Reinforcing Steel
Which best describes a mechanical connection which uses a seamless steel coupler and portable hydraulic press?
A: Cold forged steel sleeve Why: The cold forged steel sleeve is a mechanical connection which uses a seamless steel coupler and a portable hydraulic press. Reinforcing bars to be connected are inserted equal distances into the coupler. The press is used to deform the coupler around the ends of the bars. No special end preparation of the bars is required but a bar-end check must be made on the bar ends by the Fabricator prior to shipments.
What is often used for an exterior column along a property line where a square column footing would extend beyond the building line?
A: Combined footing Why: A combined footing is often used for an exterior column along a property line where a square column footing would extend beyond the building line. In this case, the exterior column is flush with the end of the footing and the footing is extended beyond the first interior column. This type of footing distributes the two column loads over a uniform soil bearing.
if the bottom of a beam is in tension, what is the top of the beam in?
A: Compression why: Steel provides reinforcement to the concrete where tensile forces exist that the concrete cannot take. Simple beams (also simple slabs, joists, girders) carrying loads, will eventually begin to arch downward. The top of the beam is in compression and the bottom is in tension, so longitudinal steel is located near the bottom to prevent the failure of the concrete in tension.
Which calculator helps estimate the concrete volume required for a pour or placement?
A: Concrete Calculator Why: The Concrete Calculators help you to estimate the concrete volume required for a pour or placement, the volume of concrete needed to fill a block wall, and the volume of concrete needed in a column. To use the Concrete Volume Calculator, enter the width, length, and thickness of your pour, and then select feet or inches as your measurement scale. The calculator will estimate the number of cubic yards of concrete that will be required.
What is usually placed to stop at the underside of the lowest supported beam or girder in the floor above?
A: Concrete for columns Why: The concrete for columns is usually placed to stop at the underside of the lowest supported beam or girder in the floor above. Then an interval of several hours to a day or more is allowed for settlement of the concrete in the column before proceeding with placing of concrete in the floor.
Which is not a step to estimating the proper amount of concrete?
A: Consult the plans Why: It can be upsetting to end up with any extra concrete. You have to pay for this concrete after all. However, realize you are doing your job a service by ordering enough concrete - which means you are going to have a little concrete left over. The three steps to ordering enough concrete are, (a) use the concrete calculator, (b) figure the depths and widths as they have been built on the site, not simply what the plans say, and (c) add a safety margin.
The concrete arch ___________
A: Curves in one direction only Why: The concrete arch is curved in one direction only and is simple and pleasing in appearance. The arch thickness is variable, being thinner at the center and gradually increasing in thickness toward the supports.
Which best describes the standard type of reinforcing bar?
A: Deformed bar Why: The standard type of reinforcing bars is the deformed bar. Each mill which rolls deformed bars may have a different pattern of deformation on the bar but all are rolled to conform to ASTM Specifications.
what is the net result of two forces called in a loaded beam or slab with horizontal shear present
A: Diagonal tension Why: In a loaded beam or slab both vertical and horizontal shear are present and the net result of the two forces is called diagonal tension. A crack resulting from these forces always occurs near the support and extends upward and outward at an angle of approximately 45 degrees to the top. These forces also are present in a slab floor around supporting columns and the result is called punching shear.
What do site drawings display?
A: Drainage structures, utility lines, Elevations Why: Site drawings show the location of the building on the property, utility lines, drainage and drainage structures, outside walks, drives and curbs, and elevations of natural ground and finished grades.
When a single span is used in a bridge, what are the end supports called?
A: Abutments Why: A simple beam bridge is commonly used for relatively short spans. When a single span is used the end supports are called abutments or end bents. When two or more spans are used, the intermediate supports are called piers or intermediate bents.
Which calculator measures the number of cubic yards required for a column?
A: concrete column Calculator Why: The Concrete Column Calculator will display the number of cubic yards required for a column. To use, enter the height and diameter of the column.
When calculating the amount of concrete needed for slabs, how much do you add to the thickness?
A: 1/4 inch Why: When calculating the amount of concrete needed for slabs, add ¼" to the thickness of your slab for your slab concrete budget. This assumes you have the job evenly graded to the right depth, and the grade is well compacted. If you check your grade and one spot is 4", some spots are 4.5" to 5"-the best solution for both the job quality and your concrete budget is to fix the grade. If you don't fix it, you have to come up with the average depth-then add your ¼" to that thickness.
How many standard deformed bar sizes are there?
A: 11 Bar sizes Why: Deformed bars are always designated by number. There are eleven standard sizes - #3 to #11 inclusive, #14 and #18. The number denotes approximately the diameter of the bar in eighths of inches. For example, a #5 bar has an approximate diameter of 5/8 inch, a #9 bar, 1 1/8 inch (9/8 inch). The nominal dimensions of a deformed bar (not including deformations) are equivalent to those of a plain round bar having the same weight per foot as the deformed bar.
In an open caisson foundation, how many feet in diameter is the hole dug?
