Though many modern civil engineers complain about old construction methods and usage of inefficient structural system in India, the construction industry and construction methods are modernized rapidly in the country. The reason for adoption of modern techniques is driven by the need for speedier construction for economy and the need for more accuracy and precision for meeting the modern client requirement and construction demands. This brings the construction processes to a more efficient stage. One among the most popular structural system is Mivan Technology. Let’s dive into some of its merits and more importantly the structural engineering aspects. In this blog ,I will write about most of the basics that a civil engineer aspiring to get in to structural design of buildings should know about MIVAN Technology.
Mivan Technology
Mivan technology or MIVAN Formwork system is a completely modern method that is best suited for the construction of large-scale structures especially when repetitive slabs and blocks are involved. This structural system is very popular for low-cost housing in large cities. It is a slip form work system which was very popular in Middle east, Europe and South East Asia much before it became very popular in India. It came in to India in the early 2000 and is very popular because of the speed of construction and hence the economy it can bring in. The name MIVAN comes from the parent company MIVAN which improvised and innovated the structural form work system. MIVAN revolutionized the speed of construction.
Advantages of MIVAN Technology
MIVAN structural system has both advantages and disadvantages like any structural system.
Mivan technology avoids wastage of workmanship, material, and machinery. In this hectic world, the Mivan technology is used as an elimination step of traditional formwork which is not cost effective or efficient. A wide range of resources can be saved while using this method. Normally, light weighted Aluminum is used for formwork that can be easily assembled or disassembled by saving time, workforce, and cost. Mivan shuttering also provides a better finish for the building. Conventional formworks, on repetitive use wears off and can result in improper finishes. Mivan also provides larger carpet area for the user.
MIVAN system has lesser number of construction joints and hence reduces leakages. This improves durability of the structure. This is a structural advantage of this system. Less number of joints also reduces the number of dowels needed and some times allows to reduce the weaknesses introduced in structural members due to joints.
Components of MIVAN Formwork System
There are majorly 4 components for MIVAN system.
The wall components, Beam components, Deck components. There are also some special components. This blog is not intending to get in to the construction aspects of MIVAN but is intended to provide the needed info for a structural engineer so that she can adopt it in structural analysis and design.
The most important aspect to note is that, the conventional masonry walls are replaced by wall elements which are fully in RCC. We will discuss about the design considerations in the next section.
Structural considerations for MIVAN System
The main difference of MIVAN structural system from a conventional RCC system with respect to structural analysis and design, is the presence of RC walls instead of masonry walls. In a conventional system the stiffness of masonry is often ignored. Even if considered, the masonry stiffness is much different from the RCC walls.
By replacing the masonry with RCC, design point of view, the stiffness of the building increases immensely. It is not really possible that we can ignore this in analysis. The seismic resistance will be different when the stiffness is more and hence it is required to consider it in the structural analysis in structural analysis tools like ETABS.
Another important point to note is that, all the walls in a MIVAN building is in concrete. Hence all the openings like windows and doors and even electrical openings, sleeves for plumbing and all MEP services shall be meticulously planned and well-coordinated. In case of a conventional structural system, the walls would have been masonry and any MEP related conduit and openings needed can be incorporated any time in the masonry wall. Any lack of coordination will affect the structural consultants. The structural engineers will have to manage a lot of revisions if the multi-disciplinary coordination is not well planned. Also, in case of a poor coordination, between MEP and structural engineers there will be a lot of alterations and core cuts needed in RC walls after the building is constructed. This may affect the quality and safety of structural members and hence the safety of buildings.
ETABS modelling of MIVAN system
The walls are modelled as shell thin or shell thick as needed. The vertical portion of the structural walls are assigned as pier in order to define it as vertically loaded members. Any horizontal portion of the wall which is predominantly a beam member like that of the portion above doors and windows are assigned as spandrels. To know what is a pier and spandrel , see this video in Civilera YouTube channel.
More attention shall be provided in analysis when there is a stilt in the building. It is recommended to avoid such situations in seismic zones. Especially a MIVAN system with a stilt is undesirable. The stiffness at the upper level of stilt will be extremely high and it is a clear case of stiffness irregularity as well as strength irregularity. Also, you need to be carefully deciding the transfer beam where the stiff RCC walls starts. You need to ensure the transfer beam is carefully attended in analysis and structural design.
Another significant point that needs to be considered is the meshing of shells. If we choose to model slabs as shells, then it needs to be noted that the walls do have openings like windows and doors and the mesh points of walls and slabs has to match. Shifting of openings by clients and Architects during design stage will create a lot of remodeling issues for structural engineers if the modelling is not carefully planned. To a very large extent, this will not be a problem if ETABS is used for modelling and analysis. The challenge is when we use software like STAAD which do not have internal auto meshing. Handling modelling, analysis and design of shells is an area where ETABS is superior to STAAD. Choose your structural analysis tool wisely when you are doing a mivan building.
Summary
Structural systems and construction methods keep changing depending up on times and needs of the civil engineering industry. It is very important that structural engineers improvise their analysis methods and replicate the construction situations and change in structural behavior to suit. Also, the engineers need to know how to use the structural analysis software to idealize the structural system. Hope this blog provided you an understanding of the MIVAN system and the considerations you need to adopt in your structural analysis. Please feel free to comment below or write to us for more information.
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