Sunday, January 26, 2020

READY MIX CONCRETE

    Ready-mix concrete is concrete that is manufactured in a batch plant, according to a set engineered mix design. Ready-mix concrete is normally delivered in two ways. First is the barrel truck or in–transit mixers. This type of truck delivers concrete in a plastic state to the site. Second is the volumetric concrete mixer.
     This delivers the ready mix in a dry state and then mixes the concrete on site. Batch plants combine a precise amount of rock, sand, water and cement together by weight, allowing specialty concrete mixtures to be developed and implemented on construction sites.



     The first ready-mix factory was built in the 1930s, but the industry did not begin to expand significantly until the 1960s, and it has continued to grow since then. Ready-mix concrete is often preferred over other materials due to the cost and wide range of uses, from bird baths to high rise buildings and bridges. It has a long life span when compared to other products of a similar use, like road ways. It has an average life span of 30 years under high traffic areas compared to the 10 to 12 year life of asphalt concrete with the same traffic.
     Ready-mix concrete, or RMC as it's also known, refers to concrete that is specifically batched or manufactured for customers' construction projects. It is a mixture of Portland cement, water and aggregates: sand, gravel, or crushed stone. All aggregates should be of a washed type material with limited amounts of fines or dirt and clay. Ready-mix concrete is bought and sold by volume - usually expressed in cubic meters.

Metered concrete :
     As an alternative to centralized batch plant system is the volumetric mobile mixer. This is often referred to as on-site concrete, site mixed concrete or mobile mix concrete. This is a mobile miniaturized version of the large stationary batch plant. They are used to provide ready mix concrete utilizing a continuous batching process or metered concrete system.
     The volumetric mobile mixer is a truck that holds sand, rock, cement, water, fiber, and some add mixtures and color depending on how the batch plant is outfitted. These trucks mix or batch the ready mix on the job site itself. This type of truck can mix as much or as little amount of concrete as needed.



     The on-site mixing eliminates the travel time hydration that can cause the transit mixed concrete to become unusable. These trucks are just as precise as the centralized batch plant system, since the trucks are scaled and tested using the same ASTM (American standard test method) like all other ready mix manufactures. This is a hybrid approach between centralized batch plants and traditional on-site mixing. Each type of system has advantages and disadvantages, depending on the location, size of the job, and mix design set forth by the engineer.

Transit mixed ready mix vs. volumetric mixed ready mix :
 a) A centralized concrete batching plant can serve a wide area. Site-mix trucks can serve an even larger area including remote locations that standard trucks cannot.

 b) The batch plants are located in areas zoned for industrial use, while the delivery trucks can service residential districts or inner cities. Site-mix trucks have the same capabilities.

 c)Volumetric trucks often have a lower water demand during the batching process. This will produce a concrete that can be significantly stronger in compressive strength compared to the centralized batch plant for the same mix design using the ASTM C109 test method.

 d)Centralized batch systems are limited by the size of the fleet. It may take upwards of 10 minutes to batch and load out one 9 - 12 yard truck depending on the plant size and type. They are unable to change mix designs during the batch process.

 e)Volumetric mixers can seamlessly change all aspects of the mix design while still producing concrete. They can continuously mix quality concrete for an indefinite time while being continuously loaded with fresh materials. They can produce 1 yard of concrete in as little as 40 seconds depending on the mix design and batch plant size outfitted.

f) For short loads, (orders under 10 yards) Transit Mixers typically return to their batch plant after each delivery. Volumetric trucks can go directly from job to job until truck is emptied, reducing traffic and fuel consumption.

Advantages of Ready Mixed Concrete:
1. Quality assured concrete:- Concrete is produced under controlled conditions using consistent quality of raw material.
2. High speed of construction- Speed of construction can be vary fast in case RMC is used.
3. Reduction in cement consumption by 10 – 12 % due to better handling and proper mixing. Further reduction is possible if mineral admixtures or cementitious materials are used.
4. Versatility in uses and methods of placing: The mix design of the concrete can be tailor made to suit the placing methods of the contractor.
5. Since ready mixed concrete (RMC) uses bulk cement instead of bagged cement, dust pollution will be reduced and cement will be saved.
6. Conservation of energy and resources because of saving of cement.
7. Environment pollution is reduced due to less production of cement.

