Standard Specifications for Road, Bridge, and Municipal Construction 2020 (M 41-10)

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Concrete Structures

6-02.3(17)B

Allowable Design Stresses and Deflections

The maximum allowable stresses listed in this section are based on the use of identifiable,
undamaged, high-quality materials. Stresses shall be appropriately reduced if lesser quality
materials are to be used.

These maximum allowable stresses include all adjustment factors, such as the short-term
load duration factor. The maximum allowable stresses and deflections used in the design
of the falsework and formwork shall be as follows:

6-02.3(17)B1 Deflection

Deflection resulting from dead load and concrete pressure for exposed visible surfaces
shall not exceed

1/360 of the span.

Deflection resulting from dead load and concrete pressure for unexposed non-visible
surfaces, including the bottom of the deck slab between girders shall not exceed

1/270

the span.

In the foregoing, the span length shall be the center line to center line distance between
supports for simple and continuous spans, and from the center line of support to the
end of the member for cantilever spans. For plywood supported on members wider than
1½ inches, the span length shall be taken as the clear span plus 1½ inches. Also, dead load
shall include the weight of all successive placements of concrete, reinforcing steel, forms
and falsework self weight. Only the self weight of falsework girders may be excluded from
the calculation of the above deflections provided that the falsework girder deflection is
compensated for by the installation of camber strips.

Where successive placements of concrete are to act compositely in the completed
Structure, deflection control becomes extremely critical. Maximum deflection of
supporting members shall not exceed

1/500 of the span for members constructed in

several successive placements (such as concrete box girder and concrete T-beam girder
Structures). Falsework components shall be sized, positioned, and/or supported to
minimize progressive increases in deflection of the Structure which would preload the
concrete or reinforcing steel before it becomes fully composite.

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6-02.3(17)B2 Timber

Each species and grade of timber/lumber used in constructing falsework and formwork
shall be identified in the drawings. The allowable stresses and loads shall not exceed the
lesser of stresses and loads given in the table below or factored stresses for designated
species and grade in Table 7.3 of the Timber Construction Manual, latest edition, by the
American Institute of Timber Construction.

Compression perpendicular to the grain reduced to 300 psi for use when

moisture content is 19 percent or more (areas exposed to rain, concrete curing

water, green lumber).

450 psi

Compression parallel to the grain but not to exceed 1,500 psi.

480,000 psi

(L/d)

Flexural stress for members with a nominal depth greater than 8 inches.

1,800 psi

Flexural stress psi for members with a nominal depth of 8 inches or less.

1,500 psi

The maximum horizontal shear.

140 psi

AXIAL tension.

1,200 psi

The maximum modulus of elasticity (E) for timber.

1,600,000 psi

Where:

is the unsupported length; and

is the least dimension of a square or rectangular column, or the width of a square of

equivalent cross-sectional area for round columns.

The allowable stress for compression perpendicular to the grain, and for horizontal
shear shall not be increased by any factors such as short duration loading. Additional
requirements are found in other parts of

Section 6-02.3(17)

. Criteria for the design of

lumber and timber connections are found in

Section 6-02.3(17)I.

Plywood for formwork shall be designed in accordance with the methods and stresses
allowed in the APA Design/Construction Guide for Concrete Forming as published by the
American Plywood Association, Tacoma, Washington. As concrete forming is a special
application for plywood, wet stresses shall be used and then adjusted for forming
conditions such as duration of load, and experience factors. Concrete pour pressures shall
be in accordance with

Section 6-02.3(17)J

6-02.3(17)B3 Steel

For identified grades of steel, design stresses shall not exceed those specified in the
Steel Construction Manual, latest edition, by the American Institute of Steel Construction,
except as follows:

Compression, flexural but not to exceed 0.6F

12,000,000 psi

Ld/bt

The modulus of elasticity (E) shall be

29,000,000 psi

When the grade of steel cannot be positively identified as with salvaged steel and if rivets
are present, design stresses shall not exceed the following:

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Yield point f

30,000 psi

Tension, axial, and flexural

16,000 psi

Compression, axial except L/r shall not exceed 120

14,150 - 0.37(KL/r)

psi

Shear on gross section of the web of rolled shapes

9,500 psi

Web crippling for rolled shapes

22,500 psi

Compression, flexural but not to exceed 16,000 psi and L/b not greater

than 39

16,000 - 5.2(L/b)

psi

The modulus of elasticity (E) shall be

29,000,000 psi

Where:

is the unsupported length;

is the least dimension of rectangular columns, or the width of a square of equivalent

cross-sectional area for round columns, or the depth of beams;

is the flange width;

is the thickness of the compression flange;

is the radius of gyration of the compression flange about the weak axis of the member;

and

is the specified minimum yield stress, psi, for the grade of steel used.

