Journal of Engineering Mechanics

The introduction of alternative reinforcement types for elastomeric bearings has rendered it necessary to consider the extensibility of the reinforcement as an additional design parameter. The extensibility of the reinforcement reduces the lateral restraint on the elastomer and, similar to the compressibility of the elastomer, influences important design parameters such as the compression modulus and bending modulus. Neglecting the compressibility of the elastomer or the extensibility of the reinforcement may result in an unconservative overestimation of these design parameters. Existing analytical solutions, which have been developed based on the pressure solution, are usually not suitable for design purposes. In this study, the analytical solutions for infinite strip, circular, square, and annular pad geometries are expanded and simplified to form geometry-specific approximations that account for reinforcement extensibility and bulk compressibility. The derived approximations closely and conservatively follow the analytical solutions over a large range of shape factors and values of the elastomer bulk modulus and reinforcement extensibility. A similar procedure used for the compression modulus and bending modulus is applied to approximate the maximum shear strain due to compression, including bulk compressibility and reinforcement extensibility. Generalized equations are proposed that can be adapted to the elastomeric pad geometries considered.

The dynamic response of moving vehicles on a bridge carries the vibration information of the bridge, which a few researchers have studied to extract the bridge modal properties such as natural frequencies and mode shapes. However, the vehicle response contains not only the frequency characteristics of the bridge and vehicle, but also other information such as the driving-related frequencies and road roughness effects, which makes the extraction difficult. To this end, the present study proposes a method using a specialized test vehicle consisting of a tractor and two following trailers, which can eliminate those effects and more efficiently extract the bridge modal properties. The two trailers towed by the tractor moving along the bridge were used as dynamic response receivers. In order to eliminate the effects previously discussed, the responses of one trailer were subtracted by the responses of the other with a time shift to obtain the residual responses. The residual responses were then processed with the fast Fourier transformation (FFT) and short-time Fourier transformation (STFT) to extract the bridge modal properties. Firstly, a theoretical study was conducted to derive the residual responses of the two trailers in a simplified vehicle-bridge coupled (VBC) system and extract the bridge mode shape squares (MSS) by applying the STFT. Then, numerical studies were conducted to demonstrate and verify the proposed method that is very effective and robust in extracting bridge modal properties, especially under ongoing traffic flows and different road surfaces. Finally, vehicle parameters, such as the trailers’ mass and stiffness, spacing, and traveling speed, were studied to design a proper test vehicle for field applications.

This paper presents a calculation procedure for externally unbonded carbon fiber–reinforced polymer (CFRP) strips anchored at their ends in flexural strengthening of existing reinforced concrete structures. Due to strain incompatibility between the composite strip and the neighboring concrete surface, the well-known conventional cross-section analysis (CSA) employed for bonded reinforcements cannot be implemented. An iterative force equilibrium and strip strain adaptation with previously defined constitutive materials laws together with an optimization procedure in a numerical computing environment are used to overcome the computational complexities. For validation purposes, two static loading tests on reinforced concrete beams with an externally prestressed CFRP strip without bond except in the anchorage zones are compared to the numerical predictions. Prior to the final evaluation, a model for the anchorage resistance is implemented in the algorithm in order to capture the ultimate load due to anchorage failure. An excellent agreement in terms of structural behavior as well as of ultimate load-carrying capacity is observed. Eventually, the differences in the structural response between bonded and unbonded strips are pointed out.

Because of limited information in site investigation, it is not possible to obtain the actual values for the trend ($t$), standard deviation ($\sigma$), and scale of fluctuation ($\delta$) of a spatially variable soil property of interest. The uncertainty in these soil parameters $\mathbf{\theta }=(t,\sigma ,\delta )$ is called the statistical uncertainty. The failure probability ($p_f$) of the geotechnical structure will increase as a result of the statistical uncertainty. This paper addresses the issue of incorporating the statistical uncertainty of $\mathbf{\theta }$ into the reliability calculation, to properly reflect the $p_f$ increase. A cone penetration test (CPT) sounding at the Wufeng District in Taichung City (Taiwan) is analyzed to illustrate the importance of treating statistical uncertainty in full and the limitations of the existing point-estimation and detrending approaches. It is shown that the statistical uncertainty can be fully characterized by drawing Markov chain Monte Carlo (MCMC) samples from the posterior PDF, $f(\mathbf{\theta }|\text{data})$. The resulting $p_f$ estimate will increase if some of these MCMC samples explore the high-risk region. The sample size in a thin soil layer is smaller than that in a thick layer. It follows that statistical uncertainty is larger for thin soil layers. It is also concluded that the point estimate for $\mathbf{\theta }$ cannot characterize the statistical uncertainty at all, nor can intermediate methods such as detrending first and then drawing MCMC samples from $f(\sigma ,\delta |t,\text{data})$ fully characterize the statistical uncertainty.

This paper presents an exact solution for the boundary-value problem which describes the linear buckling of axially compressed circular cylindrical panels with stringers attached to the straight edges. The boundary conditions differ from the classical simply supported ones, often assumed for design purposes, in the sense that the torsion resisted by the stringers are also taken into account. The presence of the stringers makes the results reported herein of practical interest and valuable as benchmark data.