Limitations of Ready Mix Concrete:
1. As the Ready Mixed Concrete is not available for placement immediately after preparation of concrete mix, loss of workability occurs. In addition, there are chances of setting of concrete if transit time involved is more. Therefore, generally admixture like plasticisers/ super plasticisers and retarders are used. Addition of retarders may delay the setting time substantially which may cause placement problems. In addition, it may also affect the strength of concrete. Therefore, it is necessary that the admixtures i.e. plasticisers and super plasticisers/ retarders used in Ready Mixed Concrete are properly tested for their suitability with the concrete. In case loss of strength is observed, the characteristic strength may have to be enhanced so that after loss of strength, required characteristic strength is available.
2. Because of large quantity of concrete available in short span, special placing and form work arrangement are required to be made in advance. The placement methods of readymix concrete plays an important role as it affects the strength and durability of concrete structures. The time of delivery, quality checks and time of placements affects the ready mix concrete. Ready mix concrete is a concrete which is manufactured as per required mix ratio in batching plant,and then is transported to construction site on continuously mixing trucks.


Ready Mix Concrete Placement Methods :
Ready Mix Concrete placement methods include following basic principles:
1. When arriving to the site the concrete transport certificate must be checked for desired              characteristics of ordered concrete (quantity, class, maximum aggregate size, slump, temperature, type cement etc.) and time duration of transport.
 2. Concrete shall be delivered to the site and discharged from the truck completely and in the forms ready for vibration within 1-1/2 hours after batching.
3. Concrete shall be placed in maximum 15 minutes after its arrival to the site, and the finishing of placement will take place before the cement starts setting.
 4. Concrete shall be stored / deposited as near as (physically and economically) possible to its final position, in crane hoisted buckets, concrete pumps, chutes etc.
 5. The receptacles used for the transport and deposition of concrete shall be cleaned and washed out at the end of each day’s work and whenever concreting is interrupted for more than 30 minutes.
 6. If the concrete, due to transport, is segregated. It should be mixed again on clean platforms, without adding water, if not possible the batch should be refused.



EFFECT OF TRANSIT TIME ON READY MIX CONCRETE :
Ready mix concrete is generally produced in large quantity and is transported to distant places for placement in structural elements. Sometimes the distance can be in many kilometers or miles.

1. Loss of workability:
The concrete should always be laid in position without loss of time to avoid setting and stiffening of concrete to reduce its workability. When the transit time is high, it will have effect on workability of concrete. This happens due to hydration reaction taking place when cement mixes with water, evaporation of mixed water in concrete and due to absorption of water by aggregates. While the workability of concrete depends on many factors such as the constituent material, mixed proportion, ambient temperature, humidity and method of transport etc., the reduction in workability may lead to difficulty in placement of concrete.

2. Setting of concrete:
When the transit time of ready mix concrete is high, the initial setting of concrete may take place. To avoid setting of concrete, retarding admixtures can be used to prolong the setting of concrete. While permitting use of retarder, it should be ensured that the suitability and dose of retarder is decided after conducting necessary trials. It may be noted that generally retarding effect of retarder is smaller at higher temperature and sometimes few retarders seem to be ineffective at extremely high temperature. Thus, it is desirable to keep the temperature of concrete as low as possible.

3. Time period for delivery of concrete:
In order to control loss of workability and setting of concrete, the concrete should be delivered completely to the site of work within one and half hours (when the atmospheric temperature is above 200C) and within two hours ( when the atmospheric temperature is at or below 200C)of adding the mixing water to the dry mix of cement and aggregate or adding the cement to the aggregate whichever is earlier. Adequacy of the time period, required for delivery of concrete, should be checked. 

STAIRCASES

INTRODUCTION :
Staircases provide means of movement from one floor to another in a structure. Staircases
consist of a number of steps with landings at suitable intervals to provide comfort and safety for the users.

PARTS OF STAIRCASE :

  1. Tread : horizontal upper portion of a step. 
  2. Riser : vertical portion of a step.
  3. Rise : vertical distance between two consecutive treads. 
  4. Flight : a series of steps provided between two landings. 
  5. Landing : a horizontal slab provided between two flights.
  6. Waist : the least thickness of a stair slab.
  7. Winder : radiating or angular tapering steps. 
  8. Soffit : the bottom surface of a stair slab. 
  9. Headroom : the vertical distance from a line connecting the nosings of all treads and the soffit above. 
  10. Nosing : The edge of the tread projecting beyond the face of the riser and the face of a cut string.

