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Because failure of roof systems in past high wind events has demonstrated the consequences of not maintaining a continuous load path from the roof to the foundation, many studies have been conducted to better understand this load path, including how loads are distributed in the system. The current study looks to add to the current knowledge of the vertical load path by focusing on uplift loads and by considering the sensitivity of different modeling parameters. This is done by developing and assessing load influence coefficient contours for various roof-to-wall (RTW) connections. An analytical model of a light-framed wood structure using finite-element software is developed. The model has a gable roof system comprised of fink trusses and is modeled in a highly detailed fashion including the explicit modeling of each connector/nail in the system. The influence coefficient plots indicate that the distribution of loads is indeed sensitive to the overall stiffness of RTW connections but is not overly sensitive to their relative stiffnesses. This was investigated by looking at cases where all connections have the same stiffness and cases where they can have different stiffnesses. However, the relative stiffness begins to have a larger impact as they begin to soften because of yielding. Furthermore, the stiffness of the sheathing connectors did not appear to have much of an impact on the distribution of load, but the sheathing stiffness itself did have a notable impact. [ABSTRACT FROM AUTHOR]

This paper presents a comprehensive overview of recent developments in the performance evaluation and flexural response of existing bridges from fundamental concepts to advanced topics. The focus is particularly on the structural evaluation to enhance the quality assessment of constructed bridge superstructures, taking into account a synthesis of the most important contributions to the flexural behavior of existing bridges, such as dynamic responses and lateral load distributions. This state-of-the-art paper provides a critical review of published literature and existing assessment methodologies in conjunction with corresponding analysis techniques, including technical comments on the code provisions. Detailed descriptions of the important parameters influencing flexural responses of existing bridges are discussed, such as the geometric effect, loading configuration, present condition of a bridge, and contribution of secondary structural elements. The review also includes the investigation methodologies, namely, the diagnostic and proof load tests. Finally, the current research needs to further advance the performance evaluation technologies for existing bridge superstructures are recommended. [ABSTRACT FROM AUTHOR]

This paper describes the procedure and results of the field tests on high-density polyethylene (HDPE), PVC, and metal large diameter pipes subjected to a highway design truck loading. Numerical simulations using finite element method are performed to determine pipe-soil system response under live load application. Comparisons of field test data with the predicted responses are made for soil pressures around and above the pipes, deformed cross-sectional pipe profiles, and pipe deflections. The field test results indicated that the buried flexible pipes, embedded with highly compacted graded sand with silt, demonstrated good performance without exhibiting any visible joint opening or structural distress. Under shallow burial conditions, the AASHTO specified deflection limit of 5% is found to be adequate for installation of the flexible pipes during the construction phase, and a vertical deflection limit of 2% is suggested for HDPE pipes based on the truck load response and repeated loading effect. [ABSTRACT FROM AUTHOR]

The general objective of this research was the construction and evaluation of a bridge using high-performance lightweight concrete (HPLWC). The resulting bridge over the Chickahominy River near Richmond, Va., consists of 15 prestressed American Association of State Highway and Transportation Officials (AASHTO) Type IV girders made of HPLWC with a density of 1,920 kg/m3 and a minimum required 28-day compressive strength of 55 MPa. The bridge also has a lightweight concrete (LWC) deck with a density of 1,850 kg/m3 and a minimum required 28-day compressive strength of 30 MPa. This research study is chiefly concerned with investigating the effects of using lightweight concrete in prestressed girders on transfer length, development length, flexural strength, girder live-load distribution factor, and dynamic load allowance. Transfer length was determined to be 432 mm, or 33 db, for several girders at the time of prestress transfer. The development length was determined to be between 1,830 and 2,440 mm, while the flexural strength ranged from 11 to 30% higher than the AASHTO flexural capacity. The measured distribution factors and dynamic load allowance were smaller than the AASHTO standard and LRFD values. [ABSTRACT FROM AUTHOR]

A nondestructive strength evaluation of the I-40 Bridge over the Rio Grande River in Albuquerque, N.M. was completed for the New Mexico Department of Transportation (NMDOT). The I-40 Bridge is a precast, prestressed concrete girder bridge located within 3 mi. of the “Big I” interchange carrying Interstates I-40 and I-25. Because of its location, the I-40 Bridge is subjected to large amounts of heavy truck traffic. The primary objective of the study reported herein was to determine a more accurate capacity rating for the I-40 Bridge and thus, reduce the number of overweight vehicle permit denials. To achieve this objective, a conventional rating analysis is first performed based on American Association of State Highway and Transportation Officials (AASHTO) guidelines. A diagnostic load test and a finite-element analysis are then completed. Details of the AASHTO rating analysis as well as the approach by which measured girder strains from the load test and finite-element results were considered in the capacity rating of the I-40 Bridge are discussed. Findings from the study confirmed that the capacity ratings of the I-40 Bridge could be safely increased by a factor of 1.7. [ABSTRACT FROM AUTHOR]

