Different Types of Earth Pressure Cells, Their Applications and Construction of Isobar Diagram Using Them-3

1.4 ISOBAR DIAGRAM

An isobar is a curve joining the points of equal stress intensity. In other words, an isobar is a contour of equal stress. An isobar is a spatial curved surface of the shape of an electrical bulb or an onion. The curved surface is symmetrical about the vertical axis passing through the load point.


The isobar of a particular intensity can be obtained using Boussinesq’s equation. The calculations are shown in a tabular form. Table 1.1. gives calculations for an isobar of intensity 0.1Q per unit area.

Fig.1.3: Pressure Bulb or Isobar Diagram for Point Load Q.

From Boussinesq’s equation,

σ_z = I_B . Q /z ²

^{Taking σ_z = 0.1Q}

0.1Q = I_B .Q/z²

or, I_B =0.1 z² …………………….(1.2)

For different depths z, the value of IB is computed from Eq. 1.2. as shown in second row of Table 1.1. The values of r/z for computed values of IB are obtained from Eq.1.4. Once the values of r/z have been determined, the radial distance r can be obtained as shown in table 1.1. It may be observed that r is zero at the load point, and it attains a maximum value at r/z = 0.75 and again decreases. As the isobar is symmetrical about the load axis, the other half can be drawn from symmetry. The shape of an isobar approaches a lemniscates curve. Fig. 1.3. shows the isobar diagram or pressure bulb for point load.

In the similar manner, the isobars of other intensity 0.2Q, 0.3Q, 0.4Q, etc. can be drawn. Obviously, the isobars of higher intensity shall lie within the isobar of 0.1Q.

Table 1.1- Calculations for Isobar of 0.1 Q

Depth z	0.25	0.5	0.75	1.0	1.25	1.5	1.75	2.0	2.185
IB	0.00625	0.25	0.05625	0.10	0.1562	0.225	0.3062	0.400	0.4775
r/z	2.16	1.50	1.16	0.93	0.75	0.59	0.44	0.27	0.000
r	0.54	0.75	0.87	0.93	0.938	0.885	0.770	0.540	0.000

Isobars are useful for determining the effect of the load on the vertical stresses at various points. The zone within which the stresses have a significant effect on the settlement of structures is known as the Pressure Bulb. The area outside the pressure bulb is assumed to have negligible stresses.

Different Types of Earth Pressure Cells, Their Applications and Construction of Isobar Diagram Using Them-2

(2) Two-to-one Load Distribution Method:- The actual distribution of load with the depth is complex. However, it can be assumed to spread approximately at a slope of two (vertical) to (horizontal). Thus the vertical pressure at any depth z below the soil surface can be determined approximately by constructing a frustum of pyramid (or cone) of depth z and side slopes(2:1). The pressure distribution is assumed to be uniform on a horizontal plane at that depth.

The average vertical stress σ_z depends upon the shape of the loaded area, as given below( fig. 1.2).

Fig.1.2: Two-to-One Distribution.

(a)	Square Area (B × B)
(b)	Rectangular Area (B ×L)
(c)	Strip Area (width B, unit length)
(d)	Circular Area (diameter D)

The above method gives fairly accurate values of the average vertical stress if the depth z is less than 2.5 times the width of the loaded area. The maximum stress is generally taken as 1.5 times the average stress determined above.

(3) Sixty Degree Distribution:- This method is similar to the preceding method. In this case, the pressure distribution is assumed along lines making an angle of 60° with the horizontal instead of 63.5⁰ (2:1). The method gives approximately the same results.

Different Types of Earth Pressure Cells, Their Applications and Construction of Isobar Diagram Using Them-1

INTRODUCTION

1.1 GENERAL

Stresses are induced in a soil mass due to weight of overlying soil and due to the applied loads. These stresses are required for the stability analysis of the soil mass, the settlement analysis of foundations and the determination of the earth pressures.

The stresses due to self weight of soils are generally large in comparison with those induced due to imposed loads. This is unlike many other civil engineering structures, such as steel bridges, wherein the stresses due to self weight are significant. In many cases the stresses due to self weight are a large proportion of the total stresses and may govern the design.

