The Importance of Structural Steel In Constructing Buildings Structural steel has become one of the most prevalent construction materials of the century, often seen as an extremely important component of modern buildings and housing. According to the World Steel Association, over 1,600 million tonnes were produced in 2016, 197 million more than the previous year. It's become viable for any kind of project and offers several benefits, which many building plans rely on for structural safety. Availability The widespread adoption of steel has made it easy to find, both as a raw alloy and pre-made components. Fabricated parts will often be openly sold by suppliers (with many factories selling both locally and overseas), allowing beams and frames to be purchased directly.  Thanks to this, companies can work under tighter deadlines and access a supply of steel parts anywhere in the world.  Steel parts can be ordered as soon as the architectural plan is agreed on, saving time that would be spent waiting for them to arrive at the site. This provides extra time to check measurements and find suitable storage, issues that could normally delay construction by several hours. Weight Its lightweight makes steel easy to transport over land and lift via a crane, reducing the amount of fuel wasted getting it to the site. In addition, this can make buildings far easier to take down: a prototype ProLogic warehouse was built at Heathrow to demonstrate how over 80% of the entire structure was reusable, which could be disassembled in a fraction of the time an average warehouse would take. Low weight can aid in moving and rebuilding structures, as shown with the 9 Cambridge Avenue warehouse relocation: the warehouse itself was dismantled and rebuilt 1 mile away, using almost no steel except the existing components. This added mobility and versatility makes steel a very desirable building material for structures that have extra land for expansion. Sustainability As the desire for eco-friendly buildings increases, steel will become more convenient for construction projects. It can easily be recycled and doesn't need to be permanently disposed of, so old buildings or temporary supports can be repurposed into new projects as needed. Roughly 97.5% of all steel from UK demolition sites is recovered and reused, according to data gathered by Steel Construction. Recovered steel components that haven't been damaged can be re-used in other projects, removing the cost of getting the alloy melted down and re-cut as a new part. If a building is being demolished and rebuilt, existing parts could be stripped out and repurposed to save money kept in storage for future projects or simply sold to another company as components (or raw alloy, if sold back to a steel fabrication company).  Strength Due to its high strength-to-weight ratio, less steel is needed in a single support or beam, reducing material costs and improving its sustainable nature. It can withstand strong physical impacts and forces, keeping building occupants safe, but won't wear away or need to be replaced afterwards. This extra strength can be retained through the design, rather than the amount of steel used. Steel I-beams are often used in modern construction since they're lighter, stronger and less wasteful than any wooden beam of the same size. The natural fire and rust resistance of alloy steel makes it viable for exterior structures, such as fire escapes or balcony supports – MIMA also suggest possible use as external walls to contain insulating materials. Price Modern regulations are very specific about how efficient construction should be: these rules often have the added benefit of cutting maintenance or material costs in the long run. Concrete remains more consistent compared to the varying price of steel, but the costs of repairing and reinforcing a concrete beam or pillar will usually make steel cheaper over a building's lifetime. As mentioned earlier, steel is entirely reusable. It retains all of its properties, so a large amount of recovered steel could drastically reduce the cost of a new structure. A small study on the cost of a London office building revealed that steel composite was roughly 8% cheaper than concrete slabs across all ten storeys. Steel constructions are widely used in several applications such as structures for buildings, stores, factories, and power plants. The scope of the research is to study a methodology to reduce the weight and the cost related to big frame steel structure warehouse during the early design phase, which is the phase where most of the project layout is defined. The main aim of this paper is the development of a platform-tool to support the automatic optimization of a steel structure using virtual prototyping tools and genetic algorithms. The focus is on the design of heavy steel structures for oil & gas power plants. This work describes in detail the design methodology and estimates the weight saving related to the re-design process of a test case structure. The design cases considered in the paper are those relevant to the operating. Steel structure workshop modular residence is the outstanding residential industrialization. It has many advantages, such as the low whole cost, high resource recovery, a high degree of industrialization. This paper compares the comprehensive benefits of steel structural in modular buildings with prefabricated reinforced concrete residential from economic benefits, environmental benefits, social benefits