A: 2 to 5 feet Why: The deep pier or open caisson foundation serves the same purpose as a group of piles. It consists of an open shaft, with or without lining. A hole from 2 to 5 feet in diameter is dug or drilled through unsuitable soil down to a firm bearing. The bottom of the hole may be "belled out" to provide the required bearing. After the pier is excavated, it is filled with concrete, sometimes plain and sometimes reinforced.
How much stronger are bars than the same equivalent area of concrete?
A: 20 Times Stronger Why: While the main purpose for steel in concrete is to resist tension forces, it is also used to advantage to resist compression forces. The most common use of steel for compression forces is in columns. If concrete alone were used, the size of column required would be so large as to be impractical and would add considerably to the weight of a structure. Since bars are about twenty times stronger than an equivalent area of concrete, they are used to carry part of the column load. The concrete and the steel work together and the resulting column are much smaller in size and lighter in weight.
When the grade number 60 is marked on the bar, where is it located
A: 4th mark in order Why: The grade mark for 60 may be either the number 60 or one (1) single line. When the number 60 is used to designate Grade 60, it is the 4th mark in order. When a single line is used to designate Grade 60, it is smaller and between the two main ribs which are on opposite sides of all US made bards. Similarly, the grade mark for the Grade 75 may be either the number 75 or two (2) grade lines.
Once pile for each footing are driven, where are they cut off?
A: 6 inches Why: After the piles for each footing are driven, they are cut off at the same level. This is usually about six inches above the bottom of the footing. In addition to being square or rectangular in shape, pile footings may be tree-sided (triangular), six-sided (hexagonal), or eight-sided (octagonal) or other shapes depending upon the number of piles in each group or the pattern by which the piles are arranged.
What size are the test cylinders for testing the strength of concrete?
A: 6 inches in diameter and 12 inches high Why: Standard steel molds are used which form the concrete into test cylinders 6 inches in diameter and 12 inches high. After 7 days or 28 days of curing, these cylinders are placed in a laboratory testing machine and crushed in compression, with gauge readings taken on the machine to determine the crushing load. For example, where 3,000 psi concrete is specified, the cylinders after 28 days should break at about 90,000 pounds load.
What do ASTM Specifications require to be printed on each reinforcement bar?
A: A symbol or marking to indicate the type of steel, a letter or symbol to show the producer's mill, and markings to designate steel grade Why: With the various grades and sizes available, it was found necessary to provide some means of easy identification. ASTM specifications require that each Bar Producer roll onto the bar (a) a letter or symbol to show the producer's mill, (b) a number corresponding to the size number of the bar, (c) a symbol or marking to indicate the type of steel, and (d) markings to designate Grades.
Which organization standardized the most common types of bends in support bars?
A: ACI Why: Bent bars are cut to length and sent to the bending area, where they are assigned to the proper bending machines best suited for the type of bend and size of the bar. There are many types of bends, but the most common types have been standardized by the American Concrete Institute. Type numbers have been given to the various bar shapes. The Ironworker will often find these bend type numbers shown on placing drawings schedules or on bar lists. A reference to a bend type will immediately identify the general shape of the bar.
When estimating footing, what information is needed?
A: Actual weights of concrete, soil tests, live loads Why: If an engineer designed the footing based on soil testing numbers and your prints, he'd add up the actual weights of the concrete, wood, and brick you'd be using in your building, factor in the required live loads, and come up with an estimate of the weight your actual structure puts on the footing. It might be a little less or a little more than the code assumes. Then he would take the known bearing strength of the soil - what a square foot of the soil can be trusted to support - and design the footing so that the area under the footing multiplied by the bearing strength of the soil would equal or exceed the actual load.
What do Typical Placing Drawings show the Ironworker?
A: Arrangement of bars in joists, bars in beams, and bars in distribution ribs Why: Sections - Typical Placing Drawings show the Ironworker the general arrangement of bars in beams, joists, distribution ribs and slabs over the joists. The Ironworker would use these in conjunction with framing plan and the beam and joist schedules. The section entitled "Typical Joist Construction" shows a number of details about the joists.
How thick should the wall footing be that a bearing wall rests upon?
A: At least 2 times its thickness Why: A bearing wall rests upon a continuous wall footing at least twice as wide as the thickness of the wall but wider, if necessary, to spread the load from the wall above to the soil. Foundation walls are also used as retaining walls to withstand earth pressure for construction below ground. When poor soil bearing conditions make it necessary, wall footings may be supported by piles to carry the weight further down to firm soil or bed rock.
Which term best describes a list of reinforcing bars that makes up a bill of materials?
A: Bar list Why: A bar list is just what the name implies - a list of reinforcing bars making up a bill of materials. It is prepared by the Fabricator to cover a particular part of the structure, including one or more truckloads or it may include only the items in each truckload. The bar items are taken from either the plans, sections or schedules on the placing drawing. They are first classified as to straight, heavy bending, light bending and special bending and they are also grouped by sizes and lengths. The largest size is grouped first, then the next smaller size and so on. Each size has the longest length listed first graduating down to the shortest.
What is used to firmly hold the bars at a required clearance during placement?
A: Bar support Why: A bar support is used to firmly hold the bars at the required clearance from the forms before and during the placing of concrete. They must be sufficiently strong and properly spaced to provide this support under normal construction conditions. The bar supports may consist of steel wire, plastic or precast concrete blocks.
