整体炉衬镍铁回转窑锚固件的设计与应用

锚固件在不定形耐火材料中起到增强牢固性的作用,所以其使用性能的好坏直接影响着不定形耐火材料的使用效果. 整体炉衬镍铁回转窑使用的锚固件为U型、Y型、V型、双R型或锚固砖. 使用合适的锚固件后炉衬的整体性好,窑体寿命长,产能高,成本低.     

一种有效提高节点定位精度的改进DV-Hop算法

免测距的DV-Hop算法的硬件开销小,但定位精度不高.为改进DV-Hop算法,分析和强调了三点近似共线问题对免测距定位的影响,给出了允许最大跳距误差率和最大跳数下检查锚节点组合有效性的三点近似共线准则.基于该准则和按未知节点与锚节点间的跳数对平均跳距进行加权计算的估计方法,提出了当未知节点得到的有效锚节点数达到给定阈值才定位并扩充为新锚节点的改进算法.仿真结果与分析表明,新算法能有效改善节点定位性能.     

Pullout Behavior of Granular Pile-Anchors in Expansive Clay Beds In Situ

Granular pile anchors (GPA) are one of the recent innovative foundation techniques devised for mitigating the problems posed by swelling clay beds. In a granular pile anchor, the footing is anchored to an anchor plate at the bottom of the granular pile. This makes the granular pile tension resistant and enables it to absorb the tensile force caused on the foundation by the swelling clay. An understanding of the amount of uplift resistance offered by the GPA is important in the design of granular pile-anchor foundations in field situations causing tensile forces on foundations, such as in expansive clay beds. This paper presents the results of a field-scale test program conducted to study the pullout response of GPAs embedded in expansive clay beds. Pullout load tests were conducted on GPAs of varying lengths and diameters. It was found from the field pullout load tests that granular pile anchors of larger surface area resulted in higher pullout capacity. Of the various single granular pile anchors with l/d values between 2.5 and 10, the GPA of length 1000?mm and diameter 200?mm (l/d = 5) showed the best pullout load response when tested alone, resulting in a failure uplift capacity of 14.71?kN. Increase in diameter and length of granular pile anchor increased the uplift capacity. When the length of the GPA was increased from 500 to 750 and 1000?mm, the percentage increase in the uplift load required for an upward movement of 25?mm was 33.3 and 55.5% respectively. The pullout load of the GPA when tested under group was 18?kN as against a 12?kN for the GPA when tested single.     

Experimental Investigation of Nonconventional Confinement for Concrete Using FRP

The present study investigates experimentally the behavior of concrete confined with fiber reinforced polymers (FRP) in the form of jackets which are applied according to a number of nonconventional techniques. First, the effectiveness of various jacketing configurations combined with anchors as a measure of increasing the strength and deformability of L-shaped columns is investigated. It is concluded that easy to install and low-cost anchors made of resin impregnated fibers properly placed at the reentrant corner of L-shaped columns enable excellent mobilization of confining stresses supplied by the FRP jackets. Next, a number of alternative confinement methods are investigated on concrete cylinders, aimed at quantifying the effectiveness of (1) unbonded jacketing, (2) spirally applied strips attached only at their ends, and (3) jacketing directly on concrete with mortar plastering. Although the study may be regarded as preliminary, it provides useful experimental support to a number of techniques which have the potential to open new horizons in the field of externally applied FRP for enhancing concrete confinement.     

Development of Mechanical Anchor for CFRP Tendons Using Integrated Sleeve

A durable and very efficient external strengthening system is achieved if steel tendons for posttensioning applications can be replaced with carbon fiber-reinforced polymer (CFRP) tendons, and if reliable anchorage systems are developed. This paper presents a newly developed and simple-to-use, two-piece wedge anchorage for CFRP tendons with an integrated sleeve and a differential angle between barrel and wedge sections. Three longitudinal slits are cut into the one-piece wedge, with one slit open and the other two stopping 1 mm from the inner wedge hole. The integrated sleeve holds the wedge’s sections together during presetting and loading, resulting in a circumferential confined gripping of the CFRP tendon and optimized surface friction area. Therefore, the one-piece wedge differs from conventional wedge systems, where the wedges act separately with adjacent spaces, wedging the separate tendon sleeve in the longitudinal direction. Evaluation of the failure modes during testing was one of the main keys in achieving an increasingly better performance of the anchorage until the final anchorage was developed. The obtained failure modes are therefore described to enlighten the importance of addressing them when testing. The test setup used and measured behavior are described further together with the loading procedure. The anchorage reached the full capacity of the CFRP tendon and was seen to ensure a stable load of fracture.     

