Journal of Performance of Constructed Facilities

Surfacing seals consist of a combination of bitumen and aggregate, and are used to provide an all-weather surfacing to protect underlying layers and provide safe access to vehicles traveling on a road. Analysis of a number of sections in Gauteng, South Africa has shown that surfacing seals lost a large proportion of their aggregate where the road was crossed by a bridge. As all original properties of the seal components and the traffic on the road were similar, it was deduced that the microclimate where the road traveled underneath the bridge should have caused this localized failure condition. In this paper, the phenomenon is investigated through analysis of the microclimate underneath the bridge, the material properties of the surfacing seal, and the combined effect of these factors on the performance of the seal. It is shown that the microclimate can affect the performance of an otherwise suitable surfacing seal to such an extent that the performance of the seal is severely compromised. A procedure for the analysis of potential microclimate effects is described in the paper.

The objective of this study was to conduct a laboratory investigation of rheological properties of non-foaming warm mix asphalt (WMA) binder after a short-term aging procedure. The conventional testing procedures such as viscosity, performance grade, creep and creep recovery, amplitude sweep, and frequency sweep were performed to determine the influences of non-foaming additives on asphalt binders. The experimental design included four binders and four non-foaming WMA additives. The test results indicated that, as expected, the non-foaming WMA additive can reduce the viscosity value of asphalt binder and thus decrease the mixing and compaction temperatures of the mixture. The failure temperatures of unaged and rolling thin film oven (RTFO) binders containing non-foam additives have a slight increase compared with the virgin binder, therefore improving the rut resistance of the mixtures. In addition, the creep recovery, amplitude, and frequency sweep tests show that the unaged and RTFO binders with Sasobit have a slightly higher complex modulus but exhibits lower creep compliance and phase angle than the binder containing other WMA additives.

In order to model perpetual pavement response, the traffic loads, pavement temperature, and mechanics responses collected from the Shandong perpetual pavement test road were used to develop axle load spectrums, temperature probability functions, and response regression models with load and temperature variables. The random sample methods of a probability distribution function were developed and the numerical simulation of parameter inputs and mechanical responses under a whole year of traffic volume and temperature cycles was realized. The results showed that the simulated mechanical response conformed to the actual response and both followed an approximate normal distribution. The response of different pavement structures was also compared. The research proves that the Monte Carlo method can help to understand the pavement mechanical response under the influence of both load and temperature. Finally, based on the simulated tensile strain distributions, the pavement fatigue life of all sections was compared.

This paper describes a new model using Finite Element Modeling Laboratory (FEMLAB). The model can be used to predict pavement strength development and consequently the pavement joint-sawing and opening times. The strength prediction was based on the temperature history of the concrete pavement, which was determined by the rate of heat generation and the heat exchange between the pavement and the environment. Pavement joint-sawing and opening times were defined as the times when concrete strength reached 4.3 and 24.1 MPa (megapascals), respectively. Using this model, the effects of weather conditions, fly ash and slag replacement, concrete placement time and temperature, and pavement thickness on concrete strength, joint-sawing time, and pavement opening time were evaluated. Results showed that weather conditions and the use of fly ash and slag had a significant effect on strength development, joint-sawing time, and pavement opening time. Based on the prediction, this model can be used to optimize the concrete mix design to select the appropriate concrete placement temperature and paving time for the optimal concrete construction and strength development under certain environmental condition.

Open-ended steel pipe piles are now widely used as the foundations for offshore structures. The pile-soil interface behavior is of particular interest in sands where shaft friction plays an important role in resisting the applied load. The rational design of the shaft capacity depends on a good understanding of the mechanisms of interface friction during pile installation and static loading. There are two new methods on the basis of the cone penetration test results that take into account the effect of friction fatigue arising from pile installation. An improvement is made in this study to account for the influence of plugging degree, which is a key issue for open-ended piles. The significance of the modified design framework lies in that it allows for the role of plugging in a more rational way by using the soil-squeezing ratio that is closely related to the radial effective stress and, consequently, the shaft capacity. The performance of the improved method is assessed against the existing methods in terms of evaluating the shaft resistance of two full-scale offshore bridge piles.

To investigate the behavior of X-section cast-in-place concrete piles (XCC pile), a series of static load tests for piled foundation are conducted on the basis of a soft soil reinforcement engineering for a sewage treatment plant in the north of Nanjing, China. The testing results are presented in load-settlement curves, pile-soil stress ratios, distributions of skin friction (side friction) and axial force, and load-sharing between side resistance and end-bearing capacity. Comparative analysis between an XCC pile and a circular section concrete pile (circular pile) with the same cross-sectional area indicates that the XCC pile with its increased perimeter can improve the vertical-bearing capacity by 20% because of the larger skin friction. Also, the XCC pile shows increasing pile-soil stress ratio and reduces settlement. The existing design standards for traditional piles can be referenced by the XCC pile composite foundation, because the axial force and skin friction distribution are the same as those of the traditional pile. It has been found that pile spacing is an important factor for XCC piles, and the XCC pile should be considered as a special friction pile because of high skin friction sharing. Above all, the XCC pile can significantly increase ground-bearing capacity.

