Development of FRP Short-Span Deployable Bridge—Experimental Results

For military and civilian applications, there exists a need for lightweight, inexpensive, short-span bridges that can be easily transported and erected with minimal equipment. Owing to its favorable properties, fiber-reinforced polymer (FRP) has been shown to be feasible for the construction of such bridges. Investigations into the behavior of a short-span bridge structural concept, adapted to the material properties of commercially available glass FRP (GFRP) pultruded products, are presented. A 4.8-m span prototype was built from GFRP sections, bonded throughout to form a tapered box beam, with a width of 1.2?m and a height at midspan of approximately 0.5?m. The box beam represents a single trackway of a double-trackway bridge, whose trackways could be connected by light structural elements. The quasi-static and dynamic behavior of the prototype box beam was investigated in ambient laboratory and field conditions to assess the design and construction techniques used, with a view to designing a full-scale 10-m GFRP bridge. Laboratory testing of the prototype box beam used single and pairs of patch loads to simulate wheel loading. These tests confirmed that the box beam had sufficient stiffness and strength to function effectively as a single trackway of a small span bridge. Field testing of the structure was undertaken using a Bison vehicle (13,000?kg), driven at varying speeds over the structure to establish its response to realistic vehicle loads and the effects of their movement across the span.     

Constructability and Economics of FRP Reinforcement Cages for Concrete Beams

This paper presents a quantitative economic analysis and a qualitative constructability analysis of three-dimensional fiber-reinforced plastic (FRP) reinforcement cages for concrete beams. Material, labor, and life-cycle costs are provided, and construction practice aspects are discussed. The results of the analyses indicate that prefabricated FRP cages can offer benefits to the construction industry. Although the initial costs of the FRP materials are likely to be higher than those of steel rebar, there is a significant potential for cost savings due to reduced maintenance and labor costs, as a result of the corrosion resistance of the FRP and the increased construction productivity. When direct life-cycle costs are considered, FRP reinforcements already constitute, in many cases, an economically competitive alternative to conventional steel reinforcement in adverse environments. If, in addition, the indirect cost savings as well as quality and safety issues are considered, the FRP reinforcement may be even more competitive.     

Retrofitting Precast Bridge Beams with Carbon Fiber-Reinforced Polymer Strips for Shear Capacity

Advancements in fiber-reinforced polymers (FRPs) have made this an attractive material for rehabilitation and strengthening of bridge superstructures. FRP has primarily been used with the intention of increasing the bending strength of bridge members. However, this paper investigates the use of externally placed FRP strips to increase shear capacity of short-span, 5.7?m (19?ft), precast concrete channel beam bridges. A statewide survey revealed that as many as 389 bridges in the state of Arkansas are comprised of these members. Notably, beams within these bridges were designed under provisions that did not require shear reinforcement. In this research, four sections were retrofitted using carbon fiber-reinforced polymer (CFRP) strips and load tested to failure to measure the repair effectiveness. The performance of the retrofitted sections far exceeded that of unretrofitted sections. It was concluded that the addition of the CFRP repair increased the deflection ductility at least 123%. In addition, beams retrofitted with the CFRP strips experienced at least 26% more deflection after the initiation of a shear crack; therefore reducing the risk of a catastrophic failure.     

Construction, Inspection, and Maintenance of FRP Deck Panels

Composite materials are clearly having a major impact on how facilities are designed, constructed, and maintained. In order to enhance the application of fiber-reinforced composites in infrastructure renewal, it will be important to understand the constructability, maintainability, operability, and inspection issues related to the use of fiber-reinforced polymer (FRP) structural components. This paper identifies these issues as well as fabrication issues, construction methods, quality, man-hour requirements, cost and productivity issues, and the skill level required to install FRP bridge deck panels. The data required for this research were collected through two questionnaire studies, personal interviews with two manufacturers of FRP bridge deck panels (i.e., Hardcore Composites and Martin Marietta Composites), and candidate projects for FRP bridge deck construction.     

Impact of Commercial Vehicle Weight Change on Highway Bridge Infrastructure

Heavy trucks represent a major load to highway bridges in the transportation infrastructure system. These loads are directly related to the truck weight limits of the jurisdiction, and largely determine the standard loads for bridge design and evaluation. Thus, truck weight limit is one of the major factors affecting bridge deterioration and expenditure for maintenance, repair, and/or replacement. Truck weight in this paper not only refers to the truck gross weight but also to the axle weights and spacings that affect load effects. This paper presents the concepts of a new methodology for estimating cost effects of truck weight limit changes on bridges in a transportation infrastructure network. The methodology can serve as a tool for studying impacts of such changes. The resulting knowledge is needed when examining new truck weight limits, several of which have been and are still being debated at both the state and federal levels in the United States. The development of this estimation method has considered maximizing the use of available data (such as the bridge inventory) at the state infrastructure system level. In application examples completed (but not reported herein), the costs for relatively inadequate strength of existing bridges and for increased design requirement for new bridges were found dominant in the total impact cost.     

