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Manual for Railway Engineering. The Manual consists of more than 5, pages of railway engineering reference material, the recommended practices for the industry. It contains principles, data, specifications, plans and economics pertaining to the engineering, design and construction of the fixed plant of railways except signals and communications , and allied services and facilities. Carousel Next. What is Scribd? Uploaded by Bruno. Did you find this document useful?
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Search inside document. Documents Similar To Manual Arema. Anonymous aZrC1EZ. The earliest designs of bridge piers and abutments included outer walls of masonry, usually limestone or granite, with the inner core filled with old rubble. The design and location of the abutments and piers are dependent on the general design of the structure as a whole.
Local conditions such as the natural features at the point of crossing, the type of traffic train consist to which the structure will be subjected, and legal requirements and property rights will govern the design. The rights of adjacent property owners, the requirements of public travel, water-borne traffic and the jurisdiction of public regulatory bodies must receive due consideration in advance of the completion of the design and certainly before construction begins.
If the bridge crosses a navigable stream within the United States or a wetland is impacted, the U. Army Corps of Engineers, the United States Coast Guard in some cases and numerous state and local regulatory agencies have jurisdiction and the proper permits must be secured. Abutments The three primary types of abutments are the "wing," the "U" and the "T.
All types possess one characteristic feature, the body or face portion, commonly called the breast, which supports the bridge seat. The "wing" abutment is the type most widely used where the embankment is not a high fill. It consists of a simple breast wall, flanked by wings.
The wings may be turned backwards at an angle of approximately 30 degrees or more with the face of the breast, when required by local conditions. The upper surface of the wings is sloped to conform to the natural slope of the surcharge that it is retaining. The counterfort and buttress types of abutments are modifications of the "wing" abutment.
This type is sometimes modified into the so-called "pulpit" abutment, where the wing length is long enough only to keep the bridge seat clean of the surcharge material behind the abutment. The "T" abutment is similar to the breast type with the addition of a stem, which extends backwards from the center of the rear face to the top of the embankment slope, and is used to stabilize the breast and to bridge the slope of the embankment.
The "breast" type of abutment is a modification of the "wing" abutment in which the wings are eliminated and square ends are provided. It is commonly used at locations where the embankment is relatively low and water flow is negligible. The "buried" abutment has an opening through the wall, where the surcharge spills around the ends and through the wall opening. This construction is desirable when the approach fill is very high because the continuous fill through the wall results in a material reduction of pressure behind an otherwise solid wall.
The "arch" abutment may be considered a modification of the "U" abutment, where the parallel sidewalls consist of one or more arches. This type is adapted to locations where embankments are so high that "wing" and "U" abutments would be uneconomical.
The number and size of the arches are dependent upon the height of the bridge and the type of superstructure. The "hollow" or "box" abutment was a type frequently adopted in grade separation work, at points where city streets are carried beneath railway tracks.
Such a unit consists of a concrete box provided with a solid rear wall, floor and top. The front is usually open and is composed of two or more columns, or an arch. This type of abutment bridges the sidewalk and supports the ends of the railway span. Design of Abutments Abutments must be stable against overturning in front of the footing or in the face of the wall, and must be safe against crushing, sliding on the foundation or on any horizontal section through the structure.
Abutments may be of the gravity wall design, where the abutment is so proportioned such that no reinforcement steel other than temperature steel is required; or they may be of the semi-gravity style, where the unit is so proportioned that some steel reinforcement is required along the back and along the lower side of the toe. The resultant force on the base of a wall or abutment should be considered to fall within the middle third of the structure if it is founded on soil and within the middle half of the structure if founded on rock, masonry or piling.
The vertical loads to be carried are the live loads except for impact , dead loads from the weight of the span and weight of the abutment and part of the earth on the footing, depending on the design of the abutment. The lateral forces parallel to the axis of the bridge are the train-produced longitudinal forces and the surcharge pressure from the earth due to both its weight and live load.
Piers Piers constitute the intermediate supports for multiple-span bridges. They should rest on stable, unyielding foundations with their bases well below frost line, and also below the elevation of any possible scouring action.
Most of the older piers are of the mass type, either solid or cellular, and are built of stone masonry, concrete or reinforced concrete. They require for their construction, the use of cofferdams or caissons conforming to the relative size of each pier and, in depth, to the elevation of suitable bearing strata.
Cofferdams generally are rectangular in shape and are built to expose the earth strata below the ground surface or the excavation within the enclosed area. They are watertight to the extent required and need strength to resist pressures from the outside. The cofferdam should be designed such that the combined cost of construction, maintenance and pumping is held to a minimum. Those of relatively small size and depth are sheeted with single or double-row sheeting, while steel sheet piling are commonly used for larger and deeper cofferdams.
Today, use of the mass-type piers in new construction has given way to more suitable and less costly types of pier. As a structural element, it is the portion of the bridge spanning the opening. The superstructure consists of arches, slabs, beams, girders, trusses or troughs, and such floor systems and bracing as may be required. Superstructures may be divided into two general classes: steel spans and concrete spans which include stone masonry.
For short height structures, trestle construction is favored due to the economies of pile bents. Conversely, taller structures over good footing are likely to be viaducts with longer spans supported by towers.
Where there is insufficient clearance over navigable waterways, moveable spans may be necessary. The addition of longer or moveable spans to clear main channels does not significantly affect the design of the balance of the structure. However, as the structure becomes taller, the economies of pile bents are diminished due to the need to strengthen the relatively slender components.
The alternative to conventional trestle construction is trestle on towers, otherwise known as viaducts. Trestle on towers can offer a significant reduction in footprint for only a moderate increase in span requirements.
It is customary for the spans to be of alternating lengths, with the short span over the tower equal to the leg spacing at the top of the tower. This ensures that each span remains a simple span with full bearing at the ends of the span. Of course, trestle construction represents the typical site conditions. More demanding site conditions may require exotic solutions.
For example, very tall, very short length conditions may lend themselves to arch construction, whereas for transit operations, very long main span requirements may lend themselves to suspension type construction and some trestles on towers may be better constructed as a series of arches. In comparison to the rest of the superstructure design, bridge deck decisions are relatively simple.
The choices are open deck and ballast deck. On open deck bridges Figure 8- 5 , the rails are anchored directly to timber bridge ties supported directly on the floor system of the superstructure.