The stresses induced in soil due to applied loads depend upon its stress-strain characteristic. The stress-strain behaviour of soils is extremely complex and it depends upon a large number of factors, such as drainage conditions, water content, void ratio, rate of loading, the load level, and the stress path. However, simplifying assumptions are generally made in the analysis to obtain stresses. It is generally assumed that the soil mass is homogeneous and isotropic. The stress-strain relationship is assumed to be linear. The theory of elasticity is used to determine the stresses in the soil mass. It involves considerable simplification of real soil behaviour and the stresses computed are approximate ones. Fortunately, the results are good enough for soil problems usually encountered in practice. For more accurate results, realistic stress-strain characteristics should be used. However, the procedure becomes complex and numerical techniques and high speed computers are required.

1.2. OBJECTIVES

The specific objectives of the study are:

1. To determine the soil stress at different depth of layers by earth pressure cells.
2. To assess for a particular soil layer with low bearing capacity, how much load can be applied at the top surface of soil.
3. To construct the curve (Pressure Bulb) showing the intensity of load at varying depth.
4. T o determine the depth of replaced materials by Isobar diagram for soil with low bearing capacity.

1.3 APPROXIMATE METHODS

The methods discussed in the preceding sections are relatively more accurate, but are time consuming. Sometimes, the engineer is interested to estimate the vertical stresses approximately for preliminary designs.

The following methods can be used:-

(1) Equivalent Point-Load Method:- The vertical stress at a point under a loaded area of any shape can be determined by dividing the loaded area into small areas and replacing the distributed load on each small area by an equivalent point load acting at the centroid of the area. E.g. in Fig.1.1, Q = qa2 for each area. The total load is thus converted into a number of point loads. The vertical stress at any point below or outside the loaded area is equal to the sum of the vertical stresses due to these equivalent point loads. Using Boussinesq’s equation 

σ_z = I_B . Q /z ²

we get

Fig.1.1. Equivalent Point Loads.

Eq. 1.1 gives fairly accurate results if the side a of the small area unit is equal to or less than one-third of the depth z of point P at which the vertical stress is required.

Special Features of Impact Resistant Windows and Doors

The impact resistant doors and windows can resist hurricane and storm related impact. With its special features it helps people in coastal or hurricane prone areas to have a nice dream or tensionless work environment. The products from MC and Lifestyle Remodeling have some special features which are summarized below:

STRENGTH

It begins with the thickness of our aluminum alloyed frames material, to the exacting engineering specifications and finally to the careful assembly in the manufacturing plant. Our frames have a 30-50% thicker gauge than the leading competitors and we only use the highest quality hardware for longer lasting performance.

SAFETY

Impact Resistant Glass

These windows and doors (hurricane windows and doors) provide 24/7 protection for you and your family against hurricanes and intruders. Hurricane safe windows need no outdoor shutters or coverings, which means that they can be opened to provide an escape route in the event of an emergency. Unlike shutters which do not offer visibility during storms and darkens the home, resistant windows create a more comfortable environment during inclement weather and you don ’t have to worry about putting up, taking down or storing shutters.

ENERGY EFFICIENCY 

With (hurricane) impact resistant windows and doors you can expect to reduce your energy costs over regular single pane glass. The low air infiltration minimizes heat transfer between the inside and the outside, thereby increasing energy efficiency. Also impact resistant windows and doors are available with Low E coatings and/or insulated glass to maximize thermal efficiency even further.     

     

UV PROTECTION

With impact resistant windows your delicate art, upholsteries, carpets and other sensitive materials are better protected from fading... Why? Because laminated glass blocks almost 99% of harmful and damaging UV rays.

NOISE REDUCTION 

Hurricane impact resistant doors and windows are designed to achieve a significant reduction in the transmission of sound. The combination of laminated glass and low air infiltration provides for a quieter, more private home or business. 

SECURITY

Impact resistant glass provides 24/7  protection against intruders for you, your family and your belongings. Even if the glass cracks, it will remain in place, resisting glass fallout.

Seismic Vulnerability of Floor Diaphragm of Wooden Building and Retrofitting Techniques

Floors in wooden buildings are usually constructed upon relatively deep spans of wood, called joists, covered with a diagonal wood planking or plywood to form a subfloor upon which the finish floor surface is laid. In many structures these are all aligned in the same direction. To prevent the beams from tipping over onto their side, blocking is used at each end, and for additional stiffness, blocking or diagonal wood or metal bracing may be placed between beams at one or more points in their spans. At the outer edge it is typical to use a single depth of blocking and a perimeter beam overall.

