Anti-seismic system placed in a shaft of a load-bearing structure

The main object of the hydraulic tie rod for construction projects of our invention along with its application method in the construction field for structural projects is to minimise the problems associated with the safety of structural projects such as buildings in the case of natural phenomena such as earthquakes, tornados and very powerful winds in general. According to the present invention, this can be achieved by a continuous pre-stressing (pulling) of both the roof of a large, geometrical part of the building structure which independent of the load-bearing structure towards the ground and of the ground towards the structure, making these two parts one body like a sandwich.

This pre-stressing force is applied by the mechanism of the hydraulic tie rod for construction projects, said mechanism mainly consisting of a steel cable penetrating free in the centre the vertical support elements of the structure, as well as the drilling length, beneath them. Said steel cable's lower end is tied to an anchor-type mechanism that is embedded into the banks (walls) of the drilling to prevent it from being uplifted. This embedding is attained due to the drilling hole being somewhat smaller than the exterior diameter of the completely opened anchor mechanism. Said steel cable's top end is also tied to a hydraulic pulling mechanism exerting a continuous uplifting force. This pulling mechanism comprises a piston, said piston reciprocating within a piston sleeve, connected to a pressure chamber beneath it. This pulling force, exerted on the top-end of the steel cable, by the hydraulic mechanism due to the hydraulic pressure originating from the rise of the chamber towards the piston, and the reaction in this pulling force originating from the embedded anchor at its other end generate the desirable compression in the construction project which in turn is tied to the ground and thus rendered resistant to the horizontal forces of an earthquake.

Utility analysis of the anti-seismic system titled: “Hydraulic Tie Rod for Construction Projects”.

Innovative step of the invention:

The forces of an earthquake (horizontal and vertical) start being transported from the bottom (base) towards the top (load-bearing structure).The horizontal and vertical (tectonic) transfer of the earthquake forces to the load-bearing structure is executed necessarily by the ground floor columns via the bases, and by means of the nodes, to the first floor and from then on from the first to the second, and so on.

However the following paradox emerges:

The first (bottom), intermediate and top plates, when oscillating each have different amplitudes, and different directions. This is due to the inertia of each one of the multiple plates, as well as the additive elasticity of the columns of each floor, in different time-space, from the bottom to the top.

This delayed transfer of the acceleration forces results in the multiple plates moving in different lateral directions, (due to the inertia exhibited by each individual plate, in different time-space). Thus, additional torques are created, as well as shearing stresses form different directions in the column nodes, said columns due to their elasticity tending to deform along the vertical axis of the structure framework, in the form of an S.

CONCLUSION

For the above reasons, it is imperative to stop this irregular vertical axial development of additional torques and shearing stresses, originating from the horizontal forces developing on the plates which in most cases are in phase difference between them depending on the floor (height). This irregular development therefore creates additional problems in the column nodes.

The above problems to be resolved, i.e. of the shearing stresses and the torques generated in the nodes due to the horizontal (lateral) acceleration of an earthquake, and of the irregular displacement of the vertical axis of the load-bearing structure, are much accentuated in the nodes of the ground floor columns.

This is because of an additional problem occurring only in the nodes of the base with the columns. These nodes are not at all elastic so as to be able to transfer smoothly the violent shearing forces imposed on them by the base embedded to the ground.

The result is that these first load-transfer nodes developing by the dynamics of an earthquake, additionally bearing increased compressive components, and in combination with the acceleration of the earthquake, are the first to fail in the event of an earthquake. For these reasons, said nodes are placed under seismic insulation by creating a double “one-piece” base, and placing elastic supports in-between.

Another major problem to be solved is the great tendency of the load-bearing structure sides to rise alternately, said tendency originating from the increase in the structure oscillation. This tendency of the load-bearing structure to rise induces additional torque on all the nodes, forcing them to develop the tendency to change their existing, until now, angle in order to receive the additional bending loads of the load-bearing structure.

The proposed solution in order to address the above reported problems induced on the load-bearing structure by the earthquake is summarised in the following three points:

• Create the conditions for controlled axial oscillation of the load-bearing structure.
• Help the columns in transferring the horizontal forces of the earthquake, to the plates, not only from the bottom to the top in different time-spaces (phase difference from plate to plate depending on the height of placement), as occurs in the current conventional structures, but also laterally in relation to the vertical axis to all the plates simultaneously from a pre-stressed rigid structure (e.g. shaft).
• Strengthen the nodes dimensionally along with additional reinforcement (or pre-stressing) in order to resist shearing.