Structural Review Report

Topics: Structural engineering, Shear stress, Reinforced concrete Pages: 14 (3506 words) Published: December 12, 2012

3.2Evaluation of Beams7
3.3Evaluation of the Slab12
5.1Proposed Modification for the structure18


Ambatale water treatment plant (Ambatale WTP) is one of the main potable water treatment plant implemented in 1960 and is operated by the National Water Supply & Drainage Board (NWS&DB) in order to serve the population in Greater Colombo Metropolitan area, the capital city of Sri Lanka. This plant is situated approximately 9km east to the Colombo city. Considering the rapid increase of the potable water demand, this water treatment plant was augmented in three stages to improve its production capacity up to 107.5 MGD. This is about 70% of the total demand of Greater Colombo Metropolitan area. The treated water produced by the Ambatale water treatment plant is transmitted through three high lift pump houses for number of distribution centers located within the Greater Colombo Metropolitan area. Considering the increasing demand of the Kotte area (North-East area of the Greater Colombo Metropolitan), NWS&DB decided to transmit more water through the existing pumping main by installing new pumps at one of the above three pump houses, named as “Jubilee Pump House” which is considered for this study. This Jubilee pump house was implemented under one of the augmentation done under the funds of third International Development Agency (IDA)in the year 1992. Under this augmentation, four number of centrifugal (vertical turbine type) pumps had been installed. The capacity and weight of the pump motor is1720m3/hr and 1750kg respectively. Subsequently, in the year 2006, two pumps were replaced by another new two pumps of increased capacity of 1980m3/hr. in order to cater the new water demand of the area. The weight of each motor of the pump is about 2000kg.This installation was done without introducing any structural modifications for the pump house. Since this installation, it is observed a significant vibration at floor slab where pump motors were installed. Considering further increase of the drinking water demand at the same area, NWS&DB presently proposed to install another two new pumps instead of the oldest two pumps. The capacity of the proposed pump and weight of the new motor is 2300 m3/hr and 4200kg respectively. The weight combination of 1750kg four motors did not record any vibration on the floor slab. But weight combination of 1750kg two motors and 2000kg two motors create the vibration. Therefore the proposed weight combination of 2000kg (Motor weight with frame 3650kg) two motor and 4200kg (Motor weight with frame 5000kg) two motor can developed the vibration having higher magnitude than present vibration. The initial design calculations are not available. Therefore it is decided to carry out structural evaluation for existing structure in order to evaluate the strength of the structure. Therefore the aim of the study is to evaluate the existing structure against the proposed new loads and proposed a suitable structural augmentation.


There is no design report available with NWSDB, but complete set of detail drawings was available. Accordingly review of pump house is as follows, * Pump house is single storied building with basement and rectangular in shape. (See fig. 01 & 02). * Pump house is reinforced concrete structure with brick infill at super structure (see fig. 01 - 04) * The floor slab of the pump house rest on the gird of primary and secondary beams and columns. (see fig. 02) * Pump Motors are installed on the secondary beam.

* The roof of the pump hose consist of roof trusses rest on the concrete column and corrugated asbestos cement sheets were used as roof material (see fig. 01). * Pumps were installed at the basement of the structure...
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