All dimensions are expressed in inches.

6-02.3(17)C

Falsework and Formwork at Special Locations

In addition to the minimum requirements specified in Sections

6-02.3(17)A

and

6-02.3(17)B

, falsework towers or posts supporting beams directly over Roadways or

railroads which are open to traffic or the public shall be designed and constructed
so that the falsework will be stable if subjected to impact by vehicles. The use of
damaged materials, unidentifiable material, salvaged steel or steel with burned holes or
questionable weldments shall not be used for falsework described in this section. For
the purposes of this Specification the following public or private facilities shall also be
considered as “Roadways”: pedestrian pathways and other Structures such as bridges,
walls, and buildings.

The dimensions of the clear openings to be provided through the falsework for Roadways,
railroads, or pedestrian pathways shall be as specified in the Contract.

Falsework posts or shoring tower systems which support members that cross over a
Roadway or railroad shall be considered as adjacent to Roadways or railroads. Other
falsework posts or shoring towers shall be considered as adjacent to Roadways or
railroads only if the following conditions apply:
1. Located in the row of falsework posts or shoring towers nearest to the Roadway or

railroad; and

2. Horizontal distance from the traffic side of the falsework to the edge of pavement is

less than the total height of the falsework and forms; or

3. The total height of the falsework and forms is greater than the horizontal clear

distance between the base of the falsework and a point 10 feet from the centerline
of track.

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The Contractor shall provide any additional features for the Work needed to ensure that
the falsework will be stable for impact by vehicles; providing adequate safeguards, safety
devices, protective equipment, and any other needed actions to protect property and
the life, health, and safety of the public; and shall comply with the provisions in Sections

1-07.23

and

6-02.3(17)M

. The falsework design at special locations, shall incorporate

the minimum requirements detailed in this section, even if protected by concrete median
barrier.

The vertical load used for the design of falsework posts and towers which support the
portion of the falsework over openings, shall be the greater of the following:
1. 150 percent of the design load calculated in accordance with

Section 6-02.3(17)B

but not including any increased or redistributed loads caused by the post-tensioning
forces; or

2. 100 percent of the design load plus the increased or redistributed loads caused by

the post-tensioning forces.

Each falsework post or each shoring tower leg adjacent to Roadways or railroads shall
consist of either steel with a minimum section modulus about each axis of 9.5 inches
cubed or sound timbers with a minimum section modulus about each axis of 250 inches
cubed.

Each falsework post or shoring tower leg adjacent to Roadways or railroads shall be
mechanically connected to its supporting footing at its base, or otherwise laterally
restrained, to withstand a force of not less than 2,000 pounds applied at the base of
the post or tower leg in any direction except toward the Roadway or railroad track.
Posts or tower legs shall be connected to the falsework cap and stringer by mechanical
connections capable of resisting a load in any horizontal direction of not less than
1,000 pounds.

For falsework spans over Roadways and railroads, all falsework stringers shall be
mechanically connected to the falsework cap or framing. The mechanical connections
shall be capable of resisting a load in any direction, including uplift on the stringer, of
not less than 500 pounds. All associated connections shall be installed before traffic is
allowed to pass beneath the span.

When timber members are used to brace falsework bents which are located adjacent to

Roadways or railroads, all connections shall be bolted through the members using ⅝-inch

diameter or larger bolts.

Concrete traffic barrier shall be used to protect all falsework adjacent to traveled
Roadways. The falsework shall be located so that falsework footings, mudsills, or piles are
at least 2 feet clear of the traffic barrier and all other falsework members shall also be at
least 2 feet clear of the traffic barrier. Traffic barrier used to protect falsework shall not
be fastened, guyed, or blocked to any falsework but shall be fastened to the pavement
according to details shown in the Plans. The installation of concrete traffic barrier shall be
completed before falsework erection is begun. The traffic barrier at the falsework shall
not be removed until allowed by the Engineer. Falsework openings which are provided
for the Contractor’s own use (not for public use) shall also use concrete traffic barrier

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to protect the falsework, except the minimum clear distance between the barrier and
falsework footings, mudsills, piles, or other falsework members shall be at least 3 inches.

Falsework bents within 20 feet of the center line of a railroad track shall be braced to
resist the required horizontal load or 2,000 pounds whichever is greater.

