Effect of Snowfall, As a Consequence of Climate Change, on Steel Structures in Palestine

Effect of snowfall, as a consequence of climate change, on steel structures in Palestine – Qualitative Risk Assessment

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N. N. Samaro

Faculty of Graduate Studies

An-Najah National University

P. O. Box 7, Nablus, Palestine

A. R. Hasan*

I. Al Qasem

Department of Civil Engineering

An-Najah National University

P. O. Box 7, Nablus, Palestine

M. B. Dwaikat

Department of Building Engineering

An-Najah National University

P. O. Box 7, Nablus, Palestine

*Corresponding Author: Dr. A. Rasem Hasan, Civil Engineering Department, An-Najah National University, E-mail: , Phone: +970597511514, Fax: +970922345982.

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Abstract-Several failures of steel structures were recently occurred in Palestine and triggered by accumulation of snowfalls. Changes in snowfall patterns in the region were studied and analyzed. Increase in snowfalls depths is expected in the 21st century and may exceed 1 m in areas with elevation greater than 1000 masl. A qualitative risk based study were conducted to analyze potential risks of snowfall events on steel structures, and to evaluate future risks that may result from excessive events through identifications of threats, hazards and consequences. The major causes for damages in steel structures due to snowfall in the country were attributed to different reasons, mainly; lack of proper design and faults in construction for properly designed structures. Finally, risk management options, were drafted in order to mitigate consequences and adapt to future expected changes in climate, and to increase the public local authorities’ awareness and preparedness of for such risks.

Keywords-Climate change; Palestine; Risk assessment; Snowfall; Steel structures.

I.  Introduction

Extreme weather events, as extreme snowfalls, can cause loss of life and significant damage to property and people (NAE, 2016). Moreover, it could act as a “threat multiplier” by increasing conflict and variation in several regions, so it should be identified and studied carefully in order to give a roadmap for future researches to better understand its instability and vulnerability (Brauch et al., 2011).

Snow disaster is one of the most serious and influenced hazards, which not only threatens human life and property, but also brings great damages to economy, society, resources, and environment (Gao, 2016). Increasing of snowfall measures (such as: depths, frequency, spatial coverage, and melting period) in Palestine and the region, are attributed to climate change.

This paper generally shed light on climate change in the region, concentrated on snowfall events as a consequence of climate change, and discusses the causes of several failures of steel structures that occurred in Palestine due to snow fall accumulation. Qualitative risk assessment (QRA) was conducted to determine causes and consequences of steel structures failures. Conclusions and recommendations were drafted based on the studied cases.

II.  Climate change – general review

Climate change could affect the whole earth and cause urgent problems such as in the environmental, social and economic. It may have negative consequences if the correct action is not taken directly (Grigoroudis et al., 2016). Climate change shifts the distributions of a set of climatic variables, including temperature, precipitation, humidity, wind speed, sunshine duration, and evaporation (Zhang et al., 2017). It also affects all regions around the world: ice shields are melting and the sea level is rising; in some regions, extreme precipitation events are becoming more common; other area are experiencing an increase in extreme heat waves and droughts (Seif-Ennasr et al., 2016). Also, may influence various components like air, water, plants, animals and human beings, which, if not respond for, may lead to catastrophes. (VijayaVenkataRaman et al., 2011). And so, climate change calls for innovative adaptive responses in order to minimize the negative impacts that may result. Different organizations have major roles in implementing mitigation and adaptation options to avoid negative effects of climate change that could affect structures and human health (Glaas et al., 2017).

Palestine, as part of the Middle East, have been and will be subjected to many serious climate changes that include increases in temperature and sea level rise, reduction in the annual rainfall also hydro-meteorological dangers such as heat waves, droughts, floods, storms. These physical impacts may cause failures in many societal and economical aspects (Pe’er and Safriel, 2000; Salem, 2011; Hawajri, 2016). According to UNEP (2003), Middle East is a meeting of many escalating environmental threats that include climate change, and so, there is a need for disaster risk reduction and management fields in Palestine. Several actions should be formulated and developed in order to minimize the hazard effects such as: legislation toward disaster preparedness and prevention, linking policies and operations, coordination of central and local governments, awareness and training, and developing a risk management database (Al Dabbeek, 2010).