Which calculator is used to estimate concrete needed for a wall?
A: Block wall Calculator Why: To use the Block Wall Calculator, enter the height and length of the wall. The calculator will estimate the number of cubic yards that will be required. Note that this is an estimate. There is significant variation in fill space among different blocks. This calculator assumes the use of double open-ended bond beam blocks.
Where would tension cracks begin once an unreinforced beam is loaded?
A: Bottom Why: Tension in concrete can be caused by bending or shear as in beams, by drying shrinkage after concrete hardens, and by temperature changes. As a beam is loaded, tension cracks will appear at the bottom of the beam and would develop rapidly in an unreinforced concrete beam with the cracks developing near mid-span. Plain concrete would be weak and brittle and would fail suddenly without warning shortly after the first crack appeared.
In which bridge does the span consist of a deck slab, a series of walls and a bottom slab, creating weight for longer spans to be used?
A: Box Girder Bridger Why: A box girder bridge is supported by abutments and piers in the same way as a simple or continuous beam bridge. The span consists of a deck slab, a series of walls, and a bottom slab. This creates weight and permits longer spans to be used in the type of bridge than in a beam and slab bridge. In shorter spans, the box girder is usually of uniform depth. In longer spans, the depth is usually variable and is accomplished by varying the depth of the walls to provide a curved under surface, similar in appearance to the under side of a rigid frame bridge.
What has no protection against rusting and is used in situations where the supports do not come in contact with exposed concrete?
A: Bright basic wire bar supports Why: Bright basic wire bar supports have no protection against rusting and are intended for use in situations where surface blemishes can be tolerated, or where the supports do not come in contact with the exposed concrete surface.
which term best describes a beam which extends beyond supports in an overhanging position with the extended end unsupported?
A: Cantilever beam Why:Cantilever beams (or slabs) loaded at the top, deflect downward and in the cantilever (or overhang) tension bars must be placed in the top. They must be carried back into the main span whenever possible; otherwise they must be securely anchored by bending or hooking into an outside beam or column.
What is the purpose of combined footings?
A: Carry column loads at two or more points Why: Combined footings carry column loads at two or more points, supported by a uniform soil pressure upward over the entire area of the footing. It tends to curl up the outer corners and to bow up between columns and at the projecting end. The forces acting on the footing are roughly the reverse of forces acting on a normal beam or slab. For this reason, such footings need to be reinforced with top bars and bottom bars. Bottom cross bars are also provided to take care of the curling effect in the short direction.
Which is the most commonly used crane for hoisting?
A: Chicago boom, Climbing crane, Hydraulic crane Why: Power equipment is normally required to raise or lower bars from one level to another or to bridge obstacles that prevent the bars from being carried manually. The type of hoisting equipment will depend upon the size for the job, whether in a congested area, or open site, and the height of the structure. The most commonly used hoists are the truck crane, the hydraulic crane, the tower crane, the climbing crane, and the Chicago Boom.
What is bar placing drawing used for?
A:To prepare a bar list Why: The Bar Fabricator uses the structural and architectural drawings to prepare bar placing drawings. At times, it may be necessary to refer to other drawings for information. A bar placing drawing contains only the information required by the Bar Fabricator to prepare bar lists and by the Ironworker to put the bars in place on the job.
What causes tension stress?
A: Drying shrinkage, weight, Temperature changes Why: Tension stresses in concrete can be caused by drying shrinkage after the concrete hardens and by temperature changes. Reinforcement is needed to hold resulting cracks tightly together. The best example is a concrete highway pavement. In continuously reinforced concrete pavement, longitudinal reinforcement eliminates the need for cross-joints. The initial drying shrinkage and first cold weather can cause cracking at regular intervals. The reinforcement is designed to hold these cracks tightly together so that the pavement essentially acts as an uncracked slab.
Which best describes a mechanical connection that can be used only for transferring compression from bar to bar?
A: End-Bearing connection Why: An end-bearing mechanical connection can be used only for transferring compression from bar to bar. It is used mainly for column vertical bars with square ends. An end-bearing connection device holds the bars in aligned position - one bearing on the other. The upper bar must be rotated to obtain the minimum gap (not to exceed 3 inches) between the bearing ends.
Who determines the amount of concrete protection that is needed for each part of the project?
A: Engineer Why: The proper embedment of bars in the concrete is very important. The Engineer determines the amount of concrete protection for each part of the project and bases the design on these cover requirements, taking into consideration the requirements of building codes, fire hazards, and possibility of corrosion and exposure to weather.
Where are the straight reinforcement bars cut?
A: Fabricator's Shop Why: Straight bars are cut to specified lengths from longer stock lengths in a Fabricator's shop. All the bars of one size and length are cut and assembled for bundling.
Which best describes the structural steel beams when a slab is used?
A: Fairly lightweight, Spaced 3 to 8 feet apart, Frame into heavier steel girders Why:A slab supported by beams or walls is the simplest type most commonly used on short spans. One form of this slab, however, is used over structural steel beams in structural steel framed buildings. The beams are fairly light in weight, are spaced approximately 3 to 8 feet apart and frame into heavier steel girders, somewhat like the reinforced concrete slab-beam-and-girder floor construction.
