Designs on corrugated steel pipe

Earlier this year, the National Corrugated Steel Pipe Association (NCSPA) conducted its first project awards competition to highlight effective, economical, and varied applications of corrugated steel pipe (CSP). NCSPA members – CSP manufacturers – submitted projects for judging in five categories: Department of transportation, Steel structural plate, CSP arch, Detention/retention, and Rehabilitation. Following are summaries of the top project selected in each category.
Department of transportation
According to the National Weather Service, Duluth, Minn., had its wettest two-day period ever when flood-producing storms washed over northeastern Minnesota on June 19-20, 2012, dropping more than 7 inches of rain. Resultant flooding washed out a drainage structure on Minnesota State Highway 210 (MN 210) at the Jay Cook State Park. The original structure was an 8-foot by 6-foot, cast-in-place concrete box. A major washout of this structure in 2006 removed the top to the concrete box and 72-inch by 120-foot reinforced concrete pipe was placed on top of the existing concrete box.
The June 2012 flooding displaced the 72-inch reinforced concrete pipe. Because of the immediate need to get this major roadway back in service, the Minnesota Department of Transportation (MnDOT) designed a replacement structure consisting of a 144-inch by 180 feet of 10 gauge, Aluminized Type 2, 5-inch by 1-inch profile CSP. MnDOT placed an order with TrueNorth Steel on July 11, 2012, and the initial load for this order was ready for delivery July 16. Other design amenities included riprap of the upstream outlet and downstream discharge areas. MnDot also designed concrete headwalls at the upstream and downstream ends of the corrugated steel structure.
MnDOT required that the structural design of the 144-inch structure be analyzed as a bridge because of the large size. Structural calculations were based on American Association of State Highway and Transportation Officials (AASHTO) Standard Specification for Highway Bridges, LRFD Bridge Design Specifications. Design analysis used was HL 93 loading.
The 180-foot structure was placed in four, 45-foot sections. Each section was delivered from the TrueNorth Steel, Fargo, N.D., plant in individual loads on a 48-foot trailer. Reuben Johnson and Son, Superior, Wis., was the contractor for construction of the new drainage structure and connecting headwalls. The contractor started at the outlet end by placing the concrete footing for the headwall. The pipe was connected to the headwall with anchor bolts spaced at 12 inches, center to center, embedded in the concrete headwall and attached to the pipe through predrilled holes in the corrugated steel.

The Minnesota Department of Transportation quickly replaced a washed out drainage structure beneath a state highway with 144-inch-diameter by 180-foot-long, 10 gauge, Aluminized Type 2, 5-inch by 1-inch profile corrugated steel pipe with concrete headwalls.

All construction was completed for the drainage structure and backfilling of the pipe on Aug. 6, 2012. The roadway was paved and open for traffic on Aug. 16.
"RJS Construction has installed many large [CSP] culverts over the years, and this project was one of the more unique challenges we had encountered given the site conditions and schedule, said Steve Picha, RJS project manager. "By using [CSP] pipe on this project, it allowed for the road to be opened quickly in order to restore access to Minnesota Power. Our crews enjoyed the flexibility to maneuver the pipe on a site that did not allow area to store material. The relatively light weight of [CSP] pipe as compared to concrete prevented us from having to bring in a large crane to set the pipe. That alone saved MnDOT considerable amount of time and money."
Information provided by TrueNorth Steel
Steel structural plate
Another phase of the famed Coalfields Expressway started in April 2010, continuing its southwesterly wind through the mountainous coal regions of southern West Virginia into southwestern Virginia. Corridor improvements to mitigate no-passing zones and areas of reduced speeds and to alleviate steep grades required filling a ravine on this $23.4 million, 2.02-mile stretch.
Providing ample drainage along the bottom of that ravine called for sizable pipe buried as much as 165 feet deep. The solution was found in the strengths and sizes available with CSP, in this case steel structural plate (SSP). Under the circumstances, SSP became the only viable option and subsequently was incorporated into the West Virginia Department of Transportation (WVDOT) project specifications.
Corrugated SSP is shipped to the site in curved plates and field assembled into its final shape by bolting. SSP can be produced in heavier gauges than that typically used for conventional CSP. Designers called for a 96-inch pipe to handle the expected drainage. At this size and depth, WVDOT specified the maximum plate thickness of 3/8 inch.
Shipments from the plate manufacturer (Lane Enterprises Inc.) began in July 2010, with assembly slated to commence the week of July 19. The 863-foot alignment included 490 plates, altogether weighing more than 250 tons. Directional changes in the alignment were facilitated with structural plate elbows. The ability to incorporate elbows into the alignment eliminated the need for manholes, deep shafts, or other costly alternatives, and at the same time provided structural continuity to the enclosure.
Project specifications required the plate manufacturer to corrugate, punch, and curve 3/8-inch plate, the thickest plate material recognized in AASHTO material specifications. This thickness requires eight 7/8-inch bolts per foot (instead of the usual four 3/4-inch bolts) to provide greater seam strength, resulting in a total of 46,000 bolts for the enclosure.
At 0.38 inch thick with a galvanized coating on each side, the 6-inch by 2-inch corrugated plate is still considered a flexible pipe material that derives its structural integrity from the soil-structure interaction system developed with a structural backfill. Project specifications called for well-graded crushed stone select material. This material provides maximum stability and pipe support for a given density due to the angular interlock particles. Compacted in lifts equally on each side of the pipe to a height of 2 feet above the crown, the composite action mobilizes the full compressive strength of the corrugated steel plate.
Standard plate widths are designated by N, the number of 9.6-inch bolt spaces along the circumferential seam. To obtain the N value, the diameter is divided by three. With N determined, any combination of the five plate widths available (3N, 5N, 6N, 7N, 8N, and 9N) can be used to form the pipe section. The ring of the 96-inch-diameter pipe consisted of six plates, four 5N plates and two 6N plates. The 6N plates were placed at the invert and crown with the 5N plates in the remaining positions.

