Resources

Alta Vista values candid communication and transparency. To that end, we encourage our team members to document and share best practices and expert knowledge openly. Explore the resources below at your leisure and, if you can't find what you are looking for, please contact us—we welcome the opportunity to begin a conversation.

Alta Vista's Publications

A Forensic Study of the Collision of a Cargo Ship with the Vincent Thomas Bridge, 2007 A. Mazen Wahbeh et al.

Abstract:

On 27 August, 2006, the Vincent Thomas Bridge, a critical 1850-m suspension bridge, located in the metropolitan Lost Angeles region had a collision with a large cargo ship, passing under the bridge. This incident left the transportation authorities wondering about the structural integrity of the bridge. Immediately after the accident, the bridge was closed to traffic until structural engineers from the California Department of Transportation (Caltrans) completed an analysis of the bridge.

Interest in the field of structural health monitoring (SHM) has been growing at a fast pace in the recent past due to the great developments in the fabrication of innovative sensors, the ease of deploying sensor networks, and the associated high growth in the computational power that is becoming readily available with personal computers. Furthermore, the development of sophisticated digital signal processing tools for the analysis of vibration signatures of dispersed civil infrastructure system has generated a lot of interest in the application of such analysis tools, in conjunction with real-time monitoring approaches, in order to perform virtually continuous condition assessment of any instrumented structure.

A real-time continuos monitoring system has been developed by the researchers at the University of Southern California, and deployed onto the Vincent Thomas Bridge since 2005. Using the monitoring system, the dynamic response of the bridge was successfully recorded before and after the incident as well as during the collision process. The analysis of these valuable data allows the transportation authorities to quantify the effects of the collision on the bridge structural condition, which would otherwise be infeasible with traditional visual bridge inspection approaches.

A forensic study was performed to assess the structural condition of the bridge before and after the incident. Relatively long time history records of the bridge oscillations were used to analyze its nearly stationary response by applying multi-sensor system identification approaches, utilizing the NExT-ERA methods. Both global and local identification methods were applied to detect significant changes in the bridge vibration signature. The identification results shown that there are no significant system changes due to the collision.

By utilizing web-based SHM system that is installed on the bridge, it is demonstrated that analysis of the acquired sensor measurements can provide the owners of critical infrastructure system with a forensic tool that enables reliable and rapid assessment to analyze the circumstances and consequences of extreme events to which the target system is subjected.

– Yun, H-B., Nayeri, R.D., Masri, S.F., Wahbeh, M., Tasbihgoo, F., Caffrey, J.P., and Sheng, L-H., (2007), “A Forensic Study of the Collision of a Cargo Ship with the Vincent Thomas Bridge,” Proc. of World Forum on Smart Materials and Smart Structures Technology 2007, 22-27 May 2007, Chongqing and Nanjinng, China.

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A Practical Guide to Welding Closed Ribs (U-Ribs), 2013 Patrick Lowry et al.

Abstract:

Closed ribs serve as the primary stiffening elements for orthotropic box girders, which when constructed in series, comprise the orthotropic steel bridge deck. Two partial joint penetration (PJP) groove welds connect each of the closed ribs to the bridge deck plates. Due to long-term fatigue cracking that can occur with poor weld quality, consistent quality in the PJP closed rib weld is essential to the structure’s ability to meet the specified design life.

The fabrication of several bridges employing the orthotropic steel deck design illustrated the challenges fabricators and contractors face when performing closed rib welding (also referred to as U-rib welding). Bridges examined in this paper include the new Tacoma Narrows Bridge in Tacoma, Washington, the Alfred Zampa Memorial (new Carquinez) Bridge in Crockett, California, the Bronx-Whitestone Bridge in New York City, New York, and the new eastern span of the San Francisco-Oakland Bay Bridge in Oakland, California.

The PJP groove weld is a non-standard joint and can create numerous challenges for fabricators. Issues that have arisen through the fabrication of closed rib welds on various orthotropic steel bridge projects are cracked tack welds, solidification cracking, and consistent maintenance of the specified weld penetration level.

This paper will discuss the practical steps fabricators and contractors can take to successfully perform closed rib welding, which include developing a careful welding procedure to control weld parameters, performing multi-pass welding, standardizing tack weld length and size, and performing NDT to identify areas requiring repair.

