Friday, June 6, 2014

Useful Ideas from the Felder-Brent Workshop on Effective Teaching for OBE

Hotel Puteri Pacific, Johor Bahru, Malaysia
I attended the Effective Teaching for Outcomes-Based Education Workshop last May 20-21, 2014 at Hotel Puteri Pacific, Johor Bahru, Malaysia. The resource persons were the OBE experts,  Prof. Richard Felder, Ph.D. ChE and Prof. Rebecca Brent, Ed.D of the North Carolina State University. The workshop was very informative and educational. I have been teaching for more than 20 years in the university, yet I didn't realize that I have been doing bad practices in some cases and there many good practices that I should have applied tomake my teaching and students' learning more effective. I would just list the useful workshop ideas that I learned in the seminar-workshop and I intend to apply them in my future teaching activities.

Brent (2nd from left) and Felder(3rd from left)

1. You can get more feedback from "active learning" and "questioning." Felder and Brent demonstrated during the workshop how active learning can be done effectively in the classroom. In active learning, students do things in class related to the course. During the workshop, Felder asked the participants to group in pairs or three members. Then he pose a question or problem which the group must discuss within a few minutes (from one minute to three minutes depending on the problem). One member is tasked to record the group's output from the short discussion. Felder then asked selected members from various groups about their outpus. In about ten minutes, we got various answers and suggestions from the participants. He compared active learning strategy to individual questioning where in the teacher asked the whole class and then look for volunteers. In this case, you will find very few students willing to answer your question because most of them are shy or passive.

Why does this strategy work? Felder says students when they have interaction with fellow students, they get engaged in the activity. And when the teacher asked for their answers, the students are less shy because what he/she is sharing to the class is a group output not only his/her own. The students are awake during the short active learning activity and participate in the group discussion because they want to be prepared for an answer in case the teachers calls them. Don't worry about the noise students make during the group discussion. It's worth it than a quiet class where learning doesn't take place.

Useful idea: In a 90-minute lecture, students get bored if the teacher is the center of the teaching-learning process. Students should be more actively engaged. Short active learning activities during the 90-minute class is effective - it makes students awake, get them engaged and thinking and the activity also promotes collaborative learning.

2. Initiate opportunities where the students start thinking. Students should not be passive learners but active learners. As stated earlier students learn more on active learning. Before coming to class, review your notes and examples. Think of questions that you may pose to the students and apply active learning to make them think during the lectures. Use varied and challenging questions so that student can apply the lower and higher thinking skills. Instead of using "Is that clear?" or "Any questions?", ask questions similar to the photo below such as "What if I use a different section?", or "How could we improve the process?"

Asking varied questions make students apply the various thinking skills
(PPT slide form the Felder-Brent Workshop).

I applied this active learning in the first meeting of my class in Theory of Structures I (TSTRUC1). I want to review the students on the principles of Statics of Rigid Bodies (STATICS) and Mechanics of Deformable Bodies (MEDEFOR) which are prerequisite courses in TSTRUC1.  So I posed the question below and asked the students to discuss with their partner their answer to the problem for only ONE MINUTE.

Active learning activity in TSTRUC1 - Meeting No. 1

During the one-minute activity, the students get engaged in the discussion, the class obviously was noisy but they are awake. After one minute I called on students randomly from various pairs and I got good answers from the various groups. I have been doing this in my class in TSTRUC1 during the first meeting but in the past they do it individually. I got better, faster and more answers this time when I use pairings. Among the responses given were: type of material, available material, available equipment, allowable stress, weight of person, number of persons, span length, cross-sectional shape, temperature, environment, site, soil type, cost and budget. From the data gathered, I discussed the basic procedure of designing a simple beam bridge using their data and the principles of structural design using concepts from STATICS and MEDEFOR only. Span length, soil type as support and total load (weight and number of persons) are needed to model the bridge and solve the reactions, maximum shear and bending moment. The cross-sectional shape is necessary to determine the moment of inertia and location of the centroid of the section. The type of material is important to make an estimate on the allowable stress and the modulus of elasticity (E) of the beam bridge. The site and its environment are important if you are consider other environmental loads (temperature, wind, seismic, flood, etc). And finally, the budget becomes a constraint to your design as it will limit the cost of the bridge. The activity was very informative and new to them as they were introduced on how theory is applied to a real world civil engineering problem. About ten minutes were used effectively to review basic concepts in STATICS and MEDEFOR.