Pedestrian openings through falsework shall be paved or surfaced with full width
continuous wood walks which shall be wheel chair accessible and shall be kept clear.
Pedestrians shall be protected from falling objects and water falling from construction
above. Overhead protection for pedestrians shall extend at least 4 feet beyond the edge
of the bridge deck. Plans and details of the overhead protection and pathway shall be
submitted with the falsework Working Drawings. Pedestrian openings through falsework
shall be illuminated by temporary lighting, constructed and maintained by the Contractor.
The temporary lighting shall be constructed in accordance with local electrical code
requirements. The temporary lighting shall be steady burning 60-watt, 120-volt lamps
with molded waterproof lamp holders spaced at 25-foot centers maximum. All costs
relating to pedestrian pathway paving, wood walks, overhead protection, maintenance,
operating costs, and temporary pedestrian lighting shall be incidental to applicable
adjacent items of Work.

6-02.3(17)D Falsework Support Systems: Foundations, Manufactured Shoring

Towers, Caps, and Posts

Foundations for falsework shall be designed for conditions stated in this Section using
methods shown in the AASHTO Standard Specifications for Highway Bridges Seventeenth
Edition – 2002 for allowable stress design, the AASHTO LRFD Bridge Design Specifications
for load and resistance factor design or the AASHTO Guide Design Specifications for Bridge
Temporary Works. Allowable stresses for materials shall not exceed stresses and conditions
allowed by Section 6-02.3(17)B.

6-02.3(17)D1 Vacant

6-02.3(17)D2 Vacant

6-02.3(17)D3 Bents, Shoring Towers, Piling, Posts, and Caps

Plans for falsework bents or shoring tower systems, including manufactured tower
systems shall have plan, cross-section, and elevation view scale drawings showing all
geometry. Show in the falsework plans the proximity of falsework to utilities or any
nearby Structures including underground Structures. The ground elevation, cross-slopes,
relation of stringers to one another, and dimensions to posts or piling shall be shown in
the falsework plans. Column, pile, or tower heights shall be indicated. Member sizes, wall
thickness and diameter of steel pipe columns or piles shall be shown in the falsework
plans. Location of wedges, minimum bearing area and type of wedge material shall be
identified in the falsework plans. Bracing size, location, material and all connections shall
be described in the falsework plans.

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The relationship of the falsework bents or shoring tower systems to the permanent
Structure’s pier and footing shall be shown. Load paths shall be as direct as possible.
Loads shall be applied through the shear centers of all members to avoid torsion and
buckling conditions. Where loads cause twisting, biaxial bending, or axial loading with
bending, the affected members shall be designed for combined stresses and stability.

Posts or columns shall be constructed plumb with tops and bottoms carefully cut to
provide full end bearing. Caps shall be installed at all bents supported by posts or piling
unless the falsework Working Drawings specifically permit otherwise. Caps shall be
fastened to the piling or posts. The falsework shall be capable of supporting non uniform
or localized loading without adverse effect. For example, the loading of cantilevered ends
of stringers or caps shall not cause a condition of instability in the adjacent unloaded
members.

Timber posts and piling shall be fastened to the caps and mudsills by through-bolted
connections, drift pins, or other accepted connections. The minimum diameter of round
timber posts shall be shown in the falsework plans. Timber caps and timber mudsills shall
be checked for crushing from columns or piling under maximum load.

Steel posts and piling shall be welded or bolted to the caps, and shall be bolted or welded
to the foundation. Steel members shall be checked for buckling, web yielding, and web
crippling.

Wedges shall be used to permit formwork to be taken up and released uniformly. Wedges
shall be oak or close-grained Douglas fir. Cedar wedges or shims shall not be used
anywhere in a falsework or forming system. Wedges shall be used at the top or bottom of
shores, but not at both top and bottom. After the final adjustment of the shore elevation
is complete, the wedges shall be fastened securely to the sill or cap beam. Only one set
of wedges (with one optional block) shall be used at one location. Screw jacks (or other
allowed devices) shall be used under arches to allow incremental release of the falsework.

