On TecQuipment Structures Teaching Apparatus

The Department of Civil Engineering (De La Salle University-Manila) will introduce a laboratory component in the undergraduate courses in the Theory of Structures and the TecQuipment’s (TQ) structures teaching apparatus will be used. Among the TQ apparatus purchased were for Frames (Deflections and Reactions), Beams Deflections, Pin-jointed Frameworks, Shear center, Unsymmetrical Bending, Beam Shear and Bending Moments. We are presently being familiarized on the use of the equipment by a local representatvie of TQ. There were some problems initially during the demo but the TecQuipment Ltd (UK) Engineering Manager, Andrew Darby BEng (Hons) immediately responded to the problems encountered. I can see a great potential for the TQ Structures Teaching Apparatus in enhancing the understanding of structural analysis concepts. I am looking forward to using these equipment in our laboratory class in structural analysis. As a matter of fact, I plan to write a teaching and learning manual using these equipment.

Two Popsicle Stick Bridges from DLSU

I would like to feature two popsicle stick bridges submitted by my undergraduate students at the 5th DLSU-CES Bridge Building Competition. Bridge No. 09 by Morgan Say and Jet Tugado is a Warren-type truss bridge. It actually ranked no. 4 in both the Strength and Design category. The bridge has the properties, L = 626 mm, W = 1073 g (quite heavy). It's deflection at P = 10 kg was only 3.2 mm but at failure, it posted a very large deflection D = 19.20 mm. Again the arrangement of the diagonal members may have contributed to the large deflection. The diagonal members in this bridge are under compression. If only the weight and the deflection were reduced, it may have joined the top 3. Actually it is ranked no. 1 based on the P/W ratio only.
The second bridge (Bridge 16) by Jefron Gaw, Allan Mariano and Lex Alviar was withdrawn from the competition because its depth D exceeds the limit, making it impossible to test the bridge using two point loads. The bridge has an arch shape. The bridge is quite heavy W=1425 g. It is a well designed bridge and it may have performed well in the competition, if it only passed the specifications. The bridge was actually tested upto failure using the UTM and observe the failure mode - a bending failure at midspan.

I would like to commend the participants for creating the nice popsicle stick bridges. You are all winners!

GRASP Analysis of the Top 3 Popsicle Stick Bridges

In the strength category of the 5th DLSU-CES Bridge Building Competition, the bridges with weight W were subjected to two-point loads using a UTM (Read the blog on bridge testing). The values of P and D at failure were noted to get the Strength rating S=P/(D*W). The bridge with the largest S wins the competition.

The value of S depends on the stiffness (P/D) of the bridge and the weight W. The competition measures how efficient the materials were used to obtain a structure with large ratio of stiffness to weight.

Using the GRASP software, the top 3 winning bridges (B13, B03 and B06) in the strength category were analyzed . Observe the very interesting deflected shapes of the models. The figure also shows the members with axial tensile forces (labeled T). Why did the top bridges perform better than the others? What are the factors that contributed to the large stiffness (P/D) of the bridges? One major factor is the material property of popsicle sticks - the tensile stress capacity is larger than the compressive stress capacity in popsicle sticks. It would be easier to break the popsicle stick due to compression than to tear it due to tension. Hence, if you want to efficiently use the strength of popsicle sticks, design your bridge such that tensile forces not compressive forces are developed in most of the members. In the top 2 bridges - B13 and B03 - relatively large tensile forces were induced in the diagonal members compared to the compressive members.

Another factor is buckling failure in the compression members. If you want to increase the capacity of the members against buckling, then provide braces. The top 2 bridges have horizontal braces at the top and bottom preventing lateral buckling of the members. Bridge B06 which is 3rd in the competition has relatively larger compressive forces in the top chord and diagonal web members. Observe the buckling failure of the top chord. If only horizontal braces were installed at the top, the bridge may have developed a larger capacity and less deflection before failure.