加强企业质量管理增强市场竞争力

从质量管理制度、质量检验方法、质量管理规定、企业标准-施工工艺标准四方面对质量管理进行了介绍，特别是企业标准-施工工艺标准的应用，提升了企业的整体质量意识，降低了企业资源成本，提高了顾客满意度，增强了企业的市场竞争力。四个方面配合运用，在质量管理中提升了企业形象，增强了企业声誉。     

Tailoring Competitive Advantages Derived from Innovation to the Needs of Construction Firms

Innovation is often classified as a cost intensive investment in the construction industry with indefinite returns. Due to the clients’ tendency to award projects based on the lowest costs, innovation is often seen as an unfeasible strategy toward the competitiveness that construction firms are seeking. This study questions whether it is indeed ineffective for construction firms to develop their competitive advantage through innovation. By the application of statistical data across 18 Organization for Economic Cooperation and Development (OECD) countries and expert interviews in Singapore, innovation systems models are developed for both manufacturing and construction firms, respectively. Through comparison of both models, the results suggest that the peculiarities of the construction industry deem innovation as a poor competitive instrument for direct profits. Instead, construction firms can develop their competitive advantage through manipulating innovations that consumers are willing to pay for and innovations that would reduce construction costs. It is recommended that construction firms first utilize quality improvements to exploit consumers’ willingness to pay for innovative products. This initiative would enable construction firms to improve their finances for innovation and develop their “brand” in construction products. Sustainable competitive advantage could then be firmly established when construction firms engage in productivity improvements that lead to lower construction costs and/or faster completion times. This study concludes that innovation can be a useful competitive tool if construction firms aptly strategize it in according to its competitive environment.     

Field Performance of FRP Bridge Repairs

Many reinforced concrete bridges throughout the United States on county and state highway systems are deteriorated and∕or distressed to such a degree that structural strengthening of the bridge or reducing the allowable truck loading on the bridge by load posting is necessary to extend the service life of the bridge. The structural performance of many of these bridges can be improved through external bonding of fiber-reinforced plastic (FRP) laminates or plates. This paper describes the rehabilitation of an existing concrete bridge in Alabama through external bonding of FRP plates to the bridge girders. Field load tests were conducted before and after application of the FRP plates, and the response of the bridge to test vehicle loadings was recorded. Results of the field tests are reported, and the effects of the FRP plates on the bridge response are identified. The repaired bridge structure exhibited a decrease in steel reinforcing bar stresses and vertical midspan deflections. These decreases ranged from 4 to 12% for various static and dynamic loading cases.     

Vehicle-Induced Dynamic Performance of FRP versus Concrete Slab Bridge

In the United States alone, about 30% of the bridges are classified as structurally deficient or functionally obsolete. To alleviate this problem, a great deal of work is being conducted to develop versatile, fully composite bridge systems using fiber-reinforced polymers (FRPs). To reduce the self-weight and also achieve the necessary stiffness, FRP bridge decks often employ hollow sandwich configurations, which may make the dynamic characteristics of FRP bridges significantly different from those of conventional concrete and steel bridges. Due to the geometric complexity of the FRP sandwich panels, dynamic analyses of FRP bridges are very overwhelming and rarely reported. The present study develops an analysis procedure for the vehicle-bridge interaction based on a three-dimensional vehicle-bridge coupled model. The vehicle is idealized as a combination of rigid bodies connected by a series of springs and dampers. A slab FRP bridge, the No-Name Creek Bridge in Kansas, is first modeled using the finite-element method to predict its modal characteristics, then the bridge and vehicle systems are integrated into a vehicle-bridge system based on the deformation compatibility. The bridge response is obtained in the time domain by using an iterative procedure employed at each time step, considering the deck surface roughness as a vertical excitation to the vehicle. The bridge dynamic response and the calculated impact factors are compared between the FRP slab bridge and a corresponding concrete slab bridge. Finally, the applicability of AASHTO impact factors to FRP bridges is discussed.     