If the blocking or nailing is inadequate, each beam can be laid flat by the shear forces applied to the building. In this position they lack most of their original strength and the structure may further collapse. As part of a retrofit the blocking may be doubled, especially at the outer edges of the building. It may be appropriate to add additional nails between the sill plate of the perimeter wall erected upon the floor diaphragm, although this will require exposing the sill plate by removing interior plaster or exterior siding. As the sill plate may be quite old and dry and substantial nails must be used, it may be necessary to pre-drill a hole for the nail in the old wood to avoid splitting.

Bracings are applied to prevent tipping over onto their side having diagonal subfloor 

 When the wall is opened for this purpose it may also be appropriate to tie vertical wall elements into the foundation using specialty connectors and bolts glued with epoxy cement into holes drilled in the foundation.

Weakness in Beam-Column Joint Connections and Retrofitting Options

Beam-column joint connections are a common structural weakness in dealing with seismic retrofitting. Prior to the introduction of modern seismic codes in early 1970s, beam-column joints were typically non-engineered or designed. Laboratory testings have confirmed the seismic vulnerability of these poorly detailed and under-designed connections. Failure of beam-column joint connections can typically lead to catastrophic collapse of a frame-building, as often observed in recent earthquakes.
 

For reinforced concrete beam-column joints - various retrofit solutions have been proposed and tested in the past 20 years. Concrete or steel jacketing have been a popular retrofit technique until the advent of composite materials such as Carbon fiber-reinforced polymer (FRP). 

 

Composite materials such as carbon FRP and aramic FRP have been extensively tested for use in seismic retrofit with some success. One novel technique includes the use of selective weakening of the beam and added external post-tensioning to the joint in order to achieve flexural hinging in the beam, which is more desirable in terms of seismic design.

Widespread weld failures at beam-column joints of low-to-medium rise steel buildings during the Northridge 1994 earthquake for example, have shown the structural defiencies of these 'modern-designed' post-1970s welded moment-resisting connections. A subsequent SAC* research project has documented, tested and proposed several retrofit solutions for these welded steel moment-resisting connections. Various retrofit solutions have been developed for these welded joints - such as

a) weld strengthening and 

b) addition of steel haunch or 'dog-bone' shape flange.

Fiber Reinforced Composite Materials as Post-Reinforcement

Fiber reinforced composites (FRCs) have been successfully used in a variety of industries such as aerospace, automobile and ship building The FRCs are unaffected by electro-mechanical deterioration and can resist corrosive effects of acids, alkalis, salts and similar aggregates under a wide range of temperatures. Such highly efficient construction material gives civil engineering a new dimension. FRCs thus hold a very distinct advantage over steel plates as an external reinforcing device. Moreover, FRCs are available in the form of laminas and different thickness and orientation can be given to different layers to tailor its strength according to specific requirements.

The difficulties encountered in using steel plates as reinforcement lead us to the use of fiber reinforced composite materials as post-reinforcements. Due to their high specific strength (strength/weight ratio) the composite reinforcements are very light and easy to handle. The composite materials are available as unidirectional fibers of a huge length. Therefore, joints in the reinforcement can be avoided very easily. Moreover, the corrosion of the reinforcements can be avoided completely. Research work is gaining momentum on the application of composite materials as post-reinforcement (Nanni et al., 1995). The potential use of fiber reinforced composites in civil structures is manifold.

Barcelona Metro: The Deepest Electrified Railways Lines Made of Steel Fiber Reinforced Composite(FRC)

RC is a compound consisting of a cementitious hydrated paste into which reinforcement fibres – usually small, steel filaments about the size of a paperclip, are mixed. 

The fibres redistribute the forces within the concrete, restraining the mechanism of formation and extension of cracks. The result is a more ductile, concrete which is able to maintain a residual capacity in the post cracking phase. The steel fibres within the concrete literally ‘stitch’ the sides of a forming crack together. 

In Spain, construction of the 43km long extension to the Barcelona Metro has made extensive use of precast tunnel lining-segments incorporating steel reinforcement fibres.

When completed, it will be the longest and one of the deepest lines in Europe and the longest metro line in the world of entirely new construction. It will also be the most expensive enterprise the Catalan government has ever undertaken. The final projected costs are thought to be close to €6.5 billion, when the project is completed in 2012.

Segment fabrication

FRC tunnel ring segments were cast off-site and comprised 7 segments of 4.56m length [48degree length of arc] plus a 24 degree keystone, per ring. Each ring has going-length of 1.80m and is 350mm thick.