On ballasted bridge Figure Open Deck Structure - Courtesy of Canadian decks, the rails are anchored directly to National timber track ties supported in the ballast section. The ballasted bridge decks require a floor to support the ballast section and such floors are designated by their types, such as timber floors, structural plate floors, buckle plate floors or concrete slab floors, all of which transfer loads directly to the superstructure.
The latter types of structures have many examples still in service today, but are not generally cost-effective for new construction. Some might consider the notion of bridge railings to be an odd bridge design consideration. Railway bridges traditionally have not been designed for the conveyance of anything other than railway traffic, which does not in and of itself, require any sort of railing whatsoever.
Recently, however, a greater focus upon railway worker safety has resulted in railings being widely incorporated. Open Bridge Decks Many different considerations enter into the choice of open or ballast decks, and the selection usually is governed by the requirements of each individual structure. Open decks are less costly and are free draining Figure , but their use over streets and highways requires additional measures such as canopies, plates or wooden flooring to protect highway traffic from falling Figure Open Deck Bridge - Courtesy of Metra objects, water or other materials during the movement of trains.
Open-deck construction establishes a permanent elevation for the rails. Normal surfacing and lining operations, particularly in curves, eventually result in line swings leading into the fixed bridge. The grade frequently is raised to the extent that the bridge eventually becomes low. The bridge dumps are of a different modulus than the rigid deck.
Thus, it becomes difficult to maintain surface off of the bridge as well. This equates to extensive maintenance costs that shortly will surpass the first cost savings gained by installing an open deck bridge over a ballast deck bridge. In welded rail, tight rail conditions can occur at the fixed ends of an open deck bridge, thus requiring an increased level of surveillance in hot weather.
Requirements for Ties For ballast deck structures, bridge ties are no different than those found in traditional track construction. However, in track constructed with concrete ties, the track is often times transitioned to timber ties before crossing the structure.
Individual railway companies have established policies relating to the use of concrete ties on or around bridge structures that should be reviewed prior to design. The tie spacing is typically 4 inches between ties for open deck bridges and the usual track tie spacing for ballast deck bridges. It must be recognized that the tie functions as a beam and it must withstand bending and shear stresses, hold the rail to gage and transfer the rail load to the supporting members of the floor system.
Open deck bridge ties typically utilize a softwood species of timber. Framing the floor system involves significant detailing and fabrication and is not often performed. The other methods are commonly employed. High speeds in all classes of train service greatly intensify the problems connected with superelevation and alignment on curves.
The eccentricity between the curve alignment and that of the bridge structure produces differences in stress in similar members of a floor system, dependent upon their location. Careful analysis must be done to insure that none of these members are overstressed. Bridge Tie Framing Bridge ties sometimes are dapped where they contact the supporting steel as an aid in maintaining good track alignment over the bridge. This necessitates adzing the tie bottom at each flange edge, which may result in undesirable horizontal shear cracks extending inward from the bottom of the dap.
Where dapping is practiced, the depth should be held to the very minimum required and careful check should be made to determine that the remaining depth of the tie is ample to carry the loads. Ballasted Decks A ballasted deck Figure provides a better riding track. The track modulus is consistent on the dumps of the bridge as well as across the bridge. Thus, one is unlikely to have surface runoff problems on the bridge dumps.
Surfacing and lining operations can continue across the bridge unimpeded. However, care must be exercised to maintain a permanent grade line in the vicinity of and over Figure Ballast Decked Bridge. Ballasted decks Figure , irrespective of the type of bridge floor, afford a considerable measure of protection to the steel floor system against damage from derailed car wheels traveling across the bridge.
Over roadways, vehicles and the public are protected from dropping ballast and material off of the cars. Ballast The depth of ballast contributes to the satisfactory functioning of ballasted decks on railway bridges.
It is generally agreed that 6 inches to 12 inches of ballast under the ties is adequate and that more than 12 inches is undesirable because of the potential of overload involved, except when provision is made in the design for a greater load. Many designers calculate the dead load on the basis of 18 inches to 24 inches of ballast to accommodate future raises. The ballast pan must have sufficient capacity to carry the heavy dead load of the floor and the ballast, and also to properly distribute the live and dead loads from various types of bridge floors to the supporting superstructure.
The arrangement of the members in a floor system supporting a bridge floor is different from the arrangement of longitudinal stringers and transverse floorbeams, which make up the floor system of many open- deck spans. A bridge floor for a ballasted deck may conform to one of several types including: a Concrete segmented girder spans incorporating the concrete ballast pan within the segmented unit. The result is a floor sloped for drainage in both directions, and the bases of which are supported by wide flange beam sets or structural plates, which bear on transverse I- beams supported on deck girders.
Trough Floors Figure Ballast Pan on Stringers - Courtesy of Metra The steel-trough bridge floor has been used in the past primarily for ballasted deck structures over city streets, particularly in connection with track elevation work. Longitudinal troughs are used at locations where crossings intersect at approximately right angles and where columns are permitted at the center of the street.
Such troughs are supported on cross girders framed to the columns, while the outside legs of the two outside troughs are extended upward to form the ballast stops. After erection, the down-troughs are filled with concrete, which also covers the entire area to a depth of about 3 inches above the tops of the troughs at the end of the bridge, and about 4 inches above the troughs at the center of the bridge.
Along the sides, the concrete filling is flared up against the ballast stops for varying distances above the top of the rail. The concrete filling is sloped for drainage in such a manner as to permit delivery of the water to drain pipes located below the bridge seat level. Suitable reinforcement should be provided immediately below the top of the concrete filling, particularly in the area above the cross girders; otherwise, deflection under live loads will cause transverse cracks in the concrete.
The use of trough floors at locations, where the intersecting angle with the street is acute, or where roadways of unusual width are required, necessitates placing the troughs transversely to the track and framing them to through girders or to through trusses.
The design details of these floors are essentially the same as for longitudinal troughs, the exception being the necessity for drain holes through the floors to avoid long, flat slopes for drainage, which in turn, requires the installation of a drainage system to dispose of the accumulated water. Drainage The primary requisites for bridge floors are economy, minimum weight and water tightness, together with strength and shallow depth. Comparisons of economy should include cost of materials, fabrication and erection.
Bridge floors not only catch water but also retain it. As the track must be removed prior, replacement and maintenance of the bridge decks can be difficult and expensive. Every precaution should be taken to insure long life, which requires that all bridge floors be protected by waterproofing. Water falling on the track percolates through the ballast to the waterproofing where it remains, unless some suitable means for quick runoff has been provided.
