Flood Loads Research Articles

Field survey assessment of flood loads and related building damage from the July 2021 event in the Ahr Valley (Germany)

Field survey assessment of flood loads and related building damage from the July 2021 event in the Ahr Valley (Germany)

STUDY ON CFD SIMULATION METHOD FOR ANALYSING FLOOD LOADS IN OPEN-CHANNEL STEADY FLOW

STUDY ON CFD SIMULATION METHOD FOR ANALYSING FLOOD LOADS IN OPEN-CHANNEL STEADY FLOW

Temporal and spatial water quality impacts of point-source versus catchment-derived nitrogen loads in an urbanised estuary

The Brisbane River estuary is an anthropogenically-impacted waterway in southeast Queensland, Australia. The estuary is over 80 km long and flows through an urbanised region. It receives over 500 t per year of total nitrogen (N) from direct point-source discharges in addition to sporadic flood loads of N from an agriculturally impacted upper catchment. Comprehensive water quality monitoring data for the estuary have been collected from at least 2001. This monitoring data includes ambient nutrient concentrations in the estuary, nutrient concentration and volume of the catchment inflows, and nutrient concentration and volume of point source discharges. This long-term data from a range of sources was used to determine temporal and spatial variations in concentrations, forms, stores and loads of N along the estuary for the period 2001 to 2022. Results showed that, during low-flow periods, the store of N in the mid-upper estuary (33–81 km upstream) is significantly determined by point-source discharges to this reach, and therefore the store of N can be modelled. Model parameters are the daily point source loads, a point source load decay factor, and a background constant store. In the lower estuary (0–33 km upstream) N store can be accurately determined based on dilution with seawater, with point sources not having significant influence on total N in the reach. Total N from large flood events was found to largely pass through the estuary without detectable removal processes, delivering catchment derived N directly to coastal waters. This work informs potential application of nutrient offsets in the estuary, guiding where and when offset options will be effective to mitigate the water quality impacts of point-source nutrients.

Analysis of the structural response and strengthening performance of prefabricated substation walls under flood loads

Introduction: The study focuses on evaluating the reliability of prefabricated perimeter walls in substations during flood events. It employs a sophisticated numerical model based on actual engineering data to assess their load-bearing capabilities. The research investigates the impact of crucial flood parameters on the structural behavior of these walls, examines the force transmission mechanisms, and suggests “W-shaped” reinforcement techniques to mitigate stress-related issues.Methods: To meet our research goals, we developed an extensive numerical model for prefabricated perimeter walls, incorporating real-world engineering data. This model enabled us to analyze critical flood parameters, such as flood depth, flow velocity, and flood erosion. Furthermore, we investigated the force transmission mechanisms within the walls and introduced “W-shaped” reinforcement strategies to improve their load-bearing capacity.Results: Our results indicate that flood depth and flow velocity have a substantial impact on the performance of prefabricated perimeter walls, while flood erosion has a minor effect. Safety concerns become prominent when flood depth exceeds 1.0 m or flow velocity surpasses 3 m per second. Analysis of force transmission mechanisms reveals greater displacements at higher water levels. Critical areas, including wall panel-column and wall panel-foundation connections, experience heightened stress levels.Discussion: Our study highlights the significant role of flood depth and flow velocity in evaluating the load-bearing capacity of prefabricated perimeter walls in substation environments. To address potential structural weaknesses, we recommend implementing “W-shaped” wall reinforcement methods, which efficiently decrease both displacement and stress. These findings carry implications for substation design and flood resilience, underscoring the importance of comprehensive flood risk management strategies to protect internal facilities during floods.

Flood-induced forces and collapse mechanism of historical multi-span masonry arch bridges: The Putang bridge case

In order to obtain an adequate understanding of the vulnerability of historical multi-span masonry bridges during flood hazards for the better conservation, a typical multi-span stone arch bridge, Putang Bridge, is chosen to carry out the study on the collapse mechanism of the bridge under flood-induced forces based on numerical simulations. This study has a twofold objective: to simulate numerically the forces exerted by floods on the bridge, and to figure out the collapse mechanism under the obtained flood loads. The hydrodynamic pressure distribution and drag and lift forces on the bridge are predicted with CFD simulation considering eight different flooding levels. The simulation method is validated in advance with existing experiments. A bridge with higher cutwaters is modeled to assess the effects of the height of cutwaters on mitigating the flood loads. A finite element model of the bridge is developed and the obtained flood loads are applied to investigate the vulnerability of arch bridges in floods. The findings of this research could contribute to a clear comprehension of the flood-induced forces on arch bridges and the structural vulnerability, and also could provide some insights on preparing the early warning strategy and preventive measures for historical masonry arch bridges.