Directional changes were facilitated with steel structural plate elbows, which eliminated the need for manholes, deep shafts, or other costly alternatives and provided structural continuity to the 96-inch-diameter, 863-foot-long pipe buried as much as 165 feet deep beneath the Coalfields Expressway.

A total of 490 plates were needed for the 863-foot alignment, with standard lengths of 10 and 12 feet to ensure that seams are appropriately staggered. On average, the six-man assembly crew installed around 16 plates per day, longitudinally equating to 30 feet. The assembly began around July 19, 2010, and was substantially complete by the end of August – a good pace considering bolt quantities were doubled, as noted above.

Corrugated steel pipe arch
The Southwestern Illinois College, located in Belleville, Ill., expanded its campus with the addition of a Liberal Arts Complex and was required to develop a parking lot on land across from a drainage ditch that split the property. Just north of campus was the Green Mount Commons retail plaza that was upstream from the university. Winter runoff created a corrosion issue that needed to be addressed in the design of this bridge project. Concentrated road salts and chemical additives for ice and snow melt reduced project life to 20 years in some cases.
Southwestern Illinois College contracted with Hoelscher Engineering to investigate options for a cost-effective "best alternative" for accessing the land with a bridge product that would outlast the project life.
Metal Culverts Inc., Jefferson City, Mo., provided the chosen solution. The culvert solution was an 80-foot run of 8 gauge, polymer-coated, 3-inch by 1-inch (3x1) corrugation, arched pipe measuring 137-inch span by 87-inch rise (114-inch round pipe). Hoelscher Engineering wanted a product that met the state of Illinois specification as well as provided a 100-year service life. The specification called for 8 gauge corrugated metal pipe. Dow Chemical's Trenchcoat product covering 2-ounze galvanized coated steel met the 100-year design life requirement.

An 8 gauge, polymer-coated, 3-inch by 1-inch corrugation, arched pipe measuring 137-inch span by 87-inch rise is expected to provide a 100-year service life in spite of corrosive runoff from an adjacent parking lot.

Baxmeyer Construction Inc. of Waterloo, Iowa, was chosen as the excavator for the project. The pipe was installed during the fall of 2011 with the project fully completed in the spring of 2012. This installation was the first known installation of 8-gauge galvanized steel with 3x1 corrugation that was polymer coated with Dow Chemical's Trenchcoat product. Metal Culverts, Inc. subsequently has provided a significant number of bridge and bridge replacements featuring 8-gauge polymer-coated galvanized steel.
Information provided by Metal Culverts Inc.
Retention/detention
Federal regulations and prolonged draught in Georgia have forced engineers and specifiers to become creative in storage and reuse of rain water. The University of West Georgia has expanded rapidly during the last several years and has asked design engineers to be resourceful when creating plans for their new developments. The university recently built new student housing with expansive green space and instead of using municipal water sources for irrigation it requested a cistern to store water from the roof drainage system.
Onsite Civil Group designed a three-tank system using 96-inch Aluminized Type 2 CSP. The cost of the CSP system was far below comparable products. There was only one problem – CSP has an allowable leakage rate according to AASHTO specifications, and cisterns are meant to be water tight. The cisterns were manufactured by Southeast Culvert Inc. (SEC), which had to use its expertise in fabrication to accomplish the goal of total water retention.
The tanks were run on long 50-foot sections and bulkheads were welded to each end. The pipe for the tanks was made custom; to achieve the leak-resistant tanks SEC manufactured the pipe with a special gasket run into the lock seam of the pipe – a point of potential leakage. The three tanks were connected using 24-inch flanged pipes with a rubber gasket compressed between the flanges. Each tank had an access manhole riser for inspection.
Once the tanks were complete, they were tested for water tightness at SEC's facilities in Winder, Ga. They passed. The tanks were shipped to the university where they were installed in place and again filled with water to test the installation practice. During a four-day period, the tanks lost less than 1/4 inch from the pump housing and all parties involved were satisfied with the performance. The cisterns will be a long-term positive for the university as it can save money on water for irrigation through stormwater reuse.

A cistern for the University of West Georgia uses a three-tank system comprising 96-inch Aluminized Type 2 corrugated steel pipe with bulkheads welded to each end. Pipe for the tanks was manufactured with a special gasket run into the lock seam of the pipe. The three tanks were connected using 24-inch flanged pipes with a rubber gasket compressed between the flanges.