Sand jacks may be used to support falsework and are used for falsework lowering only.
Sand jacks shall be constructed of steel with snug fitting steel or concrete pistons. Sand
jacks shall be filled with dry sand and the jack protected from moisture throughout its use.
They shall be designed and installed in such a way to prevent the unintentional migration
or loss of sand. All sand jacks shall be tested in accordance with

Section 6-02.3(17)G

When falsework is over or adjacent to Roadways or railroads, all details of the falsework
system which contribute to the horizontal stability and resistance to impact shall be
installed at the time each element of the falsework is erected and shall remain in place
until the falsework is removed. For other requirements see

Section 6-02.3(17)C

Transverse construction joints in the Superstructure shall be supported by falsework at
the joint location. The falsework shall be constructed in such a manner that subsequent
pours will not produce additional stresses in the concrete already in place.

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6-02.3(17)D4 Manufactured Shoring Tower Systems and Devices

Manufactured proprietary shoring tower systems shall be identified in the falsework plans
by make and model and safe working load capacity per leg. The safe working load for
shoring tower systems shall be based upon a minimum 2½ to 1 factor of safety.

The safe working load capacity, anticipated deflection (or settlement), make and model
shall be identified in the falsework plans for manufactured devices such as: single shores,
overhang brackets, support bracket and jack assemblies, friction collars and clamps,
hangers, saddles, and sand jacks. The safe working load for shop manufactured devices
shall be based on a minimum ultimate strength safety factor of 2 to 1. The safe working
load for field fabricated devices and all single shores shall be based on a minimum
ultimate strength safety factor of 3 to 1.

The safe working load of all devices shall not be exceeded. The design loads shall be as
defined by

Section 6-02.3(17)A

. The maximum allowable free end deflection of deck

overhang brackets under working loads applied shall not exceed 3/16 inch measured at the

edge of the concrete slab regardless of the fact that the deflection may be compensated
for by pre-cambering or of setting the elevations high. The Contractor shall comply with
all manufacturer’s Specifications; including those relating to bolt torque, placing washers
under nuts and bolt heads, cleaning and oiling of parts, and the reuse of material. Devices
which are deteriorated, bent, warped, or have poorly fitted connections or welds, shall not
be installed.

Shoring tower or device capacity as shown in catalogs or brochures published by the
manufacturer shall be considered as the maximum load which the shoring is able to safely
support under ideal conditions. These maximum values shall be reduced for adverse
loading conditions; such as horizontal loads, eccentricity due to unbalanced spans or
placing sequence, and uneven foundation settlement.

Copies of catalog data and/or other technical data shall be furnished with the falsework
plans to verify the load-carrying capacity, deflection, and manufacturers installation
requirements of any manufactured product or device proposed for use. Upon request
by the Engineer, the Contractor shall furnish manufacturer certified test reports and
results showing load capacity, deflection, test installation conditions, and identify
associated components and hardware for shoring tower systems or other devices. In
addition to manufacturer’s requirements, the criteria shown in the following sections
for manufactured proprietary shoring tower systems and devices shall be complied with
when preparing falsework plans, calculations, and installing these shoring tower systems
and devices as falsework.

Alternative criteria and/or systems shall be submitted as a Type 2 Working Drawing
consisting of a written statement on the manufacturer’s letterhead, signed by the shoring
or device manufacturer (not signed by a material supplier or the Contractor) addressing
the following:
1. Identity of the specific Contract on which the alternative criteria and/or system will

apply;

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2.  Description of the alternative criteria and/or system;
3.  Technical data and test reports;
4.  The conditions under which the particular alternative criteria may be followed; and
5.  That a design based on the alternative criteria will not overstress or over deflect any

shoring component or device nor reduce the required safety factor.

In any case where the falsework drawings detail a manufactured product and the
manufacturer’s safe working load, load versus deflection curves, factor of safety, and
installation requirements cannot be found in any catalog, the Engineer may require load
testing in accordance with

Section 6-02.3(17)G

to verify the safe working load and

deflection characteristics.

Tower leg loads shall not exceed the limiting values under any loading condition or
sequence. Frame extensions and any reduced capacity shall be shown in the falsework
plans. Screw jacks shall fit tight in the leg assemblies without wobble. Screw jacks shall be
plumb and straight. Shoring towers shall be installed plumb, and load distribution beams
shall be arranged such that vertical loads are distributed to all legs for all successive
concrete placements. There shall be no eccentric loads on shoring tower heads unless
the heads have been designed for such loading. Shoring towers shall remain square or
rectangular in plan view and shall not be skewed. There shall be no interchanging of parts
from one manufactured shoring system to another. Bent or faulty components shall not
be used.

For manufactured shoring towers that allow ganging of frames, the number of ganged
frames shall be limited to one frame per opposing side of a tower, and the total number
of legs per ganged tower shall not exceed eight legs. Ganged frames shall be installed
in accordance with the manufacturer’s published standards using the manufacturer’s
components. Other gang arrangements shall not be used.