Another factor which increased the stiffness of the bridges, particularly the top 2 bridges is the use of a deep box girder. This results to a relatively light-weight bridge but effective against bending. Sticking together popsicle sticks forming stiff griders like in the bridges shown result to very heavy and not very efficient bridges. They may carry a larger load (P) before failure but the ratio with weight may be smaller because of the large bridge weight.

Modeling your bridges and analyzing them using a software like GRASP before the actual construction will guide you on how to improve the bridge designs. You can redesign the arrangement of the truss members, increase the depth or know the location of braces to prevent buckling failure.

Best Popsicle-Stick Bridge Designs

In the recently concluded 5th DLSU-CES Bridge Building Competition last 7 Feb 2009, the bridges made from popsicle sticks competed for the Best Bridge Design based on the following criteria:

• Creativity and Innovativeness in the design and form: 30%
• Application of bridge design principles: 30%
• Practicality and implementability: 20%
• Neat and well-polished bridge: 20%

Four judges examined and evaluated the bridges. After about an hour of evluation, the scores were tabulated. It was a tight race for the winner. The winning bridge from Don Honorio Ventura College of Arts and Trades (DHVCAT) won by a hairline against the bridge entry from the Technological Institute of the Philippines (TIP), Manila. The 3rd placer is the bridge from the Technological Institute of the Philippines (TIP), Quezon City. Building popsicle-stick bridges using glue takes a lot of planning, patience and ingenuity. Cutting the popsicle sticks to fit the form of the bridge, gluing the sticks and polishing involves a lot of time. In general, the popsicle-stick bridges submitted were impressive. Many of the bridges were unique and may serve as models for future bridges. The students have demonstrated their skills and understanding about bridge construction.

DLSU CES 5th Bridge Building Contest

The 5th DLSU Bridge Building Contest was held on Feb 7, 2009. Seventeen bridges made from popsicle stick bridges were submitted from various engineering schools - Don Honorio Ventura College of Arts and Trades (DHVCAT), Technological Institute of the Philippines (Manila and QC), FEATI University, Far Eastern University (FEU) , Pamantasan ng Lungsod ng Maynila (PLM), University of the East (UE-Manila) and De La Salle University (DLSU-Manila). The bridge must span a distance of 560 mm and must have a width not more than 140 mm, height not more than 200 mm, depth not more than 100 mm, weight not more than 1.50 kg. There were two categories in the competition: Bridge Design and Bridge Strength. In the Bridge Design category, the criteria used were creativity, innovativeness, application of bridge design principles, practicality, implementability and neatness. The winner for this categroy is one of the entries from DHVCAT. In the Bridge Strength category, the bridges were tested using the UTM and the load P and deflection D at failure and the bridge weight W were used to get the Strength Rating (see blog on bridge testing). The winners in this category were 1st: PLM, 2nd: TIP-Manila and 3rd: DLSU-Manila.

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Introducing Structural Engineering

At DLSU-Manila, we hold a forum promoting the various specializations in civil engineering - Hydraulics and Water Resources (HWR), Transportation Engineering (TRE), Construction Technology and Management (CTM), Geotechnical Engineering (GTE) and Structural Engineering (STE). I was tasked to present the STE specialization. To introduce the STE specialization, I created a short video using Power Director and presented this during the forum.

So you want to be a structural engineer? Watch the video and explore the world of the structural engineer and how he changes the world.

Tales of Disasters: Earthquake!

Here is another film made by No Strings for programmes in South East Asia and funded by Trocaire. The movie is about Badu and the Little Girl who experienced an earthquake. It is a movie on earthquake preparedness and response. Watch this with your kids.

This video was accessed at http://cogssdpe.ning.com/.

ASEP 14th International Convention - Call for Abstracts

The Association of Structural Engineers of the Philippines, Inc. (ASEP) on its 47th year is hosting the 14th ASEP International Convention with the theme, “Structural Engineering: Coping with the Global Crisis” on May 21-22, 2009. In this regard, you are invited to submit an abstract and full paper (later) for presentation during the convention.