– Patrick Lowry, Keith Hoffman, and Aaron Prchlik. “A Practical Guide to Welding Closed Ribs (U-Ribs)”, Seventh National Seismic Conference on Bridges & Highways, Oakland, CA, May 2013.

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A Programmable Wireless Sensing System for Structural Monitoring, 2006 A. Mazen Wahbeh et al.

Abstract:

Recent work has examined the design of wireless sensor network (WSN) systems for structural health monitoring (SHM). Wireless sensors enable dense monitoring of large physical structures and promise enormous ease and flexibility of deployment of instrumentation, as well as low maintenance and deployment costs. However, programming sensing applications on a network of wireless sensors remains a difficult and time-consuming endeavor. This is due in part to the complexity of such systems. Their limited battery resources, and the highly variable performance of wireless communication in different environments represent significant constraints that, if each application developer were forced to deal with, can significantly increase the time to develop robust applications. We have been developing a networked software system called TENET that simplifies the programming of wireless sensor actuator systems. A TENET system is a two-tier networked system consisting of two classes of nodes: a higher-tier with several nodes containing 32-bit processors and IEEE 802.11b radios, and a lower-tier comprising battery-operated sensor nodes with less-capable processors, low-power radios. Our TENET software runs application code on the higher-tier nodes, and provides a generic interface for tasking sensors and actuators. This separation of functionality simplifies application development greatly, since developers can reuse networking and sensor data extraction code, thereby reducing application development time. We will report on the development of and experiences with structural data acquisition application for a long-span suspension bridge using TENET. We will report on our experiences in deploying a two-tier network of wireless sensors on the bridge. We will report on the performance of the TENET system in this setting as well.

– Jeongyeup Paek, Omprakash Gnawali, Ki-Young Jang, Daniel Nishimura Ramesh Govindan, John Caffrey, Mazen Wahbeh, and Sami Masri, (2006), “A Programmable Wireless Sensing System for Structural Monitoring”, Fourth World Conference on Structural Control and Monitoring (4WCSCM), July 2006.

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A Study of Time-Domain Techniques for Modal Parameter Identification of a Long Suspension Bridge with Dense Sensor Arrays, 2009 A. Mazen Wahbeh et al.

Abstract:

While numerous studies have been published concerning the application of a variety of system identification techniques in conjunction with vibration measurements from civil infrastructure systems, there is a paucity of publications addressing the influence of algorithm-specific control parameters that impact the correct and efficient application of the selected identification scheme. Furthermore, as dense sensor arrays become widely accessible in civil infrastructure applications, voluminous amounts of multichannel data streams are becoming available for processing, thus imposing new demands on identification procedures regarding high-dimensionality (in both the spatial as well as the temporal domains) requirements that may render some methods inapplicable if careful attention is not paid to practical implementation issues. This paper provides a comprehensive study of three time-domain identification algorithms applied in conjunction with the Natural Excitation Technique in order to extract the modal parameters of a newly constructed long-span bridge that was monitored, in its virgin state, over a relatively long period of time with a state-of-the-art dense sensor array. The three methods used are: the eigensystem realization algorithm (ERA), the ERA with data correlations, and the least squares algorithm. One of the critical issues in the mentioned algorithms is selection of the reference degree-of-freedom (DOF). Previous experiences have shown that one cannot rely on a single reference DOF for identification of all modes. Consequently, the aforementioned identification formulations were modified to include multiple reference DOF, simultaneously, or one at a time. An autonomous algorithm was presented to distinguish the genuine structural modes from spurious noise or computational modes. Based on some parameter studies, some useful guidelines for the selection of critical user-selectable parameters are presented.

– Nayeri, R., Tasbihgoo, F., Wahbeh, M., Caffrey, J., Masri, S.F., Conte, J.P., and Elgamal, A., (2009), “A Study of Time-Domain Techniques for Modal Parameter Identification of a Long Suspension Bridge with Dense Sensor Arrays” ASCE Journal of Engineering Mechanics, (July 2009), pp 669-683.

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A Vision-Based Approach for the Direct Measurement of Displacements in Vibrating Systems, 2003 A. Mazen Wahbeh et al.

– Wahbeh, A.M., and Caffrey, J.P, and Masri, S.F., (2003), “A Vision-Based Approach for the Direct Measurement of Displacements in Vibrating Systems,” Journal of Smart Materials and Structures, vol 12, pp 785-794.