For manufactured steel shoring tower systems, the Contractor shall have bracing
designed and installed for horizontal loads and falsework overturning in accordance with

Section 6-02.3(17)A

. Minimum bracing criteria and allowable leg loads are described in

the following paragraphs.

All shoring tower systems and bracing shall be thoroughly inspected by the Contractor
for plumb vertical support members, secure connections, and straight bracing members
immediately prior to, at intervals during, and immediately after every concrete placement.
For manufactured shoring tower systems, the maximum allowable deviation from the

vertical is ⅛ inch in 3 feet. If this tolerance is exceeded, concrete shall not be placed until

adjustments have brought the shoring towers within the acceptable tolerance.

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6-02.3(17)E

Stringers, Beams, Joists, Bridge Deck Support, and Deck

Overhangs

All stringers, beams, joists, and bridge deck support shall be designed for the design loads,
deflections, and allowable stresses described in the preceding

Section 6-02.3(17)A

, and

and for the following conditions.

At points of support, stringers, beams, joists, and trusses shall be restrained against
rotation about their longitudinal axis. The effect of biaxial bending shall be investigated in
all cases where falsework beams are not set plumb and the Structure cross-slope exceeds
3 percent.

For box girder and T-beam bridges, the centerline of falsework beams or stringers shall be
located within 2 feet of the bridge girder stems and preferably directly under the stems or
webs. Stringers supporting formwork for concrete box girder and T-beam slab overhangs
shall be stiff enough so that the differential deflection due to the placement of bridge

deck concrete is no more than 3/16 inch between the outside edge of the bridge deck and

the exterior web even if camber strips can compensate for the deflection.

Friction shall not be relied upon for lateral stability of beams or stringers. If the
compression flange of a beam is not laterally restrained, the allowable bending stress
shall be reduced to prevent flange buckling. If flange restraint is provided and since it is
impossible to predict the direction in which a compression flange will buckle, positive
restraint shall be provided in both directions. Flange restraint shall be designed for a
minimum load of 2 percent of the calculated compression force in the beam flange at the
point under consideration.

Camber strips shall be used to compensate for falsework take-up and deflection,
vertical alignment, and the anticipated Structure dead load deflection shown in the
camber diagram in the Contract Plans. Camber is the adjustment to the profile of a load-
supporting beam or stringer so that the completed Structure will have the lines and
grades shown in the Plans. The dead load camber diagram shown in the Contract Plans is
the predicted Structure dead load deflection due to self mass. This dead load camber shall
be increased by:
1. Amount of anticipated falsework take up,
2. Anticipated deflection of the falsework beam or stringer under the actual load

imposed, and

3. Any vertical curve compensation.

Camber strips shall be fastened by nailing to the top of wood members, or by clamping
or banding in the case of steel members. Camber strips shall have sufficient contact
bearing area to prevent crushing under total load. Camber strips are required when the
total camber adjustment exceeds ¼ inch for exterior falsework stringers and ½ inch for
interior stringers.

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On concrete box girder Structures, the forms supporting the bridge deck shall rest on
ledgers or similar supports and shall not be supported from the bottom slab except as
provided below. The form supports shall be fastened within 18 inches of the top of the
web walls, producing a clear span between web walls. The bridge deck forms may be
supported or posted from the bottom slab if the following conditions are met:
1. Permanent access, shown in the Contract Plans, is provided to the cells, and the

centerline to centerline distance between web walls is greater than 10 feet;

2. Falsework stringers designed for total load, stresses and deflections in accordance

with

Section 6-02.3(17)A

and

are located directly below each row of posts;

3. Posts have adequate lateral restraint; and
4. All forms (including the bridge deck forms), posts, and bracing are completely

removed.

The falsework and forms on concrete box girder Structures supporting a sloping web
and deck overhang shall consist of a lateral support system which is designed to resist all
rotational forces acting on the stem, including those caused by the placement of bridge
deck concrete, bridge deck formwork mass, finishing machine, and other live loads.
Stem reinforcing steel shall not be stressed by the construction of the bridge deck slab
placement. Overhang brackets shall not be used for the support of bridge deck forms
from sloping web concrete box girder bridges.

Deck slab forms between girders or webs shall be constructed such that there is no
differential settlement relative to the girders. The support systems for form panels
supporting concrete deck slabs and overhangs on girder bridges (such as steel plate
girders and prestressed girders) shall be designed as falsework. Falsework supporting deck
slabs and overhangs on girder bridges shall be supported directly by the girders so that
there will be no differential settlement between the girders and the deck forms during
placement of deck concrete.