Behavior of Flood Resistant Building and Ductile Detailing of G +7 RC Building Using IS 13920-2016

Floods are one of the most widespread and destructive natural disasters occurring in the world and with the increase in constructions along river courses and concentration of population around floodplain areas, flood-induced damages have been continuously increasing. The annual disaster record reveals that flood occurrence increased about ten folds over the past five decades. Thus, floods are posing a great threat and challenge to planers, design engineers, insurance industries, policymakers, and to the governments. Structural and non-structural measures can be used to deal with floods. Structural measures include a set of works aiming to reduce one or more hydraulic parameters like runoff volume, peak discharge, rise in water level, duration of flood, flow velocity, etc. Non-structural measures involve a wide range of measures to reduce flood risk through flood forecasting and early warning systems, emergency plans, and posing land use regulations and policies. The futuristic reinforced concrete buildings can be considered as a symbol of modern civilization. These buildings are usually constructed based on the guide lines given by the standard code books(like IS: 456:2000 and IS 13920:2016).Unfortunately, the code provisions consider the seismic loads and wind effects alone, while accounting the dead and live design loads, and exclude the flood loads. This implies the necessity to bring out corrective measures that can be adopted to reduce vulnerability before harm occurrences. In this project focuses on both the incorporation of flood loads during the analysis and design in CSI-ETABS software and the assessment of flood vulnerability of reinforced concrete residential buildings. Vulnerability is expressed as a fraction of ground floor height and maximum flood level at most immerse the building up to ground floor and first floor level. The importance of the outcome arises from the need of a strengthening solution to avoid failure of new or existing structures during floods.

Exploring the effect of building openings and orientation on induced loads due to extreme flood events

Understanding the impact of building features on flood-induced loads remains a major challenge. This study experimentally investigated the effect of building openings and orientation on horizontal forces and overturning moments by unsteady extreme floods. The physical model experiments for flood impacts were conducted concerning three intensity flood events (Hi), four porosities (P) resulting by opening, and seven orientations (γ) by building rotation. Measurement of impact forces and moments on the building model was carried out to explore the flood impacts on structures under unsteady flow conditions. By introducing a reduction coefficient of maximum horizontal force ηF, the influence of the porosity and orientation on flood loads was discussed. Results showed that either the building openings or the orientation exhibit a reduction effect on the resulting force and moment, and the magnitude of the reduction is negatively related to the flood intensity. For the permeable building with oriented exposures, the reduction coefficient ηF showed a W-shaped variation trend concerning γ at certain P, exhibiting a variable behavior of force reduction and increase with changes in P and γ. Finally, the load formulas, including maximum horizontal force and maximum overturning moment, were modified by quantifying the effects of openings and orientation, supporting hydraulic engineers for the load design of building structures.

Hydrodynamic considerations for improving the design/evaluation of over-topped bridge decks during extreme floods

Flow over an Iranian bridge deck is studied under an actual extreme flood event happening similarly nowadays in many countries due to climate change. Rigorous transient fluid-structure interaction analyses using the realizable k-ε turbulence model and the VOF Method are conducted. Geotechnical and abutments damages are neglected. Water surface profiles, velocity vectors, and hydrodynamic coefficients are determined. Based on the latest hydrological regime, particularly in supercritical flows, the results are partially compared against the latest advanced design codes, to evaluate the performance of their hydrodynamic and hydraulic provisions in similar incidents. It was acknowledged that the flood loads recommended by the Federal Highway Administration (FHWA) are fairly acceptable, Eurocode-1 predicts them rather accurately but not in extreme cases, and the Australian Standard (AS-5100.2) is less effective due to over-estimation of the hydrodynamic loads. Instead, the latter offers comprehensive user-defined hydraulic conditions. Furthermore, upon gradual rise of the water level to thrice the deck height, bridge stability is found to be at risk due to highly turbulent states. It is recommended that due to such threats, re-evaluation of flood regime, as well as its distinct hydrodynamic properties have to be accounted for, when evaluating existing bridges or designing new ones.