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Application of a Web-Enabled Real-Time Structural Health Monitoring System for Civil Infrastructure Systems, 2004 A. Mazen Wahbeh et al.

Abstract:

The system architecture of a novel structural health monitoring system that is optimized for the continuous real-time monitoring of dispersed civil infrastructures is presented. The monitoring system is based on a highly efficient multithreaded software design that allows the system to acquire data from a large number of channels, monitor and condition this data, and distribute it, in real time, over the Internet to multiple remote locations. Bandwidth and latency issues that impact the operation of monitoring systems are discussed. The application of the monitoring system under discussion to a long span, flexible bridge in the metropolitan Los Angeles region is described. The bridge had previously been instrumented with 26 strong motion accelerometers. Sample ‘quick analysis’ results continuously provided by the monitoring system are presented and interpreted. System identification results, obtained through off-line batch processing, are presented for a data set from a recent earthquake that automatically triggered the recording capability of the system. It is shown that, using a time domain system identification approach, the bridge stiffness and damping matrices can be identified from the earthquake data set and subsequently used to determine the bridge modal properties, such as frequencies and damping ratios. In this approach the bridge is modeled as a multi-input/multi-output system with order compatible with the number of available sensors. Implementation issues requiring further investigation are presented and discussed.

– Masri, S.F., Sheng, L-H, Caffrey, J.P., Nigbor, R.L., Wahbeh, M. and Abdel-Ghaffar, A.M., (2004), “Application of a Web-Enabled Real-Time Structural Health Monitoring System for Civil Infrastructure Systems,” Journal of Smart Materials and Structures, Vol 13, pp 1269-1283.

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Challenges In Fabrication Of Precast Prestressed Concrete Super Girders, 2013 Mohammad Fatemi et al.

Abstract:

Construction is underway on a California Department of Transportation (Caltrans) widening project on SR 99 in Nicolaus, CA. A major element of this project is Precast/Prestressed bulb tee super girders with a maximum height of 8’6”, up to 120’ long and weighing up to 90 tons each for a bridge over the Feather River. Fabrication of these tall and slender girders posed unique challenges such as arrangement of post tensioning ducts in a thin web, high performance concrete with compressive strength of 8,500 psi, transportation and handling issues. As the owner, California Department of Transportation enforced a rigorous Quality Assurance scheme to ensure fabrication met its challenges. This process included submission of a detailed Quality Control Plan by the fabricator. Caltrans material engineers and inspectors were involved from the onset of fabrication and worked closely with the fabricator for a quality product. This paper details the unique difficulties and challenges encountered during the course of the fabrication and how Caltrans’ and the fabricator’s combined proactive approach resulted in a successful delivery of the product.

– Mohammad J. Fatemi, PhD, PE, Robert Kim, PE, and Mike Hein, PE, “Challenges In Fabrication Of Precast Prestressed Concrete Super Girders”, PCI Convention and National Bridge Conference, Grapevine, TX, September 2013.

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Computational Validation of a Forced-Vibration Method for Structural Health Monitoring of Large-Scale Structures, 2006 A. Mazen Wahbeh et al.

– Wahbeh, A.M., Caffrey, J.P, and Masri, S.F., (2006), “Computational Validation of a Forced-Vibration Method for Structural Health Monitoring of Large-Scale Structures,” Proc Third European Workshop on Structural Health Monitoring (3EWSHM), 5-7 July 2006, Granada, Spain.

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Development of an Economic Dust Palliative for Limestone Surfaced Secondary Roads, Part 1, 1989 A. Mazen Wahbeh et al.

Abstract:

This research project was directed at laboratory and field evaluation of sodium montmorillonite clay (bentonite) as a dust palliative for limestone surfaced secondary roads. It had been postulated that the electrically charged surfaces of the clay particles could interact with the charged surfaces of the limestone and act as a bonding agent to agglomerate fine (-#200) particulates and also to bond the fine particulates to larger (+#200) limestone particles.

Laboratory testing using soda ash dispersed bentonite treatment of limestone fines indicated significant improvement of compressive strength and slaking characteristics. It was recommended that the project proceed to field trials and test roads were constructed in Dallas and Adair counties in Iowa.