Rehabilitation
Only a year after installing a triple, 60-inch-diameter reinforced concrete equalizer pipe under 30 feet of cover at Mitchell Interchange on I-94, just south of Milwaukee, the Wisconsin Department of Transportation (WisDOT) found that the pipe needed to be relined because of structural cracks. After considering its options, WisDOT chose Hel-COR pipe by Contech Engineered Solutions as more economical than two alternative products.
HEL-COR offers a wide range of wall thicknesses, corrugations, diameters, and pipe section lengths to meet any specific job requirements. Durability requirements are addressed by a variety of materials. For this project, WisDOT specified 54-inch-diameter Aluminized Type 2, 5-inch by 1-inch galvanized HEL-COR pipe instead of solid-wall HDPE.
Benefits of HEL-COR pipe include a proven service life that can exceed 100 years with proper specification, sustainability from recycled material, strength, flexibility, versatility, and lightweight material. By using homogenous material, HEL-COR eliminates failures caused by stress cracks, shrinkage cracks, and air voids.
In this project, 10 c internal expanding bands were used with flat gaskets. During install, the pipe was stage grouted in three lifts, and had two grout plugs in each piece of 20-foot pipe length.
WisDOT also chose to further protect the pipe by adding zinc chromate paint to the pipe exterior (a yellow coating on the pipe). The purpose of this extra protection was to protect the aluminized coating from the flowable fill during the curing process.

The Wisconsin Department of Transportation selected 54-inch-diameter, Aluminized Type 2, 5-inch by 1-inch galvanized corrugated steel pipe to line a cracked reinforced concrete pipe under 30 feet of cover at Mitchell Interchange on I-94, just south of Milwaukee. A zinc chromate paint (yellow coating) on the pipe exterior protects the aluminized coating from the flowable fill grout during curing.

Erection Bracing of Low-Rise Structured Steel Buildings

In high-rise construction and bridge construction the need for predetermined erection procedures and temporary support systems has long been established in the industry. Low-rise construction does not command a comparable respect or attention because of the low heights and relatively simple framing involved. Also the structures are relatively lightly loaded and the framing members are relatively light. This has lead to a number of common fallacies which are supported by anecdotal evidence. This article will guide you how to carry out the erection of steel structures for low-rise buildings step by step.
Three of the most important things that are to be noted before starting the job is as follows
(a)    After receiving the building package and before storing, all the items are required to be checked for any defects and quantities as per the list, if a single part is missing, the entire work will suffer. Hence the owner should make a check list of all the items and verify it while receiving.
(b)    Materials needs to be properly stored and handled at site during construction to avoid any undue damage.

(c)    The owner should ask the contractor an erection plan as well as safety action plan for executing the job.
Following are the broad steps for erection of bracing and other parts of low-rise structured steel buildings
A.     Site and Foundation Preparation
B.     Building Delivery and Storage
C.     Erection of Primary, Secondary Structural and Doors and Windows
D.     Sheeting (Wall and Roof)
A. Site and Foundation Preparation
Before doing the concrete foundation it is extremely important that foundation should be properly checked for its width and length and most importantly for equality of both the diagonals. After this all the column locations to be marked on the foundations very accurately and anchor bolts to be fixed then. This is a very important step, as any mistake in this step will effect the entire erection programme, since all the structures are fabricated for predetermined sizes and mistake in any span would give birth to complexity in the erection process. Hence great care to be taken while carrying out the anchor bolt setting plan. All anchor bolts should be held in place with a template or similar means, so they will remain plumb and in the correct location during placing of the concrete. Check the concrete forms and anchor bolt locations prior to the pouring of the concrete. A final check should be made after the completion of the concrete work and prior to the steel erection. This will allow any necessary corrections to be made before the costly erection labor and equipment arrives.
 
B. Building Delivery and Storage
While receiving the materials at site, place the parts around the foundation so they will be in the most convenient locations for installation. For example: place the end columns and rafters at the ends of the building and the mainframe columns and rafters at the sides. Place the bolts and nuts in a place where they will be accessible to the parts. You may want to screw the bolts and nuts together and place them with the corresponding parts. This will save time as you begin assembling the parts and also will reduce your time and cost for re shifting the materials again to the location of erection. Purlins and girts, depending on the number of bundles, are usually stored near the sidewalls clear of other packages or parts. Sheet packages are usually located along one or both sidewalls off the ground and sloping to one end to encourage drainage in case of rain. Accessories are usually unloaded on a corner of the slab or off the slab near one end of the building to keep them as much out of the way as possible from the active area during steel erection. For storage of sheets it is recommended to be stored under roof if at all possible. If sheets are to be stored outside, the following precautions should be observed:
1.     The storage area should be reasonably level, and located so as to minimize handling.
2.     When stored on bare ground, place a plastic ground cover under the bundles to minimize condensation on the sheets from ground moisture.
3.     Store bundles at least 12 inches above ground level to allow air circulation beneath the bundle, and to prevent damage from rising water.
4.     Elevate one end of each bundle slightly to permit runoff of moisture from the top of the bundle or from between sheets. A waterproof cover should be placed over the bundles to allow for air circulation under the cover.
5.     Inspect stored bundles daily and repair any tears or punctures in the waterproof cover.
6.     Re-cover opened bundles at the end of each workday to prevent subsequent moisture damage.
C. Erection of Primary, Secondary Structural and Doors and Windows
 