Quick runoff of precipitation is dependent upon clean ballast and a well-designed drainage system delivering water to outlets through the floor or to drain pipes located at the back of the abutments. Open Deck vs. Ballast Deck In addition to the obvious weight and construction costs, each of the span alternatives has their unique safety, environmental and maintenance concerns. In some instances, these intangible factors can carry more weight than the resulting cost implications.
Only the governing railway can provide guidance as to the importance of these and related issues. They are typically precast or prestressed sections placed on the structure after steel erection. This means they cannot be considered part of a composite structure and offer no structural benefit, as would a similar concrete deck in the highway counterpart. There are also operating disadvantages to the use of open deck bridges that may not be readily apparent.
Bridge maintenance must often be performed under contractual agreements by bridge and building department forces. Thus, any operation involving an open bridge deck, e. As the adjacent track is also affected by anything affecting the elevation of the rails running across the bridge deck, track department forces must also be involved. Most railways have severely reduced their bridge gang rosters.
Thus, it becomes a real logistics problem to have both groups present at the same time. On ballast deck structures, the ballasted trackage is considered track department work. Thus, surfacing operations and tie change-out can proceed unhindered. Anchorage of Bridge Ties Bridge ties on open-deck spans are held in position by bolts through the ties in line with the edge of supporting members i.
Usually two hook bolts are used on every third, fourth or fifth tie. The rail may or may not incorporate rail anchors. Anchoring rail on longer open deck structures can create alignment problems resulting from the thermal expansion of the rail.
Most traditional mechanisms for fixing the bridge ties to the bridge cannot effectively transfer longitudinal forces. The servicing railroad guidelines pertaining to the anchorage of rail over both ballast and open deck structures should be consulted for guidance in this area.
Guard Timbers Bridge ties are held to a uniform spacing by longitudinal timbers, called "guard timbers," placed outside of the track rails and fastened to the ties by bolts or lag screws. Inner Guard Rails In addition to the guard timbers, two lines of inner guard rails Figure are often used on each track on open and ballasted-deck bridges of such length as individual railways require.
The two types commonly used are structural angles with a backing timber found often on branch lines and T-rails. On new installations, T-rails are generally used, even to the extent of replacing the angle guards when their renewals are necessary. Each rail is placed on the inside of the running rail, often without the use of tie plates.
Guard rails should be spiked to every tie and spliced at every joint. They should extend beyond the bridge ends in the direction of approaching traffic. The ends should terminate in a frog point or be joined and securely fastened so that a derailed truck will be straightened in direction and guided into the space between the Figure Inside Tee Guard Rails - Courtesy of BNSF running rail and the guard rail, thereby minimizing the damage that otherwise might result.
While the advent of economical steel construction has more or less eliminated timber from new mainline structures of any size, the lower initial cost and ease of construction still makes timber construction attractive for many light density lines. Additionally, because of the relative ease of repair, many significant older timber structures remain in service today. In all of North America, timber trestles are the preponderant type of structure still found on branch lines, short lines and at temporary crossings.
The timber used for timber trestles should be of a firm, close texture, which will afford strong structural members and offer maximum resistance to decay. The timber selected should be sound, free from knots, pitch pockets and other imperfections that might impair its strength or durability.
There is seldom justification for using untreated timber. Terminology The trestle supports are designated as "bents. When the lower ends of the supporting posts are driven into the ground, the structure is known as a "pile trestle.
The outside inclined posts, known as "batter posts," the tops being tilted toward the center of the bent and serving the purpose of giving increased stability, are installed adjacent to the plumb posts. Sway bracing provides additional lateral stability by the use of planks extending diagonally across the bent, through bolted to the ends of the cap and sill and also to the posts or piles. A similar brace, but placed with the opposite direction in slope, is installed on the opposite side of the bent such that the two braces cross in the middle.
See Figure For trestles higher than 30 feet, a second bent is added to the top of the existing bent. Successive stories are added, not exceeding 20 to 30 feet in height, until the required elevation is reached. The bottom panel may be either pile or a frame bent; the upper stories are framed bents, each attached to the top of the lower panel.
Each story has its own sway bracing. Shorter bents may utilize a transverse horizontal brace on each side of the bent in lieu of the diagonal bracing where sufficient height does not exist to install conventional sway bracing.
For high timber trestles, the piles are often cut off at the ground line and the sill of the bottom story is framed on the pile tops. Attachment of the longitudinal girts and other bracing is done by through bolting the members. Caps Caps are typically inches in section width and thickness and extend the width of the bent, commonly feet for single tracks. Bent caps transfer the loads from the stringers to the pile or frame posts.
False caps of varying thickness are used to shim up the height of the deck structure when required. Sills, the bottom transverse frame bent member atop the pile, are caps of the same dimensions, but may be longer in length. Stringers The stringers are structural members extending parallel to the rail and spanning the openings between the bents. See Figure Depending on individual railway standards, they will range in size from 7 to 10 inches wide by 14 to 18 inches deep and one or two spans in length depending on their location.
The maximum span for the Figure Timber Stringers and Cap - Courtesy of Metra timber spans commonly in use today is 13 to 15 feet.
On open deck bridges, the stringers are chorded into a minimum of three and generally four or more beams with each adjacent stringer joint offset by one span length from its adjacent neighbor stringers for three span or longer structures. Each group of stringers is centered under the rail in order that load distribution is symmetrical. On ballast decked bridges, spaced stringers with planking form the pan for a ballast deck. The spacing of stringers facilitates load distribution from the deck and inspection and stringer change-out.
The longitudinal stringers should be spaced not less than 7 to 8 inches apart, as this will permit the insertion of suitable reinforcing timbers, if needed. They consist of metal rings, plates or grids, which when embedded partly in the faces of overlapping members, transmits loads from one structural member to another. Certain types, such as the split ring and the flanged shear plate, fit into precut grooves or daps.
Other types, such as the toothed ring and the spike grid, are embedded in the timbers by means of pressure. The action of the connector in the joint is to increase the shear area, which actually carries the load. In timber joints, it is in the section of the timber nearest the contacting faces that the greatest shear stresses are developed. By embedding the connectors in this highly stressed shear area, the efficiency of the joint is strengthened significantly.
In between, there is every possible combination of span and tower design. However, regardless of the specific span type, most steel structures are designed with simple spans. This facilitates ease of construction and maintenance under traffic. It also allows spans to be cascaded to different locations as needs arise.
