Bridge Substructure | Bridge Management Systems

Question 1

Commonly used criteria in selecting superstructure type:

Answer 1

1. Bridge span

Question 2

Which superstructure is perfered?

Answer 2

Flange

Question 3

Prestressed Concrete Girder:

Question 4

Timber Superstructures

Answer 4

Is less used than steel and concrete but they still maintain a niche in the highway bridge arena.

Question 5

Disadvantages of Timber Superstructures

Answer 5

Exceedingly prone to deterioration.

Question 6

Advantages of Timber Superstructures

Answer 6

*A high strength-to-weight ratio
+A replenishable material source

Question 7

Secondary members attached between girders?

Answer 7

In the vertical plane that acts to stiffen the primary member and help distribute vertical loads.

Question 8

Wearing Surface

Answer 8

Another work is wearing course or deck overlay.
Designed to resist traffic wear and, with periodic maintenance to provide smooth riding surface.

Question 9

Function of wearing surface?

Answer 9

Protects the deck proper from traffic and the superstructure and substructure elements from associated deterioration.

Question 10

Internal Forces

Answer 10

When a bridge is subject to loads, its constituent elements develop internal forces that resist those loads.

Question 11

Form of Internal Forces

Answer 11

The resisting forces take the form of:
+Bending moment
*Shear Force
*Torsional moment
*Axial force

Question 12

Abutments

Answer 12

Structures located at the ends of a bridge that provide the basic functions.

Question 13

Basic Functions of Abutments

Answer 13

1. Supporting the end of the first or last span.
2. Retaining earth underneath and adjacent to the approach roadway.
3. Supporting part of the approach roadway or approach slab, if necessary.

Question 14

Types of Abutments

Answer 14

*Mechanically Stabilized Earth (MSE) Wall Abutment
*Gravity Abutments
*Cantilever Abutment
*Full-Height Abutment
*Stub Abutment
*Semistub Abutment
*U Abutment
*Counterfort Abutment
*Spill-Through Abutment
*Pile Bent Abutment

Question 15

What is MSE

Answer 15

Utilizes modular facing units, generally made of unreinforced concrete, with metal or polymeric reinforcement (in the form of either strips or mesh) attached to the back.

Question 16

Facing Units of MSE

Answer 16

Are cast in the form of a geometric shape that lends itself to being assembled into a uniform wall

Question 17

Reinforcement Strips or Mesh for MSE

Question 18

Gravity Abutment

Question 19

Cantilever Abutment

Answer 19

Virtually identical to a cantilever retaining wall except that a cantilever abutment is designed to accommodate large vertical loads and is equipped with a bridge seat.

Question 20

Piers

Answer 20

A pier is a substructure that provides the basic function of supporting span at intermediate points between end supports (abutments)

Question 21

What are piers constructed of?

Answer 21

Constructed using concrete, although steel and, to a lesser degree, timber are also used.

Question 22

Basic Functions of Piers

Answer 22

*Carrying its own weight
*Sustaining superstructure dead loads, live loads, and lateral loads
*Transmitting all loads to the foundation.

Question 23

Hammerhead Piers

Answer 23

*Utilizes one or more columns with a pier cap in the shape of a hammer.
*Is constructed of conventionally reinforced concrete.
*The supporting columns can be either rectangular (or other polygonal shape) or circular and extend down to a supporting foundation.
*Occupy a minimum space and attractive => found in urban settings predominantly.

Question 24

Column Bent

Answer 24

*Consist of a cap beam and supporting columns in a frame-type structure.
*Represents one of the most forms of pier in a use in highway bridges: this popularity is an outgrowth of the extensive use of columns bent piers during the development of the U.S. Interstate system.
*Supported on either spread footing or deep foundation and is made of conventionally reinforced concrete.
*For moderate clearance structures with plenty of room for underpass traffic, provides a very attractive solution.

Question 25

Port Bearing

Answer 25

Consists of a shallow steel cylinder, or pot, on a vertical axis with a neoprene disk that is slightly thinner than the cylinder and fitted tightly inside.

Question 26

Port Bearing Components:

Question 27

Forces Acting on a Bearing

Answer 27

1. Reactions
2. Longitudinal forces for fixed bearings)
3. Transverse forces (for fixed or guided bearings)
4. Uplift forces (for some span arrangement)

Question 28

Movement of Bearings

Answer 28

1.Fixed bearings allow for rotation only.
2.Guided expansion bearings allow for rotation and longitudinal translation only.
3. Multidirectional expansion bearings allow for rotation and translation in any direction

Question 29

Sliding Plate Bearing

Answer 29

*Utilizes one plate sliding against another to accommodate translational movement.
*Cannot accommodate large rotation so the application is typically limited to bridges with span length less than 50ft.
*Fabricated out of PTFE or Teflon and stainless steel or bronze.

Question 30

Disk Bearing

Answer 30

*Offers lower profiles than pot bearings due to the use of hard plastic (Teflon) disc to accommodate rotation instead of using a confined elastomer, a pot, and a piston.
*Due to its simplicity, durability, and minimum number of parts, requires less maintenance than other types, and is the preferred choice for new bridges where elastomeric bearings do not have sufficient capacities to resist the design loads
*Expansion disc bearings feature slide interfaces of PTFE and polished stainless steel that offer a low coefficient of friction and the ease of movement for the structure.

Question 31

Bridge Mangement Systems (BMS)

Answer 31

*Bridge management systems assist bridge owners in selecting and performing work that is right activity, to the right bridge, at the right time, at the right cost.
*The highway bridge is one component in an expansive transportation network.
*The task of dealing with thousands of highway bridges at once is one that, over the past two decades, has gained increased prominence and importance.
*In the present environment, a BMS is a computerized management system used to tract the condition of a group of bridges in a high way network and assist in the determination of remedial measures to be taken.

Question 32

What is the difference between project level analysis and network level analysis?

Answer 32

Project level analysis: Concerns itself with individual structures and the remedial measures that are to be taken to correct any deficiencies.
Network level analysis: concerns itself with all bridges in the network and makes its decisions based on not only the needs of an individual bridge, but also those of the network as a whole.

Question 33

Predicting the Future Conditions BMS

Answer 33

Determining the type and scope of repair a bridge should receive. Possible scenarios:
1. No work is performed
2. Partial, interim measures are taken.
3. Full repair to correct all deficiencies is made.

Question 34

Deterioration Model

Answer 34

*A basic tool in making predictions
*Takes the present condition of an element and extrapolates its condition based on certain remedial measures.

Question 35

Deterioration Model

Answer 35

*A stronger wealth of knowledge available +> more accurate results
*Historical data must be taken into account
*Variations in geography, climate, and structure type will obviously have a great impact on the answers generated by deterioration model.

Question 36

Level of Service

Answer 36

Results from the deterioration modeling + Variety of decision - assisting criteria used to arrive at a general recommendation for work to be done.

Question 37

Criterion of Level of Service

Answer 37

Uses lifecycle cost methods to select the most economical preservation, maintenance, rehabilitation, and replacement alternatives for each bridge element at various condition stages.

Question 38

What algorithm does level of service use?

Answer 38

It uses liner programming algorithm to optimize the selection of levels of services of various elements, considering the repair costs, replacement costs, user costs, the element deterioration rates.