Quantifying the Environmental Impacts of Standard Bridge Designs

 “A Proposed Methodology for Quantifying the Environmental Impacts of 

Structural Elements of Standard Bridge Designs”

 A thesis prepared and submitted by:

Kevin Lawrence M. Atienza

Carla Maria B. Gonzalez

Jorge Jason K. Joaquino

Mitchel Krisia R. Martinez 

April 2015 

To take into account the environmental sustainability aspect of bridge designs, the study presented a methodology to numerically measure the amount of emission different bridges produce. The researchers gathered a total of eighteen bridge plans of various structural systems such as Reinforced Concrete Deck Girder (RCDG), Pre-stressed Concrete Deck Girder (PCDG), Reinforced Concrete Slab, Steel Girder, and Reinforced Concrete Box Culvert (RCBC). Each plan included a bill of quantities that summarized the type of material and the amount used upon construction. Using LCIA database Ecoinvent v3.1, quantities were translated into corresponding environmental impacts namely Acidification, Eutrophication, Global Warming Potential, Photochemical Oxidant Formation, Stratospheric Ozone Depletion, and Depletion of Abiotic Resources. Numerical results were divided by the total area of the bridge leaving one square meter of bridge area as the functional unit of choice.

To normalize these values, each environmental impact equivalent was divided by the largest value, which was produced by the RCBC bridge design. An Analytical Hierarchy Process (AHP) was conducted to produce the weighting factors of each impact. The normalized values were then multiplied by their corresponding weighting factors and added up to produce an Environmental Impact Score (EIS) that was used to rank and compare the environmental performance of each bridge. In this particular study, the RCDG bridge design generated the lowest score with a value of 0.451, thus indicating that it produced the least amount of impact. On the other hand, the RCBC bridge design produced the largest amount of impact with an EIS of 0.825. Through the proposed methodology of conducting a Life Cycle Impact Assessment (LCIA) and producing an EIS, structural engineers will be able quantify the environmental impacts of different bridge structural systems and in turn apply sustainability in the decision making of future bridge projects.

Special Acknowledgement: 

DPWH Staff and Engineers for sharing bridge data, 

Dr. Mike Promentilla (DLSU ChE Dept) for guidance in the AHP procedure

Greener Designs of Buildings using the Structural Sustainability Index

Sustainability is a concern that must also be addressed by structural engineers. Structural engineers must be able to discriminate as to which materials and processes would have a lesser impact to the environment, and to coordinate with the other stakeholders of the structure. The concept of the study is to enable the structural engineer to analyse the sustainability of structural systems in a quantifiable manner. 

In designing a house, or any structure, there are three things commonly considered by the structural engineer. Namely: safety, serviceability and cost. Safety and serviceability ensure that the structure can fulfill its intended purpose by satisfying code requirements on strength, ductility and deflections. Addressing economy, on the other hand, requires value engineering to produce an optimum design with reasonable cost. There is now an increasing concern about the environmental impact of structures. Sustainable design of houses must be pursued to address this concern. But what parameter may be used to guide structural designers to make their structures “greener”?

In an undergraduate thesis, the environmental impact of the structural systems and envelope of selected housing units for a middle class family in the Philippines using Life Cycle Analysis (LCA) was conducted.  The five environmental impact parameters: (a) Global Warming Potential, (b) Ocean Acidification, (c) Abiotic Material Depletion, (d) Energy Use, (e) Human Toxicity were assessed considering the manufacturing and disposal stage as the system boundary in the LCA study. A  “Structural Sustainability Index” or SSI which produces a single score aggregating the five impacts was derived by assigning weights based on an expert’s survey for each environmental impact indicator. The SSI can be used for ranking houses based on environmental impact and can be used as a parameter to guide structural engineers in comparing various design alternatives and selecting  “greener designs”.

The image below is a poster submitted to the ASEP Student Research Competition during the 16th ASEP International Conference held on May 23-25, 2013.

The Water Tour

The National Research Council of the Philippines (NRCP) organized a tour of Manila Water's Lakbayan Center at Balara, Quezon City last Jan. 28, 2011. It was an educational tour wherein lectures and video presentations about Manila Water, Path of Pat Tubig (The Mascot of Manila Water), Waste Water Treatment and Manila Water's Ondoy Activities were presented. Indeed, the lectures were enlightening. After the lectures - you will crave for Manila Water's tap water which you will realize is clean and refreshing.

The highlight of the tour is the pledging of the participants to protect the environment by signing a tumbler with some tips on environmental protection such as:

• Re-use this drinking bottle
• Practice proper waste disposal
• Plant a tree
• Support water recovery efforts so that clean water can go back to our rivers

After signing your name on your tumbler, you post a sticker leaf with your name on the wall of the Lakbayan center. After this we had a site visit of the UP STP and La Mesa Dam.

If you want to know more about water - then arrange a tour at the Lakbayan Center at Manila Water.

