In this paper effect of static densification of treated paulownia on relationship between strength properties and density was investigated. Specimens were steamed at 130 and 170oc and immediately were compressed to 35% and 45% of their original thickness in radial direction. Mechanical properties such as bending strength, brinell surface hardness and compression strength in axial and radial direction were determined for non-densified and densified wood. Indexes of density, strength, quality and strength potential were calculated to study the relationship between strength and density. The results show that the density index and strength index and also strengths significantly increased with increase in densification but strength potential indexes decreased. Steam treatment at 130oc had a slight positive effect on the strengths and strength potential indexes as effect of softening the wood but the strength potential indexes and strengths decreased due to treatment of wood at 170oc. Generally, strength potential indexes of all tested mechanical properties show that strength of densified paulownia was lower compared to what had expected for non-densified paulownia from increasing density, which in turn demonstrate the cell walls were negatively affected by compression. Axial compression strength and brinell hardness were slightly affected by densification.

Data on the physical strength capabilities are essential for design-ing safe and usable products and are useful in a wide range of clinical settings especially during treatment of disease affecting the function of the hand. The purpose of this study was to determine peak lateral pinch strength, key pinch strength, tip-to-tip pinch strength and three-jaw pinch strength exertions in a healthy Iranian children and young adult population. The study was conducted among 511 participants (242 males and 269 females) aged 7-30 years. Measurements were carried out with both dominant and non-dominant hands in standard sitting posture using a B&L pinch gauge. Two repetitions of each strength measurement were recorded for each condition and the average value of the two trials was used in the subsequent analysis. The results showed significant differences in the pinch strength data in terms of the age, gender and hand dominance. The lateral pinch strength, key pinch strength, tip-to-tip pinch strength and three-jaw pinch strength exertions by females were 68.4%, 68.8%, 78.8% and 81.8% of those exerted by males, respectively. Strength exertions with the non-dominant hand were 6.4%, 5.2%, 6.6% and 5.1% lower than strength exertions of the dominant hand for the lat-eral pinch strength, key pinch strength, tip-to-tip pinch strength and three-jaw pinch strength exertions, respectively. These findings can be used to fill the gaps in strength data for Iranian population.

The addition of fibers with different physical and strength properties has different effects on the strength properties of jointed concrete pavements at rupture and also on the residual flexural strength of the pavement. This study investigates the separate and comparative effect of micro and macro synthetic fibers on the strength properties of jointed concrete pavements, considering the residual flexural strength of the pavement. For this purpose, the effect of adding two types of macro fibers and one type of micro fiber in the content of 1, 2, and 3 kg/m3 on compressive strength, splitting tensile strength, flexural strength, and flexural performance after cracking of concrete pavement were investigated. The results showed that micro fibers in all consumption contents have the least effect on the strength properties of pavement compared to macro fibers. Also, the addition of macro fibers did not have a significant effect on the compressive strength, but the splitting tensile strength, flexural strength, and residual flexural strength of pavement were significantly increased. The effect of macro fibers on improving the splitting tensile strength and modulus of rupture of pavement occurred at dosage rates higher than 2 kg/m3. However, the most significant increase in the equivalent flexural strength ratio of fiber reinforced concrete pavement occurred in the range of 1 to 2 kg/m3, and by adding higher contents of macro fibers, the increasing growth trend of residual flexural strength decreased. It was founded that macro fibers have the most excellent effect on flexural strength and residual flexural strength of the pavement. Also, the performance of twisted and continuously embossed macro fibers in all dosage rates was approximately the same.

Muscle strength and increased concentration are very important and effective components in the success of archers. The aim of this study was to investigate the effect of six weeks strength training with EMS on salivary BDNF and back muscle strength in elite archers. In this semi-experimental study, 16 elite male archer volunteers (age range 16 to 18 years and body mass index 20-25 kg.m-2) purposeful and accessible were selected and randomly were divided into two groups; strength training with EMS and strength training with arch groups. The EMS group performed strength training (50% to 75% 1RM) with muscle electrical stimulation (Maximum output current 180 mA, output frequency 1 to 120 Hz) 3 days a week for 6 weeks, and the control group only were performed strength training similar to the EMS group. Data were analyzed using paired and independent t-test at the P<0.05. The results showed that after 6 weeks, the mean of the back-muscle strength in the strength training with EMS group was significantly higher than the strength training with arch group (p<0.001). Also, the back-muscle strength increased significantly in the strength training with EMS and strength training with arch groups compared to the pre-test (p<0.001), Salivary BDNF levels in elite archers in the strength training group with EMS were not significantly different than the strength training with arch group (p= 0.985). According to the results, it seems that strength training with EMS can increase the back-muscle strength elite archers.