Soda ash dispersed bentonite solutions can be field mixed and applied with conventional spray distribution equipment. A maximum of 1.5 percent bentonite (by weight of aggregate) can be applied at one time. Higher applications would have to be staged allowing the excess moisture to evaporate between applications. Construction of higher application treatments can be accomplished by adding dry bentonite to the surfacing material and then by dry road mixing. The soda ash water solution can then be spray applied and the treated surfacing material wet mixed by motor graders to a consistency of 3 to 4 inch slump concrete. Two motor graders working in tandem can provide rapid mixing for both methods of construction.

Calcium and magnesium chloride treatments are 2 to 3 times more effective in dust reduction in the short term (3-4 months) but are prone to washboarding and potholing due to maintenance restrictions. Bentonite treatment at the 2 to 3 percent level is estimated to provide a 30 to 40 percent dust reduction of the long term (18-24 months). Normal maintenance blading operations can be used on bentonite treated areas. Vehicle braking characteristics are not adversely affected up to the 3.0 percent treatment level.

The bentonite appears to be functioning as a bonding agent to bind small particulates to larger particles and is acting to agglomerate fine particles of limestone. This bonding capability appears recoverable from environmental effects of winter, and from alternating wet and dry periods. The bentonite appears to be able to interact with new applications of limestone maintenance material and maintains a dust reduction capability.

Soda ash dispersed bentonite treatment is approximately 10 times more cost effective per percent dust reduction than conventional chloride treatments with respect to time. However, the disadvantage is that there is not the initial dramatic reduction in dust generation as with the chloride treatment. Although dust is reduced 30 to 40 percent after treatment there is still dust being generated and the traveling public or residents may not perceive the reduction.

– A. M. Wahbeh, K. L. Bergeson, May, 1989. “Development of an Economic Dust Palliative for Limestone Surfaced Secondary Roads, Part 1,” Engineering Research Institute, Iowa State University, Ames, Iowa.

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Development of an Economic Dust Palliative for Limestone Surfaced Secondary Roads, Part 2, 1989 A. Mazen Wahbeh

Abstract:

This research project was directed at laboratory and field evaluation of sodium montmorillonite clay (bentonite) as a dust palliative for limestone surfaced secondary roads. It had been postulated that the electrically charged surfaces of the clay particles could interact with the charged surfaces of the limestone and act as a bonding agent to agglomerate fine (-#200) particulates and also to band the fine particulates to larger (+#200) limestone particles.

Laboratory testing using soda ash dispersed bentonite treatment of limestone fines indicated significant improvement of compressive strength and slaking characteristics. It was recommended that the project proceed to field trials and test roads were constructed in Dallas and Adair counties in Iowa.

Soda ash dispersed bentonite solutions can be field mixed and applied with conventional spray distribution equipment. A maximum of 1.5 percent bentonite (by weight of aggregate) can be applied at one time. Higher applications must have to be staged allowing the excess moisture to evaporate between applications. Construction of higher application treatments can be accomplished by adding dry bentonite to the surfacing material and then by dry road mixing. The soda ash water solution can then be spray applied and the treated surf acing material wet mixed by motor graders to a consistency of 3 to 4 inch slump concrete. Two motor graders working in tandem can provide rapid mixing for both methods of construction.

Calcium and magnesium chloride treatments are 2 to 3 times more effective in dust reduction in the short term (3-4 months) but are prone to washboarding and potholing due to maintenance restrictions. Bentonite treatment at the 2 to 3 percent level is estimated to provide a 30 to 40 percent dust reduction over the long term (18-24 months). Normal maintenance blading operations can be used on bentonite treated areas. Vehicle braking characteristics are not adversely affected up to the 3.0 percent treatment level.

The bentonite appears to be functioning as a banding agent to bind small particulates to larger particles and is acting to agglomerate fine particles of limestone. This bonding capability appears recoverable from environmental effects of winter, and from alternating wet and dry periods. The bentonite appears to be able to interact with new applications of limestone maintenance material and maintains a dust reduction capability.

Soda ash dispersed bentonite treatment is approximately 10 times more cost effective per percent dust reduction than conventional chloride treatments with respect to time. However, the disadvantage is that there is not the initial dramatic reduction in dust generation as with the chloride treatment. Although dust is reduced 30 to 40 percent after treatment there is still dust being generated and the traveling public or residents may not perceive the reduction.

– A. M. Wahbeh, K. L. Bergeson, December, 1989. “Development of an Economic Dust Palliative for Limestone Surfaced Secondary Roads, Part 2,” Engineering Research Institute, Iowa State University, Ames, Iowa.