Simple spans are easier to analyze and for the most part, use simple, economical details. Girder Spans For short spans, rolled or welded sections are well suited for most applications. Spans up to seventy feet have been constructed using rolled steel beams. However, fifty feet is generally considered a practical maximum for rolled steel sections exclusive of special situations. Such structures are easy to fabricate and readily accept open and ballast decks.
Additionally, they can be made more compact top of rail to lowest member by using multiple beams spaced with diaphragms. For spans over fifty feet, rolled sections generally do not offer sufficient section modulus to control deflection. For these longer spans, a built up section Figure 8- 13 is more desirable as it produces a more efficient use of the material. Such built up sections are either welded or bolted plate girders and can achieve spans of to feet. Deck plate girders Figure are typically the preferred design for locations where vertical clearance under the bridge is not critical, i.
The top flange of the deck plate girder can be utilized to support the deck, thus no flooring system is required. See Figure Figure Deck Plate Girder - Courtesy of Metra The elimination of the floor framing system and the need for girder bracing with knee braces required of through plate girders, makes the deck plate girder the more efficient and cost effective design.
Deck plate girders are well suited for either open or ballast decks. However, the engineer must consider the presence of cover plates on the top flange for long spans and make the appropriate allowances in the deck Figure Schematic of a Deck Plate Girder - Courtesy of Canadian structure.
This may require National specific dapping of the wood ties in open decks or different ballast pans in concrete ballast decks. The governing railway must be consulted for their standard details in this matter. Deck plate girders also require a greater total envelope beneath the track structure, thus limiting clearances below. As indicated above, through plate girders are less efficient than deck plate girders of equal length.
This is because the top cannot be directly supported and there is the added weight of the floor system Figure Knee braces are incorporated at each floor beam to girder connection to provide top of girder support. The stringer and floor beam flooring system Figure drives the need for a deeper girder because of the greater depth required of the stringers to carry the imposed loads on the entire panel between floor beams rather than the distributed load spread out to each close-centered floor beam.
Combined, these two factors make for a heavier span than a deck plate girder span of equal length. However, given the opportunity to decrease the depth of construction from the top of rail to lowest member, through plate girder spans are frequently employed in tight clearance situations such as over roadways.
The engineer must pay particular attention to side clearances since the track is effectively inside the structure. Special precautions must be taken when renewing bridge ties on through plate girder bridges utilizing an open deck in CWR — particularly in hot weather or in curves during cool weather. Often the rail must be cut. In the pony girder, the floor beam connections to the longitudinal girders are made about half way up the girder.
This minimizes the need for the knee brace system to support the girder, but it also reduces the vertical clearance under the structure as well, although not to the extent of the deck plate girder. Truss Spans Steel trusses Figure offer a practical solution for spans over - feet. Trusses are usually of open web design, consisting of top and bottom chord members connected by diagonal and vertical members called hangers.
These members may be either of bolted or riveted construction. A bridge truss has two major structural advantages. Both of these factors lead to economy in material and a reduced dead load.
The increased depth also leads to reduced deflections, i. The advantages are achieved at the expense of increased fabrication, inspection and maintenance costs. A truss is simply a framework for carrying a load. Like the top and bottom flanges of a girder span, the top chord members of a truss are in compression and the bottom chords are in tension. Formerly, trusses were pin connected, which freed the structure of imposed moments.
Today connections are bolted, relieving the associated problem of pin wear at the expense of proportioning members for the Figure Through Riveted Truss - Courtesy of BNSF moments created by a fixed connection. However, there are still significant numbers of pin-connected trusses in service. In this design, the diagonal web members are in compression; the vertical web members are in tension. In the Pratt truss, the vertical web members are in compression, and the diagonal members are in tension.
The panel connections were pinned connected. The Whipple truss in turn modified the Pratt truss. It uses a double system of web members, each diagonal extending over two panels. This permitted longer span lengths than achievable with the Pratt truss.
The Pennsylvania truss was another refinement of the Pratt truss. It uses sub-divided panels and curved top chords for through trusses and curved bottom chords for deck trusses. This type of truss is used for long spans, where simple Pratt or Warren trusses cannot obtain economical construction. The connections at the panel points were made by pins, but today are bolted. In the original Warren truss, all of the web members were inclined, being alternately subject to compression and tension.
This type was rarely used for pin-connected bridges. The loading and unloading of the panel continual reversal of axial force in the web members created pin wear.
However, this truss, modified by the introduction of vertical members for the support of the Figure Truss Schematic - Courtesy of Canadian National panel load and with riveted or bolted connections at the panel points, is now the truss of choice for short spans.
It is also widely used for longer spans by subdividing the panels. In Figure , the dotted lines and in Figure , the light diagonal lines are called counters. With only the dead load of the structure, the adjacent diagonals act only as tension members.
However, when a live load is introduced on the adjacent span, the formerly tensile load becomes compressive and the member may undergo critical buckling. Counters offset the applied reversal in loading. Most through trusses include overhead bracing.
Thus, interior vertical clearances must be considered in addition to side clearances. Similar to plate girders, deck trusses Figure are typically more efficient than through trusses for all the same reasons specified earlier in the discussion regarding deck plate girders versus through plate girders.
They may be composed of bents supported by suitable foundations, e. Viaducts Figure H-pile Bent - Courtesy of Metra A viaduct Figure is any series of spans, whether arches or steel girders, that is supported on high steel towers.
Typically, railway viaducts are of steel construction and are distinguished by unusual height and significant length. The spans are often alternating long and short girders, usually deck plate girders. The short or tower spans are commonly 30 ft to 50 ft in length, while the long, or intermediate spans Figure Railway Viaduct - Courtesy of Canadian Pacific Railway are 40 ft to ft long. Keeping the short span over the tower top ensures that the spans will remain as simple spans.
Sometimes a bent, instead of a tower, is used adjacent to the abutments. This bent supports the adjoining ends of two long spans, the second one terminating on the first tower. The length of the spans is dependent upon the height and length of the structure, as well as on the loads to be carried.
Consideration is given to the proper balance between the costs of the substructure and the superstructure. Generally, the longest spans are in the highest structures. Although many large and costly stone arches are still in service, reinforced concrete is used exclusively for the erection of modern masonry bridges.
Arches Stone masonry arches and boxes came into use early in the life of railways in North America. They were constructed in single and multiple spans, and a large number are still in service on important main lines after more than a century of continuous service.
