The scour around the bridge piers causes instability of them, and without applying an appropriate solution, it eventually leads to demolition of the structure. Therefore, study on the mechanism of the occurrence of the scour and effective parameters on the amount of scour are important. This study was preformed to find the effect of bridge pier’s dimension on the scour depth. Therefore, the tests were carried out for cylindrical bridge piers with diameters of 10, 20, 30, 40, 50 and 60 mm in clear water condition with relative velocities (water velocity over scour critical velocity) of 0.95, 0.86, 0.76 and 0.67 in a laboratory flume. The mean size of bed particles was equal to 0.51 mm. The results showed that with an increase of 13.15 percent in relative velocity of the flow from 0.76 to 0.86 for pier with diameter of 40 mm, also with an increase of 20 percent in the pier diameter from 50 to 60 mm at the flow relative velocity of 0.95, the scour depth increased 38.8 and 10.34 percent, respectively. In addition, by analysis of the experimental results, the pier with diameter of 40 mm was an appropriate one with suitable diameter so it was proposed for the other similar experiments.

Bridges are the most useful structures on rivers which floods cause damage to them every year. One of the known factors in bridges destruction is local scouring around the bridge piers. In this study, to investigate the scour depth around the bridge pier in the river bend, experiments were performed in a laboratory flume with a 90-degree bend with  . By placing a cylindrical pier with a diameter of 45 mm at three locations of 30, 45 and 60 degrees along the bend, for three flow Froude numbers, the scouring around the pier under clear water condition was investigated. Natural sand with an average diameter of 0.85 mm is used for the bed materials. The results showed that the maximum scour depth around the bridge pier varies at a different location along the bend. Besides, the flow discharge increase grows the depth and volume of the scour hole at all positions. Additionally, maximum and minimum depth and volume of scouring hole occurs in the second half of the bend at 60- degree position and in the middle of the bend at 45- degree position, respectively. Finally, it was recorded that the development of the sedimentary hill after the pier and its extent in the first half of the bend was higher than the second half of bend. The result also indicated that the maximum and minimum scour depths relative to the pier diameter are equal to 2.24 and 1.22, respectively.

Bridges are the most useful structures on rivers which floods cause damage to them every year. One of the known factors in bridges destruction is local scouring around the bridge piers. In this study, to investigate the scour depth around the bridge pier in the river bend, experiments were performed in a laboratory flume with a 90-degree bend with  . By placing a cylindrical pier with a diameter of 45 mm at three locations of 30, 45 and 60 degrees along the bend, for three flow Froude numbers, the scouring around the pier under clear water condition was investigated. Natural sand with an average diameter of 0.85 mm is used for the bed materials. The results showed that the maximum scour depth around the bridge pier varies at a different location along the bend. Besides, the flow discharge increase grows the depth and volume of the scour hole at all positions. Additionally, maximum and minimum depth and volume of scouring hole occurs in the second half of the bend at 60- degree position and in the middle of the bend at 45- degree position, respectively. Finally, it was recorded that the development of the sedimentary hill after the pier and its extent in the first half of the bend was higher than the second half of bend. The result also indicated that the maximum and minimum scour depths relative to the pier diameter are equal to 2.24 and 1.22, respectively.

The construction of bridges within the river beds often makes changes to the shape and direction of the rivers. These changes take the natural actions of the river, that one of them is the local scouring around the bridges' piers and can cause annually damage. Therefore, many researches have been carried out to control and reduce the scouring. One of the methods presented by researchers is using slot at piers. In present study, the effect of Pier Opening Area on local scouring around the pier with rectangular section is experimentally investigated. For this purpose, piers with square shape slots and different dimensions were used. The piers were tested at three levels (near the water level, on the bed and under the bed) and four Froude numbers. The result showed that the maximum scouring depth and the volume of hole scour had a direct relationship with slot level relative to bed and Froude number and an inverse relationship with Pier Opening Area. The best performance belonged to the slot with greater dimensions which was located under the bed level in the minimum Froude number condition that reduced the depth of scouring about 55. 4 percent.

In this study, a new structural system for either retrofitting or design of new structures has been presented that provides more resistance for lateral loading conditions in comparison with the conventional systems. This new structural system can be utilized for a wide range of steel or concrete infrastructure systems from bridges to jackets as offshore structures. In this paper, structural performance of the new systemis compared with conventional system for bridges. The structural response of piers in long- and medium-span bridges has been studied. A comparative study is carried out through static pushover analysis of four medium-span bridge piers and reveals the new system has a higher load-carrying capacity compared with the conventional system, whilst no significant changes are observed for period-based ductility. A probabilistic analysis of the structural collapse is carried out through incremental dynamic analysis (IDA). The results from IDA analyses show higher seismic safety for the new system compared to the conventional system. Besides, a time history analyses for far-field earthquake ground motions to evaluate structural response of a long span bridge was conducted. The results indicate that the stiffness degradation observed in the conventional system caused more damage than the stiffness degradation observed in the new system.

