas of ACI 440.1R 2015, AASHTO LRFD 2018, JSCE, British Standard all give forecast results smaller than the experimental value, with differences of 145%, 134%, 38%, 16%, 64% and standard deviations of 0,734, 0,699, 0,33, 0,227, 0,373, respectively The formula of TCVN 11823: 2017 gives a larger than experimental forecast, with an average difference of 6% The cause of this misalignment is due to the formula of TCVN 11823: 2017 which stipulates that reinforcement with elastic modulus is 4,44 times greater than the elastic modulus of GFRP bars In order to propose a formula to predict the punching shear of GFRP reinforced concrete bridge structure, the author used a nonlinear regression method based on the sample data in Table 2.5 The formula of Ospina (2.80) was selected to carry out the adjustment analysis, since this formula has taken into account all factors affecting the load bearing capacity of the bridge deck structure using GFRP to replace steel reinforcement such as elastic modulus of reinforcement, ratio of reinforcement, size of load tracks In addition, Ospina's formula is relatively simpler in form than others (ACI 440.1R 2015, AASHTO LRFD 2018, JSCE, El-Gamal, BS 8110) The formula (2.81) is transformed to bring it back as a non-linear function of the integral form (2.86) y = bo ( x1 ) ( x2 ) b b (2.86) Carry out the analysis of the results to obtain the coefficients: bo = 2,94; b1 = 0,32; b2 = 0,45 Instead of the input coefficients (2.86), the adjustment formula is written to (2.89) ( Vc P = 2,94 f f ' c ) 0,32 Ef Es 0,45 b1.5 d (2.89) The results of the evaluation of the proposed adjustment formula (2.89) show that the predictability is closer to the test results than the theoretical formulas already available, with the average difference of 1% in terms of safety and with a standard deviation equal to 0,198 Correlation analysis between the characteristics of deflection and crack width corresponding to the applied load levels from the studies [30], [49], [50], [105], synthesized in Table 2.8 shows that the limit of allowable deflection (control condition in the design of GFRP reinforced concrete bridge deck structure), corresponding to the average allowable mining load level reaches 30% of the load level causing sample destruction 11 between the slab spans through the spacer steel plate of the size simulating the wheel tracks (510x362)mm 3.3 Experimental preparation Materials Use is GFRP reinforcement with diameters of 10 mm, 16 mm and 20 mm with bar surface in the form of helical ridges supplied from Vietnam Polymer Fiber Reinforcement Joint Stock Company (FRP VIETNAM.JSC) (Figure 3.2), with some physical and mechanical criteria: f*fu = 900 MPa; Ef = 45 GPa; fu = 0,02 The control specimen used steel reinforcement with a diameter of 14 mm for the primary bearing layer and 10 mm for the remaining layers Some characteristics of reinforcement: fy = 420 MPa, Es = 200 GPa The concrete is designed to have a compressive strength at 28 days of age of 45 MPa (cylindrical specimen), with the composition detailed in Appendix a) GFRP - 10 b) GFRP - 16 c) GFRP - 20 Figure 3.2 GFRP reinforcing bars for laboratory use Experimental instrumentation The project uses a data acquisition and processing unit connected to sensors and computers for the collection of experimental data Test specimens The whole experiment consists of groups (12 slabs) with detailed structure as Figure 3.6, details of aggregate layout in Table 3.3 Deflection was measured with LVDT with an accuracy of 0,001 mm, installed in the top surface of the slab Compressive strain at the concrete surface is measured by 04 strain gauge located at different locations Strain of GFRP (steel) reinforcement in the bottom layer is measured by 03 strain gauge already glued to the reinforcement before concreting (Figure 