Simulated flood forces on a building due to the storm surge by Typhoon Haiyan

ABSTRACT Haiyan in 2013 was one of the most powerful typhoons to have affected the Philippines, devastating in its path a wide portion of Leyte, and causing extensive damage to structures in Tacloban City. To understand the likely impacts that would be exerted by a storm surge on a structure deemed important, the authors used a coupled model that hindcasted the flooding that took place during Haiyan. This coupled model included the use of the Weather Research and Forecasting (WRF) Model (with Bogussing scheme) to simulate the atmospheric conditions during the passage of Haiyan, the Finite Volume Coastal Ocean Model (FVCOM) to simulate the storm surge and obtain the boundary conditions for the wind and flood (hydrostatic, hydrodynamic, and breaking wave), and the Structural Analysis and Designing Program (STAAD.Pro) to calculate the corresponding axial, shear, and bending moment envelopes based on the storm surge simulation. A 4-floor public school building in Tacloban was modeled and the effects that the storm surge would have on a corner column were analyzed. Based on the results, the axial, shear, and moment at the corner column significantly increased when considering flood loads, indicating the importance of including such loads in the design of essential structures.

Non-Stationary Hydrological Regimes Due to Climate Change: The Impact of Future Precipitation in the Spillway Design of a Reservoir, Case Study: Sube y Baja Dam, in Ecuador

Changes in flood loads and reservoir levels, produced by climate change (CC), represent an increasing concern for dam safety managers and downstream populations, highlighting the need to define adaptation strategies based on the dam failure risk management framework. Currently, thousands of dams worldwide, varying in use, age, and maintenance, may represent a threat to downstream cities in the case of structural failure. Several studies relate the failure of dams to several issues in the spillway, which may be even more vulnerable in CC conditions. This study provides a review of dam safety threats due to CC and approaches for the design/redesign of the spillway to cope with CC. A general four-stage methodology is proposed: data gathering and hydro-climatic, hydrological, and hydraulic analyses. Afterward, this methodology is applied to the spillway design for the Sube y Baja dam in Ecuador. The Probable Maximum Precipitation (PMP) increases around 20% considering CC under the Representative Concentration Pathway 8.5. Such an increment derived a 25% increase in the spillway maximum flow. These results show that the non-stationary hydrological regimes related to CC require a revision of engineering design criteria for hydraulic structures in general, and call for a consensus on design variables under CC.

Comparative Review and Assessment of Various Flood Retrofit Methods for Low-Rise Residential Buildings in Coastal Areas

Recent hurricanes indicated that retrofitted residential buildings are still susceptible to wind- and flood-induced damage in coastal areas. This poor performance indicates that flood retrofit methods need to be evaluated in terms of efficiency and effectiveness to resist hurricane wind and flood loads. This paper discusses various aspects in the hurricane-resistant design and retrofit of coastal residential buildings, including potential wind and flood-induced damage, risk mitigation, cost of retrofit methods, and the need for better standards. The cost analysis is performed for a typical one-story wood-frame residential building with a gable roof system considering several flood retrofit methods. The result indicates that selecting a flood protection level higher than the basic 100-year flood level can significantly decrease the risk of damage. This result seems appropriate and essential for specific hurricane-prone regions considering recent changes in the intensity/frequency of storms. A review of actual damage types indicates that wood-frame elevated houses are susceptible to experiencing wind-induced damage to the structural system and more extensive damage to the envelope system. The performance of breakaway walls below the base flood elevation (BFE) strongly depends on the connections between such walls and structural members. The result of cost analysis indicates that the foundation type can directly affect the total cost of retrofit solutions, such as elevation, wet, and dry methods for houses in coastal areas. Regarding the elevation method, adding a freeboard higher than the BFE does not significantly increase the total cost once the elevation method is selected as the preferred retrofit solution.

Automated UAV based multi-hazard assessment system for bridges crossing seasonal rivers

