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Enhancement of Flexural Strength Capacity of RC-Beams using LC-GFRP Plates with Effective Debonding Techniques
(2026-07-01)
Rodsin, Kittipoom
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Ngamkam, Kunanon
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Parichatprecha, Rattapoohm
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Pongpeng, Jakrapong
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Mehmood, Tahir
Strengthening of reinforced concrete (RC) beams by externally bonded Carbon Fiber Reinforced Polymer (CFRP) is found to be a very effective method to increase their flexural strength capacity. However, the strengthening cost of the CFRP technique is very high and clients tend to avoid such expensive retrofitting methods. An alternative strengthening material, such as Glass Fiber Reinforced Polymer (GFRP), is a much less expensive material compared to CFRP. The GFRP strengthening method can achieve comparable strength gain and is an effective solution for strengthening RC beams. However, due to the lower strength and stiffness, a larger thickness of GFRP is required to obtain the target tensile strength. This increase in fiber thickness results in the commonly observed debonding failure of the GFRP-plated RC beams. Therefore, this study investigates the end anchoring technique by testing five beams under three-point bending. The first beam served as a controlled beam, while the second and the third beams were strengthened with one and three layers of GFRP to investigate the effect of the number of GFRP layers on debonding behavior. Anchored bolts were used to prevent debonding in the fourth specimen. The innovative W-shape inclined jacket technique was used for the last specimen. The test results revealed that the GFRP could effectively increase the beam's flexural strength. Nevertheless, when a larger number of GFRP layers was used, the debonding of GFRP occurred at an early loading stage. With the anchored bolted technique, the flexural strength of the RC beam was found to increase twice compared to the controlled specimen before failure due to the pulling off of the anchored bolts. Widespread shear cracks were observed near the failure stage. For the W-shape inclined jacket strengthening technique, the flexural strength was increased to a similar order as the anchored bolted technique, but the failure mode was due to slippage of the GFRP against the W-shape inclined jacket. Due to the use of a W-shape inclined jacket, the shear strength of the beam increased significantly. Therefore, the crack patterns near the final stage were controlled by flexure. The test results revealed that both techniques are effective methods to enhance the flexural strength of the GFRP-strengthened beam by achieving a similar magnitude of strength gain but failing in different failure mechanisms.
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Impact of contractor competitiveness on firm performance: a view from real estate developers
(2026-01-01)
Pongpeng, Jakrapong
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Rojanathamwong, Waiwit
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Peansupap, Vachara
While previous studies have identified contractor competitiveness factors as selection criteria, few have empirically examined how these factors influence firm performance. This gap limits developers’ ability to select criteria for contractor selection. This study aims to analyze the impact of contractor competitiveness on performance and investigate the underlying influencing factors. A comprehensive literature review was employed to develop a conceptual model. Data were collected through a questionnaire survey of Thai real estate developers. Structural Equation Modeling (SEM) was applied to evaluate the proposed model and test research hypotheses, thereby addressing the gap in understanding the contractor competitiveness’s role in organizational success. The SEM analysis revealed a significant positive relationship between contractor competitiveness and performance (standardized regression weight = 0.65). Moreover, the factors influencing contractor competitiveness include management, resources, and generic competitive strategies, with regression weights of 0.99, 0.76, and 0.76, respectively. This study offers theoretical contributions to research on contractor competitiveness. First, the conceptual model elucidates the impact of contractor competitiveness on firm performance from the perspective of real estate developers. Second, the model confirms the hypothesis that management, resources, and generic competitive strategies measure contractor competitiveness. Furthermore, these findings provide developers that assessing contractor competitiveness directly improves firm performance.