Intergovernmental panel on climate change (IPCC) and based on their fourth assessment report predicted that, for the southern and eastern Mediterranean, where Palestine is part of, warming over the 21st century will be larger to be between 2.2 and 5.1oC. Annual precipitation is very likely to decrease in the area up to 10% by 2020 and 20% by 2050 with an increased risk of summer droughts (IPCC, 2007; Lelieveld et al., 2012).

No predictions were found in literature for expected variation in snowfall levels in Palestine or the nearby region.

III.  Snowfall events in Palestine

The Palestinian Meteorological Department (PMD) has started to record snowfall events since 1997. No earlier record was found for West Bank, except for Jerusalem through the Israeli Metrological Services (IMS). Based on records of the PMD (2016), snowfall events occur frequently in Palestine over areas of 500+ meter above sea level (masl) (Fig.1), Gaza are all in the region that don not have records of snowfall, and so excluded from the discussion. For areas of 500-800 masl, snow has fallen with an average of 3 times per decade, and over areas of 800+ masl with an average of 4.5 times per decade, both of the 20th century. During the 20th century, most of the snowfalls occurred as once throughout the certain year that had snowfall. Multiple events as 2-3 times in a year were started in the 21st century, and specifically since 2008. The largest depth recorded was as 91 cm in Jerusalem in 1992.

Figure 1. Elevations as meter above sea level (masl) for West Bank, Palestine

To predict future snowfall events; obtained data of the IMS (2016) were analyzed. Recorded depths in cm were averaged for decades of the 20th century (Fig. 2).

Figure 2. Average snowfall depths in Jerusalem during the decades of the 20th century.

A replicated pattern of the first and second halves of the 20th century is noticed (Fig. 3; a&b). The trend line of Fig. 3a; 1st half of the 20th century has a slope of 1.51 (R2=0.69), with increasing standard deviation from the 20s to the 50s. The slope has increased for the 2nd half to be 2.09 (R2=0.69), with increase in the standard deviation. Thus, the replicated pattern has occurred for a return period around 50 years, but with increasing trend of depths, number of snowfall events, and variations; an indicator of increasing risks due to snowfalls

Figure 3a. Average snowfall depths in Jerusalem during the 1st half of the 20th century.

Figure 3b. Average snowfall depths in Jerusalem during the 2nd half of the 20th century.

It’s too early to account for data of the 21st century, but it worth mentioning that snow had fallen 6 times in Jerusalem during the 1st decade of the 21st century with an average depth of 19 cm, and for the 2nd decade up to 2017, snow has fallen 3 times in Jerusalem and other areas of Palestine that has elevations of 500+ masl, being the extremist event of snowfall was recorded in 2013 as 65 cm depth in Ramallah and Jerusalem, and 50 cm depth in Hebron, with frequent falls of snow as 3 times for the same year. Snowfall depths of 1 m and larger are expected to occur as depicted from Figure 3.

IV.  Damages of steel structures due to snowfall in Palestine

Damages of steel structure facilities due to snowfall in Palestine were gathered from different media sources. Owners of these facilities were contacted and interviewed. Design documents for damaged facilities were collected when possible. Most of the damaged structures were an arbitrarily built storage structures and animal house-farms in rural areas. Table 1 lists the major damaged structures for industrial facilities and commercial facilities that all occurred in 2013.

Table 1. Damaged steel structures in Palestine due to snowfall in 2013.

Company / Location / Elevation (masl) / Lossesa (JD) / Description of losses
Al Mahaba company for transportation / Hebron / 930 / 400,000 / Severe damages to structures, 8 trucks, and private car
Jamaeen stonecutting factory / Jamaeen, Nablus / 530 / 10,000 / Partial damages in assets
Geneva company / Ramallah / 880 / Not known / Partial damages to structure and other asserts
Italian company / Ramallah / 880 / 200,000 / Severe damages to property, materials and in the structure, stop the work temporarily
Royal company / Hebron / 930 / 0.5 Million / Damages in the company truss, trucks, and materials
Shahatet company / Hebron / 930 / 15,500 / Affected the company truss, trucks and losses in properties
a Losses were estimated in Jordanian Dinar based in currency prices of 2016, and rounded by thousands.

