Pre Cast Transom

Introduction

Lahore, capital of the Punjab is one of the fastest growth rates of urban development and industrial infrastructure in the country. This fast growing urban development also need for new systems in the city specially the transport which can be accessed from the fact that exiting transport is simply inadequate both in number of buses and quality to serve the exiting and incremental travel demand. During peak hours, vehicles are over-loaded with people hanging on the doors.

For upgrading Lahore Public transport systems, Government of Punjab constructed the bus rapid transit System. Ferozpur road was selected as a priority corridor. For rapid construction, the corridor is divided into parts.

Zahir khan Brothers and reliable Engineering Services (Pvt.) Ltd. (ZKB-JV) joint ventured to construct 3.9Km (out of 8 Km) elevated section named package llb/2 and p-lll starts from Ichra to MAO college. This projects includes an elevated corridor of 10m normal width having two lanes of 3.5 m, with 1.5m wide side wall including barrier on both sides. At station the Bridge width is 15m i.e. 8m for bus corridor and 3.5 m for station width each side’s 2 No. transfer stations are constructed having deck 22M wide.

Precast transoms was used to reduced the construction time and to achieve the best quality finishes in controlled factory environment and to ease the works at site keeping the busy road free for public most of the time, The use of precast transoms has been introduced for the first time in country as ZKB-JV has started installation of transoms for the construction of the Metro Bus Rapid Transit System (BRTS) in the Lahore City. Unlike the previous laborious technique of using shuttering for construction of parts of bridges, the use of pre-cast transoms will save a lot of time and resources and facilitate expeditious completion of the project.

Construction to cast precast transom:

  • Preparation of pre-casting Beds and Moulds
  • Mould and form work was made of steel
  • A guide mechanism was prepared in the bed of moulds to reflect the same condition as  in-situ
  • Guide notes was welded at the base of moulds as per template being used on site for casting of columns
  • A copy of the precast mould’s central portion that is to rest on in-situ RCC columns was prepared as a dummy mould for fixing of steel out of the mould
  • Activity of steel fixing was carried out independently to save the time on dummy moulds

Concrete of transom was completed in two stages

1: concrete in transom at base      2: concrete in transom at stem

  • Concrete from batching plant was received in receiving hopper and then shift to transit mixer
  • Concrete through plant mixer was transported to the bed/moulds, delivering directly into the mould fixed below ground level for ease in handling of concrete
  • After the concrete in the bed has set sufficiently to allow working on its top, forms for the transom stem part shall be fixed in portion
  • Concrete in the stem part was carried out in the same fashion as in transom base part
  • After initial setting, curing was started and continued till the member is lifted and transported to site
  • Formwork was removed within 24 hours when concrete was set
  • After three days compressive strength was checked by testing cylinder and permission was granted to lift when we achieved the required compressive strength

Transportation:

The transoms for this project are being fabricated at a distance about 40km location on Multan Road under the supervision of NESPAK. Local city police and highway police was contacted and engaged to escort the loaded trailer from precast yard to the project site. Emergency rescue vehicle were also escort the load and no other traffic was allowed in the vicinity of the trailer carrying heavy loads. Transportation from yard to the site was done at the late hours in the night to avoid traffic and public interface.

Proper support system using wooden block, rubber types and MS Girders was designed and fixed on trailer to keep the member in upright straight position for a safe travelling to the site.

These transoms are being lifted with the help of two cranes and are being placed at the top of five meters tall piles.

Launching:

Transom is 90 tons in weight. Its length is 9.8 meters, width 2.7 meters and height is 2.2 meters. These transoms are being lifted with the help of two cranes of 100 Ton capacity and are being placed at the top of five meters tall piles. Girders will be placed on these transoms and then the bridge will be constructed over them.
All area around pier shall be cordoned off and no person was allowed to come under load.

 

.