General
Many methods and procedures are in use for erecting the structural portion of metal buildings. The techniques of raising frames vary from erecting small clear spans and endwall frames in units to erecting the larger clear spans and modular frames in sections. The erection methods used depend strictly on the type of building, the available equipment, the experience level of the crews, and the individual job conditions. The variations in these factors preclude the establishment of a firm or specific set of erection rules and procedures. Consequently, the erection operation must be tailored by the erector to fit individual conditions and requirements. However, there are certain erection practices, pertaining to structural members, which are in general use and have
proven sound over the years and which can be followed for erection in all the places. In every condition Erectors are cautioned not to cut primary members (rigid frame columns, rafters, end bearing frame rafters, interior columns). These are the primary support members for the frame and are designed as such. Any cutting of these members may affect the structural stability.
The intermediate or interior frames nearest the bearing endwall are usually erected first. This bay usually contains the diagonal bracing. The proper completion and plumbing of this first bay is extremely important to the successful completion of the building.
Although several methods are used to erect rigid frames, it has been found
most satisfactory to erect the columns first, tie them together with the girts and tighten the anchor bolts. On small spans and short eave heights, columns can often be set in place by hand without the use of hoisting equipment. Temporary bracing should always be installed as soon as sections are lifted in place (See Figure 1). Once this is over the structure is ready for girt erection. At first it is needed to put one screw in the end of each girt.
At the corners put 2 screws in the end of the girts. The girt erection is shown in Figure 2a and 2b.
Once the sidewalls have been stood and all girts are on them, wind rod braces needs to be installed (See Figure 3a and 3b). These go in the same bay on both sides, preferably near the center of the length of the building. Care should be taken that these are not installed where there is a door or window opening. Once installed, these can be used to adjust the columns to be plumb. Once the columns are plumb make sure everything is snug.
    
After this attach the girts to the clips on the column and end wall legs using a single tek screw in each end. After ensuring that columns are straight then only attach the knee braces to the girts. The knee braces will bolt to the column or truss and attach to the girt with a tek screw. If columns are twisted it is needed to straighten them before attaching the knee brace (See Figure 4).
After erection of columns and installation of girts on the sidewalls the structure is ready for the roof trusses erection (See Figure 5,6). Roof trusses should be bolted together on the ground and lifted into place. Two important point to be noted before truss erection is as below
    
(a)    Knee brace angles should be installed on the truss before lifting into place.
(b)    If building is wider than forty feet it is recommended that a spreader bar should be used to pick up the trusses. If it is not used, the truss may fold in the middle and cause damage.
Knee brace fixing to the roof truss and attaching roof truss to the legs is shown in Figure 7 and 8 below.
    
     
Attaching purlins to the truss top with joint details is shown in Figure 9 and 10
Installation of wind braces in the roof truss in the same panel where it is attached in the wall is shown in Figure 11. Figure 12a and 12b shows installation of eave clip to the end of pulin.
How to Make a Framed Opening (See Figure 13a and 13b)
1.     Measure the size of the door or window to determine the size opening required.
2.     Mark the girts where you want to position the opening.
3.     Cut the girts with your abrasive saw.
4.     Slide the track over the end of the cut girts to form the opening.
5.     Insert the door or window into the opening and square it so that it functions properly.
6.     Fasten the track to the girts with tek screws and fasten the door or window to framed opening.
7.     Attach J trim with colored screws if it isn’t part of the door or window frame.
Once this step is complete the sheeting job can be started. However before proceeding for sheeting job, it is necessary to recheck and make sure everything is properly installed at this point. If anything is missing it is the time to go back and fix it before sheeting job is started.
    
Checklist for the erection job (To be carried out prior to start if sheeting job)
1. Columns and Endwallcolumns
-    All columns are properly located
-    All columns are plumb
-    All bolts are in place and tightened
    
2. Roof Trusses
-    All roof trusses are properly in place
-    All bolts are in place and tightened
-    Building is plumb
3. Purlins and Girts
-    All purlins and girts are in place and well attached
-    Fascia purlins are installed
-    6” gable track is installed
4. Bracing
-    All knee braces are bolted and tightened on columns and roof trusses
-    All knee braces are screwed to girts and purlins
-    All wind brace rods are in place
-    All wind brace rod nuts should be snugged down against the clip after building is plumb
D. Sheeting (Wall and Roof)
After completing the check the structure is ready for sheeting erection. Gang drill is recommended for drilling the sheets. The process is shown in Figures 14, 15 and 16. Not more than 20 sheet panels to be stacked together.
Wall panels are installed before roof. Base trim must be attached first with 4 screws per piece. At every location the verticality of the wall panel is to be checked.
Once the wall panel is installed, next step is installation of roofing sheets (See Figure 18). After the roofing installation it is required to check whether all the bolts caps and washers are in place or not otherwise there is possibility of leakage during rains.
Final step is to put the corner corner trim and gable trim (See Figure 19a) and end cap ( See Figure 19b).
Conclusion
It is recommended to go through across the building after completion of the work to ensure that there are no missing screws or loose parts. Everything should be checked twice to make sure it is tight and secure. During the entire construction period the owner should look after the safety aspect of the work very carefully viz. personal protective equipment’s are allotted to every worker or not, safety nets are there or not, lifting capacity of the crane/chain pulley etc. It is also recommended to make a proper work schedule day wise before starting the work in along with the contractor which will help the owner to keep a track on the erection process and avoid getting undue delay in the work.

