جستجوی مقالات مرتبط با کلیدواژه "pullout resistance" در نشریات گروه "عمران"

Unreinforced masonry (URM) buildings are rather popular around the globe due to low construction costs, even although they can be prone to substantial damage caused by even moderate earthquakes. In many cases, reconstruction is not the best choice because of financial and time restrictions. Shotcrete reinforced with steel mesh (SRS) is a cheap and simple yet effective method of repair/retrofit. This paper presents the results of experimental study with the aim of evaluating the effects of construction imperfections of steel reinforced shotcrete, as a retrofit method for URM walls, on the rebar pull-out resistance. For this purpose, a total of full scale URM speimens with one-sided 50 mm-thick shotcrete layer having a single steel rebar were made and tested. The results show in the case the wall’s finishing is not removed, the steel reabr cover is not sufficient, the plain steel reabrs is used, and , use of rebar without a tread, there is 57.8%, 55.2%, 25% and 7.5% decrease in the pullout resistance of the specimens, respectively.

In this paper, the performance of the strip of scrap tires (Geo Scrap Tire(GST)) with horizontal transverse members evaluates as reinforcement elements in mechanically stabilized earth walls (MSEWs) by large scale pullout test (i.e. 1.4 m × 0.8 m × 0.8 m). In this regards, the experimental pullout results of GST reinforcement compared with theoretical equations and conventional reinforcement of Geosynthetic Strip (GS), Steel Strip (ST) and Steel Strip with Rib (STR). The experimental pullout results showed that the innovative suggested reinforcement element performed better than the other strips so that the GST strip was capable of increasing pullout resistance by more than 3, 2.5 and 1.5 times compared to the steel strip, the geosynthetic strip and the ribbed steel strip. The results show maximum pullout resistance of GST affected by the S/B ratio and with adding three horizontal transverse members can be increasing pullout resistance by more than 5.9, 4.9 and 3.2 times compared to ST, GS and STR. Thus, using GST reinforcement with three horizontal transverse member needs a smaller length (less than 30%) comparing to conventional strip reinforcement (ST, GS, STR). Therefore, using Geo Scrap Tire reinforcement can open a new horizon in solving the problem of scrap tires and assure geotechnical engineers in achieving superior and more economical systems of reinforced soil walls.

Pullout resistance of cement-grouted soil nails is a key factor affecting the safety conditions of retaining walls, slopes and excavations. Hence, survey of resistence of pullout nail is the one of the most important parameters in designing of nailing functions. This parameter depend on critical factors including: instalation method, overburden press, grouting pressure, degree of saturation of the soil, the roughness of nail surface, changes of lengh & diameter of nail, the shear strengh of the soil and etc. Sometimes, used soil nail layers affected by cyclic loads due of traffic passing, train and so on. Hence the research aimed to study influence of this kind loadings on resistence of nail post-cyclic pullout and affective factors on it. The study pointed to apply slopes and nailed retaining walls next to traffic loads and rail-roads. Several studies conducted; according to, vary factors influence on nail pullout behavior that buried into soil. Key studies carried out in form of impression of static loading on nail pullout resistance including: overburden stress, grouting stress, impression of an addition to grouting, nail geometry, nail spaces, using spiral nails, comparison laboratory results of pullout set with direct shear test in interface grouted-nail to earn identical ratio and etc. yet, it not examineted cyclic loading impression on post-cyclic pullout resistance in nails. The study just focus on geogrid. For the first time, this research provide impression of cyclic loading on post-cyclic pullout resistance in nails. This research used nail pullout set; able to apply static and cyclic loads in conditions of force or displacement controling with differ frequencies and sinus shape of cyclic wave. This search used the notes of specifications of pullout set; also, sampling due to test and tables of done tests. In this research examined affection of variation of static, cyclic load rate. Resistance of post-cyclic pullout nail generally is more to static pullout resistance; even though , more affections of cyclic loading lead to decrease of resistance; also, obserued in the cyclic part developing in displacement.