I shared this blog to Prof. Felder on June 7, 2014 and he immediately sent me this reply (June 8). 

Dear Andres,

Thanks so much for sharing the blog entry with me. It really pleases Rebecca and me that you got as much as you did from the workshop and you put it to use in your teaching that quickly. The beam bridge exercise is excellent. I wish my statics professor had done something like it when I was taking the course many years ago.

Congratulations too on an outstanding blog. Your students are lucky to have you as a resource.

Best regards,


Richard Felder
Hoechst Celanese Professor Emeritus of Chemical Engineering
North Carolina State University

Monday, October 21, 2013

Addressing Safety & Sustainability of Infrastructures in Hazard-Prone Countries

Keynote Paper delivered at Nagoya University's
International Forum on CE Infrastructure Technology Transfer, 31 August 2013
“Civil Engineers shall hold paramount the safety, health and welfare of the public and shall strive to comply with the principles of sustainable development in the performance of their duties.” This is one of the fundamental canons of the Code of Ethics of Civil Engineers. The task of a civil engineer includes provision of safe, reliable and comfortable infrastructures for housing, transport, communication, water supply and sanitation, energy, commercial and industrial activities to meet the needs of a growing population. Today, there is an increasing demand for civil engineers to focus their efforts on the protection and preservation of the environment. With the increase in severity and frequency of natural disasters that devastated both developing and advanced countries,  planning, design and construction of infrastructures that are safe for people and at the same time reduce their impact on further deterioration of the environment becomes a major challenge. Civil engineers who are experts in the various fields of specialization in structural engineering, transportation engineering, water resources engineering, geotechnical engineering and construction engineering must embed in their tasks disaster risk reduction especially in hazard-prone regions – for when they do this, they not only address safety but also sustainability – two important issues for maintaining the balance and harmony between the built and natural environment.
Living in hazard-prone regions. Achieving safety and sustainability is a major challenge in regions or countries that are vulnerable to adverse natural hazards like earthquakes, typhoons, floods, volcanic eruptions, drought and tsunamis. The vulnerabilities of the built environment to a hazard depend on the safety provided and sustainability features. The disaster will have impacts on both the built and natural environment.


Sunday, June 9, 2013

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.

Sunday, September 16, 2012

Open Ended Problems in Mechanics of Materials

Problem solving is one learning activity that is extensively employed by engineering educators. “Problem-solving is defined as a process used to obtain a best answer to an unknown or a decision subject to some constraints” (Mourtos 2004). Through problem solving students learn to apply the theoretical equations in both hypothetical and real-world scenarios. Assigning problem sets provides students the opportunity to test their understanding of the theory and concepts. The type of problems assigned to students addresses various levels of thinking and outcomes. Traditionally, problems are designed with given parameters and students are required to determine an unknown quantity. The solution usually involves substitution of known values to an equation to solve for the unknown parameter. Problems of this type are said to be “close-ended.” Close-ended questions usually have a unique answer and the procedure of obtaining the answer is limited or straight-forward. Close-ended problems address lower levels of thinking (based on Bloom’s taxonomy) like “remembering”, “understanding” and “applying” and some higher mode of thinking like “analyzing”.

To address higher levels of thinking like “evaluating” and “creating” and transformative outcomes experienced in the real-world, “open-ended” questions should also be included in the problem sets. Sobek and Jain (2004) emphasized the need for open-ended problems. “Employers look for engineers who are effective at solving open-ended problems. Engineering accreditation demands evidence that students can tackle open-ended problems proficiently.” Open-ended problems address considerably the student outcomes on “an ability to recognize, formulate, and solve civil engineering problems” and “an ability to engage in lifelong learning.” Open-ended questions are usually ill-defined and there may be more than one valid approach to obtain the solution. As a matter of fact, the solution may not be unique because of varying assumptions made regarding some parameters. Mourtos (2004) noted in their study that “traditional exercises (close-ended) found in most engineering texts, although useful, do not adequately prepare engineering students for real-world problems. Students seem to have great difficulty approaching these (open-ended) problems; however, they also seem to enjoy the challenge and perform reasonably well if given proper guidance.”

Problem : If you were to install a
steel Z-purlin, which arrangement
would you choose to maximize the
moment capacity of the section?

