March 9, 2017

REHABILITATION OF COASTAL STRUCTURES

Jose O. Guevara, Ph.D., P.E.

Civil Engineering Department

UPR MayaguezMarch 9, 2017

VULNERABILITY

• Coastal areas are vulnerable to

damage due to

•Marine environment

VULNERABILITY

• Episodic events: Sea level changes due to seasonal peaks, hurricanes, storms and tsunamis

www/rg4rb.org

VULNERABILITY

• Chronic Conditions:

– Sea level rise due to Climate warming, land ice melting, ice sheet displacement to the sea

REHABILITATION OF STRUCTURES AFFECTED BY MARINE ENVIRONMENT

• PILE ENCAPSULATION, CONCRETE OR STEEL STRENGHTENING, ELEMENT REPLACEMENT

ESTIMATE OF THE REMAINING CAPACITY OF STRUCTURAL ELEMENTS AFFECTED BY MARINE CONDITIONS

3/9/2017 6

CONSTRUCTION LEVEL OF DAMAGE

A B C D

NEW 0.95 0.75 0.55 0.35

OLD 0.85 0.65 0.40 0.20

LEVEL OF DAMAGE

• LEVEL A: 1% of loss of rebar section, longitudinal cracks

• LEVEL B: 5% of loss of rebar section with spalling of concrete , exposed reinforcement and loss of bonding.

• LEVEL C: 25% of loss or rebar section, loss of confinement and bond

• LEVEL D: Break of stirrups, buckling of longitudinal reinforcement

3/9/2017 7

IF ONLY REPAIR IS REQUIRED

3/9/2017 8

STRESS GENERATED

3/9/2017 9

Columns

3/9/2017 10

Challenges in the repair of columns

• After surface deterioration, compressive loads within the column are redistributed around the affected area, increasing the stress level in the remaining section

• A surface repair will not carry its share of stress unless the compressive loads are removed during the repair.

• Another factor is drying shrinkage

3/9/2017 11

Column repair

3/9/2017 12

Repair strategies

3/9/2017 13

REHABILITATION OF STRUCTURES AFFECTED BY SEA LEVEL CHANGES

GLOBAL WARMING

MAY REQUIRE MAJOR IMPROVEMENTS

RETREAT

• Will require move the structure

11

ADAPT• It will require jacketing

PROTECT

• USE OF

-BREAKWATERS-SHEET PILES-GROINS-SAND AND WATER SLURRY

3/9/2017 18

3/9/2017 19

3/9/2017 20

3/09/2017 13

TSUNAMIS

• FEMA CCM CONCLUSIONS :

-Tsunami loads are too great and not feasible or practical to design normal structures to withstand these loads. - The USA building codes do not adequately address the flow velocity and subsequent structural loading during a tsunami.

BUILDING EVALUATION

3/9/2017 22

3/9/2017

• Studies– Tsunami forces often exceed the design

forces based on wind and seismic conditions

– However, a review of typical prototype moment resistant frames indicated that the capacity of individual members is often adequate for the tsunami loads

– Shear wall structures are good for earthquakes but are severely affected by tsunamis

Design Considerations

• Hydraulic Lateral Forces

-full structure

-individual elements

• Impact Force

- floating debris

• Buoyancy Force

• Scour

3/9/2017 24

Design Considerations

• Hydraulic Lateral Forces

-full structure

-individual elements

• Impact Force

- floating debris

• Buoyancy Force

• Scour

3/9/2017 25

(Cont)

• Hydraulic Lateral Forces

- Hydrostatic

- Surge Force

- Breaking Wave Force

- Hydrodynamic

• Impact Force

3/9/2017 26

Loading Combinations

• If walls not designed to break away:1. Hydrostatic force on building elevations + hydrodynamic force on

sides of structure + impact force.

2. Breaking wave force on building elevation + hydrodynamic force on sides of structure + impact force.

3. Surge force on building elevation + hydrodynamic force on sides of structure + impact force.

• Codes call for break-away walls:Infill wall capacity: min. 10 psf and max. 20psf

3/9/2017 27

BRIDGES AND PIERS

• AREAS OF CONCERN

They are supported by neoprene pads and restrainers are used to control lateral displacement only in Earthquakes, but restrainers may not be enough for tsunamis

3/9/2017 28

• BRIDGE AND PIERS

Walways and roadways are more vulnerable

Dolphins and platforms are very strong

3/9/2017 29

Bridge and piers• The initial stage of tsunami loading leads to a

combination of horizontal and uplift forces. These forces gradually increase as the tsunami free-surface elevation rises.

• The maximum uplift force during the initial impact time period is found to occur when the tsunami free-surface elevation reaches the top of the bridge or pier barrier before overtopping. After this, the uplift acting on a partially inundated pier or bridge is counterbalanced by the weight of water ponding on the deck and slamming force caused by tsunami hitting the upper surface of the deck.

3/9/2017 30

PIERS IMPROVEMENTS

• INSTALLATION OF MONOPILES WITH FENDERS PREVENT COLLISION FORCES DUE TO DRIFTING VESSELS

• USE OF CATHODIC PROTECTION ON MONOPILES AND SUPERSTRUCTURE

• BREAKWATERS CAN REDUCE UP TO 60% THE TSUNAMI HEIGHT

3/9/2017 31

TANKS• FUNDATIONS

Some tank foundation rest on compacted soil, other foundations include ring foundations or mat foundations

They may or may not include anchor bolts for inundations to avoid lifting or due to earthquake loads

Vertical tsunami forces are estimated in cases where the tsunami water entered through a gap between the tank bottom plate and foundation

3/9/2017 32

• AREAS OF CONCERN

• It will be necessary to verify the shell and foundation capacity

3/9/2017 33

TSUNAMI LOADS

3/9/2017 34

Stress on tanks

3/9/2017 35

TANKS

• Water tanks and other types of tanks usually have anchor bolts

• Oil storage tanks without bolts or weak anchors are easily damaged due to horizontal and vertical movement

• If a tsunami flows over the dike and reaches the tank, the buckling of the outer steel wall by tsunami force could occur before other damages

3/9/2017 36