Introjected Backfil Retaining Walls: A Revolutionary Technology to Reduce the Cost of Retaining Walls

It’s hard to imagine civil engineering projects without retaining walls. What is also true is that these retaining walls consume large amount of resources and space. Any economy in the retaining walls is therefore, always welcome. Now, the question arises as to how can one achieve this objective, without compromising on the quality front? Thankfully, now a solution is available in the form of a revolutionary technology “Introjected Backfil Retaining Walls”, developed by engineering consulting firm StrongGid Technologies.
StrongGid Technologies has been formed by a group of researchers and academicians and have been pioneering the inventions of many technologically sound, yet cost-effective solutions in the field of Geotechnical Engineering and Concrete Technology. ”: The technology of “Introjected Backfil Retaining walls” was invented in the year 2001 by Prof. D.R.Phatak (Retd. Professor College of Engineering, Pune) along with his student Prof. S.S.Sabnis, both part of the consultancy firm. The invention, a design innovation, is under Intellectual property rights (I.P.R’s) and is under successful implementation since from 2001. In the last three years, retaining walls worth ` 100 crore have been constructed using this technology benefiting many government and non-government organizations.
The technology has been extensively used by Govt. of Maharashtra (Water Resources Department and MSRDC) in bridge approaches and abutments, roads, irrigation projects, river training works and underground water tanks. For example, the technology has been utilized for a height of 26m by the Water Resources Department, Government of Maharashtra at Sawant-wadi near the Goa border. Another good example is available in the form of a project of Mahindra Vehicle Manufacturers Ltd, Chakan, in 2011, wherein about 3. 5km length of retaining walls with a height variation of 5m to 15m was constructed using the technology. The estimated cost of the retaining walls using conventional technique was ` 24 crore. However, by using the technique of “Introjected Backfil Retaining Walls,” the entire work was accomplished in
` 14 crore, a saving of ` 10 crore.
The technology is gaining in popularity and is being presently used by several private parties, including MNCs and infra companies to reduce the cost of constructing retaining walls. Using this technology, equity can be saved on various earth retaining structures inclu-ding, (1) Port and sea front walls, berthing walls, (2) Guide walls, divide walls in dam structures, (3) Wing walls and returns of bridges, culverts, viaducts and aqueducts, (4) Property confinement retaining walls, (5) Concrete dams, (6) Bridges spanning upto 40 m, (7) Underground oil and water tanks and (8) Underground sewage treatment plants.

Conventional Retaining Walls and their Drawbacks
The most common types of retaining walls practiced are as follows:
1.    Gravity
2.    RCC Cantilever
3.    Counterfort
Gravity retaining walls
The Gravity retaining walls are easy to construct as these involve huge amount of construction material in the form of concrete or stone masonry. The earth retention is done purely by means of the body weight of the wall and hence these walls are bulky. The base width required is 0.55 to 0.65 (Fig. 1) times the height for the wall to become stable.
RCC Cantilever retaining walls
The RCC Cantilever retaining walls retain the load of the sliding earth mass purely by the reinforcement provided in the slender concrete members (Fig.2). These walls are suitable upto about 6 m height and involve huge amount of closely spaced reinforcing bars. The quantity of reinforcement may vary between 70 to 110 kg /cu.m (1 to 1.2% of concrete quantity) for these walls. The base width required is 0.6 to 0.7 times the height for the wall to become stable.
RCC Counterfort retaining walls

The RCC cantilever retaining walls are provided with counterforts when the height exceeds 6m (Fig.3). The support in the form of counterforts facilitates raising the height of the retaining wall above 6m. But all this comes at the cost of more reinforcement and higher grade of concrete. The quantity of reinforcement may vary between 70 to 110 kg /cu.m (1 to 1.2% of concrete quantity). The base width required is 0.6 to 0.7 times the height, for the wall to become stable.
The major drawback of the commonly used conventional retaining walls is that they consume lot of resources and require great space to accommodate them.
When analyzing the role of civil engineers who use conventional retaining walls, it is seen that the site engineers have an inherent tendency to make some economy while using conventional retaining walls on the site. The economy is routinely achieved on the site by means of the following methods:
-    Use of stone masonry instead of concrete
-    Use of plums or greater MAS to make concrete
-    Change of the geometry of the walls
These routine methods of achieving economy results in a limited economy of 2 to 3 % and involve greater supervision and maintenance. Stone masonry is suitable only upto a height of 3 to 4 m as the wall demands more space for accommodation. The maintenance of the stone masonry wall may also go up in a span of 5 to 6 years. Additionally, some times the local people are also tempted to remove the stones from the constructed masonry wall for other uses. The use of plums and greater mean aggregate size to make concrete results in limited economy but at the same time the mix design of concrete has to be affirmed for its effectiveness. The method of change of geometry of walls to achieve economy results in cluster of calculations which are to be checked and re-checked for accuracy and often involves skepticism of the higher authorities before giving approvals. Often it is seen that the economy in such cases also does not exceed 3 to 4 %.
When all these factors are taken into consideration, it leads to a million dollar question- “whether any technology or methodology of retaining wall design is available, which will miraculously change the economics of the project?” Fortunately, the answer is available in the form of ‘Introjected Backfil Retaining Walls.’
 
