lecture 2 - engineering studies & site investigation

8/6/2019 LECTURE 2 - Engineering Studies & Site Investigation

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CASESThe Centre for Advanced Structural Engineering & Studies

Design of Jetties and Waterfront Structures 25-27 Nov,2010 Presidential Hotel, Port Harcourt, Rivers State

LECTURE 2:

ENGINEERING STUDIES & SITE INVESTIGATION

Engr. Samson Ivovi, B.Eng, MSc, FNIStruct.ETel: +234 803 7262 708. Email : [email protected]

LECTURE 2: ENGINEERING STUDIES & SITE INVESTIGATION

1. Introduction

The design of waterfront structures is a specialized aspect of Civil Engineering. Thesestructures include facilities for shore protection (rock groins and breakwaters), berthingand mooring of watercrafts / ships (docks piers, wharfs and bulkheads) and flood

Design of Jetties and Waterfront StructuresLecture 2: Engineering Studies & Site Investigation 1

The Centre for Advanced Structural Engineering & Studies25-27 November, 2010
mailto:[email protected]:[email protected]


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control (dikes and rock revetments). The design of these structures requires knowledgeof winds, tides, currents and the action of waves.

Shore protection, Erosion and Flood Control structures

BreakwatersA breakwater is a structure that protects the area in its lee from wave attack.Breakwaters can be connected to the shoreline (attached breakwater) or completelyisolated from the shore (detached / offshore breakwater). The basic forms ofconstruction of breakwaters include rubble mound, vertical face gravity, composite, piled,floating and pneumatic, as illustrated in Fig 1(a) (f).

Bulkhead, Seawall, RevetmentThese are structures built to separate the land from the water to prevent erosion andother damage primarily due to wave action.

Bulkheads are typically smaller structures designed to retain shore material under lesssevere wave conditions than seawalls.

Illustration

Revetments are designed to protect shorelines and waterways from erosion by currentsand small waves. They are generally a rubble mound structure built on sloping bank.Sand bags, maccaferi, reno mattresses, etc.

Seawalls are typically large and designed to withstand the full force of storm waves.Tornadoes, typhoons, Tsunamis, etc.

Groin (groyne) shore perpendicular structure, installed singly or as a field of groins,designed to trap sand from the littoral drift system or to hold sand in place. Typically arubble mound structure.

Jetty (USA) a shore perpendicular structure located near an inlet or harbour entranceto reduce in-filling of the inlet or channel, protect the entrance and provide vesselsheltering from waves. (Rubble mound structure).

DockA dock is a general term used to describe a marine structure for the berthing, mooring ortying up of vessels, for loading and unloading cargo, or for embarking and disembarkingpassengers. This includes piers, wharfs and bulkheads or, in European terminology,jetties, quays and quay walls.

Pier / Jetty is a dock, which projects into the water. Also called a mole and incombination with a breakwater, it is termed a breakwater pier. In contrast to a wharfwhich can be used for docking on one side only, a pier may be used on both sides asmay be needed subject to physical conditions of the site. A pier may be more or lessparallel to the shore and connected to it by a mole or trestle, generally at right angles to

the pier. In this case, it is commonly referred to as a T-head pier or L-shaped pier,depending upon whether the approach is at the middle or at the end.




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Wharf or Quay a dock which parallels and is generally, but not necessarily be,contiguous with the shore.

Dolphin a marine structure (usually a cluster of piles) for mooring vessels. Generally

two types: (1) a mooring Dolphin is designed only as a mooring structure and cannotsupport an in impact force, (2) a breasting dolphin is designed to support the impact of aship when berthing and also support the ship against wind that blows the ship againstthe dock.

2. Elements

An element of a section can be eitherInternal orOutstand (Fig 1.). In beams, there is a

further distinction between flange and web elements.

Outstand elements are attached to an adjacent element at one edge only, theother edge being free.

Internal elements are attached to other elements at both longitudinal edges.These include- webs comprising internal elements perpendicular to the axis of bending

- flanges comprising internal elements parallel to the axis of bending

3.0 Local buckling

Local buckling performance of an element depends on its width-to-thickness ratiob/t. Fig.5 in the code shows how b is to be measured for different sections(actually referred to as b or d). For a tapered element, t is taken as the averagethickness.

Other factors which influence local buckling are material strength, geometricimperfection, materials imperfection, the type of stress system to which theelements are subjected, the support conditions provided and whether the section

is produced by hot-rolling or welding. The greater severity of ripples and residualstress in welded plates tend to lower buckling resistance when compared to rolledsections.

4.0 Section Performance

4.1 Beams

BS 5950 recognises four (4) classes of beam section, depending on their localbuckling performance (see cl. 3.5.2).




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y= Class 1: Plastic section. Full plastic moment Mp can be

developed, with enough rotation capacity to allow plastic hinge.Local buckling can be forgotten.

y=

Class 2: Compact Section - Full plastic moment can be reached,but with limited rotation capacity. Plastic design not permitted,unless hinges are restrained.

y=

Class 3: Semi-Compact Section: Member is able to attain My,but not Mp.

y=

y

lecture 2 - engineering studies & site investigation

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