Segments were cast in curved steel formers with vibration applied to consolidate the concrete mix and heat cured at between 40-50deg C for 4-6 hours, before de-moulding and stacking them in an open yard.

Barcelona's metro station Gavarra (L5)

Consolidating the concrete in open curved moulds required a mix of stiff consistency [low workability]. In turn, this led to the need for higher amplitude vibration. Top surfaces of the segments are manually finished.

The original design for precast segments required 120kg of traditional steel reinforcement in the form of a fabricated cage, to provide the required structural strength. No fibre reinforcement was considered at this time.

An initial proposal of 30kg/cum of Maccaferri Wirand FF1 steel reinforcement fibres was made in an attempt to reduce the amount of steel bar within the segments. Ongoing testing refined the fibre reinforcement and a new fibre, Wirand FF3 with a higher L/D [length/diameter] value of 67 was developed, which offered improved performance. 

Eventually, only 25kg/cum of Wirand FF3 was found to achieve the same performance as 30kg of the FF1 fibres. Ongoing testing was implemented and the amount of steel rebar was gradually reduced. A final optimised combination of 25kg of Wirand FF3 fibres and 54kg/m3 of steel rebar gave the required structural performance (28 day compressive strength of 40MPa [5800psi]). 

This design specification gave the strength to provide adequate performance during the placement of the segments and during the early service life of the tunnel. An early age compressive strength of at least 40Mpa [2900psi] was also required to ensure sufficient crack resistance during the de-moulding and stacking phase – hence the use of accelerated curing agents within the mix. 

Reinforcement fibres are added to the concrete mix via purpose made dosing equipment, of a design specially modified by the supplier to ensure controlled introduction and consistent dispersion of the fibres. 5 feeder machines have been installed in the batching plant producing segments for all three tunnel section. 

Lines 9 and 10 of Barcelona Metro

To minimise seepage of water into the tunnel, crack widths were limited to 0.2mm, requiring a minimum 4-point loading flexural strength of 2.9MPa [4200psi]. Macro steel fibres, with high-strength / low-strain characteristics offer this performance; 25kg/cum of Wirand FF3 offered a flexural strength of 3.5MPa. 

The inclusion of reinforcement fibres also helped reduce the flexural stresses experienced during de-moulding and stacking, and controlled shrinkage cracking and thermal cracking caused by sudden temperature changes when segments were moved from the curing chamber to storage yard. 

Similarly, the lining segments were shown to have good resistance to accidental impact damage as well as the highly concentrated loads imposed during segment placement and the application of the jacking forces from the TBM; often a critical phase for precast lining segments.

Polyester Swimming Pool Coating System from Chloripur™

Polyester Swimming Pool Coating System is the ultimate choice for resurfacing concrete, metal, and fiberglass swimming pools. Whether a new swimming pool application or a restoration, the benefits of using Polyester Coating are clear. The ingredient used in this coating is not an epoxy, chlorinated rubber or flourinated polyurea.

This unique coating system for swimming pool is manufactured by Spraybilt ® and product name is ChloriPur™. ChloriPur™ is a unique polyurea formulation which will outperform all other conventional swimming pool coatings currently available to the specialty coatings industry.

Polyester Swimming Pool Coating System

ChloriPur™ is a high-build, 100% solids, fast-set coating, specifically engineered for chlorinated or chemically treated swimming pools, aquariums or other water features. ChloriPur™ has been tested for continuous water immersion applications where chlorine levels are as high as 250,000 parts per million (ppm). Containing no volatile organic compounds (VOC), this unique product is based on organic chemistry and is not harmful to human or aquatic life.

With natural anti-fouling characteristics, ChloriPur™ is easy to clean and maintain. ChloriPur™ has the most durable, abrasion and impact resistant surface of any swimming pool coating in today's market. ChloriPur™ is spray-applied and produces a completely seamless coating. For complete waterproof protection and a beautiful finish available in six standard colors, specify ChloriPur™ on your next project.

Advantages of Prefabricated Deck System Bridge Components

Bridge components can be prefabricated offsite and assembled in place in Prefabricated Deck System. This is the main advantage of this construction method.Other advantages include removing deck placement from the critical path of bridge construction schedules, cost savings, and increased quality due to controlled factory conditions. However, proper design and construction of the joints must be adequately addressed to ensure adequate performance. 