R.C.C. STAIRS :
The various advantages of reinforced concrete stairs are given below : 
• They have requisite fire resisting qualities to a great extent 
• They are durable,strong, pleasing in appearance and can be easily rendered non-slippery. 
• They can be designed for greater widths, longer spans and any height. 
• They can be moulded in any desired form to suit the requirements of the architect. 
• They can be easily cleaned. 
• The cost of maintenance is almost nil. 
• They can be pre-cast or cast-in-situ. 

DIFFERENT STAIR ARRANGEMENT IN CASE OF R.C.C. :
• Single straight flight stairs
• Inclined slab stairs with half space landings
• String beam stairs
• Cantilever stairs
• Spiral stairs

1) SINGLE STRAIGHT FLIGHT STAIRS:
Although simple in design and construction, is not popular because of the plan space it occupies          The flight behaves as simply supported slab, spanning from landing to landing.
The effective span/total horizontal going is usually taken as landing edge to edge by providing a down stand edge beam to each landing.  If these edge beams are not provided, the effective span would betaken as overall of the landings, resulting in a considerably increased bending moment and hence more reinforcement.


INCLINED SLAB STAIRS WITH HALF SPACE LANDINGS :
This type of stairs gives more compact plan layout and better circulation than the single straight flight stairs.  The half space or 180o turn landing is introduced at the midpoint of the total rise, giving equal flight spans, thus reducing the effective span and hence reducing bending moment considerably.  In most designs, the landings span crosswise on to a load bearing wall or beam and the flights span from landing to landing.

STRING BEAM STAIRS :
In this category, the slab is supported on one side by side wall  side by a stringer beam  I.e. a string or edge beam is used to span from landing to landing to resist bending moment with the steps spanning horizontally.  In this case, the waist slab is thinner and an overall saving in the concrete volume required can be achieved, but this saving in material is usually offset by the extra formwork cost required for string beam.  The string beam can be either up stand or down stand in format and can be on both sides if stairs are free standing.  Each step is designed as spanning horizontally with the bending moment equal to wll/8, where w is the uniformly distributed load per unit area on the step, inclusive of the self weight.  Sometimes, for wider steps, a central string beam spanning between the end walls or column is provided on which the stairs slab is supported.  The waist slab is designed as slab cantilevering from both the sides of the string beam.

CANTILEVER STAIRS:
They are also called spine wall stairs.  They consist of a central vertical wall from which the Space the flights and half space landing are cantilevered.  The wall provides a degree of fire resistance between the flights and is therefore used mainly for the escape stairs.  Since both flights and landings are cantilevered the reinforcement is placed in the top of the flight slab and in the upper surface of the landing to counteract the induced negative moment.  The plan arrangement can be a single straight flight or two flights with half space landings.

R.C.C.SPIRAL STAIRS :
Mainly used as accommodation stairs in the foyers of prestige buildings such as theatres, banks, commercial complexes etc.  Can be expensive to construct- normally at least seven times the cost of conventional stairs.  The plan shape is generally based on a circle; it is also possible to design an open spiral stair with an elliptical core, which is known as helical stairs. The spiral an be designed around a central large diameter circular  column, where the steps are cantilevered from that, or in case of helical stairs, can be designed as open circular well.  A large amount of steel reinforcement is used to resist the bending moment, shear force and torsional moment.  The continuous slab varies in thickness from top to bottom- less at top and increasing at the bottom.  There are two or three sets of reinforcement with top and bottom layer in each:  Continuous bars running the length of the spiral  Cross or radial bars  Diagonal bars laid tangential in two directions to the inner curve.



PRE-CAST STAIRS :
Most of the concrete stair arrangements are possible to produce as precast concrete components which can be:
• Individual steps units
• Complete flight with number of steps required

Common types of precast steps units :
• Rectangular cantilever steps
• Spandril cantilever steps
• Sector shaped cantilever units.

TOP:
In situ concrete staircase, the stairs are supported on soft pads at discrete points, a joint separate wall and stair.
MIDDLE:
Cast-in place concrete stair shaft with prefabricated stair flights, the bottom and top support for the flight include sound insulation, the landings are laterally supported on soft pads, flights separated from wall by a joint.
BOTTOM:
Staircase made completely of prefabricated elements, the flights are extended to include the landings, support points with sound insulation layer, stair is separated from wall elements.