Woody debris accumulates in front of bridge piers, reduces the flow area, deviates the flow and increases the velocity around the bridge piers. Debris accumulation in front of bridge piers increases the downward flow, and shear stress around the bridge pier, therefore, the scour hole depth increases and bed degradation accelerates. Most of previous researchers focused on the scour depth around the bridge piers, and less researchers have investigated the effect of debris accumulation on the scour depth. To the best of our knowledge, the effect of debris accumulation on the scour depth has not been reported in previously published literature, as explored in this work. The purpose of this study is to experimentally investigate the effect of accumulation of woody debris in front of a square pier with a parabolic nose on the scour depth. The experiments were performed in clear water condition, with and without debris accumulation and with 20, 30 and 40 l/s discharges and for different debris dimensions. The experiments were performed in a sixty centimeter width channel at the hydraulic laboratory of Shahrekord University. Previous field studies showed that most debris accumulates in front of bridge piers in rectangular shapes, therefore three different rectangular shapes debris are designed and are placed in front of bridge piers during the experiments. Since, performed experiments at twelve hours showed the maximum equilibrium scour depth occurs at the first seven hours, therefore, all experiments are done in 420 minutes. The results showed that when woody debris is placed over, at, and below the water surface respectively, the ratio of scour depth to the scour depth of control sample is 2.2, 2.36 and 1.44, respectively. Moreover, when the percentage of blockage (ratio of the occupied flow area by debris to the flow cross section) is 30% and when debris is located below the water surface, the maximum scour depth will occur (2.36 with respect to the control sample). Also, the comparison between a square pier with parabolic nose and a sharp nose piers at the same hydraulic condition, show when there are no debris, the scour depth around the square pier with a parabolic nose is less than the scour around a sharp nose square pier (1.5 times). For the case in which debris are placed in front of bridge pier, the scour depth, width, and length around a square pier with a parabolic nose are significantly decreased with respect to a sharp nose square pier (2.3 times). Also, using dimensional analysis an equation is presented for predicting the maximum scour depth around a square pier with a parabolic nose in presence of woody debris accumulation. The results show that there is good agreement between predicted and observed scour depth.

Introduction: Measurement of child anxiety during dental treatment is a challenge during the procedure. Several questionnaires have been developed to assess child anxiety, some of which are pictorial to facilitate their application in children. The aim of the current study was to evaluate validity of new RMS pictorial questionnaire and to compare it with previous scales, including Venham Picture Test (VPT) and Facial Image Scale (FIS), to assess child dental anxiety during their first visit in a dental office.Materials & Methods: This cross-sectional study was performed on 10 children in Shiraz in 2016, who met the inclusion and exclusion criteria. The children's anxiety was evaluated by RMS-PS, VPT and FIS questionnaires. To assess reliability, questionnaires were given to the children at a two-week interval. Data were analyzed with t-test and regression correlation test (a=0.05).Results: Age and gender had no effect on children's anxiety, but in the presence of preoperative pain, anxiety was significantly higher. RMS had a moderate (r=0.622) and significant (p value<0.001) correlation with VPT questionnaire and a good (r= 0.700) and significant (p value<0.001) correlation with the FIS questionnaire. In addition, the relationship between FIS and VPT questionnaires was moderate (r= 0.623) and significant (p value<0.001).Conclusion: The results showed that RMS questionnaire is not reliable. However, it was valid compared to FIS and VPT questionnaires. Therefore, RMS can be used to indicate child dental anxiety as a proper tool.

Determination of the volume and depth of scour hole around a bridge pier placed on a river bed has been considered as an important issue from the view point of stability. Hence, broad investigations are carrying out in order to control and reduce the local scour. The current paper with the goal of reduction in local scour has investigated the slotted pier and double-pier close to each other. Different widths of slots in a single cylindrical pier are investigated under clear-water flows in an experimental flume. The depth, volume and iso-depth of scour hole in different models are examined. The results of experimental works have shown that in a slotted single pier extended below the bed level with w/D=0.3 (in which w is the width of slot and D is the pier diameter), the depth and volume of scour hole are reduced up to 72.5% and 83.8% respectively. In other slotted single- pier models with w/D=0.3 with the slot length limited to the bed level and 0.2 with the extended and limited slot to the bed level the depth of scour hole are reduced up to 58.1, 51.2 and 44.2% respectively. In pier groups, the depth of the normalized depth of scour ds/D at w/D=0, 0.25, 0.5, 0.75 and 1 are equal to 2.9, 2.5, 2.3, 2.2 and 2.0 respectively. Among the double- pier models it is said that at w/D=1 , depth and volume of scour hole in comparison to the single solid pier, 13.2 and 15.3% are reduced which shows the appropriate behavior of such models in reduction and control of the scour depth in comparison to the single solid pier.

Local scour around bridge piers is one of the most destructing factors in bridge failure. Studies have shown that 60 percent of the bridge failure can be related to the local scour around bridge piers or other hydraulic phenomena. Up to now a good deal of research has been carried out on the effect of different factors on the development of the scour depth using physical models. In spite of considerable efforts made to understand the effect of side wall on the scour depth development, a comprehensive study of this phenomenon has yet to be established. The main aim of the present research was to improve knowledge 'of the effect of the side wall on the scour depth. Experimental results showed that, in order to achieve maximum scour depth, the D/W scale should be attained around 0.11. It was also found that scale parameter D/W greater than 0.11 created a reduction of up to 35 percent in the depth of the scour hole.