In the problem sets in my structural analysis course, open-ended problems are given. The problem shown about a Z-purlin is related to analysis of beams due to unsymmetrical bending which is similar to a problem by Singer. Deciding on the most effective set-up of the Z-section whether upright or inverted would require application of concepts in moment of inertia, equilibrium, bending moment and elastic bending stress analysis. There are various ways of determining the more efficient arrangement of the Z-section. You may compute which arrangment has the larger moment capacity. You can assume a moment and compute the maximum stresses and compare.


Mourtos, N. et al. (2004). “Open-ended problem solving skills in thermal-fluids engineering,” Global Journal of Egg Education, UICEE

Sobek, D and Jain V. (2004). “The Engineering Problem Solving Process: Good for Students?” Proc.2004 American Society for Engineering Education (ASEE) Annual Conference & Exposition

NOTE: An updated version of this article - "Challenging Students' Thinking Through Open-ended Problems" was published as e-notes in The Philippine Engineering Education (Vol. 1, No. 1, Sept 2013) - the official news magazine of the Philippines Association for Technological Education (PATE).

Tuesday, September 4, 2012

Using Visual Gobbets in Teaching

A gobbet is “an extract of text, a passage of literature, an image, a cartoon, a photograph, a map or an artifact provided as a context for analysis, translation or discussion in an assessment” (Chan 2008). “The student’s task is to identify the gobbet, explain its context, say why it is important, what it reminds them of or whatever else you would like them to comment on” (Biggs and Tang 1999). Gobbets are usually used for assessment.

I used "visual" gobbets in my class in Theory of Structures and Earthquake Engineering. Here are some examples.

In my first meeting in Theory of Structures-I, as my review of basic concepts in Statics and Mechanics of Deformable Bodies, I displayed an image of a beam bridge  and posed the problem to the students: “if you are required to design a simple beam bridge to cross a river, what information would you gather to accomplish your task and how would you use the information?

A Gobbet on Simple Beam Analysis & Design
 The responses from this gobbet include span length, beam material, weight of the person(s), number of persons crossing the bridge at one time, shape and size of the beam, soil type at the beam ends and cost. After listing their responses, I asked them on how the items in the list will be used in the analysis and design of the beam bridge. From this exercise, the students were able to reflect and learned about the relationship of the listed items to concepts in Statics and Mechanics of Deformable Bodies.

A beam bridge can be modelled as a simple beam with length, L and the weights represented as concentrated loads
Analysis means solving for reactions and maximum internal forces – moment and shear
The type of material will specify the material strength (allowable stresses) and mechanical properties (modulus of elasticity)
Designing the beam means determining the shape and size of the beam
• Various types of design can be done for comparison (strength, cost)

Another gobbet in my Earthquake Engineering class was included in an exam to assess the students’ understanding of structural failure due to earthquakes. This is an exercise on post-earthquake evaluation usually conducted by structural engineers (ASEP) after the occurrence of an earthquake. The students are shown photos of a building damaged due to earthquake. A description of the observed damage is also given. The students are required to assess the condition of the building based on the photos and description and recommend the appropriate post-earthquake posting (Safe, Limited Entry or Unsafe).

 "Safe", "Limited Entry" or "Unsafe"?

The third example of a gobbet exercise which I called “Scaling an Earthquake” was applied in the Earthquake Engineering course. One of the learning outcomes of the course is familiarization with the PHIVOLCS Earthquake Intensity Scale (PEIS). A series of photos were displayed to the class and the following problem was posted: “You are tasked to determine the intensity of the earthquake using PEIS. Assign the intensity scale for each photo. Explain your answer.” In this exercise, the students have to read and understand carefully the descriptors for each intensity scale in PEIS and relate them to the photos. 
Rate the Intensity Scale of this Earthquake
Biggs, J. and Tang, C. (1999). Teaching for Quality Learning at University, McGraw-Hill Open University Press
Chan C. (2008) “Assessment: Gobbets”, Assessment Resource Centre, University of Hong Kong []: Available: Accessed: 8/27/2012

Thursday, August 30, 2012

What is a soft story?