Finite-Element Modeling and Development of Equivalent Properties for FRP Bridge Panels

Fiber-reinforced polymer (FRP) composite materials are increasingly making their way into civil engineering applications. To reduce the self-weight and also achieve the necessary stiffness, sandwich panels are commonly used for FRP bridge decks. However, due to the geometric complexity of the FRP sandwich deck, convenient analysis and design methods for FRP bridge deck have not been developed. The present study aims at developing equivalent properties for a complicated sandwich panel configuration using finite-element modeling techniques. With equivalent properties, the hollowed sandwich panel can be transformed into an equivalent solid orthotropic plate, based on which deflection limits can be evaluated and designed. A procedure for the in-plane axial properties of the sandwich core has first been developed, followed by developing the out-of-plane panel properties for bending behavior of the panel. An application is made in the investigation of the stiffness contribution of wearing surface to the total stiffness of bridges with FRP panels. The wearing surface contribution is not usually accounted for in a typical design of bridges with traditional deck systems.     

Assessment of Load Transfer and Load Distribution in Bridges Utilizing FRP Panels

A primary means of demonstrating the feasibility and effectiveness of fiber-reinforced polymer (FRP) composite bridge materials is via in situ bridge load testing. For this study, the prescribed or assumed design factors for each of the study bridges were compared to those exhibited by the performance of the bridge. Specifically, the wheel load distribution factors and impact factors as defined by AASHTO were considered in order to assess the load transfer and distribution in structures utilizing FRP panels. The in situ testing configurations for the study bridges are outlined, including the truck and instrumentation placement to obtain the desired information. Furthermore, comparisons were drawn between the design values for deflection and those experienced by the structures during testing. It was found that although the deflections exhibited by the bridges were well within the design limits, further research is needed to be able to prescribe bridge design factors for FRP panels.     

Effect of Common Cause Failures on Indirect Costs

Next generation bridge management systems will take into consideration multiple hazard scenarios and not only traffic loading and structural deterioration as they do now. The indirect costs used in these bridge management systems to determine optimal management strategies vary according to the hazard scenarios considered. The difference depends on whether or not the bridge failures are due to a common cause, such as a single flood or earthquake, or due to load events that may be considered statistically unrelated, such as truck loads. To illustrate the effect of common cause bridge failures on indirect costs, two examples are presented that treat the failures first as if they are due to statistically independent loading events and then as if they are due to a common cause. To examine the effect of bridge failures on indirect costs of the system, estimation is performed at the network level. The first example, on a simple network, shows the indirect cost estimate for all of the network condition states. The second example, on a complex network, shows the difference in the possible reduction of total indirect costs with a single bridge intervention as well as the change in intervention sequence. The main conclusions are that total indirect costs and optimal intervention sequences differ depending on whether or not bridge failures are due to a common cause, and that the largest changes in indirect cost estimation occur when simultaneously failed bridges affect the method of indirect cost incurrence.     

Dynamic Response of Three Fiber Reinforced Polymer Composite Bridges

Fiber reinforced polymer (FRP) composite bridge decks are gaining the attention of bridge owners because of their light self-weight, corrosion resistance, and ease of installation. Constructed Facilities Center at West Virginia University working with the Federal Highway Administration and West Virginia Department of Transportation has developed three different FRP decking systems and installed several FRP deck bridges in West Virginia. These FRP bridge decks are lighter in weight than comparable concrete systems and therefore their dynamic performance is equally as important as their static performance. In the current study dynamic tests were performed on three FRP deck bridges, namely, Katy Truss Bridge, Market Street Bridge, and Laurel Lick Bridge, in the state of West Virginia. The dynamic response parameters evaluated for the three bridges include dynamic load allowance (DLA) factors, natural frequencies, damping ratios, and deck accelerations caused by moving test trucks. It was found that the DLA factors for Katy Truss and Market Street bridges are within the AASHTO 1998 LRFD specifications, but the deck accelerations were found to be high for both these bridges. DLA factors for Laurel Lick bridge were found to be as high as 93% against the typical design value of 33%; however absolute deck stress induced by vehicle loads is less than 10% of the deck ultimate stress.     

Dynamic Regression Models for Prediction of Construction Costs

Accurate prediction of construction costs in the market is essential to effectively estimate costs for construction projects. In the construction industry, cost indexes that are reported in series are often used to explain the change of construction costs. By tracking the trend of such quantitative contemporaneous cost index and making frequent and regular forecasts of the future values of the index, one can develop a deeper understanding of prices of resources used for construction. Incorporating such an understanding and prediction into estimating will help practitioners manage construction costs. This paper proposes two dynamic regression models for the prediction of construction cost index. Comparison of the proposed models with the existing methods proves that the new models provide several advantages and improvements.     

