Stainless steel refers to alloy steels with more than 10.5% of chromium and consists of several groups like austenitic, ferritic, martensitic etc. Austenitic stainless steel is normally used in structural applications because of its high corrosion resistance. Austenitic and ferritic types of stainless steel cover about 95% of stainless steel applications. Stainless steel is not stainless although it is corrosion resistant under a wide range of conditions.
What is the purpose of pedestals?
When structural steelworks are connected to the foundation, pedestals are normally designed to carry loads from metal columns through the ground surface to the footings which are located below the ground surface. With the installation of pedestals, it is the pedestals, instead of metals, which come into contact with soils.
Why are holes sometimes present in the base plates connected to footings?
The surface of footings is normally quite rough so that some leveling has to be carried out for the base plates. The interface between the base plates and footings after leveling is subsequently filled with grout.
What are the functions of different components in a painting system?
In a typical painting system, there are normally three main layers, primer, undercoat and finishing coat. The primer acts as the first coat of the painting system and adheres to the substrate. It serves to provide a foundation for other coats. The mid-coat, undercoat, is designed to increase the film thickness and hinder the background colour. Moreover, it aids in the reduction of permeability by incorporating pigments like micaceous iron oxide. Finally, the finishing coat contributes to the appearance of the painting system like colour. Sometimes, it may be designed to provide additional abrasive resistance. However, in terms of corrosion protection to steelworks, it does not add much value.
Why should protection be implemented for steelwork against fire?
Owing to the high thermal conductivity of steel, the temperature of unprotected steel is almost the same as the temperature of fire. Since the yield strength of structural steel drops approximately by half when its temperature rises to about 550oC, it is usually provided with some forms of insulation.
How do corrosion inhibitors function?
Corrosion inhibitors are chemical substances that, when added in small concentrations, stop or reduce the corrosion or reaction of the metal with the environment. It normally functions by one or more of the following mechanisms:
(i) It may alter the external environmental conditions by taking away or inactivating an aggressive agent;
What is the difference of the following types of sheetpiles Z-type, U-type, flat web and Pan-type?
Z-type: The interlocks are situated as far away from the neutral axis as possible to facilitate good shear transfer and to enhance higher strength to weight ratio. This is the most common type of sheetpiles used in many countries.
Should wide or narrow sheetpiles be adopted in temporary work?
In general, wide and deep sheetpiles tend to be more cost-effective than narrow sections because they provide the same bending strength with a lower weight per square foot. As such, with increasing width of sheetpiles sections, fewer sheetpiles are required to cover a certain length of piling operation. Hence, the cost of installation can be reduced accordingly.
What is the vibration mechanism caused by driving sheetpiles?
There are generally three main vibration mechanisms caused by driving
sheetpiles:
(a) When the sheetpiles are impacted by a hammer, a compressive wave would be formed and it travels down to the toe of sheetpiles. A large amount of energy would be used to cause downward movement of sheetpiles while some of the energy would be reflected back up to the sheetpiles. The remaining energy would be transmitted to soils which expand outward as a spherical wavefront called “P” waves.