Loess is a special kind of soil mass found all over the world. Loess mountain areas are highly vulnerable to landslides; hence, the monitoring and generation of warnings regarding a loess landslide is an important element in the risk management of side slopes in these areas. A typical line engineering area of a loess plateau in west China was used as a case study. With field investigation and data analysis, the risk indicators of the loess landslide were studied. Fuzzy synthetic evaluation of risk was conducted on the basis of geological engineering. The distribution of landslides and the geographical regional division method for determining landslide risk were also studied. On the basis of risk geographic region division, the authors completed a geology-meteorology coupling analytical model aimed at inducing the rainfall agent. The results of this model can be used in risk warning for landslides in loess slide slopes.

The implementation of landslide probability analysis was undertaken to evaluate the effect of landsliding on closures of major mountain road networks at Guoshin Township in central Taiwan. To achieve this objective, an event-based landslide probability analysis method was adopted to establish a landslide prediction model by using a set of training data from the landslides triggered by Typhoon Mindulle in July 2004. Landslide causative factors and triggering factors were selected in a logistic regression scheme so that the criteria for successfully distinguishing landslides from nonlandslides were established. Landslide occurrence probability was mapped in the whole study area and along the road route. Locations of high potential for landslide occurrence were, thus, highlighted along the road route and were proposed for road closure during typhoon events. At last, the proposed locations for road closure were validated by historical road closures caused by subsequent typhoons after Typhoon Mindulle. Validation results show that the proposed model could be used in predicting road closure resulting from storm-induced landslides.

Most construction projects involve earthmoving operations. Careful management of trucks to perform these operations is considered crucial by earthwork contractors in Taiwan. A mechanism is described that optimizes the management of the truck fleets of earthwork contractors. The proposed model integrates a discrete event simulation technique and genetic algorithms (GAs) to minimize the duration of earthmoving operations. The discrete simulation model is applied to simulate earthmoving operations and generate schedules for dispatching various trucks, and the GAs are used as a filter to screen out schedules that require long trips. Examples prove that the proposed model can determine near-optimal solutions efficiently. In addition, a user-friendly computer program is developed so that earthwork contractors can plan the dispatch schedule of earthmoving trucks easily and effectively.

The coming Chinese specification for the steel highway bridge will adopt the design method of probability limit state on the basis of the structure reliability theory. The limit-state equation with load and resistance factors plays a key role in this method, so determining the reasonable value of the factors is the foremost work in load and resistance factor design (LRFD). The primary objective of this paper is to calibrate the target reliability index of the steel highway bridge according to current specification by the first-order secondary-moment method (JC method) and to calculate the recommended resistance factors of Q235q and Q345qD (two commonly used steels for bridges in China) by means of an optimization method. The primary and adjunctive load combinations of the steel highway bridge are taken into account, respectively. The calibrated reliability index is used to calculate the five types of loading members’ factors, which are axial tensile, axial compressive, eccentric compressive, flexural, and shear member. Then the results are compared with the relative parameters in the “Unified Standard for Reliability Design of Highway Engineering Structures” (Ministry of Transport of China GB/J50283-1999). It is demonstrated that the value put forward in this study shows precision and application well. Hence, the recommended resistance factors of the steel highway bridge can be a reference for the new specification of the steel highway bridge.

To find an alternative way of improving bonding and restricting sliding displacement, a new technique that combines fiber-reinforced polymer (FRP) surface adhesion [externally bonded FRP (EB-FRP)] with a new type of mechanical fastening, namely hybrid bonding (HB-FRP), is developed. The beam specimens are investigated and compared in a new modified beam-shear program to examine the bonding behavior of HB-FRP and EB-FRP. The finite element analysis is conducted to simulate the interfacial shear on the basis of different bolt pretension force by Pretension 179 element and compact pairs of ANSYS software. Also the anchoring parameters of the hybrid bonding of FRP are studied by a drawing test program to study the anchor depth of screw bolts and by the finite element analysis to simulate the contact compression stress on the basis of different sizes of capping plate and bolt pretension for the selection of the capping plates and bolts. On the basis of experiments and the finite element analysis, the formula of calculating FRP anchor length is suggested. The results show that the new HB-FRP is a more reliable strengthening technique. The new bolt-fastening technique does not rely on bearing to transmit the interfacial shear, but increases the interfacial bond by resisting the separation of the FRP laminate from the concrete substrate by the bolt pretension instead. This study contributes to direct the design and the construction of the new HB-FRP directly.