Aqueduct Project in Sawantwadi
A relatively recent project is a testimonial to the efficacy of the technology, both in terms of obtaining quality construction, and also in terms of cost-effectiveness. The project shown in Fig.4 is an aqueduct which is carrying water from Tilari dam to Sawantwadi town and is situated on the right bank canal. The water from the Tilari dam flows in the right bank canal; passes through a tunnel of length of 1.5 km in the mountain as shown. Immediately after the mountain is a valley (in Fig. 4 the truck is standing in the valley). After the valley, again there is a hillock. Since the canal flowing through the tunnel in the mountain cannot be brought down in the valley, an aqueduct, as shown, was proposed in the year 2007. The aqueduct portion got constructed and even the tunnel face was opened and completed. The problem remained of the connecting canal between the aqueduct and the tunnel mouth. For this were required wing walls of height 26 m which are nothing but retaining walls, which would retain earth and ultimately the earth will support a canal through it.
The wings walls by conventional method (gravity type) required a base width of about 18 m. It was getting difficult to accommodate the 18 m base width of the conventional retaining walls because any excavation near to the mountain was making it unstable. Hence this technology was proposed by the Irrigation Department of Government of Maharashtra. The “Introjected Backfil Retaining Walls” technology required a base width of only 6.5 m. The stability parameters like factors of safety in overturning and factor of safety in sliding were more than 4 both in Static and Seismic conditions. The grade of concrete proposed in the wall body was M15, as the durability considerations demanded the minimum grade as M15. All the designs satisfied the Indian Codal provisions.
Not only did the technology ensure cost savings to the tune of about 27% over conventional retaining walls, it also solved the problem of space restriction. The structure has been operational from the last four years.
Salient features of the technology
Base Width: The base width of the wall is ½ to 1/3 of the conventional re-taining walls. The wall requires simultaneous backfilling during the construction process of the wall.
Concrete Grade: The “Introjected Backfil Retaining Walls” can be constructed in a concrete grade of M15. Only if the durability considerations demand a higher grade of concrete then only the grade of concrete needs to be upgraded for these walls, otherwise a concrete grade of M15 is suitable for the construction of there wall.

Reinforcement: The quantity of reinforcement required in “Introjected Backfil Retaining Walls” is between 8 to 20 kg per cu.m of concrete only.
Stability: The walls are safe both in static and seismic conditions and satisfy the Codal provisions for stability in both static and seismic conditions. The “Introjected Backfil Retaining Walls” are more stable than conventional retaining walls for the same height. The factors of safety in static conditions and seismic conditions are nearly double that of conventional retaining walls.
The construction of “Introjected Backfil Retaining Walls” is straight and does not require any batter to any face of the wall. It is the experience of the Inventors that the time required to construct “Introjected Backfil Retaining Walls” is less than conventional retaining walls of the same height. The technology can be implemented to unlimited heights.
No concerns in implementation of the technique: The material of construction remains the same as the conventional walls with no special demand for formwork or backfill material. The wall design fits as per the tender requirements with no special demand for any new item of construction. The wall design is flexible enough to adapt to the items of the existing tender and hence successfully implemented in many projects which were incomplete either due to technical reasons or due to inadequate funds.
Base width remains same even after change of height: It is seen in conventional walls that the base width changes whenever there is a change in the height of the retaining wall. The construction procedure for conventional retaining walls becomes clumsy when there is abrupt change in the height of the walls in shorter distances e.g. Wings walls/return walls of bridges. In such cases, the “Introjected Backfill Retaining Walls” maintains same base width which helps in ease and speedy construction.
 
Uniform Pressure Distribution below Walls: The wall maintains uniform pressure distribution. This is explained in Fig. 5.
Hence these walls are extremely stable in areas of low bearing capacity also.
Economy: The “Introjected Backfil Retaining Walls” give an economy between 25 to 35% over the conventional retaining walls without compromising any strength or stability parameters still satisfying the codal provisions. Interestingly, as the height of retaining walls increases the economy due to “Introjected backfil retaining walls” also increases. This is for the reason that the increase in the wall section and reinforcement is nearly proportional to the height of retention in case of conventional retaining walls. This proportionality is not followed by the “Introjected backfil retaining walls”.
On an average, the conventional retaining walls require a B/H ratio (Base width to height ratio) of about 0.65 and reinforcement in the range of 70 to 110 kg/cu.m of concrete, whereas for “Introjected backfill retaining walls” the ratio of B/H is between 0.25 to 0.35 and the requirement of reinforcement is between 10 to 25 kg/cu.m of concrete (i.e. 0.2 % of concrete quantity).

 
Cost Economics of “Introjected Backfil Retaining Walls”: The graphical representation in Fig.6 below shows the variation of cost between “Introjected Backfill Retaining Walls” and conventional retaining walls.
Another major achievement of the technology has been the fact that till date it has been found to be ideally suited to nearly all types of strata.

Types of steel bending..........

Types of Bending
 
(A) Air Bending
It is a bending process in which the punch touches the work piece and the work piece does not bottom in the lower cavity. As the punch is released, the work piece springs back a little and ends up with less bend than that on the punch (greater included angle). This is called spring-back. The amount of spring back depends on the material, thickness, grain and temper. The spring back will usually range from 5 to 10 degrees. The same angle is usually used in both the punch and the die to minimize set-up time. The inner radius of the bend is the same as the radius on the punch. In air bending, there is no need to change any equipment or dies to obtain different bending angles because the bend angles are determined by the punch stroke. The forces required to form the parts are relatively small, but accurate control of the punch stroke is necessary to obtain the desired bend angle.
 