Green Buildings and Structural Engineering

The main theme of the 33rd IABSE Symposium at Bangkok (Sept. 9-11, 2009) is "Sustainable Infrastructure." The International Association of Bridge and Structural Engineers (IABSE) recognizes the important role of structural engineers in ensuring sustainability in their creations to ensure that energy and natural resources are still available for the future generations.

The keynote lecture on "Green Buildings and Structural Engineering" by Gene Corley (USA) highlights how structural engineers can contribute to sustainability by following the LEED Green Building Rating System - a framework for asssessing building performance and meeting sustainability goals. A rating of 40 points will earn a building a LEED Certification. Structural engineers, in particular, can earn LEED points in the category of Materials and Resources and the following subcategories:

(a) Building reuse - instead of demolition, the building structure or shell is reused.

(b) Construction waste management - diverting construction and demolition waste from ladfill into other uses

(c) Materials reuse - a portion of the materials of the project must be salvaged or recycled

(d) Recycled content - use of materials with "recyled content"

(e) Regional materials - use of local materials will reduce transport and energy cost

Structural engineers should design building which are adaptable to provide for ease of alteration or amendment in use. Buildings which consists of elements that can easily be deconstructed are preferrable for possible reuse. By proper planning and efficient design and knowledgeable of sustainability concepts, green buildings can be successfully built.

The author (center) with Filipino engineers infront of the IABSE booth.

Designing for Safety & Stability Leads to Sustainability

Today, there is an increasing demand for engineers to focus their efforts on the protection and preservation of the environment. The civil engineering community, which includes structural engineers, plays a major role in maintaining the balance and harmony between the built and existing natural environment. The built environment, which includes infrastructures such as residential houses, high-rise buildings, long-span bridges, roads and expressways, and large civil structures like dams and reservoirs, provide for a livable atmosphere for all. However, the impact of these infrastructures on the natural environment especially in natural hazard-prone countries like the Philippines should be a concern. Richardson (2002) summarizes the realities of infrastructure impact on the environment as follows: It is said that 50% of the world population lives in cities today and this may grow to 75% by 2030. Cities are said to cause 75% of the world’s pollution and consume 75% of the world’s energy. Buildings are reported to produce 40% of the world’s CO2, consume 50% of the energy derived from fossil fuels, consume 3 billion tons of raw materials in construction each year and consume 75% of all energy used through artificial lighting, heating and cooling every day. 25% of all wood harvested is used in building construction.

The negative impact of infrastructures on the environment aggravates especially when natural disasters occur. Natural disasters like earthquakes, floods, typhoons, tsunamis and landslides spoil both the built and natural environment. Aside from causing numerous deaths and injuries to people, natural disasters had caused the destruction of important infrastructures such as buildings, bridges and roads and devastation of nature which contributed to environmental degradation. The 1999 Chi-Chi earthquake in Taiwan caused 2,415 deaths, 1,441 severely wounded, US$9.2 billion worth of damage, 44,338 houses completely destroyed and 41,336 houses severely damaged. The 2001 Gujarat earthquake in India was the most devastating earthquake in India in recent history. The quake destroyed 90 percent of the homes in Bhuj, several schools, and flattened a hospital. Gujarat's commercial capital and a city of 4.5 million, as many as 50 multistory buildings collapsed and several hundred people were killed. In the July 16, 1990 earthquake in the Philippines, damage to buildings, infrastructures, and properties amounted to at least P 10B. The Hyogo-ken Nanbu earthquake in Japan which hit the city of Kobe and surrounding areas in Hyogo prefecture on January 17, 1995 cause the collapse of nearly 55,000 houses in the city of Kobe. The cost of reconstruction of buildings alone was roughly estimated at between US $61-70 billion.

As a consequence of the destruction brought about by natural disasters, the natural resources, materials and energy that have been utilized in constructing these infrastructures have been put to waste. Moreover, the large amount of disaster-caused waste and debris poses another environmental problem. The most severe natural disasters generate debris in quantities that can overwhelm existing solid waste management facilities or force communities to use disposal options that otherwise would not be acceptable.

How may structural and civil engineers contribute towards the reduction of these negative impacts in a region where natural disasters like earthquakes, typhoons, tsunamis and landslides are prevalent? Structural and civil engineers have significantly contributed towards the protection and conservation of the natural environment especially when we consider the impact of natural disasters. on infrastructures and the environment. Civil and structural engineers, when they properly design structures and foundations for safety and stability, are actually contributing significantly to the preservation of the natural environment. Proper analysis, design and construction of structures will minimize damage or collapse. Refined modeling, testing and analysis of soil may prevent foundation failures. Strengthening and improvement of unstable slopes will control the occurrence of landslides. When structures are strengthened or retrofitted, the usable life of the structure is extended reducing end-of-life waste. These primary responsibilities of structural and civil engineers regarding safety and stability, in the end, leads to the reduction of non-renewable natural resources consumption and minimizing the accumulation of construction waste and disaster-caused debris waste. The responsibility of structural and civil engineers in designing for safety and stability and the role they play concerning the maintenance of environment especially in disaster-prone countries must be appreciated by everyone including the so-called “environmentalists.”

This article was published at the Philippine Star, Star Science Column, 6 March 2008