Structures of this character are built of stone masonry or of concrete. Bridges of this type are built either in single or multiple spans with the bearings for the upright supports either fixed or hinged, although hinged bearings are generally preferred.
The construction material is typically concrete or steel, which may be formed for either curved or a flat soffit. Such structures when built of concrete are slab bridges in which the horizontal member is solid; or ribbed bridges in which the horizontal member consists of ribs or girders supporting a slab floor.
When built of steel, they consist of frames supporting a concrete slab floor. The frames are spaced to facilitate attachment of bracing between them. The outside frames should be encased in concrete integral with the slab floor. Like arches, rigid-frame structures do not tolerate foundation settlement. Rigid-frame structures permit the use of quite long spans with relatively shallow construction depth. For this reason, they were frequently used in connection with grade-separation projects.
They lend themselves very readily to pleasing designs and are sometimes found more economical than simple spans under certain conditions. In some instances where construction depth is limited, the track rails are attached directly to the slabs by suitable bearing plates and fastenings direct fixation. The length of span is limited by the construction depth available and the construction cost as compared to other types of construction.
Slab bridges were very common at one time with a number still remaining in service today. There are much more economical ways of spanning small openings available to the designer today. Slab bridges may be divided into three classes: Reinforced concrete, I-beam encased, and concrete and T-rail structures. The load bearing capacity of the span in reinforced concrete structures is a function of the compressive strength of the concrete and the tensile and shear strength of the steel reinforcement.
Arema manual for railway engineering pdf download
Buy Downloadable PDF. Buy Print or Thumb Drive. Membership in AREMA demonstrates that you are a professional in your field, dedicated to improving your practical knowledge and interested in exchanging information with your peers in order to advance the railroad engineering industry. Documents Similar To Manual Arema. Anonymous aZrC1EZ. Mai Kawayapanik. Francisco Abraham Baeza. Luis Emilio Bosio. Bewok Giay. Angga Dharmawan. Dustin Rodriguez. Cao Duy Bach. Popular in Science.
Summer Roque Huaqui. Alyssa Rose Chua. Sasanka Chamara Gamage. Monica Dona. Avadhoot Rakvi. Inslley Roberth. Sebastian Flores. Wiet Sidharta. Successive stories are added, not exceeding 20 to 30 feet in height, until the required elevation is reached.
The bottom panel may be either pile or a frame bent; the upper stories are framed bents, each attached to the top of the lower panel. Each story has its own sway bracing. Shorter bents may utilize a transverse horizontal brace on each side of the bent in lieu of the diagonal bracing where sufficient height does not exist to install conventional sway bracing.
For high timber trestles, the piles are often cut off at the ground line and the sill of the bottom story is framed on the pile tops. Attachment of the longitudinal girts and other bracing is done by through bolting the members. Caps Caps are typically inches in section width and thickness and extend the width of the bent, commonly feet for single tracks. Bent caps transfer the loads from the stringers to the pile or frame posts. False caps of varying thickness are used to shim up the height of the deck structure when required.
Sills, the bottom transverse frame bent member atop the pile, are caps of the same dimensions, but may be longer in length. Stringers The stringers are structural members extending parallel to the rail and spanning the openings between the bents. See Figure Depending on individual railway standards, they will range in size from 7 to 10 inches wide by 14 to 18 inches deep and one or two spans in length depending on their location.
The maximum span for the Figure Timber Stringers and Cap - Courtesy of Metra timber spans commonly in use today is 13 to 15 feet.
On open deck bridges, the stringers are chorded into a minimum of three and generally four or more beams with each adjacent stringer joint offset by one span length from its adjacent neighbor stringers for three span or longer structures. Each group of stringers is centered under the rail in order that load distribution is symmetrical. On ballast decked bridges, spaced stringers with planking form the pan for a ballast deck.
The spacing of stringers facilitates load distribution from the deck and inspection and stringer change-out. The longitudinal stringers should be spaced not less than 7 to 8 inches apart, as this will permit the insertion of suitable reinforcing timbers, if needed. They consist of metal rings, plates or grids, which when embedded partly in the faces of overlapping members, transmits loads from one structural member to another.
Certain types, such as the split ring and the flanged shear plate, fit into precut grooves or daps. Other types, such as the toothed ring and the spike grid, are embedded in the timbers by means of pressure.
The action of the connector in the joint is to increase the shear area, which actually carries the load. In timber joints, it is in the section of the timber nearest the contacting faces that the greatest shear stresses are developed. By embedding the connectors in this highly stressed shear area, the efficiency of the joint is strengthened significantly.
In between, there is every possible combination of span and tower design. However, regardless of the specific span type, most steel structures are designed with simple spans. This facilitates ease of construction and maintenance under traffic. It also allows spans to be cascaded to different locations as needs arise. Simple spans are easier to analyze and for the most part, use simple, economical details. Girder Spans For short spans, rolled or welded sections are well suited for most applications.
Spans up to seventy feet have been constructed using rolled steel beams. However, fifty feet is generally considered a practical maximum for rolled steel sections exclusive of special situations.
Such structures are easy to fabricate and readily accept open and ballast decks. Additionally, they can be made more compact top of rail to lowest member by using multiple beams spaced with diaphragms.
For spans over fifty feet, rolled sections generally do not offer sufficient section modulus to control deflection. For these longer spans, a built up section Figure 8- 13 is more desirable as it produces a more efficient use of the material.
Such built up sections are either welded or bolted plate girders and can achieve spans of to feet. Deck plate girders Figure are typically the preferred design for locations where vertical clearance under the bridge is not critical, i.
The top flange of the deck plate girder can be utilized to support the deck, thus no flooring system is required. See Figure Figure Deck Plate Girder - Courtesy of Metra The elimination of the floor framing system and the need for girder bracing with knee braces required of through plate girders, makes the deck plate girder the more efficient and cost effective design.
Deck plate girders are well suited for either open or ballast decks. However, the engineer must consider the presence of cover plates on the top flange for long spans and make the appropriate allowances in the deck Figure Schematic of a Deck Plate Girder - Courtesy of Canadian structure. This may require National specific dapping of the wood ties in open decks or different ballast pans in concrete ballast decks. The governing railway must be consulted for their standard details in this matter.
Deck plate girders also require a greater total envelope beneath the track structure, thus limiting clearances below.
As indicated above, through plate girders are less efficient than deck plate girders of equal length. This is because the top cannot be directly supported and there is the added weight of the floor system Figure Knee braces are incorporated at each floor beam to girder connection to provide top of girder support.