6-02.3(17)F Bracing

All falsework bracing systems shall be designed to resist the horizontal design load in
all directions with the falsework in either the loaded or unloaded condition. All bracing,
connection details, specific locations of connections, and hardware used shall be shown
in the falsework plans. Falsework diagonal bracing shall be thoroughly analyzed with
particular attention given to the connections. The allowable stresses in the diagonal
braces may be controlled by the joint strength or the compression stability of the
diagonal. Timber bracing for timber falsework bents shall have connections designed in
accordance with

Section 6-02.3(17)I

. Any damaged cross-bracing, such as split timber

members shall be replaced. Steel strapping shall avoid making sharp angles or right-
angle bends. A means of preventing accidental loss of tension shall be provided for steel
strapping. See Sections

6-02.3(17)A

, and

for design loads and allowable stresses.

Bracing shall not be attached to concrete traffic barrier, guardrail posts, or guardrail.

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To prevent falsework beam or stringer compression flange buckling, cross-bracing
members and connections shall be designed to carry tension as well as compression. All
components, connection details and specific locations shall be shown in the falsework
plans. Bracing, blocking, struts, and ties required for positive lateral restraint of beam
flanges shall be installed at right angles to the beam in plan view. If possible, bracing in
adjacent bays shall be set in the same transverse plane. However, if because of skew
or other considerations, it is necessary to offset the bracing in adjacent bays, the offset
distance shall not exceed twice the depth of the beam.

All falsework and bracing shall be inspected by the Contractor for plumbness of vertical
support members, secure connections, tight cables, and straight bracing members
immediately prior to, during, and immediately after every concrete placement.

Bracing shall be provided to withstand all imposed loads during erection of the falsework
and all phases of construction for falsework adjacent to any Roadway, sidewalk, or
railroad track which is open to the public. All details of the falsework system which
contribute to horizontal stability and resistance to impact, including the bolts in bracing,
shall be installed at the time each element of the falsework is erected and shall remain in
place until the falsework is removed. The falsework plans shall show provisions for any
supplemental bracing or methods to be used to conform to this requirement during each
phase of erection and removal. Wind loads shall be included in the design of such bracing
or methods. Loads, connections, and materials for falsework adjacent to Roadways, shall
also be in accordance with

Section 6-02.3(17)C

6-02.3(17)F1 Cable or Tension Bracing Systems

When cables, wire rope, steel rod, or other types of tension bracing members are used
as external bracing to resist horizontal forces, or as temporary bracing to support bents
while falsework is being erected or removed adjacent to traffic, all elements of the
bracing system shall be shown in the falsework plans. Bracing shall not be attached to
concrete traffic barrier, guardrail posts, or guardrail. Any damaged bracing, such as frayed
and kinked guying systems shall be replaced. Wire rope shall avoid making sharp angles or
right-angle bends and a means of preventing accidental loss of tension shall be provided.
The following information shall be submitted as a Type 2 Working Drawing:
1. Cable diameter, rod, or tension member size, and allowable working load.
2. Location and method of attaching the cable, rod, or tension member to the

falsework. The connecting device shall be designed to transfer both horizontal and
vertical forces to the cable without overstressing any falsework component.

3. The type of cable connectors or fastening devices (such as U-bolt clips, plate clamps,

etc.) to be used and the efficiency factor for each type. If cables are to be spliced, the
splicing method shall be shown.

4. Method of tightening cables, rods, or tension members after installation if tightening

is necessary to ensure their effectiveness. Method of preventing accidental
loosening.

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5. Anchorage details, including the size and mass of concrete anchor blocks, the

assumed coefficient of friction for surface anchorages, and the assumed lateral soil
bearing capacity for buried anchorages.

6. Method of pre-stretching or preloading cable or tension members.
7. Determination of the potential stretch or elongation of the tension member under

the design load and if the resulting lateral deflection will cause excessive secondary
stresses in the falsework.

Copies of manufacturer’s catalog or brochure showing technical data pertaining to the
type of cable to be used shall be furnished with the falsework plans. Technical data
shall include the cable diameter, the number of strands and the number of wires per
strand, ultimate breaking strength or recommended safe working strength, and any other
information as may be needed to identify the cable.

In the absence of sufficient technical data to identify the cable, or if it is old and obviously
worn, the Contractor shall perform cable breaking tests to establish the safe working load
for each reel of cable furnished. For static guy cable the minimum factor of safety shall be
3 to 1. The Contractor shall provide the Engineer an opportunity to witness these tests.