Partial-depth prefabricated deck panels act as stay-in-place forms and not only allow more controlled fabrication than fully cast-in-place decks, but also could increase the strength of the finished bridge deck due to the utilization of prestressed panels. They have been commonly used in many states; however, there is a reported history of performance problems associated with cracking and spalling of the cast-in-place deck.

The full depth prefabricated panels allow reducing the construction time and thus traffic disruption. For example, the Dead Run and Turkey Run Bridges located on George Washington Memorial Parkway, Virginia needed to be kept open to traffic on weekdays during replacement of bridge decks in 1998. The Dead Run Bridge consists of two structures carrying two traffic lanes each; the bridge is 305 feet long with a three-span configuration (Figure 2.37). The Turkey Run Bridge is also two structures that each carry two lanes of traffic having a length of 402 feet in a four-span configuration. Both bridges have an 8-inch thick concrete deck supported on steel beams with non-composite action. The non-composite aspect of the original design, along with the use of prefabricated concrete post - tensioned full-depth deck panels, facilitated quick deck replacement and allowed the structures to be kept open to daily traffic between Monday morning and Friday evening.

The construction sequence closed the bridge on Friday evenings and included: saw-cutting the existing deck into transverse sections that included curb and rail; removing the cut sections of the deck; setting new prefabricated panels; stressing longitudinal tendons after all panels in a span were erected; grouting the area beneath the panel and above the steel beam; opening the bridge to traffic by Monday morning. This construction sequence allowed the complete replacement of one bridge span per weekend.

Extension of Barcelona Metro: The Deepest Electrified Railways Lines

The Barcelona Metro (Metro de Barcelona) run underground in central Barcelona and above ground into the city's suburbs. There have been 3 driverless lines since 2009: Line 11, Line 9 and Line 10, in chronological order. In 2002 ATM announced that two additional lines would built in the near future, L12 and L13. 


Now a 43 km long extension project is keep going with expected cost of €6.5 billion. When completed, it will be the longest and one of the deepest lines in Europe and the longest metro line in the world of entirely new construction. It will also be the most expensive enterprise the Catalan government has ever undertaken. This project is expected to end in 2012.

This project has made extensive use of precast tunnel lining-segments incorporating steel reinforcement fibres. FRC tunnel ring segments were cast off-site and comprised 7 segments of 4.56m length [48degree length of arc] plus a 24 degree keystone, per ring. Each ring has going-length of 1.80m and is 350mm thick. The lines run as follows:

Network map of Barcelona Metro Lines

Application of Fiber Reinforced (FRC) Composite in Concrete Structures

Recent developments in the field of fiber reinforced composites (FRCs) have resulted in the development of highly efficient construction materials. They have been successfully used in a variety of industries such as aerospace, automobile and ship building The FRCs are unaffected by electro-mechanical deterioration and can resist corrosive effects of acids, alkalis, salts and similar aggregates under a wide range of temperatures. FRCs thus hold a very distinct advantage over steel plates as an external reinforcing device. Moreover, FRCs are available in the form of laminas and different thickness and orientation can be given to different layers to tailor its strength according to specific requirements.
 

The difficulties encountered in using steel plates as reinforcement lead us to the use of fiber reinforced composite materials as post-reinforcements. Due to their high specific strength (strength/weight ratio) the composite reinforcements are very light and easy to handle. The composite materials are available as unidirectional fibers of a huge length. Therefore, joints in the reinforcement can be avoided very easily. Moreover, the corrosion of the reinforcements can be avoided completely. Research work is gaining momentum on the application of composite materials as post-reinforcement (Nanni et al., 1995). The potential use of fiber reinforced composites in civil structures is manifold.

FRCs can be used in the concrete structures in the following forms:

• Plates -at a face to improve the tension capacity. 

• Bars -as reinforcement in beams and slabs replacing the steel bars.

• Cables -as tendons and post tension members in suspension and bridge girders.

• Wraps -around concrete members to confine concrete and improve the compressive strength.

Becoming Popular of Fiber Reinforced Composite in Rehabilitation of RCC Structures

Reinforced concrete is an extremely popular construction material. It becomes versatile with its both compressive and tensile properties. Concrete is naturally strong in compression but its tensile and bending strength is small fraction of compressive strength. This limitation is overcome by introduction of reinforcing steel bars and in case of composite construction, structural steel sections. 