This paper studies innovative restraining solutions based on lateral nickel-titanium (NiTi) shape-memory alloy (SMA) cables. Two novel control approaches are tested, which take advantage of superelasticity and the shape-memory effect. Superelasticity is employed in a passive control approach, using the restraining cables to increase the postbuckling resistance and recentering capabilities of a compressed column while dissipating energy. A numerical model to simulate this passive control system is also proposed and validated, adequately representing both its material and geometric nonlinearities. Additional parametric tests are performed, providing more insight into the good performance of the proposed system. The shape-memory effect (SME) is used in an active control approach, using the cables as actuators to counteract the buckling motion of the column. Experimental prototypes are built and tested in order to investigate the feasibility and effectiveness of these two control solutions, which aim to demonstrate the versatility of these exceptional materials for new structural applications.

In this paper, a mechanical model and analysis method have been established to analyze the characteristics of casing-cement-formation of offshore wells in testing and production. The model, which can be simplified to a plane strain problem, has considered the combined actions of temperature and nonuniform in-situ stress with appropriate boundary conditions. Subsequently, the corresponding equations have been deduced to obtain the mechanical responses of the model under the two kinds of actions mentioned previously. Then, a finite-element analysis has been carried out in ABAQUS framework to verify the correctness and accuracy of the theoretical derivation. Meanwhile, the specific stress distribution and its degree of nonuniformity, as well the casing safety factor, have been obtained through a case study. On this basis, the influences of cement elastic modulus, Poisson’s ratio, casing grade, and wellbore temperature on the mechanical properties have been presented. Finally, some significant conclusions have been drawn based on the discussion mentioned previously.

Pipeline structures are often very flexible and susceptible to vibrations induced by many sources, such as vortex, external flow, and internal fluid flow. The pounding tuned mass damper (PTMD) is one device that may be employed to absorb and dissipate these undesired vibrations. The PTMD is a combination of the tuned mass damper and the impact damper. It utilizes the tuned mass to absorb kinetic energy and dissipates the absorbed energy through collisions. To examine the vibration control effectiveness of the PTMD, both numerical analysis and experimental study were performed. In the numerical analysis, a pounding force model was established based on the Hertz contact element. The motion equation of a pipeline structure incorporated with a PTMD was derived. Free vibration analysis and forced vibration analysis were performed. In the experimental study, an M-shaped pipeline was fabricated and installed with the PTMD. Due to safety issues the pipe was kept empty during the experiments. A free vibration experiment was first executed with and without PTMD to determine its effectiveness. Experimental data showed that the damping ratio of the pipeline structure was effectively increased when the PTMD was installed. Then the pipeline was subjected to harmonic excitation to attain resonance. Experimental results also showed that the PTMD effectively reduced the vibration of the pipeline structure.

In this paper, a cyclic elastoplastic model applicable for studying the hysteretic performance of self-centering buckling restrained braces (SC-BRBs) is established based on the rheological analysis method. The linear-elastic pretensioned rods and superelastic shape memory alloy (SMA) pretensioned rods can be taken into account, and the tube stiffness modification coefficient in consideration of fabrication tolerances is introduced in this model. In the proposed rheological model simulating the SC-BRB specimens, the prediction of the hysteretic performance accurately matched the experiments. The proposed rheological model was applied to study the influence of the key structural parameters on the SC-BRB hysteretic performance: the energy dissipation of SC-BRBs with SMA pretensioned rods is superior to that of linear-elastic pretensioned rods; an increase of pretension and the area of the pretensioned rods will have different impacts on the hysteretic performance of SC-BRBs with linear-elastic pretensioned rods and SC-BRBs with SMA pretensioned rods; increasing the section area of the core plate will result in a higher energy dissipation but a weakened self-centering capacity for the SC-BRB; and reducing the initial stiffness of the brace will have little effect on its energy dissipation.

This paper is concerned with the investigation of the temperature, displacement, and stresses due to thermal shock loading on the inner surface cavity in an infinite medium with a cylindrical cavity. The governing equations will be taken into the context of the fractional order generalized thermoelasticity theory. In the Laplace transform domain, the form of a vector-matrix differential equation has been written for the basic equations, which is then solved by an eigenvalue approach. The result provides a motivation to investigate the effect of fractional parameter on the physical quantities.

A previously developed computational model is used for wave run-up analysis in a generic two-dimensional reservoir subjected to major earthquake acceleration records. The model is based on numerical solution of the Navier-Stokes equations and pressure equation considering compressibility effects. An existing model has been revised by the volume of fluid (VOF) method with piecewise linear interface calculation (PLIC) to be able to compute violent wave motion in the reservoir and to predict the maximum wave run-up on the dam crest attributable to ground oscillations during an earthquake. The numerical method and the computer code are validated by comparing the free-surface waves with the data available in the literature. The surface wave run-up on a vertical dam is simulated for different reservoir depths using major earthquake acceleration records. Simulations show that the maximum wave height on a dam body depends on the maximum positive ground velocity. On the basis of dimensional analysis, simulation results are presented in a simple dimensionless expression that is proposed for the prediction of the maximum wave run-up on a dam face subjected to earthquake excitation. The proposed relationship can be used for estimation of safety freeboard of dams against earthquake-generated surface waves.

An improved analytical derivation was present on the drift motion of small rigid floating objects of arbitrary shapes under regular surface waves. The approach follows the slope-sliding model but with two new developments: (1) the incorporation of the Lagrangian movement of the small floating object in the wave motion including the heave motion, and (2) more detailed description of the associated hydrodynamic forces that are comprised of the gravitational force, pressure force, and viscous skin friction modeled by a drag coefficient. The analysis first yields the Stokes drift when the object is infinitely small, which is as physically expected. Subsequently, the predicted drift of a small floating circular plate is derived based on the assumption of nonseparated flows around the object. The comparison between the predicted wave-induced drift and previous experimental measurements shows satisfactory agreement with a set of tuned hydrodynamic coefficients that are consistent with previous related studies.