and technical benefits by the method of entropy evaluation. Finally, it is concluded that the comprehensive benefits of steel structural in modular buildings is better than that of prefabricated reinforced concrete residential. The conclusion of this study will provide certain reference significance to the development of steel structural in modular buildings in China. In this paper, various moment-resisting steel frames (MRSFs) are subjected to 30 narrow-band motions scaled at different ground motion intensity levels in terms of spectral acceleration at first mode of vibration  in order to perform incremental dynamic analysis for peak and residual interstory drift demands. The results are used to compute the structural reliability of the steel frames by means of hazard curves for peak and residual drifts. It is observed that the structures exceed the threshold residual drift of 0.5%, which is perceptible to human occupants, and it could lead to human discomfort according to recent investigations. For this reason, posttensioned connections (PTCs) are incorporated into the steel frames in order to improve the structural reliability. The results suggest that the annual rate of exceedance of peak and residual interstory drift demands are reduced with the use of PTC. Thus, the structural reliability of the steel frames with PTC is superior to that of the MRSFs. In particular, the residual drift demands tend to be smaller when PTCs are incorporated in the high-rise steel structure. Currently, most of the seismic design regulations recommend the use of maximum interstory drift as the main engineering demand parameter. Nevertheless, earthquake field reconnaissance has evidenced that residual drift demands after an earthquake play an important role in the seismic performance of a structure. For example, several dozen damaged reinforced concrete structures in Mexico City had to be demolished after the 1985 Michoacan earthquake because of the technical difficulties to straighten and to repair buildings with large permanent drifts [1]. Okada et al. [2] reported that several low-rise RC buildings suffered light structural damage but experienced relatively large residual deformations as a consequence of the 1995 Hyogo-Ken Nambu earthquake even though they had sufficient deformation capacity. After examining 12 low-to-mid-rise steel office buildings (particularly 10 with structural system based on steel moment-resisting frames) structurally damaged and leaned after the same earthquake, Iwata et al. [3] highlighted that the cost of repair of leaned steel buildings linearly increased as the maximum and roof residual drift increased. Based on their study, the authors suggested that steel buildings should be limited to maximum and roof residual drift about 1.4% and 0.9%, respectively, to satisfy a repairability limit state that meets both technical and economical constraints. More recently, a field investigation in Japan indicated that a residual interstory drift of about 0.5% is perceptible for building occupants [4]. Bojórquez and Ruiz-García [5] by comparing peak and residual drift demand hazard curves have observed that if steel frames exhibit peak drift demands about 3%, they could experience residual drifts larger than 0.5%, which is the threshold residual drift that could be tolerable to human occupants, and it could lead to human discomfort [4] when subjected to narrow-band earthquake ground motions of high intensity. Therefore, several researchers have demonstrated that the estimation of residual drift demands should also play an important role during the design of new buildings [6–8] and the evaluation of the seismic structural performance of existing buildings [9–13]. In the present study, motivated by the need to reduce peak and residual interstory drift demands, PTCs are incorporated into various MRSFs. Posttensioned steel moment-resisting frames are structural systems proposed in recent years as an appropriate alternative to welded connections of moment-resisting frames in seismic zones [14–27]. They are designed to prevent brittle fractures in the area of the nodes of steel frames, which can cause severe reduction in their ductility capacity, as occurred in many cases during the 1994 Northridge and the 1995 Kobe earthquakes. The philosophy of structures with PTC is that under an intense earthquake motion, beams and columns remain essentially elastic concentrating the damage on the energy dissipating elements, which can be easily replaced at low cost. Moreover, they provide capacity of energy dissipation and self-centering which can significantly reduce the residual demands. The structural performance of the selected MRSFs is compared with the structures with PTC through incremental dynamic analysis and the estimation of the structural reliability of the frames in terms of peak and residual interstory drift demands. With this aim, four MRSFs and the same structures with PTC (here named FPTC frames with posttensioned connections) are subjected to 30 long-duration ground motions recorded at the lake zone of Mexico City where most of the damages were found in buildings as a consequence of the 1985 Michoacan earthquake. In general, it is observed that the structural reliability of the steel frames with PTC is superior to that of the MRSFs. In particular, the residual drift demands tend to be smaller than 0.5% (which is perceptible for building occupants) when PTCs are incorporated into the steel structure buildings.