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Direct Measurement of Displacement in Vibrating Structures Through Vision-Based Approaches, 2003 A. Mazen Wahbeh et al.

Abstract:

This paper reports the results of an analytical and experimental study to develop, calibrate, implement and evaluate the feasibility of a novel vision-based approach for obtaining direct measurements of the absolute displacement time history at selectable locations of dispersed civil infrastructure systems such as long-span bridges. The measurements were obtained using a highly accurate camera in conjunction with a laser tracking reference. Calibration of the vision system was conducted in the lab to establish performance envelopes and data processing algorithms to extract the needed information from the captured vision scene. Subsequently, the monitoring apparatus was installed in the vicinity of the Vincent Thomas Bridge in the metropolitan Los Angeles region. This allowed the deployment of the instrumentation system under realistic conditions so as to determine field implementation issues that need to be addressed. It is shown that the proposed approach has the potential of leading to an economical and robust system for obtaining direct, simultaneous, measurements at several locations of the displacement time histories of realistic infrastructure systems undergoing complex three-dimensional deformations.

– Wahbeh, M., Masri, S., Caffrey, J.P., (2003), “Direct Measurement of Displacement in Vibrating Structures Through Vision-Based Approaches”, Proc the 9th ASEC, Abu-Dhabi, UAE, Dec. 2003.

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Direct Measurement of Displacements in Vibrating Structures Through Vision-Based Approaches, 2004 A. Mazen Wahbeh et al.

– Wahbeh, A.M., Caffrey, J.P., and Masri, S.F., (2004), “Direct Measurement of Displacements in Vibrating Structures Through Vision-Based Approaches,” Emirates Journal for Engineering Research, 9 (2), 105-110 (2004).

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Effect of Surface Evaporation and Slab Thickness on the Scaling Resistance of Concrete Containing Fly Ash, 2005 Jinesh Mehta et al.

Abstract:

Laboratory tests (conducted in accordance with ASTM C 672) frequently indicate that concrete containing fly ash may be susceptible to scaling. Based on this concern, a few northern USA states restrict the use of fly ash during the late-fall pavement construction season. However, a survey of twelve northern states revealed that scaling is rarely observed in actual pavements. In an attempt to develop a more clear understanding of the potential reasons for the apparent discrepancy between the scaling resistance of laboratory concretes and field concretes, scaling studies were conducted on concrete containing 20% of a Class C fly ash. The main variables in the study were the surface water evaporation rate (water loss was ranged from 0 to 4.5 kg/sq m 2) and the thickness of the slab specimen (55 mm to 245 mm). The selected ranges of test variables were intended to represent moisture and temperature conditions that are likely to be encountered in the field. In addition to monitoring the mass of material lost from the surface due to scaling, the temperature gradient that developed inside the specimen during freezing was measured. In addition, scanning electron microscopy was performed to assess differences in porosity of the near surface concrete. The results indicate that ASTM C 672 is too severe when compared to the environmental conditions that are likely to be encountered in the field.

– J. Mehta, J. Olek, J. Weiss, and T. Nantung, “Effect of Surface Evaporation and Slab Thickness on the Scaling Resistance of Concrete Containing Fly Ash”, Eighth International Conference on Concrete Pavements, August 2005.

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Innovation in Fabrication of the Self-Anchor Suspension Span of the San Francisco-Oakland Bay Bridge, 2010 A. Mazen Wahbeh et al.

Abstract:

The 2.2-mile-long East Span of the San Francisco-Oakland Bay Bridge (SFOBB) is currently undergoing a seismic retrofit that will completely replace the existing steel truss bridge that opened in 1936. Approximately 280,000 vehicles cross the SFOBB daily and the bridge corridor is being brought up to current seismic safety standards by replacing the existing East Span. This work is being accomplished while keeping the existing bridge open to traffic. A key component of the New East Span will be a Self-Anchored Suspension (SAS) bridge chosen by the region and legislated to be the signature span in the retrofit of one of the nation’s busiest bridges. When complete, this structure will be the world’s largest SAS. American Bridge/Fluor Enterprises (AB/F) (A Joint Venture) won the bid to build the SAS. Both companies have impressive portfolios combining years of experience that include constructing the original SFOBB. AB/F determined that the structural steel portion of the SAS would be fabricated in China at the Shanghai Zhenhua Heavy Industry Co. Ltd. (ZPMC), a subsidiary of the China Communication Construction Company (CCCC) on Changxing Island just outside Shanghai. ZPMC is the largest heavy-duty equipment manufacturer in the world and is famous for producing more than 75 percent of the world’s port cranes used in the shipping industry as well as other large scale steel bridges such as the Golden Ears Bridge in Vancouver, Canada. ZPMC implemented a number of innovations in order to expedite the fabrication process and to assure meeting the stringent quality requirements of what will soon be a world-renowned architectural icon while remaining the backbone of regional transportation in the San Francisco Bay Area.