(B) Bottoming
Bottoming is a bending process where the punch and the work piece bottom on the die. This makes for a controlled angle with very little spring back. The tonnage required on this type of press is more than in air bending. The inner radius of the work piece should be a minimum of 1 material thickness. In bottom bending, spring-back is reduced by setting the final position of the punch such that the clearance between the punch and die surface is less than the blank thickness. As a result, the material yields slightly and reduces the spring-back. Bottom bending requires considerably more force (about 50%~60% more) than air bending.
 
(C) Coining
Coining is a bending process in which the punch and the work piece bottom on the die and compressive stress is applied to the bending region to increase the amount of plastic deformation. This reduces the amount of spring-back. The inner radius of the work piece should be up to 0.75 of the material thickness.
(D) V Bending
In V-bending, the clearance between punch and die is constant (equal to the thickness of sheet blank). It is used widely. The thickness of the sheet ranges from approximately 0.5 mm to 25 mm.
 
(E) U Die Bending
U-die bending is performed when two parallel bending axes are produced in the same operation. A backing pad is used to force the sheet contacting with the punch bottom. It requires about 30% of the bending force for the pad to press the sheet contacting the punch.
(F) Wiping Die Bending
Wiping die bending is also known as flanging. One edge of the sheet is bent to 90 while the other end is restrained by the material itself and by the force of blank-holder and pad. The flange length can be easily changed and the bend angle can be controlled by the stroke position of the punch.
 
(G) Double Die Bending
Double die bending can be seen as two wiping operations acting on the work piece one after another. Double bending can enhance strain hardening to reduce spring- back.
(H) Rotary Bending
Rotary bending is a bending process using a rocker instead of the punch.
The advantages of rotary bending are:
- Needs no blank-holder

Compensates for spring-back by over-bending
- Requires less force
- More than 90 degree bending angle is available
General bending guidelines are as follows:
- The bend radius should, if possible, be kept the same for all radiuses in the part to minimize set up changes.
- For most materials, the ideal minimum inner radius should be at least 1 material thickness.

 The minimum flange width should be at least 4 times the stock thickness plus the bending radius. Violating this rule could cause distortions in the part or damage to tooling or operator due to slippage.
- Slots or holes too close to the bend can cause distortion of these holes. Holes or slots should be located a minimum of 3 stock thickness plus the bend radius. If it is necessary to have holes closer, then the hole or slot should de extended beyond the bend line
- Dimensioning of the part should take into account the stack up of dimensions that can happen and mounting holes that can be made oblong should be.
- Parts should be inspected in a restrained position, so that the natural flexure of the parts does not affect measurements. Similarly inside dimensions in an inside bend should be measured close to the bend.
Some Structures with Steel Curving (Bending)/ Examples of Steel Curving (Bending)
McDonald’s Arches
Chicago Metal Rolled Products have curved large rectangular tubing to form the parabolic arches for the new flagship McDonald’s which opened in downtown Chicago. The tube bending company matched the customer-supplied templates putting multiple radiuses into 50-foot-long tube to minimize costly weld splices and to reduce the time required for fabrication and erection on the fast-paced project. To meet the project’s tight schedule, Chicago Metal completed all the tube bending within three days after the customer supplied the material. The new design has two 60-foot-tall arches that span much of the entire site and help support the roof of the two-story restaurant. Each large arc is comprised of two 20 x 12 tubes covered by plate on all four sides. The arches are 20 inches wide and vary in thickness from 36 inches at the base to 24 inches at the top (Refer to Figure 1, 2 and 3).
University of Phoenix Stadium
For the roof trusses of the University of Phoenix Stadium in Glendale, Arizona, Chicago Metal Rolled Products’ tube bending machines curved 402 tons of 12 x 12 x 5/8 and 12 x 12 x ½ square tubing to a variety of radiuses from 1000 to 1200 feet. Across the width of the field span 256-foot-long lenticular trusses so-called because both the top and bottom chords are curved, creating a profile that resembles a convex lens. Tube bending from Chicago Metal Rolled Products of sixteen such trusses are incorporated in the two retractable roof panels. (See Figure 4 and 5).
Illinois Institute of Technology Train Tube
A new McCormick Student Center at the Illinois Institute of Technology in Chicago, designed by Dutch architect Rem Koolhaus, was to be linked to Chicago’s elevated “El” train system. Koolhaas’ solution to train noise was to create a steel-and-concrete tube to encase trains as they pass over the single-story, building. Beam bending provided by Chicago Metal Rolled Products produced 104,000 pounds of W12 x 58# beams the “hard way” to form a series of half ellipses with radiuses of approximately 12’, 24’ and 34’. (See Figure 6).
Ratner Athletic Center at the University of Chicago
Beam bending to form a reverse curve saved over $24,000 worth of weld splices (See Figure 7).
Fabricators in U.S. claim to put curves into wide-flange beams up to 44 inches tall that weigh 285 pounds per foot and do it “the hard way”—along the longest axis of the cross section. Its latest equipment acquisition is the largest beam roller ever built for anyone (See Figure 8).