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A Common Structure for Factors that Enhance Synergy in Contractor Project Teams: Executive and Practitioner Perspectives
(2024-09-01)
Pongpeng, Jakrapong
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Ratanawimol, Nareerat
Synergy in a contractor project team improves performance by integrating diverse knowledge and skills among team members, enabling the achievement of project objectives. However, according to a literature review, factors that enhance synergy among contractor project teams from the perspective of executives and practitioners have rarely been discovered, revealing a knowledge gap that needs to be filled. Therefore, the aim of this study was to identify a common structure of such factors for executives and practitioners. Data collection involved a questionnaire survey targeting large contractors in Bangkok, Thailand. Then, we compared the mean importance and rank order of synergy factors, examined differences and similarities in synergy factors between executive and practitioner perspectives using the Mann–Whitney U test, and applied confirmatory factor analysis (CFA) for the data analysis. The differences and similarities show that executives and practitioners have similar perspectives on synergy factors. The CFA results validate a factor structure that enhances synergy. This synergy factor structure for executives and practitioners can be divided into five groups, with their standardized regression weights in parentheses: coordination (0.94), organizational structure (0.92), motivation (0.80), leadership (0.75), and planning and policy (0.69). These findings contribute to the body of knowledge and the state of practice by offering a practical framework to assist executives and practitioners in contractor organizations in identifying common measures and resource allocation based on the regression weights of synergy factors. This can improve synergy among contractor project teams, potentially resulting in better performance.
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A SEM ANALYSIS OF THE IMPACT OF UNETHICAL STAKEHOLDER BEHAVIORS ON CONSTRUCTION PROJECT FAILURES: AN OIL AND GAS INDUSTRY STUDY
(2022-03-01)
Gomarn, Pittayaporn
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Pongpeng, Jakrapong
Continued unethical behavior by stakeholders within the oil and gas construction industry has a possible impact on the failure of many projects. This study therefore aims to investigate the impact of this type of behavior on the oil and gas construction industry. A conceptual framework was developed from both a literature review and interviews with 8 experts working on oil and gas construction projects in Myanmar, Malaysia and Thailand. A 31-item questionnaire was used to measure the 304 responses, from which a confirmatory factor analysis and structural equation model (SEM) were developed to investigate this impact. The results revealed that the most significant direct impact on a project's failure was a main contractor's unethical behavior. Furthermore, the study determined that the unethical behaviors of the consultant and designer had no direct impact on a project's failure but that there was an impact of the owner's unethical behavior. Ranked in order of importance, the indicators of a project failure are as follows: stakeholders' dissatisfaction; cost overrun; time overrun; negative effects on health, safety and environment; quality defects; and dispute and litigation. The results provide a guideline for developing a code of ethics to conduct unethical behavior investigations, which will help decrease future project failures.
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Social sustainability: Satisfying owners and communities by multilevel strategies of contractors
(2020-03-01)
Kawesittisankhun, Kittipos
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Pongpeng, Jakrapong
In sustainable construction/production, the social dimension regarding owner and community satisfaction has received the least focus. To promote social sustainability, the multilevel strategies of contractors should be developed for owner and community satisfaction. However, a literature review shows that there are few studies on how multilevel strategies influence such satisfaction. Hence, this study aimed to analyze such influences. A survey was conducted to gather data from the Thai construction industry, and these data were then analyzed by a structural equation model (SEM). The results, for the first time, highlight that corporate strategy influences business strategy (direct influence = 0.98), which in turn influences functional strategy (direct influence = 0.93). Additionally, only functional strategy influences owner (direct influence = 0.84) and community satisfaction (direct influence = 0.66). Furthermore, parenting, cooperation, and equipment/machinery substrategies obtain the highest weights within the management levels of corporation, business, and function (regression weights = 0.49, 0.48, and 0.55), respectively. The work productivity and site organization indicators have the largest weights for owner and community satisfaction (regression weights = 0.47 and 0.57), respectively. The findings provide a guideline that helps contractors allocate their available resources to substrategies according to their regression weights, enhancing owner and community satisfaction.
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Relationships of construction project manager, engineer, and foreman skills
(2019-10-25)
Kawesittisankhun, Kittipos
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Pongpeng, Jakrapong
Understanding the relationships of construction project manager, engineer and foreman skills can be used by contractors to develop project performance. Although there are widely discussed on construction individual skills, the relationships between individual skills having on others' skills have not been examined in previous studies. Thus, this study examined such relationships. The questionnaire was used to collect data on the important range of skills of the individual to evaluate the relationships among them. The data were then analyzed using structural equation modelling (SEM) to determine the relationships of construction manager, engineer and foreman skills. The final SEM model shows regression weights in parenthesis that construction manager skills have influence on engineer skills (0.65) and engineer skills have influence on foreman skills (0.84). Additionally, the regression weight presents that knowledge management is the most important skill for a construction manager (0.64). Problem-solving is the most important to engineer (0.59). Regarding foreman, physical skill is the most important (0.67). The findings can be used as a guideline for contractors in developing their staffs to increase project performance.