– Wahbeh, M., Siegenthaler, P., Nilsson, T., Nader, M., and Cavendish-Tribe, A. (2010), “Innovation in Fabrication of the Self-Anchor Suspension Span of the San Francisco-Oakland Bay Bridge,” Proc International Bridge Conference, June 2010, Pittsburgh, PA, USA.

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Innovations in the Production of the Seismic Members of the Self Anchored Suspension San Francisco Oakland Bay Bridge, 2013 A. Mazen Wahbeh et al.

Abstract:

The 2.2-mile-long East Span of the San Francisco-Oakland Bay Bridge (SFOBB) is currently undergoing a seismic retrofit that will completely replace the existing steel truss bridge that opened in 1936.  Approximately 280,000 vehicles cross the SFOBB daily.  The bridge corridor is being brought up to current seismic safety standards by replacing the existing East Span.  This work is being accomplished while keeping the existing bridge open to traffic.  A key component of the New East Span will be a Self-Anchored Suspension (SAS) bridge, chosen by the region to be the signature span in this retrofit of one of the nation’s busiest bridges.  When complete, the structure will be the world’s largest SAS.  Several innovations were implemented to expedite the fabrication process of seismic members of the bridge tower and to assure meeting the stringent quality requirements of what will soon be a world-renowned architectural icon in the San Francisco Bay.

This paper will discuss production innovations implemented to facilitate fabrication of the seismic members within the budgeted cost while ensuring that the required quality standards and aggressive schedule were met.  During fabrication, the California Department of Transportation (Caltrans) implemented the use of non-destructive techniques to assure the quality of structural steel members.  Meanwhile, constant and open communication between the stakeholders throughout the duration of the project led to proactive solutions to anticipated issues.  Furthermore it was determined early on that the production of half-scale and full-scale mock-ups would be instrumental for the complicated seismic performance of members.

– Mazen Wahbeh, Nina Choy, Gary Thomas, Aaron Prchlik, Laura Webb and James Reid (2013). “Innovations in the Production of the Seismic Members of the Self Anchored Suspension San Francisco Oakland Bay Bridge,” 7th National Seismic Bridge Conference, Oakland, California.

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Monitoring the Collision of a Cargo Ship with the Vincent Thomas Bridge, 2007 A. Mazen Wahbeh et al.

Abstract:

On 27 August 2006, the Vincent Thomas Bridge, a 1850-m suspension bridge located in the larger metropolitan Los Angeles region, was struck by a large cargo ship passing under the bridge. Moderate damage to the maintenance scaffolding at the main span of the bridge was observed. This incident left transportation authority’s wondering about the structural integrity of the bridge. A real-time continuous monitoring system that had been recently installed on the bridge successfully recorded dynamic response before and after the incident, as well as during the collision. Analysis of these valuable data allows transportation authorities to quantify the effects of the collision on the bridge structural condition, which would otherwise be infeasible with traditional visual bridge inspection approaches. A forensic study was performed to assess the structural condition of the bridge before and after the incident. Both global (multi-sensor) and local (single-sensor) identification methods were applied to detect whether significant changes occurred in the bridge vibration signature.

– Yun, H., Nayeri, R., Tasbihgoo, F., Wahbeh, M., Caffrey, J., Wolfe, R., Nigbor, R., Masri, S., Abdel-Ghaffar, A., and Sheng, L; (2007), “Monitoring the Collision of a Cargo Ship with the Vincent Thomas Bridge,” Journal of Structural Control and Health Monitoring, Volume 15, Issue 2, March 2008, Pages: 183-206.

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San Francisco-Oakland Bay Bridge Fabrication Quality Control and Quality Assurance, 2013 A. Mazen Wahbeh et al.