One of the requirements in my undergraduate course (STEQUAK) at DLSU is a group research related to earthquake engineering. The group has to present their topic orally using multimedia - powerpoint slides and a short video. The group of Gian Panaligan, Jerome Sy, Jospeh Oropel and Janelle Ong created a video about their topic, "How can we improve the seismic performance of a building with a soft story?" The language used is Filipino and their acting is very natural. A good story about a "soft story." Watch and enjoy.

Our last meeting - STEQUAK (Earthquake Engg) Class

Tuesday, June 5, 2012

Theory of Structures: An Introduction

Here is a powerpoint slide show of my lecture on the introduction to the Theory of Structures.

Monday, March 12, 2012

Model Popsicle-Stick Bridges of the Bridges in Asia

Chaotianmen Bridge (China)

In the recent Civil Engineering Society Bridge Building Contest, students from various civil engineering schools in Metro Manila were challenged to create popsicle stick bridges based on a segment of an actual bridge that can be found in the Asian region. The judging of the bridges took place last March 10, 2012 at the De La Salle University, Manila. It was a marvel to see the creativity of the students. There were model bridges that were really awesome and created meticulously following the photo of the actual bridge. The winner for the best design was the model of the Chaotianmen Bridge (China) submitted by the students from TIP. Marvel at the popsicle stick bridges below.

Asahibashi Bridge (Japan)

Asahibashi Bridge (Japan)

Ayala Bridge (Manila, Phils)

Zhejiang Road Bridge (China)

Merdeka Bridge (Malaysia)

Minamikawa Bridge (Japan)
Wanxian Bridge (China)

Quezon Bridge (Manila, Phils)

Dhamra Bridge (India)
Best Bridge Design

Monday, February 20, 2012

Meeting the Gurus of Outcomes-Based Teaching & Learning

John Biggs lectures at TIP (2012)
"The key to  'constructive alignment' is that all components in the teaching system - the curriculum and its intended outcomes, the teaching methods used, the assessment tasks - are aligned to each other. The teacher's job is to create a learning environment that supports the learning activities appropriate to achieving the desired learning outcomes, " says John Biggs, psychologist, educator and author and the man behind 'constructive alignment' and the SOLO taxonomy.

I met John Biggs and his wife and co-author, Catherine Tang at the International Conference on Outcomes-Based Teaching and Learning (ICOBTL) held on Feb. 16-17, 2012 at the Technological Institute of the Philippines, QC Campus. Biggs and Tang were the keynote lecturers at the ICOBTL which was attended by about 500 teachers, professors, university presidents and heads from CHED, DepED, PATE and PTC.
As I mentioned in my previous blog, I have been learning about outcomes-based education (OBE) and I have learned much from the papers of Biggs and Tang. Their rationale for constructive alignment (CA) which is an example of OBTL is quite noble. Biggs say CA is "concerned only with improving teaching and learning" unlike the other proponents who apply OBE for accrediation purposes.

 Applying OBE is not something new. The new terms  like 'constructive alignment', 'intended learning outcomes' or ILO, 'teaching and learning activities' or TLA and 'assessment tasks' or AT should not intimadate the teacher. OBE or OBTL or CA has been practiced by teachers consciously or unconsciously. What the teacher should do is simply to understand the concepts and refocus his/her teaching and learning activities and assessment tasks to address learning outcomes. With OBE, there is more focus on what the teacher and student should do. This is the challenge in OBE especially for engineering educators. How can you effectively apply OBE in the teaching of a technical course with a lot of theory like 'Engineering Mechanics' or  'Theory of Structures.' I am still groping for effective strategies aside from traditional classroom lectures and I will report on this in the future.
Catherine Tang, John Biggs, my co-faculty at DLSU - Alvin Chua and I