3.8) The crack width was measured on the underside of the base sample using a dedicated crack pattern gauge Figure 3.6 Detailed construction of the test slabs 12 Table 3.3 Details of the arrangement of reinforcement in the test samples Bottom layer Top layer No Reinforcement group Longitudinal Transverse Longitudinal Transverse steel 1310@200 11:14@250 1310@200 1310@200 GFRP 1310@200 11:16@250 1310@200 1310@200 GFRP 1310@200 25: 16@100 1310@200 1310@200 GFRP 1310@200 21: 20@125 1310@200 1310@200 Arrangement of instrumentation The instrumentation is arranged as shown in Figure 3.8 Figure 3.8 Equipment layout 3.4 Methods of conducting experiments Diagram of the experiment Figure 3.9 Diagram of test arrangement 13 Sequence of experiments The loading process controls the speed of kN/min, records the crack load value, measures the crack width corresponding to the mining load and the design load In addition, crack distribution and sabotage patterns were also collected 3.5 Test results and analysis Results of compression tests of concrete specimens cast together with the casting of specimens obtained f’c = 45.2 MPa Mode of failure and crack patterns The test results of the sample groups are summarized in Table 3.5, 3.6 The form of infestation on the top and bottom sides of the drawing is as shown in Figures 3.11, 3.12 Table 3.5 Summary of test results of slabs on load and deflection (mm) Pcr Pmax Slabs Mode of failure (kN) (kN) Ps Pc Pmax S1a S1b S1c S1-TB G1a G1b G1c G1-TB G2a G2B G2C G2-TB G3a G3b G3c G3-TB 132,2 131,3 132,8 132,1 118,3 116,5 121,4 118,7 138,5 137,5 136,6 137,5 134,3 133,6 133,2 133,7 655 665 660,1 660,1 505,2 501,5 498,4 501,7 717,6 724,9 722,2 721,5 731,1 745,0 761,1 745,7 0,58 0,45 0,49 0,51 0,59 0,57 0,58 0,58 0,57 0,56 0,55 0,56 0,52 0,54 0,53 0,53 1,5 1,01 1,11 1,21 1,73 1,82 1,79 1,78 1,45 1,61 1,52 1,53 1,51 1,52 1,50 1,51 22,79 19,98 21,98 21,58 28,67 34,03 30,92 31,21 29,26 30,84 29,39 29,83 25,61 27,94 26,25 26,60 Punching Punching Punching Punching Note: Pcr is the cracking load on the base samples, Pmax is the load that destroys the sample The deflection value mm at columns Ps, Pc, Pmax is the deflection value of the test specimens corresponding to the service design load, the facrored design load and the failure of the specimen The slabs were failure due to two-way shear (punching) and occurred suddenly with the average load capacity of the sample groups S1, G1, G2, G3 were 660 kN, 501,7 kN, 721,5 kN and 745,7 kN, respectively The top surface is perforated by the perimeter of the transmission steel plate, the cracks in the top surface are in the form of concentric circles with the outermost diameter equal to the distance between the two support beams and the radially inward cracks of the load bearing area Bottom surfaces are cracks directed into the center of the load bearing area With more content of aggregates, the slabs of group G3 has more distributed cracks than the slab of group G1 (Figure 3.11b, c) The average cracking load on slab groups S1, G1, G2, G3 is 132,1 kN, 118,7 kN and 137,5 kN, 133,7 kN, respectively, these values are greater than the service design load for the designed wheel operation HL93 (Ps = 1,33x1,0x72,5 = 96,4 kN) 14 Slabs S1a S1b S1c S1-TB G1a G1b G1c G1-TB G2a G2B G2C G2-TB G3a G3b G3c G3-TB Table 3.6 Summary of test results of slabs on strain and cracking wmax (mm) Note f () c () Ps 222 245 200 222 373 308 279 320 197 247 199 214 224 169 171 188 Pc 409 450 368 409 1461 1349 891 1233 806 748 823 793 704 538 547 596 Pmax 7223 7631 6868 7327 9818 9958 9842 9906 10185 9834 9542 9854 9500 9101 9611 9404 Ps -137 -112 -103 -117 -193 -181 -165 -180 -140 -151 -151 -147 -126 -107 -151 -128 Pc -304 -237 -216 -252 -521 -416 -500 -479 -288 -283 -339 -303 -295 -281 -323 -300 Pmax -2630 -2423 -2554 -2560 -2622 -2811 -2825 -2753 -2762 -2586 -2614 -2654 -2590 -2780 -2626 -2665 Ps - Pc 0,34 0,32 0,32 0,33 0,55 0,58 0,57 0,57 0,37 0,38 0,38 0,38 0,35 0,35 0,36 0,35 The sample does not appear cracks corresponding to the service load The sample does not appear cracks corresponding to the service load The sample does not appear cracks corresponding to the service load The sample does not appear cracks corresponding to the service load Note: The value of f at columns Ps, Pc, Pmax is the strain of the reinforcement corresponding to the design service load, the design factored load and the failure load levels; The value of c at columns Ps, Pc, Pmax is the strain of the concrete surface subjected to compression corresponding to the design service load, the design factored load and the failure load levels; The value of wmax at columns Ps, Pc is the largest crack width on the slab corresponding to the design service load and the design factored load levels The crack widths measured with the factored loads design (Pc = 1,33x1,75x72,5 = 168,7 kN) on sample groups S1, G1, G2 and G3 have mean values of 0,33 mm, 0,57 mm, 0,38 mm and 0,35 mm, respectively The crack width depends on the calculated axial stiffness (E) of the reinforcement and the spacing between the reinforcement bars a) Slab S1b b) Slab G1a c) Slab G3b Figure 3.11 Mode of failure and cracking pattern on the top surface of the slabs a) Slab S1a b) Slab G2c c) Slab G3a Figure 3.12 Cracked form on the bottom surface Concrete and reinforcement strains The graph of the relationship between load - strain of the reinforcement; load - strain of 15 the concrete of the test specimens is shown in Figure 3.17 The average strain of GFRP or steel reinforcement in test specimens S1, G1, G2, G3, with a service load rating of 222, 320, 214, 188, respectively, corresponds to the factored design load rating (calculated with the design 3-axis wheel load of HL93) of 409, 1233, 793, 596, respectively The strain values corresponding to factored design loads reach 3,1% to 9,5% of the limit strain values of GFRP bars (fd = 0,014) At the time of the failure of the slabs, the greatest strain of the reinforcement reached from 64,1% to 72,6% of the design strain value of GFRP material With the service design load (Ps = 96,4 kN), corresponding to 2,5 times the ratio of reinforcement of group G2 compared to group G1, the strain of reinforcement decreased 33,1%, with the content of aggregates increased times that of slab group G3 compared to group G1, the strain of reinforcement decreased 41,2% Strain of the concrete on the slab groups S1, G1, G2, G3 corresponds to a service design load of -117, -180, -147 , -128, corresponding to a factored load level of -252, -479, -303, -300 The greatest strain of the concrete on the top surface at the design load level is from 8,4% to 16,0% compared to the limited strain of the concrete (cu = 0,003) With the load level causing slab failure, the greatest strain of the concrete on the top surface of the slabs reaches from 80.8% to 93.6% compared to the limited strain of the concrete The slabs are destructed when the strain in the reinforcement or GFRP and concrete are both less than the limit strain value of the material Deflection behavior - Chart of relationship between load and deflection The load-deflection relationship curve of the reinforced concrete slab and GFRP reinforced concrete slab is almost linear in both the pre-cracking and post-cracking phases (Figure 3.18) The average deflection of slab groups G1, G2, G3, corresponding to the load used is 1,57 mm, 0,73 mm, 0,59 mm, respectively, these values are less than the allowable deflection (L/800 = 2,5mm) With the load level causing sample destruction, the average deflection of groups slab S1, G1, G2, G3 are 21,58 mm, 31,21 mm, 29,83 mm, 26,60 mm respectively Corresponding