The Tom’s Creek Bridge is a small-scale demonstration project involving the use of fiber-reinforced polymer (FRP) composite girders as the main load-carrying members. The project is intended to serve two purposes. First, by calculating bridge design parameters such as the dynamic load allowance, transverse wheel load distribution, and deflections under service loading, the Tom’s Creek Bridge aids in modifying current American Association of State Highway and Transportation Officials bridge design standards for use with FRP composite materials. Second, by evaluating the FRP girders after exposure to service conditions, the project begins to answer questions about the long-term performance of these advanced composite material beams when used in bridge design. This paper details the in-service analysis of the Tom’s Creek Bridge. Five load tests, at 6-month intervals, were conducted on the bridge. Using midspan strain and deflection data gathered from the FRP composite girders during these tests, the aforementioned bridge design parameters have been determined. The Tom’s Creek Bridge was determined to have a maximum dynamic load allowance, IM, of 0.90, a transverse wheel load distribution factor, g, of 0.101, and a maximum deflection of L/490. Two bridge girders were removed from the Tom’s Creek Bridge after 15 months of service loading. These FRP composite girders were tested at the Structures and Materials Research Laboratory at Virginia Tech for stiffness and ultimate strength and compared to preservice values for the same beams. These measurements indicate that, after 15 months of service, the FRP composite girders have not significantly changed in stiffness or ultimate moment capacity. [ABSTRACT FROM AUTHOR]

A new nonlinear static alternate path analysis technique coined pulldown analysis is presented as an easy-to-implement alternative to the existing pushdown analysis for assessing the load redistribution capability of a building after a critical structural element has been suddenly removed. Unlike the pushdown analysis where gravity loads within the affected bays of a building are directly amplified, the pulldown analysis is associated with a downward force that is statically applied at the removed element location. This static pulldown force is equal in value to the axial compression force in the to-be-removed column of the intact frame multiplied by a dynamic increase factor (DIF), which aims to generate the best match of the peak dynamic responses of a damaged building through a nonlinear static analysis. A seismically designed nine-story steel moment frame is used as an example to illustrate the pulldown analysis procedure. Results from progressive collapse assessment of the example frame using the pulldown analysis and pushdown analysis are critically compared. It is found that the pulldown analysis is able to estimate the peak dynamic responses of the example frame with at least the same level of accuracy as those predicted by the pushdown analysis. Moreover, the pulldown analysis may lead to improved prediction of some important structural responses such as the peak axial forces in columns next to the removed column. Finally, to demonstrate how empirical DIF formulas for the pulldown analysis can be derived for practical applications, curve-fitting of data points, each consisting of the DIF and a parameter that approximately reflects the residual capacity level of the damaged frame under a given column removal scenario, is carried out for the example frame. [ABSTRACT FROM AUTHOR]

This paper presents the results of a test program whose goal was to better understand the contribution of individual elements to the performance of typical light-frame wood structures during tsunami loading. The intent was to be able to replicate failures in a structural engineering laboratory that were observed during laboratory experiments of hydraulic loading on wood walls at the NEES Tsunami Facility at Oregon State University. The elastic and inelastic response of shear walls, out-of-plane walls, and a full light-frame wood structural system subjected to varying lateral loads were observed using digital image correlation (DIC). The DIC provided a noncontact, three-dimensional measurement system that returned displacement results measured at multiple areas of interest on the wall surface. Overall, these experiments show that the elastic stiffness and ultimate capacity of the shear wall is significantly higher at full height than intermediate heights on the wall, and the ultimate lateral capacity was higher than a full structural system. The results indicate that the out-of-plane wall behaves like a one-way slab with limited contribution from adjacent studs in carrying load. The stud to bottom plate connection failures observed during the wave tank tests were successfully reproduced and indicate that the nailed connection needs to be reinforced to utilize the available capacity of the individual framing members. [ABSTRACT FROM AUTHOR]

It is well known that the stiffness properties of diaphragms and lateral load resisting elements (LLREs) influence the load distribution between LLREs under lateral load induced by earthquake or wind. Where a more sophisticated method of calculating the load distribution in a lateral load resisting system is used, often it is based on the concept of a beam on an elastic foundation. This approach could be tedious to apply in design when there are more than a few LLREs. A multiple-spring model (MSM), whereby the translational springs are used to model the diaphragm stiffnesses and the stiffnesses of the LLREs, is proposed. The model was validated with test and finite-element results of a particular benchmark building. The lateral load distribution between LLREs with various stiffness ratios of diaphragm to LLRE was also investigated. The results show that, contrary to common belief, the forces transferred by a semirigid diaphragm to supporting LLREs may be higher than those predicted by flexible and rigid-diaphragm assumptions. Therefore, using the envelope force approach may lead to underestimation of the design forces in the shear walls. [ABSTRACT FROM AUTHOR]