Monday, January 20, 2020

ONE WAY - TWO WAY SLAB

ONE WAY SLAB :

What is slab ??
      Slabs are constructed to provide flat surfaces, usually horizontal, in building floors, roofs, bridges, and other types of structures. The slab may be supported by walls, by reinforced concrete beams usually cast monolithically with the slab, by structural steel beams, by columns, or by the ground.


       One way slab is a slab which is supported by beams on the two opposite sides to carry the load along one direction. The ratio of longer span (l) to shorter span (b) is equal or greater than 2, considered as One way slab because this slab will bend in one direction i.e in the direction along its shorter span.
       Due to the huge difference in lengths, load is not transferred to the shorter beams. Main reinforcement is provided in shorter span and distribution reinforcement in longer span. Example: Generally all the Cantilevr slabs are one Way slab. Chajjas and verandahs are an practical example of one way slab. 



TWO WAY SLAB :



       Two way slab is a slab supported by beams on all the four sides and the loads are carried by the supports along both directions. In two way slab, the ratio of longer span (l) to shorter span (b) is less than 2.
      In two way slabs, load will be carried in both the directions. So, main reinforcement are provided in both direction for two way slabs. Example: These types of slabs are used in constructing floors of multi storied building.


Difference between One way and Two way Slab :

One Way Slab :                                                                               Two Way Slab :

1) Slabs are supported by the beams on                          1)  Slabs are supported by beams on all the
    the two opposite sides.                                                      four sides.
                                               
2) Main Reinforcement is provided in                            2)  Main Reinforcement is provided along
    only one direction for one way slabs.                              both the directions in two way slabs.
                         
3) Loads are carried along one direction                        3) Loads are carried along both the directions
    in one way slab.                                                             in two way slabs.






Friday, January 17, 2020

BAMBOO IN CONSTRUCTION

Material Type : Bamboo


       Bamboo is one of the oldest and most versatile building materials with many applications in the field of construction, particularly in developing countries. It is strong and lightweight and can often be used without processing or finishing.
      The diminishing wood resource and restrictions imposed on felling in natural forests, particularly in the tropics, have focused world attention on the need to identify a substitute material which should be renewable, environmentally friendly and widely available. In view of its rapid growth (exceeding most fast growing woods), a ready adaptability to most climatic and edaphic conditions and properties superior to most juvenile fast growing wood, bamboo emerges as a very suitable alternative.

INTRODUCTION :
       Bamboo is a renewable and versatile resource, characterized by high strength and low weight, and is easily worked using simple tools. As such, bamboo constructions are easy to build, resilient to wind and even earthquake forces and readily repairable in the event of damage.



1) Durability :
    Bamboo is subject to attack by fungi and insects. For this reason, untreated bamboo structures are viewed as temporary with an expected life of no more than five years.
2)Jointing :
   Although many traditional joint types exist, their structural efficiency is low (Herbert et al. 1979). Considerable research has been directed at the development of more effective jointing methods.
3)Flammability :
   Bamboo structures do not behave well in fires, and the cost of treatment, where available, is relatively high.


PRESERVATION OF BAMBOO :
       Bamboo is subject to attack by micro-organisms and insects in almost any construction application. Unfortunately, like most lignocellulosic materials, bamboo has very low resistance to biological degrading agents. The service life is therefore mainly determined by the rate of attack.
      A variety of methods to improve the durability of bamboo have, however, been developed. Several of these techniques are described here with the aim of providing helpful guidelines to users.


DRYING OF BAMBOO :
       Green bamboo can have a moisture content of 100-150%, depending on the species, area of growth and felling season. The chemical composition of bamboo results in a comparatively higher hygroscopicity than wood. Additional problems in the drying of bamboo occur because the material lacks an efficient radial transport system and possesses a waxy coating. Therefore, the major pathway for the loss of moisture is from the ends of the culms.
     The liability to biological degradation and to deformation owing to excessive shrinkage (which occurs even above the fibre saturation point) necessitates quick drying of bamboo.