to a load of 501,7 kN (the average failure load of group G1), group G2 has 2,5 times the ratio of reinforcement compared to slab group G1 with 39,1% lower deflection, group G3 has 3,0 times the ratio of reinforcement compared to group slab G1 with 52,4% lower deflection Hình 3.18 Relation of loads a) Reinforcement (GFRP) b) Concrete Hình 3.17 The average strain of reinforcement and concrete and deflections of slab groups of slab groups The group of reinforced concrete samples (S1) has an average deflection smaller than group 16 G3 despite the smaller content of reinforcement but the axial stiffness of the reinforcement is greater (sample S1 has E = 733 MPa, sample G3 has E = 525 MPa) Compared at the limited deflection value (L/800 = 2,5 mm), the average allowable mining load of sample groups G1, G2, G3 is 162,5 kN, 213,1 kN, 221,9 kN, respectively, which is 1,7 to 2,3 times more than the service load value 3.2 Analysis and evaluation of experimental results Comparison of experimental results with theoretical formulas Experimental data were compared with El-Gamal's study [49] for samples with equivalent aggregate content, slab thickness and similar experimental scheme The calculation results show a fairly small difference, with the load level causing sample destruction, the average difference is - 2,5%, 1,9% corresponding to sample groups G2 and G3 Compared with the permissible mining load, the average difference is 8,4%, 4,5% corresponding to sample groups G2 and G3 (Table 3.7) Table 3.7 Synthesis and comparison with experimental results of El-Gamal [49] Comparison with the failure Comparison with permissible load service load level No Group VTN VTN [49] VTN VTN [49] Difference Difference (kN) (kN) (kN) (kN) G1-TB 501,7 162,5 G2-TB 721,5 740,0 -2,5% 213,1 196,60 8,4% G3-TB 745,7 732,0 1,9% 221,9 212,40 4,5% Carry out an assessment of the predictability of the proposed adjustment formula (2.89), comparing with the theoretical formulas presented in 2.6.1 Based on the comparison with the experimental results, the results are presented in Tables 3.9 and 3.19 Table 3.9 Results of comparing the prediction models to the proposed model VTN/ VTN/ VTN/ VTN/ VTN/ VTN/ VTN/ VTN/ No Slabs Vc.TCVN Vc.ACI Vc.LRFD Vc.JSCE Vc.Op Vc.El Vc.BS Vc.P G1a 0,57 2,32 2,21 1,22 1,09 1,51 1,17 0,96 G1b 0,56 2,30 2,19 1,21 1,08 1,50 1,16 0,96 G1c 0,56 2,29 2,18 1,20 1,07 1,49 1,16 0,95 G2a 0,80 2,15 2,05 1,27 1,14 1,58 1,23 1,02 G2b 0,81 2,17 2,07 1,29 1,15 1,59 1,24 1,03 G2c 0,81 2,16 2,06 1,28 1,15 1,59 1,24 1,03 G3a 0,83 2,05 1,95 1,24 1,11 1,54 1,18 1,00 G3b 0,85 2,08 1,98 1,27 1,13 1,56 1,20 1,02 G3c 0,87 2,13 2,03 1,29 1,16 1,60 1,23 1,04 Average 0,74 2,18 2,08 1,25 1,12 1,07 1,55 1,00 SD COV, % 0,135 18,2 0,098 4,5 0,093 4,5 0,036 2,9 0,032 2,9 0,031 0,044 0,034 2,9 2,8 3,4 Note: Vc.TCVN, Vc.ACI, Vc.LRFD, Vc.JSCE, Vc.Osp, Vc.El, Vc.BS, Vc.P, VTN, are the predicted puncture resistance values of the original sample according to the Road Bridge Design Standard (TCVN 11823:2017), according to ACI Guidelines (ACI 440.1R 2015), according to the AASHTO LRFD 17 Guidelines (AASHTO LRFD 2018), according to Japanese standards (JSCE - 1997), according to Ospina's proposal, according to El-Gamal's proposal, according to British standard BS 8110, according to the thesis's proposal and empirical value The results of the analysis on Table 3.9 and Figure 3.19 show that the adjusted formula recommended by the student research results is consistent with the experimental data and has a small standard deviation (0.034) Forecast values according to the formulas of El-Gamal, Ospina, British Standard, Japanese Standard, AASHTO LRFD 2018 Guidelines, ACI 440.1R 2015 are all biased towards safety with respective differences of 7%, 12%, 55%, 25%, 108%, 118%, this is explained by the compression arch effect