This paper presents on an experimental study of confined high-strength concrete columns tested under axial compression. The main objective of the research is to know the performance of spirals and hoops with medium strength (400 MPa < fy < 600 MPa) in their contribution on the behaviour of confined high-strength concrete columns. The parameters of the study were concrete strengths, confining steel characteristics i.e: type of confinement (spirals and hoops), yield strength, spacing and volumetric ratio. From the experimental results it was found that the strength enhancement and ductility of confined concrete will decrease with if both of concrete strength and spacing of spirals or hoops increase, and the strain in the test also showed that the release of a cover of concrete core occurs prematurely. Other results shows that satisfactory of circular hoops as confinement steel behaved as good as the spiral reinforcement. The spiral reinforcement provision adopted in the Indonesian Concrete Standard 2002 (SNI 03-2847-2002) is quite reliable when applied in the design of confining steel with medium strength of high-strength concrete columns, therefore it is proposed that the upper limit provision of yield strength of confining steel warrant to be modified.

This study concentrates on effect of tensile strength of fibers on shear strength of municipal solid wastes in Kahrizak landfill. These studies consisted of large scale triaxial tests in consolidated – undrained state on the new and aged (9 years aged) solid wastes in Kahrizak landfill. At first, strength properties of samples in existing condition were determined, then in order to investigate the effect of fibers on shear strength of waste, plastic fibers with 3 different tensile strengths (7, 16 and 21 MPa) with different weight contents (%12) were added. The results showed that waste’s fibers are one of the main providers for waste mass strength and with increase in tensile strength of fibers, the effect of this part in shear strength of landfill will increase, for example, with 200 percent increase of tensile strength in fibers, excessive stress will increase more than 100 percent. Application of plastic fibers in samples will lead to decrease of adhesion and increase of internal friction angle of samples. Also, other than the tensile strength, elasticity and deformations of fibers before the failure have an influence on the behavior of solid waste mass.

Evaluation of concrete strength is one of the important issues in the concrete industry and concrete structures. In most cases, during construction, samples of concrete are picked up and after curing, according to the existing standards, they are subjected to uniaxial compression and based on the applied force, the strength of the concrete is determined. Minimum strength of concrete can be predicted but in many cases, due to reasons such as lack of proper implementation, concrete strength in structure with design strength is different. Core drilling is one of the accepted in-situ tests for measuring the strength of concrete that is a destructive method. Providing a non-destructive method that can estimate the strength of concrete in a structure in many cases is a remedial. In this research, by providing concrete samples with different mix design, in addition to studying the effect of mixing ratios on concrete strength and ultrasound wave velocity, a relationship between concrete strength and ultrasonic wave velocity is presented. Also, a comprehensive relationship is presented to estimate the strength of concrete considering water to cement ratio and the ratio of fine aggregate to course aggregate.

This study aims to investigate the effects of key parameters on the interfacial bond strength between two concrete members. Different types of overlay in terms of strength (normal-strength concrete, high-strength concrete), surface roughness, and adhesive type are considered as variable factors influencing the bond behavior. First, the surface roughness of the old concrete and the compressive strength of the concrete overlay are evaluated separately. Then among the specimens, the composite with the highest bond strength is chosen as the optimum concrete composite. After finding the optimum composite, epoxy adhesive and cellulose mortar are applied to the optimum sample, and its corresponding interfacial strength is evaluated by bi-surface shear and splitting tensile strength tests. The results showed that, as the compressive strength of new concrete and concrete roughness increases, the bond strength increases. The highest bond strength achieved in composites containing high-strength concrete is 23.37% higher than that of samples with normal-strength concrete. Moreover, the interfacial bond strength of composite with the wire-brushed surface is the highest among other treatment methods, due to the interlocking action it provides. The bond strength of concrete composites containing epoxy adhesive is ∼100-200% higher than that of samples without epoxy resin. However, the addition of cellulose mortar slightly reduces the adhesion resistance of the optimum sample. Therefore, it is anticipated that the use of high-strength concrete concomitant with wire-brushed surface treatment and epoxy resin adhesive shows substantial potential as an excellent method for repair of concrete structure.