The stringer and floor beam flooring system Figure drives the need for a deeper girder because of the greater depth required of the stringers to carry the imposed loads on the entire panel between floor beams rather than the distributed load spread out to each close-centered floor beam. Combined, these two factors make for a heavier span than a deck plate girder span of equal length.
However, given the opportunity to decrease the depth of construction from the top of rail to lowest member, through plate girder spans are frequently employed in tight clearance situations such as over roadways. The engineer must pay particular attention to side clearances since the track is effectively inside the structure. Special precautions must be taken when renewing bridge ties on through plate girder bridges utilizing an open deck in CWR — particularly in hot weather or in curves during cool weather.
Often the rail must be cut. In the pony girder, the floor beam connections to the longitudinal girders are made about half way up the girder. This minimizes the need for the knee brace system to support the girder, but it also reduces the vertical clearance under the structure as well, although not to the extent of the deck plate girder. Truss Spans Steel trusses Figure offer a practical solution for spans over - feet. Trusses are usually of open web design, consisting of top and bottom chord members connected by diagonal and vertical members called hangers.
These members may be either of bolted or riveted construction. A bridge truss has two major structural advantages. Both of these factors lead to economy in material and a reduced dead load. The increased depth also leads to reduced deflections, i. The advantages are achieved at the expense of increased fabrication, inspection and maintenance costs. A truss is simply a framework for carrying a load.
Like the top and bottom flanges of a girder span, the top chord members of a truss are in compression and the bottom chords are in tension. Formerly, trusses were pin connected, which freed the structure of imposed moments.
Today connections are bolted, relieving the associated problem of pin wear at the expense of proportioning members for the Figure Through Riveted Truss - Courtesy of BNSF moments created by a fixed connection. However, there are still significant numbers of pin-connected trusses in service. In this design, the diagonal web members are in compression; the vertical web members are in tension.
In the Pratt truss, the vertical web members are in compression, and the diagonal members are in tension. The panel connections were pinned connected. The Whipple truss in turn modified the Pratt truss. It uses a double system of web members, each diagonal extending over two panels. This permitted longer span lengths than achievable with the Pratt truss.
The Pennsylvania truss was another refinement of the Pratt truss. It uses sub-divided panels and curved top chords for through trusses and curved bottom chords for deck trusses. This type of truss is used for long spans, where simple Pratt or Warren trusses cannot obtain economical construction.
The connections at the panel points were made by pins, but today are bolted. In the original Warren truss, all of the web members were inclined, being alternately subject to compression and tension. This type was rarely used for pin-connected bridges. The loading and unloading of the panel continual reversal of axial force in the web members created pin wear. However, this truss, modified by the introduction of vertical members for the support of the Figure Truss Schematic - Courtesy of Canadian National panel load and with riveted or bolted connections at the panel points, is now the truss of choice for short spans.
It is also widely used for longer spans by subdividing the panels. In Figure , the dotted lines and in Figure , the light diagonal lines are called counters.
With only the dead load of the structure, the adjacent diagonals act only as tension members. However, when a live load is introduced on the adjacent span, the formerly tensile load becomes compressive and the member may undergo critical buckling. Counters offset the applied reversal in loading. Most through trusses include overhead bracing. Thus, interior vertical clearances must be considered in addition to side clearances.
Similar to plate girders, deck trusses Figure are typically more efficient than through trusses for all the same reasons specified earlier in the discussion regarding deck plate girders versus through plate girders.
They may be composed of bents supported by suitable foundations, e. Viaducts Figure H-pile Bent - Courtesy of Metra A viaduct Figure is any series of spans, whether arches or steel girders, that is supported on high steel towers.
Typically, railway viaducts are of steel construction and are distinguished by unusual height and significant length. The spans are often alternating long and short girders, usually deck plate girders. The short or tower spans are commonly 30 ft to 50 ft in length, while the long, or intermediate spans Figure Railway Viaduct - Courtesy of Canadian Pacific Railway are 40 ft to ft long.
Keeping the short span over the tower top ensures that the spans will remain as simple spans. Sometimes a bent, instead of a tower, is used adjacent to the abutments. This bent supports the adjoining ends of two long spans, the second one terminating on the first tower. The length of the spans is dependent upon the height and length of the structure, as well as on the loads to be carried.
Consideration is given to the proper balance between the costs of the substructure and the superstructure. Generally, the longest spans are in the highest structures. Although many large and costly stone arches are still in service, reinforced concrete is used exclusively for the erection of modern masonry bridges. Arches Stone masonry arches and boxes came into use early in the life of railways in North America.
They were constructed in single and multiple spans, and a large number are still in service on important main lines after more than a century of continuous service. Structures of this character are built of stone masonry or of concrete. Bridges of this type are built either in single or multiple spans with the bearings for the upright supports either fixed or hinged, although hinged bearings are generally preferred. The construction material is typically concrete or steel, which may be formed for either curved or a flat soffit.
Such structures when built of concrete are slab bridges in which the horizontal member is solid; or ribbed bridges in which the horizontal member consists of ribs or girders supporting a slab floor. When built of steel, they consist of frames supporting a concrete slab floor.
The frames are spaced to facilitate attachment of bracing between them. The outside frames should be encased in concrete integral with the slab floor.
Like arches, rigid-frame structures do not tolerate foundation settlement. Rigid-frame structures permit the use of quite long spans with relatively shallow construction depth. For this reason, they were frequently used in connection with grade-separation projects. They lend themselves very readily to pleasing designs and are sometimes found more economical than simple spans under certain conditions. In some instances where construction depth is limited, the track rails are attached directly to the slabs by suitable bearing plates and fastenings direct fixation.
The length of span is limited by the construction depth available and the construction cost as compared to other types of construction. Slab bridges were very common at one time with a number still remaining in service today. There are much more economical ways of spanning small openings available to the designer today. Slab bridges may be divided into three classes: Reinforced concrete, I-beam encased, and concrete and T-rail structures.
The load bearing capacity of the span in reinforced concrete structures is a function of the compressive strength of the concrete and the tensile and shear strength of the steel reinforcement. The I-beam encased span and the concrete and T-rail span derive their load carrying capability from the I-beams and the T-rails.
The concrete encasement acts merely as filler and a protective covering. The I-beams used in the construction of slab bridges range in depth from 12 inches to 36 inches, according to the length of the opening with 24 inches being common. The concrete and T-rail slab was used for very short spans only, i. The rails are placed near the bottom of the slab with wire mesh directly below the base of the rails and in the ballast stops.