改进的预应力锚索模拟方法及数值验证

通过考虑预应力锚索锚固体的抗弯能力,改善数值模拟中预应力锚索的加同效果,以改变大型边坡锚索群加固效果被严重低估的现状,数值试验结果表明,在下一步开挖前,考虑抗弯能力的锚索与不考虑抗弯能力的锚索模型的作用效果完全一致,在下一步开挖后,两种锚索的作用效果出现明显差异,考虑抗弯效果的锚索单元对边坡塑性区、最小主应力的降低及边坡位移的约束效果更加明显。     

地下工程桩锚护壁体系

地下工程桩锚护壁体系的设计、施工及质量控制是一个比较复杂而且条件多变的系统工程,涉及多学科诸多条件,本文结合四个工程,不同土工物理指标、不同地点、不同深度、不同计算方法、不同的质量控制方法,谈一些自己对设计、施工、信息采集与反馈、控制与决策方面的浅见     

Tensile Capacity of GFRP Postinstalled Adhesive Anchors in Concrete

This paper presents the results of an experimental study conducted on the pullout capacity of glass fiber reinforced polymer (GFRP) postinstalled adhesive anchors embedded in concrete. A total of 90 adhesive anchors were installed using sand-coated GFRP reinforcing bars and tested under monotonic tension loading in accordance with ASTM E-488-96 in 1996. The test parameters were: (1) the GFRP bar diameter (25.4, 15.9, and 6.4?mm); (2) the embedment depth (5, 10, and 15 db where db=bar diameter); (3) the adhesive type (epoxy-based and cement-based adhesives); and (4) installation conditions (wet or partially submerged and dry holes). The tested GFRP adhesive anchors were installed in concrete slabs measuring 3,750?mm long, 1,750?mm wide, and 400?mm deep. The test specimens were kept outdoors for 7?months to be subjected to real environmental conditions including freeze-thaw cycles, wet and dry cycles, and temperature variations. The experimental results indicated the adequate performance of GFRP adhesive anchors installed in wet or partially submerged condition using epoxy-based adhesive. Similar behavior was observed for those installed with cement-based adhesive in dry conditions as well. The capacity of the GFRP bars installed with both adhesive types was achieved at an embedment depth ranging from 10 to 15 db.     

Installation of Torpedo Anchors: Numerical Modeling

Torpedo anchors are used as foundations for mooring deep-water offshore facilities, including risers and floating structures. They are cone-tipped cylindrical steel pipes ballasted with concrete and scrap metal and penetrate the seabed by the kinetic energy they acquire during free fall through the water. A mooring line is usually connected at the top of the anchor. The design of such anchors involves estimation of the embedment depth as well as short-term and long-term pullout capacities. This paper describes the development of a computational procedure that leads to prediction of torpedo-anchor embedment depth. The procedure relies on a computational fluid dynamics (CFD) model for evaluation of the resisting forces on the anchor. In the model, the soil is represented as a viscous fluid and the procedure is applied to axially symmetric penetration of the seabed. The CFD approach provides estimates of not only the embedment depth but the pressure and shear distributions on the soil-anchor interface and in the soil.     

Tensile Behavior of FRP Anchors in Concrete

Strengthening of concrete structures using fiber-reinforced polymer (FRP) systems has become a widely accepted technology in the construction industry over the past decade. Externally bonded FRP sheets are proven to be a feasible alternative to traditional methods for strengthening and stiffening deficient reinforced or prestressed concrete members. However, the delamination of FRP sheets from the concrete surface poses major concerns, as it usually leads to a brittle member failure. This paper reports on the development of FRP anchors to overcome delamination problems encountered in surface bonded FRP sheets. An experimental investigation was conducted on the performance of carbon FRP anchors that were embedded in normal- and high-strength concrete test specimens. A total of 81 anchors were tested under monotonic uniaxial loading. Test parameters included the length, diameter, and angle of inclination of the anchors and the compressive strength of the concrete. The experimental results indicate that FRP anchors can be designed to achieve high pullout capacities and hence can be used effectively to prevent or delay the delamination of externally bonded FRP sheets. The results also indicate that the diameter, length, and the angle of inclination of the anchors have a significant influence on the pullout capacity of FRP anchors.