## Why do vessel operators choose to contact the fender system at its bow instead of mid-ship location during berthing operation?

When calculating berthing energy of vessels, there is a factor called “eccentricity factor” which accounts for different berthing energy when the vessel contact the fender system at different locations of the vessel.

For instance, for mid-point berthing the eccentricity factor is unity which means there is no loss of berthing energy. For third-point berthing and quarter-point berthing, the eccentricity factor is 0.7 and 0.5 respectively. In fact, engineers always attempt to reduce the amount of berthing energy to be absorbed by fender system and pier structures. As such, it is recommended for vessels to contact fender system at its bow or stern because the reaction force would produce a rotational moment to the vessel which dissipates part of vessel’s energy.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

Filed under Marine Works | 0 Comments

## In fender design, when calculating the berthing energy absorbed by fenders, should engineers take into account energy absorbed by piers?

The design of a fender system is based on the principle of conservation of energy. The amount of energy brought about by berthing vessels into the system must be determined, and then the fender system is devised to absorb the energy within the force and stress limitations of the ship’s hull, the fender, and the pier.

Firstly, the energy released by the largest/heaviest vessel allowed to use on the pier is determined to be delivered to the pier by first impact. Then, the energy that can be absorbed by the pier would be calculated. For pier structures that are linearly elastic, the energy is one-half the maximum static load times the amount of deflection. However, in case the structure is extremely rigid, it can be assumed to absorb no energy.

The energy to be absorbed by fender system should be the total energy of berthing vessels deducting the energy absorption by pier structures. Finally, a fender system capable of absorbing the amount of energy without exceeding the maximum allowable force in the pier should be chosen from fender product catalogue.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

Filed under Marine Works | 0 Comments

## For underwater concreting, tremie pipes are normally used with the aid of hoppers. Sometimes tubes are inserted inside the hoppers. Why?

In placing concrete by tremie pipes, hoppers are connected to their top for receiving freshly placed concrete. However, air may be trapped inside the tremie pipes if there is rapid feeding of fresh concrete. To release the trapped air inside the tremie pipes, hoses (called ventilation tubes) are inserted and lowered down through the hoppers. Reference is made to Carl A. Thoresen (1988).

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

Filed under Marine Works | 0 Comments

## For typical pile bents in marine piers, how is vertical loads related to horizontal capacity of the pile bents?

Let’s consider a pile bent with a top slab supported by two ranking piles, each inclining at an equal angle to the pier slab. In designing such a system, truss action is normally adopted to analyze the pile bent. When the reaction forces of these piles, horizontal forces (e.g. due to berthing and deberthing of vessels) and vertical forces (e.g. superimposed deck loads) are analyzed by drawing a force polygon, it is noted that lateral resistance of the pile bent is dependent on the vertical load, i.e. lateral resistance is small when vertical loads are high.

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

Filed under Marine Works | 0 Comments

## Why “inadequate pile founding level” commonly occurs in piles of piers?

This question is taken from book named – A Self Learning Manual – Mastering Different Fields of Civil Engineering Works (VC-Q-A-Method) by Vincent T. H. CHU.

Filed under Marine Works | 0 Comments
Page 3 of 1312345...10...Last »

## Author

• The Best Creator Next To God Is A Civil Engineer.

## Yahoo Group - Civil Engineering Portal

Subscribe to EngineeringCivil.com