An automated unmanned aerial vehicle (UAV) based multi-hazard performance assessment system was developed to respond to rapid performance evaluation and performance prediction needs for river crossing reinforced concrete (RC) bridges. In the developed system, firstly the seasonally acquired UAV measurements were used to obtain the three-dimensional (3D) digital elevation models (DEMs) of the river bed. In conjunction with the flood simulation, the hydraulic model was verified with the previous flood event which corresponded to Q50 and the scour depths after a probable flood (Q500) were predicted by HEC-RAS software. Afterward, the 3D finite element model (FEM) of the bridge was constituted automatically with the developed code considering the scoured piles. The flood loads were exerted on the modeled bridge with regard to the HEC-RAS flood inundation map and relevant water depth estimations around the bridge piers. For the seismic evaluation, nonlinear time history analyses (THA) were conducted by using several scaled earthquake acceleration records that were acting in both principal axes of the bridge simultaneously as compatible with the region seismicity. The Bogacay-II Bridge that was located in Antalya, Turkey was selected as the case study. In the analyses, as the scour depth increased, the lateral displacements and the pile internal forces were observed to increase while the pier column internal forces kept approximately constant. Thus, it was monitored that the seismic displacement and load demands migrated from pier columns to piles with increasing scour. Therefore, the applicability of the proposed system was verified using the case study bridge.

ANALYSIS OF A SCHOOL BUILDING AGAINST TYPHOON HAIYAN STORM SURGE FORCES

In 2013 Typhoon Haiyan dealt strong winds and storm surges to Tacloban City, Philippines. After that, the standard public school buildings were designed using the load provisions of the updated 2015 National Structural Code of the Philippines. However, it is important to analyze if the school buildings can resist failure against another Haiyan storm surge event. Haiyan was simulated using the the Weather Research and Forecasting (WRF) Model, and the storm surge was simulated using the Finite Volume Community Ocean Model (FVCOM). The wind and flood loads were then calculated and applied on a two-story school building model in STAAD.Pro, and the maximum shear forces and bending moments in the 300 beams and columns were compared to its capacity.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/P3E1_aizbnE

Flood-fragility analysis of instream bridges – consideration of flow hydraulics, geotechnical uncertainties, and variable scour depth

Floods, bridge scour, and flood-associated loads have caused over sixty percent of bridge failures in the U.S. Current practices for the vulnerability assessment of instream bridges under the effect of such flood largely rely on qualitative methods, such as visual inspection, without considering uncertainties associated with structural behaviors and flood loads. Recently, numerical methods have been investigated to quantitatively consider such uncertainty effects by adapting fragility analysis concept that has been well established in the earthquake engineering area. However, river hydraulics, geotechnical uncertainties of foundation, variable scour-depth effects, and their significance in structural fragility of bridges have rarely been systematically investigated. This study proposes a comprehensive fragility analysis framework that can effectively incorporate both flow hydraulics and geotechnical uncertainties, in addition to commonly considered components in flood-fragility analysis of bridges. The significance of flow hydraulics and geotechnical uncertainties has been demonstrated through a real-bridge case study. Conventional fragility curves with maximum scour depth may not represent actual vulnerability during floods, as the scour may not reach to the maximum in many cases. Therefore, fragility surface with two intensity measures, i.e. flow discharges and scour depths, is introduced for real-time vulnerability assessment during floods in this study.

The Structure System of Bugis Traditional House in Disasters Perspective

The existence of traditional house until now could be believed as proof of a good human protector. Bugis traditional house is one of them. The research problem is how Bugis behavior and building structure performance to struggle in flood. The goal is to reveal the performance of house structure and Bugis ancestor behavior to survive after disasters. The methods are logical argumentation to explain the architectural knowledge, and modeling simulation to explain building structural performance. The results are Bugis ancestor has been leave inheritance a good behavior in survive after disasters through they architectural space arrangement. They prepare space in a safe area at their house for food storage, so when disasters happen they still have food stock without waiting for aids. The structure system as the stilt house its find in safe for the occupant because of space for human living lifted more than two meters above the ground surface. The structural performance indicates the displacement in early dangerous occur when flood loads higher than human living space. The best knowledge can be adopted in this research is the availability of food stock at own house. The better construction method to apply in flood area is the stilt house.

Identification of Factors Influencing Sustainability of Buried Continuous Pipelines

Threat to the sustainability of buried continuous pipelines (BCPs) can be associated with different factors such as corrosion, natural hazards, and third-party influences. In the past, these factors have been discussed independently by various researchers. Despite these studies, there is still space for a comprehensive review report to be performed in this domain. The purpose of this article is to manage, classify, and describe the literature work done in this sphere. Firstly, the screening of various factors based on their damage criteria has been carried out. An environmental analysis is performed to review the impact of different parameters that can influence the sustainability of BCPs. Further, a technical review on primary factors has been done to examine and measure the causes, damages, mitigation, and inspection techniques. In the last stage, review based decision has been performed. Results of the current study shows that research contribution for corrosion and earthquake factors are in an advanced stage, followed by flood and external surface loads, that are still in progress. However, temperature variations and blast factors are in a premature phase and need broad inspection and research support.