CONSTRUCTION METHODS :
        The majority of bamboo construction relates to rural community needs in developing countries. As such, domestic housing predominates and, in accordance with their rural origins, these buildings are often simple in design and construction relying on a living tradition of local skills and methods. Other common types of construction include farm and school buildings and bridges.
       Further applications of bamboo relevant to construction include its use as scaffolding, water piping, and as shuttering and reinforcement for concrete. In addition, the potential number of construction applications has been increased by the recent development of a variety of bamboo based panels.


SMALL BUILDINGS :


       Bamboo can be used to make all the components of small buildings, both structural and non-structural, with the exception of fireplaces and chimneys. It is, however, often used in conjunction with other materials, cost and availability permitting.

FOUNDATIONS :

  • Bamboo in direct ground contact 
  • Bamboo on rock or preformed concrete footings 
  • Bamboo incorporated into concrete footings 
  • Composite bamboo/concrete columns 
  • Bamboo reinforced concrete 
  • Bamboo piles
WALLS :


        The most extensive use of bamboo in construction is for walls and partitions. The major elements of a bamboo wall (posts and beams) generally constitute part of the structural framework. As such they are required to carry the self-weight of the building and also loadings imposed by the occupants, the weather and, occasionally, earthquakes. To this end, efficient and adequate jointing is of primary importance.

ROOFS :


       The roof of a building is arguably its most important component - this is what defines a construction as a shelter. As such, it is required to offer protection against extremes of weather including rain, sun and wind, and to provide clear, usable space beneath its canopy. Above all, it must be strong enough to resist the considerable forces generated by wind and roof coverings. 

DOORS AND WINDOWS :


        In traditional types of bamboo building, doors and windows are usually very simple in form and operation. Bamboo doors can be side hinged or sliding, comprising a bamboo frame with an infill of woven bamboo or small diameter culms.
       In higher grade buildings, wooden doors are common. Doors and shutters comprising bamboo mat board as panelling, or as flush skins for hollow core doors offer another solution. 
       Bamboo windows are generally left unglazed and can have bamboo bars, or a sash with woven bamboo infill. The sash can be side hinged or sliding, or, more commonly, top hinged to keep out direct sunlight and rain. At night, windows are closed to protect against insects and animals. Hinges are formed from simple bindings, or connecting bamboo elements.

WATER PIPES AND GUTTERS :


       Whole bamboo culms, with the diaphragms removed, can be used as water pipes either below or above ground. Below ground: the system is usually gravity fed. 
       To ensure watertight connections, the ends of the culms can be reamed and fitted into short sections of metal, pvc or bamboo pipe and suitably caulked. To control insect attack, the trench can be treated with insecticide before the pipes are laid. 

JOINTING TECHNIQUES IN BAMBOO :
        Effective jointing is fundamental to the structural integrity of a framed construction. Furthermore, the suitability of a material for use in framing is largely dependent upon the ease with which joints can be formed. Because of its round, tubular form, jointing of two or more bamboo members requires a different approach to that adopted for, say, solid timber.
 

      Despite its relatively high strength, bamboo is susceptible to crushing, particularly of open ends. It is also characterised by a tendency to split; the use of nails, pegs, notches or mortises can therefore result in considerable reductions in strength. Connections must also cope with variations in diameter, wall thickness and straightness.



 Traditional jointing methods rely principally on lashing or tying, with or without pegs or dowels. The basic joint types are:

TYPES :
Spliced joints 
Orthogonal joints 
Angled joints 
Through joints









Thursday, January 16, 2020

LEANING TOWER OF PISA

Building: Leaning Tower of Pisa
Location: Piazza Del Duomo Pisa, Italy
Constructed in: 1173-1372
Architect: Bonanno Pisano


         The Leaning Tower of Pisa or simply the Tower of Pisa is the campanile, or freestanding bell tower, of the cathedral of the Italian city of Pisa, known worldwide for its nearly four-degree lean, the result of an unstable foundation. The tower is situated behind the Pisa Cathedral and is the third-oldest structure in the city's Cathedral Square, after the cathedral and the Pisa Baptistry.
       