Although hundreds of thousands of successful reinforced concrete and masonry buildings are annually constructed worldwide, there are large numbers of concrete and masonry structures that deteriorate, or become unsafe due to changes in loading, changes in use, or changes in configuration. Also from the recent earthquake of Gujarat it is clear that the old structures designed for gravity loads are not able to withstand seismic forces and caused wide spread damages. Repair of these structures with like materials is often difficult, expensive, hazardous and disruptive to the operations of the building. The removal and transportation of large amounts of concrete and masonry material causes concentrations of weight, dust, excessive noise, and requires long periods of time to gain strength before the building can be reopened for service.

CARBON FIBER COLUMN WRAP

On the other hand, Fiber Reinforced Composite (FRC) materials, originally developed for the aerospace industry, are being considered for application to the repair of buildings due to their low weight, ease of handling and rapid implementation.

The (FRCs) are unaffected by electro-mechanical deterioration and can resist corrosive effects of acids, alkalis, salts and similar aggregates under a wide range of temperatures. This novel technique of rehabilitation is very effective and fast for earthquake affected structures and retrofitting of structures against possible earthquakes. This technique has been successfully applied in the earthquake-affected Gujarat. 

Appropriate configurations of fiber and polymer matrix are being developed to resist the complex and multi-directional stress fields present in building structural members. At the same time, the large volumes of material required for building repair and the low cost of the traditional building materials create a mandate for economy in the selection of FRP materials for building repair. Analytical procedures for reinforced and prestressed concrete and masonry reinforced with FRC materials need to be developed, validated, and implemented, through laboratory testing, computational analysis, full-scale prototyping, and monitoring existing installations.

Impact Resistant Windows and Doors from MC

The strong wind force or flying debris can obliterate windows and doors if shutters are not out up. When there is a hurricane warning, people become worried about their windows and doors which is not designed to withstand such condition. 

MC Impact Windows and Shutters Corp manufactures Hurricane resistant windows and doors that meet or exceed Dade County Impact Protocols. Impact resistant windows and doors complement the architectural elegance of your home and are engineered to withstand hurricane wind force and flying debris.

 

Impact Resistant Glass

These lines of windows and doors are manufactured with aluminum, which is 43 times stronger than wood and 30 times stronger than vinyl. The specially laminated glass has sound insulating properties to reduce noise by 90% and 100% UV protection to protect your artwork, drapes and furniture, as well as provide great energy savings for a cooler, more comfortable ambience.

 

The insulated impact resistant glass is composed of a piece of heavy polyvinyl butyral plastic interlayer sandwiched between two pieces of double–strength glass.

The laminated glass is then combined with another piece of double-strength tempered or anneal glass to form an insulated glass unit. This unit is then sealed together to form a strong, impact resistant bond, which is then glazed into the sash to hold the glass to the frame.

The glazing process uses a structural back bedding system to ensure the entire unit passes impact tests.

Straightening, Bending, Rolling and Cambering of Structural Steel

Material not meeting AST'M A6 tolerances and material that may have become bent or distorted during shipment and handling or in the punching operation may require straightening before further fabrication is attempted. In addition members may become distorted when they are trimmed or, in the case of W, S and M shapes, when they are split into tees. The bend press, generally used for straightening beams, channels, angles and heavy bars, is known commonly as a bulldozer, gag press or cambering press. This machine has a horizontal plunger or ram (or a set of rams or plungers) that applies pressure  at  points along   the  bent  member  to bring it into alignment. Also, the press is used to form long-radius curves in various structural members.

Long plates, which are curved slightly or cambered out of alignment longitudinally, are frequently straightened by a roll straightener. The plates are passed between three rolls. The resulting bending increases the length of the concave side and brings the plates back to acceptable tolerances of straightness.

Misalignments in structural shapes are sometimes corrected by spot or pattern heating. When heat is applied to a small area, of steel, the larger unheated portion of the surrounding material prevents expansion, causing a thickening of the heated area. Upon cooling the subsequent shrinkage produces a shortening of the member, thus pulling it back into alignment. Commonly, this method is employed to remove buckles in girder webs between stiffeners and to straighten members. Heating must be controlled. A special crayon that changes color or melts at a predetermined temperature is often used as a temperature check. 

A press brake is used to form angular bends in sheets and plates. Curved plates used in tanks and stacks are formed in a plate roll machine. 

The foregoing operations can also be used to induce curvature, rather than remove it.