John N. Karadelis

A numerical model for the computation of concrete pavement moduli: a non-destructive testing and assessment method

Abstract The falling weight deflectometer (FWD) non-destructive testing technique has been used to monitor and assess the behaviour and performance of rigid pavement systems. In addition to the full-scale site investigation, tests were also carried out with the aid of a specifically developed laboratory scaled model of the FWD. A rigorous finite element model was developed to analyse a multi-layered pavement system with various material and geometric properties and to relate the surface deflections as measured to the computed values. Evidence of non-linearity and deviation from classical linear elastic theory led to a more complex mathematical solution to fit the experimental data more accurately. The laboratory and field test results were compared with the computed values. This paper includes extensive discussion of these results and the conclusions drawn from them.

CFD Simulation for Wind Comfort and Safety in Urban Area: A Case Study of Coventry University Central Campus

Concern towards the quality of public urban areas has increased in recent years. Wind comfort and safety in pedestrian areas has become one important environmental parameter when designing new cities. Hence, architects and town planners need guidelines and simplified design tools to take account of the wind in their projects. The objectives of this study provide more insight in the pedestrian living conditions around the Hub, a newly built structure, part of Coventry University campus and at the same time study the influence of building shapes on the wind distribution. The latter is based on a series of computational fluid dynamics simulations (CFD), used to advise the Universitys Estates Department of the possibility of wind nuisance around the central campus area. The velocity field was computed using the finite volume method. The simulations were performed for dierent wind speeds and directions. The predicted results showed that the distribution of the velocity field varied and had dierent characteristics with dierent wind directions. Also, it was established that the wind speed amplification factors in diverging passages were generally larger than those in converging passages. The case study incorporated is intended to support and guide future studies of wind comfort and safety with CFD and thus makes a modest contribution in improving wind environmental quality in urban areas.

Elasto-plastic analysis with large deformation effects of a T-end plate connection to square hollow section

The behaviour and performance of a family of structural connections made of square hollow sections (SHS) has been investigated in the laboratory and a series of data have been collected and presented in a graphical form. In parallel, a rigorous finite element model was developed capable of analysing the system of the SHS, the cap-plate, the cleat-plate and its surrounding weld. Evidence of non-linearity and deviation from the classical linear elastic theory led to a more complex numerical solution to fit more closely the experimental data. Hence, a specific methodology is presented, as it applies to analyses involving plasticity and large deflections (deformations). Test results obtained in the laboratory were compared with computed values from the finite element analysis and are presented graphically in the last pages of this paper. Satisfactory agreement was obtained between recorded and computed strains and displacements. The paper includes extensive discussion of the above results and the conclusions drawn from them. A brief account of directly related future research work is also given.

Punched metal plate timber fasteners under fatigue loading

Abstract A series of uniaxial cyclic loading tests have been carried out on two types of punched metal plate timber fasteners to investigate and establish their failure criterion, provide a better understanding of their mechanism of failure and set a firm basis for optimum design of these types of joint. The mode of failure was found to be somehow different for different types of joint, whereas the initial slip values were found to be the same for both joints. Slip remained constant for one type of joint and increased with increasing number of cycles for the other type. The strain distribution across the steel plate was found to be maximum at the centre and minimum at the edges. It was concluded that present methods and procedures for punched metal plate timber fastener evaluation and design are not entirely integral and require further tests combined with rigorous analytical work.

A Stimulating Approach to Teaching, Learning and Assessing Finite Element Methods: A Case Study

Summary This paper examines the benefits of introducing finite element methods in the curriculum of undergraduate courses. It looks at the structure of the CAA/CAD module and examines to what extent it fulfils its main aims and objectives. It discusses the efficiency of the modern teaching and learning techniques used as an aid for developing the necessary skills in solving engineering problems, and monitors the developing ability and confidence of the students to tackle many stress/structural analysis and design problems, which often have no clearly defined brief, data, or even solution. Project management, leadership, presentation skills and teamwork are encouraged and assessed among students. A short account is written about the behaviour of a family of joist hangers under direct loading conditions and their subsequent mode of failure. This is followed by a design optimization study and a series of tentative conclusions. A great deal of consideration was given to the development of a finite element mod...

