Assemblages Test 2

Bolt

a fastener, usually metallic, consisting of a cylindrical body with a head at one end and a helical thread at the other, intended to be inserted through holes in adjoining pieces of material and closed with a threaded nut.

Tilt-up construction

a floor slab is cast on the ground, and reinforced concrete panels are poured over it in a horizontal position. When curing is complete, they are hoisted into position by a crane and grouted together, thereby eliminating most of the usual wall formwork

Weld

a joint between two pieces of metal formed by fusing the pieces together by the application of intense heat, usually with the aid of additional metal melted from a rod or electrode.

How do tensile structures work?

a membrane that is supported by masts or other rigid structural elements such as frames or arches. The fabric and cables transmit external loads to the rigid supports and ground anchors by means of tensile forces.

Two-way flat slab

a system suited to heavily loaded buildings such as storage and industrial buildings. The formwork is completely flat except for a thickening of the concrete to resist the high shear forces around the top of each column. Traditionally, this thickening was accomplished with both a funnel-shaped mushroom capital and a square drop panel, but today the capital is usually eliminated to achieve a greater economy of formwork cost, leaving a drop panel to do the work alone.

Insulating concrete forms

an alternative way of casting a concrete wall, particularly one that will be an exterior wall of a building, is the use of insulating concrete forms that serve both from the concrete and to remain in place permanently as thermal insulation.

Rivet

an archaic fastener in which a second head is formed after the fastener is in place; a threadless fastener used in sheet metal work.

Flying formwork

for slabs that are cast in place, flying formwork is fabricated in large sections that are supported on deep metal trusses. The sections are moved from one floor to the next crane, eliminating much of the labor usually expended on stripping and reerecting formwork.

How are rivets used to join steel members?

it is brought to a white heat in a forge inserted through holes in the member to be joined hot worked with a pneumatic hammer to produce a second head opposite the first as the rivet cools, it shrinks, clamping the joined pieces together and forming a tight joint riveting was for many decades the predominant fastening technique, but it has been replaced by the less labor intensive techniques of bolting and welding

One-way solid slab system

spans across parallel lines of support furnished by walls and/or beams.

Two-way waffle slab system

the waffle slab, or two-way concrete joist system, is the two-way equivalent of the one-way concrete joist system. Metal or plastic pans called domes are sued as formwork to eliminate nonworking concrete form the slab, allowing considerably longer spans than are feasible in the two-way flat plate system.

Lift-slab construction

used chiefly with two-way flat plate structures, virtually eliminates formwork. The floor and roof slabs of a building are cast in a stack on the ground. Then hydraulic jacks are used to lift the slabs up the columns to their final elevations, where they are welded in place using special cast-in-place steel slab collars.

slip forming

useful for tall walled structures such as elevator shafts, stairwells, and storage silos. A ring of formwork is pulled steadily upward by jacks supported on the vertical reinforcing bars, while workers add concrete and horizontal reinforcing in a continuous process.

Wide-module concrete joist system

when fire resistance requirements of the building cod dictate a slab thickness of 4 1/2 inches or more, the slab is capable of spanning a much greater distance than the normal space between joists in a one-way concrete joist system. This has led to the development of the wide-module concrete joist system, also called the skip-joist system, in which the joists are placed 4 to 6 feet apart.

What do you need to do to mortar when outdoor temperatures are below freezing?

-Warming the mixing water to produce mortar at the optimum temperature for working and curing -Enclosure -Using a Type III cement to accelerate the curing of mortar -Mixing the mortar in smaller quantities in order that it not cool excessively before it is used -Chemical accelerators and so-called "anti-freeze" admixtures are, in general, harmful to mortar and reinforcing steel and should not be used

What are the edges of steel members beveled for?

A beveled edge allows full access for the welding electrode so that the joint can be filled with weld metal to the same thickness and strength as the member being connected.

Why is a masonry cavity wall important?

A cavity wall prevents water from reaching the interior of the building by interposing a cavity between the outside and inside wythes of the wall. Insulation Reduces dead weight

What is post-tensioning used for in precast beams?

A post-tensioned, structurally continuous beam-column connection may be created by passing a tendon from a pocket in the top of one beam, through the column, to a pocket in the top of the other beam. The tendon is anchored to a plate in one pocket as it is tensioned by a jack in the other pocket.

How is welding wire fabric used?

