Ductile connections

This type of construction uses precast concrete walls with steel or concrete frames (Figure 4.2). The frame resists all vertical loads and precast shear walls resist lateral loads. Ductile connections for precast panels are an important consideration. Precast panels are made with embedded steel connection devices attached to the building frame by bolting or welding. The roof is usually a concrete slab on metal deck. The metal deck is attached to steel framing by studs or puddle welds. Tins type of construction can be economically designed to withstand blast loading on the order of 7 to 10 psi (48 to 69 kPa) side-on overpressure. 

Depending on the loads and details used for anchorage design, the anchor connections are classified as either ductile or non-ductile. For ductile connections, the embedment is proportioned using the ultimate capacity of the ductile element for non-ductile connections, the embedment is proportioned using the factored design method. 

Energy-dissipating ductile connections, based on yielding of those longitudinal bars of the elements which enter the connection and flexural plastic hinging at the end of the connected element as in cast-in-place constmction the connection and the connected elements follow the same code mles as in monolithic constmction. 

Copper and nickel can be alloyed with zinc to form nickel silvers. Nickel silvers are ductile, easily formed and machined, have good corrosion resistance, can be worked to provide a range of mechanical properties, and have an attractive white color. These alloys are used for ornamental purposes, as sHverplated and uncoated tableware and flatware in the electrical iadustry as contacts, connections, and springs and as many formed and machined parts (see Electrical connectors). 

This is to be used for ductile iron in all applications and must be of a type suitable for mbber jointing rings to BS 2494. Where the working pressure is over 75 mbar, the connections shall be anchored by means of purpose-designed anchor blocks or self-anchoring joints. 

In all blast-resistant structures (steel, concrete, or masonry) special attention should be given to the integrity of connections between structural elements up to the point of maximum response. For example, it is important to prevent premature brittle failure of welded connections to avoid stress concentrations or notches at joints in steel structures and to provide ductile reinforcement detailing in concrete/masonry structure connections. For all materials, it is recommended that connections be designed to be stronger than the connected structural members such that the more ductile member will govern the design over the more brittle connection. 

The area of the tear region (03 00) shows evidence of ductile failure, as shown in Figure 46(f). To perform the analysis it was necessary to sever this connection between the partially fractured tube pieces. Therefore, the two pieces of tubing were pulled apart. The expected result is the ductile failure that was in fact... 

Special precautions must be taken regarding end bearing for these members to avoid crushing of the web at peak response. If end bearing controls, the allowable response is limited to reduce the chance for non-ductile failure. Connections for these members also present difficulty because of the thin web material. To develop the ultimate strength of a member, multiple fasteners may be required so that the shear strength of the materia is not exceeded. 

Boundar y conditions need to be assessed based on the type of connections to be used for the member supports. The engineer must keep in mind that support details must provide sufficient strength, ductility and stability to enable the member to develop full collapse mechanism. Support capability to resist reaction forces for both the loading and rebound phases of the response must be considered when assessing boundary conditions. 

Ductility requirements are implemented through the use of appropriate connection details. 

Detailed evaluations of connection ductility are usually not performed. However, in some special cases it may be necessary to evaluate moment versus rotation characteristics. Theoretical methods for predicting connection behavior, as well an electronic database of actual test data, are available from Chen 1994. Useful information on moment versus rotation relationships for various types of connections can also be obtained from Committee 43, White 1991, and ASCE Manual 41. 

Precast walls are used for two reasons to reduce the cost of the building through decreased field labor, and to shorten the schedule by constructing the walls and foundations simultaneously, The largest drawback for the use of precast structural elements is the design and detailing of connections. As in seismic design, special attention to ductility must be used. 

Ductility limits for structural steel members are established such that gross member collapse due to failure of the member itself or its connections is precluded. It is presumed that local and gross member instabilities are prevented by providing adequate bracing and stiffeners. Shear failure modes are also to be precluded by design. Determination of failure mechanisms and corresponding capacities for flexural members and beam-columns arc adequately covered by the LRFD specifications. 

Connections structural steel members are generally designed to develop the full strength of the member. With regard to ductility evaluations for connections, explicit checks are generally not made. It is presumed that satisfaction of the gross member displacement ductility criteria ensures the integrity of the member connections. 

Thus far, we ve discussed the sources, production, and properties of some important metals. Some properties, such as hardness and melting point, vary considerably among metals, but other properties are characteristic of metals in general. For instance, all metals can be drawn into wires (ductility) or beaten into sheets (malleability) without breaking into pieces like glass or an ionic crystal. Furthermore, all metals have a high thermal and electrical conductivity. When you touch a metal, it feels cold because the metal efficiently conducts heat away from your hand, and when you connect a metal wire to the terminals of a battery, it conducts an electric current. 

Lead (Pb) The chemical symbol for lead comes from the Latin plumbum, which also gives us the word plumber. It is highly malleable and ductile and has been known since antiquity. One ancient, albeit poorly chosen, application of lead was to fashion water pipes, and, hence the connection to the word plumber. 

The first secondary transition below Tg, the so called fj-relaxation, is practically important. This became evident after Struik s (1978) finding that polymers are brittle below Tp and establish creep and ductile fracture between Tp and Tg. The p-relaxation is characteristic for each individual polymer, since it is connected with the start of free movements of special short sections of the polymer chain. In view of more recent data of Tp Boyer s relation, Eq. (6.29), is very approximate and fails completely for amorphous polymers with high Tg s (e.g. aromatic polycarbonates and polysulphones). Some rules of thumb may be given for a closer approximation. 

The dashed line connects all failure points, in ductile as well as in brittle failure this line is called the failure envelope or fracture envelope... 

This work is a contribution to the definition of an experimental protocol which aims in identifying the parameters involved in a description of crazing within a cohesive surface methodology. The results obtained for PMMA are valuable for the calibration to perform in connection to the numerical work of Estevez et al. [2]. The method of preparation needs to be improved for more ductile material in order to characterize the failure by crazing only. 

By fitting Eq. (23) to experimental data for strong interfaces where Ojihril = 2fb we can obtain a reasonable estimate of <5 and of Q, provided that the crazing stress of the more ductile material is known. These constants can then be used to predict the value of o 6n /ac for more complicated cases where either the actual areal density of effective connecting chains or the force to break a connector is not precisely known. 

The durability of cemented joint replacements depends on the properties of PMMA bone cement. A titanium fiber was used to reinforce the cement. Before the cement was applied it was centrifuged to remove entrapped air which would cause voids in the connection. The treatment also improved the ductility of the cement. Similar processes are used in many plastic industries to improve elastic properties. 

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