Barry T. Rosson

Inelastic behavior of sand-lime mortar joint masonry arches

The response of masonry arch bridges to moving wheel loads was simulated in the laboratory by hanging steel weights from the center of gravity of selected voussoirs of four arches. Elastic and plastic deformations occur in the sand-lime mortar joints, where significant plastic behavior occurs under the first few cycles of loading, then an elastic response follows when the magnitude of load and the load cycles increase. The results from the ultimate load testing show that the collapse load depends significantly on the load history of the arch and that a sliding failure can override a four-hinge mechanism. A model of the arch ring using ADINA and the Drucker-Prager material model indicates that plastic accumulations do not occur after the first load cycle; however, it is believed that sliding occurs between the voussoirs and the mortar, producing small inelastic deformations under moving loads.

Assessment of Guardrail-Strengthening Techniques

Guardrail-strengthening techniques were assessed by full-scale crash testing according to Service Level 2 conditions of NCHRP Report 230 and by BARRIER VII computer simulation. The Kansas Department of Transportations standard W-beam with steel posts guardrail was strengthened by nesting the W-beam and by reducing the post spacing. Computer simulations with BARRIER VII were used to assess the various strengthening techniques for guardrails with standard and extended post lengths installed in clay and sand. The soil—post stiffness parameters used in the program were obtained by conducting 21 post impact tests with a 1388-kg bogie striking a post at 33 km/hr. The guardrails constructed with W6 X 8.5 steel posts and 15.2 X 20.3-cm timber posts behaved similarly under all test conditions. The density of the clay has a profound effect on the lateral dynamic deflections. Nesting the W-beam to strengthen the guardrail provides very little benefit, whereas reducing the post spacing by half provides the greatest ...

TWO TEST LEVEL 4 BRIDGE RAILING AND TRANSITION SYSTEMS FOR TRANSVERSE TIMBER DECK BRIDGES

The Midwest Roadside Safety Facility, in cooperation with the Forest Products Laboratory, which is part of the U.S. Department of Agriculture’s Forest Service, and FHWA, designed two bridge railing and approach guardrail transition systems for use on bridges with transverse glue-laminated timber decks. The bridge railing and transition systems were developed and crash tested for use on higher-service-level roadways and evaluated according to the Test Level 4 safety performance criteria presented in NCHRP Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features. The first railing system was constructed with glulam timber components, whereas the second railing system was configured with steel hardware. Eight full-scale crash tests were performed, and the bridge railing and transition systems were acceptable according to current safety standards.

Elasto‐plastic Hardening and Shakedown of Masonry Arch Joints

The behavior of joints made of sand–lime mortar, such as used in a wide variety of structures from ancient times through the early twentieth century, can be clearly distinguished from the behavior of joints made with hydraulic cement mortar. Experiments on confined mortar specimens have confirmed that the weaker and more ductile sand–lime mortar can be accurately modeled as a Drucker–Prager material with a compression cap and exponential hardening on the cap portion of the yield surface. Joints of sand–lime mortar subject to axial thrust and moment are found experimentally to yield under very small loads, and to follow a linear hardening rule beyond the yield point. This behavior can be replicated analytically using a Drucker–Prager constitutive law with exponential hardening. The yield surface and hardening function for an entire mortar joint are representable by Maiers theory of piecewise linear yield function and interacting yield planes. As a consequence, an arch jointed with sand–lime mortar is found to shake down under moving loads above the yield limit and below the collapse load. The shakedown behavior of a sand–lime mortar jointed masonry arch is confirmed experimentally.Sommario. II comportamento dei giunti realizzati con malta di calce, del tipo di quelli utilizzati in un’ampia varietà di strutture dall’ antichità sino all’inizio di questo secolo, può essere chiaramente distinto dal comportamento dei giunti realizzati con malta idraulica. Esperimenti condotti su provini confinati di malta hanno infatti evidenziato che il comportamento della malta di calce, meno resistente e più duttile, può essere accuratamente modellato con un materiale di Drucker–Prager, adottando un troncamento della resistenza a compressione ed un incrudimento esponenziale della superficie di snervamento nella porzione troncata. Si è rilevato sperimentalmente che i giunti di malta di calce, soggetti a sforzo assiale e momento flettente, raggiungono lo snervamento sotto carichi molto modesti, e quindi seguono una legge di incrudimento lineare oltre il punto di snervamento. Questo comportamento può essere riprodotto analiticamente utilizzando la legge costitutiva di Drucker–Prager con incrudimento esponenziale. La superficie di snervamento e la funzione di incrudimento per un giunto di malta sono rappresentabili mediante la teoria di Maier delle funzioni di snervamento lineari a tratti e dei piani di snervamento interagenti. Di conseguenza, un arco con giunti di malta di calce perviene all’adattamento plastico (shakedown) sotto carichi mobili superiori al limite di snervamento ed inferiori al carico di collasso. Tale raggiungimento della condizione di adattamento plastico di archi di muratura con giunti di malta di calce è confermato sperimentalmente.