Wednesday, January 18, 2012

Outcomes-Based Education: As I see it

I was tasked by the dean and department chair to be a "champion" for outcomes-based education (OBE). The main motivation for this is that OBE may be used in the accreditaion of engineering programs in the Philippines following the accreditation practice (ABET) in the US.  But how can I be a champion when I don't have any idea about OBE. I attended a series of seminars conducted by DLSU educators but somehow it was difficult to comprehend the topics because the seminars combine UBD, OBE, Transformative Learning, Student-Centered Learning, etc. So I have to do my own readings of scholarly papers on OBE by experts like Spady, Biggs, Rogers and Feldman especially those related to ABET and engineering . After reading these papers and reflecting on them, I came up with a diagram (shown above) of  "the OBE Framework" as I understand it. Here are some of my thoughts about OBE.
  • OBE is a “student-centered learning philosophy that focuses on empirically measuring student performance, which are called outcomes.”
  • Outcomes are clear learning results (knowledge, skills, values, behavior) that learners have to demonstrate at the end of significant learning experiences.
  • Outcomes follow a hierarchy: (a)University level: the mission and vision defines the expected graduate attributes, (b) Program level: Program educational objectives (PEO) describe what graduates are expected to attain within three to five years after graduation, (c) Program level: Student outcomes describe what students know and can do after graduation, (d) Course level: Learning outcomes describe what the students know and can demonstrate at the end of the course.
  • Defining the outcomes is the key in curriculum and course design and delivery. The teaching methods, leanring activities, topics and assessment tools must be aligned with the outcomes.
  • At the end of the course or program, an assessment must be done to determine whether the outcomes were achieved or not. The purpose of asssessment is to provide a continuous process of planning, measuring, analyzing results, and using the results to make informed decisions that, preferably, lead to improvements.
Now that OBE has started to be come a framework in the teaching-learning process in the university, how will this affect me and my colleagues? I have been in the academe for more than 20 years (five years at UP and 17 years at DLSU). When I reflected on the OBE paradigm and my present teaching practice, I can see that I need to make a few adjustments:
  • I must explain to the students at the start of the term that they should address the learning outcomes in all their learning activities - readings assignements, exams, etc.
  • I must always refer to the syllabus and make sure that my teaching-learning activities and assessments (exams, assignments, etc) are aligned with the learning outcomes.
  • I must use various learning activities to develop the students' interest in the classroom. Available technology (youtube, internet, etc.) must be explored.
  • I must explore creative ways of delivering course content. I should  deliver only the most important content in lectures and the other related content through other means (e.g. internet).
  • I must regularly assess on whether the learning outcomes are being achieved through seatworks, recitation and homeworks. These assessments need not be part of the final grade but must be used to improve the teaching-learning process during the term. If I observe some weakness in a specific topic, then I need to make adjustments on that topic.
  • I must design an assigment on how I can assess the "skills, knowledge, behavior" of students related to the course and relate to real world tasks to achieve "transformational" outcomes.
Moving from traditional methods to outcomes-based takes time. As a start, an OBE syllabus must be designed by the faculty. Then gradually the faculty should change his/her teaching practices (e.g. combine various activities in lectures) and eventually teaching based on OBE becomes natural. This I hope to achieve.

Wednesday, October 5, 2011

Simply Mechanics: Equilibrium of a Fish Mobile

A mobile is a decorative structure that is suspended so as to turn freely in the air. A mobile usually consists of pieces of rods and decorative shapes made of metal, wood, plastic or paper suspended in midair by wires, strings or ties so that the individual parts can move independently when stirred by a breeze.

The principles in engineering mechanics about force systems in equilibrium can be demonstrated by analyzing the equilibrium condition of a mobile. Consider the fish mobile which hangs in our room. The fish mobile is an example of a parallel force system. All forces acting on the horizontal rods are vertical since only gravity loads due to the weights of the hanging objects act. I laid the mobile on a flat surface and this is how it will appear as a parallel force system.

The Fish Mobile as a Parallel Force System
Haven’t you wondered how much force each wire supports to keep the mobile in equilibrium? Let’s apply the principles of engineering mechanics to answer this query. Here is model of the fish mobile as a parallel force system and the free body diagrams (FBD) of the rods supporting the fish mobile whrere the fish shapes are represented by their weights (W) and the tensile forces acting on the wires are represented as T1, T2, T3 and T4.

To compute the force acting on wire no. 4, the FBD with T4 is used and  the equilibrium equation of summation of forces with respect to the vertical axis is applied. The upward forces should be equal to the downward forces. Hence, T4 = 2W. Similarly, the forces on the other wires can be computed by using the appropriate FBDs. Thus,
T3 = 3W.
T2 = T4 + W = 2W + W = 3W.
T1 = T2 + W + T3 = 3W + W + 3W = 7W

The mass of each fish object is about 10 g or 0.01 kg which is equivalent to 0.0981 N. Hence, the tensile force acting on wire no. 1 is T1 = 7(0.0981 N) = 0.6867 N.