The concrete used for slab construction should be dense and the upper surface should be crowned or sloped and waterproofed. On long or multiple spans, deck drainage should be provided with adequate outlets for the drains, so that the water will be carried off quickly in order to prevent seepage and consequent deterioration of the slab. Concrete Trestles Trestles of this type usually consist of concrete pile bents spaced from 14 to 20 feet apart. The height should not be greater than the span.
The bents may also consist of narrow concrete piers or concrete columns footed on concrete pedestals. A ballast deck is almost invariably used on a concrete trestle. Concrete trestles are more expensive in first cost than those of timber. The replacement of a timber trestle with one of concrete Figure may be accomplished with minimum delay to railway traffic. The concrete pile bents are driven and caps cast.
After curing, the timber deck is removed and the concrete slab placed between trains. In some cases, precast caps may be utilized over the top of H-pile or even timber pile. Caps are often prestressed units or cast-in-place with a high early strength concrete. The cap or transverse strut at the top of the piles or columns forming the bent must be designed as a reinforced concrete beam to transfer the load from the slab uniformly to the supporting piles or posts.
The floor slab or span may be poured in place after the bents have been constructed, but the use of precast panels with the ballast pan integral is common.
Concrete Girders These are sometimes adopted for the construction of bridges designed to span openings between approximately 25 ft and 60 ft in length. Through, half-through and deck types are used, although the latter is generally preferable. Common beam sections are slabs, tees and voided single and double cell boxes Figure These shapes are well suited for spans up to approximately fifty feet. In most cases, box sections are the preferred section, since they provide a solid deck suitable for ballasted track with no additional construction.
This type construction can provide ballast deck spans up to feet. However, given the time required to form and cure the cast in place concrete, this type of construction is only suited for new railway line, off-line or shoe-fly construction.
Precast, post-tensioned segmental concrete construction has also gained acceptance in new construction.
This type of bridge allows construction of very long spans. However, given the time required to set and anchor each segment, this type of construction is also only suited for new, off-line or shoe fly construction. Given the advances in precast concrete technology and acceptance, cast-in-place, reinforced concrete is seldom used in span construction.
The time required to form and cure cast-in-place concrete renders it inappropriate for construction under traffic. The common forms of moveable spans are Bascule, Lift and Swing. Variations of these structures are also found in shop environments where turntables and transfer tables are use to reposition cars and locomotives between various tracks.
Determination of whether a movable bridge to be utilized is dependent largely on the horizontal and vertical clearance requirements posed. Actual design requires additional considerations, since the structure is a precision machine that must maintain perfect alignment every time it is lowered to maintain track, signal and possibly electrical continuity.
Selecting the type of movable bridge to be used is dependent on the width of the channel and the type of navigation using the channel. Appropriate foundations must be selected. Lastly, the duration and required frequency of bridge openings and closings must be considered. The potential impact to rail and other vehicles must be evaluated.
Bascule Bridges Bascule bridges are single leaf spans of either plate girder or truss construction. They open vertically by pivoting at one end of the span to provide the navigable opening.
In the trunnion bascule bridge Figure 8- 29 , the leaf rotates about a horizontal axis with the trunnion supporting the entire structure when raised. The curved tracks, which are segmental girders with a tread plate, are attached to the tail end of the structure.
Lugs or teeth See Figure are attached to the bottom of the curved track and they engage a matched track plate girder to prevent slippage.
The entire weight of the bridge is supported by the curved track when the structure is opening. At the top pivot end of the structure is a counterweight, which offsets the weight of the span. A powered pinion gear See Figure engages a fixed horizontal rack gear attached to a frame on the adjoining span. As the pinion gear moves forward or backward on the rack, the curved track enables the horizontal motion of the rack to translate into vertical motion of the structure.
Obviously, the opening angle secured is a function of the horizontal roll distance available for the curved track to move. The bascule span rotates about the main trunnion.
The counterweight is attached to a rotating framework. The operating strut is composed of a rack gear. The outer end of the operating strut is pinned to the top chord of the bascule truss and the counterweight link. The opposite end of the counterweight link is also pinned.
A fixed pinion gear moves the operating strut towards the pivoting end of the bridge. Because of the pinned connections, the counterweight frame rotates downward, thus raising the bascule span. The counterweight offsets the weight of the bascule span. Typically, these spans are truss constructed to accommodate negative bending over the center pier while in the open position. This type of structure is suitable for short to medium span lengths on each side of the pivot pier, with the spans usually symmetric in length.
There are two types of swing span structures in common use. The center bearing swing span supports the weight of the structure by a center thrust bearing Figure The center of gravity of the structure is immediately over the bearing to ensure that the bridge is balanced when in the open position. Balance wheels stabilize the structure as it opens and closes.
The span rides on tapered rollers, which carry the weight while opening and closing as well as providing stability during movement.
Cables raise vertical lift spans vertically. The span remains in a horizontal position when raised or lowered. Unlike the previous examples, the navigable opening provided by the vertical lift span remains limited by the height of the lift towers.
These spans may be a rolled beam, plate girder or of truss construction. The weight of the span is offset by two counterweights located at the top of each tower. The lift machinery is mounted above the deck. The towers can be of either braced or unbraced construction. Access to the tower is required to grease sheaves and service lifting machinery.
A system of span guides and bridge locks ensures that the bridge is properly aligned when the span is lowered to operate trains. Any misalignment will not permit the bridge locks to engage and a proceed signal will not be displayed. Vertical lift bridges are suitable for medium to long spans where height clearance is required.
Vertical lift bridges are categorized by the location of the drive machinery. Counterweight ropes attach to the span and to the counterweight. The machinery turns the sheave, thus raising the span and lowering the counterweight. Again, the counterweight ropes attach to the span and to the counterweight, but the lifting force is provided by operating ropes cables and drums, one at each corner. A drive shaft from the motor, located in the control house extends out to the drum located at Figure Span Driven Vertical Lift - Courtesy of each end of the span.
Christian Brown, HNTB Although the weight of the span lifted is massive, the load imposed on the operating cables is relatively small, due to the offsetting weight of the counterweight. In each case, a movable bridge requires balancing the structure. Although gravity plays only a small part in opening and closing bascule and vertical lift bridges, it plays no part at all in swing bridges.
The critical balancing component is the counterweight. Typically, the counterweights are of concrete or steel-encased concrete construction. Balance pockets are provided for not less than 3. The configuration of the counterweight is important too, especially for bascule bridges.