What is most commonly used for a tag line when hoisting?
A: Fiber rope Why: When bundles are being hoisted in congested or limited areas, it may be necessary to apply a tag line to one or both ends of the bundle for the purpose of guiding the load as it is hoisted. Fiber rope is most commonly used for this purpose. Safe hoisting requires a skilled operator handling the power equipment.
what is a similarity of bridge construction and building construction?
A: Footings, Caissons, Columns Why: Some units of bridge construction are similar to those of building construction and serve a similar purpose. These are footings, piers, caissons, walls, columns, beams, slabs, girders and the like. However, the bridge Designer has somewhat more freedom than the building Designer in combining these units in the finished bridge structure.
What does a rigid frame bridge usually consist of?
A: Footings, Deck slab, Walls Why: A rigid frame bridge consists generally of footings, walls and a deck slab designed so that the walls and deck work together as a single U-shaped element or rigid frame from which it gets its name. The weight of the deck and any loads upon it help the legs to resist earth pressure
What is the difference between a beam and a girder?
A: Girder is larger Why: In the slab-beam-and-girder floor, the slabs, beams and girders are cast at the same time. A beam and a girder are really the same thing except that a girder is of considerably larger size and more heavily reinforced because it is designed to carry the load from the beams which frame into it. The beams around the outside edges of the floor are called spandrel beams or merely spandrels. The bottom of a slab, beam or girder is called a soffit. Chamfer strips (beveled edges) are often used in the forms to avoid sharp concrete edges that might tend to break off.
How are bent bars identified?
A: Given own mark Why: Straight bars are sufficiently identified when tagged to show number of pieces, size and length. Bent bars, because of the various shapes to which they are bent, may have the same size and length, but be more than one shape. To clearly distinguish a particular bent bar, it is always given a mark number of its own.
Which term best desctibes a continuous foundation wall generally extending below the frost line to good bearing soil?
A: Grade beam Why: A grade beam is a continuous foundation wall extending generally below the frost line to good bearing soils or bearing points. It usually is formed but may be cast in a neat trench without formwork. Grade beams may also span between footings, pile caps, piers, or caissons.
What is used at the end of bars when the straight length of the bar cannot provide enough embedment in the concrete to properly anchor the bar?
A: Hooks Why: Hooks are used at the end of bars when the straight length of the bar cannot provide enough embedment in the concrete to properly anchor the bar. There are three types of hooks generally used, know as 180 degree, 135 degree and 90 degree. The 180 degree and 90 degree hooks are used as standard for all bars except stirrups and column ties where 135 degree or 90 degree hooks are standard.
Which best describes a mechanical connection in which the sleeve is heated to a malleable temperature and fitted over the end of one bar?
A: Hot forged steel sleeve Why: The hot forged steel sleeve is a mechanical connection which uses a specially machined sleeve. The sleeve is heated to a malleable temperature and fitted over the end of one bar. The second bar end is inserted into the hot sleeve. A portable hydraulic forge forces the sleeve's inner wall into and around the deformations on the bars. Contraction of the sleeve upon cooling causes additional bond which provides increased tensile strength to the connection.
Which way do walls, braced at the top and bottom, and loaded with horizontal pressures on the outside face deflect?
A: Inward Why: Walls, braced at top and bottom by floor slabs and loaded with horizontal pressures on the outside face, deflect inward. This requires bars or welded wire fabric on the inside face where there is tension. Sometimes, when specified by the Engineer, bars may be required around the outside top corner.
How are bars identified, indicating where they are to be used?
A: Letter followed by numbers, marks relating to structural members, marks relating to bar size Why: To identify bars and indicate where they are to be used, bundles of bars have suitable marks on the tags. The bar mark on the tag must be identified with the same mark on a bar list and the corresponding placing drawing. There are various marking systems used. One system relates to the structural member, one to the bar size, one to both structural member and bar size and one uses a letter followed by numbers unrelated to bar location or size. Sometimes a marking system is used because it is best suited for a particular type of building, sometimes because it is best adapted to the bar Fabricator's order system and equipment.
To provide continuity in steel reinforcement, why are splices unavoidable?
A: Manufacturing, Fabrication, Transportation Limitations Why: Reinforced concrete structures are generally designed so that the separate parts act as a single unit. This makes it necessary to properly locate construction joints and provide continuity in the steel reinforcement through the joints. Just as it is impossible to cast all the concrete at one time, it is also impossible to provide full length continuous bars in most structures. This is because of manufacturing, fabrication, or transportation limitations. Since splices in reinforcement cannot be avoided, it is necessary for the Engineer to provide for properly designed splices, and to identify their lengths.
Which best describes a mechanical connection in which motion metal interlocks the grooves inside the connection sleeve with the deformations on the bar?