Except for second rod, all rods have symmetrical loading resulting to the wire located at the middle of the rod. However, for the rod where T2 acts, the force at the right is T4=2W and the force at left is W. For equilibrium, the location of the T2 is closer to right. An equation of equilibirum (summation of moments) may be used to determine the location of the wire for this rod.

The arrangement of the rods and hanging objects on a mobile will affect the magnitude of the forces acting on the wires. In the design of a mobile, the following factors should be considered: (a) Mass of the each hanging object and (b) Length of each rod. The location of the wire on the rod depends on the weights supported by the rod. If the weights are hanged symmetrically, then the wire is placed at the midspan of the rod to satisfy equilibrium. However, for unsymmetrical loading where the weight at the left is not equal to the weight at the right, the location can be obtained by applying the equation of equilibrium for moments.

Equilibrium of a fish mobile? That's simply mechanics.

Thursday, July 21, 2011

How strong is "good lumber" in compression?

Compression Failure of a short timber column

To check the safety and serviceability of wood used as columns, posts and truss members, the compressive strength of the wooden elements must be known. "Good lumber" which is available in the Philippines are usually used but their properties ae unknown. Hence, this research was conducted.

Mechanical Properties in Compression of  Commercially Available Lumber in Metro Manila
Liang Ta Chen, Francis F. Ebanos and Mark Justin K. Kung

Lumber in particular vary in strength depending on different parameters such as specie, dry density, slope of grain and others. Stress grading is used to be able to use lumber’s mechanical properties. However, many lumberyards do not have stress grading for the lumber they sell. In the survey conducted by the group on lumberyards in Metro Manila, Philippines, 81% of these lumberyards have little awareness or knowledge on what kind of wood they are selling wherein they do not know the specie of the lumber they were selling or the specie of their lumber was known but were mixed and could not be identified. The common species of these so-called “good lumber” were tangile, lauan, miranthe and saba while its source are almost half imported and half local.

This research aims to determine the mechanical properties in compression of commercially available lumber used as a structural member commonly referred to as "good lumber" in Metro Manila, Philippines. Compression members are usually used as post or truss members in roof trusses. 

Lumber that were tested had varying properties. The moisture content value of good lumber ranged from 11% to 62 % while the density ranged from 319 to 729 kg/m3. The compressive strength and modulus of elasticity of “good lumber” had high coefficient of variance which means it is very distributed. Compressive strength ranged from 3.996 to 51.386 MPa while modulus of elasticity ranged from 816.4 to 7921.3 MPa. The allowable compressive strength when ASTM D6570 is imposed is 7.372 MPa which is similar to the specie Malugai of the medium strength group with 63 % stress grade in the NSCP having an allowable compressive strength of 7.35 Mpa. On the other hand, the  modulus of elasticity when ASTM D6570 is imposed is 3510 MPa which is similar to the specie Bayok of the moderately low strength group with 63 % stress grade in the NSCP having an allowable modulus of elasticity of 3740 MPa. Tests of long columns also showed that Equation from Section 617 of NSCP holds true and showed that the values computed are much smaller than the actual failure stresses. The mechanical properties of  compression members obtained from this study may guide structural designers in their design computations.
Buckling of a long timber column

Monday, July 11, 2011

Good Lumber: How "good" are you as a structural beam?

Many low cost houses used wood as structural beams for joists in floor framing systems and for purlins in roof truss systems. When you design a beam, you must know the allowable strength properties for shear and flexure and the moduus of elasticity to check whether safety and serviceability requirements are satisfied. But when you buy wood in lumberyards in the Philippines, the wood specie is not usually known. The lumberyards simply label wood used as structural members as "good lumber" and obviously the strength properties are unknown. To address this problem of a civil engineer, the following research was conducted by DLSU undergraduate students. Here is the abstract of the thesis. A paper will be presented soon in conferences in the Philippines.

Mechanical Properties on Flexure and Shear of Commercially Available Timber Beams in the Philippines
Earl Marvin B. De Guzman, Michael Stephen C. Go, Katrina C. Tengki

Commercially available wood used as structural members are commonly referred to as “good lumber.” Good lumber consists mostly of imported lumber, and those of lesser known or unknown local species. With the wood species not clearly specified, there is a need to determine the mechanical properties of good lumber.