resulting from the bond between the slab and the support beams in the bridge deck structure, resulting in the actual load capacity of the structure being greater than that of a two-way slab structure with unrestrained-edge Road bridge design standard TCVN 11823: 2017 shows that the forecast result is greater than the experimental value, with an average difference of 26% due to the formula of this standard for steel reinforcement with elastic modulus 4,44 times higher than GFRP used Figure 3.19 Comparison of average forecast values by formulas and experiments Compare the limit load corresponding to the deflection condition (L/250) obtained from the experiment with the expected value equal to 30% of the load that destroys the sample calculated according to the adjusted formula (2.89) The results presented in Table 3.10 show that the predicted value of permissible mining load is consistent with the experimental results, with an average difference of 2% and a safety bias Therefore, it is possible to use this forecast method for testing when designing GFRP reinforced concrete bridge deck structure according to the two-way shear failure control method (punching) Table 3.10 Comparison of forecast results of permissible service load levels and experimental No Slabs VTN (kN) Vc.S (kN) Difference (%) G1a 165,5 157,3 1,05 G1b 159,2 157,3 1,01 G1c 162,7 157,3 1,03 G2a 215,5 211,3 1,02 G2B 210,3 211,3 1,00 G2C 213,5 211,3 1,01 G3a 223,3 219,9 1,02 G3b 215,9 219,9 0,98 18 G3c 226,6 219,9 Average 1,03 1,02 Note: The permissible mining load Vc.S = 0,3Vc.P, with Vc.P determined according to the formula (2.89) 3.6.2 Analysis of behavior of experimental slabs by finite element method (FEM) The deck slab was modeled and analyzed using Abaqus software The results of displacement and stress distribution on the top and bottom surfaces of the deck slab as shown in Figures 3.24, 3.25, are consistent with the deflection behavior and mode of failure of the the experiment slab a) Top side b) Bottom side Figure 3.24 Displacement distribution on the top and bottom sides of the drawing a) Top side b) Bottom side Figure 3.25 Stress distribution on the top and bottom sides of the slab The results of the analysis in Table 3.12 show that the numerical simulation method is quite suitable for experimental results, with the difference from -4,8% to 5,2% Representation of the relationship between GFRP aggregate content and load bearing capacity according to the theoretical formulas, experimental results, numerical models and suggested formulas described on Figure 3.28 shows that the formulas of ACI, LRFD, BS, JSCE, Ospina, El-Gamal have a forecast line located lower than the experimental line with an average difference of 7% to 118%, where the most difference is the forecast line of ACI 440.1R 2015 and at least the forecast line according to El-Gamal The forecast results according to the proposed formula are close to the experimental line with the average difference from -4,0% to 4,0% a) b) Figure 3.26 Load-Deflection Figure 3.27 Load-Distortion Relationship Charts of Relationship Chart of FEM and FEM and Experimental Models Experimental Models Table 3.12 Comparison between FEM analysis and experimental results ... FIBER REINFORCED POLYMER BAR REINFORCEMENT MATERIALS AND APPLICATION STUDIES IN BRIDGE DECK STRUCTURE 1.1 Overview of fiber reinforced polymer materials (FRP) A fiber reinforced polymer (FRP) is... FRP is divided into categories: glass fiber reinforced polymer (GFRP), carbon fiber reinforced polymer (CFRP) and aramid fiber reinforced polymer (AFRP) Advantages GFRP bar material is high strength,... costs and cause traffic disruption Due to its strong corrosion resistance, glass fiber reinforced polymer (GFRP) improves the durability of the bridge deck structures and minimizes the cost of repair