Strain energy release rate at interface of concrete overlaid pavements

Abstract A new method for calculating energy release rate (ERR) at the interface of concrete overlaid pavements is proposed using crack closure and the nodal force technique. This method transforms a 3D pavement system into a 2D interfacial crack model via a theoretical conversion. The interfacial ERRs of steel fibre-reinforced, roller-compacted, polymer-modified concrete overlay pavement subjected to vehicular load were calculated and compared with the measured interfacial fracture toughness of the bi-material. It was found that the ERRs considerably decrease with the increase in overlay thickness and elastic modulus of foundation. Thin overlays (less than 100 mm) should not be considered in overlay pavement design to avoid interfacial delamination induced by heavy vehicular loading. For a typical overlay pavement system subjected to complex vehicular loads, an interfacial crack suffers mainly from damage due to mode-I, opening, compared to mode-II, sliding, while mode-III, tearing damage is negligible.

Establishing the Fiber Bridging Law by an Inverse Analysis Approach

AbstractA method for establishing the relationship between stress and crack face opening for steel fiber–reinforced concrete (SFRC) beams under three-point loading was proposed using inverse analysis. The relationships were set up in two parts: Fracture mechanics theory was used before the hinge formation, followed by a classical mechanics of materials approach after the hinge was formed. This methodology did not incorporate any assumptions and was validated by the construction of experimental load versus crack mouth opening–displacement (CMOD) curves and by predicting the experimental load versus CMOD relationship for independent flexural tests on beams of different sizes. The proposed method can simulate and predict the complete flexural performance of SFRC beams under three-point bending.

Behaviour of T-end Plate Connection to RHS: Part I: Experimental Investigation

Publisher Summary Rectangular Hollow Section (RHS) members are often used as compressive members due to their good buckling stiffness. One of the simplest ways to connect tubular members is by cutting the ends and welding them together. However, depending on joint configuration and number of members connected, this may result in complex and expensive connections. The alternative would be to connect the members together through some other means. One of the most economical solution is to weld a cap plate to the tube (CHS or RHS) and then to weld on it a cleat plate. The connection could be made entirely in the workshop, thus reducing labor work on site. This chapter investigates the behavior of welded T-end plate connections through a series of tests. The DENISON machine with a capacity of 500 kN is used for the testing of joints. A tensile load is applied in increments of 10 kN up to failure. The strains and deformations are recorded for each load increment into a computer logged to the testing machine. The results suggest that considerable stress re-distribution and strain hardening takes place after the first yield. More tests are under way for true rectangular hollow section tubes.

A comparison of flexural strengths of polymer (SBR and PVA) modified, roller compacted concrete

This brief article aims to reveal the flexural performance, including the equivalent flexural strength of PVA (Polyvinyl Alcohol) modified concrete by comparing it primarily with that of SBR (Styrene Butadiene Rubber) concrete. This data article is directly related to Karadelis and Lin [6].

Shear failure in plain concrete as applied to concrete pavement overlays

This study applied the modified Iosipescu loading configuration on beams and direct shear loads on cylinders to investigate the concrete behaviour under minimal flexural and prominent shear stress conditions, particularly in plain concrete tests. It aims to make a contribution in understanding the behaviour of a concrete pavement under shear loading and failure and ultimately design an adequate overlay system. A finite element model corresponding to the modified Iosipescu beam test was set up to assist with the recognition and study of the complex stress patterns developing at high stress concentration regions and the evaluation of principal stresses. Both, normal and high strength concrete were used, to imitate the performance of the existing (old) pavement and the prospect overlay under shear. On the basis of the laboratory results and the preliminary finite element analysis, it was found that all specimens failed abruptly without warning in a typical brittle-material / shear-failure manner. Considerably higher shear strengths were achieved compared to those specified in the standards. Unexpectedly, the high strength concrete developed slightly lower shear strength than the normal concrete. This is probably attributed to insufficient compaction and relatively less effective aggregate interlock in high shear regions. The research is in progress.