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Construction project team's competencies influencing contractor business competencies
(2019-10-25)
Kawesittisankhun, Kittipos
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Pongpeng, Jakrapong
Consistent arrangement of contractor business competencies and project team's competencies helps improve project operation efficiency. Key participants in the project team are project managers, engineers, and technicians. However, a review of existing literature reveals a lack of research on the causal relationship between project teams' competencies and business competencies. Therefore, this study attempted to identify the relationship through survey contractors' opinions. The data were analyzed using structural equation modeling (SEM). The results suggest the regression weighs presented in parenthesis that business competencies are influenced by the competencies of a project manager (0.50) and engineer (0.49). The study also discovered the influence of competencies among project teams; that is, technician competencies influence engineer competencies (0.87), and engineer competencies influence project manager competencies (0.55). With the causal relationship between the project team's competencies and business competencies, contractors can suitably allocate human resources for increasing their project operation efficiency.
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Sustainable Infrastructure Assessment Model: An Application to Road Projects
(2019-03-01)
Krajangsri, Thanachon
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Pongpeng, Jakrapong
Sustainable infrastructure assessment models play an important role in sustainable development. However, the current infrastructure assessment models for road projects have several limitations; specifically, all the models do not support the involvement of various stakeholders. Most models do not consider the risk arising from uncertainty in the assessment, and are not flexible regarding changes needed for local project contexts. Accordingly, this study aims to develop a sustainable infrastructure assessment model that overcomes these limitations, which is the distinct contribution of this study. A utility function is used to address the risk, and the stakeholders’ involvement is taken into account by a social welfare function. To provide flexibility for changes, the model is programmed using Visual Basic for Application for interactive activities with stakeholders (as assessors) and Microsoft Excel for calculation activities. The model includes four phases: 1) assessor weight selection, 2) assessment criteria and weight selection, 3) sustainable infrastructure assessment, and 4) sustainability assessment report. The model was verified and validated with four actual road projects, and acceptable results were obtained. Thus, the proposed model, which reflects reality more accurately than other available sustainable infrastructure assessment models, can assist stakeholders by reducing the time and effort required for assessing the sustainability of road projects.
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The role of infrastructure sustainability and success of construction projects on owner benefits
(2018-08-14)
Krajangsri, Thanachon
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Pongpeng, Jakrapong
The infrastructure sustainability and success of construction projects likely influence owner benefits. However, these influences have rarely been examined. Thus, the research aimed to examine such influences and intervening behavior of the success of construction projects between the sustainability of infrastructure and owner benefits using structural equation modeling (SEM). The study finds that there are a direct influence of the sustainability of infrastructure on owner benefits (regression weight: 0.63) and an indirect direct influence of that (regression weight: 0.22) through the intervening role of the success of construction projects. The findings ensure that implementation of infrastructure sustainability projects can enhance the success of construction projects and owner benefits.
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Causes of construction delay from contractors and suppliers in Thailand's oil and gas platform projects
(2018-08-14)
Gomarn, Pittayaporn
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Pongpeng, Jakrapong
Construction project delays caused by contractors and suppliers are the top problems in Thailand's oil and gas industries. Recognizing this importance and their relationships between factors can help reduce the risk of delays in construction projects. Therefore, this study set out to confirm factors and inspect relationships between delay factors of contractors and suppliers. A 16 item questionnaire survey was distributed to 134 managers, engineers, and supervisors in oil and gas platform construction projects in Thailand. A confirmatory factor analysis (CFA) was performed by the use of Amos Version 20 software program. The analysis results showed that delays caused by the contractors and suppliers had high relationships, due to high regression weighs. The delays caused by the contractors included seven factors which included poor site management and supervision (17%), lack of safety rules and regulations (16%), poor communication and coordination with others (15%), poor procurement system management (15%), defective components and mistakes during construction (14%), supplier payments lateness (13%), and poor planning and scheduling (10%). The delays caused by the suppliers included six factors which included the supply of unqualified and unskilled personnel (22%), supply of low efficiency equipment (20%), late delivery of materials and equipment (20%), supply of low quality materials (16%), late supply of workers (16%), and price escalation (5%).

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