When cable bracing is used to prevent the overturning of heavy-duty shoring, attention
shall be given to the connections by which forces are transferred from the shoring to the
cables. Cable restraint shall be designed to act through the cap system to prevent the
inadvertent application of forces which the shoring is not designed to withstand. Cables
shall not be attached to any tower component.

Cable splices made by lapping and clipping with “Crosby” type clamps shall not be used.
Other splicing methods may be used; however, at each location where the cable is spliced,
cable strength shall be verified by a load test.

When cables are used as external bracing to resist overturning of a falsework system, the
horizontal load to be carried by the cables shall be calculated as follows:
1. When used with heavy-duty shoring systems, cables shall be designed to resist the

difference between 1.25 times the total overturning moment and the resistance to
overturning provided by the individual falsework towers.

2. When used with pipe-frame shoring systems where supplemental bracing is

required, cables shall be designed to resist the difference between 1.25 times the
total overturning moment and the resistance to overturning provided by the shoring
system as a whole.

3. When used as external bracing to prevent overturning of all other types of falsework,

including temporary support during erection and removal of falsework at traffic
openings, cables shall be designed to resist 1.25 times the total overturning moment.

Page 6-68

Concrete Structures

The maximum allowable cable design load shall be determined using the following
criteria:
1. If the cable is new, or is in uniformly good condition, and if it can be identified by

reference to a manufacturer’s catalog or other technical publication, the allowable
load shall be the ultimate strength of the cable as specified by the manufacturer,
multiplied by the efficiency of the cable connector, and divided by a safety factor of
3 (i.e., safe working load = breaking strength × connector efficiency/safety factor).

2. If the cable is used but still in serviceable condition, or is new or nearly new but

cannot be found in a manufacturer’s catalog, the Contractor shall perform load
breaking tests. In this case, the cable design load shall not exceed the breaking
strength, as determined by the load test, multiplied by the connector efficiency
factor, and divided by a safety factor of 3.

3. If the cable is used and still in serviceable condition, or is a new or nearly new cable

which cannot be identified, and if load breaking tests are not performed, the cable
design load shall not exceed the safe working load shown in the wire rope capacities
table multiplied by the cable connector efficiency.

Cable connectors shall be designed in accordance with criteria shown in the
following tables “Efficiency of Wire Rope Connections” and “Applying Wire Rope
Clips”. Cable safe working loads are provided in table “Wire Rope Capacities”.

Efficiency of Wire Rope Connections

(As compared to Safe Loads on Wire Rope)

Type of Connection

Connector Efficiency

Wire Rope

100%

Sockets – Zink Type

100%

Wedge Sockets

70%

Clips – Crosby Type With Thimble

80%

Knot and Clip (Contractors Knot)

50%

Plate Clamp – 3 Bolt Type With Thimble

80%

Spliced Eye and Thimble:

¼″ and smaller

100%

⅜″ to ¾″

95%

⅞″ to 1″

88%

1⅛″ to 1½″

82%

1⅝″ to 2″

75%

2⅛″ and larger

70%

Concrete Structures

6-02

Wire Rope Capacities

Safe Load in Pounds for New Plow Steel Hoisting Rope

6 Strands of 19-Wires, Hemp Center (Safety Factor of 6)

Diameter inches

Weight Lbs./Ft.

Safe Load Lbs.

0.10

1,050

0.16

1,500

⅜

0.23

2,250

7⁄16

0.31

3,070

0.40

4,030

9⁄16

0.51

4,840

⅝

0.63

6,330

0.95

7,930

⅞

1.29

10,730

1.60

15,000

1⅛

2.03

18,600

1¼

2.50

23,000

1⅜

3.03

25,900

1½

3.60

30,700

1⅝

4.23

35,700

1¾

4.90

41,300

6-02.3(17)F2 Applying Wire Rope Clips

The only correct method of attaching U-bolt wire rope clips to rope ends is to place the
base (saddle) of the clip against the live end of the rope, while the “U” of the bolt presses
against the dead end.