Topics of papers on structural engineering which address innovative approaches of coping with the global crisis and problems - financial, political, environmental, climate change, natural disasters, terrorism, poverty and sustainability - are welcome.

Specific topics include: Performanced-based design, Retrofitting and Strengthening, Structural Failures, Structural Risk, Natural Hazards and Disaster Rsis Mitigation, ISO Standards and Codes of Practice, Earthquake and Wind Engineering, Value Engineering, Engineering Ethics, Urban Planning and Infrastructure Development, Fire, Impact and Blast Loads, Case Studies on High-Rise Buildings and Long-Span Bridges, Prestresses and Pre-cast Construction, Foundation and Geotechnical Issues.

Deadline of Submission of Abstracts: 14 February 2009

Deadline of Submission of Full Papers: 24 March 2009

Send abstracts to: asep14aic@gmail.com

Disasters and Development

One of the videos in "Understanding Earthquakes and Disasters: Photo-Video Presentations for Public Awareness and Education" is entitled "Disasters and Development."

Natural disasters occur if society is highly vulnerable to the hazards. When a disaster occurs, the development and the economy of the country and local community is affected. As a country develops, the population increases and more infrastructures are constructed, and these may increase vulnerability to the hazards. . Understanding the relationship between disasters and development is important in designing a comprehensive disaster risk mitigation program.

Tales of Disasters: Tsunami!

I joined a social network - Coalition for Global School Safety & Disaster Prevention Education and learned of the various initiatives around the world in promoting disaster awareness to the public especailly in schools through the world wide web. I found interesting videos created by No Strings, a group of puppeteers who use colorful and engaging adventure films to teach life-saving messages to children.

Here is the first video on Tsunami. The story centers on Badu, a likeable but lazy villager who teaches by negative example and a Little Girl who is aware of natural hazards and disasters and their signs and effects. Watch this video with your kids as this is really very informative.

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

Understanding 2D Structural Analysis

In my computer laboratory class on "Structural Engineering Computer Methods", the students use Structural Analysis software like GRASP, ETABS and SAP2000. Learning to use the software is not the end itself but learning concepts on structural analysis is the primary objective of the course. To achive this objective, I wrote "Understanding 2D Structural Analysis" - an exploratory-type of instructional and learning material consisting of ten modules about modeling and analysis of framed structures in 2D using GRASP. Each module focuses on a specific issue on structural modeling and analysis which is discussed with the aid of graphical and tabular results obtained from GRASP. The set of learning modules is not a substitute to a textbook on structural analysis. The theory is not presented. No derivations or equations can be found. The student or reader must refer to the textbooks for definitions, equations and techniques. Each chapter begins with background information and a “case study”. The reader explores the issues raised in the case study through the “Things to Do” GRASP activities or by simply observing and analyzing the “Observation” and graphical and tabular results presented in the module. Included in the modules are “Things to Try” GRASP exercises and “Things to Ponder” comments on the analysis and design of structures. Using the set of learning modules, the reader or student with the aid of GRASP discovers important insights on the response and behavior of structures due to variations in the parameters of the model and configurations of the structure, changes in member and material properties, and also changes in the restraint and loading conditions. Through the graphical results, the student can visualize the phenomena and this would accelerate his understanding of concepts through the experience of seeing and interpreting solutions to various structural modeling and analysis problems. You may download this book from my website and use it in your class.