This study aims to determine the variation of strength properties of timber beams classified as good lumber. Standard laboratory tests were conducted to determine the range of values of the properties of good lumber such as moisture content, specific gravity, modulus of elasticity and the bending and shear strength of timber beams. The mechanical properties of good lumber were obtained through a series of laboratory tests that simulate the conditions for the loading schemes specified in the ASTM manual, on beams of nominal cross section 2”x4”. The laboratory tests results showed that good lumber has a moisture content ranging from 12-82% with 25% as average value, a relative density ranging from 0.236-0.743, and an average modulus of elasticity of 8.15GPa. The modulus of rupture ranged from 5.7 to 63.5MPa, while the shear stress at failure ranged from 0.60 to 4.15MPa. For structural design purposes, a reduction factor of 2.1 based on ASTM Standards was applied and the allowable flexural strength obtained falls within the range 11.0-18.0MPa, while the allowable shear strength obtained is within 0.77 to 1.34MPa. Comparing the strength properties to the timber species in the NSCP 2001/2010, it was found that good lumber in general would have values within the ranges for medium and moderately low strength group for 63% stress grades. With the information on the variation of strengths of good lumber obtained from the study, structural designers would be guided on appropriate allowable stresses to be used in the design of structural members made of wood such as purlins and joists.
The student researchers, Go, Tengki & De Guzman received certificates for being a finalist for the 2011 Gold Thesis Award for the Structural Engineering Division

Saturday, July 9, 2011

An Optimum Mix Design of High Strength Concrete using Genetic Algorithms

High-strength concrete (HSC) is a highly complex and evolving construction material. Careful selection of constituent materials must be employed to successfully proportion HSC mixtures. A guide for proportioning HSC by the American Concrete Institute (ACI) is available but the guide provides only a general idea of the proportions of the various components for HSC production. Presently, batching companies produce different trial mixes using the ACI guide and some trial and error considering the observed effect of each constituent material to the strength development of HSC in order to attain a target concrete strength. This method, however, requires plenty of mix design experimentation that is costly and time consuming. Through the years, trial mixes of HSC of various strengths have been compiled by batching companies. These trial mix data may be useful in deriving optimum mix designs of HSC.

This study explored the use of genetic algorithms (GA) in deriving optimum mix designs for HSC using data collected from a batching company. Three hundred ninety-six (396) HSC trial mixtures were analyzed to derive empirical equations for strength and slump which were adapted as GA fitness functions. The GA program generated optimum preliminary designs for concrete strengths in the range of 7,000 psi (48 MPA) to 10,000 psi (69 MPa) depending on the type of sand and whether silica fume is present or not. In-situ adjustments for the dosage of admixture and amount of water were applied to the GA preliminary mix designs to account for the moisture content and absorption of the aggregates. These mix designs were verified by implementing the mixture with in-situ adjustments and testing the concrete cylinders for compressive strength. The target values for strength and slump were obtained. Cost comparison also showed that the GA-HSC mix designs yielded lower material cost than the mix designs provided by the company indicating a near optimal and more economical mix design.
This is the undergraduate thesis of Iris Mae M. Malabatuan, Bertrand B. Teodosio and Analyn C. Yee Concepcion at Department of Civil Engineering, De La Salle University, Manila. CE faculty, Engr. Alden Paul Balili, who also completed his MSCE thesis on GA with application to RC Frames was a co-adviser of the group and his GA program was used in the thesis. The thesis group is a finalist for the 2011 Gold Thesis Award for the Structural Engineering Division.

The group members and the advisers wish to express their gratitude to D. M. Consunji, Inc. and its current president, Mr. Jorge A. Consunji, for granting the request to obtain concrete mix design data.

Monday, June 6, 2011

Beware of Tsunami!

Beware of Tsunami (6:30 min)

A tsunami is chain of fast moving waves that can be triggered by an earthquake. On Dec. 26, 2004, an earthquake generated a large tsunami hitting many countries around the Indian Ocean. Among the countries affected were Indonesia, India, Thailand, Malaysia and Sri Lanka. Communities near coastal areas are highly vulnerable to tsunami. The most recent earthquake and tsunami that struck Fukushima, Japan is another reminder about the effects of a tsunami in coastal areas. Hence, public awareness about the impact and mitigation of tsunamis must be promoted.

This video is part of the  Understanding Earthquakes and Disasters: Photo-Video Presentations,” a project funded by the DLSU-Manila University Research Coordination Office (URCO).