INSTRUMENTATION FOR DETERMINATION OF GUARDRAIL-SOIL INTERACTION

A series of steel posts (W150 X 12.6) and timber posts (15.2 X 20.3 cm) were instrumented with soil pressure transducers to assess the soil-post load response to a 1,388-kg bogie striking the post at 33 km/hr. Soil pressure measurements demonstrated the dramatic effects of soil shear strength and modulus on the responses of both timber and wood posts. The differences in the failure mechanisms between stiff and soft cohesive soils and noncohesive soils are demonstrated by both stress distributions and total stresses measured by the pressure transducers. The measurement system has potential applications for measurement of loads during impact testing of guardrail systems and as a tool for developing more appropriate models of soil behavior during impact loading.

Numerical simulation of dolos drop tests

Abstract A three-dimensional finite element method (FEM) analysis is conducted to simulate dolos drop tests. The FEM analysis employs a nonlinear concrete material model and utilizes a contact surface at the base of the vertical fluke. The results of the analysis predict the dynamic states of stress in the dolos and the pattern of cracking in the unit.

Static stresses in dolos concrete armor units

Abstract Concrete armor units are commonly employed for the protection of shorelines and rubble structures. A three-dimensional finite element model is used to determine the states of static stress in dolosse with varying dimensions and concrete properties. An analytical procedure is developed which accurately predicts the tensile stress in the shank and horizontal fluke of a simply supported dolos subject to self-weight loading. Several numerical examples are presented which illustrate the application of prediction and iso-stress equations.

Railing Systems for Use on Timber Deck Bridges

Bridge railing systems in the United States have historically been designed based on static load criteria given in the AASHTO Standard Specifications for Highway Bridges. In the past decade, full-scale vehicle crash testing has been recognized as a more appropriate and reliable method of evaluating bridge railing acceptability. In 1989, AASHTO published the Guide Specifications for Bridge Railings, which gave the recommendations and procedures to evaluate bridge rails by full-scale vehicle crash testing. In 1993, the National Cooperative Highway Research Program (NCHRP) published Report 350: Recommended Procedures for the Safety Performance Evaluation of Highway Features, which provided criteria for evaluating longitudinal barriers. Based on these specifications, a cooperative research program was initiated between the University of Nebraska-Lincoln and the Forest Products Laboratory, and later the FHWA, to develop and crash test 11 bridge rails for wood deck bridges. The research that resulted in successful development and testing of 11 bridge railing systems for longitudinally and transversely laminated wood bridge decks in accordance with AASHTO Performance Level 1 and 2 (PL-1 and PL-2) requirements and Test Levels 1, 2, and 4 (TL-1, TL-2, and TL-4) requirements of NCHRP Report 350 are described here.

Dynamic response of dolos armor units to drop test impact loads

Abstract Dolos concrete units have been used extensively throughout the world for the protection of shorelines and rubble structures. A three-dimensional finite element model is used to determine the states of dynamic stress in dolosse with varying dimensions and concrete properties. An analytical procedure is developed which accurately predicts the tensile stress in the shank and horizontal fluke of dolosse subject to drop test loading conditions Numerical examples are presented which illustrate the application of prediction and iso-stress equations.

Development of Two Test Level 2 Bridge Railings and Transitions for Use on Transverse Glue-Laminated Deck Bridges

The Midwest Roadside Safety Facility, in cooperation with the United States Department of Agriculture Forest Service Forest Products Laboratory and FHWA, designed two bridge railing and approach guardrail transition systems for use on transverse glue-laminated timber deck bridges. The bridge railing and transition systems were developed and crash tested for use on medium-service roadways and evaluated according to the Test Level 2 safety performance criteria provided in NCHRP Report 350. The first railing system was constructed by using steel hardware, whereas the second railing system was built by using glulam timber components. Four full-scale crash tests were performed, and the bridge railing and transition systems were determined to be acceptable according to the current safety standards in NCHRP Report 350.