Sameh S. Badie

Evaluation and Repair Procedures for Precast/Prestressed Concrete Girders with Longitudinal Cracking in the Web

This report establishes a users manual for the acceptance, repair, or rejection of precast/prestressed concrete girders with longitudinal web cracking. The report also proposes revisions to the AASHTO LRFD Bridge Design Specifications and provides recommendations to develop improved crack control reinforcement details for use in new girders. The material in this report will be of immediate interest to bridge engineers.

Analysis of shear wall structures on elastic foundations

Abstract A method for analyzing shear wall structures on elastic foundations is presented. The shear walls are modeled using a nine-noded isoparametric quadrilateral plane stress element and the soil is modeled using a three-noded quadratic element that includes the vertical subgrade reaction and soil shear stiffness. It is observed that analyzing shear wall structures as fixed cantilevers, i.e. ignoring soil-structure interaction, significantly underestimates the wall drift. It is shown that including soil shear stiffness in the analysis reduces the maximum drift and increases the normal stresses in the wall, especially for poor soil. It is also shown that ignoring the soil deformation underestimates the bending moment in the lintel beams of coupled shear walls, and the transverse bending moment in core structures.

Full-Scale Testing for Composite Slab/Beam Systems Made with Extended Stud Spacing

Investigation of the background of the 610 mm (24 in.) spacing of stud shear connectors showed that this limit was set on the basis of a small amount of testing of beams with spacing greater than this limit. The literature search showed that some attempts have been recently made to extend this limit. One of the objectives of the NCHRP 12-65 research project was to investigate the possibility of extending this limit to 1,220 mm (48 in.) for cluster of studs used for precast concrete panels made composite with steel I-beams. The experimental investigation included testing of push-off specimens and full-scale composite beams. Results of the push-off specimens have shown that the fatigue loading has no detrimental effect on the load-slip relationship when the number of studs is doubled per cluster. This paper covers the second part of the experimental investigation, which is fatigue and ultimate testing of full-scale composite beams. The full-scale testing has proven that full-composite action between precast concrete panels and steel girders can be achieved when the spacing between the stud clusters is extended up to 1,220 mm (48 in.).

Relaxing the Stud Spacing Limit for Full-Depth Precast Concrete Deck Panels Supported on Steel Girders (Phase I)

The AASHTO LRFD Bridge Design Specifications state that the spacing between the shear connectors for steel girders should not exceed 610 mm (24 in.). This decision was made based on research conducted more than three decades ago. The goal of this research is to investigate the possibility of extending this limit to 1,220 mm (48 in.) for stud clusters used with full-depth precast concrete deck panels installed on steel girders. This paper presents the history of the 610 mm (24 in.) limit, various formulas developed to calculate fatigue and design capacity for stud clusters and concerns about extending the current LRFD limit. This paper also presents information on the first phase of the experimental investigation, which is conducted on push-off specimens to validate extending the limit to 1,220 mm (48 in.).

A quadratic order elastic foundation finite element

A new quadratic order elastic foundation element is presented. It models the vertical subgrade reaction and the shear stiffness of the soil as well as the friction between the super structure and the soil. This element gives the ability to analyze the super structure with the nine-noded quadrilateral plane elements as it has the same quadrature order. Three different applications are analyzed to adapt the accuracy of the new model. All of the results are in good shape.

THREE-NODED CURVED ISOPARAMETRIC SOIL INTERFACE ELEMENT

Abstract A three-node curved isoparametric soil interface element is presented that models the vertical subgrade reaction and the shear stiffness of the soil, and the friction between the soil and the superstructure. The element is compatible with curved eight- or nine-noded isoparametric plane elements. It can be used to analyze planar structures on elastic media. Two verification problems, a curved shell on elastic foundation and a circular culvert under concentrated load, are given. Results are compared with both theoretical analysis and finite element analysis using a conventional beam on elastic foundation formulation.

Practical Steel Confinements for Wildly Spaced Clustered Large Stud ShearConnectors in Composite Bridge Deck Panel Systems

Composite bridge deck systems consist of concrete deck panels supported on top of steel girders. Clustered stud shear connectors are utilized for transferring composite actions between these members. In the last 10 years, some attempts have been made to increase the spacing of clustered large shear studs in this system from 24 inches to 48 inches, which can benefit in reducing cost and time for new and replacement bridge construction. Nevertheless, increasing the spacing of clustered studs causes high concentrated composite action and requires effective confinement to prevent local failures and separation of members. This paper presents the experimental and analytical investigation of different types of steel confinements for clustered large shear studs with 48-inch spacing in the full-depth precast concrete panel supported on steel girders. Different types of steel confinements including steel tubes and layers of steel bars were developed and tested with sixteen push-off specimens and two full-scale beams for static and fatigue loads. The experimental investigation has shown the suitability of steel confinements for widely spaced clustered large shear studs to maintain full composite action between the deck and the girders. Finite Element Analyses (FEA) of the push-off and full-scale beam models were utilized for investigating the behaviors of steel confinement and the concrete surrounding.