UCSD Structural Engineers have kept busy this summer conducting five experiments at the floating modular hybrid on the US Naval Base-San Diego. See the previous news brief for a description of the structure, test program and the first experiment. Structural testing of the deck capacity, the bollard capacity, and the fendering system (using hydraulic actuators) was recently completed. Descriptions of each test are below. The last experiment being a long term test of the retrofitted fendering system was recently completed after running for four weeks: 24 hours a day/ 7 days a week. This project was completed on schedule and under budget thanks to the hard work and detailed planning of everyone involved.
Long Term Fender Test (old news article)
Short Term Fender Test
Other MHP Photos
Combatant vessels are berthed at a pier with mooring lines that are wrapped around a steel fabricated bollard which is fixed to the pier deck. Numerous designs for bollards and for the connection to the pier are used. However there is no standard method by which the structural capacity can be tested. This test aims to set a standard for future bollard tests and aims to examine the effectiveness of the bollard used on the floating pier. The floating pier has a bollard design consisting of a 16 inch diameter concrete filled steel pipe that is welded to a base plate. The base plate is secured to the deck with six 2.5 inch diameter bolts that are fastened to a steel reaction plate underneath the deck. Mooring lines are kept on the bollard by two horns (horizontal steel pipes) as shown in the photos below.
The test setup used two 300 kip capacity jacks to apply load to a reaction beam and a wire rope assembly which pulled the bollard. The wire rope passed around the bollard to apply loading similar to a ships mooring line. The applied load was reacted by a frame with a beam along the external wall to provide a reaction into the heavily reinforced concrete deck.
Photos from the testing conducted on 9/06/07 are shown below.
Bollard Test Setup.
Top View of Bollard Test Setup showing the wire rope wrapped around the bollard and underneath the horns – to simulate the applied load from a mooring line.
Instrumentation underway with Deck Test Setup to right.
Ph.D. Candidate Hussein Okail, Prof Shing and Prof Uang examine the bollard test reaction frame.
The Operations Deck (upper deck) of the floating pier is composed of prestressed concrete beams with an overlying reinforced concrete deck containing bi-directional post tensioned strands. This heavily reinforced deck is designed to support equipment including trucks and cranes servicing berthed combatant vessels. This equipment can result in highly concentrated loading areas on the deck, of particular concern is the loading from a crane outrigger.
The objective of this test is to verify that the Operations Deck can carry an outrigger crane loading of 400 kips at a critical location without damage. Load was applied to a perceived critical location being adjacent to the external wall with a large utility (window) opening. Two 300 kip capacity hydraulic jacks were used to apply quasi-static loading to a high strength bar which passed through the deck and was fastened to a reaction beam and wall reaction fixtures in the lower level. The deck responded within the elastic range with only minor cracking in the utility window opening.
Photos from the testing conducted on 8/14/07 are shown below.
Hydraulic cylinders and the high strength load application bar (passes through the deck).
Applying instrumentation to the exterior.
Instrumentation within the lower level of the floating pier.
Test reaction within the lower level of the floating pier.
Group Photo for the Deck Test.
Navy engineers onsite for the Deck Test.
Lunch break during testing.
Short Term Fender Test
When a combatant vessel is berthed at the floating pier the forces from any impact are transferred from the pier into the rubber fendering system and main pile shaft. The rubber fenders will compress and buckle to absorb the impact and can compress up to one half of its length. Depending on the amount of compression and buckling, the fender will return to its original shape with no degradation of its stiffness. The fendering system will also compress and buckle during a seismic event therefore resulting in no seismic forces transferred into the floating pier.
The focus of this test is the pre- and post-buckling behavior of the fenders under a short term loading. Axial and bi-axial tests of the fenders were conducted using two 220 kip capacity hydraulic actuators. The actuators were connected to the pier deck and bolted to a reaction frame attached to the main pile shaft during a low tide. Due to the tidal variation of 8 ft at the pier this test had to be carefully choreographed with the lab staff, graduate students and the contractors crew so that the actuators would be connected to the shaft for less than 3 hours. In these tests data was collected from over 80 instruments which included displacement transducers, strain gages, thermocouples, inclinometers, and GPS.
Photos from the testing conducted on 9/11/07 and 9/12/07 are shown below.
Bi-axial testing underway.
Hooking up the actuators as the tide drops.
Hooking up an actuator.
Actuator connected to the reaction frame and main pile shaft. The round object at the corner of the pile shaft is a GPS antennae.
The fender system with retrofit plates and chains in place. Note this was installed after the first long term test caused an early failure.
Biaxial testing of the fendering system with retrofit plates and chains in place.
The MHP at a tilt of 1 degree during testing.
View of the setup.
Other MHP Photos
A lobster on the main pile shaft.
Mission Control. Inside the Test Control Office Trailer.
GPS Receivers and PC inside the Test Control Office Trailer.
Data Cabinets inside the Test Control Office Trailer.
Graduate Student Researcher Jerry Lee with the moonpool instrumentation.
Building some camera mounts.
Bollard test instrumentation underway with a tug boat visitor.
Research sponsors having lunch with Dr Latham (blue hat).
UCSD's Base of Operations on the Floating Pier.
Marathon Construction’s floating crane used to place test reaction fixtures.
Bringing the mini-crane into the Service Deck (lower level) of the MHP.