Based on the Canadian Standards Association (CSA) criteria,105 pullout specimens were tested to investigate the effect of different rib geometries on bond strength of glass fiber reinforced polymer (GFRP) rebars embed...Based on the Canadian Standards Association (CSA) criteria,105 pullout specimens were tested to investigate the effect of different rib geometries on bond strength of glass fiber reinforced polymer (GFRP) rebars embedded in concrete. Two kinds of conventional reinforcing rebars were also studied for comparison. Each rebar was embedded in a 150 mm concrete cube,with the embedded length being four times the rebar diameter. The experimental parameters were the rebar type,rebar component,rebar diameter,rebar surface texture,rib height,rib spacing and rib width. Theoretical analysis was also carried out to explain the experimental phenomena and results. The experimental and theoretical results indicated that the bond strength of GFRP rebars was about 13%～35% lower than that of steel rebars. The bond strength and bond-slip behavior of the specially machined rebars varied with the rebar type,rebar diameter,rebar surface texture,rib height,rib spacing and rib width. Using the results,design recom-mendations were made concerning optimum rib geometries of GFRP ribbed rebars with superior bond-slip characteristics,which concluded that the optimal rib spacing of ribbed rebars is the same as the rebar diameter,and that the optimal rib height is 6% of the rebar diameter.展开更多
This paper proposes an empirical formula to estimate the shear strength of hydraulic expansion rockbolts.The field experimental results were obtained from eleven pullout tests to evaluate the results computed by the p...This paper proposes an empirical formula to estimate the shear strength of hydraulic expansion rockbolts.The field experimental results were obtained from eleven pullout tests to evaluate the results computed by the proposed formula.It was found that shear resistance of hydraulic expansion rockbolts significantly depends on the uniaxial compressive strength and elastic modulus of rock,with high correlation coefficients of 0.7651 and0.8587,respectively.The developed formula enables estimation of the maximum pullout load in an analytical process without pullout tests in the field.Conversely,due to the poor interlocking at the initial pullout load,the measured displacements were higher than the estimated ones.To reduce the interlocking effects between bolt and rock,we recommend preloading of 29.4 kN.Preload allows reducing the distance between the measured and estimated displacement and making two load-displacement curves practically identical with marginal differences of 1.1 to 1.5 mm at the maximum pullout load.展开更多
基金Project (No. 200431882021) supported by the Western Communi-cation Construction and Science & Technological Project,China
文摘Based on the Canadian Standards Association (CSA) criteria,105 pullout specimens were tested to investigate the effect of different rib geometries on bond strength of glass fiber reinforced polymer (GFRP) rebars embedded in concrete. Two kinds of conventional reinforcing rebars were also studied for comparison. Each rebar was embedded in a 150 mm concrete cube,with the embedded length being four times the rebar diameter. The experimental parameters were the rebar type,rebar component,rebar diameter,rebar surface texture,rib height,rib spacing and rib width. Theoretical analysis was also carried out to explain the experimental phenomena and results. The experimental and theoretical results indicated that the bond strength of GFRP rebars was about 13%～35% lower than that of steel rebars. The bond strength and bond-slip behavior of the specially machined rebars varied with the rebar type,rebar diameter,rebar surface texture,rib height,rib spacing and rib width. Using the results,design recom-mendations were made concerning optimum rib geometries of GFRP ribbed rebars with superior bond-slip characteristics,which concluded that the optimal rib spacing of ribbed rebars is the same as the rebar diameter,and that the optimal rib height is 6% of the rebar diameter.
基金supported by 2016 Hongik University Research Fund and the Convergence R&D program of MSIP/NST[Convergence Research-14-2-ETRI,Development of Internet of Things(IoT)-based Urban Underground Utility Monitoring and Management System]
文摘This paper proposes an empirical formula to estimate the shear strength of hydraulic expansion rockbolts.The field experimental results were obtained from eleven pullout tests to evaluate the results computed by the proposed formula.It was found that shear resistance of hydraulic expansion rockbolts significantly depends on the uniaxial compressive strength and elastic modulus of rock,with high correlation coefficients of 0.7651 and0.8587,respectively.The developed formula enables estimation of the maximum pullout load in an analytical process without pullout tests in the field.Conversely,due to the poor interlocking at the initial pullout load,the measured displacements were higher than the estimated ones.To reduce the interlocking effects between bolt and rock,we recommend preloading of 29.4 kN.Preload allows reducing the distance between the measured and estimated displacement and making two load-displacement curves practically identical with marginal differences of 1.1 to 1.5 mm at the maximum pullout load.
文摘目的 :比较重度骨质疏松腰椎中不同剂量骨水泥强化椎弓根螺钉的稳定性,分析螺钉稳定性与骨水泥剂量间的相关关系及初步探索注射PMMA的合适剂量。方法:18个新鲜腰椎标本来自4具新鲜尸体(男性1名和女性3名,平均年龄65±9岁),测量各椎体的骨密度(bone mineral density,BMD)后将18个腰椎标本的36侧椎弓根随机分为6个实验组(A^F组)。相同方法制备钉道后,从A组到F组中,依次向钉道内注入0ml、1.0ml、1.5ml、2.0ml、2.5ml、3.0ml PMMA后拧入普通椎弓根螺钉。待骨水泥硬化后进行X线检查观察螺钉周围骨水泥的分布情况,随后进行轴向拔出实验并测量最大轴向拔出力(the maximum axial pullout strength,Fmax)。采用单因素方差分析和LSD检验比较各组中的BMD和Fmax的差异。Fmax和PMMA剂量之间进行相关性分析。结果:所有腰椎的BMD均小于0.6g/cm2,T值均小于-3.5,根据WHO的标准均诊断为重度骨质疏松椎体,各组中BMD之间的差异无统计学意义(P=0.799)。A组中,螺钉周围未见任何PMMA;B^F组中,PMMA相对均匀地分布于螺钉周围的骨质中。所有腰椎中螺钉位置良好,均未见明显PMMA渗漏。A^F组的Fmax分别为358.50±86.00N、442.67±96.02N、532.00±103.18N、740.67±120.90N、841.50±133.42N和1111.50±158.57N。与A组相比,B^F组的Fmax的提高程度分别为23.48%、48.40%、106.60%、134.73%和210.04%。A组和B组之间,B组和C组之间,E组和F组之间Fmax的差异均不具有统计学意义(P=0.230,P=0.203,P=0.152),其余各组间的差异均具有统计学意义(P<0.05)。Fmax与PMMA剂量之间存在显著的正相关关系(Pearson相关系数r=0.877,P<0.05)。结论 :PMMA可以提高重度骨质疏松腰椎中椎弓根螺钉的稳定性,螺钉稳定性与PMMA剂量成显著的正相关关系。在一定范围内,注射PMMA和增加PMMA的剂量并不能显著增加螺钉的稳定性。生物力学研究表明,重度骨质疏松腰椎中提高螺钉稳定性时注射PMMA的合适剂量是3ml。