In recent years, using too much cement has led to the production of greenhouse gases, one of the consequences was the heating of the earth. These destructive effects lead to more attention to the use of pozzolanic materials. In this study, the durability of geopolymer concrete (active alkali slag) containing silica fume and fly ash against corrosive acidic, sulfate and compressive strength, flexural strength, tensile strength, and chloride ion permeability were investigated. The corrosive properties of different environments by the compressive strength and weight loss tests were compared. After 7 days of operation in lime water, samples were placed in sulfuric acid solution, magnesium sulfate, and sodium sulfate for 180 days. At first, the weight loss of the samples, then the compressive strength of the samples after exposure to the medium corrosive was measured. The compressive strength, flexural strength, tensile strength, and chloride ion permeability were also measured. In this study, increasing the of silica fume and fly ash alternatives instead of slag in concrete, compressive strength, flexural strength, tensile strength, and durability and chloride ion permeability increased; In fact, the best sample is pure slag geopolymer concrete, which has a compressive strength of 53.45 MPa, flexural strength of 6.05 MPa, tensile strength of 5.5 MPa, chloride ion flow rate of 6067 Coulombs and compressive strength after placement in sulfuric acid, magnesium sulfate, and sodium sulfate are 43.92, 44.8 and 45.9 MPa, and also the weight loss after placing in these solutions is 21, 14 and 12 grams respectively.

Reactive powder concrete (RPC) is one of the ultra-high strength concretes with superior mechanical properties, which is made using cement and very fine powder materials such as quartz sand, microsilica, low amounts of water-cement ratio, super-lubricant and steel fibers. The main role of steel fibers in such concrete is actually a type of composite that has proper integrity and continuity and enables the use of concrete as a flexible material. The present study aimed to evaluate the effect of using different types of industrial steel fibers with different length (diameter) and percentages on the strength properties of RPC and to determine a series of experimental relationships for their estimation. To this end, by preparing three types of steel fibers with small diameters (group 1), medium (group 2) and large (group 3) and making a number of RPC samples using indigenous and common mineral materials, the strength characteristics of this type of concrete include compressive, bending and tensile strengths were determined at different ages. To investigate the effect of curing time as well as the diameter and percentage of steel fibers on the compressive strength of RPC, a total of 39 samples + 1 sample without fibers (control concrete) containing 1 to 5% of large steel fibers (with diameter of 0.8 mm), medium (with diameter of 0.6 mm) and small (with diameter of 0.4 mm) were made and their compressive strength was determined at different ages. In addition, to determine the bending and tensile strengths of RPC samples, a total of 18 standard RPC beam and cylindrical samples containing different percentages of medium diameter steel fibers were made. After these samples were cured, their 28-day strength was evaluated in comparison with the control samples. The results of compressive strength tests showed that by increase in the curing age, the strength of RPC increases in compared with the control sample (without fibers). The results of compressive strength tests showed that by reduce in the diameter of steel fibers, the 28-day compressive strength of RPC samples increased significantly and was determined to 423.5 MPa. In compared with the control sample (without fibers), the compressive strength is associated with a growth of 29.11%. Also, the optimal amount of medium steel fibers to achieve RPC with the highest strength was determined to be 2%. The results of flexural strength tests showed that 2% of group 1 steel fibers (with small diameter) and group 2 (with medium diameter) and 3% of group 3 steel fibers (with large diameter) as the optimal percentage of steel fibers to reach the maximum flexural strength in RPC. Therefore, the 28-day flexural strength of RPC samples containing 2%, 2%, and 3% of steel fibers of groups 1, 2, and 3, respectively, was equal to 40.9, 44.6, and 39.1 MPa. The highest tensile strength of RPC samples containing 1%, 2%, and 3% of steel fibers of groups 1, 2, and 3 compared to the control sample, was associated with a growth of 61.25%, 66.42%, and 68.21%, respectively. Also, the results of the tensile strength tests showed that the addition of group 2 steel fibers (medium) compared to the other two groups (small and large), had a greater impact on the growth percentage of tensile strength of RPC samples.