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Author ORCID Identifier

https://orcid.org/0000-0002-5944-4867

Document Type

Open Access Dissertation

Degree Name

Doctor of Engineering (DEng)

Degree Program

Civil Engineering

Year Degree Awarded

2019

Month Degree Awarded

May

First Advisor

Sergio F. Breña

Subject Categories

Civil Engineering | Engineering Mechanics | Mechanics of Materials | Structural Engineering | Structural Materials

Abstract

Composite construction is prevalent in advanced structural systems where components of different materials are combined in the same structure to improve the performance of strong and economic structural sections. Maintaining continuity between the different structural components to produce monolithic structural behavior is challenging because of differences in the mechanical properties of these materials in terms of stiffness, strength, and ductility. The different components of the composite section are typically joined using adhesives and/or mechanical anchors to produce partial or full composite action. This dissertation discusses two types of shear interfaces intended to result in structural composite behavior. The first type of interface that is part of this dissertation focuses on bonded and mechanically anchored externally applied FRP sheets used in concrete structure for rehabilitation of concrete structures. The second type of connection is a new wood-concrete composite that includes a perforated steel connector bonded to engineered wood elements to transfer shear stresses to cast-in-place concrete.

Fiber reinforced polymer (FRP) materials have been confirmed as an excellent option for strengthening existing or even newly constructed concrete structures. However, FRP sheets may debond before reaching a high level of FRP stress. This behavior adversely affects the efficiency of using FRP materials for strengthening concrete structures. FRP-anchors have been added to the bonded joints to delay or avoid debonding and allow FRP sheets to reach their ultimate strength. Yet, the behavior of carbon fiber anchors is not well understood, particularly the effect of the dimensional and geometric properties of the anchors on the total strength of FRP-concrete joints. Therefore, the influence of key anchor parameters on joint behavior were examined in this research through analytical simulations. The parameters investigated were; the number of anchors used in the joint, the distance between anchors, anchor shaft depth, anchor shaft diameter, anchor splay angle, and anchor splay diameter. A general-purpose finite element software (ABAQUS) was used to study the behavior of the anchored FRP-concrete joints having different anchor configurations and geometries.

Different three-dimensional finite element models were used to describe the different components of the FRP-concrete joint. These different components were categorized based on the different materials, geometric shapes and functional roles of each part or component. Consequently, five different components were considered in the finite element models to represent the FRP-concrete joint. These components are the concrete substrate, the FRP sheet, the adhesive layer, the FRP anchor, and the adhesive envelopes around the anchors (for modeling the interface between concrete, FRP sheet, and the FRP anchors).

Based on this study, design recommendations for fiber reinforced polymer anchors were developed to determine the number of anchors, distance between anchors, anchor shaft depth, anchor shaft diameter, anchor splay angle, and anchor splay diameter required to achieve a goal strength. The finite element analysis can be extended to model full-scale structural members strengthened with fiber-reinforced material under different loading conditions building on the findings from this research.

The second type of composite application included in this dissertation focuses on new structural deck systems that benefit from the use of wood as a lightweight, sustainable substructure and concrete as a wear-resistant, vibration damping top element. These systems employ metallic connectors to transfer shear stresses between the wood and the concrete leading to full or partial composite action for strength and stiffness benefits. Results of finite element analysis and a parametric investigation are presented for one type of connector similar to those available commercially: a perforated steel plate of which half is epoxied into a groove in the wood member while the other half is embedded in a concrete slab. The analysis was first validated against experimental push-out tests performed on a commercial product and then employed to examine the effect of several parameters of the connection: thickness of plate; insulation gap between concrete and wood; depth of embedment in concrete; and depth of embedment in wood. the results showed that thickness predictably affects shear capacity as well as ductility and stiffness (slip moduli) of the connector.

This dissertation highlights the importance of including parameters that affect the response of joints between dissimilar materials in order to properly capture their behavior through numerical models. The detailed parametric studies presented in this research can form the basis for development of design recommendations for these types of connections. Given the expense associated with laboratory experimentation, the tools used in this research provide an inexpensive complement to physical testing in the development of robust and reliable equations that can be incorporated into design standards.

DOI

https://doi.org/10.7275/3c40-gj78

Creative Commons License

Creative Commons Attribution-Noncommercial 4.0 License
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