The lowered counterweight must maintain clearance between other structural members of the bridge. These spans are usually supported on a center pivot pier as well as a circular track at the end of the span. Conversely, a transfer table carries locomotives or cars in a lateral direction. These spans are usually supported on a track at each end of the span.
However, they tend to be significantly sturdier due to the higher live loads, which must be supported. Each railroad has different preferences relating to the types of materials installed. Many prefer metal pipes to concrete, as they tend to be less susceptible to failure due to settlement.
Newer materials such as plastic have not generally gained wide acceptance for use under track. Box culverts Figure are almost exclusively concrete.
The preference of cast- in-place versus pre-cast differs between railways. Box culverts may be one cell, two cell or three cell, depending on the size of drainage stream. French drains are constructed adjacent to and parallel to foundation structures to drain away ground water. They are typically corrugated metal pipe with perforations along the bottom invert to allow drainage of the surrounding soil. This material may be an embankment for supporting track loads or natural earth along the edge of a cut and separated from the wall by a wedge of filled-in material.
Normally, retaining walls usually do not carry vertical loads. However, bridge abutment walls are types of retaining walls that are required to carry bridge superstructure vertical loads in addition to large net overturning moments.
Ordinarily, gravity retaining walls are built of reinforced concrete, mass concrete and formerly of stone masonry. Overturning forces are resisted by the "gravity" weight alone of the masonry or concrete. Failure of a retaining wall can occur by sliding along a horizontal plane, by overturning or rotating and by crushing of the masonry.
The design of the wall, and especially the footing, should include such special features as indicated by the character of the supporting earth at each location. Crib Walls Crib walls, also known as bin walls Figure , are composed of interlocking prefabricated members arranged to form a series of cells or "bins," that are then filled with compacted backfill.
Crib walls are frequently used as an alternative to stone or concrete retaining walls. Note: Although a carefully constructed foundation forms the base of a solid retaining wall, crib walls are ordinarily supported directly on the particular material encountered at each location.
Consequently, the use of crib walls should be confined to locations where the supporting material is reasonably firm and stable and is free of impounded water. Tensile forces within each cell resist overturning forces. The cells are anchored by "deadmen" in the back of the fill. Many old railway crib walls were often constructed using old railroad ties. Since the width of a crib wall increases as the height of the wall increases, space limitations may impose restrictions upon crib wall use.
Three different types of ready-made cribbing are available: Creosoted timber, steel and reinforced concrete. Creosoted timber cribbing is made up of two different types of units: a header, which is placed at right angles to the face of the wall, extending into the embankment and interlocking with the second or stretcher unit, which is laid parallel to the face of the wall. Each header and stretcher is dapped and bored prior to treatment. Drift bolts are driven during erection to give additional stability to the interlocking timbers.
Metal cribbing consists of box-like headers and stretchers. Each stretcher usually has lugs at both ends, which fit into corresponding slots in the header units. Every header is locked at opposite ends to the stretchers directly underneath by bolts. The stretchers usually are of a plain square section while the headers are of rectangular section with T-shaped heads for tying the stretchers together.
As excavation proceeds on one side of the wall, horizontal sections known as walers are welded or fixed to the piling to provide additional support. Sheet pile walls are fairly expensive and require extensive information on buried utilities prior to driving. Wooden sheet piling includes a variety of proprietary designs intended to provide a tongue-and-groove effect at the mating surfaces.
A variety known as Wakefield is formed of three planks fastened together to create a tongue and groove. Steel sheet pile retaining walls consist of individual sheet piles driven into the ground that are interlocked to each other to form a vertical steel wall. Submerged timber piling has long life at points where it is left as a part of the permanent construction and may sometimes be salvaged, if desired.
However, the relatively thin planks are readily split or broomed by contact with stones or other hard materials encountered in passage through the soil. Metallic piles have great penetrating power under the impact of the hammer and are less susceptible to damage in driving than timber piles.
These piles may be left as a permanent part of the under water construction, or they can be withdrawn and re-used. Concrete sheet piling, when properly and thoroughly cured before use, and under normal conditions, is permanent in water and air, and is particularly applicable where the sheet piling is to remain as a part of the permanent structure. Due to the relatively brittle nature of the material, the salvaging of such piling is difficult.
For temporary use, timber or metallic sheet piling is preferable. Sheet piling may be driven to form either single or double partitions. Steel sheet piling is frequently left in place as a part of the completed structure. Soldier pile and lagging retaining walls are cheaper than sheet pile walls and are more appropriate in areas where buried utilities are expected.
The soldier piles are usually steel rolled sections driven vertically into the ground at 5-foot to foot center-to- center distances. As excavation proceeds, concrete or timber lagging is placed horizontally between the soldier piles. Horizontal steel walers are added as bracing is needed.
MSE retaining walls represent a relatively new method of resolving earth retainage problems. Instead of regarding soil as a mass to be contained by force, the earth itself is reinforced to become an integral part of the structure. MSE Figure MSE Wall - Courtesy of Sam Dragonetti, UMA walls rely on increasing the strength and stability of earth embankments by placing corrosion resistant reinforcing straps, welded wire mesh, or geotechnical fabric within the earth embankment as it is constructed.
The walls then behave as gravity structures in an integral unit and provide structural flexibility. Native soils at the site or from excavation are usually acceptable for backfill. The resulting structure is strong, yet resilient. MSE walls generally include a fascia panel typically precast concrete, but can also be welded wire mesh, cast-in-place concrete, or other materials.
Precast panels or cast-in-place fascia allow for a wide variety of architectural treatments and finishes. An MSE constructed with a face of welded wire Figure can be covered with air- blown mortar, seeded with grass or plants, or filled with rock. MSE walls perform extremely well in a multitude of conditions.
It performs particularly well in seismic zones, due to the built-in flexibility of the system, which allows for some Figure MSE Green Wall - Courtesy of Charley Chambers movement without distressing the structure or causing cracks. It can also tolerate a certain amount of settlement, making it a desirable solution even in relatively poor subsoil conditions.
The primary reason for the use of MSE walls is its inherent low cost. Installation is fast and efficient, using a simple, repetitive construction procedure. After placing the initial course of panels, the first lift of backfill is spread and compacted. The reinforcement steel straps, welded wire or geotechnical fabric is laid on the compacted lift and connected to the panels if used.
Next, a lift of backfill is spread and compacted over the reinforcing material.
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