A: Metal filled sleeves Why: The metal filled sleeve is a mechanical connection in which molten metal or "metallic grout" interlocks the grooves inside the connection sleeve with the deformations on the bar. A crucible is attached to the side of the sleeve by use of a pouring basin aligned with a tap hole. The crucible contains a filler metal which is ignited, becomes molten and flows into the sleeve and around the bars, completely filling the space. The clamps holding the sleeve in position and the crucible are removed and reused.
When working with typical bending bars, what would omitting certain letters cause?
A: Modified shape Why: All of the bend types have a letter assigned to each dimension of the bar. When all of the dimensions are used on a bar list, the exact shape of the bar shown will be produced. By omitting certain letters, a shape may be modified from that shown. For example, by omitting the dimension "G" from Type 1, a bar with only one hook would result. By omitting dimensions "A," "G" and "I" from Type 3, a truss bar without hooks would result.
What is the difference between flat plate slab construction and a flat slab?
A: No drop panels in flat plate slab Why: Flat plate slab construction resembles a flat slab except that there are no drop panels and the columns have no capitals. Columns, in this case, are usually square instead of round and come up under a flat plate floor slab. This type of floor permits columns to be spaced irregularly if desired, while, in the flat slab, columns are usually more uniformly spaced.
In which type of bar is the upper part {which projects above the upper floor} bent to come inside the vertical bars in the column above?
A: Offset column bars Why: Offset column bars are bent so that the upper part which projects above the upper floor will come inside of the vertical bars in the column above. The corner bars in a column need to have a larger offset than the bars along the sides, but for simplified fabrication and placing, all offset bends in a column are made using the largest offset.
When only two spacers are used, where are they placed?
A: Opposite ends Why: When only two spacers are used, they are placed on opposite sides of the spiral. When more than two are used the additional ones may be placed adjacent to the two, or bundled loose with the spiral for attachment in the field. Having the spacers on opposite sides of the spiral permits the spiral to be shipped flat or "collapse," requiring less space for storage and shipment. In the field, the spirals are opened and the spacers shifted so they are about equally spaced around the circle.
What is used when the subgrade is too soft to proved adequate bearing for a normal footing?
A: Piles Why: Piles are used where the subgrade is too soft to provide adequate bearing for a normal footing. They are driven to the required depth, and carry the load partly by end-bearing and partly by friction of the subgrade material against the surface of the pile (called the friction). The common types of piles are (a) reinforced concrete, precast and driven, (b) reinforced concrete, precast and prestressed, (c) concrete cast in driven steel casings, (d) cast-in-place concrete in holes drilled or bored into earth, (e) steel H-beams, and (f) timber, plain or treated.
Where are the specifications for reinforcement cover in protect against fire, corrosion or exposure found?
A: Placing Drawings Why: In order to protect reinforcement against fire, corrosion or exposure to weather it must have a minimum cover of concrete. The amount of cover is specified in building codes and shown on placing drawings. It is measured from the face of the concrete to the outside of the reinforcement. In corrosive environments such as chemical storage and manufacturing facilities, wastewater treatment plants, structures exposed to sea water, bridges and parking structures exposed to de-icing salts, additional cover may be required, usually specified on the structural drawings. In many instances coated reinforcement is used as a corrosion-protection system for those types of structures.
Which best describes a round smooth bar?
A: Plain bar Why: Plain bars are smooth round bars without deformations on them. They are used for special purposes such as dowels at expansion joints where the bars must slide in a metal or paper sleeve, for both expansion and contractions joints in highway pavement and for column spirals
Which term best describes a process of tensioning tendons after the concrete has hardened?
A: Post tension Why: Post-tensioning is a method of prestressing in which the tendons are tensioned after the concrete has hardened and reached its required strength. The tendons are anchored at both ends of the member. Tensioning of the tendons is done by applying a force with a hydraulic jack.
what are spirals that come without spacers called?
A: Unassembled Why: Spirals that include spacers are called assembled spirals. In some cases such as piles, piers or columns where the pitch exceeds standard spacing or where the bar or wire diameter is quite small, or where the spiral bar can be accurately spaced and tied to longitudinal bars, spirals may be furnished bent into coils to the specified diameter and the proper number of turns without spacers. There are known as unassembled spirals.
When reinforcing bars are used around curved surfaces, and when no special requirements are established, what will the bars be prefabricated in accordance with?
A: Radial prefabrication table Why: When reinforcing bars are used around curved surfaces, such as domes and tanks, and when no special requirement is established in the contract, bars will be prefabricated in accordance with the criteria established in the Radial Prefabrication Table. All other conditions will be furnished straight, to be sprung in places to fit. In the smaller sizes, the bars are sprung to fit varying job conditions such as locations of splices, vertical bars, jack rods, openings and other blocked-out areas in the forms. The larger size bars, which are more difficult to spring into desired positions, are ordinarily employed in massive structures where placing tolerances are correspondingly larger.
What is similar to a combined footing but has several columns or walls resting upon it?
A: Raft Footing Why: A foundation mat or raft footing is similar to a combined footing. In this case, several columns and/or walls rest upon a mat or raft. Sometimes this type of foundation is used under the entire building. The mat or footing is reinforced to distribute the column or wall loads over a uniform soil bearing.
When reading plans, how are the columns represented?