Acoustic Emission Monitoring and Analysis of Glass Fiber-Reinforced Composites Bridge Decks

The application of fiber-reinforced composites (FRP) is gaining momentum as an alternative material for bridge replacement, repair, and rehabilitation. While a number of states now use FRP, a lack of standards, codes, and performance data for FRP bridge decks has resulted in the use of FRP technology not being widely accepted. This paper presents the performance results, based on acoustic emission (AE), of six full-scale glass FRP bridge deck panels with nominal cross-sectional depths varying from 152 mm (6 in.) to 800 mm (30 in.). The objective was to develop for use during in-service field inspections an AE monitoring strategy that will determine the structural performance of the deck. As such, the characterization of damage, e.g., fiber breakage, matrix cracking, and delamination, was part of the investigated criteria and the contributing factors for identification of a monitoring strategy. Although some factors were determined to be associated with the performance evaluation of the structural integrity of the decks, further investigation is needed.     

Fatigue Damage of Steel Bridges Due to Dynamic Vehicle Loads

This paper focuses on the fatigue damage caused in steel bridge girders by the dynamic tire forces that occur during the crossing of heavy transport vehicles. This work quantifies the difference in fatigue life of a short-span and a medium-span bridge due to successive passages of either a steel-sprung or an air-sprung vehicle. The bridges are modeled as beams to obtain their modal properties, and air-sprung and nonlinear steel-sprung vehicle models are used. Bridge responses are predicted using a convolution method by combining bridge modal properties with vehicle wheel forces. A linear elastic fracture mechanics model is employed to predict crack growth. For the short-span bridge, the steel-sprung vehicle caused fatigue failure up to 6.5 times faster than the air-sprung vehicle. For the medium-span bridge, the steel-sprung vehicle caused fatigue failure up to 277 times faster than the air-sprung vehicle.     

Vehicle Induced Dynamic Behavior of Short-Span Slab Bridges Considering Effect of Approach Slab Condition

In this paper the vehicle induced dynamic bridge responses are calculated by modeling the bridge and vehicle as one coupled system. The dynamic behavior of short slab bridges with different span lengths induced by the AASHTO HS20 truck is investigated. A parametric study is conducted to analyze the effects of different truck speeds and different road surface conditions. Critical truck speeds that result in peaks of dynamic response are found to follow the rule that describes the resonant vibration of bridges due to train loading. The approach slab condition that consists of faulting at the ends and deformation along the span is considered in the analysis. Although the effect of the along-span deformation on the dynamic response of bridges is trivial, the faulting condition of the approach slab is found to cause significantly large dynamic responses in short-span slab bridges. Impact factors obtained from numerical analyses are compared with those values specified in the AASHTO codes.     

Experimental Investigation on Torsional Behavior of Solid and Box-Section RC Beams Strengthened with CFRP Using Photogrammetry

The construction boom over the last century has resulted in a mature infrastructure network in developed countries. Lately, the issue of maintenance and repair/upgrading of existing structures has become a major issue, particularly in the area of bridges. Fiber- reinforced polymer (FRP) has shown great promise as a state-of-the-art material in flexural and shear strengthening as external reinforcement, but information on its applicability in torsional strengthening is limited. The need for torsional strengthening in bridge box girders is highlighted by the Westgate Bridge in Melbourne, Australia, one of the largest strengthening projects in the world for externally bonded carbon FRP (CFRP) laminates. This paper reports the experimental work in an overall investigation of torsional strengthening of solid and box-section reinforced concrete beams with externally bonded carbon FRP. This was found to be a viable method of torsional strengthening. Photogrammetry was a noncontact measuring technique used in the investigation. The deformation mechanisms were found to be unchanged in the strengthened specimens. Furthermore, it was found that the crack widths were reduced and aggregate interlocking action improved with the strengthened beams.     

Transverse Posttensioning Design of Adjacent Precast Solid Multibeam Bridges

Adjacent precast, prestressed multibeam bridges have often been used for medium- and short-span bridges. However, there have been longitudinal cracking problems in shear keys and overlays commonly seen on some adjacent precast multibeam bridges during their service years. The fundamental reason for the problem is the poor transverse connection. Transverse posttensioning is important to the transverse connection design, although the posttensioning varies largely from state to state. Especially for adjacent precast solid multibeam bridges without diaphragms, there are no theoretical justifications for designing the transverse posttensioning. In this study, an approach based on the concept of shear friction, which is used for designing the transverse posttensioning in adjacent precast solid multibeam bridges, is presented. Furthermore, a newly rehabilitated bridge was load tested with the primary purpose of evaluating the effect of transverse posttensioning under truck load. Also, the calibration of a numerical model was conducted. At last, suggestions about design and construction of shear keys, with reference to the experience in other states, are presented for the practice in the state of Maryland.