British Land said on Thursday: "An investigation of the fractured bolts at the Leadenhall Building was completed in January 2015, and a programme of replacement is under way.
In a statement released after the fractured bolts were discovered, state toll bridge manager Tony Anziano defended the steel used for the devices, maintained the problems seem restricted to a "small batch of rods," and declared there is no evidence of problems elsewhere on the span.
Present support theories contain a number of shortcomings in the designation of fractured roof bolt parameters of rectangular or trapezoidal coal roadways.
The paper analyses the arching action by lateral behavior of the inclined roof bolts in reinforcing the fractured roof.
This paper presents an analytical design method for the truss-bolt system in reinforcing underground fractured rock roofs in coal mines.
The analytical design method is based on the mechanical analysis of the fractured rock roof with reinforcement by inclined roof bolts and a horizontal tie-rod.
The pre-tightening forces exerted via the tie-rod also cannot be greater than its upper bound, since the excessive tightening force will cause localized failure in the rock near the bolt tail at the abutment of the fractured roof beam.
Her astonishing two-year unbeaten streak, which lasted from 2009 to early last year, saw her name mentioned in the same breath as Usain Bolt and was made all the more staggering given the fractured ankle that had threatened to end her career in 2008.
In order to develop a satisfied support scheme for roadways excavated in soft rock and subjected to large deformation in coal mines, a combined supporting system is proposed, which includes steel mesh, bolt, anchoring cable, shotcrete, compressible U-shaped steel, foamed concrete damping layer, and fractured rock cushion layer.
These include bolt-grouting support of soft rock roadways with high stress and controlled pre-stressing of fractured roofs with obviously inclined separation.