A: Rectangles Why: The exterior solid and parallel dash lines on the plan view show the floor bearing on the wall, except where beams are indicated. The supporting columns are indicated by small rectangles, the numbered circle adjacent to them is the column mark or number. The beams are shown as either two parallel solid lines or combination of dashed and solid lines. The beam mark or reference number appears alongside the beam and these numbers usually follow from the structural drawing and in sequence. The letter B is used for beams.
What is a pile considered to be driven to, once predetermined resistance is met?
A: Refusal Why: The load to be supported by the pile is normally judged by the number of blows of the pile hammer required to drive the pile the last 1 to 2 inches. When predetermined resistance is met, a pile is considered to be driven to "refusal."
What consist of a series of ribs, similar to small beams with a top slab and are cast at on time with supporting beams?
A: Reinforced concrete joist floors Why: Reinforced concrete joist floors consist of a series of ribs, similar to small beams with a top slab, all of which are cast at one time with the supporting beams. The joists are usually formed by standard inverted metal or fiber glass forms which form the side and soffit of adjacent joists and the bottom of the top slab. The forms may be multiple lapped pieces or one piece from beam to beam. These forms are shored from the floor below and after concrete has hardened sufficiently, they are removed. After cleaning and oiling they may be re-used.
what must be done to column vertical bars to keep compressions from allowing the bars to buckle?
A: Restrained Why: Column vertical bars are in compression and if not restrained in some manner the compression load would allow the bars to buckle and break out of the concrete. Column ties are spaced to prevent this. They are in tension, holding the vertical bars in position. Column spirals act in the same manner as column ties, but in addition they restrain the concrete somewhat like a stove pipe restrains a column of sand fill inside of it. Spiral turns are more closely spaced to accomplish this purpose. A spiral rod should never be cut without splicing as directed by the Engineer.
In reinforced concrete walls, temperature reinforcement is used at what angle to the main steel?
A: Right angles Why: In reinforced concrete walls, temperature reinforcement is used at right angles to the main steel for the same purpose as in the floor. Often in wall construction, temperature reinforcement may be placed horizontally and vertically in a wall face for temperature and shrinkage purposes only, even though that face of the wall does not carry any other tension forces.
Which calculator estimates the amount of hot mix or road oil you will need?
A: Road materials calculator Why: The Road Materials Calculators help you to estimate the amount of hot mix or road oil /emulsion that you will need. To use the Hot Mix Calculator, enter the width, length, and thickness of your paving job. The calculator will estimate the number of tons of hot mix that will be required. This estimate is based on a density for the mix of 150 lbs per cubic foot. Please note that densities will vary somewhat between different mixes, but this value is a standard "rule of thumb" for estimating.
Which of the following terms means to cut off as by two equal opposed forces?
A: Shear Why: Shear is a more complex force than simple tension or compression. A common example is a bolted lap joint in steel plates, producing what is called single shear. In concrete, this is best illustrated by a loaded column bracket. If a set of books were carried horizontally, they would have to be squeezed tightly together or they would slip and fall. In a beam, each imaginary vertical slice (as the case of a single book), with a load on top tends to slip down, due to what is called vertical shear.
What are units of reinforcing bars as loaded for shipment?
A: Shop lifts Why: A quantity of bundles comprises a lift. Shop lifts are units of reinforcing bars as loaded for shipment. Field lifts are units of reinforcing bars as required for field handling by the Contractor. A field lift may consist of single bundles or two or more smaller bundles tied together. A shop lift may consist of one or more bundles, the same as field lifts or consist of two or more filed lifts. Straight and bent bars will not be combined in the same lift. Maximum No. 12 gauge wire may be used for small bundles. Ties are generally spaced 10 feet to 15 feet on center with a minimum of two ties per bundle. Ties are not intended for use in lifting bundles.
How are joists represented in a set of plans?
A: Solid lines Why: The joists are shown in solid lines as this is standard practice in the industry. Rectangular openings are indicated by cross diagonal lines. Midway in the longer spans are double horizontal lines indicating a distribution rib; the Engineer shows this on the structural drawing when required. The joist mark or reference number (such as 1J2) is shown for a group of identical joists and generally follows the structural drawing but with letter suffixes (such as 1J2A) to allow for variations in the reinforcement for a so-called "typical" joist. The letter J is used for joists.
Which calculator allows you to convert English to metric units
A: Unit Conversion Calculator Why: The Unit Conversion Calculators allow you to easily convert English and Metric units for length, area, volume, weight, temperature, pressure, and force.
what provides stillness to the spiral to keep it in alignment while being erected?
A: Spacers Why: Spirals are used in spirally-reinforced columns, piers and piles and are made of deformed bar, plain bar or wire bent to a specified diameter into a form similar to that of a coiled spring. The spacing of the bar is important and spacers are sometimes provided to hold the spacing. The spacers also serve to provide sufficient stiffness to the spiral to keep it in alignment while being erected. It is usually a steel channel or angle punched with a series of "lips" to hold the spiral turns to proper pitch. Each Fabricator selects the shape of spacer best suited to the purposes to provide the required stiffness.