The clips are usually spaced about six rope diameters apart to give adequate holding
power. A wire-rope thimble shall be used in the loop eye to prevent kinking when
wire rope clips are used. The correct number of clips for safe application, and spacing
distances, are shown below:

Number of Clips and Spacing for Safe Application

Improved Plow Steel

Rope Diameter inches

Number of Clips

Minimum

Drop Forged

Other Material

Spacing (Inches)

⅜

3½

⅝

4½

⅞

5¼

1⅛

6¾

1¼

7½

1⅜

8¼

1½

Page 6-70

Concrete Structures

6-02.3(17)F3 Anchor Blocks

Concrete anchor blocks and connections used to resist forces from external bracing shall
be shown in the falsework plans. Concrete anchor blocks shall be proportioned to resist
both sliding and overturning. When designing anchor block stability, the mass of the
anchor block shall be reduced by the vertical component of the cable or brace tension
to obtain the net or effective mass to be used in the anchorage computations. The
coefficient of friction assumed in the design shall not exceed the following:

Friction Coefficient

Anchor block set on sand

0.40

Anchor block set on clay

0.50

Anchor block set on gravel

0.60

Anchor block set on pavement

0.60

Multiply the friction coefficient by 0.67 if it is likely the supporting material
is wet or will become wet during the construction period.

The method of connecting the cable or brace to the anchor block is part of the
anchor block design. The connection shall be designed to resist both horizontal and
vertical forces.

6-02.3(17)F4 Temporary Bracing for Bridge Girders During Erection

Steel girders shall be braced in accordance with

Section 6-03.3(7)A

Prestressed concrete girders shall be braced sequentially during girder erection. The
bracing shall be designed and detailed by the Contractor and shall be shown in the
falsework/formwork Working Drawings. The Contractor shall furnish, install, and remove
the bracing at no additional cost to the Contracting Agency.

At a minimum, the Contractor shall brace girders at each end and at midspan to prevent
lateral movement or rotation. This bracing shall be placed prior to the release of each
girder from the erection equipment. If the bridge is constructed with cast-in-place
concrete diaphragms, the bracing may be removed once the concrete in the diaphragms
has been placed and cured for a minimum of 24 hours.

Concrete Structures

6-02

6-02.3(17)F5 Temporary Bracing for Bridge Girders During Diaphragm

and Bridge Deck Concrete Placement

Prestressed concrete girders shall be braced to resist forces that would cause rotation or
torsion in the girders caused by the placing of precast concrete deck panels and concrete
for the bridge deck.

Bracing shall be designed and detailed by the Contractor and shall be shown in the
falsework/formwork Working Drawings. These braces shall be furnished, installed,
and removed by the Contractor at no additional cost to the Contracting Agency. The
Contractor may consider the bracing effects of the diaphragms in developing the
falsework/formwork plans. The Contractor shall account for the added load from concrete
finishing machines and other construction loadings in the design of the bracing.

Falsework support brackets and braces shall not be welded to structural steel bridge
members or to steel reinforcing bars.

6-02.3(17)G Testing Falsework Devices

The Contractor shall establish the load capacity and deflection (or settlement) of all
friction collars and clamps, brackets, hangers, saddles, sand jacks, and similar devices
utilizing a recognized independent testing Laboratory accepted by the Engineer.
Laboratory tests shall use the same materials and design that will be used on the
project. Test loads shall be applied to the device in the same manner that the device will
experience loading on the project. Any bolts or threaded rods used with the device shall
be identified as to diameter, length, type, grade, and torque. Any wedges, blocks, or shims
used with the device on the project shall also be tested with the device. Any adjustable
jack system used as a part of a device shall be tested with the device and shall have its
maximum safe working extended height identified. Devices shall not be tested in contact
with the permanent Structure. Independent members with the same properties as the
permanent Structure shall be used to test device connections.

At least 14 days prior to the test, the Contractor shall submit a Type 2 Working Drawing
consisting of the test procedure and scale drawing showing how the device will be tested
and how data will be collected. The Contractor shall provide the Engineer an opportunity
to witness these tests.

The independent testing Laboratory shall provide a certified test report which shall
be signed and dated. The test report shall clearly identify the device tested including
trademarks and model numbers; identify all parts and materials used, including grade
of steel, or lumber, member section dimensions; location, size, and the maximum tested
extended height of any adjustable jacks; indicate condition of materials used in the
device; indicate the size, length and location of all welds; indicate how much torque
was used with all bolts and threaded rods. The report shall describe how the device was
tested, report the results of the test, provide a scale drawing of the device showing the
location(s) of where deflections or settlements were measured, and show where load was
applied. Deflections or settlements shall be measured at load increments and the results
shall be clearly graphed and labeled. Prior to installation of falsework devices named

Standard Specifications for Road, Bridge, and Municipal Construction 2020 (M 41-10) - page 32