Investigation on Flooding‐Resistant Performance of Integral Abutment and Jointless Bridge

Bridge washouts connected to flood events are deemed one of the main reasons for structural collapse. Compared to traditional continuous jointed bridges, integral abutment and jointless bridges (IAJBs) have better lateral stability because there are no expansion devices. The mechanical performance of Shangban IAJ bridge, located in Fujian, China, is thoroughly investigated by Finite Element Analysis (FEA). The numerical model is created and validated based on experimental results obtained from static load tests performed on the bridge. A detailed parametric analysis is carried out to assess the correlation between the flood‐resistant performance and a number of parameters: skew angle, water‐blocking area, span number, pile section geometry, and abutment height. Except for the abutment height, other parameters significantly affect the bridge performance. Furthermore, the change in the span number has a meaningful impact only when fewer than four spans are modeled. Finally, pushover analyses estimate the maximum transverse displacement and the sequence of plastic hinge creation as well as the mechanical behaviour of the structure under lateral flood loads. The analysis results show that IAJBs have better flooding‐resistant performance than conventional jointed bridges.

Vulnerability analysis of bridge superstructures under extreme fluid actions

Vulnerability analyses of bridge structures affected by extreme flood or tsunami wave loads in terms of loading variability and structural and fluid characteristics are conducted. The numerical model is developed by a combined three-dimensional (3D)/two-dimensional analysis based on phase field theory and 3D solid modeling of the fluid and structural systems, respectively. Coupling effects between the fluid and structure are simulated by using a moving mesh method based on an arbitrary Lagrangian–Eulerian approach to take bridge deformability and moving wall conditions into consideration. The proposed model is implemented in a finite element formulation, whose solution is achieved through a substructuring approach by introducing projection map operators defined to connect the structural and fluid systems. Several wave load scenarios related to the initial impact or dam break phenomena depending on inundation and blocking ratios and Froude numbers are considered. The main aim is to quantify the dynamic amplification effects of the kinematic and stress variables produced by the external loads with respect to conventional static analyses. In addition, the influences of bridge deformations on the hydrodynamic loads and vice versa are also discussed in terms of fluid and structural characteristics.

Structural Durability Assessment of Stilt Houses to Flash Flooding: Case Study of Flash Flood-Affected Sites in Thailand

The ‘stilt house’ is found in many flood-prone areas and represents local wisdom regarding building construction to coexist with floodwaters. Most academic research projects have studied stilt houses based on two types of flood: inundation and coastal flooding. The study of pillar houses in flash floods is very limited. This research investigated whether the main structure of a stilt house could withstand strong water current to determine the suitability of the stilt house for flash flood sites. The study explored the physical appearance of stilt houses in five flash flood areas in Thailand. The styles of stilt houses in each area were simplified to generate models and to then test their tolerance toward moving water. The main findings were: 1) the main structure of the stilt house can resist flood loads at 1.00 m depth with a waterflow speed at 3.05 m/s; 2) the most vulnerable points on the main structure if struck by more rapid, deeper flows of water are the base of the column and the joint between the column and beams; and 3) the horizontal or diagonal bracing members perpendicular to the flow and not above the flood level become water blockades that increase the reactive force to the main structure.

Settlement-induced bending moments on pile-founded floodwalls

T-walls are pile-supported floodwalls commonly built in New Orleans. They are founded on long concrete or steel battered piles and include a sheet pile cut off for seepage and gradient control. Since soils in southern Louisiana contain soft and compressible silt and clay, these floodwalls need to be designed to resist flood loads and loads produced by consolidation of soft soil under the weight of new fill. In an attempt to develop a comprehensive T-wall design procedure that appropriately considers field conditions, the United States Army Corps of Engineers New Orleans District partnered with Rensselaer Polytechnic Institute and Virginia Polytechnic Institute and State University. A testing programme was developed to perform centrifuge tests that would provide insight into the mechanisms and magnitudes of settlement-induced bending moments and reliable datasets for validation of numerical models. This paper describes the experimental approach and presents two centrifuge tests with T-walls resting directly on clay. The bending moments on the battered piles significantly increased under the weight of the new fill. With settlement around the piles reaching values of 1·5 m, the bending moments at least doubled over the testing course, with maximum values observed at the top third of the pile length.