What should the Ironworker look over each placing drawing for?
A: Special notes Why: The Ironworker should look over each placing drawing for any special notes. Sometimes it is not possible to show every bit of information on the drawing itself and, instead, a simple note could cover a typical condition rather than repeating it over and over again on the drawing. One example would be notes of special instructions to the Ironworker explaining the sequence in placing bars: that is, which layer of bars is to be placed first, second, and so on, and notes of instruction in the placing of bar supports. Another note might give instructions on how much side lap and end lap to provide for welded wire fabric. Another helpful note would be to give the amount of lap in feet and inches for each size bar.
when bars are need in the top of the beam, taking the place of some of the concrete, what is used to restrain them?
A: Stirrup-Ties Why: In some beams, where compression is high or where the size of beam needs to be restricted, it may be necessary to use bars in the top of the beam. These bars take the place of some of the concrete, very much the same as the column vertical bars. When used in this manner, the bars are always restrained by closed stirrup-ties which may be one or two pieces.
What should be used to resist diagonal tension?
A: Stirrups Why: When a beam deflects under a load, shear stresses are also present. To resist the diagonal tension, small U-or W-shaped bars called stirrups are used and are placed vertically across the beam. Since shear is usually at a maximum near the support and decreases toward mid-span, the stirrups are more closely spaced near the support and spaced increasingly farther apart toward mid-span. Since the concrete is able to take some shear, stirrups can often be omitted near mid-span. Welded wire fabric cages can also be used instead of rebar stirrups to resist shear stresses.
what must be done to welded wire fabric to keep it from displacing until the concrete has set?
A: Supported Why: Sheets, rolls and cages bent from sheets are specified in various yield strengths. Welded wire fabric is made from cold drawn wire. Welded wire fabric is available in various widths and lengths. As required for reinforcing bars, welded wire fabric must be adequately supported to carry constructions loads without permitting displacement until the concrete has adequately set and hardened.
Why do roof slabs need reinforcement?
A: Temperature changes, Safety, Shrinkage Why: Roof slabs of buildings are subject to wide temperature changes as well as concrete shrinkage. Floor slabs, while not usually subjected to wide temperature changes are subject to shrinkage. It is general practice to place reinforcement in slabs at right angles to the main stress carrying steel, to provide for these effects. This reinforcement is referred to as temperature steel.
What is another name for slab reinforcement?
A: Temperature reinforcement Why: Slab reinforcement is used to control cracking in the concrete and is called temperature reinforcement. These temperature bars are indicated by short horizontal lines with arrows to show the extent covered.
How is prestress commonly introduced in reinforced concrete?
A: Tensioning the tendons Why: Prestressed concrete is reinforced concrete in which internal stresses have been introduced to reduce potential tensile stresses in the concrete resulting from loads. The prestress is commonly introduced by tensioning the tendons. A tendon is a steel element which is a wire, bar, rod or strand, or a bundle of such elements.
How is compressive strength of concrete tested on the job?
A: Test samples Why: Quality control of both concrete and steel is important to assure the Engineer or Architect that the specified design requirements are met. The compressive strength of the concrete is checked on almost every job by taking test samples.
Which best describes a mechanical connection consisting of a taper treaded sleeve that joins rebar with matching taper threads, preventing cross-treading during installation?
A: Threaded steel coupling Why:The threaded steel coupling is a mechanical connection consisting of a taper threaded sleeve that joins rebar with matching taper threads, thereby preventing cross-treading during installation. The coupling is installed by turning the bar or sleeve with wrenches to a minimum torque value as recommended by the Coupling Manufacturer. For splicing bent or curved bars, special position couplers with collars are used. Simple adaptations permit use for end anchorages in concrete or connection to structural steel members.
What is the schedule used for?
A: To aid in correctly positioning the bars Why: A schedule is a useful method for presenting details of bars for a group of similar items, such as a group of beams, joists and columns. The bars can be described clearly and compactly in a schedule. The schedule is usually used in connection with typical details, to aid in correctly positioning the bars in the forms. Schedules can be arranged in different formats, according to the ideas of the individual Detailer, and sometimes the nature of the job, but an explanation of the Beam Schedule should help the Ironworker to a better understanding of how to read and interpret one.
Why should you have a cement supplier visit the job site?
A: To check job conditions, Check your safety margin, inform you of local conditions Why: You should have the cement supplier visit your site to give his or her opinion on the quantity of cement required. Compare the figure with what you came up with. Discuss any variances. Your supplier is invaluable for checking job conditions, checking the safety margin, identifying issues you may not have thought of, and informing you of any local conditions.
Which best describes a two-way reinforced concrete joist floor with rubs running in both directions?
A: Waffle slab Why: The waffle slab is simply a two-way reinforced concrete joist floor with ribs running in both directions, but it also resembles a flat plate slab at the columns. The waffles are the hollow spaces between the joist ribs and are formed by standard forms or "domes." They are removed after the concrete has hardened and may be re-used.
How are tilt up walls cast?