A reinforcing mesh of welded wire fabric, cut to a size just a bit smaller than the dimensions of the slab, is laid over the moisture barrier or crushed stone. The fabric is most commonly used for lightly loaded slabs. The grid of wires and bars helps protect the slab against cracking that might be caused by concrete shrinkage, temperature stresses, concentrated loads, frost heaving, or settlement of the ground beneath.

What is the difference between a moment connection and a framed connection?

Moment connections- connection of flanges strongly across the joint by means of full-penetration groove welds across the beam flanges. Framed connections- joins only the web of the beam and not the flanges.

What materials can be used to fireproof steel members?

Brick, concrete, metal lath and plaster, gypsum board, spray-on fireproofing, loose insulating fill inside a sheet metal enclosure, water-filled box column made of a wide-flange shape with added steel plates, rigid slab fireproofing, suspended plaster ceiling, mineral fiber slabs, intumescent mastics and paints.

What is good and bad about adjustable masonry ties?

Adjustable masonry ties are convenient for the masons because they allow for irregularities in course heights, but they may be insufficiently rigid for some structural purposes.

What are topping slabs used for?

After the slab elements have been erected, a concrete topping is poured over them and finished to a smooth surface The topping, usually 2 inches in thickness, bonds during curing to the rough top of the precast elements and becomes a working part of their structural action Slab elements may be topped or untopped.

One-way concrete joist system (ribbed slab)

As one-way solid slab spans increase, a progressively thicker slab is required. Beyond a certain span, the slab becomes so thick that the weight of the slab itself is an excessive burden unless a substantial portion of the nonworking concrete in the lower part of the slab can be eliminated to lighten the load. This is the rationale for the one-way concrete joist system, also called a ribbed slab. The bottom steel is concentrated in spaced ribs or joists. The thin slab that spans across the top of the joists is reinforced only by shrinkage-temperature bars. There is little concrete in this system that is not working, with the result that a one-way concrete joist system can span considerably longer distances that a one-way solid slab.

What is used to connect precast elements?

Bolting, welding, and grouting are all commonly employed in these connections. The simplest joints in precast concrete construction are those that rely on gravity by placing one element atop another, as is done where slab elements rest on a bearing wall or beam, or where a beam rests on the corbel of a column. Posttensioning can be used to combine large precast elements into even larger ones on the site.

Light gauge steel framing comes in what shapes?

C-shaped (Cee) sections - Studs, joists, rafters Runner channel sections - Top and bottom track

How are light gauge steel framing members produced?

Cold-formed to differentiate from the much heavier hot-rolled shapes that are used in structural steel framing.

Columns are spliced at waist level due to what reasons?

Column splices are made at waist level above this platform, both as a matter of convenience and as a way of avoiding conflict between the column splices and the beam-to-column connections.

Why is carbon content important to steel quality?

Carbon content is a crucial determinant of the properties of a ferrous (iron-based) metal: Too much carbon makes a hard but brittle metal, while too little produces a soft, relatively weak material.

What are some types of improved beams and what is the difference between them?

Castellated beams- produced by flame cutting the web of a wide-flange section along a zigzag path, then reassembling the beam by welding its two halves point to point, thus increasing its depth without increasing its weight. Plate girders- long-span beams tailored to any loading condition custom designed and fabricated. Rigid frames- efficiently produced by welding together steel wide-flange sections or plate girders.

Which masonry units shrink after installation and which expand?

New clay masonry units tend to absorb water and expand under moisture conditions New concrete masonry units usually shrink somewhat as they give off excess water following manufacture

Does brick masonry have any tensile strength?

No, the allowable tensile strength of brick is 0 psi

Why are control joints important for a slab on grade?

Control joints must be provided at intervals in a slab on grade. A control joint is a straight, intentional crack that is formed before the concrete has hardened fully. The function of a control joint is to provide a place where the forces that cause cracking can be relieved without disfiguring the slab. The reinforcing mesh is discontinued at each control joint as a further inducement for cracking to occur in this location rather than at random.

What are the various types of two-way floor and roof framing systems?

Two-way flat slab Two-way flat plate system Two-way waffle slab system

How do you find the depth and width of a wide flange shape?

Depth is the nominal first number after the W. Width must be looked up in the Manual of Steel Construction

How do you stabilize a steel frame against lateral loads?

Diagonal bracing, eccentric bracing, moment connections, and shear panels

Where are internal flashing used?

Typically at the bottom of a wall cavity Additionally, at every location where the cavity is interrupted, such as: above heads of windows and doors below copings and window sills below lintels and above shelf angles over spandrel beams

What does efflorescence indicate?