The Fine Art of Steel Bending

Steel curving/bending is a manufacturing process by which metal can be deformed by plastically deforming the material and changing its shape. The material is stressed beyond its yield strength but below its ultimate tensile strength. There is little change to the materials surface area. Bending generally refers to deformation about one axis only. Bending is a flexible process by which a variety of different shapes can be produced though the use of standard die sets or bend brakes. The material is placed on the die, and positioned in place with stops and/or gages. It is held in place with hold- downs. The upper part of the press, the ram with the appropriately shaped punch descends and forms the v-shaped bend. Bending is done using Press Brakes. Press Brakes can normally have a capacity of 20 to 200 tons to accommodate stock from 1m to 4.5m (3 feet to 15 feet). Larger and smaller presses are used for diverse specialized applications. Programmable back gages, and multiple die sets currently available can make bending a very economical process.
Steel Curving/ Bending allows to create various architectural shapes, which is not feasible with traditional way of construction. It also allows considerable savings in the construction cost and the durability aspect of the structure is an added bonus. This story aims to provide the readers with the existing methods of bending, types of bending processes. At the end a few case studies are taken to give readers an over view of what wonders can be created with steel curving/ bending.
Methods of Bending
There are five typical methods of bending in the industry: rolling, incremental bending, hot bending, rotary-draw bending, and induction bending. Each method has its advantages. Some methods are more commonly used in the steel construction industry, while others are more common in the automobile or manufacturing industries:
- Rolling (cold bending) is the typical method of curving steel for construction and is usually the most economical for rolling members with tighter radii. A steel member is placed in a machine and curved between three rolls. Cold bending may also be called “pyramid rolling” because of the three rolls’ pyramid arrangement. Bending occurs when the distance between these rolls is manipulated before each successive pass.
- Incremental bending or gag pressing is usually used for cambering and curving to very large radii. Bending is achieved by applying point loads with a hydraulic ram or press at the member’s third point.
- Hot bending is where a structural member is heated directly and then bent. The heat source could be a direct flame or furnace. This application is used extensively in repair.
- Rotary-draw bending is where the structural member is bent by rotating it around a die. The member is clamped into a form and then is drawn through the machine until the bend is formed. This method produces tight radii and is mainly used for complicated bends in the machine and parts industry.
- Induction bending uses an electric coil to heat a short section of a structural member, and then that member is drawn through a process similar to rotary-draw and cooled with water directly after. In some cases, this process can produce a smaller, tighter radius.

IT’S ALIVE Buildings in Year 2050

 

The United Nations estimates that the urban population of emerging economies will surpass the rural population in 2020, and that around 70% of the world’s population will live in cities by 2050. The risk for cities experiencing this concentration of population is that the numerous urban issues they are currently experiencing will become even more severe. Such explosive growth will place immense pressures on infrastructure, ecosystem services, and social development. These challenges – combined with the pressing needs of climate change – require buildings that become “smarter” in how they provide services for their residents.

In its report, “Its Alive”, ARUP consultants has made an effort towards envisioning a next gen building in the year 2050 -a dynamic, living organism that adapts to the local environment by engaging with the users within through a complex network of feedback loops characterized by smart materials, sensors, data exchange and automated systems that merge together and perform the role of a highly sensitive nervous system. The building’s structure is highly adaptable and structural systems merge with energy, lighting and façade systems to provide a new type of urban experience.

The building will have flexible components designed for continuous adaptability. Prefabricated and modular systems will be monitored by robots that work together to install, detect, repair and upgrade components of the building systems. Spaces and facades will be rapidly manipulated and modified based on context and environmental cues. High performance composites with self-repair and air purification properties made from recycled and renewable elements will be used extensively as building materials.

The futuristic building will be completely self-sustainable and in fact produce more resources than it consumes. Photo-voltaic cells, vertical transportation systems and algae producing bio-fuel pods will be used for on-site production, storage and transmission of energy. Wind downdraught protection systems will also harness electric power. Modified wind turbines will manufacture drinking water from humid air. Vertical farming techniques and systems like hydroponics will optimize food production.

Facades of this next-gen structure will be sensitive and highly multi functional. Heat recovery windows with natural ventilation will allow for air to be brought in and up thus minimizing the heat normally lost through windows. The façade will be treated with nano-particles that have the capacity to neutralize airborne pollutants, capture CO2 and purify the air around the structure. The façade will ensure optimal thermal comfort for its dwellers by suitably reacting to changes in temperature, sunlight, moisture levels and wind patterns. Building systems will monitor reflectivity, heat absorption and heat balance and minimize the effects of urban heat island. Use of OLED technology will create an even more concrete light source across the building. Daylight absorbing abilities will assist in creating a “net zero energy” artificial lighting.

In brief, the smart building of the future will be self-regulating yet simultaneously functioning to integrate itself with the surrounding urban infrastructure and execute informed and calculated decisions about the optimal use and composition of structures.

India, Switzerland team up for energy-efficient buildings

With an objective to promote sustainable architecture throughout the country, India has entered into an MOU with Switzerland to utilize Swiss expertise for designing energy-efficient in the country.

“After extensive consultations and pilot projects, our two governments have signed a five-year MoU to facilitate the adoption of Swiss expertise to the Indian context,” Swiss Ambassador Linus Von Castelmur said.