Amsterdam and many other cities consist of a network of old quay walls, which sometimes have been constructed over a century ago. A large uncertainty exists concerning the current safety of these quay walls and their remaining service lifetime. In the current framework for the assessment of old urban quay walls, the influence of timber creep in the structure is being omitted. It had been expected that a part of the excessive deformations occurred are part of this timber creep as opposed to progressive failure. Hence, this research studied the influence of wood creep on the structural behaviour of old urban quay walls, using a case study based on the Herengracht. For the modelling of the quay walls, use has been made of the Embedded Beam Row (EBR) elements in Plaxis 2D. As this element type has no material model which takes into account creep,
use has been made of pseudo-elasticity. The behaviour over time had been modelled by reducing the elastic stiffness of the EBR elements with increasing creep factors. To force Plaxis to perform calculations, this stiffness reduction has been introduced as a reduced strength in the form of a custom moment-curvature diagram. At the time of writing, the Embedded Beam Row had not yet been validated for cohesive soils. Hence, a verification has been executed of the EBR using a full-scale load test performed on a pile group in Salt Lake City. In
this case, a 3x5 pile group driven in multi-layered cohesive and non-cohesive soils had been laterally loaded. The results included deformations, total horizontal load and bending moment distributions over depth. It
has been found that the EBR provides reasonable results when modelling laterally loaded pile groups. The force-displacement curve from the field test was only slightly stiffer compared to those obtained using Plaxis 2D. Maximum bending moments obtained using the EBR had been found to be 20 to 30% compared to the experimental data. The group efficiency of the pile group was initially lower for small displacements, which was likely caused by the lack of installation effects of driven piles in the Plaxis model. It has been observed
that the Interface Stiffness Factors (ISF) that are used to calibrate the EBR behaviour have a limited range. Increasing the ISF values beyond a certain limit will no longer affect results, as the interface connecting the EBR to the soil will have become practically rigid at this point. Nevertheless, it has been concluded the EBR can be used in this case to model laterally loaded pile groups. The influence of the timber creep on the structural behaviour of quay walls has been studied using a model based on the Herengracht in Amsterdam. A maximum creep factor has been applied of Φ=1.6. Two methods have been used to apply the final creep factor. With the "Direct" method, the maximum creep factor was
applied in the same phase as the load. With the "Indirect" method, the creep factor has been applied incrementally in steps of 0.1. It has been observed that the results from these methods deviate significantly. With the Indirect method, larger creep displacements have been calculated, as well as lower maximum compressive stresses in the piles. The creep behaviour has been studied in more depth using the Indirect method. In this case study, creep displacements of 2.22 times the initial displacement have been calculated. When plotted against the increasing creep factors, it has been observed a power function could be fitted to the data. In addition, a stress reduction of 0.590 times the initial maximum compressive stress has been observed in the front two pile rows. This stress reduction was achieved at φ=0.4. In the most landinwards pile row, stresses
continued to decrease, with a reduced rate beyond φ=0.4. A sensitivity analysis has been performed to study which parameters have significant influence on the creep behaviour. Conclusions were drawn based on the relative change in horizontal displacement and maximum compressive stress in the front pile row. It has been concluded that the shear strength parameters of the top layer, the elastic modulus of the timber, surface load and the geometry have the largest influence on the creep behaviour. Furthermore, it has been discovered
that the size of the creep factor steps influences the final stress and displacement. With decreasing stepsize, convergence occurred in the results. From the results it has been concluded that the structural behaviour of
old urban quay walls is significantly influenced by timber creep. The inclusion of timber creep resulted in large displacement increases, but also in stress reduction. The results suggest that excessive deformations of quay walls does not mean that an ultimate limit state has been reached. It is recommended to include the timber creep in the modelling and assessment of existing quay walls. ... Read more

At the Shonai River around Nagoya, Japan, several flood related problems occur. These problems occur at different locations, each with its own problems or limitations. The desired safety level as requested by the government is that the river should be able to have a discharge which has a probability of failure of once in 200 years. At many locations, the current probability of failure is lower than once in 50 years. This has led to the following research question:
How can the discharge capacity of the Shonai River be improved to modern standards?
The report has been divided in four phases. The first phase is used to formulate the final research question. This phase focuses on which part of the Nagoya urban area is most prone to flooding. Three kinds of flooding were examined: by peak river discharge, impact by tsunamis and impact by storm surge. The area is already well protected against tsunamis due to the natural shape of the bay Nagoya is situated to. The coastline is well protected against storm surges in the second half of the 20th century. At the river banks however, flood safety is still below the desired level. In the area, risks are relatively high along the Shonai River. Therefore, it has been decided to focus on the threats around the Shonai River. As already described above, there are several locations along the river with safety risks.

In phase 2, several locations and solutions are described to increase the capacity of the river. One major problem is the bottleneck around the Biwajima bridges, where four bridges are narrowing the river. At this location, the desired safety level of a flood discharge occurring once in 200 years is still far away. After discussion with officials of the Shonai River office, it was found that this problem was most urgent. Therefore, it had been chosen to elaborate further on this option in phase 3 and 4.
In phase 3, several options are described to remove the bottleneck. The first option is to replace the bridges with more clearance and larger spans. The second option is to remove the bridges and replace them for tunnels. The third and last option is to construct a bypass along the river, with flow through a tunnel. The Shonai River office is already working on a plan to raise the bridges, thus the first option has been dropped. The second option required large amounts of space for the tunnels. Therefore, it had been decided to work out the third option of creating a bypass. To minimise the impact of such a bypass and its construction on the surrounding area, the decision is made to construct a bored tunnel.

In the fourth and final phase the solution is verified. This is done concerning structural, hydraulic and construction method aspects. All the aspects are found to be possible. In hydraulic aspect, it is found that the required discharge capacity to reach a once in 200 year safety level equals 4250 m3/s. The current discharge capacity is found to be 2850 m3/s. Therefore, the bypass should have a minimal discharge capacity of 1400 m3/s. When using a bored tunnel, it is found that two tunnels with the maximal internal diameter of 16 m should be applied. On top of that, because the concrete surface is to rough in the best circumstances, it was decided to apply an epoxy layer on the surface. Using such a layer, it is found that the total discharge capacity becomes 1490m3/s.
The construction of the tunnel would take 137 weeks to complete. The total costs are estimated to be in the order of ¥60,000,000,000, or 60 billion yen, equivalent to 463 million euro. In comparison, the plan of the river office to replace the bridges would cost ¥68,400,000,000. It can be concluded that this option is a reasonable alternative for the current plan. ... Read more