Idicates that water has begun to enter the wall, and is best controlled by investigating and correcting the source of leakage.

Two-way flat plate system

In more lightly loaded buildings the slab need not be thickened at all over the columns. Because there are no beams and girders, only a thin slab, the story heights of the building may be kept to an absolute minimum.

How are stirrups at the top of precast elements used?

Mild steel reinforcing bars are used for stirrups. The projecting tops of the stirrups will bond to the sitecast topping.

Why are high-quality flashing materials important in masonry walls?

Flashing within a wall are almost impossible to replace if they should fail in service. Even the most expensive flashing materials cost only a very small fraction of the total price of a masonry wall, so there is little reason to use cheap ones in a misguiding effort to save money.

How are steel structural shapes formed?

In the structural mill, the hot steel blank passes through a succession of rollers that squeeze the metal into progressively more refined approximations of the desired shape and size.

What are the types of formwork used?

Insulating concrete forms Lift-slab construction Flying formwork Slip forming Tilt-up construction

Does reinforcing need to remain continuous through an expansion joint and control joint?

Joint reinforcing must be interrupted at movement joints so that it does not restrain the opening or closing of the joint.

What are the innovations in site-cast concrete?

Lightweight concrete and admixtures formwork materials and methods lift-slab flying formwork gang forms slip forms tilt-up shotcrete

What are the various types of one-way floor and roof framing systems?

One-way solid slab system One-way concrete joist system (ribbed slab) Wide-module concrete joist system

How do you know high strength bolts are tightened correctly?

Pneumatic impact wrench turn-of-nut method load indicator washer tension control bolt swaged lock pin and collar fastener

How are open-web steel joist formed?

Prefabricated steel trusses designed to carry heavy loads, particularly bays of steel joists.

What are the standard precast concrete beam and girder shapes?

Rectangular beam L-shaped beam Inverted Tee beam AASHTO beam

What are the ways of joining steel members and how are they used?

Rivets, bolts, and welds

What are the spanning differences of the precast floor elements?

Solid slabs- short spans and minimum slab depths Hollow-core slabs - intermediate spans Single Tees - longest spans Double tees - longest spans

How do you attach a steel column to a foundation?

Steel baseplates, which distribute the concentrated loads of the steel columns across a larger area of the concrete foundation, are shop welded to all but the largest of columns. The baseplate is then attached to the foundation with anchor bolts cast into the foundation.

How are concrete columns formed?

The column form may be a square box of plywood or composite panels, a cylindrical steel or plastic tube bolted together in halves so that it can later be removed, or a waxed cardboard tube that is stripped after curing by unwinding the layers of paper that make up the tube.

What happens when an internal flashing meets the exterior surface of a masonry wall?

The flashing should be carried at least 3/4" beyond the outside face of the wall Flashing should be turned down at a 45-degree angle so that draining water drips free of the wall If the internal flashing is made of a flexible material, it should be cemented to a sheet metal flashing just before it exits the wall

How do form ties work?

The form ties, which are small-diameter steel rods specially shaped to hold the formwork together under the pressure of the wet concrete, are inserted through holes provided in the formwork panels and secured to the back of the form by devices supplied with the form ties. The ties will pass straight through the concrete wall from one side to another and remain embedded permanently in the wall after it is poured.

Why are L-shaped and inverted T-shapes important?

The projecting ledgers on L-shaped beams and inverted tees provide direct support for precast slab elements. They conserve headroom in a building by supporting slabs near the bottoms of the beams.

Why is the gauge of the steel important?

The strength and stiffness of a member depends on the shape and depth of the section and the gauge (thickness) of the steel sheet from which it is made.

What are end dams used for?

To keep water from running off the ends of sill and lintel flashings

What is special about two-way floor and roof framing systems?

Two-way concrete framing systems are generally more economical than one-way systems in buildings where the columns can be spaced in bays that are square or nearly square in proportion.

How do you plump-up a steel frame building?

Using diagonal cables and turnbuckles to straighten and square the steel frame in order to make sure that the frame is level overall.

Why are reinforcing bars offset at the top of columns?

Where vertical bars overlap, the tops of the bars form the column below and are offset (bent inward) by one bar diameter to avoid interference.

What are the most common steel beam shapes

Wide-flange shapes are used for most beams and columns, superseding the older American Standard (I-beam) shapes.

What spanning systems may be supported on masonry bearing walls?

Wood balloon framing, heavy timber framing, structural steel framing, sitecast concrete framing, precast concrete framing