Abstract:

This paper describes how the Quality Assurance (QA) and Quality Control (QC) of the San Francisco – Oakland Bay Bridge (SFOBB) replacement project was implemented as mandated by the Federal Highway Administration Code of Federal Regulations (CFR) Title 23 §637.207. The SFOBB replacement project consists of four distinct sections. The Yerba Buena Island transition structure consists of two 1,452 foot long cast in place, concrete box girder bridges. The Self Anchored Suspension span consists of two 2,057 foot long side by side steel orthotropic box girders and a single tower consisting of four 525 foot tall towers that sit on a concrete and steel footing supported by 10 steel and concrete piles sunk 196 feet into bedrock. The OBG and the Tower weight 33,000 tons and were erected at 13 lifts and five lifts respectively on the jobsite. The OBG is suspended from the tower by a one mile long, single steel parallel wire strand (PWS) cable. The Skyway consists of two side by side precast and cast in place concrete box girder bridges and the Oakland touchdown which consists of two side by side concrete box girder bridges.

The QA/QC included a material release process from over 100 fabrication facilities in China, Japan, England, Germany and the United States to the jobsite in Oakland, California. Certified technicians and Welding Inspectors (CWIs) performed the inspection and Non-Destructive Testing (NDT), including Magnetic Particle Testing (MT), Ultrasonic Testing (UT), Radiographic Testing (RT), Visual Testing (VT), Penetrant Testing (PT), and Phased Array Testing (PAUT) of the welded components throughout the fabrication process. National Association of Corrosion Engineers (NACE) inspected the corrosion protection systems throughout the fabrication process. This included surface preparation, galvanizing, prime and final coatings, and powder coating. Caltrans inspectors also sampled various materials from the fabricators for testing at the department’s Structural Materials Testing Lab (SMTL). These materials consist of, but are not limited to, reinforcing couplers, bearing pad material and high strength bolt assemblies. Structural material engineers monitored the inspection process and provided specialty materials engineering services to resolve material suitability issues and to ensure that the material complied or was fit for its intended purpose according to the California Department of Transportation (Caltrans) Standard Specifications, SFOBB Special Provisions and contract plans. Finally, a Quality Assurance Database (QAD) was developed to monitor all of the essential information required by the American Welding Society for over 1,000,000 welds in the SAS span.

Mazen Wahbeh, Aaron Prchlik, and Yiannis Kourakis (2013). “San Francisco-Oakland Bay Bridge Fabrication Quality Control and Quality Assurance,” 2013 Orthotropic Bridge Conference. June 24-30, 2013, Sacramento, CA.

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Technical Fabrication Issues with Steel Orthotropic Box Girder Bridges, 2004 A. Mazen Wahbeh et al.

Abstract:

The technical difficulties with the fabrication of steel orthotropic box girder (OBG) bridges became very apparent during the construction of the third bridge crossing the Carquinez Strait at the town of Crockett, California. The new Carquinez Bridge has been officially designated the Alfred Zampa Memorial Bridge by the California Legislature. The Alfred Zampa Bridge (AZB) is located 20 miles northeast of San Francisco on I-80 and is in close proximity to several active seismic faults. The bridge was opened for traffic on November 8, 2003. The first and most complicated issue discussed in this paper is the welding of the partial joint penetrations (PJP) groove weld connecting the stiffening troughs to the steel plates of the deck, soffit, and side panels of the OBG. This critical joint in orthotropic steel bridges is prone to fatigue. The weld is subject to both normal forces and bending moments. Fatigue damage to this weld can cause significant damage to the function of the composite behavior of the steel girder box and its pavement. In addition, the repair of such a weld is extremely costly should this weld experience any fatigue damage. This paper will discuss the procedures used in developing, testing, and finally performing this weld on the AZB.

The second technical issue discussed in this paper is the how to address weld induced distortion in order to achieve the required fabrication tolerances of the OBG. The basic concept of the OBG is to utilize relatively thin steel members in order to reduce the weight of the structure while obtaining orthotropic properties. Since thin steel members are welded together to achieve such properties, the heat distortion is a major consideration when attempting to determine how best to achieve the tight tolerances for the finished geometry of the structure. This paper will discuss some of the technical difficulties encountered during the fabrication of the components of the OBG for the AZB.

– Mazen Wahbeh, Brian Boal, Jim Merrill, August 21-24, 2004. “Technical Fabrication Issues with Steel Orthotropic Box Girder Bridges”, ASCE Othotropic Bridge Conference, California, USA.

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