        The height of the tower is 55.86 metres (183.27 feet) from the ground on the low side and 56.67 metres (185.93 feet) on the high side. The width of the walls at the base is 2.44 m (8 ft 0.06 in). Its weight is estimated at 14,500 metric tons (16,000 short tons). The tower has 296 or 294 steps; the seventh floor has two fewer steps on the north-facing staircase.
        The tower began to lean during construction in the 12th century, due to soft ground which could not properly support the structure's weight, and it worsened through the completion of construction in the 14th century. By 1990 the tilt had reached 5.5 degrees. The structure was stabilized by remedial work between 1993 and 2001, which reduced the tilt to 3.97 degrees.

Architect:

                                                                    Bonanno Pisano

         There has been controversy about the real identity of the architect of the Leaning Tower of Pisa. For many years, the design was attributed to Guglielmo and Bonanno Pisano, a well-known 12th-century resident artist of Pisa, known for his bronze casting, particularly in the Pisa Duomo. Pisano left Pisa in 1185 for Monreale, Sicily, only to come back and die in his home town. A piece of cast bearing his name was discovered at the foot of the tower in 1820, but this may be related to the bronze door in the facade of the cathedral that was destroyed in 1595. A 2001 study seems to indicate Diotisalvi was the original architect, due to the time of construction and affinity with other Diotisalvi works, notably the bell tower of San Nicola and the Baptistery, both in Pisa.

Construction:


        Construction of the tower occurred in three stages over 199 years. On 5 January 1172, Donna Berta di Bernardo, a widow and resident of the house of dell'Opera di Santa Maria, bequeathed sixty soldi to the Opera Campanilis petrarum Sancte Marie. The sum was then used toward the purchase of a few stones which still form the base of the bell tower. On 9 August 1173, the foundations of the tower were laid.
         Work on the ground floor of the white marble campanile began on 14 August of the same year during a period of military success and prosperity. This ground floor is a blind arcade articulated by engaged columns with classical Corinthian capitals. Nearly four centuries later Giorgio Vasari wrote: "Guglielmo, according to what is being said, in the year 1174, together with sculptor Bonanno, laid the foundations of the bell tower of the cathedral in Pisa".
        The tower began to sink after construction had progressed to the second floor in 1178. This was due to a mere three-metre foundation, set in weak, unstable subsoil, a design that was flawed from the beginning. 
       Construction was subsequently halted for almost a century, as the Republic of Pisa was almost continually engaged in battles with Genoa, Lucca, and Florence. This allowed time for the underlying soil to settle. Otherwise, the tower would almost certainly have toppled. On 27 December 1233, the worker Benenato, son of Gerardo Bottici, oversaw the continuation of the tower's construction.


Thursday, January 2, 2020

PRITZKER AWARD

Awarded for : A career of achievement in the art of architecture
Sponsored by : Hyatt Foundation
Reward(s) : US$100,000 (79,29,880 Indian Rupee)
First awarded : 1979


       The Pritzker Architecture Prize is awarded annually "to honor a living architect or architects whose built work demonstrates a combination of those qualities of talent, vision and commitment, which has produced consistent and significant contributions to humanity and the built environment through the art of architecture". Founded in 1979 by Jay A. Pritzker and his wife Cindy, the award is funded by the Pritzker family and sponsored by the Hyatt Foundation. It is considered to be one of the world's premier architecture prizes, and is often referred to as the Nobel Prize of architecture.

        The prize is said to be awarded "irrespective of nationality, race, creed, or ideology". The recipients receive US$100,000, (79,29,880 Indian Rupee) a citation certificate, and since 1987, a bronze medallion. The designs on the medal are inspired by the work of architect Louis Sullivan, while the Latin inspired inscription on the reverse of the medallion—firmitas, utilitas, venustas (English: firmness, commodity and delight)—is from Ancient Roman architect Vitruvius. Before 1987, a limited edition Henry Moore sculpture accompanied the monetary prize.


The Executive Director of the prize, Martha Thorne, solicits nominations from a range of people, including past Laureates, academics, critics and others "with expertise and interest in the field of architecture". Any licensed architect can also make a personal application for the prize before November 1 every year. In 1988 Gordon Bunshaft nominated himself for the award and eventually won it. The jury, each year consisting of five to nine "experts ... recognized professionals in their own fields of architecture, business, education, publishing, and culture", deliberate early the following year before announcing the winner in spring. The prize Chair is Stephen Breyer; earlier chairs were J. Carter Brown (1979–2002), the Lord Rothschild (2003–2004), the Lord Palumbo (2005–2015) and Glenn Murcutt (2017–2018).