In addition to damages in Table 1, a major previous damage occurred at Birzeit University, Ramallah, where a collapse of the physical education building occurred in February 2003 due to snow accumulation. Losses were only of property due to the fact that the collapse was in the evening. Snow accumulation ranged between 20-30 cm, failure was sudden and swift bringing most of the steel structure down in seconds (Barakat, 2013).

V.  Qualitative Risk Assessment

Risk Assessment (RA) is an efficient way to predict and reduce the risk of occurrence of an accident in any system. RA techniques share a common objective, which is to provide an assurance that a process or a system is designed and operated under an “acceptable risk” (Ferdous et al., 2012). In absence of data, mainly for frequencies of occurred events, and their causes, QRA is applied to pave the way for more quantitative studies.

Causes of steel structures failures may be related to the unexpected snow load, the instability of the structure, improper design of the structural members and connections, combined natural events (of wind and snow) or combined human and natural events.

Until recently, snow loads used for design practices in Palestine are determined based on the Jordanian Code requirements. Our previous work (Samaro et al. 2017), has discussed the failure of structures in Table 1, by remodeling the structures in SAP2000, and applying the Jordanian Code of steel structures design. The results depicted that the studied structures must bear the snow loads based on code assumptions. Despite these results for the above case studies, these cases appeared to be unsafe under certain substances; therefore, a modification to the snow load in the Jordanian code was recommended.

QRA was conducted for the cases in Table 1 by: (i) identifying hazards of snow loads in cm on steel structures (Table 2), (ii) conduction of casual and frequency analysis by constructing a fault tree (Fig. 4), and (iii) analyzing accidents scenarios based on event-tree method (Fig. 5). Additionally, Bow-Tie analysis (Table 3) and risk matrices are also used to illustrate the overall risk analysis and to examine the hazardous events and threats, in addition to possible barriers and controls.

From figure (4), it is clearly noticed that the structure failure which is the “Top event” may be caused first, by natural events such as the accumulated or frequent snow events or a combined natural events may occurred. Secondly, by man-made events such as the structure may had not been designed or it may had a wrong implementation for the structure design by the contractor or the engineer, also a combined events of natural and man-made events may occurred and caused the failure.

Table 2. Hazard identification for snow loads on steel structures in Palestine.

Scenarios / Hazardous Events
Scenario one: Light Snow
Depth = 0-15 cm / 1-  Slight damage to property, materials, constructions and infrastructure
2-  More consumption of fuel/electricity and leads to more pollution to the environment
Scenario Two: Medium Snow
Depth = 15 -30 cm / 1-  More car accidents which leads to human injuries
2-  Damage to property, materials and infrastructure
3-  Loss in agricultural crops due to cold temperatures
4-  Pollution caused by higher consumption of fuel.
5-  Municipality reputation for clearing roads from snow.
6-  Hospital capacity might not be enough.
Scenario Three: Heavy Snow
Depth = 30 cm
to more / 1-  More car accidents which leads to human injuries
2-  Severe damage to property, materials and infrastructure which might cause the collapse of structures, roads, mountain sides.
3-  Loss in agricultural crops due to cold temperatures, floods
4-  Trapped in people in remote locations.
5-  Loss of vehicles.
6-  No accessibility.
7-  Pollution caused by higher consumption of fuel.
8-  Municipality reputation for clearing roads from snow.
9-  Hospital capacity might not be enough.

Figure 4. Fault tree diagram for the studied cases.

To determine and analyze the possible event sequences that can possibly happened after the occurrence of the hazardous event, event tree analysis was used for modeling and analyzing the possible accident scenarios. As it is shown in Figure (5), the resulting diagram displays the possible accident scenarios that may follow the hazardous event of snow accumulation.

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Figure 5. Event tree diagram.

In Figure (5), “Event B” describes the failure of the structure, “Event C” describes a failure in the alarm system, and “Event D” illustrates the failure of people evacuation. Moreover, several additional failure events scenarios could be also suggested to the current situation such as to have “Event E” which is the failure or existence of the safety and emergency equipment/ emergency responders.