Typical Tie Bar Configurations and Connections
Anchor assemblies will normally comprise of a series of lengths of round steel bar (depending on the maximum length capable of being produced by a manufacturer) coupled together with suitable threaded or forged connections. Connections to the front and anchorage walls can be made with simple bearing plates and nuts or articulated joints.
All connecting components to an anchor should be designed to exceed the tensile resistance (Ft,Rd ) of the bar, hence the bar shaft, or threaded part of bar determines the overall tensile resistance of the anchor (see Tensile Resistance).
Where the axis of an anchor is not perpendicular to the structure, settlement is expected, or site conditions and construction methods make it difficult to achieve connections with accuracy articulated joints are preferable. In practice most sheet piled walls are constructed in difficult and less than ideal environments so tie bar connections to walls with some degree of articulation are recommended.
Plates are required to transmit the load imposed on sheet piling to the anchors and from the anchors to the anchorages which may be constructed using sheet piles, tubular piles, insitu cast concrete or individual concrete blocks. Washer plates are used when the anchors are connected within the pans of sheet piles and bearing plates when the load is transmitted through walings. When the load is taken to a concrete wall or block, anchorage plates distribute the load to the concrete. The waling loads are transmitted to the anchorages by means of anchor bolts which also require bearing plates and washers of sufficient size to provide adequate bearing on to the sheet piling, walings etc.
At the front wall the tie bar connection can be made to walings either inside (Detail Z) or outside the sheet pile pan (Detail Y) shown in Figure 13 - Typical tie bar connections to sheet pile walings and Figure 14 - Waling connections. In areas of aggressive corrosion (eg splash zones for a quay wall) connections to the inside of the pan are preferred as they offer greater protection to corrosion, waling bolts should then be designed with sufficient sacrificial steel capacity
1. Typical Tie rod Configurations
Typical tie bar configurations and different means of connecting anchors to walls are shown here.
2. Articulation within the length of a tie rod
Any bending in an anchor, especially in the threaded length increases the stress locally with the possibility of yield or even failure if the bending is severe. In order to eliminate the risk of bending, several options are available which allow rotation of the axis of the anchor whilst maintaining its tensile capacity. These include forged eyes, ball joint or Cardan connections. Click here for examples.