A: flat and face down Why: Tilt-up walls are walls are cast flat, usually outside face down. When the required concrete strength is achieved, the walls are lifted or tilted up into vertical position, braced, and then anchored into place with a cast-in-place slab closure pour. This type of construction is used for warehouses and other industrial buildings and for office, hotel, and apartment buildings. Casting the walls flat on a slab on grade reduces formwork, allows special architectural features, and allows the wall reinforcement to be placed and tied similar to slab bars.
When ordering concrete, you should _________
A: include a safety margin Why: Never try to order the exact amount of needed concrete. Include a margin of safety. A perfectly placed order of concrete will finish the job with a small amount left over. A 20 cubic yard order with 1 cubic yard left over is a good order. A 20 cubic yard order that comes up ½ cubic yard short is not a good order. This would cause extra costs for an overtime crew, a short load charge from the ready mix supplier, and a cold joint can occur (where one pour ended and another pour began).
what will happen if there is improper positioning of the reinforcing bars?
A: reduced strength Why: The strength of any concrete member can be affected by the improper positioning of the reinforcing bars. For example, lowering the top bars or raising the bottom bars by ½ inch more than specified in a 6 inch deep slab could reduce its load carrying capacity by 20 percent. Bar supports, spaced according to industry practice for placing bar supports, should be sufficient to position the bars as required.
which best describes yield strength?
A: the load limit to which steel will stretch Why:Bars are available in different grades, according to the design requirements. Each grade has distinctive strength properties and is uniquely marked to assure that the proper material is applied to each requirement. There are parts of a structure where one grade may be used to better advantage than another and the grades are identified to assure proper use where each is required. Each grade has what is known as specified yield strength and ultimate tensile strength. Yield strength is the load limit to which the steel will stretch and return to its original length, much the same as stretching a rubber band. Ultimate tensile strength is the load limit at which the steel breaks.
Why must bars be placed at right angles, in two different directions on square or rectangle footings?
A: they tend to curl Why: Square or rectangle footings have a concentrated column load downward in the center and uniform soil pressure upward all over the base. They tend to curl up in all directions toward the corners. Bars are placed in two directions at right angles to each other and located a prescribed minimum distance from the bottom of the footing.
Why do radially prefabricated bars tend to relax the radius originally prefabricated?
A: time and normal handling Why: Radially prefabricated bars of any size tend to relax the radius originally prefabricated as a result of time and normal handling. The last few feet involved in the lap splice area often appears as a tangent rather than a pure are due to limitations of standard bending equipment. For these reasons, final adjustments are left as a field placing problem to suit conditions and tolerance requirements of a particular job.
What are forms usually made of?
A: wood, fiber board, Plastic Why: Forms are usually of wood (either boards or plywood), fiber board, metal, or plastic. They are used to contain the concrete while still in a plastic state, of all parts of a building except possibly construction below ground where the soil is firm enough to be trenched. Forms must be securely braced and shored to withstand side pressures or settlement. After the concrete has hardened, side forms can be removed, usually within a day or two, and shoring and bottom forms can be removed when the concrete is able to carry load, usually after six or eight days.
Which calculator helps estimate the aggregate tonnage required?
A:Aggregate Calculator Why: The Aggregate Calculator helps you to estimate the aggregate tonnage required for your job. To use the Aggregate Calculator, enter the width, lengths, and thickness of your job, select the thickness in feet or inches, click on Base Rock, Drain Rock, or a custom density selection. The Base Rock and Drain Rock selections will fill in the density of the rock for you; the Custom selection allows you to enter a rock density in the Density field. The calculator will estimate the number of tons of aggregate that will be required.
As a rule, what is not included in placement drawings?
A:Does not show Dimensions but shows Bar placement, Reinforcement placement Why: Electrical drawings show all electric wiring, control panels, motors, electric pumps, etc. The Ironworker is not normally concerned with all of these but does need to refer at times to structural and architectural drawings. For example, placement drawings do not as a rule show complete building dimensions since all of the formwork is presumed to be in place before the Ironworker starts the work. Where necessary, structural and architectural drawings should be consulted for dimensions and other information which might be needed to supplement the placement drawings.
what must be large enough and in the right places to accommodate building movement from earthquakes?
A:Gaps or joints between cladding Why: The cladding on the outside of some buildings can sustain damage and even fall off if it does not allow the building to flex when the ground shakes. Precast concrete cladding, with or without stone facing, is heavy. The steel connections holding it to the building must be strong enough to allow the building to move in an earthquake without failing. In addition, gaps or joints between cladding units must be large enough and in the right places to accommodate building movement.
what do architectural drawings display
A:General Outlines of finished appearance, Plans showing room arrangements, Building Elevations Why: Architectural drawings show general outlines of the finished appearance of the building in elevations, plans and sections completely dimensioned. They show the relationship of the various kinds of materials such as concrete, steel, brick, wood and stone to each other, plans showing room arrangements with sections and elevations to illustrate details, finishes such as plaster or tile walls, ceilings, floor surfaces, fixtures, etc. In short, architectural drawings are those on which all other drawings such as structural, mechanical and electrical are based.
What do mechanical drawings display?
A:Piping Why: Mechanical drawings show generally all piping, heating and air condition ducts, and mechanical equipment.