Ch. 26 and 27 Review Questions

With the help of sketches and notes, explain why the walls in a traditional masonry bearing wall structure had to be extremely thick.

- To accommodate greater gravity loads at the lower floors. - To ensure stability against overturning by wind loads (The code-required thickness was based on the assumption that all wind loads on the building were resisted by exterior walls only. In providing this resistance, each exterior wall functioned as a freestanding wall) (Highly conservative estimate)

Using sketches and notes, explain the important features of a pressure-equalized drainage wall.

- Voids in cladding for pressure equalization in the air space - Compartmentalization of the air space - Airtight backup wall

Using a sketch and notes, explain what a capillary break is and where it is commonly used.

A capillary break is a barrier that is installed to prevent the movement of water through capillary action. Capillary action is the ability of a liquid to flow in narrow spaces without the assistance of, or even in opposition to, external forces like gravity. It is commonly used in foundation walls to prevent water from seeping into the foundation and causing damage to the home.

With the help of a sketch and notes, explain what a closure strip is with respect to a tilt-up wall building.

A closure strip is a 5-ft- to 6-ft-wide strip adjoining the panels that is cast after all panels have been erected, while the rest of the slab is cast before the erection of the panels. Bent reinforcement dowels, as part of the reinforcement in the panel, are straightened and lap-spliced with the reinforcement projecting from the slab into the closure strip.

With the help of a sketch, explain what the tunnel form is, and its benefits and limitations.

A tunnel form consists of prefabricated and collapsible steel forms (of an inverted L-shape) that allow the walls and the overlying floor slabs to be cast simultaneously. The tunnel form has a number of benefits, including: - Quick and easy to assemble when reused - Strong and durable. - Inexpensive when reused - Reusable The tunnel form also has a number of limitations, including: - Difficult to transport - Requires specialized equipment - Expensive to maintain (cleaning, repairing, lubricating, painting)

Using sketches and notes, explain the difference between an anchored veneer and an adhered veneer.

Anchored Veneer: Anchors connect the veneer to the backup; therefore, they participate in transferring the wind loads from the veneer to the backup wall. An anchored veneer wall is typically designed as a drainage wall with a minimum 2" air space between the veneer and the backup wall. Adhered Veneer: A veneer adhered is face-sealed to the backup. Stucco and EIFS wall assemblies are examples of face-sealed barrier walls.

Explain the differences between a barrier wall and a drainage wall.

Barrier Wall: - Prevents water from entering a building - Waterproof barrier - Easy Install, Inexpensive - Fails if waterproof barrier is damaged Drainage Wall: - Allows water to drain away from the building - Creates a series of channel or pipes - Complex Install, Expensive - Fails if clogged

What is the purpose of bond beams, and where are they required in a typical load-bearing masonry structure?

Bond beam encases steel reinforcing in grout or concrete providing a continuous horizontal load path, and increasing the strength and lateral stability of the wall. They are required at the top and end of a load-bearing wall.

With the help of sketches and notes, explain why it is desirable to reinforce the ends, corners, and jambs around openings in the walls of load-bearing masonry buildings.

Ends Not supported by other walls on either side. Corners Subjected to both tension and compression forces. Jambs Subjected to shear forces because of the horizontal load on the jamb.

Using sketches and notes, explain the important features of a drainage-type exterior wall.

Features of Drainage Wall: - Exterior cladding - Air space - Flashing - Water-resistant backup - Weep holes

Explain why tilt-up wall panel-to-panel connections are discouraged and why they are necessary for corner panels. In which situations, panel-to-panel connections are required?

It doesn't allow the panels to expand, contract, and deflect freely. The absence of this freedom causes stress results in cracking. The movement of panels at a corner is unique because the panels move in directions perpendicular to each other. Providing a welded connection between corner panels prevents a premature failure of the sealant between panels. Welded connections between adjacent non-corner panels in seismic and high-wind regions are also recommended. Panels that are located near openings, such as doors and windows, are also subject to a lot of stress. These panels may need to be connected to provide additional strength.

Tilt-up wall sandwich panels

Sandwich panels will be the new norm for tilt-up wall construction because of the increasing emphasis on energy conservation, which precludes (or reduces) the need for interior insulation and associated CFS framing. Additionally, if the concrete in face wythe is made with white Portland cement, exterior painting of tilt-up wall panels can be avoided. However, sandwich panels are thicker, require more concrete, greater lifting capacity of cranes, and greater quality control during panel casting because the pull-out strength of ties must be verified before casting the backup concrete wythe.

Explain why the live load on the slab-on-ground in a concrete tilt-up wall building is generally higher during the construction of the building than the in-service live load.

The following are some of the factors that contribute to the higher live load during construction: - The weight of workers - The weight of materials - The weight of vehicles

Explain why the air space in a pressure-equalized drainage wall must be compartmentalized.

To equalize air pressure on both sides of the wall and prevent water from being sucked into the air space behind the wall preventing drainage.

Explain the importance of vertical reinforcement in load-bearing masonry walls.

To provide stability against bending loads, overturning (tension loads), and sliding of the wall (shear forces) caused by wind or seismic loads.

Double-sealed tilt-up wall panels

Used for greater air and water tightness.