Structural Analysis Tips to Popsicle Stick Bridge Builders (Load Application)

Using a structural analysis software like Graphical Rapid Analysis of Structures Program (GRASP ) developed by the Asian Center for Computations and Software (ACECOMS) can help popsicle stick bridge builders in designing their bridges. The behaviour of bridges depends on how and where the loads will be applied. For example, if two concentrated loads will be applied to test a bridge with a truss design, applying the load as shown in the figure at the bottom or uppr part of the bridge will make a lot of a difference. The GRASP software was used to compare the maximum deflection at the bottom horizontal elements of the two bridges. The structures were analyzed as a "frame" since the joints may be assumed rigid because of the glued connections. The deflection for Bridge 1 where the loads were applied at the bottom is 20% higher than Bridge 2 where the loads are applied at the top. For Bridge 1, the bottom horizontal elements have large bending moments and axial forces and diagonal truss members carry large axial forces - the top horizontal members had minimal stresses. For Bridge 2, on the otherhand, the top horizontal elements may have large bending moments but the axial forces are not so large compared to bridge 1. The bottom horizontal elements now contributed more in resisting the loads by carrying more axial forces as compared to bridge 1. The diagonal truss elements of bridge 2 carry almost the same magnitude of axial forces. So before designing your bridges, know how and where the loads will be applied. It will make a lot of a difference in the bridge performance!

Structural Engineering for Kids 4 - Building Up London Bridge

London Bridge is a nursery rhyme where various concepts in structural engineering may be introduced. Obviously, the concept of structural engineering failures is described in this song - London Bridge is falling down. Structural failure this time is described in relation to different types of construction materials. The behavior and strength of various structural engineering materials and members can be described while playing the song - Build it up with pins and needles…Build it up with wood and clay…Build it up with iron and steel.. Build it up with stone so strong. How the structural members fail depends on the structural properties of the materials – brittle materials like concrete break or crush, ductile materials like iron and steel bend or yield. So London Bridge failed in various ways - Pins and needles bend and break…Wood and clay will wash away…Iron and steel will bend and bow… Stone so strong will last so long. Bridge failures, however, depend on many factors as shown in the video below like the structural design of the piers including the detailing of reinforcement, the bridge deck supports, the soil and foundation...

This nursery ryhme may also be a good opportunity to introduce the concept of strengthening and retrofitting of existing structures. So when London Bridge fell, the ryhme continues - We must build it up again, Up again, Up again. We should not wait for another bridge disaster to occur. We should learn form the previous bridge disasters like those that happened to the Tacoma Narrows Bridge in 1940 or the Hanshin Expressway in 1995. We should act now to strengthen and retrofit existing bridges and structures. The last slide in the video clip shows the bridge pier retrofitted against earthquake effects.

Structural Engineering for Kids 3 - The 3 Little Pigs and the Big Bad Wolf - Lessons on Wind Loads

Remember the story of the Three Little Pigs and the Big Bad Wolf? This is a story where kids will learn the importance of designing structures against external forces such as wind due to typhoons and hurricanes. The big bad wolf wants to eat the pigs. And to do that he must be able to destroy each pig’s house by blowing on the house. The big bad wolf represents external wind forces that a house must resist. So to protect themselves, the pigs have to build their own houses. Pig 1 built a house of hay. Pig 2 built a house of twigs, while Pig 3 built a house of stone. And you all know the story’s ending, the big bad wolf’s strong blowing power destroyed the houses of hay and twigs, but not the house of stone. Structural engineers must design structures against wind loads. Codes like the National Structural Code of the Philippines (NSCP) specifies wind zones with corresponding basic wind speeds in determining the design wind loads. For example, Metro Manila belongs to Zone II with a basic wind speed of 200 kph, while the Northeastern parts of Luzon and Visayas under Zone I have a speed of 250 kph. According to the Outdoor Advertiser's Association after the Typhoon Milenyo in 2006 struck Metro Manila, they designed their billboards for 120 kph (PDI Oct. 1, 2006) and this is less than 200 kph. The toppled billboards due to Typhoon Milenyo showed us what will happen to structures not designed, constructed and maintained properly against wind forces. Photo courtesy of Engr. Willy Lopez (DPWH): Fallen billboard due to Typhoon Milenyo 2007