Wael A. Zatar

By Wael A. Zatar and Issam E. Harik

Part of the book: Earthquake Engineering

By Wael Zatar

Prestressed concrete viaduct structures are used for the construction of many highways and railways. The objective of this study was to clarify the inelastic response behavior of partially prestressed concrete viaduct structures during severe earthquake excitations. A study that includes experimental and analytical phases was carried out. Small-scaled models were employed so as to represent actual viaduct structures. Specimens representing the PC girders of the viaduct structures were tested experimentally. The first technique was statically reversed cyclic loading test to study the inelastic response behavior of the PC girders and to obtain the hysteretic-load deformational characteristics. The sub-structured pseudo-dynamic testing technique was implemented as the second testing technique. During the sub-structured pseudo-dynamic test, the PC girder was tested experimentally, and the RC columns of the viaduct structure were simulated analytically. An amplified excitation of the 1995 Hyogo Ken Nanbu earthquake was used. Response analyses for the viaduct model were carried out. A comparison between the experimental results and results obtained from response analyses was made. An agreement between the experimental and analytical results was found. The study revealed that not only the RC columns but also the PC girders may undergo extensive damage during severe earthquake excitations.

Part of the book: Natural Hazards

By Wael Zatar and Hai Nguyen

Self-consolidating concrete (SCC) has been successfully employed to reduce construction time and enhance the quality, performance, and esthetic appearance of concrete structures. This research aimed at developing environmentally friendly fiber-reinforced concrete (FRC) consisting of SCC and recycled polypropylene (PP) fibers for sustainable construction of city buildings and transportation infrastructure. The addition of the PP fibers to SCC helps reducing shrinkage cracks and providing enhanced mechanical properties, durability, and ductility of the concrete materials. Several mix designs of self-consolidating fiber-reinforced concrete (SCFRC) were experimentally examined. Material and esthetic properties of the SCFRC mixtures that include micro silica, fly ash, and PP fibers were evaluated. Trial-and-adjustment method was employed to obtain practically optimum SCFRC mixtures, mixtures that are affordable and easy to make possessing enhanced compressive strength and esthetic properties. Slump flow and air content testing methods were used to determine the fresh properties of the SCFRC mixtures, and the esthetic properties of the mixtures were also evaluated. The hardened properties of the SCFRC mixtures were examined using three- and seven-day compression tests. The amount of fine/coarse aggregate, water, and other admixtures were varied while the Portland cement content in all mixtures was maintained unchanged. The maximum three-day compressive strength was 43.17 MPa and the largest slump flow was 736.6 mm. Test results showed enhanced material properties such as slump flow, air content and compressive strength values of the SCFRC mixtures and their excellent esthetic appearance. The favorable seven-day compressive strength of the SCFRC mixture, with 4.8 percent air content and 660.4 mm slump flow, is 39.26 MPa. The mixtures’ in this study are proven to be advantageous for potential SCFRC applications in architectural structures including building façades and esthetically-pleasing bridges.

Part of the book: Design of Cities and Buildings

By Wael A. Zatar

Federal and state transportation agencies across the world face a multitude of challenges to effectively maintain cost-effective core maintenance programs for managing a safe, yet sustainable transportation assets’ program. The decision-making process involves several risk factors, and the prioritization of these factors could considerably affect both the level of utilization of these assets, as well as short- and long-term management protocols and plans for these agencies. The Moving Ahead for Progress in the 21st Century Act requires each state Department of Transportation in the United States to have a risk-based asset management plan in place to preserve the condition of their assets and improve the performance of the National Highway System. Many transportation agencies lack the financial and human resources to achieve their targets, and therefore they may opt to make trade-offs, lower targets, and perhaps drop some important objectives. Trade-off decisions can become clearer when objectives and targets are viewed through the lens of which options reduce the top-priority risks, such as reduced risk to safety, asset performance, or future costs. This chapter primarily focuses on emphasizing the importance of risk management in transportation networks and demonstrating the relationship between environmentally influenced risk management and sustainable management of state-controlled transportation assets in the United States. Several key parameters including risk assessment, financial risk and organizational behavior are addressed. Successful examples demonstrating how transportation agencies have identified how to best address a given risk, and in turn impact the resource allocation process are provided.

Part of the book: Risk Management